Observation and study of the baryonic
B
-meson decays
B
!
D
ðÞ
p
p
ð
Þð
Þ
P. del Amo Sanchez,
1
J. P. Lees,
1
V. Poireau,
1
E. Prencipe,
1
V. Tisserand,
1
J. Garra Tico,
2
E. Grauges,
2
M. Martinelli,
3a,3b
A. Palano,
3a,3b
M. Pappagallo,
3a,3b
G. Eigen,
4
B. Stugu,
4
L. Sun,
4
M. Battaglia,
5
D. N. Brown,
5
B. Hooberman,
5
L. T. Kerth,
5
Yu. G. Kolomensky,
5
G. Lynch,
5
I. L. Osipenkov,
5
T. Tanabe,
5
C. M. Hawkes,
6
A. T. Watson,
6
H. Koch,
7
T. Schroeder,
7
D. J. Asgeirsson,
8
C. Hearty,
8
T. S. Mattison,
8
J. A. McKenna,
8
A. Khan,
9
A. Randle-Conde,
9
V. E. Blinov,
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
A. N. Yushkov,
10
M. Bondioli,
11
S. Curry,
11
D. Kirkby,
11
A. J. Lankford,
11
M. Mandelkern,
11
E. C. Martin,
11
D. P. Stoker,
11
H. Atmacan,
12
J. W. Gary,
12
F. Liu,
12
O. Long,
12
G. M. Vitug,
12
C. Campagnari,
13
J. M. Flanigan,
13
T. M. Hong,
13
D. Kovalskyi,
13
J. D. Richman,
13
C. West,
13
A. M. Eisner,
14
C. A. Heusch,
14
J. Kroseberg,
14
W. S. Lockman,
14
A. J. Martinez,
14
T. Schalk,
14
B. A. Schumm,
14
A. Seiden,
14
L. O. Winstrom,
14
C. H. Cheng,
15
D. A. Doll,
15
B. Echenard,
15
D. G. Hitlin,
15
P. Ongmongkolkul,
15
F. C. Porter,
15
A. Y. Rakitin,
15
R. Andreassen,
16
M. S. Dubrovin,
16
G. Mancinelli,
16
B. T. Meadows,
16
M. D. Sokoloff,
16
P. C. Bloom,
17
W. T. Ford,
17
A. Gaz,
17
M. Nagel,
17
U. Nauenberg,
17
J. G. Smith,
17
S. R. Wagner,
17
R. Ayad,
18,
*
W. H. Toki,
18
H. Jasper,
19
T. M. Karbach,
19
J. Merkel,
19
A. Petzold,
19
B. Spaan,
19
K. Wacker,
19
M. J. Kobel,
20
K. R. Schubert,
20
R. Schwierz,
20
D. Bernard,
21
M. Verderi,
21
P. J. Clark,
22
S. Playfer,
22
J. E. Watson,
22
M. Andreotti,
23a,23b
D. Bettoni,
23a
C. Bozzi,
23a
R. Calabrese,
23a,23b
A. Cecchi,
23a,23b
G. Cibinetto,
23a,23b
E. Fioravanti,
23a,23b
P. Franchini,
23a,23b
E. Luppi,
23a,23b
M. Munerato,
23a,23b
M. Negrini,
23a,23b
A. Petrella,
23a,23b
L. Piemontese,
23a
R. Baldini-Ferroli,
24
A. Calcaterra,
24
R. de Sangro,
24
G. Finocchiaro,
24
M. Nicolaci,
24
S. Pacetti,
24
P. Patteri,
24
I. M. Peruzzi,
24,
†
M. Piccolo,
24
M. Rama,
24
A. Zallo,
24
R. Contri,
25a,25b
E. Guido,
25a,25b
M. Lo Vetere,
25a,25b
M. R. Monge,
25a,25b
S. Passaggio,
25a
C. Patrignani,
25a,25b
E. Robutti,
25a
S. Tosi,
25a,25b
B. Bhuyan,
26
V. Prasad,
26
C. L. Lee,
27
M. Morii,
27
A. Adametz,
28
J. Marks,
28
U. Uwer,
28
F. U. Bernlochner,
29
M. Ebert,
29
H. M. Lacker,
29
T. Lueck,
29
A. Volk,
29
P. D. Dauncey,
30
M. Tibbetts,
30
P. K. Behera,
31
U. Mallik,
31
C. Chen,
32
J. Cochran,
32
H. B. Crawley,
32
L. Dong,
32
W. T. Meyer,
32
S. Prell,
32
E. I. Rosenberg,
32
A. E. Rubin,
32
A. V. Gritsan,
33
Z. J. Guo,
33
N. Arnaud,
34
M. Davier,
34
D. Derkach,
34
J. Firmino da Costa,
34
G. Grosdidier,
34
F. Le Diberder,
34
A. M. Lutz,
34
B. Malaescu,
34
A. Perez,
34
P. Roudeau,
34
M. H. Schune,
34
J. Serrano,
34
V. Sordini,
34,
‡
A. Stocchi,
34
L. Wang,
34
G. Wormser,
34
D. J. Lange,
35
D. M. Wright,
35
I. Bingham,
36
C. A. Chavez,
36
J. P. Coleman,
36
J. R. Fry,
36
E. Gabathuler,
36
R. Gamet,
36
D. E. Hutchcroft,
36
D. J. Payne,
36
C. Touramanis,
36
A. J. Bevan,
37
F. Di Lodovico,
37
