Nuclear Theory·nucl-th

Thursday·December 20, 2018

14 papers—7 primary·7 cross-listed

01
Linking nuclear reactions and nuclear structure to study exotic nuclei using the dispersive optical model
W. H. Dickhoff
The dispersive optical model (DOM) is employed to simultaneously describe elastic nucleon scattering data for $^{40}$ Ca, $^{48}$ Ca, and $^{208}$ Pb as well as observables related to the ground state of these nuclei, with emphasis on the charge density. Such an analysis requires a fully non-local implementation of the DOM including its imaginary component. Illustrations are provided how ingredients thus generated provide critical components for the description of the $(d, p)$ and $(e, e^{'} p)$ reaction. For the nuclei with $N > Z$ the neutron distribution is constrained by available elastic scattering and ground-state data thereby generating a prediction for the neutron skin. We identify ongoing developments including a non-local DOM analysis for $^{208}$ Pb and point out possible extensions of the method to secure a successful extension of the DOM to rare isotopes.
nucl-thSpringer Proc.Phys.(2020)·1 citation
02
Electromagnetic currents for dressed hadrons
Helmut Haberzettl🇺🇸
We propose an extension of the minimal-substitution prescription for coupling the electromagnetic field to hadronic systems with internal structure. The resulting rules of extended substitution necessarily distinguish between couplings to scalar and Dirac particles. Moreover, they allow for the incorporation of electromagnetic form factors for virtual photons in an effective phenomenological framework. Applied to pions and nucleons, assumed to be fully dressed to all orders, the resulting dressed currents are shown to be locally gauge invariant. Moreover, half-on-shell expressions of (hadron propagator) $\times$ (electromagnetic current) needed in all descriptions of physical processes will lose \textit{all} information about hadronic dressing for real photons. The Ball-Chiu ansatz for the spin-1/2 current is seen to suffer from an incomplete coupling procedure where some essential aspects of the Dirac particle are effectively treated as those of a scalar particle. Applied to real Compton scattering on pions and nucleons, we find that \emph{all} dressing information cancels exactly when external hadrons are on shell, leaving only gauge-invariant bare Born-type contributions with physical masses. Hence, nontrivial descriptions necessarily require contact-type two-photon processes obtained by hadrons looping around two photon insertion points.
nucl-thhep-phPRD(2019)·3 citations
03
Clusterization and deformation of multi- $Λ$ hypernuclei within relativistic mean-field model
Yusuke Tanimura🇯🇵
Deformed multi- $Λ$ hypernuclei are studied within a relativistic mean-field model. In this paper, we take some $N = Z$ "hyper isotope" chains, i.e., $_{n Λ}^{8 + n} Be$ , $_{n Λ}^{20 + n} Ne$ , and $_{n Λ}^{28 + n} Si$ systems where $n = 2$ , $4$ for Be, and $n = 2$ , $8$ for Ne and Si. A sign of two- $_{2Λ}^{6}$ He cluster structure is observed in the two-body correlation in $_{4Λ}^{12}$ Be. In the Ne hyper isotopes, the deformation is slightly reduced by addition of $Λ$ hyperons whereas it is significantly reduced or even disappears in the Si hyper isotopes.
nucl-thPRC(2019)·26 citations
04
Electromagnetic Excitations and Responses in Nuclei from First Principles
R. B. Baker · K. D. Launey · N. Nevo Dinur · S. Bacca · J. P. Draayer · T. Dytrych
We discuss the role of clustering on monopole, dipole, and quadrupole excitations in nuclei in the framework of the ab initio symmetry-adapted no-core shell model (SA-NCSM). The SA-NCSM starts from nucleon-nucleon potentials and, by exploring symmetries known to dominate the nuclear dynamics, can reach nuclei up through the calcium region by accommodating ultra-large model spaces critical to descriptions of clustering and collectivity. The results are based on calculations of electromagnetic sum rules and discretized responses using the Lanczos algorithm, that can be used to determine response functions, and for 4He are benchmarked against exact solutions of the hyperspherical harmonics method. In particular, we focus on He, Be, and O isotopes, including giant resonances and monopole sum rules.
nucl-thAIP Conf.Proc.(2018)·1 citation
05
Heavy-flavor dynamics in event-by-event viscous hydrodynamic backgrounds
Roland Katz🇧🇷 · Caio A. G. Prado🇨🇳 · Jacquelyn Noronha-Hostler🇺🇸 · Alexandre A. P. Suaide🇧🇷 · Jorge Noronha🇧🇷 · Marcelo G. Munhoz🇧🇷
