of 7
Measurement of the
e
þ
e

!
b

b
Cross Section between
ffiffiffi
s
p
¼
10
:
54
and 11.20 GeV
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
L. Lopez,
3a,3b
A. Palano,
3a,3b
M. Pappagallo,
3a,3b
G. Eigen,
4
B. Stugu,
4
L. Sun,
4
G. S. Abrams,
5
M. Battaglia,
5
D. N. Brown,
5
R. N. Cahn,
5
R. G. Jacobsen,
5
L. T. Kerth,
5
Yu. G. Kolomensky,
5
G. Lynch,
5
I. L. Osipenkov,
5
M. T. Ronan,
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. Walker,
8
D. J. Asgeirsson,
9
B. G. Fulsom,
9
C. Hearty,
9
T. S. Mattison,
9
J. A. McKenna,
9
M. Barrett,
10
A. Khan,
10
V. E. Blinov,
11
A. D. Bukin,
11
A. R. Buzykaev,
11
V. P. Druzhinin,
11
V. B. Golubev,
11
A. P. Onuchin,
11
S. I. Serednyakov,
11
Yu. I. Skovpen,
11
E. P. Solodov,
11
K. Yu. Todyshev,
11
M. Bondioli,
12
S. Curry,
12
I. Eschrich,
12
D. Kirkby,
12
A. J. Lankford,
12
P. Lund,
12
M. Mandelkern,
12
E. C. Martin,
12
D. P. Stoker,
12
S. Abachi,
13
C. Buchanan,
13
J. W. Gary,
14
F. Liu,
14
O. Long,
14
B. C. Shen,
14,
*
G. M. Vitug,
14
Z. Yasin,
14
L. Zhang,
14
V. Sharma,
15
C. Campagnari,
16
T. M. Hong,
16
D. Kovalskyi,
16
M. A. Mazur,
16
J. D. Richman,
16
T. W. Beck,
17
A. M. Eisner,
17
C. J. Flacco,
17
C. A. Heusch,
17
J. Kroseberg,
17
W. S. Lockman,
17
A. J. Martinez,
17
T. Schalk,
17
B. A. Schumm,
17
A. Seiden,
17
M. G. Wilson,
17
L. O. Winstrom,
17
C. H. Cheng,
18
D. A. Doll,
18
B. Echenard,
18
F. Fang,
18
D. G. Hitlin,
18
I. Narsky,
18
T. Piatenko,
18
F. C. Porter,
18
R. Andreassen,
19
G. Mancinelli,
19
B. T. Meadows,
19
K. Mishra,
19
M. D. Sokoloff,
19
P. C. Bloom,
20
W. T. Ford,
20
A. Gaz,
20
J. F. Hirschauer,
20
M. Nagel,
20
U. Nauenberg,
20
J. G. Smith,
20
K. A. Ulmer,
20
S. R. Wagner,
20
R. Ayad,
21,
A. Soffer,
21,
W. H. Toki,
21
R. J. Wilson,
21
D. D. Altenburg,
22
E. Feltresi,
22
A. Hauke,
22
H. Jasper,
22
M. Karbach,
22
J. Merkel,
22
A. Petzold,
22
B. Spaan,
22
K. Wacker,
22
M. J. Kobel,
23
W. F. Mader,
23
R. Nogowski,
23
K. R. Schubert,
23
R. Schwierz,
23
A. Volk,
23
D. Bernard,
24
G. R. Bonneaud,
24
E. Latour,
24
M. Verderi,
24
P. J. Clark,
25
S. Playfer,
25
J. E. Watson,
25
M. Andreotti,
26a,26b
D. Bettoni,
26a
C. Bozzi,
26a
R. Calabrese,
26a,26b
A. Cecchi,
26a,26b
G. Cibinetto,
26a,26b
P. Franchini,
26a,26b
E. Luppi,
26a,26b
M. Negrini,
26a,26b
A. Petrella,
26a,26b
L. Piemontese,
26a
V. Santoro,
26a,26b
R. Baldini-Ferroli,
27
A. Calcaterra,
27
R. de Sangro,
27
G. Finocchiaro,
27
S. Pacetti,
27
P. Patteri,
27
I. M. Peruzzi,
27,
x
M. Piccolo,
27
M. Rama,
27
A. Zallo,
27
A. Buzzo,
28a
R. Contri,
28a,28b
M. Lo Vetere,
28a,28b
M. M. Macri,
28a
M. R. Monge,
28a,28b
S. Passaggio,
28a
C. Patrignani,
28a,28b
E. Robutti,
28a
A. Santroni,
28a,28b
S. Tosi,
28a,28b
K. S. Chaisanguanthum,
29
M. Morii,
29
A. Adametz,
30
J. Marks,
30
S. Schenk,
30
U. Uwer,
30
V. Klose,
31
H. M. Lacker,
31
D. J. Bard,
32
P. D. Dauncey,
32
J. A. Nash,
32
M. Tibbetts,
32
P. K. Behera,
33
X. Chai,
33
M. J. Charles,
33
U. Mallik,
33
J. Cochran,
34
H. B. Crawley,
34
L. Dong,
34
W. T. Meyer,
34
S. Prell,
34
E. I. Rosenberg,
34
A. E. Rubin,
34
Y. Y. Gao,
35
A. V. Gritsan,
35
Z. J. Guo,
35
C. K. Lae,
35
N. Arnaud,
36
J. Be
́
quilleux,
36
A. D’Orazio,
36
M. Davier,
36
J. Firmino da Costa,
36
G. Grosdidier,
36
A. Ho
̈
cker,
36
V. Lepeltier,
36
F. Le Diberder,
36
A. M. Lutz,
36
S. Pruvot,
36
P. Roudeau,
36
M. H. Schune,
36
J. Serrano,
36
V. Sordini,
36,
k
A. Stocchi,
36
G. Wormser,
36
D. J. Lange,
37
D. M. Wright,
37
I. Bingham,
38
J. P. Burke,
38
C. A. Chavez,
38
J. R. Fry,
38
E. Gabathuler,
38
R. Gamet,
38
D. E. Hutchcroft,
38
D. J. Payne,
38
C. Touramanis,
38
A. J. Bevan,
39
C. K. Clarke,
39
K. A. George,
39
F. Di Lodovico,
39
R. Sacco,
39
M. Sigamani,
39
G. Cowan,
