τ physics at Belle

43
BESIII workshop 001oct13-15 H Hayashii Nara Japan Contents 1 Tau physics at Belle 2 KEKB and Belle detector 3. Present status 4. Future Prospect PRESENT status and FUTURE prospect International Workshop o BESIII Detector τ τ physics at physics at elle elle

description

τ physics at Belle. PRESENT status  and  FUTURE prospect. H . Hayashii Nara , Japan Contents 1 . Tau physics at Belle 2 . KEKB and Belle detector 3. Present status 4. Future Prospect. International Workshop on BESIII Detector. τlepton Heaviest lepton ... Sensitive to NewPhysics - PowerPoint PPT Presentation

Transcript of τ physics at Belle

Page 1: τ physics at Belle

BESIII workshop 2

001oct13-15 

                      H . Hayashii

                        Nara , Japan

Contents1 . Tau   physics   at   Belle 2 . KEKB   and   Belle   detector3. Present   status4. Future   Prospect

PRESENT   status  and  FUTURE   prospect

International Workshop on

BESIII Detector

ττ physics at Bphysics at Belleelle

Page 2: τ physics at Belle

BESIII workshop 2

001oct13-15 

τlepton• Heaviest lepton ... Sensitive to NewPhysics• Only lepton that can decay to hadron ..….

• Less known compared to e and μ• No of tau`s

PQCDCPVCVCgs

,,2, α

Page 3: τ physics at Belle

BESIII workshop 2

001oct13-15 

ττ physics physics  at Belleat Belle(Presen(Present status)t status)

We present 3 topics  a)            decay   (   )  b)   tau   EDM   moments (CP violation in lepton sector) c) rare(forbidden) decay (Lepton Flavor Violation) c-1)  c-2) neutrinoless 3 Charged   decays

τνππτ 0

γμτ

μ2)(g

+‘forbidden` decay

Results are preliminary

Page 4: τ physics at Belle

BESIII workshop 2

001oct13-15 

IntroductionIntroduction    toto   KEKBKEKB // BelleBelle

• With   the   goal  of  measuring   CP - violating   asymmetry  inB   meson   decays ,- construction  of  KEKB   asymmetric   collider   and  the  Belle  detector   was   started   in  April 1994,  and   was   co

mpleted  in   December  1998.- Belle  Physics  run  was   started   June  1999.• Luminosity  Goal:   to  produce   more   than  108BB pairs/year(=1

00/fb/year)• Same amount of tau-pairs (108ττ ) are 

produced.

->  tau -physics:  important target at Belle

113410 scm

Page 5: τ physics at Belle

BESIII workshop 2

001oct13-15 

KEKB acceleratorKEKB acceleratorKEKB : Asymmetric e+e- collider

•CM energy : 10.580 GeV at(4S)•Two separate rings :

•e+ (LER:3.5GeV) •e- (HER:8.5GeV)

•Luminosity•Target : 1034 cm-2s-1

•Achieved : 4.5x1033 cm-

2s-1

•Design Parameters •3016 m circumference•5120 RF buckets (2ns) •2.6 A for e+, 1.1 A for e-

•22 mrad crossing angle at IP• y 3 m, x 100 m

•History•First collision : Jan. 1999•Physics run : since June 1999

Belle detector

Page 6: τ physics at Belle

BESIII workshop 2

001oct13-15 

KEKB performanceKEKB performance

225pb-1/dayIntegrated luminosity/day

Total accumulated luminosity 32.8fb-1

2001 / 7/29

Page 7: τ physics at Belle

BESIII workshop 2

001oct13-15 

SVD CDCACCTOFCsIKLMSolenoid

Belle DetectorBelle DetectorEvent reconstruction Charged tracks

Silicon Vertex Detector (SVD) Central Drift Chamber (CDC)

Electrons and photons Electromagnetic Calorimeter (CsI)

Vertexing SVD

Particle identification K/separation

CDC : dE/dx Aerogel Cherenkov Counter (ACC) Time of Flight Counter (TOF)

electron identification ECL

KL and muon identification KL and muon detector (KLM)

Page 8: τ physics at Belle

BESIII workshop 2

001oct13-15 

How Belle How Belle data look likedata look like

r- view in SVD y-z view near IP

B0 J/+Ks

+- +

Page 9: τ physics at Belle

BESIII workshop 2

001oct13-15 

τ-→π ー π 0 ντ   decay

Page 10: τ physics at Belle

BESIII workshop 2

001oct13-15 

 

ofprediction ltheoretica the get to

sobservableimportant are dMdN

N1 spectrum

massits and fraction Branching

20ππ0ππ

i

on)conservativector(currentCVCofTest

μ2)(g

)Br( τ0νππτ

accuracy1% measuredbetoneed:Br

μτνππτ 2)-(g and) 0 a

This is a trial to make a precision physics at Belle

τνππτ 0 has largest Branching fraction

)(arg

onpolarizativacuumhadronafromisainerrorestl

th

th

μ

μ

Page 11: τ physics at Belle

BESIII workshop 2

001oct13-15 

observedevent pair -tauof#N samplehπof#N

)correctionacceptance&d(backgroun2N

NB

0hπ

ττ

0

0

0

::

ττ

mesurementofmethod

:selection generic

τ0νπhτ2.

: 1.

selectionpairstepstwofromconsistsAnalysis

τ

0hπB

0hπB

→Determine Nττ ,→Determine Nhπ

●   We   first   measure

)(: 0 Korhh πνπτ τ

(from ratio)

  ratio :

     cancel   many   systematics   in   Lumi ., tracking   eff .

     can   be   used   for   Br   meas . of   other  decay   mode

Page 12: τ physics at Belle

BESIII workshop 2

001oct13-15 

Generic Generic  tautau -pair-pair   selectionselection

  

triggersEnergyand3)2,(track TriggerPhysics

)nn(n 30)(n)(n

boundaryECLpointingnottrackanycutθandMM

145θ35

N

γtrackpart

partpart

cmmiss

event

track

otherone

usesatisfy

n

GeVptGeVEGeVp

e

cm

,1

5.00.9,0.9||

42

max

If

The other hemi

One hemi

(rad - Bhabha , two - photon   rej . )

(conti ., BB   reject . )

(bhabha   rej .)

(Bhabha , μμγ   rej .)

•Signature ofττ event : low   multi ., missing   mom .

Criteria:

Cuts→As loose as possible

BBcontiqqphotontwoeeee ),(,),(),( γμμγ•B.G. :•Requirement:

Page 13: τ physics at Belle

BESIII workshop 2

001oct13-15 

MissingMissing    massmass    vsvs    ThetaTheta __ mimissingssing

2γtrackinit

2 )pp(pMM

M

M(G

eV)

Data MC( )

M

M(G

eV)

*missθ *

missθ

ττtwo  photon

rad . bhabha

Page 14: τ physics at Belle

BESIII workshop 2

001oct13-15 

MCandDatabetweenComparisonSamplePairTau

CMeventθ

otherone )(n)(naxisevent partpart

Background  6.8%  qqeefrommainly

Page 15: τ physics at Belle

BESIII workshop 2

001oct13-15 

decayhofSelection 0τνπτ

π0

GeVwithadditional No

condition

conditionπOne

hemisphereaintrackchargedOne0

0.2Eγ sγ`

9.0σ

)m(m-9.0

:π0.08GeVEγ

150γθ20 : γ

γγ

0

γγ

Veto γ γγγγσ PondepMeV .5.98.4

signal0π1417.4

416 0

fbLathK π

Page 16: τ physics at Belle

BESIII workshop 2

001oct13-15 

Pi0 momentum &Pi0 momentum &    ThetaTheta                   (τ(τ±±→→ hh ±±ππ 00

ννττ))

P π 0(Lab)

θπ 0(Lab)

Page 17: τ physics at Belle

BESIII workshop 2

001oct13-15 

Charged Particle `sCharged Particle `s    MomentumMomentum &Theta &Theta     (τ(τ±±→→ hh ±±ππ 00 ννττ))

Ph ± (Lab)

θ h ± (Lab)

Page 18: τ physics at Belle

BESIII workshop 2

001oct13-15 

ππππ 00 massmass

0ππM

Linear  scale

)2(..

0 nnhfrommainlyGBτνπτ

samplekN

fbL

h 416

417.4

0

1

π

Page 19: τ physics at Belle

BESIII workshop 2

001oct13-15 

Log scaleππππ 00 massmass

GeVsignal 3.1at' ~ρ

Page 20: τ physics at Belle

BESIII workshop 2

001oct13-15 

Br ( )Br ( )τνπhτ 0

%04.029.25)1(2

)1(

ππτ

ττπ

ττττ

εε

εττhID

hh

non

bN

bbNBr

τ-pair selection

Observed event with 4.42/fb data

sampleMNeventMN

h )193,416(42.0)695,432,1(4.1

0

π

ττ

%78.6:)(..%99.36:)(%37.33:)(

0

ττ

πτ

ττ

ττεπεττ

bfractionGBhefficiency

efficiencyh

hπ selection

%21.3%,94.9:)(..%24.48:)(

0

0

ττ

π

πεπ

non

hID

bbhfractionGBhefficiency

Current systematic errors%3.1/ ππσ hh Br

Can be improved with

Large data

Page 21: τ physics at Belle

BESIII workshop 2

001oct13-15 

Systematic ErrorSystematic Error

%3.1:

% 1.0: efficiency π* 0.51%:background *

negligible:dep.Run0.40%:Trigger*0.10%:resolutionπ

%0.35:statisticMC

)(:errorSystematic

0

0

All―――――――――――――――

00 hπhπ/Bσ

(%)33.0 0.0425.29)νπhBr(τ τ0

Numbers are preliminary.

systematics under investigation

(stat.) (sys.)

