of 5
V
OLUME
80, N
UMBER
19
PHYSICAL REVIEW LETTERS
11 M
AY
1998
Investigation of Semileptonic
B
Meson Decays to
p
-Wave Charm Mesons
A. Anastassov,
1
J. E. Duboscq,
1
D. Fujino,
1,
* K. K. Gan,
1
T. Hart,
1
K. Honscheid,
1
H. Kagan,
1
R. Kass,
1
J. Lee,
1
M. B. Spencer,
1
M. Sung,
1
A. Undrus,
1
R. Wanke,
1
A. Wolf,
1
M. M. Zoeller,
1
B. Nemati,
2
S. J. Richichi,
2
W. R. Ross,
2
P. Skubic,
2
M. Bishai,
3
J. Fast,
3
J. W. Hinson,
3
N. Menon,
3
D. H. Miller,
3
E. I. Shibata,
3
I. P. J. Shipsey,
3
M. Yurko,
3
S. Glenn,
4
S. D. Johnson,
4
Y. Kwon,
4,
S. Roberts,
4
E. H. Thorndike,
4
C. P. Jessop,
5
K. Lingel,
5
H. Marsiske,
5
M. L. Perl,
5
V. Savinov,
5
D. Ugolini,
5
R. Wang,
5
X. Zhou,
5
T. E. Coan,
6
V. Fadeyev,
6
I. Korolkov,
6
Y. Maravin,
6
I. Narsky,
6
V. Shelkov,
6
J. Staeck,
6
R. Stroynowski,
6
I. Volobouev,
6
J. Ye,
6
M. Artuso,
7
A. Efimov,
7
M. Goldberg,
7
D. He,
7
S. Kopp,
7
G. C. Moneti,
7
R. Mountain,
7
S. Schuh,
7
T. Skwarnicki,
7
S. Stone,
7
G. Viehhauser,
7
X. Xing,
7
J. Bartelt,
8
S. E. Csorna,
8
V. Jain,
8,
§
K. W. McLean,
8
S. Marka,
8
R. Godang,
9
K. Kinoshita,
9
I. C. Lai,
9
P. Pomianowski,
9
S. Schrenk,
9
G. Bonvicini,
10
D. Cinabro,
10
R. Greene,
10
L. P. Perera,
10
G. J. Zhou,
10
B. Barish,
11
M. Chadha,
11
S. Chan,
11
G. Eigen,
11
J. S. Miller,
11
C. O’Grady,
11
M. Schmidtler,
11
J. Urheim,
11
A. J. Weinstein,
11
F. Würthwein,
11
D. W. Bliss,
12
G. Masek,
12
H. P. Paar,
12
S. Prell,
12
V. Sharma,
12
D. M. Asner,
13
J. Gronberg,
13
T. S. Hill,
13
D. J. Lange,
13
S. Menary,
13
R. J. Morrison,
13
H. N. Nelson,
13
T. K. Nelson,
13
C. Qiao,
13
J. D. Richman,
13
D. Roberts,
13
A. Ryd,
13
M. S. Witherell,
13
R. Balest,
14
B. H. Behrens,
14
W. T. Ford,
14
H. Park,
14
J. Roy,
14
J. G. Smith,
14
J. P. Alexander,
15
C. Bebek,
15
B. E. Berger,
15
K. Berkelman,
15
K. Bloom,
15
D. G. Cassel,
15
H. A. Cho,
15
D. S. Crowcroft,
15
M. Dickson,
15
P. S. Drell,
15
K. M. Ecklund,
15
R. Ehrlich,
15
A. D. Foland,
15
P. Gaidarev,
15
L. Gibbons,
15
B. Gittelman,
15
S. W. Gray,
15
D. L. Hartill,
15
B. K. Heltsley,
15
P. I. Hopman,
15
S. L. Jones,
15
J. Kandaswamy,
15
P. C. Kim,
15
D. L. Kreinick,
15
T. Lee,
15
Y. Liu,
15
N. B. Mistry,
15
C. R. Ng,
15
E. Nordberg,
15
M. Ogg,
15,
k
J. R. Patterson,
15
D. Peterson,
15
D. Riley,
15
A. Soffer,
15
B. Valant-Spaight,
15
C. Ward,
15
M. Athanas,
16
P. Avery,
16
D. C. Jones,
16
M. Lohner,
16
C. Prescott,
16
J. Yelton,
16
J. Zheng,
16
G. Brandenburg,
17
R. A. Briere,
17
A. Ershov,
17
Y. S. Gao,
17
D. Y.-J. Kim,
17
R. Wilson,
17
H. Yamamoto,
17
T. E. Browder,
18
Y. Li,
18
J. L. Rodriguez,
18
T. Bergfeld,
19
B. I. Eisenstein,
19
J. Ernst,
19
G. E. Gladding,
19
G. D. Gollin,
19
R. M. Hans,
19
E. Johnson,
19
I. Karliner,
19
M. A. Marsh,
19
M. Palmer,
