Nuclear Theory·nucl-th

Tuesday·February 28, 2017

12 papers—6 primary·6 cross-listed

01
Three-particle correlations in relativistic heavy ion collisions in a multiphase transport model
Yifeng Sun🇺🇸 · Che Ming Ko🇺🇸
Using a multiphase transport model, we study three-particle mixed harmonic correlations in relativistic heavy ion collisions by considering the observable $C_{m, n, m + n} = ⟨ ⟨ cos (m ϕ_{1} + n ϕ_{2} - (m + n) ϕ_{3})⟩ ⟩$ , where $ϕ_{1, 2, 3}$ are azimuthal angles of all particle triplets. We find that except for $C_{123}$ , our results on the centrality dependence of $C_{112}$ , $C_{224}$ and $C_{235}$ as well as the relative pseudorapidity dependence of $C_{123}$ and $C_{224}$ in Au+Au collisions at $s =$ 200 GeV agree reasonable well with the experimental data from the STAR Collaboration. We discuss the implications of our results.
nucl-thPLB(2017)·4 citations
02
Fully coupled-channel complex scaling method for the $K^{-} pp$ system
Akinobu Doté🇯🇵 · Takashi Inoue🇯🇵 · Takayuki Myo🇯🇵
We have developed a fully coupled-channel complex scaling method (ccCSM) for the study of the most essential kaonic nucleus, $‘‘ K^{-} pp, "$ which is a resonant state of a $K ˉ N N$ - $π Σ N$ - $π Λ N$ coupled-channel system based on a theoretical viewpoint. By employing the ccCSM and imposing the correct boundary condition of resonance, the coupled-channel problem is completely solved using a phenomenological energy-independent potential. As a result of the ccCSM calculation of $‘‘ K^{-} pp, "$ in which all three channels are treated explicitly, we have obtained three-body resonance as a Gamow state. The resonance pole indicates that the binding energy of $‘‘ K^{-} pp "$ and the half value of its mesonic decay width are 51 MeV and 16 MeV, respectively. In the analysis of the resonant wave function obtained using the ccCSM, we clarify the spatial configuration and channel compositions of $‘‘ K^{-} pp ."$ Compared with past studies of single-channel calculations based on effective $K ˉ N$ potentials, the current study provides a guideline for the determination of the $K ˉ N$ energy to be used in effective potentials.
nucl-thnucl-exPRC(2017)·28 citations
03
Phenomenological extraction of two-photon exchange amplitudes from elastic electron-proton scattering cross section data
I. A. Qattan🇦🇪
In this work, I improve on and extend to low and high $Q^{2}$ values the extractions of the $ε$ dependence of the real parts of the two-photon exchange (TPE) amplitudes relative to the magnetic form factor, as well as the ratio $P_{l} / P_{l}^{B or n} (ε, Q^{2})$ by using world data on $σ_{R} (ε, Q^{2})$ with an emphasis on precise new data covering the low-momentum region which is sensitive to the large-scale structure of the nucleon. I provide simple parametrizations of the TPE amplitudes, along with an estimate of the fit uncertainties. The extracted TPE amplitudes are compared with previous phenomenological extractions and TPE calculations. The $P_{l} / P_{l}^{B or n}$ ratio is extracted by using the new parametrizations of the TPE amplitudes and compared to previous extractions, TPE calculations, and direct measurements at $Q^{2}$ = 2.50 (GeV/c) $^{2}$ . The extracted TPE amplitudes are on the few-percentage-points level and behave roughly linearly with increasing $Q^{2}$ where they become nonlinear at high $Q^{2}$ . Contrary to $Y_{M}$ , which is influenced mainly by elastic contributions, I find $Y_{E}$ to be influenced by inelastic contributions at large $Q^{2}$ values. While $Y_{E}$ and $Y_{3}$ differ in magnitude, they have opposite sign and tend to partially cancel each other. This suggests that the TPE correction to $σ_{R} (ε, Q^{2})$ is driven mainly by $Y_{M}$ and to a lesser extent by $Y_{3}$ in agreement with previous phenomenological extractions and hadronic TPE calculations.
nucl-thPRC(2017)·20 citations
04
Amplitude reconstruction from complete electroproduction experiments and truncated partial-wave expansions
L. Tiator · R. L. Workman · Y. Wunderlich · H. Haberzettl
We compare the methods of amplitude reconstruction, for a complete experiment and a truncated partial-wave analysis, applied to the electroproduction of pseudoscalar mesons. We give examples which show, in detail, how the amplitude reconstruction (observables measured at a single energy and angle) is related to a truncated partial-wave analysis (observables measured at a single energy and a number of angles). A connection is made to existing data.
