Search for color-suppressed
B
hadronic decay processes at the
Y
Ñ
4
S
Ö
resonance
B. Nemati, S. J. Richichi, W. R. Ross, and P. Skubic
University of Oklahoma, Norman, Oklahoma 73019
M. Bishai, J. Fast, J. W. Hinson, N. Menon, D. H. Miller, E. I. Shibata, I. P. J. Shipsey, and M. Yurko
Purdue University, West Lafayette, Indiana 47907
S. Glenn, S. D. Johnson, Y. Kwon,
*
S. Roberts, and E. H. Thorndike
University of Rochester, Rochester, New York 14627
C. P. Jessop, K. Lingel, H. Marsiske, M. L. Perl, V. Savinov, D. Ugolini, R. Wang, and X. Zhou
Stanford Linear Accelerator Center, Stanford University, Stanford, California 94309
T. E. Coan, V. Fadeyev, I. Korolkov, Y. Maravin, I. Narsky, V. Shelkov, J. Staeck, R. Stroynowski, I. Volobouev, and
J. Ye
Southern Methodist University, Dallas, Texas 75275
M. Artuso, A. Efimov, M. Goldberg, D. He, S. Kopp, G. C. Moneti, R. Mountain, S. Schuh, T. Skwarnicki, S. Stone,
G. Viehhauser, and X. Xing
Syracuse University, Syracuse, New York 13244
J. Bartelt, S. E. Csorna, V. Jain,
†
K. W. McLean, and S. Marka
Vanderbilt University, Nashville, Tennessee 37235
R. Godang, K. Kinoshita, I. C. Lai, P. Pomianowski, and S. Schrenk
Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061
G. Bonvicini, D. Cinabro, R. Greene, L. P. Perera, and G. J. Zhou
Wayne State University, Detroit, Michigan 48202
B. Barish, M. Chadha, S. Chan, G. Eigen, J. S. Miller, C. O’Grady, M. Schmidtler, J. Urheim,
A. J. Weinstein, and F. Wu
̈
rthwein
California Institute of Technology, Pasadena, California 91125
D. W. Bliss, G. Masek, H. P. Paar, S. Prell, and V. Sharma
University of California, San Diego, La Jolla, California 92093
D. M. Asner, J. Gronberg, T. S. Hill, D. J. Lange, S. Menary, R. J. Morrison, H. N. Nelson, T. K. Nelson, C. Qiao,
J. D. Richman, D. Roberts, A. Ryd, and M. S. Witherell
University of California, Santa Barbara, California 93106
R. Balest, B. H. Behrens, W. T. Ford, H. Park, J. Roy, and J. G. Smith
University of Colorado, Boulder, Colorado 80309-0390
J. P. Alexander, C. Bebek, B. E. Berger, K. Berkelman, K. Bloom, D. G. Cassel, H. A. Cho, D. S. Crowcroft, M. Dickson,
P. S. Drell, K. M. Ecklund, R. Ehrlich, A. D. Foland, P. Gaidarev, L. Gibbons, B. Gittelman, S. W. Gray, D. L. Hartill,
B. K. Heltsley, P. I. Hopman, J. Kandaswamy, P. C. Kim, D. L. Kreinick, T. Lee, Y. Liu, N. B. Mistry, C. R. Ng,
E. Nordberg, M. Ogg,
‡
J. R. Patterson, D. Peterson, D. Riley, A. Soffer, B. Valant-Spaight, and C. Ward
Cornell University, Ithaca, New York 14853
M. Athanas, P. Avery, C. D. Jones, M. Lohner, C. Prescott, J. Yelton, and J. Zheng
University of Florida, Gainesville, Florida 32611
G. Brandenburg, R. A. Briere, A. Ershov, Y. S. Gao, D. Y.-J. Kim, R. Wilson, and H. Yamamoto
Harvard University, Cambridge, Massachusetts 02138
T. E. Browder, Y. Li, and J. L. Rodriguez
University of Hawaii at Manoa, Honolulu, Hawaii 96822
PHYSICAL REVIEW D
1 MAY 1998
VOLUME 57, NUMBER 9
57
0556-2821/98/57
~
9
!
