of 7
Evidence for
X
ð
3872
Þ!
c
ð
2
S
Þ

in
B

!
X
ð
3872
Þ
K

Decays and a Study of
B
!
c

cK
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. 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
B. G. Fulsom,
9
C. Hearty,
9
T. S. Mattison,
9
J. A. McKenna,
9
M. Barrett,
10
A. Khan,
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
A. J. Martinez,
17
T. Schalk,
17
B. A. Schumm,
17
A. Seiden,
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
P. C. Bloom,
20
W. T. Ford,
20
A. Gaz,
20
J. F. Hirschauer,
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
A. Volk,
23
D. Bernard,
24
G. R. Bonneaud,
24
E. Latour,
24
M. Verderi,
24
P. J. Clark,
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
A. Adametz,
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
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
N. Arnaud,
36
J. Be
́
quilleux,
36
A. D’Orazio,
36
M. Davier,
36
J. Firmino da Costa,
36
G. Grosdidier,
36
A. Ho
̈
cker,
36
V. Lepeltier,
36
F. Le Diberder,
36
A. M. Lutz,
36
S. Pruvot,
36
P. Roudeau,
36
M. H. Schune,
36
J. Serrano,
36
V. Sordini,
36,
k
A. Stocchi,
36
G. Wormser,
36
D. J. Lange,
37
D. M. Wright,
37
I. Bingham,
38
J. P. Burke,
38
C. A. Chavez,
38
J. R. Fry,
38
E. Gabathuler,
38
R. Gamet,
38
D. E. Hutchcroft,
38
D. J. Payne,
38
C. Touramanis,
38
A. J. Bevan,
39
C. K. Clarke,
39
K. A. George,
39
F. Di Lodovico,
39
R. Sacco,
39
M. Sigamani,
39
G. Cowan,
40
H. U. Flaecher,
40
D. A. Hopkins,
40
S. Paramesvaran,
40
F. Salvatore,
40
A. C. Wren,
40
D. N. Brown,
41
C. L. Davis,
41
A. G. Denig,
42
M. Fritsch,
42
W. Gradl,
42
G. Schott,
42
K. E. Alwyn,
43
D. Bailey,
43
R. J. Barlow,
43
Y. M. Chia,
43
C. L. Edgar,
43
G. Jackson,
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
X. Li,
45
E. Salvati,
45
S. Saremi,
45
R. Cowan,
46
D. Dujmic,
46
P. H. Fisher,
46
G. Sciolla,
46
M. Spitznagel,
46
F. Taylor,
46
R. K. Yamamoto,
46
M. Zhao,
46
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
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
G. Raven,
53
H. L. Snoek,
53
C. P. Jessop,
54
K. J. Knoepfel,
54
J. M. Lo Secco,
54
W. F. Wang,
54
G. Benelli,
55
L. A. Corwin,
55
K. Honscheid,
55
H. Kagan,
56
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
S. Sitt,
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,61b
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
D. del Re,
63a,63b
E. Di Marco,
63a,63b
R. Faccini,
63a,63b
PRL
102,
132001 (2009)
PHYSICAL REVIEW LETTERS
week ending
3 APRIL 2009
0031-9007
=
09
=
102(13)
=
132001(7)
132001-1
Ó
2009 The American Physical Society
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
F. F. Wilson,
65
S. Emery,
66
M. Escalier,
66
L. Esteve,
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
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. Peliccioni,
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
(The
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
PRL
102,
132001 (2009)
PHYSICAL REVIEW LETTERS
week ending
3 APRIL 2009
132001-2
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
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
37
Lawrence Livermore National Laboratory, Livermore, California 94550, USA
38
University of Liverpool, Liverpool L69 7ZE, United Kingdom
39
Queen Mary, University of London, London, E1 4NS, United Kingdom
40
University of London, Royal Holloway and Bedford New College, Egham, Surrey TW20 0EX, United Kingdom
41
University of Louisville, Louisville, Kentucky 40292, USA
42
Johannes Gutenberg-Universita
̈
t Mainz, Institut fu
̈
r Kernphysik, D-55099 Mainz, Germany
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
CEA, Irfu, SPP, Centre de 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
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
PRL
102,
132001 (2009)
PHYSICAL REVIEW LETTERS
week ending
3 APRIL 2009
132001-3
(Received 2 September 2008; published 30 March 2009)
In a search for
B
!
c

