Search

Latest measurements of $\Delta\eta\Delta\varphi$ correlations of identified particles show differences in particle production between baryons and mesons. The correlation functions for mesons exhibit the expected peak dominated by effects of mini-jet fragmentation and are reproduced well by general purpose Monte Carlo generators. For baryon pairs (where both particles have the same baryon number) a surprising near-side anti-correlation structure is observed instead of a peak, implying that two such particles are rarely produced with similar momentum. These results present a challenge to the contemporary models and there is no definite theoretical explanation of the observation. In this proceedings an overview of the latest baryon correlation measurements yielding startling results are presented., Comment: Proceedings of ISMD2019 Conference, Santa Fe, USA

Highly energetic proton/electron beam fixed target experiments extends an opportunity to probe the sub-GeV dark matter and associated interactions. In this work we have explored the sensitivity of DUNE for sub-GeV leptophobic dark matter i.e. this dark matter barely couples with the leptons. Baryon number gauge theory can predicts the existence of a leptophobic cold dark matter particle candidates. In our work, the dark matter candidate is considered to be scalar whose mass is defined by the symmetry breaking of new baryonic gauge group $U(1)_{B}$. In this scenario a light scalar dark matter couples with the standard model candidates via vector boson mediator $V_{B}$ which belongs to the baryonic gauge group $U(1)_{B}$. This leptophobic dark matter dominantly couples to the quarks. Under this scenario new parameter space for $\alpha_{B}$ is explored by DUNE for leptophobic dark matter candidates. This new parameter space allowed $\alpha_{B}$ to get lower value than the present exiting constraint value of $\alpha_{B}$ i.e. $10^{-6}$., Comment: 11, 3

Michael Atiyah’s interest in Skyrmions and their relationship to monopoles and instantons is recalled. Some approximate models of Skyrmions with large baryon numbers are then considered. Skyrmions having particularly strong binding are clusters of unit baryon number Skyrmions arranged as truncated tetrahedra. Their baryon numbers, $B = 4 \,, 16 \,, 40 \,, 80 \,, 140 \,, 224$, are the tetrahedral numbers multiplied by four, agreeing with the magic proton and neutron numbers $2 \,, 8 \,, 20 \,, 40 \,, 70 \,, 112$ occurring in the nuclear shell model in the absence of strong spin-orbit coupling.

The breakdown of SU(6) global symmetry down to its SU(5) subgroup near the scale f > 10 TeV in the strongly interacting sector within the E_6 inspired composite Higgs model (E6CHM) gives rise to a set of pseudo-Nambu-Goldstone bosons (pNGBs) that involves one Standard Model (SM) singlet scalar, a SM-like Higgs doublet and an SU(3)_C triplet of scalar fields, $T$. We argue that the baryon number violation in the E6CHM can induce the observed matter-antimatter asymmetry if CP is violated. The coloured triplet of scalar fields with mass in the few TeV range plays a key role in this process and may lead to a distinct new physics signal that can be detected at the LHC in the near future., Presented at International Bogolyubov Conference "Problems of Theoretical and Mathematical Physics", Moscow-Dubna, Russia, 9 - 13 September, 2019. arXiv admin note: substantial text overlap with arXiv:1808.01982

We propose a new description of a baryon as a pair of mesons. This description is an extension of the previously proposed description of a nucleon as a pair of pions. The purpose of this article is to show the following two possibilities. The first one is that it shows the qualitative explanation to support our description of a nucleon as a pair of pions and the second one is that it gives the systematic way of estimation of baryon mass not only for light baryons but also for heavy baryons (charm baryons and bottom baryons). Each isospin group is constructed of both baryons and antibaryons. This way of construction is consistent with that of mesons. The results obtained are listed in tables (Tables 1-9). This shows that the generalized Gell-Mann-Nishijima relation equation holds under the condition that the baryon number is 0 and that the obtained masses are fairly good, even for heavy baryons. Our description also yields several examples of baryon decay modes.

We propose a new description of a nucleon as a pair of pions. The baryon number of our description of nucleon is not 1 but 0. However, this is probable because the proton spin crisis shows that the baryon spin cannot tell the number of composing quarks anymore. Because we use the derived pion wave function to describe a nucleon, our description has automatically the pionic degree of freedom and can be compared to the constituent quark model. Using this description, we investigate the electric charge and magnetization density functions of protons and neutrons. The electric charge density function of neutron is quite similar to those of Galster model and Maints data except the magnitude of singularity. The density functions of proton also show the similar behavior as those of Kelly’s except near origin. Taking the Fourier transform of the density functions, we obtain the Sachs electromagnetic form factors that can be compared to those in the parametrization derived by Ye et al.

We study the baryonic fluctuations of electric charge, baryon number and strangeness, by considering a realization of the Hadron Resonance Gas model in the light flavor sector of QCD. We elaborate on the idea that the susceptibilities can be saturated with excited baryonic states with a quark-diquark structure with a linearly confining interaction identical up to a constant to the quark-antiquark potential, V q D ′ ( r ) = V q q ‾ ′ ( r ) . We obtain an overall good agreement with the spectrum obtained with other quark models and with lattice data for the fluctuations.

