Measurement of branching fractions for exclusive
B
decays to charmonium final states
B. Aubert, D. Boutigny, J.-M. Gaillard, A. Hicheur, Y. Karyotakis, J. P. Lees, P. Robbe, and V. Tisserand
Laboratoire de Physique des Particules, F-74941 Annecy-le-Vieux, France
A. Palano
Universita
`
di Bari, Dipartimento di Fisica and INFN, I-70126 Bari, Italy
G. P. Chen, J. C. Chen, N. D. Qi, G. Rong, P. Wang, and Y. S. Zhu
Institute of High Energy Physics, Beijing 100039, China
G. Eigen, P. L. Reinertsen, and B. Stugu
University of Bergen, Institute of Physics, N-5007 Bergen, Norway
B. Abbott, G. S. Abrams, A. W. Borgland, A. B. Breon, D. N. Brown, J. Button-Shafer, R. N. Cahn, A. R. Clark,
M. S. Gill, A. Gritsan, Y. Groysman, R. G. Jacobsen, R. W. Kadel, J. Kadyk, L. T. Kerth, S. Kluth, Yu. G. Kolomensky,
J. F. Kral, C. LeClerc, M. E. Levi, T. Liu, G. Lynch, A. Meyer, M. Momayezi, P. J. Oddone, A. Perazzo, M. Pripstein,
N. A. Roe, A. Romosan, M. T. Ronan, V. G. Shelkov, A. V. Telnov, and W. A. Wenzel
Lawrence Berkeley National Laboratory and University of California, Berkeley, California 94720
P. G. Bright-Thomas, T. J. Harrison, C. M. Hawkes, A. Kirk, D. J. Knowles, S. W. O’Neale, R. C. Penny, A. T. Watson,
and N. K. Watson
University of Birmingham, Birmingham, B15 2TT, United Kingdom
T. Deppermann, K. Goetzen, H. Koch, J. Krug, M. Kunze, B. Lewandowski, K. Peters, H. Schmuecker, and M. Steinke
Ruhr Universita
̈
t Bochum, Institut fu
̈
r Experimentalphysik 1, D-44780 Bochum, Germany
J. C. Andress, N. R. Barlow, W. Bhimji, N. Chevalier, P. J. Clark, W. N. Cottingham, N. De Groot, N. Dyce, B. Foster,
J. D. McFall, D. Wallom, and F. F. Wilson
University of Bristol, Bristol BS8 1TL, United Kingdom
K. Abe, C. Hearty, T. S. Mattison, J. A. McKenna, and D. Thiessen
University of British Columbia, Vancouver, BC, Canada V6T 1Z1
S. Jolly, A. K. McKemey, and J. Tinslay
Brunel University, Uxbridge, Middlesex UB8 3PH, United Kingdom
V. E. Blinov, A. D. Bukin, D. A. Bukin, A. R. Buzykaev, V. B. Golubev, V. N. Ivanchenko, A. A. Korol, E. A. Kravchenko,
A. P. Onuchin, A. A. Salnikov, S. I. Serednyakov, Yu. I. Skovpen, V. I. Telnov, and A. N. Yushkov
Budker Institute of Nuclear Physics, Novosibirsk 630090, Russia
D. Best, A. J. Lankford, M. Mandelkern, S. McMahon, and D. P. Stoker
University of California at Irvine, Irvine, California 92697
A. Ahsan, K. Arisaka, C. Buchanan, and S. Chun
University of California at Los Angeles, Los Angeles, California 90024
J. G. Branson, D. B. MacFarlane, S. Prell, Sh. Rahatlou, G. Raven, and V. Sharma
University of California at San Diego, La Jolla, California 92093
C. Campagnari, B. Dahmes, P. A. Hart, N. Kuznetsova, S. L. Levy, O. Long, A. Lu, J. D. Richman, W. Verkerke,
M. Witherell, and S. Yellin
University of California at Santa Barbara, Santa Barbara, California 93106
J. Beringer, D. E. Dorfan, A. M. Eisner, A. Frey, A. A. Grillo, M. Grothe, C. A. Heusch, R. P. Johnson, W. Kroeger,
W. S. Lockman, T. Pulliam, H. Sadrozinski, T. Schalk, R. E. Schmitz, B. A. Schumm, A. Seiden, M. Turri, W. Walkowiak,
D. C. Williams, and M. G. Wilson
University of California at Santa Cruz, Institute for Particle Physics, Santa Cruz, California 95064
E. Chen, G. P. Dubois-Felsmann, A. Dvoretskii, D. G. Hitlin, S. Metzler, J. Oyang, F. C. Porter, A. Ryd, A. Samuel,
PHYSICAL REVIEW D, VOLUME 65, 032001
0556-2821/2002/65
~
3
!
/032001
~
23
!
