Toru Iijima

Nagoya University

December 19, 2006BNM-II Workshop, Nara-WU

Tauonic and Leptonic Decays

2

Contents

Introduction

BBD, X Bl

Bll (ee, , )BK(*)

Technical issues;- Tagging- Background

’s in the final state(missing energy)

3

Hunting Rare Decays

Observation of BK l+ l-

CPV in B decay

Beginning of B->K0 saga

Direct CPV in B0K+

FB asymmetry in BK* l+l-

Evidence of B

Observation of bd

High luminosity Good detector (PID, vertex…) Analysis techniques

– qq background suppression– Fully reconstructed tag

Success of B factories brought rare B decays in leptonic and neutrino modes on the stage !Success of B factories brought rare B decays in leptonic and neutrino modes on the stage !

4

Full Reconstruction Method

Fully reconstruct one of the B’s to tag– B production– B flavor/charge– B momentum

Υ(4S)

e (8GeV)

e+(3.5GeV)

B

B

full (0.1~0.3%)reconstructionBD etc.

Single B meson beam in offline !

Decays of interests BXu l , BK BD,

Powerful tools for B decays w/ neutrinos

5

B(within the SM)

Proceed via W annihilation in the SM.

Branching fraction is given by

Provide information of fB|Vub|– |Vub| from BXu l fB cf) Lattice (~10%)

– Br(B)/md |Vub| / |Vtd|

Expected branching fraction3| | (4.39 0.33) 10ubV

(0.216 0.022)Bf GeV 5

( )

(1.59 0.40) 10

Br B

HFAG [hep-ex/0603003]

HPQCD [PRL95,212001(2005)]

2006/05/15 6

BX as a Probe to Charged Higgs

Charged Higgs contribution to B decays

In two Higgs doublets model, charged Higgs exchange interferes with the helicity suppressed W-exchange.

tan cotb um m

b

u H/W

tanm

Br(SM) ~ 9 x 10-5

222

SMB

H H 2H

mr , r = 1- tan β

mBr =Br

7

The final results are deduced by unbinned likelihood fit to the obtained

EECL distributions.

The First B Evidence

Signal shape : Gauss + exponentialBackground shape : second-order polynomial

+ Gauss (peaking component)

Signal +

background

Background

B

Signal

Observe 17.2 events in the signal region. Significance decreased to 3.5 after including systematics

+ 5.3 - 4.7

: Statistical Significance

To appear in Phys. Rev. Lett.hep-ex/0604018v3

8

Results (Br & fB Extraction)

Measured branching fraction;

Product of B meson decay constant fB and CKM matrix element |Vub|

Using |Vub| = (4.39 0.33)×10-3 from HFAG

fB = 216 22 MeV

[HPQCD, Phys. Rev. Lett. 95, 212001 (2005) ]

15% 16% = 14%(exp.) + 8%(Vub)

+0.56 +0.46 -4-0.49 -0.51Br B 1.79 ×10

+1.6 +1.3 -4B ub -1.4 -1.4f V =10.1 ×10 GeV

+0.036 +0.034B -0.031 -0.0370.229f = GeV

9

Constraints on Charged Higgs

+0.56 +0.46 -4exp -0.49 -0.51

-4SM

Br =(1.79 )×10

Br =(1.59 ±0.32 0.24)×10

222B

H 2H

exp

SM

mR = 1- tan β

m

Br=1.13±0.53

Br

fB from HPQCD

These regions are excluded.

Much stronger constraint than those from energy frontier exp’s.

|Vub|

stat. syst.

fB

|Vub| from HFAG

10

Future Prospect: B Br(B) measurement:

More luminosity help to reduce both stat. and syst. errors.– Some of the syst. errors limited by statistics of the control sample.

|Vub| measurement: < 5% in future is an realistic goal.

fB from theory: ~10% now 5% ?