Fluctuations of conserved charges are sensitive to the QCD phase transition and a possible critical endpoint in the phase diagram at finite density. In this work, we compute the baryon number fluctuations up to tenth order at finite temperature and density. This is done in a QCD-assisted effective theory that accurately captures the quantum- and in-medium effects of QCD at low energies. A direct computation at finite density allows us to assess the applicability of expansions around vanishing density. By using different freeze-out scenarios in heavy-ion collisions, we translate these results into baryon number fluctuations as a function of collision energy. We show that a non-monotonic energy dependence of baryon number fluctuations can arise in the non-critical crossover region of the phase diagram. Our results compare well with recent experimental measurements of the kurtosis and the sixth-order cumulant of the net-proton distribution from the STAR collaboration. They indicate that the experimentally observed non-monotonic energy dependence of fourth-order net-proton fluctuations is highly non-trivial. It could be an experimental signature of an increasingly sharp chiral crossover and may indicate a QCD critical point. The physics implications and necessary upgrades of our analysis are discussed in detail., Comment: 23 pages, 14 figures, 2 tables, published version

In order to address the baryon asymmetry in the Universe one needs to understand the origin of baryon and lepton number violation. In this article, we discuss the mechanism of baryogenesis via leptogenesis to explain the matter-antimatter asymmetry in theories with spontaneous breaking of baryon and lepton number. In this context, a lepton asymmetry is generated through the out-of-equilibrium decays of right-handed neutrinos at the high-scale, while local baryon number must be broken below the multi-TeV scale to satisfy the cosmological bounds on the dark matter relic density. We demonstrate how the lepton asymmetry generated via leptogenesis can be converted in two different ways: (a) in the theory predicting Majorana dark matter the lepton asymmetry is converted into a baryon asymmetry, and (b) in the theory with Dirac dark matter the decays of right-handed neutrinos can generate lepton and dark matter asymmetries that are then partially converted into a baryon asymmetry. Consequently, we show how to explain the matter-antimatter asymmetry, the dark matter relic density and neutrino masses in theories for local baryon and lepton number.

We present a strangeness-neutral equation of state for QCD that exhibits critical behavior and matches lattice QCD results for the Taylor-expanded thermodynamic variables up to fourth order in $$\mu _B/T$$ . It is compatible with the SMASH hadronic transport approach and has a range of temperatures and baryonic chemical potentials relevant for phase II of the Beam Energy Scan at RHIC. We provide an updated version of the software BES-EoS, which produces an equation of state for QCD that includes a critical point in the 3D Ising model universality class. This new version also includes isentropic trajectories and the critical contribution to the correlation length. Since heavy-ion collisions have zero global net-strangeness density and a fixed ratio of electric charge to baryon number, the BES-EoS is more suitable to describe this system. Comparison with the previous version of the EoS is thoroughly discussed.

Motivated by the recent lattice study, thermal masses of the baryon parity-doublers are explored for various pion masses. A general trend of the nucleon and delta parity-doublers is consistent with the lattice QCD results, whereas hyperon masses exhibit a qualitatively different behavior, traced back to the lattice set-up with m π / m K ∼ 1 . We further investigate the fluctuations and correlations involving baryon number in hot hadronic matter with modified masses of negative-parity baryons, in the context of the hadron resonance gas. Confronting the baryon number susceptibility, baryon-charge correlation, and baryon-strangeness correlation and their ratios with the lattice QCD data, we show that the strong downward mass shift in the hyperons can accidentally reproduce some correlation ratios, however it also tends to overshoot the individual fluctuations and correlations. This indicates that in order to correctly account for the influence of the chiral symmetry restoration on the fluctuation observables, a consistent framework of in-medium effects beyond hadron mass shifts is required.

In the vicinity of the QCD phase boundary, the thermodynamic pressure receives contributions from a regular component Pr and a non-analytic component Ps. Pr describes the bulk properties of the QCD thermodynamics, whereas Ps carries information on chiral criticality. We discuss the computation of Pr in the hadronic phase within the S-matrix formulation of statistical mechanics, and the determination of Ps using high-order cumulants of net baryon number fluctuations. We show that the S-matrix approach provides a consistent description to both the lattice QCD results on the baryon electric charge correlation and on the proton production yield in heavy ion collisions at the LHC. In addition, it is suggested that chiral criticality is reflected in the energy dependence of certain ratios of net baryon number fluctuations.

In an $SU(2)_R$ extension of the standard model, it is shown how the neutral fermion $N$ in the doublet $(N,e)_R$ may be assigned baryon number $B=1$, in contrast to its $SU(2)_L$ counterpart $\nu$ in the doublet $(\nu,e)_L$ which has lepton number $L=1$. This baryon-lepton duplicity allows a scalar $\sigma$ which couples to $N_L N_L$ to be long-lived dark matter., Comment: 12 pages, 1 figure (published version)

In the context of the ongoing search for the QCD critical point at the Relativistic Heavy-Ion Collider, we study the equation of state near the critical point in the temperature and baryon chemical potential plane. We use the parametric representation introduced in earlier literature, which maps the universal 3D Ising equation of state onto the QCD phase diagram using several non-universal parameters. We focus on the quartic cumulant of the baryon number, or baryon number susceptibility~$\chi_4^B$, which can be accessed experimentally via net-proton fluctuation kurtosis measurements. It was originally predicted, through universality arguments based on the {\em leading} singular contribution, that $\chi_4^B$ and net-proton kurtosis should show a specific non-monotonic behavior due to the critical point. In particular, when following the freeze-out curve on the phase diagram by decreasing beam energy, the kurtosis is expected to dip, and then peak, when the beam energy scan passes close to the critical point. We study the effects of the non-universal and thus far unknown parameters of the Ising-to-QCD mapping on the behavior of~$\chi_4^B$. We find that, while the peak remains a solid feature, the presence of the critical point does not necessarily cause a dip in $\chi_4^B$ on the freezeout line {\em below} the transition temperature. The critical point contribution to the dip appears only for a narrow set of mapping parameters, when subleading singular terms are sufficiently suppressed., Comment: 10 pages, 4 figures

