[Brahms-l] Minutes of BRAHMS Analysis meeting 23 Feb 2007

Minutes of BRAHMS Analysis meeting 23 Feb 2007
 Submitted by Michael Murray, Selemon Bekele
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Slides are at http://indico.cern.ch/conferenceDisplay.py?confId=13058

Present: Michael, Selemon, Dipali, Dieter, Ramiro, JH Lee, Steve, Truls

Action Items:

Please have a final check of Ionut's proceedings which will be submitted in a few hours. http://folk.uio.no/ionutca/qm06_IA_proceeding_v3.pdf

Dipali: Look into normalisation of background

Ramiro: will present next week (March 2/2007)

Others are also encouraged to present their progress

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Agenda
Dipali Pal: Update on phi->kk analysis


Event selection
    - MRS trigger
    - |bbcz| < 40 cm
    - Nevent ~ 48 M
Track selection
    - 0.4 < p < 2.0 GeV/c
    - 2 sigma cut on kaon PID
    - Rejecting track pairs sharing the same
    hit info on a TOFW slat.

Produces invariant mass spectrum for real pairs and background produced by mixed event analysis. (She has 20 fake pairs for each real pair) She gets a signal by subtracting real-mixed event background. Below the phi peak there is some structure. She found that this is not due to how the event mixed  background is constructed or how kaons selected but rather our small acceptance. Monte Carlo shows low mass structure for BRAHMS acceptance but not for a mythical BRAHMS with 360 degrees azimuthual coverage. dN/dy and T are consistent with STAR measurement.

Dieter mentioned that the asymmetry in the Phi mass distribution is also
seen at other experiments such as NA49.

JH asked about the vertex bining for the event mixing having an effect on the
background subtraction. Depali mixes events which are very close to each other 
in vertex position ( events within 5 cm of each other). One could use smaller
vertex bins but the problem is there wouldn't be enough statistics for the 
event mixing.

JH asked about kaon decay corrections. Depali replied that the correction factors
(reconstructed/input) from the MC simulation of the Phi includes the decay corrections.



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