Signature of light Z boson from scalar boson decay in local L µ L τ model at the ILC

Transcription

1 Signature of light Z boson from scalar boson decay in local L µ L τ model at the ILC Takaaki Nomura (KIAS) In collaboration with; Takashi Shimomura (Miyazaki U.) (Based on arxiv: 83.84) 8-- Beyond the BSM (The 4 th Kavli IPMU-Durham IPPP KEK-KIAS Ikaho, Japan

2 Out line of the talk. Introduction. Model and constraint 4. Summary

3 . Introduction Local U() Lµ-Lτ symmetry model µ(ν µ ) and τ(ν τ ) have opposite charge He, Joshi, Lew, Volkas PRD 43 (99) He, Lew, Volkas PRD 5 (994) Ø Motivated by resolving muon (g-) anomaly ~3.3σ 3.6σ deviation Ø Light Z boson can contribute to muon (g-) Δa µ = g' 8π dx m µ x ( x) x m µ + ( x)m Z ' *g : new gauge coupling

4 . Introduction Allowed parameter region explaining g- Araki, Hoshino, Ota, Sato, Shimomura (7) Light Z with small coupling Z decay into neutrinos with small kinetic mixing

5 . Introduction We also have new scalar boson From scalar field breaking U() Lµ-Lτ It can be produced via new scalar-higgs mixing Its decay into Z bosons indicate symmetry breaking Search for the signal at the ILC

6 Out line of the talk. Introduction. Model and constraint 4. Summary

7 . Model and constraint Minimal local U() Lµ-Lτ model Ø Anomaly free Ø VEV of φ breaks U() Lµ-Lτ! # H = # # " G + (v +!H + ig ) $ & &, ϕ = & (v + ϕ!φ + ig Z ' ) % Lagrangian of the model Scalar potential Kinetic mixing

8 . Model and constraint Mass eigenstates/eigenvalues after symmetry breaking l Scalar bosons h = cosα!h + sinα!φ φ = sinα!h + cosα!φ tanα = λ Hϕvv ϕ λ H v λ ϕ v ϕ l gauge boson Z Lµ Lτ Z ' ε sinθ W Z m Z ' = g'v ϕ

9 . Model and constraint Yukawa and gauge interactions $ L sinαφ& %& f $ + cosαh& %& + m Z ' v ϕ m f v ff + m Z v Z Z µ µ + m W v W µ f m f + W µ v ff + m Z v Z Z µ µ + m W v W µ cosαφz ' µ Z ' µ + m Z ' sinαhz ' µ Z ' µ v ϕ µ + Z ' µ ( eε cosθ W J EW + g'j µ Z ' )+O(ε ) ' ) () + W µ ' ) () Ø New scalar interact with SM particles via mixing between SM Higgs Ø Z interact with µ and τ type leptons Ø Z e+e- interaction via kinetic mixing

10 . Model and constraint Decay mode of new particles l Scalar boson (dominant modes) Γ φ Z 'Z ' = g' cos α m Z ' 8π m φ Γ φ ff = m! φ # 8π " m f v $ & % 4m Z ' m φ! # # "! sin α 4m $ f # " m & φ % + m 4! φ 4m m Z ' 4 # Z ' " m φ 3 $ & % $ & & % To resolve muon g-, m φ m Z ' ~ 3 ( m Z ' ~.GeV, m φ ~ GeV ) Z Z model is dominant: BR(Φ Z Z ) >.99

11 . Model and constraint Decay mode of new particles l Z boson (dominant modes)..5 Ν Μ Τ Ν Μ Τ e e. Γ Z ' νν = g' 4π m Z ' BR Z' ff..5 Γ Z ' e + e e ε cos θ W π m Z ' Ε g' We consider ε/g = Z mainly decay into neutrinos Thus decay chain on new scalar is φ Z 'Z ' νννν Ø Missing energy at detector Ø Different from SM Higgs decay

12 . Model and constraint Constraints from invisible Higgs decay and scalar mixing SM Higgs can decay into new particles H Z 'Z ', φφ Invisible Higgs decay In addition, we apply constraints from scalar mixing BR(H invisible) <.5, sinα <.3 Excluded by CCFR Excluded by CCFR g' g' sinα= m Z' (MeV) sinα= m Z' (MeV)

13 . Model and constraint Other constrains l Z search in meson decays at NA64: Z e + e - ε / g' (.6) For m Z = (5) MeV NA64 collaboration (7) Mostly Z decays into neutrinos

14 Out line of the talk. Introduction. Model and constraint 4. Summary

15 The Signal from hidden scalar production at the ILC Signal processes e + e l + l + E mis (l = e,µ) e + e jj + E mis Background processes e + e l + l νν, τ + τ (with leptonic decay of tau) e + e jjνν, τ + τ (with hadronic decay of tau)