Composite Higgs models can be extended to the Planck scale by means of the partially unified partial compositeness (PUPC) framework. We present in detail the Techni-Pati-Salam model, based on a renormalizable gauge theory SU(8)PS×SU(2)L×SU(2)R. We demonstrate that masses and mixings for all generations of standard model fermions can be obtained via partial compositeness at low energy, with four-fermion operators mediated by either heavy gauge bosons or scalars. The strong dynamics is predicted to be that of a confining Sp(4)HC gauge group, with hyperfermions in the fundamental and two-index antisymmetric representations, with fixed multiplicities. This is motivation for lattice studies of the infrared near-conformal walking phase, with results that may validate or rule out the model. This is the first complete and realistic attempt at providing an ultraviolet completion for composite Higgs models with top partial compositeness. In the baryon-number conserving vacuum, the theory also predicts a dark matter candidate, with a mass in the few TeV range, protected by semi-integer baryon number.

The electroweak penguin B decays mediated by $b \to s \ell^+ \ell^- $ transitions are flavour-changing neutral current processes, and are thus sensitive to new physics owing to potential contributions of heavy particles in the quantum loop. Recently, LHCb has obtained interesting results, where the possible hints of lepton family universality violation (LFUV) could be seen. We report a new measurement of the LFUV observable $R_{K}$, the ratio of branching fractions of $B\to K\mu^{+}\mu^{-}$ to $B\to Ke^{+}e^{-}$, based on the full data sample recorded by Belle at the $\Upsilon(4S)$ resonance from $e^+e^-$ collisions produced by the KEKB collider. We also report results on lepton flavor violating $B$ decays, $B^{+}\to K^{+}\mu^{\pm}e^{\mp}$ and $B^{0}\to K_{S}^{0}\mu^{\pm}e^{\mp}$. The $B$-factory at KEK is also a $\tau$ factory, creating a copious amount of $\tau\tau$ pairs. We have used these data to look for lepton and baryon number violating $ \tau$ decays $\tau^{-}\to\overline{p}e^{+}e^{-}$, $pe^{-}e^{-}$, $\overline{p}e^{+}\mu^{-}$, $\overline{p}e^{-}\mu^{+}$, $\overline{p}\mu^{+}\mu^{-}$, and $p\mu^{-}\mu^{-}$. Results of the search are also reported.

Neutron-anti-neutron $(n- \bar n)$ oscillation is a baryon number violating process that requires physics beyond the Standard model. Future experiments at ESS and DUNE aim to either discover $(n- \bar n)$ oscillation or to put more stringent constraints on the oscillation time. We study the impact of such a discovery on different baryogenesis scenarios using an effective field theory framework for $(n- \bar n)$ oscillation. We also study the implications of observing the mediators at the LHC and the possibility of falsifying some of the baryogenesis scenarios in the context of some simplified UV complete scenarios.

We present a testable mechanism of low-scale baryogenesis and dark matter production in which neither baryon nor lepton number are violated. Charged $D$ mesons are produced out-of-equilibrium at tens of MeV temperatures. The $D$ mesons quickly undergo CP-violating decays to charged pions, which then decay into dark-sector leptons without violating lepton number. To transfer this lepton asymmetry to the baryon asymmetry, the dark leptons scatter on additional dark-sector states charged under lepton and baryon number. Amusingly, this transfer proceeds without electroweak sphalerons, which are no longer active at such low scales. We present two example models which can achieve this transfer while remaining consistent with current limits. The required amount of CP violation in charged $D$ meson decays, while currently allowed, will be probed by colliders. Additionally, the relevant decays of charged pions to dark-sector leptons have been constrained by the PIENU and PSI experiments and will be further explored in upcoming experiments., 10+5 pages, 3 figures; v2: corrected PIENU bound (no change to results); v3: published in PRD with minor revisions (no change to results)

In models of baryogenesis based on Grand Unified Theories (GUTs), the baryon asymmetry of the universe is generated through the CP and baryon number violating, out-of-equilibrium decays of very massive gauge or Higgs bosons in the very early universe. Recent constraints on the scale of inflation and the subsequent temperature of reheating, however, have put pressure on many such models. In this paper, we consider the role that primordial black holes may have played in the process of GUT baryogenesis. Through Hawking evaporation, black holes can efficiently generate GUT Higgs or gauge bosons, regardless of the masses of these particles or the temperature of the early universe. Furthermore, in significant regions of parameter space, the black holes evaporate after the electroweak phase transition, naturally evading the problem of sphaleron washout that is normally encountered in GUT models based on $SU(5)$. We identify a wide range of scenarios in which black holes could facilitate the generation of the baryon asymmetry through the production and decays of GUT bosons., 12 pages, 4 figures, 1 appendix

This paper deals with spherically symmetric static solutions of the relativistic field equation which represents a perfect fluid ball with given equation of state and given baryon number. We prove existence of solutions for baryon numbers that do not exceed a limiting number determined by the equation of state. The proof is based on energy minimization under the given baryon number constraint.

