Measurements of
B
ð
B
0
!
þ
c
p
Þ
and
B
ð
B
!
þ
c
p
Þ
and studies of
þ
c
resonances
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. N. Cahn,
5
R. G. Jacobsen,
5
L. T. Kerth,
5
Yu. G. Kolomensky,
5
G. Kukartsev,
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. Walker,
8
D. J. Asgeirsson,
9
T. Cuhadar-Donszelmann,
9
B. G. Fulsom,
9
C. Hearty,
9
T. S. Mattison,
9
J. A. McKenna,
9
M. Barrett,
10
A. Khan,
10
L. Teodorescu,
10
V. E. Blinov,
11
A. D. Bukin,
11
A. R. Buzykaev,
11
V. P. Druzhinin,
11
V. B. Golubev,
11
A. P. Onuchin,
11
S. I. Serednyakov,
11
Yu. I. Skovpen,
11
E. P. Solodov,
11
K. Yu. Todyshev,
11
M. Bondioli,
12
S. Curry,
12
I. Eschrich,
12
D. Kirkby,
12
A. J. Lankford,
12
P. Lund,
12
M. Mandelkern,
12
E. C. Martin,
12
D. P. Stoker,
12
S. Abachi,
13
C. Buchanan,
13
J. W. Gary,
14
F. Liu,
14
O. Long,
14
B. C. Shen,
14,
*
G. M. Vitug,
14
Z. Yasin,
14
L. Zhang,
14
V. Sharma,
15
C. Campagnari,
16
T. M. Hong,
16
D. Kovalskyi,
16
M. A. Mazur,
16
J. D. Richman,
16
T. W. Beck,
17
A. M. Eisner,
17
C. J. Flacco,
17
C. A. Heusch,
17
J. Kroseberg,
17
W. S. Lockman,
17
T. Schalk,
17
B. A. Schumm,
17
A. Seiden,
17
L. Wang,
17
M. G. Wilson,
17
L. O. Winstrom,
17
C. H. Cheng,
18
D. A. Doll,
18
B. Echenard,
18
F. Fang,
18
D. G. Hitlin,
18
I. Narsky,
18
T. Piatenko,
18
F. C. Porter,
18
R. Andreassen,
19
G. Mancinelli,
19
B. T. Meadows,
19
K. Mishra,
19
M. D. Sokoloff,
19
F. Blanc,
20
P. C. Bloom,
20
W. T. Ford,
20
A. Gaz,
20
J. F. Hirschauer,
20
A. Kreisel,
20
M. Nagel,
20
U. Nauenberg,
20
J. G. Smith,
20
K. A. Ulmer,
20
S. R. Wagner,
20
R. Ayad,
21,
†
A. Soffer,
21,
‡
W. H. Toki,
21
R. J. Wilson,
21
D. D. Altenburg,
22
E. Feltresi,
22
A. Hauke,
22
H. Jasper,
22
M. Karbach,
22
J. Merkel,
22
A. Petzold,
22
B. Spaan,
22
K. Wacker,
22
M. J. Kobel,
23
W. F. Mader,
23
R. Nogowski,
23
K. R. Schubert,
23
R. Schwierz,
23
J. E. Sundermann,
23
A. Volk,
23
D. Bernard,
24
G. R. Bonneaud,
24
E. Latour,
24
Ch. Thiebaux,
24
M. Verderi,
24
P. J. Clark,
25
W. Gradl,
25
S. Playfer,
25
J. E. Watson,
25
M. Andreotti,
26a,26b
D. Bettoni,
26a
C. Bozzi,
26a
R. Calabrese,
26a,26b
A. Cecchi,
26a,26b
G. Cibinetto,
26a,26b
P. Franchini,
26a,26b
E. Luppi,
26a,26b
M. Negrini,
26a,26b
A. Petrella,
26a,26b
L. Piemontese,
26a
V. Santoro,
26a,26b
R. Baldini-Ferroli,
27
A. Calcaterra,
27
R. de Sangro,
27
G. Finocchiaro,
27
S. Pacetti,
27
P. Patteri,
27
I. M. Peruzzi,
27,
x
M. Piccolo,
27
M. Rama,
27
A. Zallo,
27
A. Buzzo,
28a
R. Contri,
28a,28b
M. Lo Vetere,
28a,28b
M. M. Macri,
28a
M. R. Monge,
28a,28b
S. Passaggio,
28a
C. Patrignani,
28a,28b
E. Robutti,
28a
A. Santroni,
28a,28b
S. Tosi,
28a,28b
K. S. Chaisanguanthum,
29
M. Morii,
29
R. S. Dubitzky,
30
J. Marks,
30
S. Schenk,
30
U. Uwer,
30
V. Klose,
31
H. M. Lacker,
31
D. J. Bard,
32
P. D. Dauncey,
32
J. A. Nash,
32
W. Panduro Vazquez,
32
M. Tibbetts,
32
P. K. Behera,
33
X. Chai,
33
M. J. Charles,
33
U. Mallik,
33
J. Cochran,
34
H. B. Crawley,
34
L. Dong,
34
W. T. Meyer,
34
S. Prell,
34
E. I. Rosenberg,
34
A. E. Rubin,
34
Y. Y. Gao,
35
A. V. Gritsan,
35
Z. J. Guo,
35
C. K. Lae,
35
A. G. Denig,
36
M. Fritsch,
36
G. Schott,
36
N. Arnaud,
37
J. Be
́
quilleux,
37
A. D’Orazio,
37
M. Davier,
37
J. Fermino da Costa,
37
G. Grosdidier,
37
A. Ho
̈
cker,
37
V. Lepeltier,
37
F. Le Diberder,
37
A. M. Lutz,
37
S. Pruvot,
37
P. Roudeau,
37
M. H. Schune,
37
J. Serrano,
37
V. Sordini,
37,
k
A. Stocchi,
37
G. Wormser,
37
D. J. Lange,
38
D. M. Wright,
38
I. Bingham,
39
J. P. Burke,
39
C. A. Chavez,
39
J. R. Fry,
39
E. Gabathuler,
39
