1. Mixing and CPV in Charm Report from Charm WG5 (Warwick, Updated)
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, M. Sokoloff
U. Cincinnati
M. Blanke,
Technische Universitaet Muenchen
A. Palano,
INFN, Bari
Super B, Perugia, Italy, 6/18/2009
Brian Meadows, U. Cincinnati

2. FCNC, Mixing and CPV in Charm
Items Discussed:
Interest in rare decays – D0+-
CPV in Mixing
Projected expectations
Importance of aSL
Running at charm threshold
Time-Dependent Quantum Correlations (TDQC)?
Simulation Wish List
Super B, Perugia, Italy, 6/18/2009
Brian Meadows, U. Cincinnati

3. Brian Meadows, U. Cincinnati
Interest in D0  +-
Super B, Perugia, Italy, 6/18/2009
Brian Meadows, U. Cincinnati

4. (Dominant in KL  +- - NOT necessarily so in D0 case)
Search for D0  +-
There is considerable theoretical interest in the FCNC decay D0  + (see I. Bigi’s talk, Friday am)
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
[Recall that, for KL  +-, SM BF = 6.4 x 10-8 – right on the money!]
Long-range
mechanism
(Dominant in KL  +- - NOT
necessarily so in D0 case)
Super B, Perugia, Italy, 6/18/2009
Brian Meadows, U. Cincinnati

5. magnitude search window
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 c u + - qk
12k
22k
Super B, Perugia, Italy, 6/18/2009
Brian Meadows, U. Cincinnati

6. Brian Meadows, U. Cincinnati
Interest in D0  +-
Ikaros: “10-8 would be an interesting goal”
At D threshold, 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]
and Eur.Phys.J.C57: ,2008.
Super B, Perugia, Italy, 6/18/2009
Brian Meadows, U. Cincinnati

7. Brian Meadows, U. Cincinnati
D Mixing
Super B, Perugia, Italy, 6/18/2009
Brian Meadows, U. Cincinnati

8. D Mixing - What Can SuperB Do?
Major Goals:
Improve precision of x, y, |q/p|, Arg{q/p}
Examine whether CPV originates from the mixing (p = q) or from decay (Arg{Af} = Arg{Af}) ?
Possible Strategy:
Compare (x,y) for D0 with (x,y) for D0
Compare different decay channels (is CPV in mixing or in decay?)
Super B, Perugia, Italy, 6/18/2009
Brian Meadows, U. Cincinnati

9. Improve Precision – Projection of Y(4S) Measurements to SuperB
(Alan Schwartz/David Asner – private communication)
If central values persist:
Will observe >> 5 effect !! x
No-CPV point still allowed at 1σ
NOW
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.
Super B, Perugia, Italy, 6/18/2009
Brian Meadows, U. Cincinnati

10. If measurement lies on curve, CPV is ALL in MIXING
Origin of CPV - aSL
Wrong Sign (WS) lepton asymmetry measures CPV in mixing:
No CPV
See Talk by
I. Bigi
on Friday am
If measurement lies on curve, CPV is ALL in MIXING
aSL
|q/p|
Current
Measurement !
Super B, Perugia, Italy, 6/18/2009
Brian Meadows, U. Cincinnati

11. 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 DCS is Bose-suppressed.
Estimate 1,600 events per month  a = 1.4% in 4 mos.
Obviously (3770) is more efficient, but not a “gotta have it”.
Super B, Perugia, Italy, 6/18/2009
Brian Meadows, U. Cincinnati

12. Correlation with D0  Ks Asymmetry
Measurement of S(Ks) and of aSL could eliminate or refine this model:
See I. Bigi
Friday a.m.
(S) ~ 5 x10-4
(aSL) ~ 0.01
If CPV is in MIXING
Super B, Perugia, Italy, 6/18/2009
Brian Meadows, U. Cincinnati

13. Running at Charm threshold Quantum Correlations (QC)
Super B, Perugia, Italy, 6/18/2009
Brian Meadows, U. Cincinnati

14. Use Quantum-Correlations (QC)
Running at y(3770) CLEO c were able to measure K-+ strong phase:
from 281 pb-1
Including other D mixing results:
 SuperB 300 fb-1:
AND – the possibilities are that we can use OTHER channels with knowledge of strong phases
Super B, Perugia, Italy, 6/18/2009
Brian Meadows, U. Cincinnati