19
M. Selen,
19
J. J. Thaler,
19
K. W. Edwards,
20
A. Bellerive,
21
R. Janicek,
21
D. B. MacFarlane,
21
P. M. Patel,
21
A. J. Sadoff,
22
R. Ammar,
23
P. Baringer,
23
A. Bean,
23
D. Besson,
23
D. Coppage,
23
C. Darling,
23
R. Davis,
23
N. Hancock,
23
S. Kotov,
23
I. Kravchenko,
23
N. Kwak,
23
S. Anderson,
24
Y. Kubota,
24
S. J. Lee,
24
J. J. O’Neill,
24
S. Patton,
24
R. Poling,
24
T. Riehle,
24
A. Smith,
24
M. S. Alam,
25
S. B. Athar,
25
Z. Ling,
25
A. H. Mahmood,
25
H. Severini,
25
S. Timm,
25
and F. Wappler
25
(CLEO Collaboration)
1
Ohio State University, Columbus, Ohio 43210
2
University of Oklahoma, Norman, Oklahoma 73019
3
Purdue University, West Lafayette, Indiana 47907
4
University of Rochester, Rochester, New York 14627
5
Stanford Linear Accelerator Center, Stanford University, Stanford, California 94309
6
Southern Methodist University, Dallas, Texas 75275
7
Syracuse University, Syracuse, New York 13244
8
Vanderbilt University, Nashville, Tennessee 37235
9
Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061
10
Wayne State University, Detroit, Michigan 48202
11
California Institute of Technology, Pasadena, California 91125
12
University of California, San Diego, La Jolla, California 92093
13
University of California, Santa Barbara, California 93106
14
University of Colorado, Boulder, Colorado 80309-0390
15
Cornell University, Ithaca, New York 14853
16
University of Florida, Gainesville, Florida 32611
17
Harvard University, Cambridge, Massachusetts 02138
18
University of Hawaii at Manoa, Honolulu, Hawaii 96822
19
University of Illinois, Champaign-Urbana, Illinois 61801
20
Carleton University, Ottawa, Ontario, Canada K1S 5B6
and the Institute of Particle Physics, Canada
21
McGill University, Montréal, Québec, Canada H3A 2T8
and the Institute of Particle Physics, Canada
22
Ithaca College, Ithaca, New York 14850
23
University of Kansas, Lawrence, Kansas 66045
24
University of Minnesota, Minneapolis, Minnesota 55455
0031-9007
y
98
y
80(19)
y
4127(5)$15.00
© 1998 The American Physical Society
4127
V
OLUME
80, N
UMBER
19
PHYSICAL REVIEW LETTERS
11 M
AY
1998
25
State University of New York at Albany, Albany, New York 12222
(
Received 18 August 1997
)
We have studied semileptonic
B
meson decays with a
p
-wave charm meson in the final state
using
3.29
3
10
6
B
B
events collected with the CLEO II detector at the Cornell Electron-Positron
Storage Ring. We find a value for the exclusive semileptonic product branching fraction
B
s
B
2
!
D
0
1
,
2
n
,
d
B
s
D
0
1
!
D
p
1
p
2
d
s
0.373
6
0.085
6
0.052
6
0.024
d
%
and an upper limit for
B
s
B
2
!
D
p
0
2
,
2
n
,
d
B
s
D
p
0
2
!
D
p
1
p
2
d
,
0.16%
(90% C.L.). Furthermore, we present the first measurement of
the
q
2
spectrum for
B
2
!
