First Observation of
CP
Violation in
B
0
→
D
(
∗
)
CP
h
0
Decays by a Combined
Time-Dependent Analysis of
B
A
B
AR
and Belle Data
A. Abdesselam
B
,
120
I. Adachi
B
,
40, 34
A. Adametz
A
,
39
T. Adye
A
,
109
H. Ahmed
A
,
52
H. Aihara
B
,
130
S. Akar
A
,
100
M. S. Alam
A
,
117
J. Albert
A
,
136
S. Al Said
B
,
120, 58
R. Andreassen
A
,
22
C. Angelini
Aab
,
103
F. Anulli
Aa
,
107
K. Arinstein
B
,
12, 13
N. Arnaud
A
,
62
D. M. Asner
B
,
98
D. Aston
A
,
113
V. Aulchenko
B
,
12, 13
T. Aushev
B
,
84, 48
R. Ayad
AB
,
120, 24
V. Babu
B
,
121
I. Badhrees
B
,
120, 57
S. Bahinipati
B
,
43
A. M. Bakich
B
,
119
H. R. Band
A
,
140
Sw. Banerjee
A
,
136
E. Barberio
B
,
79
D. J. Bard
A
,
113
R. J. Barlow
A
,
73,
∗
G. Batignani
Aab
,
103
A. Beaulieu
A
,
136
M. Bellis
A
,
116
E. Ben-Haim
A
,
100
D. Bernard
A
,
27
F. U. Bernlochner
A
,
136
S. Bettarini
Aab
,
103
D. Bettoni
Aa
,
29
A. J. Bevan
A
,
67
V. Bhardwaj
B
,
114
B. Bhuyan
AB
,
35
F. Bianchi
Aab
,
133
M. Biasini
Aab
,
102
J. Biswal
B
,
51
V. E. Blinov
A
,
12, 13, 14
P. C. Bloom
A
,
23
A. Bobrov
B
,
12, 13
M. Bomben
A
,
100
A. Bondar
B
,
12, 13
G. R. Bonneaud
A
,
100
G. Bonvicini
B
,
139
A. Bozek
B
,
93
C. Bozzi
Aa
,
29
M. Braˇcko
B
,
74, 51
H. Briand
A
,
100
T. E. Browder
B
,
38
D. N. Brown
A
,
7
D. N. Brown
A
,
69
C. B ̈unger
A
,
108
P. R. Burchat
A
,
116
A. R. Buzykaev
A
,
12
R. Calabrese
Aab
,
29
A. Calcaterra
A
,
30
G. Calderini
A
,
100
M. Carpinelli
Aab
,
103,
†
C. Cartaro
A
,
113
G. Casarosa
Aab
,
103
R. Cenci
A
,
75
D.
ˇ
Cervenkov
B
,
20
P. Chang
B
,
92
D. S. Chao
A
,
19
J. Chauveau
A
,
100
R. Cheaib
A
,
78
V. Chekelian
B
,
77
A. Chen
B
,
89
C. Chen
A
,
50
C. H. Cheng
A
,
19
B. G. Cheon
B
,
37
K. Chilikin
B
,
48
R. Chistov
B
,
48
K. Cho
B
,
59
V. Chobanova
B
,
77
H. H. F. Choi
A
,
136
S.-K. Choi
B
,
36
M. Chrzaszcz
Aa
,
103
G. Cibinetto
Aab
,
29
D. Cinabro
B
,
139
J. Cochran
A
,
50
J. P. Coleman
A
,
65
R. Contri
Aab
,
31
M. R. Convery
A
,
113
G. Cowan
A
,
68
R. Cowan
A
,
76
L. Cremaldi
A
,
81
J. Dalseno
B
,
77, 122
S. Dasu
A
,
140
M. Davier
A
,
62
C. L. Davis
A
,
69
F. De Mori
Aab
,
133
G. De Nardo
Aab
,
87
A. G. Denig
A
,
72
D. Derkach
A
,
62
R. de Sangro
A
,
30
B. Dey
A
,
16
F. Di Lodovico
A
,
67
J. Dingfelder
B
,
9
S. Dittrich
A
,
108
Z. Doleˇzal
B
,
20
J. Dorfan
A
,
113
Z. Dr ́asal
B
,
20
A. Drutskoy
B
,
48, 83
V. P. Druzhinin
A
,
12, 13
G. P. Dubois-Felsmann
A
,
113
W. Dunwoodie
A
,
113
D. Dutta
B
,
121
M. Ebert
A
,
113
B. Echenard
A
,
19
S. Eidelman
B
,
12, 13
G. Eigen
A
,
6
A. M. Eisner
A
,
18
S. Emery
A
,
110
J. A. Ernst
A
,
117
R. Faccini
Aab
