of 10
First Observation of
CP
Violation in
̄
B
0
D
ðÞ
CP
h
0
Decays by a Combined
Time-Dependent Analysis of
BABAR
and Belle Data
A. Abdesselam,
120
,
I. Adachi,
40,34
,
A. Adametz,
39
,
T. Adye,
109
,
H. Ahmed,
52
,
H. Aihara,
130
,
S. Akar,
100
,
M. S. Alam,
117
,
J. Albert,
136
,
S. Al Said,
120,58
,
R. Andreassen,
22
,
C. Angelini,
103a,103b
,
F. Anulli,
107a
,
K. Arinstein,
12,13
,
N. Arnaud,
62
,
D. M. Asner,
98
,
D. Aston,
113
,
V. Aulchenko,
12,13
,
T. Aushev,
84,48
,
R. Ayad,
120,24
,
,
V. Babu,
121
,
I. Badhrees,
120,57
,
S. Bahinipati,
43
,
A. M. Bakich,
119
,
H. R. Band,
140
,
Sw. Banerjee,
136
,
E. Barberio,
79
,
D. J. Bard,
113
,
R. J. Barlow,
73
,§,
G. Batignani,
103a,103b
,
A. Beaulieu,
136
,
M. Bellis,
116
,
E. Ben-Haim,
100
,
D. Bernard,
27
,
F. U. Bernlochner,
136
,
S. Bettarini,
103a,103b
,
D. Bettoni,
29a
,
A. J. Bevan,
67
,
V. Bhardwaj,
114
,
B. Bhuyan,
35
,
,
F. Bianchi,
133a,133b
,
M. Biasini,
102a,102b
,
J. Biswal,
51
,
V. E. Blinov,
12,13,14
,
P. C. Bloom,
23
,
A. Bobrov,
12,13
,
M. Bomben,
100
,
A. Bondar,
12,13
,
G. R. Bonneaud,
100
,
G. Bonvicini,
139
,
A. Bozek,
93
,
C. Bozzi,
29a
,
M. Bra
č
ko,
74,51
,
H. Briand,
100
,
T. E. Browder,
38
,
D. N. Brown,
7
,
D. N. Brown,
69
,
C. Bünger,
108
,
P. R. Burchat,
116
,
A. R. Buzykaev,
12
,
R. Calabrese,
29a,29b
,
A. Calcaterra,
30
,
G. Calderini,
100
,
M. Carpinelli,
103a,103b
,
,
C. Cartaro,
113
,
G. Casarosa,
103a,103b
,
R. Cenci,
75
,
D.
Č
ervenkov,
20
,
P. Chang,
92
,
D. S. Chao,
19
,
J. Chauveau,
100
,
R. Cheaib,
78
,
V. Chekelian,
77
,
A. Chen,
89
,
C. Chen,
50
,
C. H. Cheng,
19
,
B. G. Cheon,
37
,
K. Chilikin,
48
,
R. Chistov,
48
,
K. Cho,
59
,
V. Chobanova,
77
,
H. H. F. Choi,
136
,
S.-K. Choi,
36
,
M. Chrzaszcz,
103a
,
G. Cibinetto,
29a,29b
,
D. Cinabro,
139
,
J. Cochran,
50
,
J. P. Coleman,
65
,
R. Contri,
31a,31b
,
M. R. Convery,
113
,
G. Cowan,
68
,
R. Cowan,
76
,
L. Cremaldi,
81
,
J. Dalseno,
77,122
,
S. Dasu,
140
,
M. Davier,
62
,
C. L. Davis,
69
,
F. De Mori,
133a,133b
,
G. De Nardo,
87a,87b
,
A. G. Denig,
72
,
D. Derkach,
62
,
R. de Sangro,
30
,
B. Dey,
16
,
F. Di Lodovico,
67
,
J. Dingfelder,
9
,
S. Dittrich,
108
,
Z. Dole
ž
al,
20
,
J. Dorfan,
113
,
Z. Drásal,
20
,
A. Drutskoy,
48,83
,
V. P. Druzhinin,
12,13
,
G. P. Dubois-Felsmann,
113
,
W. Dunwoodie,
113
,
D. Dutta,
121
,
M. Ebert,
113
,
B. Echenard,
19
,
S. Eidelman,
12,13
,
G. Eigen,
6
,
A. M. Eisner,
18
,
S. Emery,
110
,
J. A. Ernst,
117
,
R. Faccini,
107a,107b
,
H. Farhat,
139
,
J. E. Fast,
98
,
M. Feindt,
55
,
T. Ferber,
25
,
F. Ferrarotto,
107a
,
F. Ferroni,
107a,107b
,
R. C. Field,
113
,
A. Filippi,
133a
,
G. Finocchiaro,
30
,
E. Fioravanti,
29a,29b
,
K. T. Flood,
19
,
W. T. Ford,
23
,
F. Forti,
103a,103b
,
M. Franco Sevilla,
17
,
M. Fritsch,
72
,
J. R. Fry,
65
,
B. G. Fulsom,
98,113
,
,
E. Gabathuler,
65
,
N. Gabyshev,
12,13
,
D. Gamba,
133a,133b
,
A. Garmash,
12,13
,
J. W. Gary,
16
,
I. Garzia,
29a,29b
,
M. Gaspero,
107a,107b
,
V. Gaur,
121
,
A. Gaz,
23
,
T. J. Gershon,
138
,
D. Getzkow,
32
,
R. Gillard,
139
,
L. Li Gioi,
77
,
M. A. Giorgi,
103a,103b
,
R. Glattauer,
46
,
R. Godang,
81
,¶,
Y. M. Goh,
37
,
P. Goldenzweig,
55
,
B. Golob,
66,51
,
V. B. Golubev,
12,13
,
R. Gorodeisky,
123
,
W. Gradl,
72
,
M. T. Graham,
113
,
E. Grauges,
2
,
K. Griessinger,
72
,
A. V. Gritsan,
53
,
G. Grosdidier,
62
,
O. Grünberg,
108
,
N. Guttman,
123
,
J. Haba,
40,34
,
A. Hafner,
72
,
B. Hamilton,
75
,
T. Hara,
40,34
,
P. F. Harrison,
138
,
C. Hast,
113
,
K. Hayasaka,
86
,
H. Hayashii,
88
,
C. Hearty,
10
,
X. H. He,
101
,
M. Hess,
108
,
D. G. Hitlin,
19
,
T. M. Hong,
17
,
K. Honscheid,
96
,
W.-S. Hou,
92
,
Y. B. Hsiung,
92
,
Z. Huard,
22
,
D. E. Hutchcroft,
65
,
T. Iijima,
86,85
,
G. Inguglia,
25
,
W. R. Innes,
113
,
A. Ishikawa,
128
,
R. Itoh,
40,34
,
Y. Iwasaki,
40
,
J. M. Izen,
126
,
I. Jaegle,
38
,
A. Jawahery,
75
,
C. P. Jessop,
95
,
D. Joffe,
56
,
K. K. Joo,
21
,
T. Julius,
79
,
K. H. Kang,
61
,
R. Kass,
96
,
T. Kawasaki,
94
,
L. T. Kerth,
7
,
A. Khan,
11
,
C. Kiesling,
77
,
D. Y. Kim,
112
,
J. B. Kim,
60
,
J. H. Kim,
59
,
K. T. Kim,
60
,
P. Kim,
113
,
