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20 pages, 1797 KiB

Open AccessArticle

Hyperon Production in Bi + Bi Collisions at the Nuclotron-Based Ion Collider Facility and Angular Dependence of Hyperon Spin Polarization

by Nikita S. Tsegelnik, Vadym Voronyuk and Evgeni E. Kolomeitsev

Particles 2024, 7(4), 984-1003; https://doi.org/10.3390/particles7040060 - 13 Nov 2024

Viewed by 317

Abstract

The strange baryon production in Bi + Bi collisions at

\sqrt{s_{N N}} = 9.0

GeV is studied using the PHSD transport model. Hyperon and anti-hyperon yields, transverse momentum spectra, and rapidity spectra are calculated, and their centrality dependence and the effect of [...] Read more.

The strange baryon production in Bi + Bi collisions at

\sqrt{s_{N N}} = 9.0

GeV is studied using the PHSD transport model. Hyperon and anti-hyperon yields, transverse momentum spectra, and rapidity spectra are calculated, and their centrality dependence and the effect of rapidity and transverse momentum cuts are studied. The rapidity distributions for

\bar{Λ}

,

Ξ

,

\bar{Ξ}

baryons are found to be systematically narrower than for

Λ

s. The

p_{T}

slope parameters for anti-hyperons vary more with centrality than those for hyperons. Restricting the accepted rapidity range to

| y | < 1

increases the slope parameters by 13–30 MeV, depending on the centrality class and the hyperon mass. Hydrodynamic velocity and vorticity fields are calculated, and the formation of two oppositely rotating vortex rings moving in opposite directions along the collision axis is found. The hyperon spin polarization induced by the medium vorticity within the thermodynamic approach is calculated, and the dependence of the polarization on the transverse momentum and rapidity cuts and on the centrality selection is analyzed. The cuts have stronger effect on the polarization of

Λ

and

Ξ

hyperons than on the corresponding anti-hyperons. The polarization signal is maximal for the centrality class, 60–70%. We show that, for the considered hyperon polarization mechanism, the structure of the vorticity field makes an imprint on the polarization signal as a function of the azimuthal angle in the transverse momentum plane,

ϕ_{H}

,

cos ϕ_{H} = p_{x} / p_{T}

. For particles with positive longitudinal momentum,

p_{z} > 0

, the polarization increases with

cos ϕ_{H}

, while for particles with

p_{z} < 0

it decreases. Full article

(This article belongs to the Special Issue Infinite and Finite Nuclear Matter (INFINUM))

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8 pages, 748 KiB

Open AccessCommunication

Experimental Study of Cold Dense Nuclear Matter

by Maria Patsyuk, Timur Atovullaev, Goran Johansson, Dmitriy Klimanskiy, Vasilisa Lenivenko, Sergey Nepochatykh and Eli Piasetzky

Particles 2024, 7(1), 229-236; https://doi.org/10.3390/particles7010013 - 8 Mar 2024

Viewed by 1368

Abstract

The fundamental theory of nuclear interactions, Quantum Chromodynamics (QCD), operates in terms of quarks and gluons at higher resolution. At low resolution the relevant degrees of freedom are nucleons. Two-nucleon Short-Range Correlations (SRC) help to interconnect these two descriptions. SRCs are temporary fluctuations [...] Read more.

The fundamental theory of nuclear interactions, Quantum Chromodynamics (QCD), operates in terms of quarks and gluons at higher resolution. At low resolution the relevant degrees of freedom are nucleons. Two-nucleon Short-Range Correlations (SRC) help to interconnect these two descriptions. SRCs are temporary fluctuations of strongly interacting close pairs of nucleons. The distance between the two nucleons is comparable to their radii and their relative momenta are larger than the fermi sea level. According to the electron scattering experiments held in the last decade, SRCs have far-reaching impacts on many-body systems, the nucleon-nucleon interactions, and nuclear substructure. The modern experiments with ion beams and cryogenic liquid hydrogen target make it possible to study properties of the nuclear fragments after quasi-elastic knockout of a single nucleon or an SRC pair. Here we review the status and perspectives of the SRC program in so-called inverse kinematics at JINR (Dubna, Russia). The first SRC experiment at the BM@N spectrometer (2018) with 4 GeV/c/nucleon carbon beam has shown that detection of an intact 11B nucleus after interaction selects out the quasi-elastic knockout reaction with minimal contribution of initial- and final-state interactions. Also, 25 events of SRC-breakups showed agreement in SRC properties as known from electron beam experiments. The analysis of the second measurement of SRC at BM@N held in 2022 with an improved setup is currently ongoing. The SRC project at JINR moved to a new experimental area in 2023, where the next measurement is being planned in terms of experimental setup and physics goals. Full article

