Electroproduction of Eta Mesons in the S11(1535) Resonance Region at High Momentum Transfer

Dalton, M.M. ; Adams, G.S. ; Ahmidouch, A. ; et al.
Phys.Rev.C 80 (2009) 015205, 2009.
Inspire Record 783943 DOI 10.17182/hepdata.50548

The differential cross-section for the process p(e,e'p)eta has been measured at Q2 ~ 5.7 and 7.0 (GeV/c)2 for centre-of-mass energies from threshold to 1.8 GeV, encompassing the S11(1535) resonance, which dominates the channel. This is the highest momentum transfer measurement of this exclusive process to date. The helicity-conserving transition amplitude A_1/2, for the production of the S11(1535) resonance, is extracted from the data. This quantity appears to begin scaling as 1/Q3, a predicted signal of the dominance of perturbative QCD, at Q2 ~ 5 (GeV/c)2.

39 data tables

Total cross section for the lower Q**2 data as a function of W. The errors are statistics and systematic added in quadrature.

Total cross section for the higher Q**2 data as a function of W. The errors are statistics and systematic added in quadrature.

Lower Q**2 extracted differential cross section at W = 1.500 GeV and cos(theta(eta) = -0.917, -0.750 and -0.583.

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Measurement of the beam asymmetry $\Sigma$ in $\pi^°\eta$ production off the proton with the CBELSA/TAPS experiment

The CBELSA collaboration Gutz, E. ; Sokhoyan, V. ; van Pee, H. ; et al.
Eur.Phys.J.A 35 (2008) 291-293, 2008.
Inspire Record 788569 DOI 10.17182/hepdata.54889

In photoproduction experiments, a large number of final states yielding various resonance contributions are accessible. To extract resonance parameters via partial-wave analysis not only the measurement of differential cross-sections is necessary, but also the determination of polarization observables. At the electron accelerator ELSA (Bonn) the coherent bremsstrahlung method was used to generate a linearly polarized photon beam. Using the CBELSA/TAPS detector setup, the beam asymmetry Σ in the reaction γp → pπ 0 η was determined as a function of various masses and angles for photon energies between 970MeV and 1650MeV.

12 data tables

Measured beam asymmetry as a function of the cosine of the scattered proton angle for beam energies 0.970 to 1.200 GeV.

Measured beam asymmetry as a function of the cosine of the scattered proton angle for beam energies 1.200 to 1.450 GeV.

Measured beam asymmetry as a function of the cosine of the scattered proton angle for beam energies 1.450 to 1.650 GeV.

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Measurements of e+ e- ---> K+ K- eta, K+ K- pi0 and K0(s) K+- pi-+ cross- sections using initial state radiation events

The BaBar collaboration Aubert, Bernard ; Bona, M. ; Boutigny, D. ; et al.
Phys.Rev.D 77 (2008) 092002, 2008.
Inspire Record 765258 DOI 10.17182/hepdata.50372

This paper reports measurements of processes: e+e- -> gamma KsK+pi-, e+e- -> gamma K+K-pi0, e+e- -> gamma phi eta, and e+e- -> gamma phi pi0. The initial state radiated photon allows to cover the hadronic final state in the energy range from thresholds up to ~4.6 GeV. The overall size of the data sample analyzed is 232 fb-1, collected by the BaBar detector running at the PEP-II e+e- storage ring. From the Dalitz plot analysis of the KsK+pi- final state, moduli and relative phase of the isoscalar and the isovector components of the e+e- -> K K*(892) cross section are determined. Parameters of phi and rho recurrences are also measured, using a global fitting procedure which exploits the interconnection among amplitudes, moduli and phases of the e+e- -> KsK+pi-, K+K-pi0, phi eta final states. The cross section for the OZI-forbidden process e+e- -> phi pi0, and the J/psi branching fractions to KK*(892) and K+K-eta are also measured.

9 data tables

The cross section for E+ E- --> K0S K+ PI- + CC with statistical errors only.

The cross section for E+ E- --> K+ K- PI0 with statistical errors only.

The cross section for E+ E- --> PHI PI0 with statistical errors only.

