Transcript Charmed Meson Lifetimes, Spectra, and Hadronic Decays

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, E+M Calorimetry,
and Muon id capabilities. Includes groups from USA, Italy, Brazil, Mexico, Korea
1 million charm particles reconstructed into DK , K2 , K3
3/23/99
FOCUS first results <Jim Wiss>
1
Preliminary measurement of the Ds+ lifetime
Ds+ and Do have unique CF non-spectator decays
1400
Signal Region
1200
WA
Sideband Region
1000
Ds+
800
600
400
200
0
1.7 1.75 1.8 1.85 1.9 1.95 2
225
200
175
2.05 2.1
Region
cosSignal
K
Sideband Region
WX
Do
Theory  (Ds+) / (Do) =1.07 1.20
We use 5668
+ decays in
D
s
 (Ds+) = 0.506 
~50% of FOCUS to
0.008  sys (ps)
suppresses longlived backgnd from
D+K- + +K+
Accepted Region
Also allows us to
enhance S/N with
cos  cut
150
125
100
75
Using E791  (Ds+) = 0.518  0.014  0.007 ps
We project:WA is  (Ds+) / (Do) = 1.214  0.017
50
25
0
-1 -0.8 -0.6 -0.4 -0.2 0
0.2 0.4 0.6 0.8 1
See talk of Harry Cheung
2
PRELIMINARY D*D Mass Splittings
~50% FOCUS
D*+ -
D+
D*o - Do
IE-IE 0’s only
3/23/99
FOCUS first results <Jim Wiss>
We are seeing very
strong D*o Do 
signals in FOCUS
with our new &
improved E&M
calorimeters. Project
a final sample of
25000 D*o Do 
decays .
CLEO92 has provided
the best past data on
D0* mass, widths, and
branching ratios from
~1200 D*o Do 
decays
3
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 !
3/23/99
FOCUS first results <Jim Wiss>
HQ98 LGT
4
We are even getting our first glimpse at Ds*+
Ds*+  Ds+ 
Preliminary
~20% FOCUS
IE  only
3/23/99
FOCUS first results <Jim Wiss>
5
“Golden” signals with pi0’s
K
# per 5
MeV
K
K2
Y=2150
Y=3545
Y=12713
K3
K2
Y=996
K3
Y=303
Signals based on 20% of FOCUS
No optimization of  cuts!
•Can study a rich new set of charm decay
Y=1396
3/23/99
•Many are required to complete isospin
amplitude triangles
FOCUS first results <Jim Wiss>
6
Beyond the D*
HQET predicts a rich L=1
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* D0*2D*
The low multiplicity of primary vertex gives
photoproduction an advantage for D** study.
3/23/99
FOCUS first results <Jim Wiss>
D0*2D D+*2D
D*s?K D
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PRELIMINARY D** signals ~27% FOCUS
reflection
D1(2420)
D2
unresolved in E687
except by angular cuts
Do1 ,
D*o2 
D2*0 (2460)
*0(2460)
D*-+(D)+
D1(2420)
absent by
parity
3/23/99
•1 real peak in D+•1? peak in D0K+
Ds
+*D0K
DsJ(2573)+?
D2*+ (2460)
WS
•2 peaks in D*+•1 real peak in D0+
WS
Ds** 
(D)K+
We observe
WS
FOCUS first results <Jim Wiss>
Also see reflections
at M-m from
D*°D with
missing °
Angular distributions
can often be used to
disentangle states
and confirm HQET
predictions.
8
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.
3/23/99
FOCUS first results <Jim Wiss>
9
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 ?
3/23/99
Resonant Weak
Annihilation?
FOCUS first results <Jim Wiss>
10
Preliminary FOCUS Ds Dalitz plots (~40%)
Observe:
f2
f2
•f0(980)
•f2(1270)
•f0 (1500)
Clearer in FOCUS
No evidence for WA
•(770)
•NR
•Dominated by weird resonances with simultaneous KK and  couplings
•No evidence for non-spectator decays such as NR or 
3/23/99
FOCUS first results <Jim Wiss>
11
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!
a0(980)
2 spectator diagrams
with resonances which
couple to ’s and K’s
f0(980)
(1020)?
~50% FOCUS
a0(980)?
m²K+KY=395
f0(980)?
S/N=17
(1020)
We use D* tagging to
determine strangeness of K°s
3/23/99
FOCUS first results <Jim Wiss>
m²K+Ko
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Studies of Cabibbo Suppressed decays
•FOCUS’s 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)
3/23/99
FOCUS first results <Jim Wiss>
13
DCSD : D+  K+ +~40% of FOCUS Data
5913
Y(D+)=17228
Y(Ds+)=22421
E791
K+ +-)/K- + + =
(0.68  0.15)% PDG98
Our results already
much better than
PDG98 (  3  E791)
Preliminary FOCUS
CL1<0.1
M(K+
3/23/99
+-)
CL1<110-8
(K+ +-)/ (K- + +) = (0.650.11)%
 3 tan4Cabbibo  (+/0)  tan4C
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PRELIMINARY (~40%) D° DCSD
Y=7221.6±87.80
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
M=0.1455
W=0.91
K rs
+
K+
D0
Y=60.337±21.40
3/23/99
mixed CF
D*+
WS mass & 
fixed by RS
K ws
D0
-
rmix
+
K+
D0
D*+
DCSD
-
FOCUS first results <Jim Wiss>
15
Relative WS/RS ratio versus CITADL Cuts
Cut variations on 19/155 with K candidates.
ws/rs
PDG
error
K
Miss-id
yield
PDG
W -WK
MC study
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 world’s average but higher
than CLEO’s recent measurement at APS
3/23/99
FOCUS first results <Jim Wiss>
16
PRELIMINARY D +sK+K+~50%
PRELIMINARY
This is the first observation
of D+s DCSD
The rate relative to K-K++ is
1.5% (~6  tan4Cabbibo)
3/23/99
FOCUS first results <Jim Wiss>
17
PRELIMINARY D+ K+K-K+~40% FOCUS
•Ds+K+K-K+is a SCSD
•D+ K+K-K+ is a C = -S DCSD
which cannot occur via a spectator
diagram.
Y(D+ ) = 27±7
Y(Ds+ ) = 28±7
(D + K+K-K+)/ ( D +) = (1.450.39)10-4
Just below PDG 98 limit from E687 of
Br < 1.410-4 CL=90%
Our rarest DCSD BR yet :
(D + K+K-K+) / (K-++)  tan4C/2
No evidence for D+  K
A KKK Dalitz analysis may shed light on the
KKK decay mechanism.
3/23/99
FOCUS first results <Jim Wiss>
18
Rounding out the all kaon final states...
45% Focus
Y=208
Y=491
Y=556
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.
50% Focus
KsK
D + KsKsK+
Altogether we show SIX all kaon charm decays
3/23/99
D0  K+K-
D +  KsK
Ds+  KsK
D 0  Ks K + K-
D +  KsKsK+
D+  K+K-K+
FOCUS first results <Jim Wiss>
19
c & *c Spectroscopy
 cpK
80% FOCUS
c specta
We can study all of this spectroscopy!
3/23/99
FOCUS first results <Jim Wiss>
*c specta
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Preliminary c - c mass differences
c0 - c+
M=167.170.260.27 MeV
Theoretically one expects
M(c0) > M(c++)
c++ - c+
M= 167.450.170.36 MeV
But world’s data including our
measurement has M(c0) < M(c++)
by about 1.5
c++ -  c0
M= 0.280.310.15 MeV
3/23/99
See talk of
FOCUS first results <Jim Wiss>
Eric Vaandering
21
Kinky decays of the c+
Y=607 in ~22%
FOCUS
Y=253 in
~22%
FOCUS
E687
saw 56
events
c+- K++
~75%
FOCUS
CLEO saw
487 events
•We have unique abilities to reconstruct the - n  •Will study (1385)  since only contributions are internal W and WX
3/23/99
FOCUS first results <Jim Wiss>
22
A Gallery of +c decays
K-++
- + +
~75%
Focus
+K-+
~30%
Focus
~20%
Focus
~70%
Focus
pK-+
SCSD
1st reported by
Selex HQ98
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
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E791
Search for CP violating SCSD decays
Look for (DK+K-)  (DK+K-)
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
World’s best data
using 26% of Focus!
3/23/99
FOCUS first results <Jim Wiss>
24
Semileptonic Mixing Searches
+
RS
K-