R. Gamet,
39
D. E. Hutchcroft,
39
D. J. Payne,
39
C. Touramanis,
39
A. J. Bevan,
40
K. A. George,
40
F. Di Lodovico,
40
R. Sacco,
40
M. Sigamani,
40
G. Cowan,
41
H. U. Flaecher,
41
D. A. Hopkins,
41
S. Paramesvaran,
41
F. Salvatore,
41
A. C. Wren,
41
D. N. Brown,
42
C. L. Davis,
42
K. E. Alwyn,
43
N. R. Barlow,
43
R. J. Barlow,
43
Y. M. Chia,
43
C. L. Edgar,
43
G. D. Lafferty,
43
T. J. West,
43
J. I. Yi,
43
J. Anderson,
44
C. Chen,
44
A. Jawahery,
44
D. A. Roberts,
44
G. Simi,
44
J. M. Tuggle,
44
C. Dallapiccola,
45
S. S. Hertzbach,
45
X. Li,
45
E. Salvati,
45
S. Saremi,
45
R. Cowan,
46
D. Dujmic,
46
P. H. Fisher,
46
K. Koeneke,
46
G. Sciolla,
46
M. Spitznagel,
46
F. Taylor,
46
R. K. Yamamoto,
46
M. Zhao,
46
S. E. Mclachlin,
47,
*
P. M. Patel,
47
S. H. Robertson,
47
A. Lazzaro,
48a,48b
V. Lombardo,
48a
F. Palombo,
48a,48b
J. M. Bauer,
49
L. Cremaldi,
49
V. Eschenburg,
49
R. Godang,
49,
{
R. Kroeger,
49
D. A. Sanders,
49
D. J. Summers,
49
H. W. Zhao,
49
M. Simard,
50
P. Taras,
50
F. B. Viaud,
50
H. Nicholson,
51
G. De Nardo,
52a,52b
L. Lista,
52a
D. Monorchio,
52a,52b
G. Onorato,
52a,52b
C. Sciacca,
52a,52b
M. A. Baak,
53
G. Raven,
53
H. L. Snoek,
53
C. P. Jessop,
54
K. J. Knoepfel,
54
J. M. LoSecco,
54
W. F. Wang,
54
G. Benelli,
55
L. A. Corwin,
55
K. Honscheid,
55
H. Kagan,
55
R. Kass,
55
J. P. Morris,
55
A. M. Rahimi,
55
J. J. Regensburger,
55
S. J. Sekula,
55
Q. K. Wong,
55
N. L. Blount,
56
J. Brau,
56
R. Frey,
56
O. Igonkina,
56
J. A. Kolb,
56
M. Lu,
56
R. Rahmat,
56
N. B. Sinev,
56
D. Strom,
56
J. Strube,
56
E. Torrence,
56
G. Castelli,
57a,57b
N. Gagliardi,
57a,57b
M. Margoni,
57a,57b
M. Morandin,
57a
M. Posocco,
57a
M. Rotondo,
57a
F. Simonetto,
57a,57b
R. Stroili,
57a,57b
C. Voci,
57a,57b
P. del Amo Sanchez,
58
E. Ben-Haim,
58
H. Briand,
58
G. Calderini,
58
J. Chauveau,
58
P. David,
58
L. Del Buono,
58
O. Hamon,
58
Ph. Leruste,
58
J. Ocariz,
58
A. Perez,
58
J. Prendki,
58
L. Gladney,
59
M. Biasini,
60a,60b
R. Covarelli,
60a,60b
E. Manoni,
60a,60b
C. Angelini,
61a,61b
G. Batignani,
61a,61b
S. Bettarini,
61a,61b
M. Carpinelli,
61a,61b,
**
A. Cervelli,
61a,61b
F. Forti,
61a,61b
M. A. Giorgi,
61a,61b
A. Lusiani,
61a,61c
G. Marchiori,
61a,61b
M. Morganti,
61a,61b
N. Neri,
61a,61b
E. Paoloni,
61a,61b
G. Rizzo,
61a,61b
J. J. Walsh,
61a
J. Biesiada,
62
D. Lopes Pegna,
62
C. Lu,
62
J. Olsen,
62
A. J. S. Smith,
62
A. V. Telnov,
62
F. Anulli,
63a
E. Baracchini,
63a,63b
G. Cavoto,
63a
PHYSICAL REVIEW D
78,
112003 (2008)
1550-7998
=
2008
=
78(11)
=
112003(18)
112003-1
Ó
2008 The American Physical Society
D. del Re,
63a,63b
E. Di Marco,
63a,63b
R. Faccini,
63a,63b
F. Ferrarotto,
63a
F. Ferroni,
63a,63b
M. Gaspero,
63a,63b
P. D. Jackson,
63a
L. Li Gioi,
63a
M. A. Mazzoni,
63a
S. Morganti,
63a
G. Piredda,
63a
F. Polci,
63a,63b
F. Renga,
63a,63b
C. Voena,
63a
M. Ebert,
64
T. Hartmann,
64
H. Schro
̈
der,
64
R. Waldi,
64
T. Adye,
65
B. Franek,
65
E. O. Olaiya,
65
W. Roethel,
65
F. F. Wilson,
65
S. Emery,
66
M. Escalier,
66
L. Esteve,
66
A. Gaidot,
66
S. F. Ganzhur,
66
G. Hamel de Monchenault,
66
W. Kozanecki,
66
G. Vasseur,
66
Ch. Ye
`
che,
66
M. Zito,
66
X. R. Chen,
67
H. Liu,
67
W. Park,
67
M. V. Purohit,
67
R. M. White,
67
J. R. Wilson,
67
M. T. Allen,
68
D. Aston,
68
R. Bartoldus,
68
P. Bechtle,
68
J. F. Benitez,
68
R. Cenci,
68
J. P. Coleman,
68
M. R. Convery,
68
J. C. Dingfelder,
68
J. Dorfan,
68
G. P. Dubois-Felsmann,
68
W. Dunwoodie,
68
R. C. Field,
68
A. M. Gabareen,
68
S. J. Gowdy,
68
M. T. Graham,
68
P. Grenier,
68
C. Hast,
68
W. R. Innes,
