Nuclear Theory·nucl-th

Monday·November 14, 2022

8 papers—3 primary·5 cross-listed

01
[Submitted on 10 Nov 2022]
Toward a description of the centrality dependence of the charge balance function in the HYDJET++ model
A.S. Chernyshov🇷🇺 · G.Kh. Eyyubova🇷🇺 · V.L. Korotkikh🇷🇺 · I.P. Lokhtin🇷🇺 · L.V. Malinina🇷🇺 · S.V. Petrushanko🇷🇺 · A.M. Snigirev🇷🇺 · E.E. Zabrodin🇷🇺
Data from the Large Hadron Collider on the charge balance function in Pb+Pb collisions at center-of-mass energy 2.76~TeV per nucleon pair are analyzed and interpreted within the framework of the \hydjet++ model. This model allows us to qualitatively reproduce the experimentally observed centrality dependence of the balance function widths at relatively low transverse momentum intervals due to the different charge creation mechanisms in soft and hard processes. However, a fully adequate description of the balance function in these intervals implies an essential modification of the model by including exact charge conservation via the canonical rather than the grand canonical ensemble. A procedure is proposed for introducing charge correlations into the thermal model without changing other model parameters. With increasing transverse momenta, the default model results describe the experimental data much better because the contribution of the soft component of the model is significantly reduced in these transverse momentum intervals. In practical terms, there is a transition to a single source of charge correlations, namely, charge correlations in jets in which exact charge conservation holds at each stage.
Comments:
Matches published version
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2211.05874 [pdf]
CPC(2023)·8 citations
02
[Submitted on 11 Nov 2022]
An introduction to computational complexity and statistical learning theory applied to nuclear models
Andrea Idini
The fact that we can build models from data, and therefore refine our models with more data from experiments, is usually given for granted in scientific inquiry. However, how much information can we extract, and how precise can we expect our learned model to be, if we have only a finite amount of data at our disposal? Nuclear physics demands an high degree of precision from models that are inferred from the limited number of nuclei that can be possibly made in the laboratories. In manuscript I will introduce some concepts of computational science, such as statistical theory of learning and Hamiltonian complexity, and use them to contextualise the results concerning the amount of data necessary to extrapolate a mass model to a given precision.
Comments:
6 pages, 1 figure, proceeding INPC 2022, Cape Town, South Africa
Subjects:
Nuclear Theory (nucl-th); Machine Learning (cs.LG)
arXiv:
2211.06182 [pdf]
J.Phys.Conf.Ser.(2023)·1 citation
03
[Submitted on 11 Nov 2022]
Perspectives on few-body cluster structures in exotic nuclei
D. Bazin · K. Becker · F. Bonaiti · Ch. Elster · K. Fossez · T. Frederico · A. Gnech · C. Hebborn · M. Higgins · L. Hlophe · B. Kay · S. König and 7 other authors
It is a fascinating phenomenon in nuclear physics that states with a pronounced few-body structure can emerge from the complex dynamics of many nucleons. Such halo or cluster states often appear near the boundaries of nuclear stability. As such, they are an important part of the experimental program beginning at the Facility for Rare Isotope Beams (FRIB). A concerted effort of theory and experiment is necessary both to analyze experiments involving effective few-body states, as well as to constrain and refine theories of the nuclear force in light of new data from these experiments. As a contribution to exactly this effort, this paper compiles a collection of ``perspectives'' that emerged out of the Topical Program ``Few-body cluster structures in exotic nuclei and their role in FRIB experiments'' that was held at FRIB in August 2022 and brought together theorists and experimentalists working on this topic.
Comments:
This version should match the published one
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2211.06281 [pdf]
Few Body Syst.(2023)·9 citations
04
[Submitted on 6 Nov 2022] (cross-list from hep-th)
Geometric confinement in gauge theories
Alexander D. Popov🇩🇪
In 1978, Friedberg and Lee introduced the phenomenological soliton bag model of hadrons, generalizing the MIT bag model developed in 1974 shortly after the formulation of QCD. In this model, quarks and gluons are confined due to coupling with a real scalar field $ρ$ which tends to zero outside some compact region $S \subset R^{3}$ determined dynamically from the equations of motion. The gauge coupling in the soliton bag model is running as the inverse power of $ρ$ already at the semiclassical level. We show that this model arises naturally as a consequence of introducing the warped product metric $d s_{M}^{2} + ρ^{2} d s_{G}^{2}$ on the principal $G$ -bundle $P (M, G) ≅ M \times G$ with a non-Abelian group $G$ over Minkowski space $M = R^{3, 1}$ . Confinement of quarks and gluons in a compact domain $S \subset R^{3}$ is a consequence of the collapse of the bundle manifold $M \times G$ to $M$ outside $S$ due to shrinking of the group manifold $G$ to a point. We describe the formation of such regions $S$ as a dynamical process controlled by the order parameter field $ρ$ .
Comments:
22 pages
Subjects:
