of 27
Measurement of the semileptonic decays

B
!
D




and

B
!
D






B. Aubert,
1
M. Bona,
1
Y. Karyotakis,
1
J. P. Lees,
1
V. Poireau,
1
E. Prencipe,
1
X. Prudent,
1
V. Tisserand,
1
J. Garra Tico,
2
E. Grauges,
2
L. Lopez,
3a,3b
A. Palano,
3a,3b
M. Pappagallo,
3a,3b
G. Eigen,
4
B. Stugu,
4
L. Sun,
4
G. S. Abrams,
5
M. Battaglia,
5
D. N. Brown,
5
R. G. Jacobsen,
5
L. T. Kerth,
5
Yu. G. Kolomensky,
5
G. Lynch,
5
I. L. Osipenkov,
5
M. T. Ronan,
5,
*
K. Tackmann,
5
T. Tanabe,
5
C. M. Hawkes,
6
N. Soni,
6
A. T. Watson,
6
H. Koch,
7
T. Schroeder,
7
D. J. Asgeirsson,
8
B. G. Fulsom,
8
C. Hearty,
8
T. S. Mattison,
8
J. A. McKenna,
8
M. Barrett,
9
A. Khan,
9
V. E. Blinov,
10
A. D. Bukin,
10
A. R. Buzykaev,
10
V. P. Druzhinin,
10
V. B. Golubev,
10
A. P. Onuchin,
10
S. I. Serednyakov,
10
Yu. I. Skovpen,
10
E. P. Solodov,
10
K. Yu. Todyshev,
10
M. Bondioli,
11
S. Curry,
11
I. Eschrich,
11
D. Kirkby,
11
A. J. Lankford,
11
P. Lund,
11
M. Mandelkern,
11
E. C. Martin,
11
D. P. Stoker,
11
S. Abachi,
12
C. Buchanan,
12
H. Atmacan,
13
J. W. Gary,
13
F. Liu,
13
O. Long,
13
G. M. Vitug,
13
Z. Yasin,
13
L. Zhang,
13
V. Sharma,
14
C. Campagnari,
15
T. M. Hong,
15
D. Kovalskyi,
15
M. A. Mazur,
15
J. D. Richman,
15
T. W. Beck,
16
A. M. Eisner,
16
C. J. Flacco,
16
C. A. Heusch,
16
J. Kroseberg,
16
W. S. Lockman,
16
A. J. Martinez,
16
T. Schalk,
16
B. A. Schumm,
16
A. Seiden,
16
M. G. Wilson,
16
L. O. Winstrom,
16
C. H. Cheng,
17
D. A. Doll,
17
B. Echenard,
17
F. Fang,
17
D. G. Hitlin,
17
I. Narsky,
17
T. Piatenko,
17
F. C. Porter,
17
R. Andreassen,
18
G. Mancinelli,
18
B. T. Meadows,
18
K. Mishra,
18
M. D. Sokoloff,
18
P. C. Bloom,
19
W. T. Ford,
19
A. Gaz,
19
J. F. Hirschauer,
19
M. Nagel,
19
U. Nauenberg,
19
J. G. Smith,
19
S. R. Wagner,
19
R. Ayad,
20,
A. Soffer,
20,
W. H. Toki,
20
R. J. Wilson,
20
E. Feltresi,
21
A. Hauke,
21
H. Jasper,
21
M. Karbach,
21
J. Merkel,
21
A. Petzold,
21
B. Spaan,
21
K. Wacker,
21
M. J. Kobel,
22
R. Nogowski,
22
K. R. Schubert,
22
R. Schwierz,
22
A. Volk,
22
D. Bernard,
23
G. R. Bonneaud,
23
E. Latour,
23
M. Verderi,
23
P. J. Clark,
24
S. Playfer,
24
J. E. Watson,
24
M. Andreotti,
25a,25b
D. Bettoni,
25a
C. Bozzi,
25a
R. Calabrese,
25a,25b
A. Cecchi,
25a,25b
G. Cibinetto,
25a,25b
P. Franchini,
25a,25b
E. Luppi,
25a,25b
M. Negrini,
25a,25b
A. Petrella,
25a,25b
L. Piemontese,
25a
V. Santoro,
25a,25b
R. Baldini-Ferroli,
26
A. Calcaterra,
26
R. de Sangro,
26
G. Finocchiaro,
26
S. Pacetti,
26
P. Patteri,
26
I. M. Peruzzi,
26,
x
M. Piccolo,
26
M. Rama,
26
A. Zallo,
26
A. Buzzo,
27a
R. Contri,
27a,27b
M. Lo Vetere,
27a,27b
M. M. Macri,
27a
M. R. Monge,
27a,27b
S. Passaggio,
27a
C. Patrignani,
27a,27b
E. Robutti,
27a
A. Santroni,
27a,27b
S. Tosi,
27a,27b
K. S. Chaisanguanthum,
28
M. Morii,
28
A. Adametz,
29
J. Marks,
29
S. Schenk,
29
U. Uwer,
29
V. Klose,
30
H. M. Lacker,
30
D. J. Bard,
31
P. D. Dauncey,
31
M. Tibbetts,
31
P. K. Behera,
32
X. Chai,
32
M. J. Charles,
32
U. Mallik,
32
J. Cochran,
33
H. B. Crawley,
33
L. Dong,
33
W. T. Meyer,
33
S. Prell,
33
E. I. Rosenberg,
33
A. E. Rubin,
33
Y. Y. Gao,
34
A. V. Gritsan,
34
Z. J. Guo,
34
C. K. Lae,
34
N. Arnaud,
35
J. Be
́
quilleux,
35
A. D’Orazio,
35
M. Davier,
35
J. Firmino da Costa,
35
G. Grosdidier,
35
F. Le Diberder,
35
V. Lepeltier,
35
A. M. Lutz,
35
S. Pruvot,
35
P. Roudeau,
35
M. H. Schune,
35
J. Serrano,
35
V. Sordini,
35,
k
A. Stocchi,
35
G. Wormser,
35
D. J. Lange,
36
D. M. Wright,
36
I. Bingham,
37
J. P. Burke,
37
C. A. Chavez,
37
J. R. Fry,
37
E. Gabathuler,
37
R. Gamet,
37
D. E. Hutchcroft,
37
D. J. Payne,
37
C. Touramanis,
37
A. J. Bevan,
38
C. K. Clarke,
38
F. Di Lodovico,
38
R. Sacco,
38
M. Sigamani,
38
G. Cowan,
39
S. Paramesvaran,
39
A. C. Wren,
39
D. N. Brown,
40
C. L. Davis,
40
A. G. Denig,
41
M. Fritsch,
41
W. Gradl,
41
K. E. Alwyn,
42
D. Bailey,
42
R. J. Barlow,
42
G. Jackson,
42
G. D. Lafferty,
42
T. J. West,
42
J. I. Yi,
