1. Centennial APS Meeting
Charm Physics at CLEO
Centennial APS Meeting
Mats Selen, University of Illinois (speaking for the CLEO collaboration)
March 23, 1999
APS Centennial

2. (Charge conjugation implied throughout)
This Presentation:
New D0 mixing results
Kp mixing analysis (including lifetime) (David Asner)
CP-even KK and pp lifetime results (Tony Hill)
Charmed Meson Spectroscopy
First observation of broad D1(j=1/2) (Tim Nelson, Harry Nelson)
B(Lc  pKp ) absolute measurement
New method described
Preliminary results presented (Dave Besson, Russ Stutz)
(Charge conjugation implied throughout)
APS Centennial

3. Our Detector: (CLEO-II & II.V)
Svx + HePr
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4. Our Accelerator (CESR)
9 fb-1
CLEO II.V Integrated Luminosity
CLEO II took 4.7 fb-1 prior to this
32.3 pb-1
Daily Luminosity
1996
1997
1998
APS Centennial

5. Our Data: This Presentation: On(2/3) Off(1/3)
Mixing Analysis: 5.7 fb-1 CLEO-II.V (SVX)
DJ & Lc Analyses: 4.7 fb-1 CLEO-II
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6. Mixing Analysis: Time evolution of D & D0 mesons Decay eigenstates
Define
Where
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7. What we are sensitive to in the Kp mixing analysis:
Where D0 on
shell
pp,KK…
can be relatively
large in S.M.
off
small
in S.M.
Window on New Physics
It will eventually be very important
to disentangle “x” and “y”
CP eigenstate lifetime analysis will tell
us about “y” independent of “x”
APS Centennial

8. Mixing in D0  Kp decays: p+ “wrong-sign” D*+ p- D0 K+ RMIX = p+ D*+
“right-sign”
But “wrong-sign” events can also come from Doubly Cabibbo Supressed Decays (DCSD): p+
D*+
“wrong-sign” p- D0 K+
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9. Mixing vs DCSD: Same initial & final states !p+ p- K+
D*+ D0 p+ p- K+
Same initial & final states !
Bad news if this is all the info available
But theres more...
1) Amplitudes evolve differently in time.
2) Amplitudes can interfere.
Can use timing information to help untangle Mixing from DCSD
APS Centennial

10. The total “wrong-sign” rate is given by:
(Where t is measured in D0 lifetimes)
100% mixed
100% DCSD
cosf = 1
cosf = 0
cosf =-1
N(t)
D0 lifetimes
RMIX = RDCSD
RMIX / (RMIX+RDCSD)
t(WS) t(D0)
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11. Analysis uses excellent kinematic resolution to
5.7 MeV
Analysis uses excellent kinematic resolution to
stop K-p+ feedthrough, and relies on good
Particle-ID to suppress backgrounds.
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12. APS Centennial

13. Systematic Errors
RWS = (0.31  0.09  0.07) %
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14. Results: Aleph: RDCSD  1 CLEO-II  1 RMIX 95% CL E791 Klv 90% CL
E691 90% CL
CLEO-II.5  1
Preliminary
APS Centennial

15. t(ws) = ( 0.650.4 (stat+sys) )x t(D0)
Using Lifetime Info:
t(ws) = ( 0.650.4 (stat+sys) )x t(D0)
100% mixed
100% DCSD
cosf = 1
cosf = 0
cosf =-1
N(t)
D0 lifetimes
RMIX = RDCSD
Exploit this info
to limit RMIX
APS Centennial

16. Limits have been calculated for all cosf (ask me after)
Mixing Results:
Aleph: RDCSD  1
RMIX 95% CL
CLEO-II  1
E791
Klv
90% CL
E691 90% CL
E791  1
CLEO-II.V 90% CL
Preliminary
Limits have been calculated for all cosf (ask me after)
APS Centennial

17. What we are sensitive to in the Kp mixing analysis:
Where D0 on
shell
pp,KK…
can be relatively
large in S.M.
off
small
in S.M.
Window on New Physics
It will eventually be very important
to disentangle “x” and “y”
CP eigenstate lifetime analysis will tell
us about “y” independent of “x”
APS Centennial

