Selected Results on CP Violation From BaBar Vivek Sharma UC San Diego

Weak Interactions of Quarks & The CKM Matrix Vpq= p = u, c, t W± gVpq q = d, s, b q W - p gVqp W + gV*qp quark decay anti-quark decay Cabbibo-Kobayashi-Maskawa matrix Complex matrix elements lead to different amplitudes for quarks and anti-quarks  CP violation

CKM Matrix : Wolfenstein Parameterization λ = 0.220 ± 0.002 A = 0.85 ± 0.05 É = 0.22 ± 0.09 ¿ = 0.33 ± 0.05 CKM phases relative magnitudes = Complex elements Vtd and Vub result in large CP asymmetries in B decays

Probing The Unitarity Triangle in B System CKM phases CKM Paradigm: All CP asymmetries related to single CKM phase   SM CP violation is very predictive Experimentalist’s goal  Is this the full picture? Overconstrain the Unitarity Triangle with Multiple Measurements

this talk is not targeted at the BaBarians in the audience Outline of This Talk BaBar detector and data samples Common measurement techniques Focus on : sin2 from B  Charmonium “sin2” from Penguin mediated decays Paradigm Shift in Measurement Chasing  My apology that this talk is not targeted at the BaBarians in the audience

The BaBar Detector e+ (3.1 GeV) e- (9 GeV) Electromagnetic Calorimeter 6580 CsI(Tl) crystals 1.5 T solenoid e+ (3.1 GeV) Cerenkov Detector (DIRC) 144 quartz bars 11000 PMs e- (9 GeV) Drift Chamber 40 stereo layers Instrumented Flux Return iron / RPCs (muon / neutral hadrons) Silicon Vertex Tracker 5 layers, double sided strips SVT: 5 layers, 97% efficiency, 15 mm z hit resolution (inner layers, perp. tracks) SVT+DCH: (pT)/pT = 0.13 %  pT + 0.45 % DIRC: K- separation 4.2  @ 3.0 GeV/c  2.5  @ 4.0 GeV/c EMC: E/E = 2.3 %E-1/4  1.9 %

PEP-II Asymmetric Energy Collider at (4S) Resonance Run1 Run2 Run3 Run4 227M BB PEP-II top luminosity: 9.2 x 1033 cm-2s-1 (design 3.0 x 1033 cm-2s-1 ) Top recorded L/8 h: 240 pb-1 Top recorded L/month:16 fb-1 BABAR logging efficiency: > 96% trickle injection w/o trickle injection top-off every 30-40 min Continuous filling with trickle injection more stable machine, +35% more lumi

Time-Dependent CPV Measurements

Cartoon Of (4S) B0B0 Decay Along Beam Axis

Time Evolution And Decay For B0 Decay to a CP eigenstate (with single weak decay amplitude  and strong phase ) CP = CP of the decay final state

Time-dependent CPV Asymmetry Phase of mixing Amplitude ratio With the C and S coefficients defined as : (for single weak decay amplitude)

The Simple Case of B0 J/K0 CP = -1 (+1) for J/y K0S(L)

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

Producing B Meson and “Junk” at (4S) Resonance BB (spherical) Continuum (jet-structure) e+e-  (4S)  B+B- suppress continuum background noting event topology e+e-  (4S)  B0B0 Dominant background for charmless B decays: e+e-  qq (continuum) Off On PEP-II BABAR BB threshold B0B0 threshold

Signal and Background Event Topologies Differences in the event topology in (4S) rest frame (Isotropic B Vs jet-like Continuum) and Energy flow structure in these events used to construct continuum background suppression tools. BB qq

B Meson Reconstruction Unique kinematics at the (4S) for signal selection Beam-energy substituted mass Energy difference Correctly reconstructed BB events Combinatorial background

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]

