1. Measurement of the Ratio B (  b   c  )/ B (  b   c  ) && Search for Anomalous Production of Diphoton + e/  at CDF Shin-Shan Yu ( 余欣珊 ) Fermi National Accelerator Laboratory Academia Sinica HEP Seminar, January, 2007

2. Shin-Shan Yu2 DATA SAMPLE FOR THE ANALYSES Lambdab relative BR Sep 2003 shutdown Diphoton + e/mu Mar 2006 shutdown

3. Measurement of the Ratio B (  b   c  )/ B (  b   c  )

4. Shin-Shan Yu4 OUTLINE Why  b CDF Detector, Trigger  b Relative Branching Fractions bb udb

5. Shin-Shan Yu5 BIG PICTURE : WHY  b BARYON ? u d b Heavy Quark Effective Theory (HQET) simplifies the extraction of CKM elements Assuming m b >>  QCD Corrections expressed in the power of 1/m b and  s (m b ) Spin-independent interaction between light quarks and b quark Spin of light degrees of freedom = 0, the corrections are simpler than those of b- mesons. q ud

6. Shin-Shan Yu6 HOW B (  b   c  )/ B (  b   c  ) ? Four charged tracks in the final state Data come from the same trigger, most systematics cancel. Control samples: similar decays in the B meson system Relative BR is the yield ratio corrected for the efficiency, e.g: and But since we can not reconstruct neutrinos, several backgrounds can fake our semileptonic signals in the data ….

7. Shin-Shan Yu7 CDF DETECTOR & TRIGGER Silicon Tracker |  | < 2  vertex ~ 30  m Central Outer Tracker (COT) 96 layers drift chamber, up to |  |~1  P T /P T ~ 0.15% P T Central Muon Chamber 4 layers drift chamber outside the calorimeter |  | < 0.6 Two Displaced-track Trigger p T > 2 GeV/c, 120  m ≤ d 0 ≤ 1 mm, L xy > 200  m,  p T > 5.5 GeV/c 150 M events analyzed for this measurement

8. Shin-Shan Yu8 FORMULA REMINDER

9. Shin-Shan Yu9 ANALYSIS REQUIREMENTS 2 out of 4 tracks matched to trigger tracks (two displaced-track trigger) Muon 120  m ≤ d0 ≤ 1 mm Pt(4 trks) > 6 GeV/c Pt(Lc) > 5 GeV/c Pt( ,  ) > 2 GeV/c Pt(proton) > 2 GeV/c Chi2 of secondary vertex fit < 15 Chi2 of tertiary vertex fit < 14 c  of Lb candidate > 250  m c  of Lc candidate > -70  m 3.7 < M(Lc  ) < 5.64 GeV/c2

10. Shin-Shan Yu10 SIGNAL SAMPLE  b   c X  c  p + K -  + Inclusive Semileptonic Signal  NDF=36.6/42 Prob=70.7% Inclusive b hadron -> X  decays reconstructed as  c  Hadronic Signal Background shapes come from MC Combinatorial and b-> other c hadron semileptonic decays

11. Shin-Shan Yu11 FORMULA REMINDER

12. Shin-Shan Yu12 MC AND DATA COMPARISON We used MC to obtain relative efficiencies of signals and backgrounds. Compare MC and background subtracted signal distribution in the data. Tune our MC if MC and data disagree, e.g: P T (  b ) P T (  b ) [GeV/c] BEFOREAFTER P T (  b ) [GeV/c]

13. Shin-Shan Yu13 FORMULA REMINDER

14. Shin-Shan Yu14 SOURCES OF SEMILEPTONIC BACKGROUND Feed-down/Feed-in from single b-hadron decays Single b-hadron -> …. ->  c  additional particles e.g: Hadrons mis-identified as muons Real Lambdac and real muon from the decay of two heavy-flavor hadrons

15. Shin-Shan Yu15 FEED-DOWN/IN FROM SINGLE B-HADRON Reduced by the M(  c  ) cut Normalize the amount of background to the measured hadronic signal BR from PDG or estimated from theory and CDF preliminary measurements Reconstruct as many backgrounds as possible PDG BR(  b ->  c  X)=9.2%  constrain BR of the other backgrounds ~10% contribution

16. Shin-Shan Yu16 ?? MIS-IDENTIFIED MUONS p, K,  fake muons c  and muon d 0 cuts suppress prompt fakes Our fakes mostly come from b decays Weight “  c +TRK fail  ” events with the P fake ~3% contribution

