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Mixing and CPV in Charm WG5

Mixing and CPV in Charm WG5. Interest in rare decays Mixing and running at charm threshold Time-Dependent Quantum Correlations (TDQC) Renewed Interest in “a SL ”. Interest in D 0   +  -. Search for D 0   +  -.

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Mixing and CPV in Charm WG5

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  1. Mixing and CPV in Charm WG5 • Interest in rare decays • Mixing and running at charm threshold • Time-Dependent Quantum Correlations (TDQC) • Renewed Interest in “aSL” Brian Meadows, U. Cincinnati

  2. Interest in D0 +- Brian Meadows, U. Cincinnati

  3. Search for D0 +- • There is considerable theoretical interest in the FCNC decay D0 +- • The SM estimates a lower limit BF > 4 x 10-13 • Estimates would be improved by measurement of D0  • Only estimate so far - BF[D0  ] < 1.5 x 10-5 Dominant, long-range mechanism Brian Meadows, U. Cincinnati

  4. Reminder from KL+- • Standard model limit (“unitarity bound”) is • Measured value is (6.86 § 0.37) x 10-9 From QED: 1.20 x 10-5 Measured: 5.47 x 10-4 = 6.83 x 10-9 x L.M. Sehgal, PR 183, 1511 (1969) BNL E791, Heinson et al, PRD 51, 985 (1995) Brian Meadows, U. Cincinnati

  5. 12k + c qk - u 22k Interest in D0 +- • R-parity SUSY could increase the decay rate by up to to 7 orders to BF~3.5x10-6 • Current experimental limits are: • Super B should be able to arrive at upper limits much better than this and also measure BF[D0 ] to better understand the SM limit. Opens a 7 orders of magnitude search window Brian Meadows, U. Cincinnati

  6. Interest in D0 +- • Based on Babar Y(4S) result: • We project SuperB will reach 5 x 10-8 at Y(4S) (75 ab-1) • We need simulations to estimate the relative strength of running at the (3770): • At this energy, the +- (or ) are “back-to-back” in transverse momentum and should present an excellent signal-to-noise ratio. • Using projections based on a study by the BES III collaboration we should expect to reach 7 x 10-8 using 600 fb-1 [BESIII claim they will use 20 fb-1 to give them a 90% limit at 3 x 10-8 – apparently a mistake] http://arXiv.org/pdf/0801.1833 and Eur.Phys.J.C57:309-492,2008. Brian Meadows, U. Cincinnati

  7. D Mixing Brian Meadows, U. Cincinnati

  8. D Mixing - What Can SuperB Do? Major Goals: • Establish whether or not there is any CPV • Improve precision of these measurements • Compare (x,y) for D0 and D0 • Examine whether CPV originates from the mixing (p = q) or from decay Af = Af ? Possible Strategy: • Compare (x,y) for D0 with (x,y) for D0 • Compare different decay channels (is CPV in mixing or in decay?) Brian Meadows, U. Cincinnati

  9. Improve Precision – Projection of Y(4S) Measurements to SuperB • Assumptions: • Central values are as reported at ICHEP2008 • Scaling is done only for D0 K-+, D0Ks+- and  measurements. • Systematic errors scale as 1/sqrt(N) • The latter are mostly determined by data so this is approximately so. If central values persist: Will observe >> 5 effect !! No-CPV point still allowed at 1σ NOW x x (Alan Schwartz/David Asner – private communication) Brian Meadows, U. Cincinnati

  10. Running at y(3770) CLEO c were able to measure K-+ strong phase: from 281 pb-1 Main systematic uncertainty comes from p0 and h efficiency. Including other D mixing results:  SuperB 300 fb-1: Extend to Other Channels Use Quantum-Correlations (QC) AND – the possibilities are that we can use OTHER channels with knowledge of strong phases Brian Meadows, U. Cincinnati

  11. For multi-body channels, this means we can measure strong phases “integrated over” the final state. The “coherence” measures to what extent this is useful. CLEO measurements (using external mixing information from elsewhere): We need to clarify how we include these measurements in mixing results from the Y(4S) QC in Multi-body Channels Brian Meadows, U. Cincinnati

