Tau Physics

May 5-9, 2008 National Taiwan University, Taipei, Taiwan 1

Tau　Physics

Flavor Physics and CP Violation May 5-9, 2008, National Taiwan University,

Taiwan

Hisaki HayashiiNara Women’s University


Contents

Lepton Flavor Violation 　indecaysTau decays to strange particles2 decay and muon anomalous magnetic moment


Lepton Flavor Violation (LFV)Standard Model (SM) exactly forbids LFV.Extended SM including neutrino mixing term includes LFV. Charged Lepton Flavor Violation

can occur through loop diagram.But, extremely tiny branching ratio

below experimental sensitivity

(Marciano and Sanda, Phys.Lett. B67 (1977), Pham, EPJ C8(1999)513)

Many NP models include LFV vertex naturally.Observation of charged LFV Clear signal of new physics!

Tau lepton has many possible LFV decay modes. Wide window to probe New Physics effects.

2249 52

2w

mBR( ) 10 10

m


LFV tau decays

Predicted by many new physics models Normal NP models enhance For some NP parameters, other modes may be

enhanced instead.Reference

SM+ mixing EPJ C8(1999)513 10-49-52 10-14

SM + heavy Maj R PRD 66(2002)034008 10-9 10-10

Non-universal Z’ PLB 547(2002)252 10-9 10-8

SUSY SO(10) PRD 68(2003)033012 10-8 10-10

mSUGRA+seesaw PRD 66(2002)115013 10-7 10-9

SUSY Higgs PLB 566(2003)517 10-10 10-7


Status of LFV search at spring 2007

Current accumulated luminosity;>700fb-1 at Belle and >500fb-1 at BaBar.

Searches for 3l, lhh modes should be updated.

BelleBelle BaBarBaBar BelleBelle BaBarBaBar

UL90(10-7)

Lum(fb-1)

UL90(10-7)

Lum(fb-1)

UL90(10-7)

Lum(fb-1)

UL90(10-7)

Lum(fb-1)

0.5 535 0.7 232 e 0.8 401 1.3 339

e 1.2 535 1.1 232 3l 2-4 87 1-3 92

0.7 401 1.5 339 lhh 2-16 158 1-5 221

’ 1.3 401 1.3 339 V0 2.8-7.7 158

1.2 401 1.5 339 eV0 3.0-7.3 158

e 0.9 401 1.6 339 Ks 0.5 281

e’ 1.6 401 2.4 339 eKs 0.6 281

V0=, K*


LFV analysisSignal extraction Calc. Minv and E

E=Erec-Ebeam

Blinded signal region Event selection study

Estimate backgroundusing sideband data

Open blind and estimate signal yield Estimate upper limits

by Likelihood fit or number of events in signal region

BG reduction is important to improve the sensitivity. Find effective ways to use all information

Signal MCSignal region

Background

Minv


3 leptons; BG reduction

Signal topology

BG events

- conversion veto 　 (e-e+e- and -e+e-) - Electron-veto on the tag-side 　 (e-e+e- and e-+-)

Bhabha() ee(eeee)

Optimized event selection for each mode separately because the BG processes are different.


lll search; Belle

Data; 535fb-1

Efficiency; (6.0-12.5)% NBG; 0.0-0.4 events

Nobs; 0 events for all modesBr<(2.0-4.1)×10-8 at 90%C.L.

(Y.Miyazaki et. al., PLB 660 (2008) 154)

eee

data signal

signal region


lll search; BaBarData; 376fb-1

Efficiency; (5.5-12.4)%NBG; 0.3-1.3 events Total BG; 4.2±0.8Nobs; 6 events in totalBr<(3.7-8.0)×10-8 at 90%C.L.

(B.Aubert et. al.,PRL 99 (2007) 251803)

=MinvM


lV0 search

Belle; 543fb-1 dataTen modes are investigated,

l=e, and V0=,K*0,K*0,Main BG: SM decay;Signal Efficiency; 2.5 - 4.9 %Expected NBG; 0.0 - 1.0 eventsObserved number of events;1 event for , e, eK*0

0 events for othersBr<(5.9-18)×10-8 (Y.Nishio et. al., arXiv:0801.2475)

BaBar; 384fb-1 data Searched for , eBr<(10-11)×10-8 (B.Aubert et. al., PRL 100;071802 2008)

data signal


lf0(980) search

Scalar Higgs mediation

No search yet.Belle; 671fb-1

Use f0(980)

No event is observed.Preliminary resultBr(→l f0(980) )xBr(f0(980)→)

f0(980) : <3.3X10-8, e f0(980) : <3.4X10-8

signal MC● data

f0

ef0efficiency NBG

f0(980) 6.0% 0.11±0.08

e f0(980) 5.8% 0.10±0.07

Br(→f0): Br(→): Br (→) = 1.3 : 0.54 :1 　(C.H.Chen et.al, PRD74:035010,2006 )


Current status of LFV search

Sensitivity is improved by factors of 3-10. It comes from the luminosity increase and successful BG reduction. 3leptons sets most stringent upper limit.

