Baryon Current Research Articles

Investigation on the Ω(2012) from QCD sum rules

We investigate the recently observed Ω(2012) baryon using QCD sum rules. By constructing P-wave Ω baryon currents and performing spin projection and parity projection, we obtain the masses of the JP=1/2− and 3/2− states as M1/2−=2.07−0.07+0.07GeV and M3/2−=2.05−0.10+0.09GeV, in good agreement with experiment. This suggests that Ω(2012) is likely to be a negative parity P-wave excited state, though its spin remains undetermined and requires further study of its decay properties.

Investigation on the Ω(2012) from QCD sum rules

We study the recently observed Ω(2012) baryon in quantum chromodynamics (QCD) sum rules. We construct the P-wave Ω baryon currents with a covariant derivative, and perform spin projection to obtain the currents with total spin 1/2 and 3/2. We then apply the parity-projected QCD sum rules to separate the contributions of the positive and negative parity states. We extract the masses of JP=1/2− and 3/2− states to be M1/2−=2.07−0.07+0.07 GeV and M3/2−=2.05−0.10+0.09 GeV. Both results are in good agreement with the experimental result. Therefore, it is likely that the Ω(2012) is a negative parity state, which is interpreted as a P-wave excited state in the quark model. However, its spin is not determined in the present analysis, which can be done by detailed study on its decay properties. Published by the American Physical Society 2024

Anomalous strangeness transport

Nondissipative transport of strangeness is studied in a chiral hadronic plasma with three flavors. In the phase in which chiral symmetry is preserved, strangeness transport is found to be driven by both an external magnetic field and fluid vorticity. As for the constitutive relations of the baryon and electromagnetic currents, they exhibit vortical terms proportional to the strangeness chemical potential. In the superfluid phase, transverse nondissipative diffusion of the baryon, electromagnetic, and strangeness charges is found, which survives in the limit of vanishing chiral imbalance and mixes in a fashion similar to standard dissipative diffusion in quark-gluon plasma.

Collective dynamics of polarized spin-half fermions in relativistic heavy-ion collisions

Standard relativistic hydrodynamics has been successful in describing the properties of the strongly interacting matter produced in the heavy-ion collision experiments. Recently, there has been a significant theoretical advancement in this field to explain spin polarization of hadrons emitted in these processes. Although current models have successfully explained some of the experimental data based on the coupling between spin polarization and vorticity of the medium, they still lack a clear understanding of the differential measurements. This is commonly interpreted as an indication that the spin needs to be treated as an independent degree of freedom whose dynamics is not entirely bound to flow circulation. In particular, if the spin is a macroscopic property of the system, in equilibrium its dynamics should follow hydrodynamic laws. Here, we develop a framework of relativistic hydrodynamics which includes spin degrees of freedom from the quantum kinetic theory for Dirac fermions and use it for modeling the dynamics of matter. Following experimental observations, we assume that the polarization effects are small and derive conservation laws for the net baryon current, the energy–momentum tensor and the spin tensor based on the de Groot–van Leeuwen–van Weert definitions of these currents. We present various properties of the spin polarization tensor and its components, analyze the propagation properties of the spin polarization components, and derive the spin-wave velocity for arbitrary statistics. We find that only the transverse spin components propagate, analogously to the electromagnetic waves. Finally, using our framework, we study the space–time evolution of the spin polarization for the systems respecting certain space–time symmetries and calculate the mean spin polarization per particle, which can be compared to the experimental data. We find that, for some observables, our spin polarization results agree qualitatively with the experimental findings and other model calculations.

