Large Baryon Number Research Articles

Cumulants from short-range correlations and baryon number conservation at next-to-leading order

We calculate the baryon number cumulants within acceptance with short-range correlations and global baryon number conservation in terms of cumulants in the whole system without baryon conservation. We extract leading and next-to-leading order terms of the large baryon number limit approximation. Our results extend the findings of Refs. [1,2]. These approximations are checked to be very close to the exact results.

(Anti)nucleosynthesis in heavy-ion collisions and (anti)nuclei as "baryonmeter" of the collision

The production mechanism of light (anti)nuclei in heavy-ion collisions has been extensively studied experimentally and theoretically. Two competing (anti)nucleosynthesis models are typically used to describe light (anti)nuclei yields and their ratios to other hadrons in heavy-ion collisions: the statistical hadronization model (SHM) and the nucleon coalescence model. The possibility to distinguish these phenomenological models calls for new experimental observables. Given their large baryon number, light (anti)nuclei have a high sensitivity to the baryon chemical potential (μB) of the system created in the collision. In this talk, the first measurement of event-by-event antideuteron number fluctuations in heavy-ion collisions is presented and compared with expectations of the SHM and coalescence model. In addition, the antinuclei-to-nuclei ratios are used to obtain a measurement of μB in heavy-ion collisions with unprecedented precision.

Chern-Simons-matter theories at large baryon number

We study SU(2) Chern-Simons theories at level k coupled to a scalar on T2 × ℝ at large baryon number. We find a homogeneous but anisotropic ground state configuration for any values of k on the IR fixed-point of those models. This classical analysis is valid as long as we take the baryon number large. As a corollary, by comparing the symmetry breaking pattern at large chemical potential, we find that the theory does not reduce to the singlet sector of the O(4) Wilson-Fisher fixed-point at large-k, as expected from general grounds. This paper will be one primitive step towards quantitative analysis of Chern-Simons-matter dualities using the large charge expansion.

Quantum nucleation of up-down quark matter and astrophysical implications

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.

Skyrmions, Tetrahedra and Magic Numbers

Abstract 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.

Quarkyonic phase from quenched dynamical holographic QCD model

Chiral and deconfinement phase transitions at finite temperature T and quark number chemical potential μ are simultaneously studied in the quenched dynamical holographic QCD model within the Einstein-Dilaton-Maxwell framework. By calculating the corresponding order parameters, i.e., the chiral condensate and Polyakov loop, it is shown that the transition lines of these two phase transitions are separated in the T − μ plane. The deconfinement phase transition is shown to be always of crossover type and the transition line depends weakly on the baryon number density. Differently, the chiral transition is of crossover at small baryon number density and it turns to be of first order at sufficient large baryon number density. A critical endpoint (CEP), at which the transition becomes second order type, appears in the chiral transition line. This is the first time to realize the CEP of chiral phase transition in the (T, μ) plane using the holographic EMD (Einstein-Maxwell-Dilaton) model for two flavour case. It is observed that between these two phase transition lines, there is a region with chiral symmetry restored and color degrees still confined, which could be considered as the quarkyonic phase. Qualitatively, this behavior is in consistent with the result in the Polyakov-loop improved Nambu-Jona-Lasinio (PNJL) model.

Fluid behavior of a baryon-rich hadron resonance gas

We investigate the effects of finite baryon chemical potential on the transport properties of a hadron resonance gas. We find that a hadron resonance gas with large baryon number density is closer to the ideal fluid limit than the corresponding gas with zero baryon number. This suggests that the system created at the Relativistic Heavy Ion Collider (RHIC) at lower collision energies may behave as a fluid, with an effective fluidity close to the one found at RHIC's highest energy near phase transition. This might explain why the differential elliptic flow coefficient measured at lower collisional energies at RHIC is similar to the one observed at high energies.

Skyrmion stars and the multilayered rational map ansatz

We investigate the large baryon number sector of the Einstein-Skyrme model as a possible model for baryon stars and construct low energy configurations that resemble neutron stars. Previous studies have shown that gravitating Skyrmions produced by using rational maps can achieve spherically symmetric, multibaryon-bound states at large baryon numbers, but these configurations were hollow shells. In this paper, we improve on the previous work by constructing configurations corresponding to solid spheres with a radius-dependent baryon density.

