- There was no meeting this week. But status reports have been submitted.
Spin Density Matrix Elements -- Jon Couchman
Jon has continued his work on the spin density matrix method. He is working on a program to calculate the values of the matrix elements in bins of cos(theta). Once this is working he wants to start looking at MC with CP-violating coupling. Hence putting pressure on Paul to get ERATO working.
CP-violating TGCs -- Paul Dervan
Paul continues to fight with ERATO. He looked at the W production angle and discovered a hard cut was being applied by ERATO. Plus appling CP violating coupling still doesn't seem to affect the distributions (In-fact they are identical to the SM distributions!). Any suggestions or help would be most welcome. Paul is still in contact with Anna, to try and understand what is going wrong.
Paul also contacted Dave Charlton to see if there had been any progress with adding CP-violating couplings to EXCALIBUR. His reply was:
"The current state is that Roberto Pittau, one of the authors of EXCALIBUR,has promised to implement the CP-violating couplings. However, I recently asked him the status, and he said it was not ready, but that he was working on it. He did not give a time estimate - it could be anything from a week or two to a year! He knows we would like to use it - and that we already are keen users of EXCALIBUR."
So it looks like we're stuck with ERATO for the time being. In the long term it would be nice to have more that one generator so that cross checks can be made.
Neighest Neighbour Analysis -- Steve Betts
Steve has continued his work on backgrounds. He has proposed formulae for Maximum Likelihoods and Extended Maximum Likelihoods in the presence of non-parameter dependent background and parameter dependent background. He will be trying these in the next few days. Steve produced the diagrams for the CC20 and NC48 backgrounds. as these could form references for the group. The numbers given below each pseudo-Feynman diagram are the number of actual prosesses that each diagram represents.
Steve also had some information about the generation of 4-fermion samples:
- The eeff samples are generated separately because of the large
cross-sections due to two (ie 12) of the ee NC diagrams when both
gauge-bosons are photons (the qed 2-photon diagram is omitted because of 2))
- In practise the 2-photon diagram is not included in the
4-fermion generation because the process is not modelled well-enough (as
anyone who has looked at selection studies would tell you) by just
considering the simple multi-peripheral diagram (essentially this is because
the hadronic mass is small, and so simple perturbative calculations are not
appropriate). This worried Steve because, although the 2-photon background is
modelled well by the dedicated generators, it wasn't obvious to him that the
interference terms could be neglected. Dave Charlton informs Steve that the
interference terms should be small enough to ignore because the diagrams
populate difference regions of phase-space. Compared with the
hadronic-production modelling systematic, the interference systematic should
be negligible.
Steve is working on finishing the selection/reconstruction chapter of his thesis and on including backgrounds into his analysis.
Next Meeting: TBA