40
H. U. Flaecher,
40
D. A. Hopkins,
40
S. Paramesvaran,
40
F. Salvatore,
40
A. C. Wren,
40
D. N. Brown,
41
C. L. Davis,
41
A. G. Denig,
42
M. Fritsch,
42
W. Gradl,
42
G. Schott,
42
K. E. Alwyn,
43
D. Bailey,
43
R. J. Barlow,
43
Y. M. Chia,
43
C. L. Edgar,
43
G. Jackson,
43
G. D. Lafferty,
43
T. J. West,
43
J. I. Yi,
43
J. Anderson,
44
C. Chen,
44
A. Jawahery,
44
D. A. Roberts,
44
G. Simi,
44
J. M. Tuggle,
44
C. Dallapiccola,
45
X. Li,
45
E. Salvati,
45
S. Saremi,
45
R. Cowan,
46
D. Dujmic,
46
P. H. Fisher,
46
G. Sciolla,
46
M. Spitznagel,
46
F. Taylor,
46
R. K. Yamamoto,
46
M. Zhao,
46
P. M. Patel,
47
S. H. Robertson,
47
A. Lazzaro,
48a,48b
V. Lombardo,
48a
F. Palombo,
48a,48b
J. M. Bauer,
49
L. Cremaldi,
49
R. Godang,
49,
{
R. Kroeger,
49
D. A. Sanders,
49
D. J. Summers,
49
H. W. Zhao,
49
M. Simard,
50
P. Taras,
50
F. B. Viaud,
50
H. Nicholson,
51
G. De Nardo,
52a,52b
L. Lista,
52a
D. Monorchio,
52a,52b
G. Onorato,
52a,52b
C. Sciacca,
52a,52b
G. Raven,
53
H. L. Snoek,
53
C. P. Jessop,
54
K. J. Knoepfel,
54
J. M. LoSecco,
54
W. F. Wang,
54
G. Benelli,
55
L. A. Corwin,
55
K. Honscheid,
55
H. Kagan,
55
R. Kass,
55
J. P. Morris,
55
A. M. Rahimi,
55
J. J. Regensburger,
55
S. J. Sekula,
55
Q. K. Wong,
55
N. L. Blount,
56
J. Brau,
56
R. Frey,
56
O. Igonkina,
56
J. A. Kolb,
56
M. Lu,
56
R. Rahmat,
56
N. B. Sinev,
56
D. Strom,
56
J. Strube,
56
E. Torrence,
56
G. Castelli,
57a,57b
N. Gagliardi,
57a,57b
M. Margoni,
57a,57b
M. Morandin,
57a
M. Posocco,
57a
M. Rotondo,
57a
F. Simonetto,
57a,57b
R. Stroili,
57a,57b
C. Voci,
57a,57b
P. del Amo Sanchez,
58
E. Ben-Haim,
58
H. Briand,
58
G. Calderini,
58
J. Chauveau,
58
P. David,
58
L. Del Buono,
58
O. Hamon,
58
Ph. Leruste,
58
J. Ocariz,
58
A. Perez,
58
J. Prendki,
58
S. Sitt,
58
L. Gladney,
59
M. Biasini,
60a,60b
R. Covarelli,
60a,60b
E. Manoni,
60a,60b
C. Angelini,
61a,61b
G. Batignani,
61a,61b
S. Bettarini,
61a,61b
M. Carpinelli,
61a,61b,
**
A. Cervelli,
61a,61b
F. Forti,
61a,61b
M. A. Giorgi,
61a,61b
A. Lusiani,
61a,61c
G. Marchiori,
61a,61b
M. Morganti,
61a,61b
N. Neri,
61a,61b
E. Paoloni,
61a,61b
G. Rizzo,
61a,61b
J. J. Walsh,
61a
D. Lopes Pegna,
62
C. Lu,
62
J. Olsen,
62
A. J. S. Smith,
62
A. V. Telnov,
62
F. Anulli,
63a
E. Baracchini,
63a,63b
G. Cavoto,
63a
D. del Re,
63a,63b
E. Di Marco,
63a,63b
R. Faccini,
63a,63b
PRL
102,
012001 (2009)
PHYSICAL REVIEW LETTERS
week ending
9 JANUARY 2009
0031-9007
=
09
=
102(1)
=
012001(7)
012001-1
Ó
2009 The American Physical Society
F. Ferrarotto,
63a,63b
F. Ferroni,
63a,63b
M. Gaspero,
63a,63b
P. D. Jackson,
63a
L. Li Gioi,
63a
M. A. Mazzoni,
63a
S. Morganti,
63a
G. Piredda,
63a
F. Polci,
63a,63b
F. Renga,
63a,63b
C. Voena,
63a
M. Ebert,
64
T. Hartmann,
64
H. Schro
̈
der,
64
R. Waldi,
64
T. Adye,
65
B. Franek,
65
E. O. Olaiya,
65
F. F. Wilson,
65
S. Emery,
66
M. Escalier,
66
L. Esteve,
66
S. F. Ganzhur,
66
G. Hamel de Monchenault,
66
W. Kozanecki,
66
G. Vasseur,
66
Ch. Ye
`
che,
66
M. Zito,
66
X. R. Chen,
67
H. Liu,
67
W. Park,
67
M. V. Purohit,
67
R. M. White,
67
J. R. Wilson,
67
M. T. Allen,
68
D. Aston,
68
R. Bartoldus,
68
P. Bechtle,
68
J. F. Benitez,
68
K. Bertsche,
68
Y. Cai,
68
R. Cenci,
68
J. P. Coleman,
68
M. R. Convery,
68
F. J. Decker,
68
J. C. Dingfelder,
68
J. Dorfan,
68
G. P. Dubois-Felsmann,
68
W. Dunwoodie,
68
S. Ecklund,
68
R. Erickson,
68
R. C. Field,
68
A. Fisher,
68
J. Fox,
68
A. M. Gabareen,
68
S. J. Gowdy,
68
M. T. Graham,
68
P. Grenier,
68
C. Hast,
68
W. R. Innes,
68
R. Iverson,
68
J. Kaminski,
68
M. H. Kelsey,
68
H. Kim,
68
P. Kim,
68
M. L. Kocian,
68
A. Kulikov,
68
D. W. G. S. Leith,
68
S. Li,
68
B. Lindquist,
68
S. Luitz,
68
V. Luth,
68
H. L. Lynch,
68
D. B. MacFarlane,
68
H. Marsiske,
68