/$20.00
©2002 The American Physical Society
65
032001-1
M. Weaver, S. Yang, and R. Y. Zhu
California Institute of Technology, Pasadena, California 91125
S. Devmal, T. L. Geld, S. Jayatilleke, G. Mancinelli, B. T. Meadows, and M. D. Sokoloff
University of Cincinnati, Cincinnati, Ohio 45221
T. Barillari, P. Bloom, M. O. Dima, S. Fahey, W. T. Ford, D. R. Johnson, U. Nauenberg, A. Olivas, H. Park, P. Rankin,
J. Roy, S. Sen, J. G. Smith, W. C. van Hoek, and D. L. Wagner
University of Colorado, Boulder, Colorado 80309
J. Blouw, J. L. Harton, M. Krishnamurthy, A. Soffer, W. H. Toki, R. J. Wilson, and J. Zhang
Colorado State University, Fort Collins, Colorado 80523
T. Brandt, J. Brose, T. Colberg, G. Dahlinger, M. Dickopp, R. S. Dubitzky, E. Maly, R. Mu
̈
ller-Pfefferkorn, S. Otto,
K. R. Schubert, R. Schwierz, B. Spaan, and L. Wilden
Technische Universita
̈
t Dresden, Institut fu
̈
r Kern- und Teilchenphysik, D-01062, Dresden, Germany
L. Behr, D. Bernard, G. R. Bonneaud, F. Brochard, J. Cohen-Tanugi, S. Ferrag, E. Roussot, S. T’Jampens, C. Thiebaux,
G. Vasileiadis, and M. Verderi
Ecole Polytechnique, F-91128 Palaiseau, France
A. Anjomshoaa, R. Bernet, A. Khan, F. Muheim, S. Playfer, and J. E. Swain
University of Edinburgh, Edinburgh EH9 3JZ, United Kingdom
M. Falbo
Elon College, Elon College, North Carolina 27244-2010
C. Borean, C. Bozzi, S. Dittongo, M. Folegani, and L. Piemontese
Universita
`
di Ferrara, Dipartimento di Fisica and INFN, I-44100 Ferrara, Italy I-44100 Ferrara, Italy
E. Treadwell
Florida A&M University, Tallahassee, Florida 32307
F. Anulli,
*
R. Baldini-Ferroli, A. Calcaterra, R. de Sangro, D. Falciai, G. Finocchiaro, P. Patteri, I. M. Peruzzi,
*
M. Piccolo, Y. Xie, and A. Zallo
Laboratori Nazionali di Frascati dell’INFN, I-00044 Frascati, Italy
S. Bagnasco, A. Buzzo, R. Contri, G. Crosetti, P. Fabbricatore, S. Farinon, M. Lo Vetere, M. Macri, M. R. Monge,
R. Musenich, M. Pallavicini, R. Parodi, S. Passaggio, F. C. Pastore, C. Patrignani, M. G. Pia, C. Priano, E. Robutti, and
A. Santroni
Universita
`
di Genova, Dipartimento di Fisica and INFN, I-16146 Genova, Italy
M. Morii
Harvard University, Cambridge, Massachusetts 02138
R. Bartoldus, T. Dignan, R. Hamilton, and U. Mallik
University of Iowa, Iowa City, Iowa 52242
J. Cochran, H. B. Crawley, P.-A. Fischer, J. Lamsa, W. T. Meyer, and E. I. Rosenberg
Iowa State University, Ames, Iowa 50011-3160
M. Benkebil, G. Grosdidier, C. Hast, A. Ho
̈
cker, H. M. Lacker, V. LePeltier, A. M. Lutz, S. Plaszczynski, M. H. Schune,
S. Trincaz-Duvoid, A. Valassi, and G. Wormser
Laboratoire de l’Acce
́
le
́
rateur Line
́
aire, F-91898 Orsay, France
R. M. Bionta, V. Brigljevic
́
, D. J. Lange, M. Mugge, X. Shi, K. van Bibber, T. J. Wenaus, D. M. Wright, and C. R. Wuest
Lawrence Livermore National Laboratory, Livermore, California 94550
M. Carroll, J. R. Fry, E. Gabathuler, R. Gamet, M. George, M. Kay, D. J. Payne, R. J. Sloane, and C. Touramanis
University of Liverpool, Liverpool L69 3BX, United Kingdom
B. AUBERT
et al.
PHYSICAL REVIEW D
65
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M. L. Aspinwall, D. A. Bowerman, P. D. Dauncey, U. Egede, I. Eschrich, N. J. W. Gunawardane, J. A. Nash, P. Sanders,
and D. Smith
University of London, Imperial College, London, SW7 2BW, United Kingdom
D. E. Azzopardi, J. J. Back, P. Dixon, P. F. Harrison, R. J. L. Potter, H. W. Shorthouse, P. Strother, P. B. Vidal,
and M. I. Williams
Queen Mary, University of London, E1 4NS, United Kingdom
G. Cowan, S. George, M. G. Green, A. Kurup, C. E. Marker, P. McGrath, T. R. McMahon, S. Ricciardi, F. Salvatore,
I. Scott, and G. Vaitsas
University of London, Royal Holloway and Bedford New College, Egham, Surrey TW20 0EX, United Kingdom
D. Brown and C. L. Davis
University of Louisville, Louisville, Kentucky 40292
J. Allison, R. J. Barlow, J. T. Boyd, A. C. Forti, J. Fullwood, F. Jackson, G. D. Lafferty, N. Savvas, E. T. Simopoulos,
and J. H. Weatherall
University of Manchester, Manchester M13 9PL, United Kingdom
A. Farbin A. Jawahery, V. Lillard, J. Olsen, D. A. Roberts, and J. R. Schieck
University of Maryland, College Park, Maryland 20742
G. Blaylock, C. Dallapiccola, K. T. Flood, S. S. Hertzbach, R. Kofler, T. B. Moore, H. Staengle, and S. Willocq
University of Massachusetts, Amherst, Massachusetts 01003
B. Brau, R. Cowan, G. Sciolla, F. Taylor, and R. K. Yamamoto
Massachusetts Institute of Technology, Lab for Nuclear Science, Cambridge, Massachusetts 02139
M. Milek, P. M. Patel, and J. Trischuk
McGill University, Montre
́
al, QC, Canada H3A 2T8
F. Lanni and F. Palombo
Universita
`
di Milano, Dipartimento di Fisica and INFN, I-20133 Milano, Italy
J. M. Bauer, M. Booke, L. Cremaldi, V. Eschenburg, R. Kroeger, J. Reidy, D. A. Sanders, and D. J. Summers
University of Mississippi, University, Mississippi 38677
J. P. Martin, J. Y. Nief, R. Seitz, P. Taras, and V. Zacek
Universite
́
de Montre
́
al, Lab. Rene J. A. Levesque, Montre
́
al, QC, Canada H3C 3J7
H. Nicholson and C. S. Sutton
Mount Holyoke College, South Hadley, Massachusetts 01075
C. Cartaro, N. Cavallo,
†
G. De Nardo, F. Fabozzi, C. Gatto, L. Lista, P. Paolucci, D. Piccolo, and C. Sciacca
Universita
`
di Napoli Federico II, Dipartimento di Scienze Fisiche and INFN, I-80126, Napoli, Italy
J. M. LoSecco
University of Notre Dame, Notre Dame, Indiana 46556
J. R. G. Alsmiller, T. A. Gabriel, and T. Handler
Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831
J. Brau, R. Frey, M. Iwasaki, N. B. Sinev, and D. Strom
University of Oregon, Eugene, Oregon 97403
F. Colecchia, F. Dal Corso, A. Dorigo, F. Galeazzi, M. Margoni, G. Michelon, M. Morandin, M. Posocco, M. Rotondo,
F. Simonetto, R. Stroili, E. Torassa, and C. Voci
Universita
`
di Padova, Dipartimento di Fisica and INFN, I-35131 Padova, Italy
MEASUREMENT OF BRANCHING FRACTIONS FOR . . .