D
0
1
,
2
n
,
.
[S0031-9007(98)06078-5]
PACS numbers: 13.20.He, 14.40.Lb, 14.40.Nd
There is general agreement among a number of mea-
surements of the exclusive semileptonic
B
meson decays,
B
!
D
,
n
,
and
B
!
D
p
,
n
,
. Together they account for
approximately 60% – 70% of the inclusive
B
!
X
,
n
,
branching fraction [1]. Since the branching fraction for
b
!
u
,
n
,
is known to be small, the missing exclusive
decays must be sought among
b
!
c
,
n
,
decays to higher
mass
D
J
states or nonresonant hadronic states with a
D
or
D
p
and other hadrons. Pioneering measurements by
ARGUS [2] and CLEO [3] indicate the possible presence
of resonant and nonresonant contributions from
D
p
,
n
,
and
D
p
p
,
n
,
in
B
decays. More recent measurements
from the CERN Large Electron-Positron Collider experi-
ments [4 – 6] confirm the presence of
D
p
and
D
p
p
states
in
B
semileptonic decays. Exclusive measurements of
B
2
!
D
0
1
,
2
n
,
and
B
2
!
D
p
0
2
,
2
n
,
have been reported
previously [4,5]. In this paper we report new measure-
ments of these two decay modes.
The
D
J
mesons contain one charm quark and one light
quark with relative angular momentum
L
1
. The quark
spins can sum to
S
0
or
S
1
, so there are four spin-
parity states given by
J
P
1
1
or
0
1
,
1
1
, and
2
1
. Parity
and angular momentum conservation restrict the decays
available to the four states. According to heavy quark
effective theory (HQET), there exists an approximate
spin-flavor symmetry for hadrons consisting of one heavy
and one light quark [7]. In the limit of infinite heavy
quark mass, such mesons are described by the total
angular momentum of the light constituents
j
S
q
1
L
.
In HQET, the
D
J
mesons make up two doublets,
j
1
y
2
and
j
3
y
2
. The members of the
j
3
y
2
doublet are
predicted to decay dominantly via
d
wave and to be
relatively narrow. The
j
1
y
2
mesons are predicted to
decay only in an
s
wave and to be relatively broad. In this
analysis we study the semileptonic decays of the
B
meson
to final states containing the narrow
s
j
3
y
2
d
excited
charm mesons: the
j
L
J
3
y
2
P
2
and
3
y
2
P
1
, called
D
p
2
and
D
1
, respectively [8].
The data used in this analysis were collected with the
CLEO II detector at the Cornell Electron-Positron Storage
Ring (CESR). The CLEO II detector [9] is a multipur-
pose high energy physics detector incorporating excellent
charged and neutral particle detection and measurement.
The data sample consists of an integrated luminosity of
3.11
fb
2
1
on the
Y
s
4
S
d
resonance (ON resonance), cor-
responding to
3.29
3
10
6
B
B
events, and
1.61
fb
2
1
at a
center-of-mass energy
,
55
MeV below the
Y
s
4
S
d
reso-
nance (OFF resonance).
The exclusive
B
2
!
D
0
J
,
2
n
,
decay is studied [10] by
reconstructing the decay channel
D
0
J
!
D
p
1
p
2
using the
decay chain
D
p
1
!
D
0
p
1
, and
D
0
!
K
2
p
1
or
D
0
!
K
2
p
1
p
0
[11]. Hadronic events are required to have
at least one track identified as a lepton with momentum
between 0.8 and
2.0
GeV
y
c
for electrons and between
1.0 and
2.0
GeV
y
c
for muons. Electrons are identified
by matching energy deposited in the CsI calorimeter
and momentum measured in the drift chamber, and by
measuring their energy loss in the drift chamber gas. The
muon identification relies upon penetration through layers
of iron absorber to muon chambers. To reduce non-
B
B
background [contamination of our sample by
e
1
e
2
interactions which result in
q
q
hadronization rather than
producing an
Y
s
4
S
d
meson], each event must satisfy a
requirement on the ratio of Fox-Wolfram [12] moments,
H
2
y
H
0
,
0.4
. All charged tracks must originate from
the vicinity of the
e
1
e
2
interaction point. Charged kaon
and pion candidates, with the exception of the slow
pion from the decay of the
D
p
1
, are required to have
ionization losses in the drift chamber within 2.5 and
3.0 standard deviations, respectively, of those expected
for the hypothesis under consideration. The invariant
mass of the two photons from
p
0
!
gg
must be within
2.0 standard deviations (
s
5
MeV
y
c
2
to
8
MeV
y
c
2
,
depending on shower energies and polar angles) of the
nominal
p
0
mass.
