Nuclear Theory·nucl-th

Monday·November 28, 2016

18 papers—7 primary·11 cross-listed

08
[Submitted on 22 Nov 2016] (cross-list from hep-ph)
Backward charmonium production in $π N$ collisions
B. Pire🇫🇷 · K. Semenov-Tian-Shansky🇷🇺 · L. Szymanowski🇵🇱
The QCD collinear factorization framework allows to describe exclusive backward production of a $J / ψ$ meson in pion-nucleon collisions in terms of pion-to-nucleon transition distribution amplitudes. We calculate the scattering amplitude at the leading order in the strong coupling constant and estimate the cross section of this reaction in the backward kinematical region for a medium energy pion beam available at the J-Parc experimental facility.
Comments:
15 pages, 5 figures. Substantially revised version. version 3 matches published version in Phys.Rev.D95, 034021
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1611.07234 [pdf]
PRD(2017)·13 citations
09
[Submitted on 23 Nov 2016] (cross-list from hep-th)
Renormalization Group Flow, Stability, and Bulk Viscosity in a Large N Thermal QCD Model
Keshav Dasgupta🇨🇦 · Maxim Emelin🇨🇦 · Charles Gale🇨🇦 · Michael Richard🇨🇦
The ultraviolet completion of a large N QCD model requires introducing new degrees of freedom at certain scale so that the UV behavior may become asymptotically conformal with no Landau poles and no UV divergences of Wilson loops. These UV degrees of freedom are represented by certain anti-branes arranged on the blown-up sphere of a warped resolved conifold in a way that they are separated from the other set of branes that control the IR behavior of the theory. This separation of the branes and the anti-branes creates instability in the theory. Further complications arise from the curvature of the ambient space. We show that, despite these analytical hurdles, stability may still be achieved by switching on appropriate world-volume fluxes on the branes. The UV degrees of freedom, on the other hand, modify the RG flow in the model. We discuss this in details by evaluating the flow from IR confining to UV conformal. Finally we lay down a calculational scheme to study bulk viscosity which, in turn, would signal the inherent non-conformality in this model.
Comments:
49 pages, 8 figures; v2: Section 4.4 expanded and the bulk viscosity computations made more precise, typos corrected and figure 4 replaced by its sharper image. Final version to appear in Physical Review D
Subjects:
High Energy Physics — Theory (hep-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1611.07998 [pdf]
PRD(2017)·3 citations
10
[Submitted on 24 Nov 2016] (cross-list from hep-ph)
Parity- and Time Reversal-Violating Pion Nucleon Couplings: Higher Order Chiral Matching Relations
Chien-Yeah Seng🇺🇸 · Michael Ramsey-Musolf🇺🇸
Parity- and time reversal-violating (PVTV) pion-nucleon couplings govern the magnitude of long-range contributions to nucleon and atomic electric dipole moments. When these couplings arise from chiral symmetry-breaking CP-violating operators, such as the QCD $θ$ -term or quark chromoelectric dipole moments, one may relate hadronic matrix elements entering the PVTV couplings to nucleon and pion mass shifts by exploiting the corresponding chiral transformation properties at leading order (LO) in the chiral expansion. We compute the higher-order contributions to the lowest order relations arising from chiral loops and next-to-next-to leading order (NNLO) operators. We find that for the QCD $θ$ -term the higher order contributions are analytic in the quark masses, while for the quark chromoelectric dipole moments and chiral symmetry-breaking four-quark operators, the matching relations also receive non-analytic corrections. Numerical estimates suggest that for the isoscalar PVTV pion-nucleon coupling, the higher order corrections may be as large as $\sim 20%$ , while for the isovector coupling, more substantial corrections are possible.
Comments:
50 pages, 2 figures, 4 tables
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1611.08063 [pdf]
PRC(2017)·20 citations
11
[Submitted on 24 Nov 2016] (cross-list from hep-lat)
Gauge cooling for the singular-drift problem in the complex Langevin method --- an application to finite density QCD
Keitaro Nagata🇯🇵 · Hideo Matsufuru🇯🇵 · Jun Nishimura🇯🇵 · Shinji Shimasaki🇯🇵
We study full QCD at finite density and low temperature with light quark mass using the complex Langevin method. Since the singular drift problem turns out to be mild on a $4^{3} \times 8$ lattice we use, the gauge cooling is performed only to control the unitarity norm in this exploratory study. We report on our preliminary data obtained from the complex Langevin simulation up to certain Langevin time. While the data are still noisy due to lack of statistics, the onset of the baryon number density seems to occur at larger $μ$ than half the pion mass, which is the value for the phase quenched QCD. The validity of our simulation is tested by the recently proposed criterion based on the probability distribution of the drift term.
