Baryon Charge Research Articles

Baryon magnetic moments in relativistic quark models

It is shown that the phenomenological description of the baryon magnetic moments in the quark model carries over to the Poincaré covariant extension of the model. This applies to all the three common forms of relativistic kinematics with structureless constituent currents, which are covariant under the corresponding kinematic subgroups. In instant and front form kinematics the calculated magnetic moments depend strongly on the constituent masses, while in point form kinematics the magnetic moments are fairly insensitive to both the quark masses and the wave function model. The baryon charge radii and magnetic moments are determined in the different forms of kinematics for the light-flavor, strange and charm hyperons. The wave function model is determined by a fit to the electromagnetic form factor of the proton.

Spontaneous baryogenesis in flat directions

We discuss a spontaneous baryogenesis mechanism in flat directions. After identifying the Nambu-Goldstone mode which derivatively couples to the associated $U(1)$ current and rotates due to the A term, we show that spontaneous baryogenesis can be naturally realized in the context of the flat direction. As applications, we discuss two scenarios of baryogenesis in detail. One is baryogenesis in a flat direction with a vanishing $B\ensuremath{-}L$ charge, especially with neither baryon nor lepton charge, which was recently proposed by Chiba and the present authors. The other is a baryogenesis scenario compatible with a large lepton asymmetry.

Electromagnetic form factors of the baryon octet in the perturbative chiral quark model

We apply the perturbative chiral quark model at one loop to analyze the electromagnetic form factors of the baryon octet. The analytic expressions for baryon form factors, which are given in terms of fundamental parameters of low-energy pion-nucleon physics (weak pion decay constant, axial nucleon coupling, strong pion-nucleon form factor), and the numerical results for baryon magnetic moments, charge and magnetic radii are presented. Our results are in good agreement with experimental data.

Coexistence of different vacua in the effective quantum field theory and multiple point principle

According to the Multiple Point Principle our Universe is on the coexistence curve of two or more phases of the quantum vacuum. The coexistence of different quantum vacua can be regulated by the exchange of the global fermionic charges between the vacua, such as baryonic, leptonic or family charge. If the coexistence is regulated by the baryonic charge, all the coexisting vacua exhibit the baryonic asymmetry. Due to the exchange of the baryonic charge between the vacuum and matter which occurs above the electroweak transition, the baryonic asymmetry of the vacuum induces the baryonic asymmetry of matter in our Standard-Model phase of the quantum vacuum. The present baryonic asymmetry of the Universe indicates that the characteristic energy scale which regulates the equilibrium coexistence of different phases of quantum vacua is about 10^6 GeV.

Baryon Charges in 4d Superconformal Field Theories and Their AdS Duals

We consider general aspects of the realization of R and non-R flavor symmetries in the AdS_5 x H_5 dual of 4d N=1 superconformal field theories. We find a general prescription for computing the charges under these symmetries for baryonic operators, which uses only topological information (intersection numbers) on H_5. We find and discuss a new correspondence between the nodes of the SCFT quiver diagrams and certain divisors in the associated geometry. We also discuss connections between the non-R flavor symmetries and the enhanced gauge symmetries in non-conformal theories obtained by adding wrapped branes.

Baryogenesis in a flat direction with neither baryon nor lepton charge.

We present a new mechanism of spontaneous baryogenesis. Usually such mechanisms require a derivative coupling between a scalar field and baryon current. In our model, the scalar field instead derivatively couples to a current associated with some global symmetry U(1)(Q). In this case, baryogenesis is still possible provided that an interaction exists, which violates the baryon and U(1)(Q) symmetries simultaneously. As a concrete example, we discuss baryogenesis in a flat direction with neither baryon nor lepton charge.

Decay of Affleck–Dine condensates with application to Q-balls

Analytical and numerical estimates show that a charged Affleck–Dine condensate will fracture into Q-balls only when the Hubble time is significantly larger than the inverse soft-breaking mass of the field in question. This would generally imply that the decay of the field into light fermions will compete with Q-ball formation. We will show that for typical flat directions the large field value will significantly suppress decays of the condensate to fermions even if no baryon charge asymmetry exists. We will consider the details of the decay process for a condensate that does carry charge, and show that it is qualitatively different from that of an uncharged condensate. Finally, we will consider the possibility of resonant production of heavy bosons. We will show that this can have a strong effect on the condensate. Contrary to intuition, however, our results indicate that boson production would actually assist Q-ball formation in condensates with significant charge.

