Particles, Volume 4, Issue 1 (March 2021) – 11 articles

New analysis regarding the structure of center vortices is presented: Using data from gluonic SU(2) lattice simulation with Wilson action, a correlation of fluctuations in color space to the curvature of vortex fluxes was found. Finite size effects of the S2-homogeneity hint at color homogeneous regions on the vortex surface. Full article

Detection rates for the elastic and inelastic scattering of weakly interacting massive particles (WIMPs) off ${}^{23}$Na are calculated within the framework of Deformed Shell Model (DSM) based on Hartree-Fock states. At first, the spectroscopic properties of the detector nucleus, like energy spectra and magnetic moments, are evaluated and compared with experimental data. Following the good agreement of these results, DSM wave functions are used for obtaining elastic and inelastic spin structure functions, nuclear structure coefficients and so forth for the WIMP-${}^{23}$Na scattering. Then, the event rates are also computed with a given set of supersymmetric parameters. In the same manner, using DSM wavefunctions, nuclear structure coefficients and event rates for elastic scattering of WIMPs from ${}^{40}$Ar are also obtained. These results for event rates and also for annual modulation will be useful for the ongoing and future WIMP detection experiments involving detector materials with ${}^{23}$Na and ${}^{40}$Ar nuclei. Full article

Transport properties of dense quark matter are discussed in the strong magnetic field, B. B dependence as well as density dependence of the Hall conductivity is discussed, based on the microscopic Kubo formula. We took into account the possibility of the inhomogeneous chiral phase at moderate densities, where anomalous Hall effect is intrinsic and resembles the one in Weyl semimetals in condensed matter physics. Some theoretical aspects inherent in anomalous Hall effect are also discussed. Full article

Spectra of thermal photons carry important information on the temperature of the hot and dense medium produced in heavy ion collisions. Photons can be measured via their conversion into electron-positron pairs in the detector material. In this contribution, challenges in the photon reconstruction are discussed and feasibility studies on photon conversion measurements in the future multipurpose detector (MPD) experiment at NICA are presented. The obtained results indicate good prospects for thermal photon measurements. Full article

In this talk we presented a novel technique, based on Deep Learning, to determine the impact parameter of nuclear collisions at the CBM experiment. PointNet based Deep Learning models are trained on UrQMD followed by CBMRoot simulations of Au+Au collisions at 10 AGeV to reconstruct the impact parameter of collisions from raw experimental data such as hits of the particles in the detector planes, tracks reconstructed from the hits or their combinations. The PointNet models can perform fast, accurate, event-by-event impact parameter determination in heavy ion collision experiments. They are shown to outperform a simple model which maps the track multiplicity to the impact parameter. While conventional methods for centrality classification merely provide an expected impact parameter distribution for a given centrality class, the PointNet models predict the impact parameter from 2–14 fm on an event-by-event basis with a mean error of −0.33 to 0.22 fm. Full article

The integral parameters (mass, radius) of hot proto-quark stars that are formed in supernova explosion are studied. We use the MIT bag model to determine the pressure of up-down and strage quark matter at finite temperature and in the regime where neutrinos are trapped. It is shown that such stars are heated to temperatures of the order of tens of MeV. The maximum possible values of the central temperatures of these stars are determined. It is shown that the energy of neutrinos that are emitted from proto-quark stars is of the order of $250÷300$ MeV. Once formed, the proto-quark stars cool by neutrino emission, which leads to a decrease in the mass of these stars by about 0.16–0.25 $M_{\odot }$ for stars with the rest masses that are in the range $M_b=1.22-1.62 M_{\odot }$. Full article

The study of hadronic resonance production is an essential part of the physical programs of many heavy-ion experiments. Detailed measurement of the resonance properties is also foreseen in the future Multi-Purpose Detector (MPD) experiment at the NICA collider. In this report, we focus on the experimental challenges for the reconstruction of resonances in heavy-ion experiments and examine the MPD capabilities for the reconstruction of ρ(770)⁰, K*(892)^0,±, φ(1020), Λ(1520), Σ(1385)^± and Ξ(1530)⁰. Full article

Observations of non-random distribution of galaxies with opposite spin directions have recently attracted considerable attention. Here, a method for identifying cosine-dependence in a dataset of galaxies annotated by their spin directions is described in the light of different aspects that can impact the statistical analysis of the data. These aspects include the presence of duplicate objects in a dataset, errors in the galaxy annotation process, and non-random distribution of the asymmetry that does not necessarily form a dipole or quadrupole axes. The results show that duplicate objects in the dataset can artificially increase the likelihood of cosine dependence detected in the data, but a very high number of duplicate objects is required to lead to a false detection of an axis. Inaccuracy in galaxy annotations has relatively minor impact on the identification of cosine dependence when the error is randomly distributed between clockwise and counterclockwise galaxies. However, when the error is not random, even a small bias of 1% leads to a statistically significant cosine dependence that peaks at the celestial pole. Experiments with artificial datasets in which the distribution was not random showed strong cosine dependence even when the data did not form a full dipole axis alignment. The analysis when using the unmodified data shows asymmetry profile similar to the profile shown in multiple previous studies using several different telescopes. Full article

Hadronic resonances play an important role in the study of the physics of heavy-ion collisions. In these proceedings, we discuss how the resonances can probe the reaction dynamics, the strangeness production and the properties of the hadronic phase in heavy-ion collisions at center-of-mass energies of $\sqrt{s_{NN}}$ = 4–11 GeV. The resonance properties predicted by the general-purpose event generators are found to be very sensitive to the properties and space-time evolution of the medium produced in heavy-ion collisions. Full article