Nuclear Theory·nucl-th

Monday·February 16, 2015

9 papers—2 primary·7 cross-listed

03
Lattice QCD Thermodynamics with Physical Quark Masses
R.A. Soltz🇺🇸 · C. DeTar🇺🇸 · F. Karsch🇩🇪 · Swagato Mukherjee🇺🇸 · P. Vranas🇺🇸
Over the past few years new physics methods and algorithms as well as the latest supercomputers have enabled the study of the QCD thermodynamic phase transition using lattice gauge theory numerical simulations with unprecedented control over systematic errors. This is largely a consequence of the ability to perform continuum extrapolations with physical quark masses. Here we review recent progress in lattice QCD thermodynamics, focussing mainly on results that benefit from the use of physical quark masses: the crossover temperature, the equation of state, and fluctuations of the quark number susceptibilities. In addition, we place a special emphasis on calculations that are directly relevant to the study of relativistic heavy ion collisions at RHIC and the LHC.
↳ hep-latnucl-exnucl-thAnn.Rev.Nucl.Part.Sci.(2015)·41 citations
04
Charmed-strange Meson Spectrum: Old and New Problems
Jorge Segovia🇪🇸 · David R. Entem🇪🇸 · Francisco Fernandez🇪🇸
The LHCb Collaboration has recently reported the observation for the first time of a spin- $3$ resonance in the heavy quark sector. They have shown that the $D ˉ^{0} K^{-}$ structure seen in the $B_{s}^{0} \to D ˉ^{0} K^{-} π^{+}$ reaction and with invariant mass $2.86 GeV$ is an admixture of a spin- $1$ and a spin- $3$ resonances. Motivated by the good agreement between our theoretical predictions some time ago and the properties extracted from the experiment of the $D_{s 1}^{*} (2860)$ and $D_{s 3}^{*} (2860)$ states, we perform an extension of the study of the strong decay properties of the $D_{s J}^{*} (2860)$ and present the same analysis for the $D_{s 1}^{*} (2700)$ and $D_{s J} (3040)$ mesons. This provides a unified and simultaneous description of the three higher excited charmed-strange resonances observed until now. For completeness, we present theoretical results for masses and strong decays of the low-lying charmed-strange mesons and those experimental missing states which belong to the spin-multiplets of the discovered $D_{s 1}^{*} (2700)$ , $D_{s J}^{*} (2860)$ and $D_{s J} (3040)$ resonances. The theoretical framework used is a constituent quark model which successfully describes hadron phenomenology from light to heavy quark sectors.
↳ hep-phhep-exnucl-thPRD(2015)·50 citations
05
Electroweak Corrections to the True Muonium Hyperfine Splitting
Henry Lamm🇺🇸
In contrast to other atomic systems, in true muonium ( $μ^{+} μ^{-}$ ) the leading-order $Z$ boson corrections to the hyperfine splitting are shown to be experimentally accessible in the near future. This contribution ( $- 109$ MHz) constitutes a necessary contribution to a full $O (m α^{7})$ calculation of the true muonium hyperfine splitting. This would enable a number of solutions to the muon problem to be constrained. Additionally, we compute the general expression for a pseudovector coupling to particle-antiparticle bound states at leading order, including the annihilation channel.
↳ hep-phnucl-thPRD(2015)·20 citations
06
Photon structure functions at small $x$ in holographic QCD
Akira Watanabe🇹🇼 · Hsiang-nan Li🇹🇼
We investigate the photon structure functions at small Bjorken variable $x$ in the framework of the holographic QCD, assuming dominance of the Pomeron exchange. The quasi-real photon structure functions are expressed as convolution of the Brower-Polchinski-Strassler-Tan (BPST) Pomeron kernel and the known wave functions of the U(1) vector field in the five-dimensional AdS space, in which the involved parameters in the BPST kernel have been fixed in previous studies of the nucleon structure functions. The predicted photon structure functions, as confronted with data, provide a clean test of the BPST kernel. The agreement between theoretical predictions and data is demonstrated, which supports applications of holographic QCD to hadronic processes in the nonperturbative region. Our results are also consistent with those derived from the parton distribution functions of the photon proposed by Glück, Reya, and Schienbein, implying realization of the vector meson dominance in the present model setup.
↳ hep-phnucl-thPLB(2015)·22 citations
07
Charged charmonium-like structures and the initial single chiral particle emission mechanism
Dian-Yong Chen🇨🇳 · Xiang Liu🇨🇳 · Takayuki Matsuki🇯🇵