Improved limits for new gravity-like short-range interactions, in which a scattering potential is modeled by the Yukawa-type parametrization, have been obtained by measuring the angular distribution of 6 \AA\ neutrons scattering from atomic xenon gas. We have collected approximately $1.4 \times 10^8$ small-angle neutron scattering events. The data are interpreted as no evidence of new forces and show improved upper limits on the coupling strength in the interaction range of $0.3$ nm to $9$ nm. These improved constraints are also interpreted as new limits for a model, in which a charge of the new forces is expressed as a linear combination of the baryon number and the lepton number., Comment: 8 pages, 2 figures, 14TH ASIA-PACIFIC PHYSICS CONFERENCE (APPC2019)

We present results on the second-order fluctuations of and correlations among net baryon number, electric charge and strangeness in (2+1)-flavor lattice QCD in the presence of a background magnetic field. Simulations are performed using the tree-level improved gauge action and the highly improved staggered quark (HISQ) action with a fixed scale approach ($a\simeq$ 0.117 fm). The light quark mass is set to be 1/10 of the physical strange quark mass and the corresponding pion mass is about 220 MeV at vanishing magnetic field. Simulations are performed on $32^3\times N_\tau$ lattices with 9 values of $N_\tau$ varying from 96 to 6 corresponding to temperatures ranging from zero up to 281 MeV. The magnetic field strength $eB$ is simulated with 15 different values up to $\sim$2.5 GeV$^2$ at each nonzero temperature. We find that quadratic fluctuations and correlations do not show any singular behavior at zero temperature in the current window of $eB$ while they develop peaked structures at nonzero temperatures as $eB$ grows. By comparing the electric charge-related fluctuations and correlations with hadron resonance gas model calculations and ideal gas limits we find that the changes in degrees of freedom start at lower temperatures in stronger magnetic fields. Significant effects induced by magnetic fields on the isospin symmetry and ratios of net baryon number and baryon-strangeness correlation to strangeness fluctuation are observed, which could be useful for probing the existence of a magnetic field in heavy-ion collision experiments., Comment: 12 pages, 7 figures, invited contribution to The European Physical Journal A-Hadrons and Nuclei: Topical Issue on "QCD Phase Diagram in Strong Magnetic Fields", minor revision

Strangeness enhancement is proposed as a signature of QGP formation in high-energy nuclear collisions. The observed relative yield enhancements of hadrons increase with the strangeness content but not with the mass and baryon number of the hadron. To understand this behavior, we have studied on the simulation models. We have found the models EPOS and AMPT are not able to explain simultaneously the effect of strangeness canonical suppression in low-multiplicity events and QGP-like effect in high-multiplicity pp collisions at LHC energies.

We study the bilinear and higher-order fermion condensates in $4$-dimensional $SU(N)$ gauge theories with a single Dirac fermion in a general representation. Augmented with a mixed anomaly between the $0$-form discrete chiral, $1$-form center, and $0$-form baryon number symmetries (BC anomaly), we sort out theories that admit higher-order condensates and vanishing fermion bilinears. Then, the BC anomaly is utilized to prove, in the absence of a topological quantum field theory, that nonvanishing fermion bilinears are inevitable in infrared-gapped theories with $2$-index (anti)symmetric fermions. We also contrast the BC anomaly with the $0$-form anomalies and show that it is the former anomaly that determines the infrared physics; we argue that the BC anomaly lurks deep to the infrared while the $0$-form anomalies are just variations of local terms. We provide evidence of this assertion by studying the BC anomaly in vector-like theories compactified on a small spacial circle. These theories are weakly-coupled, under analytical control, and they admit a dual description in terms of abelian photons that determine the deep infrared dynamics. We show that the dual photons talk directly to the $1$-form center symmetry in order to match the BC anomaly, while the $0$-form anomalies are variations of local terms and are matched by fiat. Finally, we study the fate of the BC anomaly in the compactified theories when they are held at a finite temperature. The effective field theory that describes the low-energy physics is $2$-dimensional. We show that the BC anomaly cascades from $4$ to $2$ dimensions., Comment: 29 pages, 2 figures

Baryon number is an accidental symmetry in the standard model, while Peccei-Quinn symmetry is hypothetical symmetry which is introduced to solve the strong CP problem. We study the possible connections between Peccei-Quinn symmetry and baryon number symmetry. In this framework, an axion is identified as the Nambu-Goldstone boson of baryon number violation. As a result, characteristic baryon number violating processes are predicted. We developed the general method to determine the baryon number and lepton number of new scalar in the axion model., Comment: 19 pages, 6 figures, version accepted in PRD

In this paper, we consider the possibilities of generating baryon number asymmetry in thermal equilibrium within the frameworks of teleparallel and symmetric teleparallel gravities. Through the derivative couplings of the torsion scalar or the non-metricity scalar to baryons, the baryon number asymmetry is indeed 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. But the gravitational leptogenesis models within both frameworks have the possibilities to interpret the observed baryon-antibaryon asymmetry., Comment: 7 pages, to be published in Chinese Physics C

The appearance of large, none-Gaussian cumulants of the baryon number distribution is commonly discussed as a signal for the QCD critical point. We review the status of the Taylor expansion of cumulant ratios of baryon number fluctuations along the freeze-out line and also compare QCD results with the corresponding proton number fluctuations as measured by the STAR Collaboration at RHIC. To further constrain the location of a possible QCD critical point we discuss poles of the baryon number fluctuations in the complex plane. Here we use not only the Taylor coefficients obtained at zero chemical potential but perform also calculations of Taylor expansion coefficients of the pressure at purely imaginary chemical potentials., Comment: 10 pages, 5 figures, talk presented at the Workshop "Criticality in QCD and the Hadron Resonance Gas", 29-31 July 2020, Online

