Nuclear Theory·nucl-th

Thursday·September 3, 2020

16 papers—9 primary·7 cross-listed

10
[Submitted on 30 Aug 2020] (cross-list from hep-ph)
Enhancement of low-mass dileptons in ultraperipheral collisions
I.M. Dremin🇷🇺 · S.R. Gevorkyan🇷🇺 · D.T. Madigozhin🇷🇺
It is shown that production of low-mass $e^{+} e^{-}$ -pairs in ultraperipheral nuclear collisions is enhanced due to the Sommerfeld-Gamow-Sakharov (SGS) factor. This effect is especially strong near the threshold of creation of unbound $e^{+} e^{-}$ -pairs with low masses in the two-photon fusion. Coulomb attraction of the non-relativistic components of such pairs may lead to the increased intensity of 511 keV photons. It can be recorded at the NICA collider and has some astrophysical implications. The analogous effect can be observed at LHC in dilepton production.
Comments:
10 p., 3 Figs
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2008.13184 [pdf]
EPJC(2021)·8 citations
11
[Submitted on 2 Sept 2020] (cross-list from hep-th)
Covariant propagator and chiral power counting
Zhou Liu🇨🇳 · Li-Hong Wen🇨🇳 · J.-F. Yang🇨🇳
Some one-loop diagrams with one and two external baryons/nucleons are revisited using covariant baryon propagators in chiral effective theory. We showed that it is enough to separate and subtract all the local terms that violate chiral power counting to recover chiral power counting, no need to introduce extra operations. The structures of leading chiral corrections and IR enhancement or threshold effects are 'stable' or persist as long as covariant propagators are employed for all particles.
Comments:
9 pages, 11 figures, final version, accepted for publication in Nuclear Physics B
Subjects:
High Energy Physics — Theory (hep-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2009.00753 [pdf]
NPB(2021)·2 citations
12
[Submitted on 2 Sept 2020] (cross-list from nucl-ex)
Estimation of CP violating EDMs from known mechanisms in the SM
Prajwal Mohanmurthy🇺🇸 · Jeff A. Winger🇺🇸
New sources of CP violation, beyond the known sources in the standard model (SM), are required to explain the baryon asymmetry of the universe. Measurement of a non-zero permanent electric dipole moment (EDM) for fundamental particles, such as in an electron or a neutron, or in nuclei or atoms, can help us gain a handle on the sources of CP violation, both in SM and beyond. Multiple mechanisms within the SM can generate CP violating EDMs, viz.\ through the CKM matrix in the weak sector or through the QCD $θ ˉ$ parameter in the strong sector. We will estimate the maximum possible EDMs of leptons, certain baryons, select atoms and molecules in the (CKM $⨁ θ ˉ$ ) framework, assuming that the EDM wholly originates from either of the two SM mechanisms, independently. These estimates have been presented in light of the current experimental upper limits on the EDMs, in the following systems - leptons: $e^{-}$ , $μ^{-}$ , $τ^{-}$ , $ν_{e}^{0}$ , $ν_{μ}^{0}$ , $ν_{τ}^{0}$ , baryons: $n^{0}$ , $p^{+}$ , $Λ^{0}$ , $Σ^{0}$ , $Ξ^{0}$ , $Λ_{c}^{+}$ , $Ξ_{c}^{+}$ , atoms: $^{85}$ Rb, $^{133}$ Cs, $^{210}$ Fr, $^{205}$ Tl, $^{199}$ Hg, $^{129}$ Xe, $^{225}$ Ra, $^{223}$ Rn, and molecules: HfF $^{+}$ , PbO, YbF, ThO, RaF, TlF. Particularly, to drive home the point that EDMs in different systems constrain CP-violating interactions differently, we show that the same measured constraint on the EDM in two different systems may not actually be equally constraining on CP violating parameters, and to emphasize the need to measure a non-zero EDM in multiple systems before understanding the origins of these CP-violating EDMs.
Comments:
Proceedings of The 40th International Conference on High Energy Physics, ICHEP-2020; Jul 28-Aug 6, 2020, Prague, Czech Republic; Abs. ID: 97. 11 Pages, 6 Tables, 1 figure. Version 1 sets ${C_{S}, C_{T}} = 0$ , these constraints have been relaxed in version 3. Version 2 experimental values (red) are expected measurement sensitivities in the near future. Typos have been edited
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2009.00852 [pdf]
PoS(2021)·4 citations
13
[Submitted on 2 Sept 2020] (cross-list from astro-ph.HE)
GW190814: Circumstantial Evidence for Up-Down Quark Star
Zheng Cao🇨🇳 · Lie-Wen Chen🇨🇳 · Peng-Cheng Chu🇨🇳 · Ying Zhou🇨🇳
Within a confining quark matter model which considers phenomenologically the quark confinement and asymptotic freedom as well as the chiral symmetry restoration and quark deconfinement at high baryon density, we find that if the up-down quark matter ( $u d$ QM) is more stable than nuclear matter and strange quark matter (SQM), the maximum mass of static quark stars with $u d$ QM is $2.87 M_{⊙}$ under agreement with both the constraints on star tidal deformability from gravitational wave signal GW170817 and the mass-radius of PSR J0030+0451 and PSR J0740+6620 measured by NICER. In contrast, the conventional strange quark star with the SQM that is more stable than nuclear matter while the nuclear matter is more stable than $u d$ QM, has a maximum static mass of only $1.87 M_{⊙}$ and its radius significantly deviates from NICER's constraint. Our results thus provide circumstantial evidence suggesting the recently reported GW190814's secondary component with a mass of $2.5 9_{- 0.09}^{+ 0.08} M_{⊙}$ could be an up-down quark star.