R. Sacco,
37
M. Sigamani,
37
G. Cowan,
38
S. Paramesvaran,
38
A. C. Wren,
38
D. N. Brown,
39
C. L. Davis,
39
A. G. Denig,
40
M. Fritsch,
40
W. Gradl,
40
A. Hafner,
40
K. E. Alwyn,
41
D. Bailey,
41
R. J. Barlow,
41
G. Jackson,
41
G. D. Lafferty,
41
J. Anderson,
42
R. Cenci,
42
A. Jawahery,
42
D. A. Roberts,
42
G. Simi,
42
J. M. Tuggle,
42
C. Dallapiccola,
43
E. Salvati,
43
R. Cowan,
44
D. Dujmic,
44
G. Sciolla,
44
M. Zhao,
44
D. Lindemann,
45
P. M. Patel,
45
S. H. Robertson,
45
M. Schram,
45
P. Biassoni,
46a,46b
A. Lazzaro,
46a,46b
V. Lombardo,
46a
F. Palombo,
46a,46b
S. Stracka,
46a,46b
L. Cremaldi,
47
R. Godang,
47,
§
R. Kroeger,
47
P. Sonnek,
47
D. J. Summers,
47
X. Nguyen,
48
M. Simard,
48
P. Taras,
48
G. De Nardo,
49a,49b
D. Monorchio,
49a,49b
G. Onorato,
49a,49b
C. Sciacca,
49a,49b
G. Raven,
50
H. L. Snoek,
50
C. P. Jessop,
51
K. J. Knoepfel,
51
J. M. LoSecco,
51
W. F. Wang,
51
L. A. Corwin,
52
K. Honscheid,
52
R. Kass,
52
J. P. Morris,
52
N. L. Blount,
53
J. Brau,
53
R. Frey,
53
O. Igonkina,
53
J. A. Kolb,
53
R. Rahmat,
53
N. B. Sinev,
53
D. Strom,
53
J. Strube,
53
E. Torrence,
53
G. Castelli,
54a,54b
E. Feltresi,
54a,54b
N. Gagliardi,
54a,54b
M. Margoni,
54a,54b
M. Morandin,
54a
M. Posocco,
54a
M. Rotondo,
54a
F. Simonetto,
54a,54b
R. Stroili,
54a,54b
E. Ben-Haim,
55
G. R. Bonneaud,
55
H. Briand,
55
G. Calderini,
55
J. Chauveau,
55
O. Hamon,
55
Ph. Leruste,
55
G. Marchiori,
55
J. Ocariz,
55
J. Prendki,
55
S. Sitt,
55
M. Biasini,
56a,56b
E. Manoni,
56a,56b
A. Rossi,
56a,56b
C. Angelini,
57a,57b
G. Batignani,
57a,57b
S. Bettarini,
57a,57b
M. Carpinelli,
57a,57b,
k
G. Casarosa,
57a,57b
A. Cervelli,
57a,57b
F. Forti,
57a,57b
M. A. Giorgi,
57a,57b
A. Lusiani,
57a,57c
N. Neri,
57a,57b
E. Paoloni,
57a,57b
G. Rizzo,
57a,57b
J. J. Walsh,
57a
D. Lopes Pegna,
58
C. Lu,
58
J. Olsen,
58
A. J. S. Smith,
58
A. V. Telnov,
58
F. Anulli,
59a
E. Baracchini,
59a,59b
G. Cavoto,
59a
R. Faccini,
59a,59b
F. Ferrarotto,
59a
F. Ferroni,
59a,59b
M. Gaspero,
59a,59b
L. Li Gioi,
59a
M. A. Mazzoni,
59a
G. Piredda,
59a
F. Renga,
59a,59b
T. Hartmann,
60
T. Leddig,
60
H. Schro
̈
der,
60
R. Waldi,
60
T. Adye,
61
B. Franek,
61
E. O. Olaiya,
61
F. F. Wilson,
61
S. Emery,
62
G. Hamel de Monchenault,
62
G. Vasseur,
62
Ch. Ye
`
che,
62
M. Zito,
62
M. T. Allen,
63
D. Aston,
63
D. J. Bard,
63
R. Bartoldus,
63
J. F. Benitez,
63
C. Cartaro,
63
M. R. Convery,
63
J. Dorfan,
63
G. P. Dubois-Felsmann,
63
W. Dunwoodie,
63
R. C. Field,
63
M. Franco Sevilla,
63
B. G. Fulsom,
63
A. M. Gabareen,
63
M. T. Graham,
63
P. Grenier,
63
C. Hast,
63
W. R. Innes,
63
M. H. Kelsey,
63
H. Kim,
63
P. Kim,
63
M. L. Kocian,
63
D. W. G. S. Leith,
63
S. Li,
63
B. Lindquist,
63
S. Luitz,
63
V. Luth,
63
H. L. Lynch,
63
D. B. MacFarlane,
63
H. Marsiske,
63
D. R. Muller,
63
H. Neal,
63
S. Nelson,
63
C. P. O’Grady,
63
I. Ofte,
63
M. Perl,
63
T. Pulliam,
63
B. N. Ratcliff,
63
A. Roodman,
63
A. A. Salnikov,
63
V. Santoro,
63
R. H. Schindler,
63
J. Schwiening,
63
A. Snyder,
63
D. Su,
63
M. K. Sullivan,
63
S. Sun,
63
PHYSICAL REVIEW D
85,
092017 (2012)
1550-7998
=
2012
=
85(9)
=
092017(21)
092017-1
Ó
2012 American Physical Society