cK
decays with the
BABAR
detector, where
c

c
includes
J=
c
and
c
ð
2
S
Þ
, and
K
includes
K

,
K
0
S
, and
K

ð
892
Þ
, we find evidence for
X
ð
3872
Þ!
J=
c

and
X
ð
3872
Þ!
c
ð
2
S
Þ

with
3
:
6

and
3
:
5

significance, respectively. We measure the product of branching fractions
B
ð
B

!
X
ð
3872
Þ
K

Þ

B
ð
X
ð
3872
Þ!
J=
c

Þ
¼½
2
:
8

0
:
8
ð
stat
Þ
0
:
1
ð
syst
Þ
10

6
and
B
ð
B

!
X
ð
3872
Þ
K

Þ

B
ð
X
ð
3872
Þ!
c
ð
2
S
Þ

Þ
¼½
9
:
5

2
:
7
ð
stat
Þ
0
:
6
ð
syst
Þ
10

6
.
DOI:
10.1103/PhysRevLett.102.132001
PACS numbers: 13.20.Gd, 13.20.He, 14.40.Gx
The
X
ð
3872
Þ
state discovered by the Belle Collaboration
in the decay
B

!
K

X
ð
3872
Þ
,
X
ð
3872
Þ!
J=
c

þ


[
1
] is now well established [
2
].
BABAR
has seen evidence
for the decay
X
ð
3872
Þ!
J=
c

, which implies positive
C
-parity [
3
]. A variety of theoretical interpretations [
4
]
exist for this state, including conventional charmonium
interpretations [
5
] and exotic QCD proposals such as a

D
0
D

0
molecule [
6
]. While

D
0
D

0
molecular proposals
can accommodate decays to
J=
c

, the branching fraction
for decays to
c
ð
2
S
Þ

is expected to be very small [
7
].
These models allow for the possibility of an admixture of a

D
0
D

0
bound state with, for example, a
c

c
meson. Because
the

c
1
ð
2
P
Þ
state potentially decays to
c
ð
2
S
Þ

at a rate
many times higher than to
J=
c

, the decay
X
ð
3872
Þ!
c
ð
2
S
Þ

could be enhanced due to
c

c
-

D
0
D

0
mixing.
We present a study of the decay
B
!
XK
, where the
notation
X
represents any state decaying radiatively to
J=
c

or
c
ð
2
S
Þ

[the

c
1
;
2
and
X
ð
3872
Þ
states in particu-
lar], and
K
encompasses
K

,
K
0
S
,
K

ð
892
Þ
, and
K

0
ð
892
Þ
.
We consider
J=
c
mesons decaying to
e
þ
e

or

þ


, and
c
ð
2
S
Þ
decaying to
e
þ
e

,

þ


,or
J=
c

þ


. Kaons
are required to decay to final states consisting of charged
particles:
K
0
S
!

þ


,
K

!
K
0
S
ð

þ


Þ


, and
K

0
!
K



.
The data sample for this analysis consists of (
465

5
)
million
B

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

collider at SLAC. This represents
424 fb

1
of data taken at the

ð
4
S
Þ
resonance. The
BABAR
detector is described in detail elsewhere [
8
]. The event
selection, determined independently from the data, is based
on Monte Carlo (MC) simulated events with the aim of
maximizing significance.
The
J=
c
candidates are formed using pairs of leptons
whose invariant mass is in the range
ð
2
:
96
;
3
:
15
Þ
GeV
=c
2
for electrons (including bremsstrahlung photons) and
ð
3
:
06
;
3
:
13
Þ
GeV
=c
2
for muons. For
c
ð
2
S
Þ!
þ

, the
candidate invariant masses are required to be in the range
ð
3
:
61
;
3
:
73
Þ
GeV
=c
2
for electrons or
ð
3
:
65
;
3
:
72
Þ
GeV
=c
2
for muons. The
c
ð
2
S
Þ!
J=
c

þ


candidates are com-
posed of
J=
c
candidates decaying as described but with a
tighter mass requirement of
ð
3
:
01
;
3
:
15
Þ
GeV
=c
2
for the
e
þ
e

decay mode. To form a
c
ð
2
S
Þ
candidate, the
J=
c
candidate is mass constrained to the nominal PDG value
[
9
] and combined with a pair of oppositely charged tracks
requiring
ð
0
:
4
;
0
:
6
Þ
GeV
=c
2
and
ð
3
:
68
;
3
:
69
Þ
GeV
=c
2
for
the dipion and
c
ð
2
S
Þ
invariant masses, respectively. All
four final decay particles are constrained to the same decay
vertex. Electrons are identified by a likelihood-based se-
lector with
>
92%
efficiency and negligible fake rate.
Muons are selected by a neural net process with
>
85%
efficiency and a

(
K
) fake rate of
<
6%
(
<
10%
). Pions are
drawn from the list of all charged tracks in the event.
We reconstruct
X
!
c

c
candidates from a mass-
constrained
J=
c
(
c
ð
2
S
Þ
) candidate combined with a pho-
ton with an energy greater than 30(100) MeV. Additional
selection criteria are applied to the shape of the lateral
distribution (
0
:
001
<
LAT
<
0
:
5
)[
10
] and azimuthal
asymmetry (as measured by the Zernike moment
A
42
<
0
:
1
)[
11
] of the photon-shower energy. For
X
!
J=
c

, the
radiative

candidate is rejected if, when combined with
any other

from the event, it has an invariant mass con-
sistent with the

0
mass,
124
<m

<
146 MeV
=c
2
.
The
K
0
S
candidates are required to be within

17 MeV
=c
2
of the nominal
K
0
S
mass [
9
], and the signifi-
cance of the distance of the reconstructed decay vertex
from the primary vertex must be greater than 3.7 standard
deviations (

). The excited kaons are required to have an
invariant mass within the range
0
:
7
<m
ð
K

Þ
<
1
:
1 GeV
=c
2
.For
K
0
S
,
K

, and
K

0
candidates associated
with
X
!
c
ð
2
S
Þ

, additional requirements are placed on
the

2
vertex probability of the kaon,
P
ð

2
Þ
>
0
:
001
, 0.02,
and 0.002, respectively. Kaons are chosen by a likelihood-
based selector with an efficiency of

95%
and misidenti-
fication rates of

5%
,

4%
, and
<
10%
for

,

, and
p
,
respectively, over the momentum range in this analysis.
We form the final
B
candidate from an
X
candidate and a
kaon constrained to originate from the same vertex. To
identify
B
candidates, we use two kinematic variables,
m
B
and
m
miss
. The unconstrained mass of the reconstructed
B
candidate is
m
B
¼
ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
E
2
B
=c
4

p
2
B
=c
2
q
, where
E
B
and
p
B
are
obtained by summing the energies and momenta of the
particles in the candidate
B
meson. The missing mass is
defined as
m
miss
¼
ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
ð
p
e
þ
e


^
p
B
Þ
2
=c
2
p
, where
p
e
þ
e

is the
four-momentum of the beam
e
þ
e

system and
^
p
B
is the
four-momentum of the
B
candidate after applying a
B
mass
constraint. For
X
!
J=
c
½
c
ð
2
S
Þ

events, we require
m
B
to be within
þ
30

36
ð
20
Þ
MeV
=c
2
of the nominal
B
mass [
9
].
Our
B
candidate selection is further refined by imposing
criteria on the

