B meson decays to charmless meson
pairs containing # or #' mesons
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Citation
Aubert, B., et al. “B Meson Decays to Charmless Meson Pairs
Containing η or η # Mesons.” Physical Review D, vol. 80, no. 11, Dec.
2009. © 2009 American Physical Society
As Published
http://dx.doi.org/10.1103/PhysRevD.80.112002
Publisher
American Physical Society (APS)
Version
Final published version
Citable link
http://hdl.handle.net/1721.1/116881
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policy and may be subject to US copyright law. Please refer to the
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B meson decays to charmless meson pairs containing or 0 mesons
B. Aubert,1Y. Karyotakis,1J. P. Lees,1V. Poireau,1E. Prencipe,1X. Prudent,1V. Tisserand,1J. Garra Tico,2E. Grauges,2 M. Martinelli,3a,3bA. Palano,3a,3bM. Pappagallo,3a,3bG. Eigen,4B. Stugu,4L. Sun,4M. Battaglia,5D. N. Brown,5 L. T. Kerth,5Yu. G. Kolomensky,5G. Lynch,5I. L. Osipenkov,5K. Tackmann,5T. Tanabe,5C. M. Hawkes,6N. Soni,6 A. T. Watson,6H. Koch,7T. Schroeder,7D. J. Asgeirsson,8B. G. Fulsom,8C. Hearty,8T. S. Mattison,8J. A. McKenna,8
M. Barrett,9A. Khan,9A. Randle-Conde,9V. E. Blinov,10A. D. Bukin,10,*A. R. Buzykaev,10V. P. Druzhinin,10 V. B. Golubev,10A. P. Onuchin,10S. I. Serednyakov,10Yu. I. Skovpen,10E. P. Solodov,10K. Yu. Todyshev,10M. Bondioli,11
S. Curry,11I. Eschrich,11D. Kirkby,11A. J. Lankford,11P. Lund,11M. Mandelkern,11E. C. Martin,11D. P. Stoker,11 H. Atmacan,12J. W. Gary,12F. Liu,12O. Long,12G. M. Vitug,12Z. Yasin,12V. Sharma,13C. Campagnari,14T. M. Hong,14
D. Kovalskyi,14M. A. Mazur,14J. D. Richman,14T. W. Beck,15A. M. Eisner,15C. A. Heusch,15J. Kroseberg,15 W. S. Lockman,15A. J. Martinez,15T. Schalk,15B. A. Schumm,15A. Seiden,15L. Wang,15L. O. Winstrom,15 C. H. Cheng,16D. A. Doll,16B. Echenard,16F. Fang,16D. G. Hitlin,16I. Narsky,16P. Ongmongkolkul,16T. Piatenko,16
F. C. Porter,16R. Andreassen,17G. Mancinelli,17B. T. Meadows,17K. Mishra,17M. D. Sokoloff,17P. C. Bloom,18 W. T. Ford,18A. Gaz,18J. F. Hirschauer,18M. Nagel,18U. Nauenberg,18J. G. Smith,18S. R. Wagner,18R. Ayad,19,† W. H. Toki,19R. J. Wilson,19E. Feltresi,20A. Hauke,20H. Jasper,20T. M. Karbach,20J. Merkel,20A. Petzold,20B. Spaan,20
K. Wacker,20M. J. Kobel,21R. Nogowski,21K. R. Schubert,21R. Schwierz,21D. Bernard,22E. Latour,22M. Verderi,22 P. J. Clark,23S. Playfer,23J. E. Watson,23M. Andreotti,24a,24bD. Bettoni,24aC. Bozzi,24aR. Calabrese,24a,24b A. Cecchi,24a,24bG. Cibinetto,24a,24bE. Fioravanti,24a,24bP. Franchini,24a,24bE. Luppi,24a,24bM. Munerato,24a,24b
M. Negrini,24a,24bA. Petrella,24a,24bL. Piemontese,24aV. Santoro,24a,24bR. Baldini-Ferroli,25A. Calcaterra,25 R. de Sangro,25G. Finocchiaro,25S. Pacetti,25P. Patteri,25I. M. Peruzzi,25,‡M. Piccolo,25M. Rama,25A. Zallo,25
R. Contri,26a,26bE. Guido,26a,26bM. Lo Vetere,26a,26bM. R. Monge,26a,26bS. Passaggio,26aC. Patrignani,26a,26b E. Robutti,26aS. Tosi,26a,26bK. S. Chaisanguanthum,27M. Morii,27A. Adametz,28J. Marks,28S. Schenk,28U. Uwer,28
F. U. Bernlochner,29V. Klose,29H. M. Lacker,29T. Lueck,29A. Volk,29D. J. Bard,30P. D. Dauncey,30M. Tibbetts,30 P. K. Behera,31M. J. Charles,31U. Mallik,31J. Cochran,32H. B. Crawley,32L. Dong,32V. Eyges,32W. T. Meyer,32 S. Prell,32E. I. Rosenberg,32A. E. Rubin,32Y. Y. Gao,33A. V. Gritsan,33Z. J. Guo,33N. Arnaud,34J. Be´quilleux,34 A. D’Orazio,34M. Davier,34D. Derkach,34J. Firmino da Costa,34G. Grosdidier,34F. Le Diberder,34V. Lepeltier,34
A. M. Lutz,34B. Malaescu,34S. Pruvot,34P. Roudeau,34M. H. Schune,34J. Serrano,34V. Sordini,34,xA. Stocchi,34 G. Wormser,34D. J. Lange,35D. M. Wright,35I. Bingham,36J. P. Burke,36C. A. Chavez,36J. R. Fry,36E. Gabathuler,36
R. Gamet,36D. E. Hutchcroft,36D. J. Payne,36C. Touramanis,36A. J. Bevan,37C. K. Clarke,37F. Di Lodovico,37 R. Sacco,37M. Sigamani,37G. Cowan,38S. Paramesvaran,38A. C. Wren,38D. N. Brown,39C. L. Davis,39A. G. Denig,40
M. Fritsch,40W. Gradl,40A. Hafner,40K. E. Alwyn,41D. Bailey,41R. J. Barlow,41G. Jackson,41G. D. Lafferty,41 T. J. West,41J. I. Yi,41J. Anderson,42C. Chen,42A. Jawahery,42D. A. Roberts,42G. Simi,42J. M. Tuggle,42 C. Dallapiccola,43E. Salvati,43R. Cowan,44D. Dujmic,44P. H. Fisher,44S. W. Henderson,44G. Sciolla,44M. Spitznagel,44
R. K. Yamamoto,44M. Zhao,44P. M. Patel,45S. H. Robertson,45M. Schram,45P. Biassoni,46a,46bA. Lazzaro,46a,46b V. Lombardo,46aF. Palombo,46a,46bS. Stracka,46a,46bL. Cremaldi,47R. Godang,47,kR. Kroeger,47P. Sonnek,47