R. Messner,
68
D. R. Muller,
68
H. Neal,
68
S. Nelson,
68
A. Novokhatski,
68
C. P. O’Grady,
68
I. Ofte,
68
A. Perazzo,
68
M. Perl,
68
B. N. Ratcliff,
68
C. Rivetta,
68
A. Roodman,
68
A. A. Salnikov,
68
R. H. Schindler,
68
J. Schwiening,
68
J. Seeman,
68
A. Snyder,
68
D. Su,
68
M. K. Sullivan,
68
K. Suzuki,
68
S. K. Swain,
68
J. M. Thompson,
68
J. Va’vra,
68
D. Van Winkle,
68
A. P. Wagner,
68
M. Weaver,
68
C. A. West,
68
U. Wienands,
68
W. J. Wisniewski,
68
M. Wittgen,
68
W. Wittmer,
68
D. H. Wright,
68
H. W. Wulsin,
68
Y. Yan,
68
A. K. Yarritu,
68
K. Yi,
68
G. Yocky,
68
C. C. Young,
68
V. Ziegler,
68
P. R. Burchat,
69
A. J. Edwards,
69
S. A. Majewski,
69
T. S. Miyashita,
69
B. A. Petersen,
69
L. Wilden,
69
S. Ahmed,
70
M. S. Alam,
70
J. A. Ernst,
70
B. Pan,
70
M. A. Saeed,
70
S. B. Zain,
70
S. M. Spanier,
71
B. J. Wogsland,
71
R. Eckmann,
72
J. L. Ritchie,
72
A. M. Ruland,
72
C. J. Schilling,
72
R. F. Schwitters,
72
B. W. Drummond,
73
J. M. Izen,
73
X. C. Lou,
73
F. Bianchi,
74a,74b
D. Gamba,
74a,74b
M. Pelliccioni,
74a,74b
M. Bomben,
75a,75b
L. Bosisio,
75a,75b
C. Cartaro,
75a,75b
G. Della Ricca,
75a,75b
L. Lanceri,
75a,75b
L. Vitale,
75a,75b
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
3a
INFN Sezione di Bari, I-70126 Bari, Italy
3b
Dipartmento 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
Institut fu
̈
r Experimentalphysik 1, Ruhr Universita
̈
t Bochum, D-44780 Bochum, Germany
8
University of Bristol, Bristol BS8 1TL, United Kingdom
9
University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z1
10
Brunel University, Uxbridge, Middlesex UB8 3PH, United Kingdom
11
Budker Institute of Nuclear Physics, Novosibirsk 630090, Russia
12
University of California at Irvine, Irvine, California 92697, USA
13
University of California at Los Angeles, Los Angeles, California 90024, USA
14
University of California at Riverside, Riverside, California 92521, USA
15
University of California at San Diego, La Jolla, California 92093, USA
16
University of California at Santa Barbara, Santa Barbara, California 93106, USA
17
Institute for Particle Physics, University of California at Santa Cruz, Santa Cruz, California 95064, USA
18
California Institute of Technology, Pasadena, California 91125, USA
19
University of Cincinnati, Cincinnati, Ohio 45221, USA
20
University of Colorado, Boulder, Colorado 80309, USA
21
Colorado State University, Fort Collins, Colorado 80523, USA
22
Fakulta
̈
t Physik, Technische Universita
̈
t Dortmund, D-44221 Dortmund, Germany
23
Technische Universita
̈
t Dresden, Institut fu
̈
r Kern- und Teilchenphysik, D-01062 Dresden, Germany
24
Laboratoire Leprince-Ringuet, CNRS/IN2P3, Ecole Polytechnique, F-91128 Palaiseau, France
25
University of Edinburgh, Edinburgh EH9 3JZ, United Kingdom
26a
INFN Sezione di Ferrara, I-44100 Ferrara, Italy
26b
Dipartimento di Fisica, Universita
`
di Ferrara, I-44100 Ferrara, Italy
27
INFN Laboratori Nazionali di Frascati, I-00044 Frascati, Italy
28a
INFN Sezione di Genova, I-16146 Genova, Italy
PRL
102,
012001 (2009)
PHYSICAL REVIEW LETTERS
week ending
9 JANUARY 2009
012001-2
28b
Dipartimento di Fisica, Universita
`
di Genova, I-16146 Genova, Italy
29
Harvard University, Cambridge, Massachusetts 02138, USA
30
Physikalisches Institut, Universita
̈
t Heidelberg, Philosophenweg 12, D-69120 Heidelberg, Germany
31
Institut fu
̈
r Physik, Humboldt-Universita
̈
t zu Berlin, Newtonstrasse 15, D-12489 Berlin, Germany
32
Imperial College London, London, SW7 2AZ, United Kingdom
33
University of Iowa, Iowa City, Iowa 52242, USA
34
Iowa State University, Ames, Iowa 50011-3160, USA
35
Johns Hopkins University, Baltimore, Maryland 21218, USA
36
