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Hermeticity, boost factor and other issues

Hermeticity, boost factor and other issues. Koji Hara (Nagoya University). Introduction. Studies based on the physics cases are needed to validate and optimize the design of the detector performance and the accelerator. Boost factor and Hermeticity

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Hermeticity, boost factor and other issues

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  1. Hermeticity, boost factor and other issues Koji Hara (Nagoya University) BNM2008@Atami

  2. Introduction • Studies based on the physics cases are needed to validate and optimize the design of the detector performance and the accelerator. • Boost factor and Hermeticity • How the boost factor affect measurements using Dt and full reconstruction method. • KL detectionefficiency • How important for the mode with missing energy. • Test cases: • BJ/yK0, fK0 tCPV measurement • Btn Brmeasurement Based on our results from Belle data. BNM2008@Atami

  3. _ B0 Principle of tCPV measurement CP-side m+ J/y m- (4S) resonance B1 electron (8GeV) KS/L B0 positron (3.5GeV) nm B2 p- bg = 0.425 (Belle) K+ p- Flavor tag and vertex reconstruction Dz ~ 200mm (Belle) m+ • Fully reconstruct one B-meson which decays to CP eigenstate • Tag-side determines its flavor • Proper time (Dt) is measured from decay-vertex difference (Dz) BNM2008@Atami

  4. e+ (4S) B- B+ ne n n B++, +e+e B-X Btn Analysis Concepts@Belle • B decays with missing neutrinos lack the kinematic constraints which are used to separate signal events from backgrounds (Mbc and DE) • Reconstruct the decay of the non-signal B (tagging), then look for the signal decay in whatever is left over More than 2 neutrinos appear in B tn decay Tagging side : Fully reconstruct hadronic modes Signal side : Reconstruct particles from t decay BNM2008@Atami

  5. BtnSignal Selection • Extra neutral energy in calorimeter EECL - Most powerful variable for separating signal and background -Total calorimeter(ECL) energy from the neutral clusters which are not associated with the tag B Background Btn Signal BNM2008@Atami

  6. Hermeticity and boost factor • Large boost factor  better Dt resolution less acceptance in forward region • Small boost factor  worse Dt resolution more acceptance in forward region • Baseline detector design • study of adding super forward detector  K.-F. Chen’s talk BNM2008@Atami

  7. Boost factor Dependence • Toy MC results considering Dt resolution and geometrical acceptance. • Geometrical acceptance is assumed to be same as the current Belle detector. - J/yK0 tCPV - fK0 tCPV - Btn BR KEKB can operate worse better BNM2008@Atami

  8. KL Veto Efficiency for Btn • Main background in Btn are B decays with KL . • How KL detection efficiency affect the precision of Br(Btn)?  requirement for super KLM e+ B+ ne D0 KL KL BNM2008@Atami

  9. KL Veto Efficiency Dependence • Toy MC results for several KL veto efficiencies. • Current is set to 35% • guess by geant simulation + J/yKL data • Q: How can we improve KL detection efficiency of super KLM? worse better KL veto efficiency BNM2008@Atami

  10. Summary • Boost factor and Hermeticity • Considering both tCPV and Btn measurements, current KEKB energy (8x3.5) seems the preferable point within the region KEKB can operate. • KL vetoefficiency for Btn • Higher KL veto efficiency is effective for Btn measurement • How can we improve KL detection efficiency of super KLM? • Dependence of other detector performances (PID, tracking&vertexing) must be checked and optimized. • Studies based on the fast simulator are being done. BNM2008@Atami

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