The
K
2
p
1
and
K
2
p
1
p
0
combinations are required
to have an invariant mass within 16 and
25
MeV
y
c
2
s,
2
s
d
of the nominal
D
0
mass, respectively. In addition,
we select regions of the
D
0
!
K
2
p
1
p
0
Dalitz plot
to take advantage of the known resonant substructure
[13] and we enforce a minimum energy for the
p
0
.In
the
D
0
!
K
2
p
1
p
0
mode we require
j
p
D
j
.
0.8
GeV
y
c
in order to further reject fake
D
0
background.
We
then combine
D
0
candidates with
p
1
candidates to
form
D
p
1
candidates. The slow pion used to form the
D
p
1
must have a momentum of at least
65
MeV
y
c
.
The reconstructed mass difference
d
m
M
s
D
0
p
1
d
2
M
s
D
0
d
is required to be within
2
MeV
y
c
2
of the known
D
p
1
2
D
0
mass difference [8]. The
D
p
1
candidate is
then combined with an additional
p
2
in the event to form
4128
V
OLUME
80, N
UMBER
19
PHYSICAL REVIEW LETTERS
11 M
AY
1998
a
D
0
J
candidate. The
D
0
J
candidates must have a scaled
momentum
x
D
J
j
p
D
J
j
y
p
E
2
beam
2
M
2
s
D
J
d
,
0.5
, the
kinematic limit from
B
decays.
These
D
0
J
candidates are then paired with leptons
selected as described above to form candidates for
B
2
!
D
0
J
,
2
n
,
decays. There is significant background in this
analysis from real
D
p
1
’s combined with pions that are
not from
D
0
J
mesons. To suppress this background, we
select
D
0
J
,
2
pairs that are consistent with
B
2
!
D
0
J
,
2
n
,
decays and reject
D
p
1
,
2
pairs that are consistent with
B
0
!
D
p
1
,
2
n
,
. Thus, we require
D
0
J
,
2
candidates to
have
j
cos
u
B
2
D
J
,
j
#
1
and cos
u
B
2
D
p
,
,2
1
, where
cos
u
B
2
D
J
,
j
p
D
J
,
j
2
1
j
p
B
j
2
2
j
p
n
j
2
2
j
p
B
jj
p
D
J
,
j
,
(1)
and
cos
u
B
2
D
p
,
j
p
D
p
,
j
2
1
j
p
B
j
2
2
j
p
n
j
2
2
j
p
B
jj
p
D
p
,
j
.
(2)
Here,
u
B
2
D
J
,
s
u
B
2
D
p
,
d
is the angle between
p
B
and
p
D
J
,
s
p
D
p
,
d
, where
j
p
B
j
is the known magnitude of
the
B
momentum, and
p
D
J
,
s
p
D
p
,
d
is the momentum
of the
D
0
J
,
2
s
D
p
1
,
2
d
candidate. The magnitude of
the neutrino momentum
j
p
n
j
is inferred from energy
conservation, using the beam energy for the
B
meson
energy
E
B
. When the requirements
j
cos
u
B
2
D
J
,
j
#
1
and cos
u
B
2
D
p
,
,2
1
are applied together, they retain
60% of the
B
2
!
D
0
J
,
2
n
,
decays and reject 89% of
the background remaining after all other cuts. To reduce
uncorrelated background (background from events in
which the
D
0
J
comes from the
B
and the lepton from
the
B
), we require the
D
0
J
and the lepton to be in
opposite hemispheres: cos
u
D
J
,
,
0
, where
u
D
J
,
is the
angle between the
D
0
J
and the lepton. The remaining
uncorrelated background is negligible.
The
B
2
!