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
37
Lawrence Livermore National Laboratory, Livermore, California 94550, USA
38
University of Liverpool, Liverpool L69 7ZE, United Kingdom
39
Queen Mary, University of London, London, E1 4NS, United Kingdom
40
University of London, Royal Holloway and Bedford New College, Egham, Surrey TW20 0EX, United Kingdom
41
University of Louisville, Louisville, Kentucky 40292, USA
42
Institut fu
̈
r Kernphysik, Johannes Gutenberg-Universita
̈
t Mainz, D-55099 Mainz, Germany
43
University of Manchester, Manchester M13 9PL, United Kingdom
44
University of Maryland, College Park, Maryland 20742, USA
45
University of Massachusetts, Amherst, Massachusetts 01003, USA
46
Laboratory for Nuclear Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
47
McGill University, Montre
́
al, Que
́
bec, Canada H3A 2T8
48a
INFN Sezione di Milano, I-20133 Milano, Italy
48b
Dipartimento di Fisica, Universita
`
di Milano, I-20133 Milano, Italy
49
University of Mississippi, University, Mississippi 38677, USA
50
Physique des Particules, Universite
́
de Montre
́
al, Montre
́
al, Que
́
bec, Canada H3C 3J7
51
Mount Holyoke College, South Hadley, Massachusetts 01075, USA
52a
INFN Sezione di Napoli, I-80126 Napoli, Italy
52b
Dipartimento di Scienze Fisiche, Universita
`
di Napoli Federico II, I-80126 Napoli, Italy
53
NIKHEF, National Institute for Nuclear Physics and High Energy Physics , NL-1009 DB Amsterdam, The Netherlands
54
University of Notre Dame, Notre Dame, Indiana 46556, USA
55
Ohio State University, Columbus, Ohio 43210, USA
56
University of Oregon, Eugene, Oregon 97403, USA
57a
INFN Sezione di Padova, I-35131 Padova, Italy
57b
Dipartimento di Fisica, Universita
`
di Padova, I-35131 Padova, Italy
58
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
59
University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
60a
INFN Sezione di Perugia, I-06100 Perugia, Italy
60b
Dipartimento di Fisica, Universita
`
di Perugia, I-06100 Perugia, Italy
61a
INFN Sezione di Pisa, I-56127 Pisa, Italy
61b
Dipartimento di Fisica, Universita
`
di Pisa, I-56127 Pisa, Italy
61c
Scuola Normale Superiore di Pisa, I-56127 Pisa, Italy
62
Princeton University, Princeton, New Jersey 08544, USA
63a
INFN Sezione di Roma, I-00185 Roma, Italy
63b
Dipartimento di Fisica, Universita
`
di Roma La Sapienza, I-00185 Roma, Italy
64
Universita
̈
t Rostock, D-18051 Rostock, Germany
65
Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, OX11 0QX, United Kingdom
66
CEA, Irfu, SPP, Centre de Saclay, F-91191 Gif-sur-Yvette, France
67
University of South Carolina, Columbia, South Carolina 29208, USA
68
Stanford Linear Accelerator Center, Stanford, California 94309, USA
69
Stanford University, Stanford, California 94305-4060, USA
70
State University of New York, Albany, New York 12222, USA
71
University of Tennessee, Knoxville, Tennessee 37996, USA
72
University of Texas at Austin, Austin, Texas 78712, USA
73
University of Texas at Dallas, Richardson, Texas 75083, USA
74a
INFN Sezione di Torino, I-10125 Torino, Italy
74b
Dipartimento di Fisica Sperimentale, Universita
`
di Torino, I-10125 Torino, Italy
75a
INFN Sezione di Trieste, I-34127 Trieste, Italy
75b
Dipartimento di Fisica, Universita
`
di Trieste, I-34127 Trieste, Italy
76
IFIC, Universitat de Valencia-CSIC, E-46071 Valencia, Spain
77
University of Victoria, Victoria, British Columbia, Canada V8W 3P6
PRL
102,
012001 (2009)
PHYSICAL REVIEW LETTERS
week ending
9 JANUARY 2009
012001-3
78
Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom
79
University of Wisconsin, Madison, Wisconsin 53706, USA
(Received 26 September 2008; published 9 January 2009)
We report
e
þ
e