68
J. Kaminski,
68
M. H. Kelsey,
68
H. Kim,
68
P. Kim,
68
M. L. Kocian,
68
D. W. G. S. Leith,
68
S. Li,
68
B. Lindquist,
68
S. Luitz,
68
V. Luth,
68
H. L. Lynch,
68
D. B. MacFarlane,
68
H. Marsiske,
68
R. Messner,
68
D. R. Muller,
68
H. Neal,
68
S. Nelson,
68
C. P. O’Grady,
68
I. Ofte,
68
A. Perazzo,
68
M. Perl,
68
B. N. Ratcliff,
68
A. Roodman,
68
A. A. Salnikov,
68
R. H. Schindler,
68
J. Schwiening,
68
A. Snyder,
68
D. Su,
68
M. K. Sullivan,
68
K. Suzuki,
68
S. K. Swain,
68
J. M. Thompson,
68
J. Va’vra,
68
A. P. Wagner,
68
M. Weaver,
68
C. A. West,
68
W. J. Wisniewski,
68
M. Wittgen,
68
D. H. Wright,
68
H. W. Wulsin,
68
A. K. Yarritu,
68
K. Yi,
68
C. C. Young,
68
V. Ziegler,
68
P. R. Burchat,
69
A. J. Edwards,
69
S. A. Majewski,
69
T. S. Miyashita,
69
B. A. Petersen,
69
L. Wilden,
69
S. Ahmed,
70
M. S. Alam,
70
R. Bula,
70
J. A. Ernst,
70
B. Pan,
70
M. A. Saeed,
70
S. B. Zain,
70
S. M. Spanier,
71
B. J. Wogsland,
71
R. Eckmann,
72
J. L. Ritchie,
72
A. M. Ruland,
72
C. J. Schilling,
72
R. F. Schwitters,
72
B. W. Drummond,
73
J. M. Izen,
73
X. C. Lou,
73
F. Bianchi,
74a,74b
D. Gamba,
74a,74b
M. Pelliccioni,
74a,74b
M. Bomben,
75a,75b
L. Bosisio,
75a,75b
C. Cartaro,
75a,75b
G. Della Ricca,
75a,75b
L. Lanceri,
75a,75b
L. Vitale,
75a,75b
V. Azzolini,
76
N. Lopez-March,
76
F. Martinez-Vidal,
76
D. A. Milanes,
76
A. Oyanguren,
76
J. Albert,
77
Sw. Banerjee,
77
B. Bhuyan,
77
H. H. F. Choi,
77
K. Hamano,
77
R. Kowalewski,
77
M. J. Lewczuk,
77
I. M. Nugent,
77
J. M. Roney,
77
R. J. Sobie,
77
T. J. Gershon,
78
P. F. Harrison,
78
J. Ilic,
78
T. E. Latham,
78
G. B. Mohanty,
78
H. R. Band,
79
X. Chen,
79
S. Dasu,
79
K. T. Flood,
79
Y. Pan,
79
M. Pierini,
79
R. Prepost,
79
C. O. Vuosalo,
79
and S. L. Wu
79
(
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 Bristol, Bristol BS8 1TL, United Kingdom
9
University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z1
10
Brunel University, Uxbridge, Middlesex UB8 3PH, United Kingdom
11
Budker Institute of Nuclear Physics, Novosibirsk 630090, Russia
12
University of California at Irvine, Irvine, California 92697, USA
13
University of California at Los Angeles, Los Angeles, California 90024, USA
14
University of California at Riverside, Riverside, California 92521, USA
15
University of California at San Diego, La Jolla, California 92093, USA
16
University of California at Santa Barbara, Santa Barbara, California 93106, USA
17
University of California at Santa Cruz, Institute for Particle Physics, Santa Cruz, California 95064, USA
18
California Institute of Technology, Pasadena, California 91125, USA
19
University of Cincinnati, Cincinnati, Ohio 45221, USA
20
University of Colorado, Boulder, Colorado 80309, USA
21
Colorado State University, Fort Collins, Colorado 80523, USA
22
Technische Universita
̈
t Dortmund, Fakulta
̈
t Physik, D-44221 Dortmund, Germany
23
Technische Universita
̈
t Dresden, Institut fu
̈
r Kern- und Teilchenphysik, D-01062 Dresden, Germany
24
Laboratoire Leprince-Ringuet, CNRS/IN2P3, Ecole Polytechnique, F-91128 Palaiseau, France
25
University of Edinburgh, Edinburgh EH9 3JZ, United Kingdom
26a
INFN Sezione di Ferrara, I-44100 Ferrara, Italy
26b
Dipartimento di Fisica, Universita
`
di Ferrara, I-44100 Ferrara, Italy
27
INFN Laboratori Nazionali di Frascati, I-00044 Frascati, Italy
28a
INFN Sezione di Genova, I-16146 Genova, Italy
28b
Dipartimento di Fisica, Universita
`
di Genova, I-16146 Genova, Italy
29
Harvard University, Cambridge, Massachusetts 02138, USA
B. AUBERT
et al.
