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1
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1
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1
X. Prudent,
1
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1
J. Garra Tico,
2
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2
L. Lopez,
3a,3b
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3a,3b
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3a,3b
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4
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4
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4
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5
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5
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5
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5
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5,
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5
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5
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6
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7
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7
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8
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9
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9
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9
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9
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9
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10
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10
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11
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11
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11
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11
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11
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11
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11
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11
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11
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11
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12
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12
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12
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12
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12
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12
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12
E. C. Martin,
12
D. P. Stoker,
12
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13
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13
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14
J. W. Gary,
14
F. Liu,
14
O. Long,
14
G. M. Vitug,
14
Z. Yasin,
14
L. Zhang,
14
V. Sharma,
15
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16
T. M. Hong,
16
D. Kovalskyi,
16
M. A. Mazur,
16
J. D. Richman,
16
T. W. Beck,
17
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17
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17
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17
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17
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17
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17
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17
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17
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17
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17
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17
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18
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18
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18
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18
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18
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18
T. Piatenko,
18
F. C. Porter,
18
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19
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19
B. T. Meadows,
19
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19
M. D. Sokoloff,
19
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20
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20
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20
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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
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22
A. Hauke,
22
H. Jasper,
22
M. Karbach,
22
J. Merkel,
22
A. Petzold,
22
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22
K. Wacker,
22
M. J. Kobel,
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
F. Le Diberder,
36
V. Lepeltier,
36
A. M. Lutz,
36
S. Pruvot,
36
P. Roudeau,
36
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36
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36
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36,
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A. Stocchi,
36
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36
D. J. Lange,
37
D. M. Wright,
37
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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
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
S. W. Henderson,
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. 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
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
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
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
PHYSICAL REVIEW D
79,
112001 (2009)
1550-7998
=
2009
=
79(11)
=
112001(38)
112001-1
Ó
2009 The American Physical Society
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. 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, V6T 1Z1 Canada
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
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
B. AUBERT
et al.
PHYSICAL REVIEW D
79,
112001 (2009)
112001-2
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, H3A 2T8 Canada
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, H3C 3J7 Canada
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
**
Also with Universita
`
di Sassari, Sassari, Italy.
{
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.
*
Deceased.
SEARCH FOR THE
Z
ð
4430
Þ
AT
BABAR
PHYSICAL REVIEW D
79,
112001 (2009)
112001-3
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 5 November 2008; published 1 June 2009)
We report the results of a search for
Z
ð
4430
Þ
decay to
J=
c
or
c
ð
2
S
Þ
in
B
;
0
!
J=
c
K
0
;
þ
and
B
;
0
!
c
ð
2
S
Þ
K
0
;
þ
decays. The data were collected with the
BABAR
detector at the SLAC PEP-II
asymmetric-energy
e
þ
e
collider operating at center-of-mass energy 10.58 GeV, and the sample
corresponds to an integrated luminosity of
413 fb
1
. Each
K
mass distribution exhibits clear
K
ð
892
Þ
and
K
2
ð
1430
Þ
signals, and the efficiency-corrected spectrum is well described by a superposition
of the associated Breit-Wigner intensity distributions, together with an
S
-wave contribution obtained from
the LASS
I
¼
1
=
2
K
scattering amplitude measurements. Each
K
angular distribution varies
significantly in structure with
K
mass, and is represented in terms of low-order Legendre polynomial
moments. We find that each
J=
c
or
c
ð
2
S
Þ
mass distribution is well described by the reflection
of the measured
K
mass and angular distribution structures. We see no significant evidence
for a
Z
ð
4430
Þ
signal for any of the processes investigated, neither in the total
J=
c
or
c
ð
2
S
Þ
mass distribution, nor in the corresponding distributions for the regions of
K
mass for which
observation of the
Z
ð
4430
Þ
signal was reported. We obtain branching-fraction upper limits
B
ð
B
!
Z
K
0
;Z
!
J=
c
Þ
<
1
:
5
10
5
,
B
ð
B
0
!
Z
K
þ
;Z
!
J=
c
Þ
<
0
:
4
10
5
,
B
ð
B
!
Z
K
0
;Z
!
c
ð
2
S
Þ
Þ
<
4
:
7
10
5
, and
B
ð
B
0
!
