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Sep 24 – 29, 2023
US/Eastern timezone

Beam normal single-spin asymmetry in electron-proton scattering with intermediate state resonances

Sep 25, 2023, 2:00 PM
30m
Junior D3 (Durham Convention Center)

Junior D3

Durham Convention Center

Talk Low Energy Spin Physics with Lepton, Photon and Hadron Probes Low Energy Spin Physics with Lepton, Photon and Hadron Probes

Speaker

Dr Peter Blunden (University of Manitoba)

Description

We calculate the beam normal single-spin asymmetry $B_n$ in electron--proton elastic scattering from two-photon exchange amplitudes with resonance intermediate states of spin-parity $1/2^\pm$ and $3/2^\pm$ and mass $W < 1.8$ GeV. The latest CLAS exclusive meson electroproduction data are used as input for the transition amplitudes from the proton to the excited resonance states. The spin 3/2 resonances dominate by an order of magnitude over the spin 1/2 states. In general we observe cancellations between the negative contributions of the $\Delta(1232)$ and $N(1520)$ across both beam energy and scattering angle, and the positive contributions of the $\Delta(1700)$ and $N(1720)$, leading to a rather large overall uncertainty band in the total $B_n$. At forward angles and beam energies $E_\textrm{lab}<1$ GeV, where the $\Delta(1232)$ dominates, the calculated $B_n$ tend to overshoot the A4 and SAMPLE data.
The calculated $B_n$ compare well with the measured values from the A4 and $Q_{\textrm{weak}}$ experiments with $E_\textrm{lab}>1$ GeV.

Primary authors

Dr Jaseer Ahmed (Shahjalal University of Science and Technology) Dr Peter Blunden (University of Manitoba) Wally Melnitchouk (Jefferson Lab)

Presentation materials