Search for
B
0
meson decays to
0
K
0
S
K
0
S
,
K
0
S
K
0
S
, and
0
K
0
S
K
0
S
B. Aubert,
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
M. Martinelli,
3a,3b
A. Palano,
3a,3b
M. Pappagallo,
3a,3b
G. Eigen,
4
B. Stugu,
4
L. Sun,
4
M. Battaglia,
5
D. N. Brown,
5
L. T. Kerth,
5
Yu. G. Kolomensky,
5
G. Lynch,
5
I. L. Osipenkov,
5
K. Tackmann,
5
T. Tanabe,
5
C. M. Hawkes,
6
N. Soni,
6
A. T. Watson,
6
H. Koch,
7
T. Schroeder,
7
D. J. Asgeirsson,
8
B. G. Fulsom,
8
C. Hearty,
8
T. S. Mattison,
8
J. A. McKenna,
8
M. Barrett,
9
A. Khan,
9
A. Randle-Conde,
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
H. Atmacan,
12
J. W. Gary,
12
F. Liu,
12
O. Long,
12
G. M. Vitug,
12
Z. Yasin,
12
L. Zhang,
12
V. Sharma,
13
C. Campagnari,
14
T. M. Hong,
14
D. Kovalskyi,
14
M. A. Mazur,
14
J. D. Richman,
14
T. W. Beck,
15
A. M. Eisner,
15
C. A. Heusch,
15
J. Kroseberg,
15
W. S. Lockman,
15
A. J. Martinez,
15
T. Schalk,
15
B. A. Schumm,
15
A. Seiden,
15
L. Wang,
15
L. O. Winstrom,
15
C. H. Cheng,
16
D. A. Doll,
16
B. Echenard,
16
F. Fang,
16
D. G. Hitlin,
16
I. Narsky,
16
T. Piatenko,
16
F. C. Porter,
16
R. Andreassen,
17
G. Mancinelli,
17
B. T. Meadows,
17
K. Mishra,
17
M. D. Sokoloff,
17
P. C. Bloom,
18
W. T. Ford,
18
A. Gaz,
18
J. F. Hirschauer,
18
M. Nagel,
18
U. Nauenberg,
18
J. G. Smith,
18
S. R. Wagner,
18
R. Ayad,
19,
†
W. H. Toki,
19
R. J. Wilson,
19
E. Feltresi,
20
A. Hauke,
20
H. Jasper,
20
T. M. Karbach,
20
J. Merkel,
20
A. Petzold,
20
B. Spaan,
20
K. Wacker,
20
M. J. Kobel,
21
R. Nogowski,
21
K. R. Schubert,
21
R. Schwierz,
21
A. Volk,
21
D. Bernard,
22
E. Latour,
22
M. Verderi,
22
P. J. Clark,
23
S. Playfer,
23
J. E. Watson,
23
M. Andreotti,
24a,24b
D. Bettoni,
24a
C. Bozzi,
24a
R. Calabrese,
24a,24b
A. Cecchi,
24a,24b
G. Cibinetto,
24a,24b
E. Fioravanti,
24a,24b
P. Franchini,
24a,24b
E. Luppi,
24a,24b
M. Munerato,
24a,24b
M. Negrini,
24a,24b
A. Petrella,
24a,24b
L. Piemontese,
24a
V. Santoro,
24a,24b
R. Baldini-Ferroli,
25
A. Calcaterra,
25
R. de Sangro,
25
G. Finocchiaro,
25
S. Pacetti,
25
P. Patteri,
25
I. M. Peruzzi,
25,
‡
M. Piccolo,
25
M. Rama,
25
A. Zallo,
25
R. Contri,
26a,26b
E. Guido,
26a,26b
M. Lo Vetere,
26a,26b
M. R. Monge,
26a,26b
S. Passaggio,
26a
C. Patrignani,
26a,26b
E. Robutti,
26a
S. Tosi,
26a,26b
K. S. Chaisanguanthum,
27
M. Morii,
27
A. Adametz,
28
J. Marks,
28
S. Schenk,
28
U. Uwer,
28
F. U. Bernlochner,
29
V. Klose,
29
H. M. Lacker,
29
D. J. Bard,
30
P. D. Dauncey,
30
M. Tibbetts,
30
P. K. Behera,
31
M. J. Charles,
31
U. Mallik,
31
J. Cochran,
32
H. B. Crawley,
32
L. Dong,
32
V. Eyges,
32
W. T. Meyer,
32
S. Prell,
32
E. I. Rosenberg,
32
A. E. Rubin,
32
Y. Y. Gao,
33
A. V. Gritsan,
33
Z. J. Guo,
33
N. Arnaud,
34
J. Be
́
quilleux,
34
A. D’Orazio,
34
M. Davier,
34
D. Derkach,
34
J. Firmino da Costa,
34
G. Grosdidier,
34
F. Le Diberder,
34
V. Lepeltier,
34
A. M. Lutz,
34
B. Malaescu,
34
S. Pruvot,
34
P. Roudeau,
34
M. H. Schune,
34
J. Serrano,
34
V. Sordini,
34,
x
A. Stocchi,
34
G. Wormser,
34
D. J. Lange,
35
D. M. Wright,
35
I. Bingham,
36
J. P. Burke,
36
C. A. Chavez,
36
J. R. Fry,
36
E. Gabathuler,
36
R. Gamet,
36
D. E. Hutchcroft,
36
D. J. Payne,
36
C. Touramanis,
36
A. J. Bevan,
37
C. K. Clarke,
37
F. Di Lodovico,
37
R. Sacco,
37
M. Sigamani,
37
G. Cowan,
38
S. Paramesvaran,
38
A. C. Wren,
38
D. N. Brown,
39
C. L. Davis,
39
A. G. Denig,
40
M. Fritsch,
40
W. Gradl,
40
A. Hafner,
40
K. E. Alwyn,
41
D. Bailey,
41
R. J. Barlow,
41
G. Jackson,
41
G. D. Lafferty,
41
T. J. West,
41
J. I. Yi,
41
J. Anderson,
42
C. Chen,
42
A. Jawahery,
42
D. A. Roberts,
42
G. Simi,
42
J. M. Tuggle,
42
C. Dallapiccola,
43
E. Salvati,
43
S. Saremi,
43
R. Cowan,
44
D. Dujmic,
44
P. H. Fisher,
44
S. W. Henderson,
44
G. Sciolla,
44
M. Spitznagel,
44
R. K. Yamamoto,
44
M. Zhao,
44
P. M. Patel,
45
S. H. Robertson,
45
M. Schram,
45
P. Biassoni,
46a,46b
F. Cerutti,
46a,46b
A. Lazzaro,
46a,46b
V. Lombardo,
46a
F. Palombo,
46a,46b
S. Stracka,
46a,46b
J. M. Bauer,
47
L. Cremaldi,
47
R. Godang,
47,
k
R. Kroeger,
47
P. Sonnek,
47
D. J. Summers,
47
H. W. Zhao,
47
M. Simard,
48
P. Taras,
48
H. Nicholson,
49
G. De Nardo,
50a,50b
L. Lista,
50a
D. Monorchio,
50a,50b
G. Onorato,
50a,50b
C. Sciacca,
50a,50b
G. Raven,
51
H. L. Snoek,
51
C. P. Jessop,
52
K. J. Knoepfel,
52
J. M. LoSecco,
52
W. F. Wang,
52
L. A. Corwin,
53
K. Honscheid,
53
H. Kagan,
53
R. Kass,
53
J. P. Morris,
53
A. M. Rahimi,
53
J. J. Regensburger,
53
S. J. Sekula,
53
Q. K. Wong,
53
N. L. Blount,
54
J. Brau,
54
R. Frey,
54
O. Igonkina,
54
J. A. Kolb,
54
M. Lu,
54
R. Rahmat,
54
N. B. Sinev,
54
D. Strom,
54
J. Strube,
54
E. Torrence,
54
G. Castelli,
55a,55b
N. Gagliardi,
55a,55b
M. Margoni,
55a,55b
M. Morandin,
55a
M. Posocco,
55a
M. Rotondo,
55a
F. Simonetto,
55a,55b
R. Stroili,
55a,55b
C. Voci,
55a,55b
P. del Amo Sanchez,
56
E. Ben-Haim,
56
G. R. Bonneaud,
56
H. Briand,
56
J. Chauveau,
56
O. Hamon,
56
Ph. Leruste,
56
G. Marchiori,
56
J. Ocariz,
56
A. Perez,
56
J. Prendki,
56
S. Sitt,
56
L. Gladney,
57
M. Biasini,
58a,58b
E. Manoni,
58a,58b
C. Angelini,
59a,59b
G. Batignani,
59a,59b
S. Bettarini,
59a,59b
G. Calderini,
59a,59b,
{
M. Carpinelli,
59a,59b,
**
A. Cervelli,
59a,59b
F. Forti,
59a,59b
M. A. Giorgi,
59a,59b
A. Lusiani,
59a,59c
M. Morganti,
59a,59b
N. Neri,
59a,59b
E. Paoloni,
59a,59b