K. Suzuki,
63
J. M. Thompson,
63
J. Va’vra,
63
A. P. Wagner,
63
M. Weaver,
63
C. A. West,
63
W. J. Wisniewski,
63
M. Wittgen,
63
D. H. Wright,
63
H. W. Wulsin,
63
A. K. Yarritu,
63
C. C. Young,
63
V. Ziegler,
63
X. R. Chen,
64
W. Park,
64
M. V. Purohit,
64
R. M. White,
64
J. R. Wilson,
64
S. J. Sekula,
65
M. Bellis,
66
P. R. Burchat,
66
A. J. Edwards,
66
T. S. Miyashita,
66
S. Ahmed,
67
M. S. Alam,
67
J. A. Ernst,
67
B. Pan,
67
M. A. Saeed,
67
S. B. Zain,
67
N. Guttman,
68
A. Soffer,
68
P. Lund,
69
S. M. Spanier,
69
R. Eckmann,
70
J. L. Ritchie,
70
A. M. Ruland,
70
C. J. Schilling,
70
R. F. Schwitters,
70
B. C. Wray,
70
J. M. Izen,
71
X. C. Lou,
71
F. Bianchi,
72a,72b
D. Gamba,
72a,72b
M. Pelliccioni,
72a,72b
M. Bomben,
73a,73b
L. Lanceri,
73a,73b
L. Vitale,
73a,73b
N. Lopez-March,
74
F. Martinez-Vidal,
74
D. A. Milanes,
74
A. Oyanguren,
74
J. Albert,
75
Sw. Banerjee,
75
H. H. F. Choi,
75
K. Hamano,
75
G. J. King,
75
R. Kowalewski,
75
M. J. Lewczuk,
75
I. M. Nugent,
75
J. M. Roney,
75
R. J. Sobie,
75
T. J. Gershon,
76
P. F. Harrison,
76
T. E. Latham,
76
E. M. T. Puccio,
76
H. R. Band,
77
S. Dasu,
77
K. T. Flood,
77
Y. Pan,
77
R. Prepost,
77
C. O. Vuosalo,
77
and S. L. Wu
77
(
B
A
B
AR
Collaboration)
1
Laboratoire d’Annecy-le-Vieux de Physique des Particules (LAPP), Universite
́
de Savoie,
CNRS/IN2P3, 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
Dipartimento 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, Canada V6T 1Z1
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 Riverside, Riverside, California 92521, USA
13
University of California at Santa Barbara, Santa Barbara, California 93106, USA
14
University of California at Santa Cruz, Institute for Particle Physics, Santa Cruz, California 95064, USA
15
California Institute of Technology, Pasadena, California 91125, USA
16
University of Cincinnati, Cincinnati, Ohio 45221, USA
17
University of Colorado, Boulder, Colorado 80309, USA
18
Colorado State University, Fort Collins, Colorado 80523, USA
19
Technische Universita
̈
t Dortmund, Fakulta
̈
t Physik, D-44221 Dortmund, Germany
20
Technische Universita
̈
t Dresden, Institut fu
̈
r Kern- und Teilchenphysik, D-01062 Dresden, Germany
21
Laboratoire Leprince-Ringuet, CNRS/IN2P3, Ecole Polytechnique, F-91128 Palaiseau, France
22
University of Edinburgh, Edinburgh EH9 3JZ, United Kingdom
23a
INFN Sezione di Ferrara, I-44100 Ferrara, Italy
23b
Dipartimento di Fisica, Universita
`
di Ferrara, I-44100 Ferrara, Italy
24
INFN Laboratori Nazionali di Frascati, I-00044 Frascati, Italy
25a
INFN Sezione di Genova, I-16146 Genova, Italy
25b
Dipartimento di Fisica, Universita
`
di Genova, I-16146 Genova, Italy
26
Indian Institute of Technology Guwahati, Guwahati, Assam, 781 039, India
27
Harvard University, Cambridge, Massachusetts 02138, USA
28
Universita
̈
t Heidelberg, Physikalisches Institut, Philosophenweg 12, D-69120 Heidelberg, Germany
29
Humboldt-Universita
̈
t zu Berlin, Institut fu
̈
r Physik, Newtonstr. 15, D-12489 Berlin, Germany
30
Imperial College London, London, SW7 2AZ, United Kingdom
31
University of Iowa, Iowa City, Iowa 52242, USA