Baryogenesis inspired by some modified entropies

Entropy is defined as a measure of the degree of disorder or randomness in a system and is expressed in thermodynamic terms as the inability of thermal energy to be converted into mechanical work. In this work, we use different types of entropies such as Barrow entropy (BE), Sharma-Mittal entropy (SME), and generalized construction of these entropies. We use the above-mentioned entropies to discuss the issue of baryogenesis and then we find constraints on the entropies parameters to get the physical results of compared to the standard observational value. To derive the modified Friedmann field equations (FFEs), we use entropies and the first law of thermodynamics. Thus, even in the presence of the typical interaction between the Ricci scalar and baryon current, this results in non-trivial modifications to the mass density and pressure content of the Universe, which provides a viable mechanism allowing for baryogenesis. Finally, we show that even in the radiation-dominant era baryon asymmetry factor (BAF) is non-zero. We conclude, BE parameter 0 ≤ Δ < 1, SME parameters R and δ with positive δ ≥ 4.2 × 1038 (keeping fixed R = 1) while at constant δ = 9 × 1028 for all values of R and for the generalized entropy parameter positive β ≤ 2.4 × 10−28 (fixing γ = α = 5); α ≤ 3.5 × 10−23 (for γ = 1.2 and β = 3) and γ ≥ 1.1 × 106 (at α = 3 × 10−20, β = 3), we have physically desired results on the observational ground.

Lambda _b rightarrow p, N^*(1535) form factors from QCD light-cone sum rules

In this work, we calculate the transition form factors of Lambda _b decaying into proton and N^*(1535) (J^P={1/2}^+ and {1/2}^- respectively) within the framework of light-cone sum rules with the distribution amplitudes (DAs) of Lambda _b-baryon. In the hadronic representation of the correlation function, we have isolated both the proton and the N^*(1535) states so that the Lambda _b rightarrow p, N^*(1535) form factors can be evaluated simultaneously. Due to the less known properties of the baryons, we investigate three interpolating currents of the light baryons and five parametrization models for DAs of Lambda _b . Numerically, our predictions on the Lambda _b rightarrow p form factors and the branching fractions of Lambda _brightarrow pell nu from the Ioffe or the tensor currents are consistent with the Lattice simulation and the results from the light-baryon sum rules, as well as the experimental data of Br(Lambda _b^0rightarrow pmu ^-{{bar{nu }}}). The predictions on the form factors of Lambda _b rightarrow N^*(1535) are very sensitive to the choice of the interpolating currents so that the relevant measurement could be helpful to clarify the properties of baryons.

Gravitational Baryogenesis: Problems and Possible Resolution

The coupling of baryonic current to the derivative of the curvature scalar, R, inherent to gravitational baryogenesis (GBG), leads to a fourth-order differential equation of motion for R instead of the algebraic one of general relativity (GR). The fourth-order differential equation is generically unstable. We consider a possible mechanism of stabilization of GBG by the modification of gravity, introducing an R2 term into the canonical action of GR. It is shown that this mechanism allows for the stabilization of GBG with bosonic and fermionic baryon currents. We establish the region of the model parameters leading to the stabilization of R. Still, the standard cosmology would be noticeably modified.

Causal, stable first-order viscous relativistic hydrodynamics with ideal gas microphysics

We present the first numerical analysis of causal, stable first-order relativistic hydrodynamics with ideal gas microphysics, based in the formalism developed by Bemfica, Disconzi, Noronha, and Kovtun (BDNK theory). The BDNK approach provides definitions for the conserved stress-energy tensor and baryon current, and rigorously proves causality, local well-posedness, strong hyperbolicity, and linear stability (about equilibrium) for the equations of motion, subject to a set of coupled nonlinear inequalities involving the undetermined model coefficients (the choice for which defines the ``hydrodynamic frame''). We present a class of hydrodynamic frames derived from the relativistic ideal gas ``gamma-law'' equation of state which satisfy the BDNK constraints, and explore the properties of the resulting model for a series of $(0+1)\mathrm{D}$ and $(1+1)\mathrm{D}$ tests in 4D Minkowski spacetime. These tests include a comparison of the dissipation mechanisms in Eckart, BDNK, and M\"uller-Israel-Stewart theories, as well as investigations of the impact of hydrodynamic frame on the causality and stability properties of Bjorken flow, planar shockwave, and heat flow solutions.

