Nuclear Theory·nucl-th

Friday·January 18, 2019

14 papers—6 primary·8 cross-listed

07
[Submitted on 16 Jan 2019] (cross-list from hep-lat)
Calculation of Nucleon Electric Dipole Moments Induced by Quark Chromo-Electric Dipole Moments and the QCD $θ$ -term
S. Syritsyn🇺🇸 · T. Izubuchi🇺🇸 · H. Ohki🇺🇸
Electric dipole moments (EDMs) of nucleons and nuclei, which are sought as evidence of CP violation, require lattice calculations to connect constraints from experiments to limits on the strong CP violation within QCD or CP violation introduced by new physics from beyond the standard model. Nucleon EDM calculations on a lattice are notoriously hard due to large statistical noise, chiral symmetry violating effects, and potential mixing of the EDM and the anomalous magnetic moment of the nucleon. In this report, details of ongoing lattice calculations of proton and neutron EDMs induced by the QCD $θ$ -term and the quark chromo-EDM, the lowest-dimension effective CP-violating quark-gluon interaction are presented. Our calculation employs chiral-symmetric fermion discretization. An assessment of feasibility of nucleon EDM calculations at the physical point is discussed.
Comments:
proceedings XIIIth Quark Confinement and Hadron Spectrum conference (Maynooth University, Ireland, July 31-August 6, 2018); 11 pages, 13 figures. arXiv admin note: substantial text overlap with arXiv:1810.03721
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1901.05455 [pdf]
PoS(2019)·18 citations
08
[Submitted on 16 Jan 2019] (cross-list from hep-ph)
Narrow exotic hadrons in the heavy quark limit of QCD
Yiming Cai🇺🇸 · Thomas Cohen🇺🇸
This paper focuses on tetraquarks containing two heavy quarks in the formal limit where the heavy quark masses are taken to be arbitrarily large. There are well-established model-independent arguments for the existence of deeply bound exotic $q ˉ q ˉ^{'} QQ$ tetraquark in the formal limit of arbitrarily large heavy quark masses. However, these previous arguments did not address the question whether tetraquark states exist close to the threshold for breaking up into two heavy mesons. Such states are not stable under strong interactions---they can emit pions and decay to lower-lying tetraquark states. This raises the issue of whether the nature of the heavy quark limit requires such states to exist as resonances that are narrow. Here we present a model-independent argument that establishes the existence of parametrically narrow tetraquark states. The argument here is based on Born-Oppenheimer and semi-classical considerations. The results derived here are only valid in a formal limit that is well outside the regime occurring for charm quarks in nature. However the analysis may give some insight in the experimentally observed narrow near-threshold tetraquark states containing a heavy quark and antiquark.
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1901.05473 [pdf]
EPJA(2019)·7 citations
09
[Submitted on 16 Jan 2019] (cross-list from hep-ph)
Multi-particle potentials from light-like Wilson lines in quark-gluon plasmas: a generalized relation of in-medium splitting rates to jet-quenching parameters $q^$
Peter Arnold🇺🇸
A powerful historical insight about the theory of in-medium showering in QCD backgrounds was that splitting rates can be related to a parameter $q^$ that characterizes the rate of transverse-momentum kicks to a high-energy particle from the medium. Another powerful insight was that $q^$ can be defined (with caveats) even when the medium is strongly coupled, using long, narrow Wilson loops whose two long edges are light-like Wilson lines. The medium effects for the original calculations of in-medium splitting rates can be formulated in terms of 3-body imaginary-valued `potentials' that are defined with three long, light-like Wilson lines. Corrections due to overlap of two consecutive splittings can be calculated using similarly defined 4-body potentials. I give a simple argument for how such $N$ -body potentials can be determined in the appropriate limit just from knowledge of the values of $q^$ for different color representations. For $N > 3$ , the $N$ -body potentials have non-trivial color structure, which will complicate calculations of overlap corrections outside of the large- $N_{c}$ or soft bremsstrahlung limits.
Comments:
20 pages, 8 figures. Difference from v2: correction (which does not propagate) to eq. (2.16)
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1901.05475 [pdf]
PRD(2019)·12 citations
10
[Submitted on 16 Jan 2019] (cross-list from hep-th)
Simple non-perturbative resummation schemes beyond mean-field: case study for scalar $ϕ^{4}$ theory in 1+1 dimensions
Paul Romatschke🇺🇸
I present a sequence of non-perturbative approximate solutions for scalar $ϕ^{4}$ theory for arbitrary interaction strength, which contains, but allows to systematically improve on, the familiar mean-field approximation. This sequence of approximate solutions is apparently well-behaved and numerically simple to calculate since it only requires the evaluation of (nested) one-loop integrals. To test this resummation scheme, the case of $ϕ^{4}$ theory in 1+1 dimensions is considered, finding approximate agreement with known results for the vacuum energy and mass gap up to the critical point. Because it can be generalized to other dimensions, fermionic fields and finite temperature, the resummation scheme could potentially become a useful tool for calculating non-perturbative properties approximately in certain quantum field theories.
Comments:
