Nuclear Theory·nucl-th

Friday·October 21, 2016

13 papers—10 primary·3 cross-listed

11
[Submitted on 19 Oct 2016] (cross-list from hep-ph)
Helicity Evolution at Small $x$ : Flavor Singlet and Non-Singlet Observables
Yuri V. Kovchegov🇺🇸 · Daniel Pitonyak🇺🇸 · Matthew D. Sievert🇺🇸
We extend our earlier results for the quark helicity evolution at small $x$ to derive the small- $x$ asymptotics of the flavor singlet and flavor non-singlet quark helicity TMDs and PDFs and of the $g_{1}$ structure function. In the flavor singlet case we re-derive the evolution equations obtained in our previous paper on the subject, performing additional cross-checks of our results. In the flavor non-singlet case we construct new small- $x$ evolution equations by employing the large- $N_{c}$ limit. All evolution equations resum double-logarithmic powers of $α_{s} ln^{2} (1/ x)$ in the polarization-dependent evolution along with the single-logarithmic powers of $α_{s} ln (1/ x)$ in the unpolarized evolution which includes saturation effects. We solve the linearized flavor non-singlet equation analytically, obtaining an intercept which agrees with the one calculated earlier by Bartels, Ermolaev and Ryskin using the infra-red evolution equations. Our numerical solution of the linearized large- $N_{c}$ evolution equations for the flavor singlet case is presented in the accompanying Letter and is further discussed here.
Comments:
30 pages, 12 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1610.06197 [pdf]
PRD(2017)·107 citations
12
[Submitted on 19 Oct 2016] (cross-list from hep-th)
Landau-Khalatnikov-Fradkin transformation for the fermion propagator in QED in arbitrary dimensions
Shaoyang Jia🇺🇸 · M.R. Pennington🇺🇸
We explore the dependence of fermion propagators on the covariant gauge fixing parameter in quantum electrodynamics (QED) with the number of spacetime dimensions kept explicit. Gauge covariance is controlled by the the Landau-Khalatnikov-Fradkin transformation (LKFT). Utilizing its group nature, the LKFT for a fermion propagator in Minkowski space is solved exactly. The special scenario of 3D is used to test claims made for general cases. When renormalized correctly, a simplification of the LKFT in 4D has been achieved with the help of fractional calculus.
Comments:
30 pages, 2 figures
Subjects:
High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1610.06436 [pdf]
PRD(2017)·19 citations
13
[Submitted on 20 Oct 2016] (cross-list from hep-ph)
Heavy Exotic Molecules
Yizhuang Liu🇺🇸 · Ismail Zahed🇺🇸
We briefly review the formation of pion-mediated heavy-light exotic molecules with both charm and bottom, under the general strictures of chiral and heavy quark symmetries. The charm isosinglet exotic molecules with $J^{P C} = 1^{++}$ binds, which we identify as the reported neutral $X (3872)$ . The bottom isotriplet exotic with $J^{P C} = 1^{+-}$ binds, and is identified as a mixed state of the reported charged exotics $Z_{b}^{+} (10610)$ and $Z_{b}^{+} (10650)$ . The bound bottom isosinglet molecule with $J^{P C} = 1^{++}$ is a possible neutral $X_{b} (10532)$ to be observed.
Comments:
9 pages, 3 figures. arXiv admin note: text overlap with arXiv:1608.06535
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
1610.06543 [pdf]
IJMPE(2017)·6 citations

Affiliations

first authorsco-authorsvia INSPIRE

Helicity Evolution at Small x: Flavor Singlet and Non-Singlet Observables

Landau-Khalatnikov-Fradkin transformation for the fermion propagator in QED in arbitrary dimensions

Heavy Exotic Molecules

Affiliations

Helicity Evolution at Small $x$ : Flavor Singlet and Non-Singlet Observables