Nuclear Theory·nucl-th

Friday·September 22, 2017

7 papers—2 primary·5 cross-listed

03
[Submitted on 1 Jun 2017] (cross-list from hep-lat)
A complete non-perturbative renormalization prescription for quasi-PDFs
Constantia Alexandrou🇨🇾 · Krzysztof Cichy🇩🇪 · Martha Constantinou🇺🇸 · Kyriakos Hadjiyiannakou🇨🇾 · Karl Jansen🇩🇪 · Haralambos Panagopoulos🇨🇾 · Fernanda Steffens🇩🇪
In this work we present, for the first time, the non-perturbative renormalization for the unpolarized, helicity and transversity quasi-PDFs, in an RI' scheme. The proposed prescription addresses simultaneously all aspects of renormalization: logarithmic divergences, finite renormalization as well as the linear divergence which is present in the matrix elements of fermion operators with Wilson lines. Furthermore, for the case of the unpolarized quasi-PDFs, we describe how to eliminate the unwanted mixing with the twist-3 scalar operator. We utilize perturbation theory for the one-loop conversion factor that brings the renormalization functions to the MS-scheme at a scale of 2 GeV. We also explain how to improve the estimates on the renormalization functions by eliminating lattice artifacts. The latter can be computed in one-loop perturbation theory and to all orders in the lattice spacing. We apply the methodology for the renormalization to an ensemble of twisted mass fermions with Nf=2+1+1 dynamical light quarks, and a pion mass of around 375 MeV.
Comments:
24 pages, 10 figures, 2 Tables, Section 3 largely expanded compared to v1. Version accepted for publication in Nucl. Phys. B (invited Frontiers Article)
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1706.00265 [pdf]
NPB(2017)·210 citations
04
[Submitted on 20 Sept 2017] (cross-list from astro-ph.HE)
Phase transition in compact stars: nucleation mechanism and $γ$ -ray bursts revisited
Kauan D. Marquez🇧🇷 · Débora P. Menezes🇧🇷
We have revisited the nucleation process based on the Lifshitz-Kagan theory, which is the underlying mechanism of conversion of a pulsar constituted of hadronic matter to a quark star. We have selected appropriate models that have been tested against experimental and observational constraints to restrict the model arbitrariness present in previous investigations. The phase transition pressures and chemical potentials have been identified and afterwards, the tunneling probabilities and the nucleation time were computed. The critical pressures for which the half life of the metastable hadronic phase is one year were obtained. Even with the restrictions imposed to the selection of models, the results remained model dependent, but we found that the tunneling that makes possible the appearance of stable matter requires an overpressure that is practically independent of the quark matter bag constant. Finally, we have confirmed that the nucleation process can be one of the causes of gamma-ray bursts.
Comments:
21 pages, 11 figures
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
1709.07040 [pdf]
JCAP(2017)·15 citations
05
[Submitted on 20 Sept 2017] (cross-list from astro-ph.HE)
Relativistic disc line: a tool to constrain neutron star equation of state models
Sudip Bhattacharyya (TIFR, India)
Relativistic iron K $α$ spectral emission line from the inner disc of a neutron star low-mass X-ray binary (LMXB) was first detected in 2007. This discovery opened up new ways to probe strong gravity and dense matter. The past decade has seen detections of such a line from many neutron star LMXBs, and confirmation of this line from the same source with several X-ray satellites. These have firmly established the new field of relativistic disc line from neutron star systems in only ten years. Fitting the shape of such a line with an appropriate general relativistic model provides the accretion disc inner edge radius to the stellar mass ratio. In this review, we briefly discuss how an accurate measurement of this ratio with a future larger area X-ray instrument can be used to constrain neutron star equation of state models.
Comments:
10 pages, 10 figures, Has appeared in Journal of Astrophysics and Astronomy special issue on 'Physics of Neutron Stars and Related Objects', celebrating the 75th birth-year of G. Srinivasan
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
arXiv:
1709.07069 [pdf]
J.Astrophys.Astron.(2017)·2 citations
06
[Submitted on 21 Sept 2017] (cross-list from hep-ph)
New low- $Q^{2}$ measurements of the $γ^{*} N \to Δ (1232)$ Coulomb quadrupole form factor, pion cloud parametrizations and Siegert's theorem
G. Ramalho🇧🇷
The novel measurements of the $γ^{*} N \to Δ (1232)$ Coulomb quadrupole form factor in the range $Q^{2} = 0.04$ --0.13 GeV $^{2}$ changed the trend of the previous data. With the new data the electric and Coulomb form factors are both in remarkable agreement with estimates of the pion cloud contributions to the quadrupole form factors at low $Q^{2}$ . The pion cloud contributions to the electric and Coulomb form factors can be parametrized by the relations $G_{E} \propto G_{E n} / (1 + \frac{Q ^{2}}{2 M _{Δ} ( M _{Δ} - M )})$ and $G_{C} \propto G_{E n}$ , where $G_{E n}$ is the neutron electric form factor, and $M$ , $M_{Δ}$ are the nucleon and $Δ$ masses, respectively. Those parametrizations are in full agreement with Siegert's theorem, which states that $G_{E} = \frac{M _{Δ} - M}{2 M _{Δ}} G_{C}$ at the pseudothreshold, when $Q^{2} = - (M_{Δ} - M)^{2}$ , and improve previous parametrizations. Also a small valence quark component estimated by a covariant quark model contributes to this agreement. The combination of the new data with the new parametrization for $G_{E}$ concludes an intense period of studying the $γ^{*} N \to Δ (1232)$ quadrupole form factors at low $Q^{2}$ , with the agreement between theory and data.
Comments:
Published version. 6 pages, 3 figures. Extended version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1709.07412 [pdf]
EPJA(2018)·22 citations
07
[Submitted on 21 Sept 2017] (cross-list from hep-ph)
Muonic hydrogen and the proton size
Wayne W. Repko🇺🇸 · Duane A. Dicus🇺🇸
We reexamine the structure of the $n = 2$ levels of muonic hydrogen using a two-body potential that includes all relativistic, recoil and one loop corrections. The potential was originally derived from QED to describe the muonium atom and accounts for all contributions to order $α^{5}$ . Since one loop corrections are included, the anomalous magnetic moment contributions of the muon can be identified and replaced by the proton anomalous magnetic moment to describe muonic hydrogen with a point-like proton. This serves as a convenient starting point to include the dominant electron vacuum polarization corrections to the spectrum and extract the proton's mean squared radius $r_{p} = ⟨ r^{2} ⟩$ . Our results are consistent with other theoretical calculations that find that the muonic hydrogen value for $r_{p}$ is smaller than the result obtained from electron scattering.
Comments:
18 pages, 2 Tables, content added
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1709.07440 [pdf]
PRD(2018)·6 citations

Affiliations

first authorsco-authorsvia INSPIRE

A complete non-perturbative renormalization prescription for quasi-PDFs

Phase transition in compact stars: nucleation mechanism and γ-ray bursts revisited

Relativistic disc line: a tool to constrain neutron star equation of state models

New low-Q2 measurements of the γ∗N→Δ(1232) Coulomb quadrupole form factor, pion cloud parametrizations and Siegert's theorem

Muonic hydrogen and the proton size

Affiliations

Phase transition in compact stars: nucleation mechanism and $γ$ -ray bursts revisited

New low- $Q^{2}$ measurements of the $γ^{*} N \to Δ (1232)$ Coulomb quadrupole form factor, pion cloud parametrizations and Siegert's theorem