Z
K
þ
;Z
!
c
ð
2
S
Þ
Þ
<
3
:
1
10
5
at 95% con-
fidence level, where the
Z
ð
4430
Þ
mass and width have been fixed to the reported central values.
DOI:
10.1103/PhysRevD.79.112001
PACS numbers: 12.39.Mk, 12.40.Yx, 13.25.Hw, 14.40.Gx
I. INTRODUCTION
In the original paper in which he proposed the quark
model [
1
], Gell-Mann stated that ‘‘Baryons can now be
constructed from quarks using the combinations (
qqq
),
ð
qqqq
q
Þ
,
etc
., while mesons are made out of
ð
q
q
Þ
,
ð
qq
q
q
Þ
,
etc.
’’. He chose the lowest configurations to create
the representations describing the known meson and
baryon states. However, the higher configurations were
not
a priori
excluded, and experimentalists and theorists
have been seeking evidence supporting the existence of
such states ever since.
In the baryon sector, resonant structure in the
KN
system
would be indicative of five-quark content, and searches for
states of this type have been carried out since the mid-
1960s, mainly through partial-wave analysis of
KN
elastic
and charge-exchange scattering data. In recent years, there
has been a great deal of activity focused on the search for
the conjectured
ð
1540
Þ
þ
pentaquark state decaying to
K
0
p
. However, the initial low-statistics signals claimed
in a variety of experimental contexts have not withstood
high-statistics scrutiny, and the existence of this state must
be considered to be in doubt at the present time. The
subject is reviewed in Ref. [
2
], and the status is updated
in Ref. [
3
].
In the meson sector, attention has been focused over the
years mainly on the
a
0
ð
980
Þ
and the
f
0
ð
980
Þ
scalar mesons
as possible four-quark states. However, the discovery of
the
D
s
0
ð
2317
Þ
and the
D
s
1
ð
2460
Þ
, with their unexpectedly
low mass values, and the observation of many new
charmonium-like states above threshold for decay to
open charm, have led to speculation that certain of these
may be four-quark states [
4
]. The first such state, and the
most extensively studied, both theoretically and experi-
mentally, was the
X
ð
3872
Þ
discovered by the Belle
Collaboration in the decay
B
!
J=
c
þ
K
[
5
].
Confirmation of the
X
ð
3872
Þ
followed from CDF [
6
], D0
[
7
], and
BABAR
[
8
]. A CDF analysis of the
þ
mass
distribution resulting from the
X
ð
3872
Þ
decay showed that
the
J
PC
values
1
þþ
and
2
þ
were indistinguishable [
9
].
This was also the conclusion of a related angular correla-
tion study performed by CDF [
10
]. If the
X
ð
3872
Þ
indeed
has
J
PC
¼
2
þ
then it is probably the
c
2
ð
1
D
Þ
charmo-
nium ground state [
11
], and hence is not a four-quark
candidate. None of the other charmonium-like states has
been identified as four-quark in nature, and so it follows
that the recent paper from the Belle Collaboration [
12
]
which reports the observation of a resonance-like structure,
the
Z
ð
4430
Þ
, in the
c
ð
2
S
Þ
system produced in the
decays
B
;
0
!
c
ð
2
S
Þ
K
0
;
þ
[
13
] has generated a great
deal of interest (see e.g. Ref. [
14
], and references therein).
Such a state must have a minimum quark content
ð
c
cd
u
Þ
,
and would represent the unequivocal manifestation of a
four-quark meson state.
It is clearly important to seek confirmation of the Belle
observation, not only in the
c
ð
2
S
Þ
system, but also for
the
J=
c
combination, which might also show evidence
of a
Z
ð
4430
Þ
signal or of a similar lower mass state [
15
].
B. AUBERT
et al.
PHYSICAL REVIEW D
79,
112001 (2009)
112001-4
Consequently, in this paper we present a
BABAR
analysis
of the entire Dalitz plot corresponding to the decays
B
;
0
!
c
ð
2
S
Þ
K
0
;
þ
and in parallel pursue an identical
analysis of our
B
;
0
!
J=
c
K
0
;
þ
data. Both analyses
make use of the complete
BABAR
data sample accrued at
the
ð
4
S
Þ
resonance. In this regard, we first seek a repre-
sentation of the
K
mass and angular distribution struc-
tures, which dominate the final states under study, in terms
of their expected low-angular-momentum intensity contri-
butions. We then investigate the reflection of each
K
system into its associated
c
[
16
] mass distribution in
order to establish the need for any additional narrow signal.
The
BABAR
detector and the data sample are described
briefly in Sec.
II
, and the event-selection procedures are
discussed in Sec.
III
. In Sec.
IV
, the Dalitz plots and their
uncorrected invariant mass projections are shown for the
B
meson signal regions. Since the analysis emphasizes this
search for narrow structure in the
J=
c
and
c
ð
2
S
Þ
mass distributions, the mass resolution dependence on
invariant mass for these systems is analyzed in Sec.
V
.
Similarly, it is important to understand the behavior of the
event reconstruction efficiency over each final state Dalitz
plot and to correct for it before assessing the significance of
any observed mass structures. The procedure followed is
described in the appendix, and the results are summarized
in Sec.
VI
. Fits to the corrected
K
mass distributions are
discussed in Sec.
VII
, and the
K
angular distribution
structure as a function of
K
mass is represented in terms
of Legendre polynomial moments as described in
Sec.
VIII
. In Sec.
IX
, the reflections of the observed
K
mass and angular structures onto the
J=
c
and
c
ð
2
S
Þ
mass distributions are compared to the corre-
sponding efficiency-corrected distributions, and in Sec.
X
our results are discussed in relation to those in the Belle
publication. The
BABAR
c
mass distributions are fitted
in Sec.
XI
, and we present a summary and our conclusions
in Sec.
XII
.
II. THE
BABAR
DETECTOR AND DATA SAMPLE
The data used in this analysis were collected with the
BABAR
detector at the PEP-II asymmetric-energy
e
þ
e
collider operating at a center-of-mass (c.m.) energy of
10.58 GeV.
A detailed description of the
BABAR
detector can be
found in Ref. [
17
]. Charged-particle tracks are detected
with a five-layer, double-sided silicon vertex tracker (SVT)
and a 40-layer drift chamber (DCH), filled with a helium-
isobutane gas mixture, and coaxial with the cryostat of a
superconducting solenoidal magnet, which produces a
magnetic field of approximately 1.5 T. The charged-
particle momentum resolution is given by
ð
P
T
=P
T
Þ
2
¼
ð
0
:
0013
P
T
Þ
2
þð
0
:
0045
Þ
2
, where
P
T
is the transverse mo-
mentum measured in
GeV
=c
. The SVT, with a typical
coordinate resolution of
10
m
, measures the impact pa-
rameters of charged-particle tracks in both the plane trans-
verse to the beam direction and along the collision axis; it
also supports stand-alone reconstruction of low-
P
T
charged-particle tracks.
Charged-particle types are identified from specific ion-
ization energy loss (
dE=dx
) measured in the DCH and
SVT, and from Cherenkov radiation detected in a ring-
imaging Cherenkov device. Electrons are identified by
means of a CsI(Tl) electromagnetic calorimeter (EMC).
The return yoke of the superconducting coil is instru-
mented with resistive plate chambers for the identification
of muons and the detection of clusters produced by
K
L
and
neutron interactions. For the latter part of the experiment
these chambers were replaced by limited streamer tubes in
the barrel region of the detector [
18
].
In this analysis, we use a data sample corresponding to
an integrated luminosity of
413 fb
1
, which is equivalent
to the production of approximately
455
10
6
B
B
pairs.
III. EVENT SELECTION
We reconstruct events in four decay modes [
13
]:
B
!
J=
c
K
0
S
;
(1)
B
0
!
J=
c
K
þ
;
(2)
B
!
c
ð
2
S
Þ
K
0
S
;
(3)
B
0
!
c
ð
2
S
Þ
K
þ
:
(4)
The event-selection criteria were established by optimiz-
ing signal-to-background ratio using Monte Carlo (MC)
simulated signal events,
B
;
0
!
c
K
0
;
þ
, and back-
ground,
B
B
and
e
þ
e
!
q
q
(
q
¼
u; d; s; c
), events.