42
J. Anderson,
43
C. Chen,
43
A. Jawahery,
43
D. A. Roberts,
43
G. Simi,
43
J. M. Tuggle,
43
C. Dallapiccola,
44
X. Li,
44
E. Salvati,
44
S. Saremi,
44
R. Cowan,
45
D. Dujmic,
45
P. H. Fisher,
45
S. W. Henderson,
45
G. Sciolla,
45
M. Spitznagel,
45
F. Taylor,
45
R. K. Yamamoto,
45
M. Zhao,
45
P. M. Patel,
46
S. H. Robertson,
46
A. Lazzaro,
47a,47b
V. Lombardo,
47a
F. Palombo,
47a,47b
J. M. Bauer,
48
L. Cremaldi,
48
R. Godang,
48,
{
R. Kroeger,
48
D. J. Summers,
48
H. W. Zhao,
48
M. Simard,
49
P. Taras,
49
H. Nicholson,
50
G. De Nardo,
51a,51b
L. Lista,
51a
D. Monorchio,
51a,51b
G. Onorato,
51a,51b
C. Sciacca,
51a,51b
G. Raven,
52
H. L. Snoek,
52
C. P. Jessop,
53
K. J. Knoepfel,
53
J. M. LoSecco,
53
W. F. Wang,
53
L. A. Corwin,
54
K. Honscheid,
54
H. Kagan,
54
R. Kass,
54
J. P. Morris,
54
A. M. Rahimi,
54
J. J. Regensburger,
54
S. J. Sekula,
54
Q. K. Wong,
54
N. L. Blount,
55
J. Brau,
55
R. Frey,
55
O. Igonkina,
55
J. A. Kolb,
55
M. Lu,
55
R. Rahmat,
55
N. B. Sinev,
55
D. Strom,
55
J. Strube,
55
E. Torrence,
55
G. Castelli,
56a,56b
N. Gagliardi,
56a,56b
M. Margoni,
56a,56b
M. Morandin,
56a
M. Posocco,
56a
M. Rotondo,
56a
F. Simonetto,
56a,56b
R. Stroili,
56a,56b
C. Voci,
56a,56b
P. del Amo Sanchez,
57
E. Ben-Haim,
57
H. Briand,
57
G. Calderini,
57
J. Chauveau,
57
O. Hamon,
57
Ph. Leruste,
57
J. Ocariz,
57
A. Perez,
57
J. Prendki,
57
S. Sitt,
57
L. Gladney,
58
M. Biasini,
59a,59b
E. Manoni,
59a,59b
C. Angelini,
60a,60b
G. Batignani,
60a,60b
S. Bettarini,
60a,60b
M. Carpinelli,
60a,60b,
**
A. Cervelli,
60a,60b
F. Forti,
60a,60b
M. A. Giorgi,
60a,60b
A. Lusiani,
60a,60c
G. Marchiori,
60a,60b
M. Morganti,
60a,60b
N. Neri,
60a,60b
E. Paoloni,
60a,60b
G. Rizzo,
60a,60b
J. J. Walsh,
60a
D. Lopes Pegna,
61
C. Lu,
61
J. Olsen,
61
A. J. S. Smith,
61
A. V. Telnov,
61
F. Anulli,
62a
E. Baracchini,
62a,62b
G. Cavoto,
62a
R. Faccini,
62a,62b
F. Ferrarotto,
62a
F. Ferroni,
62a,62b
M. Gaspero,
62a,62b
P. D. Jackson,
62a
L. Li Gioi,
62a
M. A. Mazzoni,
62a
S. Morganti,
62a
G. Piredda,
62a
F. Renga,
62a,62b
C. Voena,
62a
M. Ebert,
63
T. Hartmann,
63
H. Schro
̈
der,
63
R. Waldi,
63
T. Adye,
64
B. Franek,
64
E. O. Olaiya,
64
F. F. Wilson,
64
S. Emery,
65
M. Escalier,
65
L. Esteve,
65
G. Hamel de Monchenault,
65
W. Kozanecki,
65
G. Vasseur,
65
Ch. Ye
`
che,
65
M. Zito,
65
X. R. Chen,
66
H. Liu,
66
W. Park,
66
M. V. Purohit,
66
R. M. White,
66
J. R. Wilson,
66
PHYSICAL REVIEW D
79,
092002 (2009)
1550-7998
=
2009
=
79(9)
=
092002(27)
092002-1
Ó
2009 The American Physical Society
M. T. Allen,
67
D. Aston,
67
R. Bartoldus,
67
J. F. Benitez,
67
R. Cenci,
67
J. P. Coleman,
67
M. R. Convery,
67
J. C. Dingfelder,
67
J. Dorfan,
67
G. P. Dubois-Felsmann,
67
W. Dunwoodie,
67
R. C. Field,
67
A. M. Gabareen,
67
M. T. Graham,
67
P. Grenier,
67
C. Hast,
67
W. R. Innes,
67
J. Kaminski,
67
M. H. Kelsey,
67
H. Kim,
67
P. Kim,
67
M. L. Kocian,
67
D. W. G. S. Leith,
67
S. Li,
67
B. Lindquist,
67
S. Luitz,
67
V. Luth,
67
H. L. Lynch,
67
D. B. MacFarlane,
67
H. Marsiske,
67
R. Messner,
67
D. R. Muller,
67
H. Neal,
67
S. Nelson,
67
C. P. O’Grady,
67
I. Ofte,
67
M. Perl,
67
B. N. Ratcliff,
67
A. Roodman,
67
A. A. Salnikov,
67
R. H. Schindler,
67
J. Schwiening,
67
A. Snyder,
67
D. Su,
67
M. K. Sullivan,
67
K. Suzuki,
67
S. K. Swain,
67
J. M. Thompson,
67
J. Va’vra,
67
A. P. Wagner,
67
M. Weaver,
67
C. A. West,
67
W. J. Wisniewski,
67
M. Wittgen,
67
D. H. Wright,
67
H. W. Wulsin,
67
A. K. Yarritu,
67
K. Yi,
67
C. C. Young,
67
V. Ziegler,
67
P. R. Burchat,
68
A. J. Edwards,
68
T. S. Miyashita,
68
S. Ahmed,
69
M. S. Alam,
69
J. A. Ernst,
69
B. Pan,
69
M. A. Saeed,
69
S. B. Zain,
69
S. M. Spanier,
70
B. J. Wogsland,
70
R. Eckmann,
71
J. L. Ritchie,
71
A. M. Ruland,
71
C. J. Schilling,
71
R. F. Schwitters,
71
B. W. Drummond,
72
J. M. Izen,
72
X. C. Lou,
72
F. Bianchi,
73a,73b
D. Gamba,
73a,73b
M. Pelliccioni,
73a,73b
M. Bomben,
74a,74b
L. Bosisio,
