Nuclear Theory·nucl-th

Tuesday·March 28, 2017

16 papers—8 primary·8 cross-listed

09
[Submitted on 25 Mar 2017] (cross-list from hep-lat)
Matching issue in quasi parton distribution approach
Tomomi Ishikawa🇨🇳 · Yan-Qing Ma🇨🇳 · Jian-Wei Qiu🇺🇸 · Shinsuke Yoshida🇺🇸
In recent years, the quasi parton distribution has been introduced for extracting the parton distribution functions from lattice QCD simulations. The quasi and standard distribution share the same perturbative collinear singularity and the renormalized quasi distribution can be factorized into the standard distribution with a perturbative matching factor. The quasi parton distribution is known to have power-law UV divergences, which do not exist in the standard distribution. We discuss in this talk the nonperturbative renormalization scheme for the power divergence. We also demonstrate the perturbative matching of the quasi quark distribution between continuum and lattice at the one-loop.
Comments:
7 pages, 2 figures, talk presented at the 34th annual International Symposium on Lattice Field Theory (Lattice 2016), 24-30 July 2016, University of Southampton, UK
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1703.08699 [pdf]
PoS(2016)·4 citations
10
[Submitted on 26 Mar 2017] (cross-list from hep-lat)
Nucleon scalar and tensor charges using lattice QCD simulations at the physical value of the pion mass
C. Alexandrou (1, 2)🇨🇾 · M. Constantinou (3)🇺🇸 · P. Dimopoulos (4)🇮🇹 · R. Frezzotti (Rome Tor Vergata)🇮🇹 · K. Hadjiyiannakou (2)🇨🇾 · K. Jansen (5)🇩🇪 · C. Kallidonis (2)🇨🇾 · B. Kostrzewa (6)🇩🇪 · G. Koutsou (2)🇨🇾 · M. Mangin-Brinet (7)🇫🇷 · A. Vaquero Avilès-Casco (8)🇺🇸 · U. Wenger (9) ((1) Univ. of Cyprus, (2) The Cyprus Inst., (3) Temple Univ., (4) Centro Fermi & Rome Tor Vergata, (5) DESY-Zeuthen, (6) Bonn Univ., (7) Grenoble, (8) Univ. of Utah, (9) Univ. of Bern)🇨🇭
We present results on the light, strange and charm nucleon scalar and tensor charges from lattice QCD, using simulations with $N_{f} = 2$ flavors of twisted mass Clover-improved fermions with a physical value of the pion mass. Both connected and disconnected contributions are included, enabling us to extract the isoscalar, strange and charm charges for the first time directly at the physical point. Furthermore, the renormalization is computed non-perturbatively for both isovector and isoscalar quantities. We investigate excited state effects by analyzing several sink-source time separations and by employing a set of methods to probe ground state dominance. Our final results for the scalar charges are $g_{S}^{u} = 5.20 (42) (15) (12)$ , $g_{S}^{d} = 4.27 (26) (15) (12)$ , $g_{S}^{s} = 0.33 (7) (1) (4)$ , $g_{S}^{c} = 0.062 (13) (3) (5)$ and for the tensor charges $g_{T}^{u} = 0.782 (16) (2) (13)$ , $g_{T}^{d} = - 0.219 (10) (2) (13)$ , $g_{T}^{s} = - 0.00319 (69) (2) (22)$ , $g_{T}^{c} = - 0.00263 (269) (2) (37)$ in the $MS$ scheme at 2~GeV. The first error is statistical, the second is the systematic error due to the renormalization and the third the systematic arising from possible contamination due to the excited states.
Comments:
20 pages and 13 figures
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1703.08788 [pdf]
PRD(2017)·78 citations
11
[Submitted on 27 Mar 2017] (cross-list from hep-ph)
Variational path-integral approach to back-reactions of composite mesons in the Nambu-Jona-Lasinio model
D. Blaschke🇷🇺 · D. Ebert🇩🇪
For the investigation of back-reactions of composite mesons in the NJL model, a variational path-integral treatment is formulated which yields an effective action $A_{eff} [D_{σ}, D_{π}; S]$ , depending on the propagators $D_{σ}$ , $D_{π}$ of $σ -$ and $π -$ mesons and on the full quark propagator $S$ . The stationarity conditions $δ A_{eff} / δ S = 0$ , $δ A_{eff} / δ D_{σ} = 0$ , $δ A_{eff} / δ D_{π} = 0$ , then lead to coupled Schwinger-Dyson (SD) equations for the quark self-energy and the meson polarization functions. These results reproduce and extend results of the so-called " $Φ -$ derivable" approach and provide a functional formulation for diagrammatic resummations of $1/ N_{c} -$ corrections in the NJL model. Finally, we perform a low-momentum estimate of the quark and meson loop contributions to the polarization function of the pion and on this basis discuss the Goldstone theorem.
Comments:
21 pages, 3 figures, minor text corrections, 2 references added, version published in Nucl. Phys. B
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1703.08964 [pdf]
NPB(2017)·8 citations
12
[Submitted on 27 Mar 2017] (cross-list from hep-ph)
Corona effect in AA collisions at LHC
V.S. Pantuev🇷🇺
Following our earlier finding based on RHIC data on the dominant jet production from nucleus corona region, we reconsider this effect in nucleus-nucleus collisions at LHC energy. Our hypothesis was based on experimental data, which raised the idea of a finite formation time for the produced medium. At RHIC energy and in low density corona region this time reaches about 2 fm/c. All observed high p_t particles are produced in the corona region and have a chance to escape during this 2 fm/c. After that, the formed high density matter absorbs all jets. Following this hypothesis, the nuclear modification factor R_{AA} should be independent on particle momentum and be flat versus p_t. At the same time, we describe the finite azimuthal anisotropy of high p_t particles, v_2. A separate prediction held that, at LHC energy, the formation time in the corona region should be two times smaller, about 1 fm/c. New data at LHC show that R_{AA} is not flat and is rising with p_t. We add to our original hypothesis an assumption that a fast parton traversing the produced medium loses the fixed portion of its energy. A shift of about 7 GeV (I would call it as a parton binding energy) from the original power law p^{-6} production cross section in pp explains well all the observed R_{AA} dependencies. The shift of about 7 GeV is also valid at RHIC energy, where the cross section follows a power law with about p^{-8} and this shift explains a very slow rise of R_{AA} seen for neutral pions with p_t above 15 GeV/c. We also show that the observed at LHC dependence of v_2 at high p_t and our previous predictions agree.
