PaperPanorama

Nuclear Theory·nucl-th

Monday·January 8, 2018

18 papers11 primary·7 cross-listed

  1. 01

    [Submitted on 4 Jan 2018]

    Nucleon Effective Masses in Neutron-Rich Matter

    Bao-An Li🇺🇸 · Bao-Jun Cai🇨🇳 · Lie-Wen Chen🇨🇳 · Jun Xu🇨🇳

    Various kinds of isovector nucleon effective masses are used in the literature to characterize the momentum/energy dependence of the nucleon symmetry potential or self-energy due to the space/time non-locality of the underlying isovector strong interaction in neutron-rich nucleonic matter. The multifaceted studies on nucleon isovector effective masses are multi-disciplinary in nature. Besides structures, masses and low-lying excited states of nuclei as well as nuclear reactions, studies of the isospin dependence of short-range correlations in nuclei from scatterings of high-energy electrons and protons on heavy nuclei also help understand nucleon effective masses especially the so-called E-mass in neutron-rich matter. A thorough understanding of all kinds of nucleon effective masses has multiple impacts on many interesting issues in both nuclear physics and astrophysics. We review some of the significant progresses made in recent years by the nuclear physics community in resolving some of the hotly debated and longstanding issues regarding nucleon effective masses especially in dense neutron-rich matter.

    Comments:
    109 pages, Progress in Particle and Nuclear Physics (2018) in press
    Subjects:
    Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    1801.01213 [pdf]
    PPNP(2018)·220 citations
  2. 02

    [Submitted on 4 Jan 2018]

    Does Compound Nucleus remember its Isospin- An Evidence from the Fission Widths

    Swati Garg · Ashok Kumar jain

    We present an evidence of isospin effects in nuclear fission by comparing the fission widths for reactions involving different isospin states of the same compound nucleus (CN). Yadrovsky suggested this possibility in 1975. Yadrovsky obtained the fission widths for two reaction data sets, namely Pb(,f) and Bi(p,f), both leading to same CN, and concluded that "a nucleus remembers the isospin value of the nuclear states leading to fission". We obtain the fission decay widths for both the and states of CN by using two appropriate reaction data sets. We then compare the fission widths for the two isospin states of CN. More specifically, we have chosen the combination of Pb(,f) and Bi(p,f) same as presented in Yadrovsky's paper and U(d,f) and U(p,f) reaction data sets in this study. A significant difference between the ratios of fission decay widths to total decay widths for different isospin values suggests that isospin plays an important role in fission.

    Comments:
    3 pages, 1 figure, 1 table, gave an oral presentation in 16th International Symposium on Capture Gamma-Ray Spectroscopy and Related Topics (CGS16) at Shanghai Jiao Tong University, China and accepted for EPJ Web of Conferences
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1801.01244 [pdf]
    EPJ Web Conf.(2018)·3 citations
  3. 03

    [Submitted on 4 Jan 2018]

    Examining empirical evidence of the effect of superfluidity on the fusion barrier

    Guillaume Scamps

    Background: Several Time-Dependent Hartree-Fock-Bogoliubov (TDHFB) calculations predict that the super- fluidity enhances the fluctuations of the fusion barrier. This effect is not fully understood and not yet revealed experimentally. Purpose: The goal of this study is to investigate empirically the effect of the superfluidity on the fusion barrier width. Method: First, the local regression method is introduce and used to determine the barrier distribution more precisely. A second method that requires only the calculation of an integral of the cross section is developed to determine accurately the fluctuations of the barrier. A benchmark is done between this two methods and with the fitting method usually used. This integral method showing a better agreement in a test case, it is applied systematically in a selection of 115 fusion reactions. Results: The fluctuations of the barrier for superfluid systems are on average larger than for magic or semi-magic nuclei. This is due to the deformation effects and the effect of the superfluidity. To disentangle those two effects, we compare the experimental width to the width estimated from a model that takes into account the tunneling, the deformation and the vibration effect. The deviation of the experimental width from this theory for reaction between superfluid nuclei shows that the superfluidity enhance the fusion barrier width. Conclusions: This analysis shows that the predicted effect of the superfluidity on the width of the barrier is real and is of the order of 1 MeV.

