Energy dependence of J/ψJ/\psi production in pp collisions with the PACIAE model

In this work we investigate the $J/\psi$ production in proton-proton collisions at the center-of-mass energy ($\sqrt{s}$) equal to 2.76, 5.02, 7, 8 and 13 TeV with a parton and hadron cascade model PACIAE 2.2a. It is based on PYTHIA but extended considering the partonic and hadronic rescatterings before and after hadronization, respectively. In the PYTHIA sector the $J/\psi$ production quantum chromodynamics processes are selected specially and a bias factor is proposed correspondingly. The calculated total cross sections, the differential cross sections as a function of the transverse momentum and the rapidity of $J/\psi$ in the forward rapidity region reproduce the corresponding experimental measurements reasonably well. In the mid-rapidity region, the double differential cross sections at $\sqrt{s}=$ 5.02, 7 and 13 TeV are also in a good agreement with the experimental data. Moreover, we predict the double differential cross section as well as the total cross section of $J/\psi$ at $\sqrt{s}=$ 8 TeV, which could be validated when the experimental data is available.Comment: 6 pages, 8 figures, 3 table

An introduction to the parton and hadron cascade model PACIAE 3.0

We introduce a parton and hadron cascade model PACIAE 3.0 based on PYTHIA 6.428 and the PACIAE 2.2 program series. The simulation framework of C-, B-, and A-loops are designed for the high energy ($\sqrt{s_{NN}}\geq 3$ GeV) and low energy ($\sqrt{s_{NN}}<3$ GeV) nuclear collisions, respectively, in PACIAE 3.0. In the C-loop simulation, the parton-parton inelastic scattering processes are added in the partonic rescattering process. The single string structure and multiple string interaction mechanism have been introduced investigating the strangeness enhancement in C- and B-loop. An improved mapping relation between the centrality percentage definition and the impact parameter definition is proposed responding the observation of $b_{max}\approx 20$ fm from ALICE, ATLAS, and CMS collaborations. We have extensively modified the phenomenological coalescence hadronization model. The PACIAE 3.0 model simulated results of particle yield, transverse momentum distribution, and rapidity distribution well reproduce, respectively, the experimental data measured at FOPI, E895, RHIC, and LHC energies.Comment: 15 pages, 15 figure

The study on the structure of exotic states χc1(3872)\chi_{c 1}(3872) via beauty-hadron decays in pppp collisions at s=8 TeV\sqrt{s}=8\,\mathrm{TeV}

A dynamically constrained phase-space coalescence (DCPC) model was introduced to study the exotic state $\chi_{c 1}(3872)$ yield for three possible structures: tetraquark state, nuclear-like state, and molecular state respectively, where the hadronic final states generated by the parton and hadron cascade model (PACIAE). The $\chi_{c 1}(3872)$/$\psi (2S)$ cross-section ratio from beauty-hadron decays (non-prompt) based on the $\chi_{c 1}(3872)$ or $\psi (2S)\to J/\psi{\pi^+}{\pi^-}$ bound state in the decay chains as a function of charged-particle multiplicity and transverse momentum in $pp$ collisions at $\sqrt{s}=8\,\mathrm{TeV}$ are calculated. A tetraquark state scenario from PACIAE+DCPC model shows better agreement with the LHCb and ATLAS measurements for the non-prompt $\chi_{c 1}(3872)$/$\psi(2S)$ cross-section ratio distributions, indicating that the $\chi_{c 1}(3872)$ is more likely to be a compact tetraquark state