Measurement of Exclusive $\pi^{+}\pi^{-}$ and $\rho^0$ Meson Photoproduction at HERA

The H1 collaboration Andreev, V. ; Baghdasaryan, A. ; Baty, A. ; et al.
Eur.Phys.J.C 80 (2020) 1189, 2020.
Inspire Record 1798511 DOI 10.17182/hepdata.102569

Exclusive photoproduction of $\rho^0(770)$ mesons is studied using the H1 detector at the $ep$ collider HERA. A sample of about 900000 events is used to measure single- and double-differential cross sections for the reaction $\gamma p \to \pi^{+}\pi^{-}Y$. Reactions where the proton stays intact (${m_Y{=}m_p}$) are statistically separated from those where the proton dissociates to a low-mass hadronic system ($m_p{<}m_Y{<}10$ GeV). The double-differential cross sections are measured as a function of the invariant mass $m_{\pi\pi}$ of the decay pions and the squared $4$-momentum transfer $t$ at the proton vertex. The measurements are presented in various bins of the photon-proton collision energy $W_{\gamma p}$. The phase space restrictions are $0.5 < m_{\pi\pi} < 2.2$ GeV, ${\vert t\vert < 1.5}$ GeV${}^2$, and ${20 < W_{\gamma p} < 80}$ GeV. Cross section measurements are presented for both elastic and proton-dissociative scattering. The observed cross section dependencies are described by analytic functions. Parametrising the $m_{\pi\pi}$ dependence with resonant and non-resonant contributions added at the amplitude level leads to a measurement of the $\rho^{0}(770)$ meson mass and width at $m_\rho = 770.8\ {}^{+2.6}_{-2.7}$ (tot) MeV and $\Gamma_\rho = 151.3\ {}^{+2.7}_{-3.6}$ (tot) MeV, respectively. The model is used to extract the $\rho^0(770)$ contribution to the $\pi^{+}\pi^{-}$ cross sections and measure it as a function of $t$ and $W_{\gamma p}$. In a Regge asymptotic limit in which one Regge trajectory $\alpha(t)$ dominates, the intercept $\alpha(t{=}0) = 1.0654\ {}^{+0.0098}_{-0.0067}$ (tot) and the slope $\alpha^\prime(t{=}0) = 0.233\ {}^{+0.067 }_{-0.074 }$ (tot) GeV${}^{-2}$ of the $t$ dependence are extracted for the case $m_Y{=}m_p$.

28 data tables

Elastic ($m_Y=m_p$) and proton-dissociative ($1<m_Y<10$ GeV) $\pi^{+}\pi^{-}$ photoproduction off protons, differential in the dipion mass. The tabulated cross sections are $\gamma p$ cross sections but can be converted to $ep$ cross sections using the effective photon flux $\Phi_{\gamma/e}$.

Elastic ($m_Y=m_p$) and proton-dissociative ($1<m_Y<10$ GeV) $\pi^{+}\pi^{-}$ photoproduction off protons, differential in the dipion mass --- statistical correlations coefficients $\rho_{ij}$ only. Only one half of the (symmetric) matrix is stored. Bins are identified by their global bin number.

Fit of elastic ($m_Y=m_p$) and proton-dissociative ($1<m_Y<10$ GeV) $\pi^{+}\pi^{-}$ photoproduction cross section off protons with a Soeding-inspired analytic function including $\rho$ and $\omega$ meson resonant contributions as well as a continuum background which interfere at the amplitude level. Parameters with subscript "el" and "pd" correspond to elastic and proton-dissociative cross sections, respectively.

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Strangeness Exchange in the Photoproduction of $K^+ \Lambda$ (1520) Between 2.8-{GeV} and 4.8-{GeV}

Barber, D.P. ; Dainton, J.B. ; Lee, L.C.Y. ; et al.
Z.Phys.C 7 (1980) 17, 1980.
Inspire Record 153887 DOI 10.17182/hepdata.14096

A tagged photon beam (2.8<Eγ<4.8 GeV) and multiparticle spectrometer have been used to study the photoproduction in hydrogen ofK+Λ(1520). Precise values for the mass and width of the Λ(1520) are given. The total cross-section is found to fall with increasing photon energy like (6.5±0.7)Eγ−(2.1±0.2) μb. The differential cross sectiondσ/dt indicates peripheral forward production and exhibits no evidence for shrinkage when compared with higher energy data. The Λ(1520) spin density matrix shows thatK exchange alone cannot account for the production mechanism. The reaction is found to resemble the process γp→K+ Λ(1115) in all measurable respects.

3 data tables

FITTED CROSS SECTION ENERGY DEPENDENCE IS SIG = (6.7 +- 0.7 MUB*GEV**2) * P**(-2.1 +- 0.2), INCLUDING HIGHER ENERGY DATA.

EXPONENTIAL SLOPE IS 6.1 +- 2.0 GEV**-2 FOR -T = 0.2 TO 0.7 GEV**2.

No description provided.


Photoproduction of $\pi \Delta(1232)$ From Hydrogen in the Energy Range 2.4-{GeV} to 4.8-{GeV}

The LAMP2 Group collaboration Barber, D.P. ; Dainton, J.B. ; Lee, L.C.Y. ; et al.
Z.Phys.C 6 (1980) 93, 1980.
Inspire Record 153944 DOI 10.17182/hepdata.14328

We present differential cross sections andΔ++ spin density matrix elements for the photoproduction processγp→π−Δ++ and differential cross sections for the processγp→π+Δ0. The incident photon energy dependence is studied and a comparison is made with previous experiments and with the predictions of a theoretical model.

5 data tables

DIFFERENTIAL CROSS SECTION AVERAGED OVER WHOLE ENERGY RANGE.

DIFFERENTIAL CROSS SECTION AVERAGED OVER WHOLE ENERGY RANGE.

DIFFERENTIAL CROSS SECTION FOR DIFFERENT ENERGY RANGES.

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Shape, transverse size, and charged hadron multiplicity of jets in pp collisions at 7 TeV

The CMS collaboration Chatrchyan, Serguei ; Khachatryan, Vardan ; Sirunyan, Albert M ; et al.
JHEP 06 (2012) 160, 2012.
Inspire Record 1111014 DOI 10.17182/hepdata.70063

Measurements of jet characteristics from inclusive jet production in proton-proton collisions at a centre-of-mass energy of 7 TeV are presented. The data sample was collected with the CMS detector at the LHC during 2010 and corresponds to an integrated luminosity of 36 inverse picobarns. The mean charged hadron multiplicity, the differential and integral jet shape distributions, and two independent moments of the shape distributions are measured as functions of the jet transverse momentum for jets reconstructed with the anti-kT algorithm. The measured observables are corrected to the particle level and compared with predictions from various QCD Monte Carlo generators.

128 data tables

The measured differential jet shape $\rho(r)$ for jets with 20 GeV $< p_{\mathrm{T}} <$ 25 GeV and 0 <|y|< 0.5. The CF in the table refers to unfolding correction factor from {\sc pythia6} Tune Z2. The systematic uncertainties from different sources, jet energy scale (JES), unfolding, and single particle response (SPR), are also presented.

The measured differential jet shape $\rho(r)$ for jets with 25 GeV $< p_{\mathrm{T}} <$ 30 GeV and 0 <|y|< 0.5. The CF in the table refers to unfolding correction factor from {\sc pythia6} Tune Z2. The systematic uncertainties from different sources, jet energy scale (JES), unfolding, and single particle response (SPR), are also presented.

The measured differential jet shape $\rho(r)$ for jets with 30 GeV $< p_{\mathrm{T}} <$ 40 GeV and 0 <|y|< 0.5. The CF in the table refers to unfolding correction factor from {\sc pythia6} Tune Z2. The systematic uncertainties from different sources, jet energy scale (JES), unfolding, and single particle response (SPR), are also presented.

