of 8
Search for
B
þ
meson decay to
a
þ
1
ð
1260
Þ
K

0
ð
892
Þ
P. del Amo Sanchez,
1
J. P. Lees,
1
V. Poireau,
1
E. Prencipe,
1
V. Tisserand,
1
J. Garra Tico,
2
E. Grauges,
2
M. Martinelli,
3b,3a
A. Palano,
3b,3a
M. Pappagallo,
3b,3a
G. Eigen,
4
B. Stugu,
4
L. Sun,
4
M. Battaglia,
5
D. N. Brown,
5
B. Hooberman,
5
L. T. Kerth,
5
Yu. G. Kolomensky,
5
G. Lynch,
5
I. L. Osipenkov,
5
T. Tanabe,
5
C. M. Hawkes,
6
A. T. Watson,
6
H. Koch,
7
T. Schroeder,
7
D. J. Asgeirsson,
8
C. Hearty,
8
T. S. Mattison,
8
J. A. McKenna,
8
A. Khan,
9
A. Randle-Conde,
9
V. E. Blinov,
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
A. N. Yushkov,
10
M. Bondioli,
11
S. Curry,
11
D. Kirkby,
11
A. J. Lankford,
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
C. Campagnari,
13
T. M. Hong,
13
D. Kovalskyi,
13
J. D. Richman,
13
A. M. Eisner,
14
C. A. Heusch,
14
J. Kroseberg,
14
W. S. Lockman,
14
A. J. Martinez,
14
T. Schalk,
14
B. A. Schumm,
14
A. Seiden,
14
L. O. Winstrom,
14
C. H. Cheng,
15
D. A. Doll,
15
B. Echenard,
15
D. G. Hitlin,
15
P. Ongmongkolkul,
15
F. C. Porter,
15
A. Y. Rakitin,
15
R. Andreassen,
16
M. S. Dubrovin,
16
G. Mancinelli,
16
B. T. Meadows,
16
M. D. Sokoloff,
16
P. C. Bloom,
17
W. T. Ford,
17
A. Gaz,
17
M. Nagel,
17
U. Nauenberg,
17
J. G. Smith,
17
S. R. Wagner,
17
R. Ayad,
18,
*
W. H. Toki,
18
T. M. Karbach,
19
J. Merkel,
19
A. Petzold,
19
B. Spaan,
19
K. Wacker,
19
M. J. Kobel,
20
K. R. Schubert,
20
R. Schwierz,
20
D. Bernard,
21
M. Verderi,
21
P. J. Clark,
22
S. Playfer,
22
J. E. Watson,
22
M. Andreotti,
23b,23a
D. Bettoni,
23a
C. Bozzi,
23a
R. Calabrese,
23b,23a
A. Cecchi,
23b,23a
G. Cibinetto,
23b,23a
E. Fioravanti,
23b,23a
P. Franchini,
23b,23a
E. Luppi,
23b,23a
M. Munerato,
23b,23a
M. Negrini,
23b,23a
A. Petrella,
23b,23a
L. Piemontese,
23a
R. Baldini-Ferroli,
24
A. Calcaterra,
24
R. de Sangro,
24
G. Finocchiaro,
24
M. Nicolaci,
24
S. Pacetti,
24
P. Patteri,
24
I. M. Peruzzi,
24,
M. Piccolo,
24
M. Rama,
24
A. Zallo,
24
R. Contri,
25b,25a
E. Guido,
25b,25a
M. Lo Vetere,
25b,25a
M. R. Monge,
25b,25a
S. Passaggio,
25a
C. Patrignani,
25b,25a
E. Robutti,
25a
S. Tosi,
25b,25a
B. Bhuyan,
26
V. Prasad,
26
C. L. Lee,
27
M. Morii,
27
A. Adametz,
28
J. Marks,
28
U. Uwer,
28
F. U. Bernlochner,
29
M. Ebert,
29
H. M. Lacker,
29
T. Lueck,
29
A. Volk,
29
P. D. Dauncey,
30
M. Tibbetts,
30
P. K. Behera,
31
U. Mallik,
31
C. Chen,
32
J. Cochran,
32
H. B. Crawley,
32
L. Dong,
32
W. T. Meyer,
32
S. Prell,
32
E. I. Rosenberg,
32
A. E. Rubin,
32
A. V. Gritsan,
33
Z. J. Guo,
33
N. Arnaud,
34
M. Davier,
34
D. Derkach,
34
J. Firmino da Costa,
34
G. Grosdidier,
34
F. Le Diberder,
34
A. M. Lutz,
34
B. Malaescu,
34
A. Perez,
34
P. Roudeau,
34
M. H. Schune,
34
J. Serrano,
34
V. Sordini,
34,
A. Stocchi,
34
L. Wang,
34
G. Wormser,
34
D. J. Lange,
35
D. M. Wright,
35
I. Bingham,
36
C. A. Chavez,
36
J. P. Coleman,
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
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. Anderson,
42
R. Cenci,
42
A. Jawahery,
42
D. A. Roberts,
42
G. Simi,
42
J. M. Tuggle,
42
C. Dallapiccola,
43
E. Salvati,
43
R. Cowan,
44
D. Dujmic,
44
G. Sciolla,
44
M. Zhao,
44
D. Lindemann,
45
P. M. Patel,
45
S. H. Robertson,
45
M. Schram,
45
P. Biassoni,
46b,46a
A. Lazzaro,
46b,46a
V. Lombardo,
46a
F. Palombo,
46b,46a
S. Stracka,
46b,46a
L. Cremaldi,
47
R. Godang,
47,
x
R. Kroeger,
47
P. Sonnek,
47
D. J. Summers,
47
X. Nguyen,
48
M. Simard,
48
P. Taras,
48
G. De Nardo,
49b,49a
D. Monorchio,
49b,49a
G. Onorato,
49b,49a
C. Sciacca,
49b,49a
G. Raven,
50
H. L. Snoek,
50
C. P. Jessop,
51
K. J. Knoepfel,
51
J. M. LoSecco,
51
W. F. Wang,
51
L. A. Corwin,
52
K. Honscheid,
52
R. Kass,
52
J. P. Morris,
52
N. L. Blount,
53
J. Brau,
53
R. Frey,
53