G. Rizzo,
59a,59b
J. J. Walsh,
59a
D. Lopes Pegna,
60
C. Lu,
60
J. Olsen,
60
A. J. S. Smith,
60
A. V. Telnov,
60
F. Anulli,
61a
E. Baracchini,
61a,61b
G. Cavoto,
61a
R. Faccini,
61a,61b
F. Ferrarotto,
61a
F. Ferroni,
61a,61b
M. Gaspero,
61a,61b
P. D. Jackson,
61a
L. Li Gioi,
61a
M. A. Mazzoni,
61a
S. Morganti,
61a
G. Piredda,
61a
F. Renga,
61a,61b
C. Voena,
61a
M. Ebert,
62
T. Hartmann,
62
H. Schro
̈
der,
62
R. Waldi,
62
T. Adye,
63
B. Franek,
63
E. O. Olaiya,
63
F. F. Wilson,
63
S. Emery,
64
L. Esteve,
64
G. Hamel de Monchenault,
64
W. Kozanecki,
64
G. Vasseur,
64
Ch. Ye
`
che,
64
M. Zito,
64
M. T. Allen,
65
D. Aston,
65
R. Bartoldus,
65
J. F. Benitez,
65
PHYSICAL REVIEW D
80,
011101(R) (2009)
RAPID COMMUNICATIONS
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=
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=
80(1)
=
011101(7)
011101-1
Ó
2009 The American Physical Society
R. Cenci,
65
J. P. Coleman,
65
M. R. Convery,
65
J. C. Dingfelder,
65
J. Dorfan,
65
G. P. Dubois-Felsmann,
65
W. Dunwoodie,
65
R. C. Field,
65
M. Franco Sevilla,
65
A. M. Gabareen,
65
M. T. Graham,
65
P. Grenier,
65
C. Hast,
65
W. R. Innes,
65
J. Kaminski,
65
M. H. Kelsey,
65
H. Kim,
65
P. Kim,
65
M. L. Kocian,
65
D. W. G. S. Leith,
65
S. Li,
65
B. Lindquist,
65
S. Luitz,
65
V. Luth,
65
H. L. Lynch,
65
D. B. MacFarlane,
65
H. Marsiske,
65
R. Messner,
65,
*
D. R. Muller,
65
H. Neal,
65
S. Nelson,
65
C. P. O’Grady,
65
I. Ofte,
65
M. Perl,
65
B. N. Ratcliff,
65
A. Roodman,
65
A. A. Salnikov,
65
R. H. Schindler,
65
J. Schwiening,
65
A. Snyder,
65
D. Su,
65
M. K. Sullivan,
65
K. Suzuki,
65
S. K. Swain,
65
J. M. Thompson,
65
J. Va’vra,
65
A. P. Wagner,
65
M. Weaver,
65
C. A. West,
65
W. J. Wisniewski,
65
M. Wittgen,
65
D. H. Wright,
65
H. W. Wulsin,
65
A. K. Yarritu,
65
C. C. Young,
65
V. Ziegler,
65
X. R. Chen,
66
H. Liu,
66
W. Park,
66
M. V. Purohit,
66
R. M. White,
66
J. R. Wilson,
66
P. R. Burchat,
67
A. J. Edwards,
67
T. S. Miyashita,
67
S. Ahmed,
68
M. S. Alam,
68
J. A. Ernst,
68
B. Pan,
68
M. A. Saeed,
68
S. B. Zain,
68
A. Soffer,
69
S. M. Spanier,
70
B. J. Wogsland,
70
R. Eckmann,
71
J. L. Ritchie,
71
A. M. Ruland,
71
C. J. Schilling,
71
R. F. Schwitters,
71
B. C. Wray,
71
B. W. Drummond,
72
J. M. Izen,
72
X. C. Lou,
72
F. Bianchi,
73a,73b
D. Gamba,
73a,73b
M. Pelliccioni,
73a,73b
M. Bomben,
74a,74b
L. Bosisio,
74a,74b
C. Cartaro,
74a,74b
G. Della Ricca,
74a,74b
L. Lanceri,
74a,74b
L. Vitale,
74a,74b
V. Azzolini,
75
N. Lopez-March,
75
F. Martinez-Vidal,
75
D. A. Milanes,
75
A. Oyanguren,
75
J. Albert,
76
Sw. Banerjee,
76
B. Bhuyan,
76
H. H. F. Choi,
76
K. Hamano,
76
G. J. King,
76