For the data sample, a
J=
c
candidate is formed by
geometrically constraining an identified
e
þ
e
or
þ
pair of tracks to a common vertex point and requiring a
fit probability
>
0
:
001
.For
þ
, the invariant mass of
the pair must in addition satisfy
3
:
06
<m
þ
<
3
:
14 GeV
=c
2
, while for
e
þ
e
the requirement is
2
:
95
<
m
e
þ
e
<
3
:
14 GeV
=c
2
. In the latter case, the mass interval
extends to lower values in order to allow for electron
bremsstrahlung energy loss; if an electron-associated pho-
ton cluster of this type is found in the EMC, its four-
momentum vector is included in the calculation of
m
e
þ
e
. The surviving
J=
c
candidates were fitted to impose
a constraint to the nominal mass value [
3
].
For
c
ð
2
S
Þ
decay to
þ
or
e
þ
e
the same selection
procedures are followed, but with invariant mass require-
ments
3
:
640
<m
þ
<
3
:
740 GeV
=c
2
or
3
:
440
<
m
e
þ
e
<
3
:
740 GeV
=c
2
.For
c
ð
2
S
Þ
decay to
J=
c
þ
,
the
J=
c
candidate is selected as previously described, and
is fit again to incorporate a constraint to its nominal mass
value [
3
]. This
J=
c
and an identified
þ
pair are
geometrically constrained to a common vertex (fit proba-
bility
>
0
:
001
), and required to have an invariant mass in
SEARCH FOR THE
Z
ð
4430
Þ
AT
BABAR
PHYSICAL REVIEW D
79,
112001 (2009)
112001-5
the range
3
:
655
<m
J=
c
þ
<
3
:
715 GeV
=c
2
. In the
same manner as for the
J=
c
, surviving candidates were
then constrained to the nominal
c
ð
2
S
Þ
mass value [
3
].
A
K
0
S
candidate is formed by geometrically constraining
a pair of oppositely charged tracks to a common vertex (fit
probability
>
0
:
001
); the tracks are treated as pions, but
without particle-identification requirements, and the in-
variant mass of the pair must satisfy
0
:
472
<m
þ
<
0
:
522 GeV
=c
2
. A charged kaon candidate from the
B
meson decay must be identified as a kaon, but no particle
identification is required of corresponding charged pion
candidates.
The
c
,
K
, and
candidates forming a
B
meson decay
candidate are geometrically constrained to a common ver-
tex, with fit probability
>
0
:
001
required. For decay modes
involving a
K
0
S
, the
K
0
S
flight length with respect to this
vertex must have
>
þ
3
standard deviation significance in
order to reduce combinatoric background. The
K
0
S
candi-
date is not mass constrained, since this was found to have a
negligible effect on resolution.
We further define
B
meson decay candidates using the
energy difference
E
¼
E
B
ffiffiffi
s
p
=
2
in the c.m. frame,
and the beam-energy substituted mass
m
ES
¼
ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
ðð
s=
2
þ
~
p
i
~
p
B
Þ
=E
i
Þ
2
~
p
2
B
q
, where
ð
E
i
;
~
p
i
Þ
is the initial
state four-momentum vector in the laboratory frame and
ffiffiffi
s
p
is the c.m. energy;
E
B
is the
B
meson energy in the c.m.
and
~
p
B
is its laboratory-frame momentum.
We require that
B
decay signal events satisfy
5
:
272
<
m
ES
<
5
:
286 GeV
=c
2
and
j
E
j
<
0
:
020 GeV
. In order
to correct for background events in the signal region,
we define a
E
sideband region by
0
:
030
<
j
E
j
<
0
:
050 GeV
; we have verified through MC studies that
sideband events in the
m
ES
signal range correctly represent
background in the
B
meson signal region. We refer to
the procedure by which we correct for background in
the signal region by subtracting the
E
sideband events
in the
m
ES
signal range by the term ‘‘sideband
subtraction.’’
In Figs.
