Nuclear Theory·nucl-th

Tuesday·August 18, 2015

16 papers—7 primary·9 cross-listed

08
[Submitted on 13 Aug 2015] (cross-list from hep-ph)
Intrinsic Fluctuations of the Proton Saturation Momentum Scale in High Multiplicity p+p Collisions
Larry McLerran🇺🇸 · Prithwish Tribedy🇺🇸
High multiplicity events in p+p collisions are studied using the theory of the Color Glass Condensate. We show that intrinsic fluctuations of the proton saturation momentum scale are needed in addition to the sub-nucleonic color charge fluctuations to explain the very high multiplicity tail of distributions in p+p collisions. The origin of such intrinsic fluctuations are presumably non-perturbative in nature. Classical Yang Mills simulations using the IP-Glasma model are performed to make quantitative estimations. We find that fluctuations as large as $O$ (1) of the average values of the saturation momentum scale can lead to rare high multiplicity events seen in p+p data at RHIC and LHC energies. Using the available data on multiplicity distributions we try to constrain the distribution of the proton saturation momentum scale and make predictions for the multiplicity distribution in 13 TeV p+p collisions.
Comments:
15 pages, 6 figures, new references and comments added, version published in Nucl Phys A
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1508.03292 [pdf]
NPA(2016)·66 citations
09
[Submitted on 15 Aug 2015] (cross-list from hep-ph)
Two-photon exchange correction in elastic unpolarized electron-proton scattering at small momentum transfer
O. Tomalak🇩🇪 · M. Vanderhaeghen (JGU Mainz)🇩🇪
We evaluate the two-photon exchange (TPE) correction to the unpolarized elastic electron-proton scattering at small momentum transfer $Q^{2}$ . We account for the inelastic intermediate states approximating the double virtual Compton scattering by the unpolarized forward virtual Compton scattering. The unpolarized proton structure functions are used as input for the numerical evaluation of the inelastic contribution. Our calculation reproduces the leading terms in the $Q^{2}$ expansion of the TPE correction and goes beyond this approximation by keeping the full $Q^{2}$ dependence of the proton structure functions. In the range of small momentum transfer, our result is in good agreement with the empirical TPE fit to existing data.
Comments:
37 pages, 11 figures, version published in Phys. Rev. D 93, 013023 (2016)
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1508.03759 [pdf]
PRD(2016)·51 citations
10
[Submitted on 15 Aug 2015] (cross-list from astro-ph.HE)
Making a soft relativistic mean-field equation of state stiffer at high density
K.A. Maslov · E.E. Kolomeitsev · D.N. Voskresensky
We study relativistic mean-field (RMF) models including nucleons interacting with scalar, vector and iso-vector mean fields and self- and cross- mean-field interaction terms. Usually, in such a models the magnitude of the scalar field increases monotonically with the nucleon density, and the nucleon effective mass decreases. We demonstrate that the latter quantity stops to decrease and the equation of state stiffens, provided the mean-field self-interaction potential rises sharply in a narrow vicinity of the values of mean fields corresponding to nucleon densities $n > n_{*} > n_{0}$ , where $n_{0}$ is the nuclear saturation density. As the result the limiting neutron star mass increases. This procedure offers a simple way to stiffen the equation of state at densities above $n_{*}$ without altering it at densities $n \leq n_{0}$ . The developed scheme allows an application to neutron stars of the RMF models, which are well fitted to finite nuclei but do not fulfill the experimental constraint on the limiting neutron star mass. The exemplary application of the method to the well-known FSUGold model allows us to increase the limiting neutron star mass from $1.72 M_{⊙}$ to $M \geq 2.01 M_{⊙}$ .
