Narrow Results

Motivated by the first measurements of the experiment CMS at the LHC at and 2.36 TeV, we discuss energy dependence of average transverse momentum of the secondary particles in hadron production in pp-collisions. We suggest a possible explanation of this dependence as a result of collective rotation of the transient state and associate its further possible decrease with flattening off at higher energies with transition to the genuine QGP state of matter.

The phenomenology of multi-particle production of hadrons is reviewed, with emphasis on the results at the Large Hadron Collider (LHC): the first part of the review focuses on the basic kinematic measurements of charged tracks and identified hadrons in minimum bias interactions; the second part reports the short- and long-range correlation studies; the third part concentrates on the underlying event phenomenology in different final states; the fourth part, which constitutes a bottom line on the phenomenology of multiple parton interactions, considers the consequences of multiple hard-scatterings in a single hadron–hadron collisions. Some relevant highlights from the heavy ion program are also discussed.

The baryonic decays of J/ψ provide a new way to study the internal structure of baryons. A simple diquark model applied to the calculation of the decay cross-sections is compared with the ordinary constituent quark model. Various models also give different predictions for the rates involving the N*(1440) resonance in the final state.

We present the first measurement of target single-spin asymmetries (A_N) in the inclusive hadron production reaction, e+³He^↑ →h+X, using a transversely polarized ³He target at an electron-nucleon center-of-mass energy GeV. The experiment was conducted at Jefferson Lab in Hall A using a 5.9-GeV electron beam. Several types of hadrons (π^±, K^± and proton) were detected with an average momentum 〈P_h〉 = 2.35 GeV/c, and an average transverse momentum 〈p_T〉 = 0.64 GeV/c. The observed asymmetry strongly depends on the type of hadron. A positive asymmetry is observed for π⁺ and K⁺. A negative asymmetry is observed for π^-. The π⁺ and π^- asymmetries measured for the ³He target and extracted the "effective- neutron" SSA. Amazingly, we found that the ratio of our observed SSA between π⁺ and π^- productions closely resemble the ratio of up- to down-quark's contributions to neutron's anomalous magnetic moment.

The HARP experiment at CERN is performing systematic measurements of hadron production for beam momenta from 1.5 to 15 GeV/c for a range of thin and thick nuclear targets. In this paper the double-differential cross section for pions produced by protons of 12.9 GeV/c momentum hitting an aluminium target and protons of 8.9 GeV/c momentum hitting a beryllium target will be reported. These results have an important role to play in the analyses of the K2K and MiniBooNE experiments.