Baryon Number Research Articles

Matter-antimatter asymmetry induced by Barbero-Immirzi parameter

We review the baryon asymmetry generated in the early Universe in the framework of the metric-spinor gravity with the Holst term, which accounts for the Barbero-Immirzi parameter. For the generation of the matter-antimatter asymmetry, we have considered the model in which the time derivative of the Ricci scalar couples with matter currents (this model is known in the literature as gravitational baryogenesis). By using the current bounds on the parameter of the asymmetry, the ratio of baryon number to the entropy density, we infer a bound on the parameters characterizing the model under consideration (that is, the cosmological model in the presence of the torsion and Barbero-Immirzi parameter).

Model dependence of the number of participant nucleons and observable consequences in heavy-ion collisions

The centrality determination and the estimated fluctuations of number of participant nucleons N_{part} in Au–Au collisions at 1.23 AGeV beam kinetic energy suffers from severe model dependencies. Comparing the Glauber Monte Carlo (MC) and UrQMD transport models, it is shown that N_{part} is a strongly model dependant quantity. In addition, for any given centrality class, Glauber MC and UrQMD predicts drastically different N_{part} distributions. The impact parameter b and the number of charged particles N_{ch} on the other hand are much more correlated and give an almost model independent centrality estimator. It is suggested that the total baryon number balance, from integrated rapidity distributions, can be used instead of N_{part} in experiments. Preliminary HADES data show significant differences to both, UrQMD simulations and STAR data in this respect.

Lee–Yang Zeroes in the Baryon Fugacity Plane: The Role of High Densities

We compute the canonical partition functions and the Lee–Yang zeros in Nf=2 lattice QCD at temperature T=1.20Tc lying above the Roberge–Weiss phase transition temperature TRW. The phase transition is characterized by the discontinuities in the baryon number density at specific values of imaginary baryon chemical potential. We further develop our method to compute the canonical partition functions using the asymptotic expression for respective integral. Then, we compute the Lee–Yang zeros and study their behavior in the limit of high baryon density.

Cosmological Lithium Solution from Discrete Gauged B-L.

The cosmological lithium problem-that theory predicts a primordial abundance far higher than the observed value-has resisted decades of attempts by cosmologists, nuclear physicists, and astronomers alike to root out systematics. We reconsider this problem in the setting of the standard model extended by gauged baryon minus lepton number, which we spontaneously break by a scalar with charge six. Cosmic strings from this breaking can support interactions converting three protons into three positrons, and we argue that an "electric"-"magnetic" interplay can give this process an amplified, strong-scale cross section in an analog of the Callan-Rubakov effect. We suggest such cosmic strings have disintegrated O(1) of the primordial lithium nuclei, and lay out what is necessary for this scheme to succeed. To our knowledge this is the first new physics mechanism with microphysical justification for the abundance of lithium uniquely to be modified after big bang nucleosynthesis.

X-Ray Detection of the Galaxy’s Missing Baryons in the Circumgalactic Medium of L* Galaxies

The number of baryons hosted in the disks of galaxies is lower than expected based on the mass of their dark matter halos and the fraction of baryon-to-total matter in the Universe, giving rise to the so-called galaxy missing-baryon problem. The presence of cool circumgalactic matter gravitationally bound to its galaxy’s halo up to distances of at least 10 times the size of the galaxy’s disk mitigates the problem but is far from being sufficient for its solution. It has instead been suggested that the galaxy’s missing baryons may hide in a much hotter gaseous phase of the circumgalactic medium, possibly near the halo virial temperature and coexisting with the cool phase. Here we exploit the best available X-ray spectra of known cool circumgalactic absorbers of L* galaxies to report the first direct high statistical significance (best estimates ranging from 4.2σ to 5.6σ, depending on fitting methodology) detection of associated O vii absorption in the stacked XMM-Newton and Chandra spectra of three quasars. We show that these absorbers trace the hot medium in the X-ray halo of these systems at logT(in K) ≃ 5.8–6.3 (comprising the halo virial temperature T vir ≃ 106 K). We estimate masses of the X-ray halo within one virial radius within the interval M ⊙. For these systems, this corresponds to galaxy missing-baryon fractions in the range , thus potentially closing the galaxy baryon census in typical L* galaxies. Our measurements contribute significantly to the solution of the long-standing galaxy missing-baryon problem and to the understanding of the continuous cycle of baryons in-and-out of galaxies throughout the life of the Universe.