PHYSICAL REVIEW D
65
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M. Benayoun, H. Briand, J. Chauveau, P. David, C. De la Vaissie
`
re, L. Del Buono, O. Hamon, F. Le Diberder, Ph. Leruste,
J. Lory, L. Roos, J. Stark, and S. Versille
́
Universite
́
s Paris VI et VII, LPNHE, F-75252 Paris, France
P. F. Manfredi, V. Re, and V. Speziali
Universita
`
di Pavia, Dipartimento di Elettronica and INFN, I-27100 Pavia, Italy
E. D. Frank, L. Gladney, Q. H. Guo, and J. H. Panetta
University of Pennsylvania, Philadelphia, Pennsylvania 19104
C. Angelini, G. Batignani, S. Bettarini, M. Bondioli, M. Carpinelli, F. Forti, M. A. Giorgi, A. Lusiani, F. Martinez-Vidal,
M. Morganti, N. Neri, E. Paoloni, M. Rama, G. Rizzo, F. Sandrelli, G. Simi, G. Triggiani, and J. Walsh
Universita
`
di Pisa, Scuola Normale Superiore and INFN, I-56010 Pisa, Italy
M. Haire, D. Judd, K. Paick, L. Turnbull, and D. E. Wagoner
Prairie View A&M University, Prairie View, Texas 77446
J. Albert, C. Bula, P. Elmer, C. Lu, K. T. McDonald, V. Miftakov, S. F. Schaffner, A. J. S. Smith, A. Tumanov, and
E. W. Varnes
Princeton University, Princeton, New Jersey 08544
G. Cavoto, D. del Re, F. Ferrarotto, F. Ferroni, K. Fratini, E. Lamanna, E. Leonardi, M. A. Mazzoni, S. Morganti,
G. Piredda, F. Safai Tehrani, M. Serra, and C. Voena
Universita
`
di Roma La Sapienza, Dipartimento di Fisica and INFN, I-00185 Roma, Italy
R. Faccini
University of California at San Diego, La Jolla, California 92093
and Universita
`
di Roma La Sapienza, Dipartimento di Fisica and INFN, I-00185 Roma, Italy
S. Christ and R. Waldi
Universita
̈
t Rostock, D-18051 Rostock, Germany
T. Adye, B. Franek, N. I. Geddes, G. P. Gopal, and S. M. Xella
Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, OX11 0QX, United Kingdom
R. Aleksan, G. De Domenico, S. Emery, A. Gaidot, S. F. Ganzhur, P.-F. Giraud, G. Hamel de Monchenault, W. Kozanecki,
M. Langer, G. W. London, B. Mayer, B. Serfass, G. Vasseur, C. Yeche, and M. Zito
DAPNIA, Commissariat a
`
l’Energie Atomique/Saclay, F-91191 Gif-sur-Yvette, France
N. Copty, M. V. Purohit, H. Singh, and F. X. Yumiceva
University of South Carolina, Columbia, South Carolina 29208
I. Adam, P. L. Anthony, D. Aston, K. Baird, E. Bloom, A. M. Boyarski, F. Bulos, G. Calderini, R. Claus, M. R. Convery,
D. P. Coupal, D. H. Coward, J. Dorfan, M. Doser, W. Dunwoodie, R. C. Field, T. Glanzman, G. L. Godfrey,
S. J. Gowdy, P. Grosso, T. Himel, M. E. Huffer, W. R. Innes, C. P. Jessop, M. H. Kelsey, P. Kim, M. L. Kocian,
U. Langenegger, D. W. G. S. Leith, S. Luitz, V. Luth, H. L. Lynch, H. Marsiske, S. Menke, R. Messner, K. C. Moffeit,
R. Mount, D. R. Muller, C. P. O’Grady, M. Perl, S. Petrak, H. Quinn, B. N. Ratcliff, S. H. Robertson,
L. S. Rochester, A. Roodman, T. Schietinger, R. H. Schindler, J. Schwiening, V. V. Serbo, A. Snyder, A. Soha, S. M. Spanier,
J. Stelzer, D. Su, M. K. Sullivan, H. A. Tanaka, J. Va’vra, S. R. Wagner, A. J. R. Weinstein, W. J. Wisniewski,
D. H. Wright, and C. C. Young
Stanford Linear Accelerator Center, Stanford, California 94309
P. R. Burchat, C. H. Cheng, D. Kirkby, T. I. Meyer, and C. Roat
Stanford University, Stanford, California 94305-4060
R. Henderson
TRIUMF, Vancouver, BC, Canada V6T 2A3
W. Bugg, H. Cohn, and A. W. Weidemann
B. AUBERT
et al.
