Some Recent Results on Charmonium and Charm Decays from CLEO

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Some Recent Results on Charmonium and Charm
Decays from CLEO
Celebrating 30 Years of Physics Results from CLEO
John Yelton University of Florida
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• My talk will be
• A retrospective look at 30 years of CLEO ee-
• physics
• 2. Some recent results on
• a) hc (L1 singlet charmonium state) physics
• b) Leptonic decays of charmed mesons and the
  decay
• constants fD

(s)
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CESR/CLEO Prehistory
Directors
Bacher
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CESR/CLEO Prehistory

• Decades of Cornell synchrotrons, beginning late
  1940s, culminating with 12-GeV Wilson
  Synchrotron (1968)

• First discussions of colliding beams 1973-74,
  with major boost from J/?.
• Idea Explore ee- collisions in 8-16 GeV
  center-of-mass range, hope for something new
• Competition PEP at SLAC, DORIS PETRA at DESY
• CESR proposed May 1975
• 8 GeV ? 8 GeV in synchrotron tunnel, design
  luminosity 1032 cm-2s-1, 2 IRs, clever design to
  maximize reuse of 12 GeV infrastructure

• RD for South Area Experiment started in 1975
  design settled construction under way by late
  1977

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Surprise After detector design
started.Discovery of hidden b by Lederman and
colleagues at Fermilab (p N ? ? ?- X at
400 GeV) .

Two upsilon states - confirmed by DORIS. A
third? More?
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CLEOs 1979-80 To-Do List

• Verify the Fermilab and DORIS observations of the
  ? states.
• Search for additional states. Spectroscopy tests
  bb hypothesis and states above threshold should
  decay to particles carrying the new flavor.
• Could there be a state for threshold B
  production analogous to the ?(3770) for Ds?
• Measure masses, branching fractions, other
  properties to verify that b has been found and is
  the fifth quark of Kobayashi and Maskawa.
• Or not!

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The Machine

• Cornell Campus
• Originally two
• interaction regions
• CUSB
• CLEO

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Inside the CESR Tunnel
Same tunnel, same synchrotron, with CESR, c. 2000.
Boyce D. McDaniel Hans Bethe in 12-GeV
Synchrotron Tunnel, 1968.
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CESR/CLEO first data late 1979
0.4 pb-1
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The Original B Factory
1.1 pb-1

• ?(4S) discovered early 1980 with 1090 nb-1 of
  CESR scan data
• (ECM 10.46-10.64 GeV)
• 1 nb enhancement in multihadron production,
  broader than other ?s
• Much agonizing over whether it was real 1st use
  of continuum suppression

Newsweek, August 11,1980 Beauty is Found Where
is Truth?.
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Measures of CLEOs Impact

• Longest-running expt. In HEP history?
• Excellent Record of Publication

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Measures of CLEOs Impact

• 508 papers in Phys. Rev Letters, Phys. Rev. D etc.

• Topcite papers in HEP SPIRES data base
• 250 7 papers 100 56 papers 50 140
  papers
• (Equally distributed by decade)
• 231 CLEO Ph.D. students (several still on the
  way)

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Why was CLEO so successful?

• The detector was kept up to date
• CLEO ? CLEO 1.V ? CLEO II ? CLEO II.V ? CLEO III
  ? CLEO_c
• (new drift chamber)
  (silicon) (no
  silicon)
• ( CsI calorimeter)
  RICH

• Variety of physics. Not just B physics, but
  charm (4 charmed mesons and 14 charmed baryons
  discovered), and tau physics.
• Collaboration stayed together
• Luck! If Upsilon was at 18 GeV, none of this
  would have
• happened

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Why CLEO-c?

• CESR/CLEO III not competitive with newer B
  factories
• But, had state-of-the-art and flexible detectors
• Heavy flavor physics began in ee- studies of c,
  but c had been neglected and studies of b and
  particles decaying into b were limited by
  knowledge of c
• Interpretation of high-precision b measurements
  limited by theoretical uncertainties (strong
  interaction). New tools (Lattice QCD) needed
  rigorous tests charm!
• CLEO-c proposed Fall 2001, approved in 2003 and
  collected data from Dec., 2003 until March, 2008

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Transition to Charm Threshold,

• CESR re-optimized for 4 GeV
• Inserted SC wigglers to increase
  damping/luminosity
• Much higher luminosity than previous experiments
• CLEO-c detector superior to previous charm
  detectors

Ecm 4170 GeV 600 pb-1 0.57M DsDs
?(2S) 54 pb-1 27M ?
?(3770) 818 pb-1 5.1M DD
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CLEO-c Detector

• Covered 93 of Solid Angle
• Tracking
• ??p/p 0.6 _at_ 1 GeV
• Calorimetry
• ??E/E 5 _at_ 0.1 GeV
• 2.2 _at_ 1 GeV
• Charged PID (RICH dE/dx)
• Good K/? separation
• over entire momentum
• range (p lt 2.5 GeV/c)