,
107
H. Farhat
B
,
139
J. E. Fast
B
,
98
M. Feindt
B
,
55
T. Ferber
B
,
25
F. Ferrarotto
Aa
,
107
F. Ferroni
Aab
,
107
R. C. Field
A
,
113
A. Filippi
Aa
,
133
G. Finocchiaro
A
,
30
E. Fioravanti
Aab
,
29
K. T. Flood
A
,
19
W. T. Ford
A
,
23
F. Forti
Aab
,
103
M. Franco Sevilla
A
,
17
M. Fritsch
A
,
72
J. R. Fry
A
,
65
B. G. Fulsom
AB
,
98, 113
E. Gabathuler
A
,
65
N. Gabyshev
B
,
12, 13
D. Gamba
Aab
,
133
A. Garmash
B
,
12, 13
J. W. Gary
A
,
16
I. Garzia
Aab
,
29
M. Gaspero
Aab
,
107
V. Gaur
B
,
121
A. Gaz
A
,
23
T. J. Gershon
A
,
138
D. Getzkow
B
,
32
R. Gillard
B
,
139
L. Li Gioi
B
,
77
M. A. Giorgi
Aab
,
103
R. Glattauer
B
,
46
R. Godang
A
,
81,
‡
Y. M. Goh
B
,
37
P. Goldenzweig
B
,
55
B. Golob
B
,
66, 51
V. B. Golubev
A
,
12, 13
R. Gorodeisky
A
,
123
W. Gradl
A
,
72
M. T. Graham
A
,
113
E. Grauges
A
,
2
K. Griessinger
A
,
72
A. V. Gritsan
A
,
53
G. Grosdidier
A
,
62
O. Gr ̈unberg
A
,
108
N. Guttman
A
,
123
J. Haba
B
,
40, 34
A. Hafner
A
,
72
B. Hamilton
A
,
75
T. Hara
B
,
40, 34
P. F. Harrison
A
,
138
C. Hast
A
,
113
K. Hayasaka
B
,
86
H. Hayashii
B
,
88
C. Hearty
A
,
10
X. H. He
B
,
101
M. Hess
A
,
108
D. G. Hitlin
A
,
19
T. M. Hong
A
,
17
K. Honscheid
A
,
96
W.-S. Hou
B
,
92
Y. B. Hsiung
B
,
92
Z. Huard
A
,
22
D. E. Hutchcroft
A
,
65
T. Iijima
B
,
86, 85
G. Inguglia
B
,
25
W. R. Innes
A
,
113
A. Ishikawa
B
,
128
R. Itoh
B
,
40, 34
Y. Iwasaki
B
,
40
J. M. Izen
A
,
126
I. Jaegle
B
,
38
A. Jawahery
A
,
75
C. P. Jessop
A
,
95
D. Joffe
B
,
56
K. K. Joo
B
,
21
T. Julius
B
,
79
K. H. Kang
B
,
61
R. Kass
A
,
96
T. Kawasaki
B
,
94
L. T. Kerth
A
,
7
A. Khan
A
,
11
C. Kiesling
B
,
77
D. Y. Kim
B
,
112
J. B. Kim
B
,
60
J. H. Kim
B
,
59
K. T. Kim
B
,
60
P. Kim
A
,
113
S. H. Kim
B
,
37
Y. J. Kim
B
,
59
G. J. King
A
,
136
K. Kinoshita
B
,
22
B. R. Ko
B
,
60
H. Koch
A
,
8
P. Kodyˇs
B
,
20
Yu. G. Kolomensky
A
,
7
S. Korpar
B
,
74, 51
D. Kovalskyi
A
,
17
R. Kowalewski
A
,
136
E. A. Kravchenko
A
,
12, 13
P. Kriˇzan
B
,
66, 51
P. Krokovny
B
,
12, 13
T. Kuhr
B
,
70
R. Kumar
B
,
106
A. Kuzmin
B
,
12, 13
Y.-J. Kwon
B
,
142
H. M. Lacker
A
,
41
G. D. Lafferty,
134
L. Lanceri
Aab
,
134
D. J. Lange
A
,
64
A. J. Lankford
A
,
15
T. E. Latham
A
,
138
T. Leddig
A
,
108
F. Le Diberder
A
,
62
D. H. Lee
B
,
60
I. S. Lee
B
,
37
M. J. Lee
A
,
7
J. P. Lees
A
,
1
D. W. G. S. Leith
A
,
113
Ph. Leruste
A
,
100
M. J. Lewczuk
A
,
136
P. Lewis
B
,
38
J. Libby
B
,
44
W. S. Lockman
A
,
18
O. Long
A
,
16
D. Lopes Pegna
A
,
105
J. M. LoSecco
A
,
95
X. C. Lou
A
,
126
T. Lueck
A
,
136
S. Luitz
A
,
113
P. Lukin
B
,
12, 13
E. Luppi
Aab
,