    Comments:
    11 pages, 14 figures
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    1801.01250 [pdf]
    PRC(2018)·20 citations
  4. 04

    [Submitted on 4 Jan 2018]

    Structures of -shell double- hypernuclei studied with microscopic cluster models

    Yoshiko Kanada-En'yo

    -orbit states in -shell double- hypernuclei (), , , , , and are investigated. Microscopic cluster models are applied to core nuclear part and a potential model is adopted for particles. The -core potential is a folding potential obtained with effective -matrix - interactions, which reasonably reproduce energy spectra of . System dependence of the - binding energies is understood by the core polarization energy from nuclear size reduction. Reductions of nuclear sizes and transition strengths by particles are also discussed.

    Comments:
    15 pages, 7 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1801.01259 [pdf]
    PRC(2018)·8 citations
  5. 05

    [Submitted on 4 Jan 2018]

    Three-body radiative capture reactions

    J. Casal · M. Rodríguez-Gallardo · J. M. Arias · J. Gómez-Camacho

    Radiative capture reaction rates for He, Be and Ne formation at astrophysical conditions are studied within a three-body model using the analytical transformed harmonic oscillator method to calculate their states. An alternative procedure to estimate these rates from experimental data on low-energy breakup is also discussed

    Comments:
    4 pages, 3 figures. Proceedings of the VIII Nuclear Physics in Astrophysics international conference (June 2017, Catania, Italy)
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1801.01272 [pdf]
    EPJ Web Conf.(2017)·1 citation
  6. 06

    [Submitted on 4 Jan 2018]

    Two-nucleon emitters within a pseudostate method: The case of Be and Be

    J. Casal

    Background: Since the first experimental observation, two-nucleon radioactivity has gained renewed attention over the past fifteen years. The Be system is the lightest two-proton ground-state emitter, while Be has been recently proposed to be the first two-neutron ground-state emitter ever observed. A proper understanding of their properties and decay modes requires a reasonable description of the three-body continuum. Purpose: Study the ground-state properties of Be and Be within a general three-body model and investigate their nucleon-nucleon correlations in the continuum. Method: The pseudostate (PS) method in hyperspherical coordinates, using the analytical transformed harmonic oscillator (THO) basis for three-body systems, is used to construct the Be and Be ground-state wave functions. These resonances are approximated as a stable PS around the known two-nucleon separation energy. Effective core- potentials, constrained by the available experimental information on the binary subsystems Li and Be, are employed in the calculations. Results: The ground state of Be is found to present a strong dineutron configuration, with the valence neutrons occupying mostly an state relative to the core. The results are consistent with previous -matrix calculations for the actual continuum. The case of Be shows a clear symmetry with respect to its mirror partner, the two-neutron halo He: The diproton configuration is dominant, and the valence protons occupy an orbit. Conclusions: The PS method is found to be a suitable tool in describing the properties of unbound ground states. For both Be and Be, the results are consistent with previous theoretical studies and confirm the dominant dinucleon configuration. This favors the picture of a correlated two-nucleon emission.

    Comments:
    10 pages, 12 figures; accepted as PRC
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1801.01280 [pdf]
    PRC(2018)·23 citations
  7. 07

    [Submitted on 4 Jan 2018]

    Chiral-partner D mesons in a heat bath within QCD sum rules

    Thomas Buchheim🇩🇪 · Thomas Hilger🇦🇹 · Burkhard Kampfer🇩🇪 · Stefan Leupold🇸🇪

    Utilizing QCD sum rules, we extract the temperature dependences of the spectral properties of the pseudo-scalar and scalar D mesons regarded as chiral partners. Besides the masses also decay constants are analyzed as the D meson yields in heavy-ion collisions may be sensitive to their altered decay properties in an ambient strongly interacting medium. Our findings are () a decreasing scalar D meson mass for growing temperatures while its pseudo-scalar partner meson seems hardly affected, which is in qualitative agreement with hadronic model calculations; () inferring an equally weak temperature dependence of the pseudo-scalar D meson decay properties the decreasing residua and decay constants of the scalar particle point towards partial chiral restoration. As a bonus of our analysis in the pseudo-scalar sector we determine the pseudo-scalar decay constant at vanishing temperature. Due to the connection to particular leptonic branching fractions this decay constant is of great interest allowing for the determination of the off-diagonal CKM matrix element at zero temperature.

