Nuclear Theory·nucl-th

Friday·September 11, 2015

14 papers—6 primary·8 cross-listed

01
Contemporary continuum QCD approaches to excited hadrons
Bruno El-Bennich🇧🇷 · Eduardo Rojas🇨🇴
Amongst the bound states produced by the strong interaction, radially excited meson and nucleon states offer an important phenomenological window into the long-range behavior of the coupling constant in Quantum Chromodynamics. We here report on some technical details related to the computation of the bound state's eigenvalue spectrum in the framework of Bethe-Salpeter and Faddeev equations.
nucl-thhep-lathep-phnucl-exEPJ Web Conf.(2016)·4 citations
02
Three Lectures on Hadron Physics
Craig D. Roberts🇺🇸
These lectures explain that comparisons between experiment and theory can expose the impact of running couplings and masses on hadron observables and thereby aid materially in charting the momentum dependence of the interaction that underlies strong-interaction dynamics. The series begins with a primer on continuum QCD, which introduces some of the basic ideas necessary in order to understand the use of Schwinger functions as a nonperturbative tool in hadron physics. It continues with a discussion of confinement and dynamical symmetry breaking (DCSB) in the Standard Model, and the impact of these phenomena on our understanding of condensates, the parton structure of hadrons, and the pion electromagnetic form factor. The final lecture treats the problem of grand unification; namely, the contemporary use of Schwinger functions as a symmetry-preserving tool for the unified explanation and prediction of the properties of both mesons and baryons. It reveals that DCSB drives the formation of diquark clusters in baryons and sketches a picture of baryons as bound-states with Borromean character. Planned experiments are capable of validating the perspectives outlined in these lectures.
nucl-thhep-lathep-phnucl-exJ.Phys.Conf.Ser.(2016)·71 citations
03
Constraining slope parameter of symmetry energy from nuclear structure
T. Inakura · H. Nakada
Four quantities deducible from nuclear structure experiments have been claimed to correlate to the slope parameter $L$ of the symmetry energy; the neutron skin thickness, the cross section of low-energy dipole (LED) mode, dipole polarizability $α_{D}$ , and $α_{D} S_{0}$ (i.e. product of $α_{D}$ and the symmetry energy $S_{0}$ ). By the calculations in the Hartree-Fock plus random-phase approximation with various effective interactions, we compare the correlations between $L$ and these four quantities. The correlation derived from different interactions and the correlation from a class of interactions that are identical in the symmetric matter as well as in $S_{0}$ are simultaneously examined. These two types of correlations may behave differently, as exemplified in the correlation of $α_{D}$ to $L$ . It is found that the neutron skin thickness and $α_{D} S_{0}$ correlate well to $L$ , and therefore are suitable for narrowing down the value of $L$ via experiments. The LED emergence and upgrowth makes the $α_{D} S_{0}$ - $L$ correlation strong, although these correlations are disarranged when neutron halo appears in the ground state.
nucl-thPRC(2015)·21 citations
04
Variation after full projection with triaxially deformed nuclear mean field
Zao-Chun Gao🇨🇳 · Mihai Horoi🇺🇸 · Y.S. Chen🇨🇳
We implemented a variation after projection (VAP) algorithm based on a triaxially deformed Hartree-Fock-Bogoliubov vacuum state. This is the first projected mean field study that includes all the quantum numbers (except parity), i.e., spin ( $J$ ), isospin ( $T$ ) and mass number ( $A$ ). Systematic VAP calculations with $J T A$ -projection have been performed for the even-even $s d$ -shell nuclei with the USDB Hamiltonian. All the VAP ground state energies are within 500 keV above the exact shell model values. Our VAP calculations show that the spin projection has two important effects: (1) the spin projection is crucial in achieving good approximation of the full shell model calculation. (2) the intrinsic shapes of the VAP wavefunctions with spin projection are always triaxial, while the Hartree-Fock-Bogoliubov methods likely provide axial intrinsic shapes. Finally, our analysis suggests that one may not be possible to associate an intrinsic shape to an exact shell model wave function.
nucl-thPRC(2015)·37 citations
05
Photoproduction of $J / ψ$ mesons in peripheral and semi-central heavy ion collisions
Mariola Kłusek-Gawenda🇵🇱 · Antoni Szczurek🇵🇱
