Observation of $B to phi phi K$ Decays

a r X i v :h e p -e x /0609016v 1 8 S e p 2006

BELLE-CONF-0626

Observation of B →φφK Decays

K.Abe,9K.Abe,49I.Adachi,9H.Aihara,51D.Anipko,1K.Aoki,25T.Arakawa,32

K.Arinstein,1Y.Asano,56T.Aso,55V.Aulchenko,1T.Aushev,21T.Aziz,47S.Bahinipati,4

A.M.Bakich,46V.Balagura,15Y.Ban,37S.Banerjee,47E.Barberio,24M.Barbero,8A.Bay,21I.Bedny,1K.Belous,14U.Bitenc,https://www.sodocs.net/doc/7116552052.html,jak,16S.Blyth,27A.Bondar,1A.Bozek,30M.Braˇc ko,23,16J.Brodzicka,9,30T.E.Browder,8M.-C.Chang,50P.Chang,29

Y.Chao,29A.Chen,27K.-F.Chen,29W.T.Chen,27B.G.Cheon,3R.Chistov,15

J.H.Choi,18S.-K.Choi,7Y.Choi,45Y.K.Choi,45A.Chuvikov,39S.Cole,46J.Dalseno,24M.Danilov,15M.Dash,57R.Dowd,24J.Dragic,9A.Drutskoy,4S.Eidelman,1Y.Enari,25

D.Epifanov,1S.Fratina,16H.Fujii,9M.Fujikawa,26N.Gabyshev,1A.Garmash,39T.Gershon,9A.Go,27G.Gokhroo,47P.Goldenzweig,4B.Golob,22,16A.Goriˇs ek,16M.Grosse Perdekamp,11,40H.Guler,8H.Ha,18J.Haba,9K.Hara,25T.Hara,35Y.Hasegawa,44N.C.Hastings,51K.Hayasaka,25H.Hayashii,26M.Hazumi,9

D.He?ernan,35T.Higuchi,9L.Hinz,21T.Hokuue,25Y.Hoshi,49K.Hoshina,54S.Hou,27W.-S.Hou,29Y.B.Hsiung,29Y.Igarashi,9T.Iijima,25K.Ikado,25A.Imoto,26K.Inami,25A.Ishikawa,51H.Ishino,52K.Itoh,51R.Itoh,9M.Iwabuchi,6M.Iwasaki,51Y.Iwasaki,9

C.Jacoby,21M.Jones,8H.Kakuno,51J.H.Kang,58J.S.Kang,18P.Kapusta,30

S.U.Kataoka,26N.Katayama,9H.Kawai,2T.Kawasaki,32H.R.Khan,52A.Kibayashi,52

H.Kichimi,9N.Kikuchi,50H.J.Kim,20H.O.Kim,45J.H.Kim,45S.K.Kim,43T.H.Kim,58Y.J.Kim,6K.Kinoshita,4N.Kishimoto,25S.Korpar,23,16Y.Kozakai,25P.Kriˇz an,22,16P.Krokovny,9T.Kubota,25R.Kulasiri,4R.Kumar,36C.C.Kuo,27

E.Kurihara,2A.Kusaka,51A.Kuzmin,1Y.-J.Kwon,https://www.sodocs.net/doc/7116552052.html,nge,5G.Leder,13J.Lee,43

S.E.Lee,43Y.-J.Lee,29T.Lesiak,30J.Li,8A.Limosani,9C.Y.Lin,29S.-W.Lin,29Y.Liu,6D.Liventsev,15J.MacNaughton,13G.Majumder,47F.Mandl,13D.Marlow,39T.Matsumoto,53A.Matyja,30S.McOnie,46T.Medvedeva,15Y.Mikami,50W.Mitaro?,13K.Miyabayashi,26H.Miyake,35H.Miyata,32Y.Miyazaki,25R.Mizuk,15D.Mohapatra,57G.R.Moloney,24T.Mori,52J.Mueller,38A.Murakami,41T.Nagamine,50Y.Nagasaka,10T.Nakagawa,53Y.Nakahama,51I.Nakamura,9E.Nakano,34M.Nakao,9H.Nakazawa,9