v1: 12 pages plus appendix, one figure; v2: matches published version; v3: minor typos corrected
Subjects:
High Energy Physics — Theory (hep-th); Statistical Mechanics (cond-mat.stat-mech); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1901.05483 [pdf]
JHEP(2019)·32 citations
11
[Submitted on 17 Jan 2019] (cross-list from nucl-ex)
Measurement of directed flow of $D^{0}$ and $D^{0} ˉ$ mesons in 200 GeV Au+Au collisions at RHIC using the STAR detector
Liang He (for the STAR Collaboration)🇺🇸
Charm quarks, owing to their large mass, are produced predominantly in the initial hard scatterings in heavy-ion collisions, and therefore can be a valuable tool for studying the early time dynamics of these collisions. The rapidity-odd directed flow at mid-rapidity in heavy-ion collisions originates from a tilt in the reaction plane of the thermalized medium caused by the asymmetry between the number of participants from projectile and target nuclei as a function of rapidity. Recently, it has been predicted that the slope of the directed flow at mid-rapidity for $D^{0}$ mesons, arising from the transport of charm quarks in the tilted medium, can be several times larger than that of light flavor hadrons. The magnitude of the slope is expected to be sensitive to the magnitude of the tilt and the charm quark drag coefficient in the medium. It has also been predicted that the transient electromagnetic field generated at early time can induce a much larger directed flow for heavy quarks than for light quarks. In these proceedings, we will report on the first measurement of the directed flow for the $D^{0}$ and $D ˉ^{0}$ mesons as a function of rapidity in Au+Au collisions at $s_{_{NN}}$ = 200 GeV using high statistics data collected with the Heavy Flavor Tracker in 2014 and 2016 RHIC runs.
Comments:
5 pages, 3 figures. Submitted in Hard Probes 2018 proceedings
Subjects:
Nuclear Experiment (nucl-ex); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1901.05622 [pdf]
PoS(2019)·3 citations
12
[Submitted on 17 Jan 2019] (cross-list from hep-ph)
$Ω N N$ and $ΩΩ N$ states
H. Garcilazo🇲🇽 · A. Valcarce🇪🇸
The lattice QCD analysis of the HAL QCD Collaboration has recently derived $Ω N$ and $ΩΩ$ interacting potentials with nearly physical quark masses ( $m_{π} ≃$ 146 MeV and $m_{K} ≃$ 525 MeV). They found an attractive interaction in the $Ω N$ $^{5} S_{2}$ channel which supports a bound state with a central binding energy of 1.54 MeV. The $ΩΩ$ $^{1} S_{0}$ channel shows an overall attraction with a bound state with a central binding energy of 1.6 MeV. In this paper we looked closely at the $Ω N N$ and $ΩΩ N$ three-body systems making use of the latest HAL QCD Collaboration $Ω N$ and $ΩΩ$ interactions. Our results show that the $Ω d$ system in the state with maximal spin $(I) J^{P} = (0) 5/ 2^{+}$ is bound with a binding energy of about 20 MeV. The $(I) J^{P} = (1) 3/ 2^{+}$ $Ω nn$ state presents a resonance decaying to $ΛΞ n$ and $ΣΞ n$ , with a separation energy of $\sim$ 1 MeV. The $(I) J^{P} = (1/2) 1/ 2^{+}$ $ΩΩ N$ state also exhibits a resonance decaying to $ΛΞΩ$ and $ΣΞΩ$ , with a separation energy of $\sim$ 4.6 MeV. We have calculated the contribution of the Coulomb potential to differentiate among the different charged states.
Comments:
14 pages. Accepted for publication in Phys. Rev. C
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1901.05678 [pdf]
PRC(2019)·24 citations
13
[Submitted on 17 Jan 2019] (cross-list from nucl-ex)
Experimental Evidence for Transverse Wobbling in $^{105}$ Pd
J. Timár🇭🇺 · Q. B. Chen🇩🇪 · B. Kruzsicz🇭🇺 · D. Sohler🇭🇺 · I. Kuti🇭🇺 · S. Q. Zhang🇨🇳 · J. Meng🇨🇳 · P. Joshi🇬🇧 · R. Wadsworth🇬🇧 · K. Starosta🇨🇦 · A. Algora🇭🇺 · P. Bednarczyk🇵🇱 and 16 other authors
New rotational bands built on the $ν$ $(h_{11/2})$ configuration have been identified in $^{105}$ Pd. Two bands built on this configuration show the characteristics of transverse wobbling: the $Δ$ $I$ =1 transitions between them have a predominant E2 component and the wobbling energy decreases with increasing spin. The properties of the observed wobbling bands are in good agreement with theoretical results obtained using constrained triaxial covariant density functional theory and quantum particle rotor model calculations. This provides the first experimental evidence for transverse wobbling bands based on a one-neutron configuration, and also represents the first observation of wobbling motion in the $A$ $\sim$ 100 mass region.
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1901.05891 [pdf]
PRL(2019)·73 citations
14
[Submitted on 17 Jan 2019] (cross-list from hep-ph)
Superheavy objects composed of nuclear and dark matter
Vakhid A. Gani🇷🇺 · Maxim Yu. Khlopov🇷🇺 · Dmitry N. Voskresensky🇷🇺
We consider a model of $O$ He atomic dark matter formed by Coulomb binding of the hypothetical stable double-charged massive $O^{--}$ particles with nuclei of primordial helium. Such a dark matter can be captured by ordinary matter forming superheavy nuclei. We propose a possibility of self-bound by nuclear and electromagnetic interaction $O$ -nuclearites as well as more massive gravitating ones and discuss effect of accumulation of $O$ He atoms in stars and their effect in stellar evolution.
Comments:
4 pages; Proceedings of the 4th International Conference on Particle Physics and Astrophysics (ICPPA-2018), Moscow, 22-26 October 2018
Subjects:
High Energy Physics — Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Nuclear Theory (nucl-th)
arXiv:
1901.05930 [pdf]
J.Phys.Conf.Ser.(2019)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE