Probing The B0 D0 K0 System:A Quick UpdateVivek SharmaUniversity of CaliforniaSan Diego

Shahram Rahatlou

Motivation: sin(2b+g) From B D(*)0K(*)0 Decays CPV due to Interference between decay and mixing as in B D(*)p systemAdvantages:Expect large CP Violation since two processes of comparable strength (?) Experimentally probe rB in self-tagging final state BDK*0 with K*0K+p-Disadvantages:CKM suppressed, Color suppressed decays, Br (B0 ->DK0) 2 Br(B0 ->D0 )Much smaller decay rates (x 102) than B D(*)pStrong phasedifferencecrucial parameter

Shahram Rahatlou

Estimating B0 D (*) 0 K(*)0 Rates From Measured RatesNaivelyBaBar

Shahram Rahatlou

Improved B0/ B0 D(*)0K(*)0 Rate MeasurementsAnalysis described in BAD 484V8 improves over analysis described in past ICHEP04 conf paper BAD 884Current analysis Runs1-4, 205.5 fb-1 at (4S)Largely eliminate reliance on MC for unobserved modes which can contribute to peaking background in mES but dont peak near E=0Analysis tuned towards measurement/constraint on rB2-dimensional fit to mES and E distributionsSignal and background model:Five free parameters: Nsig ,argus ,slope pE ,Npeak ,Ncomb

Shahram Rahatlou

B D(*)0K0 Yields and Rates: Combining 3 D0 ModesBAD 484V8205 million BBPreliminaryN104 14N17 5D0 SidebandsComb./0.01 GeVComb./0.01 GeVD0 SidebandsE(GeV)E(GeV)BaBarSignal Yields are as expected * The E fits shown above are for illustration onlyActual fits are per D decay mode and in mes Vs DE*

ModeBF (10-5)B0 D0K05.3 0.7 0.3(syst)B0 D*0K03.6 1.2 0.3(syst)

Shahram Rahatlou

B0/B0 D(*)0KS Yields & Rates From Bellehep-ex/0408108274 million BB Preliminary ICHEP04196Belle

Shahram Rahatlou

Motivation for rB : Study of B DK Sensitivity to sin(2+)Study based on Toy MC reported by Shahram Rahatlou @ CKM Angles Workshop 2003, assumptions in the study still valid http://www.slac.stanford.edu/BFROOT/www/Organization/CollabMtgs/2003/workshops/ckm2003/Thur2/rahatlou.pdfFit simulated proper time distribution of BD0 K0 events expected in 500 fb-1 to simultaneously extract amplitude ratio rB , sin(2+), phase diff

Too few data!fit converges always when rB isinput/constrained from elsewhere

Shahram Rahatlou

Isolating Vub and V cb Driven Amplitudes in B D0K*0Vcb only: B0 D0bar K*0 D0bar K+ p-,p-p0,3p K*0 K+ p-Same sign kaons

Vub only: B0 D0 K*0 D0 K- p+,p+p0,3p K*0 K+ p-Kaons with opposite sign

Shahram Rahatlou

Probing rB From Self-Tagging B0 D0K*0 & B0 D0K*0 205 million BB PreliminaryKaon Charge correlation to separate Vcb & Vub driven modesVub transitionBAD 484V8BaBarE (GeV)E (GeV)See SRs talk at next Breco meeting

ModeB.F. (in 10-5)B0 D0K*0 4.0 0.7 0.3(syst)B0 D0K*0-0.50.50.3(syst)

Belle Search For The Self-Tagging B0 D0K*0Belle 274 million BB (PreliminaryBr

Near Term PlansThe main aim in the first analysis phase was to map out the decays rates and probe rBThis is now done as well as one can with 200 fb-1 data, have comparable precision to Belle with smaller data sample need to finish the paperworkBAD484 V9, the final version of the analysis BAD expected out by 7th Oct, together with a PRD-RC draftHope to send to journal well before Xmas holidaysRelated Documents not explored in this 10 talk: Study of Time-dependent CPV in BD0K0 http://www.slac.stanford.edu/BFROOT/www/Organization/CollabMtgs/2003/ workshops/ckm2003/Thur2/rahatlou.pdf

