✁ � � � � � � � Tau Leptons at HERA Linus Lindfeld University of Zurich, Switzerland S T A U T R I I S C R E E N V S I N I S U XXXIII MDCCC Int. Workshop on Tau Lepton Physics, Nara, Japan September 14-17, 2004 Introduction Isolated taus + P t miss at ZEUS Tau pairs at H1 Isolated taus at H1 Search for H ++ τ + τ + Search for LFV LQ decays into taus 1
� � � � � The ep-collider HERA Hadron Electron Ring Accelerator (HERA): Two storage rings each with 6,3 km circumference in opposite direction for protons (E=920 GeV, I p =100 mA) and electrons/positrons (E=27.6 GeV, I e =50 mA), supported by DESY in Hamburg, Germany. Two interaction points where electrons and protons collide Detectors around interaction point to reconstruct event (H1, ZEUS) Interaction rate 10.4 MHz , every 96 ns ≈ 320 s GeV Center-of-mass energy: Integrated ep -luminosity up to now ~ 200 pb -1 Linus Lindfeld, University of Zurich TAU'04, Nara, Japan September 17, 2004 2
� � � � � The experiments ZEUS and H1 920 GeV p p e e 27.6 GeV Main components: Muon chambers Instr. iron (streamer tubes) Calorimeter Drift chambers Silicon strip detectors Linus Lindfeld, University of Zurich TAU'04, Nara, Japan September 17, 2004 3
ep-collisions – e + e + e + / ν e ν e → k’ k=(E e ,p e ) W + q=-Q q’ X q q x•P → P=(E p ,p p ) p X p X p p Neutral Current (NC) Charged Current (CC) SM Photoproduction ( Q 2 ~ 0) and Deep-Inelastic Scattering (DIS) ( Q 2 > 4 GeV 2 ) : Q 2 = -(k-k') = -q 2 four momentum transfer squared = -q 2 / (2Pq) x Bjorken scaling variable y = (qP) / (kP) inelasticity, i.e. energy loss of electron in proton rest frame = 2kP = Q 2 / (xy) s electron-proton center of mass energy squared Linus Lindfeld, University of Zurich TAU'04, Nara, Japan September 17, 2004 4
� ✁ ep-collisions with tau leptons Tau Processes at HERA: Standard Model New Physics µ + , τ + e + e + e + e + e + e + e + q’ l + b LQ t q’ λ ei λ lj W + – κ γ W + q ν l – , q u,c l - ν l l + ,q’ l + p X p p p X p q i q j W-Production Lepton-Pair-Production Anomalous top-Production Resonant Leptoquark via Photon-Photon-Fusion with W τ ν via FCNC production with LFV decay to tau σ ~ 10 pb (P t τ > 8 GeV) σ < 0.1 pb, i.e. hidden in large background less than 20 events! and more ... Tau lepton important in seaches for new physics Linus Lindfeld, University of Zurich TAU '04, Nara, Japan 5 September 17, 2004
� � ✄ ✂ ✁ � � � � � Signature of a tau lepton tau almost decays at vertex (c 88 m) decay modes: τ + e + ν e ¯ 17.9% ν τ − → τ + µ + ν µ ¯ 17.6% ν τ − → τ + h + ¯ ν τ + neutrals 50.3% − → 2 h + h − ¯ τ + ν τ + neutrals 14.0% − → ≥ 5 h ± ¯ τ + ν τ + neutrals 0.1% − → Strategy: Characteristic for hadronic decay: tau jet has low mass high-p T electron in direction of p T miss "pencil-like" jet with low charged multiplicity high-p T muon in direction of p T miss (calo.) narrow cluster narrow high-p T jet in direction of p T miss 1-3 tracks to narrow cluster Linus Lindfeld, University of Zurich TAU '04, Nara, Japan 6 September 17, 2004
