Nuclear Theory·nucl-th

Wednesday·September 14, 2016

13 papers—5 primary·8 cross-listed

06
[Submitted on 12 Sept 2016] (cross-list from hep-th)
Breaking the sound barrier in AdS/CFT
Carlos Hoyos🇪🇸 · Niko Jokela🇫🇮 · David Rodríguez Fernández🇪🇸 · Aleksi Vuorinen🇫🇮
It has been conjectured that the speed of sound in holographic models with UV fixed points has an upper bound set by the value of the quantity in conformal field theory. If true, this would set stringent constraints for the presence of strongly coupled quark matter in the cores of physical neutron stars, as the existence of two-solar-mass stars appears to demand a very stiff Equation of State. In this article, we present a family of counterexamples to the speed of sound conjecture, consisting of strongly coupled theories at finite density. The theories we consider include $N = 4$ super Yang-Mills at finite R-charge density and non-zero gaugino masses, while the holographic duals are Einstein-Maxwell theories with a minimally coupled scalar in a charged black hole geometry. We show that for a small breaking of conformal invariance, the speed of sound approaches the conformal value from above at large chemical potentials.
Comments:
41 pages, 8 figures. Published version
Subjects:
High Energy Physics — Theory (hep-th); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1609.03480 [pdf]
PRD(2016)·75 citations
07
[Submitted on 12 Sept 2016] (cross-list from hep-ph)
Dispersive treatment of $K_{S} \to γ γ$ and $K_{S} \to γ ℓ^{+} ℓ^{-}$
Gilberto Colangelo🇨🇭 · Ramon Stucki🇨🇭 · Lewis C. Tunstall🇨🇭
We analyse the rare kaon decays $K_{S} \to γ γ$ and $K_{S} \to γ ℓ^{+} ℓ^{-}$ $(ℓ = e \mbox or μ)$ in a dispersive framework in which the weak Hamiltonian carries momentum. Our analysis extends predictions from lowest order $S U (3)_{L} \times S U (3)_{R}$ chiral perturbation theory ( $χ$ PT $_{3}$ ) to fully account for effects from final-state interactions, and is free from ambiguities associated with extrapolating the kaon off-shell. Given input from $K_{S} \to π π$ and $γ γ^{(*)} \to π π$ , we solve the once-subtracted dispersion relations numerically to predict the rates for $K_{S} \to γ γ$ and $K_{S} \to γ ℓ^{+} ℓ^{-}$ . In the leptonic modes, we find sizeable corrections to the $χ$ PT $_{3}$ predictions for the integrated rates.
Comments:
12 pages, 9 figures. v2: Improved assessment of systematic uncertainties, some typos corrected, matches published version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1609.03574 [pdf]
EPJC(2016)·16 citations
08
[Submitted on 13 Sept 2016] (cross-list from hep-ph)
Hidden Local Symmetry and Beyond
Koichi Yamawaki🇯🇵
Gerry Brown was a godfather of our hidden local symmetry (HLS) for the vector meson from the birth of the theory throughout his life. The HLS is originated from very nature of the nonlinear realization of the symmetry G based on the manifold G/H, and thus is universal to any physics based on the nonlinear realization. Here I focus on the Higgs Lagrangian of the Standard Model (SM), which is shown to be equivalent to the nonlinear sigma model based on G/H= SU(2)_L x SU(2)_R/SU(2)_V with additional symmetry, the nonlinearly realized scale symmetry. Then the SM does have a dynamical gauge boson of the SU(2)_V HLS, "SM rho meson", in addition to the Higgs as a pseudo dilaton as well as the NG bosons to be absorbed into the W and Z. Based on the recent work done with S. Matsuzaki and H. Ohki, I discuss a novel possibility that the SM rho meson acquires kinetic term by the SM dynamics itself, which then stabilizes the skyrmion dormant in the SM as a viable candidate for the dark matter, what we call "Dark SM skyrmion (DSMS)".
Comments:
To appear in the Gerry Brown Memorial Book
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1609.03715 [pdf]
IJMPE(2017)·18 citations
09
[Submitted on 13 Sept 2016] (cross-list from hep-ph)
Exclusive photoproduction of a $γ ρ$ pair with a large invariant mass
R. Boussarie🇫🇷 · B. Pire🇫🇷 · L. Szymanowski🇵🇱 · S. Wallon🇫🇷
Exclusive photoproduction of a $γ ρ$ 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 where the $ρ -$ meson is either longitudinally or transversely polarized are estimated in the kinematics of the JLab 12-GeV experiments.
Comments:
published version; 54 pages, 23 figures. The cross section for the exclusive photoproduction of a $γ ρ$ pair, in the case where the final $ρ$ -meson is longitudinally polarized, has been corrected
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1609.03830 [pdf]
JHEP(2017)·78 citations
10
[Submitted on 13 Sept 2016] (cross-list from hep-ph)
The 5 MeV bump - a nuclear whodunit mystery
Patrick Huber🇺🇸
