Nuclear Theory·nucl-th

Friday·October 21, 2016

13 papers—10 primary·3 cross-listed

01
Direct Photon Elliptic Flow at BNL Relativistic Heavy Ion Collider (RHIC) and CERN Large Hadron Collider (LHC)
Young-Min Kim🇰🇷 · Chang-Hwan Lee🇰🇷 · Derek Teaney🇺🇸 · Ismail Zahed🇺🇸
We use an event-by-event hydrodynamical description of the heavy-ion collision process with Glauber initial conditions to calculate the thermal emission of photons. The photon rates in the hadronic phase follow from a spectral function approach and a density expansion, while in the partonic phase they follow from the AMY perturbative rates. The calculated photon elliptic flows are lower than those reported recently by both the ALICE and PHENIX collaborations.
nucl-thhep-phnucl-exPRC(2017)·24 citations
02
Understanding experimentally-observed fluctuations
Masakiyo Kitazawa🇯🇵 · Masayuki Asakawa
We discuss two topics on the experimental measurements of fluctuation observables in relativistic heavy-ion collisions. First, we discuss the effects of the thermal blurring, i.e. the blurring effect arising from the experimental measurement of fluctuations in momentum space as a proxy of the thermal fluctuations defined in coordinate space, on higher order cumulants. Second, we discuss the effect of imperfect efficiency of detectors on the measurement of higher order cumulants. We derive effective formulas which can carry out the correction of this effect for higher order cumulants based on the binomial model.
nucl-thActa Phys.Polon.Supp.(2017)·0 citations
03
Three Baryon Interaction Generated by Determinant Interaction of Quarks
Akira Ohnishi🇯🇵 · Kouji Kashiwa🇯🇵 · Kenji Morita🇯🇵
We discuss the three-baryon interaction generated by the determinant interaction of quarks, known as the Kobayashi-Maskawa-'t Hooft (KMT) interaction. The expectation value of the KMT interaction operator is calculated in fully-antisymmetrized quark-cluster model wave functions for one-, two- and three-octet baryon states. The three-baryon potential from the KMT interaction is found to be repulsive for $N N Λ$ and $N ΛΛ$ systems, while it is zero for the $N N N$ system. The strength and range of the three-baryon potential are found to be comparable to those for the $N N N$ three-body potential obtained in lattice QCD simulations. The contribution to the $Λ$ single particle potential in nuclear matter is found to be 0.28 MeV and 0.73 MeV in neutron matter and symmetric nuclear matter at normal nuclear density, respectively. These repulsive forces are not enough to solve the hyperon puzzle, but may be measured in high-precision hyperisotope experiments.
nucl-thPTEP(2017)·3 citations
04
Directed flow in asymmetric nucleus-nucleus collisions and the inverse Landau-Pomeranchuk-Migdal effect
V.D. Toneev🇷🇺 · V. Voronyuk🇷🇺 · E.E. Kolomeitsev🇸🇰 · W. Cassing🇩🇪
It is proposed to identify a strong electric field - created during relativistic collisions of asymmetric nuclei - via the observation of pseudorapidity and transverse momentum distributions of hadrons with the same mass but opposite charge. The results of detailed calculations within the Parton-Hadron String Dynamics (PHSD) approach for the charge-dependent directed flow $v_{1}$ are presented for semi-central Cu+Au collision at $s_{N N} = 200$ GeV incorporating the inverse Landau-Pomeranchuk-Migdal (iLPM) effect, which accounts for a delay in the electromagnetic interaction with the charged degree of freedom. Including the iLPM effect we achieve a reasonable agreement of the PHSD results for the charge splitting in $v_{1} (p_{T})$ in line with the recent measurements of the STAR Collaboration for Cu+Au collisions at $s_{N N} = 200$ GeV while an instant appearance and coupling of electric charges at the hard collision vertex overestimates the splitting by about a factor of 10. We predict that the iLPM effect should practically disappear at energies of $s_{N N} \approx$ 9 GeV, which should lead to a significantly larger charge splitting of $v_{1}$ at the future FAIR/NICA facilities.
nucl-thhep-phPRC(2017)·12 citations
05
Strong correlations of neutron star radii with the slopes of nuclear matter incompressibility and symmetry energy at saturation
