Lepton number
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t -  m - n m n t. n  p e - n e. t -decays:. Lepton Number. L i = Σ # Leptons Gen i – # Antileptons Gen i. conserved in the Standard Model. today: many examples. Wolfgang Pauli. n t. n m. Neutrino Oscillations. neutrino oscillations violate lepton number !. annihilation.

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Lepton Number

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Lepton number

t-  m- nm nt

npe- ne

t-decays:

Lepton Number

Li = Σ # LeptonsGen i – # AntileptonsGen i

conserved in the Standard Model

today: many examples

Wolfgang Pauli


Lepton number

nt

nm

Neutrino Oscillations

neutrino

oscillations

violate

lepton

number !


Lepton number

annihilation

nm nt

Leptonic tau-Decay

nt

t-

nm

W-

m-

t-  m-

forbidden:

nm nt


Lepton number

neutrino oscillation

nm

Leptonic tau-Decay

nt

t-

nm

W-

m-

t-  m-

forbidden:

nm nt

but: energy/momentum conservation


Lepton number

neutrino oscillation

nm

g

LFV-Decay

possible

decay

nt

t-

nm

W-

m-

t-  m-

g

forbidden:

nm nt

but: energy/momentum conservation


Lepton number

LFV-Decay

possible

decays

nt

t-

nm

m-

W-

g/Z

m+

m-

t-  m- m+ m-


Lepton number

LFV-Decay

possible

decays

nt

r0

Z

t-

nm

W-

m-

t-  m- r0


Lepton number

neutrino oscillation

nm

g

GIM-Mechanism

nt

t-

nm

W-

m-

t-  m-

g


Lepton number

g

GIM-Mechanism

ni

t-

Uti

W-

Umi

m-

t-  m-

g


Lepton number

The Paper of X.-Y. Pham

Euro Phys J C8 (1999) 513, hep-ph/9810484

for discussion see Tord Riemanns home-page

http://www-zeuthen.desy.de/~riemann/


Lepton number

Beyond the S.M.

new physics breaks GIM


Lepton number

mgmmm

SUSY SO(10) NPB649(2003)189 PRD68(2003)03301210-810-10

SUSY HIGGS PLB549(2002)159 PLB566(2003)21710-1010-7

mSUGRA EPJC14(2000)319 PRD66(2002)11501310-710-9

non-universal Z´PLB547(2002)25210-910-8

Heavy Maj. NRPRD66(2002)03400810-910-10

Some theoretical estimates

Beyond the S.M.

new physics breaks GIM


Lepton number

Experimental Searches


Lepton number

LVF @ b-factories

currently best limits !

BaBar

approaching 109t-pairs

t-  m- g

Belle 2004: < 3.1 10-7

BaBar 2005: < 6.8 10-8


Lepton number

LVF @ b-factories

currently best limits !

BaBar

approaching 109t-pairs

prel. ’03 final ‘05

t-  m- g

  • (r/e-tag) 5.2 % 3.8 %

  • (total) 9.4 %

    exp. BGD

    (r/e) 7.8 ev. 2.8 ev.

    (total) 6.2 ev.

    limit (10-8) < 200 < 6.8

Belle 2004: < 3.1 10-7

BaBar 2005: < 6.8 10-8

b-factories reaching the limits at x 10-8


Lepton number

LVF @ LHC

t sources at the LHC:

1 year running

low luminosity

p p  W  t nt

p p  Z/g  t t

p p  B0  t X

p p  B±  t X

p p  Bs  t X

p p  Ds  t X

1.7 108

8.0 108

4.0 1011

3.8 1011

7.9 1011

1.5 1012

plenty of taus !

no chance to see

t- m- g


Lepton number

LVF @ LHC

 Tryt-  m- m+ m-

Simulation with underlying event

low luminosity


Lepton number

LVF @ LHC

Source: W  t nt

Trigger: Single-Muon

L1: pT > 14 GeV

HLT:pT > 19 GeV

Trigger: Di-Muon

L1: pT > 3 GeV

HLT:pT > 7 GeV

Looks okay

1.7 108t per year


Lepton number

LVF @ LHC

DS - Source

Trigger: Single-Muon

L1: pT > 14 GeV

HLT:pT > 19 GeV

Trigger: Di-Muon

L1: pT > 3 GeV

HLT:pT > 7 GeV

Trigger-Eff. only 1%

1.5 1012t per year


Lepton number

LVF @ LHC

Background Problem with DS source

DS F m nm1 % br.

F  m m (g)10-5br.

Does anybody know of a generator for this process ?


Lepton number

LVF Z-Decays

m+

g/Z

nt

m-

t-

nm

m-

W-

t-  m- m+ m-


Lepton number

LVF Z-Decays

m-

g/Z

m+

nt

t-

nm

m-

W-

m- m+ t- m-


Lepton number

LVF Z-Decays

m-

g/Z

m+

nt

nm

m-

m- m+ m- t+

t+


Lepton number

LVF Z-Decays

p

g/Z

p

nt

nm

m-

p p  Zm- t+

t+


Lepton number

LVF Z-Decays

m-

nm

p

g/Z

W

p

nt

t+

p p  Zm- t+


Lepton number

Summary


Lepton number

Conclusions

LFV tau-decays 

Interesting search for physics beyond the S.M.

(SUSY and others )

b-factories will approach 10-8

Can we improve a few channels at LHC ?

Also look for LVF in Z-decays at LHC !


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