Vivek Sharma University of California at San Diego CP Violation in B Decays Ringberg Workshop 2006

2 Task: Over Constrain The Unitarity Triangle  CPV B -  DK - B 0  D 0 K 0  CPV B  K 0 (b  c c s) B  K 0 (b  s s s  CPV B 0  +  -, ,  +  - b  u l  B -  b  c l  b  d  B 0  B 0 By Measurement of UT Sides By Measurement of UT Angles Is CKM Matrix the (only) Source of CP Violation?  

3 CP Violation CP violation can be observed by comparing decay rates of particles and antiparticles The difference in decay rates arises from a different interference term for the matter Vs. antimatter process.

4 CP Violation Due to Quantum Interference Weak phase   wk changes sign under CP, strong phase  st does not  (B  f )

5 Direct CP Violation in B 0  K  T P Loop diagrams from New Physics (e.g. SUSY) can modify SM asymmetry contributing to the Penguin (P) amplitude Measurement is a simple “Counting Experiment” Classic example of Quantum Interference

6 Direct CP Violation in B 0  K +   Bkgd symmetric! 4.2 , syst. included BaBar LARGE CP Violation ! unlike Kaon system

7 CPV In Interference Between Mixing and Decay

8 Peculiarities at  (4S)  B B  (4S) E beam = 5.29 GeV e+e+ e-e- ee ee  Under symmetric energy collisions, B mesons are slow (  0.07) travel only ~30  m, not enough to measure their decay time

9 B 0 B 0 are in coherent l=1 state Since production, each of the two particles evolve in time, may mix BUT they evolve coherently (Bose statistics  |  > = |  > flavor |  > space is symmetric ) so that at any time, until one particle decays, there is exactly one B 0 and one B 0 present but never a B 0 B 0 or B 0 B 0 (quantum coherence) However when one of the particles decays, the other continues to evolve Now possible to have  (4S) final state with 2 B 0 or 2 B 0, probability is governed by the difference in time between the two B decays  (4S) B 0 Spin = 100 With l = 1

10 When One B decay tags b flavor, Other decays to f CP  (4S) B0B0 B 0 t tag t fcp  K0K0 tt Tag f CP

11 B Decays to CP Eigenstates

12 Time dependent CP Asymmetry in “Interference”

13 At  (4S): integrated asymmetry is zero  must do a time-dependent analysis ! This is achieved by producing boosted  (4S)  B B S

14 Asymmetric Energy Collider To Measure B Decay Time Electron Beam Positron Beam  (4S) Boost  (4S) in lab frame by colliding beams of unequal energy but with same E 2 CM = 4.E low E high =M 2  Daughter B mesons are boosted and the decay separation is large  Z ~ 200 , distance scale measurable with Silicon detectors

15 CP Violation Studies at Asymmetric Energy Colliders

Probing The CKM Angle 

17 CPV In B 0  J/  K 0 (Platinum Mode)  CP = -1 (+1) for J/  K 0 S(L) Same is true for a variety of B  (c c ) s final states dominated by a single decay amplitude

18 Time-Dependent CP Asymmetry with a Perfect Detector Perfect measurement of time interval t=  t Perfect tagging of B 0 and B 0 meson flavors For a B decay mode such as B 0  Ks with |  f |=1 sin 2  B0B0 B0B0 Asymmetry A CP CPV

Vivek Sharma, UCSD19 B 0  J/  K s z   (4S) = 0.55 Coherent BB pair B0B0 B0B0   distinguish B 0 Vs B 0 distinguish B 0 Vs B 0 Steps in Time-Dependent CPV Measurement

20 Effect of Mis-measurements On  t Distribution CP PDF perfect flavor tagging & time resolution realistic mis-tagging & finite time resolution

21 B  Charmonium Data Samples 6028 signal non-CP

22 Sin(2  Result From B  Charmonium K 0 Modes (2006) (c c ) K S modes (CP =  1) J/ψ K L mode (CP = +1) sin2β =  (stat)  (syst) BaBar 348M B B sin2β =  (stat)  (syst) Belle 535M B B sin2β =  Average

23 Breaking Ambiguities In Measurement of 

24 T Angle  From B 0  +  - Neglecting Penguin diagram (P) P

25 Estimating Penguin Pollution in B 0  +  -,  +  -

26 B 0  +  - System As Probe of  “Large” rate 615 ± 57 “Smaller” Penguin Pollution N  0  0 = ± 22 −31 m ES 0f00f0 0000 98 ± 22 2  A 00 A +0

27 B 0  +  - System As Probe of  Longitudinally polarized  Helicity angle

28 TD CPV Measurement in B 0  +   57 signal events CPV not yet observed here but measurement constrains 

29 Discerning  : Not Very Precise Yet

Probing The CKM Angle 

31 CP Asymmetry In B  DK Decay   Look for B decays with 2 amplitudes with relative weak phase  Relative phase: ( B –  DK – ), ( B +  DK + ) includes weak ( γ ) and strong ( δ ) phase.