32
Iowa State University, Ames, Iowa 50011-3160, USA
33
Johns Hopkins University, Baltimore, Maryland 21218, USA
34
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
35
Lawrence Livermore National Laboratory, Livermore, California 94550, USA
36
University of Liverpool, Liverpool L69 7ZE, United Kingdom
37
Queen Mary, University of London, London, E1 4NS, United Kingdom
38
University of London, Royal Holloway and Bedford New College, Egham, Surrey TW20 0EX, United Kingdom
39
University of Louisville, Louisville, Kentucky 40292, USA
40
Johannes Gutenberg-Universita
̈
t Mainz, Institut fu
̈
r Kernphysik, D-55099 Mainz, Germany
P. DEL AMO SANCHEZ
et al.
PHYSICAL REVIEW D
85,
092017 (2012)
092017-2
41
University of Manchester, Manchester M13 9PL, United Kingdom
42
University of Maryland, College Park, Maryland 20742, USA
43
University of Massachusetts, Amherst, Massachusetts 01003, USA
44
Massachusetts Institute of Technology, Laboratory for Nuclear Science, Cambridge, Massachusetts 02139, USA
45
McGill University, Montre
́
al, Que
́
bec, Canada H3A 2T8
46a
INFN Sezione di Milano, I-20133 Milano, Italy;
46b
Dipartimento di Fisica, Universita
`
di Milano, I-20133 Milano, Italy
47
University of Mississippi, University, Mississippi 38677, USA
48
Universite
́
de Montre
́
al, Physique des Particules, Montre
́
al, Que
́
bec, Canada H3C 3J7
49a
INFN Sezione di Napoli, I-80126 Napoli, Italy
49b
Dipartimento di Scienze Fisiche, Universita
`
di Napoli Federico II, I-80126 Napoli, Italy
50
NIKHEF, National Institute for Nuclear Physics and High Energy Physics, NL-1009 DB Amsterdam, The Netherlands
51
University of Notre Dame, Notre Dame, Indiana 46556, USA
52
Ohio State University, Columbus, Ohio 43210, USA
53
University of Oregon, Eugene, Oregon 97403, USA
54a
INFN Sezione di Padova, I-35131 Padova, Italy
54b
Dipartimento di Fisica, Universita
`
di Padova, I-35131 Padova, Italy
55
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
56a
INFN Sezione di Perugia, I-06100 Perugia, Italy
56b
Dipartimento di Fisica, Universita
`
di Perugia, I-06100 Perugia, Italy
57a
INFN Sezione di Pisa, I-56127 Pisa, Italy
57b
Dipartimento di Fisica, Universita
`
di Pisa, I-56127 Pisa, Italy
57c
Scuola Normale Superiore di Pisa, I-56127 Pisa, Italy
58
Princeton University, Princeton, New Jersey 08544, USA
59a
INFN Sezione di Roma, I-00185 Roma, Italy
59b
Dipartimento di Fisica, Universita
`
di Roma La Sapienza, I-00185 Roma, Italy
60
Universita
̈
t Rostock, D-18051 Rostock, Germany
61
Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, OX11 0QX, United Kingdom
62
CEA, Irfu, SPP, Centre de Saclay, F-91191 Gif-sur-Yvette, France
63
SLAC National Accelerator Laboratory, Stanford, California 94309 USA
64
University of South Carolina, Columbia, South Carolina 29208, USA
65
Southern Methodist University, Dallas, Texas 75275, USA
66
Stanford University, Stanford, California 94305-4060, USA
67
State University of New York, Albany, New York 12222, USA
68
Tel Aviv University, School of Physics and Astronomy, Tel Aviv, 69978, Israel
69
University of Tennessee, Knoxville, Tennessee 37996, USA