15. 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
m-2 (GeV2/c4)
m02 (GeV2/c4) 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
Super B, Perugia, Italy, 6/18/2009
Brian Meadows, U. Cincinnati

16. 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
m-2 (GeV2/c4)
m02 (GeV2/c4) X
Boost is ~same as for Y(4S)
Is this possible or useful ?
Super B, Perugia, Italy, 6/18/2009
Brian Meadows, U. Cincinnati

17. “Double-Dalitz” Plot Fit: An example from CLEO c
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 !
CLEO data: - It works !!
J. Napolitano
Super B, Perugia, Italy, 6/18/2009
Brian Meadows, U. Cincinnati

18. Brian Meadows, U. Cincinnati
“Super D” ?
The time-dependent “Double-Dalitz” analysis can be made on a wide variety of double-tagged events:
(Ks+-) - (Ks+-)
(Ks+-) – (Ks K+K-)
(Ks+-) – (K-+0)
(Ks+-) – (K-+)
(Ks+-) – (K-K+)
… etc.
We need a simulation to learn how well this might work in face of reduced time-resolution wrt “Super B”..
Large samples.
Highly constrained (model-dependent)
Measure |q/p| and =Arg{q/p}
direct CPV, …
Super B, Perugia, Italy, 6/18/2009
Brian Meadows, U. Cincinnati

19. Simulation Wish List for TDR
Sensitivity tests - Y(4S) simulations
Resolution in M(D0),  M and (t)
xD, yD, |q/p| using D*  D0+  Ks+-
yCP and A from D0  K+K- and K-+
(xD2+yD2)/2 from D0  K-e+e
T-odd moments analysis
Simulations at (3770)
Effectiveness of strong phase measurements at (3770) in mixing needs clarification
Time resolution acheivable– at least two configurations (DGWG)
D0  +- (with background)
TDQC simulation study
for 2009 document
Super B, Perugia, Italy, 6/18/2009
Brian Meadows, U. Cincinnati

20. Brian Meadows, U. Cincinnati
Progress Towards a TDR
Impressive work has been done both at, and since, the Valencia workshop.
For progress towards a TDR, this is an excellent starting point:
Some items not yet covered
Measurement of fD , fDs form-factors, …
Address experimental issues (tracking, end-cap PID)
Super B, Perugia, Italy, 6/18/2009
Brian Meadows, U. Cincinnati

21. Brian Meadows, U. Cincinnati
Backup Slides
Super B, Perugia, Italy, 6/18/2009
Brian Meadows, U. Cincinnati

22. “Super D” / “Super B” Comparison
Advantages:
D0’s are produced at (3770) at ~3 x the rate of B0’s at Y(4S)
D0 decay rates are typically 100xB0 decay rates
 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
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 so s ~ 30 mm is only about one D0 lifetime
We only anticipate running for ~600 fb-1 (comparable to BaBar)
Can make TD “Double-Dalitz” Plot fit with many correlations.
Super B, Perugia, Italy, 6/18/2009
Brian Meadows, U. Cincinnati

23. Brian Meadows, U. Cincinnati
Reminder from KL+-
Standard model limit (“unitarity bound”) is
Measured value is (6.86 § 0.37) x 10-9
Measured:
5.47 x 10-4
From QED:
1.20 x 10-5 x
= x 10-9
L.M. Sehgal, PR 183, 1511 (1969)
BNL E791, Heinson et al, PRD 51, 985 (1995)
Super B, Perugia, Italy, 6/18/2009
Brian Meadows, U. Cincinnati

24. Bigi, Blanke, Buras, Recksiegel
Little Higgs with
T-parity.
NOT an MFV model
arXiv:
Monika Blanke
S. Recksiegel
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!
Super B, Perugia, Italy, 6/18/2009
Brian Meadows, U. Cincinnati

25. QC in Multi-body Channels
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)
Super B, Perugia, Italy, 6/18/2009
Brian Meadows, U. Cincinnati

26. Brian Meadows, U. Cincinnati
Ikaros Bigi
… is willing to grow a beard if CPV is not observed in D decays by 2017!
Super B, Perugia, Italy, 6/18/2009
Brian Meadows, U. Cincinnati