O. Igonkina,
53
J. A. Kolb,
53
R. Rahmat,
53
N. B. Sinev,
53
D. Strom,
53
J. Strube,
53
E. Torrence,
53
G. Castelli,
54b,54a
E. Feltresi,
54b,54a
N. Gagliardi,
54b,54a
M. Margoni,
54b,54a
M. Morandin,
54a
M. Posocco,
54a
M. Rotondo,
54a
F. Simonetto,
54b,54a
R. Stroili,
54b,54a
E. Ben-Haim,
55
G. R. Bonneaud,
55
H. Briand,
55
G. Calderini,
55
J. Chauveau,
55
O. Hamon,
55
Ph. Leruste,
55
G. Marchiori,
55
J. Ocariz,
55
J. Prendki,
55
S. Sitt,
55
M. Biasini,
56b,56a
E. Manoni,
56b,56a
A. Rossi,
56b,56a
C. Angelini,
57b,57a
G. Batignani,
57b,57a
S. Bettarini,
57b,57a
M. Carpinelli,
57b,57a,
k
G. Casarosa,
57b,57a
A. Cervelli,
57b,57a
F. Forti,
57b,57a
M. A. Giorgi,
57b,57a
A. Lusiani,
57c,57a
N. Neri,
57b,57a
E. Paoloni,
57b,57a
G. Rizzo,
57b,57a
J. J. Walsh,
57a
D. Lopes Pegna,
58
C. Lu,
58
J. Olsen,
58
A. J. S. Smith,
58
A. V. Telnov,
58
F. Anulli,
59a
E. Baracchini,
59b,59a
G. Cavoto,
59a
R. Faccini,
59b,59a
F. Ferrarotto,
59a
F. Ferroni,
59b,59a
M. Gaspero,
59b,59a
L. Li Gioi,
59a
M. A. Mazzoni,
59a
G. Piredda,
59a
F. Renga,
59b,59a
T. Hartmann,
60
T. Leddig,
60
H. Schro
̈
der,
60
R. Waldi,
60
T. Adye,
61
B. Franek,
61
E. O. Olaiya,
61
F. F. Wilson,
61
S. Emery,
62
G. Hamel de Monchenault,
62
G. Vasseur,
62
Ch. Ye
`
che,
62
M. Zito,
62
M. T. Allen,
63
D. Aston,
63
D. J. Bard,
63
R. Bartoldus,
63
J. F. Benitez,
63
C. Cartaro,
63
M. R. Convery,
63
J. Dorfan,
63
G. P. Dubois-Felsmann,
63
W. Dunwoodie,
63
R. C. Field,
63
M. Franco Sevilla,
63
B. G. Fulsom,
63
A. M. Gabareen,
63
M. T. Graham,
63
P. Grenier,
63
C. Hast,
63
W. R. Innes,
63
M. H. Kelsey,
63
H. Kim,
63
P. Kim,
63
M. L. Kocian,
63
D. W. G. S. Leith,
63
S. Li,
63
B. Lindquist,
63
S. Luitz,
63
V. Luth,
63
H. L. Lynch,
63
D. B. MacFarlane,
63
H. Marsiske,
63
D. R. Muller,
63
H. Neal,
63
S. Nelson,
63
C. P. O’Grady,
63
I. Ofte,
63
M. Perl,
63
T. Pulliam,
63
B. N. Ratcliff,
63
A. Roodman,
63
A. A. Salnikov,
63
V. Santoro,
63
R. H. Schindler,
63
J. Schwiening,
63
A. Snyder,
63
D. Su,
63
M. K. Sullivan,
63
S. Sun,
63
PHYSICAL REVIEW D
82,
091101(R) (2010)
RAPID COMMUNICATIONS
1550-7998
=
2010
=
82(9)
=
091101(8)
091101-1
Ó
2010 The American Physical Society
K. Suzuki,
63
J. M. Thompson,
63
J. Va’vra,
63
A. P. Wagner,
63
M. Weaver,
63
C. A. West,
63
W. J. Wisniewski,
63
M. Wittgen,
63
D. H. Wright,
63
H. W. Wulsin,
63
A. K. Yarritu,
63
C. C. Young,
63
V. Ziegler,
63
X. R. Chen,
64
W. Park,
64
M. V. Purohit,
64
R. M. White,
64
J. R. Wilson,
64
S. J. Sekula,
65
M. Bellis,
66
P. R. Burchat,
66
A. J. Edwards,
66
T. S. Miyashita,
66
S. Ahmed,
67
M. S. Alam,
67
J. A. Ernst,
67
B. Pan,
67
M. A. Saeed,
67
S. B. Zain,
67
N. Guttman,
68
A. Soffer,
68
P. Lund,
69
S. M. Spanier,
69
R. Eckmann,
70
J. L. Ritchie,
70
A. M. Ruland,
70
C. J. Schilling,
70
R. F. Schwitters,
70
B. C. Wray,
70
J. M. Izen,
71
X. C. Lou,
71
F. Bianchi,
72b,72a
D. Gamba,
72b,72a
M. Pelliccioni,
72b,72a
M. Bomben,
73b,73a
L. Lanceri,
73b,73a
L. Vitale,
73b,73a
N. Lopez-March,
74
F. Martinez-Vidal,
74
D. A. Milanes,
74
A. Oyanguren,
74
J. Albert,
75
Sw. Banerjee,
75
H. H. F. Choi,
75
K. Hamano,
75
G. J. King,
75
R. Kowalewski,
75
M. J. Lewczuk,
75
I. M. Nugent,
75
J. M. Roney,
75
R. J. Sobie,
75
T. J. Gershon,
76
P. F. Harrison,
76
T. E. Latham,
76
E. M. T. Puccio,
76
H. R. Band,
77
S. Dasu,
77
K. T. Flood,
77
Y. Pan,
77
R. Prepost,
77
C. O. Vuosalo,
77
and S. L. Wu
77
(
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 Santa Barbara, Santa Barbara, California 93106, USA
14
University of California at Santa Cruz, Institute for Particle Physics, Santa Cruz, California 95064, USA
15
California Institute of Technology, Pasadena, California 91125, USA
16
University of Cincinnati, Cincinnati, Ohio 45221, USA
17
