Search for Bsμμ and Bdμμ with 2 fb-1 of data CDF 8925 Slava Krutelyov UCSB with D.Glenzinski, H.Held (KIT), C.-J.Lin (FNAL) T.Kamon, M.Weinberger (TAMU) M.Herndon (UWisconsin) SUSY-Group Meeting 08/29/2007 blessed on Aug 09 Motivation and history Analysis Setup Event selection: signal discriminants muon ID with LH Neural Net (optimized) Expectations and results Effects on SUSY

S. Krutelyov Search for Bs,d-->mumu with 2 fb-1 08/29/2007 S. Krutelyov Search for Bs,d-->mumu with 2 fb-1

S. Krutelyov Search for Bs,d-->mumu with 2 fb-1 Motivations: Models n l’i23 l i22 ~ m b s MSSM With RPV: can proceed at tree level couplings not constrained much otherwise In general case has a diagram ~ tan6b/MH4 tan4b/MH4 come from MSSM is a 2HDM remaining tan2b is from SUSY (stop L-R mixing) Just need large tanb, not too-high MH, some stop mixing SO(10) with Yukawa unification tanb~50 ! mSUGRA with large tanb Other BSM: with no extra flavor structure the enhancement < ~ a factor of 2 With improving limits start asking any theorist “Is it allowed by Bsμμ?” More in the end of the talk EXCLUDED Bsmm appears to get into the “model exclusion hall of fame” Near 200 citations (combined for CDF/DØ RunII) in the past ~3 years 08/29/2007 S. Krutelyov Search for Bs,d-->mumu with 2 fb-1

S. Krutelyov Search for Bs,d-->mumu with 2 fb-1 Bits of history Search for Bsmm is as old as hadron colliders First looked at by UA1 Recent limits are all from Tevatron DØ is often close to CDF Prior 08/29/2007 S. Krutelyov Search for Bs,d-->mumu with 2 fb-1

Bs(d)m+m- Ingredients Normalize to B+J/y K+ decays Construct discriminant to select Bs and suppress bgd MC sim for signal Data mass sidebands for bgd estimate Minimize expected 90% C.L. upper limit Normalization mode Signal sample (baseline) Bd Bs N(UU+UX) ~ 3×104 08/29/2007 S. Krutelyov Search for Bs,d-->mumu with 2 fb-1

Improving sensitivity: muon ID Dx c2 cut  use muon LH (LH>0.1) Combined dX, dPhi, dZ, EM, HAD add dE/dX cut Z>-0.2 Suppress combinatorics ~x2 less events (after preselection) Bring Bhh below the horizon Bhh fakes are ~0.05 for Bs and ~0.5 for Bd windows cf. ~ 0.3 (Bs) and ~2 (Bd) with Dx c2 cut 08/29/2007 S. Krutelyov Search for Bs,d-->mumu with 2 fb-1

S. Krutelyov Search for Bs,d-->mumu with 2 fb-1 Normalization mode B+J/ψK+ + c.c. 08/29/2007 S. Krutelyov Search for Bs,d-->mumu with 2 fb-1

Discriminating variables Used as inputs to Neural Net R=1 a l μ pmm Bs l/s pTmm pTm 08/29/2007 S. Krutelyov Search for Bs,d-->mumu with 2 fb-1

Preselections: signal+sidebands Vertex Requirements: c2(vtx) < 15 s(L3D) < 150 mm L3D < 1 cm 0 < l < 3 mm (l = proper decay length) l/s(l) > 2 pT(B)>4 GeV && |y(B)|<1 4669 < M(mm) < 5969 MeV In addition: Isolation>0.5 Pointing angle Da<0.7 Bsmm Search Sample: N(CMU-CMU) = 15594 N(CMU-CMX) = 15072 (completely Bgd dominated) Note: without muon LH & dE/dX ~x2 more backgrounds here 08/29/2007 S. Krutelyov Search for Bs,d-->mumu with 2 fb-1

S. Krutelyov Search for Bs,d-->mumu with 2 fb-1 Signal MC Use Pythia BGen for systematics Reweigh to follow pT distribution from data Compare using B+ data and MC 08/29/2007 S. Krutelyov Search for Bs,d-->mumu with 2 fb-1

S. Krutelyov Search for Bs,d-->mumu with 2 fb-1 NN: inputs After applying pre-selections use sidebands (bgd) and signal MC to train NN 6 inputs to NN training λ – lifetime λ/σ – lifetime significance Δα – 3D poining (vtx vs momentum) Iso pT(B) pT(μ) min – lower of the pair 08/29/2007 S. Krutelyov Search for Bs,d-->mumu with 2 fb-1

NN inputs: x-check w data B+ plots Input variables are well-modeled including pT(μ) high used in the trial NN 08/29/2007 S. Krutelyov Search for Bs,d-->mumu with 2 fb-1

S. Krutelyov Search for Bs,d-->mumu with 2 fb-1 NN: output Compared to LH (used previously) get a better (~2 times) rejection at the same efficiency LH had 3 vars: Iso, P(λ), Δα 5 var NN: add λ/σ and pT(B) 7 var NN includes both pT(μ) introduces mass biasnot used 08/29/2007 S. Krutelyov Search for Bs,d-->mumu with 2 fb-1

NN output: x-check for biases The correlation is negligible No evidence of a bias here or in other x-checks checked w/ control samples, trained on part of sidebands, bootstrap use of sidebands is justifiable 08/29/2007 S. Krutelyov Search for Bs,d-->mumu with 2 fb-1