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Jet and underlying event properties as a function of particle multiplicity in proton-proton collisions at sqrt(s) = 7 TeV

The CMS collaboration Chatrchyan, Serguei ; Khachatryan, Vardan ; Sirunyan, Albert M ; et al.
Eur.Phys.J.C 73 (2013) 2674, 2013.
Inspire Record 1261026 DOI 10.17182/hepdata.68128

Characteristics of multi-particle production in proton-proton collisions at $\sqrt{s}$=7 TeV are studied as a function of the charged-particle multiplicity, $N_{ch}$. The produced particles are separated into two classes: those belonging to jets and those belonging to the underlying event. Charged particles are measured with pseudorapidity |η|<2.4 and transverse momentum $p_T$ > 0.25 GeV/c. Jets are reconstructed from charged-particles only and required to have $p_T$ > 5 GeV/c. The distributions of jet $p_T$, average $p_T$ of charged particles belonging to the underlying event or to jets, jet rates, and jet shapes are presented as functions of $N_{ch}$ and compared to the predictions of the PYTHIA and HERWIG event generators. Predictions without multi-parton interactions fail completely to describe the $N_{ch}$-dependence observed in the data. For increasing $N_{ch}$, PYTHIA systematically predicts higher jet rates and harder $p_T$ spectra than seen in the data, whereas HERWIG shows the opposite trends. At the highest multiplicity, the data–model agreement is worse for most observables, indicating the need for further tuning and/or new model ingredients.

17 data tables

Mean $p_T$, all charged particles.

Mean $p_T$, UE charged particles.

Mean $p_T$, in-jet charged particles.

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Spin alignment and violation of the OZI rule in exclusive $\omega$ and $\phi$ production in pp collisions

The COMPASS collaboration Adolph, C. ; Akhunzyanov, R. ; Alexeev, M.G. ; et al.
Nucl.Phys.B 886 (2014) 1078-1101, 2014.
Inspire Record 1298025 DOI 10.17182/hepdata.64185

Exclusive production of the isoscalar vector mesons $\omega$ and $\phi$ is measured with a 190 GeV$/c$ proton beam impinging on a liquid hydrogen target. Cross section ratios are determined in three intervals of the Feynman variable $x_{F}$ of the fast proton. A significant violation of the OZI rule is found, confirming earlier findings. Its kinematic dependence on $x_{F}$ and on the invariant mass $M_{p\mathrm{V}}$ of the system formed by fast proton $p_\mathrm{fast}$ and vector meson $V$ is discussed in terms of diffractive production of $p_\mathrm{fast}V$ resonances in competition with central production. The measurement of the spin density matrix element $\rho_{00}$ of the vector mesons in different selected reference frames provides another handle to distinguish the contributions of these two major reaction types. Again, dependences of the alignment on $x_{F}$ and on $M_{p\mathrm{V}}$ are found. Most of the observations can be traced back to the existence of several excited baryon states contributing to $\omega$ production which are absent in the case of the $\phi$ meson. Removing the low-mass $M_{p\mathrm{V}}$ resonant region, the OZI rule is found to be violated by a factor of eight, independently of $x_\mathrm{F}$.

5 data tables

Differential cross section ratio R(PHI/OMEGA) and corresponding OZI violation factors F(OZI). R(PHI/OMEGA) is multiplied by 100 to improve readability.

Differential cross section ratio R(PHI/OMEGA) and corresponding OZI violation factors F(OZI) for different cuts on the vector meson momentum P(V). R(PHI/OMEGA) is multiplied by 100 to improve readability.

Spin alignment RHO(00) extracted from the helicity angle distributions for PHI and OMEGA production, in the latter case with various cuts on P(V). The uncertainty is the propagated uncertainty from the linear fits, which in turn includes the quadratic sum of statistical uncertainties and uncertainties from the background subtraction.

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Study of Jet Shapes in Inclusive Jet Production in pp Collisions at sqrt(s) = 7 TeV using the ATLAS Detector

The ATLAS collaboration Aad, G. ; Abbott, B. ; Abdallah, J. ; et al.
Phys.Rev.D 83 (2011) 052003, 2011.
Inspire Record 882984 DOI 10.17182/hepdata.63511

Jet shapes have been measured in inclusive jet production in proton-proton collisions at sqrt(s) = 7 TeV using 3 pb^{-1} of data recorded by the ATLAS experiment at the LHC. Jets are reconstructed using the anti-kt algorithm with transverse momentum 30 GeV < pT < 600 GeV and rapidity in the region |y| < 2.8. The data are corrected for detector effects and compared to several leading-order QCD matrix elements plus parton shower Monte Carlo predictions, including different sets of parameters tuned to model fragmentation processes and underlying event contributions in the final state. The measured jets become narrower with increasing jet transverse momentum and the jet shapes present a moderate jet rapidity dependence. Within QCD, the data test a variety of perturbative and non-perturbative effects. In particular, the data show sensitivity to the details of the parton shower, fragmentation, and underlying event models in the Monte Carlo generators. For an appropriate choice of the parameters used in these models, the data are well described.

124 data tables

Measured Differential Jet Shape RHO as a function of r for jet transverse momentum from 30 to 40 GeV and absolute values of the jet rapidity from 0 to 2.8.

Measured Differential Jet Shape RHO as a function of r for jet transverse momentum from 40 to 60 GeV and absolute values of the jet rapidity from 0 to 2.8.

Measured Differential Jet Shape RHO as a function of r for jet transverse momentum from 60 to 80 GeV and absolute values of the jet rapidity from 0 to 2.8.

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Photoproduction of $\pi^+ \pi^-$ meson pairs on the proton

The CLAS collaboration Battaglieri, M. ; De Vita, R. ; Szczepaniak, A.P. ; et al.
Phys.Rev.D 80 (2009) 072005, 2009.
Inspire Record 825040 DOI 10.17182/hepdata.74824

The exclusive reaction $\gamma p \to p \pi^+ \pi^-$ was studied in the photon energy range 3.0 - 3.8 GeV and momentum transfer range $0.4<-t<1.0$ GeV$^2$. Data were collected with the CLAS detector at the Thomas Jefferson National Accelerator Facility. In this kinematic range the integrated luminosity was about 20 pb$^{-1}$. The reaction was isolated by detecting the $\pi^+$ and proton in CLAS, and reconstructing the $\pi^-$ via the missing-mass technique. Moments of the di-pion decay angular distributions were derived from the experimental data. Differential cross sections for the $S$, $P$, and $D$-waves in the $M_{\pi^+\pi^-}$ mass range $0.4-1.4$ GeV were derived performing a partial wave expansion of the extracted moments. Besides the dominant contribution of the $\rho(770)$ meson in the $P$-wave, evidence for the $f_0(980)$ and the $f_2(1270)$ mesons was found in the $S$ and $D$-waves, respectively. The differential production cross sections $d\sigma/dt$ for individual waves in the mass range of the above-mentioned mesons were extracted. This is the first time the $f_0(980)$ has been measured in a photoproduction experiment.

198 data tables

Moments YLM(LM=00) of the di-pion angular distribution for -T.

Moments YLM(LM=00) of the di-pion angular distribution for -T.

Moments YLM(LM=00) of the di-pion angular distribution for -T.

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Measurement of Spin-Density Matrix Elements for $\phi$-Meson Photoproduction from Protons and Deuterons Near Threshold

The LEPS collaboration Chang, W.C. ; Ahn, D.S. ; Ahn, J.K. ; et al.
Phys.Rev.C 82 (2010) 015205, 2010.
Inspire Record 859164 DOI 10.17182/hepdata.55768

The LEPS/SPring-8 experiment made a comprehensive measurement of the spin-density matrix elements for $\gamma p \to \phi p$, $\gamma d \to \phi p n$ and $\gamma d \to \phi d$ at forward production angles. A linearly polarized photon beam at $E_{\gamma}$=1.6-2.4 GeV was used for the production of $\phi$ mesons. The natural-parity Pomeron exchange processes remains dominant nearthreshold. The unnatural-parity processes of pseudoscalar exchange is visible in the production from nucleons but is greatly reduced in the coherent production from deuterons. There is no strong $E_{\gamma}$-dependence, but some dependence on momentum-transfer. A small but finite value of the spin-density matrix elements reflecting helicity-nonconserving amplitudes in the $t$-channel is observed.

81 data tables

Measurements of the spin density matrix element RHO(JJ=0,MM=00) for the GAMMA P --> PHI P reaction in the helicity system as a function of T-Tmin for 3 incident photon energy regions.

Measurements of the spin density matrix element RE(RHO(JJ=0,MM=10)) for the GAMMA P --> PHI P reaction in the helicity system as a function of T-Tmin for 3 incident photon energy regions.

Measurements of the spin density matrix element RHO(JJ=0,MM=1-1) for the GAMMA P --> PHI P reaction in the helicity system as a function of T-Tmin for 3 incident photon energy regions.

