Nuclear Theory·nucl-th

Wednesday·August 30, 2017

10 papers—4 primary·6 cross-listed

05
Nucleon Axial Radius and Muonic Hydrogen - A New Analysis and Review
Richard J. Hill🇺🇸 · Peter Kammel🇺🇸 · William J. Marciano🇺🇸 · Alberto Sirlin🇺🇸
Weak capture in muonic hydrogen ( $μ$ H) as a probe of the chiral properties and nucleon structure predictions of Quantum Chromodynamics (QCD) is reviewed. A recent determination of the axial-vector charge radius squared, $r_{A}^{2} (z exp.) = 0.46 (22) fm^{2}$ , from a model independent $z$ expansion analysis of neutrino-nucleon scattering data is employed in conjunction with the MuCap measurement of the singlet muonic hydrogen capture rate, $Λ_{singlet}^{MuCap} = 715.6 (7.4) s^{- 1}$ , to update the induced pseudoscalar nucleon coupling: $g ˉ_{P}^{MuCap} = 8.23 (83)$ derived from experiment, and $g ˉ_{P}^{theory} = 8.25 (25)$ predicted by chiral perturbation theory. Accounting for correlated errors this implies $g ˉ_{P}^{theory} / g ˉ_{P}^{MuCap} = 1.00 (8)$ , confirming theory at the 8% level. If instead, the predicted expression for $g ˉ_{P}^{theory}$ is employed as input, then the capture rate alone determines $r_{A}^{2} (μ H) = 0.46 (24) fm^{2}$ , or together with the independent $z$ expansion neutrino scattering results, a weighted average $r_{A}^{2} (ave.) = 0.46 (16) fm^{2}$ . Sources of theoretical uncertainty are critically examined and potential experimental improvements are described that can reduce the capture rate error by about a factor of 3. Muonic hydrogen can thus provide a precise and independent $r_{A}^{2}$ value which may be compared with other determinations, such as ongoing lattice gauge theory calculations. The importance of an improved $r_{A}^{2}$ determination for phenomenology is illustrated by considering the impact on critical neutrino-nucleus cross sections at neutrino oscillation experiments.
↳ hep-phhep-latnucl-exnucl-thRept.Prog.Phys.(2018)·85 citations
06
Determination of electric dipole transitions in heavy quarkonia using potential non-relativistic QCD
Jorge Segovia🇩🇪 · Sebastian Steinbeißer🇩🇪
The electric dipole transitions $χ_{b J} (1 P) \to γ Υ (1 S)$ with $J = 0, 1, 2$ and $h_{b} (1 P) \to γ η_{b} (1 S)$ are computed using the weak-coupling version of a low-energy effective field theory named potential non-relativistic QCD (pNRQCD). In order to improve convergence and thus give firm predictions for the studied reactions, the full static potential is incorporated into the leading order Hamiltonian; moreover, we must handle properly renormalon effects and re-summation of large logarithms. The precision we reach is $k_{γ}^{3} / (m v)^{2} \times O (v^{2})$ , where $k_{γ}$ is the photon energy, $m$ is the mass of the heavy quark and $v$ its velocity. Our analysis separates those relativistic contributions that account for the electromagnetic interaction terms in the pNRQCD Lagrangian which are $v^{2}$ suppressed and those that account for wave function corrections of relative order $v^{2}$ . Among the last ones, corrections from $1/ m$ and $1/ m^{2}$ potentials are computed, but not those coming from higher Fock states since they demand non-perturbative input and are $Λ_{QCD}^{2} / (m v)^{2}$ or $Λ_{QCD}^{3} / (m^{3} v^{4})$ suppressed, at least, in the strict weak coupling regime. These proceedings are based on the forthcoming publication \cite{steinbeisser}
↳ hep-phhep-exhep-latnucl-thJ.Phys.Conf.Ser.(2018)·1 citation
07
Linearly polarized gluons and axial charge fluctuations in the Glasma
T. Lappi🇫🇮 · S. Schlichting🇺🇸
We calculate of the one- and two-point correlation functions of the energy density and the divergence of the Chern-Simons current in the nonequilibrium Glasma state formed in a high-energy nuclear collision. We show that the latter depends on the difference of the total and linearly polarized gluon transverse momentum distributions. Since the divergence of the Chern-Simons current provides the source of axial charge, we infer information about the statistical properties of axial charge production at early times. We further develop a simple phenomenological model to characterize axial charge distributions in terms of distributions of the energy density.
↳ hep-phnucl-thPRD(2018)·68 citations
08
The Equation of State for the Nucleonic and Hyperonic Core of Neutron Stars
