Nuclear Theory·nucl-th

Wednesday·July 1, 2020

14 papers—8 primary·6 cross-listed

09
[Submitted on 29 Jun 2020] (cross-list from hep-ph)
Ellipticity of photon emission from strongly magnetized hot QCD plasma
Xinyang Wang🇨🇳 · Igor A. Shovkovy🇺🇸 · Lang Yu🇨🇳 · Mei Huang🇨🇳
By making use of an explicit representation for the imaginary part of the photon polarization tensor in terms of transitions between the Landau levels of light quarks, we study the angular dependence of direct photon emission from a strongly magnetized quark-gluon plasma. Because of the magnetic field, the leading order photon rate comes from the three processes of the zeroth order in the coupling constant $α_{s}$ : (i) the quark splitting ( $q \to q + γ$ ), (ii) the antiquark splitting ( $q ˉ \to q ˉ + γ$ ), and (iii) the quark-antiquark annihilation ( $q + q ˉ \to γ$ ). In a wide range of moderately high temperatures, $T ≳ m_{π}$ , and strong magnetic fields, $∣ e B ∣ ≳ m_{π}^{2}$ , the direct photon production is dominated by the two splitting processes. We show that the Landau-level quantization of quark states plays an important role in the energy and angular dependence of the photon emission. Among other things, it leads to a nontrivial momentum dependence of the photon ellipticity coefficient $v_{2}$ , which takes negative values at small transverse momenta and positive values at large transverse momenta. The crossover between the two regimes occurs around $k_{T} ≃ ∣ e B ∣$ . In application to heavy-ion collisions, this suggests that a large value of $v_{2}$ for the direct photons could be explained in part by the magnetic field in the quark-gluon plasma.
Comments:
16 pages, 9 multi-panel figures; published version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2006.16254 [pdf]
PRD(2020)·56 citations
10
[Submitted on 29 Jun 2020] (cross-list from hep-ph)
Comparison of improved TMD and CGC frameworks in forward quark dijet production
Hirotsugu Fujii🇯🇵 · Cyrille Marquet🇫🇷 · Kazuhiro Watanabe🇺🇸
For studying small- $x$ gluon saturation in forward dijet production in high-energy dilute-dense collisions, the improved TMD (ITMD) factorization formula was recently proposed. In the Color Glass Condensate (CGC) framework, it represents the leading term of an expansion in inverse powers of the hard scale. It contains the leading-twist TMD factorization formula relevant for small gluon's transverse momentum $k_{t}$ , but also incorporates an all-order resummation of kinematical twists, resulting in a proper matching to high-energy factorization at large $k_{t}$ . In this paper, we evaluate the accuracy of the ITMD formula quantitatively, for the case of quark dijet production in high-energy proton-proton( $p + p$ ) and proton-nucleus ( $p + A$ ) collisions at LHC energies. We do so by comparing the quark-antiquark azimuthal angle $Δ ϕ$ distribution to that obtained with the CGC formula. For a dijet with each quark momentum $p_{t}$ much larger than the target saturation scale, $Q_{s}$ , the ITMD formula is a good approximation to the CGC formula in a wide range of azimuthal angle. It becomes less accurate as the jet $p_{t}$ 's are lowered, as expected, due to the presence of genuine higher-twists contributions in the CGC framework, which represent multi-body scattering effects absent in the ITMD formula. We find that, as the hard jet momenta are lowered, the accuracy of ITMD start by deteriorating at small angles, in the high-energy-factorization regime, while in the TMD regime near $Δ ϕ = π$ , very low values of $p_{t}$ are needed to see differences between the CGC and the ITMD formula. In addition, the genuine twists corrections to ITMD become visible for higher values of $p_{t}$ in $p + A$ collisions, compared to $p + p$ collisions, signaling that they are enhanced by the target saturation scale.
Comments:
30 pages, 13 figures. v2: version accepted for publication in JHEP
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2006.16279 [pdf]
JHEP(2020)·39 citations
11
[Submitted on 29 Jun 2020] (cross-list from astro-ph.HE)
Neutron Star Equation of State in light of GW190814
Hung Tan🇺🇸 · Jacquelyn Noronha-Hostler🇺🇸 · Nico Yunes🇺🇸
The observation of gravitational waves from an asymmetric binary opens the possibility for heavy neutron stars, but these pose challenges to models of the neutron star equation of state. We construct heavy neutron stars by introducing non-trivial structure in the speed of sound sourced by deconfined QCD matter, which cannot be well recovered by spectral representations. Their moment of inertia, Love number and quadrupole moment are very small, so a tenfold increase in sensitivity may be needed to test this possibility with gravitational waves, which is feasible with third generation detectors.