University of Colorado, Boulder, Colorado 80309, USA
18
Colorado State University, Fort Collins, Colorado 80523, USA
19
Technische Universita
̈
t Dortmund, Fakulta
̈
t Physik, D-44221 Dortmund, Germany
20
Technische Universita
̈
t Dresden, Institut fu
̈
r Kern- und Teilchenphysik, D-01062 Dresden, Germany
21
Laboratoire Leprince-Ringuet, CNRS/IN2P3, Ecole Polytechnique, F-91128 Palaiseau, France
22
University of Edinburgh, Edinburgh EH9 3JZ, United Kingdom
23a
INFN Sezione di Ferrara, I-44100 Ferrara, Italy
23b
Dipartimento di Fisica, Universita
`
di Ferrara, I-44100 Ferrara, Italy
24
INFN Laboratori Nazionali di Frascati, I-00044 Frascati, Italy
25a
INFN Sezione di Genova, I-16146 Genova, Italy
25b
Dipartimento di Fisica, Universita
`
di Genova, I-16146 Genova, Italy
26
Indian Institute of Technology Guwahati, Guwahati, Assam, 781 039, India
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
34
Laboratoire de l’Acce
́
le
́
rateur Line
́
aire, IN2P3/CNRS et Universite
́
Paris-Sud 11, center 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
P. DEL AMO SANCHEZ
et al.
PHYSICAL REVIEW D
82,
091101(R) (2010)
RAPID COMMUNICATIONS
091101-2
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
49a
INFN Sezione di Napoli, I-80126 Napoli, Italy
49b
Dipartimento di Scienze Fisiche, Universita
`
di Napoli Federico II, I-80126 Napoli, Italy
50
NIKHEF, National Institute for Nuclear Physics and High Energy Physics, NL-1009 DB Amsterdam, The Netherlands
51
University of Notre Dame, Notre Dame, Indiana 46556, USA
52
Ohio State University, Columbus, Ohio 43210, USA
53
University of Oregon, Eugene, Oregon 97403, USA
54a
INFN Sezione di Padova, I-35131 Padova, Italy
54b
Dipartimento di Fisica, Universita
`
di Padova, I-35131 Padova, Italy
55
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
56a
INFN Sezione di Perugia, I-06100 Perugia, Italy
56b
Dipartimento di Fisica, Universita
`
di Perugia, I-06100 Perugia, Italy
57a
INFN Sezione di Pisa, I-56127 Pisa, Italy
57b
Dipartimento di Fisica, Universita
`
di Pisa, I-56127 Pisa, Italy
57c
Scuola Normale Superiore di Pisa, I-56127 Pisa, Italy
58
Princeton University, Princeton, New Jersey 08544, USA
59a
INFN Sezione di Roma, I-00185 Roma, Italy
59b
Dipartimento di Fisica, Universita
`
di Roma La Sapienza, I-00185 Roma, Italy
60
Universita
̈
t Rostock, D-18051 Rostock, Germany
61
Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, OX11 0QX, United Kingdom
62
CEA, Irfu, SPP, Centre de Saclay, F-91191 Gif-sur-Yvette, France
63
SLAC National Accelerator Laboratory, Stanford, California 94309 USA
64
University of South Carolina, Columbia, South Carolina 29208, USA
65
Southern Methodist University, Dallas, Texas 75275, USA
66
Stanford University, Stanford, California 94305-4060, USA
67
State University of New York, Albany, New York 12222, USA
68
Tel Aviv University, School of Physics and Astronomy, Tel Aviv, 69978, Israel
69
University of Tennessee, Knoxville, Tennessee 37996, USA
70
University of Texas at Austin, Austin, Texas 78712, USA
71
University of Texas at Dallas, Richardson, Texas 75083, USA
72a
INFN Sezione di Torino, I-10125 Torino, Italy
72b
Dipartimento di Fisica Sperimentale, Universita
`
di Torino, I-10125 Torino, Italy
73a
INFN Sezione di Trieste, I-34127 Trieste, Italy
73b
Dipartimento di Fisica, Universita
`
di Trieste, I-34127 Trieste, Italy
74
IFIC, Universitat de Valencia-CSIC, E-46071 Valencia, Spain
75
University of Victoria, Victoria, British Columbia, Canada V8W 3P6
76
Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom
77
University of Wisconsin, Madison, Wisconsin 53706, USA
(Received 19 July 2010; published 3 November 2010)
We present a search for the decay
B
þ
!
a
þ
1
ð
1260
Þ
K

