Nuclear Theory·nucl-th

Friday·August 28, 2015

9 papers—6 primary·3 cross-listed

07
[Submitted on 26 Aug 2015] (cross-list from hep-ph)
On the proton charge extensions
Jesse R. Stryker🇺🇸 · Gerald A. Miller🇺🇸
We examine how corrections to $S$ -state energy levels, $E_{n S}$ , in hydrogenic atoms due to the finite proton size are affected by moments of the proton charge distribution. The corrections to $E_{n S}$ are computed moment by moment. The results demonstrate that the next-to-leading order term in the expansion is of order $r_{p} / a_{B}$ times the size of the leading order $⟨ r_{p}^{2} ⟩$ term. Our analysis thus dispels any concern that the larger relative size of this term for muonic hydrogen versus electronic hydrogen might account for the current discrepancy of proton radius measurements extracted from the two systems. Furthermore, the next-to-leading order term in powers of $r_{p} / a_{B}$ that we derive from a dipole proton form factor is proportional to $⟨ r_{p}^{3} ⟩$ , rather than $⟨ r_{p}^{4} ⟩$ as would be expected from the scalar nature of the form factor. The dependence of the finite-size correction on $⟨ r_{p}^{3} ⟩$ and higher odd-power moments is shown to be a general result for any spherically symmetric proton charge distribution. A method for computing the moment expansion of the finite-size correction to arbitrary order is introduced and the results are tabulated for principal quantum numbers up to $n = 7$ .
Comments:
10 pages, no figures. Clarified discussion in Sec. II, revised notation, journal version
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th); Atomic Physics (physics.atom-ph)
arXiv:
1508.06680 [pdf]
PRA(2016)·4 citations
08
[Submitted on 27 Aug 2015] (cross-list from hep-th)
Dissipative Charged Fluid in a Magnetic Field
Navid Abbasi🇮🇷 · Ali Davody🇮🇷
We study the collective excitations in a dissipative charged fluid at zero chemical potential when an external magnetic field is present. While in the absence of magnetic field, four collective excitations appear in the fluid, we find five hydrodynamic modes in presence of magnetic field. This implies that the magnetic field splits the degeneracy between the transverse shear modes. Using linear response theory, we then compute the retarded response functions. In particular, it turns out that the correlation between charge and the energy fluctuations will no longer vanish, even at zero chemical potential. By use of the response functions, we also derive the relevant Kubo formulas for the transport coefficients.
Comments:
6 pages
Subjects:
High Energy Physics — Theory (hep-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1508.06879 [pdf]
PLB(2016)·4 citations
09
[Submitted on 27 Aug 2015] (cross-list from hep-ph)
The electron in three-dimensional momentum space
Alessandro Bacchetta🇮🇹 · Luca Mantovani🇮🇹 · Barbara Pasquini (Pavia U. and INFN, Pavia)🇮🇹
We study the electron as a system composed by an electron and a photon, using lowest order perturbation theory. We derive the leading-twist transverse-momentum-dependent distribution functions for both the electron and photon in the dressed electron, thereby offering a three-dimensional description of the dressed electron in momentum space. To obtain the distribution functions, we apply both the formalism of light-front wave function overlap representation and the diagrammatic approach. We perform the calculations both in light-cone gauge and Feynman gauge, and we present a detailed discussion of the role of the Wilson lines to obtain gauge-independent results. We provide numerical results and plots for many of the computed distributions.
Comments:
25 pages, 14 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1508.06964 [pdf]
PRD(2016)·21 citations

Affiliations

first authorsco-authorsvia INSPIRE

On the proton charge extensions

Dissipative Charged Fluid in a Magnetic Field

The electron in three-dimensional momentum space

Affiliations