Z.Natkaniec,30K.Neichi,49S.Nishida,9K.Nishimura,8O.Nitoh,54S.Noguchi,26

T.Nozaki,9A.Ogawa,40S.Ogawa,48T.Ohshima,25T.Okabe,25S.Okuno,17S.L.Olsen,8

S.Ono,52W.Ostrowicz,30H.Ozaki,9P.Pakhlov,15G.Pakhlova,15H.Palka,30C.W.Park,45H.Park,20K.S.Park,45N.Parslow,46L.S.Peak,46M.Pernicka,13R.Pestotnik,16M.Peters,8L.E.Piilonen,57A.Poluektov,1F.J.Ronga,9N.Root,1J.Rorie,8M.Rozanska,30H.Sahoo,8S.Saitoh,9Y.Sakai,9H.Sakamoto,19H.Sakaue,34T.R.Sarangi,6N.Sato,25N.Satoyama,44K.Sayeed,4T.Schietinger,21O.Schneider,21P.Sch¨o nmeier,50J.Sch¨u mann,28C.Schwanda,13A.J.Schwartz,4R.Seidl,11,40T.Seki,53

K.Senyo,25M.E.Sevior,24M.Shapkin,14Y.-T.Shen,29H.Shibuya,48B.Shwartz,1V.Sidorov,1J.B.Singh,36A.Sokolov,14A.Somov,4N.Soni,36R.Stamen,9S.Staniˇc ,33M.Stariˇc ,16H.Stoeck,46A.Sugiyama,41K.Sumisawa,9T.Sumiyoshi,53S.Suzuki,41S.Y.Suzuki,9O.Tajima,9N.Takada,44F.Takasaki,9K.Tamai,9N.Tamura,32

K.Tanabe,51M.Tanaka,9G.N.Taylor,24Y.Teramoto,34X.C.Tian,37I.Tikhomirov,15

K.Trabelsi,9Y.T.Tsai,29Y.F.Tse,24T.Tsuboyama,9T.Tsukamoto,9K.Uchida,8 Y.Uchida,6S.Uehara,9T.Uglov,15K.Ueno,29Y.Unno,9S.Uno,9P.Urquijo,24

https://www.sodocs.net/doc/7116552052.html,hiroda,https://www.sodocs.net/doc/7116552052.html,ov,1G.Varner,8K.E.Varvell,46S.Villa,21C.C.Wang,29

C.H.Wang,28M.-Z.Wang,29M.Watanabe,32Y.Watanabe,52J.Wicht,21L.Widhalm,13 J.Wiechczynski,30E.Won,18C.-H.Wu,29Q.L.Xie,12B.

D.Yabsley,46A.Yamaguchi,50

H.Yamamoto,50S.Yamamoto,53Y.Yamashita,31M.Yamauchi,9Heyoung Yang,43

S.Yoshino,25Y.Yuan,12Y.Yusa,57S.L.Zang,12C.C.Zhang,12J.Zhang,9

L.M.Zhang,42Z.P.Zhang,42V.Zhilich,1T.Ziegler,39A.Zupanc,16and D.Z¨u rcher21

(The Belle Collaboration)

1Budker Institute of Nuclear Physics,Novosibirsk

2Chiba University,Chiba

3Chonnam National University,Kwangju

4University of Cincinnati,Cincinnati,Ohio45221

5University of Frankfurt,Frankfurt

6The Graduate University for Advanced Studies,Hayama

7Gyeongsang National University,Chinju

8University of Hawaii,Honolulu,Hawaii96822

9High Energy Accelerator Research Organization(KEK),Tsukuba

10Hiroshima Institute of Technology,Hiroshima

11University of Illinois at Urbana-Champaign,Urbana,Illinois61801

12Institute of High Energy Physics,

Chinese Academy of Sciences,Beijing

13Institute of High Energy Physics,Vienna

14Institute of High Energy Physics,Protvino

15Institute for Theoretical and Experimental Physics,Moscow

16J.Stefan Institute,Ljubljana

17Kanagawa University,Yokohama

18Korea University,Seoul

19Kyoto University,Kyoto

20Kyungpook National University,Taegu

21Swiss Federal Institute of Technology of Lausanne,EPFL,Lausanne

22University of Ljubljana,Ljubljana

23University of Maribor,Maribor

24University of Melbourne,Victoria

25Nagoya University,Nagoya

26Nara Women’s University,Nara

27National Central University,Chung-li

28National United University,Miao Li

29Department of Physics,National Taiwan University,Taipei

30H.Niewodniczanski Institute of Nuclear Physics,Krakow

31Nippon Dental University,Niigata

32Niigata University,Niigata

33University of Nova Gorica,Nova Gorica

34Osaka City University,Osaka

35Osaka University,Osaka

36Panjab University,Chandigarh

37Peking University,Beijing

38University of Pittsburgh,Pittsburgh,Pennsylvania15260

39Princeton University,Princeton,New Jersey08544

40RIKEN BNL Research Center,Upton,New York11973

41Saga University,Saga

42University of Science and Technology of China,Hefei

43Seoul National University,Seoul

44Shinshu University,Nagano

45Sungkyunkwan University,Suwon

46University of Sydney,Sydney NSW

47Tata Institute of Fundamental Research,Bombay

48Toho University,Funabashi

49Tohoku Gakuin University,Tagajo

50Tohoku University,Sendai

51Department of Physics,University of Tokyo,Tokyo

52Tokyo Institute of Technology,Tokyo

53Tokyo Metropolitan University,Tokyo

54Tokyo University of Agriculture and Technology,Tokyo

55Toyama National College of Maritime Technology,Toyama

56University of Tsukuba,Tsukuba

57Virginia Polytechnic Institute and State University,Blacksburg,Virginia24061

58Yonsei University,Seoul

Abstract

We report the observation of the decay B±→φφK±and?nd evidence for B0→φφK0.These results are based on a414fb?1data sample that contains449×106B

ss

Evidence of charmless B→φφK decays has been reported by the Belle collaboration using85×106B

s quark pair in a b→s

B pairs,collected with the Belle detector at the KEKB asymmetric-energy e+e?(3.5on8GeV)collider[3]operating at the Υ(4S)resonance.

The Belle detector is a large-solid-angle magnetic spectrometer that consists of a silicon vertex detector(SVD),a50-layer central drift chamber(CDC),an array of aerogel threshold ˇCerenkov counters(ACC),a barrel-like arrangement of time-of-?ight scintillation counters

(TOF),and an electromagnetic calorimeter comprised of CsI(Tl)crystals(ECL)located inside a super-conducting solenoid coil that provides a1.5T magnetic?eld.An iron?ux-return located outside of the coil is instrumented to detect K0L mesons and to identify muons (KLM).The detector is described in detail elsewhere[4].Two inner detector con?gurations were used.A2.0cm radius beampipe and a3-layer silicon vertex detector(SVD1)were used for the?rst sample of152×106B

B pairs[5].

Charged kaons are required to have impact parameters within±2cm of the interaction point(IP)along the z-axis(anti-parallel to the positron direction)and within0.2cm in the transverse plane.Each track is identi?ed as a kaon or a pion according to a K/πlikelihood ratio,R(K/π)=L K/(L K+Lπ),where L K/Lπis the likelihood of kaons/pions derived from the responses of TOF and ACC systems and the energy loss measurements from the CDC. The likelihood ratio is required to exceed0.6for kaon candidates;within the momentum range of interest,this requirement is88%e?cient for kaons and has a misidenti?cation rate for pions of8.5%.Neutral kaons are reconstructed via the decay K0S→π+π?and have an invariant mass0.482GeV/c2

B meson candidates are reconstructed in the?ve kaon?nal state.Two kinematic variables are used to distinguish signal candidates from backgrounds:the beam-energy constrained mass M bc=

q(q=u,d,s,c)continuum events.Event

topology and B?avor tagging are used to distinguish the jet-like continuum events and the spherically distributed B

N S+N BG,where N S denotes the expectedφφK signal yields based on MC simulation and the branching fraction reported in our previous measurements,and N BG denotes the expected q

[1?q i·A j CP]N j P j i(M bc,?E)),(1)

2

where i is the identi?er of the i-th event,j indicates signal or background,P(M bc,?E)is the two-dimensional PDF of M bc and?E,and q indicates the B meson?avor,+1for B+ and?1for B?,respectively.For neutral B events,1

D0(K+π?π?π+)π+events with the MC expectation.

We search for charmless B→φφK decays by requiring theφφinvariant mass(Mφφ)to be less than2.85GeV/c2,the region below the charm threshold.Candidateφmesons are identi?ed by requiring the invariant masses of K+K?pairs(M K+K?)to be in the range 1.0GeV/c2to1.04GeV/c2(±4.6σ).Figure1shows the M bc and?E projections with the

?t curves superimposed.Clear signals appear in both B ±and B 0modes with signal yields

of 37.0+6.7?6.0and 7.8+3.2?2.5,respectively.Although K +K

?

candidates are required to lie in the φmass region,non-φbackgrounds may also contribute.Figure 2(a)shows the M K +K ?vs.M K +K ?distributions for (K +K ?K +K ?)K ±candidates in the signal region,where the two K +K ?pairs are required to have invariant masses less than 1.2GeV/c 2.Events in the two φbands are used to estimate the B ±→φK +K ?K ±contribution.Figure 2(b)shows B signal yields [11]as a function of the K +K ?invariant mass after requiring the other K +K ?pair to have a mass in the φmass region.The B signal yields are ?tted with a threshold function in the region 0.98GeV/c 2

which is 4.4+0.8

?0.7events.Since events in the two φbands contain both true φmesons and non-resonant K +K ?pairs,the area underneath the φmass region in Fig.2(b)includes the φK +K ?K ±contribution but counts the non-resonant 5K component twice.Therefore,we estimate the non-resonant B →5K contribution using the B signal yield in the upper right corner of the dashed region in Fig.2(a).We assume a phase-space distribution in 4-kaon mass.We obtain 1.3±0.4non-resonant events in the φφK ±sample.After subtracting this contribution of 1.3±0.4events,the non-φφK fraction is calculated to be (7±4)%.The same procedure is applied to the φφK 0sample;here we obtain a fraction of (7±9)%.

Table I summarizes the φφK results after subtracting the non-φφK contribution.Signal e?ciencies are obtained by generating φφK MC events,where the same M φφ<2.85GeV/c 2requirement is applied.Systematic uncertainties in the ?t are obtained by performing ?ts in which the signal peak positions and resolutions of the signal PDFs are successively varied by ±1σ.The quadratic sum of each deviation from the central value of the ?t gives the systematic uncertainty of the ?t.For each systematic check,the statistical signi?cance is taken as

B 0pairs are

assumed to be equal.

TABLE I:Signal yields,e?ciencies including secondary branching fractions,signi?cances,branch-ing fractions for B →φφK and related charmonium decays.

Mode

Yields

e?ciencies(%)

Σ

B (10?6)

D 0(→K +π?π?π+)π+sample.The obtained error is 2.7-2.8%.The

systematic errors on the charged track reconstruction are estimated to be around 1%per track using partially reconstructed D ?events.Therefore,the tracking systematic error is

5

10

15

(a) φφK ±

E v e n t s / 2 M e V /c

2

05

10152025

(b) φφK ±

E v e n t s / 20 M e V

2

4

5.2

5.25 5.3

(c) φφK 0M bc (GeV/c 2

)

E v e n t s / 2 M e V /c

2

02

4

6-0.2

-0.10

0.10.2(d) φφK 0

?E (GeV)

E v e n t s / 20 M e V

FIG.1:Distributions of M bc and ?E for the decay modes B ±→φφK ±(a,b)and B 0→φφK 0(c,d),with φφinvariant mass less then 2.85GeV/c 2.The open histograms represent the data,the solid blue curves show the result of the ?t,the dash-dotted red lines represent the signal contributions and the dashed green curves show the continuum background contributions.