PHYSICAL REVIEW D
78,
112003 (2008)
112003-2
30
Universita
̈
t Heidelberg, Physikalisches Institut, Philosophenweg 12, D-69120 Heidelberg, Germany
31
Humboldt-Universita
̈
t zu Berlin, Institut fu
̈
r Physik, Newtonstr. 15, D-12489 Berlin, Germany
32
Imperial College London, London, SW7 2AZ, United Kingdom
33
University of Iowa, Iowa City, Iowa 52242, USA
34
Iowa State University, Ames, Iowa 50011-3160, USA
35
Johns Hopkins University, Baltimore, Maryland 21218, USA
36
Universita
̈
t Karlsruhe, Institut fu
̈
r Experimentelle Kernphysik, D-76021 Karlsruhe, Germany
37
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
38
Lawrence Livermore National Laboratory, Livermore, California 94550, USA
39
University of Liverpool, Liverpool L69 7ZE, United Kingdom
40
Queen Mary, University of London, E1 4NS, United Kingdom
41
University of London, Royal Holloway and Bedford New College, Egham, Surrey TW20 0EX, United Kingdom
42
University of Louisville, Louisville, Kentucky 40292, USA
43
University of Manchester, Manchester M13 9PL, United Kingdom
44
University of Maryland, College Park, Maryland 20742, USA
45
University of Massachusetts, Amherst, Massachusetts 01003, USA
46
Massachusetts Institute of Technology, Laboratory for Nuclear Science, Cambridge, Massachusetts 02139, USA
47
McGill University, Montre
́
al, Que
́
bec, Canada H3A 2T8
48a
INFN Sezione di Milano, I-20133 Milano, Italy
48b
Dipartimento di Fisica, Universita
`
di Milano, I-20133 Milano, Italy
49
University of Mississippi, University, Mississippi 38677, USA
50
Universite
́
de Montre
́
al, Physique des Particules, Montre
́
al, Que
́
bec, Canada H3C 3J7
51
Mount Holyoke College, South Hadley, Massachusetts 01075, USA
52a
INFN Sezione di Napoli, I-80126 Napoli, Italy
52b
Dipartimento di Scienze Fisiche, Universita
`
di Napoli Federico II, I-80126 Napoli, Italy
53
NIKHEF, National Institute for Nuclear Physics and High Energy Physics, NL-1009 DB Amsterdam, The Netherlands
54
University of Notre Dame, Notre Dame, Indiana 46556, USA
55
Ohio State University, Columbus, Ohio 43210, USA
56
University of Oregon, Eugene, Oregon 97403, USA
57a
INFN Sezione di Padova, I-35131 Padova, Italy
57b
Dipartimento di Fisica, Universita
`
di Padova, I-35131 Padova, Italy
58
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
59
University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
60a
INFN Sezione di Perugia, I-06100 Perugia, Italy
60b
Dipartimento di Fisica, Universita
`
di Perugia, I-06100 Perugia, Italy
61a
INFN Sezione di Pisa, I-56127 Pisa, Italy
61b
Dipartimento di Fisica, Universita
`
di Pisa, I-56127 Pisa, Italy
61c
Scuola Normale Superiore di Pisa, I-56127 Pisa, Italy
62
Princeton University, Princeton, New Jersey 08544, USA
63a
INFN Sezione di Roma, I-00185 Roma, Italy
63b
Dipartimento di Fisica, Universita
`
di Roma La Sapienza, I-00185 Roma, Italy
64
Universita
̈
t Rostock, D-18051 Rostock, Germany
65
Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, OX11 0QX, United Kingdom
66
DSM/Dapnia, CEA/Saclay, F-91191 Gif-sur-Yvette, France
67
University of South Carolina, Columbia, South Carolina 29208, USA
68
Stanford Linear Accelerator Center, Stanford, California 94309, USA
69
Stanford University, Stanford, California 94305-4060, USA
70
State University of New York, Albany, New York 12222, USA
71
University of Tennessee, Knoxville, Tennessee 37996, USA
72
University of Texas at Austin, Austin, Texas 78712, USA
73
University of Texas at Dallas, Richardson, Texas 75083, USA
{
Now at University of South Alabama, Mobile, AL 36688, USA.
k
Also with Universita
`
di Roma La Sapienza, I-00185 Roma, 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, PA 19122, USA.
**
Also with Universita
`
di Sassari, Sassari, Italy.
*
Deceased.
MEASUREMENTS OF
...
PHYSICAL REVIEW D
78,
112003 (2008)
112003-3
74a
INFN Sezione di Torino, I-10125 Torino, Italy
74b
Dipartimento di Fisica Sperimentale, Universita
`
di Torino, I-10125 Torino, Italy
75a
INFN Sezione di Trieste, I-34127 Trieste, Italy
75b
Dipartimento di Fisica, Universita
`
di Trieste, I-34127 Trieste, Italy
76
IFIC, Universitat de Valencia-CSIC, E-46071 Valencia, Spain
77
University of Victoria, Victoria, British Columbia, Canada V8W 3P6
78
Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom
79
University of Wisconsin, Madison, Wisconsin 53706, USA
(Received 31 July 2008; published 29 December 2008)
We present an investigation of the decays
B
0
!
þ
c
p
and
B
!
þ
c
p
based on
383
10
6
ð
4
S
Þ!
B
B
decays recorded with the
BABAR
detector. We measure the branching fractions of these decays; their
ratio is
B
ð
B
!
þ
c
p
Þ
=
B
ð
B
0
!
þ
c
p
Þ¼
15
:
4
1
:
8
0
:
3
. The
B
!
þ
c
p
process exhibits an
enhancement at the
þ
c
p
threshold and is a laboratory for searches for excited charm baryon states. We
observe the resonant decays
B
!
c
ð
2455
Þ
0
p
and
B
!
c
ð
2800
Þ
0
p
but see no evidence for
B
!
c
ð
2520
Þ
0
p
. This is the first observation of the decay
B
!
c
ð
2800
Þ
0
p
; however, the mass of the
observed excited
0
c
state is
ð
2846
8
10
Þ
MeV
=c
2
, which is somewhat inconsistent with previous
measurements. Finally, we examine the angular distribution of the
B
!
c
ð
2455
Þ
0
p
decays and measure
the spin of the
c
ð
2455
Þ
0
baryon to be
1
=
2
, as predicted by the quark model.
