search for bnv, lnv, lfv at (super-) belle/kekb

Search for BNV, LNV, LFV at (Super-) Belle/KEKB

September 22, 2007Search for Baryon and Lepton Number Violation Int’l Workshop @ LBL

Toru Iijima / Nagoya University

e+ source

Ares RF cavity

Belle detectorSCC RF(HER)

ARES(LER)

The KEKB Collider

e- (8.0GeV) × e+ (3.5GeV)⇒U(4S) →BB⇒Lorentz boost: bg = 0.425

Finite crossing angle- 11mrad ×2

Operation since 1999.

Peak luminosity 1.71 x 1034 cm-2s-1 !

3

Belle Detector

2007/9/22 Toru ijima, B-L workshop

~1010 BB & tt /year !!

Crabcavities

KEKB / Belle Major Upgrade

4

KEKB Integrated Luminosity

Lpeak = 1.71034cm-2s-1

Ltot = 710 fb-1 (Jun.30, 2007)

world records !

s(BB) ~ 1.1nb, s(tt) ~ 0.9nb

8.0x108 BB + 6.3x108tt

NBB/tt=O(109)

NBB/tt=O(1011)

NBB/tt=O(107)@ CESR


Unique opportunity to study BNV, LNV, LFV in higher generation !

Hou, Nagashima, Soddu, PRD72,095001 (2005) B,L violating t, D, B decays with right-handed four-fermion

couplings.

BNV in Higher Generation

2007/9/22 Toru ijima, B-L workshop 5

proton decay limits;2R 0 -4

u-39

udBr( p C) 1.6 10 5.9 10

27.5 R

0 -5 - 0s

3uuBr( pK ) 10 1.4 1C 0

2R -4 -30

uusBr( ) 1.3 10 2.3 1C 0

2R -7 -41

uudCBr( p ) 2.8 10 1.0 10t 30(p ) >25×10 yr

+ 30(p e +X) >0.6×10 yr

2R ucs+ -29Br(D ) 1.3 10C

D 2R uc0 -29

sBr(D ) 1.0 10C 2R ucd

0 -39Br(D p ) 4.0×10C

, 2Rcc 0,+ -28

ccbBr(B ) 1.0 10C

B2R

c uc

0 -30bBr(B ) 4 10C 2R ucb

-27Br(b cu ) 1.3×10C 2R -27

uubBr(b uu ) C 2.4×10

BNV t/D/B decays are strongly suppressed by the proton stability,

But

Experimental redundancy is still important !

NP search in t decays

In the 3rd generation– Probe for the NP flavor mixing between 3⇔1/3⇔2 gen.

Heavy – Rate enhancement– Q>0 for decays to baryonic final states.


BNV

LNV

LFV

t lepton is an unique laboratory to study…

t lepton is the charged lepton, which is …

t-pg, pp0, pK0, Lp-, Lp-

B-L conserving. B-L violating.

t-e+/m+ + h-h- (h=p,K)

t-e-/m- + g, l+l-, h+h-, h0, V0

BAULeptogenesis

General Analysis Procedure Signal side:

t decay of interest

Tag side: t 1 trk w/ n g + missing– 1-prong decays occupy >80% of

the t decay.– Loose constraint on n based on

Pmiss, M2miss.

Background– tt, continuum (qq), mm, ee,

…

Particle ID

Signal evaluation based on Minv ~ Mt & DE ~ 0

Signal region is open after analysis cuts are finalized.


t+

t-

p+

n

Lp-

p

p+Signal side

Tag side

DE=

ER

ec

– E

CM

Kinematical Constraint Use correlation between m2

miss and pmiss.

Signal decays distribute around m2miss ~ zero

(no. n on the signal side).


t+

t-

p+

n

Lp-

p

p+Signal side

Tag sideSignal MC Data

qq MC (uds)

tt MC

Y.Miyazaki et al., PLB632(2006)51-57

This cut removes 81% of ttand 77% of qq backgrounds, while keeping 89% of the signal.

Hadron-ID @ Belle Hadron-ID @ Belle is based on

the response of sub-detectors;– Threshold-type Aerogel

Cherenkov Counter (ACC)n = 1.011.03 depending on q

– Time-Of-Flight (TOF)– Ionization loss in CDC

(dE/dx)


Combined to form a likelihood;

Use a cut on the likelihood ratio;i i i iL =L(ACC)×L(TOF)×L(dE/ dx)

i

i j

LP(i : j ) =

L +L

Proton-ID performancew/ a nominal cut Eff(p) = 70% Fake(pp) = 4% Fake(Kp) = 11%

Pth(p) = 0.99 0.57 GeV/cPth(p) = 6.6 3.8 GeV/c

t pg, pp0 analyses use a

different cutAt Super-Belle, large improvement is expected by using Ring imaging type Cherenkov detectors

L Reconstruction The L candidates are reconstructed via

pp- decay channel. Selection parameters;

– Angle difference between PL and IP –VTX.– Flight distance of L– Closest approach of the L daughter tracks

to IP. Particle ID cut for daughter tracks.


L selection efficiency ~ 80%Purity ~ 90%


Signal MC

DataHisto: tt +qq MC

tpg, pp0

tp g (86.7fb-1) tpp0 (153.8fb-1)


Nobs = 16

Nbkg = 9.1±1.7 (expected)

Br (t-pg) < 3.0×10-7

Nobs = 70

Nbkg = 52.2±7.3 (expected)

Br (t-pp0) < 6.5×10-7

BELLE-CONF-0433hep-ex/ 0408117

5s signal box

D=6.9±4.3 D=17.8±11.1

(UL determined by an unbinned ML fit)

t Lp @154fb-1


B-L conserving (t- Lp-)

B-L violating (t- Lp-)

Con. Vio.

Eff(%) 11.8 11.7

Nside 5 5

Nbkg(exp’d) 1.7±0.8

1.7±0.8

Nobs 1 0

S90 2.77 1.47

Br (×10-7) <1.3 <0.70

We evaluate UL using 5 sellipse. BKG are extrapolated from 15s box assuming flat dist.

S90: Feldman-Cousins UL of #signals @ 90% CL. includingsystematic errors (POLE)


5 s ellipse

tt MCqq MC (uds)

BKG: tt (~1/2) + qq (~1/2) Only a few background Will be improved by 1/Lint

LFV in t Decays• Probe for 3⇔1/3 ⇔2 gen.

mixing in the charged lepton sector.

• Br(t) = O(103-5) x Br(m). Enough chance to see tmg or tlll.

• The two decays have different sensitivity for different NP models.

( )e

0

( )e223(13)l

(m )

t3l, lh

( )s

( )s

h

tlg

2 2 2

2 2 2

2 2 2

ee e e

e

e

m m m

m m m

mm m

Slepton mass matrix

tlg, lh,lh’,lp0signaldata

t→mg

t→mh(→gg)

t→mg,eg @535fb-1 (hep-ex/0705.0650 submittedd to PLB)

Br(t→mg)<4.5x10-8 (90%C.L.) Br(t→eg)<1.2x10-7 (90%C.L.)

t→e/ m + ,h h’,p0 @ 401fb-1 (PLB648, 341 (2007))

Br(t→lh,lh’,lp0) <(6.5-16)x10-8 90%C.L.

⇒Upper limits for LFV t decays are approaching O(10-8)

signal regionBkg. from tt/mm + initial state g

t→e/ m + ,h h’,p0 Only a few background Will be improved by 1/Lint

2007/9/22 14Toru ijima, B-L workshop

t→lll: Background suppression

Signal topology BG events

electron-veto on the tag-side 　 (e-e+e- and e-m+m-)g-conversion veto 　 (e-e+e- and m-e+e-)m2

miss and pmiss

　 (e-e+e-, m-m+m-, e-m+m-, m-e+e-)

