Baryon Number Research Articles

Electroweak baryogenesis in aligned two Higgs doublet models

We evaluate the baryon number abundance based on the charge transport scenario of top quarks in the CP-violating two Higgs doublet model, in which Yukawa interactions are aligned to avoid dangerous flavor changing neutral currents, and coupling constants of the lightest Higgs boson with the mass 125 GeV coincide with those in the standard model at tree level to satisfy the current LHC data. In this model, the severe constraint from the electric dipole moment of electrons, which are normally difficult to be satisfied, can be avoided by destructive interferences between CP-violating phases in Yukawa interactions and scalar couplings in the Higgs potential. Viable benchmark scenarios are proposed under the current available data and basic theoretical bounds. We find that the observed baryon number can be reproduced in this model, where masses of additional Higgs bosons are typically 300–400 GeV. Furthermore, it is found that the triple Higgs boson coupling is predicted to be 35–55 % larger than the standard model value.

Evidence for Non-Baryonic Dark Matter

There exists an infinite number of quarks u(∞) and anti-quarks at an infinite sub-layer level. These particles are considered as the ultimate building blocks of the universe, since they are structure-less and absolutely stable. These particles are also regarded as the non-baryonic dark matter, since the baryon number is zero and the Rp-parity is -1. It is emphasized that supersymmetric particle, neutralino has also the Rp-parity of -1 and well known good cold dark matter candidate. In modern particle physics, all ordinary particles have the Rp-parity of +1, while both the ultimate quark u(∞) and neutralino have the Rp-parity of -1. This means that these particles can only be created or annihilated in pairs in reactions of ordinary particles. From electron-positron annihilation experiments at high energies, it is shown that the prediction value from the ultimate quark u(∞) is in good agreement with many ring-storage collider experiments.

NCQ scaling of f0(980) elliptic flow in 200 GeV Au+Au collisions by STAR and its constituent quark content

Searching for exotic state particles and studying their properties have furthered our understanding of quantum chromodynamics (QCD). The f0(980) resonance is an exotic state with relatively high production rate in relativistic heavy-ion collisions, decaying primarily into ππ. Currently the structure and quark content of the f0(980) are unknown with several predictions from theory being a qq¯ state, a qqq¯q¯ state, a KK¯ molecule state, or a gluonium state. We report the first f0(980) elliptic flow (v2) measurement from 200 GeV Au+Au collisions at STAR. The transverse momentum dependence of v2 is examined and compared to those of other hadrons (baryons and mesons). The empirical number of constituent quark (NCQ) scaling is used to investigate the constituent quark content of f0(980), which may potentially address an important question in QCD.

Baryogenesis from ultra-slow-roll inflation

The ultra-slow-roll (USR) inflation represents a class of single-field models with sharp deceleration of the rolling dynamics on small scales, leading to a significantly enhanced power spectrum of the curvature perturbations and primordial black hole (PBH) formation. Such a sharp transition of the inflationary background can trigger the coherent motion of scalar condensates with effective potentials governed by the rolling rate of the inflaton field. We show that a scalar condensate carrying (a combination of) baryon or lepton number can achieve successful baryogenesis through the Affleck-Dine mechanism from unconventional initial conditions excited by the USR transition. Viable parameter space for creating the correct baryon asymmetry of the Universe naturally incorporates the specific limit for PBHs to contribute significantly to dark matter, shedding light on the cosmic coincidence problem between the baryon and dark matter densities today.

Net-particle number fluctuations in a hydrodynamic description of heavy-ion collisions

Utilizing viscous hydrodynamic simulations of heavy-ion collisions, we study the behavior of cumulants of (net-)(anti)proton number distributions at RHIC beam energy scan energies, incorporating non-critical contributions like baryon conservation and excluded volume. The experimental data on net-proton cumulants at √SNN > 20 GeV are consistent with simultaneous effects of global baryon conservation and repulsive interactions in baryon sector, whereas the data at lower collision energies show possible indications for sizable attractive interactions among baryons. We discuss the behavior of factorial cumulants in addition to the ordinary cumulants, and also address the quantitative difference between proton and baryon number cumulants.

Quantum Baryon Number Fluctuations in Subsystems of a Hot and Dense Relativistic Gas of Fermions

Quantum features of the baryon number fluctuations in subsystems of a hot and dense relativistic gas of fermions are analyzed. We find that the fluctuations in small systems are significantly increased compared to their values known from the statistical physics, and diverge in the limit where the system size goes to zero. The numerical results obtained for a broad range of the thermodynamic parameters expected in heavy-ion collisions are presented. They can be helpful to interpret and shed new light on the experimental data.