PHYSICAL REVIEW D
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University of Tennessee, Knoxville, Tennessee 37996
J. M. Izen, I. Kitayama, X. C. Lou, and M. Turcotte
University of Texas at Dallas, Richardson, Texas 75083
F. Bianchi, M. Bona, B. Di Girolamo, D. Gamba, A. Smol, and D. Zanin
Universita
`
di Torino, Dipartimento di Fisica Sperimentale and INFN, I-10125 Torino, Italy
L. Lanceri, A. Pompili, and G. Vuagnin
Universita
`
di Trieste, Dipartimento di Fisica and INFN, I-34127 Trieste, Italy
R. S. Panvini
Vanderbilt University, Nashville, Tennessee 37235
C. M. Brown, A. De Silva, R. Kowalewski, and J. M. Roney
University of Victoria, Victoria, BC, Canada V8W 3P6
H. R. Band, E. Charles, S. Dasu, F. Di Lodovico, A. M. Eichenbaum, H. Hu, J. R. Johnson, R. Liu, J. Nielsen, Y. Pan,
R. Prepost, I. J. Scott, S. J. Sekula, J. H. von Wimmersperg-Toeller, S. L. Wu, Z. Yu, and H. Zobernig
University of Wisconsin, Madison, Wisconsin 53706
T. M. B. Kordich and H. Neal
Yale University, New Haven, Connecticut 06511
~
BABAR Collaboration
!
~
Received 11 July 2001; published 7 January 2002
!
We report branching fraction measurements for exclusive decays of charged and neutral
B
mesons into
two-body final states containing a charmonium meson. We use a sample of 22.72
6
0.36 million
BB
̄
events
collected between October 1999 and October 2000 with the
BABAR
detector at the PEP-II storage rings at the
Stanford Linear Accelerator Center. The charmonium mesons considered here are
J
/
c
,
c
(2
S
) , and
x
c
1
, and
the light meson in the decay is either a
K
,
K
*
,or
p
0
.
DOI: 10.1103/PhysRevD.65.032001
PACS number
~
s
!
: 13.25.Hw, 11.30.Er
I. INTRODUCTION
Decays of
B
mesons to two body final states containing a
charmonium resonance (
J
/
c
,
c
(2
S
),
x
c
1
) constitute a very
sensitive laboratory for the study of electroweak transitions,
as well as the dynamics of strong interactions in heavy me-
son systems. In particular, neutral
B
decays to these final
states are expected to exhibit a significant
CP
asymmetry, the
magnitude of which is clearly related to standard model pa-
rameters
@
1
#
.
The tree level and leading penguin diagrams for the decay
modes we consider are shown in Fig. 1. Because of the con-
tributions of nonperturbative QCD interactions in the final
state, assumptions must be made in estimating the expected
branching fractions of these modes, and therefore these esti-
mates have some degree of model dependence. A number of
such estimates have appeared in the literature
@
2–12
#
. The
one model-independent element common to all of these pre-
dictions is the requirement from isospin symmetry that the
ratio of the charged to neutral partial widths should be unity,
and that this should hold separately for each light meson
accompanying the charmonium meson in the final state.
Here we report the measurement of branching fractions of
B
mesons to a charmonium resonance accompanied by a
kaon or
p
0
meson. The channels measured are listed in Table
I. Here and throughout this paper for each final state men-
tioned its charged conjugate is also implied. We reconstruct
J
/
c
decays to lepton pairs
l
1
l
2
, where
l
is either an electron
or muon.
Our large data sample permits a measurement of these
branching fractions with a precision superior to previous ex-
periments. The simultaneous measurement of a number of
final states allows us to determine ratios such as vector to
pseudoscalar kaon and heavy to light charmonium states pro-
*
Also with Universita
`
di Perugia, Perugia, Italy.
†
Also with Universita
`
della Basilicata, Potenza, Italy.
FIG. 1. Leading Feynman diagrams for the decays we consider.
MEASUREMENT OF BRANCHING FRACTIONS FOR . . .
PHYSICAL REVIEW D
65
032001
032001-5
duction. Many systematic errors cancel when these ratios are
extracted from a single data set using very similar event se-
lection criteria, further increasing the usefulness of our re-
sults for the validation or development of phenomenological
models.
Another highly relevant input for the understanding of
strong interactions in
B
decays is the measurement of polar-
ization in vector-vector final states, which is reported in an-
other publication
@
13
#
. Finally, the branching fraction of
B
!
J
/
c
p
1
is measured using a specific analysis method, re-
ported in
@
14
#
.
II. THE
BABAR
DETECTOR
The
BABAR
detector is located at the PEP-II
e
1
e
2
stor-
age rings operating at the Stanford Linear Accelerator Cen-
ter. At PEP-II, 9.0 GeV electrons collide with 3.1 GeV pos-
itrons to produce a center-of-mass energy of 10.58 GeV, the
mass of the
Y
(4
S
) resonance.