74a,74b
C. Cartaro,
74a,74b
G. Della Ricca,
74a,74b
L. Lanceri,
74a,74b
L. Vitale,
74a,74b
V. Azzolini,
75
N. Lopez-March,
75
F. Martinez-Vidal,
75
D. A. Milanes,
75
A. Oyanguren,
75
J. Albert,
76
Sw. Banerjee,
76
B. Bhuyan,
76
H. H. F. Choi,
76
K. Hamano,
76
R. Kowalewski,
76
M. J. Lewczuk,
76
I. M. Nugent,
76
J. M. Roney,
76
R. J. Sobie,
76
T. J. Gershon,
77
P. F. Harrison,
77
J. Ilic,
77
T. E. Latham,
77
G. B. Mohanty,
77
H. R. Band,
78
X. Chen,
78
S. Dasu,
78
K. T. Flood,
78
Y. Pan,
78
R. Prepost,
78
C. O. Vuosalo,
78
and S. L. Wu
78
(
B
A
B
AR
Collaboration)
1
Laboratoire de Physique des Particules, IN2P3/CNRS et Universite
́
de Savoie, F-74941 Annecy-Le-Vieux, France
2
Universitat de Barcelona, Facultat de Fisica, Departament ECM, E-08028 Barcelona, Spain
3a
INFN Sezione di Bari, I-70126 Bari, Italy
3b
Dipartmento di Fisica, Universita
`
di Bari, I-70126 Bari, Italy
4
University of Bergen, Institute of Physics, N-5007 Bergen, Norway
5
Lawrence Berkeley National Laboratory and University of California, Berkeley, California 94720, USA
6
University of Birmingham, Birmingham, B15 2TT, United Kingdom
7
Ruhr Universita
̈
t Bochum, Institut fu
̈
r Experimentalphysik 1, D-44780 Bochum, Germany
8
University of British Columbia, Vancouver, British Columbia, V6T 1Z1 Canada
9
Brunel University, Uxbridge, Middlesex UB8 3PH, United Kingdom
10
Budker Institute of Nuclear Physics, Novosibirsk 630090, Russia
11
University of California at Irvine, Irvine, California 92697, USA
12
University of California at Los Angeles, Los Angeles, California 90024, USA
13
University of California at Riverside, Riverside, California 92521, USA
14
University of California at San Diego, La Jolla, California 92093, USA
15
University of California at Santa Barbara, Santa Barbara, California 93106, USA
16
University of California at Santa Cruz, Institute for Particle Physics, Santa Cruz, California 95064, USA
17
California Institute of Technology, Pasadena, California 91125, USA
18
University of Cincinnati, Cincinnati, Ohio 45221, USA
19
University of Colorado, Boulder, Colorado 80309, USA
20
Colorado State University, Fort Collins, Colorado 80523, USA
21
Technische Universita
̈
t Dortmund, Fakulta
̈
t Physik, D-44221 Dortmund, Germany
22
Technische Universita
̈
t Dresden, Institut fu
̈
r Kern- und Teilchenphysik, D-01062 Dresden, Germany
23
Laboratoire Leprince-Ringuet, CNRS/IN2P3, Ecole Polytechnique, F-91128 Palaiseau, France
24
University of Edinburgh, Edinburgh EH9 3JZ, United Kingdom
25a
INFN Sezione di Ferrara, I-44100 Ferrara, Italy
25b
Dipartimento di Fisica, Universita
`
di Ferrara, I-44100 Ferrara, Italy
26
INFN Laboratori Nazionali di Frascati, I-00044 Frascati, Italy
27a
INFN Sezione di Genova, I-16146 Genova, Italy
27b
Dipartimento di Fisica, Universita
`
di Genova, I-16146 Genova, Italy
28
Harvard University, Cambridge, Massachusetts 02138, USA
29
Universita
̈
t Heidelberg, Physikalisches Institut, Philosophenweg 12, D-69120 Heidelberg, Germany
30
Humboldt-Universita
̈
t zu Berlin, Institut fu
̈
r Physik, Newtonstr. 15, D-12489 Berlin, Germany
31
Imperial College London, London, SW7 2AZ, United Kingdom
32
University of Iowa, Iowa City, Iowa 52242, USA
33
Iowa State University, Ames, Iowa 50011-3160, USA
34
Johns Hopkins University, Baltimore, Maryland 21218, USA
35
Laboratoire de l’Acce
́
le
́
rateur Line
́
aire, IN2P3/CNRS et Universite
́
Paris-Sud 11,
Centre Scientifique d’Orsay, B. P. 34, F-91898 Orsay Cedex, France
B. AUBERT
et al.
PHYSICAL REVIEW D
79,
092002 (2009)
092002-2
36
Lawrence Livermore National Laboratory, Livermore, California 94550, USA
37
University of Liverpool, Liverpool L69 7ZE, United Kingdom
38
Queen Mary, University of London, London, E1 4NS, United Kingdom
39
University of London, Royal Holloway and Bedford New College, Egham, Surrey TW20 0EX, United Kingdom
40
