Minutes of meeting on trigger symmetrisation and normalisation
held on 29/8/1994
Present:
M.Fidecaro, M.Dejardin, C.Touramanis, A.Schopper, T.Ruf, E.Aslanides,
M.Danielsson, A.Go, A.Soares, P.Pavlopoulos, C.Thibault, P.Kokkas

Concerning the KK events: Opposite to what was said before, HWP2 
asks for all tracks in the first three slots of the register to pass the 
kaon dE/dx cut if they are flagged as kaons. But because of the 
"OR" logic and the wide open band for pions most events will pass.
(it is always assumed that the second kaon is a misidentified pion)
  unlike sign KK            like sign KK
  K+K-pi-pi+  pass             K+pi-pi-K+    pass

  K+K-.. pi+  might not pass   K+pi-.. K+    pass

  K+K-pi-..   pass             K+pi-pi-..    pass

  K+K-....    might not pass

There are two types of event classes which are treated differently. 
I  propose to fake all kaonflags in the trigger for slot 2 and 3.
This will remove a lot of KK events, less deadtime, and puts less
asymmetry to the golden events.
What is your opinion ?

Christos presented some preliminary results for P24 and P25 
and the mixed field asymmetries. Only one LUT is necessary, that means
the physics effects in M1M2 and M2M1 are the same, geometry and
physics factorize. In order to achieve this a cut on the tranverse 	
charged kaon momentum of >400MeV/c is necessary.
The eta+- and phi+- values for the two asymmetries are in good 
agreement. Only the background contribution obtained from the fit
differs by a factor 2-3 in the two asymmetries. This will be studied.
The geometric effect becomes visible by looking at the 
K0(M1)-K0(M2) or K0bar(M1)-K0bar(M2) asymmetry as a function of the 
transverse radius.  
Andreas studied M1/M2 asymmetries using minimum bias events.
The momentum distribution for negative and positive pions in the 
same magnetic field agrees within several permille whereas the 
negative pion momentum in M1 and M2 is different; 10% asymmetries,
mean values shifted by 3.5%. Same for the positive pion momentum.
Also tracks with same curvatures have a different momentum spectrum
in M1 and M2. Reason is unknown for the moment. It was also found that the S1 
response is different for M1 and M2, whereas no difference was found for S2.

Thomas