Anomalous gauge boson couplings measurement in photonphoton collisions

Anomalous gauge boson couplings measurement in photon-photon collisions 1. 2017 V. Makarenko (INP BSU, Minsk) 2. I. Boyko (JINR, Dubna), Anomalous gauge boson couplings measurement in photon-photon collisions

Energy spectrum of colliding photons CLIC is not only a lepton collider ⇒ f(Ecms) lepton collision spectrum photon collision spectrum Te. V GUINEA-PIG simulation For 3 Te. V beams: • Leγ / Lee ~ 0. 78 • Lγγ / Lee ~ 0. 68 • Lγγ / Lee ~ 0. 27 2017 for Eγγ > 2 MW Anomalous gauge boson couplings measurement in photon-photon collisions 2

Process γγ → WW cross section, pb - Cross section in photonic collisions is much higher than in leptonic Ecms, Te. V from V. Telnov slides at LCVS’ 11 2017 Anomalous gauge boson couplings measurement in photon-photon collisions 3

Possible physics in γγ → WW - Anomalous quartic gauge boson couplings (AQGC) in AAWW-vertex: Effective field theories can be constructed to quantify potential deviations from the SM by introducing genuine AQGC 2017 Standard model Anomalous gauge boson couplings measurement in photon-photon collisions 4

AQGC: scale factor - Standard AQGC notation leads to violation of unitarity - additional form-factor is introduced: - Λcutoff is traditionally set to 500 Ge. V Latest measurements: CMS: JHEP 1608 (2016) 119 ATLAS: Phys. Rev. Lett. 115 (2015) no. 3, 031802 CERN-EP-2016 -167 LEP-2: Eur. Phys. J. C 20 (2001) 201 -215 Phys. Rev. D 70 (2004) 032005 PDG review: pdg. lbl. gov/2016/reviews/rpp 2016 -rev-wz-quartic-couplings. pdf 2017 Anomalous gauge boson couplings measurement in photon-photon collisions 5

Codes used Beam spectrum: - GUINEA-PIG, - event files from http: //clic-beam. web. cern. ch/clic-beam/ Monte-Carlo, cross sections: - own codes 2017 Anomalous gauge boson couplings measurement in photon-photon collisions 6

Can we separate γγ events by IP ? IP distribution in gamma-gamma collisions GUINEA-PIG simulation y, nm x, nm Photonic processes can't be separated by IP z, μm 2017 Anomalous gauge boson couplings measurement in photon-photon collisions 7

How to select γγWW-vertex events • WW hadronic decays rate: ~47% • included into γγ →hadrons study, • hard to separate γγWW vertex • huge background • WW semileptonic decays rate: ~7% per mode {e++jets}, {e-+jets}, {μ++jets}, {μ-+jets} • two jets with minv ~ MW • single lepton along opposite charged beam • Emiss • high background • WW leptonic decays rate: ~1% per pair of {e+e-}, {e+μ-}, {μ+e-}, {μ+μ-} • two non-collinear leptons (incl. different flavour case) • no other particles in final state • Emiss No significant background in e-μ+ and e+μ- channels! 2017 Anomalous gauge boson couplings measurement in photon-photon collisions 8

cross section, pb WW-decay: WW→eeνeνe vs. WW→eμνeνμ Ecms, Ge. V Cross sections (pb) for γγ → WW →eeνeνe, eμνeνμ γγ → ττ → eeνeνe, eμνeνμ γγ → ee Cuts: ee → WW →eeνeνe, eμνeνμ ee → ττ → eeνeνe, eμνeνμ ee → ee Cuts: e, μ polar angle cut 10 o Conclusion: due to huge background from {γγ, ee→ee} we'll use study eμ channel only 2017 Anomalous gauge boson couplings measurement in photon-photon collisions 9

γγ → eμ and background processes cross section, pb Cross sections (pb) * BR for γγ, ee → WW →eμνeνμ γγ , ee → ττ → eμνeνμ solid lines: e, μ polar angle cut 10 o dashed lines: e, μ polar angle cut 20 o Ecms , Ge. V Signal process (SM): blue lines We expect significant amount of signal events 2017 Anomalous gauge boson couplings measurement in photon-photon collisions 10

γγ → eμ and background processes Next we apply beam spectrum: N events / 1 ab-1 γγ, ee → WW →eμνeνμ γγ, ee → ττ → eμνeνμ e, μ polar angle cut: 10 o N events / 1 ab-1 Ee , Te. V Pte , Te. V 2017 Anomalous gauge boson couplings measurement in photon-photon collisions 11