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The $e^+ e^-\to 2(\pi^+\pi^-)\pi^0$, 2(\pi^+\pi^-)\eta$, $K^+ K^-\pi^+\pi^-\pi^0$ and $K^+ K^-\pi^+\pi^-\eta$ Cross Sections Measured with Initial-State Radiation

The BaBar collaboration Aubert, Bernard ; Bona, M. ; Boutigny, D. ; et al.
Phys.Rev.D 76 (2007) 092005, 2007.
Inspire Record 758568 DOI 10.17182/hepdata.51824

We study the processes $e^+ e^-\to 2(\pi^+\pi^-)\pi^0\gamma$, $2(\pi^+\pi^-)\eta\gamma$, $K^+ K^-\pi^+\pi^-\pi^0\gamma$ and $K^+ K^-\pi^+\pi^-\eta\gamma$ with the hard photon radiated from the initial state. About 20000, 4300, 5500 and 375 fully reconstructed events, respectively, are selected from 232 fb$^{-1}$ of BaBar data. The invariant mass of the hadronic final state defines the effective $e^+ e^-$ center-of-mass energy, so that the obtained cross sections from the threshold to about 5 GeV can be compared with corresponding direct \epem measurements, currently available only for the $\eta\pi^+\pi^-$ and $\omega\pi^+\pi^-$ submodes of the $e^+ e^-\to 2(\pi^+\pi^-)\pi^0$ channel. Studying the structure of these events, we find contributions from a number of intermediate states, and we extract their cross sections where possible. In particular, we isolate the contribution from $e^+ e^-\to\omega(782)\pi^+\pi^-$ and study the $\omega(1420)$ and $\omega(1650)$ resonances. In the charmonium region, we observe the $J/\psi$ in all these final states and several intermediate states, as well as the $\psi(2S)$ in some modes, and we measure the corresponding branching fractions.

11 data tables

Measured cross section for E+ E- --> 2(PI+ PI-) PI0 with statistical errorsonly.

Measured cross section for E+ E- --> ETA PI+ PI- with statistical errors only.

Measured cross section for E+ E- --> OMEGA PI+ PI- with statistical errors only.

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The $e^+ e^-\to K^+ K^- \pi^+\pi^-$, $K^+ K^- \pi^0\pi^0$ and $K^+ K^- K^+ K^-$ Cross Sections Measured with Initial-State Radiation

The BaBar collaboration Aubert, Bernard ; Bona, M. ; Boutigny, D. ; et al.
Phys.Rev.D 76 (2007) 012008, 2007.
Inspire Record 747875 DOI 10.17182/hepdata.50373

We study the processes $e^+ e^-\to K^+ K^- \pi^+\pi^-\gamma$, $K^+K^-\pi^0\pi^0\gamma$ and $K^+ K^- K^+ K^-\gamma$, where the photon is radiated from the initial state. About 34600, 4400 and 2300 fully reconstructed events, respectively, are selected from 232 \invfb of \babar data. The invariant mass of the hadronic final state defines the effective \epem center-of-mass energy, so that the $K^+ K^- \pi^+\pi^-\gamma$ data can be compared with direct measurements of the $e^+ e^-\to K^+K^- \pipi$ reaction/ no direct measurements exist for the $e^+ e^-\to K^+ K^- \pi^0\pi^0$ or $\epem\to K^+ K^- K^+ K^-$ reactions. Studying the structure of these events, we find contributions from a number of intermediate states, and we extract their cross sections where possible. In particular, we isolate the contribution from $e^+ e^-\to\phi(1020) f_{0}(980)$ and study its structure near threshold. In the charmonium region, we observe the $J/\psi$ in all three final states and several intermediate states, as well as the $\psi(2S)$ in some modes, and measure the corresponding branching fractions. We see no signal for the Y(4260) and obtain an upper limit of $\BR_{Y(4260)\to\phi\pi^+\pi^-}\cdot\Gamma^{Y}_{ee}<0.4 \ev$ at 90% C.L.

7 data tables

Measurement of the E+ E- --> K+ K- PI+ PI- cross section. Statistical errors only.

Measurement of the E+ E- --> K(892)0 K PI cross section. Statistical errors only.

Measurement of the E+ E- --> PHI PI+ PI- cross section. Statistical errors only.

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Measurement of the beam asymmetry in eta photoproduction off the proton.

The CBELSA & TAPS collaborations Elsner, D. ; Anisovich, A.V. ; Anton, G. ; et al.
Eur.Phys.J.A 33 (2007) 147-155, 2007.
Inspire Record 744568 DOI 10.17182/hepdata.43430

The beam asymmetry, $\Sigma$, was measured at ELSA in the reaction $\vec \gamma p \to \eta p$ using linearly polarised tagged photon beams, produced by coherent bremsstrahlung off a diamond. The crystal was oriented to provide polarised photons in the energy range $E_\gamma = 800$ to 1400 MeV with the maximum polarisation of $P_\gamma = 49$ % obtained at 1305 MeV. Both dominant decay modes of the $\eta$ into two photons and $3\pi^0$ were used to extract the beam asymmetry from the azimuthal modulation of the cross section. The measurements cover the angular range $\Theta_\text{cm}\simeq 50$ -- 150 degrees. Large asymmetries up to 80 % are observed, in agreement with a previous measurement. The eta-MAID model and the Bonn--Gatchina partial wave analysis describe the measurements, but the required partial waves differ significantly.