70
University of Texas at Austin, Austin, Texas 78712, USA
71
University of Texas at Dallas, Richardson, Texas 75083, USA
72a
INFN Sezione di Torino, I-10125 Torino, Italy
72b
Dipartimento di Fisica Sperimentale, Universita
`
di Torino, I-10125 Torino, Italy
73a
INFN Sezione di Trieste, I-34127 Trieste, Italy
73b
Dipartimento di Fisica, Universita
`
di Trieste, I-34127 Trieste, Italy
74
IFIC, Universitat de Valencia-CSIC, E-46071 Valencia, Spain
75
University of Victoria, Victoria, British Columbia, Canada V8W 3P6
76
Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom
77
University of Wisconsin, Madison, Wisconsin 53706, USA
(Received 21 November 2011; published 30 May 2012)
We present results for
B
-meson decay modes involving a charm meson, protons, and pions using
455
10
6
B
B
pairs recorded by the
BaBar
detector at the SLAC PEP-II asymmetric-energy
e
þ
e
collider. The branching fractions are measured for the following ten decays:
B
0
!
D
0
p
p
,
B
0
!
D
0
p
p
,
B
0
!
D
þ
p
p
,
B
0
!
D
þ
p
p
,
B
!
D
0
p
p
,
B
!
D
0
p
p
,
B
0
!
D
0
p
p
þ
,
B
0
!
D
0
p
p
þ
,
B
!
D
þ
p
p
, and
B
!
D
þ
p
p
. The four
B
and the two five-body
B
0
*
Now at Temple University, Philadelphia, PA 19122, USA
†
Also with Universita
`
di Perugia, Dipartimento di Fisica, Perugia, Italy
‡
Also with Universita
`
di Roma La Sapienza, I-00185 Roma, Italy
§
Now at University of South Alabama, Mobile, AL 36688, USA
k
Also with Universita
`
di Sassari, Sassari, Italy
OBSERVATION AND STUDY OF THE BARYONIC
B
-
...
PHYSICAL REVIEW D
85,
092017 (2012)
092017-3
modes are observed for the first time. The four-body modes are enhanced compared to the three- and the
five-body modes. In the three-body modes, the
M
ð
p
p
Þ
and
M
ð
D
ðÞ
0
p
Þ
invariant-mass distributions show
enhancements near threshold values. In the four-body mode
B
0
!
D
þ
p
p
, the
M
ð
p
Þ
distribution
shows a narrow structure of unknown origin near
1
:
5 GeV
=c
2
. The distributions for the five-body modes,
in contrast to the others, are similar to the expectations from uniform phase-space predictions.
DOI:
10.1103/PhysRevD.85.092017
PACS numbers: 13.25.Hw, 12.39.Mk, 14.20.Gk, 14.40.Nd
I. INTRODUCTION
B
-meson decays to final states with baryons have been
explored much less systematically than decays to meson-
only final states. The first exclusively reconstructed decay
modes were the CLEO observations of
B
!
þ
c
p
and
B
!
þ
c
p
[
1
] and, later, of
B
0
!
D
þ
p
p
and
B
0
!
D
p
n
[
2
]. These measurements supported the prediction
[
3
] that the final states with
c
baryons are not the only
sizable contributions to the baryonic
B
-meson decay rate,
and that the charm-meson modes of the form
B
!
D
ðÞ
N
N
0
þ
anything, where the
N
ð0Þ
represent nucleon
states, are also significant. Previous measurements show
a trend that the branching fractions increase with the
number of final-state particles. The branching fractions
for the four-body modes
B
0
!
D
ðÞþ
p
p
[
2
,
4
] are ap-
proximately 4 times larger than those for the three-body
modes
B
0
!
D
ðÞ
0
p
p
[
5
]. Furthermore, the branching frac-
tion for the three-body mode
B
!