/5363
~
7
!
/$15.00
5363
© 1998 The American Physical Society
T. Bergfeld, B. I. Eisenstein, J. Ernst, G. E. Gladding, G. D. Gollin, R. M. Hans, E. Johnson, I. Karliner, M. A. Marsh,
M. Palmer, M. Selen, and J. J. Thaler
University of Illinois, Champaign-Urbana, Illinois 61801
K. W. Edwards
Carleton University, Ottawa, Ontario, Canada K1S 5B6
and the Institute of Particle Physics, Canada
A. Bellerive, R. Janicek, D. B. MacFarlane, and P. M. Patel
McGill University, Montre
́
al, Que
́
bec, Canada H3A 2T8 and the Institute of Particle Physics, Canada
A. J. Sadoff
Ithaca College, Ithaca, New York 14850
R. Ammar, P. Baringer, A. Bean, D. Besson, D. Coppage, C. Darling, R. Davis, N. Hancock, S. Kotov,
I. Kravchenko, and N. Kwak
University of Kansas, Lawrence, Kansas 66045
S. Anderson, Y. Kubota, S. J. Lee, J. J. O’Neill, S. Patton, R. Poling, T. Riehle, and A. Smith
University of Minnesota, Minneapolis, Minnesota 55455
M. S. Alam, S. B. Athar, Z. Ling, A. H. Mahmood, H. Severini, S. Timm, and F. Wappler
State University of New York at Albany, Albany, New York 12222
A. Anastassov, J. E. Duboscq, D. Fujino,
§
K. K. Gan, T. Hart, K. Honscheid, H. Kagan, R. Kass, J. Lee, M. B. Spencer,
M. Sung, A. Undrus,
i
R. Wanke, A. Wolf, and M. M. Zoeller
Ohio State University, Columbus, Ohio 43210
~
CLEO Collaboration
!
~
Received 28 August 1997; published 30 March 1998
!
Using 3.1 fb
2
1
of data accumulated at the
Y
(4
S
) by the CLEO-II detector, corresponding to 3.3
3
10
6
BB
̄
pairs, we have searched for the color-suppressed
B
hadronic decay processes
B
̄
0
!
D
0
(
D
*
0
)X
0
, where X
0
is a
light neutral meson
p
0
,
r
0
,
h
,
h
8
or
v
. The
D
*
0
mesons are reconstructed in
D
*
0
!
D
0
p
0
and the
D
0
mesons
in
D
0
!
K
2
p
1
,
K
2
p
1
p
0
and
K
2
p
1
p
1
p
2
decay modes. No obvious signal is observed. We set 90% C.L.
upper limits on these modes, varying from 1.2
3
10
2
4
for
B
̄
0
!
D
0
p
0
to 1.9
3
10
2
3
for
B
̄
0
!
D
*
0
h
8
.
@
S0556-2821
~
98
!
05209-6
#
PACS number
~
s
!
: 13.25.Hw, 13.30.Eg, 14.40.Nd
I. INTRODUCTION
The
B
hadronic decays
B
̄
0
!
D
0
(
D
*
0
)X
0
, where X
0
is a
light neutral meson
p
0
,
r
0
,
h
,
h
8
or
v
, have not yet been
observed. These decays proceed via the internal spectator
diagram shown in Fig. 1.
The internal spectator decays are expected to be sup-
pressed relative to the decays that proceed via external spec-
tator diagrams, since the color of the quarks from the virtual
W
must match the color of the
c
quark and the accompany-
ing spectator antiquark. Therefore these decays are referred
to as color-suppressed decays, while decays via external
spectator diagrams are referred to as color-favored decays.
Measurements of these color-suppressed decays allow tests
of the factorization
@
1
#
hypothesis and provide useful infor-
mation on the scale of strong final-state interactions in the
B
meson system.
Previous CLEO papers
@
2
#
reported upper limits on these
color-suppressed
B
hadronic decays. Here we present new
results using the full CLEO-II data set and an improved
analysis method.
II. DATA SAMPLE AND EVENT SELECTION
The data used in this analysis were produced in
e
1
e
2
annihilations at the Cornell Electron Storage Ring
~
CESR
!
and collected with the CLEO-II detector
@
3
#
. The integrated
luminosity is 3.1 fb
2
1
at the
Y
(4
S
) resonance, which corre-
sponds to ( 3.32
6
0.07)
3
10
6
BB
̄
pairs, and 1.6 fb
2
1
at ener-
gies just below
BB
̄
threshold
~
henceforth referred to as the
continuum
!
.
Hadronic events are selected by requiring at least three
charged tracks, a total detected energy of at least 0.15
E
c.m.
,
and a primary vertex within 5.0 cm along the beam (
z
) axis
*
Permanent address: Yonsei University, Seoul 120-749, Korea.
†
Permanent address: Brookhaven National Laboratory, Upton,
NY 11973.
‡
Permanent address: University of Texas, Austin TX 78712
§
Permanent address: Lawrence Livermore National Laboratory,
Livermore, CA 94551.
i
Permanent address: BINP, RU-630090 Novosibirsk, Russia.
5364
57
B. NEMATI
et al.
of the interaction point. To suppress the continuum back-
ground, we require that the ratio of second to zeroth Fox-
Wolfram moments R
2
@
4
#
determined using charged tracks
and unmatched neutral showers be less than 0.3
~
0.5 for
clean decay modes involving
h
or
h
8
!
. To further reduce the
continuum background, we then require that the cosine of the
angle between the sphericity axis of the
B
meson candidate
and the sphericity axis of the remainder of the event satisfy
u
cos(
u
sphericity
)
u
,
0.8
~
0.9 for decay modes involving
h
or
h
8
!
. For a jet-like continuum event, the two axes are almost
parallel, while they are almost uncorrelated for a
BB
̄
event,
III.
B
RECONSTRUCTION
A. Selection of
D
0
and
D
*
0
candidates
The
D
0
candidates are reconstructed in the decay modes
D
0
!
K
2
p
1
,
K
2
p
1
p
0
and
K
2
p
1
p
1
p
2
~
charge-conjugate
modes are implied
!
. The
p
0
candidates are formed by com-
bining two showers whose invariant mass is within 2.5
s
of
the
p
0
mass
~
where henceforth
s
denotes rms resolution
!
.
Charged tracks are required to be consistent with coming
from the interaction region in both the
r
-
f
and
r
-
z
planes.
The measured specific ionization
~
dE/dx
!
of charged kaon
and pion candidates is required to be consistent to within 2
s
for kaon candidates and 3
s
for pion candidates. Charged
tracks are required to have a momentum greater than 250
MeV for
D
0
!
K
2
p
1
and
D
0
!
K
2
p
1
p
0
candidates and
200 MeV for
D
0
!
K
2
p
1
p
1
p
2
candidates. For the
D
0
!
K
2
p
1
p
0
decay mode, we select regions of the Dalitz plot
with large amplitude to further suppress the combinatoric
backgrounds. The invariant mass of
D
0
candidates is re-
quired to be within 2.0
s
of the nominal
D
0
mass.
The
D
*
0
candidates are reconstructed using the decay
mode
D
*
0
!
D
0
p
0
. We form
D
*
0
candidates by
D
0
candi-
dates using the above selection, then require that the
D
*
0
2
D
0
mass difference be within 2.5
s
of the measured value
@
5
#
.
B. Selection of the light neutral meson X
0
We reconstruct
p
0
candidates as described previously.
The
r
0
candidates are reconstructed in the mode
r
0
!
p
1
p
2
.
Candidate
h
and
h
8
mesons are reconstructed in their
h
!
gg
and
h
8
!
h
p
1
p
2
decay modes. The absolute value of
the cosine of the
h
decay angle is required to be less than
0.85 to remove asymmetric candidates which are primarily
background. The invariant mass of each
h
and
h
8
candidate
must be within 30 MeV of their nominal mass.
The
v
mesons are reconstructed in the decay mode
v
!
p
1
p
2
p
0
. Charged and neutral pions are required to have
momenta greater than 250 MeV, to reject soft pions from
D
*
0
or
D
*
1
decays. The
v
candidates are also required to
be within 30 MeV of the nominal
v
mass.