Many errors are canceled in the ratio

Page 22: τ physics at Belle

BESIII workshop 2

001oct13-15 

Page 23: τ physics at Belle

BESIII workshop 2

001oct13-15 

b) τElectroDipole Momentb) τElectroDipole Moment (( EDM) EDM)  d d ττ

  • EDM : CP   Violating observable

• Any   CPV   at   τ   production  vertex   can   be   parametrized   by   EDM

• current upper limit :

   |d|< 3.1 10–16 ecm (LEP L3 ; e

e )

  |Re(d)|< 4.6 10–16 ecm,

  |Im(d)| < 1.8 10–16 ecm (ARGUS)

←CP violating effective lagradian

Page 24: τ physics at Belle

BESIII workshop 2

001oct13-15 

Belle EDM analysisBelle EDM analysis

• 28.9  / fb• Use   8   combinations

• Criteria  1 - 1   prong , no   sin

gleγ  barrel   part , high   p

  track  e,μ , π : probability > 0.

95• 1.18M   events

candidate

e+

e–

e+

ρρπππρμρρμππμ ,,,,,e,,ee

Page 25: τ physics at Belle

BESIII workshop 2

001oct13-15 

SelectedSelected    datadata

ρ

μe

π

labP

Page 26: τ physics at Belle

BESIII workshop 2

001oct13-15 

SelectedSelected    datadata

labcosθe μ

πρ

Page 27: τ physics at Belle

BESIII workshop 2

001oct13-15 

 Observable Observable for EDM measurfor EDM measurementement

Use Optimal observable[PRD45,2405(1992)]

termpsskxssMe

R )()( xτ

termpsskssMe )()( --I

τ

Maximum   Sensitivity

Mean   value→  prop . to   EDM

EDMSMprod MMM

Ambiguity of tau   direction -> amplitude is avaraged

Most probable spin direction->determined from tau and decay

daughter

←CP   violating terms

Page 28: τ physics at Belle

BESIII workshop 2

001oct13-15 

ObservableObservable    distributiondistribution

Dot: exp. data

Histogram:MC

Back. :blueORe=0.00520.0041 ORe=0.00600.0105

OIm= 0.0220.022OIm= –0.0130.008

μρ πρ

Page 29: τ physics at Belle

BESIII workshop 2

001oct13-15 

EDMEDM    vsvs    ObservableObservableORe vs Re(d) from MC

In   order  take  into   account   detector  effect, coefficients   are   determined  by MC

High   sensitivity  for  hadronic  decay

Page 30: τ physics at Belle

BESIII workshop 2

001oct13-15 

EDMEDM    resultsresults

Weighted  mean

Errors   dominated  by  statistics

Page 31: τ physics at Belle

BESIII workshop 2

001oct13-15 

EDMEDM  results results(2)(2)

..%[email protected]|)Im(|109.3|)Re(|

17

17

LCecmdecmd

τ

τ

current upper limit :|d|< 3.1 10–16 ecm (LEP L3 ; )|Re(d)|< 4.6 10–16 ecm, |Im(d)| < 1.8 10–16 ecm (ARGUS)

•O ne   order  of  magnitude  improvement

•Results  are limitted by statistics

•Im: comparable to WDM results at LEP  

28.9 / fb data

..%95@):(105.1|)Im(|

):(1056.0|)Re(|17

17

LCOPALPDGecmdOPALPDGecmd

w

w

τ

τc.f.  WDM(Weak DipoleMoment )  limit :

ecmfewa 1810•Next Target

Page 32: τ physics at Belle

BESIII workshop 2

001oct13-15 

cc ) )  Rare`Forbidden` decay(LFV)Rare`Forbidden` decay(LFV)τ→μγτ→μγ

)200%,95(102.1)( 11 PDGeB γμ

n

mm

fortenhancemen

μ

τ

τ

model on dep. 2n -5=:

most at tenhancemen 10-10 65

).,.(10-10:)B(

predicts models based SUSY Some8-6-

HisanoJOkadaYorderμγτ

ettsBelle arg` :10-10Br 8-6-

Page 33: τ physics at Belle

BESIII workshop 2

001oct13-15 

τ→μγτ→μγ : : analysis based on 21/fb dataanalysis based on 21/fb data

Criteria• 2 - prong+ ≧1γ• Signal side

• Tag side track is not muon• Tau +missing

)1()1( GeVEGeVpmuon γ

150174.0||

8.0cos4.0

labmiss

labmiss GeVp

cm

θ

θμγ

))(5.4( trackeachGeVpt

Page 34: τ physics at Belle

BESIII workshop 2

001oct13-15 

3  candidates  in the signal  Box

GeVEGeVM1.025.0

85.17.1

Δμγ

GeVMμγ

GeVData MCsignal )( μγτ

)( cmbeam

cmcm EEEE γμΔ

Signal BoxSignal Box

21/fb

Page 35: τ physics at Belle

BESIII workshop 2

001oct13-15 

BackgroundBackground   evaluationevaluation

cut] d))[standar(MC( γττ cut] ardData[stand

side]-tagatvetoData[w/o μ ]/))[(( sidetagatvetoowMC μγττ

%)93...()(

exp..

IDofeffeiremainseemseventlikeee

EpositiveatexcesslainnotcanitbuteefromGBsome

μγγμμγ

ττγΔ

Page 36: τ physics at Belle

BESIII workshop 2

001oct13-15 

Background estimationBackground estimation  and uppe and upper-limitr-limit

  5.9  event

γττ ee:)(γγμμγee

# data( #B.G.)

•Efficiency  =  9.4 %

•# of   signal  at  95 % C. L. =3.5ev   (Bayesian method)

..%90100.1)( 6

LCatB μγτ

regionEhighΔ

regionElowΔ•B.G. :tacking into account

and

B.G. in   the   signal box   is estimated from data

(use muon-ID ineff. Value) to be

Page 37: τ physics at Belle

BESIII workshop 2

001oct13-15 

AchievableAchievable    SensitivitySensitivity

+•Include  Endcap (x1.35)

•Cuts optimization (x1.30)

•Improve       res.(x1.6)

    (use  TOF/ ACC  info.)

γE

?10:101:101

12358

7

machinescmaneedKEKcurrentwachievableBR

B

•High luninosity

Present condition

Page 38: τ physics at Belle

BESIII workshop 2

001oct13-15 

LFV: LFV: NeutrinoNeutrino less 3 charged deless 3 charged decaycay

0

1

1600

19mod18,23.).%90(108.1),(

MlfbwithesMMlMMlfbLCKeKBr

τ

μτ

@90 % C.L.

Page 39: τ physics at Belle

BESIII workshop 2

001oct13-15 

Neutrinoless 3 charged decayNeutrinoless 3 charged decay),( 00 eKKBr μτ :improve 2 order of

magnitude.

MarkIIOur target

Br=10-7

-10-8

90%C.L.

Page 40: τ physics at Belle

BESIII workshop 2

001oct13-15 

OutlooksOutlooks•KEKB/Belle achieved   a luminosity of :  4.5x1033   cm - 1s - 1

•Belle accumulated 33 fb-1(30x106 ττ   event) data

•10 times more data in next 5 years

•Precise measurement of spectrum function in

•Limit / find   a Rear Decays of   τ in the range 10-7—10-8

•Measure EDM target 10 - 17-10-18 ecm

•CPV in

•Tau decay to Kaon -> ms

•Michel parameters

•・・・・・

•Our PHYSICS targets are

γγμτ e,Mledch ,arg3τ

ττ νπνππτ 4,0

τνπτ K

Page 41: τ physics at Belle

BESIII workshop 2

001oct13-15 

KEKB : PlanKEKB : Plan

Limiting factors on KEKB : beam current limit to avoid arcing at masks and

bellows e+ blow up due to photoelectron cloud by

synchrotron light beam blow up due to beam-beam effect Near future : more tunings replacing masks and bellows

more bunch currentFuture possibilities : Reduce photoelectron effect

(1) Antechambers for e+ ring(2) Charge swap :

e-(8.0GeV)+e+(3.5GeV) e-(3.5GeV)+e+(8.0GeV)

Crab collision

Page 42: τ physics at Belle

BESIII workshop 2

001oct13-15 

ττ physics at Bphysics at Belleelle

BESIII workshop 2001Oct13-1BESIII workshop 2001Oct13-155 ,, BeijingBeijing ,, ChinaChina

Page 43: τ physics at Belle

BESIII workshop 2

001oct13-15 

World-Wide Activity Involving 50 Institutions

~300 members

The Belle CollaborationThe Belle Collaboration