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Diffractive Electroproduction of rho and phi Mesons at HERA

The H1 collaboration Aaron, F.D. ; Aldaya Martin, M. ; Alexa, C. ; et al.
JHEP 05 (2010) 032, 2010.
Inspire Record 835609 DOI 10.17182/hepdata.56191

Diffractive electroproduction of rho and phi mesons is measured at HERA with the H1 detector in the elastic and proton dissociative channels. The data correspond to an integrated luminosity of 51 pb^-1. About 10500 rho and 2000 phi events are analysed in the kinematic range of squared photon virtuality 2.5 &lt; Q^2 &lt; 60 GeV^2, photon-proton centre of mass energy 35 &lt; W &lt; 180 GeV and squared four-momentum transfer to the proton |t| &lt; 3 GeV^2. The total, longitudinal and transverse cross sections are measured as a function of Q^2, W and |t|. The measurements show a transition to a dominantly "hard" behaviour, typical of high gluon densities and small q\bar{q} dipoles, for Q^2 larger than 10 to 20 GeV^2. They support flavour independence of the diffractive exchange, expressed in terms of the scaling variable (Q^2 + M_V^2)/4, and proton vertex factorisation. The spin density matrix elements are measured as a function of kinematic variables. The ratio of the longitudinal to transverse cross sections, the ratio of the helicity amplitudes and their relative phases are extracted. Several of these measurements have not been performed before and bring new information on the dynamics of diffraction in a QCD framework. The measurements are discussed in the context of models using generalised parton distributions or universal dipole cross sections.

108 data tables

Q**2 dependence of the GAMMA* P elastic RHO0 meson production at mean W There is an additional overall normalization uncertainty of 3.9 PCT.

Q**2 dependence of the GAMMA* P cross section for proton dissociative RHO0 meson production at mean W There is an additional overall normalization uncertainty of 4.6 PCT.

Q**2 dependence of the GAMMA* P elastic PHI meson production at mean W There is an additional overall normalization uncertainty of 4.7 PCT.

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Measurement of J/psi photoproduction at large momentum transfer at HERA

The ZEUS collaboration Chekanov, S. ; Derrick, M. ; Magill, S. ; et al.
JHEP 05 (2010) 085, 2010.
Inspire Record 833339 DOI 10.17182/hepdata.55178

The proton-dissociative diffractive photoproduction of J/psi mesons has been studied in ep collisions with the ZEUS detector at HERA using an integrated luminosity of 112 pb^-1. The cross section is presented as a function of the photon-proton centre-of-mass energy and of the squared four-momentum transfer at the proton vertex. The results are compared to perturbative QCD calculations.

14 data tables

The differential cross section DSIG/DT as a function of T.

The differential cross section DSIG/DT as a function of W in the ABS(T) range 2.0 to 2.5 GeV**2.

The differential cross section DSIG/DT as a function of W in the ABS(T) range 2.5 to 3.0 GeV**2.

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Forward coherent Phi-meson photoproduction from deuterons near threshold.

Chang, W.C. ; Horie, K. ; Shimizu, S. ; et al.
Phys.Lett.B 658 (2008) 209-215, 2008.
Inspire Record 747086 DOI 10.17182/hepdata.26965

Differential cross sections and decay asymmetries for coherent $\phi$-meson photoproduction from deuterons were measured for the first time at forward angles by linearly polarized photons at $E_{\gamma}$= 1.5-2.4 GeV. With the elimination of isovector unnatural-parity $\pi$-meson exchange in the interaction with isoscalar deuteron target, this reaction is expected to explore natural-parity Pomeron dynamics at low energies. Our measurements show that the cross sections at zero degrees increase steadily with photon energy and the decay asymmetries demonstrate a complete dominance of natural-parity exchange processes. Nevertheless the deduced cross sections of $\phi$-mesons from nucleons contributed by isoscalar t-channel exchange processes are mostly underpredicted by conventional Pomeron model.

11 data tables

Differential cross section DSIG/DT for photon energy 1.57 to 1.67 GeV.

Differential cross section DSIG/DT for photon energy 1.67 to 1.77 GeV.

Differential cross section DSIG/DT for photon energy 1.77 to 1.87 GeV.

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Multiplicity structure of the hadronic final state in diffractive deep-inelastic scattering at HERA.

The H1 collaboration Adloff, C. ; Anderson, M. ; Andreev, V. ; et al.
Eur.Phys.J.C 5 (1998) 439-452, 1998.
Inspire Record 469495 DOI 10.17182/hepdata.44363

The multiplicity structure of the hadronic system X produced in deep-inelastic processes at HERA of the type ep -> eXY, where Y is a hadronic system with mass M_Y< 1.6 GeV and where the squared momentum transfer at the pY vertex, t, is limited to |t|<1 GeV^2, is studied as a function of the invariant mass M_X of the system X. Results are presented on multiplicity distributions and multiplicity moments, rapidity spectra and forward-backward correlations in the centre-of-mass system of X. The data are compared to results in e+e- annihilation, fixed-target lepton-nucleon collisions, hadro-produced diffractive final states and to non-diffractive hadron-hadron collisions. The comparison suggests a production mechanism of virtual photon dissociation which involves a mixture of partonic states and a significant gluon content. The data are well described by a model, based on a QCD-Regge analysis of the diffractive structure function, which assumes a large hard gluonic component of the colourless exchange at low Q^2. A model with soft colour interactions is also successful.

10 data tables

The multiplicity moment MULT as a function of the mass of the charged hadron system in the full phase space and separately in the forward and backward hemispheres.

The multiplicity moment DISPERSION as a function of the mass of the charged hadron system in the full phase space and separately in the forward and backward hemispheres.

The multiplicity moment R2 as a function of the mass of the charged hadron system in the full phase space and separately in the forward and backward hemispheres.

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Event shapes in deep inelastic scattering at HERA.

The ZEUS collaboration Chekanov, S. ; Derrick, M. ; Magill, S. ; et al.
Nucl.Phys.B 767 (2007) 1-28, 2007.
Inspire Record 714503 DOI 10.17182/hepdata.11818

Mean values and differential distributions of event-shape variables have been studied in neutral current deep inelastic scattering using an integrated {luminosity} of 82.2 pb$^{-1}$ collected with the ZEUS detector at HERA. The kinematic range was $80 &lt; Q^2 &lt; 20 480\gev^2$ and $0.0024 &lt; x &lt; 0.6$, where $Q^2$ is the virtuality of the exchanged boson and $x$ is the Bjorken variable. The data are compared with a model based on a combination of next-to-leading-order QCD calculations with next-to-leading-logarithm corrections and the Dokshitzer-Webber non-perturbative power corrections. The power-correction method provides a reasonable description of the data for all event-shape variables studied. Nevertheless, the lack of consistency of the determination of $\alpha_s$ and of the non-perturbative parameter of the model, $\albar$, suggests the importance of higher-order processes that are not yet included in the model.

69 data tables

Mean value of the event shape variable 1-THRUST(C=T).

Mean value of the event shape variable B(C=T).

Mean value of the event shape variable RHO**2.

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Measurement of event shape variables in deep-inelastic scattering at HERA.

The H1 collaboration Aktas, A. ; Andreev, V. ; Anthonis, T. ; et al.
Eur.Phys.J.C 46 (2006) 343-356, 2006.
Inspire Record 699835 DOI 10.17182/hepdata.11377

Deep-inelastic ep scattering data taken with the H1 detector at HERA and corresponding to an integrated luminosity of 106 pb^{-1} are used to study the differential distributions of event shape variables. These include thrust, jet broadening, jet mass and the C-parameter. The four-momentum transfer Q is taken to be the relevant energy scale and ranges between 14 GeV and 200 GeV. The event shape distributions are compared with perturbative QCD predictions, which include resummed contributions and analytical power law corrections, the latter accounting for non-perturbative hadronisation effects. The data clearly exhibit the running of the strong coupling alpha_s(Q) and are consistent with a universal power correction parameter alpha_0 for all event shape variables. A combined QCD fit using all event shape variables yields alpha_s(mZ) = 0.1198 \pm 0.0013 ^{+0.0056}_{-0.0043} and alpha_0 = 0.476 \pm 0.008 ^{+0.018} _{-0.059}.

71 data tables

Normalised distribution of (1-THRUST) where THRUST is w.r.t the axis which maximises the sum of the longitudinal momenta in the current hemisphere, for Q = 14.0 to 16.0 GeV and X = 0.00841 .

Normalised distribution of (1-THRUST) where THRUST is w.r.t the axis which maximises the sum of the longitudinal momenta in the current hemisphere, for Q = 16.0 to 20.0 GeV and X = 0.01180 .

Normalised distribution of (1-THRUST) where THRUST is w.r.t the axis which maximises the sum of the longitudinal momenta in the current hemisphere, for Q = 20.0 to 30.0 GeV and X = 0.02090 .

