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Register a new userContrasting Freezeouts in Large Versus Small Systems
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We study the data on mean hadron yields and contrast the chemical freezeout conditions in p+p, p+Pb and Pb+Pb at the Large Hadron Collider (LHC) energies. We study several schemes for freezeout that mainly differ in the way strangeness is treated: i. strangeness freezes out along with the non-strange hadrons in complete equilibrium (1CFO), ii. strangeness freezes out along with non-strange hadrons with an additional parameter $gamma_S$ accounting for non-equilibrium production of strangeness (1CFO+$gamma_S$), and iii. strangeness freezes out earlier than non-strange hadrons and in thermal equilibrium (2CFO). A comparison of the chisquares of the fits indicate a dependence of the freezeout scheme on the system size. The minimum bias p+p and different centralities of p+Pb and peripheral Pb+Pb data prefer 1CFO$+gamma_S$ with $gamma_S$ approaching unity as we go from p+p to central p+Pb and peripheral Pb+Pb. On the other hand, the mid-central to central Pb+Pb data prefer 2CFO over 1CFO+$gamma_S$. Such system size dependence of freezeout scheme could be an indication of the additional interaction in Pb+Pb over p+Pb and p+p.
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We illustrate the connection between electron and neutrino scattering off nuclei and show how the former process can be used to constrain the description of the latter. After reviewing some of the nuclear models commonly used to study lepton-nucleus reactions, we describe in detail the SuSAv2 model and show how its predictions compare with the available electron- and neutrino-scattering data over the kinematical range going from the quasi-elastic peak to pion-production and highly inelastic scattering.
Hexaquarks constitute a natural extension of complex quark systems like also tetra- and pentaquarks do. To this end the current status of $d^*(2380)$ in both experiment and theory is shortly reviewed. Recent high-precision measurements in the nucleon-nucleon channel and analyses thereof have established $d^*(2380)$ as an indisputable resonance in the long-sought dibaryon channel. Important features of this $I(J^P) = 0(3^+)$ state are its narrow width and its deep binding relative to the $Delta(1232)Delta(1232)$ threshold. Its decay branchings favor theoretical calculations predicting a compact hexaquark nature of this state. We review the current status of experimental and theoretical studies on $d^*(2380)$ as well as new physics aspects it may bring in the future. In addition, we review the situation at the $Delta(1232) N$ and $N^*(1440)N$ thresholds, where evidence for a number of resonances of presumably molecular nature have been found -- similar to the situation in charmed and beauty sectors. Finally we briefly discuss the situation of dibaryon searches in the flavored quark sectors.
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