We perform a combined analysis of recent NEOS and Daya Bay data on the reactor antineutrino spectrum. This analysis includes approximately 1.5 million antineutrino events, which is the largest neutrino event sample analyzed to date. We use a double ratio which cancels flux model dependence and related uncertainties as well as the effects of the detector response model. We find at 3-4 standard deviation significance level, that plutonium-239 and plutonium-241 are disfavored as the single source for the the so-called 5 MeV bump. This analysis method has general applicability and in particular with higher statistics data sets will be able to shed significant light on the issue of the bump. With some caveat this also should allow to improve the sensitivity for sterile neutrino searches in NEOS.
Comments:
4 pages, 2 figures, version to appear in Phys. Rev. Lett
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1609.03910 [pdf]
PRL(2017)·88 citations
11
[Submitted on 13 Sept 2016] (cross-list from hep-ph)
Energy loss as the origin of an universal scaling law of the elliptic flow
Carlota Andrés🇪🇸 · Mikhail Braun🇷🇺 · Carlos Pajares🇪🇸
It is shown that the excellent scaling of the elliptic flow found for all centralities, species and energies from RHIC to the LHC for $p_{T}$ less than the saturation momentum is a consequence of the energy lost by a parton interacting with the color field produced in a nucleus-nucleus collision. In particular, the deduced shape of the scaling curve describes correctly all the data. We discuss the possible extensions to higher $p_{T}$ , proton-nucleus and proton-proton collisions as well as higher harmonics.
Comments:
10 pages, 2 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1609.03927 [pdf]
EPJA(2017)·13 citations
12
[Submitted on 13 Sept 2016] (cross-list from hep-ph)
van der Waals Interactions in Hadron Resonance Gas: From Nuclear Matter to Lattice QCD
Volodymyr Vovchenko🇩🇪 · Mark I. Gorenstein🇺🇦 · Horst Stoecker🇩🇪
An extension of the ideal hadron resonance gas (HRG) model is constructed which includes the attractive and repulsive van der Waals (VDW) interactions between baryons. This VDW-HRG model yields the nuclear liquid-gas transition at low temperatures and high baryon densities. The VDW parameters $a$ and $b$ are fixed by the ground state properties of nuclear matter, and the temperature dependence of various thermodynamic observables at zero chemical potential are calculated within VDW-HRG model. Compared to the ideal HRG model, the inclusion of VDW interactions between baryons leads to a qualitatively different behavior of second and higher moments of fluctuations of conserved charges, in particular in the so-called crossover region $T \sim 140 - 190$ MeV. For many observables this behavior resembles closely the results obtained from lattice QCD simulations. This hadronic model also predicts nontrivial behavior of net-baryon fluctuations in the region of phase diagram probed by heavy-ion collision experiments. These results imply that VDW interactions play a crucial role in thermodynamics of hadron gas. Thus, the commonly performed comparisons of the ideal HRG model with the lattice and heavy-ion data may lead to misconceptions and misleading conclusions.
Comments:
7 pages, 3 figures, final version published in Physical Review Letters, minor misprints corrected
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1609.03975 [pdf]
PRL(2017)·216 citations
13
[Submitted on 13 Sept 2016] (cross-list from hep-lat)
Octet Baryon Magnetic Moments from Lattice QCD: Approaching Experiment from a Three-Flavor Symmetric Point
Assumpta Parreno🇪🇸 · Martin J. Savage🇺🇸 · Brian C. Tiburzi🇺🇸 · Jonas Wilhelm🇩🇪 · Emmanuel Chang🇺🇸 · William Detmold🇺🇸 · Kostas Orginos🇺🇸
Lattice QCD calculations with background magnetic fields are used to determine the magnetic moments of the octet baryons. Computations are performed at the physical value of the strange quark mass, and two values of the light quark mass, one corresponding to the three-flavor symmetric point, where the pion mass is 800 MeV, and the other corresponding to a pion mass of 450 MeV. The moments are found to exhibit only mild pion-mass dependence when expressed in terms of appropriately chosen magneton units- the natural baryon magneton. A curious pattern is revealed among the anomalous baryon magnetic moments which is linked to the constituent quark model, however, careful scrutiny exposes additional features. Relations expected to hold in the large-Nc limit of QCD are studied; and, in one case, a clear preference for the quark model over the large-Nc prediction is found. The magnetically coupled Lambda-Sigma system is treated in detail at the three-flavor symmetric point, with the lattice QCD results comparing favorably with predictions based on SU(3)F symmetry. This analysis enables the first extraction of the isovector transition magnetic polarizability. The possibility that large magnetic fields stabilize strange matter is explored, but such a scenario is found to be unlikely.
Comments:
30 pages, 18 figures, v2 revision corresponds to published version
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1609.03985 [pdf]
PRD(2017)·41 citations

Affiliations

first authorsco-authorsvia INSPIRE