K. Holubyev HEP2007, Manchester, UK, July 2007 CP asymmetries at D0 Kostyantyn Holubyev (Lancaster University) representing D0 collaboration HEP2007, Manchester, UK July 2007

K. Holubyev HEP2007, Manchester, UK, July 2007 Outline Direct CPV asymmetry between B + and B − in exclusive (1.6 fb -1 ) ►Good test of New Physics at tree level: Standard Model predicts 1 Feasibility: Tevatron: supplies B-s from collisions at D0 detector: excellent muon system + precision tracking/vertexing, optimized for B searches Here we present the measurements of: Semileptonic asymmetry in inclusive dimuon events (1.0 fb -1 ) Semileptonic asymmetry in exclusive B s decays (1.3 fb -1 ) ► Independently constrain - CP violating phase in B s mixing ► Standard Model predicts Good test of New Physics at loop level.

K. Holubyev HEP2007, Manchester, UK, July 2007 We look at inclusive di-muon sample CP asymmetries: constraining 2 ► accounts for other processes contributing to di-muon final state ► input from B-factories needed ► combination of B s(d) production rates and mixing probabilities and extract indirectly from di-muon asymmetry: CPV phase in B s mixing accessed via semileptonic asymmetry:

K. Holubyev HEP2007, Manchester, UK, July 2007 We look at exclusive: vs CP asymmetries: constraining 3 CPV phase in B s mixing accessed via semileptonic asymmetry: and extract directly from untagged semileptonic asymmetry:

K. Holubyev HEP2007, Manchester, UK, July 2007 Also recently looked at exclusive channel: Direct CP violation in vs In Standard Model Beyond the Standard Model can be enhanced due to new couplings at tree level: ► flavor-changing Z´ between b and s ► Charged Higgs 4 and measured: DIRECT ANNIHILATION +

K. Holubyev HEP2007, Manchester, UK, July 2007 Main concerns Standard Model predicts: Can reach above 0.01 in realistic New Physics models. We should cope with: Kaon asymmetry Detector-induced asymmetries Both are possible at D0! 5 [] [Hou etal, 2006] [Lenz and Nierste, 2006]

K. Holubyev HEP2007, Manchester, UK, July 2007 Kaon asymmetry Technical complication: ► depends on material distribution, ► estimated independently from data: 6 ( μμ) final state contains muons from (J / ψ K ) final state contains K vs large sample of D*:

K. Holubyev HEP2007, Manchester, UK, July 2007 Muon system: 1.8T toroid for local muon tracking, |η|<2 cosmic ray rejection low punch-through D0 Detector 7 Central tracking: Silicon (innermost) + fiber tracker in 2T solenoid, |η|<3 High efficiency (~95% in the central region) and resolution: 002.0/)( 2  TT pp 

K. Holubyev HEP2007, Manchester, UK, July 2007 In any case ( ) we want: Polarity reversal significantly reduces systematics from detector asymmetries apparent A Detector introduces apparent charge asymmetries. Example (for muons): range out in the toroid: But: Polarity reversal Toroid+ Toroid− Polarity reversal: reducing detector systematics 8

K. Holubyev HEP2007, Manchester, UK, July 2007 Results: Di-muon semileptonic asymmetry From di-muon events we measure: calculating from PDG taking from B -factories estimating from data we obtain: Dominated by uncertainty on 9

K. Holubyev HEP2007, Manchester, UK, July 2007 peak: 27,300 ± 300 evts Results: Untagged semileptonic asymmetry Complementary, independent measurement of : 10 double Gauss single Gauss BKG Exp Mass modeling:

K. Holubyev HEP2007, Manchester, UK, July 2007 After correcting for sample composition: Dominated by uncertainties from sample composition, mass fitting We disentangle detector asymmetries by applying a detector model. Range-out asymmetry large, but under control. Results: Untagged semileptonic asymmetry 11

K. Holubyev HEP2007, Manchester, UK, July 2007 So we have two independent measurements of from from a fit to the time- dependent angular distribution of the decay products in from CDF (consistent with SM) Results: D0 constraints on 12 We obtain:

K. Holubyev HEP2007, Manchester, UK, July 2007 charmonium easily identified Results: Direct CP violation in 13 Mass modeling: unbinned B → J/ ψ K B → J/ ψ π reflection B → J/ ψ K X BKG Gauss Threshold Exp 54,464 1,073±97 27,700±201 3,759±181 21,932±351 parame terized in E K D0 Preliminary, 1.6 fb -1