S. H. Kim,
37
,
Y. J. Kim,
59
,
G. J. King,
136
,
K. Kinoshita,
22
,
B. R. Ko,
60
,
H. Koch,
8
,
P. Kody
š
,
20
,
Yu. G. Kolomensky,
7
,
S. Korpar,
74,51
,
D. Kovalskyi,
17
,
R. Kowalewski,
136
,
E. A. Kravchenko,
12,13
,
P. Kri
ž
an,
66,51
,
P. Krokovny,
12,13
,
T. Kuhr,
70
,
R. Kumar,
106
,
A. Kuzmin,
12,13
,
Y.-J. Kwon,
142
,
H. M. Lacker,
41
,
G. D. Lafferty,
73
,
L. Lanceri,
134a,134b
,
D. J. Lange,
64
,
A. J. Lankford,
15
,
T. E. Latham,
138
,
T. Leddig,
108
,
F. Le Diberder,
62
,
D. H. Lee,
60
,
I. S. Lee,
37
,
M. J. Lee,
7
,
J. P. Lees,
1
,
D. W. G. S. Leith,
113
,
Ph. Leruste,
100
,
M. J. Lewczuk,
136
,
P. Lewis,
38
,
J. Libby,
44
,
W. S. Lockman,
18
,
O. Long,
16
,
D. Lopes Pegna,
105
,
J. M. LoSecco,
95
,
X. C. Lou,
126
,
T. Lueck,
136
,
S. Luitz,
113
,
P. Lukin,
12,13
,
E. Luppi,
29a,29b
,
A. Lusiani,
103a,103c
,
V. Luth,
113
,
A. M. Lutz,
62
,
G. Lynch,
7
,
D. B. MacFarlane,
113
,
B. Malaescu,
62
,**,
U. Mallik,
49
,
E. Manoni,
102a
,
G. Marchiori,
100
,
M. Margoni,
99a,99b
,
S. Martellotti,
30
,
F. Martinez-Vidal,
135
,
M. Masuda,
129
,
T. S. Mattison,
10
,
D. Matvienko,
12,13
,
J. A. McKenna,
10
,
B. T. Meadows,
22
,
K. Miyabayashi,
88
,
T. S. Miyashita,
19
,
H. Miyata,
94
,
R. Mizuk,
48,83
,
G. B. Mohanty,
121
,
A. Moll,
77,122
,
M. R. Monge,
31a,31b
,
H. K. Moon,
60
,
M. Morandin,
99a
,
D. R. Muller,
113
,
R. Mussa,
133a
,
E. Nakano,
97
,
H. Nakazawa,
89
,
M. Nakao,
40,34
,
T. Nanut,
51
,
M. Nayak,
44
,
H. Neal,
113
,
N. Neri,
80a
,
N. K. Nisar,
121
,
S. Nishida,
40,34
,
I. M. Nugent,
136
,
B. Oberhof,
103a,103b
,
J. Ocariz,
100
,
S. Ogawa,
127
,
S. Okuno,
54
,
E. O. Olaiya,
109
,
J. Olsen,
105
,
P. Ongmongkolkul,
19
,
G. Onorato,
87a,87b
,
A. P. Onuchin,
12
14
,
Y. Onuki,
130
,
W. Ostrowicz,
93
,
A. Oyanguren,
135
,
G. Pakhlova,
84,48
,
P. Pakhlov,
48,83
,
A. Palano,
3a,3b
,
B. Pal,
22
,
F. Palombo,
80a,80b
,
Y. Pan,
140
,
W. Panduro Vazquez,
18
,
E. Paoloni,
103a,103b
,
C. W. Park,
118
,
H. Park,
61
,
S. Passaggio,
31a
,
P. M. Patel,
78
,
,*
C. Patrignani,
31a,31b
,
P. Patteri,
30
,
D. J. Payne,
65
,
T. K. Pedlar,
71
,
D. R. Peimer,
123
,
I. M. Peruzzi,
30
,
L. Pesántez,
9
,
R. Pestotnik,
51
,
M. Petri
č
,
51
,
M. Piccolo,
30
,
PRL
115,
121604 (2015)
PHYSICAL REVIEW LETTERS
week ending
18 SEPTEMBER 2015
0031-9007
=
15
=
115(12)
=
121604(10)
121604-1
© 2015 American Physical Society
L. Piemontese,
29a
,
L. E. Piilonen,
137
,
A. Pilloni,
107a,107b
,
G. Piredda,
107a
,
S. Playfer,
28
,
V. Poireau,
1
,
F. C. Porter,
19
,
M. Posocco,
99a
,
V. Prasad,
35
,
S. Prell,
50
,
R. Prepost,
140
,
E. M. T. Puccio,
116
,
T. Pulliam,
113
,
M. V. Purohit,
114
,
B. G. Pushpawela,
22
,
M. Rama,
103a
,
A. Randle-Conde,
115
,
B. N. Ratcliff,
113
,
G. Raven,
90
,
E. Ribe
ž
l,
51
,
J. D. Richman,
17
,
J. L. Ritchie,
125
,
G. Rizzo,
103a,103b
,
D. A. Roberts,
75
,
S. H. Robertson,
78
,
M. Röhrken,
19,55
,
,
J. M. Roney,
136
,
A. Roodman,
113
,
A. Rossi,
102a
,
A. Rostomyan,
25
,
M. Rotondo,
99a
,
P. Roudeau,
62
,
R. Sacco,
67
,
Y. Sakai,
40,34
,
S. Sandilya,
121
,
L. Santelj,
40
,
V. Santoro,
29a
,
T. Sanuki,
128
,
Y. Sato,
85
,
V. Savinov,
104
,
R. H. Schindler,
113
,
O. Schneider,
63
,
G. Schnell,
4,42
,
T. Schroeder,
8
,
K. R. Schubert,
72
,
B. A. Schumm,
18
,
C. Schwanda,
46
,
A. J. Schwartz,
22
,
R. F. Schwitters,
125
,
C. Sciacca,
87a,87b
,
A. Seiden,
18
,
S. J. Sekula,
115
,
K. Senyo,
141
,
O. Seon,
85
,
S. I. Serednyakov,
12,13
,
M. E. Sevior,
79
,
M. Shapkin,
47
,
V. Shebalin,
12,13
,
C. P. Shen,
5
,
T.-A. Shibata,
131
,
J.-G. Shiu,
92
,
M. Simard,
82
,
G. Simi,
99a,99b
,
F. Simon,
77,122
,
F. Simonetto,
99a,99b
,
Yu. I. Skovpen,
12,13
,
A. J. S. Smith,
105
,
J. G. Smith,
23
,
A. Snyder,
113
,
R. Y. So,
10
,
R. J. Sobie,
136
,
A. Soffer,
123
,
Y.-S. Sohn,
142
,
M. D. Sokoloff,
22
,
A. Sokolov,
47
,
E. P. Solodov,
12,13
,
E. Solovieva,
48
,
B. Spaan,
26
,
S. M. Spanier,
124
,
M. Stari
č
,
51
,
A. Stocchi,
62
,
R. Stroili,
99a,99b
,
B. Stugu,
6
,
D. Su,
113
,
M. K. Sullivan,
113
,
M. Sumihama,
33
,
K. Sumisawa,
40,34
,
T. Sumiyoshi,
132
,
D. J. Summers,
81
,
L. Sun,
22
,
U. Tamponi,
133a,133b
,
