Experimental Aspects of CP Violation in B Decays : Lecture IV Vivek Sharma University of California, San Diego http://vsharma.ucsd.edu/prague/cpv.pdf

Outline of Lectures 3 & 4 Lecture 3 Three types of CP violation & SM expectations in B Decays Decay amplitude Weak phase structure Decay asymmetry prediction in SM General strategy for time-dependent CP asymmetry measurement Observables that probe angle  Time dependent CP asymmetry in B -> Charmonium KS modes Step-by-Step Other modes with subdominant or dominant Penguin Lecture 4 Observables that probe angle Observables that probe angle  Summary of current measurements Future prospects

CP Asymmetries and Testing  against “”

Confronting Loop Decays with Tree Dominance decays are tree and penguin diagrams, with same dominant weak phases decays are pure “internal” and “flavor-singlet” penguin diagrams High virtual mass scales involved: believed to be sensitive to New Physics Both decays dominated by single weak phase Tree: Penguin: New Physics? 3 ?

bs Penguin Observables Naive (dimensional) uncertainties on sin2 One may identify golden, silver and bronze-plated s-penguin modes: Gold Color-suppressed tree Silver Color-suppressed tree Bronze Note that within QCD Factorization these uncertainties turn out to be much smaller, but you must believe in QCD Factorization !

Results on sin2b from s-penguin modes All new! All new! 2.7s from s-penguin to sin2b (cc) 2.4s from s-penguin to sin2b (cc)

World Averages for sin2b and s-penguin modes 3.6s from s-penguin to sin2b (cc) No significant sign of Direct CP Beginning to look suspicious but must wait for 5/expt to get exciting

Comparison of Sin2 With “Sin2” From Z. Ligeti Upper limit Some modes more clean for Interpretation than others

Projections for Penguin Modes (BaBar) f0KS KSp0 jKS h’KS KKKS Luminosity expectations: 2004=240 fb-1 2009=1.5 ab-1 K*g Similar projections for Belle as well 5s discovery region if non-SM physics is 30% effect 2004 2009 Projections are statistical errors only; but systematic errors at few percent level

PEP II Luminosity Projections 0.5 ab-1 2004 2006 1.6 x 1034

Probing The CKM Angle 

Example of Class I (b u u d): B0 +- Neglecting Penguin diagram

Reality in B0 +-, + - Tree Penguin Ratio of amplitudes |P/T| and strong phase difference  can not be reliably calculated! One can measure dapeng using isospin relation and bounds to get 

Measurement of  : Reality in B0 +-, + - 3 such relations (one for each polarization) Now need to measure 

Time Dependent Asymmetry Measurement: B0 +- BABAR B0 B0

Time Dependent Asymmetry Measurement: B0 +- (372  32) +- signal 152M BB 152M BB good tag Belle claim of direct and Indirect CPV not supported by BaBar data Cpp = -0.58 0.15(stat) 0.07(syst) Spp = 1.00 0.21(stat) 0.07(syst)

Comparison of Present and Past B0 +- results Coefficients of time-dependent CP Asymmetry With large penguins and |P/T| ~ 0.3 With no penguins >3s discrepancy between BABAR & Belle 3.2s 5.2s Belle 3.2s evidence for Direct CP violation not supported by BABAR measurements Caution When averaging!

“One is too few and three is too many” -Carlo Rubbia, CERN DG, 1990 Its essenstial for an independent & similarly capable experiment to verify an experiment’s claims!

Constraining : B-  p- p0 Rate Measurement B-  p- p0 (I=2, I=1/2) has only tree amplitude, no penguin  Base of Isospin triangle u B- - B- 0 u BaBar

Constraining  : B  p0p0 Decay Diagrams Difficult to calculate rates for such processes, Smaller the better for constraining  Grossman-Quinn bound:

B  p0p0 : Rate and Flavor Tagged Rate Asymmetry First measurements B00 is large ! Measured by flavor of the other B  Btag 4.9s BaBar 6.0s Belle 274M BB Average Key ingredient for Isospin analysis And constraints on angle 

Estimate of  From B Studies Interpretation unclear because of inconsistency in B0 +- Penguin pollution  Not well constrained !

