Branching fractions and
CP
-violating asymmetries in radiative
B
decays to
K
B. Aubert,
1
M. Bona,
1
Y. Karyotakis,
1
J. P. Lees,
1
V. Poireau,
1
E. Prencipe,
1
X. Prudent,
1
V. Tisserand,
1
J. Garra Tico,
2
E. Grauges,
2
G. Eigen,
3
B. Stugu,
3
L. Sun,
3
G. S. Abrams,
4
M. Battaglia,
4
D. N. Brown,
4
R. N. Cahn,
4
R. G. Jacobsen,
4
L. T. Kerth,
4
Yu. G. Kolomensky,
4
G. Kukartsev,
4
G. Lynch,
4
I. L. Osipenkov,
4
M. T. Ronan,
4,
*
K. Tackmann,
4
T. Tanabe,
4
C. M. Hawkes,
5
N. Soni,
5
A. T. Watson,
5
H. Koch,
6
T. Schroeder,
6
D. Walker,
7
D. J. Asgeirsson,
8
T. Cuhadar-Donszelmann,
8
B. G. Fulsom,
8
C. Hearty,
8
T. S. Mattison,
8
J. A. McKenna,
8
M. Barrett,
9
A. Khan,
9
L. Teodorescu,
9
V. E. Blinov,
10
A. D. Bukin,
10
A. R. Buzykaev,
10
V. P. Druzhinin,
10
V. B. Golubev,
10
A. P. Onuchin,
10
S. I. Serednyakov,
10
Yu. I. Skovpen,
10
E. P. Solodov,
10
K. Yu. Todyshev,
10
M. Bondioli,
11
S. Curry,
11
I. Eschrich,
11
D. Kirkby,
11
A. J. Lankford,
11
P. Lund,
11
M. Mandelkern,
11
E. C. Martin,
11
D. P. Stoker,
11
S. Abachi,
12
C. Buchanan,
12
J. W. Gary,
13
F. Liu,
13
O. Long,
13
B. C. Shen,
13,
*
G. M. Vitug,
13
Z. Yasin,
13
L. Zhang,
13
V. Sharma,
14
C. Campagnari,
15
T. M. Hong,
15
D. Kovalskyi,
15
M. A. Mazur,
15
J. D. Richman,
15
T. W. Beck,
16
A. M. Eisner,
16
C. J. Flacco,
16
C. A. Heusch,
16
J. Kroseberg,
16
W. S. Lockman,
16
T. Schalk,
16
B. A. Schumm,
16
A. Seiden,
16
L. Wang,
16
M. G. Wilson,
16
L. O. Winstrom,
16
C. H. Cheng,
17
D. A. Doll,
17
B. Echenard,
17
F. Fang,
17
D. G. Hitlin,
17
I. Narsky,
17
T. Piatenko,
17
F. C. Porter,
17
R. Andreassen,
18
G. Mancinelli,
18
B. T. Meadows,
18
K. Mishra,
18
M. D. Sokoloff,
18
F. Blanc,
19
P. C. Bloom,
19
W. T. Ford,
19
A. Gaz,
19
J. F. Hirschauer,
19
A. Kreisel,
19
M. Nagel,
19
U. Nauenberg,
19
A. Olivas,
19
J. G. Smith,
19
K. A. Ulmer,
19
S. R. Wagner,
19
R. Ayad,
20,
†
A. Soffer,
20,
‡
W. H. Toki,
20
R. J. Wilson,
20
D. D. Altenburg,
21
E. Feltresi,
21
A. Hauke,
21
H. Jasper,
21
M. Karbach,
21
J. Merkel,
21
A. Petzold,
21
B. Spaan,
21
K. Wacker,
21
M. J. Kobel,
22
W. F. Mader,
22
R. Nogowski,
22
K. R. Schubert,
22
R. Schwierz,
22
J. E. Sundermann,
22
A. Volk,
22
D. Bernard,
23
G. R. Bonneaud,
23
E. Latour,
23
Ch. Thiebaux,
23
M. Verderi,
23
P. J. Clark,
24
W. Gradl,
24
S. Playfer,
24
J. E. Watson,
24
K. S. Chaisanguanthum,
25
M. Morii,
25
R. S. Dubitzky,
26
J. Marks,
26
S. Schenk,
26
U. Uwer,
26
V. Klose,
27
H. M. Lacker,
27
L. Lopez,
28a,28b
A. Palano,
28a,28b
M. Pappagallo,
28a,28b
M. Andreotti,
29a,29b
D. Bettoni,
29a
C. Bozzi,
29a
R. Calabrese,
29a,29b
A. Cecchi,
29a,29b
G. Cibinetto,
29a,29b
P. Franchini,
29a,29b
E. Luppi,
29a,29b
M. Negrini,
29a,29b
A. Petrella,
29a,29b
L. Piemontese,
29a
V. Santoro,
29a,29b
R. Baldini-Ferroli,
30
A. Calcaterra,
30
R. de Sangro,
30
G. Finocchiaro,
30
S. Pacetti,
30
P. Patteri,
30
I. M. Peruzzi,
30,
x
M. Piccolo,
30
M. Rama,
30
A. Zallo,
30
A. Buzzo,
31a
R. Contri,
31a,31b
M. Lo Vetere,
31a,31b
M. M. Macri,
31a
M. R. Monge,
31a,31b
S. Passaggio,
31a
C. Patrignani,
31a,31b
E. Robutti,
31a
A. Santroni,
31a,31b
S. Tosi,
31a,31b
A. Lazzaro,
32a,32b
V. Lombardo,
32b
F. Palombo,
32a,32b
G. De Nardo,
33a,33b
L. Lista,
33a
D. Monorchio,
33a,33b
G. Onorato,
33a,33b
C. Sciacca,
33a,33b
G. Castelli,
34a,34b
N. Gagliardi,
34a,34b
M. Margoni,
34a,34b
M. Morandin,
34a
M. Posocco,
34a
M. Rotondo,
34a
F. Simonetto,
34a,34b
R. Stroili,
34a,34b
C. Voci,
34a,34b
M. Biasini,
35a,35b
R. Covarelli,
35a,35b
E. Manoni,
35a,35b
C. Angelini,
36a,36b
G. Batignani,
36a,36b
S. Bettarini,
36a,36b
M. Carpinelli,
36a,36b,
k
A. Cervelli,
36a,36b
F. Forti,
36a,36b
M. A. Giorgi,
36a,36b
A. Lusiani,
36a,36c
G. Marchiori,
36a,36b
M. Morganti,