P. Taras,
82
,
N. Tasneem,
136
,
Y. Teramoto,
97
,
V. Tisserand,
1
,
K. Yu. Todyshev,
12,13
,
W. H. Toki,
24
,
C. Touramanis,
65
,
K. Trabelsi,
40,34
,
T. Tsuboyama,
40
,
M. Uchida,
131
,
T. Uglov,
48,84
,
Y. Unno,
37
,
S. Uno,
40,34
,
Y. Usov,
12,13
,
U. Uwer,
39
,
S. E. Vahsen,
38
,
C. Van Hulse,
4
,
P. Vanhoefer,
77
,
G. Varner,
38
,
G. Vasseur,
110
,
J. Va
vra,
113
,
M. Verderi,
27
,
A. Vinokurova,
12,13
,
L. Vitale,
134a,134b
,
V. Vorobyev,
12,13
,
C. Voß,
108
,
M. N. Wagner,
32
,
S. R. Wagner,
23
,
R. Waldi,
108
,
J. J. Walsh,
103a
,
C. H. Wang,
91
,
M.-Z. Wang,
92
,
P. Wang,
45
,
Y. Watanabe,
54
,
C. A. West,
17
,
K. M. Williams,
137
,
F. F. Wilson,
109
,
J. R. Wilson,
114
,
W. J. Wisniewski,
113
,
E. Won,
60
,
G. Wormser,
62
,
D. M. Wright,
64
,
S. L. Wu,
140
,
H. W. Wulsin,
113
,
H. Yamamoto,
128
,
J. Yamaoka,
98
,
S. Yashchenko,
25
,
C. Z. Yuan,
45
,
Y. Yusa,
94
,
A. Zallo,
30
,
C. C. Zhang,
45
,
Z. P. Zhang,
111
,
V. Zhilich,
12,13
,
V. Zhulanov,
12,13
,
and A. Zupanc
51
,
(
B
A
B
AR
Collaboration)
(Belle Collaboration)
1
Laboratoire d
Annecy-le-Vieux de Physique des Particules (LAPP), Université 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, Università di Bari, I-70126 Bari, Italy
4
University of the Basque Country UPV/EHU, 48080 Bilbao, Spain
5
Beihang University, Beijing 100191, China
6
University of Bergen, Institute of Physics, N-5007 Bergen, Norway
7
Lawrence Berkeley National Laboratory and University of California, Berkeley, California 94720, USA
8
Ruhr Universität Bochum, Institut für Experimentalphysik 1, D-44780 Bochum, Germany
9
University of Bonn, 53115 Bonn, Germany
10
University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
11
Brunel University, Uxbridge, Middlesex UB8 3PH, United Kingdom
12
Budker Institute of Nuclear Physics SB RAS, Novosibirsk 630090, Russian Federation
13
Novosibirsk State University, Novosibirsk 630090, Russian Federation
14
Novosibirsk State Technical University, Novosibirsk 630092, Russian Federation
15
University of California at Irvine, Irvine, California 92697, USA
16
University of California at Riverside, Riverside, California 92521, USA
17
University of California at Santa Barbara, Santa Barbara, California 93106, USA
18
University of California at Santa Cruz, Institute for Particle Physics, Santa Cruz, California 95064, USA
19
California Institute of Technology, Pasadena, California 91125, USA
20
Faculty of Mathematics and Physics, Charles University, 121 16 Prague, Czech Republic
21
Chonnam National University, Kwangju 660-701, South Korea
22
University of Cincinnati, Cincinnati, Ohio 45221, USA
23
University of Colorado, Boulder, Colorado 80309, USA
24
Colorado State University, Fort Collins, Colorado 80523, USA
25
Deutsches Elektronen
Synchrotron, 22607 Hamburg, Germany
26
Technische Universität Dortmund, Fakultät Physik, D-44221 Dortmund, Germany
27
Laboratoire Leprince-Ringuet, Ecole Polytechnique, CNRS/IN2P3, F-91128 Palaiseau, France
28
University of Edinburgh, Edinburgh EH9 3JZ, United Kingdom
PRL
115,
121604 (2015)
PHYSICAL REVIEW LETTERS
week ending
18 SEPTEMBER 2015
121604-2
29a
INFN Sezione di Ferrara, I-44122 Ferrara, Italy
29b
Dipartimento di Fisica e Scienze della Terra, Università di Ferrara, I-44122 Ferrara, Italy
30
INFN Laboratori Nazionali di Frascati, I-00044 Frascati, Italy
31a
INFN Sezione di Genova, I-16146 Genova, Italy
31b
Dipartimento di Fisica, Università di Genova, I-16146 Genova, Italy
32
Justus-Liebig-Universität Gießen, 35392 Gießen, Germany
33
Gifu University, Gifu 501-1193, Japan
34
SOKENDAI (The Graduate University for Advanced Studies), Hayama 240-0193, Japan
35
Indian Institute of Technology Guwahati, Guwahati, Assam 781 039, India
36
Gyeongsang National University, Chinju 660-701, South Korea
37
Hanyang University, Seoul 133-791, South Korea
38
University of Hawaii, Honolulu, Hawaii 96822, USA
39
Universität Heidelberg, Physikalisches Institut, D-69120 Heidelberg, Germany
40
High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801, Japan
41
Humboldt-Universität zu Berlin, Institut für Physik, D-12489 Berlin, Germany