Lum. B(B) exp |Vub|

414 fb-1 36% 7.5%

5 ab-1 10% 5.8%

50 ab-1 3% 4.4%

My assumption fB(LQCD) = 5%5ab-1

50ab-1

If |Vub| = 0 & fB = 0

11

Cont’d

Charged Higgs Mass Reach (95.5%CL exclusion @ tan=30)

Only exp. error(Vub=0%, fB=0%)

Vub=5%, fB=5%

Vub=2.5%, fB=2.5%

Mass

Reach

(G

eV

)

Luminsoity(ab-1)

Constraints at Super-B (cont.)

fB(LQCD) = 5%

rH

5

rH

5ab -1

50ab -1

tan / Hm

5 potential

5

Charged Higgs Mass Reach with 5

13

Ratio may help ?

Ratio to cancel out fB (G.Isidori&P.Paradisi, hep-ph/0605012)

Deviation of Br.

expH

SM

BrR =1.13±0.53=1.13 0.45 0.23 0.17

Br exp. |Vub|fB

d

d

exp

B B

SM

B B

Br(B )M

R = 1.23 0.49 0.10 0.12Br(B )

Mexp. |Vub|BBd

14

B D(*) Semileptonic tauonic decays

cb

H/W

tan cotb cm m

tanm

( )

( )

B D vB

B D v

Br(SM)~ 8 x 10-3

– Ratio (/) is modified by the charged Higgs effect.– Provide good cross check to B– Y.Okada

• H-b-u vertex by B• H-b-c vertex by BD• H-b-t vertex by LHC direct search.

15

LoI

5ab-1 50ab-1

Mode Nsig Nbkg dB/B Nsig Nbkg dB/B

280 55012.7 7.9%

2800 550040.3 2.5%

620 3600 6200 36000

0 ( )D

0 ( )D h

Expectation at 5 / 50 ab-1 for B+ decay

5 observation possible at 1ab-1

Signal selection efficiency0

0

( )

( )

e

e

D e

D

0

0

( )

( )

D

D

10.2%2.6%

26.1%13.3%

Major background sourceMissing charged and tracks from BD(*) l X (incl. slow )

16

Sensistivity to H±

Similar to B

5ab-1

FF=15%50ab-1

FF=5%

17

Be

B is the next milestone decay.

When do we see the signal ?Precision at Super-B ?

Precise B/ data provide lepton universality test.– Higgs effect itself is universal.

RH = RH

– Good probe to distinguish NP models.

Br()=1.6x10-4

Br()=7.1x10-7

Br(e)=1.7x10-11

18

Belle Results

Inclusive reconstruction– Reconstruct the accompanying B via a 4-vector sum

of everything else in the event.– Efficiency: 2.18±0.06% (), 2.39±0.06% (e)– NSM: 2.8±0.2 (), (7.3±1.4)x10-5 (ev)

hep-ex/0611045, submitted to Phys. Lett. B

e

Br() < 1.7x10-6@90%CL Br(e) < 9.8x10-7

253fb -1

19

Future Prospect: B

Method?S.Robertson at CERN WS (May 2006)– Inclusive-recon method has high efficienc

y but poor S/N.

– Hadronic tag will provide very clean and ambiguous signals, but very low efficiency.

Luminosity (ab-1)

Sta

ndard

Devia

tion

3 at 1.3ab-1

5 at 3.7ab-1

Extrapolation from the present Belle analysis(inclusive-recon.)

limit 1/ L

limit 1/ L

Extrapolation from the present Belle analysis.K.Ikado at BNM1 (Sep. 2006)

~50 events @ 5ab-1~500 events @ 50ab-1

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d l

l

Proceeds via box or penguin annihilationSM Branching fractions

Flavor violating channel (B0 e +–, etc.) are forbidden in SM.

