Observation of the Cabibbo-suppressed charmed baryon decay
L
c
1
ò
p
f
J. P. Alexander,
1
C. Bebek,
1
B. E. Berger,
1
K. Berkelman,
1
K. Bloom,
1
T. E. Browder,
1,
*
D. G. Cassel,
1
H. A. Cho,
1
D. M. Coffman,
1
D. S. Crowcroft,
1
M. Dickson,
1
P. S. Drell,
1
D. J. Dumas,
1
R. Ehrlich,
1
R. Elia,
1
P. Gaidarev,
1
M. Garcia-Sciveres,
1
B. Gittelman,
1
S. W. Gray,
1
D. L. Hartill,
1
B. K. Heltsley,
1
S. Henderson,
1
C. D. Jones,
1
S. L. Jones,
1
J. Kandaswamy,
1
N. Katayama,
1
P. C. Kim,
1
D. L. Kreinick,
1
T. Lee,
1
Y. Liu,
1
G. S. Ludwig,
1
J. Masui,
1
J. Mevissen,
1
N. B. Mistry,
1
C. R. Ng,
1
E. Nordberg,
1
J. R. Patterson,
1
D. Peterson,
1
D. Riley,
1
A. Soffer,
1
P. Avery,
2
A. Freyberger,
2
K. Lingel,
2
C. Prescott,
2
J. Rodriguez,
2
S. Yang,
2
J. Yelton,
2
G. Brandenburg,
3
D. Cinabro,
3
T. Liu,
3
M. Saulnier,
3
R. Wilson,
3
H. Yamamoto,
3
T. Bergfeld,
4
B. I. Eisenstein,
4
J. Ernst,
4
G. E. Gladding,
4
G. D. Gollin,
4
M. Palmer,
4
M. Selen,
4
J. J. Thaler,
4
K. W. Edwards,
5
K. W. McLean,
5
M. Ogg,
5
A. Bellerive,
6
D. I. Britton,
6
E. R. F. Hyatt,
6
R. Janicek,
6
D. B. MacFarlane,
6
P. M. Patel,
6
B. Spaan,
6
A. J. Sadoff,
7
R. Ammar,
8
P. Baringer,
8
A. Bean,
8
D. Besson,
8
D. Coppage,
8
N. Copty,
8
R. Davis,
8
N. Hancock,
8
S. Kotov,
8
I. Kravchenko,
8
N. Kwak,
8
Y. Kubota,
9
M. Lattery,
9
M. Momayezi,
9
J. K. Nelson,
9
S. Patton,
9
R. Poling,
9
V. Savinov,
9
S. Schrenk,
9
R. Wang,
9
M. S. Alam,
10
I. J. Kim,
10
Z. Ling,
10
A. H. Mahmood,
10
J. J. O’Neill,
10
H. Severini,
10
C. R. Sun,
10
F. Wappler,
10
G. Crawford,
11
R. Fulton,
11
D. Fujino,
11
K. K. Gan,
11
K. Honscheid,
11
H. Kagan,
11
R. Kass,
11
J. Lee,
11
M. Sung,
11
C. White,
11
A. Wolf,
11
M. M. Zoeller,
11
X. Fu,
12
B. Nemati,
12
W. R. Ross,
12
P. Skubic,
12
M. Wood,
12
M. Bishai,
13
J. Fast,
13
E. Gerndt,
13
J. W. Hinson,
13
T. Miao,
13
D. H. Miller,
13
M. Modesitt,
13
E. I. Shibata,
13
I. P. J. Shipsey,
13
P. N. Wang,
13
L. Gibbons,
14
S. D. Johnson,
14
Y. Kwon,
14
S. Roberts,
14
E. H. Thorndike,
14
T. E. Coan,
15
J. Dominick,
15
V. Fadeyev,
15
I. Korolkov,
15
M. Lambrecht,
15
S. Sanghera,
15
V. Shelkov,
15
T. Skwarnicki,
15
R. Stroynowski,
15
I. Volobouev,
15
G. Wei,
15
M. Artuso,
16
M. Gao,
16
M. Goldberg,
16
D. He,
16
N. Horwitz,
16
S. Kopp,
16
G. C. Moneti,
16
R. Mountain,
16
F. Muheim,
16
Y. Mukhin,
16
S. Playfer,
16
S. Stone,
16
X. Xing,
16
J. Bartelt,
17
S. E. Csorna,
17
V. Jain,
17
S. Marka,
17
D. Gibaut,
18
K. Kinoshita,
18
P. Pomianowski,
18
B. Barish,
19
M. Chadha,
19
S. Chan,
19
D. F. Cowen,
19
G. Eigen,
19
J. S. Miller,
19
C. O’Grady,
19
J. Urheim,
19
A. J. Weinstein,
19
F. W u
̈
rthwein,
19
D. M. Asner,
20
M. Athanas,
20
D. W. Bliss,
20
W. S. Brower,
20
G. Masek,
20
H. P. Paar,
20
J. Gronberg,
21
C. M. Korte,
21
R. Kutschke,
21
S. Menary,
21
R. J. Morrison,
21
S. Nakanishi,
21
H. N. Nelson,
21
T. K. Nelson,
21
C. Qiao,
21
J. D. Richman,
21
D. Roberts,
21
A. Ryd,
21
H. Tajima,
21
M. S. Witherell,
21
R. Balest,
22
K. Cho,
22
W. T. Ford,
22
M. Lohner,
22
H. Park,
22
P. Rankin,
22
and J. G. Smith
22
1
Cornell University, Ithaca, New York 14853
