Search for tau-e (tau-mu) flavor mixing at a linear collider

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Search for tau-e (tau-mu) flavor mixing at a linear collider. Shinya KANEMURA (Osaka Univ.) with. Yoshitaka KUNO, Toshihiko OTA (Osaka Univ) Masahiro Kuze (Tokyo Inst. Tech.). ACFA’07, Nov 11. 2004, at National Taiwan University. Introduction. - PowerPoint PPT Presentation

Transcript of Search for tau-e (tau-mu) flavor mixing at a linear collider

  • Search for tau-e (tau-mu) flavor mixing at a linear collider Shinya KANEMURA (Osaka Univ.)

    withYoshitaka KUNO, Toshihiko OTA(Osaka Univ)Masahiro Kuze (Tokyo Inst. Tech.) ACFA07, Nov 11. 2004, at National Taiwan University

  • IntroductionLFV is a clear signal for physics beyond the SM. e e

    Neutrino oscillation may indicate LFV among charged leptons.

    In SUSY models, LFV can naturally appear. Borzumati, Masiero Hisano et al.

  • In this talk, we discuss tau-associated LFV in SUSY models e &

    The Higgs mediated LFV is proportional to the Yukawa coupling Tau-associated LFV processes.It is less constraind by current data as compared to thee mixing e 1.2 1011e1.1 1012TieTi 6.1 1013 3.1 107 1.4-3.1 107 3.4 107

  • LFV in SUSYGauge mediation : LFV is induced at one loop due to slepton mixingHiggs mediation : Higgs mediation does not decouple in the large MSUSY limit

  • LFV Yukawa coupling Slepton mixing induces LFV in SUSY models. Babu, Kolda;Dedes,Ellis,Raidal;Kitano, Koike, Okadaij= Higgs LFV parameter

  • mSUSY O(1) TeVConsider that MSUSY is as large as O(1) TeV with a fixed value of ||/MSUSY While gauge mediated LFV is suppressed, the Higgs-LFV coupling ijcan be sufficiently large . Babu,Kolda; Brignole, Rossi

  • Search for Higgs mediated - e & - mixingTaus rare decays e e ()e e (). In near future, decay searches will improve the upper limit by 1-2 orders of magnitude.

    Other possibilities ? Higgs decays into a tau-mu or tau-e pair The DIS process e by a fixed target experiment at a LC ()

  • Higgs boson decay After the Higgs boson is found, we can consider the possibility to measure the LFV Higgs couplings directly from the decay of the Higgs bosons.LHC Assamagan et al; Brignole, RossiLC Kanemura, Ota, et al., PLB599(2004)83.

    Search for h (e) at LC:Simple kinematic structure (Esp. Higgssrahlung process)Precise measurements: property (mh,,,Br,) will be thoroughly measuredLess backgrounds

  • Higgs Production at a LC10^5 Higgs producedDecay branching ratio (h) The branching ratio of 10^(-4) 10^(-3) is possible.

  • SignalThe process can be identified by using Z recoil:Themomentum is reconstructed by using Ecm, mh, pZand p It is not required to measure

    The # of the signal event

    11 event for leptonic decay of Z118 event for hadronic decay

  • Backgrounds

  • FeasibilityResolution of Z momentum

    Signal / Fake 118 / 230 events (Z jj GeV) 11 / 8 events (Zll, 1GeV)For some specific parameter region, h e can be studied at a LC.No big advantage, although it depends on machine.

  • Alternative process for search of the Higgs LFV coupling?

    At future factories ( colliders) , 10^20 muons of energy 50 GeV (100-500GeV) can be available. DIS process Sher, Turan, PRD69(2004)302 Kanemura, et al, hep-ph/0410044 At a LC (Ecm=500GeV L=10^34/cm^2/s) 10^22 of 250GeV electrons available. We here consider the LFV DIS processes e by using the electron (positron) beam of a LCA fixed target experiment option of LC

  • Cross section in SUSY modelCTEQ6LEach sub-process e q (q) q is proportional to the d-type quark masses.

    For the energy > 60 GeV, the total cross section is enhanced due to the b-quark sub-process

    E50 GeV 10^(-5)fb 100 GeV 10^(-4)fb 250 GeV 10^(-3)fb

  • Energy distribution for each angleFrom the l L beam, R is emitted to the backward direction due to (1 cosCM) nature in the CM frame. In Lab-frame, tau is emitted forward direction but with large angle with a PT.E100 GeVE500 GeV2

  • SignalNumber of taus (case of electron beam) E250 GeV, L =10^34 /cm^2/s, 10^22 electrons (positrons) in a SUSY model with |3i |^2=0.310^(-6): =10^(-3) fb

    10^5 of leptons are produced for the target of =10 g/cm^2

    Naively, non-obervation of the e N X process may improve the current upper limit on the e--coupling by around 4-5 orders of magnitude We may consider its hadronic products as the signal (, a1, )missings # of hadrons 0.3(# of tau)

    Hard hadrons emitted into the same direction as the parent s Bullock, Hagiwara, Martin

  • BackgroundsHadrons from the target (N) should be softer, and more unimportant for higher energies of the initial e or beam.Hard leptons from l N l X would be be a fake signal via mis-ID of l as . (l = e or )Rate of mis-ID Emitted to forwad direction without large PT due to the Rutherford scattering 1/sin^4(cM/2) PT cuts Other factors to reduce the fakeRealistic Monte Carlo simulation is necessary.

  • SummaryPossibility of measuring LFV via e NX by using the high energy electron beam of a LC with a fixed-target.Ecm=500GeV 10^(-3) fb L=10^34/cm^2/s 10^22 electrons available 10^5 of taus are produced for =10 g/cm^2 Non-observation of the signal would improve the current limit on the -e- coupling by 10^(4-5). The signal would be hard hadrons from , a1, .... , which go along the direction.Main background: mis-ID of e from eNeX.Background simulation will be done.