Evolution of baryon-free matter produced in relativistic heavy-ion collisions

A three-fluid hydrodynamic model is introduced for simulating heavy-ion collisions at incident energies between a few and about 200 A GeV. In addition to the two baryon-rich fluids of two-fluid models, a new model incorporates a third, baryon-free (i.e., with zero net baryonic charge), fluid, which is created in the midrapidity region. Its evolution is delayed due to a formation time τ, during which the baryon-free fluid neither thermalizes nor interacts with the baryon-rich fluids. After formation, it thermalizes and starts to interact with the baryon-rich fluids. It is found that, for τ=0, the interaction strongly affects the baryon-free fluid. However, at reasonable finite formation time, τ ⋍ 1 fm/c, the effect of this interaction turns out to be substantially reduced, although still noticeable. Baryonic observables are only slightly affected by the interaction with the baryon-free fluid.

Charge radii of the meson and baryon octets in quenched and partially quenched chiral perturbation theory

We calculate the electric charge radii of the SU(3) pseudoscalar mesons and the SU(3) octet baryons in quenched and partially quenched chiral perturbation theory. We work in the isospin limit, up to next-to-leading order in the chiral expansion, and to leading order in the heavy baryon expansion. The results are necessary for the extrapolation of future lattice calculations of meson and baryon charge radii. We also derive expressions for the nucleon and pion charge radii in SU(2) flavor away from the isospin limit.

Pp ELASTIC SCATTERING AT LHC AND NUCLEON STRUCTURE

High energy elastic pp scattering at the Large Hadron Collider (LHC) at c.m. energy 14 TeV is predicted using the asymptotic behavior of σ tot (s) and ρ(s) known from dispersion relation calculations and the measured elastic [Formula: see text] differential cross-section at [Formula: see text]. The effective field theory model underlying the phenomenological analysis describes the nucleon as having an outer cloud of quark–antiquark condensed ground state, an inner core of topological baryonic charge of radius ≃ 0.44 F and a still smaller valence quark-bag of radius ≲ 0.1 F. The LHC experiment TOTEM (Total and Elastic Measurement), if carried out with sufficient precision from |t| = 0 to |t| > 10 GeV 2, will be able to test this structure of the nucleon.

The chemical potential in the transfer matrix and in the path integral formulation of QCD on a lattice

We define the chemical potential as the Lagrange multiplier of the baryon charge operator in the transfer matrix formalism of QCD on a lattice. Transforming the partition function into an Euclidean path integral we get the Hasenfratz–Karsh action both for Wilson and Kogut–Susskind fermions. In the latter case the chemical potential in the spin-diagonal basis is half that in the flavour basis. Some open problems in the spin-diagonal basis are pointed out.

CHIRAL BAG MODEL WITH CONSTITUENT QUARKS: TOPOLOGICAL AND NONTOPOLOGICAL SOLUTIONS

We consider a three-phase modification of the hybrid chiral bag model involving the intermediate constituent quark phase along with the asymptotic freedom and hadronization phases. We find self-consistent solutions of the equations of the model in 1+1 dimensions with the fermion vacuum polarization effects taken into account. We study the renormalized total energy of the bag as a function of parameters characterizing the geometry of the bag and its topological (baryon) charge. We show that for a nonzero topological charge, there exists an entire series of configurations that are local minimums of the total energy of the bag and contain all the three phases, whereas in the nontopological case, the bag energy minimum corresponds to zero sizes of the domain of the asymptotic freedom phase.

Electroweak baryogenesis mediated by locally supersymmetry-breaking defects

We consider the scenario of electroweak baryogenesis mediated by a cosmological defect in models of supersymmetry breaking. When the effective electroweak breaking scale is raised in the defect configuration, the mechanism of electroweak baryogenesis works at a higher energy scale. The baryon charge produced by the mechanism is captured in the defect. It is protected from sphalerons and then released when the defect decays.

Monopoles and dyons in SO(3) gauged Skyrme models

Three-dimensional SO(3) gauged Skyrme models characterized by specific potentials imposing special asymptotic values on the chiral field are considered. These models are shown to support finite energy solutions with nonvanishing magnetic and electrix flux, whose energies are bounded from below by two distinct charges—the magnetic (monopole) charge and a noninteger version of the Baryon charge. Unit magnetic charge solutions are constructed numerically and their properties characterized by the chosen asymptotics and the Skyrme coupling are studied. For a particular value of the chosen asymptotics, charge-2 axially symmetric solutions are also constructed and the attractive nature of the like-monopoles of this system are exhibited. As an indication toward the possible existence of large clumps of monopoles, some consideration is given to axially symmetric monopoles of charges 2,3,4.