D
0
J
,
2
n
,
signal is identified using the mass
difference
d
M
J
M
s
D
p
1
p
2
d
2
M
s
D
p
1
d
.
To avoid
multiple
D
0
J
,
2
combinations per event, we select the best
candidate based on the probability that a
D
0
J
,
2
combina-
tion is a signal event. The latter probability is calculated
from the independent observables
M
s
p
0
d
,
M
s
D
0
d
,
d
m
,
and
M
2
s
n
,
d.
M
2
B
1
M
2
s
D
J
,
d
2
2
E
B
E
s
D
J
,
d
. In the
computation of
M
2
s
n
,
d
, the
B
meson momentum
p
B
is
taken to be zero, and
E
s
D
J
,
d
is the energy of the
D
0
J
,
2
candidate.
The
d
M
J
distribution obtained by combining the two
decay modes of the
D
0
meson is shown in Fig. 1.
An unbinned likelihood fit is performed on the
d
M
J
distribution. The fitting function is the sum of a threshold
background function [14] plus Breit-Wigner resonance
functions with the masses and widths of the two narrow
D
0
J
resonances fixed [8]. Each Breit-Wigner function is
convoluted with a Gaussian function that describes the
detector resolution. The width of the Gaussian function
is estimated by Monte Carlo simulation to be
s
3570897-001
40
30
20
10
0
0.14
0.24
0.34
0.44
0.54
0.64
Events / (14 MeV / c
2
)
Data
Fit
M
J
= M (D
)
M (D
(GeV / c
2
)
*
+
+
I
I
)
*
FIG. 1. The
d
M
J
distribution from the
Y
s
4
S
d
resonance
data for
B
2
!
D
0
1
,
2
n
,
and
B
2
!
D
p
0
2
,
2
n
,
(
,
e
and
m
)
candidates obtained by combining both the
D
0
!
K
2
p
1
and
D
0
!
K
2
p
1
p
0
modes.
The dashed curve illustrates the
background function, whereas the solid line shows the sum of
the background and signal functions.
2.8
MeV
y
c
2
. The
D
0
1
and
D
p
0
2
yields obtained from the
fit are summarized in Table I.
To check that the data are consistent with the presence
of a signal, we fit the
d
M
J
distribution with only the
smooth background function. The difference between
the logarithm of the likelihood of the fit with the signal
plus the background functions and the logarithm of the
likelihood with only the background function is 18.7.
Assuming Gaussian statistics, this corresponds to a
6.1
s
statistical significance for the signal. If the mass and
the width of the
D
0
1
resonance are allowed to float, the
fitted mass and width obtained are
2420
6
4
MeV
y
c
2
and
23
6
9
MeV
y
c
2
, which are in agreement with the Particle
Data Group averages [8]. The
D
0
1
and
D
p
0
2
yields from
this fit are
62.5
6
16.7
and
10.5
6
9.8
, respectively.
The background from non-
B
B
events is obtained by
measuring the signal yields using OFF resonance data.
The results are scaled by the ratio of the luminosities and
the square of the beam energies. Fake lepton background
(the contribution in which a
D
0
J
is paired with a hadron
misidentified as a lepton) is estimated by performing the
same analysis using tracks that are not leptons. The fake
lepton yields are scaled by the appropriate misidentifica-
tion probabilities and abundances for hadrons. The sums
of these two types of backgrounds are subtracted from the
ON resonance yields as indicated in Table I.
Semileptonic
B
decays to more highly excited charmed
mesons which then decay to
D
0
J
mesons are predicted
to be small [15].
The smooth background function
accounts for both combinatoric background and possible
background from broad and nonresonant
D
p
1
p
2
X
states.
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TABLE I.
Yields and product branching fractions. The first error on the product branching fractions is statistical, the second is
experimental systematic, and the third is theoretical.
D
0
1
D
p
0
2
ON resonance yield
56.6
6
11.9
10.3
6
9.4
Background yield
3.1
6
2.8
1.5
6
2.8
Net yield
53.5
6
12.2
8.8
6
9.8
P
s
D
0
J
d
s
0.373
6
0.085
6
0.052
6
0.024
d
%
s
0.059
6
0.066
6
0.010
6
0.004
d
%
The product branching fractions
P
s
D
0
1
d;
B
s
B
2
!