Supersymmetric baryogenesis in a hybrid inflation model

We study baryogenesis in a hybrid inflation model which is embedded to the minimal supersymmetric model with right-handed neutrinos. Inflation is induced by a linear combination of the right-handed sneutrinos and its decay reheats the universe. The decay products are stored in conserved numbers, which are transported under the interactions in equilibrium as the temperature drops down. We find that at least a few percent of the initial lepton asymmetry is left under the strong wash-out due to the lighter right-handed (s)neutrinos. To account for the observed baryon number and the active neutrino masses after a successful inflation, the inflaton mass and the Majorana mass scale should be 1013 GeV and mathcal{O} (109–1010) GeV, respectively.

Net-Baryon Probability Distributions from Lattice Simulations

We use the results of lattice simulations of the net-baryon number density at imaginary baryon chemical potential in Nf=2 QCD to construct the equation of state of dense and hot strong-interacting matter both above the Roberge–Weiss temperature T>TRW and below the critical temperature T<Tc. For these cases, we also evaluate probability distributions of the net-baryon number, as well as the respective cumulants and moments. The consequences of the asymptotic behavior of these probability distributions for the problem of reconstruction of the net-baryon probability distributions from cumulants are discussed.

Semi-inclusive decays of B meson into a dark anti-baryon and baryons

Using the recently developed B-Mesogenesis scenario, we studied the semi-inclusive decays of B meson into a dark anti-baryon psi plus any possible states X containing u/c and d/s quarks with unit baryon number. The two types of effective Lagrangians proposed by the scenario are both considered in the study. The semi-inclusive decay branching fractions of Brightarrow X psi are calculated by the method of heavy quark expansion, where the non-perturbative contributions from the matrix elements of dimension-5 operators are included. We obtained the branching fractions as functions of the dark anti-baryon mass. Using the experimental upper limits of the branching fractions, we presented the constraints of the coupling constants in the B-Mesogenesis scenario.

Holographic study of higher-order baryon number susceptibilities at finite temperature and density

Holographic study of higher-order baryon number susceptibilities at finite temperature and density

Masses and magnetic moments of exotic fully heavy pentaquarks

Inspired by the observation of a resonant state X(6600) of fully charm tetraquark by the CMS experiment of LHCb Collaboration in double J/psi decay channel, we perform a systematical study of all configurations of fully heavy pentaquarks P_{Q_{1}Q_{2}Q_{3}Q_{{4}}bar{Q_{5}}} (Q_{i}=c,b, i=1,2,3,4,5) in their ground states in unified framework of MIT bag model. The color-spin wavefunctions of pentaquarks, classified via Young tableau and presented in terms of the Young–Yamanouchi bases, are used to compute masses and magnetic moments of fully heavy pentaquarks via numerical variational method, predicting a set of masses ranging from 8.229 GeV for the P_{ccccbar{c}} to 24.770 GeV for the P_{bbbbbar{b}}. Combining with computed masses of fully heavy mesons and baryons, we find that masses of fully heavy hadrons(mesons, baryons, tetraquarks and pentaquarks) with identical flavor rise almost linearly with the number of valence quarks in hadrons, being consistent with the heavy quark symmetry in the heavy-quark limit.

Inferring nuclear structure from heavy isobar collisions using Trajectum

Nuclei with equal number of baryons but varying proton number (isobars) have many commonalities, but differ in both electric charge and nuclear structure. Relativistic collisions of such isobars provide unique opportunities to study the variation of the magnetic field, provided the nuclear structure is well understood. In this work we simulate collisions using several state-of-the-art parametrizations of the ^{96}_{40}4096Zr and ^{96}_{44}4496Ru isobars and show that a comparison with the exciting STAR measurement [arXiv:2109.00131] of ultrarelativistic collisions can uniquely identify the structure of both isobars. This not only provides an urgently needed understanding of the structure of the Zirconium and Ruthenium isobars, but also paves the way for more detailed studies of nuclear structure using relativistic heavy ion collisions.

