The measurement of K * (892) 0 resonance production via its K + π − decay mode in inelastic p+p collisions at beam momentum 158 GeV/c (√ s N N = 17.3 GeV) is 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 signal and double-differential transverse momentum and rapidity spectra were obtained. The full phase-space mean multiplicity of K * (892) 0 mesons was found to be (78.44 ± 0.38(stat) ± 6.0(sys)) • 10 −3. The NA61/SHINE results are compared with the Epos1.99 and Hadron Resonance Gas models as well as with world data from p+p and nucleus-nucleus collisions.

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.

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.