Vortons in dense quark matter

At large baryon number density, it is likely that the ground state of QCD is a color-flavor-locked phase with a K0 condensate. The CFL+K0 phase is known to support superconducting vortex strings, and it has been previously suggested that it may also support vortons, which are superconducting vortex rings. We reexamine the question of the stability of vortons, taking into account electromagnetic effects, which make leading-order contributions to vorton dynamics but were not investigated in previous work. We find that current-carrying and electrically charged vortons can be stabilized either by their angular momentum, by Coulomb repulsion, or by a combination of both effects.

Note on new baryon channels to measure the photon polarization inb→sγ

At LHC a large number of b-flavored baryons will be produced. In this note we propose new baryon modes to determine the photon helicity of the penguin transition $b \to s \gamma$. The decay $\Lambda_b \to \Lambda \gamma$ has the drawback that the $\Lambda$, being neutral and long-lived, will escape detection most of the time. To overcome this difficulty, transitions of the type $\Lambda_b \to \Lambda^{*} \gamma$ have been proposed, where $\Lambda^{*}$ denotes an excited state decaying strongly within the detector into the clean mode $p K^-$. The doublet $\Xi_b$, that decays weakly, has a number of good features. The charged baryon $\Xi_b^-$ will decay into the mode $\Xi^- \gamma$, where the ground state hyperon $\Xi^-$, although it will decay most of the time outside the detector, can be detected because it is charged. We consider also the decay of $\Xi_b$ into $\Xi^{*} \gamma$, where a higher mass state $\Xi^{*}$ can decay strongly within the detector. We point out that the initial transverse polarization of $\Xi_b$ has to be known in all cases. To determine this parameter through the transition $\Xi_b \to J/\Psi\ \Xi$, we distinguish between different cases, and underline that in some situations one needs {\it theoretical input} on the asymmetry parameter $\alpha_{\Xi_b}$ of the primary decay. {\it A fortiori} the same considerations apply to the case of the $\Lambda_b$.

Higgs versus matter in the heterotic landscape

In supersymmetric extensions of the standard model there is no basic difference between Higgs and matter fields, which leads to the well-known problem of potentially large baryon and lepton number violating interactions. Although these unwanted couplings can be forbidden by continuous or discrete global symmetries, a theoretical guiding principle for their choice is missing. We examine this problem for a class of vacua of the heterotic string compactified on an orbifold. As expected, in general there is no difference between Higgs and matter. However, certain vacua happen to possess unbroken matter parity and discrete R-symmetries which single out Higgs fields in the low energy effective field theory. We present a method how to identify maximal vacua in which the perturbative contribution to the μ-term and the expectation value of the superpotential vanish. Two vacua are studied in detail, one with two pairs of Higgs doublets and one with partial gauge-Higgs unification.

Holographic nuclear physics

We analyze the phases of the Sakai-Sugimoto model at finite temperature and baryon chemical potential. Baryonic matter is represented either by 4-branes in the 8-branes or by strings stretched from the 8-branes to the horizon. We find the explicit configurations and use them to determine the phase diagram and equation of state of the model. The 4-brane configuration (nuclear matter) is always preferred to the string configuration (quark matter), and the latter is also unstable to density fluctuations. In the deconfined phase the phase diagram has three regions corresponding to the vacuum, quark-gluon plasma, and nuclear matter, with a first-order and a second-order phase transition separating the phases. We find that for a large baryon number density, and at low temperatures, the dominant phase has broken chiral symmetry. This is in qualitative agreement with studies of QCD at high density.

Baryon-Number-Induced Chern-Simons Couplings of Vector and Axial-Vector Mesons in Holographic QCD

We show that holographic models of QCD predict the presence of a Chern-Simons coupling between vector and axial-vector mesons at finite baryon density. In the Anti de Sitter/Conformal Field Theory dictionary, the coefficient of this coupling is proportional to the baryon number density and is fixed uniquely in the five-dimensional holographic dual by anomalies in the flavor currents. For the lightest mesons, the coupling mixes transverse rho and a1 polarization states. At sufficiently large baryon number densities, it produces an instability, which causes the rho and a1 mesons to condense in a state breaking both rotational and translational invariance.