The baryon asymmetry of the universe may be explained by rotations of the QCD axion in field space and baryon number violating processes. We consider the minimal extension of the Standard Model by a non-Abelian gauge interaction, $SU(2)_R$, whose sphaleron process violates baryon number. Assuming that axion dark matter is also created from the axion rotation by the kinetic misalignment mechanism, the mass scale of the $SU(2)_R$ gauge boson is fixed as a function of the QCD axion decay constant, and vise versa. Significant portion of the parameter space has already been excluded by new gauge boson searches, and the high-luminocity LHC will further probe the viable parameter space., Comment: 30 pages, 1 figure

Studying fluctuations of conserved quantities, such as baryon number (B), strangeness (S) and electric charge (Q), provides insights into the bulk properties of matter created in high-energy nuclear collisions. The higher moments of multiplicity distributions of net proton, net kaon and net charge are expected to show large fluctuations near the QCD critical point. We present results on energy and centrality dependence of higher moments of net proton, net kaon and net charge multiplicity distribution over all BES-I energies from the STAR experiment. The net proton moments product (\(S\sigma \) and \(\kappa \sigma ^{2}\)) shows deviations from Poisson baseline (unity) in the lower beam energy region (below \(\sqrt{s_{\mathrm {NN}}}\) = 27 GeV). In the most central (0–5%) collisions, the \(\kappa \sigma ^{2}\) of net proton distribution as a function of collision energy exhibit a non-monotonic behaviour and show deviation in the lower energy region from corresponding predictions from Poisson baseline, a transport model (UrQMD) and a thermal model, all of which do not include any physics of criticality.

This paper reviews our recent findings on the dynamics of transport of baryon number in proton-induced reactions at the CERN SPS. These are put in a more general context of the present understanding of baryon stopping phenomena up to LHC and cosmic ray energies. The implications of our studies, advantages to be provided by modern and high quality experimental data, and perspectives of new measurements are shortly discussed., Comment: 24 pages, 6 figures

We propose a new mechanism where asymmetric dark matter (ADM) and the baryon asymmetry are both generated in the same decay chain of a metastable weakly interacting massive particle (WIMP) after its thermal freeze-out. Dark matter and baryons are connected by a generalized baryon number that is conserved, while the DM asymmetry and baryon asymmetry compensate each other. This unified framework addresses the DM-baryon coincidence while inheriting the merit of the conventional WIMP miracle in predicting relic abundances of matter. Examples of renormalizable models realizing this scenario are presented. These models generically predict ADM with sub-GeV to GeV-scale mass that interacts with Standard Model quarks or leptons, thus rendering potential signatures at direct detection experiments sensitive to low mass DM. Other interesting phenomenological predictions are also discussed, including: LHC signatures of new intermediate particles with color or electroweak charge and DM induced nucleon decay; the long-lived WIMP may be within reach of future high energy collider experiments., Comment: 21 pages, 16 figures, 1 appendix. Freezeout mechanism changed. Matches version published in JHEP

We study the hadron-quark hybrid equation of state (EOS) of compact-star matter. The Nambu—Jona-Lasinio (NJL) local SU(3) model with vector-type interaction is used to describe the quark matter phase, while the relativistic mean field (RMF) theory with scalar-isovector $\delta$-meson effective field adopted to describe the hadronic matter phase. It is shown that the larger the vector coupling constant, the lower the threshold density for the appearance of strange quarks. For a sufficiently small value of the vector coupling constant, the functions of the mass dependence on the baryonic chemical potential have regions of ambiguity which leads to a phase transition in non-strange quark matter with an abrupt change in the baryon number density. We show that within the framework of the NJL model, the hypothesis on the absolute stability of strange quark matter is not realized. In order to describe the phase transition from hadronic matter to quark matter, the Maxwell's construction is applied. It is shown that the greater the vector coupling, the greater the stiffness of the EOS for quark matter and the phase transition pressure. Our results indicate that the infinitesimal core of the quark phase, formed in the center of the neutron star, is stable.

Quark matter with only $u$ and $d$ quarks ($ud$QM) might be the ground state of baryonic matter at large baryon number $A>A_{\rm min}$. With $A_{\rm min}\gtrsim 300$, this has no direct conflict with the stability of ordinary nuclei. An intriguing test of this scenario is to look for quantum nucleation of $ud$QM inside neutron stars due to their large baryon densities. In this paper, we study the transition rate of cold neutron stars to $ud$ quark stars ($ud$QSs) and the astrophysical implications, considering the relevant theoretical uncertainties and observational constraints. It turns out that a large portion of parameter space predicts an instantaneous transition, and so the observed neutron stars are mostly $ud$QSs. We find this possibility still viable under the recent gravitational wave and pulsar observations, although there are debates on its compatibility with some observations that involve complicated structure of quark matter. The tension could be partially relieved in the two-families scenario, where the high-mass stars ($M\gtrsim2 M_{\odot}$) are all $ud$QSs and the low-mass ones ($M\sim1.4\, M_{\odot}$) are mostly hadronic stars. In this case, the slow transition of the low-mass hadronic stars points to a very specific class of hadronic models with moderately stiff EOSs, and $ud$QM properties are also strongly constrained., 26 pages, 11 figures

We discuss proton decay in a recently proposed model of supersymmetric hybrid inflation based on the gauge symmetry SU(4)c× SU(2)L× SU(2)R. A U(1) R symmetry plays an essential role in realizing inflation as well as in eliminating some undesirable baryon number violating operators. Proton decay is primarily mediated by a variety of color triplets from chiral superfields, and it lies in the observable range for a range of intermediate scale masses for the triplets. The decay modes include p → e+(μ+) + π0, $$ p\to \overline{\nu}+{\pi}^{+} $$ p → ν ¯ + π + , p → K0 + e+(μ+), and $$ p\to {K}^{+}+\overline{\nu} $$ p → K + + ν ¯ , with a lifetime estimate of order 1034–1036 yrs and accessible at Hyper-Kamiokande and future upgrades. The unification at the Grand Unified Theory (GUT) scale MGUT (∼ 1016 GeV) of the Minimal Supersymmetric Standard Model (MSSM) gauge couplings is briefly discussed.