2
University of Florida, Gainesville, Florida 32611
3
Harvard University, Cambridge, Massachusetts 02138
4
University of Illinois, Champaign-Urbana, Illinois, 61801
5
Carleton University, Ottawa, Ontario, Canada K1S 5B6
and the Institute of Particle Physics, University of Ottawa Campus, Ottawa, Ontario, Canada K1N 9B4
6
McGill University, Montre
́
al, Que
́
bec, Canada H3A 2T8
and the Institute of Particle Physics, University of Ottawa Campus, Ottawa, Ontario, Canada K1N 9B4
7
Ithaca College, Ithaca, New York 14850
8
University of Kansas, Lawrence, Kansas 66045
9
University of Minnesota, Minneapolis, Minnesota 55455
*
Permanent address: University of Hawaii at Manoa.
P
HYSICAL
R
EVIEW
D
PARTICLES AND FIELDS
THIRD SERIES, VOLUME 53, NUMBER 3
1 FEBRUARY 1996
RAPID COMMUNICATIONS
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Physical Review D
should be no longer than five printed pages and
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not delayed for receipt of corrections unless requested by the author.
53
0556-2821/96/53
~
3
!
/1013
~
5
!
/$06.00
R1013
© 1996 The American Physical Society
10
State University of New York at Albany, Albany, New York 12222
11
Ohio State University, Columbus, Ohio, 43210
12
University of Oklahoma, Norman, Oklahoma 73019
13
Purdue University, West Lafayette, Indiana 47907
14
University of Rochester, Rochester, New York 14627
15
Southern Methodist University, Dallas, Texas 75275
16
Syracuse University, Syracuse, New York 13244
17
Vanderbilt University, Nashville, Tennessee 37235
18
Virginia Polytechnic Institute and State University, Blacksburg, Virginia, 24061
19
California Institute of Technology, Pasadena, California 91125
20
University of California, San Diego, La Jolla, California 92093
21
University of California, Santa Barbara, California 93106
22
University of Colorado, Boulder, Colorado 80309-0390
~
Received 25 July 1995
!
We report the observation of the Cabibbo-suppressed decays
L
c
1
!
pK
2
K
1
and
L
c
1
!
p
f
using data col-
lected with the CLEO II detector at CESR. The latter mode, observed for the first time with significant
statistics, is of interest as a test of color suppression in charm decays. We have determined the branching ratios
for these modes relative to
L
c
1
!
pK
2
p
1
and compared our results with theory.
PACS number
~
s
!
: 13.30.Eg, 12.39.
2
x, 14.20.Lq
The strength of color suppression in internal
W
-emission
charmed meson decays has long been in question. For ex-
ample,
B
(
D
s
1
!
K
̄
*
0
K
1
)/
B
(
D
s
1
!
f
p
1
)
.
1,
@
1,2
#
while
the expectation from color-matching requirements is that this
ratio should be about 1/9. Reasonable overall agreement with
the experimental data in the charm sector has been obtained
using factorization and taking the large
N
c
limit in a 1/
N
c
expansion approach, where
N
c
is the number of quark colors
@
3,4
#
. The Cabibbo-suppressed charmed baryon decay
L
c
1
!
p
f
, shown in Fig. 1, is also naively expected to be
color suppressed. However, using factorization and taking
the limit
N
c
!
