Nuclear Theory·nucl-th

Monday·September 24, 2018

9 papers—4 primary·5 cross-listed

05
[Submitted on 20 Sept 2018] (cross-list from hep-ph)
$Ξ (1690)^{-}$ production in the $K^{-} p \to K^{+} K^{-} Λ$ reaction process near threshold
Jung Keun Ahn🇰🇷 · Seung-il Nam🇰🇷
We investigate $Ξ (1690)^{-}$ production from the $K^{-} p \to K^{+} K^{-} Λ$ reaction within the effective Lagrangian approach at the tree-level Born approximation. We consider the $s$ - and $u$ -channel $Σ/Λ$ ground states and resonances for the $Ξ$ -pole contributions, in addition to the $s$ -channel $Λ$ , $u$ -channel nucleon pole, and $t$ -channel $K^{-}$ -exchange for the $ϕ$ -pole contributions. The $Ξ$ -pole includes $Ξ (1320)$ , $Ξ (1535)$ , $Ξ (1690) (J^{p} = 1/ 2^{-})$ ,and $Ξ (1820) (J^{p} = 3/ 2^{-})$ . We calculate the Dalitz plot density of $(d^{2} σ / d M_{K^{+} K^{-}} d M_{K^{-} Λ}$ at 4.2 GeV $/ c$ ) and the total cross sections for the $K^{-} p \to K^{+} K^{-} Λ$ reaction near the threshold. The calculation results are in good agreement with previously acquired experimental data. Using the parameters from the fit, we present the total and differential cross sections for the two-body $K^{-} p \to K^{+} Ξ (1690)^{-}$ reaction near the threshold. In our calculation, a strong enhancement at backward $K^{+}$ angles is predicted because of the dominant $u$ -channel contribution. We also demonstrate that the Dalitz plot analysis for $p_{K^{-}} = 1.915 - - 2.065$ GeV/c enables us to access direct information regarding $Ξ (1690)^{-}$ production, which can be tested by future $K^{-}$ beam experiments. The possible spin-parity states of $Ξ (1690)^{-}$ are briefly discussed as well.
Comments:
8 pages, 8 figures, Accepted for publication via Phys.Rev.D
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
1809.07765 [pdf]
PRD(2018)·4 citations
06
[Submitted on 21 Sept 2018] (cross-list from hep-ph)
Pentaquark states with the $QQQq q ˉ$ configuration in a simple model
Shi-Yuan Li🇨🇳 · Yan-Rui Liu🇨🇳 · Yu-Nan Liu🇨🇳 · Zong-Guo Si🇨🇳 · Jing Wu🇨🇳
We discuss the mass splittings for the $S$ -wave triply heavy pentaquark states with the $QQQq q ˉ$ $(Q = b, c; q = u, d, s)$ configuration which is a mirror structure of $Q Q ˉ q q q$ . The latter configuration is related with the nature of $P_{c} (4380)$ observed by the LHCb Collaboration. The considered pentaquark masses are roughly estimated with a simple method. One finds that such states are probably not narrow even if they do exist. This leaves room for molecule interpretation for a state around the low-lying threshold of a doubly heavy baryon and a heavy-light meson, e.g. $Ξ_{cc} D$ , if it were observed. As a by product, we conjecture that upper limits for the masses of the conventional triply heavy baryons can be determined by the masses of the conventional doubly heavy baryons.
Comments:
19 pages, 1 figure, 10 tables; Version accepted by Eur. Phys. J. C
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1809.08072 [pdf]
EPJC(2019)·29 citations
07
[Submitted on 20 Sept 2018] (cross-list from hep-ph)
Probing axial quark generalized parton distributions through exclusive photoproduction of a $γ π^{\pm}$ pair with a large invariant mass
G.Duplančić🇭🇷 · K.Passek-Kumerički🇭🇷 · B.Pire🇫🇷 · L.Szymanowski🇵🇱 · S.Wallon🇫🇷
Exclusive photoproduction of a $γ π^{\pm}$ pair in the kinematics where the pair has a large invariant mass and the final nucleon has a small transverse momentum is described in the collinear factorization framework. The scattering amplitude is calculated at leading order in $α_{s}$ and the differential cross sections for the process are estimated in the kinematics of the JLab~12-GeV experiments. The order of magnitude of the predicted cross-sections seems sufficient for a dedicated experiment to be performed. The process turns out to be very sensitive to the axial generalized parton distribution combination $H ~_{u} - H ~_{d}$ .
Comments:
44 pages, 16 figures. arXiv admin note: substantial text overlap with arXiv:1609.03830
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1809.08104 [pdf]
JHEP(2018)·58 citations
08