University of Louisville, Louisville, Kentucky 40292, USA
41
Johannes Gutenberg-Universita
̈
t Mainz, Institut fu
̈
r Kernphysik, D-55099 Mainz, Germany
42
University of Manchester, Manchester M13 9PL, United Kingdom
43
University of Maryland, College Park, Maryland 20742, USA
44
University of Massachusetts, Amherst, Massachusetts 01003, USA
45
Massachusetts Institute of Technology, Laboratory for Nuclear Science, Cambridge, Massachusetts 02139, USA
46
McGill University, Montre
́
al, Que
́
bec, H3A 2T8 Canada
47a
INFN Sezione di Milano, I-20133 Milano, Italy
47b
Dipartimento di Fisica, Universita
`
di Milano, I-20133 Milano, Italy
48
University of Mississippi, University, Mississippi 38677, USA
49
Universite
́
de Montre
́
al, Physique des Particules, Montre
́
al, Que
́
bec, H3C 3J7 Canada
50
Mount Holyoke College, South Hadley, Massachusetts 01075, USA
51a
INFN Sezione di Napoli, I-80126 Napoli, Italy
51b
Dipartimento di Scienze Fisiche, Universita
`
di Napoli Federico II, I-80126 Napoli, Italy
52
NIKHEF, National Institute for Nuclear Physics and High Energy Physics, NL-1009 DB Amsterdam, The Netherlands
53
University of Notre Dame, Notre Dame, Indiana 46556, USA
54
Ohio State University, Columbus, Ohio 43210, USA
55
University of Oregon, Eugene, Oregon 97403, USA
56a
INFN Sezione di Padova, I-35131 Padova, Italy
56b
Dipartimento di Fisica, Universita
`
di Padova, I-35131 Padova, Italy
57
Laboratoire de Physique Nucle
́
aire et de Hautes Energies, IN2P3/CNRS, Universite
́
Pierre et Marie Curie-Paris6,
Universite
́
Denis Diderot-Paris7, F-75252 Paris, France
58
University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
59a
INFN Sezione di Perugia, I-06100 Perugia, Italy
59b
Dipartimento di Fisica, Universita
`
di Perugia, I-06100 Perugia, Italy
60a
INFN Sezione di Pisa, I-56127 Pisa, Italy
60b
Dipartimento di Fisica, Universita
`
di Pisa, I-56127 Pisa, Italy
60c
Scuola Normale Superiore di Pisa, I-56127 Pisa, Italy
61
Princeton University, Princeton, New Jersey 08544, USA
62a
INFN Sezione di Roma, I-00185 Roma, Italy
62b
Dipartimento di Fisica, Universita
`
di Roma La Sapienza, I-00185 Roma, Italy
63
Universita
̈
t Rostock, D-18051 Rostock, Germany
64
Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, OX11 0QX, United Kingdom
65
CEA, Irfu, SPP, Centre de Saclay, F-91191 Gif-sur-Yvette, France
66
University of South Carolina, Columbia, South Carolina 29208, USA
67
Stanford Linear Accelerator Center, Stanford, California 94309, USA
68
Stanford University, Stanford, California 94305-4060, USA
69
State University of New York, Albany, New York 12222, USA
70
University of Tennessee, Knoxville, Tennessee 37996, USA
71
University of Texas at Austin, Austin, Texas 78712, USA
72
University of Texas at Dallas, Richardson, Texas 75083, USA
73a
INFN Sezione di Torino, I-10125 Torino, Italy
73b
Dipartimento di Fisica Sperimentale, Universita
`
di Torino, I-10125 Torino, Italy
74a
INFN Sezione di Trieste, I-34127 Trieste, Italy
74b
Dipartimento di Fisica, Universita
`
di Trieste, I-34127 Trieste, Italy
75
IFIC, Universitat de Valencia-CSIC, E-46071 Valencia, Spain
76
University of Victoria, Victoria, British Columbia, V8W 3P6 Canada
77
Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom
k
Also with Universita
`
di Roma La Sapienza, I-00185 Roma, Italy.
**
Also with Universita
`
di Sassari, Sassari, Italy.
x
Also with Universita
`
di Perugia, Dipartimento di Fisica, Perugia, Italy.
Now at Tel Aviv University, Tel Aviv, 69978, Israel.
Now at Temple University, Philadelphia, Pennsylvania 19122, USA.
{
Now at University of South Alabama, Mobile, Alabama 36688, USA.
*
Deceased.
MEASUREMENT OF THE SEMILEPTONIC DECAYS
...
PHYSICAL REVIEW D
79,
092002 (2009)
092002-3
78
University of Wisconsin, Madison, Wisconsin 53706, USA
(Received 16 February 2009; published 13 May 2009)
We present measurements of the semileptonic decays
B