The baryon-antibaryon asymmetry (excess of matter over antimatter in our Universe), indicated by observational data from the Cosmic Microwave Background anisotropies, predictions of primordial Nucleosynthesis, and the absence of intense radiation from matter-antimatter annihilation, constitutes an unsolved puzzle in cosmology. Two mechanisms for baryon asymmetry have been proposed as extensions of the Standard Model of Particle Physics at high energies. They rely on new couplings involving the baryon number current, one with a scalar field, called Spontaneous Baryogenesis, and the other with space-time curvature, named Gravitational Baryogenesis. These two mechanisms are investigated in the context of many bouncing scenarios, either symmetric or asymmetric around the bounce. It is shown that the constraints on the free parameters of these scenarios, imposed to yield the observed baryon-to-entropy ratio, are mild, already containing the values compatible with other observational constraints coming from the features of the power spectra of cosmological perturbations. Hence, realistic bouncing models can yield the observed baryon-antibaryon asymmetry if one of the two mechanisms proposed takes place in nature., 15 pages, 12 figures

The measurements of particle multiplicity distributions have generated considerable interest in understanding the fluctuations of conserved quantum numbers in the quantum chromodynamics (QCD) hadronization regime, in particular near a possible critical point and near the chemical freeze-out. Net-protons and net-kaons have been used as proxies for the net-baryon number and net-strangeness, respectively. We report the measurement of efficiency- and centrality-bin width-corrected cumulant ratios (C2/C1, C3/C2) of net-Λ distributions, in the context of both strangeness and baryon number conservation, as a function of collision energy, centrality, and rapidity. The results are for Au+Au collisions at five beam energies (sNN=19.6, 27, 39, 62.4, and 200 GeV) recorded with the Solenoidal Tracker at RHIC (STAR). We compare our results to the Poisson and negative binomial (NBD) expectations, as well as to ultrarelativistic quantum molecular dynamics (UrQMD) and hadron resonance gas (HRG) model predictions. Both NBD and Poisson baselines agree with data within the statistical and systematic uncertainties. UrQMD describes the measured net-ΛC1 and C3 at 200 GeV reasonably well but deviates from C2, and the deviation increases as a function of collision energy. The ratios of the measured cumulants show no features of critical fluctuations. The chemical freeze-out temperatures extracted from a recent HRG calculation, which was successfully used to describe the net-proton, net-kaon, and net-charge data, indicate Λ freeze-out conditions similar to those of kaons. However, large deviations are found when comparing with temperatures obtained from net-proton fluctuations. The net-Λ cumulants show a weak but finite dependence on the rapidity coverage in the acceptance of the detector, which can be attributed to quantum number conservation.

We use $\overline{p}p$ and ${e}^{+}{e}^{\ensuremath{-}}$ annihilation data to further strengthen lower bounds on the partial lifetimes for the baryon-number-violating dinucleon decays $nn\ensuremath{\rightarrow}{e}^{+}{e}^{\ensuremath{-}}$ and $nn\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$. These bounds are of interest since baryon number violation is expected to occur in nature and is predicted in many theories beyond the Standard Model.

We show a new mechanism for baryogenesis where the reheating temperature can be smaller than the electroweak scale. The baryon number symmetry is violated by a dimension nine operator which conserves a baryon parity. A high energy quark from the decay of a heavy particle, $e.g.$ inflaton, modulus or gravitino, undergoes flavor oscillation, and is thermalized due to the scatterings with the ambient thermal plasma. We point out that the baryon asymmetry of our universe can be generated due to the scatterings via the baryon number violating operator. Our scenario can be tested in neutron-antineutron oscillation experiments as well as other terrestrial experiments., Comment: 20pages, 4 figures, published version

In general, the constituents of the bulk matter produced in heavy-ion collisions carry, besides electric charge, multiple other conserved quantum numbers like baryon number and strangeness. Therefore, an electric field will not only generate an electric current but, at the same time, also currents in baryon number and strangeness. We propose that the impact of the electric field on these conserved currents should be characterized by additional transport coefficients, which we call cross-conductivities. In this paper, we introduce and present a calculation of these cross-conductivities from the Green-Kubo formalism within the transport code SMASH for different chemical compositions of hadron resonance gases. We find that the coefficients underlie an ordering in the active degrees of freedom and that thus the chemical composition of the system plays a crucial role. Further, we argue that in future comparisons of lattice QCD calculations with these findings, one could constrain which degrees of freedom and their corresponding charge properties are relevant for the QCD dynamics of the system., Comment: 6 pages, 5 figures