42
IKERBASQUE, Basque Foundation for Science, 48013 Bilbao, Spain
43
Indian Institute of Technology Bhubaneswar, Satya Nagar 751007, India
44
Indian Institute of Technology Madras, Chennai 600036, India
45
Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
46
Institute of High Energy Physics, Vienna 1050, Austria
47
Institute for High Energy Physics, Protvino 142281, Russian Federation
48
Institute for Theoretical and Experimental Physics, Moscow 117218, Russian Federation
49
University of Iowa, Iowa City, Iowa 52242, USA
50
Iowa State University, Ames, Iowa 50011-3160, USA
51
J. Stefan Institute, 1000 Ljubljana, Slovenia
52
Physics Department, Jazan University, Jazan 22822, Kingdom of Saudi Arabia
53
Johns Hopkins University, Baltimore, Maryland 21218, USA
54
Kanagawa University, Yokohama 221-8686, Japan
55
Institut für Experimentelle Kernphysik, Karlsruher Institut für Technologie, 76131 Karlsruhe, Germany
56
Kennesaw State University, Kennesaw, Georgia 30144, USA
57
King Abdulaziz City for Science and Technology, Riyadh 11442, Kingdom of Saudi Arabia
58
Department of Physics, Faculty of Science, King Abdulaziz University, Jeddah 21589, Kingdom of Saudi Arabia
59
Korea Institute of Science and Technology Information, Daejeon 305-806, South Korea
60
Korea University, Seoul 136-713, South Korea
61
Kyungpook National University, Daegu 702-701, South Korea
62
Laboratoire de l
Accélérateur Linéaire, IN2P3/CNRS et Université Paris-Sud 11, Centre Scientifique d
Orsay,
F-91898 Orsay Cedex, France
63
École Polytechnique Fédérale de Lausanne (EPFL), Lausanne 1015, Switzerland
64
Lawrence Livermore National Laboratory, Livermore, California 94550, USA
65
University of Liverpool, Liverpool L69 7ZE, United Kingdom
66
Faculty of Mathematics and Physics, University of Ljubljana, 1000 Ljubljana, Slovenia
67
Queen Mary, University of London, London E1 4NS, United Kingdom
68
University of London, Royal Holloway and Bedford New College, Egham, Surrey TW20 0EX, United Kingdom
69
University of Louisville, Louisville, Kentucky 40292, USA
70
Ludwig Maximilians University, 80539 Munich, Germany
71
Luther College, Decorah, Iowa 52101, USA
72
Johannes Gutenberg-Universität Mainz, Institut für Kernphysik, D-55099 Mainz, Germany
73
University of Manchester, Manchester M13 9PL, United Kingdom
74
University of Maribor, 2000 Maribor, Slovenia
75
University of Maryland, College Park, Maryland 20742, USA
76
Laboratory for Nuclear Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
77
Max-Planck-Institut für Physik, 80805 München, Germany
78
McGill University, Montréal, Québec H3A 2T8, Canada
79
School of Physics, University of Melbourne, Victoria 3010, Australia
80a
INFN Sezione di Milano, I-20133 Milano, Italy
80b
Dipartimento di Fisica, Università di Milano, I-20133 Milano, Italy
81
University of Mississippi, University, Mississippi 38677, USA
82
Université de Montréal, Physique des Particules, Montréal, Québec H3C 3J7, Canada
83
Moscow Physical Engineering Institute, Moscow 115409, Russian Federation
84
Moscow Institute of Physics and Technology, Moscow Region 141700, Russian Federation
PRL
115,
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85
Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
86
Kobayashi-Maskawa Institute, Nagoya University, Nagoya 464-8602, Japan
87a
INFN Sezione di Napoli, I-80126 Napoli, Italy
87b
Dipartimento di Scienze Fisiche, Università di Napoli Federico II, I-80126 Napoli, Italy
88
Nara Women
s University, Nara 630-8506, Japan
89
National Central University, Chung-li 32054, Taiwan
90
NIKHEF, National Institute for Nuclear Physics and High Energy Physics, NL-1009 DB Amsterdam, Netherlands
91
National United University, Miao Li 36003, Taiwan
92
Department of Physics, National Taiwan University, Taipei 10617, Taiwan
93
H. Niewodniczanski Institute of Nuclear Physics, Krakow 31-342, Poland
94
Niigata University, Niigata 950-2181, Japan
95
University of Notre Dame, Notre Dame, Indiana 46556, USA
96
Ohio State University, Columbus, Ohio 43210, USA
97