þ
c
p
[
6
]isan
order-of-magnitude larger than that for the two-body
mode
B
0
!
þ
c
p
[
7
].
We expand the scope of baryonic
B
-decay studies
with measurements of the branching fractions and the
kinematic distributions of the following ten modes
[
8
,
9
]:
B
0
!
D
0
p
p
and
B
0
!
D
0
p
p
,
B
0
!
D
þ
p
p
and
B
0
!
D
þ
p
p
,
B
!
D
0
p
p
and
B
0
!
D
0
p
p
,
B
0
!
D
0
p
p
þ
and
B
0
!
D
0
p
p
þ
,
B
!
D
þ
p
p
and
B
!
D
þ
p
p
. Six of the
modes—the four
B
and the two five-body
B
0
modes—are
observed for the first time.
We reconstruct the modes through 26 decay chains
consisting of all-hadronic final states (the list is given later
with the results in Table
I
), e.g.,
A
D
0
meson, as in the above example, is produced in
eight of the
B
modes and a
D
þ
is produced in the remain-
ing two. The
D
0
-meson candidates are reconstructed
through decays to
K
þ
,
K
þ
0
, and
K
þ
þ
;
and the
D
þ
to
K
þ
þ
. The
D
0
-meson candidates are
reconstructed through decays to
D
0
0
and the
D
þ
as
D
0
þ
.
Typical quarkline diagrams for the three- and four-body
modes with a
D
ðÞ
0
meson are shown in Fig.
1
. The
three-body modes involve internal emissions of the
W
boson, whereas the four- and five-body modes involve
internal and external emission diagrams.
Baryonic
B
decays have a distinctive phenomenology
whose features contrast with the patterns observed in
meson-only final states. Experimentally, the overall rate
enhancement of multibody decays and the low-mass
enhancement in the baryon-antibaryon subsystem are ob-
served [
10
–
15
]. Theoretically, these modes are used to
investigate a wide range of topics [
16
–
26
]. Among them
are the predictions of the relative branching fractions, the
decay dynamics, and the hypotheses involving exotic QCD
phenomena, such as tetra-, penta-, or septa-quark bound
states. In particular, there have been discussions of
p
p
peaks near threshold values and penta-quark intermediate
resonance decays
c
!
D
ðÞþ
p
with respect to our modes
[
27
–
30
].
The paper is organized as follows: Section
II
describes
the data sample and the
BaBar
detector. Section
III
presents the analysis method, introducing the key variables
M
ES
and
E
. Section
IV
shows the fits to the joint
M
ES
-
E
distributions. The fit yields and the corresponding branch-
ing fractions are given. Section
V
discusses the systematic
uncertainties. Section
VI
presents the kinematic distribu-
tions. For the three-body modes, the Dalitz plots of
M
2
ð
D
ðÞ
0
p
Þ
vs
M
2
ð
p
p
Þ
are given as well as the invariant
mass plots of the variables. For the four- and five-body
modes, the two-body subsystem invariant mass plots are
given. In the four-body modes, we investigate a narrow
structure in the
M
ð
p
Þ
distribution near
1
:
5 GeV
=c
2
.
Section
VII
states the conclusions.
II.
BABAR
DETECTOR AND DATA SAMPLE
We use a data sample with integrated luminosity of
414 fb
1
(
455
10
6
B
B
) recorded at the center-of-mass
energy
ffiffiffi
s
p
¼
10
:
58 GeV
with the
BaBar
detector at the
PEP-II
e
þ
e
collider. The
e
þ
and
e
beams circulate in
the storage rings at momenta of
3
:
1 GeV
=c
and
9 GeV
=c
,
respectively. The value of
ffiffiffi
s
p
corresponds to the
ð
4
S
Þ
mass, maximizing the cross section for
e
þ
e
!
b
b
!
ð
4
S
Þ!
B
B
events. The
B
B
production accounts for ap-
proximately a quarter of the total hadronic cross section;
the continuum processes
e
þ
e
!
u
u
,
d
d
,
s
s
, and
c
c
con-
stitute the rest.
The main components of the
BaBar
detector [
31
] are the
tracking system, the Detector of Internally-Reflected
P. DEL AMO SANCHEZ
et al.
PHYSICAL REVIEW D
85,
092017 (2012)
092017-4
Cherenkov radiation (DIRC), the electromagnetic calo-
rimeter, and the instrumented flux return.
The two-part charged particle tracking system measures
the momentum. The silicon vertex tracker, with five layers
of double-sided silicon micro-strips, is closest to the
interaction point. The tracker is followed by a wire drift
chamber filled with a helium-isobutane (
80:20
) gas
mixture, which was chosen to minimize multiple scatter-
ing. The superconducting coil creates a 1.5 T solenoidal
field.