Comments:
7 pages, 4 figures. Proceedings of the 34th International Symposium on Lattice Field Theory (Lattice 2016)
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1611.08077 [pdf]
PoS(2016)·17 citations
12
[Submitted on 24 Nov 2016] (cross-list from hep-ph)
Accessing Generalized Parton Distributions in Exclusive Photoproduction of a $γ ρ$ Pair with a Large Invariant Mass
R. Boussarie🇵🇱 · B. Pire🇫🇷 · L.Szymanowski🇵🇱 · S. Wallon🇫🇷
We propose and study the photoproduction of a $γ ρ$ pair with a large invariant mass and a small transverse momentum of the final nucleon, as a way to access generalized parton distributions. In the kinematics of JLab 12-GeV, we demonstrate the feasibility of this measurement.
Comments:
4 pages, 4 figures, proceedings of "Diffraction 2016", International Workshop on Diffraction in High-Energy Physics, Acireale (Catania, Sicily), Sept. 2-8, 2016; to be published in the conference proceedings by AIP. arXiv admin note: substantial text overlap with arXiv:1609.05144
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1611.08115 [pdf]
AIP Conf.Proc.(2017)·0 citations
13
[Submitted on 24 Nov 2016] (cross-list from hep-ph)
Influence of broken flavor and C and P symmetry on the quark propagator
Axel Maas🇦🇹 · Walid Ahmed Mian🇦🇹
Embedding QCD into the standard model breaks various symmetries of QCD explicitly, especially C and P. While these effects are usually perturbatively small, they can be amplified in extreme environments like merging neutron stars or by the interplay with new physics. To correctly treat these cases requires fully backcoupled calculations. To pave the way for later investigations of hadronic physics, we study the QCD quark propagator coupled to an explicit breaking. This substantially increases the tensor structure even for this simplest correlation function. To cope with the symmetry structure, and covering all possible quark masses, from the top quark mass to the chiral limit, we employ Dyson-Schwinger equations. While at weak breaking the qualitative effects have similar trends as in perturbation theory, even moderately strong breakings lead to qualitatively different effects, non-linearly amplified by the strong interactions.
Comments:
25 pages, 26 figures and 2 tables
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1611.08130 [pdf]
EPJA(2017)·2 citations
14
[Submitted on 24 Nov 2016] (cross-list from hep-ph)
Double quarkonium production at high Feynman- $x$
Sergey Koshkarev🇪🇪 · Stefan Groote🇪🇪
In this paper we give estimates for the proton--proton cross sections into pairs of quarkonium states $J / ψ$ , $ψ (2 S)$ , $Υ (1 S)$ and $Υ (2 S)$ at the scheduled AFTER@LHC energy of $115$ GeV. The estimates are based on the intrinsic heavy flavor mechanism which is observable for high values of $x_{F}$ , a range outside the dominance of single parton and double parton scattering.
Comments:
11 pages, 2 figures, version to be published
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1611.08149 [pdf]
NPB(2017)·6 citations
15
[Submitted on 25 Nov 2016] (cross-list from hep-ph)
Bulk viscous corrections to screening and damping in QCD at high temperatures
Qianqian Du🇨🇳 · Adrian Dumitru🇺🇸 · Yun Guo🇨🇳 · Michael Strickland🇺🇸
Non-equilibrium corrections to the distribution functions of quarks and gluons in a hot and dense QCD medium modify the "hard thermal loops" (HTL). The HTLs determine the retarded, advanced, and symmetric (time-ordered) propagators for gluons with soft momenta as well as the Debye screening and Landau damping mass scales. We compute such corrections to a thermal as well as to a non-thermal fixed point.The screening and damping mass scales are sensitive to the bulk pressure and hence to (pseudo-) critical dynamical scaling of the bulk viscosity in the vicinity of a second-order critical point. This could be reflected in the properties of quarkonium bound states in the deconfined phase and in the dynamics of soft gluon fields.