Bhabha(mm) eemm(eeee)

mode m-

m+m-e-e+e- m-e+e-

e -

m+m-

m+e-e-

e+m-m-

Dominant bkg.

ttqqmmmm

Bhabhaeeeett

eemmttmm

ttqq

2007/9/22 15Toru ijima, B-L workshop

tlll @535fb-1


tmmm

teee Efficiency: 6.0% － 12.5% Nbkg (expected) = 0 – 0.4 events No event found in the signal region Obtained upper limit (90%CL)　　 Br<(2.0-4.1)×10-8

Improved by 4.9-7.0 fromBelle previous results @ 90fb-1

　

mode U.L. of Br @90%C.L.

t-e-e+e- 3.6×10-8

t-m-m+m- 3.2×10-8

t-e-m+m- 4.1×10-8

t-m-e+e- 2.7×10-8

t-e+m-m- 2.3×10-8

t-m+e-e- 2.0×10-8

datasignal

preliminary

The most stringent upper limits among LFV t decays

New !

Still a few background Will be improved by 1/Lint

tlV0 @543fb-1


mode Belle(158fb-1)＠ 90%C.L.

Belle(543fb-1)@90%C.L.

t-m-f 7.710-7 1.310-7

t-e-f 7.310-7 7.610-8

t-m-w - 9.010-8

t-e-w - 1.810-7

t-mK*0 3.910-7 6.110-8

t-e-K*0 3.010-7 8.010-8

t-m-K*0 4.010-7 1.110-7

t-e-K*0 4.010-7 7.710-8

t-m-r0 2.010-7

t-e-r0 6.510-7

t→mf

t-m-K*0

New !

Still a few background Will be improved by 1/Lint

t signal m/e + 2 chg. trackst tag m/e + ng

Background: tt, qq

Continuum bkg. suppression by t flight length & R2

2D PDF Likelihood ratio

tlhh @158fb-1

qq

LR= >0.45

L +L

<7.3

<2.0

<3.0

<3.1

<4.8

<3.4

<8.0

<4.4

<7.2

<1.6

<1.9

<2.7

<7.3

<2.9

UL (x10-7, 90%CL)

Y.Yusa et al., PLB640(2006)138-144

Signal MCqq MC (uds)

LNV

* * * **

*2007/9/22 18Toru ijima, B-L workshop*Still a few background Will be improved by

1/Lint

Summary for non-SM t Decay Search 　

t→3leptons

t→ef,ewt→ ,mf mw

→t lg

t→lh,lh’,lp0

t→lhh’

New results this summerUpp

er li

mits

of

LFV

t d

ecay

▼▼

▼

▼▼▼▼ ▼

BNV

2007/9/22 19Toru ijima, B-L workshopULs for all LFV t decays are approaching the 10-8 level

Future prospect Extrapolated sensitivity at 5ab-1

Estimatedupper limitrange of Br

PDG2006BelleBabar

based on eff. and NBG of most sensitive analysis

Ambiguity due to the stat. error of the bkg. estimation in the preset data.

Interaction RegionCrab crossingq=30mrad.by*=3mmNew QCS

Super-KEKB

Linac upgrade

More RF power

Damping ring

New Beam pipe

L 2ere

Iyy*RLRy

Increase beam currents• 1.6 A (LER) / 1.2 A (HER) → 9.4 A (LER) / 4.1 A (HER)

Smaller by*

• 6 mm→3 mm

Increase xy

• 0.059→>0.24(W-S)

L=8x1035cm-2s-1

8GeV (e+, 4.1A) 3.5GeV (e-, 9.6A)

Crab Cavity

Superconducting crab cavities (1LER and 1HER) have been installed, and being tested at KEKB.

22

L 2ere

Iyy*


http://www-acc.kek.jp/KEKB/pictures/LER_install/ler_install.html

Crab Status Crab cavity installed in Jan. 2007. Beam-beam tune shift (0.088) achieved at low currents. Beam current gradually increased

L=1034cm-2s-1 with crab crossing by June 2007. Still need R&D/tuning to see L improvement (simulation predicts

x2).


