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Nuclear Theory·nucl-th

Friday·May 6, 2016

6 papers—4 primary·2 cross-listed

All6Primary4Cross-lists2
  1. 05

    Hunting for exotic doubly hidden-charm/bottom tetraquark states

    Wei Chen🇨🇦 · Hua-Xing Chen🇨🇳 · Xiang Liu🇨🇳 · T. G. Steele🇨🇦 · Shi-Lin Zhu🇨🇳

    We develop a moment QCD sum rule method augmented by fundamental inequalities to study the existence of exotic doubly hidden-charm/bottom tetraquark states made of four heavy quarks. Using the compact diquark-antidiquark configuration, we calculate the mass spectra of these tetraquark states. There are 18 hidden-charm tetraquark currents with , , , , , , , and . We use them to perform QCD sum rule analyses, and the obtained masses are all higher than the spontaneous dissociation thresholds of two charmonium mesons, which are thus their dominant decay modes. The masses of the corresponding hidden-bottom tetraquarks are all below or very close to the thresholds of the and , except one current of . Hence, we suggest to search for the doubly hidden-charm states in the and channels.

    ↳ hep-phhep-exhep-latnucl-thPLB(2017)·196 citations
  2. 06

    The millisecond pulsar mass distribution: Evidence for bimodality and constraints on the maximum neutron star mass

    John Antoniadis · Thomas M. Tauris · Feryal Ozel · Ewan Barr · David J. Champion · Paulo C. C. Freire

    The mass function of neutron stars (NSs) contains information about the late evolution of massive stars, the supernova explosion mechanism, and the equation-of-state of cold, nuclear matter beyond the nuclear saturation density. A number of recent NS mass measurements in binary millisecond pulsar (MSP) systems increase the fraction of massive NSs (with M) to of the observed population. In light of these results, we employ a Bayesian framework to revisit the MSP mass distribution. We find that a single Gaussian model does not sufficiently describe the observed population. We test alternative empirical models and infer that the MSP mass distribution is strongly asymmetric. The diversity in spin and orbital properties of high-mass NSs suggests that this is most likely not a result of the recycling process, but rather reflects differences in the NS birth masses. The asymmetry is best accounted for by a bimodal distribution with a low mass component centred at M and dispersed by M, and a high-mass component with a mean of and a dispersion of M. We also establish a lower limit of M at 98% C.L. for the maximum NS mass, from the absence of a high-mass truncation in the observed masses. Using our inferred model, we find that the measurement of 350 MSP masses, expected after the conclusion of pulsar surveys with the Square-Kilometre Array, can result in a precise localization of a maximum mass up to 2.15 M, with a 5% accuracy. Finally, we identify possible massive NSs within the known pulsar population and discuss birth masses of MSPs.

    ↳ astro-ph.HEastro-ph.SRnucl-th217 citations

Affiliations

first authorsco-authorsvia INSPIRE