Measurement of spectral function in the decay Motivation ~ Muon Anomalous Magnetic Moment ~Event selectionmass spectrum (unfolding)Evaluation of resultYukiko Hirano(Nara Womens Uni. , High Energy Physics Lab.)For the Belle collaborationOutline

JPS 2003 in Sendai

Motivation~ Muon Anomalous Magnetic Moment ( ) ~The prediction of Standard Modellargest error fromHadron vacuum polarization

JPS 2003 in Sendai

anddecaythe contribution of hadrom Vacuum polarization obtained from Experimental Data.difficult to obtain from first principle Cross section of Hadron system Hadron systemdecay is useful to determine the term ,

JPS 2003 in Sendai

and decay Hadron Vacuum polarization term from 2 system ( )

Spectral function is measured in this experiment.K(s) is known function.

JPS 2003 in Sendai

Present status ; Muon Anomalous Magnetic Moment ( )Exp. measured by BNL (g-2) experiment.2002.9

Theoretical prediction new data (CMD-2) and data (ALEPH) 2003.1difference by Hadron Vacuum Polarization. term is different between and base predictions.Cross check is important !

JPS 2003 in Sendai

event selection Number of charged tracks2 or 4All charge ( ) = 0event vertex position :

Separate the event into 2 hemisphere by the event axis.

Event axis direction :

Back Ground rejection (next slide)

Physics trigger

Event selection Data : accumulated from 2000.10 to 2000.12 at Belle.(corresponding to production.)

JPS 2003 in Sendai

event selection (Back ground rejection) Missing mass and Missing angle cut ( plot) about 1,300,000 events are remained.

Event selection

JPS 2003 in Sendai

signalrightleftSide-band region

JPS 2003 in Sendai

mass spectraumB.G. fraction

JPS 2003 in Sendai

Unfolding acceptanceMass square resolution : 0.03 GeV2 Acceptance include both the tau-pair and pipi0 selection.Acceptance and bin-by-bin migration effects are corrected via Singular-Value-Decomposition method.

JPS 2003 in Sendai

Unfolded mass spectrumRed line : Breit Wigner fitting function ( and are included. )

JPS 2003 in Sendai

Breit Wigner fitting formfree parameterGS model is known that it can fit wilder mass region that the commonly used BW.Gounaris and Sakurai (G&S) Model

JPS 2003 in Sendai

fit result and compare with previous Experiments parameters : good agreement with previous Exp. parameters : Belle results are most precise.

JPS 2003 in Sendai

Evaluation of

JPS 2003 in Sendai

Systematic error ()External systematics ~Normalization factors~Largest error from

JPS 2003 in Sendai

Systematic error ()Internal systematics

JPS 2003 in Sendai

resultResult of is preliminarycf. ALEPH

JPS 2003 in Sendai

Backup slide

JPS 2003 in Sendai

2.Event selectionExp. DataData reconstructionMonte Carlo simulationSimulator of event productionDetector simulation

JPS 2003 in Sendai

event selectionThere are few charged tracks in the event.72%13%There are missing of momentum and mass because of neutrino ( ) .missing

JPS 2003 in Sendai

Missing mass VS. Missing angleDataMC(tau)MC(Bhabha)MC(2photon)

JPS 2003 in Sendai

Time dependence

JPS 2003 in Sendai

Momentum of and Good agreement between Data and MC .

JPS 2003 in Sendai

Fitting result of Breit Wigner modelK&S modelG&S model

JPS 2003 in Sendai

Spectral function

JPS 2003 in Sendai

Systematic detail 1(1) BG estimation (two photon )(2) BG estimation (hadron)Two photon B.G. estimated by Data using control sample.Hadron BG contribution also estimated by Data using control sample.

JPS 2003 in Sendai

Systematic detail2(3) Energy scale(4) Gamma energy thresholdUncertainty of as gamma-threshold function.

JPS 2003 in Sendai

Hadron Vacuum polarization and DataThe term of hadron vacuum polarization

JPS 2003 in Sendai

Data and Data Iso-spin Cnserve of Vectro Current

We can treat data as same condition as data. semi-Leptonic dacayc decay

JPS 2003 in Sendai