Nuclear Theory·nucl-th

Monday·January 20, 2020

7 papers—2 primary·5 cross-listed

03
[Submitted on 16 Jan 2020] (cross-list from astro-ph.HE)
Gravitational waves or deconfined quarks: what causes the premature collapse of neutron stars born in short gamma-ray bursts?
Nikhil Sarin · Paul D. Lasky · Gregory Ashton
We infer the collapse times of long-lived neutron stars into black holes using the X-ray afterglows of 18 short gamma-ray bursts. We then apply hierarchical inference to infer properties of the neutron star equation of state and dominant spin-down mechanism. We measure the maximum non-rotating neutron star mass $M_{TOV} = 2.3 1_{- 0.21}^{+ 0.36} M_{⊙}$ and constrain the fraction of remnants spinning down predominantly through gravitational-wave emission to $η = 0.6 9_{- 0.39}^{+ 0.21}$ with $68%$ uncertainties. In principle, this method can determine the difference between hadronic and quark equation of states. In practice, however, the data is not yet informative with indications that these neutron stars do not have hadronic equation of states at the $1 σ$ level. These inferences all depend on the underlying progenitor mass distribution for short gamma-ray bursts produced by binary neutron star mergers. The recently announced gravitational-wave detection of GW190425 suggests this underlying distribution is different from the locally-measured population of double neutron stars. We show that $M_{TOV}$ and $η$ constraints depend on the fraction of binary mergers that form through a distribution consistent with the locally-measured population and a distribution that can explain GW190425. The more binaries that form from the latter distribution, the larger $M_{TOV}$ needs to be to satisfy the X-ray observations. Our measurements above are marginalised over this unknown fraction. If instead, we assume GW190425 is not a binary neutron star merger, i.e the underlying mass distribution of double neutron stars is the same as observed locally, we measure $M_{TOV} = 2.2 6_{- 0.17}^{+ 0.31} M_{⊙}$ .
Comments:
Published in Phys. Rev. D: Vol 101, Issue 6
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
arXiv:
2001.06102 [pdf]
PRD(2020)·57 citations
04
[Submitted on 15 Jan 2020] (cross-list from hep-ph)
QCD parameters and $f_{B_{c}}$ from heavy quark sum rules
Stephan Narison (LUPM-CNRS, Montpellier-FR)🇫🇷
We report results of our recent works [1,2] where we where the correlations between the c,b-quark running masses{m}_{c,b}, the gluon condensate<\alpha_s G^2> and the QCD coupling \alpha_s in the MS-scheme from an analysis of the charmonium and bottomium spectra and the B_c-meson mass. We use optimized ratios of relativistic Laplace sum rules (LSR) evaluated at the \mu-subtraction stability point where higher orders PT and D< 6-8-dimensions non-perturbative condensates corrections are included. We obtain [1] \alpha_s(2.85)=0.262(9) and \alpha_s(9.50)=0.180(8) from the (pseudo)scalar M_{\chi_{0c(0b)}}-M_{\eta_{c(b)}} mass-splittings at \mu=2.85(9.50) GeV. The most precise result from the charm channel leads to \alpha_s(M_\tau)=0.318(15) and \alpha_s(M_Z)=0.1183(19)(3) in excellent agreement with the world average: \alpha_s(M_Z)=0.1181(11)[3,4]. Updated results from a global fit of the (axial-)vector and (pseudo)scalar channels using Laplace and Moments sum rules @ N2LO [1] combined with the one from M_{B_c} [2] lead to the new tentative QCD spectral sum rules (QSSR) average : m_c(m_c)|_average= 1266(6) MeV and m_b(m_b)|_average=4196(8) MeV. The values of the gluon condensate <\alpha_s G^2> from the (axial)-vector charmonium channels combined with previous determinations in Table 1, leads to the new QSSR average [1]: <\alpha_s G^2>_average=(6.35\pm 0.35)x 10^{-2} GeV^4. Our results clarify the (apparent) discrepancies between different estimates of <\alpha_s G^2> from J/\psi sum rule but also shows the sensitivity of the sum rules on the choice of the \mu-subtraction scale. As a biproduct, we deduce the B_c-decay constants f_{B_c}=371(17) MeV and f_{B_c}(2S)< 139(6) MeV.
Comments:
Review talk presented at QCD19 (2-7 july 2019, Montpellier - FR) and at HEPMAD19 (14-20 october 2019, Antananarivo-MG). 13 pages, 1 Table. To appear in Nucl. Phys. Proceedings (2020): Reference corrected. arXiv admin note: substantial text overlap with arXiv:1801.00592
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
2001.06346 [pdf]
Nucl.Part.Phys.Proc.(2020)·6 citations
05
[Submitted on 17 Jan 2020] (cross-list from hep-ph)
