Probing the Higgs CP Nature in the H Decay Mohammad Hassan - - PowerPoint PPT Presentation

Mohammad Hassan Hassanshahi

Imperial College London

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Probing the Higgs CP Nature in the H→𝜐𝜐 Decay

26 Feb2019

Supervisors: Dr. Dave Colling, Dr. Paul Dauncey

The Large Hadron Collider (LHC)

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LHC Detectors

LHCb ATLAS ALICE CMS

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The Compact Muon Solenoid (CMS) cross sectional view

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Motivation

• Measuring properties of the Higgs: CP nature
• Already measured in H → ZZ* → 4𝑚
• CMS & ATLAS data disfavored pseudoscalar

component of the Higgs

• No surprise! If pseudoscalar component exists,

subdominant in H → ZZ*

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Motivation

• But comparable level contribution in
• Yukawa Lagrangian for 𝜐 and Higgs interaction:
• => pure scalar
• => pure pseudoscalar
• => mixing state
• Final goal: measuring

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φτ = 0

φτ = π/2

0 < φτ < π/2

φτ

Measurement method

Higgs: J=0 So for :: if if S = 0 => CP = -1 => Pseudoscalar S = 1 => CP = 1 => Scalar Problem reduced to: measuring the spin

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Measurement method

• Measuring

spin

• Parity violated in weak interaction (neutrino handedness pinned down)
• So the angle between decay planes is sensitive to CP

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Problem reduced to: measuring the angle

Results and Future work

• The angle between the planes discriminates different CP states
• Monte Carlo on the recent CMS data shows the discrimination power
• Further improvement on sensitivity needed to decrease statistics error

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Conclusion

• decay can unravel the CP nature of the Higgs
• The angle between the decay planes of the taus is sensitive to the Higgs CP
• We will soon analyze the recent CMS data to measure the CP of the Higgs

in for the first time!

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H → τ +τ − H → τ +τ −

Thank you!

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Backup

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Tau decay modes

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