`
leads to a prediction of no color suppression
@
5
#
. Since the
L
c
1
!
p
f
decay receives contributions only
from factorizable diagrams, a reliable calculation should be
obtained
using
factorization.
Observation
of
the
L
c
1
!
p
f
decay was first reported by the ACCMOR Col-
laboration with 2.8
6
1.9 events
@
9
#
. Last year the E687 Col-
laboration published results on the first observation of the
Cabibbo-suppressed charmed baryon decay
L
c
1
!
pK
2
K
1
,
along with an upper limit on the resonant substructure
L
c
1
!
p
f
@
10
#
. Herein we present new CLEO results on the
observation of
L
c
1
!
pK
2
K
1
and
L
c
1
!
p
f
decays and
discuss the implications of the results.
We use a data sample recorded with the CLEO II detector
operating at the Cornell Electron Storage Ring
~
CESR
!
. The
sample consists of
e
1
e
2
annihilations taken at and slightly
below the
Y
(4
S
) resonance, for a total integrated luminosity
of 3.46 fb
2
1
. The main detector components which are im-
portant for this analysis are the tracking system and the bar-
rel time-of-flight
~
TOF
!
particle identification system. Addi-
tional particle identification
~
ID
!
is provided by specific
ionization (
dE
/
dx
) information from the tracking system’s
main drift chamber. A more detailed description of the CLEO
II detector has been provided elsewhere
@
11
#
.
To search for the
L
c
1
signals we study
pK
2
K
1
track
combinations found by the tracking system. The
p
and
K
6
candidates are identified by combining information from the
TOF and
dE
/
dx
systems to form a combined
x
2
probability
P
i
for each mass hypothesis
i
5
p
,
K
,
p
. Using these prob-
abilities
P
i
, a normalized probability ratio
L
i
is evaluated
for
each
track
according
to
the
formula
L
i
[
P
i
/(
P
p
1
P
K
1
P
p
) . Well-identified protons form a
sharp peak near
L
p
5
1, while tracks identified as
not
being
protons form a peak near
L
p
5
0. The remainder of the can-
didates fall in the region between 0 and 1. For the proton
involved in each decay mode under study we require
L
p
.
0.9, which constitutes a strong cut. For the kaons we
apply a loose cut of
L
K
.
0.1. In addition, all protons and
kaons must pass a minimum requirement of
P
p
.
0.001 and
P
K
.
0.001, respectively. In order to reduce the large combi-
natoric background, the candidate
L
c
1
scaled momentum
x
p
5
P
L
c
/
A
E
beam
2
2
m
L
c
2
is limited to
x
p
.
0.5.
The
pK
2
K
1
invariant mass is shown in Fig. 2. The broad
enhancement in the mass region above 2.37 GeV/
c
2
is a
reflection from the decay mode
L
c
1
!
pK
2
p
1
, where the
pion has been misidentified as a kaon. The spectrum is fitted
to a Gaussian for the signal with width fixed to
s
5
4.9 MeV/
c
2
determined from Monte Carlo simulation
@
12
#
, and a
second-order Chebyshev polynomial for the smooth back-
ground. This fit yields 214
6
50 events for the inclusive
L
c
1
!
pK
2
K
1
signal with a mean mass of 2285.5
6
1.2 MeV/c
2
@
13
#
.
The
f
candidates are reconstructed through their decays
f
!
K
2
K
1
. Because the width of the
f
is comparable to
the detector mass resolution, the
f
signal shape is best de-
scribed by a convolution of a Gaussian and a Breit-Wigner
function of width
G
5
4.43 MeV/
c
2
@
1
#
. The background
is parametrized by a function of the form
b
(
m
)
FIG. 1. The decay
L
c
1
!
p
f
.
R1014
53
J. P. ALEXANDER
et al.
5
N
(
m
2
m
0
)
a
e
b
(
m
2
m
0
)
. The measured Gaussian resolution
from the fit is
s
5
1.6
6
0.2 MeV/
c
2
. In order to perform
background subtractions, 1.0121
,
m
KK
,
1.0273 GeV/
c
2
is
designated
as
the
f
‘‘signal’’
region,
while
0.990
,
m
KK
,
1.005 GeV/
c
2
and 1.035
,
m
KK
,
1.050 GeV/
c
2
are designated as the ‘‘sideband’’ regions. Integrating the
background function over the sideband and signal regions
gives a signal-to-sideband scale factor
R
f
5
0.560
6
0.016,
which is used in the
f
background subtraction below.