This paper summarizes what we have done so far to explain charged charmonium/bottomonium-like structures using a hadronic triangle diagram which we call the initial single chiral particle emission mechanism. We discuss processes like $A \to A^{'} + P + P^{'}$ in which two chiral particles $P$ and $P^{'}$ are emitted from $A$ . In the intermediate we consider a hadronic one-loop diagram in which $D^{(*)} / D_{s}^{(*)} / B^{(*)} / B_{s}^{(*)}$ are included to explain some enhancements experimentally observed. Using this mechanism we explain some of the exotic enhancements and predict a couple of enhancement structures.
↳ hep-phhep-exnucl-thAIP Conf.Proc.(2016)·1 citation
08
Slowly rotating superfluid neutron stars with isospin dependent entrainment in a two-fluid model
Apurba Kheto · Debades Bandyopadhyay
We investigate the slowly rotating general relativistic superfluid neutron stars including the entrainment effect in a two-fluid model, where one fluid represents the superfluid neutrons and the other is the charge-neutral fluid called the proton fluid, made of protons and electrons. The equation of state and the entrainment effect between the superfluid neutrons and the proton fluid are computed using a relativistic mean field (RMF) model where baryon-baryon interaction is mediated by the exchange of $σ$ , $ω$ , and $ρ$ mesons and scalar self interactions are also included. The equations governing rotating neutron stars in the slow rotation approximation are second order in rotational velocities of neutron and proton fluids. We explore the effects of the isospin dependent entrainment and the relative rotation between two fluids on the global properties of rotating superfluid neutron stars such as mass, shape, and the mass shedding (Kepler) limit within the RMF model with different parameter sets. It is observed that for the global properties of rotating superfluid neutron stars in particular, the Kepler limit is modified compared with the case that does not include the contribution of $ρ$ mesons in the entrainment effect.
↳ astro-ph.HEnucl-thPRD(2015)·6 citations
09
A revised thermonuclear rate of $^{7}$ Be( $n$ , $α$ ) $^{4}$ He relevant to Big-Bang nucleosynthesis
S.Q. Hou · J.J. He · S. Kubono · Y.S. Chen
In the standard Big-Bang nucleosynthesis (BBN) model, the primordial $^{7}$ Li abundance is overestimated by about a factor of 2--3 comparing to the astronomical observations, so called the pending cosmological lithium problem. The $^{7}$ Be( $n$ , $α$ ) $^{4}$ He reaction, which may affect the $^{7}$ Li abundance, was regarded as the secondary important reaction in destructing the $^{7}$ Be nucleus in BBN. However, the thermonuclear rate of $^{7}$ Be( $n$ , $α$ ) $^{4}$ He has not been well studied so far. This reaction rate was firstly estimated by Wagoner in 1969, which has been generally adopted in the current BBN simulations and the reaction rate library. This simple estimation involved only a direct-capture reaction mechanism, but the resonant contribution should be also considered according to the later experimental results. In this work, we have revised this rate based on the indirect cross-section data available for the $^{4}$ He( $α$ , $n$ ) $^{7}$ Be and $^{4}$ He( $α$ , $p$ ) $^{7}$ Li reactions, with the charge symmetry and detailed-balance principle. Our new result shows that the previous rate (acting as an upper limit) is overestimated by about a factor of ten. The BBN simulation shows that the present rate leads to a 1.2\% increase in the final $^{7}$ Li abundance compared to the result using the Wagoner rate, and hence the present rate even worsens the $^{7}$ Li problem. By the present estimation, the role of $^{7}$ Be( $n$ , $α$ ) $^{4}$ He in destroying $^{7}$ Be is weakened from the secondary importance to the third, and the $^{7}$ Be( $d$ , $p$ )2 $^{4}$ He reaction becomes of secondary importance in destructing $^{7}$ Be.
↳ astro-ph.COnucl-thPRC(2015)·55 citations

Affiliations

first authorsco-authorsvia INSPIRE

Lattice QCD Thermodynamics with Physical Quark Masses

Charmed-strange Meson Spectrum: Old and New Problems

Electroweak Corrections to the True Muonium Hyperfine Splitting

Photon structure functions at small x in holographic QCD

Charged charmonium-like structures and the initial single chiral particle emission mechanism

Slowly rotating superfluid neutron stars with isospin dependent entrainment in a two-fluid model

A revised thermonuclear rate of 7Be(n,α)4He relevant to Big-Bang nucleosynthesis

Affiliations

Photon structure functions at small $x$ in holographic QCD

A revised thermonuclear rate of $^{7}$ Be( $n$ , $α$ ) $^{4}$ He relevant to Big-Bang nucleosynthesis