The
BABAR
detector is described elsewhere
@
15
#
; here we
give only a brief overview. Surrounding the interaction point
is a 5 layer, double-sided silicon vertex tracker
~
SVT
!
which
gives precision spatial information for all charged particles,
and also measures their energy loss ( d
E
/d
x
) . The SVT is the
primary detection device for low momentum charged par-
ticles. Outside the SVT a 40-layer drift chamber
~
DCH
!
pro-
vides measurements of the transverse momenta
p
T
of
charged particles with respect to the beam direction. The
resolution of the
p
T
measurement for tracks with momenta
above 1 GeV/
c
is parametrized as
s
~
p
t
!
p
T
5
0.13
p
T
~
GeV/
c
!
%
1
0.45% .
~
1
!
The drift chamber also measures d
E
/d
x
with a precision of
7.5%. Beyond the outer radius of the DCH is a detector of
internally reflected Cherenkov radiation
~
DIRC
!
which is
used primarily for charged hadron identification. The detec-
tor consists of quartz bars in which Cherenkov light is pro-
duced as relativistic charged particles traverse the material.
The light is internally reflected along the length of the bar
into a water-filled stand-off box mounted on the rear of the
detector. The Cherenkov rings expand in the stand-off box
and are measured with an array of photomultiplier tubes
mounted on its outer surface. A CsI
~
Tl
!
crystal electromag-
netic calorimeter
~
EMC
!
is used to detect photons and neu-
tral hadrons, as well as to identify electrons. The resolution
of the calorimeter is parametrized as
s
~
E
!
E
5
2.3%
@
E
~
GeV
!
#
1/4
%
1.9% .
~
2
!
The EMC is surrounded by a superconducting solenoid that
produces a 1.5-T magnetic field. The instrumented flux re-
turn
~
IFR
!
consists of multiple layers of resistive plate cham-
bers
~
RPC
!
interleaved with the flux return iron. In addition
to the planar RPC layers in the flux return, there is an addi-
tional cylindrical layer just outside of the EMC. The IFR is
used in the identification of muons and neutral hadrons.
Data acquisition is triggered with a two-level system. The
first level
~
level 1
!
monitors trigger information from the
DCH and EMC, and generates a trigger upon detection of
track or cluster candidates. The second level
~
level 3
!
retains
events in which the track candidates point back to the beam
interaction region
~
L3 DCH trigger
!
, or EMC clusters candi-
dates remain after the suppression of hits which have less
energy than a minimum ionizing particle or are uncorrelated
in time with the rest of the event
~
L3 EMC trigger
!
. Over
99.9% of
BB
̄
events pass either the L3 DCH or L3 EMC
trigger. A fraction of all events that pass the level 1 trigger
are passed through level 3 to allow monitoring of the level 3
trigger performance.
III. DATA SAMPLE
The data used in these analyses were collected between
October 1999 and October 2000 and correspond to an inte-
grated luminosity of 20.7 fb
2
1
taken on the
Y
(4
S
) and 2.6
fb
2
1
taken off-resonance at an energy 0.04 GeV lower than
the peak, which is below the threshold for
BB
̄
production.
The data set contains 22.72
6
0.36 million
BB
̄
events.
IV. COORDINATE SYSTEM AND REFERENCE FRAMES
We use a right-handed coordinate system with the
z
axis
along the electron beam direction and
y
axis upwards, with
origin at the nominal beam interaction point. Unless other-
wise stated, kinematic quantities are calculated in the rest
frame of the detector. The other reference frame we com-
monly use is the center of mass of the colliding electrons and
positrons, which we will call the center-of-mass frame.
V. PARTICLE RECONSTRUCTION
The reconstruction of exclusive
B
decays begins with
identifying candidates for the decay products. Charged par-
ticles are reconstructed as tracks in the SVT and/or DCH.
Leptons and kaons are identified with information from the
DCH, the EMC
~
for electrons
!
, the IFR
~
for muons
!
, and the
TABLE I. Branching fractions and decay modes considered in
this paper. We always reconstruct the
J
/
c
in the
l
1
l
2
decay mode.
Branching fraction
measured
Secondary decay
modes used
B
0
!
J
/
c
K
0
K
0
!
K
S
0
;
K
S
0
!
p
1
p
2
or
p
0
p
0
K
0
!
K
L
0
B
1
!
J
/
c
K
1
-
B
0
!
J
/
c
K
*
0
K
*
0
!
K
1
p
2
or
K
S
0
p
0
;
K
S
0
!
p
1
p
2
B
1
!
J
/
c
K
*
1
K
*
1
!
K
1
p
0
or
K
S
0
p
1
;
K
S
0
!
p
1
p
2
B
0
!
J
/
c
p
0
-
B
0
!
c
(2
S
)
K
S
0
c
(2
S
)
!
l
1
l
2
or
J
/
c
p
1
p
2
;
K
S
0
!
p
1
p
2
B
1
!
c
(2
S
)
K
1
c
(2
S
)
!
l
1
l
2
or
c
(2
S
)
!
J
/
c
p
1
p
2
B
0
!
x
c
1
K
S
0
x
c
1
!
J
/
cg
;
K
S
0
!
p
1
p
2
B
1
!
x
c
1
K
1
x
c
1
!
J
/
cg
B
0
!
x
c
1
K
*
0
x
c
1
!
J
/
cg
;
K
*
0
!
K
1
p
2
B. AUBERT
et al.
PHYSICAL REVIEW D
65
032001
032001-6
DIRC
~
for kaons
!
. Photons are identified based on their en-
ergy deposition in the EMC, and
K
L
0
are identified from ei-
ther energy deposition in the EMC or a shower in the IFR.
A. Track selection
In general, tracks used in this analysis are required to
include at least 12 DCH hits to ensure that their momenta
and d
E
/d
x
are well measured. In addition, tracks are required
to have
p
T
.