1(a)
–
1(d)
we show the
m
ES
distributions in the
E
signal region for the decay processes of Eqs. (
1
)–(
4
),
where the filled histograms show the sideband distribu-
tions. We perform a binned Poisson maximum-likelihood
fit to each distribution using a signal Gaussian function
with mass and width as free parameters, and an ARGUS
background function [
19
] with a free exponential slope
parameter. In each figure, the solid curve represents the
total function and the dashed curve shows the background
contribution. Clear
m
ES
signals are observed in Figs.
1(a)
–
1(d)
, and in each figure the sideband distribution is con-
sistent with the fitted background, apart from a small
excess in the signal region. Simulation studies show that
there is a small peaking background in the
m
ES
signal
region which is correctly reproduced by the
E
sideband
m
ES
distributions. It is this excess which appears above the
dashed curves in Figs.
1(a)
–
1(d)
.
500
1000
1500
500
1000
1500
500
1000
1500
S
0
K
-
π
ψ
J/
→
-
B
Data
Sideband
Fit result
Background
(a)
2000
4000
2000
4000
2000
4000
+
K
-
π
ψ
J/
→
0
B
(b)
100
200
100
200
100
200
S
0
K
-
π
(2S)
ψ
→
-
B
(c)
)
2
(GeV/c
ES
m
5.2
5.22
5.24
5.26
5.28
5.3
0
200
400
600
800
)
2
(GeV/c
ES
m
5.2
5.22
5.24
5.26
5.28
5.3
0
200
400
600
800
)
2
(GeV/c
ES
m
5.2
5.22
5.24
5.26
5.28
5.3
0
200
400
600
800
+
K
-
π
(2S)
ψ
→
0
B
(d)
2
Events/2 MeV/c
200
400
200
400
200
400
200
400
S
0
K
-
π
ψ
J/
→
-
B
(e)
500
1000
1500
500
1000
1500
500
1000
1500
500
1000
1500
+
K
-
π
ψ
J/
→
0
B
(f)
50
100
50
100
50
100
50
100
S
0
K
-
π
(2S)
ψ
→
-
B
(g)
E (GeV)
∆
-0.1
-0.05
0
0.05
0.1
100
200
300
E (GeV)
∆
-0.1
-0.05
0
0.05
0.1
100
200
300
E (GeV)
∆
-0.1
-0.05
0
0.05
0.1
100
200
300
E (GeV)
∆
-0.1
-0.05
0
0.05
0.1
100
200
300
+
K
-
π
(2S)
ψ
→
0
B
(h)
Events/2 MeV
FIG. 1 (color online). The
m
ES
distributions, (a)–(d), and
E
distributions, (e)–(h), for the decay modes
B
!
J=
c
K
0
S
,
B
0
!
J=
c
K
þ
,
B
!
c
ð
2
S
Þ
K
0
S
, and
B
0
!
c
ð
2
S
Þ
K
þ
. The points show the data, and the solid curves represent the fit functions.
The dashed curves indicate the background contributions, and the filled histograms show the corresponding distributions for the
sideband regions.
B. AUBERT
et al.
PHYSICAL REVIEW D
79,
112001 (2009)
112001-6
The
E
distributions for the
m
ES
signal region
(Figs.
1(e)
–
1(h)
) exhibit clear signal peaks. We perform a
binned Poisson maximum-likelihood fit to each distribu-
tion using a linear background function and a signal func-
tion consisting of two Gaussian functions with a common
center; all parameters are free in the fits. In each case, the
filled histogram is from the
m
ES
sideband region defined by
5
:
250
<m
ES
<
5
:
264 GeV
=c
2
, and is in good agreement
with the fitted background. For the decay modes of
Eqs. (
1
)–(
4
), the fraction of events with more than one
B
meson signal candidate ranges from 0.5% to 1.1%. For
such events, the candidate with the smallest value of
j
E
j
is selected.
We summarize the principal selection criteria in Table
I
,
and in Table
II
provide an overview of the data samples in
the
B
-meson signal region used in the analysis described in
this paper.
IV. THE DALITZ PLOTS AND INVARIANT MASS
PROJECTIONS
The Dalitz plots of
m
2
c
versus
m
2
K
are shown in
Fig.
2
for the signal regions defined in Table
I
for the
B
meson decay modes specified in Eqs. (
1
)–(
4
). The corre-
sponding
m
K
,
m
c
, and
m
c
K
mass projections are
represented by the data points in Figs.
