1. Precision Leptonic, Semileptonic and Hadronic Decays of the D
at CLEO-c
Dan Cronin-Hennessy
University of Minnesota
Nov 27, 2007
BBCB WS
D. Cronin-Hennessy, U of M

2. D. Cronin-Hennessy, U of M
Talk Overview
Overview
CLEO-c Results:
D(s) Leptonic
D(s) Semileptonic
D(s) Hadronic
D. Cronin-Hennessy, U of M

3. D. Cronin-Hennessy, U of M
Impact of Physics
Vub l n B p D
Vcd K
Vcs
Vcb Bd
Vtd Bs
Vts
Vtb
Vus 
Vud e t b W
CLEO-c + Lattice QCD +B factories
CLEO-c
CLEO-c + Lattice
QCD +B factories
+ ppbar
D. Cronin-Hennessy, U of M

4. D. Cronin-Hennessy, U of M
D-Tagging
D-Tagging e+ e-
Signal D m+ n
Tag D
Event Shape discrimination no longer a powerful tool in the charm region.
Backgrounds at y(3770): continuum (18 nb),
t pair (3 nb), radiative return (~1.5 nb)
D meson has large branchings to low multiplicity modes.
Requiring a reconstructed D provides background suppression.
D-Tagging removes half the event (only a single D remains).
Simultaneously provides 4-vector of other D meson.
D. Cronin-Hennessy, U of M

5. D. Cronin-Hennessy, U of M
D-Tagging
D. Cronin-Hennessy, U of M

6. Weak Annihilation: D+ l+ nm
|fD|2 n l
|VCKM|2
Improvement in mixing constraints with better fB
Ideally one would measure B+ l+ n (rate low).
Realistic alternative: Measure fD,fDs.
fD CLEO-c and (fB/fD)lattice  fB
(And fD/fDs checks fB/fBs)
D. Cronin-Hennessy, U of M

7. D. Cronin-Hennessy, U of M
D+ m+ nm e+ e-
Signal D m+ n
Tag D
One D fully reconstructed:
Require single track
on other side: m
- PID suppresses K
- Calorimeter suppresses p+
- Require low energy in CC
Use D 4-vector to calculate
missing mass (~0 for n).
D. Cronin-Hennessy, U of M

8. D. Cronin-Hennessy, U of M
D+ m+ nm
Data (281 pb-1)
Monte Carlo (1 fb-1)
Mode Events
Data
D+p+ p
D+ Klong p
D+t+ nt
Total Bck:
CLEO-c
PRL (2005)
D. Cronin-Hennessy, U of M

9. D. Cronin-Hennessy, U of M
D+ t+ nt (tpn)
Data (281 pb-1)
If not satisfied New
physics: (Exotic
intermediate bosons) =
Preliminary
BR(D+ t+ nt)< 2.1 x 10-3 CL
Anti-cut analysis vetoes
CC energy associated with track
That is consistent with muon.
CC=Crystal Calorimeter
PRD (2006)
D. Cronin-Hennessy, U of M

10. D. Cronin-Hennessy, U of M
Ds m(t) n
(MM2 technique)
Require fully reconstructed Ds (tag).
Eight reconstruction modes used.
Require reconstructed invariant mass within 2.5 s
of Ds mass.
Number of Ds tags in 314/pb:
Calculate MM2 for Ds tag
plus photon.
Peaks at Ds mass.
Cut at 2.5 s.
N(tag+g)=
D. Cronin-Hennessy, U of M

11. D. Cronin-Hennessy, U of M
Ds m(t) n
(MM2 technique)
Constraints used in kinematic fit.
Try both hypotheses: tag from Ds and tag
from Ds*.
Choose solution with lowest c2.
MM2=(Ecm-ED-Eg-Em)2-(pcm-pD-pg-pm)2
tpn m
D. Cronin-Hennessy, U of M

12. D. Cronin-Hennessy, U of M
Ds m(t) n
(MM2 technique)
Efficiency for reconstructing p or m track 80.1%.
Ecc = Calorimeter energy associated with extra track.
Background from Ds candidate mass sidebands.
Ecc < 300 MeV:
-0.05 GeV2 < MM2 < 0.05 GeV2 (m like): evts, e= 99%, bkg=3.5
0.05 GeV2 < MM2 < 0.20 GeV2 (tpn like): 31 evts, e=60%, bkg=2.5
Ecc > 300 MeV:
-0.05 GeV2 < MM2 < 0.20 GeV2 (tpn like): 25 evts, e=40%, bkg=3
Backgrounds from real Ds are significant only for the t-like samples. The largest is from leptonic decay Ds t n
where t p p0 n. (.55 evts for Ecc < 300 MeV and .65 events for Ecc> 300 MeV). t m nn contributes .37 evts for Ecc < 300 MeV sample.
B(Dsmn) = ( )%
B(Dstn) = ( )%
PRL (2007)
PRD (2007)
D. Cronin-Hennessy, U of M

13. D. Cronin-Hennessy, U of M
Ds t nm
(t enn)
Missing Energy Technique
Analysis based on MeV
Reconstruct Ds and use recoil mass to count tags.
Require one extra track consistent with electron.
Primary background semileptonic (Ds X e n).
Suppress X by requiring low amount of extra energy in calorimeter. Shown on right.
Signal region Ecc(extra)< .4 GeV.
Backgrounds from scaled MC.
B(Dstn)=( )%
Preliminary
D. Cronin-Hennessy, U of M

14. D. Cronin-Hennessy, U of M
f D(s) Summary
D+  m n:
fD = MeV
D+  t n:
limit, SM consistency
Ds  m(t) n:
fDs = MeV
Ds  t n (tenn):
fDs = MeV
D. Cronin-Hennessy, U of M

