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 $$\pi ^{-}$$ π - mesons produced in the 5% most central$$^7$$ 7 Be + $$^9$$ 9 Be collisions at beam momenta of 19A, 30A, 40A, 75A and 150$$A\,\text{ GeV }\!/\!c$$ A GeV / c obtained by the so-called $$h^-$$ 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 central$$^7$$ 7 Be + $$^9$$ 9 Be collisions is close to that in central Pb + Pb collisions up to 75$$A\,\text{ GeV }\!/\!c$$ A GeV / 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.

The physics goal of the strong interaction program of the NA61/SHINE experiment at the CERN Super Proton Synchrotron (SPS) is to study the phase diagram of hadronic matter by a scan of particle production in collisions of nuclei with various sizes at a set of energies covering the SPS energy range. This paper presents differential inclusive spectra of transverse momentum, transverse mass and rapidity of $$\pi ^{-}$$ π -  mesons produced in central$${}^{40}$$ 40 Ar+$${}^{45}$$ 45 Sc collisions at beam momenta of 13A, 19A, 30A, 40A, 75A and 150$$A\,\text{ Ge }\text{ V }\!/\!\textit{c}$$ A Ge V / c . Energy and system size dependence of parameters of these distributions – mean transverse mass, the inverse slope parameter of transverse mass spectra, width of the rapidity distribution and mean multiplicity – are presented and discussed. Furthermore, the dependence of the ratio of the mean number of produced pions to the mean number of wounded nucleons on the collision energy was derived. The results are compared to predictions of several models.

The NA61/SHINE experiment at the CERN Super Proton Synchrotron (SPS) studies the onset of deconfinement in hadron matter by a scan 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, transverse momentum and rapidity distributions and mean multiplicities of $$\pi ^\pm $$ π ± , $$K^\pm $$ K ± , p and $$\bar{p}$$ p ¯ produced in the 20% most central$$^7$$ 7 Be+$$^9$$ 9 Be collisions at beam momenta of 19A, 30A, 40A, 75A and 150A $${\mathrm{Ge} \mathrm{V}}\!/\!c$$ Ge V / c . 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 close to those found in inelastic p+p reactions. The new results are compared to the world data on p+p and Pb+Pb collisions as well as to predictions of the Epos, Urqmd, Ampt, Phsd and Smash models.

The production of $$K^{0}_{S}$$ K S 0 mesons in inelastic p+p collisions at beam momentum 158 $$\text{ GeV }/c$$ GeV / c ($$\sqrt{s_{NN}}=17.3$$ s NN = 17.3  $$\text{ GeV }$$ 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 $$K^{0}_{S}$$ K S 0 was determined to be $$0.162 \pm 0.001 (stat.) \pm 0.011 (sys.)$$ 0.162 ± 0.001 ( s t a t . ) ± 0.011 ( s y s . ) . The results on $$K^{0}_{S}$$ K S 0 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.

Measurements of $$K^{*}(892)^0$$ K ∗ ( 892 ) 0 resonance production via its $$K^{+}\pi ^{-}$$ K + π - decay mode in inelastic p+p collisions at beam momenta 40 and 80 $$\text{ GeV }\!/\!c$$ GeV / c ($$\sqrt{s_{NN}}=8.8$$ s NN = 8.8 and 12.3 $$\text{ GeV }$$ GeV ) are presented. The data were recorded by the NA61/SHINE hadron spectrometer at the CERN Super Proton Synchrotron. The template method was used to extract the $$K^{*}(892)^0$$ K ∗ ( 892 ) 0 signal. Transverse momentum and rapidity spectra were obtained. The mean multiplicities of $$K^{*}(892)^0$$ K ∗ ( 892 ) 0 mesons were found to be $$(35.1 \pm 1.3 \mathrm {(stat)} \pm 3.6 \mathrm {(sys))} \cdot 10^{-3}$$ ( 35.1 ± 1.3 ( stat ) ± 3.6 ( sys ) ) · 10 - 3 at 40 $$\text{ GeV }\!/\!c$$ GeV / c and $$(58.3 \pm 1.9 \mathrm {(stat)} \pm 4.9 \mathrm {(sys))} \cdot 10^{-3}$$ ( 58.3 ± 1.9 ( stat ) ± 4.9 ( sys ) ) · 10 - 3 at 80 $$\text{ GeV }\!/\!c$$ GeV / c . The NA61/SHINE results are compared with the Epos1.99 and Hadron Resonance Gas models as well as with world data. The transverse mass spectra of $$K^{*}(892)^0$$ K ∗ ( 892 ) 0 mesons and other particles previously reported by NA61/SHINE were fitted within the Blast-Wave model. The transverse flow velocities are close to 0.1–0.2 of the speed of light and are significantly smaller than the ones determined in heavy nucleus-nucleus interactions at the same beam momenta.