All charged pion candidates used in X
0
reconstruction are
required to have a measured dE/dx within 3
s
of the expected
value for pions.
C. Selection of the
B
candidates
The
D
(
*
)0
candidates are combined with a light X
0
to
form a
B
meson. At CLEO the energy of the
B
meson is the
same as the beam energy and the measured beam energy is
more precise than the reconstructed
B
meson energy. Full
reconstruction of
B
mesons at CLEO makes use of this fact
by defining two variables. One is the beam-constrained mass,
M
B
[
A
E
beam
2
2
P
obser
v
ed
2
. The other one is the difference be-
tween the reconstructed energy and the beam energy,
D
E
[
E
obser
v
ed
2
E
beam
. The
D
E
variable is sensitive to missing
or extra particles in the
B
decay, as well as particle species.
For fully reconstructed
B
meson decays, the M
B
distribution
peaks at 5.28 GeV with a resolution around 2.7 MeV, and
D
E
peaks at 0.0 GeV with a resolution ranging from 18 to 50
MeV, depending on the
B
and
D
0
decay modes.
Since signal and background are in general much better
separated in
D
E
than in M
B
, instead of cutting on the
D
E
variable and fitting M
B
as in previous analyses, we cut on
M
B
and fit the
D
E
distribution for the signal yield.
IV. BACKGROUND STUDY
In our search for the color-suppressed
B
hadronic decay
modes
B
̄
0
!
D
(
*
)0
(
p
0
,
r
0
,
h
,
h
8
,
v
) , there are backgrounds
to these decays from continuum and
BB
̄
events. The con-
tinuum backgrounds are suppressed using event-shape vari-
ables. They are not expected to show any structure in the
D
E
distributions. The 1.6 fb
2
1
continuum data set is used to
monitor the continuum background levels. We find the con-
tinuum background level to be very low for all color-
suppressed modes. No accumulation around
D
E
5
0 is ob-
served in the continuum data.
The backgrounds from
BB
̄
events are dominated by
feedthrough from color-favored two-body hadronic decays
of the type
B
2
!
D
0
~
p
2
,
r
2
,
a
1
2
!
,
B
2
!
D
*
0
~
p
2
,
r
2
,
a
1
2
!
,
B
̄
0
!
D
1
~
p
2
,
r
2
,
a
1
2
!
,
B
̄
0
!
D
*
1
~
p
2
,
r
2
,
a
1
2
!
.
The branching ratios of these color-favored
B
meson decay
modes were measured previously by CLEO
@
2
#
. In most
cases the background arises when a real, energetic
D
0
or
D
*
0
from the two-body color-favored decays is combined
with a fake light meson.
The backgrounds from these color-favored processes can
have structure in the M
B
and
D
E
distributions, depending on
which color-suppressed mode is being analyzed. Particularly
important are color-favored
B
meson decays that give ex-
actly the same final state particles as our color-suppressed
signals do. Neither misidentification nor additional particles
are needed for those color-favored decays to fake some sig-
nal modes. Therefore, the M
B
distribution from these physics
FIG. 1. Internal spectator diagram of
B
hadronic decays
B
̄
0
!
D
0
(
D
*
0
)X
0
.
57
5365
SEARCH FOR COLOR-SUPPRESSED
B
HADRONI
C...
background peaks at 5.28 GeV while its
D
E
distribution
peaks at 0.0 GeV, exactly as the color-suppressed signal.
While
D
0
p
0
is not susceptible to this background
D
0
r
0
and
D
0
v
are, as shown below:
color-suppressed:
B
̄
0
!
D
0
r
0
!
D
0
p
1
p
2
,
B
̄
0
!
D
0
v
!
D
0
p
1
p
2
p
0
,
color-favored:
B
̄
0
!
D
*
1
p
2
!
D
0
p
1
p
2
,
B
̄
0
!
D
*
1
r
2
!
D
0
p
1
p
2
p
0
.
Another background that can show structure is color-
favored decay in which one of the final state particles is lost.
Examples include:
color-suppressed:
B
̄
0
!
D
0
p
0
,
B
̄
0
!
D
0
r
0
!
D
0
p
1
p
2
,
color-favored:
B
2
!
