Nuclear Theory·nucl-th

Tuesday·January 27, 2015

16 papers—11 primary·5 cross-listed

01
Single photon production induced by (anti)neutrino neutral current scattering on nucleons and nuclear targets
L. Alvarez-Ruso🇪🇸 · J. Nieves🇪🇸 · E. Wang🇪🇸
We review our theoretical approach to neutral current photon emission on nucleons and nuclei in the few-GeV energy region, relevant for neutrino oscillation experiments. These reactions are dominated by the weak excitation of the $Δ (1232)$ resonance but there are also important non-resonant contributions. We have also included terms mediated by nucleon excitations from the second resonance region. On nuclei, Pauli blocking, Fermi motion and the in-medium $Δ$ resonance broadening have been taken into account for both incoherent and coherent reaction channels. With this model, the number and distributions of photon events at the MiniBooNE and T2K experiments have been obtained. We have also compared to the NOMAD upper limit at higher energies. The implications of our findings and future perspectives are discussed.
nucl-thhep-exhep-phAIP Conf.Proc.(2015)·2 citations
02
A New Phase of Matter: Quark-Gluon Plasma Beyond the Hagedorn Critical Temperature
Berndt Müller🇺🇸
I retrace the developments from Hagedorn's concept of a limiting temperature for hadronic matter to the discovery and characterization of the quark-gluon plasma as a new state of matter. My recollections begin with the transformation more than 30 years ago of Hagedorn's original concept into its modern interpretation as the "critical" temperature separating the hadron gas and quark-gluon plasma phases of strongly interacting matter. This was followed by the realization that the QCD phase transformation could be studied experimentally in high-energy nuclear collisions. I describe here my personal effort to help develop the strangeness experimental signatures of quark and gluon deconfinement and recall how the experimental program proceeded soon to investigate this idea, at first at the SPS, then at RHIC, and finally at LHC. As it is often the case, the experiment finds more than theory predicts, and I highlight the discovery of the "perfectly" liquid quark-gluon plasma at RHIC. I conclude with an outline of future opportunities, especially the search for a critical point in the QCD phase diagram.
nucl-thhep-ph8 citations
03
Recent Advances in the Application of the Shell Model Monte Carlo Approach to Nuclei
Y. Alhassid · M. Bonett-Matiz · A. Mukherjee · H. Nakada · C. Özen
The shell model Monte Carlo (SMMC) method is a powerful technique for calculating the statistical and collective properties of nuclei in the presence of correlations in model spaces that are many orders of magnitude larger than those that can be treated by conventional diagonalization methods. We review recent advances in the development and application of SMMC to mid-mass and heavy nuclei.
nucl-thJ.Phys.Conf.Ser.(2015)·1 citation
04
Analysis of delocalization of clusters in linear-chain $α$ -cluster states with entanglement entropy
Yoshiko Kanada-En'yo
I investigate entanglement entropy of one dimension (1D) cluster states to discuss the delocalization of clusters in linear-chain $3 α$ - and $4 α$ -cluster states. In analysis of entanglement entropy of 1D Tohsaki-Horiuchi-Schuck-Röpke (THSR) and Brink-Bloch cluster wave functions, I show clear differences in the entanglement entropy between localized cluster wave functions and delocalized cluster wave functions. In order to clarify spatial regions where the entanglement entropy is generated by the delocalization of clusters, I analyze the spatial distribution of entanglement entropy. In the linear-chain $3 α$ cluster state, the delocalization occurs dominantly in a low-density tail region while it is relatively suppressed in an inner region because of Pauli blocking effect between clusters. In the linear-chain 4 $α$ state having a larger system size than the linear-chain $3 α$ state, the delocalization occurs in the whole system. The entanglement entropy is found to be a measure of the delocalization of clusters in the 1D cluster systems.
nucl-thcond-mat.str-elquant-phPRC(2015)·18 citations
05
Theoretical reaction rates of the $^{12}$ C( $α$ , $γ$ ) $^{16}$ O reaction from the potential model
M. Katsuma
The radiative capture cross sections of $^{12}$ C( $α$ , $γ$ ) $^{16}$ O and derived reaction rates are calculated from the direct capture potential model. The resulting $S$ -factor at low energies is found to be dominated by $E$ 2 transition to the $^{16}$ O ground state. The $E$ 1 and $E$ 2 $S$ -factors at $E_{c . m .} = 0.3$ MeV are $S_{E 1} \approx 3$ keV~b and $S_{E 2} = 15 0_{- 17}^{+ 41}$ keV~b, respectively. The sum of the cascade transition through the excited state of $^{16}$ O is $S_{casc} = 18 \pm 4.5$ keV~b. The derived reaction rates at low temperatures seem to be concordant with those from the previous evaluation. For astrophysical applications, our reaction rates below $T_{9} = 3$ are provided in an analytic expression.
