Abstract: Measurements of the centrality and rapidity dependence of inclusive jet production in root(NN)-N-S = 5.02 TeV proton-lead (p + Pb) collisions and the jet cross-section in root s = 2.76 TeV proton-proton collisions are presented. These quantities are measured in datasets corresponding to an integrated luminosity of 27.8 nb(-1) and 4.0 pb(-1), respectively, recorded with the ATLAS detector at the Large Hadron Collider in 2013. The p + Pb collision centrality was characterised using the total transverse energy measured in the pseudorapidity interval -4.9 < eta < -3.2 in the direction of the lead beam. Results are presented for the double-differential per-collision yields as a function of jet rapidity and transverse momentum (p(T)) for minimum-bias and centrality-selected p + Pb collisions, and are compared to the jet rate from the geometric expectation. The total jet yield in minimum-bias events is slightly enhanced above the expectation in a p(T)-dependent manner but is consistent with the expectation within uncertainties. The ratios of jet spectra from different centrality selections show a strong modification of jet production at all p(T) at forward rapidities and for large pT at mid-rapidity, which manifests as a suppression of the jet yield in central events and an enhancement in peripheral events. These effects imply that the factorisation between hard and soft processes is violated at an unexpected level in proton-nucleus collisions. Furthermore, the modifications at forward rapidities are found to be a function of the total jet energy only, implying that the violations may have a simple dependence on the hard parton-parton kinematics.

Abstract: We investigate the neutral pion photoproduction on the proton near threshold in covariant chiral perturbation theory with the explicit inclusion of A degrees of freedom. This channel is specially sensitive to chiral dynamics and the advent of very precise data from the Mainz microtron has shown the limits of the convergence of the chiral series for both the heavy baryon and the covariant approaches. We show that the inclusion of the Delta resonance substantially improves the convergence leading to a good agreement with data for a wider range of energies.

Abstract: We present measurements of Collins asymmetries in the inclusive process e(+)e(-) -> h(1)h(2)X, h(1)h(2) = KK, K pi, pi pi, at the center-of-mass energy of 10.6 GeV, using a data sample of 468 fb(-1) collected by the BABAR experiment at the PEP-II B factory at SLAC National Accelerator Center. Considering hadrons in opposite thrust hemispheres of hadronic events, we observe clear azimuthal asymmetries in the ratio of unlike sign to like sign, and unlike sign to all charged h(1)h(2) pairs, which increase with hadron energies. The K pi asymmetries are similar to those measured for the pi pi pairs, whereas those measured for high-energy KK pairs are, in general, larger.