36a,36b
N. Neri,
36a,36b
E. Paoloni,
36a,36b
G. Rizzo,
36a,36b
J. J. Walsh,
36a
F. Anulli,
37a
E. Baracchini,
37a,37b
G. Cavoto,
37a
D. del Re,
37a,37b
E. Di Marco,
37a,37b
R. Faccini,
37a,37b
F. Ferrarotto,
37a
F. Ferroni,
37a,37b
M. Gaspero,
37a,37b
P. D. Jackson,
37a
L. Li Gioi,
37a
M. A. Mazzoni,
37a
S. Morganti,
37a
G. Piredda,
37a
F. Polci,
37a
F. Renga,
37a
C. Voena,
37a
F. Bianchi,
38a,38b
D. Gamba,
38a,38b
M. Pelliccioni,
38a,38b
M. Bomben,
39a,39b
L. Bosisio,
39a,39b
C. Cartaro,
39a,39b
G. Della Ricca,
39a,39b
L. Lanceri,
39a,39b
L. Vitale,
39a,39b
D. J. Bard,
40
P. D. Dauncey,
40
J. A. Nash,
40
W. Panduro Vazquez,
40
M. Tibbetts,
40
P. K. Behera,
41
X. Chai,
41
M. J. Charles,
41
U. Mallik,
41
J. Cochran,
42
H. B. Crawley,
42
L. Dong,
42
W. T. Meyer,
42
S. Prell,
42
E. I. Rosenberg,
42
A. E. Rubin,
42
Y. Y. Gao,
43
A. V. Gritsan,
43
Z. J. Guo,
43
C. K. Lae,
43
A. G. Denig,
44
M. Fritsch,
44
G. Schott,
44
N. Arnaud,
45
J. Be
́
quilleux,
45
A. D’Orazio,
45
M. Davier,
45
J. Firmino da Costa,
45
G. Grosdidier,
45
A. Ho
̈
cker,
45
V. Lepeltier,
45
F. Le Diberder,
45
A. M. Lutz,
45
S. Pruvot,
45
P. Roudeau,
45
M. H. Schune,
45
J. Serrano,
45
V. Sordini,
45,
{
A. Stocchi,
45
G. Wormser,
45
D. J. Lange,
46
D. M. Wright,
46
I. Bingham,
47
J. P. Burke,
47
C. A. Chavez,
47
J. R. Fry,
47
E. Gabathuler,
47
R. Gamet,
47
D. E. Hutchcroft,
47
D. J. Payne,
47
C. Touramanis,
47
A. J. Bevan,
48
C. K. Chukwudi,
48
K. A. George,
48
F. Di Lodovico,
48
R. Sacco,
48
M. Sigamani,
48
G. Cowan,
49
H. U. Flaecher,
49
D. A. Hopkins,
49
S. Paramesvaran,
49
F. Salvatore,
49
A. C. Wren,
49
D. N. Brown,
50
C. L. Davis,
50
K. E. Alwyn,
51
N. R. Barlow,
51
R. J. Barlow,
51
Y. M. Chia,
51
C. L. Edgar,
51
G. D. Lafferty,
51
T. J. West,
51
J. I. Yi,
51
J. Anderson,
52
C. Chen,
52
A. Jawahery,
52
D. A. Roberts,
52
G. Simi,
52
J. M. Tuggle,
52
C. Dallapiccola,
53
S. S. Hertzbach,
53
X. Li,
53
E. Salvati,
53
S. Saremi,
53
R. Cowan,
54
D. Dujmic,
54
P. H. Fisher,
54
K. Koeneke,
54
G. Sciolla,
54
M. Spitznagel,
54
F. Taylor,
54
R. K. Yamamoto,
54
M. Zhao,
54
S. E. Mclachlin,
55,
*
P. M. Patel,
55
S. H. Robertson,
55
J. M. Bauer,
56
L. Cremaldi,
56
V. Eschenburg,
56
R. Godang,
56,
**
R. Kroeger,
56
D. A. Sanders,
56
D. J. Summers,
56
H. W. Zhao,
56
S. Brunet,
57
D. Co
ˆ
te
́
,
57
M. Simard,
57
P. Taras,
57
F. B. Viaud,
57
H. Nicholson,
58
M. A. Baak,
59
G. Raven,
59
H. L. Snoek,
59
C. P. Jessop,
60
K. J. Knoepfel,
60
J. M. LoSecco,
60
W. F. Wang,
60
G. Benelli,
61
L. A. Corwin,
61
K. Honscheid,
61
H. Kagan,
61
R. Kass,
61
PHYSICAL REVIEW D
79,
011102(R) (2009)
RAPID COMMUNICATIONS
1550-7998
=
2009
=
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=
011102(7)
011102-1
Ó
2009 The American Physical Society
J. P. Morris,
61
A. M. Rahimi,
61
J. J. Regensburger,
61
S. J. Sekula,
61
Q. K. Wong,
61
N. L. Blount,
62
J. Brau,
62
R. Frey,
62
O. Igonkina,
62
J. A. Kolb,
62
M. Lu,
62
R. Rahmat,
62
N. B. Sinev,
62
D. Strom,
62
J. Strube,
62
E. Torrence,
62
P. del Amo Sanchez,
63
E. Ben-Haim,
63
H. Briand,
63
G. Calderini,
63
J. Chauveau,
63
P. David,
63
L. Del Buono,
63
O. Hamon,
63
Ph. Leruste,
63
J. Ocariz,
63
A. Perez,
63
J. Prendki,
63
L. Gladney,
64
J. Biesiada,
65
D. Lopes Pegna,
65
C. Lu,
65
J. Olsen,
65
A. J. S. Smith,
65
A. V. Telnov,
65
M. Ebert,
66
T. Hartmann,
66
H. Schro
̈
der,
66
R. Waldi,
66
T. Adye,
67
B. Franek,
67
E. O. Olaiya,
67
W. Roethel,
67
F. F. Wilson,
67
S. Emery,
68
M. Escalier,
68
L. Esteve,
68
A. Gaidot,
68
S. F. Ganzhur,
68
G. Hamel de Monchenault,
68
W. Kozanecki,
68
G. Vasseur,
68
Ch. Ye
`
che,
68
M. Zito,
68
X. R. Chen,
69
H. Liu,
69
W. Park,
69
M. V. Purohit,
69
R. M. White,
69
J. R. Wilson,
69