Osaka City University, Osaka 558-8585, Japan
98
Pacific Northwest National Laboratory, Richland, Washington 99352, USA
99a
INFN Sezione di Padova, I-35131 Padova, Italy
99b
Dipartimento di Fisica, Università di Padova, I-35131 Padova, Italy
100
Laboratoire de Physique Nucléaire et de Hautes Energies, IN2P3/CNRS, Université Pierre et Marie Curie-Paris6,
Université Denis Diderot-Paris7, F-75252 Paris, France
101
Peking University, Beijing 100871, China
102a
INFN Sezione di Perugia, I-06123 Perugia, Italy
102b
Dipartimento di Fisica, Università di Perugia, I-06123 Perugia, Italy
103a
INFN Sezione di Pisa, I-56127 Pisa, Italy
103b
Dipartimento di Fisica, Università di Pisa, I-56127 Pisa, Italy
103c
Scuola Normale Superiore di Pisa, I-56127 Pisa, Italy
104
University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
105
Princeton University, Princeton, New Jersey 08544, USA
106
Punjab Agricultural University, Ludhiana 141004, India
107a
INFN Sezione di Roma, I-00185 Roma, Italy
107b
Dipartimento di Fisica, Università di Roma La Sapienza, I-00185 Roma, Italy
108
Universität Rostock, D-18051 Rostock, Germany
109
Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX, United Kingdom
110
CEA, Irfu, SPP, Centre de Saclay, F-91191 Gif-sur-Yvette, France
111
University of Science and Technology of China, Hefei 230026, China
112
Soongsil University, Seoul 156-743, South Korea
113
SLAC National Accelerator Laboratory, Stanford, California 94309, USA
114
University of South Carolina, Columbia, South Carolina 29208, USA
115
Southern Methodist University, Dallas, Texas 75275, USA
116
Stanford University, Stanford, California 94305-4060, USA
117
State University of New York, Albany, New York 12222, USA
118
Sungkyunkwan University, Suwon 440-746, South Korea
119
School of Physics, University of Sydney, Sydney, NSW 2006, Australia
120
Department of Physics, Faculty of Science, University of Tabuk, Tabuk 71451, Kingdom of Saudi Arabia
121
Tata Institute of Fundamental Research, Mumbai 400005, India
122
Excellence Cluster Universe, Technische Universität München, 85748 Garching, Germany
123
Tel Aviv University, School of Physics and Astronomy, Tel Aviv, 69978, Israel
124
University of Tennessee, Knoxville, Tennessee 37996, USA
125
University of Texas at Austin, Austin, Texas 78712, USA
126
University of Texas at Dallas, Richardson, Texas 75083, USA
127
Toho University, Funabashi 274-8510, Japan
128
Tohoku University, Sendai 980-8578, Japan
129
Earthquake Research Institute, University of Tokyo, Tokyo 113-0032, Japan
130
Department of Physics, University of Tokyo, Tokyo 113-0033, Japan
131
Tokyo Institute of Technology, Tokyo 152-8550, Japan
132
Tokyo Metropolitan University, Tokyo 192-0397, Japan
133a
INFN Sezione di Torino, I-10125 Torino, Italy
133b
Dipartimento di Fisica, Università di Torino, I-10125 Torino, Italy
134a
INFN Sezione di Trieste, I-34127 Trieste, Italy
134b
Dipartimento di Fisica, Università di Trieste, I-34127 Trieste, Italy
135
IFIC, Universitat de Valencia-CSIC, E-46071 Valencia, Spain
PRL
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121604-4
136
University of Victoria, Victoria, British Columbia V8W 3P6, Canada
137
CNP, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, USA
138
Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom
139
Wayne State University, Detroit, Michigan 48202, USA
140
University of Wisconsin, Madison, Wisconsin 53706, USA
141
Yamagata University, Yamagata 990-8560, Japan
142
Yonsei University, Seoul 120-749, South Korea
(Received 14 May 2015; published 16 September 2015)
We report a measurement of the time-dependent
CP
asymmetry of
̄
B
0
D
ðÞ
CP
h
0
decays, where the light
neutral hadron
h
0
is a
π
0
,
η
,or
ω
meson, and the neutral
D
meson is reconstructed in the
CP
eigenstates
K
þ
K
,
K
0
S
π
0
,or
K
0
S
ω
. The measurement is performed combining the final data samples collected at the
Υ
ð
4
S
Þ
resonance by the
BABAR
and Belle experiments at the asymmetric-energy
B
factories PEP-II at
SLAC and KEKB at KEK, respectively. The data samples contain
ð
471

