On relativization of the Sommerfeld-Gamow-Sakharov factor

The e þ e À ! p " p cross section and the proton magnetic form factor have been measured in the centerof-mass energy range from 3.0 to 6.5 GeV using the initial-state radiation technique with an undetected photon. This is the first measurement of the form factor at energies higher than 4.5 GeV. The analysis is based on 469 fb À1 of integrated luminosity collected with the BABAR detector at the PEP-II collider at e þ e À center-of-mass energies near 10.6 GeV. The branching fractions for the decays J=c ! p " p and c ð2SÞ ! p " p have also been measured.

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“…Ày Þ is the Coulomb correction factor [8], and y ¼ ð1 þ 2 Þ=. The Coulomb factor makes the cross section nonzero at threshold.…”

Section: Introductionmentioning

confidence: 99%

Measurement of thee+e−→pp¯cross section in the energy range from 3.0 to 6.5 GeV

Lees¹,

Poireau²,

Tisserand³

et al. 2013

Phys. Rev. D

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“…production angle. The Coulomb correction factor C [6,7], which accounts for the electromagnetic interaction of final states, is y/(1 − e −y ) with y = πα(1 + β 2 )/β for a charged baryon pair and 1 for a neutral baryon pair. Since at threshold, G E = G M = G by definition, the production cross section of e + e − → Λ Λ is proportional to the β near threshold, that vanishes at threshold due to β = 0 and raises with finite β above threshold.…”

Section: Introductionmentioning

confidence: 99%

Experimental Review of ΛΛ¯ Production

et al. 2022

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Exclusive hyperon-antihyperon production provides a unique insight for understanding of the intrinsic dynamics when strangeness is involved. In this paper, we review the results of ΛΛ¯ production via different reactions from various experiments, e.g., via p¯p annihilation from the LEAR experiment PS185, via electron-positron annihilation using the energy scan method at the CLEO-c and BESIII experiments and the initial-state-radiation approach utilized at the BaBar experiment. The production cross section of ΛΛ¯ near the threshold is sensitive to QCD based prediction. Experimental high precision data for p¯p→Λ¯Λ close to the threshold region is obtained. The cross section of e+e−→ΛΛ¯ is measured from its production threshold to high energy. A non-zero cross section for e+e−→ΛΛ¯ near threshold is observed at BaBar and BESIII, which is in disagreement with the pQCD prediction. However, more precise data is needed to confirm this observation. Future experiments, utilizing p¯p reaction such as PANDA experiment or electron-positron annihilation such as the BESIII and BelleII experiments, are needed to extend the experimental data and to understand the ΛΛ¯ production.

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“…where θ is the angle between the beam direction and the nucleon in the CM system, α em is the electromagnetic fine structure constant, β = √ 1 − 1/τ is the velocity of the final state nucleon, C(q 2 ) is the Coulomb enhancement factor [3], and τ = q 2 /4m 2 N a kinematical factor. In contrast to processes with charged particles in the final state, the Coulomb enhancement factor C(q 2 ) is equal to unity for a process with a pure neutral final state like the signal reaction described in this review : e + e − → n n. The leading order Feynman diagram for such a process is shown in Figure 1.…”

Section: Introductionmentioning

confidence: 99%

Electromagnetic Structure of the Neutron from Annihilation Reactions

Larin

Zhou

et al. 2022

Symmetry

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The investigation of the fundamental properties of the nucleon is one of the most important topics in the modern hadron physics. Its internal structure and dynamics can be studied through the measurement of electromagnetic form factors which represent the simplest structure observables and serve as a test ground for our understanding of the strong interaction. Since the first attempt to measure the time-like form factors of the neutron, only four experiments published results on its structure from annihilation reactions. Due to the lack of statistics and experimental challenges, no individual determination of the form factors of the neutron has been possible so far. Modern developments of electron-positron colliders and the associated detectors allow to measure the effective FF of the neutron with the process e+e−→nn¯ with unprecedented precision at the BESIII experiment, which is based at the BEPCII collider in Beijing, China. In this report, we review the published results of the form factors on the neutron in the time-like regime, describe the experimental setup, and discuss their impact on our understanding of the strong interaction. Future works at BESIII will help to improve the precision of the neutron FFs and, combined with theoretical progress in this field, help to illuminate the properties of the neutron structure.

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On relativization of the Sommerfeld-Gamow-Sakharov factor

Cited by 39 publications

References 17 publications

Measurement of thee+e−→pp¯cross section in the energy range from 3.0 to 6.5 GeV

Measurement of thee+e−→pp¯cross section in the energy range from 3.0 to 6.5 GeV

Experimental Review of ΛΛ¯ Production

Electromagnetic Structure of the Neutron from Annihilation Reactions

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