29
A. Lusiani
Aac
,
103
V. Luth
A
,
113
A. M. Lutz
A
,
62
G. Lynch
A
,
7
D. B. MacFarlane
A
,
113
B. Malaescu
A
,
62,
§
U. Mallik
A
,
49
E. Manoni
Aa
,
102
G. Marchiori
A
,
100
M. Margoni
Aab
,
99
S. Martellotti
A
,
30
F. Martinez-Vidal
A
,
135
M. Masuda
B
,
129
T. S. Mattison
A
,
10
D. Matvienko
B
,
12, 13
J. A. McKenna
A
,
10
B. T. Meadows
A
,
22
K. Miyabayashi
B
,
88
T. S. Miyashita
A
,
19
H. Miyata
B
,
94
R. Mizuk
B
,
48, 83
G. B. Mohanty
B
,
121
A. Moll
B
,
77, 122
M. R. Monge
Aab
,
31
H. K. Moon
B
,
60
M. Morandin
Aa
,
99
D. R. Muller
A
,
113
R. Mussa
Aa
,
133
E. Nakano
B
,
97
H. Nakazawa
B
,
89
M. Nakao
B
,
40, 34
T. Nanut
B
,
51
M. Nayak
B
,
44
H. Neal
A
,
113
arXiv:1505.04147v2 [hep-ex] 20 Jul 2015
2
N. Neri
Aa
,
80
N. K. Nisar
B
,
121
S. Nishida
B
,
40, 34
I. M. Nugent
A
,
136
B. Oberhof
Aab
,
103
J. Ocariz
A
,
100
S. Ogawa
B
,
127
S. Okuno
B
,
54
E. O. Olaiya
A
,
109
J. Olsen
A
,
105
P. Ongmongkolkul
A
,
19
G. Onorato
Aab
,
87
A. P. Onuchin
A
,
12, 13, 14
Y. Onuki
B
,
130
W. Ostrowicz
B
,
93
A. Oyanguren
A
,
135
G. Pakhlova
B
,
84, 48
P. Pakhlov
B
,
48, 83
A. Palano
Aab
,
3
B. Pal
B
,
22
F. Palombo
Aab
,
80
Y. Pan
A
,
140
W. Panduro Vazquez
A
,
18
E. Paoloni
Aab
,
103
C. W. Park
B
,
118
H. Park
B
,
61
S. Passaggio
Aa
,
31
P. M. Patel
A
,
78,
¶
C. Patrignani
Aab
,
31
P. Patteri
A
,
30
D. J. Payne
A
,
65
T. K. Pedlar
B
,
71
D. R. Peimer
A
,
123
I. M. Peruzzi
A
,
30
L. Pes ́antez
B
,
9
R. Pestotnik
B
,
51
M. Petriˇc
B
,
51
M. Piccolo
A
,
30
L. Piemontese
Aa
,
29
L. E. Piilonen
B
,
137
A. Pilloni
Aab
,
107
G. Piredda
Aa
,
107
S. Playfer
A
,
28
V. Poireau
A
,
1
F. C. Porter
A
,
19
M. Posocco
Aa
,
99
V. Prasad
A
,
35
S. Prell
A
,
50
R. Prepost
A
,
140
E. M. T. Puccio
A
,
116
T. Pulliam
A
,
113
M. V. Purohit
A
,
114
B. G. Pushpawela
A
,
22
M. Rama
Aa
,
103
A. Randle-Conde
A
,
115
B. N. Ratcliff
A
,
113
G. Raven
A
,
90
E. Ribeˇzl
B
,
51
J. D. Richman
A
,
17
J. L. Ritchie
A
,
125
G. Rizzo
Aab
,
103
D. A. Roberts
A
,
75
S. H. Robertson
A
,
78
M. R ̈ohrken
AB
,
19, 55
J. M. Roney
A
,
136
A. Roodman
A
,
113
A. Rossi
Aa
,
102
A. Rostomyan
B
,
25
M. Rotondo
Aa
,
99
P. Roudeau
A
,
62
R. Sacco
A
,
67
Y. Sakai
B
,
40, 34
S. Sandilya
B
,
121
L. Santelj
B
,
40
V. Santoro
Aa
,
29
T. Sanuki
B
,
128
Y. Sato
B
,
85
V. Savinov
B
,
104
R. H. Schindler
A
,
113
O. Schneider
B
,
63
G. Schnell
B
,
4, 42
T. Schroeder
A
,
8
K. R. Schubert
A
,
72
B. A. Schumm
A
,
18
C. Schwanda
B
,
46
A. J. Schwartz
B
,
22
R. F. Schwitters
A
,
125
C. Sciacca
Aab
,
87
A. Seiden
A
,
18
S. J. Sekula
A
,
115
K. Senyo
B
,
141
O. Seon