!
D
0





,
B

!
D

0





,

B
0
!
D
þ





,
and

B
0
!
D





, which are sensitive to non-standard model amplitudes in certain scenarios. The data
sample consists of
232

10
6

ð
4
S
Þ!
B

B
decays collected with the
BABAR
detector at the PEP-II
e
þ
e

collider. We select events with a
D
or
D

meson and a light lepton (
¼
e
or

) recoiling against a fully
reconstructed
B
meson. We perform a fit to the joint distribution of lepton momentum and missing mass
squared to distinguish signal

B
!
D
ðÞ





ð


!





Þ
events from the backgrounds, predominantly

B
!
D
ðÞ



. We measure the branching-fraction ratios
R
ð
D
Þ
B
ð

B
!
D




Þ
=
B
ð

B
!
D‘



Þ
and
R
ð
D

Þ
B
ð

B
!
D






Þ
=
B
ð

B
!
D




Þ
and, from a combined fit to
B

and

B
0
channels, obtain the
results
R
ð
D
Þ¼ð
41
:
6

11
:
7

5
:
2
Þ
%
and
R
ð
D

Þ¼ð
29
:
7

5
:
6

1
:
8
Þ
%
, where the uncertainties are
statistical and systematic. Normalizing to measured
B

!
D
ðÞ
0



branching fractions, we obtain
B
ð

B
!
D




Þ¼ð
0
:
86

0
:
24

0
:
11

0
:
06
Þ
%
and
B
ð

B
!
D






Þ¼ð
1
:
62

0
:
31

0
:
10

0
:
05
Þ
%
, where the additional third uncertainty is from the normalization mode. We also present, for
the first time, distributions of the lepton momentum,
j
p

j
, and the squared momentum transfer,
q
2
.
DOI:
10.1103/PhysRevD.79.092002
PACS numbers: 12.15.Hh, 13.20.