High Energy Physics — Theory (hep-th); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2211.03096 [pdf]
Symmetry(2023)·1 citation
05
[Submitted on 11 Nov 2022] (cross-list from nucl-ex)
A fast-rotating pear-shaped nucleus
A. Karmakar · P. Datta · Soumik Bhattacharya · Shabir Dar · S. Bhattacharya · G. Mukherjee · H. Pai · S. Basu · S. Nandi · S. S. Nayak · Sneha Das · R. Raut and 6 other authors
The spectroscopic studies have identified few Actinide and Lanthanide nuclei of the periodic table, which can assume the pear shape. The low frequency collective rotation of these nuclei has been established by determining the band structure of the excited levels and their gamma decay rates. In this article, we report the rotation of a pear-shaped nucleus in 100 Ru, which rotates nearly three times faster than the previously known cases. The three novel consequences of this fast rotation are: the realization of a pear-shape in an excited state, its moment of inertia becoming a constant of motion and its shape evolution. These inferences have been arrived at by comparing the characteristics of the rotational band of 100 Ru with three of the best-known examples of a rotating pear-shaped nucleus and through the theoretical interpretation of the data. The observation of a pear-shaped nucleus in the lighter mass region opens up the possibility of a systematic study of the effects of fast rotation on this shape.
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2211.06037 [pdf]
0 citations
06
[Submitted on 11 Nov 2022] (cross-list from hep-ph)
Zooming in on Multiquark Hadrons within QCD Sum-Rule Approaches
Wolfgang Lucha🇦🇹 · Dmitri Melikhov🇷🇺 · Hagop Sazdjian🇫🇷
Aiming at self-consistent descriptions of multiquark hadrons (such as tetraquarks, pentaquarks, hexaquarks) by means of QCD sum rules, we note that the totality of contributions to two-point or three-point correlation functions that involve, respectively, either two or just a single operator capable of interpolating the particular multiquark under study can be straightforwardly disentangled into two disjoint classes defined by unambiguously identifiable members. The first is formed by so-called multiquark-phile contributions which indeed might support multiquarks. In the case of flavour-exotic tetraquarks, by definition composed of four (anti-) quarks of mutually different flavours, a tetraquark-phile contribution has to exhibit two or more gluon exchanges of appropriate topology. The second consists of contributions evidently not bearing any relation to multiquarks; these must be discarded when studying multiquarks by QCD sum rules. The first class only should enter the "multiquark-adequate" QCD sum rules for exotic hadrons.
Comments:
8 pages, 8 figures, contributed to "XVth Quark Confinement and the Hadron Spectrum" (1 - 6 August 2022, Stavanger, Norway)
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2211.06356 [pdf]
EPJ Web Conf.(2022)·0 citations
07
[Submitted on 11 Nov 2022] (cross-list from hep-ph)
The impact of fluctuating initial conditions on bottomonium suppression in 5.02 TeV heavy-ion collisions
Huda Alalawi🇺🇸 · Jacob Boyd🇺🇸 · Chun Shen🇺🇸 · Michael Strickland🇺🇸
We compute bottomonium suppression and elliptic flow within the pNRQCD effective field theory using an open quantum systems approach. For the hydrodynamical background, we use 2+1D MUSIC second-order viscous hydrodynamics with IP-Glasma initial conditions and evolve bottom/antibottom quantum wave packets in real time in these backgrounds. We find that the impact of fluctuating initial conditions is small when compared to results obtained using smooth initial conditions. Including the effect of fluctuating initial conditions, we find that the Upsilon(1S) integrated elliptic flow is v_2[1S] = 0.005 +/- 0.002 +/- 0.001, with the first and second variations corresponding to statistical and systematic theoretical uncertainties, respectively.
Comments:
7 pages, 3 figures; 2 page supplement with 3 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2211.06363 [pdf]
PRC(2023)·12 citations
08
[Submitted on 11 Nov 2022] (cross-list from hep-lat)
On the Infinite Variance Problem in Fermion Models
Andrei Alexandru🇺🇸 · Paulo Bedaque🇺🇸 · Andrea Carosso🇺🇸 · Hyunwoo Oh🇺🇸
Monte Carlo calculations of fermionic systems with continuous auxiliary fields frequently suffer from a diverging variance. If a system has the infinite variance problem, one cannot estimate observables reliably even with an infinite number of samples. In this paper, we explore a method to deal with this problem based on sampling according to the distribution of a system with an extra time-slice. The necessary reweighting factor is computed both perturbatively and through a secondary Monte Carlo. We show that the Monte Carlo reweigthing coupled to the use of a non-biased estimator of the reweigthing factor leads to a method that eliminates the infinite variance problem at a very small extra cost. We compute the double occupancy in the Hubbard model at half-filling to demonstrate the method and compare the results to well established results obtained by other methods.
Comments:
9 pages, 4 figures
Subjects:
High Energy Physics — Lattice (hep-lat); Strongly Correlated Electrons (cond-mat.str-el); Nuclear Theory (nucl-th)
arXiv:
2211.06419 [pdf]
PRD(2023)·7 citations

Affiliations

first authorsco-authorsvia INSPIRE