We investigate the effects of (2+1)d event-by-event fluctuating hydrodynamic backgrounds on the nuclear modification factor and momentum anisotropies of heavy-flavor mesons. Using the state-of-the-art D and B mesons modular simulation code (the so-called DAB-mod), updated recently with heavy-light quark coalescence, we perform a systematic comparison of different transport equations, including two energy loss models and a relativistic Langevin model with two drag parametrizations. We present the resulting D $^{0}$ meson $R_{AA}$ , $v_{2}$ and $v_{3}$ , using the multiparticle cumulant method, in Pb-Pb collisions at $s_{NN} = 5.02$ TeV and compare them to the latest experimental data. We investigate the $v_{2} {4} / v_{2} {2}$ ratio as a function of centrality for different initial conditions (MCKLN vs. Trento) and different system geometries and sizes (coming from Pb-Pb collisions at $s_{NN} = 5.02$ TeV, spherical and prolate Xe-Xe collisions at $s_{NN} = 5.44$ TeV).
nucl-thPoS(2018)·3 citations
06
Exploring New Small System Geometries in Heavy Ion Collisions
S.H. Lim🇺🇸 · J. Carlson🇺🇸 · C. Loizides🇺🇸 · D. Lonardoni🇺🇸 · J.E. Lynn🇩🇪 · J.L. Nagle🇺🇸 · J.D. Orjuela Koop🇺🇸 · J. Ouellette🇺🇸
Relativistic heavy ion collisions produce nuclei-sized droplets of quark-gluon plasma whose expansion is well described by viscous hydrodynamic calculations. Over the past half decade, this formalism was also found to apply to smaller droplets closer to the size of individual nucleons, as produced in $p$ $+$ $p$ and $p$ $+$ $A$ collisions. The hydrodynamic paradigm was further tested with a variety of collision species, including $p$ $+$ Au, $d$ $+$ Au, and $^{3}$ He $+$ Au producing droplets with different geometries. Nevertheless, questions remain regarding the importance of pre-hydrodynamic evolution and the exact medium properties during the hydrodynamic evolution phase, as well as the applicability of alternative theories that argue the agreement with hydrodynamics is accidental. In this work we explore options for new collision geometries including $p$ $+$ O and O $+$ O proposed for running at the Large Hadron Collider, as well as, $^{4}$ He $+$ Au, C $+$ Au, O $+$ Au, and $^{7, 9}$ Be $+$ Au at the Relativistic Heavy Ion Collider.
nucl-thnucl-exPRC(2019)·67 citations
07
Physics perspectives with heavy ions in the HL-LHC phase and beyond
Stefan Floerchinger🇩🇪
The current state of research on high-energy heavy ion physics, including its motivations and purpose is reviewed from a theorist's perspective. Possible future directions are discussed, in particular the possibility of investigating the regime of small transverse momenta in more detail and an improved interplay between experiments and dedicated theory development.
nucl-thhep-phPoS(2018)·0 citations
08
New physics searches with heavy-ion collisions at the LHC
Roderik Bruce🇨🇭 · David d'Enterria🇨🇭 · Albert de Roeck🇨🇭 · Marco Drewes🇧🇪 · Glennys R. Farrar🇺🇸 · Andrea Giammanco🇧🇪 · Oliver Gould🇫🇮 · Jan Hajer🇧🇪 · Lucian Harland-Lang🇬🇧 · Jan Heisig🇧🇪 · John M. Jowett🇨🇭 · Sonia Kabana🇫🇷 and 9 other authors
This document summarises proposed searches for new physics accessible in the heavy-ion mode at the CERN Large Hadron Collider (LHC), both through hadronic and ultraperipheral $γ γ$ interactions, and that have a competitive or, even, unique discovery potential compared to standard proton-proton collision studies. Illustrative examples include searches for new particles -- such as axion-like pseudoscalars, radions, magnetic monopoles, new long-lived particles, dark photons, and sexaquarks as dark matter candidates -- as well as new interactions, such as non-linear or non-commutative QED extensions. We argue that such interesting possibilities constitute a well-justified scientific motivation, complementing standard quark-gluon-plasma physics studies, to continue running with ions at the LHC after the Run-4, i.e. beyond 2030, including light and intermediate-mass ion species, accumulating nucleon-nucleon integrated luminosities in the accessible fb $^{- 1}$ range per month.
↳ hep-phhep-exnucl-exnucl-thJ.Phys.G(2020)·95 citations
09
Clusters in light stable and exotic nuclei
C. Beck🇫🇷
Since the discovery of molecular resonances in $^{12}$ C+ $^{12}$ C in the early sixties a great deal of research work has been undertaken to study alpha-clustering. Our knowledge on physics of nuclear molecules has increased considerably and nuclear clustering remains one of the most fruitful domains of nuclear physics, facing some of the greatest challenges and opportunities in the years ahead. Occurrence of "exotic" shapes and Bose-Einstein Condensates in light alpha-cluster nuclei are investigated. Various approaches of superdeformed/hyperdeformed shapes associated with quasimolecular resonant structures are discussed. The astrophysical reaction rate of 12C+12C is extracted from recent fusion measurements at deep subbarrier energies near the Gamov window. Evolution of clustering from stability to the drip-lines is examined.
↳ nucl-exnucl-th9 citations
10
Semi-inclusive jets recoiling from $γ_{d i r}$ and $π^{0}$ triggers in central Au+Au collisions at $s_{NN}$ = 200 GeV in STAR
Nihar Ranjan Sahoo (For the STAR Collaboration)🇺🇸