B
,
85
S. I. Serednyakov
A
,
12, 13
M. E. Sevior
B
,
79
M. Shapkin
B
,
47
V. Shebalin
B
,
12, 13
C. P. Shen
B
,
5
T.-A. Shibata
B
,
131
J.-G. Shiu
B
,
92
M. Simard
A
,
82
G. Simi
Aab
,
99
F. Simon
B
,
77, 122
F. Simonetto
Aab
,
99
Yu. I. Skovpen
A
,
12, 13
A. J. S. Smith
A
,
105
J. G. Smith
A
,
23
A. Snyder
A
,
113
R. Y. So
A
,
10
R. J. Sobie
A
,
136
A. Soffer
A
,
123
Y.-S. Sohn
B
,
142
M. D. Sokoloff
A
,
22
A. Sokolov
B
,
47
E. P. Solodov
A
,
12, 13
E. Solovieva
B
,
48
B. Spaan
A
,
26
S. M. Spanier
A
,
124
M. Stariˇc
B
,
51
A. Stocchi
A
,
62
R. Stroili
Aab
,
99
B. Stugu
A
,
6
D. Su
A
,
113
M. K. Sullivan
A
,
113
M. Sumihama
B
,
33
K. Sumisawa
B
,
40, 34
T. Sumiyoshi
B
,
132
D. J. Summers
A
,
81
L. Sun
A
,
22
U. Tamponi
Aab
,
133
P. Taras
A
,
82
N. Tasneem
A
,
136
Y. Teramoto
B
,
97
V. Tisserand
A
,
1
K. Yu. Todyshev
A
,
12, 13
W. H. Toki
A
,
24
C. Touramanis
A
,
65
K. Trabelsi
B
,
40, 34
T. Tsuboyama
B
,
40
M. Uchida
B
,
131
T. Uglov
B
,
48, 84
Y. Unno
B
,
37
S. Uno
B
,
40, 34
Y. Usov
B
,
12, 13
U. Uwer
A
,
39
S. E. Vahsen
B
,
38
C. Van Hulse
B
,
4
P. Vanhoefer
B
,
77
G. Varner
B
,
38
G. Vasseur
A
,
110
J. Va’vra
A
,
113
M. Verderi
A
,
27
A. Vinokurova
B
,
12, 13
L. Vitale
Aab
,
134
V. Vorobyev
B
,
12, 13
C. Voß
A
,
108
M. N. Wagner
B
,
32
S. R. Wagner
A
,
23
R. Waldi
A
,
108
J. J. Walsh
Aa
,
103
C. H. Wang
B
,
91
M.-Z. Wang
B
,
92
P. Wang
B
,
45
Y. Watanabe
B
,
54
C. A. West
A
,
17
K. M. Williams
B
,
137
F. F. Wilson
A
,
109
J. R. Wilson
A
,
114
W. J. Wisniewski
A
,
113
E. Won
B
,
60
G. Wormser
A
,
62
D. M. Wright
A
,
64
S. L. Wu
A
,
140
H. W. Wulsin
A
,
113
H. Yamamoto
B
,
128
J. Yamaoka
B
,
98
S. Yashchenko
B
,
25
C. Z. Yuan
B
,
45
Y. Yusa
B
,
94
A. Zallo
A
,
30
C. C. Zhang
B
,
45
Z. P. Zhang
B
,
111
V. Zhilich
B
,
12, 13
V. Zhulanov
B
,
12, 13
and A. Zupanc
B
,
51
(The
A
B
A
B
AR
and
B
Belle Collaborations)
1
Laboratoire d’Annecy-le-Vieux de Physique des Particules (LAPP),
Universit ́e de Savoie, CNRS/IN2P3, F-74941 Annecy-Le-Vieux, France
2
Universitat de Barcelona, Facultat de Fisica, Departament ECM, E-08028 Barcelona, Spain
3
INFN Sezione di Bari
a
; Dipartimento di Fisica, Universit`a di Bari
b
, 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 Universit ̈at Bochum, Institut f ̈ur Experimentalphysik 1, D-44780 Bochum, Germany
9
University of Bonn, 53115 Bonn, Germany
10
University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z1
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
3
26
Technische Universit ̈at Dortmund, Fakult ̈at 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