17. Shin-Shan Yu17  c  FROM TWO HEAVY-FLAVOR HADRONS Charm and  from different b- or charmed hadrons Suppressed due to the c  and P T (  ) cuts Rely on Pythia MC Most sensitive to hard gluon splitting ~0.2% contribution Assign 100% uncertainties c+c+ p+p+ p+p+ c+c+

18. Shin-Shan Yu18 SEMILEPTONIC SAMPLE FRACTION

19. Shin-Shan Yu19 CONSISTENCY CHECK

20. Shin-Shan Yu20 UNCERTAINTY SUMMARY fractional uncertainty (%) Measured BR +3.5 -10.5  8.2  2.3 Estimated BR  2.5  9.2  6.2 CDF Internal Mass fitting  3.2  4.1 < 0.1 Muon fake  0.9  0.7  0.4 Pt spectrum+1.4-2.5  3.2  2.2 CDF material  1.1  1.7  1.3  scaling  0.4  0.5  0.4  0.2  2.2  1.3  b,c polarizations  1.9 --  c Dalitz  0.4 --  b lifetime  1.1 --  b decay model  2.9 --  6.0  6.1  3.4 Statistical  15.0  10.2  13.0 Feed-in/down background and hadronic signal branching fractions MC modeling of production, decay, efficiency and acceptance

21. Shin-Shan Yu21 CONTROL SAMPLE RESULT Consistent with the 2004 world average 7.8  1.0 at the 1  level New world average ratio 8.3  0.9 Consistent with the 2004 world average 19.7  1.7 at the 0.7  level New world average ratio 19.1  1.4

22. Shin-Shan Yu22 SIGNAL SAMPLE RESULT Experimental uncertainties dominated by data sample size

23. Unexpected and additional physics results

24. Shin-Shan Yu24 FIRST OBSERVATION of NEW  b DECAYS Estimated BR of the reconstructed background based on the first observation  c ++ CDF Run II Preliminary 360 pb -1  c (2593)  c (2625) CDF Run II Preliminary 360 pb -1 c0c0  c ++,+,0  c (2625)  c (2593)

25. Shin-Shan Yu25 CROSS-SECTION RATIO AND B(  b   c  Consistent with the prediction 0.45% (Phys. Lett. B586, 337) ??? Make use of previous CDF measurements  b P T spectrum using fully reconstructed decay was not available for CDF I Correct the CDF I cross-section ratio using measured P T spectrum Acceptance correction Different P T thresholds affect the ratio 10 GeV/c vs. 6 GeV/c

26. Shin-Shan Yu26   AND  b PT SPECTRA FROM DATA

27. Shin-Shan Yu27 WHAT DO WE KNOW ABOUT  b NOW?  c l  c  20.0  3.7  c (2593) + l  seen  c (2625) + l  seen  c ++   l  seen  c 0   l  seen (4.1  2.0) x 10 -3

28. Siganature-based Search for Anomalous Production of Diphoton + e/  at CDF

29. Shin-Shan Yu29 MOTIVATION ✔ CDF Run I “ee  +MET” event: 86 pb -1 ✔ Dominant SM: WW   8  10 -7 events ✔ Total: ~10 -6 events ✔ Personal ✔ Use calorimeters ✔ Learn high-pt physics Phys. Rev. D59, 092002 (1999) by Toback, et al

30. Shin-Shan Yu30 RUN II PHOTON ANALYSES Diphoton + X X = e, , , , met, b-jet, jet Expand photon analysis to a more systematic search Do not optimize cuts based on any model Only compare kinematic distributions and number of events Look for excess above background prediction Not a blind analysis Lepton + photon + X X = met, e, ,  met + b jet Other model-dependent photon analyses RS graviton to diphoton search more …  +X signatures SUSY:  +MET+X b`b`  bb  l*l*  ll , q*q*  qq  New dynamics

31. Shin-Shan Yu31 A RUN II  e EVENT Is it from SM? Fakes from jets or electrons ? Or new physics?

32. Shin-Shan Yu32 ANALYSIS OVERVIEW Require two central photons and lepton objects photons |  | < 1.0 muons |  | < 1.0 electrons |  | < 2.0 Specific detector requirements for each lepton type Data sample ~ 1.1 fb-1 collected with diphoton trigger 2 EM clusters with Et > 12 GeV isolation, E_had/E_em, shower profile requirements Compare prediction with observation by applying several levels of loose and tight photon requirements Includes a wire chamber at showermax