D. J. Summers,47H. W. Zhao,47M. Simard,48P. Taras,48H. Nicholson,49G. De Nardo,50a,50bL. Lista,50a D. Monorchio,50a,50bG. Onorato,50a,50bC. Sciacca,50a,50bG. Raven,51H. L. Snoek,51C. P. Jessop,52K. J. Knoepfel,52 J. M. LoSecco,52W. F. Wang,52L. A. Corwin,53K. Honscheid,53H. Kagan,53R. Kass,53J. P. Morris,53A. M. Rahimi,53
S. J. Sekula,53Q. K. Wong,53N. L. Blount,54J. Brau,54R. Frey,54O. Igonkina,54J. A. Kolb,54M. Lu,54R. Rahmat,54 N. B. Sinev,54D. Strom,54J. Strube,54E. Torrence,54G. Castelli,55a,55bN. Gagliardi,55a,55bM. Margoni,55a,55b M. Morandin,55aM. Posocco,55aM. Rotondo,55aF. Simonetto,55a,55bR. Stroili,55a,55bC. Voci,55a,55bP. del Amo Sanchez,56
E. Ben-Haim,56G. R. Bonneaud,56H. Briand,56J. Chauveau,56O. Hamon,56Ph. Leruste,56G. Marchiori,56J. Ocariz,56 A. Perez,56J. Prendki,56S. Sitt,56L. Gladney,57M. Biasini,58a,58bE. Manoni,58a,58bC. Angelini,59a,59bG. Batignani,59a,59b
S. Bettarini,59a,59bG. Calderini,59a,59b,{M. Carpinelli,59a,59b,**A. Cervelli,59a,59bF. Forti,59a,59bM. A. Giorgi,59a,59b A. Lusiani,59a,59cM. Morganti,59a,59bN. Neri,59a,59bE. Paoloni,59a,59bG. Rizzo,59a,59bJ. J. Walsh,59aD. Lopes Pegna,60
C. Lu,60J. Olsen,60A. J. S. Smith,60A. V. Telnov,60F. Anulli,61aE. Baracchini,61a,61bG. Cavoto,61aR. Faccini,61a,61b F. Ferrarotto,61aF. Ferroni,61a,61bM. Gaspero,61a,61bP. D. Jackson,61aL. Li Gioi,61aM. A. Mazzoni,61aS. Morganti,61a G. Piredda,61aF. Renga,61a,61bC. Voena,61aM. Ebert,62T. Hartmann,62H. Schro¨der,62R. Waldi,62T. Adye,63B. Franek,63
E. O. Olaiya,63F. F. Wilson,63S. Emery,64L. Esteve,64G. Hamel de Monchenault,64W. Kozanecki,64G. Vasseur,64 Ch. Ye`che,64M. Zito,64M. T. Allen,65D. Aston,65R. Bartoldus,65J. F. Benitez,65R. Cenci,65J. P. Coleman,65
M. R. Convery,65J. C. Dingfelder,65J. Dorfan,65G. P. Dubois-Felsmann,65W. Dunwoodie,65R. C. Field,65 M. Franco Sevilla,65A. M. Gabareen,65M. T. Graham,65P. Grenier,65C. Hast,65W. R. Innes,65J. Kaminski,65 M. H. Kelsey,65H. Kim,65P. Kim,65M. L. Kocian,65D. W. G. S. Leith,65S. Li,65B. Lindquist,65S. Luitz,65V. Luth,65 H. L. Lynch,65D. B. MacFarlane,65H. Marsiske,65R. Messner,65,*D. R. Muller,65H. Neal,65S. Nelson,65C. P. O’Grady,65
I. Ofte,65M. Perl,65B. N. Ratcliff,65A. Roodman,65A. A. Salnikov,65R. H. Schindler,65J. Schwiening,65A. Snyder,65 D. Su,65M. K. Sullivan,65K. Suzuki,65S. K. Swain,65J. M. Thompson,65J. Va’vra,65A. P. Wagner,65M. Weaver,65
C. A. West,65W. J. Wisniewski,65M. Wittgen,65D. H. Wright,65H. W. Wulsin,65A. K. Yarritu,65C. C. Young,65 V. Ziegler,65X. R. Chen,66H. Liu,66W. Park,66M. V. Purohit,66R. M. White,66J. R. Wilson,66M. Bellis,67P. R. Burchat,67
A. J. Edwards,67T. S. Miyashita,67S. Ahmed,68M. S. Alam,68J. A. Ernst,68B. Pan,68M. A. Saeed,68S. B. Zain,68 A. Soffer,69S. M. Spanier,70B. J. Wogsland,70R. Eckmann,71J. L. Ritchie,71A. M. Ruland,71C. J. Schilling,71 R. F. Schwitters,71B. C. Wray,71B. W. Drummond,72J. M. Izen,72X. C. Lou,72F. Bianchi,73a,73bD. Gamba,73a,73b M. Pelliccioni,73a,73bM. Bomben,74a,74bL. Bosisio,74a,74bC. Cartaro,74a,74bG. Della Ricca,74a,74bL. Lanceri,74a,74b L. Vitale,74a,74bV. Azzolini,75N. Lopez-March,75F. Martinez-Vidal,75D. A. Milanes,75A. Oyanguren,75J. Albert,76
Sw. Banerjee,76B. Bhuyan,76H. H. F. Choi,76K. Hamano,76G. J. King,76R. Kowalewski,76M. J. Lewczuk,76 I. M. Nugent,76J. M. Roney,76R. J. Sobie,76T. J. Gershon,77P. F. Harrison,77J. Ilic,77T. E. Latham,77 G. B. Mohanty,77E. M. T. Puccio,77H. R. Band,78X. Chen,78S. Dasu,78K. T. Flood,78Y. Pan,78R. Prepost,78
C. O. Vuosalo,78and S. L. Wu78 (BABARCollaboration)
1
Laboratoire d’Annecy-le-Vieux de Physique des Particules (LAPP), Universite´ de Savoie, CNRS/IN2P3, F-74941 Annecy-Le-Vieux, France
2Universitat de Barcelona, Facultat de Fisica, Departament ECM, E-08028 Barcelona, Spain
3aINFN Sezione di Bari, I-70126 Bari, Italy
3bDipartimento di Fisica, Universita` di Bari, I-70126 Bari, Italy
4University of Bergen, Institute of Physics, N-5007 Bergen, Norway
5Lawrence Berkeley National Laboratory and University of California, Berkeley, California 94720, USA
6University of Birmingham, Birmingham, B15 2TT, United Kingdom
7Ruhr Universita¨t Bochum, Institut fu¨r Experimentalphysik 1, D-44780 Bochum, Germany
8University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z1
9Brunel University, Uxbridge, Middlesex UB8 3PH, United Kingdom
10Budker Institute of Nuclear Physics, Novosibirsk 630090, Russia
11University of California at Irvine, Irvine, California 92697, USA
12University of California at Riverside, Riverside, California 92521, USA
13University of California at San Diego, La Jolla, California 92093, USA