Viola Sordinis exercise at CKM2005 combining phenomenology and exptal results to obtain constraints on rB and projected sensitivity to Sin2+ from B D(*)0K0 decays : http://ckm2005.ucsd.edu/WG/WG5/thu2/Sordini-WG5-S3.pdf

Shahram Rahatlou

Bottom Line: B DKSLike with most pursuits of , knowing the bu amplitude is keySo far no observation, only limits on rB from B0D(*)0K*0 modes, rB DK rates and constraining various contributing amplitudes suggests rBDKs=0.260.16. Is this approach theoretically kosher?ToyMC based time-dependent CPV studies indicate that with 500 fb-1 samples, mild information only on sin(2b+g) provided rB obtained from elsewhereMore B modes need to be added Self tagging decay B D**0 KS decays (poor Br. for self tagging modes)B DKs, D Ks mode not prolific (yield ~4x smaller than DKp mode)Precise measurements require > ab-1 data samplesThere are no shortcuts in clean measurements of !

Shahram Rahatlou

Unused Slides

Shahram Rahatlou

rB from fits to 2D fit to mES and DERatio rB defined as

Signal yields measured with separate 2D fits to distributions of mES and DE for Vub (B0D0K*0) and Vcb (B0D0K*0) modesEach D0 mode fitted seperately

Modify fit to determine directly rBFix yield and efficiency of Vcb modeUse uncertainties assigned as systematic error

Fit provides raw likelihood versus rB2 for each D0 modeConvolve with Gaussian to account for systematic errors

Total likelihood given by product of likelihoods from 3 D0 modes

Determine limit on rB2 by integrating the convolved likelihood function

Shahram Rahatlou

Upper Limit on rB2 with Bayesian ApproachUpper limit x at 90% confidence level computed as

Two different priors used to determine the limit L(rB2): likelihood function convoluted with systematic errorp0(rB2): prior with different hypothesis

Flat in Rb2p0=1 if rB2>0 p0=0 if rB20 p0=0 if rB

Likelihood functions including systematic errorKpKpp0KpppAll modes

Shahram Rahatlou

Shahrams TD Sensitivity Studies (Angles03 WS)

Shahram Rahatlou

Time-Dependent Decay Distributions Similar to BD*p time-distributionBut r expected to be much larger (x 10-20)Linear dependency on r: can it be measured in the fit (?)Tag-side DCS effects are small compared to signal amplitudeBut there are other potential complications due to DCS decays on reco side (20%)One solution: sin2(2b+g)

The other one: cos2DS+S-fit for rB and sin(2b+g-d) and sin(2b+g+d)

Shahram Rahatlou

Assumptions Used In This Toy StudySignal Yield: 0.3 events / fb-1 160 reconstructed events (BD0Ks only for now)Yields can be 50% higher (Br. Ratio knowledge, better event selection)Additional modes can increase signal yield but wont be as clean

No combinatorial or peaking backgroundSignal asymmetries expected to be weakly correlated with background parameters b=233, g=5919 2b+g=10520 (1.83 rad)Use 3 values in toys: 0.9, 1.88, and 2.8 rad

No Knowledge of strong phase Use different values d = 0.0, 0.8, 2.4 rad

Realistic BaBar Flavor Tagging circa 03105 tagged events in 500 fb-1

Vertexing: realistic resolution function10% tail and 0.2% outliers with category dependent bias Parameters fixed in the fit

CategoryEfficiencyDilutionDilu. Diff.Lepton10.3%0.9330.028Kaon 117%0.8010.022Kaon 219.4%0.5820.084Other19.9%0.3680.058