18. CP-even Lifetime Analysis:
Look for G(D0K-p+ )  G(D0p-p+, K- K+ )
This is a direct measure of DG ! (i.e. measure “y” independent of “x”)
Plan:
Measure t(D0K-p+ )
t(D0p-p+)
t(D0K- K+ )
Both CP=+1
Should have the
same lifetimes
D0K-p+ , D0p-p+, and D0K- K+
are easy to distinguish kinematically
Don’t need particle-ID
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19. CP-even Yields:
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20. Lifetime Fits: Use unbinned maximum likelihood fit to
extract signal lifetimes:
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21. Based on our present measurement:
Extracting “y”:
Look for G(D0K-p+ )  G(D0p-p+, K- K+ )
Where t+ (t-) are the CP even (odd) lifetimes,
and tKp = (t+ + t- )/2
Based on our present measurement:
y =  0.034 or
 y  (90% CL)
CLEO II.V Preliminary
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22. Putting it all togethery x
CLEO II.V Preliminary
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23. Future mixing prospects
CP odd eigenstate
lifetime analysis
sneak
preview
Lots more data to analyze
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24. Charm Meson Spectroscopy
j=1/2
j=3/2
j=3/2
j=1/2
We search for
D1(j=1/2)
D1(j=3/2)
D2*(j=3/2)
Previously not seen
B-  p-
Previously seen
D*+p-
D0p+
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25. B-  DJ0p-; DJ0  D*+p-; D*+  D0p+
Analysis Technique
Partial reconstruction:
B-  DJ0p-; DJ0  D*+p-; D*+  D0p+
Measure 4-momenta of p-p-p+.
Extract signal via 4-D Max Likelihood Fit
Fitting Technique
4 independent variables:
helicity q2, helicity q3, azimuth , M(D*p)
Fit parameters:
Yields (3 resonant, 1 non-resonant)
Mass and width of broad D1(j=1/2)
Mixing and interference between resonances.
Strong phases relative to D1(2420)
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26. Total Background 1+ d-wave 1+ s-wave 2+ d-wave cos q3 vs cos q2
c vs cos q2
c vs cos q1
Total Background
cos q3 vs cos q2
c vs cos q2
c vs cos q1
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27. Fit Results Total background (see below) D1(2420)0 D2*(2460)0
D01(j=1/2)
Fit
Results
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28. Weighted Fit Components
1+ d-wave Weighted
1+ s-wave Weighted
2+ d-wave Weighted
Background Weighted
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29. Preliminary Results Properties of D1(j=1/2)
With 5.7s
significance
(second systematic error due to
uncertainty modeling strong phases)
Spin-Parity assigned to 1+
Tests of JP favor 1+ over 0-
(closest alternative).
Quark Model:
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30. Tag charm with one of these
B(Lc  pKp ) Absolute
Why?
One of the 4 measured quantities used to normalize all charm analyses
B(D0K-p+),B(D+K-p+p+),B(Dsfp+), B(LcpK-p+)
Not well determined at present B(LcpK-p+) = (51.3)% PDG
Our Technique (NEW):
e e-
c c
D*-
D p-s
X e- ne p Lc
Tag charm with one of these
pK-p+
Baryon tag
Divide event into hemispheres
APS Centennial

31. Two versions: p c c D*- D p-s pK-p+ Lc X e- ne p c c D*- D p-s Lc
Triple correlation analysis (x2): p
c c
D*- or
D p-s
pK-p+ Lc
X e- ne p
c c
D*- or
D p-s
anything Lc
X e- ne
Double correlation analysis: p
c c
anything
pK-p+ Lc p
c c
D*-
D p-s
anything Lc
Kp...
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32. Yield examples: LcpK-p+ D0K-p+ (Double correlation analysis)
“numerator”
LcpK-p+
(same hemisphere
as anti-proton tag)
“denominator”
D0K-p+
(opposite hemisphere
from anti-proton tag)
Apply efficiency correction and get answer...
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33. Sounds easy, but... c c D p N p c c D p+ K- D c c D
Biggest Backgrounds/Corrections:
c c D p N
Falsely increased denominator p
c c
anything
Count
and correct D
p+ K- D
c c D
Falsely increased denominator
Fake p tag
Study Kaon fake rate as a function proton
momentum and correct (15% effect):
After correction,
p momentum spectrum
looks OK.
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34. Preliminary Results B(LcpK-p+ ) B(LcpK-p+ ) = (5.0  0.5  1.5) %
Make the physics corrections mentioned on previous page (and other smaller ones):
Make appropriate efficiency corrections.
B(LcpK-p+ )
Double correlation (4.9  0.5)%
Triple correlation (ps tag) (5.2  1.3)%
Triple correlation (e tag) (5.6  2.5)%
Weighted average:
B(LcpK-p+ ) = (5.0  0.5  1.5) %
APS Centennial

35. Future Prospects CLEO-III Several New Detector Components
RICH, Drift Chamber, Silicon
New CESR cavities & IR
Lots more luminosity
APS Centennial