Data on the multiplicity and inclusive spectra of γ produced in inelastic pNe20 and pN interactions at 300 GeV are presented. The γ multiplicity for pNe20 interactions is 11.43±0.23, and the ratio of 〈nγ〉 for pNe20 and pN interactions is 1.48±0.05. From an analysis of the effective-mass distributions, 〈nπ0〉=4.91±0.52 and 〈nη0〉=1.47±0.33. In fact, η0 production is much higher in pNe20 interactions [R(η0π0)=0.66±0.12 for np≥21] than in pN interactions [R(η0π0)=0.06±0.04]. No η′(958) signal is seen. Strong correlations between 〈nγ〉 and np, the number of secondary protons, are observed, primarily from the central and target fragmentation regions. Inclusive y* and p⊥ spectra are analyzed and evidence for low-energy cascading and rescattering of fast particles in the projectile fragmentation region is discussed. The data are compared to the predictions of the additive quark model, the Lund model, and the dual parton model.
No description provided.
GAMMA-MULTIPLICITY FOR (PROTON-NUCLEON)-INTERACTION WAS OBTAINED AT AVERAGING OVER (PP) AND (PN) EVENTS, AND THEN WAS USED IN THE PRESENTED RATIO.
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We have searched for direct photons of low PT (≤1.0 GeV/c) at θc.m.=90° in pp collisions at √s =63 GeV. We used two independent methods: direct detection in NaI crystals and conversion to e+e− pairs. No signal is observed; the photon spectrum is well described by the decay of hadrons. The result is consistent with a direct low-PT photon signal reported at √s =12 GeV, but excludes a rapid growth of soft-photon production with √s .
No description provided.
The data on the total inelastic and partial cross sections in pNe interactions at 300 GeV are presented. It is found that the total cross section, σin(pNe)=356±13 mb, and multiplicity distributions of the number of negative and relativistic charged particles are in good agreement with predictions of a multiple-scattering model based on Glauber's approach. The multiplicity of negative particles obeys the Koba-Nielsen-Olesen (KNO) scaling, but it is observed that the KNO function depends on the atomic mass number of the target. From an analysis of the average multiplicities of secondary particles, it is shown that approximately 10 percent of the fast (p≳1.2 GeV) positive secondaries are protons, which are derived from the nucleons in the neon nucleus.
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A measurement of direct photon production in pp collisions at a center of mass energy ∝ s =63 GeV is reported. Arrays of lead-glass calorimeters and multiwire proportional chambers were used as photon detectors. Data are presented in the transverse momentum range from 4.5 to 10 GeV/ c and compared with QCD predictions. The event structure of this sample is compared with that of a set dominated by high transverse momentum π O ́ ' s .
Final Average Results from inside and outside detector.
Results for the inside detector.
Results for the outside detector.
The production of direct photons has been measured relative to π 0 's in the rapidity range 2.00 < y < 2.75 in pp collisions at s = 63 GeV at the CERN Intersecting Storage Rings. The γ/π 0 ratio increases from ⪅2% at p T = 1.5 GeV/ c to ∼8% at p T = 4.25 GeV/ c , similar to the value observed near 90°. The results indicate no strong enhancement of single-photon production due to quark bremsstrahlung in this kinematic region.
No description provided.
We have measured the production of direct photons, π 0 's, and η's in p p and pp collisions at √ s =53 GeV in the range 2≈ p T ≈6 GeV/ c for the central rapidity region | y | 0.4. No statistically significant difference between pp̄ and pp interactions is observed.
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Errors are combined statistical and systematic.
Errors are combined statistical and systematic.
Errors are combined statistical and systematic.
We present measurements of the cross section and double-helicity asymmetry $A_{LL}$ of direct-photon production in $\vec{p}+\vec{p}$ collisions at $\sqrt{s}=510$ GeV. The measurements have been performed at midrapidity ($|\eta|<0.25$) with the PHENIX detector at the Relativistic Heavy Ion Collider. At relativistic energies, direct photons are dominantly produced from the initial quark-gluon hard scattering and do not interact via the strong force at leading order. Therefore, at $\sqrt{s}=510$ GeV, where leading-order-effects dominate, these measurements provide clean and direct access to the gluon helicity in the polarized proton in the gluon-momentum-fraction range $0.02<x<0.08$, with direct sensitivity to the sign of the gluon contribution.