N events / 1 ab-1 γγ → eμ and background processes Minv(eμ) variable γγ, ee → WW →eμνeνμ γγ, ee → ττ → eμνeνμ e, μ polar angle cut: 10 o Meμ , Te. V N events / 1 ab-1 Pt(eμ) variable Clear signal events separation Pteμ , Te. V 2017 Anomalous gauge boson couplings measurement in photon-photon collisions 12

CLIC vs. LHC N events / 1 ab-1 Compare events number to latest CMS results: JHEP 1608 (2016) 119 Meμ , Te. V Signal events factor CLIC / LHC ~104 2017 Anomalous gauge boson couplings measurement in photon-photon collisions 13

CLIC vs. LHC Constant • Energy scale similar to LHC study Previous limit (95% CL) • Signal events ~104 times more Estimated CLIC limit (95% CL) a 0/Λ 2 , Ge. V-2 ac/Λ 2 , Ge. V-2 − 1. 5 … + 1. 5 x 10− 4 − 5 … +5 x 10 − 4 ~ − 1 … +1 x 10 − 6 ~ − 4 … +4 x 10 CLIC extimate JHEP 1608 (2016) 119 2017 Anomalous gauge boson couplings measurement in photon-photon collisions − 6

Conclusions • The background photon collisions may be used for search of new physics γγWW couplings. • The WW decay into leptons with different flavour looks promising. • The process γγ→ WW →eμνeνμ provides a clear test for anomalous quartic gauge boson couplings: • low background • basic background from tau-lepton decays • high event number (~104 factor to current to LHC data) ⇒ significant increase is expected for previous AQGC limits 2017 Anomalous gauge boson couplings measurement in photon-photon collisions 15

Backup slides 2017 Anomalous gauge boson couplings measurement in photon-photon collisions 16

Luminosity measurement in photon-photon collisions Different measurement schemes are required for two helicity modes: photon-photon collisions J=2 J=0 Luminosity can be measured using: • γγ→e+e– process • exclusive γγ→e+e–γ process • huge cross section • small cross section • huge background from e+e–→e+e • huge background from γγ→eeγ • can be suppressed by applying scattering in J=2 events cut on M(ee): M(ee)<< Enominal 2017 Anomalous gauge boson couplings in photon-photon collisions 17

Luminosity measurement in J=0 mode exclusive γγ→e+e–γ process event spectrum solid: fixed initial energy • Cross section in J=2 mode is much higher (solid lines on plot) • In experiment J=2 and J=0 events are mixed ⇒ dashed: CLIC spectrum we need to suppress J=2 events! Possible selection scheme Cross section, pb J 2 J 0 0. 0312 0. 0018 3 Te. V spectrum 1. 476 0. 300 2 W production region 0. 448 0. 059 0. 0165 0. 0158 Conclusion: 0. 00024 • Approx. 104 signal events / 1 ab-1 • Probably enough to measure luminosity with reasonable precision 3 Te. V fixed energy Photon selection E>200 Ge. V Photon selection E>1000 Ge. V 2017 0. 00013 Final photon energy, Te. V Anomalous gauge boson couplings in photon-photon collisions 18

γγ → eμ and background processes Next we apply beam spectrum: N events / 1 ab-1 γγ, ee → WW →eμνeνμ γγ, ee → ττ → eμνeνμ e, μ polar angle cut: 10 o N events / 1 ab-1 Ee , Te. V Pte , Te. V 2017 Anomalous gauge boson couplings measurement in photon-photon collisions 19

γγ → eμ and background processes Minv(eμ) variable N events / 1 ab-1 γγ, ee → WW →eμνeνμ γγ, ee → ττ → eμνeνμ e, μ polar angle cut: 10 o Meμ , Te. V N events / 1 ab-1 Pt(eμ) variable Clear signal events separation Pteμ , Te. V 2017 Anomalous gauge boson couplings measurement in photon-photon collisions 20

CLIC vs. LHC N events / 1 ab-1 Compare events number to latest CMS results: JHEP 1608 (2016) 119 Meμ , Te. V Signal events factor CLIC / LHC ~104 2017 Anomalous gauge boson couplings measurement in photon-photon collisions 21

CLIC vs. LHC N events / 1 ab-1 Compare events number to latest CMS results: JHEP 1608 (2016) 119 Meμ , Te. V Signal events factor CLIC / LHC ~104 2017 Anomalous gauge boson couplings measurement in photon-photon collisions 22