CP Violation in B0 Decays: Some Highlights Vivek Sharma University of California at San Diego SheldonFest, May 20, 2006

1987: Argus Discovers large B0B0 Oscillation Rate First time I heard the word CP violation and B mesons spoken together Started a chain of activities which ultimately led to the construction & operation of the asymmetric energy B factories Much skepticism initially about how well these machines would perform

PEP-II Asymmetric B Factory & BaBar

Machine Performance Exceeds Design (x3) Peak luminosity (cm-2 s-1) 1.0025 x 1034 Best shift 247.2 pb-1 Best day 710.5 pb-1 Best week 4.464 fb-1 Best month 17.036 fb-1 BABAR logged 343 fb-1 96% efficiency over the entire history of BABAR BABAR, Run 5 KEK-B operation even more spectacular !

BaBar Physics Productivity Publication Luminosity Submitted BABAR Belle Journal Papers 201 163 As of April 3 As of April 12 ‘06 BaBar papers by topic: BaBar papers by area: Plan to exceed 220 publications by summer 2006

Direct CP Violation in B0 K Loop diagrams from New Physics (e.g. SUSY) can modify SM asymmetry via Penguin diagram Need reliable knowledge of T/P and relative strong phase to extract /3 Clean mode with a “large” rate: Measurement is a “Counting Experiment”

Direct CP Violation in B0 K : BaBar 4.2, syst. included BABAR

Direct CP Violation in B0 K : Belle (386M BB) Combined significance >> 6 Belle 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

CPV In Interference Between Mixing and Decay + 2  B0 fcp CP asymm. can be very large and “cleanly” related to CKM angles Requires time dependent measurement of CP Asymmetry

Time-dependent CP Asymmetry Due to Interference in Mixing and Decay Phase of mixing Amplitude ratio (direct CPV) (indirect) (for single weak decay amplitude)

The “Platinum” Mode : B0 J/K0 CP = -1 (+1) for J/y K0S(L)

Visualizing Time-Dependent CPV Measurement

Steps in Time-Dependent CPV Measurement z distinguish B0 Vs B0 m- K- bgU(4S) = 0.55 Coherent BB pair B0 B0  J/y Ks Vivek Sharma , UCSD

Effect of Mis-measurements on Dt Distribution perfect flavor tagging & time resolution realistic mis-tagging & finite time resolution CP PDF Determine flavor mis- tag rates w and Dt resolution function R from large control samples of B0  D(*)p/r/a1,J/K* BB Mixing PDF

B Charmonium Data Samples MES [GeV] MES [GeV] CP sample NTAG purity ηCP J/ψ KS (KS→π+π-) 2751 96% -1 J/ψ KS (KS→π0π0) 653 88% ψ(2S) KS (KS→π+π-) 485 87% χc1 KS (KS→π+π-) 194 85% ηc KS (KS→π+π-) 287 74% Total for ηCP=-1 4370 92% J/ψ K*0(K*0→ KSπ0) 572 77% +0.51 J/ψ KL 2788 56% +1 Total 7730 78% BABAR J/ψ KL signal J/ψ X background Non-J/ψ background (ηCP = +1) ΔE [MeV]

Sin(2b) Result From B Charmonium K0 Modes (2004) (cc) KS modes (CP = -1) J/ψ KL mode (CP = +1) background hep-ex/0408127 sin2β = 0.722  0.040 (stat)  0.023 (syst) (PRL 89, 201802 (2002): sin(2β) = 0.741 ± 0.067 ± 0.034)

Belle 2005 (386M BB)

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

UT With CPV & CP Conserving Measurements Incredible consistency between measurements ! Paradigm shift ! Look for NP as correction to the CKM picture

<< Testing  Vs “” >> Searching For NP << Testing  Vs “” >>

Must be if one amplitude dominates Compare sin2 with “sin2” from CPV in Penguin decays of B0 Both decays dominated by single weak phase Tree: Penguin: New Physics? 3 ? Must be if one amplitude dominates

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

CP Asymmetry in B φ KS : LP2003 Penguin Lust ! CP Asymmetry in B φ KS : LP2003 Belle Belle 140 fb-1 68±11 sin2φ1eff = -0.96 ±0.50 Then WA: sin(2φ1)ccs = 0.731±0.056 3.5σ different !

