1. 1 Searching for New Physics in Beauty and Charm Brendan Casey Brown University Stony Brook HEP Seminar February 13, 2007

2. 2 What is new physics? Current theories explain the entire dynamics of our universe from about 1 second after birth. What was happening before the 1 st second? –New physics is what ever it takes to answer this question.

3. 3 Matter at t ≥ 1 second: BBN Burles, Nollett, Turner astro-ph/99003300 Evolution of light elements in first hour of the universe Extraordinary success of GR, astro, particle, nuclear physics But: Small excess of baryons is an initial condition of BBN, not a prediction. No explanation of the evolution of anti- elements

4. 4 CPV: Standard Model to the rescue? mass basis, d,s,b weak basis, d, s, b quarks: d I = V ij d j antiquarks: d i = V ij *d j Provides a mechanism to generate a net baryon number through decay of heavy to light particles V ub ≠ V ub *, V td ≠ V td *  CPV production decay

5. 5 Standard Model CPV Mag(CPV) ≈ f(m 2 j -m 2 i ) × f(  ij ) × sin  CP Three properties govern size of CPV in SM: quarks: –Large mass splitting ↑ –Small mixing angles ↓ –Large  CP  ↑ neutrinos: –small mass splitting ↓ –large mixing angles ↑ –  CP  ? ~15 orders of magnitude too small Huet, Sather PRD51 379 (1995) Jury still out Need new sources of CPV! More generations, more interactions….new particles

6. 6 Direct versus Indirect Year quark mass (GeV/c 2 ) t t 1 TeV p 5 GeV B t t b d b d W W charm discovered 1974 bottom discovered 1977 top discovered 1995 charm predicted, mass scale set by K→  1970 bottom and top predicted from CPV in kaon mixing 1973 Top mass scale set from B d mixing 1987 direct indirect

7. 7 Cast of Characters Mesons B 0 : ( b d ), B s : ( b s ), D + : ( c d ), D s : ( c s ) Flavor Changing Interactions b t s b t s Box: Penguin:

8. 8 Apparatus

9. 9 The Tevatron and DØ Detector 400 MeV 150 GeV ~1 TeV + 1 TeV

10. 10 Why the Tevatron? Don’t they do B physics at B factories now? B factory on  (4S) @ L = 10 34 cm -2 s -1 Tevatron @ L = 10 32 cm -2 s -1 B production rate~10 Hz~1 kHz B s production rate0~100 Hz Longitudinal boost~0.5~1-2 Transverse boost~0~1-2 Tevatron is the only B s factory

11. 11 Why DØ? Excellent muon identification Large semileptonic B samples ideal for mixing and CPV studies Uranium Iron

12. 12 Why DØ? Excellent vertexing capabilities for flight length determination Just enough resolution to probe SM expected value of the B s mixing frequency Error on the flight length determination

13. 13 Tevatron Data Set >2.3 fb -1 delivered FY01 FY02 FY03 FY04 FY05 FY06 FY07 Run IIa: 1.3 fb -1 on tape Run IIb: 700 pb-1 analyzed

14. 14 Tevatron Data Set >2.3 fb -1 delivered FY01 FY02 FY03 FY04 FY05 FY06 FY07 Run IIa: 1.3 fb -1 on tape Run IIb: 700 pb-1 analyzed Fast turn around in the heavy flavor group 10 1.0 fb -1 results last winter Pushing for close to 2 fb -1 results this winter

15. 15 B s Mixing

16. 16 General rule of neutral flavor changing processes: –New physics: Second order loop or box New particles can enter the loop SM contribution is suppressed –Precision SM tests: no new physics? Measure fundamental Standard Model parameters clean in B mesons –b quark is heavy, –top loop dominates. Every measurement of mixing has lead to a major discovery: K: CPV, 3 rd generation, B d : top mass, : neutrino mass Why Mixing? b ??? s b t V td(s) s,d Rate ≈ ( m t / m W ) 2 s,d

17. 17 Analysis Overview ++    K+K+ KK  +,e +  q B s Candidate Recoil system Primary and secondary vertices Reconstruct the B s in a flavor specific final state Determine lifetime in the B s rest frame Determine initial flavor by studying recoil system Extract the mixing frequency from the time dependence of mixed and unmixed samples

18. 18 Mixing Frequency Extraction Reconstructed decay length (cm)

19. 19 Mixing Frequency Extraction Reconstructed decay length (cm) Looking for this Reconstructed decay length (cm)

20. 20 Mixing Frequency Extraction Reconstructed decay length (cm) Perform a Fourier analysis of the decay length distribution to extract the mixing frequency Power Spectrum for winter data set Time domain Frequency domain 1/  m mm

21. 21 Winter 06 Mixing Frequency Results  m s < 21 ps -1 @ 90% CL Maximum likelihood at  m s = 19 ps -1 1 fb -1 First time  m s bounded on both sides!!!!! Change in –log(L) versus  m s D s →  only

22. 22Reflections m(    ) m(  S  ) D s →K*K D + →K   c →pK  D s →K S K D + →K S   c →K S p Original results based on D s →  Needed to add more channels: K*K and K S K Difficult to include these modes without particle identification

23. 23 Taming Reflections Momentum asymmetry between K S and K candidate Take advantage of the fact that the mass shift is a function of the particle momentum D + →K S  MC m(  S  ) m(  *  ) High p low p

24. 24 Fall 06 Results   K*K   e  S  Extra data ‘cured’ fluctuation

25. 25 Time Evolution of Results LEP/SLD/CDF I were able to exclude values below about 15 ps -1 New Physics Realm msms LEP/SLD Era SM expectation

