Transverse momentum ( p T ) distributions of inclusive photons and neutral pions at midrapidity are measured with a lead glass calorimeter in 60 and 200 A GeV 16 O + nucleus and proton + nucleus reactions . The variation of the average transverse momentum is investigated as function of centrality, determined by measurements of the remaining energy of the projectile and the charged particle multiplicity. For small values of the entropy, deduced from the multiplicity density, an increase in average p T is observed levelling off for larger values of entropy. The target-mass and energy dependence of π 0 p T distributions are presented.
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The inclusive cross sections for production of prompt photons and π0s by 280 GeV/c protons incident on a liquid hydrogen target, have been measured forpT in the range 4.0 to 6.5 GeV/c and for |xF|<0.45. A quantitative comparison of the prompt photon cross section with next-to-leading order QCD predictions using Duke and Owens structure functions is performed. Phenomenological fits to the π0 and prompt photon cross sections are given.
Invariant cross section.
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Invariant cross section.
The inclusive cross sections for prompt photon production by π− and π+ on protons have been measured with a beam momentum of 280 GeV/c using a fine grained electromagnetic calorimeter and the CERN Omega spectrometer. The transverse momentum and FeynmanxF ranges covered are 4.0<pT<7.0GeV/c and −0.45<xF<0.55 respectively. A quantitative comparison of the prompt photon cross section with next-to-leading order QCD predictions using Duke and Owens structure functions is performed.
Invariant cross section.
Invariant cross section. UPDATE (03 DEC 2018): systematic error of 4th bin for PT = 4.37 GEV/C corrected from 13.5 to 13.2, slight corrections to PT weighted averages (4.11 -> 4.12, 4.36 -> 4.37, 4.61 -> 4.62, 5.72 -> 5.71, 6.37 -> 6.36).
Invariant cross section.
The inclusive cross sections for π0 production by π− and π+ on protons have been measured with a beam momentum of 280 GeV/c using a fine grained electromagnetic calorimeter and the CERN Omega spectrometer. The transverse momentum and FeynmanxF ranges covered are 4.0<pT<7.0 GeV/c and −0.45<xF<0.6 respectively. The data are compared with leading order QCD calculations.
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In a study of proton-proton interactions at\(\sqrt s= 26GeV\), inclusive distributions of single pions and systems of pions of various charge combinations are presented, as well as the production ratio obtained in association with various trigger particles. The results are compared to current phenomenological models in an attempt to understand multiparticle productions in hadron collisions.
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Cross sections for the inclusive processes p+A→KS0+X and p+A→Λ0+X (A=Be, Cu, and W) have been measured for incident protons at 12 GeV. Data are obtained at five laboratory production angles of 3.5°, 5.0°, 6.5°, 8.0°, and 9.5°, covering the kinematic range 0.3≤xF≤0.8 and 0.4≤pT≤1.3 GeV/c for KS0’s and 0.2≤xF≤0.9 and 0.4≤pT≤1.7 GeV/c for Λ0’s. The results are discussed in terms of the pT dependence, the xF dependence, the A dependence, the cross-section ratio KS0/Λ0, and triple-Regge behavior. The A dependence of KS0 and Λ0 spectra is analyzed in the constituent-quark model. The average pT2’s of quarks and diquarks involved in the KS0 and Λ0 production processes are discussed.
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Cross sections for inclusive direct photon production in π−p, π+p, and pp collisions at 300 GeV/c are measured at transverse momenta pT up to 7 GeV/c (xT=0.6). For π−p→γX also the rapidity distribution is presented. The cross-section ratio σ(π−p→γX)/σ(π+p→γX) is found to be 1 at pT=4 GeV/c and rises with increasing pT. This observation signals the occurrence of valence-quark–antiquark annihilation. The results are in good agreement with QCD predictions.
THERE IS ALSO A 1 PCT UNCERTAINTY IN THE PT SCALE AND A 7 PCT UNCERTAINTY IN THE NORMALISATION.
Cross sections for inclusive π0 production at large transverse momentum pT were measured in π−p, π+p, and pp collisions at 300 GeV/c. The cross-section ratio σ(π−p→π0X)/σ(π+p→π0X) was found to be consistent with unity in the pT region of 1 to 5 GeV/c. The cross-section ratio σ(π+p→π0X)/σ(pp→π0X) however is growing with increasing pT and increasing π0 c.m.-system rapidity in agreement with parton-model expectations, where the partons in the pions have on average higher momenta than in the proton.