Comments:
5 pages, 4 figures, revised version accepted for publication
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
1508.03771 [pdf]
PRC(2015)·48 citations
11
[Submitted on 17 Aug 2015] (cross-list from hep-ph)
Pentaquarks from intrinsic charms in $Λ_{b}$ decays
Y.K. Hsiao🇹🇼 · C.Q. Geng🇨🇳
We study the three-body $Λ_{b}$ decays of $Λ_{b} \to J / ψ pM$ with $M = K^{-}$ and $π^{-}$ . The two new states $P_{c 1} \equiv P_{c} (4380)^{+}$ and $P_{c 2} \equiv P_{c} (4450)^{+}$ observed recently as the resonances in the $J / ψ p$ invariant mass spectrum of $Λ_{b} \to J / ψ p K^{-}$ can be identified to consist of five quarks, $uu d c c ˉ$ , being consistent with the existence of the pentaquark states. We argue that, in the doubly charmful $Λ_{b}$ decays of $Λ_{b} \to J / ψ p K^{-}$ through $b \to c c ˉ s$ , apart from those through the non-resonant $Λ_{b} \to p K^{-}$ and resonant $Λ_{b} \to Λ^{*} \to p K^{-}$ transitions, the third contribution with the non-factorizable effects is not the dominant part for the resonant $Λ_{b} \to K^{-} P_{c 1, c 2}, P_{c 1, c 2} \to J / ψ p$ processes, such that we propose that the $P_{c 1, c 2}$ productions are mainly from the charmless $Λ_{b}$ decays through $b \to u ˉ u s$ , in which the $c c ˉ$ content in $P_{c 1, c 2}$ arises from the intrinsic charms within the $Λ_{b}$ baryon. We hence predict the observables related to the branching ratios and the direct CP violating asymmetries to be $B (Λ_{b} \to π^{-} (P_{c 1, c 2} \to) J / ψ p) / B (Λ_{b} \to K^{-} (P_{c 1, c 2} \to) J / ψ p) = 0.8 \pm 0.1$ , $A_{C P} (Λ_{b} \to π^{-} (P_{c 1, c 2} \to) J / ψ p) = (- 3.9 \pm 0.2) %$ , and $A_{C P} (Λ_{b} \to K^{-} (P_{c 1, c 2} \to) J / ψ p) = (5.8 \pm 0.2) %$ , which can alleviate the inconsistency between the theoretical expectations from the three contributions in the doubly charmful $Λ_{b}$ decays and the observed data.
Comments:
10 pages, 2 figures, revised version accepted by PLB
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
1508.03910 [pdf]
PLB(2015)·30 citations
12
[Submitted on 17 Aug 2015] (cross-list from hep-ph)
Nontopological Soliton in the Polyakov Quark Meson Model
Jinshuang Jin🇨🇳 · Hong Mao🇨🇳
Within a mean field approximation, we study a nontopological soliton solution of the Polyakov quark-meson model in the presence of a fermionic vacuum term with two flavors at finite temperature and density. The profile of the effective potential exhibits a stable soliton solution below a critical temperature $T \leq T_{χ}^{c}$ for both the crossover and the first-order phase transitions, and these solutions are calculated here with appropriate boundary conditions. However, it is found that only if $T \leq T_{d}^{c}$ ,the energy of the soliton $M_{N}$ is less than the energy of the three free constituent quarks $3 M_{q}$ . As $T > T_{d}^{c}$ , there is an instant delocalization phase transition from hadron matter to quark matter. The phase diagram together with the location of a critical end point (CEP) has been obtained in $T$ and $μ$ plane. We notice that two critical temperatures always satisfy $T_{d}^{c} \leq T_{χ}^{c}$ . Finally, we present and compare the result of thermodynamic pressure at zero chemical potential with lattice data.
Comments:
17 pages, 9 figures, Accepted for publication in Physical Review C. arXiv admin note: text overlap with arXiv:1301.6227
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1508.03920 [pdf]
PRC(2016)·8 citations
13
[Submitted on 17 Aug 2015] (cross-list from physics.atom-ph)
Electric dipole moments of superheavy elements - A case study on copernicium
Laima Radžiūtė · Gediminas Gaigalas · Per Jönsson · Jacek Bieroń
The multiconfiguration Dirac-Hartree-Fock (MCDHF) method was employed to calculate atomic electric dipole moments (EDM) of the superheavy element copernicium (Cn, $Z = 112$ ). The EDM enhancement factors of Cn, here calculated for the first time, are about one order of magnitude larger than those of Hg. The exponential dependence of enhancement factors on atomic number $Z$ along group 12 of the periodic table was derived from the EDMs of the entire homolog series, $_{30}^{69}$ Zn, $_{148}^{111}$ Cd, $_{180}^{199}$ Hg, $_{112}^{285}$ Cn, and $_{162}^{482}$ Uhb. These results show that superheavy elements with sufficiently large half-lives are good candidates for EDM searches.