K. Holubyev HEP2007, Manchester, UK, July Results: Direct CP violation in contains A K A CP (B + → J/ψ(1S) K + ) = ± (stat) ± (syst) world’s most precise! A K estimated independently: X, MC INACCURACYFLUCTUATES

K. Holubyev HEP2007, Manchester, UK, July 2007 Conclusions For the first time is constrained by measuring consistent with SM 15 PDG-2007 update: We measure ±0.0074± consistent, x2 more precise

K. Holubyev HEP2007, Manchester, UK, July 2007 BACKUP SLIDES

K. Holubyev HEP2007, Manchester, UK, July 2007 Muon selection Hits in all 3 layers of muon chambers; Associated central track; Good quality of track; P T > 4.2 GeV or |P Z |>6.4 GeV; 3.0 < P T < 15 GeV; Impact parameter to primary interaction: < 0.3 cm; at least one scintillator hit with |Δt|<5 ns; Cuts on di-muons ΔP > 0.2 GeV 10° < Opening angle < 170° Δz < 2 cm Distance between hits in muon chamber Δr > 5 cm;

K. Holubyev HEP2007, Manchester, UK, July 2007 Systematics in ● from J/ψKX: repeat the analysis with fraction of J/ψKX fixed to 0 ● from A(J/ψπ), A(J/ψKX): repeat the analysis with A(J/ψπ), A(J/ψKX) artificially suppressed by fixing the ratios R = (J/ψπ fraction)/(BKG fraction), (J/ψKX fraction)/(BKG fraction) in every subsample to the value determined from “all” fit. suppressed this deviates maximally from the nominal A= –

K. Holubyev HEP2007, Manchester, UK, July 2007 Kaon asymmetry detector Technical complication: μμ and J/ ψ K samples are affected by: for μμ : Estimated from distance to calorimeter and K − d, K + d cross-sections for J / ψ K : Measured directly by comparing: vs no physics asymmetry, For p K =10 GeV: σ(K−d)=38mb, σ(K+d)=28 mb

K. Holubyev HEP2007, Manchester, UK, July 2007 Details: Kaon asymmetry in different bins: - wrong charge corr., background or - right charge corr., D* peak or

K. Holubyev HEP2007, Manchester, UK, July 2007 max SIG SIDE Details: Kaon asymmetry

K. Holubyev HEP2007, Manchester, UK, July 2007 Details: Kaon asymmetry To get Kaon asymmetry in J/ψK sample: unknown reco efficiency of some D* decay modes A K (p K ) was measured (detector characteristics) … and convoluted with pdf of p K in J/ ψ K sample to give

K. Holubyev HEP2007, Manchester, UK, July 2007 In any case ( ) we want: Polarity reversal significantly reduces systematics from detector asymmetries apparent A Detector introduces apparent charge asymmetries. Example (for muons): range out in the toroid: But: Polarity reversal Toroid+ Toroid− Polarity reversal: reducing detector systematics 7 - linear - includes higher order effects

K. Holubyev HEP2007, Manchester, UK, July 2007 Detector effects To account for detector-induced asymmetries to all orders – generalize to detector model charge - the one we are after forward-backward North-South range out the remaining two complete the system - total number of events in the sample, and - fraction of events with toroid/solenoid polarity If then #events with specific: toroid/solenoid polarity sign of particle pseudorapidity particle charge depends on asymmetries: To consistently account for correlations and errors: Divide sample into 8 subsamples according to the signs of by whatever method In each subsample extract Solve 8 simultaneous equations for and asymmetries,,,,

K. Holubyev HEP2007, Manchester, UK, July 2007 : 8 subsamples 3,216±76 3,391±78 3,586±79 3,225±76 3,532±79 3,370±773,353±77 3,616±80

K. Holubyev HEP2007, Manchester, UK, July ,376±57 3,343±57 3,399±57 3,369±57 3,546±59 3,467±58 3,626±59 3,565±59 : 8 subsamples D0 Preliminary, 1.6 fb -1

K. Holubyev HEP2007, Manchester, UK, July 2007 If n 1 and n 2 independent: we neglect Therefore for any asymmetry: If A K : therefore Some math