Nuclear Theory·nucl-th

Monday·May 25, 2020

7 papers—2 primary·5 cross-listed

01
[Submitted on 22 May 2020]
Convergence of electric quadrupole rotational invariants from the nuclear shell model
J. Henderson
Nuclei exhibit both single-particle and collective degrees of freedom, with the latter often subdivided into vibrational and rotational motions. Experimentally identifying the relative roles of these collective modes is extremely challenging, particularly in the face of possible shape coexistence. Model-independent, invariant quantities describing the deformation of a nucleus in the intrinsic frame have long been known but their determination potentially requires a large quantity of experimental data to achieve convergence. Through comparison with the nuclear shell model, the question of convergence will be addressed. Shell-model calculations performed in the $s d$ - and $p f$ -shell model spaces are used to determine electric-quadrupole matrix elements for a multitude of low-lying states. Relative contributions to the rotationally invariant quantities from multiple states can therefore be determined. It is found that on average, the inclusion of four intermediate states results in the leading-order invariant, $⟨ Q^{2} ⟩$ , converging to within 10% of its true value and the triaxiality term, $⟨ cos (3 δ) ⟩$ , converging to its true value, though some variance remains. Higher-order quantities relating to the softness of the nuclear shape are found to converge more slowly. The convergence of quadrupole rotationally invariant sum rules was quantified in the $s d$ - and $p f$ -shell model spaces and indicates the challenge inherent in a full determination of nuclear shape. The present study is limited to relatively small valence spaces. Larger spaces, such as the rare-earth region, potentially offer faster convergence.
Comments:
Submitted to Physical Review C
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2005.11210 [pdf]
PRC(2020)·16 citations
02
[Submitted on 22 May 2020]
Heavy flavor dynamics across system size at the LHC
Roland Katz🇫🇷 · Caio A. G. Prado🇨🇳 · Jacquelyn Noronha-Hostler🇺🇸 · Alexandre A. P. Suaide🇧🇷
One of the fundamental signatures of the Quark Gluon Plasma has been the suppression of heavy flavor (specifically D mesons), which has been measured via the nuclear modification factor, $R_{AA}$ and azimuthal anisotropies, $v_{n}$ , in large systems. However, multiple competing models can reproduce the same data for $R_{AA}$ to $v_{n}$ . In this talk we break down the competing effects that conspire together to successfully reproduce $R_{AA}$ and $v_{n}$ in experimental data using Trento+v-USPhydro+DAB-MOD. Then using our best fit model we make predictions for $R_{AA}$ and $v_{n}$ across system size for $^{208} P b P b$ , $^{129} X e X e$ , $^{40} A r A r$ , and $^{16} O O$ collisions. We find that 0--10\% centrality has a non-trivial interplay between the system size and eccentricities such that system size effects are masked in $v_{2}$ whereas in 30--50\% centrality the eccentricities are approximately constant across system size and, therefore, is a better centrality class to study D meson dynamics across system size.
Comments:
8 pages, 5 figures, proceedings for the 36th edition of the Winter Workshop on Nuclear Dynamics
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2005.11237 [pdf]
J.Phys.Conf.Ser.(2020)·0 citations
03
[Submitted on 21 May 2020] (cross-list from hep-ph)
Exploring $J / ψ$ production mechanism at the future Electron-Ion Collider
Jian-Wei Qiu🇺🇸 · Xiang-Peng Wang🇺🇸 · Hongxi Xing🇨🇳
We propose to use transverse momentum $p_{T}$ distribution of $J / ψ$ production at the future Electron Ion Collider (EIC) to explore the production mechanism of heavy quarkonia in high energy collisions. We apply QCD and QED collinear factorization to the production of a $c c ˉ$ pair at high $p_{T}$ , and non-relativistic QCD factorization to the hadronization of the pair to a $J / ψ$ . We evaluate $J / ψ$ $p_{T}$ -distribution at both leading and next-to-leading order in strong coupling, and show that production rates for various color-spin channels of a $c c ˉ$ pair in electron-hadron collisions are very different from that in hadron-hadron collisions, which provides a strong discriminative power to determine various transition rates for the pair to become a $J / ψ$ . We predict that the $J / ψ$ produced in electron-hadron collisions is likely unpolarized, and the production is an ideal probe for gluon distribution of colliding hadron (or nucleus). We find that the $J / ψ$ production is dominated by the color-octet channel, providing an excellent probe to explore the gluon medium in large nuclei at the EIC.
Comments:
6 pages, 6 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2005.10832 [pdf]
Chin.Phys.Lett.(2021)·21 citations
04
[Submitted on 21 May 2020] (cross-list from hep-th)
BPS Skyrme neutron stars in generalized gravity
C. Adam🇪🇸 · M. Huidobro🇪🇸 · R. Vazquez🇪🇸 · A. Wereszczynski🇵🇱