D
0
r
2
!
D
0
p
0
~
p
2
!
,
B
̄
0
!
D
*
1
r
2
!
D
0
p
1
p
2
~
p
0
!
.
These background events can peak in M
B
around 5.28 GeV
when the missing
p
2
or
p
0
from the
r
2
decay is very soft
and does not contribute much to the beam-constrained mass
FIG. 2.
D
E
distributions of
B
̄
0
!
D
0
p
0
and
B
̄
0
!
D
*
0
p
0
decay
modes. Solid histograms are the
D
E
distributions of the 3.1 fb
2
1
of
data collected on the
Y
(4
S
) resonance, which are fit using back-
ground and signal functions. Dashed histograms are from the
1.6 fb
2
1
continuum data sample.
FIG. 3.
D
E
distributions of
B
̄
0
!
D
0
r
0
and
B
̄
0
!
D
*
0
r
0
decay
modes. Solid histograms are the
D
E
distributions of the 3.1 fb
2
1
of
data collected on the
Y
(4
S
) resonance, which are fit using back-
ground and signal functions. Dashed histograms are from the
1.6 fb
2
1
continuum data sample.
TABLE I. Selection efficiencies and yields of all color-suppressed modes. The three efficiencies and
yields of each
B
̄
0
!
D
0
(
D
*
0
)
X
0
correspond to the three
D
0
!
K
2
p
1
,
K
2
p
1
p
0
and
K
2
p
1
p
1
p
2
modes.
Decay mode
Selection
efficiencies
~
3
D
0
submodes
!
Yields
~
3
D
0
submodes
!
B
̄
0
!
D
0
p
0
( 26.1
6
2.2) , ( 7.8
6
1.0) , ( 12.5
6
1.3) %
2
0.3
6
6.4,
2
6.7
6
4.3,
2
3.3
6
7.0
B
̄
0
!
D
*
0
p
0
( 14.1
6
1.8) , ( 3.7
6
0.7) , ( 5.4
6
0.9) %
2.5
6
2.6, 5.0
6
3.4,
2
1.2
6
3.4
B
̄
0
!
D
0
r
0
( 8.4
6
0.4) , ( 2.6
6
0.3) , ( 3.9
6
0.3) %
1.4
6
3.0,
2
3.0
6
4.3, 3.1
6
5.0
B
̄
0
!
D
*
0
r
0
( 4.0
6
0.4) , ( 1.0
6
0.2) , ( 1.5
6
0.2) %
2
1.0
6
1.4, 1.4
6
1.6, 0.8
6
1.3
B
̄
0
!
D
0
h
( 24.5
6
3.0) , ( 7.0
6
1.2) , ( 11.4
6
1.6) %
2
1.4
6
2.0,
2
3.1
6
3.1,
2
6.0
6
4.0
B
̄
0
!
D
*
0
h
( 10.5
6
1.8) , ( 3.4
6
0.8) , ( 4.9
6
0.9) %
0, 0, 0
B
̄
0
!
D
0
h
8
( 13.4
6
1.9) , ( 3.6
6
0.7) , ( 5.9
6
1.0) %
0, 0.8
6
2.2, 1.8
6
3.0
B
̄
0
!
D
*
0
h
8
( 5.9
6
1.1) , ( 1.7
6
0.4) , ( 2.5
6
0.5) %
0, 0, 1
B
̄
0
!
D
0
v
( 12.4
6
1.3) , ( 2.8
6
0.4) , ( 3.2
6
0.5) %
2
4.1
6
4.0, 6.2
6
3.8, 3.6
6
5.6
B
̄
0
!
D
*
0
v
( 4.8
6
0.7) , ( 1.0
6
0.2) , ( 1.3
6
0.2) %
1.8
6
1.2, 0.8
6
1.8,
2
0.2
6
1.2
5366
57
B. NEMATI
et al.
calculation. However, the
D
E
for these background events
differs from zero by more than one pion mass, due to the
missing
p
2
or
p
0
from the
r
2
decay. For these types of
color-favored backgrounds, the color-suppressed signals are
much better separated from background in
D
E
.
