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Mixing and CPV in Charm Report of WG5

Delve into latest findings on charm mixing and CPV from WG5, including interest in rare decays, quantum correlations, and potential future measurements. Discover theoretical insights and experimental limits.

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Mixing and CPV in Charm Report of WG5

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  1. Mixing and CPV in CharmReport of WG5 D. Asner, Carleton U, I. Bigi, U. Notre Dame, F. Martinez Vidal, A. Oyanguren, IFIC, Universitat de Valencia-CSIC N. Neri, Universit`a di Pisa, B. Meadows, U. Cincinnati M. Blanke, Technische Universitaet Muenchen A. Palano, INFN, Bari Brian Meadows, U. Cincinnati

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

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

  4. 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

  5. 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

  6. 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

  7. Interest in D0 +- • Ikaros: “10-8 would be an interesting goal” • At this energy, the +- (or ) are “back-to-back” in transverse momentum and should present an excellent signal-to-noise ratio. [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

  8. D Mixing Brian Meadows, U. Cincinnati

  9. 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

  10. 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

  11. Compare Mixing for D0 with D0 - 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

  12. 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

  13. Measurement of S(Ks) and of aSL could eliminate or refine this model: (S) ~ 0.05 % ;  aSL ~ 1 % Comments on LHT Model … From Monika and Ikaros Brian Meadows, U. Cincinnati

  14. Bigi, Blanke, Buras, Recksiegel Little Higgs with T-parity. NOT an MFV model arXiv:0904.1545 S. Recksiegel Monika Blanke A. Buras Ikaros Bigi … bets his beard that LHT models would lead to observable CPV in D decays! Later … is willing to grow a beard if CPV is not observed in D decays by 2017! Brian Meadows, U. Cincinnati

  15. Running at Charm thresholdQuantum Correlations (QC) Brian Meadows, U. Cincinnati

  16. 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

  17. 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

  18. 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

  19. 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

  20. 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 ~600 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 ~300K • If KL+- could be added we would have 1.2M double-tagged events • Can make TD “Double-Dalitz” Plot fit with many correlations. Brian Meadows, U. Cincinnati

  21. 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 ! 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

  22. TDQC – A Conclusion ? • The time-dependent “Double-Dalitz” analysis can be made on a wide variety of events: • (Ks+-) - (Ks+-) • (Ks+-) – (Ks K+K-) • (Ks+-) – (K-+0) • (Ks+-) – (K-+) • (Ks+-) – (K-K+) • … etc. • We need a simulation to examine how well this might work. • A large sample. • Model-dependent • Highly constrained • Measures |q/p| and  • … Brian Meadows, U. Cincinnati

  23. 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: • A few issues need work • Y(4S) vs. (3770) signal/background needs clarification • Effectiveness of strong phase measurements at (3770) in mixing needs clarification • Issue of TDQC needs simulation study • Some other items not yet covered • Measurement of fD , fDs form-factors, … • Address experimental issues (tracking, end-cap PID) Brian Meadows, U. Cincinnati

  24. Ikaros Bigi … is willing to grow a beard if CPV is not observed in D decays by 2017! I believe the charm agenda will e advanced significantly this year: (i) There is Charm 09 in May in Heidelberg. I will talk there on CPV in charm. (ii) In June there is SuperB in Perugia. (iii) There is a heavy Flavour WS in Sept. in the Balkans – Thomas Mannel is one of the oranizers. (iv) More and more papers on CPV in charm will appear from several groups of authors. (v) I expect a paper by the Rio group and me to appear in May or June on some novel ideas about CPV in charm Dalitz studies. Brian Meadows, U. Cincinnati

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