Cross sections for inclusive and isolated direct photons as a function of $p_T$. Not shown are 10% absolute luminosity uncertainties.
Double helicity asymmetry $A_{LL}$ $vs$ $p_{T}$ for isolated direct-photon production in polarized $\vec{p}+\vec{p}$ collisions at $\sqrt{s}=510$ GeV at midrapidity. Not shown are $3.9 \times 10^{-4}$ shift uncertainty from relative luminosity and 6.6% scale uncertainty from polarization.
Measurements of inclusive and direct photon production at mid-rapidity in pp collisions at $\sqrt{s}=2.76$ and 8 TeV are presented by the ALICE experiment at the LHC. The results are reported in transverse momentum ranges of $0.4<p_{T}<10$ GeV/$c$ and $0.3<p_{T}<16$ GeV/$c$, respectively. Photons are detected with the electromagnetic calorimeter~(EMCal) and via reconstruction of e$^+$e$^-$ pairs from conversions in the ALICE detector material using the central tracking system. For the final measurement of the inclusive photon spectra the results are combined in the overlapping $p_{T}$ interval of both methods. Direct photon spectra, or their upper limits at 90% C.L. are extracted using the direct photon excess ratio $R_{\gamma}$, which quantifies the ratio of inclusive photons over decay photons generated with a decay-photon simulation. An additional hybrid method, combining photons reconstructed from conversions with those identified in the EMCal, is used for the combination of the direct photon excess ratio $R_{\gamma}$, as well as the extraction of direct photon spectra or their upper limits. While no significant signal of direct photons is seen over the full $p_{T}$ range, $R_{\gamma}$ for $p_{T}>7$ GeV/$c$ is at least one $\sigma$ above unity and consistent with expectations from next-to-leading order pQCD calculations.
Double Ratio RGAMMA in inelastic pp collisions at center-of-mass energy 2.76 TeV. RGAMMA is the ratio of inclusive GAMMA to decay GAMMA.
Double Ratio RGAMMA in inelastic pp collisions at center-of-mass energy 8 TeV. RGAMMA is the ratio of inclusive GAMMA to decay GAMMA.
Invariant differential cross section of inclusive GAMMA produced in inelastic pp collisions at center-of-mass energy 2.76 TeV, the uncertainty of $\sigma_{MB}$ of 2.5% is not included in the systematic error. Values are given in the center of the PT bin.
A study of multiplicity and pseudorapidity distributions of inclusive photons measured in pp and p$-$Pb collisions at a center-of-mass energy per nucleon$-$nucleon collision of $\sqrt{s_{\rm NN}} = 5.02$ TeV using the ALICE detector in the forward pseudorapidity region $2.3 < \eta_{\rm lab} < 3.9$ is presented. Measurements in p$-$Pb collisions are reported for two beam configurations in which the directions of the proton and lead ion beam were reversed. The pseudorapidity distributions in p$-$Pb collisions are obtained for seven centrality classes which are defined based on different event activity estimators, i.e., the charged-particle multiplicity measured at midrapidity as well as the energy deposited in a calorimeter at beam rapidity. The inclusive photon multiplicity distributions for both pp and p$-$Pb collisions are described by double negative binomial distributions. The pseudorapidity distributions of inclusive photons are compared to those of charged particles at midrapidity in \pp collisions and for different centrality classes in p$-$Pb collisions. The results are compared to predictions from various Monte Carlo event generators. None of the generators considered in this paper reproduces the inclusive photon multiplicity distributions in the reported multiplicity range. The pseudorapidity distributions are, however, better described by the same generators.
Inclusive photon multiplicity distribution measured within $2.3<\eta_{\rm lab}<3.9$ in pp collisions at $\sqrt{s} = 5020~\mathrm{GeV}$.
Inclusive photon multiplicity distribution measured within $2.3<\eta_{\rm lab}<3.9$ in p-Pb collisions at $\sqrt{s_\mathrm{NN}} = 5020~\mathrm{GeV}$.
Inclusive photon multiplicity distribution measured within $2.3<\eta_{\rm lab}<3.9$ in Pb-p collisions at $\sqrt{s_\mathrm{NN}} = 5020~\mathrm{GeV}$.
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