For decay modes involving
h
or
h
8
, combinatoric back-
ground is the dominating source. Therefore, backgrounds for
these color-suppressed processes have no accumulation in
the M
B
and
D
E
distributions.
For
B
̄
0
!
D
*
0
X
0
, there is no corresponding color-favored
B
meson decay that fakes our signal as
B
̄
0
!
D
*
1
p
2
fakes
B
̄
0
!
D
0
r
0
. Also the background level from color-favored
B
meson decays is very low for
B
̄
0
!
D
*
0
X
0
decay processes,
due to the good resolution on the
D
*
0
2
D
0
mass difference.
Almost all the discrimination power against color-favored
physics backgrounds come from selection cuts on X
0
.We
make full use of mass, momentum, decay angle and other
kinematic variables of X
0
to suppress backgrounds while
keeping the signal efficiency as high as possible.
The X
0
candidates in
B
̄
0
!
D
(
*
)0
X
0
are very energetic due
to the hard spectrum of two-body
B
meson decays. We re-
quire the momentum of the
p
0
candidate to range from 2.1
GeV to 2.5 GeV. Similar momentum requirements are im-
posed on the other light neutral meson X
0
candidates.
For
B
̄
0
!
D
0
r
0
decays, there are color-favored physics
backgrounds from
B
̄
0
!
D
*
1
p
2
that give exactly the same
final state particles. The
B
2
!
D
0
r
2
decay can also fake our
color-suppressed signal by substituting the soft
p
0
from
r
2
decay by a soft
p
1
from the other
B
meson. In these physics
backgrounds, the
p
2
is always much more energetic than the
p
1
from
D
*
1
!
D
0
p
1
decay. There exists a correlation be-
tween the
D
0
and the fast
p
2
~
slow
p
1
!
from the fake
r
0
.
To suppress these physics backgrounds, we require the
D
0
candidate to be associated with a fast
p
1
~
slow
p
2
!
from the
r
0
candidate. There is still a contribution from color-favored
physics backgrounds even after this requirement, because a
FIG. 4.
D
E
distributions of
B
̄
0
!
D
0
h
and
B
̄
0
!
D
*
0
h
decay
modes. Solid histograms are the
D
E
distributions of the 3.1 fb
2
1
of
data collected on the
Y
(4
S
) resonance, which are fit using back-
ground and signal functions. Dashed histograms are from the
1.6 fb
2
1
continuum data sample.
FIG. 5.
D
E
distributions of
B
̄
0
!
D
0
h
8
and
B
̄
0
!
D
*
0
h
8
decay
modes. Solid histograms are the
D
E
distributions of the 3.1 fb
2
1
of
data collected on the
Y
(4
S
) resonance, which are fit using back-
ground and signal functions. Dashed histograms are from the
1.6 fb
2
1
continuum data sample.
FIG. 6.
D
E
distributions of
B
̄
0
!
D
0
v
and
B
̄
0
!
D
*
0
v
decay
modes. Solid histograms are the
D
E
distributions of the 3.1 fb
2
1
of
data collected on the
Y
(4
S
) resonance, which are fit using back-
ground and signal functions. Dashed histograms are from the
1.6 fb
2
1
continuum data sample.
57
5367
SEARCH FOR COLOR-SUPPRESSED
B
HADRONI
C...
D
0
decay has a certain chance of being misidentified as a
D
̄
0
decay. For the
D
0
’s from our signal process, together with
the dE/dx and
D
0
mass requirements, this misidentification
rate is determined to be less than 20%. After further suppres-
sion due to the
r
0
mass and momentum requirements, the
contribution from color-favored physics backgrounds is neg-
ligible. Since the
r
0
from
B
̄
0
!
D
0
r
0
decay is longitudinally
polarized, we also cut on the
r
0
decay angle
~
the angle be-
tween the direction of the pion in the
r
0
rest frame and the
direction of the
r
0
in the laboratory frame
!
to reduce combi-
natoric backgrounds.
Similarly for
B
̄
0
!
D
0
v
decays where
v
!
p
1
p
2
p
0
,
there are color-favored physics backgrounds from
B
̄
0
!