nucl-thastro-ph.SRnucl-exPoS(2015)·0 citations
06
Near-threshold $η$ production in $pp$ collisions
Qi-Fang Lü🇨🇳 · De-Min Li🇨🇳
We study near-threshold $η$ meson production in $pp$ collisions within an effective Lagrangian approach combined with the isobar model, by allowing for the various intermediate nucleon resonances due to the $π$ , $η$ , and $ρ$ -meson exchanges. It is shown that the $ρ$ -meson exchange is the dominant excitation mechanism for these resonances, and the contribution from the $N^{*} (1720)$ is dominant. The total cross section data can be reasonably reproduced, and the anisotropic angular distributions of the emitted $η$ meson are consistent with experimental measurements. Besides, the invariant mass spectra of $pp$ and $p η$ explain the data well at excess energy of 15 MeV, and are basically consistent with the data at excess energy of 40 MeV. However, our model calculations cannot reasonably account for the two-peak structure in the $p η$ distribution at excess energies of 57 and 72 MeV, which suggests that a more complicated mechanism is needed at higher energy region.
nucl-thhep-phCPC(2015)·5 citations
07
Analytical formula for numerical evaluations of the Wigner rotation matrices at high spins
Naoki Tajima
The Wigner d function, which is the essential part of an irreducible representation of SU(2) and SO(3) parameterized with Euler angles, has been know to suffer from a serious numerical errors at high spins, if it is calculated by means of the Wigner formula as a polynomial of cos and sin of half of the second Euler angle. This paper shows a way to avoid this problem by expressing the d functions as the Fourier series of the half angle. A precise numerical table of the coefficients of the series is obtainable from a web site.
nucl-thphysics.atom-phphysics.chem-phphysics.comp-phPRC(2015)·20 citations
08
Effective model for in-medium $K ˉ N$ interactions including the $L = 1$ partial wave
Aleš Cieplý🇨🇿 · Vojtěch Krejčiřík🇯🇵
Coupled channels model of meson-baryon interactions based on the effective chiral Lagrangian is extended to account explicitly for the $Σ (1385)$ resonance that dominates the $P$ -wave $K ˉ N$ and $π Σ$ interactions at energies below the $K ˉ N$ threshold. The presented model aims at a uniform treatment of the $Λ (1405)$ and $Σ (1385)$ dynamics in the nuclear medium. We demonstrate the applicability of the model by confronting its predictions with the vacuum scattering data, then we follow with discussing the impact of nuclear matter on the $π Σ$ mass spectrum and on the energy dependence of the $K^{-} p$ branching ratios.
nucl-thNPA(2015)·14 citations
09
Neutrino-nucleus interactions and the determination of oscillation parameters
Omar Benhar🇮🇹 · Patrick Huber🇺🇸 · Camillo Mariani🇺🇸 · Davide Meloni🇮🇹
We review the status and prospects of theoretical studies of neutrino-nucleus interactions, and discuss the influence of the treatment of nuclear effects on the determination of oscillation parameters. The models developed to describe the variety of reaction mechanisms contributing to the nuclear cross sections are analysed, with emphasis placed on their capability to reproduce the available electron scattering data.The impact of the uncertainties associated with the description of nuclear dynamics on the the oscillation parameters is illustrated through examples, and possible avenues towards a better understanding of the signals detected by long baseline experiments are outlined.
nucl-thhep-phPhys.Rept.(2017)·95 citations
10
Exploring the properties of the phases of QCD matter - research opportunities and priorities for the next decade
U. Heinz (Ohio State)🇺🇸 · P. Sorensen (BNL)🇺🇸 · A. Deshpande (Stony Brook)🇺🇸 · C. Gagliardi (Texas A&M)🇺🇸 · F. Karsch (BNL & Bielefeld)🇺🇸 · T. Lappi (Jyvaskyla)🇫🇮 · Z.-E. Meziani (Temple U)🇺🇸 · R. Milner (MIT)🇺🇸 · B. Muller (BNL & Duke)🇺🇸 · J. Nagle (Colorado)🇺🇸 · J.-W. Qiu (BNL)🇺🇸 · K. Rajagopal (MIT)🇺🇸 · G. Roland (MIT)🇺🇸 · R. Venugopalan (BNL)🇺🇸
This document provides a summary of the discussions during the recent joint QCD Town Meeting at Temple University of the status of and future plans for the research program of the relativistic heavy-ion community. A list of compelling questions is formulated, and a number of recommendations outlining the greatest research opportunities and detailing the research priorities of the heavy-ion community, voted on and unanimously approved at the Town Meeting, are presented. They are supported by a broad discussion of the underlying physics and its relation to other subfields. Areas of overlapping interests with the "QCD and Hadron Structure" ("cold QCD") subcommunity, in particular the recommendation for the future construction of an Electron-Ion Collider, are emphasized. The agenda of activities of the "hot QCD" subcommunity at the Town Meeting is attached.