29
INFN Sezione di Ferrara
a
; Dipartimento di Fisica e Scienze della Terra, Universit`a di Ferrara
b
, I-44122 Ferrara, Italy
30
INFN Laboratori Nazionali di Frascati, I-00044 Frascati, Italy
31
INFN Sezione di Genova
a
; Dipartimento di Fisica, Universit`a di Genova
b
, I-16146 Genova, Italy
32
Justus-Liebig-Universit ̈at 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
Universit ̈at Heidelberg, Physikalisches Institut, D-69120 Heidelberg, Germany
40
High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801, Japan
41
Humboldt-Universit ̈at zu Berlin, Institut f ̈ur 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 f ̈ur Experimentelle Kernphysik, Karlsruher Institut f ̈ur Technologie, 76131 Karlsruhe, Germany
56
Kennesaw State University, Kennesaw GA 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’Acc ́el ́erateur Lin ́eaire, IN2P3/CNRS et Universit ́e Paris-Sud 11,
Centre Scientifique d’Orsay, F-91898 Orsay Cedex, France
63
́
Ecole Polytechnique F ́ed ́erale 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-Universit ̈at Mainz, Institut f ̈ur 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
Massachusetts Institute of Technology, Laboratory for Nuclear Science, Cambridge, Massachusetts 02139, USA
77
Max-Planck-Institut f ̈ur Physik, 80805 M ̈unchen, Germany
78
McGill University, Montr ́eal, Qu ́ebec, Canada H3A 2T8
79
School of Physics, University of Melbourne, Victoria 3010, Australia
80
INFN Sezione di Milano
a
; Dipartimento di Fisica, Universit`a di Milano
b
, I-20133 Milano, Italy
81
University of Mississippi, University, Mississippi 38677, USA
82
Universit ́e de Montr ́eal, Physique des Particules, Montr ́eal, Qu ́ebec, Canada H3C 3J7
83
Moscow Physical Engineering Institute, Moscow 115409, Russian Federation
84
Moscow Institute of Physics and Technology, Moscow Region 141700, Russian Federation
85
Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
86
Kobayashi-Maskawa Institute, Nagoya University, Nagoya 464-8602, Japan
87
INFN Sezione di Napoli
a
; Dipartimento di Scienze Fisiche,
Universit`a di Napoli Federico II
b
, I-80126 Napoli, Italy
4
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, The 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
99
INFN Sezione di Padova
a
; Dipartimento di Fisica, Universit`a di Padova
b
, I-35131 Padova, Italy
100
Laboratoire de Physique Nucl ́eaire et de Hautes Energies,
IN2P3/CNRS, Universit ́e Pierre et Marie Curie-Paris6,
Universit ́e Denis Diderot-Paris7, F-75252 Paris, France
101
