Nuclear Theory·nucl-th

Wednesday·April 19, 2017

15 papers—9 primary·6 cross-listed

01
Jet modifications in event-by-event hydrodynamically evolving media
Jacquelyn Noronha-Hostler🇺🇸
The nearly perfect fluid-like nature of the Quark Gluon Plasma may be understood through two key experimental signatures: collective flow and jet suppression. Event-by-event relativistic viscous hydrodynamics (with an extremely small shear viscosity to entropy density ratio) has been very successful at describing collective flow observables for the last 7 years. More recently, the effects of event-by-event fluctuations have been studied in the context of high $p_{T}$ particles that lose energy as they pass through the dense Quark Gluon Plasma liquid. In this summary of the corresponding plenary talk at Quark Matter 2017, the recent developments on the effects of event-by-event fluctuations on jet suppression are summarized.
nucl-thhep-phnucl-exNPA(2017)·0 citations
02
Pairing in the BCS and LN approximations using continuum single particle level density
R. M. Id Betan · C. E. Repetto
Understanding the properties of drip line nuclei requires to take into account the correlations with the continuum spectrum of energy of the system. This paper has the purpose to show that the continuum single particle level density is a convenient way to consider the pairing correlation in the continuum. Isospin mean-field and isospin pairing strength are used to find the Bardeen-Cooper-Schrieffer (BCS) and Lipkin-Nogami (LN) approximate solutions of the pairing Hamiltonian. Several physical properties of the whole chain of the Tin isotope, as gap parameter, Fermi level, binding energy, and one- and two-neutron separation energies, were calculated and compared with other methods and with experimental data when they exist. It is shown that the use of the continuum single particle level density is an economical way to include explicitly the correlations with the continuum spectrum of energy in large scale mass calculation. It is also shown that the computed properties are in good agreement with experimental data and with more sophisticated treatment of the pairing interaction.
nucl-thNPA(2017)·4 citations
03
Determination of the density region of the symmetry energy probed by the $π^{-} / π^{+}$ ratio
Gao-Chan Yong🇨🇳 · Yuan Gao🇨🇳 · Gao-Feng Wei🇨🇳 · Ya-Fei Guo🇨🇳 · Wei Zuo🇨🇳
The studies, from several independent methods, consistently show that $π^{-} / π^{+}$ ratio in the $^{132}$ Sn+ $^{124}$ Sn reaction at 300 MeV/nucleon, which is being carried out at Radioactive Isotope Beam Facility (RIBF) in Japan, just probes the symmetry energy around saturation density.
nucl-thnucl-exJ.Phys.G(2019)·13 citations
04
Green's function relativistic mean field theory for $Λ$ hypernuclei
Su-Hong Ren🇨🇳 · Ting-Ting Sun🇨🇳 · Wei Zhang🇨🇳
The relativistic mean-field theory with Green's function method is extended to study $Λ$ hypernuclei. Taking hypernucleus $_{Λ}^{61}$ Ca as an example, the single-particle resonant states for $Λ$ hyperons are investigated by analyzing density of states and the corresponding energies and widths are given. Different behaviors are observed for the resonant states, i.e., the distributions of the very narrow $1 f_{5/2}$ and $1 f_{7/2}$ states are very similar as bound states while that of the wide $1 g_{7/2}$ and $1 g_{9/2}$ states are like scattering states. Besides, the impurity effect of $Λ$ hyperons on the single-neutron resonant states are investigated. For most of the resonant states, both the energies and widths decrease with adding more $Λ$ hyperons due to the attractive $Λ N$ interaction. Finally, the energy level structure of $Λ$ hyperons in the Ca hypernucleus isotopes with mass number $A = 53 - 73$ are studied, obvious shell structure and small spin-orbit splitting are found for the single- $Λ$ spectrum.
