Jun 2 – 7, 2019
Carnegie Mellon University
America/New_York timezone

Measurement of the proton polarizabilities at MAMI

Jun 3, 2019, 4:00 PM
Rangos 3

Rangos 3

Invited Hadron Spectroscopy Electroweak Probes


Edoardo Mornacchi (University of Mainz)


Polarizabilities are fundamental properties related to the internal structure and dynamics of the nucleon. They play a crucial role not only in our understanding of the nucleon, but also in other areas such as atomic physics. The A2@MAMI Collaboration has undertaken a comprehensive program of real Compton scattering experiments in order to accurately determine these parameters at the MAinz MIcrotron (MAMI), using the Crystal Ball/TAPS setup. A new high quality data set has been collected both on the differential cross section and on the beam asymmetry $\Sigma_3$ below the pion production threshold using a polarized photon beam and an unpolarized liquid hydrogen target. This measurement will allow an extraction of the proton scalar polarizabilities $\alpha_{E1}$ and $\beta_{M1}$ with a significant improvement to the large uncertainties of the present values. Moreover, the use of linearly and circularly polarized photon beams in conjunction with polarized targets will also allow an extraction of the different proton spin polarizabilities, which at the moment have only been determined in various linear combinations. To study these, the asymmetries $\Sigma_{2x}$, $\Sigma_{2z}$ and $\Sigma_3$ were measured above the pion production threshold. This talk will give the current status as well as the present and expected results on all different proton polarizabilities that can be obtained at Mainz.
$^*$On the behalf of A2 Collaboration.

Early Consideration No
Graduate Student Yes

Primary author

Edoardo Mornacchi (University of Mainz)

Presentation materials