Comments:
10 pages, 3 figures
Subjects:
Atomic Physics (physics.atom-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1508.03974 [pdf]
PRA(2016)·8 citations
14
[Submitted on 17 Aug 2015] (cross-list from hep-ph)
The Pion-Cloud Contribution to the Electromagnetic Nucleon Form Factors
Daniel Kupelwieser🇦🇹 · Wolfgang Schweiger🇦🇹
We study the electromagnetic structure of the nucleon within a hybrid constituent-quark model that comprises, in addition to the $3 q$ valence component, also a $3 q$ + $π$ non-valence component. To this aim we employ a Poincaré-invariant multichannel formulation based on the point-form of relativistic quantum mechanics. With a simple 3-quark wave function for the bare nucleon, i.e. the $3 q$ -component, we obtain reasonable results for the nucleon form factors and predict the meson-cloud contribution to be significant only below $Q^{2} ≲ 0.5$ \,GeV $^{2}$ amounting to about 10\% for $Q^{2} \to 0$ , in accordance with the findings of other authors.
Comments:
Contribution presented by W. Schweiger at the 21st International Conference on Few-Body Problems in Physics, Chicago IL, May 18-22, 2015; 4 pages, 2 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1508.03991 [pdf]
EPJ Web Conf.(2016)·4 citations
15
[Submitted on 17 Aug 2015] (cross-list from hep-ph)
Vector meson spectral function and dilepton rate in the presence of strong entanglement effect between the chiral and the Polyakov loop dynamics
Chowdhury Aminul Islam🇮🇳 · Sarbani Majumder🇮🇳 · Munshi G. Mustafa🇮🇳
In this work we have re-explored our earlier study on the vector meson spectral function and its spectral property in the form of dilepton rate in a two-flavour Polyakov loop extended Nambu-Jona-Lasinio (PNJL) model in presence of a strong entanglement between the chiral and Polyakov loop dynamics. The entanglement considered here is generated through the four-quark scalar type interaction in which the coupling strength depends on the Polyakov loop and runs with temperature and chemical potential. The entanglement effect is also considered for the four-quark vector type interaction in the same manner. We observe that the entanglement effect relatively enhances the color degrees of freedom due to the running of the both scalar and vector couplings. This modifies the vector meson spectral function and thus the spectral property such as the dilepton production rate in low invariant mass also gets modified.
Comments:
12 Pages, 18 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1508.04061 [pdf]
PRD(2015)·7 citations
16
[Submitted on 17 Aug 2015] (cross-list from cond-mat.supr-con)
Superconductivity and Superfluidity as Universal Emergent Phenomena
Mike Guidry · Yang Sun
Superconductivity (SC) or superfluidity (SF) is observed across a remarkably broad range of fermionic systems: in BCS, cuprate, iron-based, organic, and heavy-fermion superconductors, and superfluid helium-3 in condensed matter; in a variety of SC/SF phenomena in low-energy nuclear physics; in ultracold, trapped atomic gases; and in various exotic possibilities in neutron stars. The range of physical conditions and differences in microscopic physics defy all attempts to unify this behavior in any conventional picture. Here we propose a unification through the shared symmetry properties of the emergent condensed states, with microscopic differences absorbed into parameters. This, in turn, forces a rethinking of specific occurrences of SC/SF such as cuprate high-temperature superconductivity, which becomes far less mysterious when seen as part of a continuum of behavior shared by a variety of other systems.
Subjects:
Superconductivity (cond-mat.supr-con); Strongly Correlated Electrons (cond-mat.str-el); Nuclear Theory (nucl-th)
arXiv:
1508.04092 [pdf]
Front.Phys.(Beijing)(2015)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE