The time substructure of jets and boosted object tagging

We propose the study of the time substructure of jets, motivated by the fact that the next generation of detectors at particle colliders will resolve the time scale over which jet constituents arrive. This effect is directly related to the fragmentation and hadronization process, which transforms partons into massive hadrons with a distribution of velocities. We review the basic predictions for the velocity distribution of jet hadrons, and suggest an application for this information in the context of boosted object tagging. By noting that the velocity distribution is determined by the properties of the color string which ends on the parton that initiates the jet, we observe that jets originating from boosted color singlets, such as Standard Model electroweak bosons, will exhibit velocity distributions that are boosted relative to QCD jets of similar jet energy. We find that by performing a simple cut on the corresponding distribution of charged hadron arrival times at the detector, we can discriminate against QCD jets that would otherwise give a false positive under a traditional spatial substructure based boosted object tagger.

Charged pion, kaon, proton and antiproton production in large collision systems

The main goal of PHENIX expirement, located at Relativistic Heavy-ion collider, is the investigation of quark-gluon plasma (QGP). One of the aspects of the QGP study is describing the process of its hadronization. Very important contribution to understanding of hadronization process was given by discovering of anomaly large ratio of protons production to pions production (ρ/π) in Au+Au collisions in comparison to the same ratio in proton-proton collisions. This effect was called baryon puzzle and was explained in a frame of recombination model of hadronization. Although charged hadrons production has been previously studied in elementary proton-proton collisions and symmetric Au+Au collisions, it has never been investigated before in the large asymmetric collisions systems (such as Cu+Au) or the collisions of large deformed nuclei (U+U). The study of such large collisions systems allows to study features of baryon and meson production versus collision geometry and system size.

A framework for hadronic rescattering in pp collisions

In this article, a framework for hadronic rescattering in the general-purpose Pythia event generator is introduced. The starting point is the recently presented space–time picture of the hadronization process. It is now extended with a tracing of the subsequent motion of the primary hadrons, including both subsequent scattering processes among them and decays of them. The major new component is cross-section parameterizations for a range of possible hadron–hadron combinations, applicable from threshold energies upwards. The production dynamics in these collisions has also been extended to cope with different kinds of low-energy processes. The properties of the model are studied, and some first comparisons with LHC $$\mathrm {p}\mathrm {p}$$ p p data are presented. Whereas it turns out that approximately half of all final particles participated in rescatterings, the net effects in $$\mathrm {p}\mathrm {p}$$ p p events are still rather limited, and only striking in a few distributions. The new code opens up for several future studies, however, such as effects in $$\mathrm {p}$$ p A and AA collisions.

STATISTICS OF BIRTH PIONS FROM THE HADRON "FIREBALL"

The paper studies the statistics of pion production in the processes of inelastic hadronhadron collisions at high energies. It is assumed that the multiple birth of particles occurs as a result of the hadronization process of the quark-gluon "fireball". Based on the two selected states – the state of thermal equilibrium and the coherent state – the statistics of the production of pions is calculated

Heavy Hadrons Production by Coalescence Plus Fragmentation in AA Collisions at RHIC and LHC

The hadronization process of heavy hadrons with bottom and charm quarks, especially for baryons Λ c , in a dense QGP medium is largely not understood. We present within a coalescence plus fragmentation model the predictions for D 0 and Λ c spectra and the related baryon to meson ratios at RHIC and LHC. We will discuss how our model can predict values for Λ c / D 0 of the order of O(1), which is much larger than the expectations from fragmentation, and in agreement whit early data from STAR collaboration. Furthermore in the same scheme can be predicted a baryon to meson ratio Λ c / D 0 in pp collisions assuming that at the LHC top energies there can be the formation of QGP matter. The results show a considerable volume effects that significantly reduce the ratios, but still predict quite larger values with respect to fragmentation, in agreement with recent data from ALICE in pp collisions.

Hyperon \(\Omega\) Production in \(pp\) Collisions at Energy 8 TeV

Because strange quark produced copiously in pp collisions, strange hyperon production is one of the ideal tools to investigate the hadronization process and baryon transport theory. We are especially interested in the hyperon Ω production because this baryon contents only strange quark. Our new studies of the pure strange hyperon Ω produced in pp collision at s = 8 TeV are shown in this report. The following strategy is used to reconstruct the strange hyperon Ω. In the LHCb experiment, the hadrons p, π and K are identified by the RICH detector with PT threshold > 100 MeV. Only Lambda (from channel Λ → p + π) with PT > 500 MeV are chosen to combine with kaon daughter particle in order to reconstruct a strange hyperon Ω. The reconstructed particles are accepted as Ω candidates in the case it satisfies several criteria such as its invariance mass must be located within the window mas ± 50 MeV/c2 around the nominal value. More than 63 millions selected events are used for this analysis and about 8100 hyperon Ω candidates are reconstructed.

Hadron formation from interaction among quarks

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.