D
*
1
r
2
where
r
2
!
p
2
p
0
that give exactly the same fi-
nal state particles. Because the momentum of the soft
p
1
from the
D
*
1
!
D
0
p
1
decay cannot exceed 250 MeV due
to the kinematics, we can get rid of these color-favored phys-
ics backgrounds by requiring that each pion from the
v
!
p
1
p
2
p
0
candidate have momentum greater than 250
MeV. An additional track from the other
B
meson is then
needed to combine with
B
̄
0
!
D
*
1
r
2
or
B
2
!
D
0
r
2
back-
grounds to fake the
B
̄
0
!
D
0
v
signal. With further suppres-
sion due to the
v
mass requirement, the contribution from
these backgrounds is negligible.
Signal selection efficiencies for all the color-suppressed
decay modes are shown in Table I. The systematic error due
to the detection of charged and neutral tracks, together with
the Monte Carlo statistical error, is included in the error on
the efficiency for each decay mode.
V. RESULTS
The
D
E
distributions for the
Y
(4
S
) and continuum data
samples of all the color-suppressed signal processes after all
cuts are shown in Figs. 2–6. The
D
E
distribution of each
color-suppressed mode is fit with a Gaussian and a back-
ground shape function. The mean value and width of the
Gaussian distribution are fixed with values determined from
signal Monte Carlo simulation. We use various color-favored
decay modes
B
2
!
D
0
p
2
,
B
2
!
D
0
r
2
,
B
2
!
D
*
0
p
2
,
B
2
!
D
*
0
r
2
,
B
̄
0
!
D
1
p
2
,
B
̄
0
!
D
1
r
2
to check that the
D
E
resolutions in the data and Monte Carlo simulation agree
well. Possible differences between the data and Monte Carlo
simulation in the
D
E
distributions are considered and in-
cluded in the yield error as systematic errors.
Various
D
E
background shape functions have been used
to fit for the signal yield: a simple second-order polynomial
or a background shape using Monte Carlo simulation
BB
̄
events plus a continuum component represented by a second-
order polynomial. For the latter shape, the
BB
̄
contribution is
scaled to the known luminosity while the continuum compo-
nent is allowed to float. Our results are found to be insensi-
tive to different background shapes, and both of them de-
scribe the
D
E
distributions reasonably well. Differences in
the yield due to the choice of
D
E
background shape are
included in the yield error to account for the systematic un-
certainties. For each signal process with several
D
0
decay
submodes, the yield for each
D
0
submode is obtained sepa-
rately, since the
D
E
resolutions are different for the different
modes. The results are shown in Table I. The yields of the
D
0
submodes are added independently to get the total yield.
The formulas used to calculate the branching fractions
are:
B
~
B
̄
0
!
D
0
X
0
!
5
N
obs
N
BB
̄
3
@
(
i
5
1
3
efficiency
~
i
!
3
B
~
D
i
0
!
#
3
P
B
~
X
0
!
~
1
!
B
~
B
̄
0
!
D
*
0
X
0
!
5
N
obs
N
BB
̄
3
B
~
D
*
0
!
D
0
p
0
!
3
@
(
i
5
1
3
efficiency
~
i
!
3
B
~
D
i
0
!
#
3
P
B
~
X
0
!
~
2
!
TABLE II. Particle Data Group branching ratios that are used in
the upper limit calculation for color-suppressed
B
hadronic decays.
Decay mode
PDG
branching
ratio
Decay mode
PDG
branching
ratio
D
0
!
K
2
p
1
( 4.01
6
0.14) %
r
0
!
p
1
p
2
100%
D
0
!
K
2
p
1
p
0
( 13.8
6
1.0) %
h
!
gg
( 38.8
6
0.5) %
D
0
!
K
2
p
1
p
1
p
2
( 8.1
6
0.5) %
h
8
!
h
p
1
p
2
( 43.7
6
1.5) %
D
*
0
!
D
0
p
0
( 63.6
6
2.8) %
v
!
p
1
p
2
p
0
( 88.8
6
0.7) %
TABLE III. 90% C.L. upper limits in branching ratios
~
BR’s
!
of
all color-suppressed modes, together with comparison with theoret-
ical predictions in
@
6,7
#
.