Comments:
19 pages. no figure, added corrections of quadratic order in the bulk pressure to the symmetric gluon self energy, to appear in JHEP
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1611.08379 [pdf]
JHEP(2017)·32 citations
16
[Submitted on 25 Nov 2016] (cross-list from hep-ph)
From $J / ψ$ to LHCb pentaquark
F. Fernández🇪🇸 · D. R. Entem🇪🇸 · P. G. Ortega🇪🇸 · J. Segovia🇩🇪
The original charmonium two-body problem, like the $c c ˉ$ structure of the $J / ψ$ meson, has become more involved in the last few years with the discovery of new resonances such as the tentative molecular state $X (3872)$ or the possible pentaquark one $P_{c} (4380)^{+}$ . We discuss herein how these exotic states (and others) can be described in a unified way adding higher Fock state components to the naive quark model picture. In particular, we present our theoretical results on the pentaquark states $P_{c} (4380)^{+}$ and $P_{c} (4450)^{+}$ , and on the new charmonium-like resonances $X (4140)$ , $X (4274)$ , $X (4500)$ and $X (4700)$ that have been reported in $2016$ by the LHCb Collaboration.
Comments:
Contribution to the proceedings of the 23rd European Conference on Few-Body Problems in Physics (EFB23). August 8-12, 2016. Aarhus, Denmark
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1611.08533 [pdf]
0 citations
17
[Submitted on 25 Nov 2016] (cross-list from hep-ph)
From $J / ψ$ to LHCb pentaquarks
F. Fernández🇪🇸 · D. R. Entem🇪🇸 · P. G. Ortega🇪🇸 · J. Segovia🇩🇪
The two exotic $P_{c}^{+} (4380)$ and $P_{c}^{+} (4450)$ discovered in $2015$ by the LHCb Collaboration, together with the four resonances $X (4140)$ , $X (4274)$ , $X (4500)$ and $X (4700)$ , reported in $2016$ by the same collaboration, are described in a constituent quark model which has been able to explain the properties of charmonium states from the $J / ψ$ to the $X (3872)$ . Using this model we found a $D ˉ Σ_{c}^{*}$ bound state with $J^{P} = \frac{3}{2}^{-}$ that may be identified with the $P_{c}^{+} (4380)$ . In the $D ˉ^{*} Σ_{c}$ channel we found three possible candidates for the $P_{c}^{+} (4450)$ with $J^{P} = \frac{1}{2}^{-}$ , $\frac{3}{2}^{-}$ and $\frac{3}{2}^{+}$ with almost degenerated energies. The $X (4140)$ resonance appears as a cusp in the $J / ψ ϕ$ channel due to the near coincidence of the $D_{s}^{\pm} D_{s}^{*\pm}$ and $J / ψ ϕ$ mass thresholds. The remaining three $X (4274)$ , $X (4500)$ and $X (4700)$ resonances appear as conventional charmonium states with quantum numbers $3^{3} P_{1}$ , $4^{3} P_{0}$ and $5^{3} P_{0}$ , respectively; and whose masses and widths are slightly modified due to their coupling with the corresponding closest meson-meson thresholds.
Comments:
Contribution to the proceedings of the VIII International Workshop on Charm Physics (CHARM2016). September 5-9, 2016. Bologna, Italy
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1611.08534 [pdf]
PoS(2016)·2 citations
18
[Submitted on 25 Nov 2016] (cross-list from physics.data-an)
Event Shape Sorting: selecting events with similar evolution
Boris Tomasik🇸🇰 · Renata Kopecna🇩🇪
We present novel method for the organisation of events. The method is based on comparing event-by-event histograms of a chosen quantity Q that is measured for each particle in every event. The events are organised in such a way that those with similar shape of the Q-histograms end-up placed close to each other. We apply the method on histograms of azimuthal angle of the produced hadrons in ultrarelativsitic nuclear collisions. By selecting events with similar azimuthal shape of their hadron distribution one chooses events which are likely that they underwent similar evolution from the initial state to the freeze-out. Such events can more easily be compared to theoretical simulations where all conditions can be controlled. We illustrate the method on data simulated by the AMPT model.
Comments:
6 pages, 4 figures, proceedings from XII Quark Confinement and the Hadron Spectrum, Thessaloniki, Grece, 28.8.2016-4.9.2016
Subjects:
Data Analysis, Statistics and Probability (physics.data-an); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1611.08575 [pdf]
EPJ Web Conf.(2017)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE