Elsevier Science Home
Computer Physics Communications Program Library
Full text online from Science Direct
Programs in Physics & Physical Chemistry
CPC Home

[Licence| Download | New Version Template] adtj_v2_0.tar.gz(1110 Kbytes)
Manuscript Title: BCVEGPY2.0: An upgraded version of the generator BCVEGPY with the addition of hadroproduction of the P-wave Bc states
Authors: Chao-Hsi Chang, Jian-Xiong Wang, Xing-Gang Wu
Program title: BCVEGPY
Catalogue identifier: ADTJ_v2_0
Distribution format: tar.gz
Journal reference: Comput. Phys. Commun. 174(2006)241
Programming language: FORTRAN 77/90.
Computer: Any computer with FORTRAN 77 or 90 compiler. The program has been tested on HP-SC45 Sigma-X parallel computer, Linux PCs and Windows PCs with Visual Fortran.
Operating system: UNIX, Linux and Windows.
RAM: About 2.0 MB
Keywords: Event generator, hadronic production, Bc meson, S-wave and P-wave states.
PACS: 13.85.Ni, 12.38.Bx, 14.40.Nd, 14.40.Lb.
Classification: 11.5.

Nature of problem:
Hadronic production of Bc meson itself and its excited states.

Solution method:
The code with option can generate weighted and un-weighted events. For jet hadronization, an interface to PYTHIA is provided.

Reasons for new version:
There are two reasons. One is to provide additional codes for the hadronic production of P-wave excited Bc states; the four via color-singlet P-wave state directly and the two via color-octet S-wave state accordingly. The other one is to decompose the color-flow factor for the amplitude by an approximate way, that is adopted in PYTHIA.

Summary of revisions:
  1. The integration efficiency over the momentum fractions of the initial partons x1 and x2 are improved;
  2. The amplitudes for the hadronic production of the color-singlet components corresponding to the four P-wave states, B*cJ,L=1 or 1P1 and 3Pj (J=0,1,2), are included;
  3. The amplitudes for P-wave production via the two color-octet components |(cbbar)8(1S0)g⟩ and |(cbbar)8(3S1)g⟩ are included;
  4. For comparison, the S-wave (1S0 and 3S1) hadronic production via the light quark-antiquark annihilation mechanism is also included;
  5. For convenience, 24 data files to record the information of the generated events in one run are added;
  6. An additional file, parameter.for, is added to set the initial values of the parameters;
  7. Two new parameters 'IMIX' (IMIX =0 or 1) and 'IMIXTYPE' (IMIXTYPE =1, =2 or =3) are added to meet the needs of generating the events for simulating `mixing' or `separate' event samples for various Bc and its excited states correctly;
  8. One switch, `IVEGGRADE', is added to determine whether to use the existing importance sampling function to generate a more precise importance sampling function or not;
  9. Two parameters, `IOUTPDF' and `IPDFNUM', are added to determine which type of PDFs to use;
  10. The color-flow decomposition for the amplitudes is rewritten by an approximate way, that is adopted in PYTHIA.

The hadronic production of (cbbar)-quarkonium in S-wave and P-wave states via the mechanism of gluon-gluon fusion are given by the 'complete calculation' approach of the leading order QCD. The contributions from the other mechanisms for P-wave production which are small comparatively are not included.

Running time:
Generally speaking, it depends on which option is used to drive PYTHIA when generating the Bc events. Typically, for the hadronic production of the S-wave (cbbar)-quarkonium, if the PYTHIA parameter IDWTUP= 1, then it takes about 20 hours on a 1.8 GHz Intel P4-processor machine to generate 1000 events; however if IDWTUP= 3, to generate 106 events, it takes only about 40 minutes. For the hadronic production of the P-wave (cbbar)-quarkonium, the necessary time will be almost two times longer than the S-wave quarkonium production.