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Rare Charm Decays Recent Results from FOCUS (+Theory) Will E. Johns (for the FOCUS collaboration) FPCP5 (05/17/02) SM MSSM Exotics

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Recent Results from FOCUS Concentrate on Background Effects In the Confidence Limit Calculation Background Fluctuations Treat like a nuisance parameter? Include as a systematic? Include in likelihood: Rolke-Lopez [hep-ph v2]

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Probability of finding a signal rate and a background rate b given x events in a signal region and y events in background sidebands. Where is the ratio of the number of background events(using MC!) in the sideband regions to the signal region:

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And it’s not just my P.O.V. … A reminder during “Journeys of an Accidental Statistician” [Gary Feldman, Fermilab conference on CL, March 2000] from the 1998 PDG [Euro. Phys. J. C3(1998)]: “…we suggest that… a measure of sensitivity should be reported whenever expected background is larger or comparable to the number of observed counts.”

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In the Event Selection Too! Optimizing a cut grid in the presence of background can still bias You can easily choose a downward fluctuation in the background and produce (you hope) an over-conservative limit. Approach: BOOTSTRAP (two ways) Best Limits, Optimizing Sensitivity (Dual) Best Limit, Optimizing Cuts w/Sensitivity (as a check on the Dual Bootstrap) (Bootstrap = Sample with replacement)

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Dual Bootstrap (NIM article in draft from Rolke-Lopez)

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Cut Bootstrap (Developed by Dan Engh for his thesis)

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Data from run of FOCUS Over 1,000,000 Reco’d. Charm Excellent: -Vertex Resolution -Particle ID -Momentum Res. -Lots of Pubs… FOCUS Detector References: [NIM A320(1992) 519] [NIM A329(1993) 62] [hep-ex/ ] [hep-ex/ ] [hep-ex/ ]

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Look at decays with 2 or more muons Cut Grid, based on vertexing, Particle ID L/ – vary from >5-21 L pp ss ISO1 – CL DK’s in prim (vary <0.1 –0.001) Vary Cerenkov cuts for ’s and K’s (likelihood differences) DCL – CL of DK vertex (>1 -- 4%) MuCL – CL for Muon ID (>1 – 10%) Cut on P, (bigger MCS, more h- at low P)

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Normalize Rare modes to Golden/Silver modes Ds+ +-+Ds+ +-+ D+ -+-D+ -+- Goal (loosest cuts)

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After 1 st Bootstrap After 2 nd Bootstrap Raw Cut Grid Sensitivities D + + + - Dual Bootstrap Results Preliminary

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D + + + - Dual Bootstrap Results Raw Branching Ratios (All Cuts) 2 nd Bootstrap Branching ratios Remember: Cuts chosen by optimizing Sensitivity (Box Closed) in the 1 st Bootstrap Preliminary

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D + + + - Dual Bootstrap Results Preliminary Sensitivity vs. Branching Ratio (as promised…)

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And in case you’re curious… Rolke-Lopez compare to Unified (Feldman-Cousins) Preliminary D+ ++-D+ ++- (sorry, using mean values here…)

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Why Bother? MSSM R-Parity Violating Terms Boost Rates [hep-ph/ v2] (SM calcs are SO low…) -Look for new Physics!- (Burdman, Golowich, Hewett, Pakvasa) (Away from poles!)

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Acceptance is important! Monte Carlo relative efficiencies for events generated flat across the dalitz surface 1 2 3

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Decay Mode Dual Bootstrap Sys. Error Result W/sys Sensitivity W/sys Single Cut(w/sys) Previous (E791) D+ ++-D+ ++- 9.1x % 9.2x x x x10 -5 D+ -++D+ -++ 1.3x % 1.3x x x x10 -5 D+ ++-D+ ++- 8.8x % 8.8x x x x10 -5 D+ -++D+ -++ 4.9x % 4.8x x x x10 -5 Ds+ ++-Ds+ ++- 3.3x % 3.6x x x x10 -4 Ds+ -++Ds+ -++ 1.3x % 1.3x x x x10 -4 Ds+ ++-Ds+ ++- 2.4x % 2.6x x x x10 -4 Ds+ -++Ds+ -++ 2.6x % 2.9x x x x10 -4 (E687) Dominated by PDG rate to normalizing mode All other modes, nearly final (still preliminary) FOCUS results (Many thanks to Dan Engh for all his work!)

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Decay Fraction Result W/sys MSSM R-Parity SM-1SM-2 D+ ++-D+ ++- 9.2x x10 -9 D+ -++D+ -++ 1.3x10 -5 D+ ++-D+ ++- 8.8x x x x10 -6 D+ -++D+ -++ 4.8x10 -6 Ds+ ++-Ds+ ++- 3.6x x10 -8 Ds+ -++Ds+ -++ 1.3x10 -5 Ds+ ++-Ds+ ++- 2.6x x10 -6 Ds+ -++Ds+ -++ 2.9x10 -5 All other modes, nearly final (still preliminary) FOCUS results Compared to recent Theory [hep-ph/ v1] [hep-ph/ v2] Sets New Limit!

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Not quite ready for prime time from FOCUS D0 +-D0 +- Preliminary! FOCUS Sensitivity: 1.2x10 -6 Theory R-Parity MSSM: 3.5x10 -6 SM1: 3.0x PDG:<4.1x10 -6 Expect D + + + - soon (Hugo Hernandez UPR) (from Dan Engh too)

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Wrap-Up FOCUS results will set new limits (x10 in some cases) New Limit on R-Parity Violating MSSM Bootstrapping gives you more info when calculating limits More results coming soon from FOCUS Room for x10 stats before SM kicks in

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