0
ð
892
Þ
. The data, collected with the
BABAR
detector at the SLAC National Accelerator Laboratory, represent
465

10
6
B

B
pairs produced in
e
þ
e

annihilation at the energy of the

ð
4
S
Þ
. We find no significant signal and set an upper limit at 90%
*
Present address: Temple University, Philadelphia, PA 19122, USA
Also at Universita
`
di Perugia, Dipartimento di Fisica, Perugia, Italy
Also at Universita
`
di Roma La Sapienza, I-00185 Roma, Italy
x
Present address: University of South AL, Mobile, AL 36688, USA
k
Also at Universita
`
di Sassari, Sassari, Italy
{
Also with Universita
`
di Sassari, Sassari, Italy.
SEARCH FOR
B
þ
MESON DECAY TO
a
þ
1
ð
1260
Þ
K

0
ð
892
Þ
PHYSICAL REVIEW D
82,
091101(R) (2010)
RAPID COMMUNICATIONS
091101-3
confidence level on the product of branching fractions
B
ð
B
þ
!
a
þ
1
ð
1260
Þ
K

0
ð
892
ÞÞ
B
ð
a
þ
1
ð
1260
Þ!

þ



þ
Þ
of
1
:
8

10

6
.
DOI:
10.1103/PhysRevD.82.091101
PACS numbers: 13.25.Hw, 12.15.Hh, 11.30.Er
Measurements of the branching fractions and polariza-
tions of charmless hadronic
B
decays are useful tests of the
standard model and a means to search for new physics
effects. In decays of
B
mesons to a pair of spin-one mesons,
the longitudinal polarization,
f
L
, is particularly interesting.
Simple helicity arguments favor
f
L
to be close to 1, but
several vector-vector (
VV
) decay modes such as
B
!
K

[
1
] and
B
þ
!

þ
K

0
[
2
,
3
] are observed to favor
f
L

0
:
5
.
Possible explanations for this discrepancy have been pro-
posed within the standard model [
4
] as well as in new
physics scenarios [
5
].
New ways to explore the size of contributing amplitudes
in charmless
B
meson decays and their helicity structure
may come from measurements of the branching fractions
and polarization of charmless decays of
B
mesons to an
axial-vector meson and a vector meson (
AV
) or to an axial-
vector meson and a pseudoscalar meson (
AP
)[
6
].
Theoretical decay rates have been predicted with the
naı
̈
ve factorization (NF) [
7
] and QCD factorization
(QCDF) [
8
] approaches. The NF calculations find the decay
rates of
B
!
AV
modes to be smaller than the correspond-
ing
B
!
AP
modes. The more complex QCDF calculations
find the reverse. For example, QCDF predicts a branching
fraction of
ð
11
þ
6
:
1
þ
31
:
9

4
:
4

9
:
0
Þ
10

6
for
B
þ
!
a
þ
1
K

0
and
ð
32
þ
16
:
5
þ
12
:
0

14
:
7

4
:
6
Þ
10

6
for
B
0
!
b

1

þ
, while NF predicts
a branching fraction of
0
:
51

10

6
and
1
:
6

10

6
, re-
spectively. The first uncertainty on the QCDF prediction
corresponds to the uncertainties due to the variation of
Gegenbauer moments, decay constants, quark masses,
form factors, and a
B
meson wave function parameter and
the second uncertainty corresponds to the uncertainties due
to the variation of penguin annihilation parameters. The NF
prediction does not give an uncertainty on their value.
B
meson decays to charmless
AV
final states are sensi-
tive to penguin annihilation contributions, which enhance
some decay modes while suppressing others. Thus, inves-
tigating decays to many final states will help determine the
size of the contributing amplitudes.
A number of searches for
AV
decays to the final states
a
þ
1


,
b
1

,and
b
1
K

are presented in Refs. [
9
,
10
], with
upper limits on the branching fractions of
30

10

6
at 90%
confidence level (C.L.) for
a
þ
1


and from 1.4 to
8
:
0

10

6
at 90% C.L. for the
b
1

and
b
1
K

final states. In this
paper, we present a search for the decay
B
þ
!
a
þ
1
K

0
.
The data for this measurement were collected with the
BABAR
detector [
11
] at the PEP-II asymmetric-energy
e
þ
e

storage ring located at the SLAC National
Accelerator Laboratory. An integrated luminosity of
424 fb

1
, corresponding to
ð
465

5
Þ
10
6
B

B
pairs,
was produced in
e
þ
e

annihilation at the

ð
4
S
Þ
resonance
(center-of-mass energy
ffiffiffi
s
p
¼
10
:
58 GeV
).
A detailed Monte Carlo program (MC) is used to simu-
late the
B
meson production and decay sequences, and the
detector response [
12
]. Dedicated samples of MC events
for the decay
B
þ
!
a
þ
1
K

0
with
a
þ
1
!

0

þ
and
K

0
!
K
þ


were produced. For the
a
þ
1
meson parameters, we
use the values given in Ref. [
13
] for studies with MC while
for fits to the data we use a mass of
1229 MeV
=c
2
and a
width of
393 MeV
=c
2
, which were extracted from
B
0
!
a
þ
1


decays [
14
]. We account for the uncertainties of
these resonance parameters in the determination of system-
atic uncertainties. The
a
þ
1
!

þ



þ
decay proceeds
mainly through the intermediate states

0

þ
and

þ
[
13
]. No attempt is made to separate contributions of the
dominant
P
wave

0
from the
S
wave

in the channel

þ


. The difference in efficiency for the
S
wave and
P
wave cases is accounted for as a systematic uncertainty.
We reconstruct
a
þ
1
candidates through the decay se-
quence
a
þ
1
!

0

þ
and

0
!