v, 13.20.He, 14.40.Nd
I. INTRODUCTION
Semileptonic decays of
B
mesons to the

lepton—the
heaviest of the three charged leptons—provide a new
source of information on standard model (SM) processes
[
1
3
], as well as a new window on physics beyond the SM
[
4
9
]. In the SM, semileptonic decays occur at tree level
and are mediated by the
W
boson, but the large mass of the

lepton provides sensitivity to additional amplitudes, such
as those mediated by a charged Higgs boson.
Experimentally,
b
!
c




decays
1
are challenging to
study because the final state contains not just one, but
two or three neutrinos as a result of the

decay.
Theoretical predictions for semileptonic decays to ex-
clusive final states require knowledge of the form factors,
which parametrize the hadronic current as functions of
q
2
¼½
p
B

p
D
ðÞ

2
:
For light leptons

e
,

,
2
there is
effectively one form factor for

B
!
D‘



, while there
are three for

B
!
D




.Ifa

lepton is produced
instead, one additional form factor enters in each mode.
The form factors for

B
!
D
ðÞ



decays
3
involving the
light leptons have been measured [
10
12
], providing direct
information on four of the six form factors. Heavy quark
symmetry (HQS) relations [
13
] allow one to express the
two additional form factors for

B
!
D
ðÞ





in terms of
the form factors measurable from decays with the light
leptons. With sufficient data, one could probe the addi-
tional form factors and test the HQS relations.
Branching fractions for semileptonic
B
decays to

leptons are predicted to be smaller than those to light
leptons. Calculations based on the SM predict
B
ð

B
0
!
D
þ





Þ¼ð
0
:
69

0
:
04
Þ
%
and
B
ð

B
0
!
D





Þ¼
ð
1
:
41

0
:
07
Þ
%
[
8
], which account for most of the pre-
dicted inclusive rate
B
ð

B
!
X
c





Þ¼ð
2
:
30

0
:
25
Þ
%
[
2
] (here,
X
c
represents all hadronic final states from the
b
!
c
transition). In multi-Higgs doublet models [
4
8
],
substantial departures, either positive or negative, from the
SM decay rate could occur for
B
ð

B
!
D




Þ
, while
smaller departures are expected for
B
ð

B
!
D






Þ
.
Thus, measurements of
B
ð

B
!
D




Þ
are more sensitive
to non-SM contributions than either
B
ð

B
!
D






Þ
or
the inclusive rate. In addition to the branching fractions,
several other observables are sensitive to possible non-SM
contributions, including
q
2
distributions and
D

and

polarization [
4
6
,
8
,
14
].
The first measurements of semileptonic
b
-hadron decays
to

leptons were performed by the LEP experiments [
15
]
operating at the
Z
0
resonance, yielding an average [
16
]
inclusive branching fraction
B
ð
b
had
!
X




Þ¼ð
2
:
48

0
:
26
Þ
%
, where
b
had
represents the mixture of
b
-hadrons
produced in
Z
0
!
b

b
decays. The Belle experiment has
reported
B
ð

B
0
!
D





Þ¼ð
2
:
02
þ
0
:
40

0
:
37

0
:
37
Þ
%
[
17
].
The
BABAR
Collaboration has presented a measurement
of the branching fractions for

B
!
D




and

B
!
D






for both charged and neutral
B
mesons [
18
]. In
this article, we describe the analysis in greater detail, with
particular emphasis on several novel features of the event
selection and fit technique. We also present distributions of
two important kinematic variables, the lepton momentum
j
p

j
and the squared momentum transfer
q
2
.
A. Analysis overview and strategy
We determine the branching fractions of four exclusive
decay modes:
B

!
D
0





,
B

!
D

0





,

B
0
!
D
þ





, and

B
0
!
D





, each of which is measured
as a branching-fraction ratio
R
relative to the correspond-
ing
e
and

modes. To reconstruct the

, we use the decays


!
e



e


and


!







, which are experimen-
tally the most accessible. The main challenge of the mea-
surement is to distinguish

B
!
D
ðÞ





decays, which
1
Charge-conjugate modes are implied throughout.
2
Throughout this article, we use the symbol
to refer only to
the light charged leptons
e
and

.
3
The symbol
D
ðÞ
refers either to a
D
or a
D

meson.
B. AUBERT
et al.
PHYSICAL REVIEW D
79,
092002 (2009)
092002-4
have three neutrinos, from

B
!
D
ðÞ



decays, which
have the same observable final-state particles but only one
neutrino.
The analysis strategy is to reconstruct the decays of both
B
mesons in the

ð
4
S
Þ!
B

B
event, providing powerful
constraints on unobserved particles. One
B
meson, denoted
B
tag
, is fully reconstructed in a purely hadronic decay
chain. The remaining charged particles and photons are
required to be consistent with the products of a
b
!
c
semileptonic
B
decay: the daughter charm meson (either
a
D
or
D

) and a lepton (
e
or

). The lepton may be either
primary or from


!