Peking University, Beijing 100871, China
102
INFN Sezione di Perugia
a
; Dipartimento di Fisica, Universit`a di Perugia
b
, I-06123 Perugia, Italy
103
INFN Sezione di Pisa
a
; Dipartimento di Fisica,
Universit`a di Pisa
b
; Scuola Normale Superiore di Pisa
c
, 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
107
INFN Sezione di Roma
a
; Dipartimento di Fisica,
Universit`a di Roma La Sapienza
b
, I-00185 Roma, Italy
108
Universit ̈at 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, 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 Universit ̈at M ̈unchen, 85748 Garching
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
133
INFN Sezione di Torino
a
; Dipartimento di Fisica, Universit`a di Torino
b
, I-10125 Torino, Italy
134
INFN Sezione di Trieste
a
; Dipartimento di Fisica, Universit`a di Trieste
b
, I-34127 Trieste, Italy
135
IFIC, Universitat de Valencia-CSIC, E-46071 Valencia, Spain
136
University of Victoria, Victoria, British Columbia, Canada V8W 3P6
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
We report a measurement of the time-dependent
CP
asymmetry of
B
0
→
D
(
∗
)
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
+
K
−
,
K
0
S
π
0
or
K
0
S
ω
. The measurement is performed combining the final data
5
samples collected at the
Υ
(4
S
) resonance by the
B
A
B
AR
and Belle experiments at the asymmetric-
energy
B
factories PEP-II at SLAC and KEKB at KEK, respectively. The data samples contain
(471
±
3)
×
10
6
B
B
pairs recorded by the
B
A
B
AR
detector and (772
±
11)
×
10
6
B
B
pairs recorded by the
Belle detector. We measure the
CP
asymmetry parameters
−
η
f
S
= +0
.
66
±
0
.
10 (stat
.
)
±
0
.
06 (syst
.
)
and
C
=
−
0
.
02
±
0
.
07 (stat
.
)
±
0
.
03 (syst
.
). These results correspond to the first observation of
CP
violation in
B
0
→
D
(
∗
)
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.
PACS numbers: 11.30.Er, 12.15.Hh, 13.25.Hw
In the standard model (SM) of electroweak interac-
tions,
CP
violation arises from an irreducible complex
phase in the three-family Cabibbo-Kobayashi-Maskawa
(CKM) quark-mixing matrix [1]. The
B
A
B
AR
and Belle
experiments have established
CP
violating effects in the
B
meson system [2–5]. Both experiments use their mea-
surements of the mixing-induced
CP
violation in
b
→
c
̄
cs
transitions [6, 7] to determine precisely the parame-
ter sin(2
β
)
≡
sin(2
φ
1
) [
B
A
B
AR
uses
β
and Belle uses
φ
1
, hereinafter
β
is used]. The angle
β
is defined as
arg [
−
V
cd
V
∗
cb
/V
td
V
∗
tb
], where
V
ij
is the CKM matrix ele-
ment of quarks
i
,
j
.
