nucl-th digest · Oct 13, 2017

[Submitted on 12 Oct 2017] (cross-list from hep-ph)

Features of $ω$ photoproduction off nucleon target at forward angles : Dominance of $π$ exchange with Regge cuts and scaling of differential cross sections

Byung-Geel Yu🇰🇷 · Tae Keun Choi🇰🇷 · Kook-Jin Kong🇰🇷

We investigate photoproduction of $ω$ off a nucleon target $γ N \to ω N$ by using a Reggeized model where $π (135) + σ (500) + f_{1} (1285) + f_{2} (1270)$ +Pomeron exchanges are included in the $t$ -channel for the reaction at forward angles. The reaction mechanism at low energy is featured by the dominance of the $π$ exchange with the absorptive cuts introduced to modulate the pion contribution to both $γ p \to ω p$ and $γ n \to ω n$ reactions. Necessity of $σ$ exchange is illustrated in the analysis of the cross section from natural parity exchanges. Cross sections for differential, total, and spin density matrix with beam polarization are reproduced and compared with existing data on $γ p \to ω p$ . Scaled differential cross sections of Jefferson Lab data on $γ p \to ω p$ are investigated at the production angle $θ = 9 0^{\circ}$ with the nonlinear trajectories for a saturation. Differential and total cross sections for the $γ n \to ω n$ reaction are analyzed to compare with recent experimental data at the CBELSA/TAPS Collaboration. An application to the $γ p \to ω Δ^{+}$ reaction is presented to demonstrate the significance of the $π$ exchange in the total and differential cross sections.

Comments:: 11 pages, 12 figures, 2 tables
Subjects:: High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:: 1710.04511 [pdf]

J.Phys.G(2019)·11 citations

Dissecting the hadronic contributions to

(g - 2)_{μ}

by Schwinger's sum rule

The theoretical uncertainty of

(g - 2)_{μ}

is currently dominated by hadronic contributions. In order to express those in terms of directly measurable quantities, we consider a sum rule relating

g - 2

to an integral of a photo-absorption cross section. The sum rule, attributed to Schwinger, can be viewed as a combination of two older sum rules: Gerasimov-Drell-Hearn and Burkhardt-Cottingham. The Schwinger sum rule has an important feature, distinguishing it from the other two: the relation between the anomalous magnetic moment and the integral of a photo-absorption cross section is linear, rather than quadratic. The linear property makes it suitable for a straightforward assessment of the hadronic contributions to

(g - 2)_{μ}

. From the sum rule we rederive the Schwinger

α /2 π

correction, as well as the formula for the hadronic vacuum-polarization contribution. As an example of the light-by-light contribution we consider the single-meson exchange.

Comments:: 6 pages, 10 figures, published version extended by a few clarifying remarks and an Appendix
Subjects:: High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:: 1710.04571 [pdf]

PRL(2018)·30 citations

Friday·October 13, 2017

Features of $ω$ photoproduction off nucleon target at forward angles : Dominance of $π$ exchange with Regge cuts and scaling of differential cross sections

Dissecting the hadronic contributions to $(g - 2)_{μ}$ by Schwinger's sum rule

Affiliations

Features of ω photoproduction off nucleon target at forward angles : Dominance of π exchange with Regge cuts and scaling of differential cross sections

Dissecting the hadronic contributions to (g−2)μ​ by Schwinger's sum rule

Affiliations

Features of $ω$ photoproduction off nucleon target at forward angles : Dominance of $π$ exchange with Regge cuts and scaling of differential cross sections

Dissecting the hadronic contributions to $(g - 2)_{μ}$ by Schwinger's sum rule