Measurement of negatively charged pion spectra in inelastic p+p interactions at plab = 20, 31, 40, 80 and 158 GeV/c

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 158GeV/c (√s = 6.3, 7.7,8.8, 12.3 and 17.3GeV, 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 CERNSPS. 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.

Measurement of Muon Antineutrino Oscillations with an Accelerator-Produced Off-Axis Beam

T2K reports its first measurements of the parameters governing the disappearance of νµ in an off-axis beam due to flavor change induced by neutrino oscillations. The quasimonochromatic νµ beam, produced with a peak energy of 0.6 GeV at J-PARC, is observed at the far detector SuperKamiokande, 295 km away, where the νµ survival probability is expected to be minimal. Using a dataset corresponding to 4.01×10²⁰ protons on target, 34 fully contained µ-like events were observed. The best-fit oscillation parameters are sin²(θ₂₃) = 0.45 and |∆m^2_32| = 2.51 × 10⁻³ eV² with 68% confidence intervals of 0.38 - 0.64 and 2.26 - 2.80 ×10⁻³ eV² respectively. These results are in agreement with existing antineutrino parameter measurements and also with the νµ disappearance parameters measured by T2K.