Chiral effective Lagrangian for heavy-light mesons from QCD
Qing-Sen Chen🇨🇳 · Hui-Feng Fu🇨🇳 · Yong-Liang Ma🇨🇳 · Qing Wang🇨🇳
We derive the chiral effective Lagrangian for heavy-light mesons in the heavy quark limit from QCD under proper approximations. The low energy constants in the effective Lagrangian are expressed in terms of the light quark self-energy. With typical forms of the running coupling constant of QCD and the quark self-energy obtained from Dyson-Schwinger equations as well as lattice QCD, we estimate the low energy constants in the model and the strong decay widths. A comparison with data and some discussions of the numerical results are presented.
Comments:
Published version
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2001.06418 [pdf]
PRD(2020)·4 citations
06
[Submitted on 17 Jan 2020] (cross-list from nucl-ex)
Beam energy dependence of net- $Λ$ fluctuations measured by the STAR experiment at RHIC
STAR Collaboration: J. Adam🇺🇸 · L. Adamczyk🇵🇱 · J. R. Adams🇺🇸 · J. K. Adkins🇺🇸 · G. Agakishiev🇷🇺 · M. M. Aggarwal🇮🇳 · Z. Ahammed🇮🇳 · I. Alekseev🇷🇺 · D. M. Anderson🇺🇸 · A. Aparin🇷🇺 · E. C. Aschenauer🇺🇸 · M. U. Ashraf🇨🇳 and 346 other authors
The measurements of particle multiplicity distributions have generated considerable interest in understanding the fluctuations of conserved quantum numbers in the Quantum Chromodynamics (QCD) hadronization regime, in particular near a possible critical point and near the chemical freeze-out. We report the measurement of efficiency and centrality bin width corrected cumulant ratios ( $C_{2} / C_{1}$ , $C_{3} / C_{2}$ ) of net- $Λ$ distributions, in the context of both strangeness and baryon number conservation, as a function of collision energy, centrality and rapidity. The results are for Au + Au collisions at five beam energies ( $s_{N N}$ = 19.6, 27, 39, 62.4 and 200 GeV) recorded with the Solenoidal Tracker at RHIC (STAR). We compare our results to the Poisson and negative binomial (NBD) expectations, as well as to Ultra-relativistic Quantum Molecular Dynamics (UrQMD) and Hadron Resonance Gas (HRG) model predictions. Both NBD and Poisson baselines agree with data within the statistical and systematic uncertainties. The ratios of the measured cumulants show no features of critical fluctuations. The chemical freeze-out temperatures extracted from a recent HRG calculation, which was successfully used to describe the net-proton, net-kaon and net-charge data, indicate $Λ$ freeze-out conditions similar to those of kaons. However, large deviations are found when comparing to temperatures obtained from net-proton fluctuations. The net- $Λ$ cumulants show a weak, but finite, dependence on the rapidity coverage in the acceptance of the detector, which can be attributed to quantum number conservation.
Comments:
12 pages, 9 figures, 3 tables, submitted to Phys.Rev.C
Subjects:
Nuclear Experiment (nucl-ex); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2001.06419 [pdf]
PRC(2020)·32 citations
07
[Submitted on 17 Jan 2020] (cross-list from hep-ph)
On gauge invariance of transverse momentum dependent distributions at small x
Renaud Boussarie🇺🇸 · Yacine Mehtar-Tani🇺🇸
The interplay between the small x limit of QCD amplitudes and QCD factorization at moderate x has been studied extensively in recent years. It was finally shown that semiclassical formulations of small x physics can have the form of an infinite twist framework involving Transverse Momentum Dependent (TMD) distributions in the eikonal limit. In this work, we demonstrate that small x distributions can be formulated in terms of transverse gauge links. This allows in particular for direct and efficient decompositions of observables into subamplitudes involving gauge invariant sub-operators which span parton distributions.
Comments:
21 pages, 5 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2001.06449 [pdf]
PRD(2021)·38 citations

Affiliations

first authorsco-authorsvia INSPIRE

Gravitational waves or deconfined quarks: what causes the premature collapse of neutron stars born in short gamma-ray bursts?

QCD parameters and fBc​​ from heavy quark sum rules

Chiral effective Lagrangian for heavy-light mesons from QCD

Beam energy dependence of net-Λ fluctuations measured by the STAR experiment at RHIC

On gauge invariance of transverse momentum dependent distributions at small x

Affiliations

QCD parameters and $f_{B_{c}}$ from heavy quark sum rules

Beam energy dependence of net- $Λ$ fluctuations measured by the STAR experiment at RHIC