Nuclear Theory·nucl-th

Wednesday·February 21, 2018

12 papers—7 primary·5 cross-listed

08
[Submitted on 17 Feb 2018] (cross-list from hep-ph)
Disentangling covariant Wigner functions for chiral fermions
Jian-Hua Gao🇨🇳 · Zuo-Tang Liang🇨🇳 · Qun Wang🇨🇳 · Xin-Nian Wang🇨🇳
We develop a general formalism for the quantum kinetics of chiral fermions in a background electromagnetic field based on a semiclassical expansion of covariant Wigner functions in the Planck constant $ℏ$ . We demonstrate to any order of $ℏ$ that only the time-component of the Wigner function is independent while other components are explicit derivative. We further demonstrate to any order of $ℏ$ that a system of quantum kinetic equations for multiple-components of Wigner functions can be reduced to one chiral kinetic equation involving only the single-component distribution function. These are remarkable properties of the quantum kinetics of chiral fermions and will significantly simplify the description and simulation of chiral effects in heavy ion collisions and Dirac/Weyl semimetals. We present the unintegrated chiral kinetic equations in four-momenta up to $O (ℏ^{2})$ and the integrated ones in three-momenta up to $O (ℏ)$ . We find that some singular terms emerge in the integration over the time component of the four-momentum, which result in a new source term contributing to the chiral anomaly, in contrast to the well-known scenario of the Berry phase term. Finally we rewrite our results in any Lorentz frame with a reference four-velocity and show how the non-trivial transformation of the distribution function in different frames emerges in a natural way.
Comments:
RevTex 4, 14 pages, no figure. Section II and III have been re-organized and expended to three sections (II-IV) to include more details of calculations. Section V has been expanded to include more discussions. A new section (VI) is added about Wigner functions in a general Lorentz frame. Some references are added
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1802.06216 [pdf]
PRD(2018)·85 citations
09
[Submitted on 16 Feb 2018] (cross-list from hep-ph)
Landau Damping in a strong magnetic field: Dissociation of Quarkonia
Mujeeb Hasan🇮🇳 · Binoy Krishna Patra🇮🇳 · Bhaswar Chatterjee🇮🇳 · Partha Bagchi🇮🇳
We have investigated the effects of strong magnetic field on the properties of quarkonia immersed in a thermal medium of quarks and gluons and studied its quasi-free dissociation due to the Landau-damping. Thermalizing the Schwinger propagator in the lowest Landau levels for quarks and the Feynman propagator for gluons in real-time formalism, we have calculated the resummed retarded and symmetric propagators, which in turn give the real and imaginary components of dielectric permittivity, respectively. The magnetic field affects the large-distance interaction more than the short-distance interaction, as a result, the real part of potential becomes more attractive and the magnitude of imaginary part too becomes larger, compared to the thermal medium in absence of strong magnetic field. As a consequence the average size of $J / ψ$ 's and $ψ^{'}$ 's are increased but $χ_{c}$ 's get shrunk. Similarly the magnetic field affects the binding of $J / ψ$ 's and $χ_{c}$ 's discriminately, i.e. it decreases the binding of $J / ψ$ and increases for $χ_{c}$ . However, the further increase in magnetic field results in the decrease of binding energies. On contrary the magnetic field increases the width of the resonances, unless the temperature is sufficiently high. We have finally studied how the presence of magnetic field affects the dissolution of quarkonia in a thermal medium due to the Landau damping, where the dissociation temperatures are found to increase compared to the thermal medium in absence of magnetic field. However, further increase of magnetic field decreases the dissociation temperatures. For example, $J / ψ$ 's and $χ_{c}$ 's are dissociated at higher temperatures at 2 $T_{c}$ and 1.1 $T_{c}$ at a magnetic field $e B \approx 6 and 4 m_{π}^{2}$ , respectively, compared to the values 1.60 $T_{c}$ and 0.8 $T_{c}$ in the absence of magnetic field, respectively.
Comments:
28 pages with 11 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1802.06874 [pdf]
NPA(2020)·25 citations
10
[Submitted on 19 Feb 2018] (cross-list from hep-th)
BFKL Spectrum of N=4 SYM: non-Zero Conformal Spin
