We look for fluctuations expected for the QCD critical point using an intermittency analysis in the transverse momentum phase space of protons produced around midrapidity in the 12.5\% most central ...C+C, Si+Si and Pb+Pb collisions at the maximum SPS energy of 158\(A\)~GeV. We find evidence of power-law fluctuations for the Si+Si data. The fitted power-law exponent \(\phi_{2} = 0.96^{+0.38}_{-0.25}\text{ (stat.)}\) \(\pm 0.16\text{ (syst.)}\) is consistent with the va\-lue expected for critical fluctuations. Power-law fluctuations had previously also been observed in low-mass \(\pi^+ \pi^-\) pairs in the same Si+Si collisions.
A special normalization is proposed for strongly intensive quantities used in the study of event-by-event fluctuations in high energy collisions. It ensures that these measures are dimensionless and ...yields a common scale required for a quantitative comparison of fluctuations of different, in general dimensional, extensive quantities. Namely, the properly normalized strongly intensive quantities assume the value one for fluctuations given by the model of independent particle production and zero in the absence of event-by-event fluctuations.
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 \$\DeltaP_{T},N\$, \$\SigmaP_{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.
Phys. Rev. C 92, 044905 (2015) 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 $\DeltaP_T, N$ and $\SigmaP_T, N$. 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 $\DeltaP_T, N$ and $\SigmaP_T, N$, 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.
NA61/SHINE (SPS Heavy Ion and Neutrino Experiment) is a multi-purpose experimental facility to study hadron production in hadron-proton, hadron-nucleus and nucleus-nucleus collisions at the CERN ...Super Proton Synchrotron. It recorded the first physics data with hadron beams in 2009 and with ion beams (secondary 7Be beams) in 2011. NA61/SHINE has greatly profited from the long development of the CERN proton and ion sources and the accelerator chain as well as the H2 beamline of the CERN North Area. The latter has recently been modified to also serve as a fragment separator as needed to produce the Be beams for NA61/SHINE. Numerous components of the NA61/SHINE set-up were inherited from its predecessors, in particular, the last one, the NA49 experiment. Important new detectors and upgrades of the legacy equipment were introduced by the NA61/SHINE Collaboration. This paper describes the state of the NA61/SHINE facility - the beams and the detector system - before the CERN Long Shutdown I, which started in March 2013.
Spectra of K0S mesons and Lambda hyperons were measured in p+C interactions at 31 GeV/c with the large acceptance NA61/SHINE spectrometer at the CERN SPS. The data were collected with an isotropic ...graphite target with a thickness of 4% of a nuclear interaction length. Interaction cross sections, charged pion spectra, and charged kaon spectra were previously measured using the same data set. Results on K0S and Lambda production in p+C interactions serve as reference for the understanding of the enhancement of strangeness production in nucleus-nucleus collisions. Moreover, they provide important input for the improvement of neutrino flux predictions for the T2K long baseline neutrino oscillation experiment in Japan. Inclusive production cross sections for K0S and Lambda are presented as a function of laboratory momentum in intervals of the laboratory polar angle covering the range from 0 up to 240 mrad. The results are compared with predictions of several hadron production models. The K0S mean multiplicity in production processes and the inclusive cross section for K0S production were measured and amount to 0.127 +- 0.005 (stat) +- 0.022 (sys) and 29.0 +- 1.6 (stat) +- 5.0 (sys) mb, respectively.
The T2K long-baseline neutrino oscillation experiment in Japan needs precise predictions of the initial neutrino flux. The highest precision can be reached based on detailed measurements of hadron ...emission from the same target as used by T2K exposed to a proton beam of the same kinetic energy of 30 GeV. The corresponding data were recorded in 2007-2010 by the NA61/SHINE experiment at the CERN SPS using a replica of the T2K graphite target. In this paper details of the experiment, data taking, data analysis method and results from the 2007 pilot run are presented. Furthermore, the application of the NA61/SHINE measurements to the predictions of the T2K initial neutrino flux is described and discussed.
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 \(\DeltaP_T, N\) and \(\SigmaP_T, N\). 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 \(\DeltaP_T, N\) and \(\SigmaP_T, N\), 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.
Spectra of positively charged kaons in p+C interactions at 31 GeV/c were measured with the NA61/SHINE spectrometer at the CERN SPS. The analysis is based on the full set of data collected in 2007 ...with a graphite target with a thickness of 4% of a nuclear interaction length. Interaction cross sections and charged pion spectra were already measured using the same set of data. These new measurements in combination with the published ones are required to improve predictions of the neutrino flux for the T2K long baseline neutrino oscillation experiment in Japan. In particular, the knowledge of kaon production is crucial for precisely predicting the intrinsic electron neutrino component and the high energy tail of the T2K beam. The results are presented as a function of laboratory momentum in 2 intervals of the laboratory polar angle covering the range from 20 up to 240 mrad. The kaon spectra are compared with predictions of several hadron production models. Using the published pion results and the new kaon data, the K+/\pi+ ratios are computed.
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