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K L 2 p 0 search

K L 2 p 0 search. Analysis Criteria Efficiency and Rejection Power Sample Composition Selected Data from 3.89 pb -1 Improvements Summary. Analysis Criteria. The events with KL tag e s = e b = 0.784

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K L 2 p 0 search

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  1. KL 2p0 search • Analysis Criteria • Efficiency and Rejection Power • Sample Composition • Selected Data from 3.89 pb-1 • Improvements • Summary

  2. Analysis Criteria • The events with • KL tag es = eb = 0.784 • at least one reconstructed neutral vertex es = 0.866 eb = 0.918 • 4 photons es = 0.714 eb = 0.083 have been considered es = 0.485 eb = 0.060 • The events have been processed by the global fit, allowing the variation of • Beam : Pz sqrt(s) vx vz • Ks : Px Py Pz vx vy vz • photons : E t cluster position and imposing • Energy conservation and K0 mass at the F decay point • Ks and F decay points on the Ks line of flight • KL decay point on the KL line of flight • photons momenta pointing to the KL decay point • Energy and Momenta conservation at the KL decay point for a subsample of events • the p0 mass and theEp0_rfKL = 248.8 MeV for a subsample of events

  3. Photon pairing • To apply the constraints on the p0 mass and on the p0 energy in the KL rest frame, the photon energies and momenta are requested to be in the region expected for the signal. This request replaces the old cut on the p0 mass, for the events with 4 and 3 photons and improves both, the efficiency for the signal, and the rejection power for the background. 63% of the signal against 2% of the background has 2 reconstructed pions. • Moreover, the contraint on the p0 energy (useless in the case of two pions) helps to isolate the signal when only one p0 has been found.

  4. Efficiency and Rejection Power • Starting point es = 0.485 eb = 0.060 • Fiducial Volume 30.<r<155. Abs(z)<155. es = 0.7 eb = 0.48 • I : es = 0.95 eb = 0.25 • Energy and Momenta conservation at the KL decay point must be applied A OR • the p0 mass and theEp0_rfKL = 248.8 MeV must be applied B • II : es = 0.89 eb = 0.04 • 2 pions have been found OR • AANDB OR • B AND 1 pion has been used AND cut on the DEi MFi plane OR • A AND 1 pion has been found AND cut on the DE cosD plane

  5. Sample Composition • In 1 pb-1 we expect : • Back 3.1 106 0.341 0.6861 0.2112 0.461 0.060 0.480.010= 7.06 104 0.0600.480.010= 20 • Signal 3.1 106 0.341 0.6861 9 10-4 0.461 0.485 0.710.845= 3.01 102 0.485 0.710.845 = 87 • The overall efficiency is 29% and the Rejection Power is 3530 • Starting Data sample (on disk) consists of 3.89 pb-1 , so I expect • 416 (20) selected events with 78 KL 3p0 inside and I found • 441 events

  6. Improvements • Efficiency: • neutral vertex search - • photon pairing - • Rejection Power • QCAL • Covariances • Global-fit function and F, Ks, Photon contribution analysis

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