Transcript Document
Proposal for search of @ ATLAS V.Zhuravlov NEOVP-ATLAS December 22, 2006 JINR ATLAS meeting 1 Tau decays with Lepton Flavor Violation • SM: forbidden no reason for lepton number conservation • SM + neutrino oscillations: allowed but BR is very small Br (τ μμμ) ~ 10-14 sensitive to m2/m3, but not accessible at recent colliders December 22, 2006 JINR ATLAS meeting Zμ μ 2 Sources of LFV decays model τ μ τ μμμ reference SM + neutrino oscillations 10-40 10-14 hep-ph/9810484 SM + heavy Majorana neutrino 10-9 10-10 PRD66(2002)034008 mSUGRA + seesaw 10-7 10-9 hep-ph/0206110 SUSY + SU(5) 10-4 SUSY SO(10) + seesaw 10-5 SUSY + anomalous U(1) 10-7 Neutral SUSY Higgs 10-10 10-7 hep-ph/0304081 Non-universal Z’ (technicolor) 10-9 10-8 PLB547(2002)252 Extra dimensions 10-11 December 22, 2006 JINR ATLAS meeting hep-ph/0303071 10-10 hep-ph/0405017 hep-ph/0308093 hep-ph/0210021 3 Current limits (90% C.L.) •BaBar (91.5 fb-1) Br(τ μμμ) < 1.9·10-7 •BELLE (87.1 fb-1) Br(τ μμμ) <2.0·10-7 •CLEO (4.79 fb-1) Br(τ μμμ) <1.9·10-6 Expected limits: • CMS (10 fb-1) Br(τ μμμ) <7.0 ·10-8 • LHCb (2 fb -1) -7 Br( τ μμμ ) < 1.2·10 December 22, 2006 JINR ATLAS meeting 4 Sources of tleptons at LHC 1 year of low luminosity = 10 fb-1 pp W tnt pp Z tt pp BB tDnt December 22, 2006 s = 17 nb 170106 t s = 1.5 nb 15 106 tt s = 24 b 0.241012 t JINR ATLAS meeting 5 Signal: Pythia generator + developed decay , uniformly distributed in phase space s + t + u = 3m2 + mt2 s > m2 + mt2 t > m2 + mt2 u > m2 + mt2 December 22, 2006 JINR ATLAS meeting 6 τ μμμ background pp ccbar Dx Ds Ds μ (Br = 1.2 %) μ μ (Br = 0.03 %) Background - 300 000 of μμμ events Signal - 35 events for BaBar limit December 22, 2006 JINR ATLAS meeting 7 τ μμμ: Background rejection 3 reconstructed muons with Pt > 2 GeV Signal efficiency: 26% Background efficiency: 0.9 % muon Pt (GeV) December 22, 2006 JINR ATLAS meeting 8 τ μμμ: Background rejection (2) PtMiss, GeV December 22, 2006 JINR ATLAS meeting Isolation, deg 9 Isolation cut: possibility of improvement? Number of hadron tracks in the cone R<0.4 around muons December 22, 2006 JINR ATLAS meeting 10 τ μμμ: Background rejection (3) cut = 10 deg muon angle December 22, 2006 Inv. Mass of muon pair JINR ATLAS meeting 11 Background rejection (4) PtMiss > 20 GeV Isolation > 6 deg Muon Angle < 10 deg BABAR limit Selection efficiency: 14% Background rejection: 550 Inv.Mass E [1.73, 1.82] expected background 2.9 events December 22, 2006 JINR ATLAS meeting 12 Conclusion Exp. Background: 2.9 events 90% C.L. belt 90% C.L. Nsignal < 4.4 Br (τ μμμ) = 1.8x10-7 Better than B-factories already after 1st year December 22, 2006 JINR ATLAS meeting 13 List “to do” • add other background sources: pp bbbar 2 muons + 1 miss-id muon 2 muons + 1 decayed to muon … • selection cut optimization (S/B improvement) • resolution of MS (only ID implemented so far) • common vertex cut December 22, 2006 JINR ATLAS meeting 14