BelleBelle BaBarBaBar BelleBelle BaBarBaBarUL90(10-7)

Lum(fb-1)

UL90(10-7)

Lum(fb-1)

UL90(10-7)

Lum(fb-1)

UL90(10-7)

Lum(fb-1)

0.5 535 0.7 232 e 0.8 401 1.3 339

e 1.2 535 1.1 232 3l 2-40.2-0.4

87535

1-30.4-0.8

92376

0.7 401 1.5 339 lhh 2-16 158 1-5 221

’ 1.3 401 1.3 339 V0 2.8-7.70.6-1.3

158543 1.0() 384

1.2 401 1.5 339 eV0 3.0-7.30.6-1.8

158543 1.1(e) 384

e 0.9 401 1.6 339 f0 0.33 671

e’ 1.6 401 2.4 339 ef0 0.34 671

V0=, K*


B-factories improved LFV tau Br limit by factor 10-100Limits can be improved by factor 2-4

analyzing all planned B-factories yield.Super B-factories expected to

improve search region again by factor 10-100 dep. on bkg.

l; scale as ~1/L ee is irreducible BG. ~10-8 level at super B-factory

lll, lX0; scale as ~1/L BG can be reduced by lepton-ID

or mass requirement for X0

O(10-9) level at super B-factory

LFV Searches Prospects


Tau　 decays to strange particles

B-factory detectors have a good /K separation, useful to discriminate Cabibbo-suppressed s decays

Inclusive s can potentially achieve most precise/clean Vus measurement (0.7%): by Pich 　 In s decays the uncertainty on Vus is dominated by ex

perimental uncertainties. For 3-body K decays, the uncertainty on Vus is limited by

theory determination of the form-factor :f(0)+

(%?). If spectral functions are also measured, Vus and ms can be determined by a simultaneous fit.


Approaches to Vus

Inclusive measurement

by summing up all decay modes.


Before B factories: Br(s )

Precision: 4-10%


Before B factories: Vus and ms

kl kl,non strange ,strangekl

,Theory s 2 2ud us

R RR (m )

| V | | V |

00

e

( had)R R

( e )

Hadronic Width:

Flavour SU(3) Breaking:2

k lmkl

2 20

dRs sR 1

m m ds

where

Ms (GeV)

Ｍａｌｔｍａｎ，　ｈｅｐ -ph/061１ 1８０

Vus


Strength at B-factories

Good K- SeparationHigh Statistics

Well separated in space


0Br( K )

(0.808 0.004 0.026)%

Br(-K)

PRD 76 (2007) 051104(R)

K-

-Ks

PL B654 (2007) 65

0Br( K )

(0.439 0.003 0.021)%

78K e/ tagged events

53K e/ tagged events

230 fb-1 data

351 fb-1 data


Exclusive Br(-h-h+h-)

PRL 100 (2008) 011801


hep-ex/0707.3058

Update on Vus using B Factor Results

[1] M. Palutan, Kaon’07

2 2 2ud us ub| V | | V | | V | 1

1/ 2

,

,2 ,| |

sus

V Ath

ud

RV

R

VRt

t

t +

æ ö÷ç ÷ç ÷ç ÷ç ÷ç ÷=ç ÷ç ÷÷ç - ÷ç ÷ç ÷ç ÷ød

èçBy Pich

S.Banerjee, arXiv:0707.3054v4

Babar:-K-PRD 76 (2007) 051104(R)

-K-- PRL 100 (2008) 011801

Belle:- KsPLB 654 (2007) 65

Theory prediction assuming universality

Br(- K-) from Br(K- )

Updated Results

[1]

[2]

[2]

[2] M. Jamin, Moriond EW ‘07

thR 0.216(16) A.Pich

3.3


and a

has the largest Br CVC 　 relation with e+e-→

Plays an important role for the h. v. p. term in the muon anomalous magnetic moment.

aa=(g=(g-2)/2-2)/2

hadron

+CVC

W

0


Status of a

Recent data indicate that there is a systematic difference between the 2 system in e+e － reaction and -decays, even after applying known isospin violation correction. Main difference btw and is from 2 mode.

3.3not yet published

not yet published

preliminary

a(exp)-a(th) is

ICHEP-2006(M.Davier et al.):

A 　 hint to New Physics

beyond the SM!?

a

eea

How about


Pion Form Factor |Fπ|2

From 23Mpairs, Belle selects 5.4M events!

Error bars include both statistical and systematic

Interference between ’ and ”: 　　 ”　 signal significance 6.5

　　　　　　　 Fit with BW

± 0 2(Mπ π )2 2( / )GeV c

|F

π

|2

2F

Unfolded by Singular Value Decomposition Method.