B0l+l-

0 + - -15d

0 + - -10d

0d

Br(B e e ) ~10

Br(B ) ~10

Br(B ) =zero

d l

l

New Physics can enhance the branching fractions by orders of magnitude.

ex.) loop-induced FCNC Higgs coupling

b

dA0,Hh0

6

4A

tan βm

21

B0l+l- (e+e-,+-,e+-)

B(B0 e+e–) < 6.1 × 10-8 (90%CL) B(B0 +–) < 8.3 × 10-8 (90%CL)

B(B0 e+ –) < 18 × 10-8 (90%CL)

e+e– +–

e-+

Signal regions Events observed

Phys. Rev. Lett. 94, 221803 (2005)

B(B0 e+e–) < 1.9 × 10-7 (90%CL) B(B0 +–) < 1.6 × 10-7 (90%CL)

B(B0 e+ –) < 1.7 × 10-7 (90%CL)

B(B0d) < 2.3×10-8 (90% CL)

Phys. Rev. D 68, 111101 (2003)

78 fb-1

780 pb-1

111 fb-1

22

B0l+l- at B factories ?

Pre-LHC era Present CDF limit;Br(Bs) < 2.3x10-8 (90%CL) is equivalent to Br

(Bd) < 1x10-9. Interesting to see results with full Belle/BaBar data.

LHC era Who knows the background at LHC ? Bs from (5S) runs at Super-B ?

– We can study background using the present (5S) data! Bd is an unique opportunity at B factories.

But, how clean are they ?

2

τ

μ

mBr(B )= 300

Br(B ) m

2

s ts

d td

Br(B ) V= 25

Br(B ) V

See talk by E. Baracchini 

23

B0+ - (BaBar @ 210fb-1)

Experimentally very very challenging (2-4 neutrinos in the final state ! )

High sensitive to NP Bs at hadron machines

Analysis• Reconstruct one B in a fully

hadronic final state B D(*) X=>280k events

• In the event remainder, look fortwo decays (l, , )

• Kinematics of charged partilcemomenta and residual energyare fed into a neutral networkto separate signal and BG

Data Controlsample

Nobs=263±19 Nexpect=281±48

Phys. Rev. Lett. 96, 241802 (2006)

-3Br(B ) <4.1×10 @90%C.L.

24

Plots to be made…

Region in tan-mH for 5 evidence.– B + BD – LHC direct search for the same 5 effect– Other measurements from B decays

• BXs• Bll

Combine B and D(*) to show– mH reach at tan=30 as a function of L.

– Significance at tan=30 and mH=500GeV as a function of L.

Precision for Br(), Br() and their ratio as a function of L

25

Need to study… Tagging strategy for neutrino modes

– Inclusive recon.– Semileptonic tag.– Hadronic tag.

Data quality in large L environment– Tagging efficiency– Beam background– Neutrino reconstruction

BaBar’s B search (324x106 BB)Tag by BDlXTag B recon. eff.=0.7%

Extra energy distribution inBelle’s B search

26

Backup

27

New Physics in large tan Leptonic decays (Bl, ll) are theoretically clean, free from hadronic

uncertainty. In particular, they are good probes in large tanregion, together with

other measurements; mBS, Bs, BXs and also decays (, ). Ex.) G.Isidori & P.Paradisi, hep-ph/0605012

b

uH

b

dA0,Hh0

Charged Higgs

Neutral Higgs

tan

MH(GeV)See talk by A.Weiler

28

Constraint to Charged Higgs

Once branching fraction is measured, we can constrain R.

tanW

H

MR

M

Form factor error

M.Tanaka, Z.Phys. C67 (1995) 321

11R at 5ab-1 can be determined experimentallyby B semiletonic decays

29

Future Prospect: BK

Belle @ 250fb-1 (preliminary)Fully reconstructed tag (by modifying the PID criteria used in B analysis).

Consistent with BG expected

Belle preliminary

Signif. Lum (ab-1)3 12

5 33

Need Super-B !

cf.) K.Ikado @ BNM2006