!
b

b
cross section measurements by the
BABAR
experiment performed during an
energy scan in the range of 10.54 to 11.20 GeVat the SLAC PEP-II
e
þ
e

collider. A total relative error of
about 5% is reached in more than 300 center-of-mass energy steps, separated by about 5 MeV. These
measurements can be used to derive precise information on the parameters of the

ð
10860
Þ
and

ð
11020
Þ
resonances. In particular we show that their widths may be smaller than previously measured.
DOI:
10.1103/PhysRevLett.102.012001
PACS numbers: 13.66.Bc, 13.25.Gv, 14.40.Gx
Recent discoveries of nonbaryonic charmonium states
that do not behave as two-quark states [
1
] call for a search
for other resonances belonging to this possible new spec-
troscopy. Given the charmonium content of these new
states, one could infer the presence of similar resonances
containing
b
quark pairs. The observed
J
PC
¼
1

exotic
states [
Y
ð
4260
Þ
,
Y
ð
4350
Þ
, and
Y
ð
4660
Þ
[
2
]] scaled up by the
mass difference between the
J=
c
and the

ð
1
S
Þ
(

M

6360 MeV
=c
2
) would be exotic bottomonium states with
masses above the

ð
4
S
Þ
and below 11.2 GeV. Moreover,
the

ð
10860
Þ
and the

ð
11020
Þ
states, which are candidate

ð
5
S
Þ
and

ð
6
S
Þ
, respectively, were observed in the same
region [
3
,
4
].
Between March 28 and April 7, 2008 the SLAC PEP-II
e
þ
e

collider [
5
] delivered colliding beams at a center-of-
mass energy (
ffiffiffi
s
p
) in the range of 10.54 to 11.20 GeV. First,
an energy scan over the whole range in 5 MeV steps,
collecting approximately
25 pb

1
per step for a total of
about
3
:
3fb

1
, was performed. It was then followed by a
600 pb

1
scan in the range of
ffiffiffi
s
p
¼
10
:
96
to 11.10 GeV, in
8 steps with nonregular energy spacing, performed in order
to investigate the

ð
6
S
Þ
region. This data set outclasses the
previous scans [
3
,
4
] by a factor
>
30
in the luminosity and

4
in the size of the energy steps. Across the scan, the
energy of the positron beam was kept fixed at 3.12 GeV,
while the electron beam energy was varied accordingly, to
set the required
ffiffiffi
s
p
. This produced a variation of the boost
of the center-of-mass frame during the scan.
In this Letter we present, for each step in
ffiffiffi
s
p
, the
measurement of
R
b
ð
s
Þ¼

b
ð
s
Þ
=
0

ð
s
Þ
, where

0

¼
4

2
=
3
s
is the lowest-order cross section for
e
þ
e

!