14University 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
16California Institute of Technology, Pasadena, California 91125, USA
17University of Cincinnati, Cincinnati, Ohio 45221, USA
18University of Colorado, Boulder, Colorado 80309, USA
19Colorado State University, Fort Collins, Colorado 80523, USA
20Technische Universita¨t Dortmund, Fakulta¨t Physik, D-44221 Dortmund, Germany
21Technische Universita¨t Dresden, Institut fu¨r Kernund Teilchenphysik, D-01062 Dresden, Germany
22Laboratoire Leprince-Ringuet, CNRS/IN2P3, Ecole Polytechnique, F-91128 Palaiseau, France
23University of Edinburgh, Edinburgh EH9 3JZ, United Kingdom
24aINFN Sezione di Ferrara, I-44100 Ferrara, Italy
24bDipartimento di Fisica, Universita` di Ferrara, I-44100 Ferrara, Italy
25INFN Laboratori Nazionali di Frascati, I-00044 Frascati, Italy
26aINFN Sezione di Genova, I-16146 Genova, Italy
26bDipartimento di Fisica, Universita` di Genova, I-16146 Genova, Italy
27Harvard University, Cambridge, Massachusetts 02138, USA
28Universita¨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
30Imperial College London, London, SW7 2AZ, United Kingdom
31University of Iowa, Iowa City, Iowa 52242, USA
32Iowa State University, Ames, Iowa 50011-3160, USA
34Laboratoire 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
35Lawrence Livermore National Laboratory, Livermore, California 94550, USA
36University of Liverpool, Liverpool L69 7ZE, United Kingdom
37Queen Mary, University of London, London, E1 4NS, United Kingdom
38University of London, Royal Holloway and Bedford New College, Egham, Surrey TW20 0EX, United Kingdom
39University of Louisville, Louisville, Kentucky 40292, USA
40Johannes Gutenberg-Universita¨t Mainz, Institut fu¨r Kernphysik, D-55099 Mainz, Germany
41
University of Manchester, Manchester M13 9PL, United Kingdom
42University of Maryland, College Park, Maryland 20742, USA
43University of Massachusetts, Amherst, Massachusetts 01003, USA
44Massachusetts Institute of Technology, Laboratory for Nuclear Science, Cambridge, Massachusetts 02139, USA
45McGill University, Montre´al, Que´bec, Canada H3A 2T8
46aINFN Sezione di Milano, I-20133 Milano, Italy
46bDipartimento di Fisica, Universita` di Milano, I-20133 Milano, Italy
47University of Mississippi, University, Mississippi 38677, USA
48Universite´ de Montre´al, Physique des Particules, Montre´al, Que´bec, Canada H3C 3J7
49Mount Holyoke College, South Hadley, Massachusetts 01075, USA
50aINFN Sezione di Napoli, I-80126 Napoli, Italy
50bDipartimento di Scienze Fisiche, Universita` di Napoli Federico II, I-80126 Napoli, Italy
51NIKHEF, National Institute for Nuclear Physics and High Energy Physics, NL-1009 DB Amsterdam, The Netherlands
52University of Notre Dame, Notre Dame, Indiana 46556, USA
53Ohio State University, Columbus, Ohio 43210, USA
54University of Oregon, Eugene, Oregon 97403, USA
55a
INFN Sezione di Padova, I-35131 Padova, Italy
55bDipartimento di Fisica, Universita` di Padova, I-35131 Padova, Italy
56Laboratoire de Physique Nucle´aire et de Hautes Energies, IN2P3/CNRS, Universite´ Pierre et Marie Curie-Paris6,
Universite´ Denis Diderot-Paris7, F-75252 Paris, France
57University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
58aINFN Sezione di Perugia, I-06100 Perugia, Italy
58bDipartimento di Fisica, Universita` di Perugia, I-06100 Perugia, Italy
59aINFN Sezione di Pisa, I-56127 Pisa, Italy
59bDipartimento di Fisica, Universita` di Pisa, I-56127 Pisa, Italy
59cScuola Normale Superiore di Pisa, I-56127 Pisa, Italy
60Princeton University, Princeton, New Jersey 08544, USA
61aINFN Sezione di Roma, I-00185 Roma, Italy
61bDipartimento di Fisica, Universita` di Roma La Sapienza, I-00185 Roma, Italy
62Universita¨t Rostock, D-18051 Rostock, Germany
63Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, OX11 0QX, United Kingdom
64CEA, Irfu, SPP, Centre de Saclay, F-91191 Gif-sur-Yvette, France
65SLAC National Accelerator Laboratory, Stanford, California 94309 USA
66University of South Carolina, Columbia, South Carolina 29208, USA
67Stanford University, Stanford, California 94305-4060, USA
68State University of New York, Albany, New York 12222, USA
69Tel Aviv University, School of Physics and Astronomy, Tel Aviv, 69978, Israel
70University of Tennessee, Knoxville, Tennessee 37996, USA
71University of Texas at Austin, Austin, Texas 78712, USA
72
University of Texas at Dallas, Richardson, Texas 75083, USA
73aINFN Sezione di Torino, I-10125 Torino, Italy
73bDipartimento di Fisica Sperimentale, Universita` di Torino, I-10125 Torino, Italy