3
Þ
×
10
6
B
̄
B
pairs recorded by
the
BABAR
detector and
ð
772

11
Þ
×
10
6
B
̄
B
pairs recorded by the Belle detector. We measure the
CP
asymmetry parameters
η
f
S
¼þ
0
.
66

0
.
10
ð
stat
Þ
0
.
06
ð
syst
Þ
and
C
¼
0
.
02

0
.
07
ð
stat
Þ
0
.
03
ð
syst
Þ
.
These results correspond to the first observation of
CP
violation in
̄
B
0
D
ðÞ
CP
h
0
decays. The hypothesis
of no mixing-induced
CP
violation is excluded in these decays at the level of 5.4 standard deviations.
DOI:
10.1103/PhysRevLett.115.121604
PACS numbers: 13.25.Hw, 11.30.Er, 12.15.Hh
In the standard model (SM) of electroweak interactions,
CP
violation arises from an irreducible complex phase
in the three-family Cabibbo-Kobayashi-Maskawa (CKM)
quark-mixing matrix
[1]
. The
BABAR
and Belle experiments
have established
CP
violating effects in the
B
meson system
[2
5]
. Both experiments use their measurements of the
mixing-induced
CP
violation in
b
c
̄
cs
transitions
[6,7]
to determine precisely the parameter sin
ð
2
β
Þ
sin
ð
2
φ
1
Þ
(
BABAR
uses
β
and Belle uses
φ
1
, hereinafter
β
is used). The
angle
β
is defined as arg
½
V
cd
V

cb
=V
td
V

tb

, where
V
ij
is the
CKM matrix element of quarks
i
,
j
.
A complementary and theoretically clean approach to
access
β
is provided by
̄
B
0
D
ðÞ
0
h
0
decays, where
h
0
f
π
0
;
η
;
ω
g
denotes a light neutral hadron. These decays are
dominated by CKM-favored
b
c
̄
ud
tree amplitudes.
CKM-disfavored
b
u
̄
cd
amplitudes carrying different
weak phases also contribute to the decays, but are sup-
pressed by
V
ub
V