DOI:
10.1103/PhysRevD.78.112003
PACS numbers: 13.25.Hw, 13.60.Rj, 14.20.Lq
I. INTRODUCTION
Baryonic decays of
B
mesons, which contain a heavy
bottom quark and a light up or down quark, provide a
laboratory for a range of particle physics investigations:
trends in decay rates and baryon production mechanisms;
searches for exotic states such as pentaquarks and glueballs
[
1
,
2
]; searches for excited baryon resonances; examination
of the angular distributions of
B
-meson decay products to
determine baryon spins; and measurements of radiative
baryonic
B
decays that could be sensitive to new physics
through flavor-changing neutral currents [
3
,
4
]. The latter
measurements rely on improving our theoretical under-
standing of baryonic
B
decays in general [
5
,
6
].
The inclusive branching fraction for baryonic
B
decays
is
ð
6
:
8
0
:
6
Þ
%
[
7
], and many exclusive baryonic
B
decay
modes have been observed [
8
]. If we order the measured
decays by
Q
value,
Q
¼
m
B
X
f
m
f
;
(1)
where
m
f
is the mass of each daughter in the final state of
the
B
decay, we find that for each type of baryonic
B
decay,
the branching fractions decrease as the
Q
value increases.
The smallest measured branching fraction is of the order
10
6
, which also corresponds to our experimental sensi-
tivity for measuring these branching fractions. Potentially
interesting
B
-meson decays such as
B
!
p
p
,
B
!
,
and
B
!
þ
c
c
have not yet been seen.
Theoretical approaches to calculating baryonic
B
decays
include pole models [
9
,
10
], diquark models [
11
], and QCD
sum rules [
12
,
13
]. Recently, theoretical calculations have
focused on pole models, where the
B
decay proceeds
through an intermediate
b
-flavored baryon state, which
then decays weakly into one of the final-state baryons
[
14
,
15
]. However, it is not clear that the pole model is
reliable for baryon poles, and the predictions given in the
literature vary significantly. Perhaps the most satisfying
theoretical interpretation of baryonic
B
decay rates is the
qualitative one proposed by Hou and Soni in 2001 [
16
],
who argue that
B
decays are favored if the baryon and
antibaryon in the final-state configuration are close to-
gether in phase space. A consequence is that decay rates
to two-body baryon-antibaryon final states are suppressed
relative to rates of three-body final states containing the
same baryon-antibaryon system plus an additional meson.
In the three-body case, the baryon and antibaryon can be in
the favored configuration—close together in phase space—
rather than back-to-back as in the two-body case.
In this paper, we investigate the decays
B
0
!
þ
c
p
and
B
!
þ
c
p
[
17
]. We investigate baryon production in
B
decays by comparing the two-body (
B
0
!
þ
c
p
) and
three-body (
B
!
þ
c
p
) decay rates directly. The dy-
namics of the baryon-antibaryon (
þ
c
p
) system in the
three-body decay provide insight into baryon production
mechanisms. Additionally, the
B
!
þ
c
p
system is a
laboratory for studying excited baryon states and is used to
measure the spin of the
c
ð
2455
Þ
0
. This is the first mea-
surement of the spin of this state.
II.
BABAR
DETECTOR AND DATA SAMPLE
The measurements presented in this paper are based on
383
10
6
ð
4
S
Þ!
B
B
decays recorded with the
BABAR
detector [
18
] at the PEP-II
e
þ
e
asymmetric-energy
B
Factory at the Stanford Linear Accelerator Center. At the
interaction point, 9 GeV electrons collide with 3.1 GeV
positrons at the
ð
4
S
Þ
resonance with a center-of-mass
energy of
10
:
58 GeV
=c
2
.
B. AUBERT
et al.
PHYSICAL REVIEW D
78,
112003 (2008)
112003-4
Charged particle trajectories are measured by a five-
layer silicon vertex tracker (SVT) and a 40-layer drift
chamber (DCH) immersed in a 1.5 T axial magnetic field.
Charged particle identification is provided by ionization
energy (
dE=dx
) measurements in the SVT and DCH along
with Cherenkov radiation detection by an internally reflect-
ing ring-imaging detector.
Exclusive
B
-meson decays are simulated with the
Monte Carlo (MC) event generator
EVTGEN
[
19
].
Background continuum MC samples (
e
þ
e
!
q
q
, where
q
¼
u
,
d
,
s
,
c
) are simulated using
JETSET7
:
4
[
20
]to
model generic hadronization processes. Background MC
samples of
e
þ
e
!
B
þ
B
and
B
0
B
0
are based on simu-
lations of many exclusive
B
decays (also using
EVTGEN
).
The large samples of simulated events are generated and
propagated through a detailed detector simulation using the
GEANT4
simulation package [
21
].
III. CANDIDATE SELECTION
We select candidates that are kinematically consistent
with
B
0
!
þ
c
p
and
B
!
þ
c
p
. For the decay mode
B
!
þ
c
p
, we reconstruct
þ
c
candidates in the
pK
þ
,
pK
0
S
,
pK
0
S
þ
, and
þ
decay modes, requiring the
invariant mass of each
þ
c
candidate to be within
10 MeV
=c
2
of the world average value [
8
]. For
B
!
þ
c
p
, we also reconstruct
þ
c
candidates in the
þ
þ
decay mode, and require all of the
þ
c
candi-
dates to have an invariant mass within
12 Mev
=c
2
of the
world average value.