5%(5tracks)for the φφK ±mode and 4%for the φφK 0mode.The kaon identi?cation e?ciency is studied using samples of inclusive D ?+→D 0π+,D 0→K ?π+decays.The K 0S reconstruction is veri?ed by comparing the ratio of D +→K 0S π+and D +→K ?π+π+

yields.The resulting K 0

S detection systematic error is 4.9%.The uncertainty in the number of B

1

1.051.1

1.151.2

M K K (G e V /c 2

)

51015202530M KK (GeV/c 2

)

FIG.2:(a)The +K ?for the K +K ?K +K ?K ±candidates in the M bc ??E signal c 2.The two K +K ?bands indicate the φmass region (1.0GeV/c 22).The horizontal and vertical dashed lines are located at M K +K ?on the upper right is the φφsideband region;events in this B →5K contribution.(b)B signal yields as a function the other K +K ?pair has a mass in the φmass region.The ?t curve and events with 1.0GeV/c 2

to investigate this CP asymmetry is 0.15+0.16

?0.17±0.02,which is consistent with no We study B yields with M 4K between 2.8GeV/c 2and 3.2GeV/c 2.may decay to φK +K ?and 2(K +K ?)pairs,a mass scan is requirement that the K +K ?pair lie in the φmass region.As J/ψresonances are visible in the φK +K ?and 4K samples in the φφmode.

We obtain the K ±and B ±→J/ψK ±by performing binned histogram ?ts to J/ψsignal PDF is modeled with a Gaussian function while the function convolved with a Gaussian resolution width as the J/ψPDF.Since sizable signals are observed in are determined using the 4K sample and the same signal PDFs +K ?and φφsamples.The obtained Gaussian

width is performing a ?t with a 2

nd

order Chebyshev polynomial as excluding events in the ηc mass region (2.94GeV/c 2

the nominal ηc width is measured to be 25.2+7.7

?6.0±0.3MeV/c 2,where the central value is consistent with the world average and the second error is due to the uncertainty in the mass resolution.

For the φK +K ?and φφmodes,the non-φcontribution is determined from the B signal yields for events with one K +K ?pair in the φsideband region (1.05GeV/c 2

M φφ (GeV/c 2

)

M φφ (GeV/c 2

)

M φKK (GeV/c 2

)

B s i g n a l y i e l d s /(5 M e V /c 2

)

M 4K (GeV/c 2

)

FIG.3:B signal yields as a function of (a,b)M φφ,(c)M φK +K ?and (d)M 4K .In (a)we use di?erent bin sizes for M φφless than 3GeV/c 2and greater than 3GeV/c 2.The subset with M φφfrom 2.8GeV/c 2to 3.2GeV/c 2is shown in (b).

1.09GeV/c 2)and the 4K and φK +K ?masses are in the charmonium resonance region,

respectively.We ?nd 3.0+2.0?1.4events in the ηc →φφmode,6.4+5.4?4.4events in the ηc →φK +K

?

mode,and 3.4+3.6?2.6in the J/ψ→φK +K ?

mode.After subtracting the feed-down yields,we obtain the results listed in Table I.

Signal e?ciencies are determined using signal MC and the detection systematic uncertain-ties are similar to what was described in the charmless φφK part.Fit systematic uncertain-ties are estimated by successively varying the peak positions and resolutions of the M bc ??E signal PDFs as well as the convolution Gaussian width in the ?t.The quadratic sum of each deviation gives the ?t systematic errors.Since the sub-decay branching fractions of ηc and J/ψmesons to 4K,φKK and φφ?nal states are not precisely known,we provide the product of branching fractions for various decays in Table https://www.sodocs.net/doc/7116552052.html,ing the known branching fractions of B (B ±→ηc K ±)=(9.1±1.3)×10?4and B (B ±→J/ψK ±)=(1.008±0.035)×10?3[12],the subdecay branching fractions are calculated and listed in Table II.

In summary,we have observed the charmless decay B ±→φφK ±and evidence of B 0→φφK 0.We also report the CP asymmetry of the charged decay and measurements of other closely related charmonium decays.The results are consistent with the previous measurements,but have considerably improved precision due to the increase in statistics.

TABLE II:The measured branching fractions of secondary charmonium decays and the world averages[12].

Decay mode B(measured)B(PDG2006value)