M. T. Allen,
70
D. Aston,
70
R. Bartoldus,
70
P. Bechtle,
70
J. F. Benitez,
70
R. Cenci,
70
J. P. Coleman,
70
M. R. Convery,
70
J. C. Dingfelder,
70
J. Dorfan,
70
G. P. Dubois-Felsmann,
70
W. Dunwoodie,
70
R. C. Field,
70
A. M. Gabareen,
70
S. J. Gowdy,
70
M. T. Graham,
70
P. Grenier,
70
C. Hast,
70
W. R. Innes,
70
J. Kaminski,
70
M. H. Kelsey,
70
H. Kim,
70
P. Kim,
70
M. L. Kocian,
70
D. W. G. S. Leith,
70
S. Li,
70
B. Lindquist,
70
S. Luitz,
70
V. Luth,
70
H. L. Lynch,
70
D. B. MacFarlane,
70
H. Marsiske,
70
R. Messner,
70
D. R. Muller,
70
H. Neal,
70
S. Nelson,
70
C. P. O’Grady,
70
I. Ofte,
70
A. Perazzo,
70
M. Perl,
70
B. N. Ratcliff,
70
A. Roodman,
70
A. A. Salnikov,
70
R. H. Schindler,
70
J. Schwiening,
70
A. Snyder,
70
D. Su,
70
M. K. Sullivan,
70
K. Suzuki,
70
S. K. Swain,
70
J. M. Thompson,
70
J. Va’vra,
70
A. P. Wagner,
70
M. Weaver,
70
C. A. West,
70
W. J. Wisniewski,
70
M. Wittgen,
70
D. H. Wright,
70
H. W. Wulsin,
70
A. K. Yarritu,
70
K. Yi,
70
C. C. Young,
70
V. Ziegler,
70
P. R. Burchat,
71
A. J. Edwards,
71
S. A. Majewski,
71
T. S. Miyashita,
71
B. A. Petersen,
71
L. Wilden,
71
S. Ahmed,
72
M. S. Alam,
72
R. Bula,
72
J. A. Ernst,
72
B. Pan,
72
M. A. Saeed,
72
S. B. Zain,
72
S. M. Spanier,
73
B. J. Wogsland,
73
R. Eckmann,
74
J. L. Ritchie,
74
A. M. Ruland,
74
C. J. Schilling,
74
R. F. Schwitters,
74
B. W. Drummond,
75
J. M. Izen,
75
X. C. Lou,
75
S. Ye,
75
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
Facultat de Fisica, Departament ECM, Universitat de Barcelona, E-08028 Barcelona, Spain
3
University of Bergen, Institute of Physics, N-5007 Bergen, Norway
4
Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
and University of California, Berkeley, California 94720, USA
5
University of Birmingham, Birmingham, B15 2TT, United Kingdom
6
Ruhr Universita
̈
t Bochum, Institut fu
̈
r Experimentalphysik 1, D-44780 Bochum, Germany
7
University of Bristol, Bristol BS8 1TL, United Kingdom
8
University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z1
9
Brunel University, Uxbridge, Middlesex UB8 3PH, United Kingdom
10
Budker Institute of Nuclear Physics, Novosibirsk 630090, Russia
11
University of California at Irvine, Irvine, California 92697, USA
12
University of California at Los Angeles, Los Angeles, California 90024, USA
13
University of California at Riverside, Riverside, California 92521, USA
14
University of California at San Diego, La Jolla, California 92093, USA
15
University of California at Santa Barbara, Santa Barbara, California 93106, USA
16
University of California at Santa Cruz, Institute for Particle Physics, Santa Cruz, California 95064, USA
17
California Institute of Technology, Pasadena, California 91125, USA
18
University of Cincinnati, Cincinnati, Ohio 45221, USA
19
University of Colorado, Boulder, Colorado 80309, USA
20
Colorado State University, Fort Collins, Colorado 80523, USA
21
Technische Universita
̈
t Dortmund, Fakulta
̈
t Physik, D-44221 Dortmund, Germany
22
Technische Universita
̈
t Dresden, Institut fu
̈
r Kern- und Teilchenphysik, D-01062 Dresden, Germany
23
Laboratoire Leprince-Ringuet, CNRS/IN2P3, Ecole Polytechnique, F-91128 Palaiseau, France
24
University of Edinburgh, Edinburgh EH9 3JZ, United Kingdom
25
Harvard University, Cambridge, Massachusetts 02138, USA
26
Universita
̈
t Heidelberg, Physikalisches Institut, Philosophenweg 12, D-69120 Heidelberg, Germany
27
Humboldt-Universita
̈
t zu Berlin, Institut fu
̈
r Physik, Newtonstr. 15, D-12489 Berlin, Germany
28a
INFN Sezione di Bari, I-70126 Bari, Italy
28b
Dipartmento di Fisica, Universita
`
di Bari, I-70126 Bari, Italy
29a
INFN Sezione di Ferrara, I-44100 Ferrara, Italy;
B. AUBERT
et al.