D0
+
D*+
WS
+
K+
D0
 from
another
event
D*+
I RS (t )  e
D0
rmix
 t

-
rmix 2 2 t
IWS (t ) 
t e
2
Limit follows from fitting time evolution of
WS and RS signal. No DCSD interference.
3/23/99
FOCUS first results <Jim Wiss>
25
Mixing sensitivity
•FOCUS projected sensitivity is rmix ~ 0.15%
•Including electrons we project rmix ~ 0.1%
•Present E791 limit rmix < 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
()/ < 1.5%
3/23/99
FOCUS first results <Jim Wiss>
26
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 E&M
calorimeter and an enhanced outer E&M calorimeter.
K*l from 80% Focus
•We project a ~50 fold increase over E687 which
published form factors for each of these states
RS-WS = 64244
M(K)
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
3/23/99
27
~
+
Soft pion
tagging as means to absolute BF

K+

D0
__
D (recoil)
D*+
+
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 ?
30% FOCUS
Proof 2: Can we
reconstruct both
D’s in an event?
Already have a
copious sample of
very clean events
with both
reconstructed D’s
Expect 7500
3/23/99
28
What I left out
•Production dynamics => Unique tests of QCD
•Xf , PT and E 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!
3/23/99
FOCUS first results <Jim Wiss>
29