. To distinguish signal
events from the normalization modes

B
!
D
ðÞ



,we
calculate the missing four-momentum,
p
miss
¼
p
e
þ
e


p
tag

p
D
ðÞ

p
(1)
of any particles recoiling against the observed
B
tag
þ
D
ðÞ
system. A large peak at zero in
m
2
miss
¼
p
2
miss
corresponds
to semileptonic decays with one neutrino, whereas signal
events produce a broad tail out to
m
2
miss

8
ð
GeV
=c
2
Þ
2
.
To separate signal and background events, we perform a
fit (described in Sec.
VII
) to the joint distribution of
m
2
miss
and the lepton momentum (
j
p

j
) in the rest frame of the
B
meson. In signal events, the observed lepton is the daughter
of the

and typically has a soft spectrum; for most back-
ground events, this lepton typically has higher momentum.
The fit is performed simultaneously in eight channels, with
a set of constraints relating the event yields between the
channels. The fit is designed to maximize the sensitivity to
the

B
!
D




signals by using events in the
D


channels to constrain the dominant backgrounds,

B
!
D






feed-down, in which the final-state
D

meson is
not completely reconstructed. Similarly, we use a set of
D

control samples to constrain the feed-down back-
ground to both the
D




and
D






signals.
4
We perform a relative measurement, extracting both
signal

B
!
D
ðÞ





and normalization

B
!
D
ðÞ



yields from the fit to obtain the four branching-fraction
ratios
R
ð
D
0
Þ
,
R
ð
D
þ
Þ
,
R
ð
D

0
Þ
, and
R
ð
D
Þ
, where, for
example,
R
ð
D

0
Þ
B
ð
B

!
D

0





Þ
=
B
ð
B

!
D

0



Þ
. In the ratio, many systematic uncertainties can-
cel, either partially or completely. These ratios are normal-
ized such that
represents only one of
e
or

; however,
both light lepton species are included in the measurement.
We multiply these branching-fraction ratios by previous
measurements of
B
ð

B
!
D
ðÞ



Þ
to derive absolute
branching fractions.
II. THE
BABAR
DETECTOR AND DATA SETS
We analyze data collected with the
BABAR
detector at
the PEP-II
e
þ
e

storage rings at the Stanford Linear
Accelerator Center. PEP-II is an asymmetric-energy
B
factory, colliding 9.0 GeV
e

with 3.1 GeV
e
þ
at a
center-of-mass energy of 10.58 GeV, corresponding to
the

ð
4
S
Þ
resonance. The data sample used consists of
208
:
9fb

1
of integrated luminosity recorded on the

ð
4
S
Þ
resonance between 1999 and 2004, yielding
232

10
6

ð
4
S
Þ!
B

B
decays. This data sample can be divided
into two major periods: Runs 1–3, comprising
109
:
0fb

1
taken from 1999 to June 2003, and Run 4, comprising
99
:
9fb

1
taken from September 2003 to July 2004. The
accelerator background conditions were significantly dif-
ferent between Runs 1–3 and Run 4, which could affect
missing-energy analyses such as this one; for this reason,
the two running periods have been independently vali-
dated, and the fraction of signal-like events found in the
Run 4 sample is used as a cross-check of the results, as
described in Sec.
X
.
The
BABAR
detector is a large, general-purpose mag-
netic spectrometer and is described in detail elsewhere
[
19
]. Charged particle trajectories are measured in a track-
ing system consisting of a five-layer double-sided silicon
strip detector and a 40-layer drift chamber, both of which
operate in the 1.5 T magnetic field of a superconducting
solenoid. A detector of internally reflected Cherenkov light
(DIRC) is used to measure charged particle velocity for
particle identification (PID). An electromagnetic calorime-
ter (EMC), consisting of 6580 CsI(Tl) crystals, is used to
reconstruct photons and in electron identification. The steel
flux return of the solenoid is segmented and instrumented
with resistive plate chambers (IFR) for muon and neutral
hadron identification.
All detector systems contribute to charged particle iden-
tification. Ionization energy losses in the tracking systems
and the Cherenkov light signature in the DIRC are used for
all charged particle types. Electrons are also identified on
the basis of shower shape in the EMC and the ratio of
energy deposited in the EMC to the track momentum.
Muon identification is based on a minimum-ionization
energy deposit in the EMC and on the measured interaction
length in the IFR.
This analysis relies on measurement of the missing
momentum carried off by multiple neutrinos, and the large
solid angle coverage (hermeticity) of the detector is there-
fore crucial. The tracking system, calorimeter, and IFR
cover the full azimuthal range and the polar angle range
from approximately
0
:
3
<<
2
:
7 rad
in the laboratory
frame, corresponding to a