We investigate the stability and ${e}^{+}{e}^{\ensuremath{-}}$ pair creation of supercritically charged superheavy nuclei, $ud\mathrm{QM}$ nuggets, strangelets, and strangeon nuggets based on the Thomas-Fermi approximation. The model parameters are fixed by reproducing masses and charge properties of these supercritically charged objects reported in earlier publications. It is found that $ud\mathrm{QM}$ nuggets, strangelets, and strangeon nuggets may be more stable than $^{56}\mathrm{Fe}$ at the baryon number $A\ensuremath{\gtrsim}315$, $5\ifmmode\times\else\texttimes\fi{}{10}^{4}$, and $1.2\ifmmode\times\else\texttimes\fi{}{10}^{8}$, respectively. For those stable against neutron emission, the most massive superheavy element has a baryon number $\ensuremath{\sim}965$, while $ud\mathrm{QM}$ nuggets, strangelets, and strangeon nuggets need to have baryon numbers larger than 39, 433, and $2.7\ifmmode\times\else\texttimes\fi{}{10}^{5}$. The ${e}^{+}{e}^{\ensuremath{-}}$ pair creation will inevitably start for superheavy nuclei with charge numbers $Z\ensuremath{\ge}177$, for $ud\mathrm{QM}$ nuggets with $Z\ensuremath{\ge}163$, for strangelets with $Z\ensuremath{\ge}192$, and for strangeon nuggets with $Z\ensuremath{\ge}212$. A universal relation $Q/{R}_{e}=({m}_{e}\ensuremath{-}{\overline{\ensuremath{\mu}}}_{e})/\ensuremath{\alpha}$ is obtained at a given electron chemical potential ${\overline{\ensuremath{\mu}}}_{e}$, where $Q$ is the total charge and ${R}_{e}$ the radius of electron cloud. The maximum number of $Q$ without causing ${e}^{+}{e}^{\ensuremath{-}}$ pair creation is then fixed by taking ${\overline{\ensuremath{\mu}}}_{e}=\ensuremath{-}{m}_{e}$. For supercritically charged objects with ${\overline{\ensuremath{\mu}}}_{e}l\ensuremath{-}{m}_{e}$, the decay rate for ${e}^{+}{e}^{\ensuremath{-}}$ pair production is estimated based on the Jeffreys-Wentzel-Kramers-Brillouin (JWKB) approximation. It is found that most positrons are emitted at $t\ensuremath{\lesssim}{10}^{\ensuremath{-}15}\text{ }\text{ }\mathrm{s}$, while a long lasting positron emission can be observed for large objects with $R\ensuremath{\gtrsim}1000\text{ }\text{ }\mathrm{fm}$. The emission of positrons and electron-positron annihilation from supercritically charged objects may be partially responsible for the short $\ensuremath{\gamma}$-ray burst during the merger of binary compact stars, the 511 keV continuum emission, as well as the narrow faint emission lines in x-ray spectra from galaxies and galaxy clusters.

It is entirely plausible that during the primordial quark-hadron phase transition, microseconds after the big bang, the Universe may experience supercooling accompanied by mini inflation leading to a first-order phase transition from quarks to hadrons. The relics, in the form of quark nuggets, with baryon number beyond a critical value will survive the evolution of the Universe. The quark nuggets are candidates of strange quark matter. It is conjectured that color confinement turns the physical vacuum to an event horizon for quarks and gluons. The horizon can be crossed only by quantum tunneling. The process just mentioned is the QCD counterpart of Hawking radiation from gravitational black holes. Tunneling of neutrons from the nuggets is equivalent to Hawking radiation from the gravitational black hole. Thus, when the Hawking temperature of the quark nuggets gets turned off, tunneling will stop and the nuggets will survive forever. The baryon number and the mass of these nuggets are derived using this theoretical format. The results agree well with the prediction using other phenomenological models. Further, the variation of Hawking temperature as a function of baryon number and mass of the nugget mimics chiral phase transition, somewhat similar to the QCD phase transition. Finally, the strange quark nuggets may well be the candidates of baryonic dark matter.

We present new results on up to sixth-order cumulants of net baryon-number fluctuations at small values of the baryon chemical potential, μB, obtained in lattice QCD calculations with physical values of light and strange quark masses. Representing the Taylor expansions of higher-order cumulants in terms of the ratio of the two lowest-order cumulants, MB/σB2=χ1B(T,μB)/χ2B(T,μB), allows for a parameter-free comparison with data on net proton-number cumulants obtained by the STAR Collaboration in the Beam Energy Scan at RHIC. We show that recent high-statistics data on skewness and kurtosis ratios of net proton-number distributions, obtained at a beam energy sNN=54.4 GeV, agree well with lattice QCD results on cumulants of net baryon-number fluctuations close to the pseudocritical temperature, Tpc(μB), for the chiral transition in QCD. We also present first results from a next-to-leading-order expansion of fifth- and sixth-order cumulants on the line of the pseudocritical temperatures.

Within the ultra-relativistic quantum molecular dynamics (UrQMD) model, in which the Lorentz-covariant treatment of nuclear mean-field potential is considered, the fluctuations of net-baryon, net-charge and deuterons multiplicity distributions in Au+Au head-on collisions at $\sqrt{s_{NN}}=3.0-5.0$ GeV are calculated. The results show that the nuclear mean-field potential can significantly enhance the magnitude of baryon number fluctuations in narrow rapidity windows, and this enhancement rapidly weakens with increasing beam energy. However, for proton and net-charge number fluctuations, the mean-field effects are less noticeable than that for baryon number. In addition, for net-charge number fluctuations, the negative binomial distribution agrees well with the calculated results at mid-pseudorapidity window. Finally, the event-by-event fluctuations of deuteron number in the coalescence production picture are calculated as well, it is found that its cumulant ratios decrease linearly with increasing the average multiplicity of deuterons per event, i.e., increase with increasing beam energy.