HER LER

Crab OFF

Crab ON22mrad crossing

crab crossing

y (beam-beam simulation)

24

Belle Upgrade

SC solenoid1.5T

New readout and computing systems

CsI(Tl) 16X0

g pure CsI (endcap) Aerogel Cherenkov counter + TOF counter

g “TOP” + RICH

Si vtx. det. 4 lyr. DSSDg 2 pixel/striplet lyrs. + 4 lyr. DSSD

Tracking + dE/dx small cell + He/C2H5

remove inner lyrs.

Use fast gas

m / KL detection 14/15 lyr. RPC+Fe

g tile scintillator


Summary• B-factories provide an unique opportunity to

study BNV, LNV, LFV in higher generation.

• The present KEKB provides 6x108 tt pairs New results for LFV search using the full data sets are approaching to O(10-8).

• Super-KEKB will provide x ~50-100 statistics. The search region will enter into O(10-9) for many decays. Good chance to see LFV t decays. BNV can be tested too.

Backup Slides

International Collaboration: Belle

13 countries, 55 institutes, ~400 collaborators

Aomori U.BINPChiba U.Chonnam Nat’l U.U. of CincinnatiEwha Womans U.Frankfurt U.Gyeongsang Nat’l U.U. of HawaiiHiroshima Tech.IHEP, BeijingIHEP, Moscow

Nagoya U.Nara Women’s U.National Central U.National Taiwan U.National United U.Nihon Dental CollegeNiigata U.Osaka U.Osaka City U.Panjab U.Peking U.U. of PittsburghPrinceton U.RikenSaga U.USTC

Seoul National U.Shinshu U.Sungkyunkwan U.U. of SydneyTata InstituteToho U.Tohoku U.Tohuku Gakuin U.U. of TokyoTokyo Inst. of Tech.Tokyo Metropolitan U.Tokyo U. of Agri. and Tech.Toyama Nat’l CollegeU. of TsukubaVPIYonsei U.

IHEP, ViennaITEPKanagawa U.KEKKorea U.Krakow Inst. of Nucl. Phys.Kyoto U. Kyungpook Nat’l U. EPF Lausanne

Jozef Stefan Inst. /

U. of Ljubljana /

U. of MariborU. of Melbourne

b s

• CP violation

• Precise CKM

• Rare decays– FCNC decays

– Tauonic decays

• t decays 　– Lepton flavor violation

– CPV in lepton sector

Physics Targets at Super-B

, .b s s etc

, .b c etc

Using O(1010) B and t (~100 x now)

1 1 1, , , | |, | |ub tdV V

.etc

0 0 0, ,B K K K K K

Search for new origin of flavor mixing and CPV.

Br~O(10-89) at Super B factory !

T LFV Prospect

tmg

tmh

tmmm

tmg suffers frombackground due to ISR.

Super-KEKB (cont’d)

Head-on collision w/ Crab cavityNew crab cavity

Ante-chamber /solenoid for reduction of electron clouds

Circular-chamber

Build-up ofelectron clouds

Ante-chamberAnte-chamberwith solenoid field

Will be tested in 2006.

Detector Upgrade

Higher background

Higher event rate

Require special features- low p m identification - full recon. eff.- hermeticity ; n “reconstruction”

- radiation damage and occupancy- fake hits and pile-up noise in the EM

- higher rate trigger, DAQ and computing

Issues4 Vertexing

4 Tracking

4 Particle ID

4 EM Cal

4 KL & m

4 Vertexing

4 Tracking

4 Particle ID

4 EM Cal

4 KL & m

Pixel det.

Small cellFast gasSi-tracker

F-DIRC+TOPAerogel RICH

Pure CsILiquid-Xe etc.

LSTScintillator

4 Fully pipelined readout4 Large scale computing

4 Fully pipelined readout4 Large scale computing

New Challenge! Intensive R&Ds!

search for bnv, lnv, lfv at (super-) belle/kekb

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