Charmed Meson Lifetimes, Spectra, and Hadronic Decays

1
Over 1 million reconstructed!!
Successor to E687. Designed to study charm
particles produced by 200 GeV photons using a
fixed target spectrometer with upgraded
Vertexing, Cerenkov, EM Calorimetry, and Muon id
capabilities. Includes groups from USA, Italy,
Brazil, Mexico, Korea 1 million charm particles
reconstructed into D?K? , K2? , K3?
2
Preliminary measurement of the Ds lifetime
Ds and Do have unique CF non-spectator decays
WA
WX

Theory ? (Ds) /? (Do) 1.07? 1.20
We use 5668 Ds??? decays in 50 of FOCUS to
suppresses long-lived backgnd from D?K- ?
??K Also allows us to enhance S/N with cos ?
cut
cos ??K?
Using E791 ? (Ds) 0.518 ? 0.014 ? 0.007 ps
We projectWA is ? (Ds) /? (Do) 1.214 ? 0.017
See talk of Harry Cheung
3
PRELIMINARY D?D?? Mass Splittings
50 FOCUS
We are seeing very strong Do ?Do ?? signals in
FOCUS with our new improved EM calorimeters.
Project a final sample of 25000 Do ?Do ?? decays
. CLEO92 has provided the best past data on D0
mass, widths, and branching ratios from 1200 Do
?Do ?? decays
Do - Do
D - D
IE-IE ?0s only
4
PRELIMINARY Mass splittings
Isosplittings depend on same physics as the D
decay constant
PDG98
24 of FOCUS
PDG98
S/N

• Both ?samples consistent with PDG98 already w/
  smaller errors !

HQ98 LGT
5
We are even getting our first glimpse at Ds
Ds ? Ds ?
Preliminary 20 FOCUS IE ? only
6
Golden signals with pi0s
per 5 MeV
Signals based on 20 of FOCUS No optimization of
?? cuts!

• Can study a rich new set of charm decay
• Many are required to complete isospin amplitude
  triangles

7
Beyond the D

• HQET predicts a rich L1 spectrum
• 2 broad states with s-wave ? decays (CLEO has
  evidence for 1)
• 2 narrow states with d-wave ? decays (seen in e
  e- ? N)
• Predictions are made for masses, widths, and
  angular distributions and the relationship to B
  splitting.
• FOCUS has PRELIMINARY signals for
• D01??D D02??D
• D02??D D2??D
• Ds??K D

The low multiplicity of primary vertex gives
photoproduction an advantage for D study.
8
PRELIMINARY D signals 27 FOCUS
reflection

• We observe
• 2 peaks in D?-
• 1 real peak in D?-
• 1 real peak in D0?
• 1? peak in D0K
• Also see reflections at M-m? from D??D with
  missing ?
• Angular distributions can often be used to
  disentangle states and confirm HQET predictions.

D20 (2460)
D1(2420)
D20(2460)
D1(2420) absent by parity
unresolved in E687 except by angular cuts
WS
Do1 , Do2 ? D-??(D??)?
Ds?D0K
Ds ? (D???)K
DsJ(2573)?
D2 (2460)
WS
WS
9
Dalitz Amplitude Analyses

• Dalitz analyses are a traditional strength of
  E687 which has published on
• K- ? ? K-? ?o Ks?-? K-K?-
  ???-
• Dalitz analysis provides powerful probes on
  charm hadronic decay
• Underscores the importance of quasi-two body
  decay and extends tests of factorization models
  to vector-pseudoscalar decay
• Often highly unusual resonances dominate charm
  Dalitz plots.
• Allows one to directly investigate non-spectator
  effects such as W-annihilation
• Provides new handles on charm CP violation by
  comparing the phases and amplitudes that one gets
  for particles versus antiparticle decay. Best in
  Cabibbo suppressed decays.
• Provides a preview of the FSI complication for
  beauty
• Studies on many Dalitz plots studied by E687 are
  already underway. I will discuss two interesting
  Dalitz plots featuring decays with an unusual
  number of final state kaons.

