Abstract
For several processes at colliding beams, macroscopically large impact parameters give an essential contribution to the standard cross section. These impact parameters may be much larger than the transverse sizes of the colliding bunches. In that case, the standard calculations have to be essentially modify. The corresponding formulae for such a beam-size effect were given twenty years ago without taking into account correlations of particle coordinates in the beams. In the present paper we derive formulae which necessary to take into account quantitatively the effect of particle correlations in the spectrum of bremsstrahlung as well as in pair production. Besides, we consider critically recent papers of Baier and Katkov [Phys. Rev. D {\bf 66}, 053009 (2002) and hep-ph/0305304] in which it was calculated a new additional ``subtraction term'' related to the coherent contribution into beam-size effect. We show that this result is groundless and point out the origin of the mistake.
Highlights
The so-called beam-size or MD effect is a phenomenon discovered in experiments at the MD-1 detector on the VEPP-4 collider, Novosibirsk 1981
Since the MD effect considerably reduced the effective cross section of this process, the calculated beam lifetime in these storage rings was larger by about 25% for TRISTAN [14] and by about 40% for LEP-I [15] than without taking into account the MD effect
We describe the MD effect using the ep ! ep process as an example. [Below we use the following notations: Ne and Np are the numbers of electrons and protons in the bunches, z l is the longitudinal, x and y are the horizontal and vertical transverse sizes of the proton bunch, e
Summary
The so-called beam-size or MD effect is a phenomenon discovered in experiments at the MD-1 detector on the VEPP-4 collider, Novosibirsk 1981 (the term ‘‘MD effect’’ is used in honor of the MD-1 group) It was observed [1] that the number of measured photons in the process e e ! Since the MD effect considerably reduced the effective cross section of this process, the calculated beam lifetime in these storage rings was larger by about 25% for TRISTAN [14] and by about 40% for LEP-I [15] (in accordance with the experimental data) than without taking into account the MD effect. In the present paper we derive formulas which are necessary to take into account quantitatively the effect of particle correlations in the spectrum of bremsstrahlung as well as in pair production.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: Physical Review Special Topics - Accelerators and Beams
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
