1. Mass Origin and Supersymmetry
The tau Lepton
and
Flavour Violation
Title page; Lepton Flavor Violation  Connection to Supersymmetry
Achim Stahl
RWTH Aachen
University
Mass Origin and Supersymmetry
March
Tsukuba

2. Lepton Number Li = Σ # LeptonsGen i – # AntileptonsGen i t-decays:
conserved in the Standard Model
n  p e- ne
today: many examples
Lepton Number in the SM. intro, definition, examples
t-  m- nm nt
t-decays:
Wolfgang Pauli

3. Neutrino Oscillationsnm nt
Neutrino Oscillations
LFV in neutrino oscillations
neutrino
oscillations
violate
lepton
number !

4. Leptonic tau-Decay t- m- t-  m- nm nt nm  nt nt nm annihilation W-
forbidden:
nm  nt

5. Leptonic tau-Decay t- m- t-  m- nm  nt nt nm nm neutrino oscillationW- m-
t-  m-
forbidden:
nm  nt
but: energy/momentum conservation

6. LFV-Decay t- m- t-  m- nm  nt possible decay nt nm nm g g
neutrino oscillation nm t- nm g W- m-
t-  m- g
forbidden:
nm  nt
but: energy/momentum conservation

7. LFV-Decay
possible
decays nt t- nm m- W-
g/Z m+ m-
t-  m- m+ m-

8. LFV-Decay
possible
decays nt r0 Z t- nm W- m-
t-  m- r0

9. GIM-Mechanism nt
neutrino oscillation nm t- nm g W- m-
t-  m- g

10. GIM-Mechanism t- m- t-  m- ni g g = Uti W- Umi = unitarity condition
Ue1 Ue2 Ue3
Um1 Um2 Um3
Ut1 Ut2 Ut3 n1 n2 n3 ne nm nt = t-
Uti g W-
Umi * m-
Ue1 Ue2 Ue3
Um1 Um2 Um3
Ut1 Ut2 Ut3
Ue1 Um1 Ut1
Ue2 Um2 Ut2
Ue3 Um3 Ut3 =
* * *
unitarity condition
t-  m- g
A  S Uti Umi f(mi2) ≈ 0 *
A  S Uti Umi = 0 *
A  S Uti Umi = ? *
br ≈ 10-40

11. for discussion see Tord Riemanns home-page
The Paper of X.-Y. Pham
Is this true ?
Paper von PHAM ?
Euro Phys J C8 (1999) 513, hep-ph/
for discussion see Tord Riemanns home-page

12. Beyond the S.M.
LFV beyond the SM; SUSY etc.
new physics breaks GIM

13. Beyond the S.M. Some theoretical estimates new physics breaks GIM
mg mmm
SUSY SO(10) NPB649(2003)189 PRD68(2003)
SUSY HIGGS PLB549(2002)159 PLB566(2003)
mSUGRA EPJC14(2000)319 PRD66(2002)
non-universal Z´ PLB547(2002)
Heavy Maj. NR PRD66(2002)
Some theoretical estimates
LFV beyond the SM; SUSY etc.
new physics breaks GIM

14. Experimental Searches

15. Experimental Searches
Signal:
t-  m- g
Background:
e+e-  m+m- g
e+e-  t+t-
t-  m- nm nt g _
e+e-  q q

16. LVF @ b-factories t-  m- g currently best limits ! BaBar
approaching 109 t-pairs
t-  m- g
Belle 2004: <
BaBar 2005: <
Perspectives at b-factories

17. LVF @ b-factories t-  m- g currently best limits ! BaBar
approaching 109 t-pairs
prel. ’03 final ‘05
t-  m- g
(r/e-tag) % %
(total) %
exp. BGD
(r/e) ev ev.
(total) ev.
limit (10-8) < < 6.8
Belle 2004: <
BaBar 2005: <
Perspectives at b-factories
b-factories reaching the limits at x 10-8

18. LVF @ LHC t sources at the LHC: t-  m- g 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
plenty of taus !
LFV-decays at the LHC
no chance to see
t-  m- g

19. Simulation with underlying event
LHC
 Try t-  m- m+ m-
Some plots from CMS
Simulation with underlying event
low luminosity

20. 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
 t per year

21. 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%
 t per year

22. LVF @ LHC F  m m (g) 10-5 br. Background Problem with DS source
DS  F m nm 1 % br.
F  m m (g) br.
Does anybody know of a generator for this process ?

23. LVF Z-Decays m+ m- t- m- t-  m- m+ m- g/Z nt nm W-
Connection to Z  tau mu
t-  m- m+ m-

24. LVF Z-Decays m- m+ t- m- m- m+ t-  m- g/Z nt nm W-
Connection to Z  tau mu
m- m+ t-  m-

25. LVF Z-Decays m- m+ m- m- m+  m- t+ t+ g/Z nt nm
Connection to Z  tau mu
m- m+  m- t+ t+

26. LVF Z-Decays m- t+ g/Z nt nm p p p p  Z  m- t+
Connection to Z  tau mu
p p  Z  m- t+ t+

27. LVF Z-Decays m- t+ nm g/Z nt p p p p  Z  m- t+ W
Connection to Z  tau mu
p p  Z  m- t+

28. Summary
Outlook CMS: mu-ID, Vertex-Fit; Phi  mu mu gamma background

29. 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 !