Baryon Number Research Articles

Toward a universal description of hadronic phase of QCD

Mean-field model quantum field theories of hadrons were traditionally developed to describe cold and dense nuclear matter and are by now very well constrained from the recent neutron star merger observations. We show that when augmented with additional known hadrons and resonances but not included earlier, these mean-field models can be extended beyond its regime of applicability. Calculating some specific ratios of baryon number susceptibilities for finite temperature and moderate values of baryon densities within mean-field approximation, we show that these match consistently with the lattice QCD data available at lower densities, unlike the results obtained from a noninteracting hadron resonance gas model. We also estimate the curvature of the line of constant energy density, fixed at its corresponding value at the chiral crossover transition in QCD, in the temperature-density plane. The number density at low temperatures and high density is found to be about twice the nuclear saturation density. Moreover from this line we can indirectly constrain the critical endpoint of QCD to be beyond μB=596 MeV for temperature ∼125 MeV. Published by the American Physical Society 2024

Matter-antimatter asymmetry and dark matter stability from baryon number conservation

There is currently no evidence for a baryon asymmetry in our universe. Instead, cosmological observations have only demonstrated the existence of a quark-antiquark asymmetry, which does not necessarily imply a baryon asymmetric Universe, since the baryon number of the dark sector particles is unknown. In this paper we discuss a framework where the total baryon number of the Universe is equal to zero, and where the observed quark-antiquark asymmetry arises from neutron portal interactions with a dark sector fermion N that carries baryon number. In order to render a baryon symmetric universe throughout the whole cosmological history, we introduce a complex scalar χ, with opposite baryon number and with the same initial abundance as N. Notably, due to the baryon number conservation, χ is absolutely stable and could have an abundance today equal to the observed dark matter abundance. Therefore, in this simple framework, the existence of a quark-antiquark asymmetry is intimately related to the existence (and the stability) of dark matter.

Interplay of baryonic chiral partners in fluctuations of netbaryon number density

In this contribution, we use the parity doublet model to investigate the fluctuations of the net-baryon number density. We discuss the systematics of the susceptibilities and their ratios for nucleons of positive and negative parity, as well as their correlator. We demonstrate that the fluctuations of positiveparity nucleon do not reflect the fluctuations of the total net-baryon number at the chiral phase transition.

An Illuminating Physical Model for Production on free Positron and Electron — Energy Basic State Field of the Universe (V)

In this paper, we introduce Dirac equation, the hole theory of positive and negative matter, and Anderson localization theory briefly. We analyze physical conditions of localization: [Formula: see text] inequality relation. On this basis, we try to put forward the physical mode of production of free positron and electron. In this model, when [Formula: see text] rays travel through a vacuum, due to the action in which quantum superfluid rushes to the heat source ([Formula: see text] ray), the quantum superfluid polymerization, local disorder, two-model quantum superfluid shunt, quantum superfluid in a vacuum is localized by the electro-vector and magnetic-vector in the electromagnetic field of the [Formula: see text] ray to form electrons and positrons; in essence, the electro-vector and magnetic-vector are components of [Formula: see text] quantum in the electromagnetic field ([Formula: see text] ray); and the spin of the [Formula: see text] ray is composed of two components. After localization, positive and negative polarities whose phases are opposite are formed. The positron and electron charges produced in this model have the same quantum numbers such as the mass, spin and average lifetime, and the additive quantum numbers such as charge, baryon number, lepton number, and singularity number should be equal but opposite, the magnetic moment direction of the positive and negative particles are opposite when their spin directions are the same. We can take experimental verification of this model. Once verified, the localization theory also seems to open a door for us to study the structure of sub-quarks and lepton, and also provides a theoretical basis for harnessing the enormous energy generated by the annihilation of positive and negative matter.

High order fluctuations of conserved charges in the continuum limit

We calculate the grand canonical fluctuations of the net baryon number and net strangeness in the region of chiral crossover from lattice QCD. We continuum extrapolate the results in a finite volume using the new 4HEX discretization scheme up to χ6B and also for χ8B at a single temperature. Our results contradict recent estimates at a finite lattice spacing. See Ref. [1] for the full version of this work.

Systematic classification of aGUT models in five dimensions: the SU(N) kinship

Asymptotic Grand Unification theories (aGUTs) in five dimensions provide a valid alternative to standard quantitative unification. We define the pathway towards viable models starting from a general unified bulk gauge symmetry. Imposing the presence of ultra-violet fixed points for both gauge and Yukawa couplings strongly limits the possibilities. Within the SU(N) kinship, we identify and characterise only two realistic minimal models, both based on a bulk SU(6) symmetry. Both models feature the generation of either up or down-type Yukawas via gauge scalars, two Higgs doublets with build-in minimal flavour violation at low energies, and conservation of baryon number. We also propose interesting avenues beyond the minimality criterion.

