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Discussing tau lepton decay processes, neutrino oscillations, LFV mechanisms, and experimental searches for new physics beyond the Standard Model. Opportunity for discoveries in LHC data.
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The tau Lepton and Flavour Violation Mass Origin and Supersymmetry March 6 -8 2006 Tsukuba Achim Stahl RWTH Aachen University
t- m- nm nt npe- ne t-decays: Lepton Number Li = Σ # LeptonsGen i – # AntileptonsGen i conserved in the Standard Model today: many examples Wolfgang Pauli
nt nm Neutrino Oscillations neutrino oscillations violate lepton number !
annihilation nm nt Leptonic tau-Decay nt t- nm W- m- t- m- forbidden: nm nt
neutrino oscillation nm Leptonic tau-Decay nt t- nm W- m- t- m- forbidden: nm nt but: energy/momentum conservation
neutrino oscillation nm g LFV-Decay possible decay nt t- nm W- m- t- m- g forbidden: nm nt but: energy/momentum conservation
LFV-Decay possible decays nt t- nm m- W- g/Z m+ m- t- m- m+ m-
LFV-Decay possible decays nt r0 Z t- nm W- m- t- m- r0
neutrino oscillation nm g GIM-Mechanism nt t- nm W- m- t- m- g
Ue1 Ue2 Ue3 Um1 Um2 Um3 Ut1 Ut2 Ut3 ne nm nt n1 n2 n3 = 1 0 0 0 1 0 0 0 1 Ue1 Um1 Ut1 Ue2 Um2 Ut2 Ue3 Um3 Ut3 Ue1 Ue2 Ue3 Um1 Um2 Um3 Ut1 Ut2 Ut3 unitarity condition * * * * * * * * * g = t- m- g A SUti Umif(mi2) ≈ 0 A SUti Umi = ? A SUti Umi = 0 * * * GIM-Mechanism ni t- Uti W- * Umi m- br ≈ 10-40
The Paper of X.-Y. Pham Is this true ? Euro Phys J C8 (1999) 513, hep-ph/9810484 for discussion see Tord Riemanns home-page http://www-zeuthen.desy.de/~riemann/
Beyond the S.M. new physics breaks GIM
mg mmm SUSY SO(10) NPB649(2003)189 PRD68(2003)033012 10-8 10-10 SUSY HIGGS PLB549(2002)159 PLB566(2003)217 10-10 10-7 mSUGRA EPJC14(2000)319 PRD66(2002)115013 10-7 10-9 non-universal Z´ PLB547(2002)252 10-9 10-8 Heavy Maj. NRPRD66(2002)034008 10-9 10-10 Some theoretical estimates Beyond the S.M. new physics breaks GIM
t- m- nm nt g t- m- g Experimental Searches Signal: Background: e+e- m+m-g e+e- t+t- _ e+e- q q
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
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
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
LVF @ LHC Tryt- m- m+ m- Simulation with underlying event low luminosity
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
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
LVF @ LHC Background Problem with DS source DS F m nm 1 % br. F m m (g) 10-5br. Does anybody know of a generator for this process ?
LVF Z-Decays m+ g/Z nt m- t- nm m- W- t- m- m+ m-
LVF Z-Decays m- g/Z m+ nt t- nm m- W- m- m+ t- m-
LVF Z-Decays m- g/Z m+ nt nm m- m- m+ m- t+ t+
LVF Z-Decays p g/Z p nt nm m- p p Zm- t+ t+
LVF Z-Decays m- nm p g/Z W p nt t+ p p Zm- t+
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 !