The DIRC measures the opening angle of the Cherenkov
light cone,
C
, produced by a charged particle traversing
one of the 144 radiator bars of fused silica. The light
propagates in the bar by total internal reflection and is
projected onto an array of photomultiplier tubes surround-
ing a water-filled box mounted at the back end of the
tracking system. The DIRC’s ability to distinguish pions,
kaons, and protons complements the energy loss measure-
ments,
dE=dx
, in the tracking volume.
The calorimeter measures the energies and positions of
electron-photon showers with an array of 6580 finely-
segmented Tl-doped CsI crystals.
FIG. 1. Typical
quarkline
diagrams
representing
(a)
B
0
!
D
ðÞ
0
p
p
and (b)
B
!
D
ðÞ
0
p
p
modes. The gluon
lines are omitted.
TABLE I. Intermediate values for Table
II
:
B
-meson branching fractions for the decay chains.
N
sig
is the yield,
N
peak
is the measured
contamination (item xvii in Table
IV
), and
is the reconstruction efficiency. The uncertainties are statistical.
B
modes,
D
modes
N
sig
sig
N
peak
(%)
B
stat
(
10
4
)
B
0
!
D
0
p
p
,
K
351
20
7.6
19.0
1
:
02
0
:
06
B
0
!
D
0
p
p
,
K
0
431
28
24
7.0
0
:
95
0
:
06
B
0
!
D
0
p
p
,
K
448
27
10
9.9
1
:
21
0
:
07
B
0
!
D
0
p
p
,
K
110
12
1
:
4
9.4
1
:
08
0
:
12
B
0
!
D
0
p
p
,
K
0
148
15
3.9
3.2
1
:
17
0
:
12
B
0
!
D
0
p
p
,
K
95
14
5.5
5.2
0
:
76
0
:
12
B
0
!
D
þ
p
p
,
K
1816
53
55
12.6
3
:
32
0
:
10
B
0
!
D
þ
p
p
,
K
392
21
2.3
6.8
4
:
79
0
:
26
B
0
!
D
þ
p
p
,
K
0
601
28
21
3.1
4
:
53
0
:
22
B
0
!
D
þ
p
p
,
K
378
22
20
3.7
3
:
92
0
:
24
B
!
D
0
p
p
,
K
1078
38
13
15.9
3
:
79
0
:
14
B
!
D
0
p
p
,
K
0
1176
54
41
5.5
3
:
34
0
:
16
B
!
D
0
p
p
,
K
1296
57
33
7.8
4
:
38
0
:
20
B
!
D
0
p
p
,
K
328
22
2.1
7.7
3
:
86
0
:
26
B
!
D
0
p
p
,
K
0
482
35
47
2.9
3
:
99
0
:
32
B
!
D
0
p
p
,
K
343
31
32
4.0
3
:
37
0
:
34
B
0
!
D
0
p
p
þ
,
K
438
32
7.7
8.2
2
:
97
0
:
22
B
0
!
D
0
p
p
þ
,
K
0
663
65
160
2.9
2
:
83
0
:
36
a
B
0
!
D
0
p
p
þ
,
K
770
68
40
3.8
5
:
28
0
:
48
a
B
0
!
D
0
p
p
þ
,
K
61
12
1.8
2.9
1
:
87
0
:
38
B
0
!
D
0
p
p
þ
,
K
0
142
32
37
1.3
2
:
19
0
:
66
a
B
0
!
D
0
p
p
þ
,
K
163
30
13
1.3
4
:
93
0
:
99
a
B
!
D
þ
p
p
,
K
475
37
6.6
6.7
1
:
66
0
:
13
B
!
D
þ
p
p
,
K
57
9
12
2.9
1
:
98
0
:
26
B
!
D
þ
p
p
,
K
0
94
14
0
:
6
1.3
1
:
82
0
:
27
B
!
D
þ
p
p
,
K
66
12
4.8
1.5
1
:
61
0
:
32
a
The rows marked by an ‘‘a’’ have large systematic uncertainties; see text. The charges of the pions are implied as well as the
D
0
!
D
0
0
and
D
þ
!
D
0
þ
decays, when applicable.
OBSERVATION AND STUDY OF THE BARYONIC
B
-
...
PHYSICAL REVIEW D
85,
092017 (2012)
092017-5
The flux return is instrumented with a combination of
resistive plate chambers and limited streamer tubes for the
detection of muons and neutral hadrons.
A data event display is given in Fig.