PHYSICAL REVIEW D
79,
011102(R) (2009)
RAPID COMMUNICATIONS
011102-2
29b
Dipartimento di Fisica, Universita
`
di Ferrara, I-44100 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, Universita
`
di Genova, I-16146 Genova, Italy
32a
INFN Sezione di Milano, I-20133 Milano, Italy
32b
Dipartimento di Fisica, Universita
`
di Milano, I-20133 Milano, Italy
33a
INFN Sezione di Napoli, I-80126, Napoli, Italy
33b
Dipartimento di Scienze Fisiche, Universita
`
di Napoli Federico II, I-80126, Napoli, Italy
34a
INFN Sezione di Padova, I-35131 Padova, Italy
34b
Dipartimento di Fisica, Universita
`
di Padova, I-35131 Padova, Italy
35a
INFN Sezione di Perugia, I-06100 Perugia, Italy
35b
Dipartimento di Fisica, Universita
`
di Perugia, I-06100 Perugia, Italy
36a
INFN Sezione di Pisa, I-56127 Pisa, Italy
36b
Dipartimento di Fisica, Universita
`
di Pisa, I-56127 Pisa, Italy
36c
Scuola Normale Superiore di Pisa, I-56127 Pisa, Italy
37a
INFN Sezione di Roma, I-00185 Roma, Italy
37b
Dipartimento di Fisica, Universita
`
di Roma La Sapienza, I-00185 Roma, Italy
38a
INFN Sezione di Torino, I-10125 Torino, Italy
38b
Dipartimento di Fisica Sperimentale, Universita
`
di Torino, I-10125 Torino, Italy
39a
INFN Sezione di Trieste, I-34127 Trieste, Italy
39b
Dipartimento di Fisica, Universita
`
di Trieste, I-34127 Trieste, Italy
40
Imperial College London, London, SW7 2AZ, United Kingdom
41
University of Iowa, Iowa City, Iowa 52242, USA
42
Iowa State University, Ames, Iowa 50011-3160, USA
43
Johns Hopkins University, Baltimore, Maryland 21218, USA
44
Universita
̈
t Karlsruhe, Institut fu
̈
r Experimentelle Kernphysik, D-76021 Karlsruhe, Germany
45
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
46
Lawrence Livermore National Laboratory, Livermore, California 94550, USA
47
University of Liverpool, Liverpool L69 7ZE, United Kingdom
48
Queen Mary, University of London, E1 4NS, United Kingdom
49
University of London, Royal Holloway and Bedford New College, Egham, Surrey TW20 0EX, United Kingdom
50
University of Louisville, Louisville, Kentucky 40292, USA
51
University of Manchester, Manchester M13 9PL, United Kingdom
52
University of Maryland, College Park, Maryland 20742, USA
53
University of Massachusetts, Amherst, Massachusetts 01003, USA
54
Massachusetts Institute of Technology, Laboratory for Nuclear Science, Cambridge, Massachusetts 02139, USA
55
McGill University, Montre
́
al, Que
́
bec, Canada H3A 2T8
56
University of Mississippi, University, Mississippi 38677, USA
57
Universite
́
de Montre
́
al, Physique des Particules, Montre
́
al, Que
́
bec, Canada H3C 3J7
58
Mount Holyoke College, South Hadley, Massachusetts 01075, USA
59
NIKHEF, National Institute for Nuclear Physics and High Energy Physics, NL-1009 DB Amsterdam, The Netherlands
60
University of Notre Dame, Notre Dame, Indiana 46556, USA
61
Ohio State University, Columbus, Ohio 43210, USA
62
University of Oregon, Eugene, Oregon 97403, USA
63
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
64
University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
65
Princeton University, Princeton, New Jersey 08544, USA
66
Universita
̈
t Rostock, D-18051 Rostock, Germany
67
Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, OX11 0QX, United Kingdom
68
DSM/Dapnia, CEA/Saclay, F-91191 Gif-sur-Yvette, France
69
University of South Carolina, Columbia, South Carolina 29208, USA
70
Stanford Linear Accelerator Center, Stanford, California 94309, USA
71
Stanford University, Stanford, California 94305-4060, USA
72
State University of New York, Albany, New York 12222, USA
73
University of Tennessee, Knoxville, Tennessee 37996, USA
74
University of Texas at Austin, Austin, Texas 78712, USA
75
University of Texas at Dallas, Richardson, Texas 75083, USA
76
IFIC, Universitat de Valencia-CSIC, E-46071 Valencia, Spain
77
University of Victoria, Victoria, British Columbia, Canada V8W 3P6
BRANCHING FRACTIONS AND
CP
-VIOLATING
...