N. Alam · B. K. Agrawal · M. Fortin · H. Pais · C. Providência · Ad. R. Raduta · A. Sulaksono
We examine the correlations of neutron star radii with the nuclear matter incompressibility, symmetry energy, and their slopes, which are the key parameters of the equation of state (EoS) of asymmetric nuclear matter. The neutron star radii and the EoS parameters are evaluated using a representative set of 24 Skyrme-type effective forces and 18 relativistic mean field models, and two microscopic calculations, all describing 2 $M_{⊙}$ neutron stars. Unified EoSs for the inner-crust-core region have been built for all the phenomenological models, both relativistic and non-relativistic. Our investigation shows the existence of a strong correlation of the neutron star radii with the linear combination of the slopes of the nuclear matter incompressibility and the symmetry energy coefficients at the saturation density. Such correlations are found to be almost independent of the neutron star mass in the range $0.6 - 1.8 M_{⊙}$ . This correlation can be linked to the empirical relation existing between the star radius and the pressure at a nucleonic density between one and two times saturation density, and the dependence of the pressure on the nuclear matter incompressibility, its slope and the symmetry energy slope. The slopes of the nuclear matter incompressibility and the symmetry energy coefficients as estimated from the finite nuclei data yield the radius of a $1.4 M_{⊙}$ neutron star in the range $11.09 - 12.86$ km.
nucl-thastro-ph.HEastro-ph.SRPRC(2016)·96 citations
06
Influence of the vector interaction and an external magnetic field on the isentropes near the chiral critical end point
Pedro Costa🇵🇹
The location of the critical end point (CEP) and the isentropic trajectories in the QCD phase diagram are investigated. We use the (2+1) Nambu $-$ Jona-Lasinio model with the Polyakov loop coupling for different scenarios, namely by imposing zero strange quark density, which is the case in the ultra relativistic heavy-ion collisions, and $β$ -equilibrium. The influence of strong magnetic fields and of the vector interaction on the isentropic trajectories around the CEP is discussed. It is shown that the vector interaction and the magnetic field, having opposite effects on the first-order transition, affect the isentropic trajectories differently: as the vector interaction increases, the first-order transition becomes weaker and the isentropes become smoother; when a strong magnetic field is considered, the first-order transition is strengthened and the isentropes are pushed to higher temperatures. No focusing of isentropes in region towards the CEP is seen.
nucl-thhep-phPRD(2016)·14 citations
07
Two-solar-mass hybrid stars: a two model description with the Nambu-Jona-Lasinio quark model
Renan Câmara Pereira🇵🇹 · Pedro Costa🇵🇹 · Constança Providência🇵🇹
Hybrid stars with a quark phase described by the Nambu $-$ Jona-Lasinio model are studied. The hadron-quark model used to determine the stellar matter equation of state favors the appearance of quark matter: the coincidence of the deconfinement and chiral transitions and a low vacuum constituent quark mass. These two properties are essential to build equations of state that predict pure quark matter in the center of neutron stars. The effect of vector-isoscalar and vector-isovector terms is discussed, and it is shown that the vector-isoscalar terms are necessary to describe 2 $M_{⊙}$ hybrid stars, and the vector-isovector terms result in larger quark cores and a smaller deconfinement density.
nucl-thhep-phPRD(2016)·56 citations
08
A quarksonic matter at high isospin density
Gaoqing Cao🇨🇳 · Lianyi He🇨🇳 · Xu-Guang Huang🇨🇳
Analogous to the quarkyonic matter at high baryon density in which the quark Fermi seas and the baryonic excitations coexist, it is argued that a "quarksonic matter" phase appears at high isospin density where the quark (antiquark) Fermi seas and the mesonic excitations coexist. We explore this phase in detail in both large $N_{c}$ and asymptotically free limits: In large $N_{c}$ limit, we sketch a phase diagram for the quarksonic matter. In the asymptotically free limit, we study the pion superfluidity and thermodynamics of the quarksonic matter by using both perturbative calculations and effective model.