R. Kowalewski,
76
M. J. Lewczuk,
76
I. M. Nugent,
76
J. M. Roney,
76
R. J. Sobie,
76
T. J. Gershon,
77
P. F. Harrison,
77
J. Ilic,
77
T. E. Latham,
77
G. B. Mohanty,
77
E. M. T. Puccio,
77
H. R. Band,
78
X. Chen,
78
S. Dasu,
78
K. T. Flood,
78
Y. Pan,
78
R. Prepost,
78
C. O. Vuosalo,
78
and S. L. Wu
78
(
B
A
B
AR
Collaboration)
1
Laboratoire d’Annecy-le-Vieux de Physique des Particules (LAPP), Universite
́
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, Universita
`
di Bari, I-70126 Bari, Italy
4
University of Bergen, Institute of Physics, N-5007 Bergen, Norway
5
Lawrence Berkeley National Laboratory and University of California, Berkeley, California 94720, USA
6
University of Birmingham, Birmingham, B15 2TT, United Kingdom
7
Ruhr Universita
̈
t Bochum, Institut fu
̈
r Experimentalphysik 1, D-44780 Bochum, Germany
8
University of 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 Riverside, Riverside, California 92521, USA
13
University of California at San Diego, La Jolla, California 92093, USA
14
University of California at Santa Barbara, Santa Barbara, California 93106, USA
15
University of California at Santa Cruz, Institute for Particle Physics, Santa Cruz, California 95064, USA
16
California Institute of Technology, Pasadena, California 91125, USA
17
University of Cincinnati, Cincinnati, Ohio 45221, USA
18
University of Colorado, Boulder, Colorado 80309, USA
19
Colorado State University, Fort Collins, Colorado 80523, USA
20
Technische Universita
̈
t Dortmund, Fakulta
̈
t Physik, D-44221 Dortmund, Germany
21
Technische Universita
̈
t Dresden, Institut fu
̈
r Kern- und Teilchenphysik, D-01062 Dresden, Germany
22
Laboratoire Leprince-Ringuet, CNRS/IN2P3, Ecole Polytechnique, F-91128 Palaiseau, France
23
University of Edinburgh, Edinburgh EH9 3JZ, United Kingdom
24a
INFN Sezione di Ferrara, I-44100 Ferrara, Italy
24b
Dipartimento di Fisica, Universita
`
di Ferrara, I-44100 Ferrara, Italy
25
INFN Laboratori Nazionali di Frascati, I-00044 Frascati, Italy
26a
INFN Sezione di Genova, I-16146 Genova, Italy
26b
Dipartimento di Fisica, Universita
`
di Genova, I-16146 Genova, Italy
27
Harvard University, Cambridge, Massachusetts 02138, USA
28
Universita
̈
t Heidelberg, Physikalisches Institut, Philosophenweg 12, D-69120 Heidelberg, Germany
29
Humboldt-Universita
̈
t zu Berlin, Institut fu
̈
r Physik, Newtonstr. 15, D-12489 Berlin, Germany
30
Imperial College London, London, SW7 2AZ, United Kingdom
31
University of Iowa, Iowa City, Iowa 52242, USA
32
Iowa State University, Ames, Iowa 50011-3160, USA
33
Johns Hopkins University, Baltimore, Maryland 21218, USA
B. AUBERT
et al.