THERE IS ALSO A 1 PCT UNCERTAINTY IN THE PT SCALE AND A 7 PCT UNCERTAINTY IN THE NORMALISATION.
Using the UA2 apparatus, the inclusive cross section has been measured for production of high- p T direct photons in p̄p collisions at s =546 GeV and s =630 GeV . The results are in good agreement with QCD predictions.
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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.
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.
We present results on the production of hadrons in collisions of 400-GeV/c protons with beryllium, copper, and tungsten nuclei. The data cover the region from 5.6 to 8.0 GeV/c in the transverse momentum of the final-state hadron and from 73° to 102° in the proton-nucleon center-of-momentum frame production angle theta*. The restriction of the data to values of xT (xT=2pT/ √s ) greater than 0.4 enriches the sample with hard collisions of valence quarks. Asymmetries about theta*=90° reflect the presence of neutrons in the target nuclei. The variation of the atomic-weight dependence parameter α with production angle is discussed in the context of the phenomenology of nucleonic structure within nuclei. We also extrapolate our measurements to a ‘‘deuteron’’ target to minimize nuclear effects and compare the result to QCD calculations.
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Inclusive production cross sections have been measured for the processes p+A→Ξ0+X (A=Be, Cu, Pb) and for p+Be→Ξ¯0+X. Data were taken at angles of 0, 2, 3.5, 7.3, and 9.8 mrad between the incident 400-GeV proton beam and the outgoing hyperon beam. Production cross sections for Λ and Λ¯ production were measured at the same time. The A dependence of the Ξ0 cross sections is discussed, along with interpretations in terms of various models.
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Direct photon production has been studied by an experiment performed with the NA3 spectrometer at CERN, using incident negative and positive beams at 200 GeV/c interacting with an isoscalar Carbon target. Two different triggers have been used; one of them requires the photon conversion. The experiment is sensitive to direct photons produced with 3.0≦PT≦6 GeV/c and center-of-mass rapidity −0.4≦y*≦1.2. Inclusive cross sections are given for incident π± and protons, and compared with second order QCD predictions; finally an estimation of the gluon structure function of the nucleon is given.
Data from conversion trigger. Statistical errors only.
Data from calorimeter trigger. Statistical errors only.
Inclusive photoproduction of ϕ,K*0(890),\(\bar K*^0 \) andK*0(1420),\(\bar K*^0 \) has been studied in γp collisions with photons of energy 20 to 70 GeV and in the range 0.1≦xF≦0.95 [0.4≦xF≦0.8 for the\(\mathop K\limits^{( - )} *\)(1420)],xF being the Feynman variable of the vector/tensor meson. The cross-sections for these processes, averaged over the photon energy range and integrated overxF are given. The inclusive ϕ production in the forward direction can be described quantitatively by a triple-Regge model calculation. The remaining ϕ production and the totalK*0(890) and\(\bar K*^0 \) production are consistent with a quark fusion picture.
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Using the UA5 detector, the inclusive central production of Ks<sup loc="post">0</sup> and K<sup loc="post">±</sup> mesons has been measured in non-single-diffractive interactions at the CERN SPS <math altimg="si1.gif"><ovl type="bar" style="s">p</ovl>p</math> Collider at a c.m. energy of 540 GeV. The average transverse momentum is found to be 〈pT〉 = 0.57±0.03 GeV/c in the rapidity range |y|<2.5, which is an increase of about 30% over the top ISR energy. The K/π ratio has increased from about 8% at ISR energies to 9.5±0.9±0.7% (the last error is systematic) at 540 GeV. The average number of Ks<sup loc="post">0</sup> per non-single-diffractive event is 1.1±0.1 and the inclusive inelastic cross section is estimated at 49±5 mb.
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The production of antideuterons has been observed in electron-positron annihilations at center-of-mass energies around 10 GeV. Antideuterons have been identified unambiguously by their energy loss in the drift chamber, their time-of-flight and the pattern of their energy deposition in the shower counters of the ARGUS detector. The production rate in the momentum range (0.6−1.8) GeV/ c is (1.6 −0.7 +1.0 ) × 10 −5 per hadronic event.
Results from 6 antideuterons detected (3 from UPSI(2S), 2 from (IS) and 1 from (4S)).
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We have measured the total cross sections of Ω− and Ω¯+ forward (xF>~0) inclusive production in KL0-carbon interactions in the range EK0=80 to 280 GeV to be 3.5±1.4 and 2.4±1.0 μb, respectively. We observe that the xF distributions for both of these states are increasing from xF=0 to xF≈0.6. The p⊥2 distributions are described as an exponential function in p⊥ with an average p⊥2 of 0.540 GeV2/c2.