þ


. The other primary
daughter of the
B
meson is reconstructed as
K

0
!
K
þ


.
Candidates for the charged kaons must have particle iden-
tification signatures consistent with those of kaons.
Candidates for the charged pions must not be classified
as protons, kaons, or electrons. We constrain the range of
mass of reconstructed final-state candidates: between 0.55
and
1
:
0 GeV
=c
2
for the

0
, between 0.9 and
1
:
8 GeV
=c
2
for the
a
þ
1
, and between 0.8 and
1
:
0 GeV
=c
2
for the
K

0
.
B
þ
candidates are formed by combining
a
þ
1
and
K

0
candidates. The five final decay tracks in a candidate are fit
to a common vertex. Candidates which have a

2
proba-
bility for the fit greater than 0.01 are retained. For these
candidates, we calculate the energy substituted mass,
m
ES
¼
ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
1
4
s

p
2
B
q
, and the energy difference,

E
¼
E
B

1
2
ffiffiffi
s
p
, where
ð
E
B
;
p
B
Þ
is the
B
meson energy-momentum
four-vector, all values being expressed in the

ð
4
S
Þ
rest
frame. We keep candidates with
5
:
25 GeV
=c
2
<m
ES
<
5
:
29 GeV
=c
2
and
j

E
j
<
100 MeV
.
We also impose restrictions on the helicity-frame decay
angle

K

0
of the
K

0
mesons. The helicity frame of a
meson is defined as the rest frame of that meson, where
the
z
axis is the direction along which the boost is per-
formed from the parent’s frame to this frame. For the decay
K

0
!
K
þ


,

K

0
is the polar angle of the daughter kaon,
and for
a
þ
1
!

0

þ
,

a
þ
1
is the polar angle of the normal to
the
a
þ
1
!
3

decay plane. We define
H
i
¼
cos
ð

i
Þ
, where
i
¼ð
K

0
;a
þ
1
Þ
. Since many background candidates accumu-
late near
j
H
K

0
1
, we require

0
:
98

H
K

0

0
:
8
.
Backgrounds arise primarily from random combinations
of particles in continuum
e
þ
e

!
q

q
events (
q
¼
u
,
d
,
s
,
c
). We reduce this background source with a requirement
on the angle

T
between the thrust axis [
15
] of the
B
þ
P. DEL AMO SANCHEZ
et al.
PHYSICAL REVIEW D
82,
091101(R) (2010)
RAPID COMMUNICATIONS
091101-4
candidate in the

ð
4
S
Þ
frame and that of the charged tracks
and neutral calorimeter clusters of the rest of the event.
The distribution is sharply peaked near
j
cos

T
1
for
jetlike continuum events, and nearly uniform for
B
meson
decays. Optimizing the ratio of the signal yield to its (back-
ground dominated) uncertainty, we require
j
cos

T
j
<
0
:
8
.
A secondary source of background arises from
b
!
c
transitions. We reduce this background by eliminating
events in which one of the pions in the
B
þ
candidate is
also part of a
D
candidate.
Such
D
candidates, reconstructed from
K


þ
and
K


þ

þ
, are required to have an invariant mass within
0
:
02 GeV
=c
2
of the nominal
D
meson mass.
The number of events which pass the selection is 15 802.
The average number of candidates found per event in the
selected data sample is 1.5 (2.0 to 2.4 in signal MC depend-
ing on the polarization).
We define a neural network for use in selecting the best
B
þ
candidate. The

2
probability of the vertex fit and the

meson mass were the input variables to the neural network.
Thereby we find 13% to 22%, depending on the polariza-
tion, of the candidates were incorrectly reconstructed from
particles in events that contain a true signal candidate.
To further discriminate against
q

q
background we con-
struct a Fisher discriminant
F
[
16
] which is a function of
four variables: the polar angles of the
B
þ
candidate mo-
mentum and of the
B
þ
thrust axis with respect to the beam
axis in the

ð
4
S
Þ
rest frame; and the zeroth (second)
angular moment
L
0
(
L
2
) of the energy flow, excluding
the
B
candidate, with respect to the
B
thrust axis. 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 a track or
neutral cluster
i
, and
p
i
is its momentum.
We obtain yields and the longitudinal polarization
f
L
from an extended maximum likelihood (ML) fit with the
seven input observables

E
,
m
ES
,
F
, the resonance masses
m
a
þ
1
and
m
K

0
, and the helicity variables
H
K

0
and
H
a
þ
1
.
Since the correlation between the observables in the se-
lected data and in MC signal events is small, we take the
probability density function (PDF) for each event to be a
product of the PDFs for the individual observables.
Corrections for the effects of possible correlations, referred
to as fit bias yield, are made on the basis of MC studies
described below. The components in the ML fit used are
signal,
q

q
background, charm
B

B
background, charmless
B

B
background, and
B
þ
!
a
þ
2
K

0
background. The signal
component includes true signal events where decay prod-
ucts of intermiediate resonances are incorrectly assigned,
or particles from the rest of the event are included
We determine the PDFs for the signal and
B

B
back-
ground components from fits to MC samples. We develop
PDF parametrizations for the
q

q
background with fits to
the data from which the signal region (
5
:
26 GeV
=c
2
<
m
ES
<
5
:
29 GeV
=c
2
and
j

E
j
<
60 MeV
) has been
excluded.
For the signal, the
m
ES
and

E
distributions are
parametrized as a sum of a crystal-ball function [
17
]
and a Gaussian function. In the case of
m
ES
for
q

q
and
B

B
backgrounds we use the threshold function
x
ffiffiffiffiffiffiffiffiffiffiffiffiffiffi
1

x
2
p
exp
½

ð
1

x
2
Þ
, where the argument
x

2
m
ES
=
ffiffiffi
s
p
and

is a shape parameter. This function is
discussed in more detail in Ref. [
18
]. In the case of

E
for
q

q
and
B

B
backgrounds we use a polynomial function.
The PDFs for the Fisher discriminant
P
j
ð
F
Þ
are parame-
trized as a single Gaussian function or a sum of two such
functions. The PDFs for the invariant masses of the
a
þ
1
and
K

0
mesons for all components are constructed as sums of
a relativistic Breit-Wigner function and a polynomial func-
tion. We use a joint PDF
P
j
ð
H
K

