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Accidentals et al.

Accidentals et al.

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Accidentals et al.

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  1. Accidentals et al. • MC study of Early-Time window • Calibration of P1A, P2A in MC • Accidental rate and spectra: • - comparison MC vs Data • Identification of a problem ... S.Miscetti MC meeting 1-Dec-2004 S.Miscetti

  2. SAMPLEs used for the MC calibration • Ks in 2pi0 with 4, 5, 6 gamma in TW. • Only drawback is the impossibility to test the probability of stoling the • T0 (work already done with Ks to pippim ..). If this method gives satisfactory • results it can be then done also with other samples. • Aside the small correction for the T0 losses this is a powerfull sample • to look to the early timing window and compare with the MC accidentals • in time window • We define 2 categories: • Nacci Early (T-R/C between –68ns,-13.6ns ) • Nacci Early in acceptance ( E>7 costhe <0.915) but application of TW.. Then ... • Compare with events with Kine=0 • Count accidentals in acceptance and in TW after rephasing to 2*Trf and then divide by the number of peaks in early tw (10)

  3. Timing spectrum in the MC • Accidental clusters • are IN with a flat • rate vs T-R/C • in the MC they can be • identified accurately

  4. Nacci early vs Early in acceptance • Let’s check the rates: • we have measured • the P1A,P2A, P(>=1A) • in early TW w and w/o • acceptance cut • ( excluding the timing) • the time spectra looks • wider in MC than in • data • the rates look • different! • (Table in a while)

  5. Data vs MC energy and costhe spectra The energy and angular spectra are well reproduced!

  6. MC calib: rephased events from ETW vs acci in TW • Acci in TW MC (Ng=5) • • 1Acc exp by ETW We also tried to quantify, using MC, how well we can calibrate the expected Events in TW from early TW. P1A in TW expected by ETW compared with 1A in Ng=5 P2A in TW expected by ETW Compared with 2A in Ng=6 • Acci in TW MC (Ng=6) • • 2 Acc exp by ETW Not too bad .. expecially for 1A Precision 10-20%

  7. Accidental Rates: Data vs MC 2001

  8. Accidental Rates: Data vs MC 2002

  9. Rate EarlyTW ( Data vs MC) 2001 • ev 1Acc in ETW scaled to TW • (DATA) • • ec 1Acc in ETW scaled to TW • (MC) • Normalization by number of Ks2pi0 xP1A(data)/P1A(MC) • ev 2Acc in ETW scaled to TW • (DATA) • • ev 2Acc in ETW scaled to TW • (MC) • Normalization by number of Ks2pi0 xP2A(data)/P2A(MC)

  10. Rate EarlyTW ( Data vs MC) 2002 • ev 1Acc in ETW scaled to TW • (DATA) • • ev 1Acc in ETW scaled to TW • (MC) • Normalization by number of Ks2pi0 xP1A(data)/P1A(MC) • ev 2Acc in ETW scaled to TW • (DATA) • • ev 2Acc in ETW scaled to TW • (MC) • Normalization by number of Ks2pi0 xP2A(data)/P2A(MC)

  11. Summary of the calibration ... • Using Ks2pi0 sample with 4 gamma and studying the Early TW we have calibrated how to quantify the P1A, P2A in TW • (with a precision of 10-20%) and compared data and MC: • Energy and angular distributions OK • T-R/C spectra are slightly wider in MC events • Rate comparison • There is a large DATA-MC difference both in P1A ,P2A. The difference remains “almost” constant with and without acceptance requirements. • P2A in TW slightly larger in data even after a scale correction. • This difference is much larger in 2002 S.Miscetti

  12. Identification of the rate problem ?? The problem of P1A is related to the fact that in BGG files there is always at least one accidental hit which is a condition mostly satisfied in 2001 (testing sample) Not at all in 2002! The rate problem can be partially fixed by measuring P1A for the whole 2001-2002 period and scaling it whenever P1A < 100% S.Miscetti