PHYSICAL REVIEW D
79,
011102(R) (2009)
RAPID COMMUNICATIONS
011102-3
78
Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom
79
University of Wisconsin, Madison, Wisconsin 53706, USA
(Received 12 May 2008; published 15 January 2009)
We present measurements of the
CP
-violation parameters
S
and
C
for the radiative decay
B
0
!
K
0
S
;
for
B
!
K
we also measure the branching fractions and for
B
þ
!
K
þ
the time-integrated charge
asymmetry
A
ch
. The data, collected with the
BABAR
detector at the Stanford Linear Accelerator Center,
represent
465
10
6
B
B
pairs produced in
e
þ
e
annihilation. The results are
S
¼
0
:
18
þ
0
:
49
0
:
46
0
:
12
,
C
¼
0
:
32
þ
0
:
40
0
:
39
0
:
07
,
B
ð
B
0
!
K
0
Þ¼ð
7
:
1
þ
2
:
1
2
:
0
0
:
4
Þ
10
6
,
B
ð
B
þ
!
K
þ
Þ¼ð
7
:
7
1
:
0
0
:
4
Þ
10
6
, and
A
ch
¼ð
9
:
0
þ
10
:
4
9
:
8
1
:
4
Þ
10
2
. The first error quoted is statistical and the second
systematic.
DOI:
10.1103/PhysRevD.79.011102
PACS numbers: 13.20.He, 11.30.Er, 12.15.Hh
Radiative
B
meson decays have long been recognized as
a sensitive probe to test the standard model (SM) and to
look for new physics (NP) [
1
]. In the SM, flavor-changing
neutral current processes, such as
b
!
s
, proceed via
radiative loop diagrams. The loop diagrams may also con-
tain new heavy particles, and therefore are sensitive to NP.
In the SM the photon polarization in radiative decays is
dominantly left (right) handed for
b
(
b
) decays, resulting in
the suppression of mixing-induced
CP
asymmetries [
2
].
There are however NP scenarios predicting large values of
mixing-induced
CP
asymmetries [
3
,
4
]. We search also for
direct
CP
asymmetry in charged
B
decays, measuring the
charge asymmetry
A
ch
ð
þ
Þ
=
ð
þ
þ
Þ
, where
is the partial decay width of the
B
meson, and the
superscript corresponds to its charge. Direct
CP
asymme-
try in the SM is expected to be very small [
5
]. Observation
of significant
CP
violation in these radiative decay modes
would provide a clear sign of NP [
6
].
In this paper, we present the first measurement of the
mixing-induced
CP
violation in the decay mode
B
0
!
K
0
. Branching fractions for the decay modes
B
0
!
K
0
and
B
þ
!
K
þ
[
7
] and time-integrated charge
asymmetry for
B
þ
!
K
þ
have been measured previ-
ously by the Belle [
8
] and
BABAR
[
9
] Collaborations. We
update our previous measurements with a data sample that
is twice as large.
The results presented here are based on data collected
with the
BABAR
detector [
10
] at the PEP-II asymmetric-
energy
e
þ
e
collider [
11
] located at the Stanford Linear
Accelerator Center. We use an integrated luminosity of
423 fb
1
, corresponding to
ð
465
5
Þ
10
6
B
B
pairs, re-
corded at the
ð
4
S
Þ
resonance (at a center-of-mass energy
of
ffiffiffi
s
p
¼
10
:
58 GeV
).
Charged particles are detected by a combination of a
vertex tracker (SVT) consisting of five layers of double-
sided silicon microstrip detectors, and a 40-layer central
drift chamber (DCH), both operating in the 1.5 T magnetic
field. Photons and electrons are identified using a CsI(Tl)
electromagnetic calorimeter (EMC). Further charged-
particle identification is provided by the average energy
loss (
d
E=
d
x
) in the tracking devices and by an internally
reflecting ring-imaging Cherenkov detector (DIRC) cover-
ing the central region. We reconstruct the primary photon
using an EMC shower not associated with a track. The
primary photon energy, calculated in the
ð
4
S
Þ
frame, is
required to be in the range
1
:
6
–
2
:
7 GeV
. Charged
K
can-
didates are selected from tracks, by using particle identi-
fication from the DIRC and the
d
E=
d
x
measured in the
SVT and DCH.
The
B
decay daughter candidates are reconstructed
through their decays
0
!
,
!
(
), and
!
þ
0
(
3
). Here we require the laboratory energy of
the photons to be greater than 50 MeV. We impose the
following requirements on the invariant mass in
MeV
=c
2
of these particles’ final states:
120
<m
ð
Þ
<
150
for
0
,
490
<m
ð
Þ
<
600
for
,
520
<m
ð
þ
0
Þ
<
570
for
3
. Secondary pions in
candidates are rejected if
their DIRC and
d
E=
d
x
signatures satisfy tight requirements
for being consistent with protons, kaons, or electrons.
Neutral
K
candidates are formed from pairs of oppositely
charged tracks with a vertex
2
probability larger than
0.001,
486
<m
ð
þ
Þ
<
510 MeV
=c
2
and a recon-
structed decay length greater than 3 times its uncertainty.
