BESIII reports Born cross sections for e+e- to p pbar at 47 energies between 3.51 and 4.95 GeV and determines |GE/GM| and |GM| for the first time from angular distributions at large timelike momentum transfer.
Unexpected features of e+e-->ppbar and e+e-->lambda-lambdabar cross sections near threshold
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abstract
Unexpected features of the BaBar data on e+e- in baryon-antibaryon cross sections are discussed. These data have been collected, with unprecedented accuracy, by means of the initial state radiation technique, which is particularly suitable in giving good acceptance and energy resolution at threshold. A striking feature observed in the BaBar data is the non-vanishing cross section at threshold for all these processes. This is the expectation due to the Coulomb enhancement factor acting on a charged fermion pair. In the case of e+e- in proton-antiproton it is found that Coulomb final state interactions largely dominate the cross section and the form factor is |G^p(4M^2_p)|~1, which could be a general feature for baryons. In the case of neutral baryons an interpretation of the non-vanishing cross section at threshold is suggested, based on quark electromagnetic interaction and taking into account the asymmetry between attractive and repulsive Coulomb factors. Besides strange baryon cross sections are compared to U-spin invariance predictions.
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hep-ex 1years
2026 1verdicts
UNVERDICTED 1representative citing papers
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Measurement of Born cross sections for $e^+e^-\to p\bar p$ at $\sqrt{s} =3.510-4.946$ GeV
BESIII reports Born cross sections for e+e- to p pbar at 47 energies between 3.51 and 4.95 GeV and determines |GE/GM| and |GM| for the first time from angular distributions at large timelike momentum transfer.