10
Favored D decays with unusual numbers of kaons
Conventional spectator but with weird resonances?
Too few kaons! An example is Ds???? BR is large
1.4 suggesting a Cabibbo favored decay Cabibbo
favored would produce a s s u d as final quarks
and no kaons appear in the final state. How are
they lost?
NR Weak Annihilation ?
Resonant Weak Annihilation?
11
Preliminary FOCUS Ds???? Dalitz plots (40)

• Observe
• f0(980)
• f2(1270)
• f0 (1500)
• Clearer in FOCUS
• No evidence for WA
• ?(770)
• NR

f2
f2

• Dominated by weird resonances with simultaneous
  KK and ?? couplings
• No evidence for non-spectator decays such as NR
  or ??

12
PRELIMINARY D0?Ks K K- Dalitz plot
Too many kaons Here we have only an s u d quarks
in the final state yet three kaons appear!
2 spectator diagrams with resonances which couple
to ?s and Ks
a0(980)?
m²KK-
f0(980)?
f(1020)
We use D tagging to determine strangeness of Ks
m²KKo
13
Studies of Cabibbo Suppressed decays

• FOCUSs powerful Cerenkov ID and very large data
  sample gives it unique opportunities to study
  Cabibbo Suppressed Decays
• Will present evidence for five DCS Decays (
  2.5?0.5 decays are new!)
• See talk of Jon Link
• Historically the pattern of Cabibbo suppression
  has been full of surprises and has yielded unique
  insight into hadronic decay mechanisms to
  challenge models
• The rate for DCSD is often very different than
  tan4?C
• D DCSD interferes with hadronic decay mixing.
  This is good news / bad news since small
  amplitudes are best measured through interference
• Differences in DCSD/CF Dalitz plots can probe Do
  mixing (T. Liu)

14
DCSD D ? K ??-
40 of FOCUS Data
Y(D)172?28Y(Ds)224?21
K ??-)/K- ?? (0.68 ? 0.15) PDG98 Our
results already much better than PDG98 ( ? 3 ?
E791)
Preliminary FOCUS
CL1lt0.1
CL1lt1?10-8
?(K ??-)/ ?(K- ?? ) (0.65?0.11) ? 3?
tan4?Cabbibo ? (?/?0) ? tan4?C
M(K ??-)
15
PRELIMINARY (40) D DCSD
Here we look for WS D decays where the kaon has
the same sign as the D decay pion. This is also
a classic way to search for mixing and could
interfere with mixing. BR(DCSD) ?WS/RS
K? rs
mixed CF
D
Y60.33721.40
?-
WS mass ? fixed by RS
?
K
DCSD
D0
K? ws
D
?-
16
Relative WS/RS ratio versus CITADL Cuts
Cut variations on ?19/?155 with K? candidates.
ws/rs
Miss-id yield
MC study
W? -WK
W? -WK
Slight variation in BR as pid cuts are
tightened. Would expect exponential decrease if
double mis-id. The signal level is consistent
with existing worlds average but higher than
CLEOs recent measurement at APS
17
PRELIMINARY D s?KK?-
This is the first observation of Ds DCSD The
rate relative to K-K? is ?1.5 (6 ?
tan4?Cabbibo)
50 PRELIMINARY
18
PRELIMINARY D ?KK-K40 FOCUS

• Ds?KK-Kis a SCSD
• D ?KK-K is a ?C -?S DCSD which cannot occur
  via a spectator diagram.
• ?(D ?KK-K)/ ?( D ) (1.45?0.39)?10-4
• Just below PDG 98 limit from E687 of
  Br lt 1.4?10-4 CL90
• Our rarest DCSD BR yet
  ?(D ?KK-K) / ?(K-???) ?? tan4?C/2
• No evidence for D ?? K
• A KKK Dalitz analysis may shed light on the KKK
  decay mechanism.