The invariant mass of
K
system is required to be less
than
3
:
25 GeV
=c
2
.A
B
meson candidate is reconstructed
by combining an
candidate, a charged or neutral kaon,
and a primary photon candidate. It is characterized kine-
matically by the energy-substituted mass
m
ES
ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
ð
s=
2
þ
p
0
p
B
Þ
2
=E
2
0
p
2
B
q
and energy difference
E
E
B
1
2
ffiffiffi
s
p
, where the subscripts 0 and
B
refer to the initial
ð
4
S
Þ
and to the
B
candidate in the lab frame, respectively,
and the asterisk denotes the
ð
4
S
Þ
rest frame. We require
5
:
25
<m
ES
<
5
:
29 GeV
=c
2
and
j
E
j
<
0
:
2 GeV
.
From a candidate
B
B
pair we reconstruct a
B
0
decaying
into
K
0
S
(
B
rec
). We also reconstruct the decay point of
*
Deceased.
†
Now at Temple University, Philadelphia, PA 19122, USA.
‡
Now at Tel Aviv University, Tel Aviv, 69978, Israel.
x
Also with Universita
`
di Perugia, Dipartimento di Fisica,
Perugia, Italy.
k
Also with Universita
`
di Sassari, Sassari, Italy.
{
Also with Universita
`
di Roma La Sapienza, I-00185 Roma,
Italy.
**
Now at University of South Alabama, Mobile, AL 36688,
USA.
B. AUBERT
et al.
PHYSICAL REVIEW D
79,
011102(R) (2009)
RAPID COMMUNICATIONS
011102-4
the other
B
meson (
B
tag
) and identify its flavor. The differ-
ence
t
t
rec
t
tag
of the proper decay times
t
rec
and
t
tag
of the reconstructed and tag
B
mesons, respectively, is
obtained from the measured distance between the
B
rec
and
B
tag
decay vertices and from the boost (
¼
0
:
56
)
of the
e
þ
e
system. The
t
distribution [
12
] is given by
F
ð
t
Þ¼
e
j
t
j
=
4
½
1
w
ð
1
2
w
Þð
S
sin
ð
m
d
t
Þ
C
cos
ð
m
d
t
ÞÞ
:
(1)
The upper (lower) sign denotes a decay accompanied by a
B
0
(
B
0
) tag,
is the mean
B
0
lifetime,
m
d
is the mixing
frequency, and the mistag parameters
w
and
w
are the
average and difference, respectively, of the probabilities
that a true
B
0
is incorrectly tagged as a
B
0
or vice versa. In
the flavor tagging algorithm [
13
] there are six mutually
exclusive tagging categories of different response purities
and untagged events with no tagging informations.
We reconstruct the
B
0
!
K
0
S
decay point, using the
knowledge of the
K
0
S
trajectory and the average interaction
point in a geometric fit [
12
]. In about 70% of the selected
events the
t
resolution is sufficient for the time-dependent
CP
-violation measurement. For the remaining events the
t
information is not used. For both
K
0
S
and
3
K
0
S
modes we require
j
t
j
<
20 ps
and
t
<
2
:
5ps
, where
t
is the per-event error on
t
.
We obtain signal event yields and
CP
-violation parame-
ters from unbinned extended maximum-likelihood (ML)
fits. We indicate with
j
the species of event: signal,
q
q
continuum background,
B
B
peaking background (
BP
), and
B
B
nonpeaking background (
BNP
). The input observables
are
m
ES
,
E
, the output of a Neural Network (
NN
), the
invariant mass
m
, and
t
. The
NN
combines four varia-
bles: the absolute values of the cosines of the polar angles
with respect to the beam axis in the
ð
4
S
Þ
frame of the
B
candidate momentum and the
B
thrust axis, the ratio of the
second and zeroth Fox-Wolfram moments [
14
], and the
absolute value of the cosine of the angle
T
between the
thrust axis of the
B
candidate and that of the rest of the
tracks and neutral clusters in the event, calculated in the
ð
4
S
Þ
frame.
For each species
j
and tagging category
c
and with
n
j
defined to be the number of events of the species
j
and
f
j;c
the fraction of events of species
j
for each category
c
,we
write the extended likelihood function for all events be-
longing to category
c
as
L
c
¼
exp
X
j
n
j
f
j;c
Y
N
c
i
ð
n
sig
f
sig
;c
P
i
sig
;c
þ
n
q
q
f
q
q;c
P
i
q
q
þ
n
BNP
f
BNP;c
P
i
BNP
þ
n
BP
f
BP;c
P
i
BP
Þ
;
(2)
where
P
i
j;c
is the total probability function (PDF) for event
i
and
N
c
the number of events of category
c
in the sample.
We fix
f
sig
;c
,
f
BNP;c
, and
f
BP;c
to
f
B
flav
;c
, the values mea-
sured with a large sample of
B
-decays to fully recon-
structed flavor eigenstates (
B
flav
)[
15
]. The total
likelihood function
L
d
for decay mode
d
is given as the
product over the seven tagging categories. Finally, when
combining decay modes we form the grand likelihood
L
¼
Q
L
d
.
The PDF
P
sig
ð
t;
t
;
c
Þ
, for each category
c
, is the
convolution of
F
ð
t
;
c
Þ
[Eq. (
1
)] with the signal resolution
function (sum of three Gaussians) determined from the
B
flav
sample. The other PDF forms are the sum of two
Gaussians for
P
sig
ð
m
ES
Þ
,
P
sig
ð
E
Þ
, and
P
sig
ð
m
Þ
; the sum
of three Gaussians for
P
q
q
ð
t
Þ
,
P
BNP
ð
t
Þ
, and
P
BP
ð
t
Þ
;a
nonparametric step function for
P
j
ð
NN
Þ
[
16
]; a linear
dependence for
P
q
q
ð
E
Þ
,
P
BNP
ð
E
Þ
, and
P
BP
ð
E
Þ
;a
first-order polynomial plus a Gaussian for
P
q
q
ð
m
Þ
,
P
BNP
ð
m
Þ
, and
P
BP
ð
m
Þ
; and for
P
q
q
ð
m
ES
Þ
,
P
BNP
ð
m
ES
Þ
, and
P
BP
ð
m
ES
Þ
, the function
x
ffiffiffiffiffiffiffiffiffiffiffiffiffi
1
x
2
p
exp
½
ð
1
x
2
Þ
, with
x
2
m
ES
=
ffiffiffi
s
p
[
17
], where for the
BP
PDFs we add a Gaussian. We allow
q
q
background
PDF parameters to vary in the fit.
