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Nuclear Theory·nucl-th

Thursday·July 19, 2018

10 papers—6 primary·4 cross-listed

All10Primary6Cross-lists4
  1. 07

    Proof of Color Octet NRQCD Factorization of P-Wave Heavy Quarkonium Production at All Orders in Coupling Constant

    Gouranga C Nayak

    Recently we have proved color octet NRQCD factorization of S-wave heavy quarkonium production at all orders in coupling constant at high energy colliders in Eur. Phys. J. C76 (2016) 448. In this paper we extend this to prove color octet NRQCD factorization of P-wave heavy quarkonium production at all orders in coupling constant at high energy colliders. We find that while the color octet NRQCD S-wave non-perturbative matrix element contains two gauge-links in the adjoint representation of SU(3), the color octet NRQCD P-wave non-perturbative matrix element contains four gauge-links in the fundamental representation of SU(3).

    ↳ hep-phnucl-th1 citation
  2. 08

    Actinide Production in Neutron-Rich Ejecta of a Neutron Star Merger

    Erika M. Holmbeck · Rebecca Surman · Trevor M. Sprouse · Matthew R. Mumpower · Nicole Vassh · Timothy C. Beers · Toshihiko Kawano

    The rapid-neutron-capture ("r") process is responsible for synthesizing many of the heavy elements observed in both the solar system and Galactic metal-poor halo stars. Simulations of r-process nucleosynthesis can reproduce abundances derived from observations with varying success, but so far fail to account for the observed over-enhancement of actinides, present in about 30% of r-process-enhanced stars. In this work, we investigate actinide production in the dynamical ejecta of a neutron star merger and explore if varying levels of neutron richness can reproduce the actinide boost. We also investigate the sensitivity of actinide production on nuclear physics properties: fission distribution, beta-decay, and mass model. For most cases, the actinides are over-produced in our models if the initial conditions are sufficiently neutron-rich for fission cycling. We find that actinide production can be so robust in the dynamical ejecta that an additional lanthanide-rich, actinide-poor component is necessary in order to match observations of actinide-boost stars. We present a simple actinide-dilution model that folds in estimated contributions from two nucleosynthetic sites within a merger event. Our study suggests that while the dynamical ejecta of a neutron star merger is a likely production site for the formation of actinides, a significant contribution from another site or sites (e.g., the neutron star merger accretion disk wind) is required to explain abundances of r-process-enhanced, metal-poor stars.

    ↳ astro-ph.SRastro-ph.HEnucl-thApJ(2019)·63 citations
  3. 09

    Role of system size on freezeout conditions extracted from transverse momentum spectra of hadrons

    Ajay Kumar Dash🇮🇳 · Ranbir Singh🇮🇳 · Sandeep Chatterjee🇵🇱 · Chitrasen Jena🇮🇳 · Bedangadas Mohanty🇮🇳

    The data on hadron transverse momentum spectra in different centrality classes of p+Pb collisions at TeV has been analysed to extract the freezeout hypersurface within a simultaneous chemical and kinetic freezeout scenario. The freezeout hypersurface has been extracted for three different freezeout schemes that differ in the way strangeness is treated: i. unified freezeout for all hadrons in complete thermal equilibrium (1FO), ii. unified freezeout for all hadrons with an additional parameter which accounts for possible out-of-equilibrium production of strangeness (1FO), and iii. separate freezeout for hadrons with and without strangeness content (2FO). Unlike in heavy ion collisions where 2FO performs best in describing the mean hadron yields as well as the transverse momentum spectra, in p+Pb we find that 1FO with one less parameter than 2FO performs better. This confirms expectations from previous analysis on the system size dependence in the freezeout scheme with mean hadron yields: while heavy ion collisions that are dominated by constituent interactions prefer 2FO, smaller collision systems like proton + nucleus and proton + proton collisions with lesser constituent interaction prefer a unified freezeout scheme with varying degree of strangeness equilibration.

    ↳ hep-phnucl-thPRC(2018)·4 citations
  4. 10

    Revisiting heavy quark radiative energy loss in nuclei within the high-twist approach

    Yi-Lun Du🇨🇳 · Yayun He🇨🇳 · Xin-Nian Wang🇨🇳 · Hongxi Xing🇨🇳 · Hong-Shi Zong🇨🇳

    We revisit the calculation of multiple parton scattering of a heavy quark in nuclei within the framework of recently improved high-twist factorization formalism, in which gauge invariance is ensured by a delicate setup of the initial partons' transverse momenta. We derive a new result for medium modified heavy quark fragmentation functions in deeply inelastic scattering. It is consistent with the previous calculation of light quark energy loss in the massless limit, but leads to a new correction term in the heavy quark case, which vanishes in the soft gluon radiation limit. We show numerically the significance of the new correction term in the calculation of heavy quark energy loss as compared to previous studies and with soft gluon radiation approximation.

    ↳ hep-phnucl-thPRD(2018)·11 citations

Affiliations

first authorsco-authorsvia INSPIRE