74aINFN Sezione di Trieste, I-34127 Trieste, Italy
**Also at Universita` di Sassari, Sassari, Italy.
{Also at 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.
kNow at University of South Alabama, Mobile, AL 36688, USA.
xAlso at Universita` di Roma La Sapienza, I-00185 Roma, Italy.
‡
Also at Universita` di Perugia, Dipartimento di Fisica, Perugia, Italy.
†Now at Temple University, Philadelphia, PA 19122, USA.
74bDipartimento di Fisica, Universita` di Trieste, I-34127 Trieste, Italy
75IFIC, Universitat de Valencia-CSIC, E-46071 Valencia, Spain
76University of Victoria, Victoria, British Columbia, Canada V8W 3P6
77Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom
78University of Wisconsin, Madison, Wisconsin 53706, USA
(Received 13 July 2009; revised manuscript received 9 November 2009; published 9 December 2009)
We present updated measurements of the branching fractions for B0 meson decays to K0, , ,
!, 0K0, 00, 0, and 0!, and branching fractions and CP-violating charge asymmetries for Bþ
decays to þ, Kþ, 0þ, and 0Kþ. The data represent the full data set of 467 106 B B pairs
collected with the BABAR detector at the PEP-II asymmetric-energy eþecollider at the SLAC National
Accelerator Laboratory. Besides large signals for the four charged B decay modes and for B0! 0K0, we
find evidence for three B0 decay modes at greater than 3:0 significance. We find BðB0! K0Þ ¼
ð1:15þ0:43
0:38 0:09Þ 106, BðB0! !Þ ¼ ð0:94þ0:350:30 0:09Þ 106, and BðB0! 0!Þ ¼
ð1:01þ0:46
0:38 0:09Þ 106, where the first (second) uncertainty is statistical (systematic). For the Bþ!
Kþ decay mode, we measure the charge asymmetryAchðBþ! KþÞ ¼ 0:36 0:11 0:03.
DOI:10.1103/PhysRevD.80.112002 PACS numbers: 13.25.Hw, 11.30.Er, 12.15.Hh
Experimental measurements of branching fractions and CP-violating charge asymmetries in rare B decays play an important role in testing the theoretical predictions of the standard model and its extensions. We report the results of branching fraction measurements for B0 meson decays to
K0, , , !, 0K0, 00, 0, and 0! final states
and of branching fraction and charge asymmetry measure-ments for Bþdecays to þ, Kþ, 0þ, and 0Kþ[1]. We search for charge asymmetry by measuring
Ach
þ
þ þ; (1)
where ¼ ðB! fÞ is the decay width for a given charged final state f. These branching fraction and charge asymmetry measurements represent an improvement over previous results published by BABAR [2] and Belle [3].
The branching fractions and charge asymmetries of the charmless hadronic B decays are predicted using ap-proaches based on QCD factorization [4–7] and flavor SU(3) symmetry [8–10]. These B decays proceed through loop (penguin) and suppressed tree diagram amplitudes, as shown in Fig.1. The branching fraction and charge asym-metry measurements may provide sensitivity to the pres-ence of heavy nonstandard model particles in the loop diagrams [11]. The measured 0K branching fraction is found to be much larger than the K one [2,3]. Many suggestions have been proposed to explain such a differ-ence, including flavor singlet enhancement [12], intrinsic charm [13], and constructively interfering internal penguin diagrams [14,15]. This last approach is supported by next-to-leading order QCD factorization calculations [6].
The CP-violating parameters S0Kand SK, measured in
the time-dependent analysis of 0K0and K0decays [16],
are expected to equal Sc cs sin2, where Sc cs is
mea-sured in the Cabibbo-Kobayashi-Maskawa (CKM) favored b ! c cs decays, if penguin b ! s transitions are domi-nant. However, CKM-suppressed amplitudes and
color-suppressed tree diagrams can introduce additional weak phases whose contributions may not be negligible [6,17,18]. As a consequence, deviations from sin2 may occur even within the standard model. Rates of the decay modes to , , 00, and 0 are used in flavor SU(3)-based calculations of thejSc cs Sfj (with f ¼ 0K, K) bound [17]. This bound may be improved by more precise measurements of the branching fractions of these modes.
