CalcHEP

Explicit calculation of the cross section for any process

Asked by Ribella

Hi,

I want to see an explicit calculation of the cross section for any process via Calchep.

For example, the cross section for the complete process pp → pγγp → pe- e+p can be obtained by integrating the cross section for the subprocess γγ → e- e+.

The cross section for this process is obtained by means of a four-fold integral.

What is the explicit expression indicating the limits of this integral?

Kind Regards,

Murat

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Launchpad Janitor (janitor) said : 		#1

This question was expired because it remained in the 'Open' state without activity for the last 15 days.

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Alexander Belyaev (alexander.belyaev) said : 		#2

Code disposed in c_source/strfun/sf_epp.c See comments in the file:

// * *********************************************************
// * Equivalent photon approximation structure function. *
// * Improved Weizsaecker-Williams formula *
// * V.M.Budnev et al., Phys.Rep. 15C (1975) 181 *
// * see details on page 273 *
// * The code was written by Muriel Vander Donckt *
// * *********************************************************

   f+=(1-b)*y/(4*qq*qq1*qq1*qq1);
 // here sign is differnt with Budnev et al
 // realization by Muriel Vander Donckt. Investigation by Richard Ruiz rev
 // Budnev et al have mistake in this place.

====================

Code for photons emitted by electron is stored in epa.c file.

/* ********************************************************* */
/* Equivalent photon approximation structure function. * */
/* Improved Weizsaecker-Williams formula * */
/* C.F.Weizsaecker, Z.Phys. 88 (1934) 612 * */
/* E.J.Williams, Phys.Rev. 45 (1934) 729 * */
/* * */
/* V.M.Budnev et al., Phys.Rep. 15C (1975) 181 * */

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Ribella (ribella) said : 		#3

Hi, Belyaev,

This solved my problem.

Sincerely yours,

Murat