The
p
,
K
, and
candidates must be well reconstructed
in the DCH and are identified with likelihood-based parti-
cle selectors using information from the SVT, DCH, and
internally reflecting ring-imaging detector.
The
K
0
S
candidates are reconstructed from two oppo-
sitely charged pion candidates that come from a common
vertex;
candidates are formed by combining a proton
candidate with an oppositely charged pion candidate that
comes from a common vertex. The invariant mass of each
K
0
S
and
candidate must be within
10 MeV
=c
2
of the
world average value [
8
] and the flight significance (defined
as the flight distance from the
þ
c
vertex in the
x
y
plane
divided by the measurement uncertainty) must be greater
than 2. The mass of each
K
0
S
and
candidate is then
constrained to the world average value [
8
].
A mass constraint is applied to all of the
þ
c
candidates,
and all
þ
c
daughter tracks must come from a common
vertex. The
þ
c
candidates are then combined with an
antiproton to form a
B
0
!
þ
c
p
candidate, or with an
antiproton and a pion to form a
B
!
þ
c
p
candidate.
The daughters of each
B
candidate must come from a
common vertex, and the candidate with the largest
2
probability in each event is selected.
Additional background suppression is provided by in-
formation about the topology of the events. A Fisher
discriminant [
22
] is constructed based on the absolute
value of the cosine of the angle of the
B
candidate mo-
mentum vector with respect to the beam axis in the
e
þ
e
center-of-mass (CM) frame, the absolute value of the
cosine of the angle between the
B
candidate thrust axis
[
23
] and the thrust axis of the rest of the event in the
e
þ
e
CM
frame, and the moments
L
0
and
L
2
. The quantity
L
j
is defined as
P
i
p
i
j
cos
i
j
j
, where
i
is the angle with
respect to the
B
candidate thrust axis of the
i
th charged
particle or neutral cluster in the rest of the event and
p
i
is
its momentum. The optimal maximum value of the Fisher
discriminant is chosen separately for each
þ
c
and
B
decay
mode.
Kinematic properties of
B
-meson pair production at the
ð
4
S
Þ
provide further background discrimination. We de-
fine a pair of observables,
m
m
and
m
r
, that are uncorrelated
and exploit these constraints:
m
m
¼
ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
ð
q
e
þ
e
^
q
þ
c
p
ð
Þ
Þ
2
q
and
m
r
¼
ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
ð
q
þ
c
p
ð
Þ
Þ
2
q
m
B
:
(2)
The variable
m
m
is based on the apparent recoil mass of the
unreconstructed
B
meson in the event, where
q
e
þ
e
is the
four-momentum of the
e
þ
e
system and
^
q
þ
c
p
ð
Þ
is the
four-momentum of the reconstructed
B
candidate after
applying a mass constraint. The variable
m
r
is the differ-
ence between the unconstrained mass of the reconstructed
B
candidate and
m
B
, the world average value of the mass of
the
B
meson [
8
]. Signal events peak at
m
B
in
m
m
and 0 in
m
r
. This set of variables was first used in [
24
] and is chosen
as an uncorrelated alternative to
E
¼
E
B
1
2
ffiffiffi
s
p
and the
energy-substituted mass
m
ES
¼
ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
1
4
s
p
2
B
q
(where
s
¼
q
2
e
þ
e
and the asterisk denotes the
e
þ
e
rest frame), which
exhibit a
30%
correlation for
B
!
þ
c
p
.
The event selection criteria are optimized based on
studies of sideband data (in the region
0
:
10
<m
r
<
0
:
20 GeV
=c
2
) and simulated signal MC samples. The
data in a signal region (approximately
2
wide in
m
m
and
m
r
) were blinded until the selection criteria were
determined and the signal extraction procedure was speci-
fied and validated.
B
candidates that satisfy
m
m
>
5
:
121 GeV
=c
2
and
j
m
r
j
<
0
:
10 GeV
=c
2
are used in the
maximum likelihood fit.
IV. BACKGROUNDS
The primary source of background for
B
0
!
þ
c
p
can-
didates is continuum
e
þ
e
!
q
q
events. Backgrounds due
to decays such as
B
!
þ
c
p
,
B
0
!
þ
c
p
0
, and
B
!
0
c
p;
,
0
c
!
þ
c
are rejected by the criterion
j
m
r
j
<
0
:
10 GeV
=c
2
.
Approximately equal amounts of continuum
e
þ
e
!
q
q
and
e
þ
e
!
B
B
events make up the background for
B
!
þ
c
p
events. Again, the requirement
j
m
r
j
<
0
:
10 GeV
=c
2
rejects most of the contributions from such
MEASUREMENTS OF
...
PHYSICAL REVIEW D
78,
112003 (2008)
112003-5
decays as
B
0
!
þ
c
p
þ
and
B
!
þ
c
p
0
.
Approximately 1% of the background in the fit region is
due to these four-body events, but they do not peak in
m
m
and
m
r
. A small peaking background is present from
B
0
!
þ
c
p
,
þ
c
!
þ
c
0
events, especially when the
0
has low
momentum. Based on a branching fraction measurement of
the isospin partner decay
B
ð
B
!
c
ð
2455
Þ
0
p
Þ¼ð
3
:
7
0
:
7
0
:
4
1
:
0
Þ
10
5
[
25
], where the uncertainties are
statistical, systematic, and the uncertainty due to
B
ð
þ
c
!
pK
þ
Þ
, respectively, we expect
11
:
5
2
:
5
peaking
background events in the signal region for
B
!
þ
c
p
,
þ
c
!
pK
þ
. A correction is applied and a
systematic uncertainty is assigned to compensate for these
events.
V. DETECTION EFFICIENCY
The detection efficiencies for
B
0
!
þ
c
p
and
B
!