The charge asymmetry is expected to be sizable in Kþ and suppressed in 0Kþdecays [6,9,19]. However, differ-ent approaches predict the two asymmetries to have the same [9] or opposite [6] signs; precise measurement of such asymmetries can discriminate between these models. Furthermore, the charge asymmetries in 0þ and þ decays are expected to be sizable [6,9], with model-dependent predictions for their magnitudes.
FIG. 1. Examples of Feynman diagrams involved in decays
studied in this paper: (a), (b) penguin diagrams, (c) Cabibbo-suppressed tree diagram, (d) gluonic penguin diagram.
The results presented here are based on the full data set collected with the BABAR detector [20] at the PEP-II asymmetric-energy eþe collider located at the SLAC National Accelerator Laboratory. An integrated luminosity of 426 fb1, corresponding to NB B¼ 467 106B B pairs,
was recorded at the ð4SÞ resonance (center-of-mass en-ergy pffiffiffis¼ 10:58 GeV). A further 44 fb1 was collected approximately 40 MeV below the resonance (off-peak) for the study of the eþe! q q background, where q is a u, d, s, or c quark.
Charged particles are detected, and their momenta mea-sured, by a combination of a vertex tracker, consisting of five layers of double-sided silicon microstrip detectors, and a 40-layer drift chamber, both operating in the 1.5 T mag-netic field of a superconducting solenoid. We identify photons and electrons using a CsI(Tl) electromagnetic calorimeter (EMC). Further charged-particle identification (PID) is provided by the average energy loss (dE=dx) measurements in the tracking devices and by the informa-tion provided by an internally reflecting ring-imaging Cherenkov detector (DIRC) covering the central region.
We select , 0, , 0, K0
S, !, and 0 candidates
through the decays ! (), ! þ0 (3),
0! þ with ! (0 ), 0! 0 (0),
! KþK, 0 ! þ, K0
S! þ, ! !
þ0, and 0 ! . We do not study the decay B0 ! 00 with both 0 mesons decaying to , because it suffers large backgrounds. Requirements applied to the photon energy E and to the invariant mass of the B
daughters are listed in Table I. The requirements on the and 0 invariant masses depend on the decay mode. Branching fractions of charged B decays with 0 in the final state and of B0! 0K0Sare higher than those of the
other neutral B modes. In neutral decay modes we apply a tighter requirement on 3 invariant mass in order to
prevent possible contamination from B B background. The different requirements on the 0 mass increase the purity of the charged B and 0K0
Smodes and enhance the
selection efficiency for the other neutral B decay modes. The energy (momentum) of the 0 () candidates is
re-quired to exceed 200 MeV (200 MeV=c) in the laboratory frame. The prompt charged tracks in Bþ! 0þ and secondary charged tracks in , 0, and ! candidates are required to have DIRC, dE=dx, and EMC signatures sistent with the pion hypothesis. After selection, we con-strain the , 0, and 0 masses to their world average
values [21]. The prompt charged track in Bþ ! 0Kþ is required to be consistent with the kaon hypothesis. The signatures for the charged kaons from decays are re-quired to be inconsistent with hypotheses for electrons, pions and protons. For the prompt charged track in Bþ decays to Kþ and þ, we define the variablesCK and Cas CK;¼ meas K; exp K; meas K; ; (2) where meas K; ( exp
K;) is the measured (expected) DIRC
Cherenkov angle and meas
K; is its uncertainty, for the
kaon and pion hypothesis, respectively. We require 3 < CK< 13 and 13 < C< 3. For KS0candidates we require
a vertex 2 probability larger than 0.001 and a
recon-structed decay length greater than 3 times its uncertainty. We reconstruct the B meson candidate by combining the four-momenta of the final state particles and imposing a vertex constraint. A B meson candidate is kinematically characterized by the energy-substituted mass mES¼
ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi s=4 p2
B
q
and energy difference E ¼ EB12
ffiffiffi s p
, where (EB,pB) is the B-meson four-momentum vector expressed
TABLE I. Selection requirements on the invariant masses of the signal resonances and on the
laboratory energies of the photons coming from their decays.
State Invariant mass (MeV=c2) E
(MeV) 0 120 < m < 150 >30 Prompt 505 < m< 585 >100 Secondary 490 < m< 600 >50a 3 in Bþdecays 534 < m< 561 3 in B0decays 535 < m< 555 0 in Bþand B0! 0KS0decays 945 < m< 970 0 in other B0 decays 930 < m< 990 0in Bþ decays 930 < m< 980 >200 0in B0! 0KS0 930 < m< 980 >100 0in other B0decays 910 < m< 990 >200 0 470 < m < 990 ! 735 < m< 825 1012 < mKþK< 1026 K0 S 486 < m< 510 a
in the ð4SÞ rest frame. For signal events, the mESand E
distributions peak around 5:28 GeV=c2 and zero, respec-tively. We require 5:25 < mES< 5:29 GeV=c2andjEj <
0:2 GeV for all decay modes except B0! K0
S, where we
require0:15 < E < 0:2 GeV in order to suppress most of the background from radiative B decays.
Backgrounds arise primarily from random combinations of tracks and neutral clusters in eþe! q q continuum events. We use large samples of Monte Carlo (MC) simu-lated [22] events and control samples to optimize criteria to suppress the background. We reject continuum events by using the angle Tbetween the thrust axis of the B
candi-date in the ð4SÞ frame and that of the rest of the event. The thrust axis of the B candidate is given by the thrust axis of the B decay products. The distribution of j cos Tj is
sharply peaked near 1.0 for jetlike q q pair events and is nearly uniform for ð4SÞ ! B B events. We require j cos Tj < 0:9 (0.85 for 0þ, 0.8 for ! and
0!). To discriminate against -pair and two-photon
backgrounds, and to better describe the event shape, we require the event to contain at least three charged tracks, or one track beyond the minimum required for the signal decay topology, whichever is larger.