6 data tables

Photon asymmetry for eta photoproduction at incident photon energy of 850 MeV.

Photon asymmetry for eta photoproduction at incident photon energy of 950 MeV.

Photon asymmetry for eta photoproduction at incident photon energy of 1050 MeV.

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Separated structure functions for the exclusive electroproduction of K+ Lambda and K+ Sigma0 final states.

The CLAS collaboration Ambrozewicz, P. ; Carman, D.S. ; Feuerbach, R.J. ; et al.
Phys.Rev.C 75 (2007) 045203, 2007.
Inspire Record 732363 DOI 10.17182/hepdata.4994

We report measurements of the exclusive electroproduction of $K^+\Lambda$ and $K^+\Sigma^0$ final states from a proton target using the CLAS detector at the Thomas Jefferson National Accelerator Facility. The separated structure functions $\sigma_T$, $\sigma_L$, $\sigma_{TT}$, and $\sigma_{LT}$ were extracted from the $\Phi$- and $\epsilon$-dependent differential cross sections taken with electron beam energies of 2.567, 4.056, and 4.247 GeV. This analysis represents the first $\sigma_L/\sigma_T$ separation with the CLAS detector, and the first measurement of the kaon electroproduction structure functions away from parallel kinematics. The data span a broad range of momentum transfers from $0.5\leq Q^2\leq 2.8$ GeV$^2$ and invariant energy from $1.6\leq W\leq 2.4$ GeV, while spanning nearly the full center-of-mass angular range of the kaon. The separated structure functions reveal clear differences between the production dynamics for the $\Lambda$ and $\Sigma^0$ hyperons. These results provide an unprecedented data sample with which to constrain current and future models for the associated production of strangeness, which will allow for a better understanding of the underlying resonant and non-resonant contributions to hyperon production.

531 data tables

Cross sections for incident energy 2.567 GeV for the Q**2 range 0.5 to 0.8 GeV**2 and W range 1.6 to 1.7 GeV.

Cross sections for incident energy 2.567 GeV for the Q**2 range 0.5 to 0.8 GeV**2 and W range 1.70 to 1.75 GeV.

Cross sections for incident energy 2.567 GeV for the Q**2 range 0.5 to 0.8 GeV**2 and W range 1.75 to 1.80 GeV.

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Inclusive Lambda/c production in e+ e- annihilations at s**(1/2) = 10.54-GeV and in Upsilon(4S) decays.

The BaBar collaboration Aubert, Bernard ; Bona, M. ; Boutigny, D. ; et al.
Phys.Rev.D 75 (2007) 012003, 2007.
Inspire Record 725377 DOI 10.17182/hepdata.22089

We present measurements of the total production rates and momentum distributions of the charmed baryon $\Lambda_c^+$ in $e^+e^- \to$ hadrons at a center-of-mass energy of 10.54 GeV and in $\Upsilon(4S)$ decays. In hadronic events at 10.54 GeV, charmed hadrons are almost exclusively leading particles in $e^+e^- \to c\bar{c}$ events, allowing direct studies of $c$-quark fragmentation. We measure a momentum distribution for $\Lambda_c^+$ baryons that differs significantly from those measured previously for charmed mesons. Comparing with a number of models, we find none that can describe the distribution completely. We measure an average scaled momentum of $\left< x_p \right> = 0.574\pm$0.009 and a total rate of $N_{\Lambda c}^{q\bar{q}} = 0.057\pm$0.002(exp.)$\pm$0.015(BF) $\Lambda_c^+$ per hadronic event, where the experimental error is much smaller than that due to the branching fraction into the reconstructed decay mode, $pK^-\pi^+$. In $\Upsilon (4S)$ decays we measure a total rate of $N_{\Lambda c}^{\Upsilon} = 0.091\pm$0.006(exp.)$\pm$0.024(BF) per $\Upsilon(4S)$ decay, and find a much softer momentum distribution than expected from B decays into a $\Lambda_c^+$ plus an antinucleon and one to three pions.

