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Title Normal single-spin asymmetries in electron-proton scattering: two-photon exchange with intermediate state resonances
Authors Jaseer Ahmed, P.G. Blunden, W. Melnitchouk
JLAB number JLAB-THY-23-3835
LANL number (None)
Other number DOE/OR/23177-6260
Document Type(s) (Journal Article) 
Associated with EIC: No
Supported by Jefferson Lab LDRD Funding: No
Funding Source: Nuclear Physics (NP)

Compiled for Physical Review C
Volume 108
Page(s) 055202
Publication Abstract: We calculate the beam ($B_n$) and target ($A_n$) normal single-spin asymmetries 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 $W \lesssim 1.8$~GeV. The latest CLAS exclusive meson electroproduction data are used as input for the transition amplitudes from the proton to the excited resonance states. For $B_n$, 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 $E_{\rm lab} < 1$~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 $E_{\rm lab} > 1$~GeV.
Experiment Numbers: other
Document: pdf
Accepted Manuscript: PhysRevC.108.055202.pdf
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