(This article belongs to the Special Issue Infinite and Finite Nuclear Matter (INFINUM))

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10 pages, 833 KiB

Open AccessArticle

Diquarks and Λ⁰/π⁺, Ξ⁻/π⁺ Ratios in the Framework of the EPNJL Model

by Alexandra Friesen and Yuriy Kalinovsky

Particles 2023, 6(4), 876-885; https://doi.org/10.3390/particles6040056 - 10 Oct 2023

Viewed by 1107

Abstract

The applicability of the effective models to the description of baryons and the behaviour of ratios of strange baryons to pions is discussed. In the framework of the EPNJL model, the Bethe–Salpeter equation is used to find masses of baryons, which are considered [...] Read more.

The applicability of the effective models to the description of baryons and the behaviour of ratios of strange baryons to pions is discussed. In the framework of the EPNJL model, the Bethe–Salpeter equation is used to find masses of baryons, which are considered to be in a diquark-quark state. Baryon melting is discussed at a finite chemical potential, and a flavor dependence of the hadronic deconfinement temperature is pointed out. It is shown that the description of the diquark-quark state at finite chemical potential is limited due to the occurrence of Bose condensate. This effect is strongly manifested in the description of light diquarks and baryons. Both the

Λ^{0} / π^{+}

and

Ξ^{-} / π^{+}

ratios show a sharp behaviour as functions of the

T / μ_{B}

variable, where T and

μ_{B}

are calculated along the melting lines. Full article

(This article belongs to the Special Issue Infinite and Finite Nuclear Matter (INFINUM))

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17 pages, 2187 KiB

Open AccessArticle

Hyperonic Interactions in Neutron Stars

by Semyon Mikheev, Dmitry Lanskoy, Artur Nasakin and Tatiana Tretyakova

Particles 2023, 6(3), 847-863; https://doi.org/10.3390/particles6030054 - 8 Sep 2023

Cited by 2 | Viewed by 1646

Abstract

The matter of neutron stars is characterised by the density of the order of typical nuclear densities; hence, it can be described with methods of nuclear physics. However, at high densities, some effects that are absent in nuclear and hypernuclear physics can appear, [...] Read more.

The matter of neutron stars is characterised by the density of the order of typical nuclear densities; hence, it can be described with methods of nuclear physics. However, at high densities, some effects that are absent in nuclear and hypernuclear physics can appear, and this makes neutron stars a good place for studying the properties of baryonic interactions. In the present work, we consider neutron stars consisting of nucleons, leptons and

Λ

hyperons with Skyrme baryonic forces. We study the character of the

Λ N

interactions taking place in neutron stars at high densities. In particular, we show the difference between three-body

Λ N N

and density-dependent

Λ N

forces. We also demonstrate that the Skyrme

Λ N

forces proportional to nuclear density are better suited for the modelling of neutron stars than the forces proportional to fractional powers of density. Finally, we emphasize the importance of the point of appearance of hyperons in a further search for parameterizations which are suitable for describing neutron stars. Full article

(This article belongs to the Special Issue Infinite and Finite Nuclear Matter (INFINUM))

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13 pages, 1145 KiB

Open AccessArticle

Lee–Yang Zeroes in the Baryon Fugacity Plane: The Role of High Densities

by Nikolai Gerasimeniuk, Vitaly Bornyakov, Vladimir Goy, Roman Rogalyov, Anatolii Korneev, Alexander Molochkov and Atsushi Nakamura

Particles 2023, 6(3), 834-846; https://doi.org/10.3390/particles6030053 - 7 Sep 2023

Viewed by 1212

Abstract

We compute the canonical partition functions and the Lee–Yang zeros in

N_{f} = 2

lattice QCD at temperature

T = 1.20 T_{c}

lying above the Roberge–Weiss phase transition temperature

T_{R W}

. The phase transition is characterized by the discontinuities [...] Read more.