100 MeV/
c
, and to point back to the nominal
interaction point within 1.5 cm in
xy
and3cmin
z
. Roughly
95% of the solid angle about the interaction point in the
center-of-mass frame is covered by 12 or more DCH layers.
We make exceptions to this requirement for two types of
particles: pions from
K
S
0
, which do not originate at the nomi-
nal interaction point, and pions from
c
(2
S
)
!
J
/
c
p
1
p
2
,
which frequently do not have sufficient transverse momenta
to traverse 12 layers of the DCH. Any track found in the
DCH or SVT is used in reconstructing these particles.
B. EMC cluster reconstruction
The energy deposited in contiguous crystals of the EMC
is summed into a cluster. The distribution of energy among
the crystals is used to discriminate between clusters arising
from electromagnetic and hadronic showers. The variables
used to describe this distribution are the lateral energy
~
LAT
!
@
16
#
and the Zernike moments
A
mn
@
17
#
. LAT is a measure of
the radial energy profile of the cluster; the Zernike moment
A
42
measures the asymmetry of the cluster about its maxi-
mum. Electromagnetic showers have LAT peaked at about
0.25 and
A
42
close to zero, while showers from hadrons have
a broader distribution in LAT and extend to larger values of
A
42
.
C. Photon candidate selection
Photons are identified as EMC clusters that do not have a
spatial match with a charged track, and that have a minimum
energy of 30 MeV. To reject clusters arising from noise hits,
LAT is required to be less than 0.8.
D. Electron and muon identification
We derive substantial background rejection from the posi-
tive identification of electrons and muons within the sample
of charged tracks. For electrons, the variables that distinguish
signal from background include LAT and
A
42
, the ratio of
energy measured in the EMC to momentum measured in the
tracking spectrometer (
E
/
p
), d
E
/d
x
measured in the DCH,
and the Cherenkov angle
u
C
measured in the DIRC.
For identifying muons, the presence of an energy deposi-
tion consistent with a minimum ionizing particle in the
EMC, and the details of the distribution of hits in the IFR are
used. In particular, the number of interaction lengths tra-
versed in the IFR
N
l
must be consistent with expectations
for a muon, both the average and variance of the number of
hits per layer must be small, and the fit of a track to the hits
must have low
x
2
, both within the IFR (
x
IFR
2
) and in the
match between the IFR and central detector track (
x
match
2
).
Since the optimal tradeoff between efficient selection and
suppression of backgrounds varies between decay modes,
there are several sets of criteria used to select leptons. These
are defined in Table II for electrons and Table III for muons.
In addition to these criteria, we also restrict the lepton selec-
tion to a fiducial region within which the efficiency is well
known from control samples, and the material in the detector
is accurately modeled in the Monte Carlo. The accepted
range in polar angle
u
is 0.410
,
u
,
2.409 rad for electrons
and 0.30
,
u
,
2.70 rad for muons. This corresponds to a cov-
erage of 84% of the solid angle in the center-of-mass frame
for electrons, and 92% for muons.
To increase the efficiency of the event selection, electron
candidate tracks are combined with photon candidates to re-
cover some of the energy lost through bremsstrahlung. In
addition to the photon selection criteria listed above, photons
used in bremsstrahlung recovery are required to have
A
42
,
0.25. They are also required to be within 35 mrad in
u
from the track, and to have azimuthal angle
f
intermediate
between the initial track direction and the centroid of the
EMC cluster arising from the track. The initial track direc-
tion is estimated by subtracting 50 mrad opposite to the bend
direction from the
f
of the fitted track measured at the ori-
TABLE II. Summary of electron identification criteria. Variables used are: d
E
/d
x
, the energy loss measured in the DCH;
E
/
p
, the ratio
of the EMC cluster energy to the momentum measured in the tracking spectrometer;
N
crys
, the number of EMC crystals forming the cluster;
LAT, the lateral energy distribution
@
16
#
of the EMC cluster;
A
42
, one of the Zernike moments
@
17
#
of the EMC cluster; and
u
C
, the
Cherenkov angle measured in the DIRC. In addition, the fraction of electrons in inclusive
J
/
c
events that pass each set of criteria is shown,
along with the fraction of pions with momentum above 1 GeV/
c
that pass the selection requirements.
DCH only
Loose
Tight
Very tight
d
E
/d
x
~
measured-expected
!
2
2to
1
4
s
meas
2
3to
1
7
s
meas
2
3to
1
7
s
meas
2
2to
1
4
s
meas
E
/
p
-
0.65
2
5.0
0.75
2
1.3
0.89
2
1.2
N
crys
-
.
3
.
3
.
3
LAT
-
-
0.0
2
0.6
0.1
2
0.6
A
42
---
,
0.11
u
C
~
measured-expected
!
---
2
3to
1
3
s
meas
Efficiency
~
%
!
94.9
97.2
95.4
88.2
p
misID
~
%
!
21.6
4.8
1.2
0.1
MEASUREMENT OF BRANCHING FRACTIONS FOR . . .
PHYSICAL REVIEW D
65
032001
032001-7
gin. The procedure increases the efficiency for reconstructing
charmonium decays to
e
1
e
2
by about 30%.
E.
K
L
0
candidate selection
We identify neutral hadrons through the presence of an
energy deposition in the EMC or a cluster in the IFR. Neutral
hadrons must be spatially separated from all tracks in the
event. In reconstructing the decay
B
0
!
J
/
c
K
L
0
neutral had-
rons are taken as
K
L
0
candidates, with requirements specifi-
cally tailored for this mode.