In order to obtain the
L
c
1
!
p
f
signal, the
pK
2
K
1
mass
plot is made both for
m
K
2
K
1
in the
f
signal region and the
f
sideband regions. Figure 3 shows the results. The spectra
are fitted to a Gaussian for the signal with width fixed to
s
5
4.9 MeV/
c
2
from Monte Carlo simulation, and a second-
order Chebyshev polynomial for the smooth background.
The fit to the
pK
2
K
1
mass spectrum corresponding to the
f
signal region yields 54
6
12 events with a confidence level
of 97%. The mean mass for the signal is measured to be
2288.2
6
1.3 MeV/
c
2
. In fitting the
pK
2
K
1
mass corre-
sponding to the
f
sideband region, the mean
L
c
1
mass is
fixed to that obtained from the
f
signal region and the
s
is
fixed to the Monte Carlo value as before. This gives
2
16.4
6
9.6 events for the
f
sideband
L
c
1
yield. Since the
true contribution must be positive definite we set the central
value to zero and use 0
6
9.6 as the best estimate of the
L
c
1
!
pK
2
K
1
contribution. After scaling this by
R
f
and
subtracting we find that the net
L
c
1
!
p
f
yield is 54
6
13
events.
As a check of the nonresonant contribution to the
L
c
1
!
p
f
signal we fit the
K
2
K
1
mass spectra correspond-
ing to the
L
c
1
signal and sideband regions as determined
from the inclusive
pK
2
K
1
mass spectrum. The
f
yield ob-
tained from the
L
c
1
sideband regions, 2.246
,
m
pKK
,
2.266
and 2.306
,
m
pKK
,
2.326 GeV/
c
2
, is subtracted from that for
the
L
c
1
signal region, 2.276
,
m
pKK
,
2.296 GeV/
c
2
. Figure
4 shows the fits to the
K
2
K
1
spectra from the
L
c
1
signal and
sideband regions, which yield
f
signals of 92.2
6
17.0 events
and 36.5
6
13.5 events, respectively. The
L
c
1
sideband
K
2
K
1
mass spectrum in Fig. 4 has been scaled by the
L
c
1
signal-to-sideband scale factor of
R
L
c
1
5
0.502
6
0.013, ob-
tained by integrating the background function in Fig. 2 over
FIG. 2. Invariant mass of inclusive
pK
2
K
1
combinations pass-
ing all requirements. No
f
cut is applied. The region above 2.37
GeV/
c
2
,
where
there
is
a
large
enhancement
from
L
c
1
!
pK
2
p
1
decays, is not included in the fit.
FIG. 3. Invariant mass of
pK
2
K
1
combinations corresponding
to
K
2
K
1
mass in the
f
signal and sideband regions.
FIG. 4. Fit to
K
2
K
1
mass from combinations belonging to
the
L
c
1
signal and sideband regions. The region above 1.06 GeV/
c
2
is not included in the fit because of
K
*
0
feed-up when the
p
is
misidentified as a
K
.
FIG. 5. Invariant mass of
pK
2
p
1
combinations found in the
same data sample. The
L
c
1
!
pK
2
p
1
signal is used for normaliza-
tion of the
L
c
1
!
p
f
branching ratio.
53
R1015
OBSERVATION OF THE CABIBBO-SUPPRESSED CHARMED . . .
the
L
c
1
signal and sideband regions. This gives 56
6
22
events for the
L
c
1
!
p
f
signal, which is in agreement with
the first method.
A check is also made for a possible reflection from
D
s
1
!
f
p
1
, where the pion is misidentified as a proton. It is
found that the reflection is a broad enhancement in the mass
region above the signal. The effect of this background is
minimized by the tight particle-ID requirement on the pro-
ton. Consequently, the overall fake rate is less than 1%, caus-
ing negligible reduction of the
L
c
1
!
p
f
signal yield from
the fit.
The decay
L
c
1
!
pK
2
p
1
is used as the normalization
mode for the
L
c
1
!
p
f
relative branching ratio. In finding
the
L
c
1
!
pK
2
p
1
yield, the same cuts are applied as in the
L
c
1
!
pK
2
K
1
analysis to minimize systematic errors, ex-
cept that the particle ID for the
p
1
is loosened to a consis-
tency requirement:
P
p
.