PHYSICAL REVIEW D
80,
011101(R) (2009)
RAPID COMMUNICATIONS
011101-2
34
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
35
Lawrence Livermore National Laboratory, Livermore, California 94550, USA
36
University of Liverpool, Liverpool L69 7ZE, United Kingdom
37
Queen Mary, University of London, London, E1 4NS, United Kingdom
38
University of London, Royal Holloway and Bedford New College, Egham, Surrey TW20 0EX, United Kingdom
39
University of Louisville, Louisville, Kentucky 40292, USA
40
Johannes Gutenberg-Universita
̈
t Mainz, Institut fu
̈
r Kernphysik, D-55099 Mainz, Germany
41
University of Manchester, Manchester M13 9PL, United Kingdom
42
University of Maryland, College Park, Maryland 20742, USA
43
University of Massachusetts, Amherst, Massachusetts 01003, USA
44
Massachusetts Institute of Technology, Laboratory for Nuclear Science, Cambridge, Massachusetts 02139, USA
45
McGill University, Montre
́
al, Que
́
bec, Canada H3A 2T8
46a
INFN Sezione di Milano, I-20133 Milano, Italy
46b
Dipartimento di Fisica, Universita
`
di Milano, I-20133 Milano, Italy
47
University of Mississippi, University, Mississippi 38677, USA
48
Universite
́
de Montre
́
al, Physique des Particules, Montre
́
al, Que
́
bec, Canada H3C 3J7
49
Mount Holyoke College, South Hadley, Massachusetts 01075, USA
50a
INFN Sezione di Napoli, I-80126 Napoli, Italy
50b
Dipartimento di Scienze Fisiche, Universita
`
di Napoli Federico II, I-80126 Napoli, Italy
51
NIKHEF, National Institute for Nuclear Physics and High Energy Physics, NL-1009 DB Amsterdam, The Netherlands
52
University of Notre Dame, Notre Dame, Indiana 46556, USA
53
Ohio State University, Columbus, Ohio 43210, USA
54
University of Oregon, Eugene, Oregon 97403, USA
55a
INFN Sezione di Padova, I-35131 Padova, Italy
55b
Dipartimento di Fisica, Universita
`
di Padova, I-35131 Padova, Italy
56
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
57
University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
58a
INFN Sezione di Perugia, I-06100 Perugia, Italy
58b
Dipartimento di Fisica, Universita
`
di Perugia, I-06100 Perugia, Italy
59a
INFN Sezione di Pisa, I-56127 Pisa, Italy
59b
Dipartimento di Fisica, Universita
`
di Pisa, I-56127 Pisa, Italy
59c
Scuola Normale Superiore di Pisa, I-56127 Pisa, Italy
60
Princeton University, Princeton, New Jersey 08544, USA
61a
INFN Sezione di Roma, I-00185 Roma, Italy
61b
Dipartimento di Fisica, Universita
`
di Roma La Sapienza, I-00185 Roma, Italy
62
Universita
̈
t Rostock, D-18051 Rostock, Germany
63
Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, OX11 0QX, United Kingdom
64
CEA, Irfu, SPP, Centre de Saclay, F-91191 Gif-sur-Yvette, France
65
SLAC National Accelerator Laboratory, Stanford, California 94309 USA
66
University of South Carolina, Columbia, South Carolina 29208, USA
67
Stanford University, Stanford, California 94305-4060, USA
68
State University of New York, Albany, New York 12222, USA
69
Tel Aviv University, School of Physics and Astronomy, Tel Aviv, 69978, Israel
70
University of Tennessee, Knoxville, Tennessee 37996, USA
71
University of Texas at Austin, Austin, Texas 78712, USA
72
University of Texas at Dallas, Richardson, Texas 75083, USA
73a
INFN Sezione di Torino, I-10125 Torino, Italy
73b
Dipartimento di Fisica Sperimentale, Universita
`
di Torino, I-10125 Torino, Italy
74a
INFN Sezione di Trieste, I-34127 Trieste, Italy
**
Also with Universita
`
di Sassari, Sassari, Italy.
{
Also with 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.
k
Now at University of South Alabama, Mobile, AL 36688, USA.
x
Also with Universita
`
di Roma La Sapienza, I-00185 Roma, Italy.
‡
Also with Universita
`
di Perugia, Dipartimento di Fisica, Perugia, Italy.
†
Now at Temple University, Philadelphia, PA 19122, USA.
*
Deceased.
SEARCH FOR
B
0
MESON DECAYS TO
...