Laura Tolos🇪🇸 · Mario Centelles🇪🇸 · Angels Ramos🇪🇸
We reexamine the equation of state for the nucleonic and hyperonic inner core of neutron stars that satisfies the 2 $M_{⊙}$ observations as well as the recent determinations of stellar radii below 13 km, while fulfilling the saturation properties of nuclear matter and finite nuclei together with the constraints on the high-density nuclear pressure coming from heavy-ion collisions. The recent nucleonic FSU2R and hyperonic FSU2H models are fine tuned improving the density dependence of pure neutron matter at subsaturation densities. The corresponding nuclear matter properties at saturation, the symmetry energy and its slope turn out to be compatible with recent experimental and theoretical determinations. We obtain the mass, radius and composition of neutron stars for the two updated models and study the impact on these properties of the uncertainties in the hyperon-nucleon couplings estimated from hypernuclear data. We find that the onset of appearance of each hyperon strongly depends on the hyperon-nuclear uncertainties, whereas the maximum masses for neutron stars differ by at most 0.1 $M_{⊙}$ , although a larger deviation should be expected tied to the lack of knowledge of the hyperon potentials at the high densities present in the center of $2 M_{⊙}$ stars. For easier use, we provide tables with the results from the FSU2R and FSU2H models for the equation of state and the neutron star mass-radius relation.
↳ astro-ph.HEnucl-thPubl.Astron.Soc.Austral.·113 citations
09
Isothermal compressibility of hadronic matter formed in relativistic nuclear collisions
Maitreyee Mukherjee🇮🇳 · Sumit Basu🇺🇸 · Arghya Chatterjee🇮🇳 · Sandeep Chatterjee🇵🇱 · Souvik Priyam Adhya🇮🇳 · Sanchari Thakur🇮🇳 · Tapan K. Nayak🇮🇳
We present the first estimates of isothermal compressibility (\kT) of hadronic matter formed in relativistic nuclear collisions ( $s_{NN} = 7.7$ GeV to 2.76~TeV) using experimentally observed quantities. \kT~is related to the fluctuation in particle multiplicity, temperature, and volume of the system formed in the collisions. Multiplicity fluctuations are obtained from the event-by-event distributions of charged particle multiplicities in narrow centrality bins. The dynamical components of the fluctuations are extracted by removing the contributions to the fluctuations from the number of participating nucleons. From the available experimental data, a constant value of \kT~has been observed as a function of collision energy. The results are compared with calculations from UrQMD, AMPT, and EPOS event generators, and estimations of \kT~are made for Pb-Pb collisions at the CERN Large Hadron Collider. A hadron resonance gas (HRG) model has been used to calculate \kT~as a function of collision energy. Our results show a decrease in \kT~at low collision energies to \sNN~ $\sim$ ~20~GeV, beyond which the \kT~values remain almost constant.
↳ nucl-exhep-exhep-phnucl-thPLB(2018)·23 citations
10
Heavy and heavy-light mesons and the Lorentz structure of the quark-antiquark interaction
Sofia Leitão🇵🇹 · Alfred Stadler🇵🇹 · M. T. Peña🇵🇹 · Elmar P. Biernat🇵🇹
We solve a Minkowski-space integral equation, derived in the Covariant Spectator Theory, for quark-antiquark bound states describing heavy and heavy-light mesons. The equation's kernel contains a one-gluon exchange interaction and a covariant generalization of a linear confining potential with a mixed scalar, pseudoscalar, and vector Lorentz structure, characterized by a continuous mixing parameter. We investigate to what extent the Lorentz structure of the confining kernel can be determined by fitting the mixing parameter to the meson spectrum.
↳ hep-phnucl-thActa Phys.Polon.Supp.(2017)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE

Nucleon Axial Radius and Muonic Hydrogen - A New Analysis and Review

Determination of electric dipole transitions in heavy quarkonia using potential non-relativistic QCD

Linearly polarized gluons and axial charge fluctuations in the Glasma

The Equation of State for the Nucleonic and Hyperonic Core of Neutron Stars

Isothermal compressibility of hadronic matter formed in relativistic nuclear collisions

Heavy and heavy-light mesons and the Lorentz structure of the quark-antiquark interaction

Affiliations