3
–
5
, respectively.
In each figure the filled histogram is obtained from the
relevant
E
sideband region.
In Fig.
3
, the contributions due to the
K
ð
892
Þ
dominate
the mass distributions. Small, but clear,
K
2
ð
1430
Þ
signals
are evident for the
J=
c
decay modes, and these seem
to be present for the
c
ð
2
S
Þ
modes also. Previous
analyses [
20
,
21
] have shown that, for the
J=
c
modes,
the region between the
K
ð
892
Þ
and
K
2
ð
1430
Þ
signals
ð
1
:
1
–
1
:
3 GeV
=c
2
Þ
contains a significant
K
S
-wave
contribution. In the
K
ð
892
Þ
region, the presence of the
S
-wave amplitude has been demonstrated through its in-
terference with the
K
ð
892
Þ
P
-wave amplitude [
21
]. This
interference yields a strong forward-backward asymmetry
in the
K
angular distribution, as is seen in the vertical
K
ð
892
Þ
bands of Figs.
2(b)
and
2(d)
, and as is shown in
Sec.
VII
, Figs.
14(a)
and
14(c)
. These features of the
K
mass and angular distributions will be analyzed in detail in
Secs.
VII
and
VIII
below.
The
m
c
distributions of Fig.
4
show no peaking
structure at the mass reported for the
Z
ð
4430
Þ
[
12
]
(indicated by the dashed vertical line in each figure). In
Fig.
4(b)
there seems to be a peak at
4
:
65 GeV
=c
2
and
perhaps a weaker one just below
4
:
4 GeV
=c
2
, while in
Figs.
4(c)
and
4(d)
there seems to be a peak just below
4
:
5 GeV
=c
2
. These features are discussed in Secs.
X
and
XI
in conjunction with reflections resulting from the
K
mass and angular structures.
Similarly, the
m
c
K
distributions of Fig.
5
show no
evidence of narrow structure. In fact, in overall shape these
distributions approximate mirror images of those in Fig.
4
.
This is not unexpected if both result primarily from
K
reflection, since then the high-mass region of one distribu-
tion would be correlated strongly with the low mass region
of the other, and
vice versa
. Since Fig.
5
shows no evidence
of interesting features, and since our emphasis in this paper
is on the search for the
Z
ð
4430
Þ
, we do not discuss the
c
K
systems any further in the present analysis.
TABLE I. Summary of the principal criteria used to select
B
candidates.
Selection category
criterion
J=
c
!
e
þ
e
2
:
95
<m
ee
<
3
:
14 GeV
=c
2
J=
c
!
þ
3
:
06
<m
<
3
:
14 GeV
=c
2
c
ð
2
S
Þ!
e
þ
e
3
:
44
<m
ee
<
3
:
74 GeV
=c
2
c
ð
2
S
Þ!
J=
c
þ
(
J=
c
!
e
þ
e
)
3
:
655
<m
J=
c
<
3
:
715 GeV
=c
2
c
ð
2
S
Þ!
þ
3
:
64
<m
<
3
:
74 GeV
=c
2
c
ð
2
S
Þ!
J=
c
þ
(
J=
c
!
þ
)
3
:
655
<m
J=
c
<
3
:
715 GeV
=c
2
K
0
S
!
þ
0
:
472
<m
<
0
:
522 GeV
=c
2
Flight length significance
>
þ
3
m
ES
signal region
5
:
272
<m
ES
<
5
:
286 GeV
=c
2
E
signal region
j
E
j
<
0
:
020 GeV
TABLE II. The data samples used in the analysis.
Decay mode
Signal region events
E
sideband events
Net analysis sample
B
!
J=
c
K
0
S
4229
65
485
22
3744
68
B
0
!
J=
c
K
þ
14 251
119
1269
36
12 982
124
B
!
c
ð
2
S
Þ
K
0
S
703
26
161
13
542
29
B
0
!
c
ð
2
S
Þ
K
þ
2405
49
384
20
2021
53
SEARCH FOR THE
Z
ð
4430
Þ
AT
BABAR
PHYSICAL REVIEW D
79,
112001 (2009)
112001-7