Baryon number violating rate as a function of the proton-proton collision energy

Baryon number violating rate as a function of the proton-proton collision energy

Study on muon MDM and lepton EDM in BLMSSM via the mass insertion approximation

In the framework of the MSSM extension with local gauged baryon and lepton numbers (BLMSSM), we calculate the muon anomalous magnetic dipole moment (MDM) and lepton (e, μ, τ) electric dipole moment (EDM), and discuss how the muon MDM and lepton EDM depend on the parameters within the mass insertion approximation. Among many parameters, , g L , m L and μ H are more sensitive parameters for . Considering the experimental limitations, our best numerical result of is around 2.5 × 10−9, which can well compensate the departure between the experiment data and standard model (SM) prediction. The CP violating phases in BLMSSM are more than those in the MSSM, including new parameters and θ L . They can give large contributions, which play an important role in exploring the source of CP violation and probing new physics beyond SM.

Primordial non-Gaussianity as a probe of seesaw and leptogenesis

We present the possibility that the seesaw mechanism and nonthermal leptogenesis can be investigated via primordial non-Gaussianities in the context of a majoron curvaton model. Originating as a massless Nambu-Goldstone boson from the spontaneous breaking of the global baryon (B) minus lepton (L) number symmetry at a scale vB−L, majoron becomes massive when it couples to a new confining sector through anomaly. Acting as a curvaton, majoron produces the observed red-tilted curvature power spectrum without relying on any inflaton contribution, and its decay in the post-inflationary era gives rise to a nonthermal population of right-handed neutrinos that participate in leptogenesis. A distinctive feature of the mechanism is the generation of observable non-Gaussianity, in the parameter space where the red-tilted power spectrum and sufficient baryon asymmetry are produced. We find that the non-Gaussianity parameter fNL ≳ O\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{O} $$\\end{document}(0.1) is produced for high-scale seesaw (vB−L at O\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{O} $$\\end{document}(1014−17) GeV) and leptogenesis (M1 ≳ O\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{O} $$\\end{document}(106) GeV) where the latter represents the lightest right-handed neutrino mass. While the current bounds on local non-Gaussianity excludes some part of parameter space, the rest can be fully probed by future experiments like CMB-S4, LSST, and 21 cm tomography.

Flavor-dependent U(1) extension inspired by lepton, baryon and color numbers

There is no reason why the gauge symmetry extension is family universal as in the standard model and the most well-motivated models, e.g. left-right symmetry and grand unification. Hence, we propose a simplest extension of the standard model – a flavor-dependent U(1) gauge symmetry – and find the new physics insight. For this aim, the U(1) charge, called X, is expressed as X=xB+yL\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$X=x B+y L$$\\end{document} in which x and y are free parameters as functions of flavor index, e.g. for a flavor i they take xi\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$x_i$$\\end{document} and yi\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$y_i$$\\end{document} respectively, where B and L denote normal baryon and lepton numbers. Imposing a relation involved by the color number 3, i.e. -x1,2,…,n=xn+1,n+2,…,n+m=3y1,2,…,n+m≡3z\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$-x_{1,2,\\ldots ,n}=x_{n+1,n+2,\\ldots ,n+m}=3y_{1,2,\\ldots ,n+m}\\equiv 3z$$\\end{document}, for arbitrarily nonzero z, we achieve a novel U(1) theory with implied X-charge. This theory not only explains the origin of the number of observed fermion families but also offers a possible solution for both neutrino mass and dark matter, which differs from B-L\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B-L$$\\end{document} extension. Two typical models based on this idea are examined, yielding interesting results for flavor-changing neutral currents and particle colliders, besides those of neutrino mass and dark matter.

Neutron Star Constraints on Neutron Dark Decays

Motivated by the neutron lifetime puzzle, it is proposed that neutrons may decay into new states yet to be observed. We review the neutron star constraints on dark fermions carrying unit baryon number with masses around 939 MeV, and discuss the interaction strengths required for the new particle. The possibility of neutrons decaying into three dark fermions is investigated. While up to six flavors of dark quarks with masses around 313 MeV can be compatible with massive pulsars, any such exotic states lighter than about 270 MeV are excluded by the existence of low-mass neutron stars around ∼1.2M⊙. Light dark quarks in the allowed mass range may form a halo surrounding normal neutron stars. We discuss the potential observable signatures of the halo during binary neutron star mergers.

How Long Does the Hydrogen Atom Live?

It is possible that the proton is stable while atomic hydrogen is not. This is the case in models with new particles carrying baryon number which are light enough to be stable themselves, but heavy enough so that proton decay is kinematically blocked. Models of new physics that explain the neutron lifetime anomaly generically have this feature, allowing for atomic hydrogen to decay through electron capture on a proton. We calculate the radiative hydrogen decay rate involving the emission of a few hundred keV photon, which makes this process experimentally detectable. In particular, we show that the low energy part of the Borexino spectrum is sensitive to radiative hydrogen decay, and turn this into a limit on the hydrogen lifetime of order 1030s or stronger. For models where the neutron mixes with a dark baryon, χ, this limits the mixing angle to roughly 10−11, restricting the n→χγ branching to 10−4, over a wide range of parameter space.