nucl-thPRC(2017)·36 citations
05
$p Ξ^{-}$ Correlation in Relativistic Heavy Ion Collisions with Nucleon-Hyperon Interaction from Lattice QCD
Tetsuo Hatsuda🇯🇵 · Kenji Morita🇯🇵 · Akira Ohnishi🇯🇵 · Kenji Sasaki🇯🇵
On the basis of the $p Ξ^{-}$ interaction extracted from (2+1)-flavor lattice QCD simulations at the physical point, the momentum correlation of $p$ and $Ξ^{-}$ produced in relativistic heavy ion collisions is evaluated. $C_{SL} (Q)$ defined by a ratio of the momentum correlations between the systems with different source sizes is shown to be largely enhanced at low momentum due to the strong attraction between $p$ and $Ξ^{-}$ in the $I = J = 0$ channel. Thus, measuring this ratio at RHIC and LHC and its comparison to the theoretical analysis will give a useful constraint on the $p Ξ^{-}$ interaction.
nucl-thhep-latnucl-exNPA(2017)·53 citations
06
Initial conditions for hydrodynamics from kinetic theory equilibration
Aleksi Kurkela🇨🇭 · Aleksas Mazeliauskas🇺🇸 · Jean-François Paquet🇺🇸 · Sören Schlichting🇺🇸 · Derek Teaney🇺🇸
We use effective kinetic theory to study the pre-equilibrium dynamics in heavy-ion collisions. We describe the evolution of linearized energy perturbations on top of out-of-equilibrium background to the energy-momentum tensor at a time when hydrodynamics becomes applicable. We apply this description to IP-Glasma initial conditions and find an overall smooth transition to hydrodynamics. In a phenomenologically favorable range of $η / s$ values, early time dynamics can be accurately described in terms of a few functions of a scaled time variable $τ T / (η / s)$ . Our framework can be readily applied to other initial state models to provide the pre-equilibrium dynamics of the energy momentum tensor.
nucl-thhep-phNPA(2017)·5 citations
07
On the norm overlap between many-body states. I. Uncorrelated overlap between arbitrary Bogoliubov product states
B. Bally🇫🇷 · T. Duguet🇫🇷
State-of-the-art multi-reference energy density functional calculations require the computation of norm overlaps between different Bogoliubov quasiparticle many-body states. It is only recently that the efficient and unambiguous calculation of such norm kernels has become available under the form of Pfaffians~[L. M. Robledo, Phys. Rev. C79, 021302 (2009)]. The goals of this work is (i) to propose and implement an alternative to the Pfaffian method to compute unambiguously the norm overlap between arbitrary Bogoliubov quasiparticle states and (ii) to extend the first point to explicitly correlated norm kernels at play in recently developped particle-number-restored Bogoliubov coupled-cluster (PNR-BCC) and particle-number-restored many-body perturbation (PNR-BMBPT) ab initio theories~[T. Duguet and A. Signoracci, J. Phys. G44, 015103 (2017)]. Point (i) constitutes the purpose of the present paper while point (ii) is addressed in a forthcoming companion paper. We generalize the method used in~[T. Duguet and A. Signoracci, J. Phys. G44, 015103 (2017)] to obtain the norm overlap between arbitrary Bogoliubov product states under a closed-form expression. The formula is physically intuitive, accurate, versatile and relies on elementary linear algebra operations. It equally applies to norm overlaps between Bogoliubov states of even or odd number parity. Numerical applications illustrate these features and provide a transparent representation of the content of the norm overlaps. Furthermore, the closed-form expression extends naturally to correlated overlaps at play in PNR-BCC and PNR-BMBPT. As such, the straight overlap between Bogoliubov states is the zeroth-order reduction of more involved norm kernels to be studied in the forthcoming paper.
nucl-thPRC(2018)·21 citations
08
A Detailed Study and Synthesis of Flow Observables in the IP-Glasma+MUSIC+UrQMD Framework
Scott McDonald🇨🇦 · Chun Shen🇨🇦 · Francois Fillion-Gourdeau🇨🇦 · Sangyong Jeon🇨🇦 · Charles Gale🇨🇦
In this work we use the IP-Glasma+MUSIC+UrQMD framework to systematically study a wide range of hadronic flow observables at 2.76 TeV. In addition to the single particle spectra and anisotropic flow coefficients $v_{n}$ previously studied in \cite{1609.02958}, we consider event-plane correlations, non-linear response coefficients $χ_{n pq}$ , and event shape engineering. Taken together, these observables provide a wealth of insight into the collective behavior of the QGP and initial state fluctuations. They shed light on flow fluctuations, flow at fixed system size but different initial geometries, as well as the non-linear hydrodynamic response to the initial state spatial eccentricities. By synthesizing this information we can gain further insight into the transport properties of the QGP as well as the fluctuation spectrum of the initial state.
