Nuclear Theory·nucl-th

Friday·December 14, 2018

8 papers—4 primary·4 cross-listed

01
[Submitted on 12 Dec 2018]
Distribution Amplitudes of Heavy-Light Mesons
Daniele Binosi🇮🇹 · Lei Chang🇨🇳 · Minghui Ding🇮🇹 · Fei Gao🇪🇸 · Joannis Papavassiliou🇪🇸 · Craig D. Roberts🇺🇸
A symmetry-preserving approach to the continuum bound-state problem in quantum field theory is used to calculate the masses, leptonic decay constants and light-front distribution amplitudes of empirically accessible heavy-light mesons. The inverse moment of the $B$ -meson distribution is particularly important in treatments of exclusive $B$ -decays using effective field theory and the factorisation formalism; and its value is therefore computed: $λ_{B} (ζ = 2 GeV) = 0.54 (3)$ GeV. As an example and in anticipation of precision measurements at new-generation $B$ -factories, the branching fraction for the rare $B \to γ (E_{γ}) ℓ ν_{ℓ}$ radiative decay is also calculated, retaining $1/ m_{B}^{2}$ and $1/ E_{γ}^{2}$ corrections to the differential decay width, with the result $Γ_{B \to γ ℓ ν_{ℓ}} / Γ_{B} = 0.47 (15)$ on $E_{γ} > 1.5$ GeV.
Comments:
6 pages, 6 figure, 5 tables
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1812.05112 [pdf]
PLB(2019)·52 citations
02
[Submitted on 12 Dec 2018]
Suppression of light nuclei production in collisions of small systems at the Large Hadron Collider
Kai-Jia Sun🇺🇸 · Che Ming Ko🇺🇸 · Benjamin Dönigus🇩🇪
We show that the recently observed suppression of the yield ratio of deuteron to proton and of helium-3 to proton in p+p collisions compared to those in p+Pb or Pb+Pb collisions by the ALICE Collaboration at the Large Hadron Collider (LHC) can be explained if light nuclei are produced from the coalescence of nucleons at the kinetic freeze-out of these collisions. This suppression is attributed to the non-negligible sizes of deuteron and helium-3 compared to the size of the nucleon emission source in collisions of small systems, which reduces the overlap of their internal wave functions with those of nucleons. The same model is also used to study the production of triton and hypertriton in heavy-ion collisions at the LHC. Compared to helium-3 in events of low charged particle multiplicity, the triton is less suppressed due to its smaller size and the hypertriton is even more suppressed as a result of its much larger size.
Comments:
6 pages and 2 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1812.05175 [pdf]
PLB(2019)·129 citations
03
[Submitted on 12 Dec 2018]
Two-neutron transfer reactions and shape phase transitions in the microscopically-formulated interacting boson model
K. Nomura · Y. Zhang
Two-neutron transfer reactions are studied within the interacting boson model based on the nuclear energy density functional theory. Constrained self-consistent mean-field calculations with the Skyrme energy density functional are performed to provide microscopic input to completely determine the Hamiltonian of the IBM. Spectroscopic properties are calculated only from the nucleonic degrees of freedom. This method is applied to study the $(t, p)$ and $(p, t)$ transfer reactions in the assorted set of rare-earth nuclei $^{146 - 158}$ Sm, $^{148 - 160}$ Gd, and $^{150 - 162}$ Dy, where spherical-to-axially-deformed shape phase transition is suggested to occur at the neutron number $N \approx 90$ . The results are compared with those from the purely phenomenological IBM calculations, as well as with the available experimental data. The calculated $(t, p)$ and $(p, t)$ transfer reaction intensities, from both the microscopic and phenomenological IBM frameworks, signal the rapid nuclear structural change at particular nucleon numbers.
Comments:
12 pages, 12 figures, 2 tables
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1812.05197 [pdf]
PRC(2019)·16 citations
04
[Submitted on 13 Dec 2018]
The unitarity expansion for light nuclei
Sebastian König
I is argued here that (at least light) nuclei may reside in a sweet spot: bound weakly enough to be insensitive to the details of the interaction, but dense enough to be insensitive to the exact values of the large two-body scattering lengths as well. In this scenario, a systematic expansion of nuclear observables around the unitarity limit converges. In particular, in this scheme the nuclear force is constructed such that the gross features of states in the nuclear chart are determined by a very simple leading-order interaction, whereas---much like the fine structure of atomic spectra---observables are moved to their physical values by small perturbative corrections. Explicit evidence in favor of this conjecture is shown for the binding energies of three and four nucleons.
Comments:
10 pages, 3 figures. Contribution to proceedings of the XXII International Conference on Few-Body Problems in Physics (FB22) in Caen, France, July 2018
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1812.05327 [pdf]
Springer Proc.Phys.(2020)·2 citations
05
[Submitted on 12 Dec 2018] (cross-list from hep-ph)
Sorting out quenched jets
Jasmine Brewer🇺🇸 · José Guilherme Milhano🇵🇹 · Jesse Thaler🇺🇸
