Narrow Results

Spin transfer in high energy fragmentation process is determined by the hadronization mechanism and spin structure of hadrons. It can be studied by measuring the polarizations of hyperons and/or vector mesons in e⁺e^- annihilation, in the current fragmentation region of polarized deeply inelastic lN-scatterings, and high p_T-jets in polarized pp-collisions. Theoretical calculations have been made using different models. In this talk, I will briefly summarize the main features of the models, the results obtained and the comparison with available data. They can be used for future tests by experiments.

The influence of the nuclear environment on the hadronization of charged pions, kaons and (anti)protons in semi-inclusive deep inelastic scattering has been studied by the HERMES experiment at DESY using a 27.5 GeV positron beam. Identified hadron multiplicities have been measured for helium, neon and krypton relative to thate of deuterium as a function of ν, z and . A large increase in the multiplicity ratios with was observed, clarifying the role of FSI in the nuclear transverse momentum broadening. In addition, double-hadron production in the nuclear medium was investigated. Nuclear effects on the double hadron-production ratio provided an additional tool for studying modifications of hadronization in nuclear matter.

We analyzed the identified hadron multiplicity predictions of the generalized thermodynamical model of the multiparticle production processes with nonextensive statistics. The multiplicities measured recently at LHC experiments seem to be consistent with this approach and thermodynamical parameter values are found already by analyzing transverse momentum distributions. The information about the mechanism of the strangeness suppression has been derived to some extent from multistrange hadron abundances.

We investigate the formation and evolution of hot systems comprising charmed and light hadrons using non-extensive thermodynamics. We analyze data from pp, p–Pb, and Pb–Pb collisions at center-of-mass energies ranging from $\sqrt{s_{\mathrm{\text{NN}}}}=2.76$TeV to 13TeV, measured by the CERN LHC ALICE experiment. The hadron species examined include charged pions and kaons, ${\mathrm{\text{K}}}_{\mathrm{\text{s}}}^0$, (anti)protons, $\varphi$ mesons, ${\mathrm{\Lambda }}^0$ hyperons, and D mesons. Employing our previously established methods, we determine the common Tsallis parameters $T_{\mathrm{\text{eq}}}$ and $q_{\mathrm{\text{eq}}}$ for each hadron type. While charm comes from earlier than light hadrons, we see that $T_{\mathrm{\text{eq}}}$ is ordered by mass, reflecting a similar ordering in the time-scale relevant for the spectrum. Our results also allow for constraining the heat capacity of the system. The current analysis thus enhances our understanding of hadron production dynamics and thermal properties in high-energy collisions.

The recent discussion about experimental evidence for pentaquark states has revitalized the interest in exotic hadrons. If such states really exist, it is natural to assume that they will be formed at the late hadronization stage of ultra-relativistic heavy ion collisions, given the success of quark recombination models in the description of hadronization. Here, we apply the qMD model to study the formation of color neutral exotic multi-quark clusters at hadronization. We search for color neutral clusters made up of up to six color charges, respectively. We thus obtain estimates for the numbers and phase space distributions of exotic hadronic states produced by clustering in heavy ion collisions, including the members of the pentaquark multiplets. We obtain particle abundances that are smaller than thermal model predictions. Moreover, the results obtained in recombination from ultra-relativistic heavy ion collisions can be compared to the estimates based on equal population of the corresponding multiplets, and to results from fully thermalized systems. We find that the distribution of exotic hadrons from recombination over large multiplets provides a sensitive signal for thermalization and decorrelation of the initial, non-equilibrium state of the collision.

This paper deals with the hadronization process of quark system. A phenomenological potential is introduced to describe the interaction between a quark pair. The potential depends on the color charge of those quarks and their relative distances. Those quarks move according to classical equations of motion. Due to the color interaction, coloring quarks are separated to form color neutral clusters which are supposed to be the hadrons.

A quantum algorithm of SU($N$) Yang–Mills theory is formulated in terms of quantum circuits. It can nonperturbatively calculate the Dyson series and scattering amplitudes with polynomial complexity. The gauge fields in the interaction picture are discretized on the same footing with the lattice fermions in momentum space to avoid the fermion doubling and the gauge symmetry breaking problems. Applying the algorithm to the quantum simulation of quantum chromodynamics, the quark and gluon’s wave functions evolved from the initial states by the interactions can be observed and the information from wave functions can be extracted at any discrete time. This may help us understand the natures of the hadronization which has been an outstanding question of significant implication on high energy phenomenological studies.

Results from recent soft QCD measurements by LHC experiments ALICE, ATLAS, CMS, LHCb, LHCf and TOTEM are reported. The measurements include total, elastic and inelastic cross sections, inclusive and identified particle spectra, underlying event and hadronic chains. Results from particle correlations in all three collision systems, namely pp, pPb and PbPb, exhibit unexpected similarities.

Hadronic events at the Z pole have been investigated in search for Colour Reconnection effects and QCD coherence. Colour Reconnection effects are searched for in three-jet events and the data results are compared to the predictions of different Monte Carlo models. QCD colour coherence effects are tested through the multiplicity distributions of hadrons with restricted momenta, and the LEP1 e⁺e^- data is compared to HERA e⁺p data under the equivalence assumption of the e⁺e^- hemisphere with the current region of the Breit frame of reference.