Proton decay in a supersymmetric SO(10) model with missing partner mechanism

The extended supersymmetric SO(10) model with missing partner mechanism is studied. An intermediate vacuum expectation value is incorporated which corresponds to the see-saw scale. Gauge coupling unification is not broken explicitly. Proton decay is found to satisfy the present experimental limits at the cost of fine-tuning some parameters.Comment: 14 pages; Several improvements, References adde

Connection between proton decay suppression and seesaw mechanism in supersymmetric SO(10) models

We propose a mechanism to suppress proton decay induced by dimension-5 operators in a supersymmetric SO(10) model. Proton lifetime is directly connected with the intermediate vacuum expectation value which is responsible for the seesaw mechanism. The model shows many consistencies with the present theoretical results such as the components of the two Higgs doublets in the minimal supersymmetric standard model.Comment: 11 pages, no figure. Several minor correction

Probing initial baryon stopping and equation of state with rapidity-dependent directed flow of identified particles

Using a (3+1)-dimensional hybrid framework with parametric initial conditions, we study the rapidity-dependent directed flow $v_1(y)$ of identified particles, including pions, kaons, protons, and lambdas in heavy-ion collisions. Cases involving Au+Au collisions are considered, performed at $\sqrt{s_{\rm NN}}$ ranging from 7.7 to 200 GeV. The dynamics in the beam direction is constrained using the measured pseudo-rapidity distribution of charged particles and the net proton rapidity distribution. Within this framework, the directed flow of mesons is driven by the sideward pressure gradient from the tilted source, and that of baryons mainly due to the initial asymmetric baryon distribution with respect to the beam axis driven by the transverse expansion. Our approach successfully reproduces the rapidity- and beam energy-dependence of $v_1$ for both mesons and baryons. We find that the $v_1(y)$ of baryons has strong constraining power on the initial baryon stopping, and together with that of mesons, the directed flow probes the equation of state of the dense nuclear matter at finite chemical potentials.Comment: v1: 6+3 pages, 4 figures; v2: add discussion on the Lund string mode

Dilepton production at NLO and intermediate invariant-mass observables

The thermal QCD dilepton production rate is calculated at next-to-leading order in the strong coupling and at finite baryon chemical potential. The two-loop virtual photon self-energy is evaluated using finite temperature field theory and combined consistently with the self-energy in the Landau-Pomeranchuk-Migdal regime. We present new results for a dense baryonic plasma. The rates are then integrated using (3+1)-dimensional fluid-dynamical simulations calibrated to reproduce hadronic experimental results obtained at RHIC at energies ranging from those of the Beam Energy Scan to $\sqrt{s_{_{\rm NN}}} = 200$ GeV. We elaborate on the ability for dileptons to relay information about the plasma baryonic content and temperature.Comment: 19 pages, 15 figure

Virtual Photons Shed Light on the Early Temperature of Dense QCD Matter

Dileptons produced during heavy-ion collisions represent a unique probe of the QCD phase diagram, and convey information about the state of the strongly interacting system at the moment their preceding off-shell photon is created. In this study, we compute thermal dilepton yields from Au+Au collisions performed at different beam energies, employing a (3+1)-dimensional dynamic framework combined with emission rates accurate at next-to-leading order in perturbation theory and which include baryon chemical potential dependencies. By comparing the effective temperature extracted from the thermal dilepton invariant mass spectrum with the average temperature of the fluid, we offer a robust quantitative validation of dileptons as effective probe of the early quark-gluon plasma stage.Comment: 6+2 pages, 4+2 figure

Initial Stages 2021

At Relativistic Heavy Ion Collider (RHIC) Beam Energy Scan (BES) energies, the dynamics of the pre-hydrodynamic stage and the effects from a nonzero net baryon current become essential components of the dynamical evolution of the collision fireball. We develop a (3+1)-dimensional initial stage model for both energy-momentum and the net baryon current, as dynamical initial conditions for a hydrodynamic evolution module, before the colliding nuclei interpenetrate and the produced system gets completely hydrodynamized. More specifically, during the initial pre-hydrodynamic stage, the four-momenta and baryon numbers carried by secondary particles created within a transport module (modified-UrQMD), after a short hydrodynamization time, are deposited continuously into a (3+1)-dimensional viscous hydrodynamic evolution module (BEShydro). The sensitivity of the hydrodynamic evolution to its initialization will be studied by comparing this approach to other previously proposed dynamical initialization algorithms. We show the dependence on the hydrodynamization time of correlations between rapidity and space-time rapidity of the secondary particles from UrQMD. We also present the interplay between the hydrodynamic module and the dynamical initial conditions by comparing the evolution of eccentricities, temperature and flow velocities, etc., with and without the hydrodynamic module. Supported by DOE (award no. DE-SC0004286) and NSF (JETSCAPE, award no. ACI-1550223)

Hybrid model with dynamical sources for heavy-ion collisions at BES energies

We develop a (3+1)-dimensional hybrid evolution model for heavy-ion collisions with dynamical sources for the energy-momentum tensor and baryon current. During an initial pre-equilibrium stage based on UrQMD, the four-momenta and baryon numbers carried by secondary particles created within UrQMD are fed continuously, after a short thermalization time, into a (3+1)-dimensional viscous hydrodynamic evolution module including baryon transport. The sensitivity of the initial conditions to model parameters and the effect of baryon diffusion on the hydrodynamic evolution are studied

Fluctuation dynamics near the QCD critical point

© 2020 American Physical Society. The evolution of nonhydrodynamic slow processes near the QCD critical point is explored with the novel hydro+ framework, which extends the conventional hydrodynamic description by coupling it to additional explicitly evolving slow modes describing long wavelength fluctuations. Their slow relaxation is controlled by critical behavior of the correlation length and is independent from gradients of matter density and pressure that control the evolution of the hydrodynamic quantities. In this exploratory study, we follow the evolution of the slow modes on top of a simplified QCD matter background, allowing us to clearly distinguish and study, both separately and in combination, the main effects controlling the dynamics of critical slow modes. In particular, we show how the evolution of the slow modes depends on their wave number, the expansion of and advection by the fluid background, and the behavior of the correlation length. Nonequilibrium contributions from the slow modes to bulk matter properties that affect the bulk dynamics (entropy, pressure, temperature, and chemical potential) are discussed and found to be small