[Tpe] Fwd: Re: TPE

[Larry Weinstein]

FYI

-------- Original Message --------
Subject: 	Re: TPE
Date: 	Mon, 20 Jun 2011 08:51:02 -0500 (CDT)
From: 	John R. Arrington <johna at anl.gov>
To: 	Hugh Montgomery <mont at jlab.org>
CC: 	Larry Weinstein <weinstei at jlab.org>, Peter Blunden 
<blunden at physics.umanitoba.ca>, "'Wally Melnitchouk'" 
<wmelnitc at jlab.org>, "'Rolf Ent'" <ent at jlab.org>, "'Bob McKeown'" 
<bmck at jlab.org>



Dear Mont,

I believe that this is one of the papers I came across in looking at
previous e+/e- and mu+/mu- measurements.  In some cases, it was assumed
that TPE effects were negligible and so the data were treated in the Born
approximation and used to extract other observables such as the muon
anomalous magnetic moment or electroweak couplings.  In this case, the
analysis was focused on electroweak couplings and the asymmetry they
extract can't be directly relate to TPE (although it may require TPE and
gamma-Z corrections).

BCDMS obviously has the data needed to look at TPE, but I don't see any
indication that the unpolarized charge asymmetry was extracted. The
extraction of TPE contributions from DIS charge asymmetry wasn't usually
considered very interesting, since the e-q or mu-q TPE effect can be
calculated exactly if you treat the quarks as free.

It might be interesting to go back and look at all of the lepton DIS
charge asymmetry data, but first one has to know exactly what TPE
corrections (if any) were applied to the data for each measurement.  To
the best of my knowledge, there hasn't been an attempt to make this kind
of a global comparison.  Egle Tomasi-Gustafsson, et al., tried to do a
similar analysis for elastic scattering, although I believe that the work
had several significant flaws.  She did included inelastic and DIS data,
and while the global average of all the measurements is consistent with no
TPE to high precision, it may be that many of the experiments already
applied a TPE correction (or didn't apply the charge-dependent
bremsstrahlung correction).

-John


On Mon, 20 Jun 2011, Hugh Montgomery wrote:

>  Dear All,
>
>
>
>  It has been bugging me for as while that there was a measurement of an
>  asymmetry in DIS muon scattering by BCDMS in the early eighties which
>  pertains to TPE. They were aiming to measure the parity violating asymmetry
>  in muon scattering but for various practical reasons flipped both helicity
>  and charge. That implies that their result is the combined measurement of
>  the electro weak and the TPE. The accuracy was quite good.
>
>
>
>  The primary paper is attached.
>
>
>
>  Have you guys looked at this? Is it relevant? If not why not?
>
>
>
>  Mont
>
>

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