4 data tables

LAMBDA/C+ differential production rate per hadronic event for the continuum at cm energy 10.54 GeV.

The integrated number of LAMBDA/C+'s per hadronic event for the continuum at cm energy 10.54 GeV.

LAMBDA/C+ differential production rate per UPSILON(4S) decay at cm energy 10.58 GeV.

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Evidence for a narrow structure at W approx. 1.68-GeV in eta photoproduction on the neutron.

The GRAAL collaboration Kuznetsov, Viacheslav ; Churikova, S. ; Gervino, G. ; et al.
Phys.Lett.B 647 (2007) 23-29, 2007.
Inspire Record 720508 DOI 10.17182/hepdata.26995

New results on quasi-free $\eta$ photoproduction on the neutron and proton bound in a deuteron target are presented. The $\gamma n \to \eta n$ quasi-free cross section reveals a bump-like structure which is not seen in the cross section on the proton. This structure may signal the existence of a relatively narrow ($M\sim 1.68$ GeV, $\Gamma \leq 30$ MeV) baryon state.

6 data tables

Quasi free differential cross section for the reaction GAMMA N --> ETA N at COS(THETA(CM)) from -0.9 to -0.5.

Quasi free differential cross section for the reaction GAMMA N --> ETA N at COS(THETA(CM)) from -0.3 to 0.1.

Quasi free differential cross section for the reaction GAMMA N --> ETA N at COS(THETA(CM)) from 0.1 to 0.5.

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The e+ e- ---> 3(pi+ pi-), 2(pi+ pi- pi0) and K+ K- 2(pi+ pi-) cross sections at center-of-mass energies from production threshold to 4.5-GeV measured with initial-state radiation

The BaBar collaboration Aubert, Bernard ; Barate, R. ; Boutigny, D. ; et al.
Phys.Rev.D 73 (2006) 052003, 2006.
Inspire Record 709730 DOI 10.17182/hepdata.41843

We study the processes e+ e- --> 3(pi+pi-)gamma, 2(pi+pi-pi0)gamma and K+ K- 2(pi+pi-)gamma, with the photon radiated from the initial state. About 20,000, 33,000 and 4,000 fully reconstructed events, respectively, have been selected from 232 fb-1 of BaBar data. The invariant mass of the hadronic final state defines the effective e+e- center-of-mass energy, so that these data can be compared with the corresponding direct e+e- measurements. From the 3(pi+pi-), 2(pi+pi-pi0) and K+ K- 2(pi+pi-) mass spectra, the cross sections for the processes e+ e- --> 3(pi+pi-), e+ e- --> 2(pi+pi-pi0) and e+ e- --> K+ K- 2(pi+pi-) are measured for center-of-mass energies from production threshold to 4.5 GeV. The uncertainty in the cross section measurement is typically 6-15%. We observe the J/psi in all these final states and measure the corresponding branching fractions.

3 data tables

The cross section for E+ E- --> 3PI+ 3PI- as measured with the ISR data. Errors are statistical only.

The cross section for E+ E- --> 2PI+ 2PI- 2PI0 as measured with the ISR data. Errors are statistical only.

The cross section for E+ E- --> K+ K- 2PI+ 2PI- as measured with the ISR data. Errors are statistical only.


Analysis of the pi+ pi- pi+ pi- and pi+ pi0 pi- pi0 final states in quasi-real two-photon collisions at LEP.

The L3 collaboration Achard, P. ; Adriani, O. ; Aguilar-Benitez, M. ; et al.
Phys.Lett.B 638 (2006) 128-139, 2006.
Inspire Record 705125 DOI 10.17182/hepdata.48674

The reactions gamma gamma -> pi^+pi^-pi^+pi^- and gamma gamma -> pi^+pi^0pi^-pi^0 are studied with the L3 detector at LEP in a data sample collected at centre-of-mass energies from 161GeV to 209GeV with a total integrated luminosity of 698/pb. A spin-parity-helicity analysis of the rho^0 rho^0 and rho^+ rho^- systems for two-photon centre-of-mass energies between 1GeV and 3GeV shows the dominance of the spin-parity state 2+ with helicity 2. The contribution of 0+ and 0- spin-parity states is also observed, whereas contributions of 2- states and of a state with spin-parity 2+ and zero helicity are found to be negligible.

4 data tables

Cross section for 4PI and (RHO0 RHO0) production.

Cross section for 4PI and (RHO+ RHO-) production.

Spin parity analysis fits for RHO0 RHO0.

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Measurement of the reaction gamma p --> K0 Sigma+ at photon energies up to 2.6-GeV.

Lawall, R. ; Barth, J. ; Bennhold, C. ; et al.
Eur.Phys.J.A 24 (2005) 275-286, 2005.
Inspire Record 680746 DOI 10.17182/hepdata.43595

The reaction gamma p --> K0 Sigma+ was measured in the photon energy range from threshold up to 2.6 GeV with the SAPHIR detector at the electron stretcher facility, ELSA, in Bonn. Results are presented on the reaction cross section and the polarization of the Sigma+ as a function of the kaon production angle in the centre-of-mass system, cos(Theta_K^{c.m.}), and the photon energy. The cross section is lower and varies less with photon energy and kaon production angle than that of gamma p --> K+ Sigma0. The Sigma+ is polarized predominantly at cos(Theta_K^{c.m.}) \approx 0. The data presented here are more precise than previous ones obtained with SAPHIR and extend the photon energy range to higher values. They are compared to isobar model calculations.

14 data tables

Axis error includes +- 10/10 contribution (Normalization uncertainty already included.).

Axis error includes +- 10/10 contribution (Normalization uncertainty already included.).

Axis error includes +- 10/10 contribution (Normalization uncertainty already included.).

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The e+ e- ---> pi+ pi- pi+ pi-, K+ K- pi+ pi-, and K+ K- K+ K- cross sections at center-of-mass energies 0.5-GeV to 4.5-GeV measured with initial-state radiation

The BaBar collaboration Aubert, Bernard ; Barate, R. ; Boutigny, D. ; et al.
Phys.Rev.D 71 (2005) 052001, 2005.
Inspire Record 676691 DOI 10.17182/hepdata.22111

We study the process $e^+e^-\to\pi^+\pi^-\pi^+\pi^-\gamma$, with a hard photon radiated from the initial state. About 60,000 fully reconstructed events have been selected from 89 $fb^{-1}$ of BaBar data. The invariant mass of the hadronic final state defines the effective \epem center-of-mass energy, so that these data can be compared with the corresponding direct $e^+e^-$ measurements. From the $4\pi$-mass spectrum, the cross section for the process $e^+e^-\to\pi^+\pi^-\pi^+\pi^-$ is measured for center-of-mass energies from 0.6 to 4.5 $GeV/c^2$. The uncertainty in the cross section measurement is typically 5%. We also measure the cross sections for the final states $K^+ K^- \pi^+\pi^-$ and $K^+ K^- K^+ K^-$. We observe the $J/\psi$ in all three final states and measure the corresponding branching fractions. We search for X(3872) in $J/\psi (\to\mu^+\mu^-) \pi^+\pi^-$ and obtain an upper limit on the product of the $e^+e^-$ width of the X(3872) and the branching fraction for $X(3872) \to J/\psi\pi^+\pi^-$.

3 data tables

Measured PI+ PI- PI+ PI- cross sections. The errors are statistical only.

Measured K+ K- PI+ PI- cross sections. The errors are statistical only.

Measured K+ K- K+ K- cross sections. The errors are statistical only.


Photoproduction of rho0 mesons and Delta-baryons in the reaction gamma p ---> p pi+ pi- at energies up to s**(1/2) = 2.6-GeV

Wu, C. ; Barth, J. ; Braun, W. ; et al.
Eur.Phys.J.A 23 (2005) 317-344, 2005.
Inspire Record 678798 DOI 10.17182/hepdata.43532

The photoproduction of ρ0-mesons and Δ-baryons at photon energies up to 2.6 GeV has been studied with the SAPHIR detector at the electron stretcher ELSA. Total and differential cross-sections were obt

29 data tables

Total cross sections for (PI+ PI-) photoproduction from one run with 1.6 GeV electron beam.. Statistical errors only.

Total cross section for (PI+ PI-) photoproduction from 4 runs. (3 with 2.8 GeV electron beam and 1 with 2.6 GeV).

Differential cross section DSIG/DT for (PI+ PI-) photoproduction .

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Neutral pion photoproduction off protons in the energy range 0.3-GeV < E(gamma) < 3-GeV.