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Diffractive photoproduction of rho mesons with large momentum transfer at HERA.

The H1 collaboration Aktas, A. ; Andreev, V. ; Anthonis, T. ; et al.
Phys.Lett.B 638 (2006) 422-431, 2006.
Inspire Record 712738 DOI 10.17182/hepdata.45698

The diffractive photoproduction of rho mesons, e p \to e rho Y, with large momentum transfer squared at the proton vertex, |t|, is studied with the H1 detector at HERA using an integrated luminosity of 20.1 pb^{-1}. The photon-proton centre of mass energy spans the range 75 &lt; W &lt; 95 GeV, the photon virtuality is restricted to Q^2 &lt; 0.01 GeV^2 and the mass M_Y of the proton remnant is below 5 GeV. The t dependence of the cross section is measured for the range 1.5 &lt; |t| &lt; 10.0 GeV^2 and is well described by a power law, dsigma/ d|t| \propto |t|^{-n}. The spin density matrix elements, which provide information on the helicity structure of the interaction, are extracted using measurements of angular distributions of the rho decay products. The data indicate a violation of s-channel helicity conservation, with contributions from both single and double helicity-flip being observed. The results are compared to the predictions of perturbative QCD models.

5 data tables

The normalized differential cross section as a function of T.

Normalised decay angular distribution w.r.t. the polar angle THETA.

Normalised decay angular distribution w.r.t. the polar angle THETA.

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Diffractive Phi-meson photoproduction on proton near threshold.

The LEPS collaboration Mibe, T. ; Chang, W.C. ; Nakano, T. ; et al.
Phys.Rev.Lett. 95 (2005) 182001, 2005.
Inspire Record 684863 DOI 10.17182/hepdata.31587

Photoproduction of $\phi$-meson on protons was studied by means of linearly polarized photons at forward angles in the low-energy region from threshold to $E_{\gamma}$= 2.37 GeV. The differential cross sections at $t = -|t|_{min}$ do not increase smoothly as $E_{\gamma}$ increases, but show a local maximum at around 2.0 GeV. The angular distributions demonstrate that $\phi$-mesons are photo-produced predominantly by helicity-conserving processes, and the local maximum is not likely due to unnatural-parity processes.

14 data tables

Differential cross section as a function of T+ABS(TMIN) in the photon energy range 1.57 to 1.67 GeV.

Differential cross section as a function of T+ABS(TMIN) in the photon energy range 1.67 to 1.77 GeV.

Differential cross section as a function of T+ABS(TMIN) in the photon energy range 1.77 to 1.87 GeV.

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Study of jet shapes in inclusive jet production in p anti-p collisions at s**(1/2) = 1.96-TeV

The CDF collaboration Acosta, D. ; Adelman, J. ; Affolder, T. ; et al.
Phys.Rev.D 71 (2005) 112002, 2005.
Inspire Record 682179 DOI 10.17182/hepdata.42780

We report on a study of jet shapes in inclusive jet production in $p \bar{p}$ collisions at $\sqrt{s} = 1.96 {\rm TeV}$ using the upgraded Collider Detector at Fermilab in Run II (CDF II) based on an integrated luminosity of $170 \rm pb^{-1}$. Measurements are carried out on jets with rapidity $0.1 < |Y^{\rm jet}| < 0.7$ and transverse momentum 37 GeV/c $< P_T^{\rm jet} < 380$ GeV/c. The jets have been corrected to the hadron level. The measured jet shapes are compared to leading-order QCD parton-shower Monte Carlo predictions as implemented in the PYTHIA and HERWIG programs. PYTHIA, tuned to describe the underlying event as measured in CDF Run I, provides a better description of the measured jet shapes than does PYTHIA or HERWIG with their default parameters.

13 data tables

The measured differential jet shape.

The measured differential jet shape.

The measured differential jet shape.

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Exclusive electroproduction of Phi mesons at HERA.

The ZEUS collaboration Chekanov, S. ; Derrick, M. ; Magill, S. ; et al.
Nucl.Phys.B 718 (2005) 3-31, 2005.
Inspire Record 679957 DOI 10.17182/hepdata.45894

Exclusive electroproduction of $\phi$ mesons has been studied in $e^\pm p$ collisions at $\sqrt{s}=318 \gev$ with the ZEUS detector at HERA using an integrated luminosity of 65.1 pb$^{-1}$. The $\gamma^*p$ cross section is presented in the kinematic range $2<Q^2<70 \gev^2$, $35<W<145 \gev$ and ${|t|}<0.6 \gev^2$. The cross sections as functions of $Q^2$, $W$, $t$ and helicity angle $\theta_h$ are compared to cross sections for other vector mesons. The ratios $R$ of the cross sections for longitudinally and transversely polarized virtual photons are presented as functions of $Q^2$ and $W$. The data are also compared to predictions from theoretical models.

23 data tables

Exclusive GAMMA* P --> PHI P cross section in the Q**2 range 2 to 3 GeV**2.

Exclusive GAMMA* P --> PHI P cross section in the Q**2 range 3 to 5 GeV**2.

Exclusive GAMMA* P --> PHI P cross section in the Q**2 range 5 to 9 GeV**2.

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Studies of hadronic event structure in e+ e- annihilation from 30-GeV to 209-GeV with the L3 detector

The L3 collaboration Achard, P. ; Adriani, O. ; Aguilar-Benitez, M. ; et al.
Phys.Rept. 399 (2004) 71-174, 2004.
Inspire Record 652683 DOI 10.17182/hepdata.54900

In this Report, QCD results obtained from a study of hadronic event structure in high energy e^+e^- interactions with the L3 detector are presented. The operation of the LEP collider at many different collision energies from 91 GeV to 209 GeV offers a unique opportunity to test QCD by measuring the energy dependence of different observables. The main results concern the measurement of the strong coupling constant, \alpha_s, from hadronic event shapes and the study of effects of soft gluon coherence through charged particle multiplicity and momentum distributions.

68 data tables

Jet fractions using the JADE algorithm as a function of the jet resolution parameter YCUT at c.m. energy 130.1 GeV.

Jet fractions using the JADE algorithm as a function of the jet resolution parameter YCUT at c.m. energy 136.1 GeV.

Jet fractions using the JADE algorithm as a function of the jet resolution parameter YCUT at c.m. energy 161.3 GeV.

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W boson polarisation at LEP2.

The OPAL collaboration Abbiendi, G. ; Ainsley, C. ; Akesson, P.F. ; et al.
Phys.Lett.B 585 (2004) 223-236, 2004.
Inspire Record 635790 DOI 10.17182/hepdata.49660

Elements of the spin density matrix for W bosons in e+e- -> W+W- -> qqln events are measured from data recorded by the OPAL detector at LEP. This information is used calculate polarised differential cross-sections and to search for CP-violating effects. Results are presented for W bosons produced in e+e- collisions with centre-of-mass energies between 183 GeV and 209 GeV. The average fraction of W bosons that are longitudinally polarised is found to be (23.9 +- 2.1 +- 1.1)% compared to a Standard Model prediction of (23.9 +- 0.1)%. All results are consistent with CP conservation.

7 data tables

The fraction of longitudinal polarization for leptonically and hadronically decaying W bosons. The average values for all the centre of mass energies and for both lepton and hadron decay combined are also given.

The luminosity weighted average over all the centre of mass energies of the diagonal elements of the RHO++ and RHO-- SDM as a function of the cosine of the angle of the W- boson for the leptonic decay channel.

The luminosity weighted average over all the centre of mass energies of the diagonal element of the RHO00 SDM as a function of the cosine of the angle of the W- boson for both leptonic and hadronic decay channels, and combined.

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Measurement of event shapes in deep inelastic scattering at HERA.

The ZEUS collaboration Chekanov, S. ; Krakauer, D. ; Loizides, J.H. ; et al.
Eur.Phys.J.C 27 (2003) 531-545, 2003.
Inspire Record 602252 DOI 10.17182/hepdata.46536

Inclusive event-shape variables have been measured in the current region of the Breit frame for neutral current deep inelastic ep scattering using an integrated luminosity of 45.0 pb^-1 collected with the ZEUS detector at HERA. The variables studied included thrust, jet broadening and invariant jet mass. The kinematic range covered was 10 < Q^2 < 20,480 GeV^2 and 6.10^-4 < x < 0.6, where Q^2 is the virtuality of the exchanged boson and x is the Bjorken variable. The Q dependence of the shape variables has been used in conjunction with NLO perturbative calculations and the Dokshitzer-Webber non-perturbative corrections (`power corrections') to investigate the validity of this approach.

