Nuclear Theory·nucl-th

Thursday·May 4, 2017

10 papers—6 primary·4 cross-listed

01
[Submitted on 2 May 2017]
Multi moment cancellation of participant fluctuations - MMCP method
Viktor Begun🇵🇱 · Maja Mackowiak-Pawlowska🇵🇱
We propose a new way to correct for finite centrality bin width effect i.e. participant fluctuations in fluctuation analysis in high energy nucleus-nucleus collisions. The MMCP method allows to separate participant fluctuations and obtain fluctuations from one participant - a source - from a combination of the experimentally measured first four moments. The EPOS model is used for the numerical check of the MMCP for the net electric charge fluctuations in the forward rapidity region in Ar+Sc reactions at beam momentum 150 GeV/c. We show that using the existing methods - decreasing a centrality bin width, or using the Centrality Bin Width Correction procedure, one may still leave some residual participant fluctuations in the sample. Moreover, we show that the Centrality Bin Width Correction procedure may alter the fluctuation measures. The most important advantage of the MMCP is it's precision even when the amount of measured events does not allow to decrease the centrality bin width, or the experimental determination of participants is difficult, e.g. in collider experiments. Even for the largest centrality bin in the considered case, $c = 0 - 20%$ , the relative error of the MMCP for the scaled variance of a source is below 2\%. It is especially important in determination of the base line of the fluctuations in the search for the QCD Critical Point and the signals of the QCD phase transition.
Comments:
We expand the derivation and justification of the MMCP, see Eqs.(12-37), (45), (46) in the revised version, and the corresponding text. A new figure with the estimation of the MMCP parameters is added, see Fig. 1 left. Misprints in the last column of Table I are corrected. 15 new references are added
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1705.01110 [pdf]
6 citations
02
[Submitted on 3 May 2017]
Higher moments of net-proton multiplicity distributions in a heavy-ion event pile-up scenario
P. Garg🇺🇸 · D. K. Mishra🇮🇳
High-luminosity modern accelerators, like the Relativistic Heavy Ion Collider (RHIC) at BNL and Large Hadron Collider (LHC) at CERN, inherently have event pile-up scenarios which significantly contribute to physics events as a background. While state-of-the-art tracking algorithms and detector concepts take care of these event pile-up scenarios, several offline analytical techniques are used to remove such events from the physics analysis. It is still difficult to identify the remaining pile-up events in an event sample for physics analysis. Since the fraction of these events is significantly small, it may not be as serious of an issue for other analysis as it would be for an event-by-event analysis. Particularly, when the characteristics of the multiplicity distribution are observable, one needs to be very careful. In the present work, we demonstrate how a small fraction of residual pile-up events can change the moments and their ratios of an event-by-event net-proton multiplicity distribution, which are sensitive to the dynamical fluctuations due to the QCD critical point. For this study we assume that the individual event-by-event proton and antiproton multiplicity distributions follow Poisson, negative binomial or binomial distributions. We observe a significant effect in cumulants and their ratios of net-proton multiplicity distributions due to pile-up events, particularly at lower energies. It might be crucial to estimate the fraction of pile-up events in the data sample while interpreting the experimental observable for the critical point.
Comments:
9 pages, 11 Figures. Published in Physical Review C
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1705.01256 [pdf]
PRC(2017)·12 citations
03
[Submitted on 3 May 2017]
Toroidal high-spin isomers in the nucleus $^{304} 120$
A. Staszczak · Cheuk-Yin Wong · A. Kosior
Strongly deformed oblate superheavy nuclei form an intriguing region where the toroidal nuclear structures may bifurcate from the oblate spheroidal shape. The bifurcation may be facilitated when the nucleus is endowed with a large angular moment about the symmetry axis with $I = I_{z}$ . The toroidal high- $K$ isomeric states at their local energy minima can be theoretically predicted using the cranked self-consistent Skyrme-Hartree-Fock method. We use the cranked Skyrme-Hartree-Fock method to predict the properties of the toroidal high-spin isomers in the superheavy nucleus $^{304} 120_{184}$ .
Comments:
12 pages, 11 figures, 1 table, accepted to Phys. Rev. C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1705.01408 [pdf]
