1. K. Holubyev HEP2007, Manchester, UK, 19-25 July 2007 CP asymmetries at D0 Kostyantyn Holubyev (Lancaster University) representing D0 collaboration HEP2007, Manchester, UK 19-25 July 2007

2. K. Holubyev HEP2007, Manchester, UK, 19-25 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.

3. K. Holubyev HEP2007, Manchester, UK, 19-25 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:

4. K. Holubyev HEP2007, Manchester, UK, 19-25 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:

5. K. Holubyev HEP2007, Manchester, UK, 19-25 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 +

6. K. Holubyev HEP2007, Manchester, UK, 19-25 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]

7. K. Holubyev HEP2007, Manchester, UK, 19-25 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*:

8. K. Holubyev HEP2007, Manchester, UK, 19-25 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 

9. K. Holubyev HEP2007, Manchester, UK, 19-25 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

10. K. Holubyev HEP2007, Manchester, UK, 19-25 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

11. K. Holubyev HEP2007, Manchester, UK, 19-25 July 2007 peak: 27,300 ± 300 evts Results: Untagged semileptonic asymmetry Complementary, independent measurement of : 10 double Gauss single Gauss BKG Exp Mass modeling:

12. K. Holubyev HEP2007, Manchester, UK, 19-25 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

13. K. Holubyev HEP2007, Manchester, UK, 19-25 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:

14. K. Holubyev HEP2007, Manchester, UK, 19-25 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

15. K. Holubyev HEP2007, Manchester, UK, 19-25 July 2007 14 Results: Direct CP violation in contains A K A CP (B + → J/ψ(1S) K + ) = + 0.0067 ± 0.0074(stat) ± 0.0026(syst) world’s most precise! A K estimated independently: X, MC INACCURACYFLUCTUATES

16. K. Holubyev HEP2007, Manchester, UK, 19-25 July 2007 Conclusions For the first time is constrained by measuring consistent with SM 15 PDG-2007 update: We measure +0.0067±0.0074±0.0026 consistent, x2 more precise

17. K. Holubyev HEP2007, Manchester, UK, 19-25 July 2007 BACKUP SLIDES

18. K. Holubyev HEP2007, Manchester, UK, 19-25 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;

19. K. Holubyev HEP2007, Manchester, UK, 19-25 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= – 0.0072

20. K. Holubyev HEP2007, Manchester, UK, 19-25 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

21. K. Holubyev HEP2007, Manchester, UK, 19-25 July 2007 Details: Kaon asymmetry in different bins: - wrong charge corr., background or - right charge corr., D* peak or

22. K. Holubyev HEP2007, Manchester, UK, 19-25 July 2007 max SIG SIDE Details: Kaon asymmetry

23. K. Holubyev HEP2007, Manchester, UK, 19-25 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

24. K. Holubyev HEP2007, Manchester, UK, 19-25 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

25. K. Holubyev HEP2007, Manchester, UK, 19-25 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,,,,

26. K. Holubyev HEP2007, Manchester, UK, 19-25 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

27. K. Holubyev HEP2007, Manchester, UK, 19-25 July 2007 3,376±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

28. K. Holubyev HEP2007, Manchester, UK, 19-25 July 2007 If n 1 and n 2 independent: we neglect Therefore for any asymmetry: If A K : therefore Some math