In ! () decays, we define H (H) as the
cosine of the angle between the direction of a daughter (K) and the flight direction of the parent of () in the () rest frame; for 0, H is the cosine of the angle
between the direction of a daughter pion and the flight direction of the 0 in the rest frame. For B decays containing an ! meson in the final state we define H!
as the cosine of the angle between the B recoil direction and the normal to the plane defined by the ! daughters in the ! rest frame. We require jHj < 0:95 in B0 !
decay modes. We reject candidate events if jHj > 0:9 ( > 0:75 in the Bþ! 0þ decay mode).
For the B0 !
K0S (Bþ! hþ, hþ ¼ Kþ, þ)
decay, the main source of B B background is the B0 ! 0K0
S (Bþ! 0hþ) decay. To suppress this background,
we search for 0 candidates with a photon in common
(overlapping) with the candidate from the reconstructed signal B candidate. We require the 0mass not to be in the
range ð0:117; 0:152Þ GeV=c2 for the B0 ! K0S decay
mode, and ð0:118; 0:150Þ GeV=c2 for the Bþ!
hþ
decay modes. Further suppression of this background is obtained with suitable requirements onjHj and on the energy of the second (nonoverlapping with ) 0 photon
(E2nd ). We optimize these requirements by maximizing
S=pffiffiffiffiffiffiffiffiffiffiffiffiffiS þ B, where S (B) is the number of signal (back-ground) events surviving the selection. We find the optimal criteria to bejHj < 0:966 and E2nd
< 0:207 GeV for the
B0 ! K0Sdecay mode, andjHj < 0:977 and E2nd <
0:143 GeV for the Bþ! hþ decay modes.
We find a mean number of B candidates per event in the range 1.0–1.4, depending on the final state. Signal events
are divided into two categories: a correctly reconstructed (CR) signal where all candidate particles come from the correct signal B, and a self cross-feed (SCF) signal where at least one candidate particle is exchanged with a particle coming from the rest of the event. Simulations show that the fraction of SCF candidates is in the range (3–7)% in charged B decay modes and (2–20)% in neutral B decay modes. If an event has multiple B candidates, we select the candidate with the highest B vertex 2 probability,
deter-mined from a vertex fit that includes both charged and neutral particles [23]. This algorithm selects the correct candidate, if present, with an efficiency of (91–99)% and introduces negligible bias.
We obtain yields from unbinned extended maximum-likelihood (ML) fits. The main input observables are E, mES, and a Fisher discriminantF [24]. Where relevant, the
invariant masses mres of the intermediate resonances and
angular variablesH are used. The Fisher discriminant F combines five variables: the angles with respect to the beam axis of the B momentum and B thrust axis, the zeroth and second angular moments L0;2of the energy flow about
the B thrust axis, and the absolute value of the continuous output of a flavor-tagging algorithm. The first four varia-bles are evaluated in the ð4SÞ rest frame. The moments are defined by Lr¼
P
sps j cos sjr, where s is the
angle with respect to the B thrust axis of track or neutral cluster s with momentum ps, and the sum excludes the B
candidate. Flavor-tagging information is derived from an analysis of the decay products of the non-signal candidate B meson (Btag), using a neural network based technique
[25]. The output value of the tagging algorithm reflects the different final states identified in Btag decay. In particular,
the presence of a lepton in the final state usually results in a large tagging output value, for both B0B0 and BþB
events. Since leptons are not generally present in contin-uum background events, the inclusion of the tagging algo-rithm output in F improves its discriminating power between continuum background and B B events. The coef-ficients of F are chosen to maximize the separation be-tween the signal and the continuum background. They are determined from studies of MC signal events and off-peak data.
The set of probability density functions (PDF) used in the ML fits, specific to each decay mode, is determined on the basis of studies with MC samples. We estimate B B backgrounds using MC samples of B decays. Where needed, we add components to account for B B background events with a mES or E distribution that peaks in the
signal region and for background from B meson decays with charmed particles in the final state.
The extended likelihood function is
L ¼ expX3 j¼1 nj YN i¼1 X3 j¼1 njPjðxiÞ ; (3)
where N is the number of input events, njis the number of
events for hypothesis j (j ¼ 1 for signal, j ¼ 2 for con-tinuum background, and j ¼ 3 for B B background), and PjðxiÞ is the corresponding PDF evaluated with the
ob-servablesxi of the ith event. In the B0 ! 0!, 0, and 0! decay modes the signal includes both the CR and
SCF signal components with the SCF fraction fixed to the value estimated from simulation. Because of the similar kinematics and branching fractions of the Kþ and þ decay modes, we perform a combined fit to extract the two signal yields and charge asymmetries. In this fit we use the CKandCvariables to discriminate the mass hypothesis of
the prompt track. Since the correlations among the observ-ables in the data are small, we assume eachPj to be the product of the PDFs for the separate variables. Correlations between the Kþand þsignal yields (charge asymme-tries) are below 5% (7%).
We determine the PDF functional form and parameters from MC simulation for the signal and B B backgrounds, and from sideband data (5:25 < mES< 5:27 GeV=c2;
0:1 < jEj < 0:2 GeV) for the continuum background. For Bþ ! hþ decay modes, PDF functional form and parameters for the continuum background are determined using off-peak data. We parameterize each of the functions P1ðmESÞ, P1ðEÞ, PjðF Þ, and the peaking components of
PjðmresÞ with either a symmetric or a bifurcated Gaussian,
the sum of two symmetric or bifurcated Gaussian shapes, a bifurcated Gaussian distribution with exponential tails [26] or a Crystal Ball function [27], as required to describe the distribution. Slowly varying distributions (mresand E for
the continuum background, and angular variables) are represented by linear or quadratic functions. For the con-tinuum background, the mES distribution is described by
the ARGUS function [28]. Large data control samples of B decays to charmed final states of similar topologies are used to verify the simulated resolutions in mES and E.
Where the control samples reveal differences between data and MC samples in mass (energy) resolution, we correct the mean and scale the width of the mass (energy) distri-bution used in the likelihood fits.