Study of baryon number transport using model simulations in pp collisions at LHC energies

Study of baryon number transport using model simulations in pp collisions at LHC energies

Multi-skyrmion states in the Skyrme model with a false vacuum potential* *Y. L. M. was supported in part by the National Science Foundation of China (11875147, 12147103).

We study multi-skyrmion states using the Skyrme model with a false vacuum potential up to baryon number using the product ansatz. It is found that both the false and true vacuum potentials can result in a cluster structure for the multi-skyrmion states. We also analyze the effect of explicit chiral breaking on the masses and contour surfaces of the baryon number density of the multi-skyrmion states.

Electroweak baryogenesis between broken phases in multi-step phase transition

Possibility of electroweak baryogenesis (EWBG) via multi-step phase transition (PT) is considered. We investigate the EWBG between SU(2) broken phases in the second step PT of the two-step PT. The produced baryon number asymmetry is evaluated using a prototypical model with a SU(2) charged CP-odd scalar field. We show that the second step PTs where the sphaleron rate is possible to be un-suppressed before the PTs, which can reproduce the sufficient baryon number asymmetry. Our studies can be adapted to models with extra SU(2) scalar fields. We discuss specific models suitable for our scenario.

Gauged Le − Lμ − Lτ symmetry, fourth generation, neutrino mass and dark matter

We present two models where the familiar leptonic symmetry Le−Lμ−Lτ is a gauge symmetry. We show how anomaly cancellation constrains the allowed theories, with one of them requiring a fourth sequential chiral standard model fermion generation and a second one with three generations, requiring gauging of (Le−Lμ−Lτ)−(B1−B2−B3) with Ba representing the baryon number of the ath generation quarks. Unlike global Le−Lμ−Lτ models which always leads to inverted mass hierarchy for neutrinos, the gauged version can lead to normal hierarchy. We show how to construct realistic models in both the cases and discuss the dark matter candidate in both. In our model, the breaking of U(1)Le−Lμ−Lτ is responsible for neutrino mass via type-I mechanism whereas the real part of U(1)Le−Lμ−Lτ breaking scalar field (called ϕ here) plays the role of freeze-in dark matter candidate. Since ϕ is unstable, for it to qualify as dark matter, its lifetime must be larger than the age of the Universe, implying that the relic of ϕ is generated through freeze-in mechanism and its mass must be less than an MeV. We also discuss the possibility of explaining both muon and electron g−2 while being consistent with the DM relic density and lifetime constraints.

New insights into the limit of the magnetic monopole flux and the heating source in white dwarfs* *Supported in part by the National Natural Science Foundation of China (11965010, 11565020), the Natural Science Foundation of Hainan Province of China (118MS071, 2019RC239), the Counterpart Foundation of Sanya (2016PT43, 2019PT76), the Special Foundation of Science and Technology Cooperation for Advanced Academy and

Based on the magnetic monopole (MM) catalytic nuclear decay (Rubakov-Callan (RC) effect), we propose five new models to discuss the limit of the MM flux and the heating energy resources of white dwarfs (WDs) based on observations of 13 red giant branch (RGB) stars. We find that the number of MMs captured can reach a maximum value of when GeV, , . The good agreement of our calculated luminosities for WDs with observation provides support for our model based on the RC effect by MMs. We obtain a new limit of the MM flux of , and at when , , and , respectively. Our results show that the RC effect could cause heating that prevents white dwarfs from cooling down into a stellar graveyard. Our results will also provide a new idea for further research on the upper limit of MM flow (note: are the baryon number density, reaction cross section, mass, MM flux, and the new limit of the MM flux, respectively, and is the ratio of the speed of MMs to that of light).

