Nuclear Theory·nucl-th

Thursday·June 20, 2019

9 papers—5 primary·4 cross-listed

06
[Submitted on 18 Jun 2019] (cross-list from hep-ph)
QCD evolution of the orbital angular momentum of quarks and gluons: Genuine twist-three part
Yoshitaka Hatta🇺🇸 · Xiaojun Yao🇺🇸
We present the numerical solution of the one-loop QCD evolution equation for the genuine twist-three part of the orbital angular momentum (OAM) distributions of quarks and gluons inside a longitudinally polarized nucleon. This is based on the observation that the evolution is identical to that of the Efremov-Teryaev-Qiu-Sterman function for transverse single spin asymmetry. Together with the known evolution of the Wandzura-Wilczek part, the one-loop evolution of OAM distributions is now practically under control. We also study, for the first time, the scale dependence of the potential angular momentum defined as the difference between the Ji and Jaffe-Manohar definitions of OAM.
Comments:
12 pages, 5 figures; minor changes;
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1906.07744 [pdf]
PLB(2019)·14 citations
07
[Submitted on 18 Jun 2019] (cross-list from hep-th)
Nonlinear Langevin dynamics via holography
Bidisha Chakrabarty🇮🇳 · Joydeep Chakravarty🇮🇳 · Soumyadeep Chaudhuri🇮🇳 · Chandan Jana🇮🇳 · R. Loganayagam🇮🇳 · Akhil Sivakumar🇮🇳
In this work, we consider non-linear corrections to the Langevin effective theory of a heavy quark moving through a strongly coupled CFT plasma. In AdS/CFT, this system can be identified with that of a string stretched between the boundary and the horizon of an asymptotically AdS black-brane solution. We compute the Feynman-Vernon influence phase for the heavy quark by evaluating the Nambu-Goto action on a doubled string configuration. This configuration is the linearised solution of the string motion in the doubled black-brane geometry which has been proposed as the holographic dual of a thermal Schwinger-Keldysh contour of the CFT. Our expression for the influence phase passes non-trivial consistency conditions arising from the underlying unitarity and thermality of the bath. The local effective theory obeys the recently proposed non-linear fluctuation dissipation theorem relating the non-Gaussianity of thermal noise to the thermal jitter in the damping constant. This furnishes a non-trivial check for the validity of these relations derived in the weak coupling regime.
Comments:
31 pages + appendices. Minor revision added on integrating out ghost fields in the path integral
Subjects:
High Energy Physics — Theory (hep-th); Statistical Mechanics (cond-mat.stat-mech); Nuclear Theory (nucl-th)
arXiv:
1906.07762 [pdf]
JHEP(2020)·63 citations
08
[Submitted on 19 Jun 2019] (cross-list from hep-ph)
Visible narrow cusp structure in $Λ_{c}^{+} \to p K^{-} π^{+}$ enhanced by triangle singularity
Xiao-Hai Liu · Gang Li🇨🇳 · Ju-Jun Xie🇨🇳 · Qiang Zhao🇨🇳
A resonance-like structure as narrow as 10 MeV is observed in the $K^{-} p$ invariant mass distributions in $Λ_{c}^{+} \to p K^{-} π^{+}$ at Belle. Based on the large data sample of about 1.5 million events and the small bin width of just 1 MeV for the $K^{-} p$ invariant mass spectrum, the narrow peak is found precisely lying at the $Λ η$ threshold. While lacking evidence for a quark model state with such a narrow width at this mass region, we find that this narrow structure can be naturally identified as a threshold cusp but enhanced by the nearby triangle singularity via the $Λ$ - $a_{0} (980)^{+}$ or $η$ - $Σ (1660)^{+}$ rescatterings.
Comments:
6 pages, 4 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1906.07942 [pdf]
PRD(2019)·35 citations
09
[Submitted on 17 Jun 2019] (cross-list from hep-lat)
Possible New Phase of Thermal QCD
Andrei Alexandru🇺🇸 · Ivan Horváth🇺🇸
Using lattice simulations, we show that there is a phase of thermal QCD, where the spectral density $ρ (λ)$ of Dirac operator changes as $1/ λ$ for the infrared eigenvalues $λ < T$ . This behavior persists over the entire low energy band we can resolve accurately, over three orders of magnitude on our largest volumes. We propose that in this "IR phase", the well-known non-interacting scale invariance at very short distances (UV, $λ \to \infty$ , asymptotic freedom), coexists with very different interacting type of scale invariance at long distances (IR, $λ < T$ ). Such dynamics may be responsible for the unusual fluidity properties of the medium observed at RHIC and LHC. We point out its connection to the physics of Banks-Zaks fixed point, leading to the possibility of massless glueballs in the fluid. Our results lead to the classification of thermal QCD phases in terms of IR scale invariance. The ensuing picture naturally subsumes the standard chiral crossover feature at $" T_{c} " \approx 155$ MeV. Its crucial new aspect is the existence of temperature $T_{I R}$ (200 MeV $< T_{I R} <$ 250 MeV) marking the onset of IR phase and possibly a true phase transition.
Comments:
18 pages, 7 figures; v2: 19 pages, 7 figures, few presentation improvements, published version
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1906.08047 [pdf]
PRD(2019)·64 citations

Affiliations

first authorsco-authorsvia INSPIRE

QCD evolution of the orbital angular momentum of quarks and gluons: Genuine twist-three part

Nonlinear Langevin dynamics via holography

Visible narrow cusp structure in Λc+​→pK−π+ enhanced by triangle singularity

Possible New Phase of Thermal QCD

Affiliations

Visible narrow cusp structure in $Λ_{c}^{+} \to p K^{-} π^{+}$ enhanced by triangle singularity