6 data tables

Mean value of the event shape variables 1-THRUST(C=T) in different Q**2 and X bins.

Mean value of the event shape variables B(C=T) in different Q**2 and X bins.

Mean value of the event shape variables RHO**2 in different Q**2 and X bins.

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Differential cross sections, charge production asymmetry, and spin-density matrix elements for D*(2010)+- produced in 500-GeV/c pi- nucleon interactions.

The Fermilab E791 collaboration Aitala, E.M ; Amato, S ; Anjos, J.C ; et al.
Phys.Lett.B 539 (2002) 218-226, 2002.
Inspire Record 587686 DOI 10.17182/hepdata.42892

We report differential cross sections for the production of D*(2010) produced in 500 GeV/c pi^- nucleon interactions from experiment E791 at Fermilab, as functions of Feynman-x (x_F) and transverse momentum squared (p_T^2). We also report the D* +/- charge asymmetry and spin-density matrix elements as functions of these variables. Investigation of the spin-density matrix elements shows no evidence of polarization. The average values of the spin alignment are \eta= 0.01 +- 0.02 and -0.01 +- 0.02 for leading and non-leading particles, respectively.

8 data tables

Acceptance corrected differential cross sections for D*+- production as a function of XL, Feynman X.

Acceptance corected differential cross sections for D*+- production as a function of PT**2.

Charge production asymmetry as a function of Feynman X.

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Determination of alpha(s) from hadronic event shapes in e+ e- annihilation at 192-GeV <= s**(1/2) <= 208-GeV

The L3 collaboration Achard, P. ; Adriani, O. ; Aguilar-Benitez, M. ; et al.
Phys.Lett.B 536 (2002) 217-228, 2002.
Inspire Record 586115 DOI 10.17182/hepdata.49741

Results are presented from a study of the structure of high energy hadronic events recorded by the L3 detector at sqrt(s)>192 GeV. The distributions of several event shape variables are compared to resummed O(alphaS^2) QCD calculations. We determine the strong coupling constant at three average centre-of-mass energies: 194.4, 200.2 and 206.2 GeV. These measurements, combined with previous L3 measurements at lower energies, demonstrate the running of alphaS as expected in QCD and yield alphaS(mZ) = 0.1227 +- 0.0012 +- 0.0058, where the first uncertainty is experimental and the second is theoretical.

9 data tables

The measured ALPHA_S at three centre-of-mass energies from fits to the individual event shape distributions. The first error is statistcal, the first DSYS error is the experimental systematic uncertainty, and the second DSYS error is the theoryuncertainty.

Updated ALPHA_S measurements from the BT, BW and C-Parameter distributions,from earlier L3 data at lower centre-of-mass energies.. The first error is the total experimental error (stat+sys in quadrature) and the DSYS error is the theory uncertainty.

Combined ALPHA_S values from the five event shape variables. The first error is statistical, the first DSYS error is the experimental systematic uncertainity, the second DSYS error is the uncertainty from the hadronisdation models, andthethird DSYS errpr is the uncertainty due to uncalculated higher orders in the QCDpredictions.

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A study of spin alignment of rho(770)+- and omega(782) mesons in hadronic Z0 decays.

The OPAL collaboration Abbiendi, G. ; Ackerstaff, K. ; Alexander, G. ; et al.
Eur.Phys.J.C 16 (2000) 61-70, 2000.
Inspire Record 502750 DOI 10.17182/hepdata.49099

The helicity density matrix elements rho[00] of rho(770)+- and omega(782) mesons produced in Z decays have been measured using the OPAL detector at LEP. Over the measured meson energy range, the values are compatible with 1/3, corresponding to a statistical mix of helicity -1, 0 and +1 states. For the highest accessible scaled energy range 0.3 < x_E < 0.6, the measured rho[00] values of the rho(770)+- and the omega are 0.373 +- 0.052 and 0.142 +- 0.114, respectively. These results are compared to measurements of other vector mesons.

2 data tables

The errors are statistical and systematic unceratinties added in quadrature. The statistical errors (STAT=...) are also given.

The errors are statistical and systematic unceratinties added in quadrature. The statistical errors (STAT=...) are also given.


Measurement of jet shapes in high Q**2 deep inelastic scattering at HERA

The ZEUS collaboration Breitweg, J. ; Derrick, M. ; Krakauer, D. ; et al.
Eur.Phys.J.C 8 (1999) 367-380, 1999.
Inspire Record 468803 DOI 10.17182/hepdata.44312

The shapes of jets with transverse energies, E_T(jet), up to 45 GeV produced in neutral- and charged-current deep inelastic e+p scattering (DIS) at Q**2 > 100 GeV**2 have been measured with the ZEUS detector at HERA. Jets are identified using a cone algorithm in the eta-phi plane with a cone radius of one unit. The jets become narrower as E_T(jet) increases. The jet shapes in neutral- and charged-current DIS are found to be very similar. The jets in neutral-current DIS are narrower than those in resolved processes in photoproduction and closer to those in direct-photon processes for the same ranges in E_T(jet) and jet pseudorapidity. The jet shapes in DIS are observed to be similar to those in e+e- interactions and narrower than those in pbarp collisions for comparable E_T(jet). Since the jets in e+e- interactions and e+p DIS are predominantly quark initiated in both cases, the similarity in the jet shapes indicates that the pattern of QCD radiation within a quark jet is to a large extent independent of the hard scattering process in these reactions.

24 data tables

Measured differential jet shapes, corrected to the hadron level, in neutral-current DIS for jets with ET greater than 14 GeV in different etarap regions.

Measured differential jet shapes, corrected to the hadron level, in neutral-current DIS for jets with ET greater than 14 GeV in different etarap regions.

Measured differential jet shapes, corrected to the hadron level, in neutral-current DIS for jets with ET greater than 14 GeV in different etarap regions.

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Continuum charged D* spin alignment at s**(1/2) = 10.5-GeV.

The CLEO collaboration Brandenburg, G. ; Briere, Roy A. ; Ershov, A. ; et al.
Phys.Rev.D 58 (1998) 052003, 1998.
Inspire Record 467595 DOI 10.17182/hepdata.47207

A measurement of the spin alignment of charged D^* mesons produced in continuum e^+ e^- \to c \bar{c} events at \sqrt{s}=10.5 GeV is presented. This study using 4.72 fb^{-1} of CLEO II data shows that there is little evidence of any D^* spin alignment.

4 data tables

Systematic errors are not given.

Systematic errors are not given.

Two decay modes of D0 --> K- PI+ and D0 --> K- PI+ PI0 are combined.

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Measurement of the spin density matrix for the rho0, K*(892)0 and Phi produced in Z0 decays.

The DELPHI collaboration Abreu, P. ; Adam, W. ; Adye, T. ; et al.
Phys.Lett.B 406 (1997) 271-286, 1997.
Inspire Record 444150 DOI 10.17182/hepdata.47452

The spin density matrix elements for the ϱ 0 , K ∗0 (892) and F produced in hadronic Z 0 decays are measured in the DELPHI detector. There is no evidence for spin alignment of the K ∗0 (892) and F in the region x p ≤ 0.3 ( x p = p p beam ), where ϱ 00 = 0.33 ± 0.05 and ϱ 00 = 0.30 ± 0.04, respectively. In the fragmentation region, x p ≥ 0.4, there is some indication for spin alignment of the ϱ 0 and K ∗0 (892), since ϱ 00 = 0.43 ± 0.05 and ϱ 00 = 0.46 ± 0.08, respectively. These values are compared with those found in meson-induced hadronic reactions. For the F, ϱ 00 = 0.30 ± 0.04 for x p ≥ 0.4 and 0.55 ± 0.10 for x p ≥ 0.7. The off-diagonal spin density matrix element ϱ 1-1 is consistent with zero in all cases.

3 data tables

Helicity density matrices elements. The statistical and systematic errors are combined quadratically.

Helicity density matrices elements. The statistical and systematic errors are combined quadratically.

Helicity density matrices elements. The statistical and systematic errors are combined quadratically.


Study of Phi(1020), D*+- and B* spin alignment in hadronic Z0 decays.

