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Register a new userMultiplicity and transverse momentum fluctuations in inelastic proton-proton interactions at the CERN Super Proton Synchrotron
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Measurements of multiplicity and transverse momentum fluctuations of charged particles were performed in inelastic p+p interactions at 20, 31, 40, 80 and 158 GeV/c beam momentum. Results for the scaled variance of the multiplicity distribution and for three strongly intensive measures of multiplicity and transverse momentum fluctuations $Delta[P_{T},N]$, $Sigma[P_{T},N]$ and $Phi_{p_T}$ are presented. For the first time the results on fluctuations are fully corrected for experimental biases. The results on multiplicity and transverse momentum fluctuations significantly deviate from expectations for the independent particle production. They also depend on charges of selected hadrons. The string-resonance Monte Carlo models EPOS and UrQMD do not describe the data. The scaled variance of multiplicity fluctuations is significantly higher in inelastic p+p interactions than in central Pb+Pb collisions measured by NA49 at the same energy per nucleon. This is in qualitative disagreement with the predictions of the Wounded Nucleon Model. Within the statistical framework the enhanced multiplicity fluctuations in inelastic p+p interactions can be interpreted as due to event-by-event fluctuations of the fireball energy and/or volume.
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Measurements of multiplicity fluctuations of identified hadrons produced in inelastic p+p interactions at 31, 40, 80, and 158~GeVc beam momentum are presented. Three different measures of multiplicity fluctuations are used: the scaled variance $omega$ and strongly intensive measures $Sigma$ and $Delta$. These fluctuation measures involve second and first moments of joint multiplicity distributions. Data analysis is performed using the Identity method which corrects for incomplete particle identification. Strongly intensive quantities are calculated in order to allow for a direct comparison to corresponding results on nucleus-nucleus collisions. The results for different hadron types are shown as a function of collision energy. A comparison with predictions of string-resonance Monte-Carlo models: Epos, Smash and Venus, is also presented.
Results on two-particle $DeltaetaDeltaphi$ correlations in inelastic p+p interactions at 20, 31, 40, 80, and 158~GeV/c are presented. The measurements were performed using the large acceptance NA61/SHINE hadron spectrometer at the CERN Super Proton Synchrotron. The data show structures which can be attributed mainly to effects of resonance decays, momentum conservation, and quantum statistics. The results are compared with the EPOS and UrQMD models.
Results from the NA49 experiment at the CERN SPS are presented on event-by-event transverse momentum and multiplicity fluctuations of charged particles, produced at forward rapidities in central Pb+Pb interactions at beam momenta 20$A$, 30$A$, 40$A$, 80$A$, and 158$A$ GeV/c, as well as in systems of different size ($p+p$, C+C, Si+Si, and Pb+Pb) at 158$A$ GeV/c. This publication extends the previous NA49 measurements of the strongly intensive measure $Phi_{p_T}$ by a study of the recently proposed strongly intensive measures of fluctuations $Delta[P_T, N]$ and $Sigma[P_T, N]$. In the explored kinematic region transverse momentum and multiplicity fluctuations show no significant energy dependence in the SPS energy range. However, a remarkable system size dependence is observed for both $Delta[P_T, N]$ and $Sigma[P_T, N]$, with the largest values measured in peripheral Pb+Pb interactions. The results are compared with NA61/SHINE measurements in $p+p$ collisions, as well as with predictions of the UrQMD and EPOS models.
Project Thermalization (Experiment SERP-E-190 at IHEP) is aimed to study the proton - proton interactions at 50 GeV with large number of secondary particles. In this report the experimentally measured topological cross sections are presented taking into account the detector response and procession efficiency. These data are in good agreement with gluon dominance model. The comparison with other models is also made and shows no essential discrepancies.
We analyze the measured spectra of $pi^pm$, $K^pm$, $p$($bar p$) in $pp$ collisions at $sqrt {s}$ = 0.9, 2.76 and 7 TeV, in the light of blast-wave model to extract the transverse radial flow velocity and kinetic temperature at freeze-out for the system formed in $pp$ collisions. The dependency of the blast-wave parameters on average charged particle multiplicity of event sample or the `centrality of collisions has been studied and compared with results of similar analysis in nucleus-nucleus ($AA$) and proton-nucleus ($pA$) collisions. We analyze the spectra of $K_{s}^0$, $Lambda$($bar Lambda$) and $Xi^-$ also to see the dependence of blast-wave description on the species of produced particles. Within the framework of the blast-wave model, the study reveals indication of collective behavior for high-multiplicity events in $pp$ collisions at LHC. Strong transverse radial flow in high multiplicity $pp$ collisions and its comparison with that in $pA$ and $AA$ collisions match with predictions from a very recent theoretical work [Shuryak and Zahed 2013 arXiv:1301.4470] that addresses the conditions for applicability of hydrodynamics in $pp$ and $pA$ collisions.
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