D
0
1
,
2
n
,
d
B
s
D
0
1
!
D
p
1
p
2
d
and
P
s
D
p
0
2
d;
B
s
B
2
!
D
p
0
2
,
2
n
,
d
B
s
D
p
0
2
!
D
p
1
p
2
d
are obtained by dividing
the yields by the total numbers of
B
2
events in our data
sample and the sum of the products of the efficiencies
times the
D
p
1
and
D
0
branching fractions for the modes
used. The reconstruction efficiencies
s
́
D
J
d
for
B
2
!
D
0
J
,
2
n
,
(
,
e
and
m
) are
́
K
p
D
1
s
4.37
6
0.09
d
%
,
́
K
pp
0
D
1
s
1.09
6
0.02
d
%
,
́
K
p
D
p
2
s
4.61
6
0.09
d
%
, and
́
K
pp
0
D
p
2
s
1.10
6
0.02
d
%
. Our event selection efficien-
cies were obtained using Monte Carlo data generated
according to the ISGW2 model [15]. The quoted errors
on the efficiencies are statistical only. We assume that
the branching fractions of
Y
s
4
S
d
to charged and neutral
B
B
pairs are each 50%. The values of the
D
p
1
and
D
0
branching fractions are taken from Ref. [8].
The
contributions of the systematic uncertainties are listed
in Table II. Details on the estimation of the systematic
uncertainties can be found elsewhere [10]. The theoretical
uncertainties associated with the model dependence of
the efficiency is obtained by varying the parameters and
the form factors used in the ISGW2 model. We choose
TABLE II. Experimental systematic errors on the product
branching fractions. Tracking uncertainties are for all charged
particles other than the slow
p
.
Source of
systematic error
P
s
D
0
1
d
P
s
D
p
0
2
d
M
D
J
1.0%
1.1%
G
D
J
10.0%
14.0%
Background function
4.0%
5.0%
Uncorrelated background
0.5%
0.4%
Lepton fake
1.0%
1.0%
Lepton ID
1.3%
1.3%
Monte Carlo statistics
1.5%
1.5%
B
s
D
p
1
!
D
0
p
1
d
2.0%
2.0%
B
f
D
0
!
K
2
p
1
s
p
0
dg
3.5%
3.5%
Slow
p
efficiency
5.0%
5.0%
Tracking efficiency
4.0%
4.0%
p
0
reconstruction
2.4%
2.4%
Dalitz weight
1.9%
1.9%
Multiple counting
1.4%
1.4%
Particle identification
1.0%
1.0%
Luminosity
2.0%
2.0%
Total
14.0%
17.3%
to quote the product of branching fractions because the
branching fractions for
D
0
J
!
D
p
1
p
2
have not been
measured. We find
P
s
D
0
1
d
s
0.373
6
0.085
6
0.052
6
0.024
d
%,
(3)
P
s
D
p
0
2
d
s
0.059
6
0.066
6
0.010
6
0.004
d
%
,
0.16%
s
90%
C.L.
d
,
(4)
where the errors are statistical, systematic, and theoretical,
respectively.
For the quoted upper limit, we add the
experimental systematic and the theoretical uncertainties in
quadrature, and add the result to the upper limit computed
with the statistical error only.
In order to estimate the contribution of these decays
to the total semileptonic
B
meson branching fraction,
we need to make some assumptions about the branching
fractions of the
D
0
J
mesons. Isospin conservation and
CLEO measurements [16] of the decays of the
D
0
J
mesons
suggest that
B
s
D
0
1
!
D
p
1
p
2
d
67%
and
B
s
D
p
0
2
!
D
p
1
p
2
d
20%
. Using these estimates, we find
B
s
B
2
!
D
0
1
,
2
n
,
d
s
0.56
6
0.13
6
0.08
6
0.04
d
%,
(5)
B
s
B
2
!
D
p
0
2
,
2
n
,
d
,
0.8%
s
90%
C.L.
d
.
(6)
This leads to an upper limit of
R
B
s
B
2
!
D
p
0
2
,
2
n
,
d
B
s
B
2
!
D
0
1
,
2
n
,
d
,
1.5
s
90%
C.L.
d
.