We compute the canonical partition functions and the Lee–Yang zeros in

N_{f} = 2

lattice QCD at temperature

T = 1.20 T_{c}

lying above the Roberge–Weiss phase transition temperature

T_{R W}

. 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. Full article

(This article belongs to the Special Issue Infinite and Finite Nuclear Matter (INFINUM))

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17 pages, 818 KiB

Open AccessArticle

Stripping Model for Short GRBs: The Impact of Nuclear Data

by Andrey Yudin, Nikita Kramarev, Igor Panov and Anton Ignatovskiy

Particles 2023, 6(3), 784-800; https://doi.org/10.3390/particles6030050 - 24 Aug 2023

Viewed by 1435

Abstract

We investigate the impact of forthcoming nuclear data on the predictions of the neutron star (NS) stripping model for short gamma-ray bursts. The main area to which we pay attention is the NS crust. We show that the uncertain properties of the NS [...] Read more.

We investigate the impact of forthcoming nuclear data on the predictions of the neutron star (NS) stripping model for short gamma-ray bursts. The main area to which we pay attention is the NS crust. We show that the uncertain properties of the NS equation of state can significantly influence the stripping time

t_{str}

, the main dynamical parameter of the model. Based on the known time delay (

t_{str} \approx 1.7

s) between the peak of the gravitational wave signal GW170817 and the detection of gamma photons from GRB170817A, we obtain new restrictions on the nuclear matter parameters, in particular, the symmetry energy slope parameter:

L < 114.5

MeV

. In addition, we study the process of nucleosynthesis in the outer and inner crusts of a low-mass NS. We show that the nucleosynthesis is strongly influenced by both the forthcoming nuclear data and the equation of state of the NS matter. Full article

(This article belongs to the Special Issue Infinite and Finite Nuclear Matter (INFINUM))

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13 pages, 390 KiB

Open AccessArticle

Net-Baryon Probability Distributions from Lattice Simulations

by Roman Rogalyov and Vladimir Goy

Particles 2023, 6(3), 771-783; https://doi.org/10.3390/particles6030049 - 23 Aug 2023

Cited by 1 | Viewed by 1265

Abstract

We use the results of lattice simulations of the net-baryon number density at imaginary baryon chemical potential in

N_{f} = 2

QCD to construct the equation of state of dense and hot strong-interacting matter both above the Roberge–Weiss temperature [...] Read more.

We use the results of lattice simulations of the net-baryon number density at imaginary baryon chemical potential in

N_{f} = 2

QCD to construct the equation of state of dense and hot strong-interacting matter both above the Roberge–Weiss temperature

T > T_{R W}

and below the critical temperature

T < T_{c}

. For these cases, we also evaluate probability distributions of the net-baryon number, as well as the respective cumulants and moments. The consequences of the asymptotic behavior of these probability distributions for the problem of reconstruction of the net-baryon probability distributions from cumulants are discussed. Full article

(This article belongs to the Special Issue Infinite and Finite Nuclear Matter (INFINUM))

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11 pages, 796 KiB

Open AccessArticle

Neutrino Spectrum and Energy Loss Rates Due to Weak Processes on Hot ⁵⁶Fe in Pre-Supernova Environment

by A. A. Dzhioev, A. V. Yudin, N. V. Dunina-Barkovskaya and A. I. Vdovin

Particles 2023, 6(3), 682-692; https://doi.org/10.3390/particles6030041 - 28 Jun 2023

Cited by 2 | Viewed by 1297

Abstract

Applying TQRPA calculations of Gamow–Teller strength functions in hot nuclei, we compute the (anti)neutrino spectra and energy loss rates arising from weak processes on hot

^{56}

Fe under pre-supernova conditions. We use a realistic pre-supernova model calculated by the stellar evolution code MESA. [...] Read more.

Applying TQRPA calculations of Gamow–Teller strength functions in hot nuclei, we compute the (anti)neutrino spectra and energy loss rates arising from weak processes on hot

^{56}

Fe under pre-supernova conditions. We use a realistic pre-supernova model calculated by the stellar evolution code MESA. Taking into account both charged and neutral current processes, we demonstrate that weak reactions with hot nuclei can produce high-energy (anti)neutrinos. We also show that, for hot nuclei, the energy loss via (anti)neutrino emission is significantly larger than that for nuclei in their ground state. It is found that the neutral current de-excitation via the

ν \bar{ν}

-pair emission is presumably a dominant source of antineutrinos. In accordance with other studies, we confirm that the so-called single-state approximation for neutrino spectra might fail under certain pre-supernova conditions. Full article

(This article belongs to the Special Issue Infinite and Finite Nuclear Matter (INFINUM))

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