PHYSICAL REVIEW D
80,
011101(R) (2009)
RAPID COMMUNICATIONS
011101-3
74b
Dipartimento di Fisica, Universita
`
di Trieste, I-34127 Trieste, Italy
75
IFIC, Universitat de Valencia-CSIC, E-46071 Valencia, Spain
76
University of Victoria, Victoria, British Columbia, Canada V8W 3P6
77
Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom
78
University of Wisconsin, Madison, Wisconsin 53706, USA
(Received 7 May 2009; published 23 July 2009)
We describe searches for
B
0
meson decays to the charmless final states
0
K
0
S
K
0
S
,
K
0
S
K
0
S
, and
0
K
0
S
K
0
S
.
The data sample corresponds to
467
10
6
B
B
pairs produced in
e
þ
e
annihilation and collected with the
BABAR
detector at the SLAC National Accelerator Laboratory. We find no significant signals and
determine the 90% confidence level upper limits on the branching fractions, in units of
10
7
,
B
ð
B
0
!
0
K
0
S
K
0
S
Þ
<
9
,
B
ð
B
0
!
K
0
S
K
0
S
Þ
<
10
, and
B
ð
B
0
!
0
K
0
S
K
0
S
Þ
<
20
.
DOI:
10.1103/PhysRevD.80.011101
PACS numbers: 13.25.Hw, 12.15.Hh, 11.30.Er
The observation of mixing-induced
CP
violation in
B
0
!
J=
c
K
0
S
decays [
1
], as well as in the charmless
penguin-diagram dominated
B
0
!
0
K
0
decays [
2
], and
of direct
CP
violation both in the neutral kaon system [
3
]
and in
B
0
!
K
þ
decays [
4
], are in agreement with
predictions of the standard model (SM) of electroweak
interactions [
5
]. Further information about
CP
violation
and hadronic
B
decays can be provided by the measure-
ment of branching fractions and time-dependent
CP
asym-
metries in
B
decays to three-body final states containing
two identical neutral spin zero particles and another
CP
eigenstate spin zero particle [
6
].
CP
violating asymmetries
have already been measured in
B
0
decays to
K
0
S
K
0
S
K
0
S
[
7
]
and to
0
0
K
0
S
[
8
], and a search has been performed in
B
!
0
0
K
[
9
]. Other examples, in which study of time-
dependent
CP
violation asymmetry might be particularly
interesting, are the
B
0
decays to
0
K
0
S
K
0
S
,
K
0
S
K
0
S
, and
0
K
0
S
K
0
S
. There are no theoretical estimations for the
branching fractions of these SM-suppressed decay modes.
Contributions from physics beyond the SM may appear in
these decays.
Among
B
meson decays to final states containing two
kaons and an additional light meson, only
B
þ
!
K
þ
K
þ
has been observed, with a branching fraction
of
ð
5
:
0
0
:
5
0
:
5
Þ
10
6
[
10
]. In this analysis an un-
expected peak was observed around
1
:
5 GeV
=c
2
in the
K
þ
K
invariant-mass spectrum. Studies of decays with
two neutral or charged kaons in the final state, such as those
presented herein, may help to elucidate the nature of this
structure [
11
].
We present the results of searches for neutral
B
decays to
charmless final states
0
K
0
S
K
0
S
,
K
0
S
K
0
S
, and
0
K
0
S
K
0
S
,
which are studied for the first time. The results are based
on data collected with the
BABAR
detector [
12
] at the PEP-
II asymmetric-energy
e
þ
e
collider located at the SLAC
National Accelerator Laboratory. We use an integrated
luminosity of
426 fb
1
, corresponding to
467
10
6
B
B
pairs, recorded at the
ð
4
S
Þ
resonance (center-of-mass
energy
ffiffiffi
s
p
¼
10
:
58 GeV
) and, for the study of the back-
ground,
44 fb
1
collected 40 MeV below the resonance
(off-peak).
Charged particles from the
e
þ
e
interactions are de-
tected, and their momenta measured, by a combination of
five layers of double-sided silicon microstrip detectors and
a 40-layer drift chamber. Both systems operate in the 1.5 T
magnetic field of a superconducting solenoid. Photons and
electrons are identified with a CsI(Tl) crystal electromag-
netic calorimeter. Charged particle identification is pro-
vided by the average energy loss (
d
E=
d
x
) in the tracking
devices and by an internally reflecting, ring-imaging
Cherenkov detector covering the central region (DIRC).