Decay mode
BR upper limit
~
at 90% C.L.
!
Predictions
in
@
6
#
Predictions
in
@
7
#
B
̄
0
!
D
0
p
0
,
1.2
3
10
2
4
0.7
3
10
2
4
( 4.1
6
1.8)
3
10
2
4
B
̄
0
!
D
*
0
p
0
,
4.4
3
10
2
4
1.0
3
10
2
4
( 3.3
6
1.4)
3
10
2
4
B
̄
0
!
D
0
r
0
,
3.9
3
10
2
4
0.7
3
10
2
4
( 0.61
6
1.22)
3
10
2
4
B
̄
0
!
D
*
0
r
0
,
5.6
3
10
2
4
1.7
3
10
2
4
( 2.2
6
1.4)
3
10
2
4
B
̄
0
!
D
0
h
,
1.3
3
10
2
4
0.5
3
10
2
4
( 1.1
6
0.5)
3
10
2
4
B
̄
0
!
D
*
0
h
,
2.6
3
10
2
4
0.6
3
10
2
4
( 0.86
6
0.42)
3
10
2
4
B
̄
0
!
D
0
h
8
,
9.4
3
10
2
4
B
̄
0
!
D
*
0
h
8
,
19
3
10
2
4
B
̄
0
!
D
0
v
,
5.1
3
10
2
4
0.7
3
10
2
4
( 0.61
6
1.22)
3
10
2
4
B
̄
0
!
D
*
0
v
,
7.4
3
10
2
4
1.7
3
10
2
4
( 2.2
6
1.4)
3
10
2
4
5368
57
B. NEMATI
et al.
where
N
obs
is the total yield summed over the three
D
0
sub-
modes,
N
BB
̄
is the number of
BB
̄
pairs, efficiency
~
i
!
is the
selection efficiency for
B
̄
0
!
D
0
(
D
*
0
)
X
0
decay in the
i
th
D
0
submode,
B
(
D
i
0
) is the branching ratio of the
i
th
D
0
decay
mode, and
P
B
(
X
0
) is the product over all the relevant
branching fractions of the X
0
decay chain. Particle Data
Group values for
D
0
,
D
*
0
,
h
,
h
8
and
v
branching ratios
@
5
#
are used in the upper limits calculation and are listed in
Table II.
The upper limits of color-suppressed branching ratios are
determined by the method described in Sec. 17 of the Par-
ticle Data Group
@
5
#
. 90% C.L. upper limits on branching
ratios of color-suppressed
B
hadronic decay processes, to-
gether with theoretical predictions
@
6
#
, are shown in Table
III. Among all the decay modes, the upper limit for the
B
̄
0
!
D
0
p
0
mode is the lowest at 1.2
3
10
2
4
, which is lower
than predictions in
@
7
#
. All the other upper limits on branch-
ing ratios are still higher than theoretical predictions
@
6,7
#
.
Compared with factorization and QCD based calculations,
no dramatic enhancement of color-suppressed
B
hadronic de-
cay branching ratios is observed, indicating that there is no
sign of a large scale final-state interaction in these
B
meson
decay modes.
ACKNOWLEDGMENTS
We gratefully acknowledge the effort of the CESR staff in
providing us with excellent luminosity and running condi-
tions. J.P.A., J.R.P., and I.P.J.S. thank the NYI program of
the NSF, M.S. thanks the PFF program of the NSF, G.E.
thanks the Heisenberg Foundation, K.K.G., M.S., H.N.N.,
T.S., and H.Y. thank the OJI program of the DOE, J.R.P.,
K.H., M.S. and V.S. thank the A.P. Sloan Foundation, R.W.
thanks the Alexander von Humboldt Stiftung, and M.S.
thanks Research Corporation for support. This work was
supported by the National Science Foundation, the U.S. De-
partment of Energy, and the Natural Sciences and Engineer-
ing Research Council of Canada.
@
1
#
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6
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M. Neubert, V. Rieckert, B. Stech and Q. P. Xu, in
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Flavours
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~
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!
;
M.
Neubert
and
B.
Stech,
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57
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SEARCH FOR COLOR-SUPPRESSED
B
HADRONI
C...