Octet baryon charge radii, chiral symmetry, and decuplet intermediate states

We compute the octet baryon charge radii to O(1/Heavy^3) in heavy baryon chiral perturbation theory. We examine the effect of including the decuplet of spin-3/2 baryons explicitly. We find that it does no t improve the level of agreement between the HBchiPT and experimental values for the Sigma^- charge radius.

Incorporating chiral symmetry and heavy quark theory in extrapolations of octet baryon charge radii

We extrapolate lattice calculations of electric charge radii of the spin-1/2 baryon octet to the physical regime. The extrapolation procedure incorporates chiral perturbation theory and heavy quark effective theory in the appropriate limits. In particular, this procedure includes the non-analytic, logarithmic terms from pion loops. The electric charge radii of the nucleons and Σ − obtained from the chiral extrapolations agree well with experimental data. We make predictions for the charge radii of the remaining baryons in anticipation of future experimental measurements.

Possible origin of antimatter regions in the baryon dominated universe

We discuss the evolution of U(1) symmetric scalar field at the inflation epoch with a pseudo Nambu-Goldstone tilt revealing after the end of exponential expansion of the Universe. The U(1) symmetry is supposed to be associated with baryon charge. It is shown that quantum fluctuations lead in natural way to baryon dominated Universe with antibaryon excess regions. The range of parameters is calculated at which the fraction of Universe occupied by antimatter and the size of antimatter regions satisfy the observational constraints, survive to the modern time and lead to effects, accessible to experimental search for antimatter.

Numerical study of dense adjoint matter in two color QCD

We identify the global symmetries of SU(2) lattice gauge theory with N flavors of staggered fermion in the presence of a quark chemical potential mu, for fermions in both fundamental and adjoint representations, and anticipate likely patterns of symmetry breaking at both low and high densities. Results from numerical simulations of the model with N=1 adjoint flavor on a 4^3x8 lattice are presented, using both hybrid Monte Carlo and Two-Step Multi-Boson algorithms. It is shown that the sign of the fermion determinant starts to fluctuate once the model enters a phase with non-zero baryon charge density. HMC simulations are not ergodic in this regime, but TSMB simulations retain ergodicity even in the dense phase, and in addition appear to show superior decorrelation. The HMC results for the equation of state and the pion mass show good quantitative agreement with the predictions of chiral perturbation theory, which should hold only for N>=2. The TSMB results incorporating the sign of the determinant support a delayed onset transition, consistent with the pattern of symmetry breaking expected for N=1.

QCD-like theories at finite baryon density

We study QCD-like theories with pseudoreal fermions at finite baryon density. Such theories include two-color QCD with quarks in the fundamental representation of the color group as well as any-color QCD with quarks in the adjoint color representation. In all such theories the lightest baryons are diquarks. At zero chemical potential μ they are, together with the pseudoscalar mesons, the Goldstone modes of a spontaneously broken enlarged chiral symmetry group. Using symmetry principles, we derive the low-energy effective Lagrangian for these particles. We find that a second order phase transition occurs at a value of μ equal to half the mass of the Goldstone modes. For values of μ beyond this point the scalar diquarks Bose condense and the diquark condensate is nonzero. We calculate the dependence of the chiral condensate, the diquark condensate, the baryon charge density, and the masses of the diquark and pseudoscalar excitations on μ at finite bare quark mass and scalar diquark source. The relevance of our results to lattice QCD calculations and to real three-color QCD at finite baryon density is discussed.

Orbifold projection in supersymmetric QCD at Nf⩽ Nc

Supersymmetric orbifold projection of N=1 SQCD with relatively small number of flavors ( N f ⩽ N c ) is considered. The purpose is to check whether orbifolding commutes with the infrared limit. On the one hand, one considers the orbifold projection of SQCD and obtains the low-energy description of the resulting theory. On the other hand, one starts with the low-energy effective theory of the original SQCD, and only then performs orbifolding. It is shown that at finite N c the two low-energy theories obtained in these ways are different. However, in the case of stabilized run-away vacuum these two theories are shown to coincide in the large N c limit. In the case of quantum modified moduli space, topological solitons carrying baryonic charges are present in the orbifolded low-energy theory. These solitons may restore the correspondence between the two theories provided that the soliton mass tends to zero in the large N c limit.