We introduce a new 'quantile' analysis strategy to study the modification of jets as they traverse through a droplet of quark-gluon plasma. To date, most jet modification studies have been based on comparing the jet properties measured in heavy-ion collisions to a proton-proton baseline at the same reconstructed jet transverse momentum ( $p_{T}$ ). It is well known, however, that the quenching of jets from their interaction with the medium leads to a migration of jets from higher to lower $p_{T}$ , making it challenging to directly infer the degree and mechanism of jet energy loss. Our proposed quantile matching procedure is inspired by (but not reliant on) the approximate monotonicity of energy loss in the jet $p_{T}$ . In this strategy, jets in heavy-ion collisions ordered by $p_{T}$ are viewed as modified versions of the same number of highest-energy jets in proton-proton collisions, and the fractional energy loss as a function of jet $p_{T}$ is a natural observable ( $Q_{AA}$ ). Furthermore, despite non-monotonic fluctuations in the energy loss, we use an event generator to validate the strong correlation between the $p_{T}$ of the parton that initiates a heavy-ion jet and the $p_{T}$ of the vacuum jet which corresponds to it via the quantile procedure ( $p_{T}^{quant}$ ). We demonstrate that this strategy both provides a complementary way to study jet modification and mitigates the effect of $p_{T}$ migration in heavy-ion collisions.
Comments:
5 pages, 4 figures; v2: to match journal version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1812.05111 [pdf]
PRL(2019)·50 citations
06
[Submitted on 13 Dec 2018] (cross-list from hep-th)
Stochastic hydrodynamics and long time tails of an expanding conformal charged fluid
M. Martinez🇺🇸 · Thomas Schaefer🇺🇸
We investigate the impact of hydrodynamic fluctuations on correlation functions in a scale invariant fluid with a conserved $U (1)$ charge. The kinetic equations for the two-point functions of pressure, momentum and heat energy densities are derived within the framework of stochastic hydrodynamics. The leading non-analytic contributions to the energy-momentum tensor as well as the $U (1)$ current are determined from the solutions to these kinetic equations. In the case of a static homogeneous background we show that the long time tails obtained from hydro-kinetic equations reproduce the one-loop results derived from statistical field theory. We use these results to establish bounds on transport coefficients. We generalize the stochastic equation to a background flow undergoing Bjorken expansion. We compute the leading fractional power $O ((τ T)^{- 3/2})$ correction to the $U (1)$ current and compare with the first order gradient term.
Comments:
20 pages. v2 matches with the published version
Subjects:
High Energy Physics — Theory (hep-th); Statistical Mechanics (cond-mat.stat-mech); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1812.05279 [pdf]
PRC(2019)·56 citations
07
[Submitted on 13 Dec 2018] (cross-list from hep-ph)
A new pQCD based Monte Carlo event generator for jets in the quark-gluon plasma
Paul Caucal🇫🇷 · Edmond Iancu🇫🇷 · Alfred H. Mueller🇺🇸 · Gregory Soyez🇫🇷
A main difficulty in understanding the dynamics of jets produced in the high-density environment of ultrarelativistic heavy ion collision, is to provide a unified description for the two sources of radiation that are a priori expected: the "vacuum-like" emissions responsible for the parton shower from large virtualities down to the hadronisation scale and the "medium-induced" emissions responsible for the energy loss by the jet. In the recent paper arXiv:1801.09703, we demonstrated that these two mechanisms can be factorized from each other within a controlled, "double-logarithmic" approximation in perturbative QCD. In this proceeding we recall the main features of the jet evolution in a dense QCD medium. We emphasize that the in-medium parton showers differ from those in the vacuum in two crucial aspects: their phase-space is reduced and the first emission outside the medium can violate angular ordering. Based on this factorized picture, which is Markovian, we have recently developed a Monte Carlo event generator which includes both vacuum-like and medium-induced emissions and goes beyond the double logarithmic approximation. We here present our first results for the fragmentation function and the energy loss by the jet.
Comments:
8 pages, 6 figures, for the International Conference on Hard and Electromagnetic Probes of High-Energy Nuclear Collisions, 30 September - 5 October 2018 in Aix-Les-Bains, Savoie, France
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1812.05393 [pdf]
PoS(2019)·12 citations
08
[Submitted on 13 Dec 2018] (cross-list from hep-ph)
Polarized baryon production in heavy ion collisions: an analytic hydrodynamical study
Balint Boldizsar🇭🇺 · Marton I. Nagy🇭🇺 · Mate Csanad🇭🇺
We utilize known exact analytic solutions of perfect fluid hydrodynamics to analytically calculate the polarization of baryons produced in heavy ion collisions. Assuming local thermodynamical equilibrium also for spin degrees of freedom, baryons get a net polarization at their formation (freeze-out). This polarization depends on the time evolution of the Quark-Gluon Plasma (QGP), which can be described as an almost perfect fluid. By using exact analytic solutions, we thus can analyze the necessity of rotation (and vorticity) for non-zero net polarization. In this paper we give the first analytical calculations for the polarization four-vector. We use two hydrodynamical solutions; one is the spherically symmetric Hubble flow (a somewhat oversimplified model, to demonstrate the methodology). The other solution which we use is a somewhat more involved one that corresponds to a rotating and accelerating expansion, and is thus well suited to investigate some main features of the time evolution of the QGP created in peripheral heavy-ion collisions (although there are still many numerous features of a real collision geometry that are beyond the reach of this simple model). Finally we illustrate and discuss our results on the polarization.
Comments:
12 pages, 3 figures; presented at the 18th Zimanyi School Winter Workshop
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1812.05587 [pdf]
Universe(2019)·8 citations

Affiliations

first authorsco-authorsvia INSPIRE