cd
=V
cb
V

ud
0
.
02
relative to the leading
amplitudes. An interference between the decay amplitudes
without and with
B
0
̄
B
0
mixing emerges if the neutral
D
meson decays to a
CP
eigenstate
D
CP
. Neglecting the
suppressed amplitudes, the time evolution of
̄
B
0
D
ðÞ
CP
h
0
decays is governed by
β
[8]
. Because only tree-level
amplitudes contribute to
̄
B
0
D
ðÞ
0
h
0
decays, these
decays are not sensitive to most models of physics beyond
the standard model (BSM). However, the measurement of
the time-dependent
CP
violation enables testing of the
measurements of
b
c
̄
cs
transitions
[6,7]
and provides a
SM reference for the BSM searches in the mixing-induced
CP
violation of
b
s
penguin-mediated
B
meson decays
[9
12]
. Any sizable deviation in the
CP
asymmetry of
̄
B
0
D
ðÞ
CP
h
0
decays from processes involving
b
c
̄
cs
or penguin-mediated
b
s
transitions would point to
BSM. Such deviations could, for example, be caused by
unobserved heavy particles contributing to loop diagrams
in
b
c
̄
cs
or
b
s
penguin transitions
[13]
.
An experimental difficulty in the use of
̄
B
0
D
ðÞ
CP
h
0
decays arises from low
B
and
D
meson branching
fractions [
O
ð
10
4
Þ
and
O
ð
10
2
Þ
, respectively] and low
reconstruction efficiencies. Previous measurements per-
formed separately by the
BABAR
and Belle Collaborations
were not able to establish
CP
violation in these or related
decays
[14
16]
.
In this Letter, we present a measurement of the time-
dependent
CP
violation in
̄
B
0
D
ðÞ
CP
h
0
decays. For the
first time, we combine the large final data samples collected
by the
BABAR
and Belle experiments. This new approach
enables time-dependent
CP
violation measurements in the
neutral
B
meson system with unprecedented sensitivity.
The time-dependent rate of a neutral
B
meson decaying
to a
CP
eigenstate is given by
g
ð
Δ
t
Þ¼
e
j
Δ
t
j
=
τ
B
0
4
τ
B
0
f
1
þ
q
½
S
sin
ð
Δ
m
d
Δ
t
Þ
C
cos
ð
Δ
m
d
Δ
t
Þg
;
ð
1
Þ
where
q
¼þ
1
ð
1
Þ
represents the
b
-flavor content when
the accompanying
B
meson is tagged as a
B
0
(
̄
B
0
) and
Δ
t
denotes the proper time interval between the decays of the
two
B
mesons produced in an
Υ
ð
4
S
Þ
decay. The neutral
B
meson lifetime is represented by
τ
B
0
, and the
B
0
̄
B
0
mixing frequency by
Δ
m
d
. Neglecting the CKM-disfavored
decay amplitudes in
̄
B
0
D
ðÞ
CP
h
0
decays, the SM predicts
S
¼
η
f
sin
ð
2
β
Þ
and
C
¼
0
, where
η
f
is the
CP
eigenvalue
of the final state, and
S
and
C
, respectively, quantify
mixing-induced and direct
CP
violation
[17]
.
This analysis is based on data samples collected
at the
Υ
ð
4
S
Þ
resonance containing
ð
471

3
Þ
×
10
6
B
̄
B
PRL
115,
121604 (2015)
PHYSICAL REVIEW LETTERS
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121604-5
pairs recorded with the
BABAR
detector at the PEP-II
asymmetric-energy
e
þ
e
(3.1 on 9 GeV) collider
[18]
and
ð
772

11
Þ
×
10
6
B
̄
B
pairs recorded with the Belle detector
at the KEKB asymmetric-energy
e
þ
e
(3.5 on 8 GeV)
collider
[19]
.At
BABAR
(Belle) the
Υ
ð
4
S
Þ
is produced with
a Lorentz boost of
βγ
¼
0
.
560
(0.425), allowing the
measurement of
Δ
t
from the displacement of the decay
vertices of the two
B
mesons. The
BABAR
and Belle
detectors are described in Refs.
[20,21]
.
Reconstructed tracks of charged particles are considered
as kaon and pion candidates. Kaons are identified using the
particle identification techniques described in Refs.
[20,21]
.
Photons are reconstructed from energy deposits in the
electromagnetic calorimeters; the energy of photon candi-
dates is required to be at least 30 MeV. Combinations of
two photons are considered as
π
0
meson candidates if
the reconstructed invariant mass is between 115 and
150
MeV
=c
2
. Candidate
η
mesons are reconstructed in
the decay modes
η
γγ
and
π
þ
π
π
0
. The invariant mass
is required to bewithin
20
MeV
=c
2
of the nominalmass
[22]
for
η
γγ
candidates, and within
10
MeV
=c
2
for
η
π
þ
π
π
0
candidates. For each photon in the
η
γγ
decay mode a minimal energy of 50 MeV is required.
For
ω
mesons the decay mode
ω
π
þ
π
π
0
is recon-
structed with invariant mass required to be within
15
MeV
=c
2
of the nominal mass
[22]
. Neutral kaons are
reconstructed in the decay mode
K
0
S
π
þ
π
, with invari-
ant mass required to be within
15
MeV
=c
2
of the nominal
mass
[22]
. The requirements exploiting the
K
0
S
decay
vertex displacement from the interaction point (IP)
described in Refs.
[15,23]
are applied. Neutral
D
mesons
are reconstructed in the decay modes to
CP
eigenstates
D
CP
K
þ
K
,
K
0
S
π
0
, and
K
0
S
ω
. The invariant mass is
required to be within
12
MeV
=c
2
of the nominal mass
[22]
for
D
CP
K
þ
K
candidates, within
25
MeV
=c
2
for
D
CP
K
0
S
π
0
candidates, and within
20
MeV
=c
2
for
D
CP
K
0
S
ω
candidates. We reconstruct
D