Nudged Elastic Bands and Lightly Bound Skyrmions

It has become clear in recent years that the configuration space of the nuclear Skyrme model has, in each topological class, many almost degenerate local energy minima and that the number of such minima grows with the degree (or baryon number) $B$. Rigid body quantization, in which one quantizes motion on the spin-isospin orbit of just one minimum, is thus an ill-justified approximation. Instead, one should identify a (finite-dimensional) moduli space of configurations containing all local minima (for a given $B$) as well as fields interpolating smoothly between them. This paper proposes a systematic computational scheme for generating such a moduli space: one constructs an energy minimizing path between each pair of local minima, then defines the moduli space to be the union of spin-isospin orbits of points on the union of these curves, a principal bundle over a graph. The energy minimizing curves may be constructed in practice using the nudged elastic band method, a standard tool in mathematical chemistry for analyzing reaction paths and computing activation energies. To illustrate, we apply this scheme to the lightly bound Skyrme model in the point particle approximation, constructing the graphs for $5\leq B\leq 10$. We go on to complete the quantization for $B=7$, in which the graph has two vertices and a single edge. The low-lying quantum states with isospin $1/2$ do not strongly localize around either of the local energy minima (the vertices). Their energies rise monotonically with spin, conflicting with experimental data for Lithium-7.

Skyrme crystals with massive pions

The crystalline structure of nuclear matter is investigated in the standard Skyrme model with massive pions. A semi-analytic method is developed to determine local minima of the static energy functional with respect to variations of both the field and the period lattice of the crystal. Four distinct Skyrme crystals are found. Two of these were already known–the cubic lattice of half-skyrmions and the α-particle crystal–but two are new. These new solutions have lower energy per baryon number and less symmetry, being periodic with respect to trigonal but not cubic period lattices. Minimal energy crystals are also constructed under the constraint of constant baryon density, and it is shown that the two new non-cubic crystals tend to chain and multi-wall solutions at low densities.

Chiral asteroseismology: seismic oscillations caused by chiral transport in neutron stars and supernovae

We study the novel asteroseismology of the chiral magnetic wave (CMW) of the quark number density in relativistic quark matter inside neutron stars and core-collapse supernovae and the chiral vortical wave (CVW) of the neutrino number density in relativistic neutrino matter at the core of supernovae.We call the oscillation modes for these chiral waves the chiral magnetic mode (CM-mode) and chiral vortical mode (CV-mode), respectively.We derive the dispersion relations of these new modes in the presence of the chirality flipping due to the finite quark mass and diffusion. We then estimate the possible frequencies of these modes and amplitudes of the resulting gravitational waves. In particular, since the CM-mode can exist only in quark matter with nearly gapless quarks (such as the two-flavor color superconductivity) for a sufficiently strong magnetic field, corresponding gravitational waves provide a new possible probe for such quark matter and the magnetic field in neutron stars.

Rational Skyrmions

A new method is introduced to construct approximations to Skyrmions that are explicit rational functions of the spatial Cartesian coordinates. The scheme uses ADHM data of a Yang–Mills instanton to produce a Skyrmion with a baryon number that is equal to the instanton number. The formula for the Skyrmion involves only the evaluation of the ADHM data, in contrast to the Atiyah–Manton construction that requires the solution of a differential equation that can only be solved explicitly in the case of a spherically symmetric Skyrmion. Examples with baryon numbers one and two are studied in detail. The energy of the rational Skyrmion with baryon number one is lower than that of the Atiyah–Manton Skyrmion, which is already within one percent of the energy of the true numerically computed Skyrmion. A family of baryon number two Skyrmions is presented, which includes an axially symmetric Skyrmion that smoothly transforms to a pair of well-separated single Skyrmions as the parameter is varied.

Electroweak baryogenesis via top-charm mixing

We investigate a scenario of electroweak baryogenesis in the two Higgs doublet model with quark flavor mixing. In general, off-diagonal components of quark Yukawa interactions with additional Higgs bosons are strongly constrained by the data for flavor changing neutral currents. However, top-charm quark mixing is not the case, so that a large off-diagonal element can be taken, which can contribute to generating baryon asymmetry of the universe. It turns out that CP violating phases of the off-diagonal element in the source term in the Boltzmann equation are eliminated by the rephasing. This result is somewhat different from previous works on electroweak baryogenesis by flavor off-diagonal Yukawa couplings. Instead, we find that the absolute value of the top-charm off-diagonal element enhances CP violating phases in the Higgs potential, by which sufficient amount of the baryon number can be generated to explain the observed baryon asymmetry of the universe. We find that such a scenario is viable under the current experimental data. The model can be tested by the current and future measurements of various flavor experiments like Kaon rare decays, in addition to high energy collider experiments as well as gravitational wave observations. Characteristic predictions of our model would be deviations in Kaon rare decays. Branching ratios of K+→π+νν¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {K}^{+}\ o {\\pi}^{+}\ u \\overline{\ u} $$\\end{document} and KL→π0νν¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {K}_L\ o {\\pi}^0\ u \\overline{\ u} $$\\end{document} can deviate by the order of 10% and 1%, respectively, which may be tested at future Kaon experiments such as NA62 and KOTO step-2.

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.