Nuclear Theory·nucl-th

Thursday·May 4, 2017

10 papers—6 primary·4 cross-listed

01
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.
nucl-thhep-exhep-phnucl-ex6 citations
02
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.
nucl-thhep-phnucl-exPRC(2017)·12 citations
03
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 $^{304} 120_{184}$ .
nucl-thPRC(2017)·11 citations
04
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.
nucl-thhep-phnucl-exPRC(2018)·78 citations
05
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.
nucl-thhep-phnucl-exNPA(2017)·8 citations
06
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.
nucl-th1 citation

Affiliations

first authorsco-authorsvia INSPIRE

Multi moment cancellation of participant fluctuations - MMCP method

Higher moments of net-proton multiplicity distributions in a heavy-ion event pile-up scenario

Toroidal high-spin isomers in the nucleus 304120

Coherent J/ψ photoproduction in hadronic heavy-ion collisions

Extracting q^​ in event-by-event hydrodynamics and the centrality/energy puzzle

Workshop on Chiral Forces in Low Energy Nuclear Physics - the LENPIC Meeting

Affiliations

Toroidal high-spin isomers in the nucleus $^{304} 120$

Coherent J/ $ψ$ photoproduction in hadronic heavy-ion collisions

Extracting $q^$ in event-by-event hydrodynamics and the centrality/energy puzzle