A
K=
separation of better than 4 standard deviations (
)
is achieved for momenta below
3 GeV
=c
. Detector details
may be found elsewhere [
12
].
The
B
daughter candidates are reconstructed through
their dominant decays:
!
(
),
!
þ
0
(
3
) where
0
!
,
0
!
þ
(
0
) where
!
, and
0
!
0
(
0
) where
0
!
þ
. We require
the laboratory energy of the photons to be greater than
30 MeV for
0
in
3
, 50 MeV for
in
0
, and
100 MeV for
0
, and for
0
and
produced directly
from the
B
decay. We impose the following requirements
on the invariant mass (in
MeV
=c
2
) of the candidate final
states:
120
<m
ð
Þ
<
150
for
0
,
510
<m
ð
Þ
<
585
for
produced directly from the
B
decay,
490
<
m
ð
Þ
<
600
for
in
0
,
538
<m
ð
þ
0
Þ
<
558
for
3
,
945
<m
ð
þ
Þ
<
970
for
0
,
930
<
m
ð
þ
Þ
<
980
for
0
, and
470
<m
ð
þ
Þ
<
980
for
0
. Tracks from
and
0
candidate decays are rejected
if their particle identification signatures from the DIRC and
d
E=
d
x
are consistent with those of protons, kaons, or
electrons. Candidate
K
0
S
decays are formed from pairs of
oppositely charged tracks with
486
<m
ð
þ
Þ
<
510 MeV
=c
2
, a decay vertex
2
probability larger than
0.001, and a reconstructed decay length greater than 3
times its uncertainty.
We reconstruct the
B
meson candidate by combining
two
K
0
S
candidates and a
0
,
,or
0
candidate. From the
kinematics of the
ð
4
S
Þ
decays we determine the energy-
substituted mass
m
ES
¼
ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
1
4
s
p
2
B
q
and the energy differ-
ence
E
¼
E
B
1
2
ffiffiffi
s
p
, where
ð
E
B
;
p
B
Þ
is the
B
meson 4-
B. AUBERT
et al.
PHYSICAL REVIEW D
80,
011101(R) (2009)
RAPID COMMUNICATIONS
011101-4
momentum vector, and all values are expressed in the
ð
4
S
Þ
rest frame. The resolution is
3
:
0 MeV
=c
2
for
m
ES
and in the range (12–32) MeV for
E
, depending on the
decay mode. We require
5
:
25
<m
ES
<
5
:
29 GeV
=c
2
and
j
E
j
<
0
:
2 GeV
.
Backgrounds arise primarily from continuum
e
þ
e
!
q
q
events (
q
¼
u
,
d
,
s
,
c
). We reduce these with a require-
ment on the angle
T
between the thrust axis of the
B
candidate in the
ð
4
S
Þ
rest frame and that of the rest of the
charged tracks and neutral calorimeter clusters in the event
[
13
]. The distribution is sharply peaked near
j
cos
T
j¼
1
for
q
q
jet pairs and is nearly uniform for
B
meson decays.
The requirement is
j
cos
T
j
<
0
:
9
. For the
0
decays we
also use
j
cos
j
where the helicity angle
is defined as
the angle between the momenta of a daughter pion and the
0
, measured in the
0
meson rest frame. For
decays
we use
j
cos
j
where the decay angle
is defined as the
angle between the momenta of the most energetic daughter
photon and the
B
0
meson, measured in the
meson rest
frame. We require
j
cos
ð
Þ
j
<
0
:
9
. Events are retained
only if they contain at least one charged track in the decay
products of the other
B
meson (
B
tag
) from the
ð
4
S
Þ
decay.
This requirement improves the precision of the determi-
nation of
B
tag
thrust axis. The
B
0
!
0
K
0
S
K
0
S
decay has
background from
B
0
!
D
0
K
0
S
, with
D
0
!
0
K
0
S
, which
has the same final state as the signal mode. In order to
suppress this background, we define
m
ð
0
K
0
S
Þ
as the closer
of the two invariant-mass combinations to the nominal
D
0
mass [
14
]. By requiring
m
ð
0
K
0
S
Þ
to be outside the range
1
:
815
–
1
:
899 GeV
=c
2
, we veto 80% of this background.