33. Shin-Shan Yu33 ANALYSIS REQUIREMENTS cutsTight cutsLoose cuts Photon E T >13 GeV Showermax fiduciality|X CES |<21.0 cm; 9.0 cm<|Z CES |<230.0 cm Average CES  2 <20 Had/Em<0.055+0.00045*E T <0.125 Calorimeter Energy Isolation<2.0+0.02(E T -20) or <0.1*E T if E T <20.0 GeV <3.0+0.02(E T -20) or <0.15*E T if E T <20.0 GeV Track Pt Isolation<2.0+0.005*E T <5.0 Tracks point to photon candidate 0,1 Track Pt if there ’ s one track pointing <1.0+0.005*E T <0.25*E T 2 nd Showermax cluster (wire or strip) <0.14*E T if E T <18 GeV 18 GeV No cut

34. Shin-Shan Yu34 DIPHOTON + e/   FROM SM AND FAKES W  Z  : Madgraph MC, weighted with data/MC ID scale factor, luminostiry, trigger efficiency, K factor to correct LO to NLO cross-section Fake leptons + real photons: apply lepton fake rates to the events with 2 photon candidate + fakeable object, then scale with the true photon fraction obtained from MC and data (showermax and preshower radiator) True photon fraction ~ 30% for photon Et > 13 GeV Leptons + fake photons from jets: apply jet faking photon rate to the events with lepton candidate + photon candidate + a central jet W  Z  + jet  + 2 jets where 1 jet fake lepton W or Z + 2 jets where both jets fake photons Z + jet where electron fakes a photon Leptons + fake photons from electrons: apply electron faking photon rate to the events with lepton candidate + photon candidate + an electron Z  where the electron comes from decay of Z Z + jet where the jet fakes a photon

35. Shin-Shan Yu35 DOMINANT BACKGROUND electron channel ee  from Z  where one electron fakes the photon muon channel Z  Z Z Z l

36. Shin-Shan Yu36 REJECT FAKE PHOTONS USING SILICON TRK Electron can fake a photon due to track-loss, FSR or BREM Background from BREM can be reduced by removing photons matched to silicon tracks tracks seeded by event vertex and a cluster in the EM calorimeter Measure the fake rate Compare Z peak from ee and e  Get Et dependence from MC Normalize to data Silicon-track rejections reduce the fake rate by a factor of 3-4 0.36% at 45 GeV Silicon track rejection applied

37. Shin-Shan Yu37 Result Before Sili rejectionAfter Sili rejection Channel  e  e  Prediction6.82±0.750.79±0.113.79±0.540.71±0.10 Obseverd3010 M(e  )=129.5 GeV/c 2 M(e  1 )= 93.0 GeV/c 2 M(e  2 )= 88.3 GeV/c 2 The event which survives silicon-track rejection. = Sum Et of observed objects and missing Et

38. Shin-Shan Yu38 CONCLUSION We have measured the Lb relative branching fraction using 173 pb-1 We have made the first observation of 4 Lb semileptonic decays We have the first evidence that the Lb pt spectrum is softer than that of the B0 meson. Although Bs mixing is already observed, there’re still interesting B physics to do at the Tevatron. With current available data, we could make a more precise measurements of b-baryon properties or search for unobserved b-baryons. We have searched for anomalous production of diphoton + e/mu events in 1 fb-1 of data. No excess is observed. Removing photons matched to silicon tracks reduce the electron faking photon rate by a factor of 4 Keep looking …

39. Back Up Slides

40. Shin-Shan Yu40 Control Sample    DX, D +  K -  +  + Background shapes come from MC Hadronic SignalInclusive Semileptonic Signal

41. Shin-Shan Yu41 Control Sample    D*X, D* +  D 0  +, D 0  K -  + Inclusive Semileptonic Signal Background shapes come from MC Hadronic Signal

42. Shin-Shan Yu42 Physics Background

43. Shin-Shan Yu43 Dominant Systematics Physics background and hadronic signal branching fractions Measured: from PDG Estimated: multiply the BR by 2 or 0 Mass fitting model Vary the constant parameters in the fit Several background shapes come from inclusive MC vary BR of the dominant decays MC modeling of acceptance and efficiency pT spectrum affect the efficiency and B (  b   c   b semileptonic decay model size of the independent MC for reweighting the phase space distribution uncertainty on the predicted form factors

44. Shin-Shan Yu44 MC Tuning Flat phase space Form factor weighted

45. Shin-Shan Yu45  b Polarization