Centennial APS Meeting

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Charm Physics at CLEO

• Centennial APS Meeting
• Mats Selen, University of Illinois(speaking for
  the CLEO collaboration)
• March 23, 1999

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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(j1/2)(Tim Nelson,
  Harry Nelson)
• B(Lc ? pKp ) absolute measurement
• New method described
• Preliminary results presented(Dave Besson, Russ
  Stutz)
• (Charge conjugation implied throughout)

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Our Detector(CLEO-II II.V)
Svx HePr
4
Our Accelerator(CESR)
9 fb-1
CLEO II.VIntegratedLuminosity
CLEO IItook 4.7 fb-1prior to this
32.3 pb-1
DailyLuminosity
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Our Data
On(2/3)
Off(1/3)
This Presentation Mixing Analysis 5.7 fb-1
CLEO-II.V (SVX) DJ Lc Analyses 4.7 fb-1
CLEO-II
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Mixing Analysis
Time evolution of D D0 mesons
Decay eigenstates
Define
Where
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What we are sensitive to in the Kp mixing
analysis
Where
It will eventually be very important to
disentangle x and y
CP eigenstate lifetime analysis will tell us
about y independent of x
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Mixing in D0 ? Kp decays
wrong-sign
RMIX
right-sign
But wrong-sign events can also come fromDoubly
Cabibbo Supressed Decays (DCSD)
p
wrong-sign
D
p-
D0
K
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Mixing vs DCSD
Mixing
DCSD

• 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
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The total wrong-sign rate is given by
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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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(No Transcript)
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Systematic Errors
RWS (0.31 ? 0.09 ? 0.07)
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Results
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Using Lifetime Info
t(ws) ( 0.65?0.4 (statsys) )x t(D0)
Exploit this info to limit RMIX
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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)
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What we are sensitive to in the Kp mixing
analysis
Where
It will eventually be very important to
disentangle x and y
CP eigenstate lifetime analysis will tell us
about y independent of x
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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 CP1 Should have the same lifetimes
D0?K-p , D0?p-p, and D0?K- K are easy to
distinguish kinematically Dont need
particle-ID
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CP-even Yields
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Lifetime Fits
Use unbinned maximum likelihood fit to extract
signal lifetimes
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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 -0.032 ?
0.034 or -0.076 ? y ? 0.012 (90 CL)
CLEO II.V Preliminary
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Putting it all together
y
x
CLEO II.V Preliminary
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Future mixing prospects
CP odd eigenstate lifetime analysis
sneak preview
Lots more data to analyze
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Charm Meson Spectroscopy
j1/2
j3/2
j3/2
j1/2
We search for
D1(j1/2) D1(j3/2) D2(j3/2)
Previously not seen
B- ? p-
Previously seen
Dp-
D0p
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• Analysis Technique
• Partial reconstruction
• B- ? DJ0p- DJ0 ? Dp- 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(Dp)

Fit parameters Yields (3 resonant, 1
non-resonant) Mass and width of broad
D1(j1/2) Mixing and interference between
resonances. Strong phases relative to D1(2420)
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1 d-wave
1 s-wave
2 d-wave
cos q3vscos q2
cvscos q2
cvscos q1
Total Background
cvscos q2
cvscos q1
cos q3vscos q2
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Fit Results
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Weighted Fit Components
1 s-wave Weighted
1 d-wave Weighted
2 d-wave Weighted
Background Weighted
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Preliminary Results

• Properties of D1(j1/2)

(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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B(Lc ? pKp ) Absolute

• Why?
• One of the 4 measured quantities used to
  normalize all charm analyses
• B(D0?K-p),B(D?K-pp),B(Ds?fp), B(Lc?pK-p)
• Not well determined at present B(Lc?pK-p)
  (5?1.3) PDG
• Our Technique (NEW)

Divide event into hemispheres
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Two versions
Triple correlation analysis (x2)
c c
D-
or
D p-s
pK-p
Lc
X e- ne
c c
D-
or
D p-s
Lc
anything
X e- ne
Double correlation analysis
p
c c
anything
pK-p
Lc
p
c c
D-
D p-s
Lc
anything
Kp...
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Yield examples
(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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Sounds easy, but...
Biggest Backgrounds/Corrections
Falsely increased denominator
c c
anything
Count
and correct
D
c c
D
D
p K-
Falsely increased denominator
Study Kaon fake rate as a function proton
momentum and correct (15 effect)
After correction, p momentum spectrum looks OK.
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Preliminary Results

• 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)
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Future Prospects CLEO-III

• Several New Detector Components
• RICH, Drift Chamber, Silicon
• New CESR cavities IR
• Lots more luminosity