We calculate total and differential cross sections for $J / ψ$ photoproduction in ultrarelativistic lead-lead collisions at the LHC energy $s_{N N} = 2.76$ TeV. In the present approach we use a simple model based on vector dominance picture and multiple scattering of the hadronic ( $c c ˉ$ ) state in a cold nucleus as an example. In our analysis we use both the classical mechanics and quantum (Glauber) formulae for calculating $σ_{t o t} (J / ψ P b)$ which is a building block of our model. We compare our UPC results with ALICE and CMS data. For semi-central collisions ( $b < R_{A} + R_{B}$ ) a modification of the photon flux seems necessary. We discuss different physics motivated approximations. We try to estimate the cross sections for different centrality bins and for $J / ψ$ mesons emitted in forward rapidity range ( $2.5 < y < 4$ ) corresponding to recent ALICE experimental results. Reasonable results are obtained but open questions are discussed.
nucl-thhep-exhep-phPRC(2016)·62 citations
06
In-medium nucleon-nucleon elastic cross sections determined from nucleon-induced reaction cross sections data
Li Ou · Xueying He
Within the framework of the improved quantum molecular dynamics model, the medium modifications on the free nucleon-nucleon elastic cross sections are investigated. By using various in-medium nucleon-nucleon elastic cross sections in the model, the nucleon-induced reactions on various targets are simulated, and the excitation functions of reaction cross sections in the energy range from 25 MeV to 1 GeV are calculated. By comparing the calculations with the experimental data, an isospin, density, and momentum-dependence medium correction factor on free nucleon-nucleon elastic cross sections is determined.
nucl-thCPC(2019)·7 citations
07
Quasiparticle equation of state for anisotropic hydrodynamics
Mubarak Alqahtani🇺🇸 · Mohammad Nopoush🇺🇸 · Michael Strickland🇺🇸
We present a new method for imposing a realistic equation of state in anisotropic hydrodynamics. The method relies on the introduction of a single finite-temperature quasiparticle mass which is fit to lattice data. By taking moments of the Boltzmann equation, we obtain a set of coupled partial differential equations which can be used to describe the 3+1d spacetime evolution of an anisotropic relativistic system. We then specialize to the case of a 0+1d system undergoing boost-invariant Bjorken expansion and subject to the relaxation-time approximation collisional kernel. Using this setup, we compare results obtained using the new quasiparticle equation of state method with those obtained using the standard method for imposing the equation of state in anisotropic hydrodynamics. We demonstrate that the temperature evolution obtained using the two methods is nearly identical and that there are only small differences in the pressure anisotropy. However, we find that there are significant differences in the evolution of the bulk pressure correction.
↳ hep-phnucl-thPRC(2015)·75 citations
08
Data Selection Criteria for Spectroscopic Measurements of Neutron Star Radii with X-ray Bursts
Feryal Ozel · Dimitrios Psaltis · Tolga Guver
Data selection and the determination of systematic uncertainties in the spectroscopic measurements of neutron star radii from thermonuclear X-ray bursts have been the subject of numerous recent studies. In one approach, the uncertainties and outliers were determined by a data-driven Bayesian mixture model, whereas in a second approach, data selection was performed by requiring that the observations follow theoretical expectations. We show here that, due to inherent limitations in the data, the theoretically expected trends are not discernible in the majority of X-ray bursts even if they are present. Therefore, the proposed theoretical selection criteria are not practical with the current data for distinguishing clean data sets from outliers. Furthermore, when the data limitations are not taken into account, the theoretically motivated approach selects a small subset of bursts with properties that are in fact inconsistent with the underlying assumptions of the method. We conclude that the data-driven selection methods do not suffer from the limitations of this theoretically motivated one.
↳ astro-ph.HEgr-qcnucl-th4 citations
09
Jet Quenching from QCD Evolution
Yang-Ting Chien🇺🇸 · Alexander Emerman🇺🇸 · Zhong-Bo Kang🇺🇸 · Grigory Ovanesyan🇺🇸 · Ivan Vitev🇺🇸