nucl-thhep-phnucl-exNPA(2017)·8 citations
09
Chiral Vortical and Magnetic Effects in Anomalous Hydrodynamics
Xingyu Guo🇨🇳 · Dmitri E. Kharzeev🇺🇸 · Xu-Guang Huang🇨🇳 · Wei-Tian Deng🇨🇳 · Yuji Hirono🇺🇸
We employ a 3+1D anomalous hydrodynamics with initial condition generated by HIJING to simulate the chiral vortical effect and the chiral magnetic effect in heavy-ion collisions. This allows us to calculate the charge-dependent two-particle correlations with respect to the reaction plane at different collision energies and centralities. We then compare the computed results with the experimental data and give discussions on the possible background effects.
nucl-thhep-phnucl-exNPA(2017)·10 citations
10
High statistics study of in-medium S- and P-wave quarkonium states in lattice Non-relativistic QCD
Seyong Kim🇰🇷 · Peter Petreczky🇺🇸 · Alexander Rothkopf🇩🇪
Many measurements of quarkonium suppression at the LHC, e.g. the nuclear modification factor $R_{AA}$ of $J /Ψ$ , are well described by a multitude of different models. Thus pinpointing the underlying physics aspects is difficult and guidance based on first principles is needed. Here we present the current status of our ongoing high precision study of in-medium spectral properties of both bottomonium and charmonium based on NRQCD on the lattice. This effective field theory allows us to capture the physics of quarkonium without modeling assumptions in a thermal QCD medium. In our study a first principles and realistic description of the QCD medium is provided by state-of-the-art lattices of the HotQCD collaboration at almost physical pion mass. Our updated results corroborate a picture of sequential modification of states with respect to their vacuum binding energy. Using a novel low-gain variant of the Bayesian BR method for reconstructing spectral functions we find that remnant features of the Upsilon may survive up to $T \sim 400$ MeV, while the $χ_{b}$ signal disappears around $T \sim 270$ MeV. The $c c ˉ$ analysis hints at melting of $χ_{c}$ below $T \sim 190$ MeV while some $J /Ψ$ remnant feature might survive up to $T \sim 245$ MeV. An improved understanding of the numerical artifacts in the Bayesian approach and the availability of increased statistics have made possible a first quantitative study of the in-medium ground state masses, which tend to lower values as $T$ increases, consistent with lattice potential based studies.
↳ hep-lathep-phnucl-thNPA(2017)·2 citations
11
Thermal effects on $ρ$ meson properties in an external magnetic field
Snigdha Ghosh🇮🇳 · Arghya Mukherjee🇮🇳 · Mahatsab Mandal🇮🇳 · Sourav Sarkar🇮🇳 · Pradip Roy🇮🇳
A detailed study of the analytic structure of 1-loop self energy graphs for neutral and charged $ρ$ mesons is presented at finite temperature and arbitrary magnetic field using the real time formalism of thermal field theory. The imaginary part of the self energy is obtained from the discontinuities of these graphs across the Unitary and Landau cuts, which is seen to be different for $ρ^{0}$ and $ρ^{\pm}$ . The magnetic field dependent vacuum contribution to the real part of the self energy, which is usually ignored, is found to be appreciable. A significant effect of temperature and magnetic field is seen in the self energy, spectral function, effective mass and dispersion relation of $ρ^{0}$ as well as of $ρ^{\pm}$ relative to its trivial Landau shift. However, for charged $ρ$ mesons, on account of the dominance of the Landau term, the effective mass appears to be independent of temperature. The trivial coupling of magnetic moment of $ρ^{\pm}$ with external magnetic field, when incorporated in the calculation, makes the $ρ^{\pm}$ to condense at high magnetic field.
↳ hep-phnucl-thPRD(2017)·40 citations
12
Real-Time dynamics and phase separation in a holographic first order phase transition
Romuald A. Janik🇵🇱 · Jakub Jankowski🇵🇱 · Hesam Soltanpanahi🇮🇷
We study the fully nonlinear time evolution of a holographic system possessing a first order phase transition. The initial state is chosen in the spinodal region of the phase diagram, and includes an inhomogeneous perturbation in one of the field theory directions. The final state of the time evolution shows a clear phase separation in the form of domain formation. The results indicate the existence of a very rich class of inhomogeneous black hole solutions.