nucl-thhep-phCPC(2017)·13 citations
09
Theoretical approaches to low energy $K ˉ N$ interactions
Ales Cieply🇨🇿 · Maxim Mai🇺🇸
We provide a direct comparison of modern theoretical approaches based on the SU(3) chiral dynamics and describing the low energy $K ˉ N$ data. The model predictions for the $K ˉ N$ amplitudes and pole content of the models are discussed.
nucl-thhep-phEPJ Web Conf.(2016)·1 citation
10
Status and Future of Nuclear Matrix Elements for Neutrinoless Double-Beta Decay: A Review
Jonathan Engel🇺🇸 · Javier Menéndez🇯🇵
The nuclear matrix elements that govern the rate of neutrinoless double beta decay must be accurately calculated if experiments are to reach their full potential. Theorists have been working on the problem for a long time but have recently stepped up their efforts as ton-scale experiments have begun to look feasible. Here we review past and recent work on the matrix elements in a wide variety of nuclear models and discuss work that will be done in the near future. Ab initio nuclear-structure theory, which is developing rapidly, holds out hope of more accurate matrix elements with quantifiable error bars.
nucl-thhep-exhep-phnucl-exRept.Prog.Phys.(2017)·645 citations
11
Helicity Evolution at Small $x$ : Flavor Singlet and Non-Singlet Observables
Yuri V. Kovchegov🇺🇸 · Daniel Pitonyak🇺🇸 · Matthew D. Sievert🇺🇸
We extend our earlier results for the quark helicity evolution at small $x$ to derive the small- $x$ asymptotics of the flavor singlet and flavor non-singlet quark helicity TMDs and PDFs and of the $g_{1}$ structure function. In the flavor singlet case we re-derive the evolution equations obtained in our previous paper on the subject, performing additional cross-checks of our results. In the flavor non-singlet case we construct new small- $x$ evolution equations by employing the large- $N_{c}$ limit. All evolution equations resum double-logarithmic powers of $α_{s} ln^{2} (1/ x)$ in the polarization-dependent evolution along with the single-logarithmic powers of $α_{s} ln (1/ x)$ in the unpolarized evolution which includes saturation effects. We solve the linearized flavor non-singlet equation analytically, obtaining an intercept which agrees with the one calculated earlier by Bartels, Ermolaev and Ryskin using the infra-red evolution equations. Our numerical solution of the linearized large- $N_{c}$ evolution equations for the flavor singlet case is presented in the accompanying Letter and is further discussed here.
↳ hep-phnucl-thPRD(2017)·107 citations
12
Landau-Khalatnikov-Fradkin transformation for the fermion propagator in QED in arbitrary dimensions
Shaoyang Jia🇺🇸 · M.R. Pennington🇺🇸
We explore the dependence of fermion propagators on the covariant gauge fixing parameter in quantum electrodynamics (QED) with the number of spacetime dimensions kept explicit. Gauge covariance is controlled by the the Landau-Khalatnikov-Fradkin transformation (LKFT). Utilizing its group nature, the LKFT for a fermion propagator in Minkowski space is solved exactly. The special scenario of 3D is used to test claims made for general cases. When renormalized correctly, a simplification of the LKFT in 4D has been achieved with the help of fractional calculus.
↳ hep-thnucl-thPRD(2017)·19 citations
13
Heavy Exotic Molecules
Yizhuang Liu🇺🇸 · Ismail Zahed🇺🇸
We briefly review the formation of pion-mediated heavy-light exotic molecules with both charm and bottom, under the general strictures of chiral and heavy quark symmetries. The charm isosinglet exotic molecules with $J^{P C} = 1^{++}$ binds, which we identify as the reported neutral $X (3872)$ . The bottom isotriplet exotic with $J^{P C} = 1^{+-}$ binds, and is identified as a mixed state of the reported charged exotics $Z_{b}^{+} (10610)$ and $Z_{b}^{+} (10650)$ . The bound bottom isosinglet molecule with $J^{P C} = 1^{++}$ is a possible neutral $X_{b} (10532)$ to be observed.
↳ hep-phhep-exnucl-thIJMPE(2017)·6 citations

Affiliations

first authorsco-authorsvia INSPIRE