A complementary and theoretically clean approach to
access
β
is provided by
B
0
→
D
(
∗
)0
h
0
decays, where
h
0
∈ {
π
0
,η,ω
}
denotes a light neutral hadron. These
decays are dominated by CKM-favored
b
→
c
̄
ud
tree am-
plitudes. CKM-disfavored
b
→
u
̄
cd
amplitudes carrying
different weak phases contribute also to the decays, but
are suppressed 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
. Ne-
glecting the suppressed amplitudes, the time evolution
of
B
0
→
D
(
∗
)
CP
h
0
decays is governed by
β
[8]. Because
only tree-level amplitudes contribute to
B
0
→
D
(
∗
)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
(
∗
)
CP
h
0
decays from processes in-
volving
b
→
c
̄
cs
or penguin-mediated
b
→
s
transitions
would point to BSM. Such deviations could for exam-
ple be caused by unobserved heavy particles contributing
to loop diagrams in
b
→
c
̄
cs
or
b
→
s
penguin transi-
tions [13].
An experimental difficulty in the use of
B
0
→
D
(
∗
)
CP
h
0
decays arises from low
B
and
D
meson branching frac-
tions [
O
(10
−
4
) and
O
(
≤
10
−
2
), respectively] and low
reconstruction efficiencies. Previous measurements per-
formed separately by the
B
A
B
AR
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
(
∗
)
CP
h
0
decays. For the
first time, we combine the large final data samples col-
lected by the
B
A
B
AR
and Belle experiments. This new
approach enables time-dependent
CP
violation measure-
ments in the neutral
B
meson system with unprecedented
sensitivity.
The time-dependent rate of a neutral
B
meson decay-
ing to a
CP
eigenstate is given by
g
(∆
t
) =
e
−|
∆
t
|
/τ
B
0
4
τ
B
0
{
1 +
q
[
S
sin(∆
m
d
∆
t
)
−C
cos(∆
m
d
∆
t
)]
}
,
(1)
where
q
= +1 (
−
1) represents the
b
-flavor content when
the accompanying
B
meson is tagged as a
B
0
(
B
0
) and
∆
t
denotes the proper time interval between the decays
of the two
B
mesons produced in an
Υ
(4
S
) decay. The
neutral
B
meson lifetime is represented by
τ
B
0
, and the
B
0
-
B
0
mixing frequency by ∆
m
d
. Neglecting the CKM-
disfavored decay amplitudes in
B
0
→
D
(
∗
)
CP
h
0
decays, the
SM predicts
S
=
−
η
f
sin(2
β
) and
C
= 0, where
η
f
is
the
CP
eigenvalue of the final state, and
S
and
C
, re-
spectively, quantify mixing-induced and direct
CP
viola-
tion [17].
This analysis is based on data samples collected at
the
Υ
(4
S
) resonance containing (471
±
3)
×
10
6
B
B
pairs recorded with the
B
A
B
AR
detector at the PEP-II
asymmetric-energy
e
+
e
−
(3.1 on 9 GeV) collider [18] and
(772
±
11)
×
10
6
B
B
pairs recorded with the Belle detector
at the KEKB asymmetric-energy
e
+
e
−
(3.5 on 8 GeV)
collider [19]. At
B
A
B
AR
(Belle) the
Υ
(4
S
) is produced
with a Lorentz boost of
βγ
= 0
.
560 (0
.
425), allowing the
measurement of ∆
t
from the displacement of the decay
vertices of the two
B
mesons. The
B
A
B
AR
and Belle de-
tectors are described in Refs. [20, 21].
Reconstructed tracks of charged particles are consid-
ered as kaon and pion candidates. Kaons are identi-
fied using the particle identification techniques described
in Refs. [20, 21]. Photons are reconstructed from en-
ergy deposits in the electromagnetic calorimeters, and
the energy of photon candidates 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
+
π
−
π
0
.