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Inclusive particle production cross-sections have been measured at the\(Sp\bar pS\) collider using the UA2 detector in various ranges of transverse momentum (PT) and pseudo-rapidity (η). Cross-section measurements are presented forπ0 production (PT≦15 GeV/c, |η|≦0.85 andPT≦40 GeV/c, 1.0≦|η|≦1.8), for η meson production (3≦PT≦6 GeV/c, |η|≦0.85) and for charged particle production (PT≦10 GeV/c, 1.0≦|η|≦1.8). Results are compared with the predictions of QCD calculations.
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The reactions\(K^ -Be \to {}^(\bar K^) *^0 (890)X,\pi ^ -Be \to {}^(\bar K^) *^0 (890)X\), have been studied in a 175 GeV unseparated hadron beam in the kinematic range 0<xF<1.0 andpT2<5 GeV2. Integrated cross-sections and the dependence of the cross-sections on the longitudinal and transverse momentum are presented, together with quark counting rules predictions. The nuclear dependence ofK− fragmentation intoK*0(890) with respect to Feynmanx is investigated from hydrogen to beryllium.
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We report on measurements of charged pion production cross sections at θ ≅ 50°, p T ≅ 3–9 GeV / c and √ s = 45 GeV , taken with the Split Field Magnet Detector at the CERN Intersecting Storage Rings (ISR). Together with previous data at √ s = 62 GeV , this allows the calculation of the exponent n assuming a power law dependence p n T . Values of n ≈ 8 are found at low x T = 2 p T /√ s which drop to about 7 at x T ≈ 0.3. The measured values of π + /π − rise with x T and approach ≈ 2 at x T ≈ 0.3. A first-order QCD calculations is reasonably consistent with the data.
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We present final results on inclusive production ofK*+(890),K*+(1430) andK*−(890) in\(\bar K^ +p\) interactions at 32 GeV/c, based on a statistics of ∼27 events/μb. Total cross sections,pT-andx-dependence of inclusive distributions are compared with experiments at other energies and with the Lund fragmentation model. Spin density matrix elements of theK*+(890) are also discussed. The results suggest that “recombination” of both initial state valence quarks\(\bar s\) andu of theK+ intoK*+(890), responsible in the Lund model for ∼45% of theK*+(890) cross section, is strongly suppressed.
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Measurements are presented of inclusive distributions in pp and p p interactions at √ s = 53 GeV. The data were obtained at the CERN ISR using the Split Field Magnet spectrometer with a minimum bias trigger. The inclusive distributions are analyzed as functions of the transverse momentum, the rapidity and the Feynman- x variable.
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We have studied inclusive production of KS0, Λ, and Λ¯ particles in 20-GeV γp interactions and have found features similar to those observed in both hadronic and leptonic interactions. The production cross sections, charged-particle multiplicities, and average Λ polarization are reported. Inclusive distributions of x and pT are shown and discussed in terms of quark fragmentation models. Production cross sections for K*(890) and Σ*(1385) are also reported.
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The production properties ofKs0,\(\bar \Lambda\) andK+p interactions at 32 GeV/c are investigated using the final statistics of the experiment. We present total and semi-inclusive cross sections and aver-age multiplicities. Estimates are given of the diffractive dissociation contributions to total and differential cross sections. Thex-,pT−, and transverse mass dependence of inclusive and semi-inclusive distributions is discussed as well as properties of “prompt”Ks0's. The ratio of “prompt”K890+ (K8900) to “prompt”K0 cross sections is measured to be 1.03±0.12 (0.98±0.17). From a comparison of\(\bar \Lambda\) production inK±p interactions at 32 GeV/c, we estimate a strange sea-quark suppression of 0.26 ±0.02. The double differential cross sections ofKs0's is studied as a function of Feynman-x andpT2, and a Triple-Regge fit performed. The data are compared in detail to versions of the Lund-model for low-pT hadronic collisions.
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Data are reported on the momentum distributions of Λ, Λ (1520), φ (1020), Λ and p , inclusively produced between 1° and 2° with respect to one of the primary proton beams at the CERN Intersecting Storage Rings. In addition, the decay angular distribution of the Λ(1520), the ratio of the cross sections for the production of Σ − (1385) and Σ + (1385) and the ratios among different charge states of the pairs Λπ , Λ K, Δ ++ (1232) π and ππ have been measured. These data are confronted with current ideas on fragmentation.
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