Towards Skyrmion stars: Large baryon configurations in the Einstein-Skyrme model

We investigate the large baryon number sector of the Einstein-Skyrme model as a possible model for baryon stars. Gravitating hedgehog skyrmions have been investigated previously and the existence of stable solitonic stars excluded due to energy considerations [P. Bizon and T. Chmaj, Phys. Lett. B 297, 55 (1992).]. However, in this paper we demonstrate that by generating gravitating Skyrmions using rational maps, we can achieve multibaryon bound states while recovering spherical symmetry in the limit where B becomes large.

Charge, strangeness and radius of strangelets

We investigate, at both zero and finite temperatures, the properties of strangelets versus the electric charge Z and strangeness S. The strangelet radius is not a monotonic function of either charge or strangeness, and a minimum is reached in the (Z, S) plane. However, the thermodynamically stable strangelets do not correspond to the radius minimum. The minimum radius always appears at positive strangeness, while the stable radius may appear at negative strangeness for very small baryon numbers. For large baryon numbers, the stable radius is proportional to the cubic root of baryon numbers, but inversely proportional to the square root of the confinement parameter in the present model. If bulk strange quark matter is absolutely stable, the reduced size of strangelets is about 1 fm, which may be relevant for the analysis of the strangelet production and detection.

COLOR FERROMAGNETIC QUARK MATTER IN NEUTRON STARS

Color superconducting state has been known as a possible phase of quark matter with sufficiently large baryon number density so as for perturbative analysis to be valid. We point out that a color ferromagnetic state is another possible phase of such a sufficiently dense quark matter. Furthermore, we show under reasonable choices of parameters that the color ferromagnetic phase is energetically more favored than the color superconducting phase in the quark matter with smaller baryon number density. Supposing that increasing baryon density in neutron stars transforms nuclear matter into the quark matter of the color ferromagnetic phase, not color superconducting phase, we find that a critical mass of the neutron star with such an internal structure is about 1.6M⊙.

Skyrmions with massive pions

In the Skyrme model with massless pions, the minimal energy multi-Skyrmions are shell-like, with the baryon density localized on the edges of a polyhedron that is approximately spherical and generically of the fullerene-type. In this paper we show that in the Skyrme model with massive pions these configurations are unstable for sufficiently large baryon number. Using numerical simulations of the full nonlinear field theory, we show that these structures collapse to form qualitatively different stable Skyrmion solutions. These new Skyrmions have a flat structure and display a clustering phenomenon into lower charge components, particularly components of baryon numbers three and four. These new qualitative features of Skyrmions with massive pions are encouraging in comparison with the expectations based on real nuclei.

Finkelstein–Rubinstein constraints for the Skyrme model with pion masses

The Skyrme model is a classical field theory modelling the strong interaction between atomic nuclei. It has to be quantized in order to compare it to nuclear physics. When the Skyrme model is semi-classically quantized it is important to take the Finkelstein–Rubinstein constraints into account. Recently, a simple formula has been derived to calculate the constraints for Skyrmions which are well approximated by rational maps. However, if a pion mass term is included in the model, Skyrmions of sufficiently large baryon number are no longer well approximated by the rational map ansatz. This paper addresses the question how to calculate Finkelstein–Rubinstein constraints for Skyrme configurations which are only known numerically.

Mass terms in the Skyrme model

We consider various forms of the mass term that can be used in the Skyrme model and their implications on the properties of baryonic states. It is shown that modifications of the mass term, without changing the asymptotic behavior of the profile function at large $r$, can considerably alter the mass term contribution to the classical mass of the soliton. We find that, for some choices of this mass term, multibaryon configurations can be classically bound at large baryon numbers. It is pointed out that some restrictions on the possible form of the mass term can follow from studies of multimeson interactions.

Color SU(2) Lattice QCD High Density State

We report our numerical study on a high density state of a lattice two-color QCD with Wilson fermions. With a large chemical potential, the Polyakov line, the energy density and the number density shows the confinement-deconfinement transition-like behavior. Propagators of a gluon, meson and baryons are investigated. A strange modification of the vector meson propagators is observed; the vector meson mass may drop at a large baryon number density.