þ
c
p
signal events are determined from signal MC
samples with 175 000 to over 1 600 000 events in each
sample, depending on the
þ
c
decay mode. To account
for inaccuracies in the simulation of the detector, each
MC event is assigned a weight based on each daughter
particle’s momentum and angle. These weights are deter-
mined from studies comparing large pure samples of pro-
tons, kaons, and pions in MC samples and data. Small
corrections (0.4%–1.6%) are also applied to account for
tracking inefficiencies due to the displaced
K
0
S
and
vertices. These corrections depend on the
K
0
S
and
daugh-
ter trajectories’ transverse momentum and angle, and the
distance between the beam spot and the displaced vertex.
The detection efficiency (
"
l
) for
B
0
!
þ
c
p
signal
events in each
þ
c
decay mode (
l
) is determined from the
number of signal events extracted from an extended un-
binned maximum likelihood fit to signal MC events. These
events pass the same selection criteria as applied to data.
The fit is performed in two dimensions,
m
m
and
m
r
. The
probability distribution function (PDF) for the background
consists of a threshold function [
26
]in
m
m
multiplied by a
first-order polynomial in
m
r
; this is the same as the back-
ground PDF used in the fit to the
B
0
!
þ
c
p
data. The
signal PDF consists of a Gaussian in
m
m
multiplied by a
modified asymmetric Gaussian with a tail parameter in
m
r
.
The detection efficiencies in each
þ
c
decay mode are
summarized in Table
I
.
The detection efficiency for
B
!
þ
c
p
signal
events in each
þ
c
decay mode varies considerably across
the Dalitz plane of the three-body decay. For reference, we
quote the average efficiencies in Table
I
, but we apply a
more sophisticated treatment to these events. We parame-
trize the physical Dalitz region using the variables
cos
h
and the
þ
c
invariant mass,
m
c
. The helicity angle
h
is defined as the angle between the
and the
p
in the
B
rest frame. The quantity
cos
h
can be expressed in terms of
Lorentz-invariant products of four-vectors. We divide the
kinematic region into reasonably sized bins that are uni-
form in
cos
h
(0.2 units wide) and nonuniform in
m
c
(
60
–
200 MeV
=c
2
wide). This choice of variables is more
conducive to rectangular bins than the traditional set of
Dalitz variables. The
m
c
bins are narrower near the
kinematic limits where the efficiency changes more rapidly
and are centered on expected resonances. For
B
!
þ
c
p
,
þ
c
!
pK
þ
near
cos
h
¼
0
, the efficiency
varies from approximately 13% at low
m
c
, to 16% in the
central
m
c
region, to 8% at high
m
c
. The efficiency is
fairly uniform with respect to
cos
h
, except at
cos
h
1
and low
m
c
, where it drops to 7.4%. The other
þ
c
decay
modes exhibit similar variations in efficiency.
VI. SIGNAL EXTRACTION
To extract the number of signal events in data, a two-
dimensional (
m
m
vs
m
r
) extended unbinned maximum
likelihood fit is performed simultaneously across
þ
c
decay
modes.
B
0
!
þ
c
p
candidates and
B
!
þ
c
p
candi-
dates are fit separately.
The background PDF for each fit is a threshold function
[
26
]in
m
m
multiplied by a first-order polynomial in
m
r
.
The shape parameter (
~
s
bkg
) of the threshold function is free
but is common to all of the
þ
c
decay modes. The slope
a
of the first-order polynomial is allowed to vary indepen-
dently for each
þ
c
decay mode.
The signal PDF is a single Gaussian distribution in
m
m
multiplied by a single Gaussian distribution in
m
r
for
B
0
!
þ
c
p
and multiplied by a double Gaussian distribution in
m
r
for
B
!
þ
c
p
. A single Gaussian is sufficient to
describe the signal PDF for
B
0
!
þ
c
p
because of the
small number of expected signal events. All of the shape
parameters of the signal PDF (
~
s
sig
) are free but are shared
among the
þ
c
decay modes. Separate signal (
N
sig
;l
) and
background (
N
bkg
;l
) yields are extracted for each
þ
c
decay
mode
l
.
The total likelihood is the product of the likelihoods for
each
þ
c
decay mode:
L
tot
¼
Y
l
L
l
ð
~
y
l
;
N
sig
;l
;N
bkg
;l
;
~
s
sig
;
~
s
bkg
;a
l
Þ
:
(3)
TABLE I. Detection efficiency for
B
0
!
þ
c
p
signal events,
determined from signal Monte Carlo samples and separated by
þ
c
decay mode. The numbers correspond to the efficiency for
B
0
!
þ
c
p
ð
B
!
þ
c
p
Þ
,
þ
c
!
f
l
, where
f
l
is a given final
state. The efficiencies quoted for the
B
!
þ
c
p
decays are
averaged across phase space.
Efficiency for
þ
c
!
f
l
f
l
B
0
!
þ
c
pB
!
þ
c
p
pK
þ
22.9%
15.4%
pK
0
S
21.6%
14.3%
pK
0
S
þ
9.6%
5.6%
þ
17.2%
11.6%
þ
þ
4.0%
B. AUBERT
et al.
PHYSICAL REVIEW D
78,
112003 (2008)
112003-6
The symbol
~
y
represents the variables used in the 2D fit,
f
m
m
;m
r
g
.
The full simultaneous fit is validated using independent
samples of signal MC events to simulate signal events and
toy MC samples (generated from the background MC
sample distribution) to represent background events in
the fit region. For both
B
0
!
þ
c
p
and
B
!
þ
c
p
,
we perform fits to 100 combined MC samples and find that
the fit is robust and the results are unbiased.
The results of the 2D fits to data are shown in projections
of
m
m
and
m
r
for each
þ
c
decay mode. Figure
1
shows the
result of the fit to
B
0
!
þ
c
p
candidates and Fig.
2
shows
the result of the fit to
B
!
þ
c
p
candidates. The
signal yields from the fits are summarized in Table
II
.