2
probability for the
B
vertex: for all
X
!
J=
c

modes,
P
ð

2
Þ
>
0
:
0001
, and for
X
!
c
ð
2
S
Þ

modes,
P
ð

2
Þ
>
0
:
01
, 0.002, and 0.05 for the
K

,
K
0
S
,
PRL
102,
132001 (2009)
PHYSICAL REVIEW LETTERS
week ending
3 APRIL 2009
132001-4
and
K

modes, respectively. The ratio of the second and
zeroth Fox-Wolfram moments (
R
2
<
0
:
45
)[
12
] is used to
separate isotropic
B
events from continuum background
events. Once a
B
candidate has been established, it and its
daughter decays are refit with the
B
mass constrained to the
known value [
9
].
We perform a one(two)-dimensional unbinned extended
maximum-likelihood (UML) fit to
m
miss
(and
m
K

, if ap-
plicable), and use the
s
Plot
formalism [
13
] to project our
signal events into
m
X
, the invariant mass of the
X
candi-
date. This is a background-subtraction technique by
weighting each event based on how signal- or
background-like it is. The
s
Plot
displays the number of
B
!
XK
signal-like events as a function of
m
X
. We extract
the signal yield for a given decay mode by fitting this
resultant
m
X
distribution with shapes for signal and back-
ground determined from MC simulation.
The signal event probability density functions (PDFs)
are determined from MC-simulated
B
!

c
1
K
and
B
!
X
ð
3872
Þ
K
events. Only reconstructed events exactly
matching the generated decay chain particles are used to
parameterize the signal PDFs. The PDF shapes for
B
!

c
2
K
are the same as for

c
1
, with the below-noted ex-
ception of the
m
X
distribution. The
m
miss
distribution is
modeled with a Crystal Ball function [
14
],
m
X
with a single
Gaussian for the

c
2
decay modes and narrower core
Gaussian plus a second wider Gaussian sharing the same
mean for all other signal modes, and
m
K

with the con-
volution of a Breit-Wigner and a Gaussian.
The background PDFs are determined from fits to ge-
neric
B
þ
B

,
B
0

B
0
,
q

q
, and

þ


MC samples, and are
dominated by events from
B

B
decays that include a
J=
c
or
c
ð
2
S
Þ
in their decay chain. For the
B

!
XK

and
B
0
!
XK
0
S
decay modes, the background in
m
miss
consists of two
parts: a nonpeaking combinatoric component modeled
with an ARGUS function [
15
], and a peaking component
that shares the Crystal Ball parameterization used for sig-
nal events. These backgrounds are modeled as linear in
m
X
.
The
K

decay modes have three background components:
events that peak in
m
miss
but are flat in
m
K

(‘‘nonreso-
nant’’) and vice versa (‘‘
K

combinatoric’’), and those that
do not peak in either distribution (‘‘combinatoric’’). The
peaking
m
miss
and
m
K

distributions use the same parame-
terization and values found by fitting to the signal MC
sample. The nonpeaking
m
miss
distributions are fit with an
ARGUS function, while the nonpeaking
m
K

distribution is
modeled with a linear function. Both combinatoric back-
ground types are flat in
m
X
, while the nonresonant back-
grounds (typically
B
!
XK
) have a flat and peaking
component in
m
X
. However, because none of these back-
ground events are signal-like in both
m
miss
and
m
K

, they
are not present in the
s
Plot
projection in
m
X
.
To account for potential differences between data and
MC calculations, the values for the
m
miss
ARGUS and
m
X
TABLE I. Summary of the analysis results.
N
S
is the bias-corrected number of signal events extracted from the
m
Xs
Plot
,

is the
total significance of the signal yield
N
S
measured in standard deviations (statistical and systematic uncertainties combined in
quadrature) from the null result,

is the total efficiency for the decay mode, and derived
B
is the measurement (with 90% confidence
level upper limit [
16
]) of
B
ð
B
!

