[Theory-seminars] Theory seminar tomorrow (1pm)

[Miguel Albaladejo]

Dear all,

this is a reminder on tomorrow's seminar.

Regards,
Carlota, Raza, Miguel

Date and time: Monday, April 27, 1:00PM
Speaker: Oleksandr Tomalak (U. of Kentucky)
Bluejeans connection: https://bluejeans.com/610445877
Title: Two-photon exchange corrections in elastic lepton-proton scattering and low-energy nucleon structure


Abstract: Two experimental approaches, with and without polarized protons, gave strikingly different results for the ratio of the electric to magnetic proton form factors. Moreover, a significant discrepancy has been observed in the extraction of the proton charge radius from muon spectroscopy versus electron spectroscopy and electron scattering. The two-photon exchange (TPE) correction is a source of the largest theoretical uncertainty in these measurements. In my talk, I will present the TPE estimate with proton and inelastic intermediate states accounting for lepton-mass effects. I will present the dispersion relation approach to evaluate the TPE in the elastic electron-proton scattering accounting for the leading elastic and first inelastic pion-nucleon intermediate states. I will compare theoretical calculations to the recent data and will discuss applications to the extraction of nucleon form factors. The future precise measurements of the ground state hyperfine splitting (HFS) in muonic hydrogen by CREMA and FAMU collaborations as well as at J-PARC will provide strict constraints on the low-energy proton structure. Exploiting the precise 1S HFS measurements in electronic hydrogen, I will extract the TPE correction and make an accurate prediction for the HFS in muonic hydrogen. Moreover, I will present TPE correction to the Lamb shift and HFS on the neutron inside a nucleus and contrast it with the correction on the proton.
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