  12. Running at Charm thresholdTime-Dependent Quantum Correlations (TDQC) Brian Meadows, U. Cincinnati

  13. m-2 (GeV2/c4) m02 (GeV2/c4) Time-Integrated QC in Multi-body Channels • For multi-body channels, we could measure relative phases “bin-by-bin” in their phase-space. Quantum correlations remove necessity for model describing phase space. Probably ONLY way to obtain a true PWA fit. X X For higher multiplicities, we would measure “coherence” and a single strong phase. For 3-body final states this provides model-independent measurement of strong phase variation over the Dalitz plot - Useful for CKM measurement Brian Meadows, U. Cincinnati

  14. m-2 (GeV2/c4) m02 (GeV2/c4) Time-dependent QC Decays – “Super D”? • The moving CMS means we could measure time-dependent (TD) strong phases resulting from D0 mixing. Leads to model-independent time-dependent phase space distribution. X X Boost is ~same as for Y(4S) Is this possible or useful ? Brian Meadows, U. Cincinnati

  15. Super B - Super D Comparison • Handicaps wrt TDQC for B’s at Y(4S): • D0’s also have little transverse momentum at y(3770) so we rely on the boost- bg=p/m[~same as at Y(4S)] for time measurements • BUT tD0 < 1/3tB0 sos ~ 30 mm is only about one D0 lifetime • We only anticipate running for ~300 fb-1 (comparable to BaBar) • Advantages: • D0’s are produced at (3770) at ~3 x the rate of B0’s at Y(4S) • D0 decay rates ~10-(3-4) are typically 100xB0’s  So there are many more “double-tags” than in B’s from Y(4S) • Example: CLEO have 420 double-tagged Ks+- events from 818 pb-1 that suggests “Super D” will have ~ 150K • If KL+- could be added we would have ~600K double-tagged events • Can make TD Double-Dalitz-Plot fit with many correlations. Brian Meadows, U. Cincinnati

  16. e+e- (3770)  (Ks+-) (Ks+-) There are two Dalitz plots correlated in a time-dependent way: If you select CP-odd Ks0 in one, you see “no”Ks0 in the other. If you select RS K*-+ in one, you see only (opp. sign) RS K*+- in the other. EXCEPT: There will be a small signal arising from MIXING. This has a definite time-dependence, making it more identifiable above background. Backgrounds at (3770) are small ! Do TD “Double-Dalitz Plot” fit: An example from CLEO c CLEO data: - It works !! J. Napolitano http://indico.ihep.ac.cn/conferenceDisplay.py?confId=176 Brian Meadows, U. Cincinnati

  17. TDQC – A Conclusion ? • We cannot yet say if the handicaps will outweigh the tantalizing advantages in a TDQC mixing analysis. • We need a simulation of to examine how well this might work. Brian Meadows, U. Cincinnati

  18. Renewed Interest in “aSL” Brian Meadows, U. Cincinnati

  19. Sensitivity to CPV in Mixing - aSL • Wrong Sign (WS) lepton asymmetry measures CPV: • Assuming CPV is in mixing: • Precise measurement would restrict possible parameter space in BBRB LHT model. • May also restrict other models. No CPV Current measurement From Monika and Ikaros Brian Meadows, U. Cincinnati

  20. Sensitivity to CPV in Mixing - aSL • Can measure aSL at Y(4S) with D* tagging: • Large backgrounds (much reduced using Dreco sample) • We estimate 13,500 events / yr.  A = 1% per year. • Measure it at (3770) • Much cleaner reconstruction • Can include WS hadrons since no DCS • Estimate 1,600 events per month  A = 1% in 4 mos. • Obviously (3770) is more efficient, but not a “gotta have it”. Brian Meadows, U. Cincinnati

  21. Measurement of S(Ks) and of aSL could eliminate or refine this model. Comments on LHT Model … From Monika and Ikaros Brian Meadows, U. Cincinnati

  22. Summary • Impressive work has been done both at, and since, the Valencia workshop. http://www.slac.stanford.edu/spires/find/hep/www?irn=8013667 • For progress towards a TDR, this is an excellent starting point: • Issue of TDQC needs simulation study • Y(4S) vs. (3770) signal/background needs clarification • Effectiveness of strong phase measurements at (3770) in mixing needs clarification • Some other items not covered yet • Measurement of fD , fDs form-factors, … • Address experimental issues (tracking, end-cap PID) Brian Meadows, U. Cincinnati

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