nucl-thhep-exhep-phnucl-ex37 citations
11
Production of Heavy Clusters with an Expanded Coalescence Model in CEM
Leslie M. Kerby · Stepan G. Mashnik
The production of heavy clusters in nuclear reactions is important in a wide variety of applications: radiation shielding, space engineering and design, medical physics, accelerator design, and more. According to the Cascade Exciton Model (CEM), there are three ways high-energy heavy clusters can be produced. The first way is via coalescence of nucleons produced in the IntraNuclear Cascade (INC). The second way is via the preequilibrium model. The last way is via Fermi breakup. Previous work in CEM examines the impact of expansions of the preequilibrium model and Fermi breakup model on heavy cluster production. The present work studies the impact of expanding the coalescence model on heavy cluster spectra. CEM03.03, the default event generator in the Monte Carlo N-Particle transport code version 6 (MCNP6) for intermediate-energy nuclear reactions, is capable of producing light fragments up to He4 in its coalescence model. In the present study, we have expanded the coalescence model to be able to produce up to Be7. Preliminary results are promising.
nucl-th0 citations
12
Chaoticity and Coherence in Bose-Einstein Condensation and Correlations
Cheuk-Yin Wong🇺🇸 · Wei-Ning Zhang🇨🇳 · Jie Liu🇨🇳 · Peng Ru🇨🇳
We review the properties of chaoticity and coherence in Bose-Einstein condensation and correlations, for a dense boson system in its mean-field represented approximately by a harmonic oscillator potential. The order parameter and the nature of the phase transition from the chaotic to the condensate states are studied for different fixed numbers of bosons. The two-particle correlation function in momentum space is calculated to investigate how the Bose-Einstein correlation depends on the degree of condensation and other momentum variables. We generalize the Bose-Einstein correlation analysis to three-particle correlations to show its dependence on the degree of condensation.
↳ hep-phcond-mat.quant-gasnucl-thphysics.atom-ph1 citation
13
Single-particle spectral density of the unitary Fermi gas: Novel approach based on the operator product expansion, sum rules and the maximum entropy method
Philipp Gubler🇮🇹 · Naoki Yamamoto🇯🇵 · Tetsuo Hatsuda🇯🇵 · Yusuke Nishida🇯🇵
Making use of the operator product expansion, we derive a general class of sum rules for the imaginary part of the single-particle self-energy of the unitary Fermi gas. The sum rules are analyzed numerically with the help of the maximum entropy method, which allows us to extract the single-particle spectral density as a function of both energy and momentum. These spectral densities contain basic information on the properties of the unitary Fermi gas, such as the dispersion relation and the superfluid pairing gap, for which we obtain reasonable agreement with the available results based on quantum Monte-Carlo simulations.
↳ cond-mat.quant-gashep-phnucl-thAnnals Phys.(2015)·8 citations
14
Quantum Life of R.I. Jibuti
R. Ya. Kezerashvili
This article is dedicated to the 80th birthday of the outstanding Georgian and Soviet nuclear physicist Professor R. I. Jibuti (1934-1992).
↳ physics.hist-phnucl-th0 citations
15
Quantum and stringy corrections to the equation of state of holographic QCD matter and the nature of the chiral transition
T. Alho🇮🇸 · M. Jarvinen🇫🇷 · K. Kajantie🇫🇮 · E. Kiritsis🇫🇷 · K. Tuominen🇫🇮
We consider the finite temperature phase diagram of holographic QCD in the Veneziano limit (Nc large, Nf large with xf=Nf/Nc fixed) and calculate one string-loop corrections to the free energy in certain approximations. Such corrections, especially due to the pion modes are unsuppressed in the Veneziano limit. We find that under some extra assumptions the first order transition following from classical gravity solutions can become second order. If stringy asymptotics are of a special form and there are residual interactions it may even become of third order. Operationally these computations imply modelling the low temperature chiral symmetry breaking phase with a hadron gas containing Nf^2 massless Goldstone bosons and an exponential spectrum of massive hadrons. A third order transition is possible only if repulsive hadron interactions via the excluded volume effect are included.
↳ hep-phhep-lathep-thnucl-thPRD(2015)·50 citations
16
Instantons and Monopoles
Adriano Di Giacomo🇮🇹 · Masayasu Hasegawa🇷🇺
This study is part of a research program aimed to investigate the relations between instantons, monopoles, and chiral symmetry breaking. Monopoles are important 3-dimensional topological configurations existing in QCD, which are believed to produce colour confinement. Instantons are 4-dimensional topological configurations and are known to be related to chiral symmetry breaking. To study the relation between monopoles and instantons we generate configurations adding to the vacuum state static monopole-antimonopole pairs of opposite charges by use of a monopole creation operator. We observe that the monopole creation operator only adds long monopole loops to the configurations. We then count the number of fermion zero modes using Overlap fermions as a tool. As a result we find that each monopole-antimonopole pair of magnetic charge one adds one zero mode of chirality $\pm 1$ , i.e. one instanton of topological charge $\pm 1$ .
↳ hep-lathep-phhep-thnucl-thPRD(2015)·20 citations

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