NN outputs: x-check w data B+ Good agreement 08/29/2007 S. Krutelyov Search for Bs,d-->mumu with 2 fb-1

S. Krutelyov Search for Bs,d-->mumu with 2 fb-1 Control Samples Independent bkg control samples to cross check bkg estimate procedure OS - : Opposite-sign dimuon sample with ct<0 SS+ : Same-sign dimuon sample with ct>0 SS- : Same-sign dimuon sample with ct<0 FM : Fake muon sample ct>0 (require at least one muon leg to fail our muon likelihood and dE/dX requirement) 08/29/2007 S. Krutelyov Search for Bs,d-->mumu with 2 fb-1

Control Samples: NN x-checks NN performance: observation is consistent with expectations Using a wider ± 150 MeV signal window for cross-check For obsv<pred, prob= probability for making an observation ≤ obsv 08/29/2007 S. Krutelyov Search for Bs,d-->mumu with 2 fb-1

Applying NN: getting expected bgd CMU-CMU CMU-CMX Shape in sidebands give contribution of combinatorial bgd to signal bins Separate fit in each NN bin: pol1 in bins 1, 2; pol0 in bin 3 08/29/2007 S. Krutelyov Search for Bs,d-->mumu with 2 fb-1

Inputs to the (exp./obs.) limit Inputs to be used in the “main” formula The biggest uncertainty is from fu/fs (after bgd stat) 08/29/2007 S. Krutelyov Search for Bs,d-->mumu with 2 fb-1

Optimization: choice of NN bins Relative (unnormalized) numbers are shown The choice (of 3 bins) is [0.8, 0.95]U(0.95, 0.995]U(0.995, 1] 08/29/2007 S. Krutelyov Search for Bs,d-->mumu with 2 fb-1

S. Krutelyov Search for Bs,d-->mumu with 2 fb-1 Bhh contributions Contribution to Bdμμ Contribution to Bsμμ The contribution to Bs is small, considerable for Bd 08/29/2007 S. Krutelyov Search for Bs,d-->mumu with 2 fb-1

Expectations and observations: Bs 08/29/2007 S. Krutelyov Search for Bs,d-->mumu with 2 fb-1

Expectations and observations: Bd 08/29/2007 S. Krutelyov Search for Bs,d-->mumu with 2 fb-1

S. Krutelyov Search for Bs,d-->mumu with 2 fb-1 Results: limits New world-best result 08/29/2007 S. Krutelyov Search for Bs,d-->mumu with 2 fb-1

S. Krutelyov Search for Bs,d-->mumu with 2 fb-1 Results: 2D plots P-value with bgd-only hypothesis, 10K pseudoexperiments CMU-CMU CMU-CMX Bsmm 16% 67% Bdmm 7% 58% Observed events are consistent with expectation 08/29/2007 S. Krutelyov Search for Bs,d-->mumu with 2 fb-1

Results: 2D plot combined 08/29/2007 S. Krutelyov Search for Bs,d-->mumu with 2 fb-1

S. Krutelyov Search for Bs,d-->mumu with 2 fb-1 Results: 1D plots Bs 2 events in CMU-CMU channel 1 event in CMU-CMX channel 08/29/2007 S. Krutelyov Search for Bs,d-->mumu with 2 fb-1

S. Krutelyov Search for Bs,d-->mumu with 2 fb-1 Limits history Getting better and better faster than 1/sqrt(Lumi), slower than 1/Lumi Unofficial Tevatron combination: Br(Bsμμ) < 4.5x10-8 @ 95% 08/29/2007 S. Krutelyov Search for Bs,d-->mumu with 2 fb-1

S. Krutelyov Search for Bs,d-->mumu with 2 fb-1 08/29/2007 S. Krutelyov Search for Bs,d-->mumu with 2 fb-1

SUSY contemplations (1) The importance of Bsμμ grows with tanβ SUSY with large tanβ becomes more popular driven by a more significant aμ now at ~3.4 σ away from SM The SO(10) scenario by Raby et al. is practically excluded now R. Dermisek et al., hep-ph/0507233 (2005) [easy model to exclude] SO(10) 08/29/2007 S. Krutelyov Search for Bs,d-->mumu with 2 fb-1

SUSY contemplations (2) Light MSSM Higgs scenario is next in line for significant exclusion. Belyaev et al. SUSY07 08/29/2007 S. Krutelyov Search for Bs,d-->mumu with 2 fb-1

SUSY contemplations (3) CDF Limit 5.8x10-8 2 fb-1 The limit eats further into the mSUGRA space now not as significant with bsγ constraint considered 08/29/2007 S. Krutelyov Search for Bs,d-->mumu with 2 fb-1

SUSY contemplations (4) Start getting beyond bsγ at high tanβ Still a way to go  2x10-8 will be way more noticeable 08/29/2007 S. Krutelyov Search for Bs,d-->mumu with 2 fb-1

S. Krutelyov Search for Bs,d-->mumu with 2 fb-1 Summary We have updated the Bmm analysis with 2 fb-1 The limits improved significantly: Br(Bsmm)<5.8×10-8 @ 95%CL Br(Bdmm)<1.8×10-8 @ 95%CL Both limits are the best in the world!!!! Plan to prepare/publish in PRL draft in progress ( to GPs this week?) 08/29/2007 S. Krutelyov Search for Bs,d-->mumu with 2 fb-1

S. Krutelyov Search for Bs,d-->mumu with 2 fb-1 backup 08/29/2007 S. Krutelyov Search for Bs,d-->mumu with 2 fb-1