0
;
H
a
þ
1
Þ
for the helicity
distributions. The signal and the
B
þ
!
a
þ
2
K

0
background
component is parametrized as the product of the corre-
sponding ideal angular distribution in
H
K

0
and
H
a
þ
1
times an empirical acceptance function
G
ð
H
K

0
;
H
a
þ
1
Þ
.
The ideal angular distribution from Ref. [
19
] where

, the
angle between the decay planes of the
a
þ
1
meson candidate
and the
K

0
meson candidate, is integrated out are
P
ideal
signal
ð
H
K

0
;
H
a
þ
1
Þ¼
f
L
1

H
2
K

0
Þ
H
2
a
þ
1
þ
1
4
ð
1

f
L
Þð
1
þ
H
2
K

0
Þð
1

H
2
a
þ
1
Þ
for signal component and
P
ideal
B
þ
!
a
þ
2
K

0
ð
H
K

0
;
H
a
þ
1
Þ¼
f
L

H
2
K

0
ð
1

H
2
K

0
Þ
H
2
a
þ
1
þ
1
4
ð
1

f
L
Þ
1
3
ð
4
H
4
K

0

3
H
2
K

0
þ
1
Þð
1

H
2
a
þ
1
Þ
for the
B
þ
!
a
þ
2
K

0
background component. The helicity
PDF for the
q

q
and
B

B
background components is simply
the product of the helicity PDFs for
H
K

0
and
H
a
þ
1
. The
H
i
distributions for these components are based on
Gaussian and polynomial functions.
The likelihood function is
L
¼
e


P
j
Y
j

N
!
Y
N
i
X
j
Y
j

P
j
ð
m
ES
i
Þ
P
j
ð
F
i
Þ
P
j
ð

E
i
Þ

P
j
ð
m
i
a
þ
1
Þ
P
j
ð
m
i
K

0
Þ
P
j
ð
H
i
K

0
;
H
i
a
þ
1
Þ
;
where
N
is the number of events in the sample, and for each
component
j
(signal,
q

q
background,
b
!
c
transition
B

B
background, charmless
B

B
background, or
B
þ
!
a
þ
2
K

0
background),
Y
j
is the yield of component
j
, and
P
j
ð
x
i
Þ
is
the probability for variable
x
of event
i
to belong to
component
j
. We allow the most important parameters
(first coefficient of the polynomial function for

E
, the
invariant masses of the
a
þ
1
and the
K

0
, and the width of
the Breit-Wigner for the invariant mass of the
K

0
) for the
determination of the combinatorial background PDFs to
vary in the fit, along with the yields for the signal,
q

q
background, and
b
!
c
transition
B

B
background.
SEARCH FOR
B
þ
MESON DECAY TO
a
þ
1
ð
1260
Þ
K

0
ð
892
Þ
PHYSICAL REVIEW D
82,
091101(R) (2010)
RAPID COMMUNICATIONS
091101-5
We validate the fitting procedure by applying it to en-
sembles of simulated experiments with the
q

q
component
drawn from the PDF, and with embedded known numbers
of signal and
B

B
background events randomly extracted
from the fully simulated MC samples. By tuning the num-
ber of embedded events until the fit reproduces the yields
found in the data, we find a positive bias yield
Y
b
,tobe
subtracted from the observed signal yield
Y
. The fit bias
yield arises from the neglected correlations in signal and
B

B
background events.
The corresponding numbers are reported in Table
I
.We
do not find a significant signal thus we do not report a
measurement on the quantity
f
L
. In order to obtain the
most conservative upper limit, we assume
f
L
¼
1
in esti-
mating the branching fraction.
We compute the branching fraction by subtracting the fit
bias yield from the measured yield and dividing the result by
the number of produced
B

B
pairs and by the product of the
selection efficiency and the branching ratio for the
B
ð
K

0
!
K
þ

þ
Þ
decay. We assume that the branching fractions of
the

ð
4
S
Þ
to
B
þ
B

and
B
0

B
0
are equal, consistent with
measurements [
13
]. The efficiency for longitudinally and
transversely polarized signal events, obtained from the MC
signal model, is 12.9% and 18.6%, respectively. The results
are given in Table
I
, along with the significance,
S
, com-
puted as the square root of the difference between the value
of

2ln
L
(with additive systematic uncertainties included)
for zero signal and the value at its minimum. In Fig.
1
we
show the projections of data with PDFs overlaid. The data
plotted are subsamples enriched in signal with the require-
ment of a minimum value of the ratio of signal to total
likelihood, computed without the plotted variable. We used
0.9 as the requirement on the ratio in Fig.
1
for each variable.
The efficiency of these requirements for signal is between
57% and 70% depending on the variable.
Systematic uncertainties on the branching fraction arise
from the imperfect knowledge of the PDFs,
B

B
back-
grounds, fit bias yield, and efficiency. PDF uncertainties
not already accounted for by free parameters in the fit are
estimated from varying the signal-PDF parameters within
their uncertainties. For
K

0
resonance parameters we use
the uncertainties from Ref. [
13
] and for the
a
þ
1
resonance
parameters from Ref. [
14
]. The uncertainty from fit bias
yield (Table
I
) includes its statistical uncertainty from the
simulated experiments, and half of the correction itself,
added in quadrature.
To determine the systematic uncertainty arising from our
imperfect knowledge of the branching fractions of charm-
less
B
decays, we vary the charmless
B

B
background
component yield by 100%. We conservatively assume
that the branching ratio of
B
þ
!
a
þ
2
K

0
could be as large
as that of
B
þ
!
a
þ
1
K

0
and vary the
B
þ
!
a
þ
2
K

0
from 0
to 18 events around a fixed yield of 9 events used for the
B
þ
!
a
þ
2
K

0
component in the likelihood function.
The uncertainty associated with
f
L
is estimated by tak-
ing the difference in the measured branching fraction
between the nominal fit (
f
L
¼
1
) and the maximum and
minimum values found in the scan along the range [0, 1].
We divide these values by
ffiffiffi
3
p
, motivated by our assump-
tion of a flat prior for
f
L
in its physical range.
Uncertainties in our knowledge of the tracking effi-
ciency are 0.4% per track in the
B
þ
candidate. This is
estimated within the tracking efficiency determination,
which is based on
lepton decays. The uncertainties in
TABLE I. Summary of results for
B
þ
!
a
þ
1
K

0
. Signal yield
Y
, fit bias yield
Y
b
, the branching fraction
B
¼
B
ð
B
þ
!
a
þ
1
K

0
Þ
B
ð
a
þ
1
!