ACP(t) in B0r+r- Decays Run1-3 data (122M BB) 314±34 Signal Events (205 tagged) fL=1.00±0.02 Events with cleanest tags mES DE Fit: total Fit: bkgd After cuts on likelihood ratio BaBar prelim BaBar prelim

ACP(t) in B0r+r- Decays 314±34 Signal Events B0+- Distribution of ± helicity distributions in data Clear demonstration of strong longitudinal polarization fL=1.00±0.02

Results for sin2eff from B  r+ r- decays Extraction of a similar to pp, but with advantage of larger rate ( 5) & smaller Penguin pollution because BABAR Time-dependent CP Asymmetry

Isospin Corrections for a From Measurements Vs Compare with 35o for pp Can Measure  more precisely Geometric limit on 2dapeng: Grossman-Quinn bound

B is an example of the fact that if you build a good detector and take lots of data, people (with help from nature) will find unpredictable & innovative ways to surmount difficult sticky situations! e.g: B for precise measurement of  was never seriously discussed at conferences till last year

Summary Of Measurements of Angle  Confidence level =1  Favored result

Towards The Angle : The phase in Vub Look for B decays with 2 amplitudes with relative weak phase  Direct CP Asymmetry  Angle 

Angle  from B±DK±: Critical Requirement Relative size of the 2 B decay amplitudes matters for interference Want rb to be large to get more interference  Large CP asymmetry Diff. between rb=0.1 and rb=0.2 substantial for precision on  Theory cannot calculate r reliably must measure experimentally Color suppression: Fcs  [0.2,0.5] Left side U.T.: Ru  0.4 Expected range

Angle  from B±D0 K±: Current Status Even with ~250 fb-1 data in hand for each experiment, reconstructed samples of B±DK± events are too few for a meaningful measurement of the angle  (and r, and strong phase ) E.g: Effective Br. Ratio for (B±D0 K±)(D0K+-) 10-7 The exception is the case when B±D0 K± and D0KS+- , a Cabbibo favored decay accessible to both D0 and D0. Entire resonant substructure can be used with Cabbibo-allowed and suppressed modes in D0KS + - interfering directly

 from B±D0 K±: D0 KS + - Dalitz Analysis 2 Schematic view of the interference

 from B±D0 K±: D0 KS + - Dalitz Analysis Sensitivity to g A functional form (model) for f(m2+ ,m2- ) obtained from high statistics D*+D0 sample can fix phase variation dD across Dalitz plot. Fit Dalitz distribution for B+ and B- simultaneously using A- & A+ forms to extract r,  and  simultaneously. No additional assumptions necessary Only two-fold ambiguity in g extraction g=75,d=180,rB=0.125 First and most precise such measurement from Belle 

D0 Dalitz Plot Model From High Statistics D*+ Sample Characterize Dalitz distribution with 15 two-body amplitudes

B+ D0K+ Samples B+ D(*)0K+ signal B+ D0K+ D0  Ksπ+π– B+ D*0K+ misID 146 events 112±12 signal 25% background ΔE (GeV) Mbc (GeV) B+ D*0K+ D*0 D0π0 D0  Ksπ+π– D*0K D*0π misID 39 events 33.6±6.2 signal 12% background 140 fb-1 ΔE (GeV) Mbc (GeV)

 from B±D0 K±: D0 KS + - Dalitz Analysis Belle 140 fb-1 M2(KSp-) [GeV2] M2(KSp+) [GeV2] 73 events 73 events Visible asymmetry in Dalitz plots 20 events 19 events Large ! Good start for direct measurement of  already, 2 data in hand Ultimate sensitivity will depend on precise value of rb

 from B±D0 K±: D0 KS +- Dalitz Analysis 261 19 D0K 83 11 D*0(D0p0)K 40 8 D*0(D0g)K

With measurement of CKM element magnitudes and Angles , ,  in hand, Lets Look at the - plane to see if all these measurements hang together in 2004 ! Courtesy: The CKMfitter Group

Bd mixing + CPV in K mixing (K) Allowed region Allowed region

Add |Vub/ Vcb|

+ BS Mixing constraint

+ Sin2

+  constraint

All measurements consistent, apex of (,) well defined +  measurement

Summary Of Results B factories producing data at record breaking pace ! In just 4 years of data taking, CP Violation firmly established in the B system by BaBar & Belle CPV in interference of Decay and Mixing: sin2=0.7260.037 Direct CPV: ACP(B0K-+)= -0.110.02 Limits on CPV in B mixing Unlike in the Kaon system, CPV in B system is O(1) effect “sin2”=0.300.08 from bs penguin decays 3.5 from sin2K Needs careful investigation B+- provides the best measurement of angle  First measurement of  from B±D0 K±, D0 + - Dalitz analysis  the most promising technique with added statistics But precise & redundant measurements of  will be difficult All observables yield a consistent picture. The - plane is now sharply defined

