1. 1 Search for FCNC Decays B s(d) → μ  μ - Motivation Analysis Method Results Conclusion Matthew Herndon, University of Wisconsin For Doug Glenzinski, Hauke Held, Teruki Kamon, Vyacheslav Krutelyov, Cheng-Ju Lin, Michael Weinberger CDF Paper Seminar

2. 2 Why Beyond Standard Model? Standard Model predictions validated to high precision, however Billions of B and Charm events on tape Can look for some very unusual processes M. Herndon Gravity not a part of the SM What is the very high energy behaviour? At the beginning of the universe? Dark Matter? Astronomical observations of indicate that there is more matter than we see Where is the Antimatter? Why is the observed universe mostly matter? How to look for new physics Direct Searches - limited by energy reach of accelerator Indirect searches: Standard Model fails to answer many fundamental questions CDF Paper Seminar 2007

3. 3 B s(d) → μ + μ - Beyond the SM Look at processes that are suppressed in the SM Excellent place to spot small contributions from non SM contributions B s(d) →  μ  μ - SM: No tree level decay CKM,GIM and helicity suppressed BF(B s →  μ  μ - ) = 3.5x10 -9 New Physics: Loop: MSSM: mSugra, Higgs Doublet 3 orders of magnitude enhancement Rate  tan 6 β/(M A ) 4 M. Herndon Same particles/vertices occur in both B decay diagrams and in dark matter scattering or annihilation diagrams CDF Paper Seminar 2007

4. 4 B s → μμ  Experimental Challenge M. Herndon Primary problem is large background at hadron colliders Analysis and trigger cuts must effectively reduce the large background around m Bs = 5.37GeV/c 2 to find a possible handful of events Key elements of the analysis are determining the efficiency and rejection of the discriminating variables and estimating the background level 200M Events CDF Paper Seminar 2007

5. 5 Data Sample M. Herndon Start the with di-muon trigger: 1.9fb -1 2 CMU muons or 1 CMU and 1CMX muon with  p Tμ > 5.0GeV/c CMU: p T (μ) > ~1.5 GeV/c, |η| ~2.0 GeV/c, 0.6 < |η| < 1.0 Apply basic quality cuts Track, vertex and muon quality cuts Muon Likelihood and dE/dx selection (New Element) High efficiency: 97%, Removes 35% combinatoric background (46K previously) Reduces B  hh to negligible levels (tenth of an event or less) Loose preselection on analysis cuts P T (μ  μ - ) > 4.0 GeV/c, 3D Decay length significance > 2 … In the mass region around the B s : 4.669 < M μμ < 5.969 GeV/c 2 Blind region: 4σ(M μμ ), 5.169 < M μμ < 5.469 GeV/c 2 Sideband region 0.5 GeV/c 2 on either side of the blinded region 200M Events 30K Events CDF Paper Seminar 2007

6. 6 B s(d) → μ + μ - Method M. Herndon Relative normalization search Measure the rate of B s(d) → μ + μ - decays relative to B  J/  K + Apply same sample selection criteria Systematic uncertainties will cancel out in the ratios of the normalization Example: muon trigger efficiency same for J/  or B s  s for a given p T 1.9 X 10 8 B + events CDF Paper Seminar 2007

7. Need to discriminate signal from background Reduce background by a factor of > 1000 Signal characteristics Final state fully reconstructed B s is long lived (cτ = 438 μm) B fragmentation is hard: few additional tracks Background contributions and characteristics Sequential semi-leptonic decay: b → cμ - X → μ + μ - X Double semileptonic decay: bb → μ + μ - X Continuum μ + μ - μ + fake, fake+fake Partially reconstructed, lower p T, short lived, has additional tracks 7 Signal vs. Background M. Herndon ++ -- L 3D primary vertex di-muon vertex P(  ) L 3D primary vertex di-muon vertex ++ -- P(  ) L 3D - Cut on mass, lifetime, p T, how well p points to the vertex and isolation 30K Events CDF Paper Seminar 2007