þ



þ
Þ
, significance
S
(see text), and
upper limit (UL). The given uncertainties on fit yields are
statistical only, while the uncertainties on the fit bias yield
include the corresponding systematic uncertainties. The branch-
ing fraction of
K

0
!
K
þ


is assumed to be
2
3
.
YY
b
B
ð
10

6
Þ
S
UL
ð
10

6
Þ
61
þ
23

21
34

17
0
:
7
þ
0
:
5
þ
0
:
6

0
:
5

1
:
3
0.5
1.8
)
2
(GeV/c
ES
m
5.25 5.26 5.27 5.28 5.29
5.3
2
Events / 3.6 MeV/c
0
20
40
a)
E (GeV)
-0.1
-0.05
0
0.05
0.1
Events / 14.3 MeV
0
10
20
30
40
b)
-2
-1
0
1
2
Events / 0.22
0
20
40
60
80
c)
)
2
(GeV/c
+
π
0
ρ
m
1
1.2
1.4
1.6
1.8
2
Events / 90 MeV/c
0
20
40
60
d)
)
2
(GeV/c
-
π
+
K
m
0.8
0.85
0.9
0.95
1
2
Events / 20 MeV/c
0
20
40
60
80
e)
*0
K
-0.5
0
0.5
Events / 0.22
0
50
100
f)
+
1
a
-1
-0.5
0
0.5
1
Events / 0.16
0
20
40
60
g)
FIG. 1 (color online). Distributions for signal-enhanced sub-
sets (see text) of the data projected onto the fit observables for
the decay
B
þ
!
a
þ
1
K

0
; (a)
m
ES
, (b)

E
, (c)
F
, (d)
m
ð

Þ
for
the
a
þ
1
candidate, (e)
m
ð
K
Þ
for the
K

0
candidate, (f)
H
K

0
,
and (g)
H
a
þ
1
. The solid lines represent the results of the fit, and
the dot-dashed and dashed lines the signal and background
contributions, respectively. These plots are made with require-
ments (see text) on the ratio of signal to total likelihood,
computed without the plotted variable.
P. DEL AMO SANCHEZ
et al.
PHYSICAL REVIEW D
82,
091101(R) (2010)
RAPID COMMUNICATIONS
091101-6
the efficiency from the event selection are below 0.6%. The
systematic uncertainty on the measurement of the inte-
grated luminosity is 1.1%. All systematic uncertainties
on the branching fraction are summarized in Table
II
.
We obtain a central value for the product of branching
fractions:
B
ð
B
þ
!
a
þ
1
K

0
Þ
B
ð
a
þ
1
!

þ



þ
Þ
¼ð
0
:
7
þ
0
:
5
þ
0
:
6

0
:
5

1
:
3
Þ
10

6
;
where the first uncertainty quoted is statistical, the second
systematic. Including systematic uncertainties, this result
corresponds to an upper limit at 90% confidence level of
1
:
8

10

6
.
Assuming
B
ð
a

1
ð
1260
Þ!

þ




Þ
is equal to
B
ð
a

1
ð
1260
Þ!



0

0
Þ
, and that
B
ð
a

1
ð
1260
Þ!
3

Þ
is equal to 100%, we obtain a central value:
B
ð
B
þ
!
a
þ
1
K

0
Þ¼ð
1
:
3
þ
1
:
1
þ
1
:
1

1
:
0

2
:
6
Þ
10

6
;
where the first uncertainty quoted is statistical, the second
systematic. Including systematic uncertainties, this result
corresponds to an upper limit at 90% confidence level of
3
:
6