Only the measured direction of the neutral hadron is used
for
K
L
0
reconstruction, as its energy is poorly measured. The
direction of the
K
L
0
candidate is defined by the line joining
the vertex of the
J
/
c
candidate and the centroid of the EMC
or IFR cluster.
For a
K
L
0
to reach the IFR it must traverse the EMC ma-
terial, which amounts to approximately one nuclear interac-
tion length. As a consequence, half of the
K
L
0
mesons un-
dergo detectable interactions in the EMC. We consider EMC
clusters with energy in the 0.2–2.0 GeV range. Most clusters
arising from
K
L
0
interactions have energy below the upper
bound; below the lower bound the contamination from noise
becomes significant. All such EMC clusters which are spa-
tially separated from a track are considered as
K
L
0
candidates,
except those that combined with another neutral cluster give
an invariant mass compatible with a
p
0
.
About 60% of
K
L
0
mesons from
B
0
!
J
/
c
K
L
0
leave a de-
tectable signal in the IFR. We select
K
L
0
candidates in the IFR
starting with clusters of hits not spatially matched to a track.
IFR clusters with hits only in the outer layers of the forward
endcap are rejected to reduce the contribution from beam
backgrounds.
VI. EVENT SELECTION AND
B
MESON COUNTING
A determination of
B
meson branching fractions depends
upon an accurate measurement of the number of
B
mesons in
the data sample. We find the number of
BB
̄
pairs by com-
paring the rate of multihadron events in data taken on the
Y
(4
S
) resonance to that in data taken off-resonance. The
BB
̄
purity of the sample is enhanced by requiring the events to
pass the following selection criteria, in which all tracks
~
in-
cluding those that do not satisfy our usual selection require-
ments
!
in the fiducial region 0.410
,
u
,
2.54 rad and all neu-
tral clusters with energy greater than 30 MeV in the region
0.410
,
u
,
2.409 rad are considered:
The event must satisfy either the L3 DCH or L3 EMC
trigger.
There must be at least three tracks that satisfy the standard
selection requirements in the fiducial region.
The ratio of the second to the zeroth Fox-Wolfram mo-
ment
@
18
#
must be less than 0.5.
The event vertex is calculated by an iterative procedure
that begins by considering every track in the event, and then
discards those that contribute a large
x
2
to the fit
~
these are
presumed to arise from the decay of long-lived particles
!
until the vertex fit is stable. This vertex must be within 0.5
cm of the beam spot center in
xy
and within 6 cm in
z
. The
beam spot has a rms width of about 120
m
min
x
, 5.9
m
min
y
, and 0.9 cm in
z
. The point of closest approach of a high-
momentum track to the beam spot is measured with a reso-
lution of 23
m
min
x
and
y
, and 29
m
min
z
, as determined
with dimuon events.
TABLE III. Summary of muon identification criteria. Variables used are:
E
EMC
, the energy deposited by
the muon candidate in the EMC
~
this requirement is only applied for tracks within the fiducial coverage of the
EMC
!
;
N
layers
, the number of IFR layers with hits;
N
l
, the number of nuclear interaction lengths traversed;
u
N
l
2
N
l
( exp)
u
, the difference between the number of nuclear interaction lengths traversed and the expecta-
tion for a muon of the measured momentum;
^
N
hit
&
, the average number of hits per IFR layer; RMS
hit
, the
RMS of the distribution of the number of hits on each layer;
f
hit
, the fraction of layers between the innermost
and outermost hit layers that also have hits
~
this requirement is only applied in the region covered partly or
entirely by the endcap IFR system, 0.3
,
u
,
1.0
!
;
x
IFR
2
, the
x
2
of the track in the IFR; and
x
match
2
, the
x
2
of
the match between the IFR track and the track from the central detector. In addition, the fraction of muons in
inclusive
J
/
c
events that pass each set of criteria is shown, along with the fraction of pions with momentum
above 1 GeV/
c
that pass the selection requirements.
MIP
Very Loose
Loose
Tight
Very tight
E
EMC
~
GeV
!
,
0.5
,
0.5
,
0.5
0.05
2
0.4
0.05
2
0.4
N
layers
-
.
1
.
1
.
1
.
1
N
l
-
.
2
.
2
.
2.2
.
2.2
u
N
l
2
N
l
( exp)
u
-
,
2.5
,
2.0
,
1
,
0.8
^
N
hit
&
-
,
10
,
10
,
8
,
8
RMS
hit
-
,
6
,
6
,
4
,
4
f
hit
-
.
0.1
.
0.2
.
0.3
.
0.34
x
IFR
2
--
,
4
3
N
layers
,
3
3
N
layers
,
3
3
N
layers
x
match
2
--
,
7
3
N
layers
,
5
3
N
layers
,
5
3
N
layers
Efficiency
~
%
!
99.6
92.2
86.2
70.3
67.0
p
misID
~
%
!
57.9
14.5
7.0
2.4
2.1
B. AUBERT
et al.
PHYSICAL REVIEW D
65
032001
032001-8
The total energy of charged and neutral particles is re-
quired to be greater than 4.5 GeV.
These requirements are 95.4
6
1.4% efficient for
BB
̄
events, as estimated from a Monte Carlo simulation. All
events used in the branching fraction analyses are required to
pass this selection.
