[Brahms-l] Fw: Release of STAR Ultra-Peripheral Collision Paper

FYI
----------------------------------------------------------------
Flemming Videbaek
Physics Department
Brookhaven National Laboratory

e-mail: videbaek@bnl.gov
phone: 631-344-4106
----- Original Message ----- 
From: "Timothy Hallman" <hallman@bnl.gov>
To: "Kirk, Tom" <tkirk@bnl.gov>; "William A. Zajc"
<zajc@nevis.columbia.edu>; "Videbaek, Flemming" <videbaek@bnl.gov>; "Baker,
Mark" <mdbaker@bnl.gov>
Cc: <hallman@bnl.gov>
Sent: Friday, March 19, 2004 10:26 PM
Subject: Release of STAR Ultra-Peripheral Collision Paper


> Dear Tom, Bill, Flemming, and Mark,
>
> I am pleased to announce STAR's intention to submit a new
> paper on "Production of e+e- Pairs Accompanied by Nuclear
> Dissociation in Ultra-Peripheral Heavy Ion Collisions"
> to Physical Review Letters one week from today. The title
> and abstract for the paper are enclosed.
>
>                       Sincerely,
>
>                        Tim
>
>
>
>
> Title:     "Production of e+e- Pairs Accompanied by Nuclear
>            Dissociation in Ultra-Peripheral Heavy Ion Collisions"
>
> Abstract:  We present the first data on e+e- pair production accompanied
>            by nuclear breakup in ultra-peripheral gold-gold collisions
>            at a center of mass energy of 200 GeV per nucleon pair. The
>            nuclear breakup requirement selects events at small impact
>            parameters, where higher-order corrections to the pair
>            production cross section should be enhanced. We compare the
>            pair kinematic distributions with two calculations: one based
>            on the equivalent photon approximation, and the other using
>            lowest-order quantum electrodynamics (QED); the latter
>            includes the photon virtuality. The cross section, pair mass,
>            rapidity and angular distributions are in good agreement
>            with both calculations. The pair transverse momentum, Pt,
>            spectrum agrees with the QED calculation, but not with the
>            equivalent photon approach. We set limits on higher-order
>            contributions to the cross section. The e+ and e- Pt
>            spectra are similar, with no evidence for interference
>            effects due to higher-order diagrams.
>


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