Baryogenesis in non-extensive Tsallis Cosmology

Non-extensive Tsallis thermostatistics is a widespread paradigm to describe large-scale gravitational systems. In this work we use Tsallis Cosmology to study thermodynamic gravity and derive modified Friedmann equations. We show that corrections induced by non-extensivity affect the Hubble function evolution during the radiation-dominated epoch. In turn, this leads to non-trivial modifications of the mass density and pressure content of the Universe, which provide a viable mechanism allowing for baryogenesis, even in the presence of the standard interaction between the Ricci scalar and baryon current. By demanding consistency with current observational bounds on baryogenesis, we constrain Tsallis δ parameter to be |δ−1|≃10−3. Based on the recently established connection between Tsallis thermostatistics and the quantum gravitational generalization of the uncertainty principle at Planck scale (GUP), we finally show that this bound is in agreement with the estimation of the GUP parameter predicted by many quantum gravity models.

The paradigm of warm quintessential inflation and spontaneous baryogenesis

In this paper, we consider a scenario of spontaneous baryogenesis in a framework of warm quintessential inflation where the residual inflaton field, left out after warm inflation, plays the role of quintessence field at late times and is coupled to a non-conserved baryonic current. Assuming a four fermion (B – L) violating effective interaction, we have demonstrated that the required baryon asymmetry can be produced successfully in this case. We show that the post-inflationary evolution, with the underlying scalar field potential, V(ϕ) = V 0 4exp(–αϕ n/M 4 Pl), n > 1 well suited to warm inflation, exhibits scaling behaviour soon after a brief kinetic regime. We show that the coupling of the scalar field to massive neutrino matter can give rise to exit from the scaling regime to cosmic acceleration at late times as massive neutrinos turn non-relativistic. The proposed model is shown to successfully describe the cosmic history from inflation to late time acceleration, with the evolution independent of initial conditions, along with the generation of baryon asymmetry during the post-inflationary era. A brief analysis of relic gravity waves produced in the scenario is presented.

Baryon asymmetry from the generalized uncertainty principle

The unexplained observed baryon asymmetry in the Universe is a long-standing problem in physics, with no satisfactory resolution so far. To explain this asymmetry, three Sakharov conditions must be met. An interaction term which couples space-time and the baryon current is considered, which satisfies the first two Sakharov conditions. Furthermore, it is shown that the Generalized Uncertainty Principle (GUP) from quantum gravity induces corrections to the Friedmann equations in cosmology, via the holographic principle. GUP also induces variations of energy and pressure density in the radiation dominated era, which satisfies the third Sakharov condition. Therefore, this construction provides a viable explanation for the observed baryon asymmetry. This also fixes the GUP parameters to α0≈104 and β0≈−108.

Super-exceptional embedding construction of the heterotic M5: Emergence of SU(2)-flavor sector

A new super-exceptional embedding construction of the heterotic M5-brane's sigma-model was recently shown to produce, at leading order in the super-exceptional vielbein components, the super-Nambu-Goto (Green-Schwarz-type) Lagrangian for the embedding fields plus the Perry-Schwarz Lagrangian for the free abelian self-dual higher gauge field. Beyond that, further fields and interactions emerge in the model, arising from probe M2- and probe M5-brane wrapping modes. Here we classify the full super-exceptional field content and work out some of its characteristic interactions from the rich super-exceptional Lagrangian of the model. We show that SU(2)×U(1)-valued scalar and vector fields emerge from probe M2- and M5-branes wrapping the vanishing cycle in the A1-type singularity; together with a pair of spinor fields of U(1)-hypercharge ±1 and each transforming as SU(2) iso-doublets. Then we highlight the appearance of a WZW-type term in the super-exceptional PS-Lagrangian and find that on the electromagnetic field it gives the first-order non-linear DBI-correction, while on the iso-vector scalar field it has the form characteristic of the coupling of vector mesons to pions via the Skyrme baryon current. We discuss how this is suggestive of a form of SU(2)-flavor chiral hadrodynamics emerging on the single (N=1) M5 brane, different from, but akin to, holographic large-N QCD.