    Comments:
    25 pages, 11 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1801.01472 [pdf]
    J.Phys.G(2018)·8 citations
  8. 08

    [Submitted on 5 Jan 2018]

    Nambu--Jona-Lasinio model in a parallel electromagnetic field

    Lingxiao Wang🇨🇳 · Gaoqing Cao🇨🇳 · Xu-Guang Huang🇨🇳 · Pengfei Zhuang🇨🇳

    We explore the features of the and chiral symmetry breaking of the Nambu--Jona-Lasinio model without the Kobayashi-Maskawa-'t Hooft determinant term in the presence of a parallel electromagnetic field. We show that the electromagnetic chiral anomaly can induce both finite neutral pion condensate and isospin-singlet pseudo-scalar condensate and thus modifies the chiral symmetry breaking pattern. In order to characterize the strength of the symmetry breaking, we evaluate the susceptibility associated with the charge. The result shows that the susceptibility contributed from the chiral anomaly is consistent with the behavior of the corresponding condensate. The spectra of the mesonic excitations are also studied.

    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th)
    arXiv:
    1801.01682 [pdf]
    PLB(2018)·20 citations
  9. 09

    [Submitted on 5 Jan 2018]

    Covariant kinetic theory for effective fugacity quasi particle model and first order transport coefficients for hot QCD matter

    Sukanya Mitra🇮🇳 · Vinod Chandra🇮🇳

    An effective relativistic kinetic theory has been constructed for an interacting system of quarks, anti-quarks and gluons within a quasi-particle description of hot QCD medium at finite temperature and baryon chemical potential, where the interactions are encoded in the gluon and quark effective fugacities with non-trivial energy dispersions. The local conservations of stress-energy tensor and number current require the introduction of a mean field term in the transport equation which produces non-vanishing contribution to the first order transport coefficients. Such contribution has been observed to be significant for the temperatures which are closer to the QCD transition tem- perature, however, induces negligible contributions beyond a few times the transition temperature. As an implication, impact of the mean field contribution on the the temperature dependence of the shear viscosity, bulk viscosity and thermal conductivity of a hot QCD medium in the presence of binary, elastic collisions among the constituents, has been investigated. Visible effects have been observed for the temperature regime closer to the QCD transition temperature.

    Comments:
    10 pages, 3 figures, two column
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1801.01700 [pdf]
    PRD(2018)·41 citations
  10. 10

    [Submitted on 5 Jan 2018]

    Bulk Properties of the Matter Produced at Energies of the Beam Energy Scan Program

    Yu. B. Ivanov🇷🇺 · A. A. Soldatov🇷🇺

    Recent STAR data on the bulk observables in the energy range of the Beam-Energy Scan Program at the Relativistic Heavy-Ion Collider are analyzed within the model of the three-fluid dynamics (3FD). The simulations are performed with different equations of state (EoS). The purely hadronic EoS fails to reproduce the data. A good, though imperfect, overall reproduction of the data is found within the deconfinement scenarios. The crossover EoS turns out to be slightly preferable. For this reproduction a fairly strong baryon stopping in the quark-gluon phase is required. The 3FD model does not need two separate freeze-outs (i.e. kinetic and chemical ones) to describe the STAR data. A unified freeze-out is applied at all energies.

    Comments:
    9 pages, 8 figures. 1 figure added, minor corrections, version published in Phys. Rev. C
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    1801.01764 [pdf]
    PRC(2018)·15 citations
  11. 11

    [Submitted on 5 Jan 2018]

    Collective motion in triaxial nuclei within minimal length concept

    M. Chabab🇲🇦 · A. El Batoul🇲🇦 · A. Lahbas🇲🇦 · M. Oulne🇲🇦

    The concept of minimal length, inspired by Heisenberg algebra, is applied to the geometrical collective Bohr- Mottelson model (BMM) of nuclei. With the deformed canonical commutation relation and the Pauli-Podolsky prescription, we have derived the quantized Hamiltonian operator for triaxial nuclei as we have previously done for axial prolate -rigid ones (M. Chabab et al., Phys. Lett. B 758 (2016) 212-218). By considering an infinite square well like potential in collective shape variable, the eigenvalues of the Hamiltonian are obtained in terms of zeros of Bessel functions of irrational order with an explicit dependence on the minimal length parameter. Moreover, the associated symmetry with the model that we have constructed here can be considered as a new quasi-dynamical critical point symmetries (CPSs) in nuclear structure. The theoretical results indicate a dramatic contribution (Low effect) of the minimal length to energy levels for lower values of the angular momentum and regular (significant effect) for higher values. In fact, these features show that the minimal length scenario which is useful in recognizing the properties of real deformed nuclei having high spins or strong rotations. Finally, numerical calculations are performed for some nuclei such as Xe and Pd revealing a qualitative agreement with the experimental data.