The validity of the fit procedure and PDF parameteriza-tion, including the effects of unmodeled correlations among observables, is checked with simulated experi-ments. This is done by embedding a number of signal and peaking B B background events from fully simulated MC samples and by drawing a number of q q and charm B B events from PDFs, according to the values found in the data. In each fit the free parameters are the yields, the charge asymmetry for the signal and continuum back-ground, and several parameters describing the E, mES,
andF distributions of the continuum background. A sys-tematic uncertainty due to fixing signal and background parameters in the fit is accounted. The charge asymmetry for B B background is fixed to zero in the fit. A systematic is evaluated to account for this restriction.
Tables II andIII show, for B0 and Bþ decays,
respec-tively, the measured yields, fit biases, efficiencies, and products of daughter branching fractions for each decay mode. The efficiency is calculated as the ratio of the number of signal MC events after the event selection to the total generated, and is corrected for known differences between simulations and data. We compute the branching fractions from the fitted signal event yields, reconstruction efficiencies, daughter branching fractions, and the number of produced B mesons NB B, assuming equal production
rates of charged and neutral B pairs from ð4SÞ decays. We correct the yields for any bias measured with the simula-tions. We combine results from different subdecays by adding the values of 2 lnðL=LmaxÞ (parameterized in
terms of the branching fraction or charge asymmetry), where Lmax is the value of L at its maximum, taking
into account the correlated and uncorrelated systematic errors. We report the branching fractions for the individual decay channels and their significances S in units of stan-dard deviations (). For B0 ! 0K0
Sand all charged decay
modes, where the significance of the branching fraction is always greater than 7, the value of S is omitted. For the combined measurements we also report the 90% confi-dence level (CL) upper limits of the branching fraction for the B0modes where the significance is less than 5. For
charged B decays we give the combined result for the charge asymmetry Ach and its significance SA in units of .
The statistical uncertainty on the signal yield and charge asymmetry is calculated as the change in the central value when the quantity2 lnL increases by one from its mini-mum. The significance is calculated as the square root of 2 lnðL0=LmaxÞ, with systematic uncertainties included,
where L0 is the value ofL for zero signal events or zero
value for the charge asymmetry. We determine a Bayesian 90% CL upper limit on the branching fraction, assuming a uniform prior probability distribution, by finding the branching fraction below which lies 90% of the total of the likelihood integral in the positive branching fraction region.
Figures2and3show the projections onto the mESand
E variables for the four neutral decay modes that have a branching fraction significance greater than 3, and for the four charged decay modes, respectively. For each decay mode we optimize a requirement on the probability ratio P1=ðP1þ P2þ P3Þ in order to enhance the visibility of
the signal. The probabilities Pj are evaluated without using the variable shown. The points show the data that satisfy such a requirement, while the solid curves show the total rescaled fit functions. In 0! decays, a fit performed on ! mass sidebands m< 735 MeV=c2 or m>
825 MeV=c2 shows that contamination from possible
B0! 0þ0 background is negligible.
The main sources of systematic error include ML fit bias (0–14 events) and uncertainties in the PDF
parameteriza-TABLE II. Fitted signal event yield and fit bias in events (ev), detection efficiency , daughter branching fraction productQBi,
significanceS, and measured branching fraction B with statistical error for each B0decay mode. For the combined measurements we
give the significance (with systematic uncertainties included) and the branching fraction with the statistical and systematic uncertainties (in parentheses the 90% CL upper limit). Significances greater than 7 standard deviations () are omitted.
Mode Yield (ev) Fit bias (ev) (%) QBi(%) SðÞ Bð106Þ
K0 21þ109 0 32.1 13.6 2.5 1:03þ0:490:44 3K0 12þ76 0 20.6 7.9 2.5 1:56þ0:920:79 K0 3:5 1:15þ0:43 0:38 0:09 ( < 1:8) 13þ109 þ1 23.9 15.5 1.4 0:7þ0:60:5 3 9þ65 þ1 18.0 17.9 1.5 0:5þ0:40:3 33 0:2þ2:41:7 0:1 11.1 5.2 0.1 0:1þ0:90:6 1:9 0:5 0:3 0:1 ( < 1:0) 0þ65 0 29.3 19.4 0.1 0:0 0:2 3 4þ43 0 18.3 11.2 1.9 0:4þ0:40:3 1:4 0:2 0:2 0:1 ( < 0:5) ! 36þ1312 þ3 18.7 35.1 3.4 1:08þ0:420:39 3! 8þ75 þ1 13.1 20.2 1.8 0:59þ0:570:40 ! 3:7 0:94þ0:35 0:30 0:09 ( < 1:4) 0K0 490þ2524 2 26.6 6.1 64:9þ3:33:2 0K0 1003 41 þ27 28.3 10.2 72:4 3:0 0K0 68:5 2:2 3:1 00 1:6þ2:11:1 0 19.9 3.1 2.2 0:6þ0:70:3 00 8þ97 þ2 19.8 10.3 0.8 0:6þ0:90:7 00 1:0 0:6þ0:5 0:4 0:4 ( < 1:7) 0 2þ21 0 24.4 8.6 0.0 0:2þ0:20:1 0 5þ87 0 23.9 14.5 0.7 0:3þ0:50:4 0 0:5 0:2 0:2 0:3 ( < 1:1) 0! 14þ76 þ1 17.9 15.6 3.4 1:03þ0:540:46 0! 16þ1715 2 15.2 26.2 1.2 0:94þ0:910:81 0! 3:6 1:01þ0:46 0:38 0:09 ( < 1:8)
TABLE III. Fitted signal event yield and fit bias in events (ev), detection efficiency , daughter branching fraction productQBi,
measured branching fractionB, charge asymmetry Achwith statistical error, and significanceSAof the charge asymmetry for each
charged decay mode. For the combined measurements we give the branching fraction, the charge asymmetry and the significance of the charge asymmetry with the statistical and systematic uncertainties.
Mode Yield (ev) Fit bias (ev) (%) QBi(%) Bð106Þ Ach SAðÞ
þ 286þ3130 þ18 35.1 39.3 4:16þ0:480:47 0:02þ0:100:11 0.4 3þ 95þ1918 þ7 23.4 22.7 3:53þ0:770:73 þ0:06 0:18 0.4 þ 4:00 0:40 0:24 0:03 0:09 0:03 0:3 Kþ 215þ3130 þ21 34.0 39.3 3:11þ0:500:48 0:37 0:12 3.1 3Kþ 69þ1615 þ6 22.9 22.7 2:60þ0:660:62 0:32 0:22 1.5 Kþ 2:94þ0:39 0:34 0:21 0:36 0:11 0:03 3:3 0þ 96þ2019 þ1 29.4 17.5 4:0 0:8 0:25 0:19 1.3 0þ 111þ3129 þ7 25.9 29.4 2:9þ0:90:8 þ0:56þ0:290:27 2.1 0þ 3:5 0:6 0:2 þ0:03 0:17 0:02 0:2 0Kþ 1601þ4443 5 28.7 17.5 68:5þ1:91:8 0:004 0:027 0.2 0Kþ 2991þ7271 10 29.3 29.4 74:6 1:8 þ0:016 0:023 0.7 0Kþ 71:5 1:3 3:2 þ0:008þ0:017 0:018 0:009 0:4
tion (0–12 events). The ML fit bias systematic error is taken to be half of the bias, summed in quadrature with its statistical uncertainty. The uncertainties related to the PDF parameterization are obtained by varying the PDF parameters within their errors. Published world averages [21] provide the uncertainties of the B-daughter branching fractions (0–4)%. These uncertainties are the main contri-bution to the systematic errors of the B ! 0K decay modes. The uncertainty on NB B is 1.1%. Other sources of
systematic uncertainty are track (1%) and neutral particle (3–6)% reconstruction efficiencies; selection efficiency uncertainties are 1% each for the cos T and PID
require-ments. Using large inclusive kaon and B decay samples we estimate a systematic uncertainty forAch of 0.005 due to the dependence of the reconstruction efficiency on the charge of the high momentum K. Other sources of sys-tematic uncertainties forAch are the fit bias (0–0.02) and the presence of a fit bias in the signal yield (0.02–0.03). The systematic uncertainty due to fixing the value of the charge asymmetry in B B background components is taken to be the largest deviation observed when varying this value of 10%, and is in range (0–0.02).
In summary we present updated measurements of branching fractions for eight B0 and four Bþ decays to charmless meson pairs. The results shown in Tables II and III are consistent with, but generally more precise than, previous measurements [2,3] and supersede our pre-vious ones [2]. The branching fraction results are in agreement with predictions within the theoretical uncer-tainties that limit discrimination between different models [4–10]. We find evidence for three B0 decay modes: K0
(3:5), ! (3:7) and 0! (3:6). In the decay mode Bþ! Kþ we find evidence at 3:3 for nonzero charge asymmetry, in agreement with theoretical predictions [6,9,19]. Discrimination between QCD factorization [6] and flavor SU(3) [9] symmetry models, based on the relative sign of the charge asymmetry in Bþ! Kþand Bþ! 0Kþdecays, is limited by the accuracy of the latter measurement. The measurement ofAchfor 0þshows a
slightly better agreement with the QCD factorization pre-diction [6] than with the flavor SU(3) symmetry based model [9], within large theoretical and experimental uncertainties. 5.250 5.26 5.27 5.28 5.29 10 20 30 40 5.250 5.26 5.27 5.28 5.29 10 20 30 40 -0.1 0 0.1 0.2 0 10 20 30 -0.1 0 0.1 0.2 0 10 20 30 (b) ) a ( 2
Events / 2 MeV/c Events / 15 MeV
5.25 5.26 5.27 5.28 5.29 0 10 20 5.25 5.26 5.27 5.28 5.29 0 10 20 -0.2 -0.1 0 0.1 0.2 0 5 10 15 20 -0.2 -0.1 0 0.1 0.2 0 5 10 15 20 5.25 5.26 5.27 5.28 5.29 0 100 200 300 400 5.25 5.26 5.27 5.28 5.29 0 100 200 300 400 -0.2 -0.1 0 0.1 0.2 0 200 400 -0.2 -0.1 0 0.1 0.2 0 200 400 ) 2 (GeV/c ES m 5.250 5.26 5.27 5.28 5.29 10 20 30 ) 2 (GeV/c ES m 5.250 5.26 5.27 5.28 5.29 10 20 30 E (GeV) ∆ -0.2 -0.1 0 0.1 0.2 0 10 20 E (GeV) ∆ -0.2 -0.1 0 0.1 0.2 0 10 20 (c) (d) (e) (f) (g) (h) 2
Events / 2 MeV/c Events / 20 MeV
FIG. 2 (color online). The B0candidate mESand E projections for KS0[(a), (b)], ! [(c), (d)], 0KS0[(e), (f )], and 0! [(g), (h)]
decays, with subdecays combined. Points with errors represent the data, solid curves the full fit functions, and dashed curves the background functions.
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 Forschungs-gemeinschaft (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 Educacio´n y Ciencia (Spain), and the Science and Technology Facilities Council (United Kingdom). Individuals have received sup-port from the Marie-Curie IEF program (European Union) and the A. P. Sloan Foundation.
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![FIG. 3 (color online). The B þ candidate m ES and E projections for þ [(a), (b)], K þ [(c), (d)], 0 þ [(e), (f )], and 0 K þ [(g), (h)] decays, with subdecays combined](https://thumb-eu.123doks.com/thumbv2/123doknet/14140071.470264/11.918.207.707.68.563/fig-color-online-candidate-projections-decays-subdecays-combined.webp)