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THE CHARMONIUM SPECTRUM
Notation n 2S1 L J
y(2S)
ccJ
n2
y(3770)
?c(2S)
hc
D mesons
J/y
2K,2K2p,4p,6p
?c
n1
ll-
S 0 1
0 1 0 1
L 0
1 2
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CLEO finding the hc Over 1,000 events
reconstructed
Method 1 look for bump in ?0 recoil mass
spectrum in events with a ? with correct energy
for hc ??c ? decay
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Method 2 use many (15!) different decay modes
of the ?c and completely reconstruct the event.
The two methods agree and are consistent with
the previous CLEO measurement.
B(?(2S)??0hc)x B(hc???c) (4.19 0.32
0.45) x 10-4 M(hc)3528.28
0.19 0.12 MeV ltM(?cJ)gt M(hc)
0.02 0.10 0.13 MeV
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But there is no reason that the hc has to decay
radiatively can it be seen directly into
hadrons? We looked in decays into odd number of
pions.
5? mode good signal 7? mode
hint of a signal
Product branching fraction indicates around 5 of
??c (indicates hadronic decays same order of
magnitude as radiative decays)
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BES III preliminary data based on 100,000,000
?(2S) events
Select inclusive p0 A fit of Gaussian signal
4th order polynomial bkg yield N(hc)
9233935 Combined inclusive and photon tagged
spectrum yields Br(hc???c) (55.76.3(stat))
of total decay rate (but systematics still under
consideration).
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D(s)?l?l

• Premise
• Given the CKM factors, a measurement of the
  branching fraction for a leptonic decay gives the
  decay constant fP
• A theory that calculates fP can be verified and
  applied to other SM (CKM) measurements that mix
  strong and weak
• B0 and Bs mixing needs fBs/fB, Vub from exclusive
  needs form factors

Lattice QCD (unquenched) is asserted to have
reached the needed precision. We need to test!
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D Physics with Tags

• ?(3770) provides large ?(DD)
• High efficiency tagging of hadronic decays
  defines beam of Ds on other side of event
• Low multiplicity and clean

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460,000 D- tags!
mbc (GeV)
MM2 (GeV2)
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Paper also includes limits on ?? and e?
So far, so good data agrees well with LQCD for
fD
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Now look for f(Ds)
A little harder best place to run produces DsDs
We call the tag side the Ds- 70514 Ds- events
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Now add the photon, and look at the missing mass
squared to find the events and see the Ds
43,859 reconstructed Ds before we look at any of
its tracks
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Look for occasions when track is
MinIonizing (mostly Ds ???) or more than
MinIonizing (mostly Ds???????)
Overall Fit Blue Ds ??? - Grey Ds??????? -
Purple Non Ds background Red Ds background -
Green
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We find B(Ds ???) 0.565 0.045 0.017 By
this method B(Ds???) 6.42 0.81 0.18 but
there are other methods.Look for Ds???, ?e??
Here the business plot is the extra energy
found in events with a Ds, an e candidate and no
other tracks. B(Ds???) 5.300.470.22
But were not done yet.
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Look for events where Ds???????? ??0?? High
branching fractions high backgrounds.
Total Fit Signal K0??0
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Putting the Ds results together MODE
B()
f(Ds) (MeV) Ds???? ??? 6.42 0.81
0.18 278.0 17.5 4.4 Ds????e??
5.30 0.47 0.22 252.6 11.2
5.6 Ds??????????0?? 5.52 0.57 0.21
257.8 13.3 5.2 Ds ???
0.565 0.045 0.017 257.6 10.3
4.3 assuming the SM f(Ds) 259.0
6.2 3.0 MeV But the lattice
says f(Ds) 241 3 MeV
(HPQCDUKQCD collaboration for lattice) 2.4
standard deviation discrepency remember that
f(D) has very good agreement.
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Another thing that was done with the Ds data
I got interested in an old question can
we find baryonic decays of the Ds only one such
decay possible, Ds ? p n
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Reconstruct on Ds to KK? and other modes,
reconstruct a ? plus a firmly identified proton
(and no other tracks). Look at the missing mass
of the event, and see if It peaks at the
(anti-)neutron mass. (Note that no attempt is
made to reconstruct the (anti-)neutron). Much use
made of kinematic fitting.
PRL 100181802 (2008)
Small, but clean signal corresponding to a
branching fraction of (1.3 0.36)x10-3
This order of magnitude post-dicted by Chan,
Cheng and Hsiao using a model invoking long-distan
ce enhancement of the W-exchange diagram.
This is first and only decay of a charmed meson
into baryons ever observed!
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• CONCLUSIONS
• CLEO has now stopped taking data. It produced 30
  years
• of physics, and we look forward to several more
  years
• BES III is now taking over as the premier
  charmonium factory.
• I showed some recent results
• The hc is now well measured, and shown to decay
  directly
• to hadrons at a similar rate to the radiative
  decays.
• 2. The charm decay constants are well-measured.
  The D
• is in very good agreement with lattice
  calculations. The
• Ds one is not.
• These are just a few of the many topics still
  under investigation
• expect many more CLEO talks in years to come.