Universal scaling of meson and baryon spectra in p-Pb collisions at 5.02TeV

We systematically investigate the scaling property of mesons (pions and kaons) and baryons (protons, [Formula: see text], [Formula: see text] and [Formula: see text]) transverse momentum ([Formula: see text]) spectra at different centrality classes (0–5[Formula: see text], 5–10[Formula: see text], 10–20[Formula: see text], 20–40[Formula: see text], 40–60[Formula: see text], 60–80[Formula: see text] and 80–100[Formula: see text]) in proton-lead collisions with center of mass energy per nucleon pair 5.02[Formula: see text]TeV. In the low [Formula: see text] region with [Formula: see text][Formula: see text]GeV/c, a universal scaling independent of the centrality is observed in the pion (kaon, proton, [Formula: see text], [Formula: see text] and [Formula: see text]) spectra when a dilatation, [Formula: see text], is applied. Here, [Formula: see text] is a scaling parameter depending on the centrality class. We find that the rates at which ln[Formula: see text] changes with the logarithmic value of the average value of the number of participating nucleons, ln[Formula: see text], are stronger for baryons than those for mesons. In the high [Formula: see text] region, there is a deviation from the scaling. The more peripheral the collisions are, the more obvious the violation of the scaling is. In the framework of the color string percolation (CSP) model, we show that mesons and baryons are generated from the decay of clusters formed by strings overlapping in the transverse plane with the same size dispersion but with different mean size. The mean size of clusters for baryons is smaller than that of mesons. For the same hadrons at different centrality classes, the mean size of clusters decreases with the increase of centrality. The fragmentation functions for cluster decay are different for different hadrons, while they are universal for the same hadrons at different centrality classes. The universal scaling of the meson and baryon spectra in the low [Formula: see text] region can be quantitatively understood with the CSP model at the same time.

Baryon spectra and antiparticle-to-particle ratios from the improved AMPT model

The current version of a multi-phase transport (AMPT) model with string melting can reasonably describe the dN/dy yields, pT spectra and anisotropic flows of pions and kaons at low pT in heavy ion collisions at RHIC and LHC energies, although it failed to reproduce the dN/dy and pT spectra of baryons. In this work, we improve the quark coalescence mechanism in AMPT by removing the forced separate number conservations of mesons, baryons and antibaryons in each event. We find that the improved AMPT model can better describe the yields at midrapidity, the pT spectra and elliptic flow of low-pT baryons in comparison with the experimental data. Antiparticle-to-particle ratios of strange baryons are also significantly improved.

Spectroscopy of Charmed and Bottom Hadrons using Lattice QCD

We present preliminary results on the light, charmed and bottom baryon spectra using overlap valence quarks on the background of 2+1+1 flavours HISQ gauge configurations of the MILC collaboration. These calculations are performed on three different gauge ensembles at three lattice spacings (a ∼ 0.12 fm, 0.09 fm and 0.06 fm) and for physical strange, charm and bottom quark masses. The SU(2) heavy baryon chiral perturbation theory is used to extrapolate baryon masses to the physical pion mass and the continuum limit extrapolations are also performed. Our results are consistent with the well measured charmed baryons. We predict the masses of many other states which are yet to be discovered.

Lattice study of the scalar and baryon spectra in many-flavor QCD

In the search for a composite Higgs boson in walking technicolor models, many flavor QCD, in particular with [Formula: see text], is an attractive candidate, and has been found to have a composite flavor-singlet scalar as light as the pion. Based on lattice simulations of this theory with the HISQ action, we will present our preliminary results on the scalar decay constant using the fermionic bilinear operator, and on the mass of the lightest baryon state which could be a dark matter candidate. Combining these two results, implications for dark matter direct detection are also discussed.