Search for New Physics through Rare B Decays

Transcription

1 Search for New Physics through Rare B Decays S. Uozumi for the CDF-II collaboration 21 th Feb 2012 Lake Louis Winter Institute NP? NP?

2 B s µ + µ Search SM Expectation Br : (3.2 ± 0.2) 10 9 Rouzbeh Allahverdi, Bhaskar Dutta, Yudi Santoso arxiv: CDMS II JHEP 1009 (2010)106 Slepton/sqqark mass (GeV) Br enhancement By New Physics Excluded by a 1)Rare B decay b sγ 2)No CDM candidate 3)Muon magnetic moment b c Gaugino mass (GeV)

3 B s/d µ + µ Method: Relative normalization counting Same method with previous 6.9 fb -1 results last summer (PRL 107, ) This analysis updates results with whole 9.7 fb -1 of CDF Run-II data Measure the rate of B s/d μ + μ - decays relative to B + J/ψK + control sample 1. Apply same event pre-selection to both sample 2. B s μ + μ - sample is highly purified by Neural Network (NN) event selection 3. NN takes 14 kinematic variables and output value ranging 0 (BG like)~1 (signal like) 4.B s μ + μ - candidates are categorized into 8 different NN value bins for counting 5. BG shape is determined from di-muon mass sideband fitting Original B s μ + μ - and B + J/ψK + samples Pre-selected B + J/ψK + Pre-selection Pre-selected B s μ + μ - Neural Network Final B s μ + μ - sample NN out= NN out= NN out= Typial BG fitting For one NN output bin B s /B d Signal region

4 B s µ + µ old result with 7 fb -1 (Aug 2011) CDF II 7 fb -1 Central-Central muons Central-Forward muons Observed a >2σ excess over background only, fit for the signal branching ratio and obtain Br(B s µ + µ ) < 4.0 (3.5) 10 8 at 95% (90%) C.L. From a small excess, we have set double-sided limit Br( B µ µ ) = which is ~2σ away from SM expectation. s Now we update the result on the whole Run II data sample WITHOUT CHANGING anything in the 7 fb -1 analysis (PRL 107, ).

5 M µµ for B d µ + µ - with CDF-II full dataset Observed events are fairly consistent with background. Set Br. upper limit Br(B d µ + µ ) < 4.6 (3.8) 10 9 at 95% (90%) C.L. 5

6 M µµ for B s µ + µ - with CDF-II full dataset CDF II Preliminary 9.7 fb -1 Central-Central muons Central-Forward muons Excess not reinforced by new data but still there. Best fit estimates a 2σ excess of signal over background yielding 6

7 B s µ + µ - Double-sided Br. Limit with 9.7fb -1 SM prediction with SM prediction Br(3.2 ± 0.2) 10 9 p-values assuming B s background only : 0.94% B s SM+background : 7.1% still ~2σ away from SM Single-sided upper limit : Br(B s µ + µ ) < at 95% C.L. From previous 7.0 fb -1 result, central value of Br. fraction shifted to lower value, however still stays around ~2σ region from the SM. 7 Public note and paper preparation underway.

8 B s µ + µ - LHCb, CMS and CDF Expected CDF single-sided limit (95%) Observed CDF single-sided limit (95%) CDF double-sided limit 8

9 b sµ + µ for New Physics Strongly suppressed in SM due to 2 nd order weak interaction New physics in a loop can change Br. Fraction and kinematics of those event NP? Many channels with different spectator quark flavors available to explore b sµ + µ decays Tools to go beyond SM : Br. fraction of several B baryons into b sµ + µ process Direction, angle of outgoing particles may differ depending on intermediate new physics model 9

10 Reconstructed b sµ + µ events and Br. fractions CDF II 6.7 fb -1, Phys. Rev. Lett 107, (2011) Br(Λ b0 Λμ + μ - ) =[1.73±0.42(stat)±0.55(syst)] 10-6 Br(B s0 φμ + μ - ) =[1.47±0.24±0.46] 10-6 Br(B + K + μ + μ - ) =[0.46±0.04±0.02] 10-6 Br(B 0 K *0 μ + μ - ) =[1.02±0.10±0.06] 10-6 Br(B 0 K 0 μ + μ - ) =[0.32±0.10±0.02] 10-6 Br(B + K *+ μ + μ - ) =[0.95±0.32±0.08] 10-6 World s first observation!! Other B 0/+ K µ + µ channels have comparably large statistics with B factories & LHC. 10

11 Event-shape (A FB ) analysis for b sµ + µ decay There are various event-shape parameters to access physics beyond the SM (arxiv: ) Most interesting parameter is FB asymmetry as a function of q 2 =M µµ 2 compared with muon polar angle in B rest frame : CDF 6.8 fb -1 Current CDF result based on 6.8fb -1 (arxiv: ) Both CDF and LHCb results are approaching to SM prediction. From LHC talk onaug 11 by P. Koppenburg CDF is finishing analysis using full 9.7fb -1 of data. Stay tuned! 11

12 Summary & Conclusions B rare decays are excellent stage to search for New Physics effect. Using full 9.7 fb -1 of CDF Run-II data sample, we measured : Latest CDF result stays ~2σ from SM Various b sµ + µ decay channels are observed with 6.8 fb -1 of data : Br(Λ b0 Λμ + μ - ) =[1.73±0.42(stat)±0.55(syst)] 10-6 Br(B s0 φμ + μ - ) =[1.47±0.24±0.46] 10-6 Br(B + K + μ + μ - ) =[0.46±0.04±0.02] 10-6 Br(B 0 K *0 μ + μ - ) =[1.02±0.10±0.06] 10-6 Br(B 0 K 0 μ + μ - ) =[0.32±0.10±0.02] 10-6 Br(B + K *+ μ + μ - ) =[0.95±0.32±0.08] 10-6 world s first!! A FB result with full CDF Run-II data analysis will come out soon!