VII. MESON CANDIDATE SELECTION
The next step in the analysis is to combine sets of tracks
and/or neutral clusters to form candidates for the initial or
intermediate mesons in the decay. Our general strategy when
forming these candidates is to assign the expected masses to
tracks and neutral clusters, and to apply a vertex constraint
before computing the invariant mass. In rare instances
~
less
than 1% of all meson candidates
!
the vertex fit does not
converge. The sum of the track and/or cluster four-vectors is
used to compute the invariant mass for such candidates. If
one or more decay products from a given particle are them-
selves intermediate states, we constrain them to their known
masses. At each step in the decay chain, we require that
mesons have masses consistent with their assumed particle
type. The mass resolutions observed for all of the intermedi-
ate mesons considered in this paper are listed in Table IV.
We choose meson selection criteria to maximize the ex-
pected precision of our branching fraction measurements.
Therefore we use well-understood quantities in our selection,
which lead to a smaller systematic uncertainty. We set the
selection values to maximize the ratio
S
/
A
S
1
B
where
S
and
B
are the expected number of signal and background events
respectively, as estimated from Monte Carlo calculations. If a
given mode has been previously observed,
S
is estimated
using the known branching fraction. Otherwise, selection
values similar to those in previously-observed modes are
taken as a starting point, and then modified to reduce back-
ground
~
as measured in the kinematic sidebands
!
or increase
signal efficiency
~
as measured using Monte Carlo simulated
signal events
!
. In most cases, we find that
S
/
A
S
1
B
does not
change significantly when selection values are varied near
their optima. This allows us to choose standard selection
values across most final states.
A. Charmonium meson candidate selection
1. J
’
c
selection
J
/
c
candidates are required to have an invariant mass in
the
range
2.95
,
M
J
/
c
,
3.14 GeV/
c
2
and
3.06
,
M
J
/
c
,
3.14 GeV/
c
2
for
J
/
c
!
e
1
e
2
and
J
/
c
!
m
1
m
2
decays,
respectively. Unless otherwise stated, for
J
/
c
!
e
1
e
2
de-
cays, one track is required to pass the tight electron selection
and the other the loose selection. Tracks not associated to an
EMC cluster that pass the DCH-only selection are also ac-
cepted. For
J
/
c
!
m
1
m
2
decays, we require one track to
pass the loose selection and the other to pass the MIP selec-
tion.
The mass distribution for
J
/
c
candidates in the data is
shown in Fig. 2.
2.
c
(2S) selection
c
(2
S
)
!
m
1
m
2
candidates are required to have a mass
within 50 MeV/
c
2
of the known
c
(2
S
) value of 3.69 GeV/
c
2
@
19
#
. For
c
(2
S
)
!
e
1
e
2
candidates the lower bound is re-
laxed to 250 MeV/
c
2
below the known value. For decays of
the
c
(2
S
)to
J
/
c
p
1
p
2
, the difference in mass between the
c
(2
S
) and
J
/
c
candidates is required to be within
15 MeV/
c
2
of the expected value, and the
p
1
p
2
invariant
mass
m
p
1
p
2
is required to be between 0.4 and 0.6 GeV/
c
2
.
The latter requirement takes advantage of the fact that
m
p
1
p
2
is most often in the upper portion of the kinemati-
cally allowed range
@
20
#
. All
c
(2
S
) candidates are required
to have a momentum in the center-of-mass frame between
1.0 and 1.6 GeV/
c
, consistent with
B
!
c
(2
S
)
K
decays.
We have used the same lepton identification requirements
as for the
J
/
c
reconstruction. These are applied either to the
leptons from
c
(2
S
)
!
l
1
l
2
decays, or to the leptons from
the
J
/
c
in
c
(2
S
)
!
J
/
c
p
1
p
2
decays.
The mass and mass difference distributions for
c
(2
S
)
candidates in the data are shown in Fig. 3. For Figs. 3, 4, and
6 a background subtraction is performed using the observed
distribution of candidates in the
D
E
sidebands
~
see Sec.
VII C
!
.
3.
x
c1
selection
In reconstructing
x
c
1
!
J
/
cg
,
J
/
c
and photon candi-
dates are selected as described above. The muon identifica-
tion requirements are subsequently tightened by demanding
that one lepton from the
J
/
c
pass the loose selection and the
other the very loose selection
~
rather than the MIP selection
!
.
In addition, the photon cluster is required to satisfy
E
.
150 MeV and
A
42
,
0.15 and to have a centroid in the an-
TABLE IV. Summary of observed invariant mass or mass dif-
ference
D
m
widths for all intermediate mesons considered in this
paper. For most mesons the width is dominated by experimental
resolution, and the value reported in the table is the width
s
from a
Gaussian fit to the data. For the
K
*
modes the natural width of the
resonance dominates, and the value reported is the full width of a
Breit-Wigner fit to the data. The width for
J
/
c
and
c
(2
S
) decaying
to
e
1
e
2
is greater than that for
m
1
m
2
due to the energy lost
through bremsstrahlung.
Quantity
Decay mode
Width ( MeV/
c
2
)
J
/
c
mass
e
1
e
2
17
6
2
m
1
m
2
13
6
1
c
(2
S
) mass
e
1
e
2
29
6
6
m
1
m
2
21
6
3
D
m
Ñ
c
(2
S
)
2
J
/
c
Ö
c
(2
S
)
!
J
/
c
p
1
p
2
;7
6
1
J
/
c
!
l
1
l
2
D
m
(
x
c
1
2
J
/
c
)
J
/
c
!
l
1
l
2
14
6
1
K
S
0
mass
p
1
p
2
3.5
6
0.2
p
0
p
0
15
6
2
K
*
0
mass
K
1
p
2
and
60
6
7
K
S
0
p
0
K
*
1
mass
K
S
0
p
1
and
50
6
10
K
1
p
0
MEASUREMENT OF BRANCHING FRACTIONS FOR . . .
PHYSICAL REVIEW D
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