↳ hep-thgr-qchep-phnucl-thPRL(2017)·60 citations
13
Universality regained: Kibble-Zurek dynamics, off-equilibrium scaling and the search for the QCD critical point
Swagato Mukherjee🇺🇸 · Raju Venugopalan🇺🇸 · Yi Yin🇺🇸
We generalize and apply the key elements of the Kibble-Zurek framework of nonequilibrium phase transitions to study the non-equilibrium critical cumulants near the QCD critical point. We demonstrate the off-equilibrium critical cumulants are expressible as universal scaling functions. We discuss how to use off-equilibrium scaling to provide powerful model-independent guidance in searches for the QCD critical point.
↳ hep-phnucl-thNPA(2017)·7 citations
14
Cosmic rays, anti-helium, and an old navy spotlight
Kfir Blum🇮🇱 · Kenny Chun Yu Ng🇮🇱 · Ryosuke Sato🇮🇱 · Masahiro Takimoto🇯🇵
Cosmic-ray anti-deuterium and anti-helium have long been suggested as probes of dark matter, as their secondary astrophysical production was thought extremely scarce. But how does one actually predict the secondary flux? Anti-nuclei are dominantly produced in pp collisions, where laboratory cross section data is lacking. We make a new attempt at tackling this problem by appealing to a scaling law of nuclear coalescence with the physical volume of the hadronic emission region. The same volume is probed by Hanbury Brown-Twiss (HBT) two-particle correlations. We demonstrate the consistency of the scaling law with systems ranging from central and off-axis AA collisions to pA collisions, spanning 3 orders of magnitude in coalescence yield. Extending the volume scaling to the pp system, HBT data allows us to make a new estimate of coalescence, that we test against preliminary ALICE pp data. For anti-helium the resulting cross section is 1-2 orders of magnitude higher than earlier estimates. The astrophysical secondary flux of anti-helium could be within reach of a five-year exposure of AMS02.
↳ astro-ph.HEhep-phnucl-thPRD(2017)·116 citations
15
$P$ -wave $π π$ scattering and the $ρ$ resonance from lattice QCD
Constantia Alexandrou🇨🇾 · Luka Leskovec🇺🇸 · Stefan Meinel🇺🇸 · John Negele🇺🇸 · Srijit Paul🇨🇾 · Marcus Petschlies🇩🇪 · Andrew Pochinsky🇺🇸 · Gumaro Rendon🇺🇸 · Sergey Syritsyn🇺🇸
We calculate the parameters describing elastic $I = 1$ , $P$ -wave $π π$ scattering using lattice QCD with $2 + 1$ flavors of clover fermions. Our calculation is performed with a pion mass of $m_{π} \approx 320 MeV$ and a lattice size of $L \approx 3.6$ fm. We construct the two-point correlation matrices with both quark-antiquark and two-hadron interpolating fields using a combination of smeared forward, sequential and stochastic propagators. The spectra in all relevant irreducible representations for total momenta $∣ P ∣ \leq 3 \frac{2 π}{L}$ are extracted with two alternative methods: a variational analysis as well as multi-exponential matrix fits. We perform an analysis using Lüscher's formalism for the energies below the inelastic thresholds, and investigate several phase shift models, including possible nonresonant contributions. We find that our data are well described by the minimal Breit-Wigner form, with no statistically significant nonresonant component. In determining the $ρ$ resonance mass and coupling we compare two different approaches: fitting the individually extracted phase shifts versus fitting the $t$ -matrix model directly to the energy spectrum. We find that both methods give consistent results, and at a pion mass of $a m_{π} = 0.18295 (36)_{s t a t}$ obtain $g_{ρ π π} = 5.69 (13)_{s t a t} (16)_{sy s}$ , $a m_{ρ} = 0.4609 (16)_{s t a t} (14)_{sy s}$ , and $a m_{ρ} / a m_{N} = 0.7476 (38)_{s t a t} (23)_{sy s}$ , where the first uncertainty is statistical and the second is the systematic uncertainty due to the choice of fit ranges.
↳ hep-lathep-phnucl-thPRD(2017)·133 citations

Affiliations

first authorsco-authorsvia INSPIRE