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D 0 D 0 bar Mixing and CP Violation at BESIII

D 0 D 0 bar Mixing and CP Violation at BESIII. Kanglin He June 2006, Beijing. OutLine. D 0 D 0 bar Mixing CKM γ / ϕ 3 measurements CP violation Dalitz Plot analysis Time-Independent measurements using The Quantum Correlation Analysis (TQCA) Summary. D 0 D 0 bar Mixing.

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D 0 D 0 bar Mixing and CP Violation at BESIII

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  1. D0D0bar Mixing and CP Violation at BESIII Kanglin He June 2006, Beijing

  2. OutLine • D0D0bar Mixing • CKM γ/ϕ3measurements • CP violation • Dalitz Plot analysis • Time-Independent measurements using The Quantum Correlation Analysis (TQCA) • Summary

  3. D0D0bar Mixing • Flavor eigenstate == mass eigenstate • Expected to be very small in Standard Model • Sensitive to New Physics • x, y =0 in the SU(3) limit • Experiments are beginning to probe interesting region of mixing parameter space (x, y ~10-3)

  4. Mixing in the Standard Model and Beyond Common hadronic final states Standard Model (real, on-shell) (virtual, off-shell) New Physics Loops provide sensitivity new physics via x FSI may enhance both x and y in SM

  5. Mixing Parameters Mixing rate Strong phase difference of CF decay and DCS decay, important to measure CP eigenstate lifetime difference CP violation phase CPV in mixing CP violation in mixing/decay interference If CP is conserved, ϕ=0, Δ=0, yCP=y

  6. Theoretical Predictions x, y in range of 10-7-10-2 Standard Model New Physics From A. Petrov Charm Physics: Theoretical Review hep-ph/0311371 Theoretical predictions are very variable

  7. Mixing in High Energy Experimentflavor tag by D*π+D0fitting the time distribution Wrong-sign semileptonic decays(K(*)ev), measure Rmix (E791, FOCUS, BELLE, BaBar, etc) Decay to CP eigenstates(KK), measure yCP (E791, FOCUS, BELLE, BaBar, CLEO, etc) Wrong-sign Kπdecays, measure x ’2 and y ’ (CLEO, FOCUS, Belle, BaBar, etc) Dalitz plot analysis (CLEO, Belle, BaBar, etc)

  8. Experimental Situation yCP measurements PDG06 (Close to confirm) No evidence of mixing has been reported in the charm sector Hopefully to be found in near future

  9. D0D0bar Mixing at BESIII • Charm events at threshold are very clean • Ratio of signal to background is optimum • Lots of systematic uncertainties cancellation while applying double tag method • Mixing at threshold • Bad news: no time-dependent information • Good news: Quantum coherence, CP tags • The coherence of two initial D allows simple methods to measure DDbar mixing, strong phase and CP violation • Sophisticated methods combining semileptoinc, CP and hadronic modes provide additional sensitivity

  10. D0D0bar Mixing (Kπ) D0 decays as D0bar Key Point: Separate Mixing from DCSD

  11. Separate Mixing from DCSD Two path to D0D0bar decay final state: 1. D0K+π- (DCSD) 2. D0D0bar－>K+π- (MIX) In the case of no mixing, (K+π-)(K+π - ) is forbidden by Bose-Einstein statistics D0Kπ and D0barKπ require L even, but for Ψ(3770) decay, L = 1 mixing D0 DCSD D0 K+π- CF

  12. Challenge to PID • BESIII PID system • dE/dx, resolution (6-7)% • Two layer barrel TOF, time resolution ~100ps, ~83% solid angle coverage • 1 layer endcap TOF, ~110ps • Selection efficiency is >20% with a K/π double mis-identification rate at < 10-4 level

  13. Mixing in double semi-leptonic decays (Kev channel) at BESIII • Two missing neutrinos in events • Electron PID can suppress background • The selection efficiency is similar as the Kπ channel • Background level is also negligible while running a small MC data sample (~1% of 20fb-1). More detail study is needed.