15. Exclusive Semileptonic Decays
Motivation
Direct access to CKM elements (Vcs,Vcd)
High resolution measurement of q2 spectrum.
Confronts form factor predictions.  Better
extraction of Vxb from exclusive semileptonic B
decays.
Opportunity for first observations.
D. Cronin-Hennessy, U of M

16. Exclusive Semileptonic Decays
Technique
D-Tag event
Identify electron
Reconstruct the
hadronic component
Check for consistency
with neutrino
U=Emiss-|Pmiss|
Signal component
from fit to variable U
From fit of Mbc
and DE for
number of tags
CLEO III
CLEO-c
From Monte
Carlo/Data
D. Cronin-Hennessy, U of M
Dp l n

17. D. Cronin-Hennessy, U of M
D+ and D0 Tag Modes
281/pb (1.8M DDbar)
D-Tagging Eff:
~10% for D+
~15% for D0
Tagging provides absolute BR measurements with low backgrounds
D. Cronin-Hennessy, U of M

18. First Observations of Cabibbo Suppressed Modes
Preliminary (281/pb)
D. Cronin-Hennessy, U of M

19. Exclusive Semileptonic Decays
Preliminary (281/pb)
D. Cronin-Hennessy, U of M

20. D. Cronin-Hennessy, U of M
Untagged D0 K(p) e n
Uses neutrino reconstruction:
Identify semileptonic decay.
Reconstruct neutrino 4-momentum from
all measured energy in the event.
Use K(p), e, and missing 4-momentum and require consistency in energy and beam-energy constrained mass.
Higher efficiency but larger backgrounds and larger systematics.
Mbc distributions fitted simultaneously in 5 q2 bins to obtain d(BF)/dq2. Integrate to get branching fractions and fit to obtain form-factor parameters.
D. Cronin-Hennessy, U of M

21. D. Cronin-Hennessy, U of M
D0K(p) e n Summary
Precision measurements from Belle, Babar, CLEO-c.
Experimental uncertainties smaller than theory.
D. Cronin-Hennessy, U of M

22. Exclusive Semileptonic Decays Form Factors and Vcx
From 281/pb, Preliminary
Modified pole model used as example:
Normalization uncertainty is 2%. Consistent with LQCD.
CLEO-c prefers smaller value for shape parameter, a.
D. Cronin-Hennessy, U of M

23. Exclusive Semileptonic Decays Form Factors and Vcx
From 281/pb, Preliminary
Modified pole model used as example:
Normalization uncertainty is 4%. Consistent with LQCD.
D. Cronin-Hennessy, U of M

24. Exclusive Semileptonic Decays Form Factors and Vcx
From 281/pb, Preliminary
We measure |Vcx| f+(0) and use f+(0)
From Becher-Hill Parameterization with FNAL/MILC/HPQCD
D. Cronin-Hennessy, U of M

25. Inclusive Semileptonic Decays
Motivation:
BR(DXln)
Precision measurement of lepton momentum spectrum.
Compare Gsl(D0)/Gsl(D+)
Test HQT with Gsl(D0)/Gsl(Ds)
Technique:
D-Tag
Electron ID
Gold DTags only
K-p+ and K- p+p+
Charge correlation
D. Cronin-Hennessy, U of M

26. Inclusive Semileptonic Decays
From 281/pb
B (D+Xe+n) = ( )%
(S D+ exclusive =15.1 %)
B(D0Xe+n) = ( )%
(S D0 exclusive =6.1%)
Gsl(D+)/Gsl(D0) =
PRL (2006)
D. Cronin-Hennessy, U of M

27. Absolute Hadronic BR for D0, D+ and Ds
We use the double-tag method for measuring BRs.
Determines absolute BR scale for normalizing modes such as Kp, Kpp, KKp.
Refinement of D meson simulation in B factory MC.
Normalizes exclusive modes used in exclusive Vcb analyses.
Provides a count of the DD-bar pairs produced.
Results from Ecm=3770 MeV based on 281/pb
Results from Ecm=4170 MeV based on 298/pb
D. Cronin-Hennessy, U of M

28. D. Cronin-Hennessy, U of M
Double Tags
Single Tag D+K-p+p+,
Single tags:
Double tags:
Syst unc cancels.
To first order Bi independent of tag modes and efficiencies.
Simultaneous fit for all BR and cross sections.
All correlations taken into account.
Doubly Tag
D+K-p+p+ D-K+p-p-
D. Cronin-Hennessy, U of M

29. D. Cronin-Hennessy, U of M
Results for D0 and D+
Accepted by PRD: hep-ex/
DFSR shows the impact of ignoring final state radiation in the simulation.
D. Cronin-Hennessy, U of M

30. D. Cronin-Hennessy, U of M
Data collected at Ecm=4170 MeV.
298/pb collected.
Optimal energy for DsDs* production.
Analysis same as for DDbar.
Eight decay modes used in analysis.
Single tag Ds mass plots shown left.
Or order 1000 double tags (~3.5% statistical uncertainty).
Ds Hadronic BRs
D. Cronin-Hennessy, U of M

31. D. Cronin-Hennessy, U of M
Results for Ds
Results based on 298/pb.
Ds  f p in progress.
Preliminary (298/pb)
D. Cronin-Hennessy, U of M

32. D. Cronin-Hennessy, U of M
Summary
Leptonic:
Presented results and updates on BR’s for
D m(t) n, Dsm(t) n and associated decay constants.
Semileptonic:
Presented Exclusive and Inclusive semileptonic D decays, CKM
elements and FF extractions.
Hadronic:
Presented significant improvements in the Ds and D hadronic BR.
Opportunities for the future: Decay constants with uncertainties at the % level, rare semileptonic decays, improved FF measurements (p l n)
D. Cronin-Hennessy, U of M