c
1
;
2
K
Þ
or
B
ð
B
!
X
ð
3872
Þ
K
Þ

B
ð
X
!
c

c
Þ
. Uncertainties are statistical and systematic,
respectively.
Decay
N
S

ð
%
Þ
Derived
B

c
1

10

4

c
1
K

1018

34

14
28
11.0
4
:
5

0
:
1

0
:
3

c
1
K
0
242

16

5
14
8.7
4
:
2

0
:
3

0
:
3

c
1
K

71

13

8
4.7
5.7
2
:
6

0
:
5

0
:
4

c
1
K

0
255

25

11
9.5
7.9
2
:
5

0
:
2

0
:
2

c
2

10

5

c
2
K

14
:
0

7
:
9

1
:
1
1.8
12.3
1
:
0

0
:
6

0
:
1
ð
<
1
:
8
Þ

c
2
K
0
6
:
1

3
:
9

1
:
1
1.5
11.1
1
:
5

0
:
9

0
:
3
ð
<
2
:
8
Þ

c
2
K

1
:
2

4
:
7

6
:
1
0.2
4.2
1
:
1

4
:
3

5
:
5
ð
<
12
Þ

c
2
K

0
38
:
8

10
:
5

1
:
1
3.7
8.3
6
:
6

1
:
8

0
:
5
X
ð
3872
Þð
J=
c

Þ

10

6
XK

23
:
0

6
:
4

0
:
6
3.6
14.5
2
:
8

0
:
8

0
:
1
XK
0
5
:
3

3
:
6

0
:
2
1.5
11.0
2
:
6

1
:
8

0
:
2
ð
<
4
:
9
Þ
XK

0
:
6

2
:
3

0
:
1
0.3
6.9
0
:
7

2
:
6

0
:
1
ð
<
4
:
8
Þ
XK

0
2
:
8

5
:
2

0
:
4
0.5
10.4
0
:
7

1
:
4

0
:
1
ð
<
2
:
8
Þ
X
ð
3872
Þð
c
ð
2
S
Þ

Þ

10

6
XK

25
:
4

7
:
3

0
:
7
3.5
10.4
9
:
5

2
:
7

0
:
6
XK
0
8
:
0

3
:
9

0
:
5
2.0
8.4
11
:
4

5
:
5

1
:
0
ð
<
19
Þ
XK

1
:
9

2
:
9

2
:
9
0.5
5.0
6
:
4

9
:
8

9
:
6
ð
<
28
Þ
XK

0

1
:
4

3
:
3

0
:
3

6.7

1
:
3

3
:
1

0
:
3
ð
<
4
:
4
Þ
PRL
102,
132001 (2009)
PHYSICAL REVIEW LETTERS
week ending
3 APRIL 2009
132001-5
linear parameters for the background events are left as free
parameters in the final fit to data. We also allow the height
of the
m
X
Gaussian peaks to float, which we use to derive
the number of signal events.
The effectiveness of the signal extraction method is
validated on fully simulated MC events for

c
1
;
2
and
X
ð
3872
Þ
signal events, with random samples generated
from the MC background distribution. Successful perform-
ance of the fit is verified on simulated datasets assuming
the number of signal and background events from the
known branching fractions and efficiencies. We apply
small corrections (
<
5%
) to account for bias in the results
of the MC fit validation.
We determine the efficiency from the fraction of the
events generated in MC simulation that survive the analy-
sis selection criteria and are returned by the fitting proce-
dure. We calculate the branching fraction for each decay
mode using
B
ð
B
!
XK
Þ¼
N
S
=
ð
N
B

B



f
Þ
where
N
S
is the bias-corrected number of signal events from the fit to
the
m
Xs
Plot
,
N
B

B
is the number of
B

B
pairs in the data set,

is the total signal extraction efficiency, and
f
represents
all secondary branching fractions. The fit results, efficien-
cies, and derived branching fractions are summarized in
Table
I
.
For most of the
B
!
X
ð
3872
Þ
K
decay channels, the
largest source of systematic uncertainty affecting the signal
yield comes from the uncertainty in the true
X
ð
3872
Þ
mass
and width (

2%
for the
K

modes). In the case of the
K

and
K
0
S
decay modes for
X
ð
3872
Þ!
c
ð
2
S
Þ

, an alternate
parametrization of the
m
X
shape was considered for back-
ground events, as indicated by the MC simulation. A
correction equal to half the difference between the results
of the two background model choices, with a systematic
error equal to this amount, is applied to the final result. This
is the largest yield-related systematic uncertainty for the
X
ð
3872
Þð
c
ð
2
S
Þ

