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Measurements of inclusive spectra and mean multiplicities of π ± , K ± , p and p ¯ 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) were performed at the CERN Super Proton Synchrotron using the large acceptance NA61/SHINE hadron spectrometer. Spectra are presented as function of rapidity and transverse momentum and are compared to predictions of current models. The measurements serve as the baseline in the NA61/SHINE study of the properties of the onset of deconfinement and search for the critical point of strongly interacting matter.

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 hadron production in p + C interactions at 31 GeV/ c are performed using the NA61/SHINE spectrometer at the CERN SPS. The analysis is based on the full set of data collected in 2009 using a graphite target with a thickness of 4 % of a nuclear interaction length. Inelastic and production cross sections as well as spectra of π ± , K ± , p, K S 0 and Λ are measured with high precision. These measurements are essential for improved calculations of the initial neutrino fluxes in the T2K long-baseline neutrino oscillation experiment in Japan. A comparison of the NA61/SHINE measurements with predictions of several hadroproduction models is presented.

This paper presents results on multiplicity fluctuations of positively and negatively charged hadrons as well as net-electric charge fluctuations measured in central Ar+Sc interactions at beam momenta 13A, 19A, 30A, 40A, 75A, and 150 A GeV/c. The fluctuation analysis is one of the tools to search for the predicted critical point of strongly interacting matter. Results are corrected for the experimental biases and quantified using cumulant ratios. In most instances, multiplicity and net-charge distributions appear narrower than the corresponding Poisson or Skellam distributions. Cumulant ratios are compared with the EPOS1.99 model predictions, which provide a qualitative description that aligns with observations for positively and negatively charged particles. The obtained results are also compared to earlier NA61/SHINE results from inelastic p+p interactions in the same analysis acceptance.

Measurements of particle emission from a replica of the T2K 90 cm-long carbon target were performed in the NA61/SHINE experiment at CERN SPS, using data collected during a high-statistics run in 2009. An efficient use of the long-target measurements for neutrino flux predictions in T2K requires dedicated reconstruction and analysis techniques. Fully-corrected differential yields of π ± -mesons from the surface of the T2K replica target for incoming 31 GeV/ c protons are presented. A possible strategy to implement these results into the T2K neutrino beam predictions is discussed and the propagation of the uncertainties of these results to the final neutrino flux is performed.

The NA61/SHINE experiment at the CERN Super Proton Synchrotron studies the onset of deconfinement in strongly interacting matter through a beam energy scan of particle production in collisions of nuclei of varied sizes. This paper presents results on inclusive double-differential spectra, transverse momentum and rapidity distributions and mean multiplicities of$$\\pi ^\\pm $$π ± ,$$K^\\pm $$K ± , p and$$\\bar{p}$$p ¯ produced in$$^{40}\\hbox {Ar+}^{45}\\hbox {Sc}$$40 Ar+ 45 Sc collisions at beam momenta of 13 A , 19 A , 30 A , 40 A , 75 A and 150 A  $$\\text{ Ge }\\hspace{-1.00006pt}\\text{ V }\\!/\\!c$$Ge V / c . The analysis uses the 10% most central collisions, where the observed forward energy defines centrality. The energy dependence of the$$K^\\pm $$K ± /$$\\pi ^\\pm $$π ± ratios as well as of inverse slope parameters of the$$K^\\pm $$K ± transverse mass distributions are placed in between those found in inelastic$$p+p$$p + p and central Pb + Pb collisions. The results obtained here establish a system-size dependence of hadron production properties that so far cannot be explained either within statistical or dynamical models.

We present measurements of ρ 0 , ω and K ∗ 0 spectra in π - + C production interactions at 158  GeV / c and ρ 0 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 x F in the range 0 < x F < 1 and 0 < x F < 0.5 for 158 and 350  GeV / c respectively. Furthermore, we show comparisons with previous measurements and predictions of several hadronic interaction models. These measurements are essential for a better understanding of hadronic shower development and for improving the modeling of cosmic ray air showers.

Results on ϕ meson production in inelastic p + p collisions at CERN SPS energies are presented. They are derived from data collected by the NA61/SHINE fixed target experiment, by means of invariant mass spectra fits in the ϕ → K + K - decay channel. They include the first ever measured double differential spectra of ϕ mesons as a function of rapidity y and transverse momentum p T for proton beam momenta of 80 GeV / c and 158 GeV / c , as well as single differential spectra of y or p T for beam momentum of 40 GeV / c . The corresponding total ϕ yields per inelastic p + p event are obtained. These results are compared with existing data on ϕ meson production in p + p collisions. The comparison shows consistency but superior accuracy of the present measurements. The emission of ϕ mesons in p + p reactions is confronted with that occurring in Pb + Pb collisions, and the experimental results are compared with model predictions. It appears that none of the considered models can properly describe all the experimental observations.

This paper reports measurements of two-pion femtoscopic correlations in Be+Be collisions at a beam momentum of 150$$A\\,\\hbox {GeV}\\!/\\!c$$A GeV / c  (energy available in the center-of-mass system for nucleon pair$$\\sqrt{s_{\\text {NN}}} = 16.84$$s NN = 16.84 GeV) by the NA61/SHINE experiment at the CERN SPS accelerator. The obtained momentum space correlation functions can be well described by a Lévy distributed source model. The transverse mass dependence of the Lévy source parameters is presented, and their possible theoretical interpretations are discussed. The results show that the Lévy exponent$$\\alpha $$α is approximately constant as a function of$$m_{\\text {T}}$$m T  , and far from both the Gaussian case of$$\\alpha = 2$$α = 2 or the conjectured value at the critical endpoint,$$\\alpha = 0.5$$α = 0.5 . The radius scale parameter R shows a slight decrease in$$m_{\\text {T}}$$m T  , which can be explained as a signature of transverse flow. Finally, an approximately constant trend of the intercept parameter$$\\lambda $$λ as a function of$$m_{\\text {T}}$$m T  was observed, similar to previous NA44 S + Pb results (obtained with a Gaussian approximation, but unlike RHIC results).

The production of Ξ ( 1321 ) - and Ξ ¯ ( 1321 ) + hyperons in inelastic p+p interactions is studied in a fixed target experiment at a beam momentum of 158  Ge / c . Double differential distributions in rapidity y and transverse momentum p T are obtained from a sample of 33M inelastic events. They allow to extrapolate the spectra to full phase space and to determine the mean multiplicity of both Ξ - and Ξ ¯ + . The rapidity and transverse momentum spectra are compared to transport model predictions. The Ξ - mean multiplicity in inelastic p+p interactions at 158  Ge / c is used to quantify the strangeness enhancement in A+A collisions at the same centre-of-mass energy per nucleon pair.