The invariant mass is required to be within 20 MeV/
c
2
of
the nominal mass [22] for
η
→
γγ
candidates, and within
6
10 MeV/
c
2
for
η
→
π
+
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
+
π
−
π
0
is re-
constructed 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
+
π
−
, with in-
variant 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
+
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
+
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
= +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
+
K
−
), and in
the
CP
-odd (
η
f
=
−
1) final states
B
0
→
D
CP
π
0
,
D
CP
η
,
D
CP
ω
(with
D
CP
→
K
+
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
=
√
(
E
∗
beam
/c
2
)
2
−
(
p
∗
B
/c
)
2
[
B
A
B
AR
uses
m
ES
and Belle
uses
M
bc
, hereinafter
M
bc
is used] and by the energy
difference ∆
E
=
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
+
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
<
∆
E <
100 MeV, except for
B
0
→
D
(
∗
)
CP
π
0
decays, where
−
75 MeV
<
∆
E <
100 MeV is required to
exclude tails from partially reconstructed
B
−
→
D
(
∗
)0
ρ
−
decays peaking at ∆
E
≈−
250 MeV.
In
B
0
→
D
0
ω
and in
D
0
→
K
0
S
ω
decays, the
ω
vec-
tor mesons are polarized. The angular distribution of
ω
→
π
+
π
−
π
0
decays is exploited to discriminate against
background. The quantity cos
θ
N
is defined as the co-
sine of the angle between the neutral
B
meson direction
and the normal to the
π
+
π
−
π
0
plane in the
ω
meson rest
frame. A requirement of
|
cos
θ
N
|
>
0
.
3 is applied.
After applying the above selection requirements, the
average multiplicity of reconstructed
B
0
→
D
(
∗
)
CP
h
0
can-
didates 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
(
∗
)
and
h
0
meson masses from the nominal values. The
probability for this method to select the correct signal is
82% (81%) for
B
A
B
AR
(Belle).
In
B
0
→
D
(
∗
)
CP
h
0
decays, the dominant source of back-
ground originates from
e
+
e
−
→
q
q
(
q
∈ {
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 [27], 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
B
A
B
AR
(Belle).
5
.
21
5
.
23
5
.
25
5
.
27
5
.
29
M
bc
(GeV/c
2
)
0
20
40
60
80
100
120
140
160
Events / 1 MeV/c
2
(a)
B
A
B
AR
5
.
21
5
.
23
5
.
25
5
.
27
5
.
29
M
bc
(GeV/c
2
)
0
20
40
60
80
100
120
140
160
Events / 1 MeV/c
2
(b) Belle
FIG. 1. The
M
bc
distributions (data points with error bars)
and fit projections (solid line) of
B
0
→
D
(
∗
)
CP
h
0
decays for (a)
B
A
B
AR
and (b) Belle. The dashed (dotted) lines represent
projections of the signal (background) fit components.
The signal yields are determined by unbinned maxi-
mum likelihood fits to the
M
bc
distributions. In the fits,
the signal component is parametrized by a Crystal Ball
function [28] and the background component is modeled
by an ARGUS function [29]. The experimental
M
bc
dis-
tributions and fit projections are shown in Fig. 1. The
signal yields are summarized in Table I.
TABLE I. Summary of
B
0
→
D
(
∗
)
CP
h
0
signal yields.
Decay mode
B
A
B
AR
Belle
B
0
→
D
CP
π
0
241
±
22
345
±
25
B
0
→
D
CP
η
106
±
14
148
±
18
B
0
→
D
CP
ω
66
±
10
151
±
17
B
0
→
D
∗
CP
π
0
72
±
12
80
±
14
B
0
→
D
∗
CP
η
39
±
8
39
±
10
B
0
→
D
(
∗
)
CP
h
0
total
508
±
31
757
±
44
The time-dependent
CP
violation measurement is per-
formed using established
B
A
B
AR
and Belle techniques for
the vertex reconstruction, the flavor-tagging, and the
modeling of ∆
t
resolution effects (see Refs. [6, 7, 30–33])
and is briefly summarized below. The proper time inter-
val ∆
t
is given as
∆
z
c
βγ
, where ∆
z
is the distance between