The OPAL collaboration Ackerstaff, K. ; Alexander, G. ; Allison, John ; et al.
Z.Phys.C 74 (1997) 437-449, 1997.
Inspire Record 440103 DOI 10.17182/hepdata.47515

Measurements of helicity density matrix elements have been made for the φ(1020), D*± and B* vector mesons in multihadronic Z0 decays in the OPAL experiment at LEP. Results for inclusive φ produced with high energy show evidence for production preferentially in the helicity zero state, with ρ00 = 0.54 ± 0.08, compared to the value of 1/3 expected for no spin alignment. The corresponding element for the D*± has a value of 0.40 ± 0.02, also suggesting a deviation from 1/3. The B* result, with ρ00 = 0.36 ± 0.09, is consistent with no spin alignment. Off-diagonal elements have been measured for the f and D* mesons; for the D* the element Re ρ1−1 is non-zero, indicating non-independent fragmentation of the primary quarks.

4 data tables

Helicity density matrices elements. Helicity beam frame is used.

Charge conjugated states are understood.

Helicity density matrices elements. Charge conjugated states are understood.

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Spin alignment of leading K*(892)0 mesons in hadronic Z0 decays.

The OPAL collaboration Ackerstaff, K. ; Alexander, G. ; Allison, John ; et al.
Phys.Lett.B 412 (1997) 210-224, 1997.
Inspire Record 447146 DOI 10.17182/hepdata.47440

Helicity density matrix elements for inclusive K*(892)^0 mesons from hadronic Z^0 decays have been measured over the full range of K^*0 momentum using data taken with the OPAL experiment at LEP. A preference for occupation of the helicity zero state is observed at all scaled momentum x_p values above 0.3, with the matrix element rho_00 rising to 0.66 +/- 0.11 for x_p > 0.7. The values of the real part of the off-diagonal element rho_1-1 are negative at large x_p, with a weighted average value of -0.09 +/- 0.03 for x_p > 0.3, in agreement with new theoretical predictions based on Standard Model parameters and coherent fragmentation of the qq(bar) system from the Z^0 decay. All other helicity density matrix elements measured are consistent with zero over the entire x_p range. The K^*0 fragmentation function has also been measured and the total rate determined to be 0.74 +/- 0.02 +/- 0.02 K*(892)^0 mesons per hadronic Z^0 decay.

4 data tables

Inclusive K*= cross section.

Helicity density matrices elemnts.

Ratios of helicity density matrices elements.

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Measurement of elastic omega photoproduction at HERA.

The ZEUS collaboration Derrick, M. ; Krakauer, D. ; Magill, S. ; et al.
Z.Phys.C 73 (1996) 73-84, 1996.
Inspire Record 422159 DOI 10.17182/hepdata.44712

The reaction $\gamma p \rightarrow \omega p$ $(\omega \rightarrow \pi~+\pi~-\pi~0$ and $\pi~0\rightarrow\gamma\gamma)$ has been studied in $ep$ interactions using the \mbox{ZEUS} detector at photon-proton centre-of-mass energies between $70$ and $90\uni{GeV}$ and $|t| < 0.6\uni{GeV}~2$, where $t$ is the squared four momentum transferred at the proton vertex. The elastic \ome photoproduction cross section has been measured to be $\sigma_{\gamma p\rightarrow \omega p} = 1.21\pm 0.12\pm 0.23 \mu\mbox{b}$. The differential cross section $d\sigma_{\gamma p\rightarrow \omega p} /d|t|$ has an exponential shape $\mbox{e}~{-b |t|}$ with a slope $b = 10.0\pm 1.2\pm 1.3\uni{GeV}~{-2}$. The angular distributions of the decay pions are consistent with {\it s}-channel helicity conservation. When compared to low energy data, the features of $\omega$ photoproduction as measured at HERA energies are in agreement with those of a soft diffractive process. Previous measurements of the $\rho~0$ and $\phi$ photoproduction cross sections at HERA show a similar behaviour.

4 data tables

Total Elastic Cross Section.

No description provided.

SLOPE OF DSIG/DT distribution.

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Production of f2 (1270) and f0 (975) mesons by photons and hadrons of energy 65-GeV - 175-GeV

The Omega Photon collaboration Apsimon, R.J. ; Atkinson, M. ; Baake, M. ; et al.
Z.Phys.C 56 (1992) 185-192, 1992.
Inspire Record 339969 DOI 10.17182/hepdata.16122

Measurements are reported of inclusivef2(1270) andf0(975) production in γp, π±p andK±p collisions at photon beam energies of 65 to 175 GeV and hadron beam energies of 80 and 140 GeV. Thef2 andf0 mesons were found at masses of 1.250 GeV and 0.961 GeV respectively. Inclusivef2 production at lowxF was found to have a similarpT dependence for each beam type, whereas an additional pion-exchange contribution was found for production by pions at highxF. Cross sections are compared with those for ρ0 production and give no indication of a non-q\(\bar q\) component in eitherf-meson state.

26 data tables

No description provided.

No description provided.

No description provided.

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Test of spin dependence in charm-quark fragmentation to D*.

The TPC/Two-Gamma collaboration Aihara, H. ; Alston-Garnjost, M. ; Avery, R.E. ; et al.
Phys.Rev.D 43 (1991) 29-33, 1991.
Inspire Record 316132 DOI 10.17182/hepdata.22830

We have measured the polarization of D*, the energy dependence of the polarization, and the spin-density matrix of D* in e+e− annihilation at a center-of-mass energy of 29 GeV using the Time Projection Chamber detector at the SLAC storage ring PEP. In 147 pb−1 of data we see no strong evidence for polarization, alignment, or final-state interactions in this fragmentation process.

2 data tables

Polarization is the factor alpha(z) in the expression d width (D*-->D pi)/domega = C(1+alpha(z)cos(theta)**2).

Spin density matrices for D* --> D0 pi+.


HIGH STATISTICS INCLUSIVE phi MESON PRODUCTION AT SPS ENERGIES

The ACCMOR collaboration Dijkstra, H. ; Bailey, R. ; Belau, E. ; et al.
Z.Phys.C 31 (1986) 375-389, 1986.
Inspire Record 18260 DOI 10.17182/hepdata.15894

Inclusive ϕ meson production has been measured for 100 GeV/c and 200 GeV/c incident π−,\(\bar p\) andK−, and for 120 GeV/c and 200 GeV/c incident π+,p andK+, using a Be target. A total of 630,000 ϕ mesons has been recorded in the kinematic range 0<xF<0.4. Presented are the differential cross sectionsdσ/dxF anddσ/dpT2. The longitudinal momentum distributions show that the strange valence quarks of the incidentK mesons play an important role in ϕ meson production, even at smallxF. The decay angular distribution of the ϕ meson is evaluated in the Gottfried-Jackson frame and is expressed in the elements of the density matrix. There is a small but significant cos2θGJ dependence for smallpT, which decreases for increasingpT.

34 data tables

Note that the data is plotted in fig. 5 a factor 5 too large. The numbers here are correct.

Note that the data is plotted in fig 5 a factor of 5 too large. The numbers here are correct.

Note that the data is plotted in fig. 5 a factor of 5 too large. CT = The numbers here are correct.

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Measurement of the Reaction $\pi^+$ Polarized $n \to \pi^+ \pi^- p$ at 5.98-{GeV}/$c$ and 11.85-{GeV}/$c$ Using a Transversely Polarized Deuteron Target

de Lesquen, A. ; van Rossum, L. ; Svec, M. ; et al.
Phys.Rev.D 32 (1985) 21, 1985.
Inspire Record 206003 DOI 10.17182/hepdata.3934

In an experiment carried out at the CERN Proton Synchrotron and using the CERN polarized deuteron target, the reaction π+n↑→π+π−p has been measured in the region -t=0.1–1.0 (GeV/c)2 and m(π+π−)=0.36–1.04 GeV at incident momenta of 5.98 and 11.85 GeV/c. We present the m and t dependence of the measured 14 linearly independent spin-density-matrix elements and of the bounds on the moduli squared of the S- and P-wave recoil transversity amplitudes. The results show the presence of ‘‘A1’’ exchange in the unnatural nucleon-helicity-nonflip amplitudes. The natural ‘‘A2’’-exchange amplitudes dominate at large t. In the range 0.2≤-t≤0.4 (GeV/c)2 the mass dependence shows that the unnatural exchange amplitudes with transversity ‘‘down’’ are generally larger than those with transversity ‘‘up.’’ The opposite is true for the natural exchange. In this range of t and at the ρ0 mass, the P-wave unnatural amplitudes with both transversities contribute in equal amounts while the production by natural exchange proceeds entirely with transversity up. We observe rapid changes of the moduli within the ρ0 mass range and variations of the width and the position of the ρ0 peak in spin-averaged partial-wave cross sections. These structures have not been seen in previous polarization experiments and reveal spin dependence of ρ0 production. Our bounds cannot exclude an S-wave resonance in the range 700–800 MeV. The results emphasize the need for a better experimental and theoretical understanding of the mass dependence of the production mechanism.