The CB-ELSA collaboration Bartholomy, O. ; Crede, V. ; van Pee, H. ; et al.
Phys.Rev.Lett. 94 (2005) 012003, 2005.
Inspire Record 654179 DOI 10.17182/hepdata.41902

Single pi0 photoproduction has been studied with the CB-ELSA experiment at Bonn using tagged photon energies between 0.3 and 3.0 GeV. The experimental setup covers a very large solid angle of about 98% of 4 pi. Differential cross sections (d sigma)/(d Omega) have been measured. Complicated structures in the angular distributions indicate a variety of different resonances being produced in the s channel intermediate state gamma p --> N* (Delta*) --> p pi0. A combined analysis including the data presented in this letter along with other data sets reveals contributions from known resonances and evidence for a new resonance N(2070)D15.

14 data tables

Total cross section for GAMMA P --> P PI0 obtained by integration of the angular distributions and extrapolation into the forward and backward regions using the PWA result.

Differential cross section as a function of c.m. angle for the photon energy range 300 to 425 GeV.

Differential cross section as a function of c.m. angle for the photon energy range 425 to 550 GeV.

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Measurement of exclusive rho+ rho- production in high-Q**2 two-photon collisions at LEP.

The L3 collaboration Achard, P. ; Adriani, O. ; Aguilar-Benitez, M. ; et al.
Phys.Lett.B 597 (2004) 26-38, 2004.
Inspire Record 654177 DOI 10.17182/hepdata.48589

Exclusive rho^+ rho^- production in two-photon collisions involving a single highly-virtual photon is studied with data collected at LEP at centre-of-mass energies 89 GeV &lt; \sqrt{s} &lt; 209 GeV with a total integrated luminosity of 854.7 pb^-1. The cross section of the process gamma gamma^* -> rho^+ rho^- is determined as a function of the photon virtuality, Q^2, and the two-photon centre-of-mass energy, W_gg, in the kinematic region: 1.2 GeV^2 &lt; Q^2 &lt; 30 GeV^2 and 1.1 GeV &lt; W_gg &lt; 3 GeV. The \rho^+\rho^- production cross section is found to be of the same magnitude as the cross section of the process gamma gamma^* -> rho^0 rho^0, measured in the same kinematic region by L3, and to have similar W_gg and Q^2 dependences.

9 data tables

Cross sections for the reaction E+ E- --> E+ E- RHO+ RHO-. The differentialcross sections are corrected to the centre of each bin.

Cross sections for the two photon production of RHO+ RHO-.

Differential cross section for the process E+ E- --> E+ E- (RHO+ PI- PI0 + RHO+ RHO- PI0 PI0) corrected to bin centre.

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Photoproduction of eta mesons off protons for 0.75-GeV < E(gamma) < 3-GeV.

The CB-ELSA collaboration Crede, Volker ; Bartholomy, Olivia ; Anisovich, A. ; et al.
Phys.Rev.Lett. 94 (2005) 012004, 2005.
Inspire Record 633776 DOI 10.17182/hepdata.41904

Total and differential cross sections for the reaction p(gamma, eta)p have been measured for photon energies in the range from 750 MeV to 3 GeV. The low-energy data are dominated by the S11 wave which has two poles in the energy region below 2 GeV. Eleven nucleon resonances are observed in their decay into p eta. At medium energies we find evidence for a new resonance N(2070)D15 with (mass, width) = (2068+-22, 295+-40) MeV. At photon energies above 1.5 GeV, a strong peak in forward direction develops, signalling the exchange of vector mesons in the t channel.

10 data tables

Total cross section determined by summing the angular bins and extrapolating outside the angular range of the experiment.

Differential cross section as a function of c.m. angle for the photon energy range 750 to 950 GeV.

Differential cross section as a function of c.m. angle for the photon energy range 950 to 1150 GeV.

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Measurement of gamma p --> K+ Lambda and gamma p --> K+ Sigma0 at photon energies up to 2.6 GeV

Glander, K.H. ; Barth, J. ; Braun, W. ; et al.
Eur.Phys.J.A 19 (2004) 251-273, 2004.
Inspire Record 626695 DOI 10.17182/hepdata.51677

The reactions gamma p --> K+ Lambda and gamma p --> K+ Sigma0 were measured in the energy range from threshold up to a photon energy of 2.6 GeV. The data were taken with the SAPHIR detector at the electron stretcher facility, ELSA. Results on cross sections and hyperon polarizations are presented as a function of kaon production angle and photon energy. The total cross section for Lambda production rises steeply with energy close to threshold, whereas the Sigma0 cross section rises slowly to a maximum at about E_gamma = 1.45 GeV. Cross sections together with their angular decompositions into Legendre polynomials suggest contributions from resonance production for both reactions. In general, the induced polarization of Lambda has negative values in the kaon forward direction and positive values in the backward direction. The magnitude varies with energy. The polarization of Sigma0 follows a similar angular and energy dependence as that of Lambda, but with opposite sign.