Limits of Future Explorations

PEP II Luminosity Projections 0.5 ab-1 2004 2006 1.6 x 1034 Similar projections for Belle

Future Prognostications BaBar & Belle have just begun and have a long term and a rich program for B physics (>2007) [I showed only 10% of results !] Most CP asymmetry measurements are statistics limited S-Penguins Alpha & Gamma measurements (multiple to be sure) CPV in B mixing remains to be discovered Rare decays such as Radiative and Electroweak are a very clean probe of new physics. e.g. F-B Asymmetry in b s l+ l- CPV in B  s  etc Tevatron is accumulating large B samples: They are the only current laboratory for studying Bs and b properties Immediate focus : Bs oscillation search till xs 20 B Physics return to Europe in 2007 with LHC-B !! Will be the ultimate instrument for precision B physics Precise exploration of CPV in BS and Bd systems

LHC-b Reduced material Improved level-1 trigger

LHC-b: Example of CKM Physics Reach (107 s) Reaction Para-meter LHC Yield S/B Sensitivity† Bop+p- Asym 26,000 >1.4 BoJ/y KS , J/y l+ l- sin(2b) 241,000 1.2 0.02 Bs Ds K- g-2c g 5,400 >1 14o Bs Ds p- xS 80,000 3 <100† B-Do (K+p-) K- g B-Do (K+K-) K- B0 D0(Kp)K*0 B0 D0CPbar K*0 B0 D0CP K*0bar B-KS p- BoK+p- Reaction Parameter Bor+p- a Boropo BsJ/y h, J/y l+ l- sin(2c) BsJ/y h, BsJ/y f DGS/GS

Thank You & Best Wishes !

Backup Slides

Strategy for CP violation study in B0  + - Helicity Frame Pure CP-eigenstate In a simultaneous fit we measure 4 quantities: +- yield and Polarization (fraction of longitudinal events) CLong and SLong CP parameters The additional parameters CTran and STran are fixed to zero (vary within (-1.0 ; 1.0) in the study of the systematics) . Longitudinal polarization Pure CP-eigenstate Transverse polarization Mix of CP-eigenstate (not useful…) 53

Ingredients of +- analysis Event selection: As the longitudinal polarization was expected to be large (>90%) we have optimized our analysis to be able to treat the events with large values of |cos(H)| (Longitudinal events have for the helicity distribution which is in ~cos(H)2). See details in BAD #634, #798. Rejection of continuum: NN approach. Combine discriminating variables: L0 and L2 monomials for charged and neutral particles Sum of transverse momentum Cosine of the B thrust with z axis Cosine of the thrust of the r.o.e with the B thrust Cosine of the B direction with z axis. 0 angular distribution. Choice of best candidate: Multiplicity per event ~ 1.8 Choose one candidate per event with best 2. transverse longitudinal qqbar 54

Likelihood Fit 4 types of events: Likelihood: 8 discriminating variables  mES , E, NN output and t Vector particle information (m1, m2, cos(1), cos(2)). 4 types of events: True Signal. Self Cross-Feed (~50% of the events come from 0 mis-reconstruction): Longitudinal  (SCF fraction: 49%), Transverse  (SCF fraction: 25%). Continuum. floating parameters to model PDFs B backgrounds: Charmless B background (B0+-, B+0  +…. ). Charm B (bc) background. 19 distinct PDFs!!! Likelihood: The likelihood is the sum over the types of events of the terms : Pdf(xNN)  Pdf( E)  Pdf( mB ),  Pdf( t)  Pdf( m1)  cos(1)  Pdf(m2)  cos(2) Minimization and Pdf modeling based on the RhoRhoTools package (RooFit technology). Self Cross-Feed True Signal mES mES 55

Angle  from B±DK± : 3 Sets Of Observables D decays to CP eigenstates (p+p-, Ksp0, …) Interference term small D decays to definite flavor states (K-p+) Interference term large D decays to 3-body states (Dalitz analysis of D0 decay) Interference varies in 2-D Dalitz plot Common parameters for all analyses :

B±DK± : D0 Decays to CP Eigenstates (a.k.a. GLW technique) Babar & Belle averages Note: rb and db different for each B mode (DK,DK*,D*K) No sign of large direct CP violation (rb is not anomalously large)

B±DK± : D0 decays to Definite Flavor (a.k.a. ADS technique) Favored (b c) favored suppressed Suppressed (b u) Babar preliminary Belle Events / 10 MeV Results for Hints of signals Rules out very optimistic scenario (very large rb) Favors small rb Belle ICHEP 2004 Babar hep-ex/0408028