16 Numerical analysis for signals/bgs at the ILC l We carry out simulation study using MADGRAPH/MADEVENT l Applying PYTHIA6 for ISR/FSR and hadronization l Detector simulation applying DELPHES (ILD card based on arxiv:36.639) We also apply polarized beam at the ILC 5 GeV (e +, e - ) polarization (+,-) polarization (e +, e - ) polarization (-,+) RR polarization Max integrated luminosity is taken as 9 fb - each polarization : (e +, e - ) polarization (+3%,-8%) with L=9 fb - RR: (e +, e - ) polarization (-3%,+8%) with L=9 fb - With more realistic polarization ratio

17 The cross section for scalar production ΦZ RR ΦΝΝ RR ΚΑ Σ fb.. ΚΑ Σ fb.. Φe e RR ΦZ ΦΝΝ Φe e. ΦZ RR ΦΝΝ RR ΦZ ΦΝΝ. Φe e RR Φe e m Φ GeV m Φ GeV The cross section for SM backgrounds (κ α =(.5/sinα) ) σ (e + e l + l νν) ~.99(.86) pb, σ (e + e jjνν) ~.398(.58) pb σ (e + e τ + τ ) ~.36(.94) pb For (RR) polarization

18 Kinematical cuts and mass reconstruction l Basic cuts p T (l ± ) > 7 GeV, η(l ± ) <.5 p T ( j) > GeV, η( j) < 5. For charged leptons For jets l Invariant mass cuts m Z GeV < M l + l < m Z + GeV m Z GeV < M jj < m Z + 5 GeV For charged leptons For jets l Scalar mass reconstruction M rec φ = s + m Z ( E l + E ) + / j l s / j

19 Signal 4 3 s 5 GeV L 9 fb m Φ 65 GeV e e ZΦ 4Ν Basic cut only Distributions for leptonic signal/bgs s 5 GeV L 9 fb e e ΝΝ RR s 5 GeV L 9 fb e e Τ Τ 5 5 M GeV 5 5 M GeV 5 5 M GeV 4 e e ZΦ 4Ν e e ΝΝ e e Τ Τ 3 m Φ 3 GeV m Φ 65 GeV s 5 GeV L 9 fb 5 5 M rec Φ GeV + M ll cut 4 s 5 GeV L 9 fb RR 5 5 M rec Φ GeV s 5 GeV L 9 fb 5 5 M rec Φ GeV

20 Signal 4 3 s 5 GeV L 9 fb m Φ 65 GeV e e ZΦ 4Ν Basic cut only Invariant mas cut Distributions for leptonic signal/bgs s 5 GeV L 9 fb e e ΝΝ Finally we impose reconstructed RR mass cut s 5 GeV L 9 fb e e Τ Τ 5 5 M GeV 5 5 M GeV 5 5 M GeV 4 e e ZΦ 4Ν e e ΝΝ e e Τ Τ 3 m Φ 3 GeV m Φ 65 GeV s 5 GeV L 9 fb 5 5 M rec Φ GeV + M ll cut 4 s 5 GeV L 9 fb RR 5 5 M rec Φ GeV s 5 GeV L 9 fb 5 5 M rec Φ GeV

21 # of events before/after kinematical cuts Comparing different polarizations

22 Signal s 5 GeV L 9 fb m Φ 65 GeV e e ΦZ jj 4Ν Basic cut only Distributions for hadronic signal/bgs s 5 GeV L 9 fb e e jjνν RR s 5 GeV L 9 fb e e Τ Τ M jj GeV s 5 GeV L 9 fb m Φ 3 GeV e e ΦZ jj 4Ν m Φ 65 GeV 5 5 M rec Φ j GeV + M jj cut 5 5 M jj GeV 4 s 5 GeV L 3 fb e e jjνν RR 5 5 M rec Φ j GeV M jj GeV 4 s 5 GeV L 9 fb e e Τ Τ 5 5 M rec Φ j GeV

23 Signal s 5 GeV L 9 fb m Φ 65 GeV e e ΦZ jj 4Ν Basic cut only Invariant mas cut 4 Distributions for hadronic signal/bgs s 5 GeV L 9 fb e e jjνν RR Finally we impose reconstructed mass cut s 5 GeV L 9 fb e e Τ Τ M jj GeV s 5 GeV L 9 fb m Φ 3 GeV e e ΦZ jj 4Ν m Φ 65 GeV 5 5 M rec Φ j GeV + M jj cut 5 5 M jj GeV 4 s 5 GeV L 3 fb e e jjνν RR 5 5 M rec Φ j GeV M jj GeV 4 s 5 GeV L 9 fb e e Τ Τ 5 5 M rec Φ j GeV

24 # of events before/after kinematical cuts Comparing different polarizations

25 Summary and Discussions p Minimal U() Lµ-Lτ model ü Anomaly free model ü Resolve anomalous muon magnetic moment ü We have new Z and scalar bosons p Signal at the ILC ü Scalar production via mixing between the SM Higgs ü New scalar dominantly decay into Z Z followed by Z νν ü Signal: Dilepton or Dijet + missing energy ü Testable at the ILC experiment Thanks for listening!