Mikhail Alfimov🇫🇷 · Nikolay Gromov🇬🇧 · Grigory Sizov🇫🇷
We developed a general non-perturbative framework for the BFKL spectrum of planar N=4 SYM, based on the Quantum Spectral Curve (QSC). It allows one to study the spectrum in the whole generality, extending previously known methods to arbitrary values of conformal spin $n$ . We show how to apply our approach to reproduce all known perturbative results for the Balitsky-Fadin-Kuraev-Lipatov (BFKL) Pomeron eigenvalue and get new predictions. In particular, we re-derived the Faddeev-Korchemsky Baxter equation for the Lipatov spin chain with non-zero conformal spin reproducing the corresponding BFKL kernel eigenvalue. We also get new non-perturbative analytic results for the Pomeron eigenvalue in the vicinity of $∣ n ∣ = 1, Δ = 0$ point and we obtained an explicit formula for the BFKL intercept function for arbitrary conformal spin up to the 3-loop order in the small coupling expansion and partial result at the 4-loop order. In addition, we implemented the numerical algorithm of arXiv:1504.06640 as an auxiliary file to this arXiv submission. From the numerical result we managed to deduce an analytic formula for the strong coupling expansion of the intercept function for arbitrary conformal spin.
Comments:
70 pages, 5 figures, 1 txt, 2 nb and 2 mx files; v2: references added, typos fixed and nb file with Mathematica stylesheet attached; v3: more typos fixed; v4: the text edited according to the report of the referee
Subjects:
High Energy Physics — Theory (hep-th); High Energy Physics — Phenomenology (hep-ph); Mathematical Physics (math-ph); math.MP (math.MP); Nuclear Theory (nucl-th)
arXiv:
1802.06908 [pdf]
JHEP(2018)·45 citations
11
[Submitted on 20 Feb 2018] (cross-list from hep-ph)
Multiplicity distribution and normalized moments in p $-$ p collisions at LHC in forward rapidity using Weibull model
Ranjit Nayak🇮🇳 · Sadhana Dash🇮🇳
The measured charged particle multiplicity distribution in the forward rapidity region of the p $-$ p collisions at $s$ = 0.9 TeV, 7 TeV and 8 TeV at the LHC have been described using the Weibull distribution function. The higher order (up to $5^{t h}$ order ) normalized moments and the factorial moments are also calculated using the extracted parameters. The multiplicity distributions in forward region are observed to be well described by the Weibull regularity and the higher order moment calculations confirm the violation of KNO scaling that has been observed at mid-rapidity and lower energies. The Weibull parameters and moments for p $-$ p collisions at $s$ = 13 TeV are also estimated for the forward region.
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1802.06990 [pdf]
J.Phys.G(2019)·4 citations
12
[Submitted on 20 Feb 2018] (cross-list from hep-ph)
Soft-photon corrections to the Bethe-Heitler process in the $γ p \to l^{+} l^{-} p$ reaction
Matthias Heller🇩🇪 · Oleksandr Tomalak🇩🇪 · Marc Vanderhaeghen🇩🇪
We report on the calculation of first-order QED corrections for the $γ p \to l^{+} l^{-} p^{'}$ process. An upcoming experiment at MAMI (Mainz) aims to compare the cross sections of muon- and electron-pair production in this reaction to test lepton universality. Precise knowledge of the electromagnetic radiative corrections is needed for these measurements. As a first step, we present the leading QED radiative corrections in the soft-photon approximation when accounting for the finite lepton mass. For the kinematics at MAMI, we find corrections of the percent level for muons, and of order $10%$ for electrons.
Comments:
23 pages, 10 figures, fixed typo in Eqs 64 and 66, minor corrections in text and figures, Version published in Phys. Rev. D
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1802.07174 [pdf]
PRD(2018)·15 citations

Affiliations

first authorsco-authorsvia INSPIRE

Disentangling covariant Wigner functions for chiral fermions

Landau Damping in a strong magnetic field: Dissociation of Quarkonia

BFKL Spectrum of N=4 SYM: non-Zero Conformal Spin

Multiplicity distribution and normalized moments in p−p collisions at LHC in forward rapidity using Weibull model

Soft-photon corrections to the Bethe-Heitler process in the γp→l+l−p reaction

Affiliations

Multiplicity distribution and normalized moments in p $-$ p collisions at LHC in forward rapidity using Weibull model

Soft-photon corrections to the Bethe-Heitler process in the $γ p \to l^{+} l^{-} p$ reaction