Br( )

Normalized to the number of -pairs

Tau-pair selection acceptance : 32.6 0.05% 　　 : 1.112 　 0.003 background : 7.4 0.03%

0 selection Acceptance: 41.0 0.1 % Background feed down: 7.02 0.08 % qq-conti. : 2.22 0.05 %

Br= (25.12 0.04 （ stat) 0.38(sys))%

feed-down non-2

22 2

(1 ) 1

2 (1 )

obs

obs IDbg

N b bBr

N b

25.12 0.04 0.38Belle

2bf

Preliminary ALEPHB (25.471 0.097 0.085)%


Systematic on Br Measurement

Source Tracking efficiency 0.47 0 efficiency 1.4 Background in-pair 0.36 Feed down background 0.16 Continuum background 0.20 veto 0.20 Trigger 0.32 MC statistics 0.08 Total 1.6

Systematic is dominated by the uncertainty of the 0 efficiency Calibrated by signals ( ). Checked by using electron tracks. (→ can use to improve0 efficiency in near future.)

/ (%)B B

0 0 0 /


Systematic on the Mass Spectrum/Form Factor

M2 threshol

d region ’

region” region

Unfolding (MC) 0.79 0.31 1.5 1.50

Unfolding 　(cond)

0.53 0.09 　 0.58 9.19

BKG (continuum)

0.09 0.01 0.52 5.76

BKG (feed-down )

0.65 0.10 --- 0.50

BKG(non-0) 4.80 --- --- ---

Acceptance 1.44 0.03 0.15 0.40

Energy scale 1.08 0.59 0.05 0.50

Total 5.3 0.7 1.8 11.4

( %)

Systematic Region Dominant Factor 0.7-1.8% ’ Energy scale/Unfolding 5% threshold Background (0, feed down) 10% ’’ Continuum BG/Unfolding

Check by known MC distribution


Belle-CLEO consistent,

ALEPH is higher

at (M2 > 0.8 GeV2

Effect on a

?

i

Comparison with previous exp.

Fit: Fit to Belle Data


Results a

2

2,

4

(( )

)

had LO

m

K sa ds

sv s

0

0

02

2 2

12

2

2( 1 1

6)

1

eud EW

dN

N ds

mv

B

BV Ss

s sm m

range (GeV2)

Belle ALEPH

0.08-0.20 39.57 38.23

0.20-0.35 70.65 66.89

0.35-0.50 123.30 119.20

0.50-0.65 196.90 194.20

0.65-0.80 62.37 62.39

0.80-0.95 15.64 16.41

0.95-1.10 5.74 6.50

1.10-1.25 2.86 3.27

1.25-1.40 1.65 1.89

1.40-3.20 2.43 2.77

0.08-3.20 521.1 511.5

Belle> ALEPH

Belle<ALEPH

No iso-spin violation correction

is applied

X 10 -10

Total


Isospin Violation Correction

Ref. V. Cirigliano et al., J. High Energy Phys. 08, 002(2002) A.Flores-Tlalpa et al., Phys. Rev. D 74, 071301 (2006)

Source Correction Uncertainty

Short distance rad. Cor (SEW) -12.0 0.2Long distance rad. Cor.(GEM) -1.0m- m0

(in phase space) -7.0-interference +3.5 0.6 m- m0

(in decay width) +4.2Electromagnetic decays -1.4m0 m – - 1.4

Total -13.7 2.0

X10-10


10a (519.4 1.5(exp.) 2.7(Br) 2.5(isospin))x10

a comparison and e+e-

10a (520.1 2.4(exp.) 2.7(Br) 2.5(isospin))x10

10a (504.6 3.1(exp.) 0.9(rad.))x10

Belle()

ALEPH, CLEO, OPAL ()

CMD2,SND (e+e)

After applying the known iso-spin violation correction.Integrated region: 21.8 GeV/cs m

results are higher than those from e+ e-.

Ref. Eur. Phys. J. C27, 497 (2003)

Ref. Nucl. Phys. Proc. Suppl. 169, 288 (2007)


LFV Searches Good experimental coverage New searches for 3-prong final state

3l, lV0, lf0 using 400~700 fb-1 of data Better sensitivity than previous analysis

LFV sensitivities are Br~O(10-8) LFV are Super B-factory Golden channels

Sensitivity will reach Br~O(10-9).Vus from s inclusive Results on several Br, Vus are updated. 3.3 discrepancy w.r.t Kaons and unitarity

Spectrum measurement: cross check + determine Vus and ms, simultaneously.

High statistics study on

Br and mass spectrum are updated. In 　 addition to(700), ’(1400),the production of ’’(1700) is unamb

iguously identified and its parameters are determined. Belle results for agree with the previous based results but are hig

her than those from e+ e-.

Conclusions/Summary

a


int. based on the Hidden Local Symmetry can explain the difference

of 2 spec. between e+e- and

(M. Benayoun et al. arxiv:0711.4482)


Backup Slide


External parametersItem Value

1.0233±0.0006 ±0.32

0.9734±0.0008 ±0.42

(17.84±0.06)% ±1.82

(25.42±0.11)% ±2.30

Total ±３．０

10( : 10 )

unita

World average is calculated combining our new result and the preceding measurements of other experiments.

- 0τBr(τ π π ν )

CKM matrix elementudV ：

ee Branching Fraction eB ：0

0 Branching Fraction B :

electroweak radiative correctionEWS ：

0

0 Branching Fraction B :


Davier et al. Mod. Phys. 78,1043 (2007)



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Tau Physics