07/07/2020

From GlueXWiki
Revision as of 13:26, 7 July 2020 by Deurpam (Talk | contribs) (Created page with "Present: M.D., A.D., J.S., S.Š General: M.D: S.Š: (By email): I have coded the unpolarized Bethe-Heitler cross-section for a nuclear (carbon) target, and the result is sh...")

(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
Jump to: navigation, search

Present: M.D., A.D., J.S., S.Š

General:

M.D:

S.Š: (By email): I have coded the unpolarized Bethe-Heitler cross-section for a nuclear (carbon) target, and the result is shown in the attached figure in orange: the elastic part (dotted), the elastic+quasielastic (dashed) and the elastic+quasielastic+inelastic = total (full curve). I used the parameterizations (B49), (B52,53) and (B56,57) from Tsai (1974). Now how does that compare to the free proton case? For now the only meaningful comparison I was able to make was in the elastic part. Assuming (B49) for the nuclear elastic form-factor I learn that this scales as mass*Z^2 (!!!). So I have multiplied the elastic part of free-proton Bethe-Heitler by 12*36 (!!!) and got the green dotted line. Am I telling you that we should have multiplied the proton BH cross-sections by 12*36 = 432 instead of 6 or 12 ?? I was hoping that the target mass ("mi" in the paper) cancels somewhere, but it does not seem so. In Eq. (2.1), for instance, there is a mi in the numerator, but (k*pi) in the denominator is just Egamma*mi, so both mi cancel. So there is this unfortunate 12 in the form-factor and there is a 36 factor due to the charge in (B49), I am afraid, unless I am missing something. It is harder to compare the inelastic parts on the same plot, as these scale linearly with Z, as in (B52,53) and (B56,57).


J. S.:

A. D.: