Article
Reference
Observation of B
s0->ψ(2S)ϕ and Measurement of the Ratio of Branching Fractions B (B
s0->ψ(2S)ϕ)/ B (B
s0->J/ψϕ)
CDF Collaboration
CAMPANELLI, Mario (Collab.), et al .
Abstract
We report the first observation of B0s→ψ(2S)ϕ decay in pp¯ collisions at s√=1.96 TeV using 360 pb−1 of data collected by the CDF II detector at the Fermilab Tevatron. We observe 20.2±5.0 and 12.3±4.1 B0s→ψ(2S)ϕ candidates, in ψ(2S)→μ+μ− and ψ(2S)→J/ψπ+π− decay modes, respectively. We present a measurement of the relative branching fraction B(B0s→ψ(2S)ϕ)/B(B0s→J/ψϕ)=0.52±0.13(stat)±0.04(syst)±0.06(BR) using the ψ(2S)→μ+μ−
decay mode.
CDF Collaboration, CAMPANELLI, Mario (Collab.), et al . Observation of B
s0->ψ(2S)ϕ and Measurement of the Ratio of Branching Fractions B(B
s0->ψ(2S)ϕ)/B(B
s0->J/ψϕ). Physical Review Letters , 2006, vol. 96, no. 23, p. 231801
DOI : 10.1103/PhysRevLett.96.231801
Available at:
http://archive-ouverte.unige.ch/unige:38338
Disclaimer: layout of this document may differ from the published version.
1 / 1
Observation of B
0s! 2S and Measurement of the Ratio of Branching Fractions B B
0s! 2S= B B
0s! J=
A. Abulencia,23D. Acosta,17J. Adelman,13T. Affolder,10T. Akimoto,55M. G. Albrow,16D. Ambrose,16S. Amerio,43 D. Amidei,34A. Anastassov,52K. Anikeev,16A. Annovi,18J. Antos,1M. Aoki,55G. Apollinari,16J.-F. Arguin,33 T. Arisawa,57A. Artikov,14W. Ashmanskas,16A. Attal,8F. Azfar,42P. Azzi-Bacchetta,43P. Azzurri,46N. Bacchetta,43 H. Bachacou,28W. Badgett,16A. Barbaro-Galtieri,28V. E. Barnes,48B. A. Barnett,24S. Baroiant,7V. Bartsch,30G. Bauer,32
F. Bedeschi,46S. Behari,24S. Belforte,54G. Bellettini,46J. Bellinger,59A. Belloni,32E. Ben Haim,44D. Benjamin,15 A. Beretvas,16J. Beringer,28T. Berry,29A. Bhatti,50M. Binkley,16D. Bisello,43R. E. Blair,2C. Blocker,6B. Blumenfeld,24 A. Bocci,15A. Bodek,49V. Boisvert,49G. Bolla,48A. Bolshov,32D. Bortoletto,48J. Boudreau,47A. Boveia,10B. Brau,10
C. Bromberg,35E. Brubaker,13J. Budagov,14H. S. Budd,49S. Budd,23K. Burkett,16G. Busetto,43P. Bussey,20 K. L. Byrum,2S. Cabrera,15M. Campanelli,19M. Campbell,34F. Canelli,8A. Canepa,48D. Carlsmith,59R. Carosi,46 S. Carron,15M. Casarsa,54A. Castro,5P. Catastini,46D. Cauz,54M. Cavalli-Sforza,3A. Cerri,28L. Cerrito,42S. H. Chang,27 J. Chapman,34Y. C. Chen,1M. Chertok,7G. Chiarelli,46G. Chlachidze,14F. Chlebana,16I. Cho,27K. Cho,27D. Chokheli,14
J. P. Chou,21P. H. Chu,23S. H. Chuang,59K. Chung,12W. H. Chung,59Y. S. Chung,49M. Ciljak,46C. I. Ciobanu,23 M. A. Ciocci,46A. Clark,19D. Clark,6M. Coca,15G. Compostella,43M. E. Convery,50J. Conway,7B. Cooper,30 K. Copic,34M. Cordelli,18G. Cortiana,43F. Cresciolo,46A. Cruz,17C. Cuenca Almenar,7J. Cuevas,11R. Culbertson,16
D. Cyr,59S. DaRonco,43S. D’Auria,20M. D’Onofrio,3D. Dagenhart,6P. de Barbaro,49S. De Cecco,51A. Deisher,28 G. De Lentdecker,49M. Dell’Orso,46F. Delli Paoli,43S. Demers,49L. Demortier,50J. Deng,15M. Deninno,5D. De Pedis,51
P. F. Derwent,16C. Dionisi,51J. R. Dittmann,4P. DiTuro,52C. Do¨rr,25S. Donati,46M. Donega,19P. Dong,8J. Donini,43 T. Dorigo,43S. Dube,52K. Ebina,57J. Efron,39J. Ehlers,19R. Erbacher,7D. Errede,23S. Errede,23R. Eusebi,16 H. C. Fang,28S. Farrington,29I. Fedorko,46W. T. Fedorko,13R. G. Feild,60M. Feindt,25J. P. Fernandez,31R. Field,17 G. Flanagan,48L. R. Flores-Castillo,47A. Foland,21S. Forrester,7G. W. Foster,16M. Franklin,21J. C. Freeman,28I. Furic,13
M. Gallinaro,50J. Galyardt,12J. E. Garcia,46M. Garcia Sciveres,28A. F. Garfinkel,48C. Gay,60H. Gerberich,23 D. Gerdes,34S. Giagu,51P. Giannetti,46A. Gibson,28K. Gibson,12C. Ginsburg,16N. Giokaris,14K. Giolo,48M. Giordani,54 P. Giromini,18M. Giunta,46G. Giurgiu,12V. Glagolev,14D. Glenzinski,16M. Gold,37N. Goldschmidt,34J. Goldstein,42
G. Gomez,11G. Gomez-Ceballos,11M. Goncharov,53O. Gonza´lez,31I. Gorelov,37A. T. Goshaw,15Y. Gotra,47 K. Goulianos,50A. Gresele,43M. Griffiths,29S. Grinstein,21C. Grosso-Pilcher,13R. C. Group,17U. Grundler,23 J. Guimaraes da Costa,21Z. Gunay-Unalan,35C. Haber,28S. R. Hahn,16K. Hahn,45E. Halkiadakis,52A. Hamilton,33 B.-Y. Han,49J. Y. Han,49R. Handler,59F. Happacher,18K. Hara,55M. Hare,56S. Harper,42R. F. Harr,58R. M. Harris,16
K. Hatakeyama,50J. Hauser,8C. Hays,15A. Heijboer,45B. Heinemann,29J. Heinrich,45M. Herndon,59D. Hidas,15 C. S. Hill,10D. Hirschbuehl,25A. Hocker,16A. Holloway,21S. Hou,1M. Houlden,29S.-C. Hsu,9B. T. Huffman,42 R. E. Hughes,39J. Huston,35J. Incandela,10G. Introzzi,46M. Iori,51Y. Ishizawa,55A. Ivanov,7B. Iyutin,32E. James,16
D. Jang,52B. Jayatilaka,34D. Jeans,51H. Jensen,16E. J. Jeon,27S. Jindariani,17M. Jones,48K. K. Joo,27S. Y. Jun,12 T. R. Junk,23T. Kamon,53J. Kang,34P. E. Karchin,58Y. Kato,41Y. Kemp,25R. Kephart,16U. Kerzel,25V. Khotilovich,53 B. Kilminster,39D. H. Kim,27H. S. Kim,27J. E. Kim,27M. J. Kim,12S. B. Kim,27S. H. Kim,55Y. K. Kim,13L. Kirsch,6
S. Klimenko,17M. Klute,32B. Knuteson,32B. R. Ko,15H. Kobayashi,55K. Kondo,57D. J. Kong,27J. Konigsberg,17 A. Korytov,17A. V. Kotwal,15A. Kovalev,45A. Kraan,45J. Kraus,23I. Kravchenko,32M. Kreps,25J. Kroll,45 N. Krumnack,4M. Kruse,15V. Krutelyov,53S. E. Kuhlmann,2Y. Kusakabe,57S. Kwang,13A. T. Laasanen,48S. Lai,33
S. Lami,46S. Lammel,16M. Lancaster,30R. L. Lander,7K. Lannon,39A. Lath,52G. Latino,46I. Lazzizzera,43 T. LeCompte,2J. Lee,49J. Lee,27Y. J. Lee,27S. W. Lee,53R. Lefe`vre,3N. Leonardo,32S. Leone,46S. Levy,13J. D. Lewis,16 C. Lin,60C. S. Lin,16M. Lindgren,16E. Lipeles,9A. Lister,19D. O. Litvintsev,16T. Liu,16N. S. Lockyer,45A. Loginov,36 M. Loreti,43P. Loverre,51R.-S. Lu,1D. Lucchesi,43P. Lujan,28P. Lukens,16G. Lungu,17L. Lyons,42J. Lys,28R. Lysak,1
E. Lytken,48P. Mack,25D. MacQueen,33R. Madrak,16K. Maeshima,16T. Maki,22P. Maksimovic,24S. Malde,42 G. Manca,29F. Margaroli,5R. Marginean,16C. Marino,23A. Martin,60V. Martin,38M. Martı´nez,3T. Maruyama,55 H. Matsunaga,55M. E. Mattson,58R. Mazini,33P. Mazzanti,5K. S. McFarland,49P. McIntyre,53R. McNulty,29A. Mehta,29 S. Menzemer,11A. Menzione,46P. Merkel,48C. Mesropian,50A. Messina,51M. von der Mey,8T. Miao,16N. Miladinovic,6 J. Miles,32R. Miller,35J. S. Miller,34C. Mills,10M. Milnik,25R. Miquel,28A. Mitra,1G. Mitselmakher,17A. Miyamoto,26 N. Moggi,5B. Mohr,8R. Moore,16M. Morello,46P. Movilla Fernandez,28J. Mu¨lmensta¨dt,28A. Mukherjee,16Th. Muller,25 R. Mumford,24P. Murat,16J. Nachtman,16J. Naganoma,57S. Nahn,32I. Nakano,40A. Napier,56D. Naumov,37V. Necula,17
C. Neu,45M. S. Neubauer,9J. Nielsen,28T. Nigmanov,47L. Nodulman,2O. Norniella,3E. Nurse,30T. Ogawa,57S. H. Oh,15 Y. D. Oh,27T. Okusawa,41R. Oldeman,29R. Orava,22K. Osterberg,22C. Pagliarone,46E. Palencia,11R. Paoletti,46 V. Papadimitriou,16A. A. Paramonov,13B. Parks,39S. Pashapour,33J. Patrick,16G. Pauletta,54M. Paulini,12C. Paus,32 D. E. Pellett,7A. Penzo,54T. J. Phillips,15G. Piacentino,46J. Piedra,44L. Pinera,17K. Pitts,23C. Plager,8L. Pondrom,59 X. Portell,3O. Poukhov,14N. Pounder,42F. Prakoshyn,14A. Pronko,16J. Proudfoot,2F. Ptohos,18G. Punzi,46J. Pursley,24
J. Rademacker,42A. Rahaman,47A. Rakitin,32S. Rappoccio,21F. Ratnikov,52B. Reisert,16V. Rekovic,37 N. van Remortel,22P. Renton,42M. Rescigno,51S. Richter,25F. Rimondi,5L. Ristori,46W. J. Robertson,15A. Robson,20
T. Rodrigo,11E. Rogers,23S. Rolli,56R. Roser,16M. Rossi,54R. Rossin,17C. Rott,48A. Ruiz,11J. Russ,12V. Rusu,13 H. Saarikko,22S. Sabik,33A. Safonov,53W. K. Sakumoto,49G. Salamanna,51O. Salto´,3D. Saltzberg,8C. Sanchez,3
L. Santi,54S. Sarkar,51L. Sartori,46K. Sato,55P. Savard,33A. Savoy-Navarro,44T. Scheidle,25P. Schlabach,16 E. E. Schmidt,16M. P. Schmidt,60M. Schmitt,38T. Schwarz,34L. Scodellaro,11A. L. Scott,10A. Scribano,46F. Scuri,46
A. Sedov,48S. Seidel,37Y. Seiya,41A. Semenov,14L. Sexton-Kennedy,16I. Sfiligoi,18M. D. Shapiro,28T. Shears,29 P. F. Shepard,47D. Sherman,21M. Shimojima,55M. Shochet,13Y. Shon,59I. Shreyber,36A. Sidoti,44P. Sinervo,33
A. Sisakyan,14J. Sjolin,42A. Skiba,25A. J. Slaughter,16K. Sliwa,56J. R. Smith,7F. D. Snider,16R. Snihur,33 M. Soderberg,34A. Soha,7S. Somalwar,52V. Sorin,35J. Spalding,16M. Spezziga,16F. Spinella,46T. Spreitzer,33 P. Squillacioti,46M. Stanitzki,60A. Staveris-Polykalas,46R. St. Denis,20B. Stelzer,8O. Stelzer-Chilton,42D. Stentz,38 J. Strologas,37D. Stuart,10J. S. Suh,27A. Sukhanov,17K. Sumorok,32H. Sun,56T. Suzuki,55A. Taffard,23R. Takashima,40
Y. Takeuchi,55K. Takikawa,55M. Tanaka,2R. Tanaka,40N. Tanimoto,40M. Tecchio,34P. K. Teng,1K. Terashi,50 S. Tether,32J. Thom,16A. S. Thompson,20E. Thomson,45P. Tipton,49V. Tiwari,12S. Tkaczyk,16D. Toback,53S. Tokar,14
K. Tollefson,35T. Tomura,55D. Tonelli,46M. To¨nnesmann,35S. Torre,18D. Torretta,16S. Tourneur,44W. Trischuk,33 R. Tsuchiya,57S. Tsuno,40N. Turini,46F. Ukegawa,55T. Unverhau,20S. Uozumi,55D. Usynin,45A. Vaiciulis,49 S. Vallecorsa,19A. Varganov,34E. Vataga,37G. Velev,16G. Veramendi,23V. Veszpremi,48R. Vidal,16I. Vila,11R. Vilar,11
T. Vine,30I. Vollrath,33I. Volobouev,28G. Volpi,46F. Wu¨rthwein,9P. Wagner,53R. G. Wagner,2R. L. Wagner,16 W. Wagner,25R. Wallny,8T. Walter,25Z. Wan,52S. M. Wang,1A. Warburton,33S. Waschke,20D. Waters,30 W. C. Wester III,16B. Whitehouse,56D. Whiteson,45A. B. Wicklund,2E. Wicklund,16G. Williams,33H. H. Williams,45
P. Wilson,16B. L. Winer,39P. Wittich,16S. Wolbers,16C. Wolfe,13T. Wright,34X. Wu,19S. M. Wynne,29A. Yagil,16 K. Yamamoto,41J. Yamaoka,52T. Yamashita,40C. Yang,60U. K. Yang,13Y. C. Yang,27W. M. Yao,28G. P. Yeh,16J. Yoh,16
K. Yorita,13T. Yoshida,41G. B. Yu,49I. Yu,27S. S. Yu,16J. C. Yun,16L. Zanello,51A. Zanetti,54I. Zaw,21F. Zetti,46 X. Zhang,23J. Zhou,52and S. Zucchelli5
(CDF Collaboration)
1Institute of Physics, Academia Sinica, Taipei, Taiwan 11529, Republic of China
2Argonne National Laboratory, Argonne, Illinois 60439, USA
3Institut de Fisica d’Altes Energies, Universitat Autonoma de Barcelona, E-08193, Bellaterra (Barcelona), Spain
4Baylor University, Waco, Texas 76798, USA
5Istituto Nazionale di Fisica Nucleare, University of Bologna, I-40127 Bologna, Italy
6Brandeis University, Waltham, Massachusetts 02254, USA
7University of California, Davis, Davis, California 95616, USA
8University of California, Los Angeles, Los Angeles, California 90024, USA
9University of California, San Diego, La Jolla, California 92093, USA
10University of California, Santa Barbara, Santa Barbara, California 93106, USA
11Instituto de Fisica de Cantabria, CSIC-University of Cantabria, 39005 Santander, Spain
12Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
13Enrico Fermi Institute, University of Chicago, Chicago, Illinois 60637, USA
14Joint Institute for Nuclear Research, RU-141980 Dubna, Russia