Baryogenesis via relativistic bubble expansion

We present a novel baryogenesis mechanism in which the asymmetry is sourced from heavy particles which either gain their mass or are created during bubble expansion in a strong first order phase transition. These particles then decay in a CP and baryon number violating way inside the bubble. The particles are inherently out-of-equilibrium and sufficiently dilute after wall crossing so the third Sakharov condition is easily met. Washout is avoided provided the reheat temperature is sufficiently below the scale of the heavy particles. The mechanism relies on moderate supercooling and relativistic walls which -- in contrast to electroweak baryogenesis -- generically leads to a sizable gravitational wave signal, although in the simplest realisations at frequencies beyond upcoming detectors. We present a simple example model and discuss the restrictions on the parameter space for the mechanism to be successful. We find that high reheat temperatures $T_{\rm RH} \gtrsim 10^{10}$ GeV are generally preferred, whereas stronger supercooling allows for temperatures as low as $T_{\rm RH} \sim 10^{6}$ GeV, provided the vacuum energy density is sufficiently suppressed. We briefly comment on using resonantly enhanced CP violation to achieve even lower scales.

Induced surface and curvature tension equation of state for hadron resonance gas in finite volumes and its relation to morphological thermodynamics

Here, we develop an original approach to investigate the grand canonical partition function of the multicomponent mixtures of Boltzmann particles with hard-core interaction in finite and even small systems of the volumes above 20 fm3. The derived expressions of the induced surface tension equation of state (EoS) are analyzed in detail. It is shown that the metastable states, which can emerge in the finite systems with realistic interaction, appear at very high pressures at which the hadron resonance gas, most probably, is not applicable at all. It is shown how and under what conditions the obtained results for finite systems can be generalized to include into a formalism the equation for curvature tension. The applicability range of the obtained equations of induced surface and curvature tensions for finite systems is discussed and their close relations to the equations of the morphological thermodynamics are established. The hadron resonance gas model on the basis of the obtained advanced EoS is worked out. Also, this model is applied to analyze the chemical freeze-out of hadrons and light nuclei with the number of (anti-) baryons not exceeding 4. Their multiplicities were measured by the ALICE Collaboration in the central lead–lead collisions at the center-of-mass energy [Formula: see text] TeV.

Gravitational leptogenesis in teleparallel and symmetric teleparallel gravities * *Supported by NSFC (12075231, 11653002, 12047502, 11947301)

In this study, we investigate the possibilities of generating baryon number asymmetry under thermal equilibrium within the frameworks of teleparallel and symmetric teleparallel gravities. Through the derivative couplings of the torsion scalar and the non-metricity scalar to baryons, baryon number asymmetry is produced in the radiation dominated epoch. For gravitational baryogenesis mechanisms in these two frameworks, the produced baryon-to-entropy ratio is too small to be consistent with observations. However, the gravitational leptogenesis models within both frameworks have the potential to explain the observed baryon-antibaryon asymmetry.

˄C˄C 4 He and ˄C˄C 4 H hypernuclei

In our article we consider charmed hypernuclei states having the number of baryons B = 4 and containing two Ae hyperons. To do this we use the technique of the dispersion relations. We obtain the relativistic equations which describe these states. The relativistic amplitudes for 12-quark states, including the constituent quarks of three flavors u, d, c are considered. We find the approximate solutions of these equations and take into account main singularities of the amplitudes. We calculate masses and binding energies of the hypernuclei states ˄C˄C 4 He, ˄C˄C 4 H.

Dark matter to baryon ratio from scalar triplets decay in type-II seesaw

We propose a minimal model for the cosmic coincidence problem Omega _mathrm{DM}/Omega _B sim 5 and neutrino mass in a type-II seesaw scenario. We extend the standard model of particle physics with a mathrm SU(2) singlet leptonic Dirac fermion chi , which represents the candidate of dark matter (DM), and two triplet scalars Delta _{1,2} with hierarchical masses. In the early Universe, the CP violating out-of-equilibrium decay of lightest Delta generates a net B-L asymmetry in the visible sector (comprising of SM fields), where B and L represents the total baryon and lepton number respectively. A part of this asymmetry gets transferred to the dark sector (comprising of DM chi ) through a dimension eight operator which conserves B-L. Above the electroweak phase transition, the B-L asymmetry of the visible sector gets converted to a net B-asymmetry by the B+L violating sphalerons, while the B-L asymmetry of the dark sector remains untouched which we see today as relics of DM. We show that the observed DM abundance can be explained for a DM mass about 8 GeV. We then introduce an additional singlet scalar field phi which mixes with the SM-Higgs to annihilate the symmetric component of the DM resonantly which requires the singlet scalar mass to be twice the DM mass, i.e. around 16 GeV, which can be searched at collider experiments. In our model, the active neutrinos also get small masses by the induced vacuum expectation value (vev) of the triplet scalars Delta _{1,2}. In the later part of the paper we discuss all the constraints on model parameters coming from invisible Higgs decay, Higgs signal strength, DM direct detection and relic density of DM.