Comments:
8 pages, 5 figures, v2 updated figures and text
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
arXiv:
2006.16296 [pdf]
PRL(2020)·178 citations
12
[Submitted on 30 Jun 2020] (cross-list from hep-ph)
QCD sum rules with spectral densities solved in inverse problems
Hsiang-nan Li🇹🇼 · Hiroyuki Umeeda🇹🇼
We construct QCD sum rules for nonperturbative studies without assuming the quark-hadron duality for the spectral density at low energy on the hadron side. Instead, both resonance and continuum contributions to the spectral density are solved with the operator-product-expansion input on the quark side by treating sum rules as an inverse problem. This new formalism does not involve the continuum threshold, does not require the Borel transformation and stability analysis, and can be extended to extract properties of excited states. Taking the two-current correlator as an example, we demonstrate that the series of $ρ$ resonances can emerge in our formalism, and the decay constants $f_{ρ (770)} (f_{ρ (1450)}, f_{ρ (1700)}, f_{ρ (1900)}) \approx$ 0.22 (0.19, 0.14, 0.14) GeV for the masses $m_{ρ (770)} (m_{ρ (1450)}, m_{ρ (1700)}, m_{ρ (1900)}) \approx$ 0.78 (1.46, 1.70, 1.90) GeV are determined. We also show that the decay width $Γ_{ρ (770)} \approx 0.17$ GeV can be obtained by substituting a Breit-Wigner parametrization for the $ρ (770)$ pole on the hadron side. It is observed that quark condensates of dimension-six on the quark side are crucial for establishing those $ρ$ resonances. Handling the conventional sum rules with the duality assumption as an inverse problem, we find that the multiple pole sum rules widely adopted in the literature do not describe the $ρ$ excitations reasonably. The precision of our theoretical outcomes can be improved systematically by including higher-order and higher-power corrections on the quark side. Broad applications of this formalism to abundant low energy QCD observables are expected.
Comments:
17 pages, 14 figures, version accepted for publication in Phys. Rev. D, title is changed
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2006.16593 [pdf]
PRD(2020)·26 citations
13
[Submitted on 30 Jun 2020] (cross-list from hep-ph)
Real time warm pions from the lattice using an effective theory
Sourendu Gupta🇮🇳 · Rishi Sharma🇮🇳
Lattice measurements provide adequate information to fix the parameters of long distance effective field theories in Euclidean time. Using such a theory, we examine the analytic continuation of long distance correlation functions of composite operators at finite temperature from Euclidean to Minkowski space time. We show through an explicit computation that the analytic continuation of the pion correlation function is possible and gives rise to non-trivial effects. Among them is the possibility, supported by lattice computations of Euclidean correlators, that long distance excitations can be understood in terms of (very massive) pions even at temperatures higher than the QCD cross over temperature.
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2006.16626 [pdf]
Int.J.Mod.Phys.A(2020)·6 citations
14
[Submitted on 30 Jun 2020] (cross-list from astro-ph.HE)
Can Pulsars in the inner parsecs from Galactic Centre probe the existence of Dark Matter?
Antonino Del Popolo🇷🇺 · Maksym Deliyergiyev🇵🇱 · Morgan Le Delliou🇨🇳 · Laura Tolos🇩🇪 · Fiorella Burgio🇮🇹
We discuss the formation of dark compact objects in a dark matter environment in view of the possible mass dependence of pulsars on the distribution of dark matter in the Galaxy. Our results indicate that the pulsar masses should decrease going towards the center of the Milky Way due to dark matter capture, thus becoming a probe for the existence and nature of dark matter. We thus propose that the evolution of the pulsar mass in a dark matter rich environment can be used to put constraints, when combined with future experiments, on the characteristics of our Galaxy halo dark matter profile, on the dark matter particle mass and on the dark matter self-interaction strength.
Comments:
5 pages, 2 figures, EPS-HEP2019, Ghent, Belgium, 10-17 July. Conference proceedings
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2006.16838 [pdf]
PoS(2020)·1 citation

Affiliations

first authorsco-authorsvia INSPIRE

Ellipticity of photon emission from strongly magnetized hot QCD plasma

Comparison of improved TMD and CGC frameworks in forward quark dijet production

Neutron Star Equation of State in light of GW190814

QCD sum rules with spectral densities solved in inverse problems

Real time warm pions from the lattice using an effective theory

Can Pulsars in the inner parsecs from Galactic Centre probe the existence of Dark Matter?

Affiliations