B Flavor Tagging By examining decay product in recoiling Btag Tagging performance Category e(%) w(%) Q(%) Lepton 8.6 ±0.1 3.2 ±0.4 7.5 ±0.2 Kaon I 10.9 ±0.1 4.6 ±0.5 9.0 ±0.2 Kaon II 17.1 ±0.1 15.6 ±0.5 8.1 ±0.2 K-p 13.7 ±0.1 23.7 ±0.6 3.8 ±0.2 Pion 14.5 ±0.1 33.9 ±0.6 1.7 ±0.1 Other 10.0 ±0.1 41.1 ±0.8 0.3 ±0.1 Total 74.9 ±0.2 30.5 ±0.4

Effect of Vertex Resolution 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

Sin(2b) Result From Charmonium Modes (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)

Testing  Vs “”

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

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

The « Golden » Penguin mode B0   K0 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 (Opposite CP) S(fKS) = +0.29 ± 0.31(stat) S(fKL) = -1.05 ± 0.51(stat) Combined fit result (assuming fKL and fKS have opposite CP) Standard Model Prediction S(fK0) = sin2b = 0.72 ± 0.05 C(fK0) = 1-|l| = 0 0.9s hfK0

The Silver penguin modes: B0  h’KS & B0  f0KS hep-ex/0502017 hep-ex/0406040 B0  h’KS B0  f0(980)KS Large statistics mode Reconstruct many modes ’   + –, 0      ,  + –0 KS  + – ,00 Modest statistics mode CP analysis more difficult Requires thorough estimate of CP dilution due to interference in B0   + –KS Dalitz plot Fit finds 819 ± 38 events Fit finds 152 ± 19 events

The Silver penguin modes: B0  h’KS & B0  f0KS hfK0 hfK0 sin2 [cc] @ 3.0 sin2 [cc] @ 0.6

Sin2b from bs penguins – summary of BaBar results None of the individual results (except perhaps h’KS) has a sizeable discrepancy with SM But penguin average 2.8s away from Charmonium result Note that new physics will generally have different effect on modes – so averaging not necessarily sensible…

sin2 from bs Penguins: World averages BaBar/Belle agree on results. Discrepancy is 3.7s if averaged Caveat: uncertainty due to sub-leading SM contributions are ignored in this view of the discrepancy Theory needs to refine SM prediction for sin(2b) various penguin modes (conversations in progress!) -hf×S (‘sin2b’)=0.43 ± 0.07 C (‘direct CPV’)= -0.021 ± 0.05

All Penguin Measurements Are Luminosity Limited Expect double BABAR luminosity in summer 2006: 2004: 246 fb-1 2006: 500 fb-1 f0KS KSp0 jKS KKKS h’KS K*g 5s discovery region if non-SM physics is a 30% effect 2004 2006

Time Dependent CPV and Angle : Plan “B” Works Better !

CPV in b u u d Process : B0 +- Neglecting Penguin diagram

Reality in B0 +-, + - Tree Penguin Ratio of amplitudes |P/T| and strong phase difference  can not be reliably calculated! If no penguins  Spp ~ -0.34 Gronau& London: Estimate dapeng = eff - using isospin relations

Estimating Penguin Pollution in B0 +-, + -

Rates and Asymmetries in B+ 0 , B0 0

Angle  From B+ - : Bottomline B+ - TD CPV Very weak constraint on  [67o -131o] Needs more precise C00 measurements

B System As Probe of  This system seems to have had the Pope’s blessings ! Two years ago few would have bet that this system would play a defining role in  measurement !

B0 + - System As Probe of  Blessing # 1 Likelihood projection Although 2 0’s make efficiency small

B0 + - System As Probe of  Blessing # 2 Blessing # 3 |a-aeff|<11o @ 68%C.L. bkgd total  Helicity angle

TD CPV Measurement in B0 + - Shown here are events from the Lepton and Kaon1 tagging categories only total likelihood total background In total 617 52 signal events Preliminary

Systematic Uncertainties in TD analysis

Discerning  No result from Belle on + - yet B0 + - Br(r+r-) (30±6) 10-6 Br(r+r0) (26±6) 10-6 Br(r0r0) <1.1 10-6 B0 + - No result from Belle on + - yet