Equations of state for hot neutron stars

We review the equation of state (EoS) models covering a large range of temperatures, baryon number densities and electron fractions presently available on the \textsc{CompOSE} database. These models are intended to be directly usable within numerical simulations of core-collapse supernovae, binary neutron star mergers and proto-neutron star evolution. We discuss their compliance with existing constraints from astrophysical observations and nuclear data. For a selection of purely nucleonic models in reasonable agreement with the above constraints, after discussing the properties of cold matter, we review thermal properties for thermodynamic conditions relevant for core-collapse supernovae and binary neutron star mergers. We find that the latter are strongly influenced by the density dependence of the nucleon effective mass. The selected bunch of models is used to investigate the EoS dependence of hot star properties, where entropy per baryon and electron fraction profiles are inspired from proto-neutron star evolution. The $\Gamma$-law analytical thermal EoS used in many simulations is found not to describe well these thermal properties of the EoS. However, it may offer a fair description of the structure of hot stars whenever thermal effects on the baryonic part are small, as shown here for proto-neutron stars starting from several seconds after bounce.

Neutron-antineutron oscillations as a probe of baryogenesis

A signal of neutron-antineutron () oscillations at experiments like the Deep Underground Neutrino Experiment or the European Spallation Source, would directly imply baryon number violation and will point towards physics beyond the Standard Model. The discovery of such a signal would have important implications for baryogenesis mechanisms in the early Universe, which can explain the observed baryon asymmetry of the Universe today. Here we discuss how an observed rate for oscillations can directly be correlated with the washout of baryon asymmetry in the early Universe and therefore, can probe high- and low-scale baryogenesis scenarios in synergy with collider searches.

Large hadron collider constraints on some simple Z^prime models for brightarrow s mu ^+mu ^- anomalies

We examine current Large Hadron Collider constraints on some simple Z^prime models that significantly improve on Standard Model fits to brightarrow s mu ^+mu ^- transition data. The models that we consider are the ‘third family baryon number minus second family lepton number’ ({B_3-L_2}) model and the ‘third family hypercharge’ model and variants. The constraints are applied on parameter regions of each model that fit the brightarrow s mu ^+mu ^- transition data and come from high-mass Drell–Yan di-muons and measurements of Standard Model processes. This latter set of observables place particularly strong bounds upon the parameter space of the {B_3-L_2} model when the mass of the Z^prime boson is less than 300 GeV.

Hyper-order baryon number fluctuations at finite temperature and density

The authors study the fluctuations of baryon number at finite temperature and density near the QCD phase transition from quark-gluon plasma to hadronic matter. Performing the calculations up to tenth order, they find a non-monotonic dependence of baryon number fluctuations on collision energy, which can arise in the non-critical crossover region of the phase diagram. The results compare well with recent experimental measurements from the STAR collaboration.

Phase structures of neutral dense quark matter and applicationto strange stars * *Supported in part by the National Natural Science Foundation of China (11905107), the National Natural Science Foundation of Jiangsu Province of China (BK20190721), Natural Science Foundation of the Jiangsu Higher Education Institutions of China (19KJB140016), Nanjing University of Posts and Telecommunications Science Foundation (NY129032), Innovation Program of Jiangsu

In the contact interaction model, the quark propagator has only one solution, namely, the chiral symmetry breaking solution, at vanishing temperature and density in the case of physical quark mass. We generalize the condensate feedback onto the coupling strength from the 2 flavor case to the 2+1 flavor case, and find the Wigner solution appears in some regions, which enables us to tackle chiral phase transition as two-phase coexistences. At finite chemical potential, we analyze the chiral phase transition in the conditions of electric charge neutrality and equilibrium. The four chemical potentials, , , and , are constrained by three conditions, so that one independent variable remains: we choose the average quark chemical potential as the free variable. All quark masses and number densities suffer discontinuities at the phase transition point. The strange quarks appear after the phase transition since the system needs more energy to produce a -quark than an -quark. Taking the EOS as an input, the TOV equations are solved numerically, and we show that the mass–radius relation is sensitive to the EOS. The maximum mass of strange quark stars is not susceptible to the parameter we introduced.