2
for the candidate
decay
B
0
!
D
0
p
p
,
D
0
!
K
þ
.
III. ANALYSIS METHOD
This section describes the branching fraction measure-
ment in four parts. Section
III A
describes the Monte Carlo-
simulated event samples that are used to evaluate the
performance of the method. Section
III B
lists the discrimi-
nating variables and their requirements for the event se-
lection. Section
III C
defines the
M
ES
and
E
variables and
presents their distributions for the newly observed modes.
Lastly, Sec.
III D
describes the fit to the
M
ES
-
E
distribu-
tion used to extract the signal yield.
A. Monte Carlo-simulated event samples
Monte Carlo (MC) event samples are produced and used
to evaluate the analysis method. Two types of samples—
signal and generic—are described below.
The particle decays are generated using a combination
of
EVTGEN
[
32
] and
JETSET
7.4 [
33
]. The interactions of the
decay products traversing the detector are modeled by
GEANT
4[
34
]. The simulation takes into account varying
detector conditions and beam backgrounds during the data-
taking periods.
The signal MC sample is generated to characterize
events with a
B
meson that decays to one of the signal
modes (the accompanying
B
decays generically). The typi-
cal size of
3
10
5
events per decay chain is 2 orders of
magnitude larger than the expected signal in data.
The generic MC sample is generated to characterize the
entire data sample. The size is approximately twice that of
the
BaBar
data sample.
B. Event selection
The
e
þ
e
events are filtered for a signal
B
-meson
candidate through the pre- and the final selections.
The preselection requires the presence of proton-
antiproton pair and a
D
0
-ora
D
þ
-meson candidate (writ-
ten as
D
without a charge designation) in one of the 26
decay chains listed in Sec.
I
.
Protons are identified with a likelihood-based algorithm
using the
dE=dx
and the
C
measurements as described in
Sec.
II
.Fora
1
:
0 GeV
=c
proton in the lab frame (typical of
those produced in a signal mode), the selection efficiency
is 98% and the kaon fake rate is 1%.
The
D
-meson candidates are selected using the invariant
mass [
35
],
M
ð
D
Þ
, and a kaon identification algorithm
similar to that used for protons. The
M
ð
D
Þ
is required to
be within 7 times its resolution around the PDG value [
6
]
(superseded later during final selection). For a
0
:
9 GeV
=c
kaon in the lab frame (typical of those produced in a signal
mode), the selection efficiency is 85% and the pion fake
rate is 2%.
For the
D
0
!
K
þ
0
and
D
0
!
D
0
0
subdecay
modes, the
0
!
candidates are formed from
two well-separated photons with
115
<M
ð
Þ
<
150 MeV
=c
2
or from two unseparated photons by using
the second moment of the overlapping calorimeter energy
deposits.
The charged particles from the decay chain are required
to have a distance of closest approach to the beam spot of
less than 1.5 cm.
The final selection requires the presence of a fully
reconstructed signal
B
-meson candidate. Requirements
on the discriminating variables described below are opti-
mized by maximizing the signal precision
z
¼
S=
ffiffiffiffiffiffiffiffiffiffiffiffiffi
S
þ
B
p
,
where
S
is the expected signal yield using the signal MC
sample and
B
the expected background yield using the
generic MC sample. The signal is normalized using the
measured branching fractions for the modes
B
0
!
D
ðÞ
0
p
p
and
B
0
!
D
þ
p
p
[
2
,
5
]; for the rest of the modes the
latter value is used. The quantity
z
is computed for each
discriminating variable for each decay chain. For the var-
iables with a broad maximum in
z
, the cut values are
chosen to be consistent across similar modes.
In order to select
D
-meson candidates,
M
ð
D
Þ
is required
to be within
3
M
ð
D
Þ
of the PDG value [
6
]. The resolutions
M
ð
D
Þ
for
D
0
!
K
þ
,
K
þ
0
,
K
þ
þ
, and
D
þ
!
K
þ
þ
are approximately 6, 10, 5, and
5 MeV
=c
2
, respectively. For the modes involving
D
0
!
K
þ
0
decays, the combinatoric background events due
FIG. 2 (color online). Event display for the candidate decay
B
0
!
D
0
p
p
,
D
0
!
K
þ
. The labeled tracks in the tracking
system and DIRC rings at the perimeter correspond to the
particles in the reconstructed decay chain. The remaining un-
labeled tracks and rings are due to the decay of the other
B
0
meson in the event. The beam axis is perpendicular to the image.
P. DEL AMO SANCHEZ
et al.
PHYSICAL REVIEW D
85,
092017 (2012)
092017-6