nucl-thnucl-exPRC(2017)·22 citations
05
Effect of nuclear matter incompressibility on the 16O+208Pb system
O.N.Ghodsi · F.Torabi
To analyze the property of nuclear matter in the 16O+208Pb collision system, the internuclear potential of the fusion reaction is calculated by using the Skyrme forces associated with an extensive nuclear matter incompressibility K range in the semiclassical energy density formalism. Comparison of the experimental fusion cross sections and those obtained by using potentials derived from different forces with various K values shows that the incompressibility of nuclear matter changes during the fusion process at different bombarding energies. The results indicate that, as the energy increases, the nuclear matter becomes more incompressible.
nucl-thPRC(2016)·6 citations
06
The effect of deformation and vibration on the alpha decay half-life
O. N. Ghodsi · E. Gholami
In this work, we expand upon our previous study, the effect of surface vibrations (low-lying vibrational states) on the calculation of penetration probability in alpha decay of spherical isotopes [Phys.Rev.C91,034611(2015)]. To this aim, the Coulomb and proximity potential model, taking in to account the ground state deformations of the involved nuclei along with the surface vibrations in the daughter nucleus, is used to evaluate the alpha decay probability. The results are compared with those obtained by spherical potential barrier, which shows the dramatic effect of employing the ground state deformations in case of deformed nuclei. As well, including of surface vibrations give rise to an increase in the value of tunneling probability in better agreement with experimental data.
nucl-thPRC(2016)·4 citations
07
Quasinormal modes of charged magnetic black branes & chiral magnetic transport
Martin Ammon🇩🇪 · Matthias Kaminski🇺🇸 · Roshan Koirala🇺🇸 · Julian Leiber🇩🇪 · Jackson Wu🇺🇸
We compute quasinormal modes (QNMs) of the metric and gauge field perturbations about black branes electrically and magnetically charged in the Einstein-Maxwell-Chern-Simons theory. By the gauge/gravity correspondence, this theory is dual to a particular class of field theories with a chiral anomaly, in a thermal charged plasma state subjected to a constant external magnetic field, $B$ . The QNMs are dual to the poles of the two-point functions of the energy-momentum and axial current operators, and they encode information about the dissipation and transport of charges in the plasma. Complementary to the gravity calculation, we work out the hydrodynamic description of the dual field theory in the presence of a chiral anomaly, and a constant external $B$ . We find good agreement with the weak field hydrodynamics, which can extend beyond the weak $B$ regime into intermediate regimes. Furthermore, we provide results that can be tested against thermodynamics and hydrodynamics in the strong $B$ regime. We find QNMs exhibiting Landau level behavior, which become long-lived at large $B$ if the anomaly coefficient exceeds a critical magnitude. Chiral transport is analyzed beyond the hydrodynamic approximation for the five (formerly) hydrodynamic modes, including a chiral magnetic wave.
↳ hep-thhep-phnucl-thJHEP(2017)·54 citations
08
What are the low- $Q$ and large- $x$ boundaries of collinear QCD factorization theorems?
E. Moffat🇺🇸 · W. Melnitchouk🇺🇸 · T. C. Rogers🇺🇸 · N. Sato🇺🇸
Familiar factorized descriptions of classic QCD processes such as deeply-inelastic scattering (DIS) apply in the limit of very large hard scales, much larger than nonperturbative mass scales and other nonperturbative physical properties like intrinsic transverse momentum. Since many interesting DIS studies occur at kinematic regions where the hard scale, $Q \sim$ 1-2 GeV, is not very much greater than the hadron masses involved, and the Bjorken scaling variable $x_{bj}$ is large, $x_{bj} ≳ 0.5$ , it is important to examine the boundaries of the most basic factorization assumptions and assess whether improved starting points are needed. Using an idealized field-theoretic model that contains most of the essential elements that a factorization derivation must confront, we retrace the steps of factorization approximations and compare with calculations that keep all kinematics exact. We examine the relative importance of such quantities as the target mass, light quark masses, and intrinsic parton transverse momentum, and argue that a careful accounting of parton virtuality is essential for treating power corrections to collinear factorization. We use our observations to motivate searches for new or enhanced factorization theorems specifically designed to deal with moderately low- $Q$ and large- $x_{bj}$ physics.