PRC(2017)·11 citations
04
[Submitted on 2 May 2017]
Coherent J/ $ψ$ photoproduction in hadronic heavy-ion collisions
W. Zha🇨🇳 · S.R. Klein🇺🇸 · R. Ma🇺🇸 · L. Ruan🇺🇸 · T. Todoroki🇺🇸 · Z. Tang🇨🇳 · Z. Xu🇨🇳 · C. Yang🇨🇳 · Q. Yang🇨🇳 · S. Yang🇺🇸
A significant excess of J/ $ψ$ yield at very low transverse momentum ( $p_{T} < 0.3$ GeV/c) was observed by the ALICE and STAR collaborations in peripheral A+A collisions, which points to evidence of coherent photoproduction of J/ $ψ$ in violent hadronic interactions. Theoretically, the photoproduction of J $/ ψ$ in hadronic collisions raises questions about how spectator and non-spectator nucleons participate in the coherent reaction. For the first time, we argue that the strong interactions in the overlapping region of incoming nuclei may disturb the coherent production, leaving room for different coupling assumptions. Furthermore, first considerations of the destructive interference between photoproduction on ions moving in opposite directions in hadronic heavy-ion collisions are included. This letter presents calculations of J $/ ψ$ production from coherent photon-nucleus ( $γ + A \to J / ψ + A$ ) interactions in hadronic A+A collisions at RHIC and LHC energies with both nucleus and spectator coupling hypotheses. The coherent J/ $ψ$ yield as a function of centrality and differential distributions as a function of transverse momentum, azimuthal angle and rapidity in different centrality bins are shown and found to be significantly different for different coupling scenarios, calling for future experimental measurements.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1705.01460 [pdf]
PRC(2018)·78 citations
05
[Submitted on 3 May 2017]
Extracting $q^$ in event-by-event hydrodynamics and the centrality/energy puzzle
Carlota Andres🇪🇸 · Nestor Armesto🇪🇸 · Harri Niemi🇩🇪 · Risto Paatelainen🇪🇸 · Carlos A. Salgado🇪🇸 · Pia Zurita🇺🇸
In our analysis, we combine event-by-event hydrodynamics, within the EKRT formulation, with jet quenching -ASW Quenching Weights- to obtain high- $p_{T}$ $R_{AA}$ for charged particles at RHIC and LHC energies for different centralities. By defining a $K$ -factor that quantifies the departure of $q^$ from an ideal estimate, $K = q^/ (2 ϵ^{3/4})$ , we fit the single-inclusive experimental data for charged particles. This $K$ -factor is larger at RHIC than at the LHC but, surprisingly, it is almost independent of the centrality of the collision.
Comments:
4 pages, 2 figures, proceedings for Quark Matter 2017
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1705.01493 [pdf]
NPA(2017)·8 citations
06
[Submitted on 3 May 2017]
Workshop on Chiral Forces in Low Energy Nuclear Physics - the LENPIC Meeting
J.Golak · R.Skibinski · (editors)
We present mini-proceedings of the international workshop on "Chiral Forces in Low Energy Nuclear Physics - the LENPIC Meeting" held at the Jagiellonian University, Krakow, Poland from February 10 to 11, 2017. The workshop focused on the new generation of chiral forces with the semi-local regularization and their applications to few- and many-nucleon systems. Included short contributions summarize talks given by E.Epelbaum, K.Hebeler, R.Roth, H.Witala, A.Calci, P.Reinert, J.P.Vary, H.Kamada, I.Ciepal, H.Krebs, H.Le, K.Topolnicki, K.Vobig and Yu.Volkotrub.
Comments:
29 pages, 4 figures, proceedings
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1705.01530 [pdf]
1 citation
07
[Submitted on 3 May 2017] (cross-list from physics.atom-ph)
Significance of distinct electron correlation effects in determining the P,T-odd electric dipole moment of $^{171}$ Yb
B. K. Sahoo🇰🇷 · Yashpal Singh🇰🇷
Parity and time-reversal violating electric dipole moment (EDM) of $^{171}$ Yb is calculated accounting for the electron correlation effects over the Dirac-Hartree-Fock (DHF) method in the relativistic Rayleigh-Schrödinger many-body perturbation theory, with the second (MBPT(2) method) and third order (MBPT(3) method) approximations, and two variants of all-order relativistic many-body approaches, in the random phase approximation (RPA) and coupled-cluster (CC) method with singles and doubles (CCSD method) framework. We consider electron-nucleus tensor-pseudotensor (T-PT) and nuclear Schiff moment (NSM) interactions as the predominant sources that induce EDM in a diamagnetic atomic system. Our results from the CCSD method to EDM ( $d_{a}$ ) of $^{171}$ Yb due to the T-PT and NSM interactions are found to be $d_{a} = 4.85 (6) \times 1 0^{- 20} ⟨ σ ⟩ C_{T} ∣ e ∣ c m$ and $d_{a} = 2.89 (4) \times 1 0^{- 17} S / (∣ e ∣ f m^{3})$ , respectively, where $C_{T}$ is the T-PT coupling constant and $S$ is the NSM. These values differ significantly from the earlier calculations. The reason for the same has been attributed to large correlation effects arising through non-RPA type of interactions among the electrons in this atom that are observed by analyzing the differences in the RPA and CCSD results. This has been further scrutinized from the MBPT(2) and MBPT(3) results and their roles have been demonstrated explicitly.