Comments:
Published version, 4 pages, 5 figures. Only on-line abstract changed by adding notation "parton binding energy"
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1703.09021 [pdf]
JETP Lett.(2017)·0 citations
13
[Submitted on 27 Mar 2017] (cross-list from hep-ph)
Generating a resonance-like structure in the reaction $B_{c} \to B_{s} π π$
Xiao-Hai Liu🇩🇪 · Ulf-G. Meißner🇩🇪
We investigate the process $B_{c}^{+} \to B_{s}^{0} π^{+} π^{0}$ via $B K ˉ^{*}$ rescattering. The kinematic conditions for triangle singularities are perfectly satisfied in the rescattering diagrams. A resonance-like structure around the $B K ˉ$ threshold, which we denote as $X (5777)$ , is predicted to be present in the invariant mass distribution of $B_{s}^{0} π^{+}$ . Because the relative weak $B K ˉ$ $(I = 1)$ interaction does not support the existence of a dynamically generated hadronic molecule, the $X (5777)$ can be identified as a pure kinematical effect due to the triangle singularity. Its observation may help to establish a non-resonance interpretation for some $X Y Z$ particles.
Comments:
5 pages, 3 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
1703.09043 [pdf]
EPJC(2017)·25 citations
14
[Submitted on 27 Mar 2017] (cross-list from nucl-ex)
Cumulants of event-by-event net-strangeness distributions in Au+Au collisions at $s_{NN}$ =7.7-200 GeV from UrQMD model
Chang Zhou🇨🇳 · Ji Xu🇨🇳 · Xiaofeng Luo🇨🇳 · Feng Liu🇨🇳
Fluctuations of conserved quantities, such as baryon, electric charge and strangeness number, are sensitive observables in heavy-ion collisions to search for the QCD phase transition and critical point. In this paper, we performed a systematical analysis on the various cumulants and cumulant ratios of event-by-event net-strangeness distributions in Au+Au collisions at $s_{N N}$ =7.7, 11.5, 19.6, 27, 39, 62.4 and 200 GeV from UrQMD model. We performed a systematical study on the contributions from various strange baryons and mesons to the net-strangeness fluctuations. The results demonstrate that the cumulants and cumulant ratios of net-strangeness distributions extracted from different strange particles show very different centrality and energy dependence behavior. By comparing with the net-kaon fluctuations, we found that the strange baryons play an important role in the fluctuations of net-strangeness. This study can provide useful baselines to study the QCD phase transition and search for the QCD critical point by using the fluctuations of net-strangeness in heavy-ion collisions experiment. It can help us to understand non-critical physics contributions to the fluctuations of net-strangeness.
Comments:
8 pages, 8 figures
Subjects:
Nuclear Experiment (nucl-ex); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1703.09114 [pdf]
PRC(2017)·28 citations
15
[Submitted on 27 Mar 2017] (cross-list from cond-mat.str-el)
Bound states of skyrmions and merons near the Lifshitz point
Y. A. Kharkov🇦🇺 · O. P. Sushkov🇦🇺 · M. Mostovoy🇳🇱
We study topological defects in anisotropic ferromagnets with competing interactions near the Lifshitz point. We show that skyrmions and bi-merons are stable in a large part of the phase diagram. We calculate skyrmion-skyrmion and meron-meron interactions and show that skyrmions attract each other and form ring-shaped bound states in a zero magnetic field. At the Lifshitz point merons carrying a fractional topological charge become deconfined. These results imply that unusual topological excitations may exist in weakly frustrated magnets with conventional crystal lattices.
Comments:
5 pages, 4 figures
Subjects:
Strongly Correlated Electrons (cond-mat.str-el); nlin.PS (nlin.PS); Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
arXiv:
1703.09173 [pdf]
PRL(2017)·36 citations
16
[Submitted on 27 Mar 2017] (cross-list from hep-ph)
Charmed mesons with a symmetry-preserving contact interaction
Fernando E. Serna🇧🇷 · Bruno El-Bennich🇧🇷 · Gastão Krein🇧🇷
A symmetry-preserving treatment of a vector-vector contact interaction is used to study charmed heavy-light mesons. The contact interaction is a representation of nonperturbative kernels used in Dyson-Schwinger and Bethe-Salpeter equations of QCD. The Dyson-Schwinger equation is solved for the $u, d, s$ and $c$ quark propagators and the bound-state Bethe-Salpeter amplitudes respecting spacetime-translation invariance and the Ward-Green-Takahashi identities associated with global symmetries of QCD are obtained to calculate masses and electroweak decay constants of the pseudoscalar $π, K$ , $D$ and $D_{s}$ and vector $ρ$ , $K^{*}$ , $D^{*}$ , and $D_{s}^{*}$ mesons. The predictions of the model are in good agreement with available experimental and lattice QCD data.
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1703.09181 [pdf]
PRD(2017)·57 citations

Affiliations

first authorsco-authorsvia INSPIRE