↳ hep-phhep-exnucl-thPRD(2017)·21 citations
09
Event-by-event mean $p_{T}$ fluctuations and transverse size of color flux tube generated in $p$ - $p$ collisions at $s$ =0.90TeV
Takeshi Osada🇯🇵 · Masamichi Ishihara🇯🇵
We propose a novel phenomenological model of mean transverse momentum fluctuations based on the Geometrical Scaling hypothesis. Bose-Einstein correlations between two gluons generated from an identical color flux tube are taken into account as a source of the fluctuation. We calculate an event-by-event fluctuation measure $C_{m} / ⟨ p_{T} ⟩$ and show that ALICE data observed at $s =$ 0.90 TeV for $p$ + $p$ collisions are reproduced. By fitting our model to the experimental data, we evaluate the transverse size of the color flux tube as a function of the multiplicity.
↳ hep-phnucl-thJ.Phys.G(2018)·13 citations
10
Effective Model of QCD Magnetic Monopoles From Numerical Study of One- and Two-Component Coulomb Quantum Bose Gases
Adith Ramamurti🇺🇸 · Edward Shuryak🇺🇸
Magnetic monopoles are suggested to play an important role in strongly coupled quark-gluon plasma (sQGP) near the deconfinement temperature. So far, their many-body treatment has only been done classically, with just binary scattering solved in quantum mechanics. In this paper we start quantum many-body studies of the monopole ensembles. Specifically, we carry out numerical simulations of the path integral for one- and two-component Coulomb Bose systems. We determine the relation between the critical temperature for the Bose-Einstein condensation phase transition $T_{c}$ and the Coulomb coupling strength using two methods, the classic finite-size scaling of the condensate and a lattice-tested method based on permutation cycles. For a one-component Coulomb Bose gas, we observe the same behavior of the critical temperature -- initially rising slightly then falling as interaction strength is increased -- as seen in the case of hard spheres; we also observe the same behavior for a two-component Coulomb Bose gas. We then calculate sets of radial correlation functions between the like and unlike charged particles. By matching those with the correlation functions previously calculated on the lattice, we derive an effective quantum model of color magnetic monopoles in QCD. From this matched model, we are able to extract the monopole contribution to QCD equation of state near $T_{c}$ .
↳ hep-phhep-latnucl-thPRD(2017)·10 citations
11
Fluctuations In The Inhomogeneous Chiral Transition
T. Tatsumi🇯🇵 · R. Yoshiike🇯🇵 · T.-G. Lee🇯🇵
Chiral pair fluctuation are considered near the phase boundary of the inhomogeneous chiral phase (iCP). The fluctuations are then bosonized and an effective action for the chiral pair fluctuation is basically constructed by considering the ring diagram of the polarization function. We can evaluate the self-energy and effective four point interaction among fluctuations in a consistent way. The peculiar dispersion of the fluctuation, reflecting the spatially inhomogeneous transition, gives rise to interesting and qualitative results. Thermal fluctuations prohibit the second-order transition, while the effect of the quantum fluctuations is rather modest. Quantum and thermal fluctuations changes the second-order transition to the first one by changing the sign of the effective four-point interaction between effective mesons. These features may be observed by relativistic heavy-ion collisions through the analysis of the thermodynamic observables. Distinct from the second-order phase transition, the first moment such as entropy production exhibits an anomalous behavior due to fluctuations, which is one of the signals of the phase transition to iCP. Some similar aspects are also remarked between iCP and the FFLO state in superconductivity.
↳ hep-phnucl-thPoS(2017)·0 citations
12
Hybrid Quark Stars With Strong Magnetic Field
T. Tatsumi🇯🇵 · H. Sotani🇯🇵
Discovery of huge magnetic field in magnetars has stimulated a renewed interest about the magnetic field and physics of compact stars, where microphysics such as QED or QCD may play active parts. Here we discuss the equation of state (EOS) of quark matter in the core of compact stars by taking into account the strong magnetic field. We show that quark EOS becomes very stiff in the presence of the strong magnetic field, and becomes stiffest under the causality condition beyond the threshold strength of $B_{c} \sim O (1 0^{19})$ G. This is because quarks make the Landau levels in the presence of the magnetic field and thereby only the lowest Landau level is occupied in the extreme case beyond $B_{c}$ . Thus quarks can freely move along the magnetic field with localization in the perpendicular plane, which resembles the quasi-one dimensional systems and gives rise to a stiff EOS. Consequently, we may easily produce high-mass stars beyond two solar mass. As another interesting possibility, we discuss the appearance of the third family of compact stars, succeeding white dwarfs and neutron stars, before collapsing into black holes. We demonstrate an example, which is specified by a discontinuous increase of the adiabatic index at the hadron-quark phase transition. Such new family may affect the supernova explosions or the gravitational wave emitted from the neutron star mergers.
↳ astro-ph.HEhep-phnucl-thPoS(2017)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE