Minutes of the 13th October 1999

Pascal Coyle: More on the sneutrino RPV-UDD "excess"
Pascal, together with Dominique, has done some more studies on the sneutrino RPV-UDD excess showed in Siena . The topology searched for is of the kind  snu -> nu chi -> nu q q q.
 
With respect to Siena the Wen background has been added.
Pascal showed that some of the properties (theta_miss and Mvis) of the events in the "excess" region look more similar to the Wen background than to the signal.
The addition of the Wen background source does not completely explain the excess which is of about 14 events with an expected  background of about 5 (in the most significant M12+M34 bin).

At 202 GeV no events are found in this bin where a background of about 1 event is expected and a  signal of about 1.4 events  (based on the best interpretation of the 200 GeV excess: Msnu=90 GeV, Mchi=20 GeV).

The conclusion is that it is very likely that the small sneutrino "excess" is due to a fluctuation of the Wen background in our 200 GeV data sample.

Peter has pointed out that the Wen simulation based on PYTHIA is not very reliable, it must be cross-checked with the GRACE MC.
 

 
Paolo Azzurri (presented by Marcello Maggi): First look to charginos at 200 and 202 GeV
Paolo produced the first results for the chargino topologies at 200-202 GeV. He also updated of the 192-196 results (last update was for Tampere).
First a comparison between data and MC for some relevant variables at 196 GeV has been shown. Globally a small deficit of data w.r.t. MC is observed (606 Data vs 668 MC).  This deficit concentrates in the region dominated by coplanar (back-to-back) hadronic events.

After chargino selections no excess has been found in any topology and for any Elep(192,196,200,202). In total:

Large m0  Data=6   MC=10.9
Small m0   Data=17 MC=28.9

One nice candidate at 202 GeV has been shown by Marcello.
 

Fabio Cerutti: What to present at the LEPC
Fabio showed a list of plots that should be ready for the LEPC in the "no discovery" scenario. These list can be found  here . These plots are the same as the ones sent to Tampere. After a brief discussion it has been decided to use for the LEPC results all the luminosity provided by the DATA-Quality meeting which will be held on Tuesday the 2nd of November. Consequently our next SUSYTF meeting should be moved on Thursday or Friday morning; Marcello will investigate about both possibilities.
 
 


Submitted by:  Fabio Cerutti