Effects of dissipative baryon current in heavy-ion collisions at RHIC-BES energies

The CLVisc (3+1)D viscous hydrodynamic model is extended to include the equation of net baryon conservation and the Israel-Stewart-like equations for dissipative baryon current. Using the NEOSB equation of state, we simulate the dynamical evolution and collectivity of the quark-gluon plasma with finite chemical potential, assuming smooth energy density and net baryon density distributions at the initial proper time. Numerical results are shown for the impact of net-baryon dissipation on particle yields and pT spectra in heavy-ion collisions at beam energy scan energies.

Spacetime picture of baryon stopping in the color-glass condensate

We discuss baryon stopping in the Color Glass Condensate description of high energy scattering. We consider the scattering of a distribution of valence quarks on an ultra-relativistic sheet of colored charge. We compute the distribution of scattered quarks from a composite projectile, and calculate the baryon currents before and after the collisions and on an event by event basis. We obtain simple analytic estimates of the baryon number compression and rapidity shifts, which in the idealized case of plane wave scattering, produce results that agree with considerations of Anishetty-Koehler-McLerran.

Hybrid model with dynamical sources for heavy-ion collisions at BES energies

We develop a (3+1)-dimensional hybrid evolution model for heavy-ion collisions with dynamical sources for the energy-momentum tensor and baryon current. During an initial pre-equilibrium stage based on UrQMD, the four-momenta and baryon numbers carried by secondary particles created within UrQMD are fed continuously, after a short thermalization time, into a (3+1)-dimensional viscous hydrodynamic evolution module including baryon transport. The sensitivity of the initial conditions to model parameters and the effect of baryon diffusion on the hydrodynamic evolution are studied.

Net-baryon diffusion in fluid-dynamic simulations of relativistic heavy-ion collisions

A hybrid (hydrodynamics + hadronic transport) theoretical framework is assembled to model the bulk dynamics of relativistic heavy-ion collisions at energies accessible in the Beam Energy Scan (BES) program at the Relativistic Heavy-Ion Collider (RHIC) and the NA61/SHINE experiment at CERN. The system's energy-momentum tensor and net baryon current are evolved according to relativistic hydrodynamics with finite shear viscosity and non-zero net baryon diffusion. Our hydrodynamic description is matched to a hadronic transport model in the dilute region. With this fully integrated theoretical framework, we present a pilot study of the hadronic chemistry, particle spectra, and anisotropic flow. Phenomenological effects of a non-zero net-baryon current and its diffusion on hadronic observables are presented for the first time. The importance of the hadronic transport phase is also investigated.

Residues of ΛQ -type and ΣQ -type baryons in the Bethe-Salpeter equation approach

We study the residues of ${\mathrm{\ensuremath{\Lambda}}}_{Q}$-type baryons (${\mathrm{\ensuremath{\Lambda}}}_{Q}$ and ${\mathrm{\ensuremath{\Xi}}}_{Q}^{A}$) $(Q=b,c)$ and ${\mathrm{\ensuremath{\Sigma}}}_{Q}$-type baryons (${\mathrm{\ensuremath{\Sigma}}}_{Q}^{(*)}$, ${\mathrm{\ensuremath{\Xi}}}_{Q}^{S(*)}$ and ${\mathrm{\ensuremath{\Omega}}}_{Q}^{(*)}$) in the quark-diquark model within the Bethe-Salpeter (BS) formalism. These residues can be used, e.g., in the calculations of the amplitudes in the scattering processes. After constructing the baryonic currents in the BS formalism, we derive the relations between the BS wave functions and the residues for these baryons. The BS equations are solved numerically with the kernel including the scalar confinement and the one-gluon-exchange terms and with the covariant instantaneous approximation being employed in the calculations. Finally, we obtain the numerical values of the residues $0.103\text{ }\text{ }\mathrm{GeV}\ensuremath{\sim}0.224\text{ }\text{ }\mathrm{GeV}$ for ${\mathrm{\ensuremath{\Lambda}}}_{Q}$, $0.143\text{ }\text{ }\mathrm{GeV}\ensuremath{\sim}0.215\text{ }\text{ }\mathrm{GeV}$ for ${\mathrm{\ensuremath{\Xi}}}_{Q}^{A}$, $0.262\text{ }\text{ }\mathrm{GeV}\ensuremath{\sim}0.361\text{ }\text{ }\mathrm{GeV}$ for ${\mathrm{\ensuremath{\Sigma}}}_{Q}^{(*)}$, $0.313\text{ }\text{ }\mathrm{GeV}\ensuremath{\sim}0.460\text{ }\text{ }\mathrm{GeV}$ for ${\mathrm{\ensuremath{\Xi}}}_{Q}^{S(*)}$ and $0.473\text{ }\text{ }\mathrm{GeV}\ensuremath{\sim}0.571\text{ }\text{ }\mathrm{GeV}$ for ${\mathrm{\ensuremath{\Omega}}}_{Q}^{(*)}$ in the ranges of the parameters in our model.