We report the first measurement of fully corrected semi-inclusive charged recoil jets for both direct-photon ( $γ_{d i r}$ ) and $π^{0}$ triggers, within two trigger transverse energy ranges between 9 GeV and 15 GeV, in central Au+Au collisions at $s_{NN}$ = 200 GeV using data with an integrated luminosity of 13 $n b^{- 1}$ collected by the STAR experiment. A comparison between $π^{0}$ -triggered recoil jets in p+p collisions and PYTHIA is discussed. A comparison is also presented between the suppression of $γ_{d i r}$ - and $π^{0}$ -triggered recoil jets in central Au+Au collisions with respect to their corresponding PYTHIA references. A strong and similar level of suppression is observed in recoil-jet yields as a function of jet transverse momentum for $γ_{d i r}$ +jet and $π^{0}$ +jet.
↳ nucl-exhep-exhep-phnucl-thPoS(2018)·1 citation
11
Nucleon-nucleon correlations and the single-particle strength in atomic nuclei
S. Paschalis · M. Petri · A.O. Macchiavelli · O. Hen · E. Piasetzky
We propose a phenomenological approach to examine the role of short- and long-range nucleon-nucleon correlations in the quenching of single-particle strength in atomic nuclei and their evolution in asymmetric nuclei and neutron matter. These correlations are thought to be the reason for the quenching of spectroscopic factors observed in $(e, e^{'} p)$ , $(p, 2p)$ and transfer reactions. We show that the recently observed increase of the high-momentum component of the protons in neutron-rich nuclei is consistent with the reduced proton spectroscopic factors. Our approach connects recent results on short-range correlations from high-energy electron scattering experiments with the quenching of spectroscopic factors and addresses for the first time quantitatively this intriguing question in nuclear physics, in particular regarding its isospin dependence. We also speculate about the nature of a {\sl quasi-proton} (nuclear polaron) in neutron matter and its kinetic energy, an important quantity for the properties of neutron stars.
↳ nucl-exnucl-thPLB(2020)·36 citations
12
Lepton-jet Correlations in Deep Inelastic Scattering at the Electron-Ion Collider
Xiaohui Liu🇨🇳 · Felix Ringer🇺🇸 · Werner Vogelsang🇩🇪 · Feng Yuan🇺🇸
We propose the lepton-jet correlation in deep inelastic scattering as a unique tool for nucleon/nucleus tomography at the electron-ion collider. The azimuthal angular correlation between the final state lepton and jet depends on the transverse momentum dependent quark distributions. We take the example of single transverse spin asymmetries to show the sensitivity to the quark Sivers function. When the correlation is studied in lepton-nucleus collisions, transverse momentum broadening effects can be used to explore cold nuclear matter effects. These features make lepton-jet correlations an important new hard probe at the EIC.
↳ hep-phnucl-exnucl-thPRL(2019)·113 citations
13
Direct photon production and flow at low transverse momenta in pp, p-Pb and Pb-Pb collisions
Nicolas Schmidt (for the ALICE Collaboration)🇺🇸
Low transverse momentum direct photon measurements have been carried out by the ALICE experiment at the CERN LHC in small collision systems (pp, $s = 2.76$ and 8 TeV and p--Pb, $s_{NN} = 5.02$ TeV) as well as in heavy-ion collisions (Pb--Pb, $s_{NN} = 2.76$ TeV). For the first time, also the multiplicity dependence of direct photon production was investigated in p--Pb collisions. Whereas in the small systems no significant thermal photon signal was observed, a $\sim 15%$ excess has been measured in central Pb--Pb collisions in the region of $p_{T} < 3$ GeV/ $c$ . A signal of prompt photon production at high transverse momentum consistent with binary scaling has been observed in all collision systems following NLO pQCD predictions. Direct photon flow has been measured in central and semi-central Pb--Pb collisions and found to be of similar size as the charged hadron and decay photon flow.
↳ nucl-exhep-exhep-phnucl-thPoS(2018)·7 citations
14
Hyperons and quarks in proto-neutron stars
J. Roark🇺🇸 · X. Du🇺🇸 · C. Constantinou🇺🇸 · V. Dexheimer🇺🇸 · A. W. Steiner🇺🇸 · J. R. Stone🇺🇸
In this work, we study matter in the cores of proto-neutron stars, focusing on the impact of their composition on the stellar structure. We begin by examining the effects of finite temperature (through a fixed entropy per baryon) and lepton fraction on purely nucleonic matter by making use of the DSH model . We then turn our attention to a relativistic mean-field model containing exotic degrees of freedom, the Chiral Mean Field (CMF) model, again, under the conditions of finite temperature and trapped neutrinos. In the latter, since both hyperons and quarks are found in the cores of large-mass stars, their interplay and the possibility of mixtures of phases is taken into account and analyzed. Finally, we discuss how stellar rotation can affect our results.
↳ astro-ph.HEastro-ph.SRnucl-thMNRAS(2019)·31 citations

Affiliations

first authorsco-authorsvia INSPIRE