  14. Rmix sensitivity at BESIII • With 20fb-1(4-5 years running) Ψ(3770) data sample, we may get • ~20,000 right sign Kπ events • ~20,000 right sign Kev events • If more electronic channels and muonic channels are applied (need further MC studies), more right sign events will be obtained • BESIII will probe Rmix <10-4 (At least) in combined Kπ and semileptonic channels

  15. CP + K+K- (3.89X10-3 ) π+π-(1.38X10-3 ) Ks π0π0 π0π0(8.4X10-4) KSKS (7.1X10-4) ρ0 π0 (3.2x10-3) CP – KSπ0(0.012) Ksη (3.9X10-3) KSη’ (0.0094) KSρ0 (0.0078) Ksω (0.012) KSφ (4.7X10-3) CP eigenstate Tags Dalitz Analysis KL modes can also be applied partially In 20fb-1Ψ(3770) data, we can get > 4.5x105 CP+ tags and > 3.6x105 CP- tags With large sample of CP tags, we may improve the measurements of strong phase, probe the direct CP, and other mixing parameters

  16. CKMγ/ϕ3 measurement Unitarity Triangle Extract γ/ϕ3 from BDK decays, where D decays to • D to CP eigenstates (GLW): improved constraints on charm mixing amplitude • D to flavor eigenstates Kπ (ADS): measurement of relative rate and strong phase • D to Ksππ(Dalitz plot analysis): studies of charm Dalitz plots tagged by flavor or CP eigenstates Need help from charm sector

  17. K+ KS KS K+ p0 K- p0 K- p- p- p- p- CP- eigenstate CP- eigenstate K+ K+ K+ K+ = 2 r cosd Useful for probing r & d Strong Phase (I) CP+ eigenstate Asymmetry = CP+ eigenstate Ratio of DSCD/CF If CPV=0 Mixing is small

  18. Strong Phase (II) In 20fb-1Ψ(3770) data, we can get > 10,000 CP+ vs Kπ double tags > 10,000 CP- vs Kπ double tags The precision of cosδ< 0.06 level is expected at BESIII, Be helpful to improve the precision of γ/ϕ3 measurement

  19. CP Violation 1. Direct CP Violation (in decay) 2. Indirect CP Violation (in mixing) 3. CP violation in the interference between decays with/without mixing

  20. CP violation in Charm decays • In SM, no Direct CP asymmetry in CF and DCS modes. New physics • Buccella et al. predict CP asymmetries in decay in the range of 0.002%0.14%, may up to 10-3 level • Indirect CPV due to mixing is a possibility for D0 decays • CP studies in charm transitions represent an almost 0-background search for New Physics (Bigi and Sanda) • If New Physics intervenes through DCSD, then it would have the cleanest impact on D+KS,Lπ+ (Bigi and Sanda)

  21. Need two paths (CKMweak +FSIstrong) from initial D to final state f D Find: f Compare Df to Df D f Direct CP Violation Singly Cabbibo Suppressed decays (SCSD) should be the good choice to measure a sizeable asymmertry Not too diff.

  22. Experimental search CP Violation in Charm decays • A Cabbibo allowed reference states is needed to calibrate the known production/detection asymmetries Define Where η is the ratio of N (searched) / N (referenced) D0: K-K+, π-π+, Ksπ0, etc D+: K-K+π+, Ksπ+, KsK+, etc Ds: KsK+, Ksπ+, etc D0: K-π+, D+: K-π+π+, Ds: K-K+π+ DCSD mode: D+K+π+π- D0K+π-π-π+ Probe New Physics

  23. CP asymmetry measurement 1% level reached for some decay modes, no evidence of CP Violation

  24. CP Violation at BESIII • Quantum Coherence • Psi(3770) -- D(CP+)D(CP+), D(CP-)D(CP-) • CP asymmetry in D+ and Ds decays • Lots of modes, include DCSD • CP asymmetry in D0 decays • Have to pay price for tag • Flavor tag with semileptonic mode at Ψ(3770) • Flavor tag with D-K+π-π- modes above DD* threshold (4.03GeV / 4.17 GeV) • Indirect CP asymmetry is too hard to BESIII

  25. Quantum Coherence Suppose Both D0 decay to CP eigenstate f1 and f2 . Thus if a final state such as (KK)(ππ) observed, we immediately have evidence of CP violation In 20 fb-1Ψ(3770) data, > 1000 double CP+ and CP- tags can be obtained. if 100%CPV, it lead to ACP~10-3 level

  26. CP Violation in Charm decays (I) In 20fb-1 data, BESIII can obtain the precision of CP asymmetry in decays of charmed mesons for the DCSD modes, BESIII can probe New Physics at ACP ~(10-2 10-4) level