Isolated tau leptons + P T miss at ZEUS Jet-Shape observables combined with a D dn dn + d d �ZEUS 99-00 e p� N N �CC DIS� 1 1 probability-density-estimation method �W � → τ ν -1 -1 ρ sig (x) 10 10 to a discriminant variable: D(x)= -2 -2 10 10 ρ sig (x)+ ρ bg (x) L int = 130 pb -1 -3 -3 10 10 0 0 0.5 0.5 1 1 D Preselection: 7 / 2.2 events (obs. / exp.) +0.39 3 3 3 3 10 10 10 10 -0.58 Events Events Events Events + �ZEUS 99-00 e p� 2 2 2 2 �CC DIS� 10 10 10 10 +0.12 D > 0.95: 3 / 0.4 �W → τ ν � -0.13 10 10 10 10 +0.05 P t had > 25 GeV: 2 / 0.2 1 1 1 1 -0.05 -1 -1 -1 -1 10 10 10 10 +0.02 P t had > 40 GeV: 1 / 0.07 -2 -2 -2 -2 -0.02 10 10 10 10 2 2 -3 -3 -3 -3 10 10 10 10 10 10 0 0 1 1 2 2 3 3 4 4 0 0 0.5 0.5 1 1 1.5 1.5 2 2 Events Events �ZEUS 94-00 data� �SM� -log(1-L -log(1-L ) ) -log(R -log(R ) ) 10 10 �Single Top MC� �W only� mean mean mean mean 3 3 3 3 10 10 10 10 overflow Events Events Events Events 1 1 2 2 2 2 10 10 10 10 -1 -1 10 10 10 10 10 10 -2 -2 10 10 1 1 1 1 -3 -3 10 10 -1 -1 -1 -1 10 10 10 10 -4 -4 -2 -2 -2 -2 10 10 10 10 10 10 0 0 1 1 D 2 2 3 3 > 0.95 -3 -3 -3 -3 D -log(1- ) -log(1- ) 10 10 10 10 0 0 1 1 2 2 3 3 4 4 0 0 0.5 0.5 1 1 1.5 1.5 2 2 -log(L -log(L ) ) -log(R -log(R ) ) rms rms rms rms Events Events D>0.95 3 3 3 3 10 10 10 10 Events Events Events Events 1 1 2 2 2 2 10 10 10 10 10 10 10 10 -1 -1 10 10 1 1 1 1 -1 -1 -1 -1 10 10 10 10 -2 -2 10 10 -2 -2 -2 -2 10 10 10 10 -3 -3 -3 -3 -3 -3 10 10 10 10 10 10 0 0 10 10 20 20 30 30 0 0 5 5 10 10 0 0 20 20 40 40 60 60 80 80 100 100 M M (GeV) (GeV) N N P P had had (GeV) (GeV) subj subj jet jet T T Linus Lindfeld, University of Zurich TAU '04, Nara, Japan 7 September 17, 2004
Isolated tau leptons + P t miss at ZEUS P tau candidate, p =39 GeV T T Linus Lindfeld, University of Zurich TAU '04, Nara, Japan 8 September 17, 2004
Tau pairs at H1 Search for hadronic „one-prong“ and „three-prong“ e + e + tau decays with a neural network algorithm based on hadronic jet-shape variables yields: l + 15 / 17.6 ± 3.9 unlike-sign events (obs. / exp.) 1 / 1.9 ± 1.2 like-sign event (obs. / exp.) l - unlike-sign like-sign p X p H1 Preliminary H1 Preliminary 3 3 3 3 10 10 10 10 L int = 108 pb -1 Events Events Events Events H1 Data (prelim.) H1 Data (prelim.) N = 15 N = 1 data data All SM Processes All SM Processes 2 2 2 2 10 10 10 10 N = 1.9 1.2 N = 17.6 3.9 ± ± SM SM SM error SM error TauPair TauPair 10 10 10 10 1 1 1 1 -1 -1 -1 -1 10 10 10 10 -2 -2 -2 -2 10 10 10 10 0 0 5 5 10 10 15 15 20 20 25 25 30 30 35 35 40 40 45 45 50 50 0 0 5 5 10 10 15 15 20 20 25 25 30 30 35 35 40 40 45 45 50 50 P P / GeV / GeV P P / GeV / GeV T T T T Linus Lindfeld, University of Zurich TAU '04, Nara, Japan 9 September 17, 2004