VII. BRANCHING FRACTION MEASUREMENTS
For the three-body mode
B
!
þ
c
p
, the efficiency
variation across the Dalitz plane requires a correction for
each signal event in order to extract the branching fraction
for this mode. We use the
s
P
lot
method [
27
] to calculate a
weight for each event
e
based on the 2D fit to the variables
~
y
.Wehave
N
s
¼
2
species (signal and background) for
each
þ
c
decay mode and define
f
j;k
as the signal (
j; k
¼
1
)
or background (
j; k
¼
2
) PDF. The
s
P
lot
weights are
calculated as
s
P
n
ð
~
y
e
Þ¼
P
N
s
j
¼
1
V
nj
f
j
ð
~
y
e
Þ
P
N
s
k
¼
1
N
k
f
k
ð
~
y
e
Þ
;
(4)
where
s
P
n
ð
~
y
e
Þ
is the
s
P
lot
weight for species
n
,
V
is the
covariance matrix for signal and background yields,
f
j;k
ð
~
y
e
Þ
is the value of PDF
f
j;k
for event
e
, and
~
y
e
is the
m
m
and
m
r
value for event
e
. The elements of the inverse of
the covariance matrix
V
are calculated as follows:
20
40
60
20
40
60
(a)
5
10
5
10
(c)
5
10
15
5
10
15
(e)
)
2
(GeV/c
m
m
0
5
10
)
2
(GeV/c
m
m
0
5
10
5.15
5.20
5.25
5.30
(g)
10
20
30
10
20
30
(b)
2
4
6
8
2
4
6
8
(d)
5
10
5
10
(f)
)
2
(GeV/c
r
m
-0.10
-0.05
0.00
0.05
0.10
0
2
4
6
8
)
2
(GeV/c
r
m
-0.10
-0.05
0.00
0.05
0.10
0
2
4
6
8
(h)
)
2
Events / ( 0.008 GeV/c
)
2
Events / ( 0.008 GeV/c
FIG. 1 (color online). Projections of
m
m
(left) and
m
r
(right) in data for
B
0
!
þ
c
p
candidates, separated by
þ
c
decay mode:
ð
a; b
Þ
are
þ
c
!
pK
þ
,
ð
c; d
Þ
are
þ
c
!
pK
0
S
,
ð
e; f
Þ
are
þ
c
!
pK
0
S
þ
, and
ð
g; h
Þ
are
þ
c
!
þ
. The
m
m
projections
ð
a; c; e; g
Þ
are
for
j
m
r
j
<
0
:
030 GeV
=c
2
and the
m
r
projections
ð
b; d; f; h
Þ
are for
m
m
>
5
:
27 GeV
=c
2
. The solid curves correspond to the PDF from
the simultaneous 2D fit to candidates for the four
þ
c
decay modes, and the dashed curves represent the background component of the
PDF.
MEASUREMENTS OF
...
PHYSICAL REVIEW D
78,
112003 (2008)
112003-7
V
1
nj
¼
@
2
ð
ln
L
Þ
@N
n
@N
j
¼
X
N
e
¼
1
f
n
ð
~
y
e
Þ
f
j
ð
~
y
e
Þ
ð
P
N
s
k
¼
1
N
k
f
k
ð
~
y
e
ÞÞ
2
;
(5)
where the sum is over the
N
candidates. Note that in the
calculation of the covariance matrix, the data are refit to the
same simultaneous PDF described above, except that all fit
parameters other than the yields are fixed to the values
from the original fit.
We use these
s
P
lot
weights to generate a signal or
background distribution for any quantity that is not corre-
TABLE II. Signal yields from simultaneous fits (across
þ
c
decay modes) to
B
0
!
þ
c
p
and
B
!
þ
c
p
candidates.
N
sig
Mode
B
0
!
þ
c
pB
!
þ
c
p
pK
þ
90
11
991
45
pK
0
S
10
4
165
15
pK
0
S
þ
14
586
14
þ
3
3
114
13
þ
þ
88
13
200
400
600
200
400
600
(a)
50
100
50
100
(c)
20
40
60
80
20
40
60
80
(e)
20
40
60
80
20
40
60
80
(g)
)
2
(GeV/c
m
m
0
50
100
)
2
(GeV/c
m
m
0
50
100
5.15
5.20
5.25
5.30
(i)
100
200
300
100
200
300
(b)
20
40
60
20
40
60
(d)
20
40
20
40
(f)
20
40
20
40
(h)
)
2
(GeV/c
r
m
-0.10
-0.05
0.00
0.05
0.10
0
20
40
)
2
(GeV/c
r
m
-0.10
-0.05
0.00
0.05
0.10
0
20
40
(j)
)
2
Events / ( 0.008 GeV/c
)
2
Events / ( 0.008 GeV/c
FIG. 2 (color online). Projections of
m
m
(left) and
m
r
(right) in data for
B
!
þ
c
p
candidates, separated by
þ
c
decay mode:
ð
a; b
Þ
are
þ
c
!
pK
þ
,
ð
c; d
Þ
are
þ
c
!
pK
0
S
,
ð
e; f
Þ
are
þ
c
!
pK
0
S
þ
,
ð
g; h
Þ
are
þ
c
!
þ
, and
ð
i; j
Þ
are
þ
c
!
þ
þ
.
The
m
m
projections
ð
a; c; e; g; i
Þ
are for
j
m
r
j
<
0
:
030 GeV
=c
2
and the
m
r
projections
ð
b; d; f; h; j
Þ
are for
m
m
>
5
:
27 GeV
=c
2
. The
solid curves correspond to the PDF from the simultaneous 2D fit to candidates for the five
þ
c
decay modes, and the dashed curves
represent the background component of the PDF.
B. AUBERT
et al.
PHYSICAL REVIEW D
78,
112003 (2008)
112003-8