  27. CP Violation in Charm decays (II) Flavor tagged by D-K+π-π- If 20fb-1 data taking at 4.03GeV, ~9,000 D0 CP tags 4.17GeV, ~5,000 D0 CP tags Expected to be obtained The precision of CP asymmetry will be

  28. CPV interference with Mixing Two interesting case with semileptonic tag + CP tags CPV in Mixing is small, Δ=0 • In 20fb-1 psi(3770) data, • 10,000 SL+CP(+) tags • 10,000 SL+CP(-) tags ΔyCP and ΔAΓ~ 1% level Applying the inclusive semileptonic tag Can improve the measurements

  29. Dalitz Plot Analysis • Developed by CLEO, BaBar, Belle, etc • Modes: Ksπ+π-, K-π+π0, K-K+π+, π-π+π0, etc • Time-dependent Mixing measurements • DCSD branching ratio measurement (including phase) • CP Violation studies • Measurements of γ/ϕ3in BD(*)K(*) • Strong phase measurement The powerful tool will be applied in BESIII • What will we do next? • Understanding the ππ or Kπ S-wave scattering (learn from BESII J/Psi analysis and other experiments, such as: applying K-matrix formulism etc) • Currently, we have a piece of FORTRAN code. Develop a OO version PWA package for charm decays in future

  30. CPV in Dalitz Analysis Strong phase, do not change sign under CP conjugation CPV phase, change sign under CP conjugation Phase difference hints that CP is violated CP asymmetry across Dalitz plots • Advantage of using Dalitz plot Analysis: • Measure CP asymmetries • Direct access to the phase

  31. Dalitz Analysis at BESIIIInteresting topic (I) • K-π+π0,Ksπ+π- vs CP tags, measure strong phase of Kρ, K*π • K-π+π0,Ksπ+π- vs flavor tags, measure Br of DCSD • Ksπ+π-, π-π+π0 vs CP tags,search for CP Violation (via same sign CP Tags) • CP asymmetries across Dalitz Plots • Ksπ+π-, π-π+π0 vs flavor tags • D+  K-K+π+

  32. Dalitz Analysis at BESIIIInteresting topic (II) • Simultaneously fit two Dalitz plots of K-π+π0 vs K-π+π0 and Ksπ+π- vsKsπ+π- , search for Mixing in Kρ, K*π modes • PWA analysis to DVV vs CP Tags, search for CP violation and measure the strong phase • more and more, …… Lots of interesting modes can be applied, to improve the measurements of Mixing parameters and search for CP violations in charm decays Key point: Quantum Coherence

  33. Time-independent Quantum Coherence • The Quantum Coherence Analysis (TQCA) • Ψ(3770)D0D0bar C=-1 • Ψ(4040)/Ψ(4160)(mγ)(nπ0)D0D0bar C=(-1)m+1 • measure RM, r, cosδKπ, y and xsinδKπ(at Ψ(4040) or Ψ(4160)) • Suggested by D. Asner and Sun etc, part of CLEO-c physics program • Will be applied at BES III

  34. TQCA at psi(3770) RM= (x2+y2)/2 r = Amp DCS/Amp CF See PRD 73 034024 (2006) [hep-ph/0507238] by Asner and Sun DT ST Measure RM, r, cosδKπ and decay fractions

  35. TQCA (C=+1) DT ST Have a chance to measure y and xsinδKπ

  36. Estimated uncertainties (stat.) of Mixing parameters using TQCA Scale to BESIII From PRD 73 034024 (2006) by Asner and Sun Have to identify C=+1 of γD0D0bar and γD0D0barπ0 from D*Dbar and D*D*bar decays

  37. Summary • Mixing parameters • Rmix < 10-4 in Kπ and Kev channels • ΔcosδKπ < 0.05 • Probe y: yCP ~ 10-4, ΔyCP ~ 1%, Probe x: 4.03/4.17 GeV • Possible to probe CPV phase ϕ if x is sizeable • CP Violation • ΔACP~10-3 in D+ decays, • Probe new physics at ACP<10-2 level in DCSD • Probe ACP<10-3 level with DT CP tags • Dalitz Plot Analysis are expected to improve the measurements • TQCA method can improve the measurements • A lot of work need to do in future Excited results can be produced at BESIII in Mixing and CP Violation in Charm sector!!!

  38. Thank You ! 谢谢

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