� Tau pairs at H1 Run 248568 Event 27325 Class: 4 11 12 13 15 16 19 20 24 28 29 . e + τ + τ − (X) e + p Tau-Pair Candidate + p + + ( e e X ) TA U-PA IR CANDID AT E µ + ν µ ν τ h + h - h - ν τ µ + h h + h µ µ + µ + e+ p e e+ h h + h h h + h Z H1 Linus Lindfeld, University of Zurich TAU '04, Nara, Japan 10 September 17, 2004
Isolated tau leptons + P t miss at H1 H1 Preliminary H1 Preliminary Cut-based analysis is restricted to 10 10 3 3 10 10 3 3 Events Events H1 Data (prelim.) H1 Data (prelim.) hadronic „one-prong“ tau decays: N = 26 N = 26 All SM Processes All SM Processes data data N = 24.2 4.4 N = 24.2 ± 4.4 ± SM Error SM Error 10 10 2 2 SM 10 10 2 2 SM SM W SM W A jet with one isolated track 10 10 10 10 pointing to a typical narrow hadronic energy depositon 1 1 1 1 -1 -1 -1 -1 10 10 10 10 H1 Preliminary -2 -2 -2 -2 10 10 10 10 0 0 10 10 20 20 30 30 40 40 50 50 60 60 70 70 80 80 0 0 0.1 0.1 0.2 0.2 0.3 0.3 0.4 0.4 0.5 0.5 0.6 0.6 2 2 10 10 R X Events P / GeV H1 Data (prelim.) Jet T N = 5 All SM Processes data N = 5.8 1.3 L int = 108 pb -1 ± SM Error SM 10 10 SM W single top (arb. norm) Preselection: 26 events (obs. / exp.) 1 1 R Jet < 0.12: 5 / 5.81±1.36 P t X > 25 GeV: 0 / 0.53±0.10 -1 -1 10 10 P t X > 40 GeV: 0 / 0.22±0.05 10 10 -2 -2 0 0 10 10 20 20 30 30 40 40 50 50 60 60 70 70 80 80 X P / GeV T Linus Lindfeld, University of Zurich TAU '04, Nara, Japan 11 September 17, 2004
� Search for H ++ τ + τ + H ++(--) e -(+) H ++(--) e +(-) e +(-) e +(-) e -(+) H ++(--) e -(+) γ (Z) γ (Z) γ (Z) p p,X p p,X p p,X L int = 65 pb -1 H1 Higgs search: H ±± limits σ *BR (pb) H1 Preliminary 0.4 Search for like-sign tau pairs is based on two isolated high P T tracks and includes leptonic 0.3 H ±± → τ ± τ ± and hadronic decays of the tau shows: 0.2 1 / 2.12 ± 0.32 unlike-sign events (obs. / exp.) H ±± → µ ± µ ± 0 / 1.03 ± 0.19 like-sign events (obs. / exp.) 0.1 H ±± → e ± e ± 0.09 0.08 0.07 0.06 0.05 H ±± → e ± µ ± 0.04 80 90 100 110 120 130 140 150 M H (GeV) Linus Lindfeld, University of Zurich TAU '04, Nara, Japan 12 September 17, 2004
� Search for LFV LQ decays into taus Leptoquarks couple to both quarks and leptons: µ + , τ + e + ( ν e ) µ + , τ + e + e + e + λ ej LQ λ lj LQ λ ei γZ ( W + ) λ il q i q j q i q j q i q i ¯ ¯ SM DIS s-channel u-channel narrow resonance in x at: x 0 = M 2 LQ Leptoquarks Parameters s color triplet bosons mass fractional charge coupling Both lepton and baryon number 0 quantum numbers Linus Lindfeld, University of Zurich TAU '04, Nara, Japan 13 September 17, 2004
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