Proton number fluctuation is sensitive observable to search for the QCD critical point in heavy-ion collisions. In this paper, we studied rapidity acceptance dependence of the proton cumulants and correlation functions in most central Au+Au collisions at sNN=5GeV from a microscopic hadronic transport model [the jet AA microscopic transportation model (JAM)]. At midrapidity, we found the effects of resonance weak decays and hadronic rescattering on the proton cumulants and correlation functions are small, but those effects get larger when further increasing the rapidity acceptance. On the other hand, we found the baryon number conservation is a dominant background effect on the rapidity acceptance dependence of proton number fluctuations. It leads to a strong suppression of cumulants and cumulant ratios as well as the negative proton correlation functions. We also studied those two effects on the energy dependence of cumulant ratios of net-proton distributions in most central Au+Au collisions at sNN=5−200GeV from the JAM model. This paper can serve as a noncritical baseline for a future QCD critical point search in heavy-ion collisions at the high baryon density region.

We explore the generation of the baryon asymmetry in an extension of the Standard Model where the lepton number is promoted to a $U(1)_\ell$ gauge symmetry with an associated $Z^\prime$ gauge boson. This is based on a novel electroweak baryogenesis mechanism first proposed by us in Ref. \cite{Carena:2018cjh}. Extra fermionic degrees of freedom - including a fermionic dark matter $\chi$ - are introduced in the dark sector for anomaly cancellation. Lepton number is spontaneously broken at high scale and the effective theory, containing the Standard Model, the $Z^\prime$, the fermionic dark matter, and an additional complex scalar field $S$, violates CP in the dark sector. The complex scalar field couples to the Higgs portal and is essential in enabling a strong first order phase transition. Dark CP violation is diffused in front of the bubble walls and creates a chiral asymmetry for $\chi$, which in turn creates a chemical potential for the Standard Model leptons. Weak sphalerons are then in charge of transforming the net lepton charge asymmetry into net baryon number. We explore the model phenomenology related to the leptophilic $Z^\prime$, the dark matter candidate, the Higgs boson and the additional scalar, as well as implications for electric dipole moments. We also discuss the case when baryon number $U(1)_B$ is promoted to a gauge symmetry, and discuss electroweak baryogenesis and its corresponding phenomenology., Comment: 44 pages, 12 figures, 1 table. v2 matches the published version

We study the chameleon field dark matter, dubbed \textit{scalaron}, in $F(R)$ gravity in the Big Bang Nucleosynthesis (BBN) epoch. With an $R^{2}$-correction term required to solve the singularity problem for $F(R)$ gravity, we first find that the scalaron dynamics is governed by the $R^{2}$ term and the chameleon mechanism in the early universe, which makes the scalaron physics model-independent regarding the low-energy scale modification. In viable $F(R)$ dark energy models including the $R^{2}$ correction, our analysis suggests the scalaron universally evolves in a way with a bouncing oscillation irrespective of the low-energy modification for the late-time cosmic acceleration. Consequently, we find a universal bound on the scalaron mass in the BBN epoch, to be reflected on the constraint for the coupling strength of the $R^2$ term, which turns out to be more stringent than the one coming from the fifth force experiments. It is then shown that the scalaron naturally develops a small enough fluctuation in the BBN epoch, hence can avoid the current BBN constraint placed by the latest Planck 2018 data, and can also have a large enough sensitivity to be hunted by the BBN, with more accurate measurements for light element abundances as well as the baryon number density fraction., Comment: 29 pages, 7 figures, Prepared for submission to JHEP

It is known that limits on baryon-violating nucleon decays do not, in general, imply corresponding suppression of $n - \bar n$ transitions. In the context of a model with fermions propagating in higher dimensions, we investigate a related question, namely the implications of limits on $\Delta L=-1$ proton and bound neutron decays mediated by four-fermion operators for rates of nucleon decays mediated by $k$-fermion operators with $k =6$ and $k=8$. These include a variety of nucleon and dinucleon decays to dilepton and trilepton final states with $\Delta L=-3, \ -2, \ 1$, and $2$. We carry out a low-energy effective field theory analysis of relevant operators for these decays and show that, in this extra-dimensional model, the rates for these decays are strongly suppressed and hence are in accord with experimental limits., Comment: 29 pages, latex

We study the thermodynamic geometry of the Quark-Meson model, focusing on the curvature, $R$, around the chiral crossover at finite temperature and baryon chemical potential. We find a peculiar behavior of $R$ in the crossover region, in which the sign changes and a local maximum develops; in particular, the height of the peak of $R$ in the crossover region becomes large in proximity of the critical endpoint and diverges at the critical endpoint. The appearance of a pronounced peak of $R$ close to the critical endpoint supports the idea that $R$ grows with the correlation volume around the phase transition. We also analyze the mixed fluctuations of energy and baryon number, $\langle\Delta U\Delta N\rangle$, which grow up substantially in proximity of the critical endpoint: in the language of thermodynamic geometry these fluctuations are responsible for the vanishing of the determinant of the metric, which results in thermodynamic instability and are thus related to the appearance of the second order phase transition at the critical endpoint., Comment: 10 pages, 6 figures

We explore the QCD phase diagram at finite density with four-flavor staggered fermions using the complex Langevin method, which is a promising approach to overcome the sign problem. In our previous work on an $8^3 \times 16$ lattice at $\beta = 5.7$ with the quark mass $m = 0.01$, we have found that the baryon number density has a clear plateau as a function of the chemical potential. In this study, we use a $16^3 \times 32$ lattice to reduce finite volume effects and find that the plateau structure survives. Moreover, the number of quarks in the plateau region turns out to be 24, which is exactly the same as the one obtained previously on the $8^3 \times 16$ lattice. We provide a simple interpretation of this number, which suggests that the Fermi sphere is starting to form., Comment: 7 pages, 2 figures, submitted to the proceedings for 37th International Symposium on Lattice Field Theory - Lattice2019