Comments:
11 pages, 4 figures and 4 tables
Subjects:
Atomic Physics (physics.atom-ph); Nuclear Theory (nucl-th); Computational Physics (physics.comp-ph); Quantum Physics (quant-ph)
arXiv:
1705.01283 [pdf]
PRA(2017)·8 citations
08
[Submitted on 3 May 2017] (cross-list from nucl-ex)
Experimental Determination of $η$ / $s$ for Finite Nuclear Matter
Debasish Mondal🇮🇳 · Deepak Pandit🇮🇳 · S. Mukhopadhyay🇮🇳 · Surajit Pal🇮🇳 · Balaram Dey🇮🇳 · Srijit Bhattacharya🇮🇳 · A. De🇮🇳 · Soumik Bhattacharya🇮🇳 · S. Bhattacharyya🇮🇳 · Pratap Roy🇮🇳 · K. Banerjee🇮🇳 · S. R. Banerjee🇮🇳
We present, for the first time, simultaneous determination of shear viscosity ( $η$ ) and entropy density ( $s$ ) and thus, $η / s$ for equilibrated nuclear systems from $A$ $\sim$ 30 to $A$ $\sim$ 208 at different temperatures. At finite temperature, $η$ is estimated by utilizing the $γ$ decay of the isovector giant dipole resonance populated via fusion evaporation reaction, while $s$ is evaluated from the nuclear level density parameter ( $a$ ) and nuclear temperature ( $T$ ), determined precisely by the simultaneous measurements of the evaporated neutron energy spectra and the compound nuclear angular momenta. The transport parameter $η$ and the thermodynamic parameter $s$ both increase with temperature resulting in a mild decrease of $η$ / $s$ with temperature. The extracted $η$ / $s$ is also found to be independent of the neutron-proton asymmetry at a given temperature. Interestingly, the measured $η$ / $s$ values are comparable to that of the high-temperature quark-gluon plasma, pointing towards the fact that strong fluidity may be the universal feature of the strong interaction of many-body quantum systems.
Comments:
Accepted for publication in Physical Review Letters, 6 pages, 4 figures
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1705.01286 [pdf]
PRL(2017)·30 citations
09
[Submitted on 3 May 2017] (cross-list from hep-ph)
Heavy and Strange Holographic Baryons
Yizhuang Liu🇺🇸 · Ismail Zahed🇺🇸
We extend the $D 4$ - $D 8$ holographic construction to include three chiral and one heavy flavor, to describe heavy-light baryons with strangeness and their exotics. At strong coupling, the heavy meson always binds to the bulk instanton in the form of a flavor zero mode in the fundamental representation. We quantize the ensuing bound states using the collective quantization method, to obtain the spectra of heavy and strange baryons with both explicit and hidden charm and bottom. Our results confirm the existence of two low-lying charmed penta-quark states with $\frac{1}{2}^{-}, \frac{3}{2}^{-}$ assignments, and predict many new ones with both charm and bottom. They also suggest a quartet of low-lying neutral $Ω_{c}^{0}$ with assignments $\frac{1}{2}^{\pm}, \frac{3}{2}^{\pm}$ that are heavier than the quintuplet of neutral $Ω_{c}^{0}$ recently reported by LHCb.
Comments:
14 pages, 1 figure. arXiv admin note: substantial text overlap with arXiv:1704.03412
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1705.01397 [pdf]
PRD(2017)·21 citations
10
[Submitted on 3 May 2017] (cross-list from hep-ph)
Quasi-PDFs, momentum distributions and pseudo-PDFs
A. V. Radyushkin🇺🇸
We show that quasi-PDFs may be treated as hybrids of PDFs and primordial rest-frame momentum distributions of partons. This results in a complicated convolution nature of quasi-PDFs that necessitates using large $p_{3} \sim 3$ GeV momenta to get reasonably close to the PDF limit. As an alternative approach, we propose to use pseudo-PDFs $P (x, z_{3}^{2})$ that generalize the light-front PDFs onto spacelike intervals and are related to Ioffe-time distributions $M (ν, z_{3}^{2})$ , the functions of the Ioffe time $ν = p_{3} z_{3}$ and the distance parameter $z_{3}^{2}$ with respect to which it displays perturbative evolution for small $z_{3}$ . In this form, one may divide out the $z_{3}^{2}$ dependence coming from the primordial rest-frame distribution and from the problematic factor due to lattice renormalization of the gauge link. The $ν$ -dependence remains intact and determines the shape of PDFs.
Comments:
6 pages, 3 figures, changes in text and references
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1705.01488 [pdf]
PRD(2017)·418 citations

Affiliations

first authorsco-authorsvia INSPIRE