Computer Physics Communications Program LibraryPrograms in Physics & Physical Chemistry |

[Licence| Download | New Version Template] adcg_v1_0.gz(19 Kbytes) | ||
---|---|---|

Manuscript Title: SABSPV: a Monte Carlo integrator for small-angle Bhabha scattering. | ||

Authors: M. Cacciari, G. Montagna, O. Nicrosini, F. Piccinini | ||

Program title: SABSPV | ||

Catalogue identifier: ADCG_v1_0Distribution format: gz | ||

Journal reference: Comput. Phys. Commun. 90(1995)301 | ||

Programming language: Fortran. | ||

Computer: DEC VAX. | ||

Operating system: VMS, UNIX. | ||

RAM: 40K words | ||

Word size: 32 | ||

Keywords: Particle physics, Elementary, High energy electron Positron collisions, Small-angle bhabha Scattering, Luminosity determination, Qed corrections, Electron structure Functions, Experimental cuts, Monte carlo integration. | ||

Classification: 11.4. | ||

Nature of problem:The precise determination of the theoretical Bhabha scattering cross section in the small-angle regime is a key ingredient for precision luminometry at LEP. To this aim, QED radiative corrections to the tree-level Standard Model Cross section have to be taken into account, together with vacuum polarization effects. Particular care has to be devoted to higher-order corrections. The theoretical formulation must allow the computation of the cross section for a wide variety of cuts on the final-state particles. | ||

Solution method:A suitable matching of a fixed-order calculation with the structure- function techniques for resumming large initial- and final-state leading logarithmic corrections [2] is performed. A Monte Carlo integration with weighted events has been implemented in order to mimic as close as possible the experimental triggering conditions. The importance- sampling techinque [3] is employed to take care of the peaking behaviour of the integrand. | ||

Restrictions:The O(alpha) QED corrections are computed exactly only for the dominant contribution to the small-angle cross section, namely the square of gamma-exchange in the t-channel; all the other contributions to the cross sections are corrected at the leading-logarithmic level. The contribution of additional hadronic or leptonic pairs is at present neglected. Starting from O(alpha**2), QED corrections are implemented at the leading-logarithmic level. | ||

Unusual features:None (Routines from the CERN Program Library are used.) | ||

Running time:On a HP 9000/735 the code takes about 2 * 10**-4 seconds per event, with standard cuts. A one per mille relative error can be achieved with about 10**7 events. | ||

References: | ||

[1] | F. James, Comput. Phys. Commun. 79(1994)111. | |

[2] | M. Cacciari, G. Montagna, O. Nicrosini and F. Piccinini, in "Reports of the Working Group on Precision Calculations for the Z Resonance", eds. D. Bardin, W. Hollik and G. Passarino (CERN Report 95-03, Geneva, 1995), p.389, and references therein. | |

[3] | F. James, Rep. Prog. Phys. 34(1980)1145. |

Disclaimer | ScienceDirect | CPC Journal | CPC | QUB |