þ


and

b
is the total cross section for
e
þ
e

!
b

b
ð

Þ
, including
b

b
states produced in initial state radia-
tion (ISR) below the open beauty threshold, i.e., the

ð
1
S
Þ
,

ð
2
S
Þ
, and

ð
3
S
Þ
resonances.
The particles produced in the collisions are detected by
the
BABAR
detector, described elsewhere [
6
]. Charged-
particle tracking is provided by a five-layer silicon vertex
tracker and a 40-layer drift chamber (DCH). In addition to
providing precise position information for tracking, the
silicon vertex tracker and DCH also measure the specific
ionization (
dE=dx
), which is used for particle identifica-
tion of low-momentum charged particles. At higher mo-
menta (
p>
0
:
7 GeV
=c
) pions and kaons are identified by
Cherenkov radiation detected in a ring-imaging device
(DIRC). The position and energy of neutral clusters (pho-
tons) are measured with an electromagnetic calorimeter
consisting of 6580 thallium-doped CsI crystals. These
systems are mounted inside a 1.5-T solenoidal supercon-
ducting magnet. Muon identification is provided by the
magnetic flux return system instrumented with resistive
plate chambers and limited streamer tubes. The full detec-
tor is simulated, for background and efficiency studies,
with a Monte Carlo program (MC) based on
GEANT4
[
7
].
To measure
R
b
, we count the number of events passing a
selection that enriches the sample in events containing
B
mesons (
N
h
) and those passing an independent di-muon
selection (
N

) at each energy point and at a reference
energy below the open beauty production threshold.
Indicating with a prime the quantities at the reference
energy, we write
N
h
ð
s
Þ¼

½
R
b
ð
s
Þ

0

ð
s
Þ

ISR
ð
s
Þ

B
ð
s
Þ
þ
X
X

X
ð
s
Þ

X
ð
s
Þþ

ISR
ð
s
Þ

ISR
ð
s
Þ

L
ð
s
Þ
;
(1)
N
0
h
¼

X
X

0
X

0
X
þ

0
ISR

0
ISR

L
0
;
(2)
N

ð
s
Þ¼


ð
s
Þ


ð
s
Þ
L
ð
s
Þ
;
(3)
N
0

¼

0


0

L
0
;
(4)
where

B
is the efficiency for open
b
production to satisfy
the hadronic selection,
X
represents the different back-
ground components described later,

i
represents the cross
sections for the process
i
,

i
the corresponding efficiency,
and
L
is the integrated luminosity collected at a given
value of
ffiffiffi
s
p
. Measurements of
N

and
N
0

are needed in
order to normalize the hadronic rates to the collected
luminosities. As reference we choose the sample collected
at
ffiffiffi
s
p
¼
10
:
54 GeV
, about 40 MeV below the

ð
4
S
Þ
mass,
taken during 2006–2007. Special mention is made of the
ISR sample, the production of

ð
nS
Þ
(
n
¼
1
;
2
;
3
) mesons
via initial state radiation: albeit part of the signal, this
process can occur at the reference energy and has an
PRL
102,
012001 (2009)
PHYSICAL REVIEW LETTERS
week ending
9 JANUARY 2009
012001-4
efficiency and an energy dependence of the cross section
different from the open beauty production.
Solving the system of equations one obtains
R
b
¼

N
h
ð
s
Þ
N

ð
s
Þ

N
0
h
N
0



ð
s
Þ



ð
s
Þ



B
ð
s
Þ
þ
R
ISR
ð
s
Þ
;
(5)
where we defined


ð
s
Þ¼

0



ð
s
Þ
P
X
R
X
ð
s
Þ

X
ð
s
Þþ
R
ISR
ð
s
Þ

ISR
ð
s
Þ
P
X
R
0
X

0
X
þ
R
0
ISR

0
ISR
;
(6)
and
R
i
¼

i
=
0

for each process and


¼


=
0

,
assumed independent of
ffiffiffi
s
p
. It should be noted that these
equations assume that the background scales with the
integrated luminosity, i.e., that the machine background
is negligible, and that the di-muon selection leaves a
negligible level of background.
We select the
b
-enriched sample by requiring at least
three tracks in the event, a total visible energy in the event
greater than 4.5 GeV, and a vertex reconstructed from the
observed charged tracks within 5 mm of the beam crossing
point in the plane transverse to the beam axis and 6 cm
along the beam axis. These quantities are computed using
exclusively tracks in the fiducial volume of the DCH (i.e.,
forming an angle with the beam axis
0
:
41
< <
2
:
54 rad
).
A further rejection of the main backgrounds,
e
þ
e

!
q

q
,
q
¼
u; d; s; c
events (‘‘continuum’’ events), and
e
þ
e

!
þ

,
¼
e; ;
events, is obtained by means of a cut on
the ratio of the second and zeroth Fox-Wolfram moments
[
8
],
R
2
, calculated using only the charged tracks. After
optimization of the statistical sensitivity, we require
R
2
<
0
:
2
. Events that pass this selection at the reference energy
comprise 91% continuum, 2% two-photon (
e
þ
e

!
e
þ
e





!
e
þ
e

X
h
), and 7% ISR (
e
þ
e

!