Corrections to the hadron resonance gas from lattice QCD and their effect on fluctuation-ratios at finite density

The hadron resonance gas (HRG) model is often believed to correctly describe the confined phase of QCD. This assumption is the basis of many phenomenological works on QCD thermodynamics and of the analysis of hadron yields in relativistic heavy ion collisions. We use first-principle lattice simulations to calculate corrections to the ideal HRG. Namely, we determine the sub-leading fugacity expansion coefficients of the grand canonical free energy, receiving contributions from processes like kaon-kaon or baryon-baryon scattering. We achieve this goal by performing a two dimensional scan on the imaginary baryon number chemical potential ($\mu_B$) - strangeness chemical potential ($\mu_S$) plane, where the fugacity expansion coefficients become Fourier coefficients. We carry out a continuum limit estimation of these coefficients by performing lattice simulations with temporal extents of $N_\tau=8,10,12$ using the 4stout-improved staggered action. We then use the truncated fugacity expansion to extrapolate ratios of baryon number and strangeness fluctuations and correlations to finite chemical potentials. Evaluating the fugacity expansion along the crossover line, we reproduce the trend seen in the experimental data on net-proton fluctuations by the STAR collaboration.

Azimuthal anisotropy of strange and multi-strange hadrons in U+U collisions at sNN = 193GeV at STAR

In this paper, we present systematic measurements of azimuthal anisotropy for strange hadrons ([Formula: see text], [Formula: see text] and [Formula: see text]) and multi-strange hadrons ([Formula: see text] and [Formula: see text]) at mid-rapidity ([Formula: see text]) in U[Formula: see text]U collisions at [Formula: see text] GeV using the STAR detector at the Relativistic Heavy Ion Collider (RHIC). Flow coefficients ([Formula: see text], [Formula: see text] and [Formula: see text]) are presented as a function of transverse momentum ([Formula: see text]) for minimum bias and three different centrality intervals. The [Formula: see text] sub-event plane method is used to obtain the results. These measurements are compared with the published results from Au[Formula: see text]Au collisions at [Formula: see text] GeV. Number of Constituent Quark (NCQ) scaling of the measured flow coefficients in U[Formula: see text]U collisions is discussed. We also present the ratio of [Formula: see text] scaled by the participant eccentricity ([Formula: see text]) to explore system size dependence and collectivity in U[Formula: see text]U collisions. The measured flow coefficients are compared with hydrodynamic and transport model calculations.

Elliptic flow for φ-mesons in Cu+Au and U+U collisions

An important goal of current ultra-relativistic heavy ion research is the investigation of the quark-gluon plasma (QGP). Measurements of elliptic flow lend insight on reaction dynamics and are important for defining parameters of viscous hydrodynamic, which can describe QGP behavior. In this paper elliptic flow for φ-mesons in Cu+Au collisions at and in U+U collisions at GeV is studied as a function of kinetic properties and centrality. The obtained results are compared to hydrodynamic model predictions. New FVTX detector and combinations of different approaches of flow measurements provide a possibility to measure the elliptic flow for the φ-mesons for the first time as a function of centrality at PHENIX. The elliptic flow for φ-mesons in Cu+Au and U+U collisions as function of transverse kinetic energy per one quark follows the trend for other hadrons with respect to the number of quarks in hadrons, regardless of centrality. This result along with agreement of obtained data to hydrodynamic model iEBE-VISHNU predictions suggests that QGP can be described with viscous hydrodynamic with specific viscosity η/s = 1/(4π).

Non-spherical nucleon clusters in the mantle of a neutron star: CLDM based on Skyrme-type forces

Neutron stars are superdense compact astrophysical objects. The central region of the neuron star (the core) consists of locally homogeneous nuclear matter, while in the outer region (the crust) nucleons are clustered. In the outer crust these nuclear clusters represent neutron-rich atomic nuclei and all nucleons are bound within them. Whereas in the inner crust some neutrons are unbound, but nuclear clusters still keeps generally spherical shape. Here we consider the region between the crust and the core of the star, so-called mantle, where non-spherical nuclear clusters may exist. We apply compressible liquid drop model to calculate the energy density for several shape types of nuclear clusters. It allows us to identify the most energetically favorable configuration as function of baryon number density. Employing four Skyrme-type forces (SLy4 and BSk24, BSk25, BSk26), which are widely used in the neutron star physics, we faced with strong model dependence of the ground state composition. In particular, in agreement with previous works within liquid drop model, mantle is absent for SLy4 (nuclear spheres directly transit into homogeneous nuclear matter; exotic nuclear shapes do not appear).