15Duke University, Durham, North Carolina 27708, USA
16Fermi National Accelerator Laboratory, Batavia, Illinois 60510, USA
17University of Florida, Gainesville, Florida 32611, USA
18Laboratori Nazionali di Frascati, Istituto Nazionale di Fisica Nucleare, I-00044 Frascati, Italy
19University of Geneva, CH-1211 Geneva 4, Switzerland
20Glasgow University, Glasgow G12 8QQ, United Kingdom
21Harvard University, Cambridge, Massachusetts 02138, USA
22Division of High Energy Physics, Department of Physics, University of Helsinki, FIN-00014, Helsinki, Finland and Helsinki Institute of Physics, FIN-00014, Helsinki, Finland
231801-2
23University of Illinois, Urbana, Illinois 61801, USA
24The Johns Hopkins University, Baltimore, Maryland 21218, USA
25Institut fu¨r Experimentelle Kernphysik, Universita¨t Karlsruhe, 76128 Karlsruhe, Germany
26High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305, Japan
27Center for High Energy Physics: Kyungpook National University, Taegu 702-701, Korea;
Seoul National University, Seoul 151-742, Korea;
and SungKyunKwan University, Suwon 440-746, Korea
28Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
29University of Liverpool, Liverpool L69 7ZE, United Kingdom
30University College London, London WC1E 6BT, United Kingdom
31Centro de Investigaciones Energeticas Medioambientales y Tecnologicas, E-28040 Madrid, Spain
32Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
33Institute of Particle Physics: McGill University, Montre´al, Canada H3A 2T8; and University of Toronto, Toronto, Canada M5S 1A7
34University of Michigan, Ann Arbor, Michigan 48109, USA
35Michigan State University, East Lansing, Michigan 48824, USA
36Institution for Theoretical and Experimental Physics, ITEP, Moscow 117259, Russia
37University of New Mexico, Albuquerque, New Mexico 87131, USA
38Northwestern University, Evanston, Illinois 60208, USA
39The Ohio State University, Columbus, Ohio 43210, USA
40Okayama University, Okayama 700-8530, Japan
41Osaka City University, Osaka 588, Japan
42University of Oxford, Oxford OX1 3RH, United Kingdom
43Istituto Nazionale di Fisica Nucleare, Sezione di Padova-Trento, University of Padova, I-35131 Padova, Italy
44LPNHE-Universite Pierre et Marie Curie-Paris 6, UMR7585, Paris F-75005 France; IN2P3-CNRS
45University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
46Istituto Nazionale di Fisica Nucleare Pisa, Universities of Pisa, Siena and Scuola Normale Superiore, I-56127 Pisa, Italy
47University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
48Purdue University, West Lafayette, Indiana 47907, USA
49University of Rochester, Rochester, New York 14627, USA
50The Rockefeller University, New York, New York 10021, USA
51Istituto Nazionale di Fisica Nucleare, Sezione di Roma 1, University of Rome ‘‘La Sapienza,’’ I-00185 Roma, Italy
52Rutgers University, Piscataway, New Jersey 08855, USA
53Texas A&M University, College Station, Texas 77843, USA
54Istituto Nazionale di Fisica Nucleare, University of Trieste/Udine, Italy
55University of Tsukuba, Tsukuba, Ibaraki 305, Japan
56Tufts University, Medford, Massachusetts 02155, USA
57Waseda University, Tokyo 169, Japan
58Wayne State University, Detroit, Michigan 48201, USA
59University of Wisconsin, Madison, Wisconsin 53706, USA
60Yale University, New Haven, Connecticut 06520, USA (Received 3 February 2006; published 12 June 2006) We report the first observation of B0s ! 2S decay in pp collisions at ps
1:96 TeV using 360 pb1of data collected by the CDF II detector at the Fermilab Tevatron. We observe20:25:0and 12:34:1B0s! 2Scandidates, in 2S !and 2S !J= decay modes, respec- tively. We present a measurement of the relative branching fractionBB0s ! 2S=BB0s!J=
0:520:13stat 0:04syst 0:06BRusing the 2S !decay mode.
DOI:10.1103/PhysRevLett.96.231801 PACS numbers: 13.25.Hw, 14.40.Nd
The decays of B mesons to charmonium final states have been studied extensively in the past, and the measure- ments [1– 3] show that the ratio of the branching frac- tions of B and B0 decay to the 2S final states over the J= final states are approximately 60% as shown in Table I. The B;0 !J= K;0 [ 2SK;0] and B0s ! J= [ 2S] are color-suppressed Cabibbo-favored decays that have the same tree-level decay topology as shown in Fig. 1. The relative branching ratio between B0s ! 2S and B0s !J= has not been measured.
Only oneB0s ! 2Scandidate event has been reported, at LEP in 1993 [5].
TheB0s !J= mode has recently been used to deter- mine the decay widths for the heavy and light B0s mass eigenstates by measuring the relative contribution of the CP-odd andCP-even components to the observed angular distribution as a function of the decay time [6,7].
Observing theB0s! 2Swould allow an independent measurement of the decay widths for the heavy and light B0s mass eigenstates in the future. In particular, the spin
alignment ofB0s ! 2Scould be different from that of B0s !J= .
In this Letter, we report the observation of B0s ! 2S in both 2S ! and 2S ! J= decay modes produced in pp collisions at
s
p 1:96 TeV. We also measure the ratio of branching fractions for B0s !J= and B0s ! 2S. Many sys- tematic effects cancel in the measurement of the ratio, including uncertainties in total integrated luminosity, bottom-quark production and fragmentation, and trigger and reconstruction efficiencies. In addition, for this ratio of branching fractions measurement we use only the 2S ! decay mode in order to guarantee identical top- ologies for the J= and 2S channels. Similar decay modes, such as B!J= K and B! 2SK, are used as control samples to perform consistency checks, and study the systematic uncertainties. Charge conjugate modes are implied throughout this Letter. The data sample is comprised of about 3106J= !, 1 105 2S !, and 1:6104 2S !J=
candidates. The total integrated luminosity is approxi- mately 360 pb1 and was collected using the Collider Detector at Fermilab (CDF II) between February 2002 and July 2004.
The CDF II detector is described in detail elsewhere [8].
The main components for this analysis are tracking and muon systems. The tracks are reconstructed by the silicon microstrip detector [9,10], and the Central Outer Tracker (COT) [11], which are immersed in a uniform axial 1.4 T magnetic field provided by a superconducting solenoid.
Planar drift chambers [12] located outside the calorimeter are used to identify muons in the central region (jj<1:0, where is the pseudorapidity). The events are selected with a three-level trigger system. At Level 1, charged particle trajectories in the plane transverse to the beam direction are reconstructed from the COT hits using a hardware processor [13]. The trigger requires tracks with transverse momentumpT>1:5 GeV=cto be matched to hits in the muon detector. At Level 2, opening angle and opposite-charge cuts are imposed on the muon pairs. At Level 3, the two muon tracks are required to be oppositely charged with invariant mass between 2.7 and4:0 GeV=c2.
We reconstruct B0s !J= and B0s ! 2S fol- lowed by 2S ! and 2S !J= , where J= ! and!KK. For the measure- ment of the relative branching fraction between B0s! J= andB0s! 2S, it is desirable to have selection criteria similar for both decay modes. All three B0s decay channels involve only the well-knownJ= , 2Sand decays, which have been used extensively in other mea- surements at CDF, and their selection criteria are well established. In this analysis, we follow the selection re- quirements developed in thebhadron mass measurements [14] and apply them to the three B0s decay modes of interest.
The reconstruction begins by selecting J= ! or 2S ! candidates, with pairs of oppositely charged tracks that satisfy the muon pair trigger require- ments. The reconstructedinvariant mass is required to be within80 MeV=c2of theJ= or 2Smass [4]. The 2S !J= is reconstructed by associating a J= ! candidate (with its mass constrained to the J= mass) with a pair of tracks, each with pT>
0:4 GeV=c. The invariant mass of J= is required to be within20 MeV=c2 of the world average 2Smass [4]. Once aJ= or 2Scandidate is selected, we search for a !KK candidate with a pair of additional tracks. The invariant mass of KK is required to be within 10 MeV=c2 of the mass [4]. The pT of the candidate is required to be greater than2:0 GeV=c. TheB0s meson candidates are then reconstructed by associating a J= or 2Scandidate with acandidate. All tracks [4 tracks in B0s !J= or B0s! 2S followed by 2S ! and 6 tracks in B0s ! 2S followed by 2S !J= ] are required to be consistent with having originated from a common vertex satisfying vertex quality requirements. Prompt background, with tracks coming directly from the primary vertex, can be reduced by exploiting variables sensitive to the long lifetime of the B0s meson. To reduce prompt background, the transverse decay length (Lxy) of theB0sis required to exceed100m, whereLxyis defined as the transverse vector from the beam axis to the B0s decay vertex projected onto the transverse momentum of theB0scandidate. To ensure a well measured B meson decay vertex, each track is required to have a measurement in at least three axial layers of the silicon detector. The transverse momentum of theB0scandidates is
b
u, d, s
c c s W+
u, d, s
s
, B0 d
, B0 u
B+
ψ(2s) ψ, J/
φ
*0,
+, K K
FIG. 1. Tree-level Feynman diagram ofBmesons decaying to charmonium final states.
TABLE I. The current relative branching ratio of B meson decays to charmonium final states.
Decay channel Value Reference
BB ! 2SK
BB!J= K 0:640:060:07 BABAR[1]
BB0! 2SK0
BB0!J= K0 0:610:10 PDG [4]
BB0! 2SK0
BB0!J= K0 0:820:130:12 PDG [4]
231801-4
required to be greater than 6:5 GeV=c to further reduce combinatoric background. To improve the Bmeson mass resolution, the mass is constrained to the J= or 2S mass, while theJ= mass is constrained to the 2Smass.
Two sources of background are expected in theB0ssignal region: combinatoric background and kinematic ‘‘reflec- tion’’ of B0!J= K0 (for B0s !J= ) or B0 ! 2SK0 [for B0s! 2S], where the pion from the K0 decay is misassigned as a kaon. The combinatoric background is modeled by a first order polynomial. The B0 !J= K0[B0 ! 2SK0] reflection background re- sults in a broad distribution near and above theB0s signal region. The fraction of B0 !J= K0 [B0! 2SK0] events that fall into theB0s!J= [B0s ! 2S] signal region is estimated using a Monte Carlo simulation. The background contribution from reflection in our data sample is then calculated by multiplying the fraction determined from Monte Carlo simulation by the number of theB0 ! J= K0 andB0! 2SK0 candidates in the same data.
The contribution of the B0 !J= K0 reflection in the B0s !J= signal region is estimated to be 6:60:3 events. The contribution of theB0 ! 2SK0 reflection in the B0s ! 2S signal region is estimated to be 0:340:05 and 0:190:03 events for 2S ! and 2S !J= modes, respectively. The B0 ! J= K0[B0 ! 2SK0] reflection background is highly suppressed because only a small fraction of the misidenti- fied K0 !K can satisfy the !KK mass requirement.
An unbinned log-likelihood fit is used to extract signal yields from the reconstructed mass spectra, as shown in
Fig. 2. The signal distribution is modeled as a Gaussian, and the background distribution is modeled as a first order polynomial. The background component from misidenti- fied K0 decays is also included, with a shape obtained from the Monte Carlo simulation. The width for each of the two B0s! 2S modes is fixed in the following way. We take the ratio of the widths for B0s! 2S relative to B0s!J= as a scale factor determined from Monte Carlo simulation, and we then calculate the width for B0s ! 2S, using the width of B0s !J= from data. A comparison of the Monte Carlo calculation and data for the control samples of B!J= K andB! 2SKshows that the relative ratio of the widths of the two modes can be well predicted by Monte Carlo simula- tion. The signal yields, fitted masses, and mass resolution of the three decay channels are summarized in Table II. A consistency check (Monte Carlo calculation independent) is performed by fitting the !KK invariant mass spectra for events in the Bs signal region after sideband subtraction. The !KK signal yield obtained this way in data is consistent with that from fitting the Bs mass spectra, indicating that theB0 reflection background from B0!J= K0 [B0 ! 2SK0] or other decay modes is indeed negligible.
The background contribution in the signal region (de- fined as a window 6 times the expected mass resolution, as shown in Table II, around the mean value of theBs signal peak) forB0s ! 2S, followed by 2S !and 2S !J= decays, is estimated to be10:03:2 and 6:52:6 events, respectively. The probability of a statistical fluctuation of the expected total background in the signal region to the observed or higher number of
2) ) (GeV/c K-
K+
µ-
µ+
M(
5.1 5.15 5.2 5.25 5.3 5.35 5.4 5.45 5.5 5.55 5.6 2 Entries per 5 MeV/c
0 1 2 3 4 5 6 7 8 9 10
φ ψ(2S)
→
s
B0
→ ψ(2S) µ+µ-
2) ) (GeV/c K-
K+
π-
π+
µ-
µ+
M(
5.1 5.15 5.2 5.25 5.3 5.35 5.4 5.45 5.5 5.55 5.6 2 Entries per 5 MeV/c
0 1 2 3 4 5 6 7 8 9 10
φ ψ(2S)
→
s
B0
→ ψ(2S) J/ψπ+π-
2) ) (GeV/c K-
K+
µ-
µ+
M(
5.1 5.15 5.2 5.25 5.3 5.35 5.4 5.45 5.5 5.55 5.6 2 Entries per 5 MeV/c
0 10 20 30 40 50 60
70 s→ J/ψφ B0
→ ψ J/ µ+µ-
FIG. 2 (color online). Invariant mass distributions for B0s!J= (bottom), and for B0s! 2S, followed by 2S ! (upper left), or 2S !J= (upper right). The curves are the results of the fits described in the text.
events is 2:5107 for B0s ! 2S with 2S ! and 1:6105 for 2S !J= . These correspond to 5:0 and4:2 one-sided Gaussian signifi- cance for the two decay modes, respectively. The com- bined probability of the two modes is 1:11010, corresponding to a 6:4 significance for the observation ofB0s! 2S.
We measure the relative branching fraction between B0s !J= and B0s ! 2S using only the J= ! decay mode, and the control sample data [B ! J= KandB! 2SK] are used to study the system- atic uncertainties. The relative branching ratio for the mode is extracted using the formula:
BB0s ! 2S
BB0s!J= N 2S
NJ=
BJ= ! B 2S ! J=
2S; (1)
where J= = 2S 0:9250:006 is the ratio of the combined trigger and selection efficiencies derived from Monte Carlo simulation (with the error due to the size of the simulated samples), andNJ= orN 2S is the total number of reconstructed B0s mesons for each mode. The
BJ= !andB 2S !are the world
average branching fractions [4].
In our analysis, we use a Monte Carlo simulation to determine the relative efficiency for the two decay modes, and the control sample data are used to study the system- atic uncertainties. The simulation of the CDF II detector is based on aGEANTdescription [15]. Transverse momentum and rapidity distributions of singlebquarks are generated based on next-to-leading-order (NLO) pertubative QCD [16]. The B0s meson spectrum used in the Monte Carlo simulation is consistent with the data from inclusiveB! J= X [8]. The EVTGENprogram [17] is used to decay B mesons into the final states of interest.
Since both modes are B0s decays, and the decay top- ologies are very similar, most systematic uncertainties cancel in the ratio. Systematic uncertainties originate from fitting the invariant mass distributions to obtain signal yields, from determination of the relative efficiencies, and from the measured branching fractions ofJ= and 2S decays taken from Ref. [4]. Consistency checks are per- formed on the fitting method by varying the range and using different functions, and no statistically significant
variation is found. Systematic uncertainty from the fitting method is evaluated by dropping the fixed width constraint.
Systematic uncertainties on the ratio of efficiencies are due to the differences in the kinematics of the two decay modes. For example, due to the mass difference between 2S and J= , the pT distributions are somewhat different between the two decay modes. To take into ac- count the difference in pT distributions, the single muon efficiency measured from data [18] is used to re- weight the Monte Carlo samples, and the relative effi- ciency (central value and error) is recalculated. We vary the measured muon efficiency, and find that the systematic uncertainty due to the difference in pTdistributions is negligible. The main systematic uncertainty due to decay kinematics difference comes from lack of knowledge of the angular correlation in theB0s ! 2Sdecay. The central value of the relative efficiency is determined by assuming that the angular correlation of theB0s ! 2Sdecay is the same as that of theB0s !J= . To evaluate the effects on our measurement, we generate Monte Carlo samples with pure CP-even andCP-odd decays forB0s! 2S and recalculate the relative efficiency. We take the differ- ence betweenCP-even andCP-odd cases as the systematic uncertainty, which turns out to be the major component (5.5%). The systematic uncertainty from the fitting con- tributes at the 3.9% level. The total systematic uncertainty is 6.7%.
The contribution from the branching fractions is calcu- lated by propagating the world average uncertainties. The dominant contribution is due to the measured branching ratioB 2S ! 0:730:08%[4].
Using Eq. (1), we derive the ratio of relative branching fractions:
BB0s ! 2S
BB0s!J= 0:520:13stat 0:04syst
0:06BR (2)
where the first error is statistical, the second is systematic, and the third is due to the branching ratios of J= ! and 2S !.
In summary, we present the first observation of B0s! 2S decay, in both 2S ! and 2S ! J= modes inpp collisions at
ps
1:96 TeVus- ing the CDF II detector. We also present the measurement of the ratio of branching fractions betweenB0s! 2S and B0s!J= using the 2S ! decay mode.
TABLE II. The numbers of observed signal events, the fitted masses, and the signal width (Gaussian sigma, or mass resolution) for each of the threeB0s decay channels.
Decay Mean MeV=c2 Width MeV=c2 Yield
B0s !J= 5366:760:66 9:420:58 292:215:9
B0s ! 2S; 2S ! 5366:501:86 6.63 (fixed) 20:25:0 B0s ! 2S; 2S !J= 5366:633:20 7.77 (fixed) 12:34:1
231801-6
This result forB0sis consistent with the ratios of branching fractions for the corresponding decays ofB andB0 [4], indicating that the relative branching ratio of B meson decays between 2SandJ= final states is independent of the flavor of the lighter quark.
We thank the Fermilab staff and the technical staffs of the participating institutions for their vital contributions.
This work was supported by the U.S. Department of Energy and National Science Foundation; the Italian Istituto Nazionale di Fisica Nucleare; the Ministry of Education, Culture, Sports, Science and Technology of Japan; the Natural Sciences and Engineering Research Council of Canada; the National Science Council of the Republic of China; the Swiss National Science Founda- tion; the A. P. Sloan Foundation; the Bundesministerium fu¨r Bildung und Forschung, Germany; the Korean Science and Engineering Foundation and the Korean Research Foundation; the Particle Physics and Astronomy Re- search Council and the Royal Society, UK; the Russian Foundation for Basic Research; the Comisio´n Inter- ministerial de Ciencia y Tecnologı´a, Spain; in part by the European Community’s Human Potential Programme under Contract No. HPRN-CT-2002-00292; and the Academy of Finland.
[1] S. J. Richichiet al.(BABARCollaboration), Phys. Rev. D 65, 032001 (2002).
[2] B. Aubertet al.(CLEO Collaboration), Phys. Rev. D63, 031103 (2001).
[3] F. Abe et al. (CDF Collaboration), Phys. Rev. D 58, 072001 (1998).
[4] S. Eidelman et al. (Particle Data Group), Phys. Lett. B 592, 1 (2004).
[5] D. Buskulicet al.(ALEPH Collaboration), Phys. Lett. B 311, 425 (1993).
[6] D. Acostaet al.(CDF Collaboration), Phys. Rev. Lett.94, 101803 (2005).
[7] V. M. Abazovet al.(D0 Collaboration), Phys. Rev. Lett.
95, 171801 (2005).
[8] D. Acosta et al.(CDF Collaboration), Phys. Rev. D71, 032001 (2005).
[9] A. Sillet al., Nucl. Instrum. Methods Phys. Res., Sect. A 447, 1 (2000).
[10] T. Affolderet al., Nucl. Instrum. Methods Phys. Res., Sect.
A453, 84 (2000).
[11] T. Affolderet al., Nucl. Instrum. Methods Phys. Res., Sect.
A526, 249 (2004).
[12] G. Ascoliet al., Nucl. Instrum. Methods Phys. Res., Sect.
A268, 33 (1988).
[13] E. J. Thomson et al., IEEE Trans. Nucl. Sci. 49, 1063 (2002).
[14] D. Acostaet al.(CDF Collaboration), Phys. Rev. Lett.96, 202001 (2006).
[15] R. Brun, R. Hagelberg, M. Hansroul, and J. C. Lassalle, CERN Report No. CERN-DD-78-2-REV, 1987; CERN Report No. CERN-DD-78-2, 1987.
[16] P. Nason, S. Dawson, and R. K. Ellis, Nucl. Phys.B303, 607 (1988).
[17] D. Lange, Nucl. Instrum. Methods Phys. Res., Sect. A462, 152 (2001).
[18] A. Abulenciaet al.(CDF Collaboration), Phys. Rev. Lett.
95, 221805 (2005).
