Super B, Elba, Italy, 5/30-6/05/2010 Brian Meadows, U. Cincinnati Report from Charm WG (White Paper  TDR) D. Asner, Carleton U, I. Bigi, U. Notre Dame, R. Andreassen, B. Meadows, M. Sokoloff U. Cincinnati for the charm team Running at “Charm Threshold” and Rare Decays

2 Super B, Elba, Italy, 5/30-6/05/2010 Brian Meadows, U. Cincinnati Outline  Running at charm threshold  General  Improved precision in mixing parameters  Semi-leptonic asymmetries – a SL  Time-Dependent Quantum Correlations (TDQC)?  Rare decays  D 0   +  -  D 0  , hl + l -  Summary

Threshold Running Scenario  The run envisaged here is a 500 fb -1 exposure at  (3770)  About 1000 x CLEO-c and (50-100) x BES III  Just above DD threshold  At one-tenth nominal luminosity, Super B can complete this in a few months  Set up and tuning of final focus may take another few months  Perhaps a year altogether – maybe less?  Possible schedules (in order of preference)  Plan this in as a run after 25 ab -1 at  (4S)  Run because of a discovery at  (4S)  Start-up Super B with this run  Do this only at the end of 10 years at  (4S)

General Reasons for a  (3770) Run  It is possible (likely?) that an unusual effect – perhaps due to NP – will be found in the charm sector from  (4S) running  A true confirmation in the entirely different charm scenario at  (3770) will trump a simple repeat performance with more luminosity at  (4S)  A 500 fb -1 run will improve both our own, and also LHCb’s CKM  measurement by a factor ~ 3.  Decays of  (3770)  D 0 D 0 produce coherent (C=-1) pairs of D 0 ’s. Quantum correlations in their subsequent decays allow measurements of strong phases  Required for improved measurement of CKM   Also required for D 0 mixing studies

General Reasons for a  (3770) Run  A record exists of several cases where CLEO-c, sometimes with just 281 pb -1 of their 818 pb -1 sample at  (3770), has successfully competed with BaBar’s ~0.5 ab -1 and Belle’s ~1 ab -1 at  (4S). Examples:  Measurement of decay constants – f D and f Ds  Studies of leptonic and semi-leptonic decays,  Measurements of absolute hadronic branching fractions  Other runs for CLEO-c at other CM masses have produced useful and novel results for D s as well as D decays from  (3770).   Is a program at  (4S) complete without the “service” of one at  (3770), etc.?

CLEO-c Hadronic Charm Decays at  (3770) Single Tags Only  E ~ 0 in signal  E sidebands in yellow

Semi-Leptonic Decays  Example of D 0  K - e + e decay from CLEO-c’s 818 pb -1 exposure at  (3770).  Quantity plotted is U = E miss – c P miss (Note background level ~0)

8 Super B, Elba, Italy, 5/30-6/05/2010 Brian Meadows, U. Cincinnati Quantum-Correlations (QC)  Running at  (3770) CLEO c were able to measure K -  + strong phase: from 281 pb -1  Including other D mixing results:  ALSO, they were able to measure bin-by-bin strong phase variations in, for example, the K s  +  - Dalitz plot  Of value to improved (model-independent) measurement of CKM   Also of value in D 0 mixing measurements

9 Super B, Elba, Italy, 5/30-6/05/2010 Brian Meadows, U. Cincinnati Time-Integrated QC in Multi-body Channels Relative phases “bin-by-bin” in multi-body phase-space. m - 2 (GeV 2 /c 4 ) m 0 2 (GeV 2 /c 4 ) Quantum correlations remove necessity for model describing phase space. Probably ONLY way to obtain a true PWA fit. X X For higher multiplicities, we could 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

10 Super B, Elba, Italy, 5/30-6/05/2010 Brian Meadows, U. Cincinnati “Double-Dalitz” Plot Fit: An example from CLEO c e + e -   (3770)  (K s  +  - ) (K s  +  - )  There are two Dalitz plots correlated in a time-dependent way:  If you select CP-odd K s  0 in one, you see “no” K s  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

DD Threshold Measurements  Data from DD threshold provide measurement of strong phases such as  K  and.  They also provide measured values of  in Dalitz plot bins This can be used (with a model for the values for r) to significantly reduce uncertainties in the Dalitz plot model used in the golden channel analyses.  As a basis for projection, we take results from CLEO-c: N. Lowrey et al, PRD80, (2009),  We assume that new data from threshold will reduce the uncertainties in model uncertainty:  BES III – ~factor 3 improvement in model uncertainty  Super B 500 fb -1 DD threshold run – ~factor 10 improvement.

