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We present experimental results on inclusive spectra and mean multiplicities of negatively charged pions produced in inelastic p+p interactions at incident projectile momenta of 20, 31, 40, 80 and 158 GeV/ c ( s = 6.3, 7.7, 8.8, 12.3 and 17.3 GeV, respectively). The measurements were performed using the large acceptance NA61/SHINE hadron spectrometer at the CERN super proton synchrotron. Two-dimensional spectra are determined in terms of rapidity and transverse momentum. Their properties such as the width of rapidity distributions and the inverse slope parameter of transverse mass spectra are extracted and their collision energy dependences are presented. The results on inelastic p+p interactions are compared with the corresponding data on central Pb+Pb collisions measured by the NA49 experiment at the CERN SPS. The results presented in this paper are part of the NA61/SHINE ion program devoted to the study of the properties of the onset of deconfinement and search for the critical point of strongly interacting matter. They are required for interpretation of results on nucleus–nucleus and proton–nucleus collisions.

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 Δ [ P T , N ] , Σ [ P T , N ] and Φ 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 U r qmd 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.

The production of KS0 mesons in inelastic p+p collisions at beam momentum 158 GeV/c (sNN=17.3 GeV) was measured with the NA61/SHINE spectrometer at the CERN Super Proton Synchrotron. Double-differential distributions were obtained in transverse momentum and rapidity. The mean multiplicity of KS0 was determined to be 0.162±0.001(stat.)±0.011(sys.). The results on KS0 production are compared with model predictions (EPOS 1.99, SMASH 2.0, PHSD and UrQMD 3.4 models) as well as with published world data.

The NA61/SHINE collaboration studies at the CERN Super Proton Synchrotron (SPS) the onset of deconfinement in hadronic matter by the measurement of particle production in collisions of nuclei with various sizes at a set of energies covering the SPS energy range. This paper presents results on inclusive double-differential spectra and mean multiplicities of π- mesons produced in the 5% most central7Be + 9Be collisions at beam momenta of 19A, 30A, 40A, 75A and 150AGeV/c obtained by the so-called h- method which does not require any particle identification. The shape of the transverse mass spectra differs from the shapes measured in central Pb + Pb collisions and inelastic p+p interactions. The normalized width of the rapidity distribution decreases with increasing collision energy and is in between the results for inelastic nucleon–nucleon and central Pb + Pb collisions. The mean multiplicity of pions per wounded nucleon in central7Be + 9Be collisions is close to that in central Pb + Pb collisions up to 75AGeV/c. However, at the top SPS energy the result lies between those for nucleon–nucleon and Pb + Pb interactions. The results are discussed in the context of predictions for the onset of deconfinement at the CERN SPS collision energies.

Double-differential yields of Ξ15300 and Ξ¯15300 resonances produced in p+p interactions were measured at a laboratory beam momentum of 158 GeV/c. This measurement is the first of its kind in p+p interactions below LHC energies. It was performed at the CERN SPS by the NA61/SHINE collaboration. Double-differential distributions in rapidity and transverse momentum were obtained from a sample of 26×106 inelastic events. The spectra are extrapolated to full phase space resulting in mean multiplicity of Ξ15300 (6.73±0.25±0.67)×10-4 and Ξ¯15300 (2.71±0.18±0.18)×10-4. The rapidity and transverse momentum spectra and mean multiplicities were compared to predictions of string-hadronic and statistical model calculations.

Results on two-particle Δ η Δ ϕ 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.

We present measurements of ρ0, ω and K∗0 spectra in π-+ C production interactions at 158 GeV/c and ρ0 spectra at 350 GeV/c using the NA61/SHINE spectrometer at the CERN SPS. Spectra are presented as a function of the Feynman’s variable xF in the range 0

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