0.001. The
L
c
1
!
pK
2
p
1
mass
spectrum is shown in Fig. 5. The parametrization of the fit is
the same as the
L
c
1
!
p
f
mass fit in Fig. 3, except that the
width of the Gaussian is allowed to vary. The fit yields
5683
6
138 observed signal events with a mean of
2286.8
6
0.2 MeV/
c
2
and a width of 6.4
6
0.2 MeV/
c
2
. If the
width of the Gaussian is fixed to the Monte Carlo prediction
of 5.8 MeV/
c
2
, the yield changes by 4%. This dependence is
included in the systematic error.
Monte Carlo simulation is used to determine all aspects of
the detection efficiency except particle ID. The particle-ID
efficiency for protons is obtained using a sample of 33 000
L
!
p
p
2
decays with a signal-to-background ratio of 50:1
@
14
#
. For protons thus identified, the momentum spectrum
after the particle-ID cuts (
L
p
.
0.9,
P
p
.
0.001) is divided by
the momentum spectrum before these cuts, bin by bin, yield-
ing the particle-ID efficiencies versus momentum. The mea-
sured particle-ID efficiency is incorporated into the Monte
Carlo simulation by randomly rejecting the corresponding
fraction of tracks in each momentum bin. The particle-ID
(
L
K
.
0.1,
P
K
.
0.001) efficiency for the kaons is derived in
an analogous manner, except that the kaons are taken from
D
*
decays through the cascade process
D
*
1
!
D
0
p
1
,
D
0
!
K
2
p
1
. A sample of 11 000 such
D
0
!
K
2
p
1
decays
is obtained with an 8:1 signal-to-background ratio
@
14
#
. The
particle-ID efficiency for protons is near 90% from 300
MeV/
c
to 1.1 GeV/
c
falling off to below 10% by 2.5 GeV/
c
.
For kaons the particle-ID efficiency remains relatively flat at
about 95%.
Using a Monte Carlo sample of
L
c
1
!
p
f
decays, where
the
L
c
1
fragmentation takes place according to the Lund
JETSET
Monte Carlo simulation
@
15
#
, the full detection effi-
ciency is determined, with the particle-ID portion folded in
as described above. For
L
c
1
!
p
f
, the overall efficiency is
0.178
6
0.004 including the particle-ID efficiency which is
0.425
6
0.011. For
L
c
1
!
pK
2
K
1
and
L
c
1
!
pK
2
p
1
the
overall efficiencies are 0.216
6
0.005 and 0.224
6
0.005, re-
spectively.
Since for all the decay modes the requirement
x
p
.
0.5
is applied, the relative branching ratio for each mode is
found simply by dividing the corrected yields. Table I
gives the details, listing only the statistical errors. The es-
timates for the main sources of systematic error include
the
L
c
1
!
p
f
and
L
c
1
!
pK
2
K
1
signal shapes
~
7% and
11%, respectively
!
and background shapes
~
2% and
10%,
respectively
!
,
particle-ID
efficiency
~
6%
!
,
and
the
L
c
1
!
pK
2
p
1
fit
~
4%
!
.
In
addition,
for
the
L
c
1
!
p
f
mode, varying the
f
signal and sideband regions
gives a 5% variation in the yield. Finally, there is a
1.8% contribution to the
L
c
1
!
p
f
systematic error from
the
f
!
K
2
K
1
branching ratio uncertainty. Thus we esti-
mate 12% systematic error in
B
(
p
f
)/
B
(
pK
p
) , 17%
in
B
(
pKK
)/
B
(
pK
p
) , and 18% in
B
(
p
f
)/
B
(
pKK
).
The final results appear in Table II, along with those
from NA32
@
9
#
and E687
@
10
#
and theoretical predictions
from Cheng and Tseng
@
5
#
,Ko
̈
rner and Kra
̈
mer
@
6
#
,
Z
̇
enczykowski
@
7
#
, and Datta
@
8
#
. From Table I we also
find
B
(
L
c
1
!
pK
2
K
1
@
non-
f
#!
5
0.029
6
0.010
6
0.005 for
L
c
1
!
pK
2
K
1
decays not arising from
L
c
1
!
p
f
.
