K  fake rates from D ⁰ →K -  + Vs D ⁰ →K ±  ∓

1. K  fake rates from D⁰→K-+ Vs D⁰→K± ∓ Sadia Khalil & Sheldon Stone EHEP Group Meeting Oct 2007

2. Objective Study the RICH efficiency and fake rates for kaons and pions. Method D0D0→ K-+, K± (CC is implied) Selection Criteria TagSide Signal Side -0.174<E1<0.17 -0.174<E2<0.17 1.86<mbc1<1.87 1.86<mbc2<1.87 For Trk1, nK ≥3 and for Trk2n ≥3 For Trk1, nK ≥3 and for Trk2n ≥3 For Trk2, LK<L and forTrk2LK>L For Trk2, LK<L and for Trk2LK>L Tracks are within RICH solid angle Tracks are within RICH solid angle }NoPID Charge of (KTag = Ksignal) Charge of (KTag≠ Ksignal) Rigth Sign Wrong Sign

3. No PID

4. Kaon with RICH

5. Pion with RICH

6. Double ID

7. To ascertain the backgrounds we checked mbc(Kpi) Vs mbc(Kpi) plot The signal side is described with the RICH applied.

8. Result(600pb-1) The 2 events in WS-Double ID can be only from mixing as doubly Cabbibo decays are forbidden due to Bose-Einsitien statistics or they can be background. We subtract these 2 (actually RS) events from the other WS candidates. Efficiencies and Fake Rates εK = 90.6 %, ε = 97.4 % fK→ = (2.41± 0.52) % f→K = (1.08± 0.34) %