ð
nS
Þ

ISR
) events.
To select di-muon events, we require that two tracks
have an invariant mass greater than
7
:
5 GeV
=c
2
; their
angle with the beam axis in the center-of-mass frame,
c
:
m
:
s
:
, must satisfy
cos
c
:
m
:
s
:
<
0
:
7485
, and the two muons
must be collinear to within 10

. To exploit the fact that
muons are minimum ionizing particles, we require that at
least one of them leaves a signal in the electromagnetic
calorimeter, and neither deposits more than 1 GeV.
In the following we describe the method used to derive
the inputs to Eq. (
5
) and the corresponding errors, separat-
ing correlated and uncorrelated errors. The covariance ma-
trix for the measurements of
R
b
at different energies is
V
ij
¼½

2
stat
ð
s
i
Þþ

2
unc
ð
s
i
Þ
ij
þ

corr
ð
s
i
Þ

corr
ð
s
j
Þ
, where

stat
ð
s
i
Þ
,

corr
ð
s
i
Þ
, and

unc
ð
s
i
Þ
are the statistical, corre-
lated, and uncorrelated systematic error, respectively, and
ij
is the Kronecker delta.
The efficiency for the di-muon selection


is extracted
from a sample of fully simulated MC events generated with
KK2F
[
9
] at several values of
ffiffiffi
s
p
. Because of the change in
boost this efficiency is found to change by 1.5% over the
whole range, and the MC statistics error we assign to the
corresponding correction is 0.2%. The correlated uncer-
tainty on the absolute scale of the efficiency is estimated to
be 1% and to come primarily from uncertainties in the
simulation of the trigger, of the quantities used in the
selection, and of the tracking efficiency. We also account
for differences in the trigger configurations between the
scan data and the reference data taken during the year 2007
and estimate the efficiency on the reference data to be
lower by
ð
0
:
5

0
:
2
Þ
%
. The same generator is consistently
used to extract


¼
1
:
48

0
:
02
, where this correlated
error is due to the uncertainty on the cross section.
The efficiency for
e
þ
e

!
b

b
events is estimated by
using
EVTGEN
[
10
] as generator, separately for each pos-
sible two-body final state including
B
,
B
s
, and
B

s
mesons,
and at different values of
ffiffiffi
s
p
. Because we ignore the
relative composition in terms of final states at each energy
we consider the largest and the smallest efficiencies among
the allowed final states and take their mean value as the
central value and half their difference as uncorrelated error.
The correlated error on the absolute scale of

B
is estimated
by varying the selection criteria and it is found to amount to
1.3%.
The calculation of the double ratio


requires the
dependence on
ffiffiffi
s
p
of


, which has already been dis-
cussed, and the cross sections and efficiencies for the
ISR and the background processes.
The ISR cross section is computed to second order
according to Ref. [
11
]. The corresponding efficiency
(

ISR
) is estimated with MC simulation to be 41% on
average. The relative efficiency change across the scan,
estimated to be

5%
, is used as a correlated uncertainty
and it propagates to an error on
R
b
of at most 0.7%.
The cross section for two-photon events scales as the
square of the logarithm of
s
, and the corresponding effi-
ciency is considered to be flat. The product of the cross
section and the efficiency (




) before the
R
2
is fitted
from the distribution of the direction of the missing mo-
mentum and then multiplied by the
R
2
cut efficiency. We
attribute 50% uncertainty to this estimate, leading to a
relative correlated error of at most 0.2%. Finally, the
product of the continuum cross section and efficiency is
computed by subtracting the ISR and two photon compo-
nents from
N
0
h
[see Eq. (
2
)]. The continuum contribution to
R
(
R
cont
) is assumed to be constant with
ffiffiffi
s
p
, while the
corresponding efficiency (

cont
) was estimated on a sample
of MC events generated with
JETSET
[
12
]. No correction to
account for the fact that the reference data were taken in a
different data-taking period was found necessary. The
relative change of

cont
over the whole scan range is
estimated to be 3%, and a 0.2% systematic error due to
MC statistics is assigned to it. We also find that the distri-
bution of
R
2
in continuum events is not perfectly repro-
duced by the MC simulations. We therefore estimate the
scaling of

cont
separately with and without the
R
2
<
0
:
2
PRL
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012001 (2009)
PHYSICAL REVIEW LETTERS
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9 JANUARY 2009
012001-5
requirement and take the difference among the results as a
correlated systematic error. Its contribution depends on the
value of
R
b
, and it is at most 2%.
To measure
ffiffiffi
s
p
of each point we fit the distribution of the
invariant mass of the two muons in the selected di-muon
sample with a function made of a Gaussian with an ex-
ponential tail on the side below the peak mass. We then use
the mean of the Gaussian as estimator of
ffiffiffi
s
p
and we
determine a bias of
ð
20
:
9