19 data tables

No description provided.

'Y' components of RHO.

'X' components of RHO.

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Test of S Channel Helicity Conservation in Inelastic $\rho^0$ Diffraction in 20-{GeV} Photoproduction

The SLAC Hybrid Facility Photon collaboration Abe, K. ; Bacon, T.C. ; Ballam, Joseph ; et al.
Phys.Rev.D 32 (1985) 2288, 1985.
Inspire Record 209692 DOI 10.17182/hepdata.23546

The reaction γp→ρfast0pπ+π− has been studied with the linearly polarized 20-GeV monochromatic photon beam at the SLAC Hybrid Facility to test the prediction of s-channel helicity conservation in inelastic diffraction for t’<0.4 (GeV/c)2. In a sample of 1934 events from this reaction, the ρ0 decay-angular distributions and spin-density-matrix elements are consistent with s-channel helicity conservation, the π+π− mass shape displays the same skewing as seen in the reaction γp→pπ+π−, and the pπ+π− mass distribution compares well and scales according to the vector dominance model with that produced in π±p→πfast±pπ+π−.

3 data tables

No description provided.

No description provided.

SPIN DENSITY MATRIX ELEMENTS FOR THE DIFFRACTIVE RHO0 MESON FROM STUDY OF THE ANGULAR DISTRIBUTIONS. CORRECTION HAS BEEN MADE FOR THE (20 +- 5) PCT NON DIFFRACTIVE BACKGROUND IN THE FINAL DATA SAMPLE, ASSUMING IT TO HAVE AN ISOTOPIC ANGULAR DISTRIBUTION.


EXCLUSIVE rho0 PRODUCTION IN DEEP INELASTIC MUON PROTON SCATTERING

The European Muon collaboration Aubert, J.J. ; Bassompierre, G. ; Becks, K.H. ; et al.
Phys.Lett.B 161 (1985) 203, 1985.
Inspire Record 214930 DOI 10.17182/hepdata.30353

Exclusive ϱ 0 production has been measured in 120, 200 and 280 GeV muon-proton interactions at high Q 2 (1 GeV 2 < Q 2 < 25 GeV 2 ) and W (6 GeV < W < 19 GeV). The photoproduction cross section decreases as 1/ Q 4 . A shallow t distribution, typical of a hard scattering process is observed and the ϱ 0 is found to be dominantly in the helicity zero spin state. The ϱ 0 s are mainly produced by transverse photons and s -channel helicity conservation seems to be invalid. The data cannot be described by the vector meson dominance model. These data show that at high Q 2 even exclusive ϱ 0 muoproduction is a hard scattering process and that the soft hadron-like properties of the photon have disappeared.

8 data tables

No description provided.

No description provided.

SYSTEMATIC ERROR ON SLOPE IN 0.8.

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A STUDY OF THE REACTIONS GAMMA P ---> OMEGA P AND GAMMA P ---> OMEGA DELTA+

The LAMP2 Group collaboration Barber, D.P. ; Dainton, J.B. ; Lee, L.C.Y. ; et al.
Z.Phys.C 26 (1984) 343-351, 1984.
Inspire Record 215619 DOI 10.17182/hepdata.16143

The differential and total corss sections and the decay density matrix elements have been measured for the reactions, γp→ωp and γp→ωΔ+ (1232) in the photon energy range 2.8 to 4.8 GeV. The total cross sections for ωΔ+ (1232) photo-production are found to be slightly larger than those for elastic ω photo-production in this energy range. The data are compared to the predictions of a theoretical model and the contributing exchange mechanics are discussed.

14 data tables

No description provided.

No description provided.

No description provided.

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Study of pi+ p four prong interactions from 2.95-GeV/c to 4.08-GeV/c

Brown, David ; Gidal, George ; Birge, Robert W. ; et al.
Phys.Rev.D 1 (1970) 3053, 1970.
Inspire Record 74876 DOI 10.17182/hepdata.25065

In a study of the production mechanism of quasi-two-body final states at the five incident π+ momenta 2.95, 3.2, 3.5, 3.75, and 4.08 GeV/c, approximately 40 000 events with four outgoing charged particles were investigated. The cross sections for the processes π+p→N*++ρ, π+p→N*++ω, π+p→N*++η, and π+p→N*++f have been measured as a function of the pion energy. The differential cross sections and the decay density-matrix elements are discussed in terms of one-meson-exchange models [with absorption (OPEA) and with form factor (OPEW)] and Regge models. For the N*++ρ and the N*++ω reactions, the joint-decay matrix elements are calculated. The formation of N*(2850) in the direct channel is also investigated.

30 data tables

No description provided.

No description provided.

No description provided.

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K- d interactions at 5.5 gev/c - sigma-+ pi+- pi-(pi0), sigma- k+, k- and k- pi- p final states in which a hyperon is produced

Kropac, W. ; Ammar, R. ; Davis, R. ; et al.
Phys.Rev.D 7 (1973) 585-599, 1973.
Inspire Record 82572 DOI 10.17182/hepdata.22114

The results presented in this paper are obtained from an analysis of bubble-chamber pictures of K−d interactions at an incident K− momentum of 5.5 GeV/c. Generally, the quasitwo-body final states are produced peripherally, with a small backward peak occurring in some of the final states. The final states Σ−ω, Σ−ρ0, and Σ−φ appear to be produced primarily by vector-meson exchange. In the final state Λ(1520)π− the decay distributions of the Λ(1520) hyperon are found to be consistent with a vector-exchagne production process with M2 coupling at the nucleon vertex. The predictions of the independent-quark model and of other symmetry schemes, namely that the forward cross sections for Σ−ρ0, Σ−ω, Σ−φ production be in the ratios 1: 1: 2, are not inconsistent with our experimental values.

5 data tables

No description provided.

FRACTIONAL FORWARD HYPERON CROSS SECTION AFTER BACKGROUND SUBTRACTION.

No description provided.

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K*0 (890) POLARIZATION MEASUREMENTS IN THE HYPERCHARGE EXCHANGE REACTION PI- P ---> K*0 (890) LAMBDA0 / SIGMA0 AT 10-GEV/C

The BARI-BONN-CERN-DARESBURY-GLASGOW-LIVERPOOL-MILAN-VIENNA collaboration Evangelista, C. ; Ghidini, B. ; Palano, A. ; et al.
Nucl.Phys.B 165 (1980) 383-394, 1980.
Inspire Record 157497 DOI 10.17182/hepdata.34585

K ∗0 (890) production in the hyperchange exchange reaction π − p → K ∗0 (890) Λ 0 Σ 0 at 10 GeV/ c (28 448 events) is discussed. An amplitude analysis in the t ′ range up to 1 GeV 2 shows that the production mechanism is dominated by natural parity exchange (∼84%). Comparisons are made with predictions from a Regge model and a quark model.

2 data tables

DENSITY MATRIX ELEMENTS IN THE GOTTFRIED-JACKSON SYSTEM ALLOWING FOR COHERENT S-WAVE BACKGROUND TO P-WAVE BREIT-WIGNER K*(892)0 RESONANCE.

No description provided.


Charged $\rho$ Photoproduction in the Energy Range 2.8-{GeV} - 4.8-{GeV}

Barber, D.P. ; Dainton, J.B. ; Lee, L.C.Y. ; et al.
Z.Phys.C 2 (1979) 1-6, 1979.
Inspire Record 140681 DOI 10.17182/hepdata.16353

Measurements of the photoproduction processes γρ→ρ+n and γρ→ρ-Δ++ (1236) are reported in the energy range 2.8 to 4.8 GeV. The data show shrinkage of the differential cross section in this energy region for the process γρ→ρ-Δ++ (1236); no shrinkage is observed for the ρ+n process. The energy dependences of the ρ+n and ρ-Δ++ (1236) total cross sections are much steeper than current model prediction. The ρ spin density matrices for each process are also presented.

3 data tables

No description provided.

SLOPE AND INTERCEPT OF D(SIG)/DT.

No description provided.