New Physics ? Standard Model

B0   K0 Since LP03 BaBar: 222M BB hep-ex/0502019 Modes with KS and KL are both reconstructed (Opposite CP) full background continuum bkg 114 ± 12 signal events 98 ± 18 signal events Plots shown are ‘signal enhanced’ through a cut on the likelihood on the dimensions that are not shown, and have a lower signal event count

CP analysis of ‘golden penguin mode’ B0   K0 BaBar (Opposite CP) S(fKS) = +0.29 ± 0.31(stat) S(fKL) = -1.05 ± 0.51(stat) Standard Model Prediction S(fK0) = sin2b = 0.69 ± 0.03 C(fK0) = 1-|l| = 0 Combined fit result 0.8s hfK0

Other (More Prolific) Golden penguin mode: B0  h’K0 hep-ex/0502017,0507087 B0  h’KS B0  h’K0 Large statistics mode Reconstruct many modes ’   + –, 0      ,  + –0 KS  + – ,00 BaBar hfK0  sin2 [cc] @ 2.7 ’KS 819 ± 38 signal events (Ks mode) 440 ± 54 signal events (KL mode)

Taken individually, each decay mode in reasonable agreement with SM but (almost) all measurements are lower than sin2 from ccs Naïve b  s penguin average sin2eff = 0.50 0.06 Theory models predict SM pollution to increase sin2eff !!

How good is the SM Theoretical Prediction? 2-body: Beneke, PLB 620 (2005) 143 Calculations within framework of QCD factorization 3-body: Cheng, Chua & Soni, hep-ph/0506268

Direct CPV in s-Penguins ? No sign of direct CPV !

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… 2.4s? discrepancy

Possible Evolution by Summer 2008 Luminosity expectations: K*g 2004=240 fb-1 2008=1.0 ab-1 f0KS KSp0 jKS h’KS KKKS 4s discovery region if non-SM physics is 0.19 effect 2004 2008 Individual modes reach 4-5 sigma level Projections are statistical errors only; but systematic errors at few percent level

An Optimist’s Global CKM fit ? : 2008 (1 fb-1 each) 95% contours ?

Backup Slides

Projected data sample growth: BaBar Expectation 20 Double again from 2006 to 2008 ICHEP08 Integrated Luminosity [fb-1] PEP-II: IR-2 vacuum, 2xrf stations, BPM work, feedback systems BABAR: LST installation 4-month down for LCLS, PEP-II & BABAR 17 Double from 2004 to 2006 ICHEP06 12 Lpeak = 9x1033

PEP-II overall parameters and goals Units Design Oct 2005 2007 goal I+ mA 2140 2940 4000 I- 750 1740 2200 Number of bunches 1658 1732 by* mm 15-20 11 8-8.5 Bunch length 15 11-12 8.5-9 xy 0.03 0.044-0.065 0.054-0.07 Luminosity x1033 3.0 10.0 20 Int lumi / day pb-1 130 727.8 1300 40% 30% 10% Factor 2!

Only More Data Can Reveal The True Picture Possible evolution of deviations From SM average BABAR+ Belle 2008 BABAR 2008 h’KS Assuming fluctuations around present central values  KS standard deviations Number of Integrated luminosity (fb-1)

B0  D0h0 Belle’s New Method for Direct measurement of f1 _ B0  D0h0 Belle’s New Method for Direct measurement of f1 (D0  KSp+p-) AB0D0h0(Dt) = M(KSp-) M(KSp+) f-+ cos(DMDt/2) M(KSp+) M(KSp-) f+- -ei2f1 hh0 sin(DMDt/2) Vivek Sharma , UCSD

Reconstruction of B0  D[KSp+p-]h0 _ Reconstruction of B0  D[KSp+p-]h0 D0 p0 D0 w D0 h D*0 p0, h Nsig = 157 ±24 purity : 59% Nsig = 67 ±10 purity : 86% Nsig = 58 ±13 purity : 60% Nsig = 27 ±11 purity : 52% D*0  D0 p0 D*  D0 pi0 D*pi0 : 22 +- 9 D*eta : 5+- 6 TOTAL Nsig = 309 ±31 purity : 63% Vivek Sharma , UCSD

Time-Dependent Dalitz fit results Belle preliminary Final state f1 (o) D0 p0 11 ± 26 D0 w, h 28 ± 32 D*0 p0, h 25 ± 35 combined 16 ±21(stat) ±11(syst) -30o < f1 < 62o (95% C.L.) Vivek Sharma , UCSD

Implications of Time-dependent Dalitz analysis Consistent with B0J/yK* results cos2f1 = 0.87 ±0.75, hep-ex/0504046 f1~70o ? Disfavored >2s sin2f1 (^_^) ? f1~20o f1 2-fold ambiguity resolved ! Vivek Sharma , UCSD

A Completely Reconstructed (4S) Event at BaBar All particles accounted for Nothing Missing !

An (4S)B B Event : Along The Beam Line Z

Close Up of a Reconstructed (4S) B0 B0 Event

Sin2b BaBar 2004: Belle 2005: background

Three Kinds of CP Violation in B0 Meson System Indirect CPV Direct CPV