24 data tables

Differential cross sections for the reaction GAMMA P --> K+ LAMBDA in the energy region 0.9 to 1.0 GeV.

Differential cross sections for the reaction GAMMA P --> K+ LAMBDA in the energy region 1.0 to 1.2 GeV.

Differential cross sections for the reaction GAMMA P --> K+ LAMBDA in the energy region 1.2 to 1.4 GeV.

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Backward electroproduction of pi0 mesons on protons in the region of nucleon resonances at four momentum transfer squared Q**2 = 1.0-GeV**2.

The JLab Hall A collaboration Laveissiere, G. ; Degrande, N. ; Jaminion, S. ; et al.
Phys.Rev.C 69 (2004) 045203, 2004.
Inspire Record 625669 DOI 10.17182/hepdata.25226

Exclusive electroproduction of pi0 mesons on protons in the backward hemisphere has been studied at Q**2 = 1.0 GeV**2 by detecting protons in the forward direction in coincidence with scattered electrons from the 4 GeV electron beam in Jefferson Lab's Hall A. The data span the range of the total (gamma* p) center-of-mass energy W from the pion production threshold to W = 2.0 GeV. The differential cross sections sigma_T+epsilon*sigma_L, sigma_TL, and sigma_TT were separated from the azimuthal distribution and are presented together with the MAID and SAID parametrizations.

12 data tables

Cross section SIG(T) + EPSILON*SIG(L) for COS(THETA*) = -0.975.

Cross section SIG(T) + EPSILON*SIG(L) for COS(THETA*) = -0.925.

Cross section SIG(T) + EPSILON*SIG(L) for COS(THETA*) = -0.875.

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A kinematically complete measurement of the proton structure function F2 in the resonance region and evaluation of its moments.

The CLAS collaboration Osipenko, M. ; Ricco, G. ; Taiuti, M. ; et al.
Phys.Rev.D 67 (2003) 092001, 2003.
Inspire Record 612145 DOI 10.17182/hepdata.12253

We measured the inclusive electron-proton cross section in the nucleon resonance region (W < 2.5 GeV) at momentum transfers Q**2 below 4.5 (GeV/c)**2 with the CLAS detector. The large acceptance of CLAS allowed for the first time the measurement of the cross section in a large, contiguous two-dimensional range of Q**2 and x, making it possible to perform an integration of the data at fixed Q**2 over the whole significant x-interval. From these data we extracted the structure function F2 and, by including other world data, we studied the Q**2 evolution of its moments, Mn(Q**2), in order to estimate higher twist contributions. The small statistical and systematic uncertainties of the CLAS data allow a precise extraction of the higher twists and demand significant improvements in theoretical predictions for a meaningful comparison with new experimental results.

46 data tables

No description provided.

No description provided.

No description provided.

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Cross section measurement of charged pion photoproduction from hydrogen and deuterium.

The Jefferson Lab Hall A collaboration Zhu, L.Y. ; Arrington, J. ; Averett, T. ; et al.
Phys.Rev.Lett. 91 (2003) 022003, 2003.
Inspire Record 601768 DOI 10.17182/hepdata.31722

We have measured the differential cross section for the gamma n --> pi- p and gamma p --> pi+ n reactions at center of mass angle of 90 degree in the photon energy range from 1.1 to 5.5 GeV at Jefferson Lab (JLab). The data at photon energies greater than 3.3 GeV exhibit a global scaling behavior for both pi- and pi+ photoproduction, consistent with the constituent counting rule and the existing pi+ photoproduction data. Possible oscillations around the scaling value are suggested by these new data The data show enhancement in the scaled cross section at a center-of-mass energy near 2.2 GeV. The cross section ratio of exclusive pi- to pi+ photoproduction at high energy is consistent with the prediction based on one-hard-gluon-exchange diagrams.

1 data table

Differential cross section at THETA(CM) = 90 degrees.


Search for new heavy particles in the W Z0 final state in p anti-p collisions at s**(1/2) = 1.8-TeV

The CDF collaboration Affolder, T. ; Akimoto, H. ; Akopian, A. ; et al.
Phys.Rev.Lett. 88 (2002) 071806, 2002.
Inspire Record 560924 DOI 10.17182/hepdata.42895

We present a search for new heavy particles, $X$, which decay via $X \to WZ \to e\nu +jj$ in $p{\bar p}$ collisions at $\sqrt{s}$ = 1.8 TeV. No evidence is found for production of $X$ in 110 pb$^{-1}$ of data collected by the Collider Detector at Fermilab. Limits are set at the 95% C.L. on the mass and the production of new heavy charged vector bosons which decay via $W'\to WZ$ in extended gauge models as a function of the width, $\Gamma (W')$, and mixing factor between the $W'$ and the Standard Model $W$ bosons.