Y(D ) 277 Y(Ds ) 287
19
Rounding out the all kaon final states...
45 Focus
These two are difficult for us to study because
charm in FOCUS is brought out through vertexing
and the Ks in FOCUS generally verticize
downstream of the SSD.
Y208
Y491
Y556
50 Focus
KsK
D ?KsKsK
Altogether we show SIX all kaon charm decays D0 ?
KK- D ? KsK Ds ? KsK D0? Ks
K K- D ? KsKsK D ? KK-K
20
?c ?c Spectroscopy
? c?pK?
80 FOCUS
?c specta
?c specta
We can study all of this spectroscopy!
21
Preliminary ?c - ?c mass differences
?c0 - ?c
?M167.17?0.26?0.27 MeV
Theoretically one expects M(?c0) gt M(?c) But
worlds data including our measurement has M(?c0)
lt M(?c) by about 1.5?
?c - ?c
?M 167.45?0.17?0.36 MeV
?c - ? c0
?M 0.28?0.31?0.15 MeV
See talk of Eric Vaandering
22
Kinky decays of the ?c
?c??- K?
75 FOCUS
Y607 in 22 FOCUS
Y253 in 22 FOCUS
E687 saw 56 events
CLEO saw 487 events

• We have unique abilities to reconstruct the ?- ?n
  ? -
• Will study ?(1385) ?? since only contributions
  are internal W and WX

23
A Gallery of ?c decays
?K-?
?K-??
?- ? ?
30 Focus
75 Focus
20 Focus
Using the 3 favored decay modes, we project a
sample of 860 ?c decays 30 times the E687
lifetime sample which provides the best ?c
lifetimes
pK-? SCSD
70 Focus
1st reported by Selex HQ98
24
Search for CP violating SCSD decays
E791
Look for ?(D?KK-) ? ?(D?KK-) Tag D charm
through D?? D??
D?K?
We normalize to D??K-? to eliminate ?4
production asymmetry.
FOCUS (26)
Much less D?K? Reflection
?Worlds best data using 26 of Focus!
25
Semileptonic Mixing Searches
D
D
? from another event
Limit follows from fitting time evolution of WS
and RS signal. No DCSD interference.
26
Mixing sensitivity

• FOCUS projected sensitivity is rmix 0.15
• Including electrons we project rmix 0.1
• Present E791 limit rmix lt 0.50 (90 CL)

We have unique advantages in searching for direct
?? differences between CP-even eigenstates such
as D?K K- and states of mixed CP such as D? K-
? or CP odd states such as Ks? or Ks? We expect
a yield of from 5000-10000 D?K K- decays. This
should give us a lifetime measurement for CP even
states of better than ?(?)/? lt 1.5
27
FOCUS Semileptonic Physics

• We improved all aspects of our lepton id system
  including an entirely rebuilt inner muon system,
  a new outer muon system, a rebuilt inner EM
  calorimeter and an enhanced outer EM
  calorimeter.

• We project a 50 fold increase over E687 which
  published form factors for each of these states

Our projected Kl? yield should make us very
competitive with other charm experiments! Our
vertex tagging gives us the ability to study Kl?
without D tagging ? Enormous yield
28
Soft pion tagging as means to absolute BF
Can tag the presence of a D by observing a right
sign ?? which ?balances Pt with a reconstructed
D . You then count the number of D decays into a
particular final state, correct by efficiency
and ratio to find an absolute branching fraction.
Low primary vertex multiplicity is a big
advantage.
Proof of Principle 1 Is there an excess of RS
over WS events at low Pt ?
Proof 2 Can we reconstruct both Ds in an
event? Already have a copious sample of very
clean events with both reconstructed Ds Expect
?7500
?30 FOCUS
29
What I left out

• Production dynamics gt Unique tests of QCD
• Xf , PT and Eg dependence compared to NLO ?-g
  fusion
• Charm/Anticharm asymmetry as probes of
  fragmentation
• Kinematic correlations in D D events as probes of
  NLO QCD
• Amplitude analyses for 4 body and 5 body final
  states
• Semileptonic decays
• Semileptonic Form factor measurement.
• Cabibbo suppressed semileptonic decay
• Rare or forbidden decays
• Many of these studies are already underway or
  will start shortly!