We obtain the signal event yields from unbinned ex-
tended maximum likelihood (ML) fits. The observables
used in the fit are
E
,
m
ES
, and a Fisher discriminant
F
.
The Fisher discriminant
F
[
15
] is a linear combination of
four event shape variables and
j
T
j
, the absolute value of
the continuous output of a flavor tagging algorithm [
16
].
The event shape variables used for
F
are the angles, with
respect to the beam axis, of the
B
momentum and the
B
thrust axis in the
ð
4
S
Þ
frame, and the zeroth and second
angular moments,
L
0
;
2
, of the energy flow about the
B
thrust axis [
17
]. The moments are defined by
L
j
¼
P
i
p
i
j
cos
i
j
j
, where
i
is the angle, with respect to the
B
thrust
axis, of track or neutral cluster
i
, and
p
i
is its momentum.
The sum excludes the
B
candidate daughters. We use a
neural network based technique [
16
] to determine the
flavor at decay of the
B
tag
.
The coefficients of
F
are chosen to maximize the sepa-
ration between the signal and the continuum background.
They are determined from studies of Monte Carlo (MC)
[
18
] simulated signal data and off-peak data. Signal MC
events are distributed uniformly across the Dalitz plot.
Correlations among the ML input observables are below
10%. The average number of candidates found per selected
event is between 1.13 and 1.22, depending on the final
state. We choose the candidate with the highest
B
vertex
2
probability, determined from a vertex fit that includes both
charged and neutral particles [
19
]. From simulated events
we find that this algorithm selects the correct candidate in
(92–98)% of the events containing multiple candidates,
depending on the final state, and introduces negligible bias.
We use a MC simulation to estimate backgrounds from
other
B
decays, including final states with and without
charm. These contributions are negligible for the
0
mode. In all the other modes we introduce a non-peaking
B
B
component in the fit. In the
0
K
0
S
K
0
S
analysis we also
introduce a
B
B
background component that peaks in
m
ES
and
E
, to take into account the main contribution to
background from
B
0
!
K
0
S
K
0
S
K
0
S
decay mode. We consider
three components in the likelihood fit: signal, continuum,
and
B
B
background. We have studied the possibility of
misreconstruction of our
B
candidates. We divide signal
events into two subcomponents: correctly reconstructed
(COR) signal and self cross feed (SCF) signal, where at
least one
B
candidate daughter has been exchanged with a
particle from the rest of the event. The signal component is
split according to this classification. The fractions of SCF
events are fixed in the fit to the values found in MC
simulated events, which are in the range (10–21)%, de-
pending on the final state. For the
0
K
0
S
K
0
S
decay mode,
which has the lowest SCF fraction (6.6%), we use one
signal component, comprising COR and SCF events.
For each event
i
and component
j
, we define the proba-
bility density function (PDF)
P
i
j
¼
P
j
ð
m
i
ES
Þ
P
j
ð
E
i
Þ
P
j
ð
F
i
Þ
(1)
and the likelihood function
L
¼
e
ð
P
n
j
Þ
Y
N
i
¼
1
X
j
n
j
P
i
j
;
(2)
where
N
is the number of reconstructed events and
n
j
is the
number of events in component
j
which is returned by the
fit. We determine the PDF parameters from MC simulation
of the signal and
B
B
backgrounds, while we use
m
ES
and
E
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
background.
We parameterize
P
ð
m
ES
Þ
as a Chrystal Ball function
[
20
] for the COR and SCF signal subcomponents, an
ARGUS function [
21
] for continuum and non-peaking
B
B
background components, and by an ARGUS function
plus an asymmetric Gaussian distribution for peaking
B
B
background. The
P
ð
E
Þ
distribution is described by an
asymmetric Gaussian distribution plus an exponential tail
(AGT) [
22
] for the COR signal subcomponent, an asym-
metric Gaussian distribution plus a linear Chebyshev poly-
nomial or an AGT for the SCF, and Chebyshev
polynomials for continuum and
B
B
background compo-
nents. The distribution of
F
is described with an asym-
metric Gaussian distribution plus a Gaussian distribution
SEARCH FOR
B
0
MESON DECAYS TO
...
PHYSICAL REVIEW D
80,
011101(R) (2009)
RAPID COMMUNICATIONS
011101-5