We determine the PDF parameters from Monte Carlo
(MC) simulation for the signal and
B
B
backgrounds, while
using sideband data (
5
:
25
<m
ES
<
5
:
27 GeV
=c
2
;
0
:
1
<
j
E
j
<
0
:
2 GeV
) to model the PDFs of continuum back-
ground. Large control samples of
B
decays to charmed
final states with similar topology and a smearing procedure
applied to photons during the event reconstruction are used
to verify the simulated resolutions in
m
ES
and
E
. The
largest shift in
m
ES
is
0
:
6 MeV
=c
2
. Any bias in the fit is
determined from a large set of simulated experiments.
We compute the branching fractions and charge asym-
metry from fits made without
t
and flavor tagging. The
free parameters in the fit are the signal,
q
q
,
BNP
and
BP
background yields; the bin weights of the step function for
P
q
q
ð
NN
Þ
; the slopes of
P
q
q
ð
E
Þ
and
P
q
q
ð
m
Þ
;
; and for
charged modes the signal and background
A
ch
. As free
parameters we have also
S
,
C
, the parameters of the
P
q
q
ð
t
Þ
PDF, and the
f
q
q;c
fractions.
Table
I
lists the results of the fits. The corrected signal
yield is the fitted yield minus the fit bias which is in the
range 2%–4%. The efficiency is calculated as the ratio of
the number of signal MC events entering the ML fit to the
total generated. We compute the branching fractions from
the corrected signal yields, reconstruction efficiencies,
daughter branching fractions, and the number of produced
B
mesons. We assume that the branching fractions of the
ð
4
S
Þ
to
B
þ
B
and
B
0
B
0
are each equal to 50%. We
combine results from different channels by adding the
values of
2ln
L
(parameterized in terms of the branching
fractions), taking into account the correlated and uncorre-
lated systematic errors.
The statistical error on the signal yield,
S
,
C
and the
signal charge asymmetry is taken as the change in the
central value when the quantity
2ln
L
increases by one
unit from its minimum value. The significance
S
(
) is the
BRANCHING FRACTIONS AND
CP
-VIOLATING
...
PHYSICAL REVIEW D
79,
011102(R) (2009)
RAPID COMMUNICATIONS
011102-5
square root of the difference between the value of
2ln
L
(with systematic uncertainties included) for zero signal and
the value at its minimum.
Figure
1
shows, as representative fits, the projections
onto
m
ES
and
E
while Fig.
2
shows the projections onto
t
and the raw asymmetry between
B
0
and
B
0
tags. In
these projections a subset of the data is used for when the
signal likelihood (computed without the variable plotted)
exceeds a threshold that optimizes the sensitivity.
Figure
3
shows the distribution of the
K
invariant mass
for signal events obtained by the event-weighting tech-
nique (sPlot) described in Ref. [
18
]. There is some evi-
dence of a structure near
1
:
5 GeV
=c
2
.
The main sources of systematic uncertainties for the
time-dependent measurements come from the variation of
the signal PDF shape parameters within their errors (0.08
for
S
, 0.04 for
C
), and from
B
B
backgrounds (0.09 for
S
,
0.06 for
C
). Other minor sources are SVT alignment, beam
spot position and size, and interference between the CKM-
suppressed
b
!
uc
d
amplitude and the favored
b
!
c
ud
amplitude for some tag-side
B
decays [
19
]. The
B
flav
sample is used to determine the errors associated with
the signal
t
resolutions, tagging efficiencies, and mistag
rates. We use specific signal MC samples to evaluate the
systematic uncertainty associated with the appropriateness
of using
B
flav
parameters for the signal
t
resolution (0.02
for
S
, 0.01 for
C
). Published measurements [
20
] for
and
m
d
are used to determine the errors associated with them.
Summing all systematic errors in quadrature, we obtain
0
:
12
for
S
and
0
:
07
for
C
.
The main sources of systematic uncertainties for the
branching fraction measurements include uncertainties in
the PDF parameterization and ML fit bias. For the signal,
the uncertainties in PDF parameters are estimated by com-
paring MC and data in control samples. Varying the signal
PDF parameters within these errors, we estimate yield
uncertainties of 3–23 events, depending on the mode.
The uncertainty (1–3 events) from fit bias is taken as half
the correction itself. Systematic uncertainties due to lack of
knowledge of the primary photon spectrum are estimated
to be in the range 2%–3% depending on the decay mode.
Uncertainties in our knowledge of the efficiency, found
from auxiliary studies [
21
], include
0
:
4%
N
t
and
1
:
8%
N
, where
N
t
and
N
are the numbers of tracks
0
2
Events / 4 MeV/c
0
50
100
150
200
0
Events / 40 MeV
0
50
100
150
)
2
(GeV/c
ES
m
5.25
5.26 5.27
5.28
5.29
0
20
40
60
80
E (GeV)
∆
-0.2
-0.1
0
0.1
0.2
0
10
20
30
40
(a)
(b)
(c)
(d)
FIG. 1 (color online). The
B
candidate
m
ES
and
E
projec-
tions (see text) for
K
þ
(a, b),
K
0
(c, d). Points with error
bars (statistical only) represent the data, the solid line the full fit
function, and the dashed line its background component.