Chasing Gamma ! (Not a Pretty Picture With Current Dataset)

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 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

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

Modelling D0 KS + - Dalitz Distribution D Decay amplitudes etc obtained from fit to 81K D*D0 sample Use 16 2-body modes

Sensitivity to  : Not all events are Equal

Event Samples and  Sensitivity Vs rB Event samples (from 227M BB ) are clean but small (when divided into B ) Further, error on  depends on rB value, poor sensitivity at low rB 448 28220 9011

(Poor) Constraints on  Bayesian C.L.s 68% 95% D*K DK g 180° 0° -180° 0.1 0.3 rB g = 70°±26°±10°±10°(Dalitz) PRELIMINARY DK : rB < 0.19 (90% C.L.) dB = 114°±41°±8°±10°(Dalitz) D*K : rB = 0.155 +0.070 ± 0.040 ± 0.020 -0.077 dB = 303°±34°±14°±10° (Dalitz)

(Poor) Constraints on  : Need More Statistics

Summary: In Pictures All interesting measurements are data starved; need multiple times current data samples for a precision probe of the CKM paradigm Waiting impatiently for more data !

Good News: Email (Sunday) From BaBar Counting Room Dear colleagues, yesterday afternoon our colleagues from the machine have been able to inject the first electrons into PEP. After only a few hours, they were able to store a 100 mA beam. Positrons are expected within a few days. This means that collisions and physics data taking should resume very soon. This is really great news. Our PEP/Linac colleagues have done an outstanding work taking into account that they restarted the machine 10 days ago. One hopes that BaBar doubles its dataset by mid 2006 and doubles it again by end of 2008 In the future LHC-b not enough, need SuperBFactory

See http://ckm2005.ucsd.edu for detailed presentation of topics discussed here

 from B±D0 K±: D0 KS + - Dalitz Analysis BELLE’05

B Mixing Phenomenology

B0 B0 – Mixing: the Formalism Generic neutral B-meson state Time evolution governed by Schroedinger Equation Hamiltonian is diagonal in basis of heavy and light mass eigenstates (G=GH=GL and |q/p|=1)

B0 Decay Amplitudes Time evolution of physical states Decay amplitudes weak phase , strong phase d

(Time-dependent) Decay Rates General case:

Decay Rates to Final States with specific Flavor (BB Mixing) No CP asymmetry, if “unmixed” “mixed”

B0B0 Oscillation Measurements Di-Leptons B0  D*ln D(*) p/r/a1, J/K* B0B0 oscillation frequency precisely determined from flavor specific final states: Dm = 0.502 ± 0.006 ps-1 (world average) B0  D*ln

CP Eigenstate: 2 interfering Amplitudes Vcb b c Without mixing  W - c B0 s Vcs K0 KS d d Vcb b b c With mixing  + c W B0 B0 BB mixing s Vcs K0 KS d d d

Interference of 2 Amplitudes Consider pure B0 initial state (B0 is the same) ΔmΔt = 0: P(B0B0) = 0  no mixing, no interference ΔmΔt = p: P(B0B0) = 1  full mixing, no interference ΔmΔt = p/2: P(B0B0) = 1/2  maximal interference, resulting in CP violation ! only B0 final state f BB mixing only B0

CPV: B Decays With 2 Amplitudes With Relative Weak Phase : Need to Reorganize this

Some Relevant B Decay Diagrams Color Suppressed Spectator Tree Diagrams Gluonic Penguin W-Exchange

Penguin Lust !

CPV: B Decays With 2 Amplitudes With Relative Weak Phase : Need to Reorganize this

Golden Decay Modes: (cc)K0 decays B0 mixing B0 decay K0 mixing c d b s b d c t W+ s t d b d s d d CP = -1 (+1) for J/y K0S(L)

Example: Time Dependent CPV In B0 J/K0 B0 mixing B0 decay K0 mixing c d b s b d c t W+ s t d b d s d d CP = -1 (+1) for J/y K0S(L)