    Comments:
    8 pages,1 figure, LaTeX, contribution to the Proceedings of the 36-th International Workshop on Nuclear Theory (IWNT-36), Rila Mountains, Bulgaria, June 25-July 1, 2017. Editors: M. Gaidarov and N. Minkov, Published by Heron Press Ltd., Sofia, Bulgaria, ISSN 1313-2822
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1801.01870 [pdf]
    Nucl.Theor.(2017)·0 citations
  12. 12

    [Submitted on 3 Jan 2018] (cross-list from hep-ph)

    Colored Dark Matter

    Valerio De Luca🇮🇹 · Andrea Mitridate🇮🇹 · Michele Redi🇮🇹 · Juri Smirnov🇮🇹 · Alessandro Strumia🇮🇹

    We explore the possibility that Dark Matter is the lightest hadron made of two stable color octet Dirac fermions . The cosmological DM abundance is reproduced for TeV, compatibly with direct searches (the Rayleigh cross section, suppressed by , is close to present bounds), indirect searches (enhanced by recombination), and with collider searches (where manifests as tracks, pair produced via QCD). Hybrid hadrons, made of and of SM quarks and gluons, have large QCD cross sections, and do not reach underground detectors. Their cosmological abundance is times smaller than DM, such that their unusual signals seem compatible with bounds. Those in the Earth and stars sank to their centers; the Earth crust and meteorites later accumulate a secondary abundance, although their present abundance depends on nuclear and geological properties that we cannot compute from first principles.

    Comments:
    36 pages, 7 figures. v3: improved computation of the relic abundance; revised estimate of the indirect detection cross section
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Nuclear Theory (nucl-th)
    arXiv:
    1801.01135 [pdf]
    PRD(2018)·117 citations
  13. 13

    [Submitted on 4 Jan 2018] (cross-list from hep-ph)

    A remark on the sign change of the four-particle azimuthal cumulant in small systems

    Adam Bzdak🇵🇱 · Guo-Liang Ma🇨🇳

    The azimuthal cumulants, and , originating from the global conservation of transverse momentum in the presence of hydro-like elliptic flow are calculated. We observe the sign change of for small number of produced particles. This is in a qualitative agreement with the recent ATLAS measurement of multi-particle azimuthal correlations with the subevent cumulant method.

    Comments:
    8 pages, 2 figures; PLB version, less equations, experimental points added
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1801.01277 [pdf]
    PLB(2018)·10 citations
  14. 14

    [Submitted on 4 Jan 2018] (cross-list from nucl-ex)

    Chronology of the three-body dissociation of He

    B. Laurent🇫🇷 · F.M. Marqués🇫🇷 · C. Angulo🇧🇪 · N.I. Ashwood🇬🇧 · M.J.G. Borge🇪🇸 · V. Bouchat🇧🇪 · W.N. Catford · N.M. Clarke🇬🇧 · N. Curtis🇬🇧 · M. Freer🇬🇧 · F. Hanappe🇧🇪 · V. Kinnard🇧🇪 and 11 other authors

    The space and time configurations of the dissociation of He into He++, on C and Pb targets, have been explored simultaneously for the first time. The final-state interactions in the - and He- channels are successfully described within a model that considers independent emission of neutrons from a Gaussian volume with a given lifetime. The dissociation on C target exhibits a dominant sequential decay through the ground state of He, consistent with neutrons being emitted from a Gaussian volume of ~fm with a - delay in the sequential channel of ~fm/, in agreement with the lifetime of He. The lower-statistics data on Pb target correspond mainly to direct breakup, and are well described using the - volume measured, without any - delay. The validity of the phenomenological model used is discussed.

