Nuclear Theory·nucl-th

Thursday·July 30, 2015

10 papers—3 primary·7 cross-listed

04
Deep inelastic scattering cross sections from the gauge/string duality
Ezequiel Koile🇦🇷 · Nicolas Kovensky🇦🇷 · Martin Schvellinger🇦🇷
Differential cross sections of deep inelastic scattering of charged leptons from hadrons are investigated by using the gauge/string duality. We consider vector mesons derived from different holographic dual models obtaining a general expression. We focus on the strongly coupled regime of dual gauge theories for different values of the Bjorken parameter. We find new predictions which are particularly interesting for differential scattering cross sections of polarized leptons scattered off polarized vector mesons. We also carry out a detailed comparison of the moments of the structure functions with lattice QCD results.
↳ hep-thhep-lathep-phnucl-thJHEP(2015)·21 citations
05
Unraveling the pattern of the $X Y Z$ mesons
J. Vijande🇪🇸 · A. Valcarce🇪🇸
We present a plausible mechanism for the origin of the $X Y Z$ mesons in the heavy meson spectra within a standard quark-model picture. We discuss the conditions required for the existence of four--quark bound states or resonances contributing to the heavy meson spectra, being either compact or molecular. We concentrate on charmonium and bottomonium spectra, where several new states, difficult to understand as simple quark-antiquark pairs, have been reported by different experimental collaborations. The pivotal role played by entangled meson-meson thresholds is emphasized.
↳ hep-phnucl-thPLB(2014)·19 citations
06
Multiquark contributions to charm baryon spectroscopy
T.F. Carames🇪🇸 · A. Valcarce🇪🇸
We study possible multiquark contributions to the charm baryon spectrum by considering higher order Fock space components. For this purpose we perform two different calculations. In a first approach we do a coupled-channel calculation of the $N D$ system looking for molecular states. In a second step we allow for the coupling to a heavy baryon--light meson two-hadron system looking for compact exotic five--quark structures. Both calculations have been done within the framework of a chiral constituent quark model. The model, tuned in the description of the baryon and meson spectra as well as the $N N$ interaction, provides parameter-free predictions for charm $+ 1$ molecular or compact two-hadron systems. Unlike the $N D ˉ$ system, no sharp quark-Pauli effects are found. However, the existence of different two-hadron thresholds for the five-quark system will make the coupled-channel dynamics relevant. Only a few channels are candidates to lodge molecular or compact hadrons with a five-quark structure, being specially relevant the $(T) J^{P} = (0) 1/ 2^{-}$ and $(T) J^{P} = (2) 5/ 2^{-}$ channels. The identification of molecular states and/or compact hadrons with multiquark components either with or without exotic quantum numbers is a challenge of different collaborations like $P ˉ$ ANDA, LHCb, ExHIC or J-PARC.
↳ hep-phnucl-thPRD(2014)·10 citations
07
Nonexistence of a $Λ nn$ bound state
H. Garcilazo · A. Valcarce
It has been recently suggested the existence of a neutral bound state of two neutrons and a $Λ$ hyperon, $_{Λ}^{3} n$ . We point out that using either simple separable potentials or a full-fledged calculation with realistic baryon-baryon interactions derived from the constituent quark cluster model there is no possibility for the existence of such a $Λ nn$ bound state. For this purpose, we performed a full Faddeev calculation of the $Λ nn$ system in the $(I, J^{P}) = (1, 1/ 2^{+})$ channel using the interactions derived from the constituent quark cluster model which describe well the two-body $N N$ and $N Y$ data and the $Λ n p$ hypertriton.
↳ nucl-thhep-phPRC(2014)·55 citations
08
Spontaneous mass generation and the small dimensions of the Standard Model gauge groups U(1), SU(2) and SU(3)
Guillermo Garcia Fernandez🇪🇸 · Jesus Guerrero Rojas🇪🇸 · Felipe J. Llanes-Estrada (U. Complutense Madrid)🇪🇸
The gauge symmetry of the Standard Model is SU(3)_c x SU(2)_L x U(1)_Y for unknown reasons. One aspect that can be addressed is the low dimensionality of all its subgroups. Why not much larger groups like SU(7), or for that matter, SP(38) or E7? We observe that fermions charged under large groups acquire much bigger dynamical masses, all things being equal at a high e.g. GUT scale, than ordinary quarks. Should such multicharged fermions exist, they are too heavy to be observed today and have either decayed early on (if they couple to the rest of the Standard Model) or become reliquial dark matter (if they don't). The result follows from strong antiscreening of the running coupling for those larger groups (with an appropriately small number of flavors) together with scaling properties of the Dyson-Schwinger equation for the fermion mass.
↳ hep-phhep-thnucl-thNPB(2017)·7 citations
09
Dark Compact Planets
Laura Tolos🇩🇪 · Juergen Schaffner-Bielich🇩🇪 · Yannick Dengler
We investigate compact objects formed by dark matter admixed with ordinary matter made of neutron star matter and white dwarf material. We consider non-self annihilating dark matter with an equation-of-state given by an interacting Fermi gas. We find new stable solutions, dark compact planets, with Earth-like masses or lower and radii about one meter for weakly interacting dark matter. For the strongly interacting dark matter case, we obtain dark compact planets with Jupiter-like masses or lower and radii of a kilometer. These objects could be formed primordially and accrete white dwarf material subsequently. They could be detected by observing exoplanets with unusually small radii. Moreover, we find that the recently observed 2 $M_{⊙}$ pulsars set limits on the amount of dark matter inside neutron stars which is, at most, $1 0^{- 5} M_{⊙}$ .
↳ astro-ph.HEhep-phnucl-thPRD(2015)·97 citations
10
Numerical study of the unitary Fermi gas across the superfluid transition
Olga Goulko🇺🇸 · Matthew Wingate🇬🇧
We present results from Monte Carlo calculations investigating the properties of the homogeneous, spin-balanced unitary Fermi gas in three dimensions. The temperature is varied across the superfluid transition allowing us to determine the temperature dependence of the chemical potential, the energy per particle and the contact density. Numerical artifacts due to finite volume and discretization are systematically studied, estimated, and reduced.
↳ cond-mat.quant-gashep-latnucl-thPRA(2016)·14 citations

Affiliations

first authorsco-authorsvia INSPIRE

Deep inelastic scattering cross sections from the gauge/string duality

Unraveling the pattern of the XYZ mesons

Multiquark contributions to charm baryon spectroscopy

Nonexistence of a Λnn bound state

Spontaneous mass generation and the small dimensions of the Standard Model gauge groups U(1), SU(2) and SU(3)

Dark Compact Planets

Numerical study of the unitary Fermi gas across the superfluid transition

Affiliations

Unraveling the pattern of the $X Y Z$ mesons

Nonexistence of a $Λ nn$ bound state