Recent advances in soft-collinear effective theory with Glauber gluons have led to the development of a new method that gives a unified description of inclusive hadron production in reactions with nucleons and heavy nuclei. We show how this approach, based on the generalization of the DGLAP evolution equations to include final-state medium-induced parton showers, can be combined with initial-state effects for applications to jet quenching phenomenology. We demonstrate that the traditional parton energy loss calculations can be regarded as a special soft-gluon emission limit of the general QCD evolution framework. We present phenomenological comparison of the SCET $_{G}$ -based results on the suppression of inclusive charged hadron and neutral pion production in $s_{N N} = 2.76$ TeV lead-lead collisions at the Large Hadron Collider to experimental data. We also show theoretical predictions for the upcoming $s_{N N} ≃ 5.1$ TeV Pb+Pb run at the LHC.
↳ hep-phnucl-exnucl-thPRD(2016)·142 citations
10
Multi-particle long-range rapidity correlations from fluctuation of the fireball longitudinal shape
Adam Bzdak🇵🇱 · Piotr Bozek🇵🇱
We calculate the genuine long-range multi-particle rapidity correlation functions, $C_{n} (y_{1}, ..., y_{n})$ for $n = 3, 4, 5, 6$ , originating from fluctuations of the fireball longitudinal shape. In these correlation functions any contribution from the short-range two-particle correlations, and in general up to $(n - 1)$ -particle in $C_{n}$ , is suppressed. The information about the fluctuating fireball shape in rapidity is encoded in the cumulants of coefficients of the orthogonal polynomial expansion of particle distributions in rapidity.
↳ hep-phhep-exnucl-thPRC(2016)·20 citations
11
Finite coupling corrections to holographic predictions for hot QCD
Sebastian Waeber🇩🇪 · Andreas Schaefer🇩🇪 · Aleksi Vuorinen🇫🇮 · Laurence G. Yaffe🇺🇸
Finite 't Hooft coupling corrections to multiple physical observables in strongly coupled $N = 4$ supersymmetric Yang-Mills plasma are examined, in an attempt to assess the stability of the expansion in inverse powers of the 't Hooft coupling $λ$ . Observables considered include thermodynamic quantities, transport coefficients, and quasinormal mode frequencies. Although large $λ$ expansions for quasinormal mode frequencies are notably less well behaved than the expansions of other quantities, we find that a partial resummation of higher order corrections can significantly reduce the sensitivity of the results to the value of $λ$ .
↳ hep-thnucl-thJHEP(2015)·55 citations
12
Strong Couplings of Charmed Mesons and Quarkonia
Wolfgang Lucha🇦🇹 · Dmitri Melikhov🇷🇺 · Hagop Sazdjian🇫🇷 · Silvano Simula🇮🇹
We extract the strong coupling constants of three mesons, each of which is composed of either two charm quarks or one charm quark and one light (i.e., $u$ , $d$ , or $s$ ) quark, from the matrix elements for the transitions of two of these mesons induced by appropriate quark currents within the framework of a relativistic dispersion approach to the constituent-quark picture of mesons. Among others, we also analyse the impact of the violation of the SU(3) flavour symmetry by the quark masses. In the case of mesons containing one light quark, we observe, in two respects, discrepancies between our findings and the predictions of QCD sum rules: our strong couplings exceed considerably the ones emerging from QCD sum rules, and, in our approach, the replacement of a light quark by a strange quark entails, in contrast to QCD sum rules, a reduction of the magnitudes of the strong couplings.
↳ hep-phnucl-thPoS(2015)·1 citation
13
Photon and dilepton spectra from nonlinear QED effects in supercritical magnetic fields induced by heavy-ion collisions
Koichi Hattori🇯🇵 · Kazunori Itakura🇯🇵
We discuss properties of photons in extremely strong magnetic fields induced by the relativistic heavy-ion collisions. We investigate the vacuum birefringence, the real-photon decay, and the photon splitting which are all forbidden in the ordinary vacuum, but become possible in strong magnetic fields. These effects potentially give rise to anisotropies in photon and dilepton spectra.
↳ hep-phastro-ph.HEnucl-thNucl.Part.Phys.Proc.(2016)·3 citations
14
Hanbury-Brown-Twiss measurements at large rapidity separations, or can we measure the proton radius in p-A collisions?
T. Altinoluk🇪🇸 · N. Armesto🇪🇸 · G. Beuf🇮🇱 · A. Kovner🇺🇸 · M. Lublinsky🇮🇱
We point out that current calculations of inclusive two-particle correlations in p-A collisions based on the Color Glass Condensate approach exhibit a contribution from Hanbury-Brown-Twiss correlations. These HBT correlations are quite distinct from the standard ones, in that they are apparent for particles widely separated in rapidity. The transverse size of the emitter which is reflected in these correlations is the gluonic size of the proton. This raises an interesting possibility of measuring the proton size directly by the HBT effect of particle pairs produced in p-A collisions.
↳ hep-phnucl-thPLB(2016)·35 citations

Affiliations

first authorsco-authorsvia INSPIRE