1
:
5
Þ
MeV
for this quantity
by comparing the

ð
3
S
Þ
mass measured on the data taken
during the

100 pb

1
scan performed by PEP-II at the
beginning of the last data-taking period with the resonant
depolarization result [
13
]. We correct for this bias, that
comes from the (strongly) nonlinear impact of the momen-
tum resolution in the invariant mass, and verify on simu-
lated events that it does not depend on
ffiffiffi
s
p
.
The resulting measurements of
R
b
as a function of
ffiffiffi
s
p
are shown in Fig.
1
, where the error bars represent the sum
of the statistical and uncorrelated systematic errors and
dotted lines show the different
B
meson production thresh-
olds. The relative correlated systematic errors on
R
b
are
summarized in Table
I
. The numerical results for each
energy point, together with the estimated ISR cross section,
can be found in Ref. [
14
]. It is important to stress that
radiative corrections have not been applied since they
would require an
a priori
knowledge of the resonant re-
gion. The measured
R
b
therefore includes all final- or
initial-state radiation processes.
The large statistics and the small energy steps of this
scan make it possible to observe clear structures corre-
sponding to the opening of new thresholds: dips corre-
sponding to the
B
ðÞ
B

and
B
s
B

s
openings and a plateau
close to the
B

s
B

s
one. It is also evident that the

ð
10860
Þ
and

ð
11020
Þ
behave differently above and below the
corresponding peaks. Finally, the plateau above the

ð
11020
Þ
is clearly visible.
We fit the following simple model to our data between
10.80 and 11.20 GeV: a flat component representing
b

b
-continuum states not interfering with resonance decays,
added incoherently to a second flat component interfering
with two relativistic Breit-Wigner (BW) resonances, i.e.,

¼j
A
nr
j
2
þj
A
r
þ
A
10860
e
i
10860
BW
ð
M
10860
;

10860
Þþ
A
11020
e
i
11020
BW
ð
M
11020
;

11020
Þj
2
, with
BW
ð
M;

Þ¼
1
=
½ð
s

M
2
Þþ
iM


. The results summarized in Table
II
and Fig.
1
differ substantially from the PDG values [
15
]. In
particular, the
B

s
B
s
and
B

s
B

s
thresholds have a very large
impact on the determination of the

ð
10860
Þ
width.
TABLE I. Contributions to the relative correlated systematic
error on
R
b
. The last three contributions depend on the energy
point and only the largest value is reported.
Contribution
Relative error (%)

MC statistics
0.2

radiative corrections
1.4


1.3

B
1.3

cont
<
2
:
0

ISR
<
0
:
7




<
0
:
2
TABLE II. Fit results for the

ð
10860
Þ
and

ð
11020
Þ
reso-
nances resulting from the fit described in the text. The
phases
are relative to the interfering continuum. The corresponding
world averages [
15
] are also reported.

ð
10860
Þ

ð
11020
Þ
Mass (GeV)
10
:
876

0
:
002
10
:
996

0
:
002
Width (MeV)
43

437

3
(rad)
2
:
11

0
:
12
0
:
12

0
:
07
PDG mass (GeV)
10
:
865

0
:
008
11
:
019

0
:
008
PDG width (MeV)
110

13
79

16
[GeV]
s
10.6
10.7
10.8
10.9
11
11.1
11.2
b
R
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
B
B
B
B*
*
B
B*
s
B
s
B
*
s
B
s
B
*
s
B
*
s
B
[GeV]
s
10.6
10.7
10.8
10.9
11
11.1
11.2
R
b
0
0.1
0.2
0.3
0.4
0.5
0.6
FIG. 1. Left: Measured
R
b
as a function of
ffiffiffi
s
p
with the position of the opening thresholds of the
e
þ
e

!
B
ðÞ
ð
s
Þ

B
ðÞ
ð
s
Þ
processes indicated
by dotted lines. Right: A zoom of the same plot with the result of the fit described in the text superimposed. The errors on data
represent the statistical and the uncorrelated systematic errors added in quadrature.
PRL
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012001 (2009)
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week ending
9 JANUARY 2009
012001-6
The number of states is,
a priori
, unknown as are their
energy dependencies. Therefore, a proper coupled channel
approach [
16
,
17
] including the effects of the various
thresholds outlined earlier would be likely to modify the
results obtained from our simple fit. As an illustration of
the systematic uncertainties arising from the assumptions
in our fit, a simple modification is to replace the flat non-
resonant term by a threshold function at
ffiffiffi
s
p
¼
2
m
B
. This
leads to a larger width (
74

4 MeV
) and a lower mass
(
10 869

2 MeV
) for the

ð
10860
Þ
.
In summary, we have performed an accurate measure-
ment of
R
b
in fine grained center-of-mass energy steps and
have shown that these measurements have the potential to
yield information on the bottomonium spectrum and pos-
sible exotic extensions.
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 (U.S.A.), NSERC
(Canada), CEA and CNRS-IN2P3 (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.
*
Deceased.
Present address: Temple University, Philadelphia, PA
19122, USA.
Present address: Tel Aviv University, Tel Aviv, 69978,
Israel.
x
Also at: Dipartimento di Fisica, Universita
`
di Perugia,
Perugia, Italy.
k
Also at: Universita
`
di Roma La Sapienza, I-00185 Roma,
Italy.
{
Present address: University of South Alabama, Mobile,
AL 36688, USA.
**
Also at: Universita
`
di Sassari, Sassari, Italy.
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