Þ
K

mode (

2%
). For
B
!

c
1
;
2
K
, un-
certainty in the fit bias, PDF parameters, and MC-data
differences for the mean value
m
X
for signal events all
contribute in varying though roughly equal amounts.
Regarding systematic uncertainties related to the
branching fraction calculations, one of the main contrib-
utors is the total uncertainty associated with the identifica-
tion of all particle types (

4%
). The uncertainty in
secondary branching fractions, beyond the control of this
analysis, is the dominant systematic uncertainty for
B
ð
B
!

c
1
K
Þ
and
B
ð
B
0
!

c
2
K

0
Þ
(

6%
). Effects from
tracking, photon corrections and
B
counting are also con-
sidered, but are all less than 2%.
Figure
1
shows the fit to
m
X
in the mass range
3
:
411
<
m
X
<
3
:
611 GeV
=c
2
. We observe all of the expected
B
!

c
1
K
decay modes, in good agreement with previous
measurements. We find
3
:
7

evidence for
B
0
!

c
2
K

0
,
and set upper limits for the remaining
B
!

c
2
K
decays.
Fits to
m
X
in the range
3
:
772
<m
X
<
3
:
972 GeV
=c
2
are
shown in Fig.
2
for decays to
J=
c

. We confirm evidence
for the decay
X
ð
3872
Þ!
J=
c

in
B

!
X
ð
3872
Þ
K

,
measuring
B
ð
B

!
X
ð
3872
Þ
K

Þ

B
ð
X
ð
3872
Þ!
J=
c

Þ
¼½
2
:
8

0
:
8
ð
stat
Þ
0
:
1
ð
syst
Þ
10

6
with a sig-
nificance of
3
:
6

. This value is in good agreement with the
previous
BABAR
result [
3
], which it supersedes, and rep-
resents the most precise measurement of this branching
)
2
(GeV/c
X
m
3.45
3.5
3.55
3.6
)
2
Events / (5 MeV/c
0
100
200
300
(a)
)
2
(GeV/c
X
m
3.45
3.5
3.55
3.6
)
2
Events / (5 MeV/c
0
20
40
60
80
(b)
)
2
(GeV/c
X
m
3.45
3.5
3.55
3.6
)
2
Events / (5 MeV/c
0
10
20
30
40
(c)
)
2
(GeV/c
X
m
3.45
3.5
3.55
3.6
)
2
Events / (5 MeV/c
0
50
100
(d)
FIG. 1.
s
Plot
of the number of signal events versus
m
X
for
(a)
B

!

c
1
;
2
K

, (b)
B
0
!

c
1
;
2
K
0
S
, (c)
B

!

c
1
;
2
K

, and
(d)
B
0
!

c
1
;
2
K

0
. The solid curve is the fit to the data.
)
2
(GeV/c
X
m
3.8
3.85
3.9
3.95
)
2
Events / (5 MeV/c
-5
0
5
10
(a)
)
2
(GeV/c
X
m
3.8
3.85
3.9
3.95
)
2
Events / (5 MeV/c
-5
0
5
10
(b)
)
2
(GeV/c
X
m
3.8
3.85
3.9
3.95
)
2
Events / (5 MeV/c
-5
0
5
10
(c)
)
2
(GeV/c
X
m
3.8
3.85
3.9
3.95
)
2
Events / (5 MeV/c
-5
0
5
10
(d)
FIG. 2.
s
Plot
of the number of extracted signal events versus
m
X
for (a)
B

!
X
ð
3872
Þ
K

, (b)
B
0
!
X
ð
3872
Þ
K
0
S
,
(c)
B

!
X
ð
3872
Þ
K

, and (d)
B
0
!
X
ð
3872
Þ
K

0
, where
X
ð
3872
Þ!
J=
c

. The solid curve is the fit to the data.
PRL
102,
132001 (2009)
PHYSICAL REVIEW LETTERS
week ending
3 APRIL 2009
132001-6