10

6
.
This upper limit is in agreement with the prediction from
naı
̈
ve factorization and lower than, but not inconsistent
with that of QCD factorization.
We are grateful for the extraordinary contributions of
our PEP-II colleagues in achieving the excellent luminos-
ity and machine conditions that have made this work
possible. The success of this project also relies critically
on the expertise and dedication of the computing organ-
izations that support
BABAR
. The collaborating institutions
wish to thank SLAC for its support and the kind hospitality
extended to them. This work is supported by the U.S.
Department of Energy and National Science Foundation,
the Natural Sciences and Engineering Research Council
(Canada), the Commissariat a
`
l’Energie Atomique and
Institut National de Physique Nucle
́
aire et de Physique
des Particules (France), the Bundesministerium fu
̈
r
Bildung und Forschung and Deutsche Forschungsge-
meinschaft (Germany), the Istituto Nazionale di Fisica
Nucleare (Italy), the Foundation for Fundamental
Research on Matter (The Netherlands), the Research
Council of Norway, the Ministry of Education and
Science of the Russian Federation, Ministerio de Ciencia
e Innovacio
́
n (Spain), and the Science and Technology
Facilities Council (United Kingdom). Individuals have
received support from the Marie-Curie IEF program
(European Union), the A. P. Sloan Foundation (USA) and
the Binational Science Foundation (USA-Israel).
[1] B. Aubert
et al.
(
B
A
B
AR
Collaboration),
Phys. Rev. Lett.
91
, 171802 (2003)
; K. F. Chen
et al.
(Belle Collaboration),
Phys. Rev. Lett.
91
, 201801 (2003)
.
[2] Charge-conjugate reactions are implied.
[3] K. Abe
et al.
(Belle Collaboration),
Phys. Rev. Lett.
95
,
141801 (2005)
; B. Aubert
et al.
(
B
A
B
AR
Collaboration),
Phys. Rev. Lett.
97
, 201801 (2006)
.
[4] C. W. Bauer
et al.
,
Phys. Rev. D
70
, 054015 (2004)
;P.
Colangelo, F. De Fazio, and T. N. Pham,
Phys. Lett. B
597
,
291 (2004)
; A. L. Kagan,
Phys. Lett. B
601
, 151 (2004)
;
M. Ladisa
et al.
,
Phys. Rev. D
70
, 114025 (2004)
;H.Y.
Cheng, C. K. Chua, and A. Soni,
Phys. Rev. D
71
, 014030
(2005)
; H.-n. Li and S. Mishima,
Phys. Rev. D
71
, 054025
(2005)
; H.-n. Li,
Phys. Lett. B
622
, 63 (2005)
.
[5] A. K. Giri and R. Mohanta,
Phys. Rev. D
69
, 014008
(2004)
; E. Alvarez
et al.
,
Phys. Rev. D
70
, 115014
(2004)
; P. K. Das and K. C. Yang,
Phys. Rev. D
71
,
094002 (2005)
; C.-H. Chen and C.-Q. Geng,
Phys. Rev.
D
71
, 115004 (2005)
; Y.-D. Yang, R. M. Wang, and G. R.
Lu,
Phys. Rev. D
72
, 015009 (2005)
; A. K. Giri and R.
Mohanta,
Eur. Phys. J. C
44
, 249 (2005)
; S. Baek
et al.
,
Phys. Rev. D
72
, 094008 (2005)
; W. Zou and Z. Xiao,
Phys. Rev. D
72
, 094026 (2005)
; Q. Chang, X.-Q. Li, and
Y. D. Yang,
J. High Energy Phys. 06 (2007) 038
.
TABLE II. Summary of systematic uncertainties of the deter-
mination of the
B
þ
!
a
þ
1
K

0
branching fraction.
Source of systematic uncertainty
Additive uncertainty (events)
PDF parametrization
4
a
þ
1
meson parametrization
6
ML fit bias yield
17
Nonresonant charmless
B

B
background
3
B
þ
!
a
þ
2
K

0
charmless background
6
Remaining charmless
B

B
background
7
Total additive (events)
22
Multiplicative uncertainty (%)
Tracking efficiency
1.8
Determination of the integrated luminosity
1.1
MC statistics (signal efficiency)
0.6
Differences in selection efficiency for
a
þ
1
decay
3.3
Particle identification
1.4
Event shape restriction (
cos

T
)
1.0
Total multiplicative (%)
4.3
Variation of
f
L
[
B
ð
10

6
Þ
]
þ
0
:
0

1
:
2
Total systematic uncertainty [
B
ð
10

6
Þ
]
þ
0
:
6

1
:
3
SEARCH FOR
B
þ
MESON DECAY TO
a
þ
1
ð
1260
Þ
K

0
ð
892
Þ
PHYSICAL REVIEW D
82,
091101(R) (2010)
RAPID COMMUNICATIONS
091101-7
[6] H.-Y. Cheng and J. G. Smith,
Annu. Rev. Nucl. Part. Sci.
59
, 215 (2009)
.
[7] G. Calderon, J. H. Munoz, and C. E. Vera,
Phys. Rev. D
76
,
094019 (2007)
.
[8] H.-Y. Cheng and K.-C. Yang,
Phys. Rev. D
78
, 094001
(2008)
.
[9] B. Aubert
et al.
(
B
A
B
AR
Collaboration),
Phys. Rev. D
74
,
031104 (2006)
.
[10] B. Aubert
et al.
(
B
A
B
AR
Collaboration),
Phys. Rev. D
80
,
051101(R) (2009)
.
[11] B. Aubert
et al.
(
BABAR
Collaboration),
Nucl.
Instrum. Methods Phys. Res., Sect. A
479
,1
(2002)
.
[12] The
B
A
B
AR
detector Monte Carlo simulation is based on
GEANT4
and
EVTGEN
: S. Agostinelli
et al.
,
Nucl. Instrum.
Methods Phys. Res., Sect. A
506
, 250 (2003)
; D. J. Lange,
Nucl. Instrum. Methods Phys. Res., Sect. A
462
, 152
(2001)
, respectively.
[13] C. Amsler
et al.
(Particle Data Group),
Phys. Lett. B
667
,1
(2008)
.
[14] B. Aubert
et al.
(
B
A
B
AR
Collaboration),
Phys. Rev. Lett.
97
, 051802 (2006)
.
[15] A. de Ru
́
jula, J. Ellis, E. G. Floratos, and M. K. Gaillard,
Nucl. Phys.
B138
, 387 (1978)
.
[16] R. A. Fisher, Annals Eugen.
7
, 179 (1936).
[17] M. J. Oreglia, Ph.D. thesis [Report No. SLAC-236, 1980],
Appendix D; J. E. Gaiser, Ph.D. thesis [Report No. SLAC-
255, 1982], Appendix F; T. Skwarnicki, Ph.D. thesis
[Report No. DESY F31-86-02, 1986], Appendix E.
[18] B. Aubert
et al.
(
B
A
B
AR
Collaboration),
Phys. Rev. D
70
,
032006 (2004)
.
[19] A. Datta,
Phys. Rev. D
77
, 114025 (2008)
.
P. DEL AMO SANCHEZ
et al.
PHYSICAL REVIEW D
82,
091101(R) (2010)
RAPID COMMUNICATIONS
091101-8