8. 8 Discriminating Variables M. Herndon Mass m  2.5σ  window: σ = 24MeV/c 2 λ=cτ/cτ Bs,  λ  α : |φ B – φ vtx | in 3D Isolation: p TB /(  trk + p TB ) p T  and p T second muon Combine all but m  in NN(New Element) Removes 25% of the background Set limits in using 3 NN bins and 5 mass bins (New Element) Improves expected limit by 25% Unbiased optimization Based on simulated signal and data sidebands 7 primary discriminating variables DSU 2007CDF Paper Seminar 2007

9. 9 Expectations NN Efficiencies and Background: B s M. Herndon Expected B s limit: 4.9x10 -8 95% CL Previous CDF publication 2.4x10 -7 NN  NN B  hh Background Total Background Expected SM Signal 0.995-1.044% 0.0393.5 ± 0.20.3 ± 0.1 0.95-0.99523% 0.02018.0 ± 0.70.15 ± 0.05 0.8-0.9512% 0.01149.5 ± 0.90.08 ± 0.03 An extrapolation based on the previous publication using 364pb -1 indicated that we would have expected 8x10 -8 We achieved a factor of 5 improvement: Progression in the limit with  L CDF Paper Seminar 2007

10. Previous B s result: 2.0  10 -7 10 B s(d) → μ + μ - Search Results M. Herndon BF(B s   +  - ) < 5.8x10 -8 at 95% CL BF(B d   +  - ) < 1.8x10 -8 at 95% CL NN Total Background Observed Events 0.995-1.0 3.5 ± 0.23 0.95-0.995 18.0 ± 0.721 0.8-0.95 49.5 ± 0.944 1 event in most signal like bin and one in the adjoining bin! The hint of the first B s(d) → μ + μ - signal? What does it all mean? CDF Paper Seminar 2007

11. 11 B s → μ + μ -  Physics Reach Strongly limits specific SUSY models: SUSY SO(10) models Allows for massive neutrino Incorporates dark matter results BF(B s   +  - ) < 5.8x10 -8 at 95% CL Excluded at 95% CL (CDF result only) BF(B s   +  - ) = 1.0x10 -7 BF(B s   +  - ) = 5x10 -8 Dark matter constraints L. Roszkowski et al. JHEP 0509 2005 029 A close shave for the theorists Typical example of SUSY Constraints However, large amount of recent work specifically on dark matter CDF Paper Seminar 2007

12. 12 B s → μ + μ - and Dark Matter B s →  μ  μ - correlated to dark matter searches CMSSM supergravity model B s →  μ  μ - and neutralino scattering cross sections are both a strong functions of tanβ In high tanβ(tanβ ~ 50), positive μ, CDM allowed Current bounds on B s →  μ  μ - exclude parts of the parameter space for direct dark matter detection M. Herndon More general scan in m 0, m 1/2 and A 0, allowed region S. Baek, D.G. Cerdeno Y.G. Kim, P. Ko, C. Munoz, JHEP 0506 017, 2005 CDF Paper Seminar 2007 R. Austri, R. Trotta, L. Roszkowski, hep-ph/0705.2012

13. 13 B Physics and Dark Matter Putting everything together including most recent theory work on b  s  and g-2 M. Herndon Current experiments starting to probe interesting regions Analysis shows a preference for the Focus Point region Higgsino component of Neutralino is enhanced. Enhances dominant Higgs exchange scattering diagrams and B s → μ + μ - Interesting relative to SUSY Higgs searches at Tevatron and LHC However Xenon 10 Preliminary Excluded by new B s →  μ  μ - tan  =50 CDF Paper Seminar 2007 R. Austri, R. Trotta, L. Roszkowski, JHEP 0605 002, 2006 S. Baek, et.al.JHEP 0506 017, 2005

14. M. Herndon14 Conclusions Best B s and B d results: well ahead of D0 and the B factories Limit excludes part of parameter space allowed by SO(10) models Expanding sensitivity to interesting areas of MSSM parameter space Results correlated with some of the other most interesting topics in physics such as Higgs searches and dark matter! B (s,d) →  μ + μ -  results BF(B s   +  - ) < 5.8x10 -8 at 95% CL BF(B d   +  - ) < 1.8x10 -8 at 95% CL Worlds Best Limits! CDF Paper Seminar 2007