1 data table

CONST(NAME=XI) is the mixing factor between WPRIME and W-boson.


Search for narrow diphoton resonances and for gamma gamma + w /z signatures in p anti p collisions at s**(1/2) = 1.8-TeV

The CDF collaboration Affolder, T. ; Akimoto, H. ; Akopian, A. ; et al.
Phys.Rev.D 64 (2001) 092002, 2001.
Inspire Record 557012 DOI 10.17182/hepdata.42918

We present results of searches for diphoton resonances produced both inclusively and also in association with a vector boson (W or Z) using 100 $pb^{-1}$ of $p\bar{p}$ collisions using the CDF detector. We set upper limits on the product of cross section times branching ratio for both $p\bar{p} \to \gamma \gamma + X$ and $p \bar{p} \to \gamma \gamma + W/Z$. Comparing the inclusive production to the expectations from heavy sgoldstinos we derive limits on the supersymmetry-breaking scale $\sqrt{F}$ in the TeV range, depending on the sgoldstino mass and the choice of other parameters. Also, using a NLO prediction for the associated production of a Higgs boson with a W or Z boson, we set an upper limit on the branching ratio for $H \to \gamma \gamma$. Finally, we set a lower limit on the mass of a 'bosophilic' Higgs boson (e.g. one which couples only to $\gamma, W,$ and $Z$ bosons with standard model couplings) of 82 GeV/$c^2$ at 95% confidence level.

2 data tables

No description provided.

No description provided.


Search for first-generation scalar and vector leptoquarks

The D0 collaboration Abazov, V.M. ; Abbott, B. ; Abdesselam, A. ; et al.
Phys.Rev.D 64 (2001) 092004, 2001.
Inspire Record 557085 DOI 10.17182/hepdata.42922

We describe a search for the pair production of first-generation scalar and vector leptoquarks in the eejj and enujj channels by the D0 Collaboration. The data are from the 1992--1996 ppbar run at sqrt{s} = 1.8 TeV at the Fermilab Tevatron collider. We find no evidence for leptoquark production; in addition, no kinematically interesting events are observed using relaxed selection criteria. The results from the eejj and enujj channels are combined with those from a previous D0 analysis of the nunujj channel to obtain 95% confidence level (C.L.) upper limits on the leptoquark pair-production cross section as a function of mass and of beta, the branching fraction to a charged lepton. These limits are compared to next-to-leading-order theory to set 95% C.L. lower limits on the mass of a first-generation scalar leptoquark of 225, 204, and 79 GeV/c^2 for beta=1, 1/2, and 0, respectively. For vector leptoquarks with gauge (Yang-Mills) couplings, 95% C.L. lower limits of 345, 337, and 206 GeV/c^2 are set on the mass for beta=1, 1/2, and 0, respectively. Mass limits for vector leptoquarks are also set for anomalous vector couplings.

3 data tables

No description provided.

No description provided.

No description provided.


A measurement of the electric form-factor of the neutron through d(pol.)(e(pol.),e' n)p at Q**2 = 0.5-(GeV/c)**2.

The E93026 collaboration Zhu, H. ; Ahmidouch, A. ; Anklin, H. ; et al.
Phys.Rev.Lett. 87 (2001) 081801, 2001.
Inspire Record 556212 DOI 10.17182/hepdata.31418

We report the first measurement of the neutron electric form factor $G_E^n$ via $\vec{d}(\vec{e},e'n)p$ using a solid polarized target. $G_E^n$ was determined from the beam-target asymmetry in the scattering of longitudinally polarized electrons from polarized deuterated ammonia, $^{15}$ND$_3$. The measurement was performed in Hall C at Thomas Jefferson National Accelerator Facility (TJNAF) in quasi free kinematics with the target polarization perpendicular to the momentum transfer. The electrons were detected in a magnetic spectrometer in coincidence with neutrons in a large solid angle segmented detector. We find $G_E^n = 0.04632\pm0.00616 (stat.) \pm0.00341 (syst.)$ at $Q^2 = 0.495$ (GeV/c)$^2$.

1 data table

No description provided.