A Variational Approach to Resistive General Relativistic Two-Temperature Plasmas

We develop an action principle to construct the field equations for dissipative/resistive general relativistic two-temperature plasmas, including a neutrally charged component. The total action is a combination of four pieces: an action for a multifluid/plasma system with dissipation/resistivity and entrainment; the Maxwell action for the electromagnetic field; the Coulomb action with a minimal coupling of the four-potential to the charged fluxes; and the Einstein–Hilbert action for gravity (with the metric being minimally coupled to the other action pieces). We use a pull-back formalism from spacetime to abstract matter spaces to build unconstrained variations for the neutral, positively, and negatively charged fluid species and for three associated entropy flows. The full suite of field equations is recast in the so-called “3+1” form (suitable for numerical simulations), where spacetime is broken up into a foliation of spacelike hypersurfaces and a prescribed “flow-of-time”. A previously constructed phenomenological model for the resistivity is updated to include the modified heat flow and the presence of a neutrally charged species. We impose baryon number and charge conservation as well as the Second Law of Thermodynamics in order to constrain the number of free parameters in the resistivity. Finally, we take the Newtonian limit of the “3+1” form of the field equations, which can be compared to existing non-relativistic formulations. Applications include main sequence stars, neutron star interiors, accretion disks, and the early universe.

Chiral Nelson-Barr models: Quality and cosmology

It was recently shown that domain walls from the spontaneous breaking of CP symmetry are exactly stable, and must be inflated away to recover a viable cosmology. We investigate the phenomenological implications of this result in Nelson--Barr solutions of the strong CP problem. Combined with the upper bound on the scale of spontaneous CP breaking necessary to suppress contributions from dangerous, nonrenormalizable operators to $\bar{\theta}$, this puts an upper bound on the scale of inflation and the reheating temperature after inflation. Minimal Nelson--Barr models are therefore in tension with thermal leptogenesis, models of large-field inflation, or potential future observations of signals from topological remnants of an unrelated, subsequent phase transition. We study how extending Nelson--Barr models with a new, continuous chiral gauge symmetry can ameliorate this tension by forbidding the dangerous dimension-five operators. In particular, we show that gauging a linear combination of baryon number and hypercharge allows for an economic, anomaly-free extension of the minimal Nelson--Barr model, and discuss the phenomenological implications.

Light (anti)nuclei production in Pb-Pb collisions at sNN=5.02 TeV

The measurement of the production of deuterons, tritons and He3 and their antiparticles in Pb-Pb collisions at sNN=5.02TeV is presented in this article. The measurements are carried out at midrapidity (|y|< 0.5) as a function of collision centrality using the ALICE detector. The pT-integrated yields, the coalescence parameters and the ratios to protons and antiprotons are reported and compared with nucleosynthesis models. The comparison of these results in different collision systems at different center-of-mass collision energies reveals a suppression of nucleus production in small systems. In the Statistical Hadronisation Model framework, this can be explained by a small correlation volume where the baryon number is conserved, as already shown in previous fluctuation analyses. However, a different size of the correlation volume is required to describe the proton yields in the same data sets. The coalescence model can describe this suppression by the fact that the wave functions of the nuclei are large and the fireball size starts to become comparable and even much smaller than the actual nucleus at low multiplicities.Received 10 February 2023Accepted 16 May 2023DOI:https://doi.org/10.1103/PhysRevC.107.064904Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.©2023 CERN, for the ALICE CollaborationPhysics Subject Headings (PhySH)Research AreasParticle & resonance productionParticle correlations & fluctuationsRelativistic heavy-ion collisionsPropertiesA ≤ 5Accelerators & BeamsNuclear Physics

Possibility of antiquark nuggets detection using meteor searching radars

Within the quark nugget model, dark matter particles may be represented by compact composite objects composed of a large number of quarks or antiquarks. Due to strong interaction with visible matter, antiquark nuggets should manifest themselves in the form of rare atmospheric events on the Earth. They may produce ionized trails in the atmosphere similar to the meteor trails. There are, however, several features which should allow one to distinguish antiquark nugget trails from meteor ones. We study the properties of ionized trails from antiquark nuggets in the air and show that they may be registered by standard meteor radar detectors. Non-observation of such trails pushes up the mean baryon charge number in the quark nugget model, $|B|>4\times 10^{27}$.