(c)
t (ps)
∆
-5
0
5
Asymmetry
-1
0
1
-5
0
5
(b)
-5
0
5
0
20
40
60
-5
0
5
(a)
-5
0
5
0
20
40
60
Events / 2 ps
FIG. 2 (color online). Projections (see text) onto
t
of the data
(points with error bars), fit function (solid line), and background
function (dashed line), for (a)
B
0
and (b)
B
0
tagged events, and
(c) the raw asymmetry
ð
N
B
0
N
B
0
Þ
=
ð
N
B
0
þ
N
B
0
Þ
between
B
0
and
B
0
tags.
TABLE I. Number of events
N
in the sample, corrected signal yield, detection efficiency
, daughter branching fraction product
Q
B
i
, significance
S
(
) (including systematic uncertainties), and measured branching fraction
B
with statistical error for each decay
mode. For the combined measurements we give
S
(
) and the branching fraction with statistical and systematic uncertainty. For the
neutral mode we give the
S
and
C
parameters for each decay mode and for their combination. For the charged modes we also give the
measured signal charge asymmetry
A
ch
.
Mode
N
Yield
(%)
Q
B
i
ð
%
Þ
S
ð
Þ
B
ð
10
6
Þ
A
ch
(
10
2
)
SC
K
0
3690 58
þ
19
18
12
13
:
63
:
37
:
4
þ
2
:
5
2
:
3
0
:
04
0
:
62
0
:
24
0
:
44
3
K
0
2282 24
þ
13
12
10
7
:
82
:
16
:
6
þ
3
:
6
3
:
2
0
:
45
0
:
81
0
:
71
0
:
87
K
0
3
:
97
:
1
þ
2
:
1
2
:
0
0
:
4
0
:
18
þ
0
:
49
0
:
46
0
:
12
0
:
32
þ
0
:
40
0
:
39
0
:
07
K
þ
11620
266
þ
37
36
19
39.4
6.5
7
:
8
þ
1
:
1
1
:
0
4
12
3
K
þ
10738
111
þ
26
24
14
22.4
4.5
7
:
4
þ
1
:
7
1
:
6
24
20
K
þ
8
:
07
:
7
1
:
0
0
:
4
9
:
0
þ
10
:
4
9
:
8
1
:
4
B. AUBERT
et al.
PHYSICAL REVIEW D
79,
011102(R) (2009)
RAPID COMMUNICATIONS
011102-6
and photons, respectively, in the
B
candidate. There is a
systematic error of 2.1% in the efficiency of
K
0
S
reconstruc-
tion. The uncertainty in the total number of
B
B
pairs in the
data sample is 1.1%. Published data [
20
] provide the un-
certainties in the
B
daughter branching fraction products
(0.7%–1.8%).
A systematic uncertainty of 0.014 is assigned to
A
ch
.
This uncertainty is estimated from studies with signal MC
events and data control samples and from calculation of the
asymmetry due to particles interacting in the detector.
In conclusion, we measure the time-dependent
CP
vio-
lation parameters in the decay mode
B
0
!
K
0
S
:
S
¼
0
:
18
þ
0
:
49
0
:
46
0
:
12
and
C
¼
0
:
32
þ
0
:
40
0
:
39
0
:
07
. We also
measure the branching fractions, in units of
10
6
,
B
ð
B
0
!
K
0
Þ¼
7
:
1
þ
2
:
1
2
:
0
0
:
4
and
B
ð
B
þ
!
K
þ
Þ¼
7
:
7
1
:
0
0
:
4
, in agreement with the results from Belle [
8
] and the
previous
BABAR
results [
9
]. The measured charge asym-
metry in the decay
B
þ
!
K
þ
is consistent with zero. Its
confidence interval at 90% confidence level is [
0
:
25
,
0.08]. All the results are consistent with SM expectations.
Because of the large statistical uncertainties, interesting
constraints on NP in these decay modes need a data sample
available only at higher luminosity
B
factories (as pro-
posed at KEK [
22
] and Frascati [
23
]).
We are grateful for the excellent luminosity and machine
conditions provided by our PEP-II colleagues and for the
substantial dedicated effort from the computing organiza-
tions that support
BABAR
. The collaborating institutions
wish to thank SLAC for its support and kind hospitality.
This work is supported by DOE and NSF (USA), NSERC
(Canada), CEA and CNRS-IN
2
P
3
(France), BMBF and
DFG (Germany), INFN (Italy), FOM (The Netherlands),
NFR (Norway), MES (Russia), MEC (Spain), and STFC
(United Kingdom). Individuals have received support from
the Marie Curie EIF (European Union) and the A. P. Sloan
Foundation.
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)
2
(GeV/c
K
η
m
1
1.5
2
2.5
3
2
Events / 100 MeV/c
0
20
40
60
80
(a)
)
2
(GeV/c
K
η
m
1
1.5
2
2.5
3
2
Events / 100 MeV/c
-10
0
10
20
30
(b)
FIG. 3. Plot of
K
invariant mass for signal for the combined
subdecay modes: (a)
B
þ
!
K
þ
, (b)
B
0
!
K
0
. Errors are
statistical only.
BRANCHING FRACTIONS AND
CP
-VIOLATING
...
PHYSICAL REVIEW D
79,
011102(R) (2009)
RAPID COMMUNICATIONS
011102-7