32  from B ±  D 0 K ± : D 0  K S  +  - Dalitz Analysis 2 Schematic view of the interference

33 B  Samples From Belle ( 357 fb -1 ) Clean signals but poor statistics for a Dalitz analysis ! 331±17 evnt B   DK  81±8 events 54±8 evnt B   D*K  B   DK* 

34 The B->D 0 K  Dalitz Distributions: Belle B-B- B+B+ B -  DK - B +  DK + Direct CP Violation lies in in the dissimilarity between the two Dalitz distributions: See any ?

35 Measurement Of CKM Angle  /  3 Belle ( 357 fb -1 ) W.A. combining all  measurements γ = (82 ± 19) o 95% CL γ = (-98 ± 19) 0 95% CL

36 The Unitarity Triangle Defined By CPV Measurements Precise Portrait of UT Triangle from CPV Measurements

37 UT With CPV & CP Conserving Measurements Inputs: Incredible consistency between measurements  Paradigm shift ! CKM Picture well describes observed CPV  Look for NP as correction to the CKM picture

38 Searching For New Physics by Comparing pattern of CP asymmetry in b  s Penguin decays With goldplated b  c c s (Tree)

39 Tree Penguin 33 New Physics Comparing CP Asymmetries : Penguins Vs Tree In SM both decays dominated by a single amplitude with no additional weak phase New physics coupling to Penguin decays can add additional amplitudes with different CPV phases

40 New Physics ? Standard Model

41 Naïve Ranking Of Penguin Modes by SM “pollution” Bronze Gold Supergold Decay amplitude of interestSM Pollution Naive (dimensional) uncertainties on sin2  Note that within QCD Factorization these uncertainties turn out to be much smaller !  

42 First Observation of TD CPV in B 0   ’K 0 Large statistics mode 1252 signal events (K s +K L mode) 5.5 measurement BaBar 384M  ’K S similar result from Belle

43 Golden Penguin Mode : B 0   K 0 Belle: 535M B B 307  21  K S signal 114  17  K L signal 307  21  K S signal 114  17  K L signal S  K0 =  0.50  0.21(stat)  0.06(syst) C  K0 =  0.07  0.15(stat)  0.05(syst) S  K0 =  0.50  0.21(stat)  0.06(syst) C  K0 =  0.07  0.15(stat)  0.05(syst)

44 Golden Penguin Mode : B 0  K 0 K 0 K 0 Belle 535M B B S KsKsKs =  0.30  0.32(stat)  0.08(syst) C KsKsKs =  0.31  0.20(stat)  0.07(syst) S KsKsKs =  0.30  0.32(stat)  0.08(syst) C KsKsKs =  0.31  0.20(stat)  0.07(syst) 185  17 K S K S K S signal 185  17 K S K S K S signal  background subtracted  good tags

45 Summary of sin2  eff In b  s Penguins But smaller than b  c c s in all 9 modes ! But smaller than b  c c s in all 9 modes ! Interesting ! Measurements statistically limited ! Naïve b  s penguin average sin2  eff = 0.52  0.05 Compared to Tree: sin2  eff = 0.68  0.03  2.6  difference Theoretical models predict SM pollution to increase sin2  eff !! Individually, each decay mode in reasonable agreement with SM

46 Theory Predictions, Accounting For subdominant SM Amplitudes 2-body: Beneke, PLB 620 (2005) body: Cheng, Chua & Soni, hep-ph/ Calculations within framework of QCD factorization  sin2  eff > 0.68  points to an even larger discrepancy !

