TauSpinner project

Z. Was homepage | Z. Czyczula e-mail: Zofia.Czyczula (at) cern.ch | T. Przedzinski hompege

TauSpinner: tau spin reweight algorithm
Authors: Z. Czyczula, T. Przedzinski, Z. Was

PHYSICS PURPOSE:
For previously generated sample involving tau, its spin effects can be:

validated. Eg. if spin effects were taken into account when events were generated
calculate spin weght for previously generated events and stored on the tape.
- In original sample spin effects could have been missing.
  Then spin weight will be in range (0 , 2ⁿ);
  n denotes number of taus in final state.
- In original sample spin effects are eg for W+ and we would like to see how it would look if H+ was present instead.
reweight on flight such events with spin weight. Such unweighted events can be then monitored with MC-Tester for quick evaluation of spin effects

At present only nine main decay channels of tau have their spin effects used in algorithm.
These channels cover already now above 95% of total tau width.

For more information on agorithm use see README
(This README is included in distribution tarball as well)

DOWNLOAD: version 1.0 (as of 07.Dec.11)

Development version

QUICK LOOK AT SUBDIRECTORIES, NUMERICAL RESULTS AND OLD VERSIONS:

Online source code of the last version
Numerical results obtained using MC-TESTER
MC-tester-analysis contains an example how to run MC-tester analysis step on lxplus as well as several root files used for creating booklets stored in directory 'results'. See 'README' in this directory for more details. Tarball with analysis files only can be downloaded here.
Old versions of the distribution tar ball also some older test results

LIST OF HARD PROCESSES:
* W^- &rarr tau^- nu_tau W^+ &rarr tau^+ nu_tau * H^- &rarr tau^- nu_tau H^+ &rarr tau^+ nu_tau	* gamma^* &rarr tau^+ tau^- Z &rarr tau^+ tau^- * h &rarr tau^+ tau^- a &rarr tau^+ tau^-
Partial kinematical information is used (4 momenta of taus and their parent only). Only longitudinal spin effects.

LIST OF TAU DECAY CHANNELS WHEN SPIN EFFECTS ARE TAKEN:
1 tau^- &rarr e^- anti_nu_e nu_tau [+ gamma] tau^+ &rarr e^+ nu_e anti_nu_tau [+ gamma] 2 tau^- &rarr mu^- anti_nu_mu nu_tau [+ gamma] tau^+ &rarr mu^+ nu_mu anti_nu_tau [+ gamma] 3 tau^- &rarr pi^- nu_tau tau^+ &rarr pi^+ anti_nu_tau 4 tau^- &rarr pi^- pi^0 nu_tau tau^+ &rarr pi^+ pi^0 anti_nu_tau 5 tau^- &rarr pi^- pi^0 pi^0 nu_tau tau^+ &rarr pi^+ pi^0 pi^0 anti_nu_tau tau^- &rarr pi^- pi^- pi^+ nu_tau tau^+ &rarr pi^+ pi^+ pi^- anti_nu_tau	6 tau^- &rarr K^- nu_tau tau^+ &rarr K^+ anti_nu_tau 7 tau^- &rarr K^- pi^0 nu_tau tau^+ &rarr K^+ pi^0 anti_nu_tau tau^- &rarr pi^- K_S0 nu_tau tau^+ &rarr pi^+ K_S0 anti_nu_tau tau^- &rarr pi^- K_L0 nu_tau tau^+ &rarr pi^+ K_L0 anti_nu_tau 8 tau^- &rarr pi^- pi^- pi^+ pi^0 nu_tau tau^+ &rarr pi^+ pi^+ pi^- pi^0 anti_nu_tau 9 tau^- &rarr pi^0 pi^0 pi^0 pi^- nu_tau tau^+ &rarr pi^0 pi^0 pi^0 pi^+ anti_nu_tau
For other channels spin weight at present will not be calculated. 1.0 will be returned.

ACKNOWLEDGMENTS:

The first functional version of this algorithm was created on inspiration and with help from Dimitris Varouchas, Claire Gwenlan, Soshi Tsuno, Andy Buckley, Elzbieta Richter-Was and other members of ATLAS MC group.

USER INPUT OUTPUT METHODS; FURTHER PARTICIPATION NEEDED:

We need help from pilot users. In particular methods to read events stored in formats used in experiments MC simulations need to be prepared.

Last update: 8 November 2011