In summary, we have observed the Cabibbo-suppressed
decays
L
c
1
!
p
f
and
L
c
1
!
pK
2
K
1
. The results appear in
Table II, which show that the phenomenological treatments
TABLE I. Calculation of the branching ratios for
L
c
1
!
p
f
and
L
c
1
!
pK
2
K
1
relative to
L
c
1
!
pK
2
p
1
and
L
c
1
!
pK
2
K
1
. The
errors are statistical only.
Decay mode:
L
c
1
!
p
f
L
c
1
!
pK
2
K
1
L
c
1
!
pK
2
p
1
Raw yield
54
6
13
214
6
50
5683
6
138
Efficiency
0.178
6
0.004
0.216
6
0.005
0.224
6
0.005
B
(
f
!
K
2
K
1
)
0.491
6
0.005
Corr. yield
618
6
138
991
6
233
25371
6
837
B
/
B
(
pK
2
p
1
) 0.024
6
0.006
0.039
6
0.009
1
B
/
B
(
pK
2
K
1
)
0.62
6
0.20
1
TABLE II. Final results on
L
c
1
!
p
f
and
L
c
1
!
pK
2
K
1
.
Ratio of interest
B
(
p
f
)/
B
(
pK
2
p
1
)
B
(
p
f
)/
B
(
pK
2
K
1
)
B
(
pK
2
K
1
)/
B
(
pK
2
p
1
)
This experiment
0.024
6
0.006
6
0.003
0.62
6
0.20
6
0.12
0.039
6
0.009
6
0.007
NA32
@
9
#
0.04
6
0.03
E687
@
10
#
,
0.58 at 90% C.L.
0.096
6
0.029
6
0.010
Cheng and Tseng
@
5
#
0.045
6
0.011
Z
̇
enczykowski
0.023
Ko
̈
rner and Kra
̈
mer
@
6
#
0.05
Datta
@
8
#
0.01
a
Reference
@
7
#
, using Ref.
@
1
#
for
B
(
L
c
1
!
pK
2
p
1
).
R1016
53
J. P. ALEXANDER
et al.
of the
L
c
1
!
p
f
decay rate agree within a factor of 2 or 3
with
our
result.
Our
measured
branching
ratio
B
(
p
f
)/
B
(
pKK
) is consistent with the E687 upper limit,
while our measurement of
B
(
pKK
)/
B
(
pK
p
) differs from
the E687 result by 1.7
s
. Within the factorization approach
using a 1/
N
c
expansion, our result supports the validity of
taking the large
N
c
limit in charm baryon decays.
We gratefully acknowledge the effort of the CESR staff
in providing us with excellent luminosity and running con-
ditions. This work was supported by the National Science
Foundation, the U.S. Department of Energy, the Heisenberg
Foundation, the Alexander von Humboldt Stiftung, the Natu-
ral Sciences and Engineering Research Council of Canada,
and the A. P. Sloan Foundation.
@
1
#
Particle Data Group, L. Montanet
et al.
, Phys. Rev. D
50
, 1173
~
1994
!
.
@
2
#
Unless otherwise specified, reference to a state also implies
reference to the charge conjugate state.
@
3
#
A. J. Buras, J.-M. Ge
́
rard, and R. Ru
̈
ckl, Nucl. Phys.
B268
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~
1986
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@
4
#
M. Bauer, B. Stech, and M. Wirbel, Z. Phys. C
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1987
!
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5
#
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@
6
#
J. G. Ko
̈
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̈
mer, Z. Phys. C
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, 659
~
1992
!
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@
7
#
P. Z
̇
encykowski, Phys. Rev. D
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, 402
~
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!
.
@
8
#
A. Datta, Report No. UH-511-824-95, April 1995
~
unpub-
lished
!
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@
9
#
S. Barlag
et al.
, Z. Phys. C
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!
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@
10
#
P. L. Frabetti
et al.
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!
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@
11
#
Y. Kubota
et al.
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~
1992
!
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@
12
#
The Monte Carlo simulation employs the CERN
GEANT
pack-
age: R. Brun
et al.
,
GEANT 3.14
, CERN DD/EE/84-1.
@
13
#
The quoted uncertainties in mass measurements refer to statis-
tical error only.
@
14
#
The remaining background is removed by sideband subtrac-
tion.
@
15
#
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53
R1017
OBSERVATION OF THE CABIBBO-SUPPRESSED CHARMED . . .