We study the coupling of nuclear matter described by the BPS Skyrme model to generalized gravity. Concretely, we consider the Starobinsky model which provides the leading-order correction to the Einstein-Hilbert action. Static solutions describing neutron stars are found both for the full field theory and for the mean-field approximation. We always consider the full Starobinsky model in the nonperturbative approach, using appropriately generalized shooting methods for the numerical neutron star calculations. Many of our results are similar to previous investigations of neutron stars for the Starobinsky model using other models of nuclear matter, but there are some surprizing discrepancies. The "Newtonian mass" relevant for the surface redshift, e.g., results larger than the ADM mass in our model, in contrast to other investigations. This difference is related to the particularly high stiffness of nuclear matter described by the BPS Skyrme model and offers an interesting possibility to distinguish different models of nuclear matter within generalized gravity.
Comments:
LaTex, 28 pages, 13 figures; v2: minor changes
Subjects:
High Energy Physics — Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
arXiv:
2005.10834 [pdf]
JCAP(2020)·2 citations
05
[Submitted on 22 May 2020] (cross-list from hep-ph)
Model comparison for initial density fluctuations in high energy heavy ion collisions
Stefan Floerchinger🇩🇪 · Eduardo Grossi🇺🇸 · Kianusch Vahid Yousefnia🇩🇪
Four models for the initial conditions of a fluid dynamic description of high energy heavy ion collisions are analysed and compared. We study expectation values and event-by-event fluctuations in the initial transverse energy density profiles from Pb-Pb collisions. Specifically, introducing a Fourier-Bessel mode expansion for fluctuations, we determine expectation values and two-mode correlation functions of the expansion coefficients. The analytically solveable independent point-sources model is compared to an initial state model based on Glauber theory and two models based on the Color Glass Condensate framework. We find that the large wavelength modes of all investigated models show universal properties for central collisions and also discuss to which extent general properties of initial conditions can be understood analytically.
Comments:
18 pages, 8 figures, results are attached as ancillary files; presentation in section IV rephrased for clarification, typos corrected, references added
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2005.11284 [pdf]
PRC(2020)·7 citations
06
[Submitted on 22 May 2020] (cross-list from hep-th)
Analytic SU(N) Skyrmions at finite Baryon density
Pedro D. Alvarez🇨🇱 · Sergio L. Cacciatori🇮🇹 · Fabrizio Canfora🇨🇱 · Bianca L. Cerchiai🇮🇹
We construct analytic (3+1)-dimensional Skyrmions living at finite Baryon density in the SU(N) Skyrme model that are not trivial embeddings of SU(2) into SU(N). We used Euler angles decomposition for arbitrary N and the generalized hedgehog Ansatz at finite Baryon density. The Skyrmions of high topological charge that we find represent smooth Baryonic layers whose properties can be computed explicitly. In particular, we determine the energy to Baryon charge ratio for any N showing the smoothness of the large N limit. The closeness to the BPS bound of these configurations can also be analyzed. The energy density profiles of these finite density Skyrmions have \textit{lasagna-like} shape in agreement with recent experimental findings. The shear modulus can be precisely estimated as well and our analytical result is close to recent numerical studies in the literature.
Comments:
36 pages, REVTeX, accepted for publication in Phys. Rev. D, added some references
Subjects:
High Energy Physics — Theory (hep-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2005.11301 [pdf]
PRD(2020)·29 citations
07
[Submitted on 22 May 2020] (cross-list from hep-ph)
On the connection between quark propagation and hadronization
Alberto Accardi🇺🇸 · Andrea Signori🇮🇹
We investigate the properties and structure of the recently discussed "fully inclusive jet correlator", namely, the gauge-invariant field correlator characterizing the final state hadrons produced by a free quark as this propagates in the vacuum. Working at the operator level, we connect this object to the single-hadron fragmentation correlator of a quark, and exploit a novel gauge invariant spectral decomposition technique to derive a complete set of momentum sum rules for quark fragmentation functions up to twist-3 level; known results are recovered, and new sum rules proposed. We then show how one can explicitly connect quark hadronization and dynamical quark mass generation by studying the inclusive jet's gauge-invariant mass term. This mass is, on the one hand, theoretically related to the integrated chiral-odd spectral function of the quark, and, on the other hand, is experimentally accessible through the $E$ and $E ~$ twist-3 fragmentation function sum rules. Thus, measurements of these fragmentation functions in deep inelastic processes provide one with an experimental gateway into the dynamical generation of mass in Quantum Chromodynamics.
Comments:
version accepted for publication in EPJ-C
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
2005.11310 [pdf]
EPJC(2020)·23 citations

Affiliations

first authorsco-authorsvia INSPIRE

Convergence of electric quadrupole rotational invariants from the nuclear shell model

Heavy flavor dynamics across system size at the LHC

Exploring J/ψ production mechanism at the future Electron-Ion Collider

BPS Skyrme neutron stars in generalized gravity

Model comparison for initial density fluctuations in high energy heavy ion collisions

Analytic SU(N) Skyrmions at finite Baryon density

On the connection between quark propagation and hadronization

Affiliations

Exploring $J / ψ$ production mechanism at the future Electron-Ion Collider