 Two improvements in mixing precision come from threshold data: Value of Strong Phase Measurements  Dalitz plot model uncertainty shrinks  Information on overall strong phase is added Uncertainty in x D improves more than that of y D

Origin of CPV from a SL  Wrong Sign (WS) lepton asymmetry measures CPV that can arise ONLY from mixing: Current Measurement ! If measurement lies on curve, CPV is ALL in MIXING See Talk by I. Bigi here ? No CPV a SL |q/p|

Precision of a SL Uncertainty from a signal S over background B is

Measurement of a SL – Needs  (3770) Data!  Decays to wrong-sign (WS) leptons proceed through mixing  Rate is very small R M =(x 2 +y 2 )/2 x ~ 5x and not yet observed:  a sl ) for 75 ab -1 ~ 0.20  4S): D 0 tagged by D *+  D 0  + Right-sign (RS) Decays D 0  K - e + e + c.c.  (3770): D 0 tagged 344 fb -1 Another D In event 492 fb fb -1   not reconstructed   fully reconstructed Background limits WS data Include Hadronic decays * * At  (3770). We need CLEO-c data to refine our knowledge of backgrounds we can expect. R M < 13x10 -4 R M < 6x10 -4  a sl ) for 75 ab -1 ~ 0.80  a sl ) for 500 fb -1 ~ 0.20

16 Super B, Elba, Italy, 5/30-6/05/2010 Brian Meadows, U. Cincinnati a SL from  (3770) Data (Needs evaluation from simulation)  Two un-ambiguous possibilities.  One ambiguous possibility.  Could resolve ambiguity using difference in time- dependence of mixing (t 2 e -t ) vs. direct DCS decay (e -t ).  K + e - e  (3770)  Bose statistics requires that one D 0 had to mix  (3770) K + e - e  (3770)  K + e - e D 0  K +  - 5 x more likely to be DCS than D 0 ->K + e - e is from mixing (coherent) Can we do this anyway?

Summary of CPV Sensitivity from Mixing 17 Super B, Elba, Italy, 5/30-6/05/2010 Brian Meadows, U. Cincinnati

18 Super B, Elba, Italy, 5/30-6/05/2010 Brian Meadows, U. Cincinnati Time-dependent QC Decays – “Super D” ? The moving CMS means we could measure time-dependent (TD) strong phases resulting from D 0 mixing. m - 2 (GeV 2 /c 4 ) m 0 2 (GeV 2 /c 4 ) X X Boost is ~same as for Y(4S) but  D 0 ~ 0.4  B 0 Is this possible or useful ? Samples are large. E.g. K s  +  - (on both sides) will have about 500K events.

19 Super B, Elba, Italy, 5/30-6/05/2010 Brian Meadows, U. Cincinnati “Super D” ?  The time-dependent “Double-Dalitz” analysis can be made on a wide variety of double-tagged events:  (K s  +  - ) - (K s  +  - )  (K s  +  - ) – (K s K + K - )  (K s  +  - ) – (K -  +  0 )  (K s  +  - ) – (K -  + )  (K s  +  - ) – (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, …

20 Super B, Elba, Italy, 5/30-6/05/2010 Brian Meadows, U. Cincinnati Rare Decay D 0   +  -

21 Super B, Elba, Italy, 5/30-6/05/2010 Brian Meadows, U. Cincinnati Search for D 0   +  -  There is considerable theoretical interest in the FCNC decay D 0   +  - (see I. Bigi’s talk, Perugia, Friday am)  The SM estimates a lower limit BF > 4 x  Estimates would be improved by measurement of D 0    Only estimate so far - BF[D 0   ] < 1.5 x [Recall that, for K L   +  -, SM BF = 6.4 x – right on the money!] Long-range mechanism (Dominant in K L   +  - - NOT necessarily so in D 0 case)

22 Super B, Elba, Italy, 5/30-6/05/2010 Brian Meadows, U. Cincinnati  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[D 0   ] to better understand the SM limit. Interest in D 0   +  - c u ++ -- qkqk 12k 22k Opens a 7 orders of magnitude search window for NP

23 Super B, Elba, Italy, 5/30-6/05/2010 Brian Meadows, U. Cincinnati  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 – apparently a mistake] and Eur.Phys.J.C57: ,2008.  Further study of CLEO-c data at threshold will show if a better limit can be reached. Interest in D 0   +  -

D 0    Best limit so far comes from CLEO 2.9x10 -5 using 13.8 fb -1 at  (4S)  BaBar “expects” 2.5 x from 481 fb -1 at  (4S) (limits gluino enhancement to factor 70) which implies, for Super B ~2 x from 75 ab -1 at  (4S)  A recent CLEO-c study (private communication from D. Asner) has shown that an efficiency of 5% has been achieved with no background events in the full 818 pb -1 sample. This implies a limit of about ~few x from 500 fb -1 at  (3770) !!  David Asner will follow up on this interesting analysis

Summary  A strong case for a 500 fb -1 run at  (3770), based upon a single study of NP is NOT difficult to make.  The best candidate(s) may be a clean search for D 0   +  - decays with a limit near or below  This requires study of CLEO-c data and a better idea of PID performance at Super B AND a much improved limit on D 0    A great breadth of excellent results to support other findings at Super B related to charm physics or spectroscopy could, however, be made.  Though a convincing argument for this run is hard to make based on a single result, it is also hard to allow the opportunities it opens up to pass un-defended.

26 Super B, Elba, Italy, 5/30-6/05/2010 Brian Meadows, U. Cincinnati Ikaros Bigi … willing to grow a beard if CPV is not observed in D decays by 2017! Get well soon, Ikaros !! David Asner … our young man, heading West. Expert at running at DD threshold.