[Submitted on 20 Sept 2018] (cross-list from astro-ph.HE)
Dense matter equation of state for neutron star mergers
S. Lalit🇺🇸 · M. A. A. Mamun🇺🇸 · C. Constantinou🇺🇸 · M. Prakash🇺🇸
In simulations of binary neutron star mergers, the dense matter equation of state (EOS) is required over wide ranges of density and temperature as well as under conditions in which neutrinos are trapped, and the effects of magnetic fields and rotation prevail. Here we assess the status of dense matter theory and point out the successes and limitations of approaches currently in use. A comparative study of the excluded volume (EV) and virial approaches for the $n p α$ system using the equation of state of Akmal, Pandharipande and Ravenhall for interacting nucleons is presented in the sub-nuclear density regime. Owing to the excluded volume of the $α$ -particles, their mass fraction vanishes in the EV approach below the baryon density 0.1 fm $^{- 3}$ , whereas it continues to rise due to the predominantly attractive interactions in the virial approach. The EV approach of Lattimer et al. is extended here to include clusters of light nuclei such as d, $^{3}$ H and $^{3}$ He in addition to $α$ -particles. Results of the relevant state variables from this development are presented and enable comparisons with related but slightly different approaches in the literature. We also comment on some of the sweet and sour aspects of the supra-nuclear EOS. The extent to which the neutron star gravitational and baryon masses vary due to thermal effects, neutrino trapping, magnetic fields and rotation are summarized from earlier studies in which the effects from each of these sources were considered separately. Increases of about $20% (≳ 50%)$ occur for rigid (differential) rotation with comparable increases occurring in the presence of magnetic fields only for fields in excess of $1 0^{18}$ Gauss. Comparatively smaller changes occur due to thermal effects and neutrino trapping. Some future studies to gain further insight into the outcome of dynamical simulations are suggested.
Comments:
Revised manuscript with one additional figure and previous Fig. 4 replaced, 19 additional references and new text
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
1809.08126 [pdf]
EPJA(2019)·27 citations
09
[Submitted on 21 Sept 2018] (cross-list from hep-ph)
Chiral Cherenkov and chiral transition radiation in anisotropic matter
Kirill Tuchin🇺🇸
A significant contribution to the electromagnetic radiation by a fast electric charge moving in anisotropic chiral matter arises from spontaneous photon radiation due to the chiral anomaly. While such a process, also known as the "vacuum Cherenkov radiation", is forbidden in the QED vacuum, it can occur in chiral matter, where it is more appropriate to call it the "chiral Cherenkov radiation". Its contribution to the radiation spectrum is of order $α^{2}$ compared to $α^{3}$ of the bremsstrahlung. I derive the frequency spectrum and the angular distribution of this radiation in the high energy limit. The quantum effects due to the hard photon emission and the fermion mass are taken into account. The obtained spectra are analyzed in the case the quark-gluon plasma and a Weyl semimetal.
Comments:
13 pages, 6 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Nuclear Theory (nucl-th)
arXiv:
1809.08181 [pdf]
PRD(2018)·18 citations

Affiliations

first authorsco-authorsvia INSPIRE

Ξ(1690)− production in the K−p→K+K−Λ reaction process near threshold

Pentaquark states with the QQQqqˉ​ configuration in a simple model

Probing axial quark generalized parton distributions through exclusive photoproduction of a γπ± pair with a large invariant mass

Dense matter equation of state for neutron star mergers

Chiral Cherenkov and chiral transition radiation in anisotropic matter

Affiliations

$Ξ (1690)^{-}$ production in the $K^{-} p \to K^{+} K^{-} Λ$ reaction process near threshold

Pentaquark states with the $QQQq q ˉ$ configuration in a simple model

Probing axial quark generalized parton distributions through exclusive photoproduction of a $γ π^{\pm}$ pair with a large invariant mass