ð
4
S
Þ
center-of-mass coverage
of approximately 90% [the direction

¼
0
corresponds to
the direction of the high-energy beam, and therefore to the

ð
4
S
Þ
boost]. The DIRC fiducial volume is slightly
smaller, corresponding to a center-of-mass frame coverage
of about 84%.
4
Throughout this paper, we use the symbol
D

to represent all
charm resonances heavier than the
D

ð
2010
Þ
, as well as non-
resonant
D
ðÞ
n
systems with
n

1
.
MEASUREMENT OF THE SEMILEPTONIC DECAYS
...
PHYSICAL REVIEW D
79,
092002 (2009)
092002-5
Within the active detector volume, the efficiency for
reconstructing charged tracks and photons is very high,
typically greater than 95% over most of the momentum
range. At low momenta, however, the reconstruction effi-
ciency drops off, leading to an increased contribution from
feed-down processes to which special attention is paid
throughout this analysis. Feed-down occurs when the pho-
ton from
D

!
D
or the

0
from
D

!
D
0
is not
reconstructed (in the case of the

0
, either one or both of
the photons from

0
!

may be missed). Care must
therefore be taken to avoid confusing
D

feed-down events
for
D
signals.
We use a Monte Carlo simulation (MC) of the produc-
tion and decay of signal and background events based on
EVTGEN
[
20
]. A sample of simulated inclusive
B

B
events
equivalent to about five times the integrated luminosity is
used to study backgrounds and to optimize event selection
criteria. Large samples of many individual semileptonic
B
decays (discussed in Sec.
III
) are used to parameterize the
distributions of variables used in the fit. Final-state radia-
tion is simulated using
PHOTOS
[
21
]. Simulation of the
detector response is performed with
GEANT
[
22
] and the
resulting efficiencies and resolutions are validated in mul-
tiple data control samples.
III. SEMILEPTONIC DECAY MODELS
In the SM, the matrix element for a semileptonic
B
meson decay can be written as
M
ð

B
!
D
ðÞ
ð

=

Þ


Þ¼
i
g
2
8
m
2
W
V
cb
L

H

;
(2)
where
g
is the weak coupling constant,
m
W
is the
W
mass,
V
cb
is the quark mixing matrix element, and
L

and
H

are
the leptonic and hadronic currents, respectively. Here, we
have used a simplified form for the
W
propagator appro-
priate for energies much less than
m
W
. The leptonic current
is exactly known,
L

¼

u


ð
1


5
Þ
v

;
(3)
and the hadronic current is given by
H

¼h
D
ðÞ
j

c

ð
1


5
Þ
b
j
B
i
:
(4)
In the case of a

B
!
D
transition, the axial-vector part of
the current does not contribute to the decay, and we may
write the hadronic current in terms of two form factors
f
þ
ð
q
2
Þ
and
f

ð
q
2
Þ
:
h
D
j
V

j
B
i¼ð
p
þ
p
0
Þ

f
þ
ð
q
2
Þþð
p

p
0
Þ

f

ð
q
2
Þ
;
(5)
with
V



c

b
and where
p
and
p
0
are the four-
momenta of the
B
and
D
mesons, respectively. For the

B
!
D

transition, the axial-vector term contributes to the decay
as well, and we write the hadronic current in terms of form
factors
V
ð
q
2
Þ
,
A
1
ð
q
2
Þ
,
A
2
ð
q
2
Þ
,
A
3
ð
q
2
Þ
, and
A
0
ð
q
2
Þ
:
h
D

j
V


A

j
B
2
i

m
B
þ
m
D

"


p
0

p
V
ð
q
2
Þ
m
B
þ
m
D

Þ
"


A
1
ð
q
2
Þþ
"

q
m
B
þ
m
D

p
þ
p
0
Þ

A
2
ð
q
2
Þþ
2
m
D

"

q
q
2

q

A
3
ð
q
2
Þ
2
m
D

"

q
q
2
q

A
0
ð
q
2
Þ
;
(6)
where
A



c


5
b
and
"
is the
D

polarization vector.
The form factor
A
3
ð
q
2
Þ
is related to two other form factors
as
A
3
ð
q
2
Þ¼
m
B
þ
m
D

2
m
D

A
1
ð
q
2
Þ
m
B

m
D

2
m
D

A
2
ð
q
2
Þ
(7)
so that there are only four independent form factors.
In the limit of massless leptons, any terms proportional
to
q

p

p
0
Þ

vanish when the hadronic current is
contracted with the leptonic current. For this reason, the
contributions from the form factors
f

ð
q
2
Þ
and
A
0
ð
q
2
Þ
are
essentially negligible for electrons and muons, as men-
tioned above.
0
0.05
0.1
0.15
0.2
024681012
0
0.1
0.2
(a)
(b)
FIG. 1. Generated
q
2
distributions for (a)

B
!
D‘



and

B
!
D




; (b)

B
!
D




and

B
!
D






. The two
curves in each plot show
q
2
for the light lepton (dashed line)
and for the

(solid line). All distributions use the CLN form
factor model with experimentally measured shape parameters.
The distributions are normalized to equal areas.
B. AUBERT
et al.
PHYSICAL REVIEW D
79,
092002 (2009)
092002-6