Matter\u2013antimatter asymmetry induced by a running vacuum coupling

We show that a CP-violating interaction induced by a derivative coupling between the running vacuum and a non-conserving baryon current may dynamically break CPT and trigger baryogenesis through an effective chemical potential. By assuming a non-singular class of running vacuum cosmologies which provides a complete cosmic history (from an early inflationary de Sitter stage to the present day quasi-de Sitter acceleration), it is found that an acceptable baryon asymmetry is generated for many different choices of the model parameters. It is interesting that the same ingredient (running vacuum energy density) addresses several open cosmological questions/problems: avoids the initial singularity, provides a smooth exit for primordial inflation, alleviates both the coincidence and the cosmological constant problems, and, finally, is also capable of explaining the generation of matter-antimatter asymmetry in the very early Universe.

Baryogenesis in nonminimally coupled f(R) theories

We generalize the mechanism for gravitational baryogensis in the context of $f(R)$ theories of gravity, including a nonminimal coupling between curvature and matter. In these models, the baryon asymmetry is generated through an effective coupling between the Ricci scalar curvature and the net baryon current that dynamically breaks Charge Conjugation, Parity and Time Reversal (CPT) invariance. We study the combinations of characteristic mass scales and exponents for both non-trivial functions present in the modified action functional and establish the allowed region for these parameters: we find that very small deviations from General Relativity are consistent with the observed baryon asymmetry and lead to temperatures compatible with the subsequent formation of the primordial abundances of light elements. In particular, we show the viability of a power-law nonminimal coupling function $f_2(R) \sim R^n$ with $ 0 < n \lesssim 0.078 $ and determine its characteristic curvature scale.

Betti multiplets, flows across dimensions and c-extremization

We consider 4d mathcal{N} = 1 SCFTs, topologically twisted on compact constant curvature Riemann surfaces, giving rise to 2d mathcal{N} = (0, 2) SCFTs. The exact R-current of these 2d SCFT extremizes the central charge c2d, similarly to the 4d picture, where the exact R-current maximizes the central charge a4d. There are global currents that do not mix with the R-current in 4d but their mixing becomes non trivial in 2d. In this paper we study the holographic dual of this process by analyzing a 5d mathcal{N} = 2 truncation of T1,1 with one Betti vector multiplet, dual to the baryonic current on the CFT side. The holographic realization of the flow across dimensions connects AdS5 to AdS3 vacua in the supergravity picture. We verify the existence of the flow to AdS3 solutions and we retrieve the field theory results for the mixing of the Betti vector with the graviphoton. Moreover, we extract the central charge from the Brown-Henneaux formula, matching with the results obtained in field theory. We develop a general formalism to obtain the central charge of a 2d SCFT from 5d mathcal{N} = 2 gauged supergravity with a generic number of vector multiplets, showing that its extremization corresponds to an attractor mechanism for the scalars in the supergravity picture.