Shahram Rahatlou

Summary of Signal efficiencies and yields circa 2003 K*0Ksp0:Expected events: N(K+p-) x 0.5 (BF) x 0.5 (p0 eff) x 0.75 (Ks eff) ~ 50 eventsBut more background from p0

D0Kspp: done but not included for technical reason. Fewer events than D0K mode D0KK, pp: Branching fraction ~ 10 smaller than BF(Kp)

B0 D**0 K(*)0: similar to B0 D*0 K(*)0 but reduced by intermediate branching fractionYields for 500 fb-1with BF = 4 x 10-5Assuming D*0 reco. efficiency of 50%

KpiKpipi0K3piTotalD0KsProduced2639085201691Efficiency0.230.060.10Reco615451167D0K*0(K+pi-)Produced527181610403382Efficiency0.150.040.08Reco818079240D*0KsProduced1635623221047Efficiency0.120.030.05Reco19171652D*0K*0(K+pi-)Produced32611246432093Efficiency0.080.020.04Reco25252474

Shahram Rahatlou

Fit Validation with 50 ab-1: rBValidate fit with 500 experiments of 50 ab-1rB(gen) = 0.4, 2b+g = 1.88, d=0.0rB(fit) rB(gen)rB(fit) uncertaintyrB(fit) uncertainty vs. rB(fit) No bias in the fitted values for any parameterSlightly better errors for larger rBMean: 0.014RMS: 0.001m: -0.0020.006s: 0.0130.006rB

Shahram Rahatlou

First ToyFit Attempt for 500 fb-1 sample: fit 3 parameters rB, sin(2b+gd)Problem with fit convergence

Small values of rB are problematicrB constrained to be positive in the fit

~10% of fits with rB close to the limit2b+g=1.88 d=0.82b+g=1.88 d=0.0

Frac. Failed Fitsd=0.0d=0.8d=2.42b+g=0.903.0%2.4%3.6%2b+g=1.882.6%2.2%3.4%2b+g=2.803.8%2.4%3.0%

Shahram Rahatlou

Plan B Sensitivity for sin(2b+gd) with rB=0.4 (fixed)All fits successful!Problems with MINOS errors in some fitsUnder investigationNot perfect Gaussian shapeBad errors mostly for the positive error Probably hitting non-physical region in LL

Residue sin(2b+g+d) RMSd=0.0d=0.8d=2.42b+g=0.900.630.700.652b+g=1.880.640.690.602b+g=2.800.650.630.56

Residue sin(2b+g-d) RMSd=0.0d=0.8d=2.42b+g=0.900.650.640.662b+g=1.880.640.620.612b+g=2.800.600.610.59

Shahram Rahatlou

Summary of Preliminary Toy Study

Sensitivity with 0.5 ab-1?Simultaneous determination of rB, and sin(2b+gd) probably not be feasible with current method with 500 fb-1 samples (too few data)With 500 fb-1, expected uncertainty on sin(2b+gd) ~ 0.6-0.7 provided rB known from elsewhere. ignoring DCS effects which at ~22% is small compared to expected errors and where CLEO-c can help ?

Sensitivity with 5 ab-1?No problem measuring rB and sin(2b+gd) All simultaneous fits successfulUncertainty on rB: ~ 0.04-0.05Uncertainty on sin(2b+g): ~0.15-0.20The errors now scale with luminosity

Shahram Rahatlou

Estimating rB by Hook or by Crook Viola Sordini

Shahram Rahatlou

Getting to rB By Hook or By Crook ! : Exercise@CKM2005 by Viola Sordini et alLearning Today From Data on B DK Family of Decays

Shahram Rahatlou

Getting to rB By Hook or By Crook ! : Exercise@CKM2005 by Viola Sordini

Shahram Rahatlou

Viola Sordini et alsin(2+) Relative Error

Shahram Rahatlou

Mention the sensitivity to sin2b+gMention the sensitivity to sin2b+g