    Comments:
    Accepted for publication in J. Phys. G, 11 pages, 5 figures
    Subjects:
    Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1801.01333 [pdf]
    J.Phys.G(2019)·9 citations
  15. 15

    [Submitted on 4 Jan 2018] (cross-list from hep-ph)

    Form Factors based on a Covariant Quark Model

    G. Ramalho🇧🇷

    We discuss the results of the covariant spectator quark model for the several transitions, where is the nucleon and a nucleon excitation. More specifically, we present predictions for the form factors and transition amplitudes associated with the resonances , , , and . The estimates based on valence quark degrees of freedom are compared with the available data, particularly with the recent Jefferson Lab data at low and large momentum transfer (). In general, the estimates are in good agreement with the empirical data for GeV, with a few exceptions. The results are discussed in terms of the role of the valence quarks and the meson cloud excitations for the different resonances . We also review our results for the resonance and discuss the relevance of the pion cloud component for the magnetic dipole form factor and the electric and Coulomb quadrupole form factors.

    Comments:
    Proceedings of the 11th International Workshop on the Physics of Excited Nucleons (NSTAR 2017), August 20-23, 2017, Columbia, USA. Published version. 29 pages, 15 figures. Typos corrected. Section 4 extended
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1801.01476 [pdf]
    Few Body Syst.(2018)·25 citations
  16. 16

    [Submitted on 5 Jan 2018] (cross-list from hep-ph)

    Unintegrated dipole gluon distribution at small transverse momentum

    Raktim Abir🇿🇦 · Khatiza Banu🇿🇦 · Trambak Bhattacharyya🇿🇦 · Mariyah Siddiqah🇿🇦 · Nahid Vasim🇿🇦

    We derive analytical results for unintegrated color dipole gluon distribution function at small transverse momentum. By Fourier transforming the -matrix for large dipoles we derive the results in the form of a series of Bells polynomials. Interestingly, when resumming the series in leading log accuracy, the results showing up striking similarity with the Sudakov form factor with role play of coupling is being done by a constant that stems from the saddle point condition along the saturation line.

    Comments:
    10 pages, 1 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
    arXiv:
    1801.01637 [pdf]
    PRD(2018)·9 citations
  17. 17

    [Submitted on 5 Jan 2018] (cross-list from hep-ph)

    photoproduction in high energy nuclear collisions

    Baoyi Chen · Carsten Greiner🇩🇪 · Wei Shi · Wangmei Zha🇨🇳 · Pengfei Zhuang🇨🇳

    We study coherent photoproduction of and the subsequent suppression in high energy nuclear collisions. The hot medium effect on charmonium photoproduction is controlled by the competition between the fireball size and nuclear size. When the former is smaller than the later, the photoproduction is only slightly affected by the hot medium. We calculate the yield ratio of to in semi-central Pb-Pb collisions at LHC energy, while the high limit is characterized by the fireball, its value in low limit can still reach the significant enhancement by photoproduction.

    Comments:
    5 pages, 3 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1801.01677 [pdf]
    5 citations
  18. 18

    [Submitted on 5 Jan 2018] (cross-list from nucl-ex)

    Proton charge radius from electron scattering

    Ingo Sick🇨🇭

    The rms-radius of the proton charge distribution is a fundamental quantity needed for precision physics. This radius, traditionally determined from elastic electron-proton scattering via the slope of the Sachs form factor extrapolated to momentum transfer =0, shows a large scatter. We discuss the approaches used to analyze the e-p data, partly redo these analyses in order to identify the sources of the discrepancies, and explore alternative parameterizations. The problem lies in the model dependence of the parameterized needed for the extrapolation. This shape of is closely related to the shape of the charge density at large radii , a quantity which is ignored in most analyses. When using our {\em physics} knowledge about this large- density together with the information contained in the high- data, the model dependence of the extrapolation is reduced and different parameterizations of the pre-2010 data yield a consistent value for . This value disagrees with the more precise value determined from the Lamb shift in muonic hydrogen.

    Comments:
    To be published in special issue of Atoms "High precision mesurements of fundamental constants"
    Subjects:
    Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1801.01746 [pdf]
    Atoms(2018)·45 citations

Affiliations

first authorsco-authorsvia INSPIRE