0
mesons in
the decay mode
D

0
D
0
π
0
, and the invariant mass must
be within
3
MeV
=c
2
of the nominal mass
[22]
.
Neutral
B
mesons are reconstructed in the
CP
-even
(
η
f
¼þ
1
) final states
̄
B
0
D
CP
π
0
and
D
CP
η
(with
D
CP
K
0
S
π
0
,
K
0
S
ω
),
̄
B
0
D
CP
ω
(with
D
CP
K
0
S
π
0
),
̄
B
0
D

CP
π
0
and
D

CP
η
(with
D
CP
K
þ
K
), and in the
CP
-odd (
η
f
¼
1
) final states
̄
B
0
D
CP
π
0
,
D
CP
η
,
D
CP
ω
(with
D
CP
K
þ
K
), and
̄
B
0
D

CP
π
0
and
D

CP
η
(with
D
CP
K
0
S
π
0
)
[24]
.
Neutral
B
mesons are selected by the beam-energy-
constrained mass
M
bc
m
ES
¼
ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
ð
E

beam
=c
2
Þ
2
ð
p

B
=c
Þ
2
p
(
BABAR
uses
m
ES
and Belle uses
M
bc
, hereinafter
M
bc
is
used) and by the energy difference
Δ
E
¼
E

B
E

beam
,
where
E

beam
denotes the energy of the beam, and
p

B
and
E

B
are the momentum and energy of the
B
meson
candidates, evaluated in the
e
þ
e
center-of-mass (c.m.)
frame. The selected regions are
5
.
2
GeV
=c
2
<M
bc
<
5
.
3
GeV
=c
2
and
100
MeV
<
Δ
E<
100
MeV, except for
̄
B
0
D
ðÞ
CP
π
0
decays, where
75
MeV
<
Δ
E<
100
MeV
is required to exclude tails from partially reconstructed
B
D
ðÞ
0
ρ
decays peaking at
Δ
E
≈−
250
MeV.
In
̄
B
0
D
0
ω
and in
D
0
K
0
S
ω
decays, the
ω
vector
mesons are polarized. The angular distribution of
ω
π
þ
π
π
0
decays is exploited to discriminate against back-
ground. The quantity cos
θ
N
is defined as the cosine of the
angle between the neutral
B
meson direction and the
normal to the
π
þ
π
π
0
plane in the
ω
meson rest frame.
A requirement of
j
cos
θ
N
j
>
0
.
3
is applied.
After applying the above selection requirements, the
average multiplicity of reconstructed
̄
B
0
D
ðÞ
CP
h
0
candi-
dates in an event is 1.3. In case of multiple
B
meson
candidates in an event, one candidate is selected using a
criterion based on the deviations of the reconstructed
D
ðÞ
and
h
0
meson masses from the nominal values. The
probability for this method to select the correct signal is
82% (81%) for
BABAR
(Belle).
In
̄
B
0
D
ðÞ
CP
h
0
decays, the dominant source of back-
ground originates from
e
þ
e
q
̄
q
ð
q
f
u; d; s; c
con-
tinuum events. This background is suppressed by using
neural network (NN) multivariate classifiers that combine
information characterizing the shape of an event
[25]
.
The observables included in the NNs are the ratio
R
2
of
the second to the zeroth order Fox-Wolfram moment, a
combination of 16 modified Fox-Wolfram moments
[26]
,
the sphericity of the event
[29]
, and cos
θ

B
, where
θ

B
is the
angle between the direction of the reconstructed
B
meson
and the beam direction in the c.m. frame. The NN selection
reduces the background by 89.3% (91.8%) and has a signal
efficiency of 75.5% (74.3%) for
BABAR
(Belle).
The signal yields are determined by unbinned maximum
likelihood fits to the
M
bc
distributions. In the fits, the signal
component is parametrized by a Crystal Ball function
[30]
and the background component is modeled by an ARGUS
function
[31]
. The experimental
M
bc
distributions and fit
projections are shown in Fig.
1
. The signal yields are
summarized in Table
I
.
The time-dependent
CP
violation measurement is per-
formed using established
BABAR
and Belle techniques for
the vertex reconstruction, the flavor tagging, and the
modeling of
Δ
t
resolution effects (see Refs.
[6,7,32
35]
),
and is briefly summarized below. The proper time interval
Δ
t
is given as
Δ
z=
c
βγ
, where
Δ
z
is the distance between
the decay vertices of the signal
B
meson and of the
accompanying
B
meson. The
̄
B
0
D
ðÞ
CP
h
0
signal decay
vertex is reconstructed by a kinematic fit including
information about the IP position. For Belle, an iterative
hierarchical vertex reconstruction algorithm following a
bottom-up approach starting with the final state particles
is applied, while for
BABAR
the vertex reconstruction
includes simultaneously the complete
B
meson decay
PRL
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