Comments:
6 pages, 2 figures. Results updated and discussions added. Accepted version to appear in PRD
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2009.00942 [pdf]
PRD(2022)·64 citations
14
[Submitted on 2 Sept 2020] (cross-list from hep-ph)
Holography in Quark-Gluon Plasma and Neutron Stars
Govert Nijs🇳🇱
In this thesis, QCD is studied from three different directions, with one overarching theme: holography. The holographic duality allows certain strongly coupled QFTs to be described in terms of much simpler classical gravity in one dimension more. The first direction from which QCD is studied in this thesis is by examining the effects of an external magnetic field on a particular holographic model of QCD, yielding interesting qualitative insight. The second approach examines how, in the same model, one can describe dense baryonic configurations, providing a new way to study the matter composing neutron stars. Indeed, the equation of state produced in this way is subsequently used to compute several neutron star properties which are observable, or will be in the near future. The last direction contains no holographic computations per se, but does incorporate several qualitative insights from holography into a new heavy ion code called Trajectum. This will in the near future be used to perform a Bayesian analysis, whereby it is hoped that these qualitative insights from holography can be tested on experimental data, to see how well the ideas coming from holography match up with experiment.
Comments:
PhD Thesis, 202 pages, 49 figures, http://dspace.library.uu.nl/handle/1874/397298
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2009.01138 [pdf]
1 citation
15
[Submitted on 2 Sept 2020] (cross-list from hep-ph)
Strange quark mass turns magnetic domain walls into multi-winding flux tubes
Geraint W. Evans🇬🇧 · Andreas Schmitt🇬🇧
Dense quark matter is expected to behave as a type-II superconductor at strong coupling. It was previously shown that if the strange quark mass $m_{s}$ is neglected, magnetic domain walls in the so-called 2SC phase are the energetically preferred magnetic defects in a certain parameter region. Computing the flux tube profiles and associated free energies within a Ginzburg-Landau approach, we find a cascade of multi-winding flux tubes as "remnants" of the domain wall when $m_{s}$ is increased. These flux tubes exhibit an unconventional ring-like structure of the magnetic field. We show that flux tubes with winding numbers larger than one survive for values of $m_{s}$ up to about 20% of the quark chemical potential. This makes them unlikely to play a significant role in compact stars, but they may appear in the QCD phase diagram in the presence of an external magnetic field.
Comments:
25 pages, 6 figures; v2: minor improvements, extended discussion on length scales of the flux tubes, to appear in J.Phys.G
Subjects:
High Energy Physics — Phenomenology (hep-ph); Superconductivity (cond-mat.supr-con); Nuclear Theory (nucl-th)
arXiv:
2009.01141 [pdf]
J.Phys.G(2021)·5 citations
16
[Submitted on 2 Sept 2020] (cross-list from nucl-ex)
Accessing the Single-Particle Structure of the Pygmy Dipole Resonance in $^{208}$ Pb
M. Spieker · A. Heusler · B. A. Brown · T. Faestermann · R. Hertenberger · G. Potel · M. Scheck · N. Tsoneva · M. Weinert · H.-F. Wirth · A. Zilges
New experimental data on the neutron single-particle character of the Pygmy Dipole Resonance (PDR) in $^{208}$ Pb are presented. They were obtained from $(d, p)$ and resonant proton scattering experiments performed at the Q3D spectrograph of the Maier-Leibnitz Laboratory in Garching, Germany. The new data are compared to the large suite of complementary, experimental data available for $^{208}$ Pb and establish $(d, p)$ as an additional, valuable, experimental probe to study the PDR and its collectivity. Besides the single-particle character of the states, different features of the strength distributions are discussed and compared to Large-Scale-Shell-Model (LSSM) and energy-density functional (EDF) plus Quasiparticle-Phonon Model (QPM) theoretical approaches to elucidate the microscopic structure of the PDR in $^{208}$ Pb.
Comments:
9 pages, 4 figures
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2009.01151 [pdf]
PRL(2020)·30 citations

Affiliations

first authorsco-authorsvia INSPIRE

Enhancement of low-mass dileptons in ultraperipheral collisions

Covariant propagator and chiral power counting

Estimation of CP violating EDMs from known mechanisms in the SM

GW190814: Circumstantial Evidence for Up-Down Quark Star

Holography in Quark-Gluon Plasma and Neutron Stars

Strange quark mass turns magnetic domain walls into multi-winding flux tubes

Accessing the Single-Particle Structure of the Pygmy Dipole Resonance in 208Pb

Affiliations

Accessing the Single-Particle Structure of the Pygmy Dipole Resonance in $^{208}$ Pb