26. 26 Time Evolution of Results March 06: DØ provides first upper bound on the B s oscillation frequency. Rules out large new physics effects at high confidence level. Still 5% chance of background fluctuation. msms New Physics Realm SM expectation DØ, March 2006

27. 27 Time Evolution of Results Confirmed by CDF in April 2006. >5  measurement Fall 2006. Closes the chapter on the magnitude of the Bs oscillation frequency. msms New Physics Realm SM expectation Tevatron Era 17.7+/- 0.12 ps -1

28. 28 Indirect Searches so far Now reached SM level for one of our key indirect NP search modes,  m s. –No new physics. Not just a Tevatron problem, problem for B physics in general. Choice: –Wait for new energy frontier –Expand current physics program beauty → charm

29. 29 Flavor Changing Neural Current Charm Decay

30. 30 Up versus Down Generation Mass (MeV/c 2 ) up line q = 2/3 down line q =  1/3 t c u d s b

31. 31 Up versus Down Generation Mass (MeV/c 2 ) up line q = 2/3 down line q =  1/3 t c u d s b Very different mass hierarchy

32. 32 Up versus Down Generation Mass (MeV/c 2 ) t c u d s b c u b W+W+ WW up FCNC ~ ( m b / m W ) 2 WW W+W+ b s t down FCNC ~ ( m t / m W ) 2

33. 33 Up versus Down Generation Mass (MeV/c 2 ) t c u d s b c u b W+W+ WW up FCNC ~ ( m b / m W ) 2 WW W+W+ b s t down FCNC ~ ( m t / m W ) 2 Down the down line: suppressed but measurable (eg. mixing) Down the up line: almost impossible for SM, any signal = new physics

34. 34 Why 3 body FCNC charm? D +     m(       GeV) 0.5 1.0 1.5 (1/  )(d  /dm 2 )  GeV -2 ) 10 -4 10 -6 10 -8 10 -10 Long distance Short distance c u   Two processes: Long distance (strong scale), short distance (weak scale) Clear separation of long distance and short distance components New Physics only effects short distance. (rare clean channel)   c s s u d D+D+ ++  D→  D→ 

35. 35 New Phenomena in c  u     New Phenomena in c  u     Strict limits from b  s, interesting scenarios effect up sector quarks and not down sector quarks.

36. 36 New Phenomena in c  u     New Phenomena in c  u     Strict limits from b  s, interesting scenarios effect up sector quarks and not down sector quarks. D +     m(      GeV) 0.5 1.0 1.5 (1/  )(d  /dm 2 )  GeV -2 ) 10 -4 10 -6 10 -8 10 -10 RPV in the up sector and not the down sector Burdman et al. hep-ph/0112235 c  u    

37. 37 New Phenomena in c  u     New Phenomena in c  u     Strict limits from b  s, interesting scenarios effect up sector quarks and not down sector quarks. D +     m(      GeV) 0.5 1.0 1.5 (1/  )(d  /dm 2 )  GeV -2 ) 10 -4 10 -6 10 -8 10 -10 RPV in the up sector and not the down sector Burdman et al. hep-ph/0112235 c  u     Little Higgs models with new up sector vector quark Fajfer et al. hep-ph/0511048 factors of >1000 over SM not ruled out.

38. 38 D Selection Require well reconstructed track in the muon spectrometer matched to a central track with p T >2 GeV, p > 3 GeV First select     0.96 < m(  ) < 1.06 GeV  1.3 fb -1 Combine     with a track in the same jet and select D candidate 1.4 < m  ) < 2.4 GeV   

39. 39 Best Track Selection Large track multiplicity leads to several candidates per event. Select best track based on the D vertex  2, and distance between the track and the dimuon system M =  2 +  R 2 All candidates false candidates correct candidate Candidate multiplicity 0 5 10 15 20 25  MC

40. 40 Background Suppression Isolation Flight length significance  impact parameter significance Colinearity angle SS D s MC D + MC data sidebands

41. 41 Results for Resonance Production Long Distance D  Dimuon invariant mass n(D + ) = 115 +/- 33 > 4 sigma n(D s ) = 254 +/- 38 BF( D         (1.41 +/- 0.40 +/- 0.46) x 10 -6 (PRL for 1.3 fb -1 result about to be released.) D significance > 5 Pion IP significance > 0.5 1.3 fb -1

42. 42 Next Step: Continuum Production By making a cut on m(  ) around the , we clearly see the long distance component Now make a  veto Large background → enormous background Long Distance D  n(D + ) = 115 +/- 33 > 4 sigma n(D s ) = 254 +/- 38 1.3 fb -1

43. 43 More Background Reduction Next step: continuum production. Much larger dimuon phase space requires more stringent requirements

44. 44 Continuum Results n = 19 n(bkg) = 31 +/- 4 Short Distance D  (PRL for 1.3 fb -1 result about to be released.) 1.3 fb -1 BF( D  )<2.85×10  6 @90% CL

45. 45 Continuum Results n = 19 n(bkg) = 31 +/- 4 Short Distance D  How are we doing? factor of ~4 better than dedicated charm experiments Factor of ~10 better than B factories 1.3 fb -1 BF( D  )<2.85×10  6 @90% CL (PRL for 1.3 fb -1 result about to be released.)

46. 46 Conclusions

47. 47Conclusions DØ Heavy Flavor program producing several world’s first or world’s best results –4 years ago prevailing opinion was that you don’t do B physics at DØ Presented today: –First upper limit on the B s mixing frequency no smoking gun for new physics in  m s –Best limits on new physics in rare charm decays. Basically rules out possibility of finding a smoking gun in charm. Results: –Demonstrated a lack of enhancement in almost all low energy FCNC processes. Tells you that the next theory beyond the standard model must have mechanisms that supress FCNC Next steps: –Go find these new particles directly at the LHC