Particles

10 pages, 404 KiB

Open AccessArticle

Constraints on CP-Odd ALP Couplings from EDM Limits of Fermions

by Dmitri V. Kirpichnikov, Valery E. Lyubovitskij and Alexey S. Zhevlakov

Particles 2020, 3(4), 719-728; https://doi.org/10.3390/particles3040047 - 16 Dec 2020

Cited by 9 | Viewed by 2447

We discuss constraints on soft CP-violating couplings of axion-like particles with photon and fermions by using data on electric dipole moments of standard model particles. In particular, for the axion-like particle (ALP) leptophilic scenario, we derive bounds on CP-odd ALP-photon-photon coupling from data of the ACME collaboration on electron EDM. We also discuss prospects of the storage ring experiment to constrain the ALP–photon–photon coupling from data on proton EDM for the simplified hadrophilic interactions of ALP. The resulting constraints from experimental bounds on the muon and neutron EDMs are weak. We set constraint on the CP-odd ALP coupling with electron and derive bounds on combinations of coupling constants, which involve soft CP-violating terms. Full article

(This article belongs to the Collection Dark Matter and New Physics of Hidden Particles)

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13 pages, 673 KiB

Open AccessEditor’s ChoiceArticle

Spin Susceptibility in Neutron Matter from Quantum Monte Carlo Calculations

by Luca Riz, Francesco Pederiva, Diego Lonardoni and Stefano Gandolfi

Particles 2020, 3(4), 706-718; https://doi.org/10.3390/particles3040046 - 26 Nov 2020

Cited by 3 | Viewed by 2957

Abstract

The spin susceptibility in pure neutron matter is computed from auxiliary field diffusion Monte Carlo calculations over a wide range of densities. The calculations are performed for different spin asymmetries, while using twist-averaged boundary conditions to reduce finite-size effects. The employed nuclear interactions include both the phenomenological Argonne AV8′ + UIX potential and local interactions that are derived from chiral effective field theory up to next-to-next-to-leading order. Full article

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13 pages, 494 KiB

Open AccessArticle

Neutron Star Cooling Within the Equation of State With Induced Surface Tension

by Stefanos Tsiopelas and Violetta Sagun

Particles 2020, 3(4), 693-705; https://doi.org/10.3390/particles3040045 - 21 Nov 2020

Cited by 3 | Viewed by 2430

Abstract

We study the thermal evolution of neutron stars described within the equation of state with induced surface tension (IST) that reproduces properties of normal nuclear matter, fulfills the proton flow constraint, provides a high-quality description of hadron multiplicities created during the nuclear-nuclear collision experiments, and it is equally compatible with the constraints from astrophysical observations and the GW170817 event. The model features strong direct Urca processes for the stars above

1.91 M_{⊙}

. The IST equation of state shows very good agreement with the available cooling data, even without introducing nuclear pairing. We also analysed the effect of the singlet proton/neutron and triplet neutron pairing on the cooling of neutron stars of different mass. We show that the description of the compact object in the center of the Cassiopeia A does not necessarily require an inclusion of neutron superfluidity and/or proton superconductivity. Our results indicate that data of Cassiopeia A can be adequately well reproduced by a

1.66 M_{⊙}

star with an atmosphere of light elements. Moreover, the IST EoS reproduces each of the observational datasets for the surface temperature of Cassiopeia A either by a rapidly cooling ∼

1.955 M_{⊙}

star with paired and unpaired matter or by a

1.91 M_{⊙}

star with the inclusion of neutron and proton pairings in the singlet channel. Full article

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17 pages, 337 KiB

Open AccessFeature PaperArticle

Direct Photons from Hot Quark Matter in Renormalized Finite-Time-Path QED

by Ivan Dadić, Dubravko Klabučar and Domagoj Kuić

Particles 2020, 3(4), 676-692; https://doi.org/10.3390/particles3040044 - 20 Oct 2020

Cited by 2 | Viewed by 2292

Abstract

Within the finite-time-path out-of-equilibrium quantum field theory (QFT), we calculate direct photon emission from early stages of heavy ion collisions, from a narrow window, in which uncertainty relations are still important and they provide a new mechanism for production of photons. The basic difference with respect to earlier calculations, leading to diverging results, is that we use renormalized QED of quarks and photons. Our result is a finite contribution that is consistent with uncertainty relations. Full article

(This article belongs to the Collection High Energy Physics)

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16 pages, 578 KiB

Open AccessArticle

Equation of State of Strongly Magnetized Matter with Hyperons and Δ-Resonances

by Vivek Baruah Thapa, Monika Sinha, Jia Jie Li and Armen Sedrakian

Particles 2020, 3(4), 660-675; https://doi.org/10.3390/particles3040043 - 13 Oct 2020

Cited by 21 | Viewed by 2667

Abstract

We construct a new equation of state for the baryonic matter under an intense magnetic field within the framework of covariant density functional theory. The composition of matter includes hyperons as well as

Δ

-resonances. The extension of the nucleonic functional to the [...] Read more.

Δ

-resonances. The extension of the nucleonic functional to the hypernuclear sector is constrained by the experimental data on

Λ

and

Ξ

-hypernuclei. We find that the equation of state stiffens with the inclusion of the magnetic field, which increases the maximum mass of neutron star compared to the non-magnetic case. In addition, the strangeness fraction in the matter is enhanced. Several observables, like the Dirac effective mass, particle abundances, etc. show typical oscillatory behavior as a function of the magnetic field and/or density which is traced back to the occupation pattern of Landau levels. Full article

(This article belongs to the Special Issue Selected Papers from “The Modern Physics of Compact Stars and Relativistic Gravity 2019”)

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Particles, Volume 3, Issue 4 (December 2020) – 5 articles

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