(7)
A clear picture of the exclusive modes which make
up the 30% – 40% of the
B
semileptonic decays that are
not
D
,
n
,
and
D
p
,
n
,
has not yet emerged. However,
it appears that no more than half of the excess can be
due to exclusive semileptonic decays to
D
0
1
s
2420
d
and
D
p
0
2
s
2460
d
. It should be noted that this interpretation
holds under specific assumptions: we assume the con-
tribution of three body,
r
, and
h
decays of the narrow
D
J
to be negligible.
Several theoretical models make predictions for the
decay rate of exclusive semileptonic decays of the
B
me-
son to excited charm mesons [15,17 – 21]. Our measure-
ments seem to disfavor all of the theoretical predictions
that advocate small
L
QCD
y
m
Q
corrections for semilep-
tonic decays of the
B
meson to
p
-wave charm mesons in
the framework of HQET.
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3570897-002
2.00
1.50
1.00
0.50
0
1
3
2
456
7
8
I
d / dq
2
[
ns
1
/ (2 GeV
2
/ c
4
)
]
q
2
(GeV
2
/ c
4
)
FIG. 2. The
q
2
spectrum for
B
2
!
D
0
1
,
2
n
,
data after back-
ground subtraction and efficiency correction. The error bar on
each data point is statistical only. The dashed line is the pre-
diction from the ISGW2 model.
Despite the fact that this analysis is statistically limited,
we are nevertheless able to study the
q
2
spectrum for
B
2
!
D
0
1
,
2
n
,
. The
q
2
spectrum is extracted by fitting
the
d
M
J
distribution in four bins of
q
2
, keeping the
mass and width of the
D
0
1
fixed.
In each bin, the
appropriate non-
B
B
and fake lepton yields are subtracted
from the fitted yield. The final or net yield
n
D
1
s
q
2
d
is then
corrected by the reconstruction efficiency
́
D
1
s
q
2
d
, which
was computed for the same
q
2
bin. The
q
2
spectrum is
then the differential decay rate:
d
G
dq
2
n
D
1
s
q
2
dy
́
D
1
s
q
2
d
2
t
B
2
N
Y
s
4
S
d
B
s
D
0
1
!
D
p
1
p
2
d
B
D
p
1
B
D
0
.
(8)
The
B
2
lifetime is taken to be
t
B
2
s
1.62
6
0.06
d
ps
[8]. We assume
B
s
D
0
1
!
D
p
1
p
2
d
67%
. The
D
p
1
and
D
0
branching fractions are
B
D
p
1
and
B
D
0
, respec-
tively [8]. The resulting
q
2
spectrum is shown in Fig. 2.
In summary, we have studied exclusive semileptonic
decays of the
B
mesons to
p
-wave charm mesons. We
measured a branching fraction for
B
s
B
2
!
D
0
1
,
2
n
,
d
and
an upper limit for
B
s
B
2
!
D
p
0
2
,
2
n
,
d
. These results
indicate that a substantial fraction
s
*
18%
d
of the inclusive
B
semileptonic rate is from modes other than
D
,
n
,
,
D
p
,
n
,
,
D
1
,
n
,
, and
D
p
2
,
n
,
.
Our measurements are
consistent with ALEPH [4] and OPAL [5]. We also
presented the first measurement of the
q
2
spectrum for
B
2
!
D
0
1
,
2
n
,
.
We gratefully acknowledge the effort of the CESR staff
in providing us with excellent luminosity and running
conditions. This work was supported by the National
Science Foundation, the U.S. Department of Energy, the
Heisenberg Foundation, the Alexander von Humboldt
Stiftung, the Natural Sciences and Engineering Research
Council of Canada, le Fonds Québécois pour la Formation
de Cercheurs et l’Aide à la Recherche, and the A. P. Sloan
Foundation.
*Permanent address: Lawrence Livermore National Labo-
ratory, Livermore, CA 94551.
Permanent
address: BINP, RU-630090 Novosibirsk,
Russia.
Permanent address: Yonsei University, Seoul 120-749,
Korea.
§
Permanent address: Brookhaven National Laboratory,
Upton, NY 11973.
k
Permanent address: University of Texas, Austin, TX
78712.
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4131