47 What Are s-Penguins Telling Us ? This could be one of the greatest discoveries of the century, depending, of course, on how far down it goes… 2.6  discrepancy

48 Need More Data To Understand The Puzzle K*K* 4  discovery region if non-SM physics is 0.19 effect 2004=240 fb =1.0 ab -1 Individual modes reach 4-5 sigma level Projections are statistical errors only; but systematic errors at few percent level Luminosity expectations : f 0 K S K S  0  K S  ’K S KKK S

49 Projected Data Sample Growth Integrated Luminosity [fb -1 ] L peak = 9x10 33 oPEP-II: IR-2 vacuum, 2xrf stations, BPM work, feedback systems oBABAR: LST installation 4-month down for LCLS, PEP-II & BABAR Double from 2004 to 2006 ICHEP06 Double again from 2006 to 2008 ICHEP08 Expect each experiment to accumulate 1000 fb -1 by 2008

50 Summary & Prospects CP Violation in B decays systematically studied at BaBar & Belle. A Comprehensive picture emerging Standard Model picture (3 generation CKM matrix) of CP Violation consistent will all observations New Physics (in loops) can still contribute to observed CPV but is unlikely to be the dominant source CPV violation in the clean b  s Penguin Decays appears lower than SM predictions (> 2.6  ) –more data needed to reveal true nature of discrepancy –B-factories expect to triple data sets by 2008 LHC-B will probe the B s sector…Super B-factories ?

51 Suggested Reading: A Partial List Reviews of |Vub| & |Vcb|, CKM Matrix, B Mixing & CP Violation in the Particle Data Book – CP violation and the CKM matrix : A. Hocker & Z. Ligeti –hep-ph/ BaBar Physics Book available online at – Discovery Potential of a Super B factory: – B Physics at the Tevatron: Run II and Beyond : –hep-ph/ Textbooks: –Heavy Quark Physics: Manohar & Wise; Published by Cambridge –CP Violation: Branco,Lavoura,Silva; Published by Clarendon Press –CP Violation by Bigi & Sanda; Published by Cambridge Press

Backup Slides

53 Penguin:: u,c,t loops Tree 

54 The Unitarity Triangle For B System Angles of Unitarity Triangle Specific forms of CP Violation in B decay provide clean information about the angles of the UT triangle Same triangle also defined by length of its sides (from CP conserving B decay processes such as b  u l nu )  Overconstrained triangle

55 Rules out Superweak model Establishes CPV not just due to phase of B Mixing But hadronic uncertainties preclude determination of CKM angle   challenge to theory Combined significance >> 6  Direct CP Violation in B 0  K  : Belle (386M BB) Belle

56

57 The Unitarity Triangle Defined By CPV Measurements New B Factory milestone: Comparable UT precision from CPV in B decays alone

58 Belle and Babar Detectors: Optimized For CP Studies ee ee  Enough energy to barely produce 2 B mesons, nothing else! B mesons are entangled  Need for Asymm energy collisions

59 B 0 B 0 are in coherent l=1 state Each of the two particles evolve in time (can mix till decay) BUT they evolve in tandem since Bose statistics requires overall symm. wavefn So that at any time, until one particle decays, there is exactly one B 0 and one B 0 present  ( EPR !) However after one of the particles decays, the other continues to evolve Now possible to have a  (4S) event final state with 2 B 0 or 2 B 0 probability is governed by the time difference  t between the two B decays  (4S) B 0 Spin = 100 With l = 1

60 Quantum Correlation at  (4S) Decay of first B ( B 0 ) at time t tag ensures the other B is B 0 –End of Quantum entanglement ! Defines a ref. time (clock) At t > t tag, B 0 has some probability to oscillate into B 0 before it decays at time t flav into a flavor specific state Two possibilities in the  (4S) event depending on whether the 2nd B mixed/oscillated or not:  (4S) B0B0 t tag B 0 B 0 t flav tt X Y

61 Time Dependent B 0 Oscillation (Or Mixing)

62 B 0 Decays to CP Eigenstates  (4S) B0B0 B 0 t tag t fcp  K0K0 tt Tag f CP

63 B 0 Decays to CP Eigenstates

64 At  (4S): integrated asymmetry is zero  must do a time-dependent analysis ! This is impossible to do in a conventional symmetric energy collider producing  (4S)  BB !!

65 Summary of |V ub | From Inclusive Measurements

66 Unitarity Triangle From Measurement of Sides ρ = ± η = ± ± Put all these measurements together  UT Definition from angles 

67 When One B decay tags b flavor, Other decays to f CP  (4S) B0B0 B 0 t tag t fcp  K0K0 tt Tag f CP