POLARIZATION MEASUREMENTS IN K+ N CHARGE EXCHANGE AT 6-GeV/c AND 12-GeV/c

Fujisaki, M. ; Babou, M. ; Bystricky, J. ; et al.
Phys.Lett.B 80 (1979) 314, 1979.
Inspire Record 132911 DOI 10.17182/hepdata.27365

The polarization in K + n↑ → K 0 p has been measured at 6 and 12 GeV/ c in the interval 0.1 < |t| < 1.0 using a polarized deuteron target. The results are compared to predictions from SU(3), exchange degeneracy (EXD) and line reserval, and from various phenomenological models.

4 data tables

NARROW BINS.

WIDE BINS.

No description provided.

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Forward and Wide Angle Elastic $\phi$ - Meson Photoproduction on Hydrogen Between 2.8-{GeV} and 4.8-{GeV}

The LAMP2 Group collaboration Barber, D.P. ; Dainton, J.B. ; Lee, L.C.Y. ; et al.
Phys.Lett.B 79 (1978) 150-156, 1978.
Inspire Record 131968 DOI 10.17182/hepdata.27382

The s and t dependence of φ (1019) photoproduction has been investigated in the incident photon energy range 2.8 to to 4.8 GeV. Differential cross-sections and density matrix elements are presented for a t range extending from t min out to −1.3 (GeV/ c ) 2 . The results are discussed in terms discussed in terms of an effective Regge trajectory in the t -channel.

5 data tables

DIFFERENTIAL CROSS SECTIONS AVERAGED OVER TWO RANGES OF INCIDENT PHOTON ENERGY.

VARIATION OF SMALL -T DIFFERENTIAL CROSS SECTION WITH PHOTON ENERGY.

INTERCEPT AND SLOPE FROM FITS TO D(SIG)/DT AT SMALL -T.

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Elastic and Inelastic $\phi$ - Photoproduction

Behrend, H.-J. ; Bodenkamp, J. ; Hesse, W.P. ; et al.
Nucl.Phys.B 144 (1978) 22-60, 1978.
Inspire Record 130415 DOI 10.17182/hepdata.34982

The differential cross section of the reaction ( γ p → p φ ) has been measured in the t range 0 ⩽ t ⩽ 0.4 GeV 2 and for photon energies from 3.0 to 6.7 GeV. In particular for the small t region the measurement accuracy was better than 10%. We obtained for the slope parameter B in an exponential parametrization of the differential cross section d σ /d t = A e − Bt values of B ⋍ 6 ± 0.5 GeV −2 which are significantly larger than the slopes obtained by most other experiments at higher t values. This indicates a t dependence of B particularly in the small t region.

5 data tables

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Production of the k- pi+ pi- n final state in k- d interactions at 5.5 gev/c

Davis, R. ; Ammar, R. ; Kropac, W. ; et al.
Nucl.Phys.B 44 (1972) 45-82, 1972.
Inspire Record 75079 DOI 10.17182/hepdata.32866

The reaction K − d → K − π + π − n p s was studied in a bubble chamber experiment. The cross section was measured to be 1.3 ± 0.2 mb. The final state is dominated by K ∗0 (890) , K ∗0 (1420) and Δ − (1236) production. Partial cross sections, differential cross sections and decay angular distributions of the K ∗0 (890) δ − (1236) final state were found to give good agreement with the predictions of Białas and Zalewski obtained from the quark model. The final state K − π + Δ − (1236) is analyzed by use of the Van Hove plot.

9 data tables

DEUTERIUM CROSS SECTIONS WITH SPECTATOR PROTON. PROBABLY NOT CORRECTED FOR K* BRANCHING RATIO INTO <K- PI+>.

SLOPE IS 5.75 +- 0.46 GEV**2 FOR -TP < 0.4 GEV**2.

GOTTFRIED-JACKSON FRAME.

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Production of a20 and omega-prime (1675) in the Reaction pi- p --> pi+ pi- pi0 n at 12-GeV/c and 15-GeV/c

Corden, M.J. ; Dowell, J.D. ; Garvey, J. ; et al.
Nucl.Phys.B 138 (1978) 235-252, 1978.
Inspire Record 121463 DOI 10.17182/hepdata.35053

Data on the reaction π − p → π + π − π 0 have been taken at 12 and 15 GeV/ c with the CERN Omega multiparticle spectrometer. In a 3-pion partial-wave analysis strong production of A 2 0 (1310) and ω ∗ (1675) is observed. Total and differential cross sections are determined and density matrix elements presented as a function of t in the t - and s -channel frames. The energy dependence of A 2 0 production is studied, and a comparison of ω(780), A 2 0 (1310) and ω ∗ (1675) production is made.

10 data tables

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F0 (1270) Production in the Reaction pi- p --> pi+ pi- n at 12-GeV/c and 15-GeV/c

Alexander, G. ; Dagan, S. ; Gnat, Y. ; et al.
Nucl.Phys.B 131 (1977) 365-385, 1977.
Inspire Record 127448 DOI 10.17182/hepdata.35193

The production of the f 0 (1270) has been studied in the reaction π − p → π + π − n at 12 and 15 GeV/ c in the momentum transfer range 0.02 to 0.80 GeV 2 . Differential and total cross sections for the reaction π − p → f 0 n have been determined. The f 0 decay density matrix elements have been evaluated requiring all the matrix eigenvalues to be non-negative. The relative unnatural and natural parity exchange contributions to the f 0 production have been studied. The results are compared with a Regge exchange model formulated in terms of the pion and A 2 exchanges including cut contributions.

7 data tables

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Partial Wave Analysis of the (anti-K0 pi- pi0)-System Produced in the q-Mass Region in K- p --> (anti-K0 pi- pi0) p at 10-GeV/c and 16-GeV/c

The Aachen-Berlin-CERN-London-Vienna collaboration Otter, G. ; Barnham, Keith W J ; Cocconi, Vanna T ; et al.
Nucl.Phys.B 96 (1975) 29-44, 1975.
Inspire Record 98691 DOI 10.17182/hepdata.31971

A partial-wave analysis has been performed of the diffractively produced low-mass ( K ̄ 0 π − π 0 ) system in the reaction K − p → ( K ̄ 0 π − π 0 ) p at 10 and 16 GeV/ c . Thus information complementary to that derived from the K − p → (K − π + π − )p) channel is obtained. The presence of the K ϱ decay mode, besides the dominant K ∗ (890)π mode, for the state J P = 1 + , is confirmed. It is also confirmed that for this 1 + state the assumption of factorization of the amplitude into “production” and “decay” does not hold: the two decay modes K ∗ π and K ϱ have different polarisation properties (helicity is approximately conserved in the t -channel for the first, in the s -channel for the second). The assumption that the ( K ̄ 0 π − π 0 ) system has isospin I = 1 2 has been tested and found to hold. From the cross sections for the various J P states, assuming I = 1 2 , the cross sections for the (K − π + π − ) system are predicted and compared with the experimental ones. In general, agreement is found.

2 data tables

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A Comparative Investigation of Low Mass (pi+ omega) and (K- omega) Systems at Various Energies

The Aachen-Berlin-Bonn-CERN-Heidelberg-London-Vienna collaboration Otter, G. ; Becker, L ; Dornan, P J ; et al.
Nucl.Phys.B 87 (1975) 189-206, 1975.
Inspire Record 91251 DOI 10.17182/hepdata.32066

A comparison is made of the properties and production mechanisms of the π + ω and K − ω systems produced in the reactions π + p → π + ω p at 4, 5, 8 and 16 GeV/ c and K − p → K − ω p at 10 and 16 GeV/ c . In the π + ω case apeak is observed at 1.23 GeV (the B meson), while the K − ω mass distribution has a threshold enhancement. The cross section of the low mass (<2.0 GeV) π + ω system falls as p lab −2 , while that of the low mass (<2.0 GeV) K − ω system is almost constant with energy, indicating diffractive production of the K − ω system, but not of the πω system. Using a modified version of the Illinois partial-wave analysis program, it is found that the K − ω system is dominantly produced in the J P = 1 + state with small contributions of 0 − and 2 + , mainly by natural parity exchange - as is found for reactions such as K − p → (K − π + π − )p which are predominantly diffractive. For the π + ω system in the B mass region, J P = 1 + states, produced mainly by natural parity exchange are found; the contributions of 0 − P, 1 − P, 2 − P and 2 + D are consistent with zero. The 1 + D state occurs in the π + ω case but not in the K − ω system, nor in the K ππ − system produced in the K − p → K ππ p reaction.

4 data tables

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FROM BREIT-WIGNER FIT TO B EVENTS AND CORRECTED FOR UNSEEN OMEGA DECAY MODES.

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