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Higgs pair production in a Photon Collider

Higgs pair production in a Photon Collider. Tohru Takahashi Hiroshima University for S.Kawada , N.Maeda , K.Ikematsu , K.Fujii,Y.Kurihara ,,,. LCWS12 Arlington, TX. Higgs selfcoupling. A Higgs like particle found at LHC! Higgs?, SM Higgs or …. coupling to fermions, gauge bosons

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Higgs pair production in a Photon Collider

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  1. Higgs pair production in a Photon Collider Tohru Takahashi Hiroshima University for S.Kawada, N.Maeda, K.Ikematsu, K.Fujii,Y.Kurihara ,,, LCWS12 Arlington, TX

  2. Higgs selfcoupling • A Higgs like particle found at LHC! • Higgs?, SM Higgs or …. • coupling to fermions, gauge bosons • mass generation • selfcoupling • symmetry breaking even tough with the e+e- How can the PLC do ? T.Takahashi Hiroshima

  3. Self-coupling constant in the SM Parameter of deviation from the SM This study S.Kawada.. et.al, Phys. Rev. D 85, 113009 (2012) Final goal: Study of Higgs self-coupling See feasibility of the measurement of Higgs pair creation in PLC. how may events expected? possible to suppress background? 17th General Meeting @ KEK

  4. Sensitivity vs energy η=η’=1,ηB=0 T.Takahashi Hiroshima

  5. Beam parameters (based on TESLA optimistic) T.Takahashi Hiroshima

  6. Luminosity Distribution(CAIN) x=3.76

  7. Signal backgrounds 100 gg->WW 270GeV 10 1 gg->ZZ 10-1 10-2 10-3 10-4

  8. gg->WW 1.462*107events/year) • gg->ZZ 1.187*104events/year Signal & Backgrounds Signal gg->HH(－＞bbbb) 16.4events/year 106 Backgrounds • gg->bbbb1.187*104events/year Assumption for the study integrated luminosity of 5 years of PLC run

  9. Event generation and Detector simulation • detector simulation • MC events • HH • WW • zz • bbbb dead !

  10. Analysis • Signal • gg->HH->bbbb • Kinematics and flavor information • Jet clustering • forced 4 Jets • Jet pairing • b tagging • Event selection • pre-selection to reduced number of events • optimization with Neural Net

  11. jet paring The jet of the least χ2 was chosen to be the most probable combination. M1, M2：reconstructed mass MH：Higgs mass are defined the same way (Mbb=10GeV)

  12. Analysis ~ b tagging~ • impact parameter <- simple ! Nsig: Number of displaced tracks in a jet • L

  13. Selection (1) pre-selection: cut tacks to forward/backward region loose b- tagging # Jet w/ more 0 off-vertex(>3s) tracks > 3 # Jet w/ more than 1 off-vertex(>3s) tracks > 2 b-tagging β：Lorentz factor of a particle θ：Angle between a particle and the beam

  14. Selection (2) --- Neural Network (NN) • parameters： • χH2 ,χZ2, χbb2 • transverse (longitudinal) momentum, • # of jets with displaced vertex jets, • visible energy, • Ycutvalue of jet clustering, • # of tracks • Maximize statistical significance N: # of events occurring in 5 years η: selection efficiency Sig: signal BG: background

  15. Example parameters For WW HH HH WW WW

  16. Example of parameters for 4b HH HH bbbb bbbb

  17. example parameters for ZZ HH HH ZZ ZZ

  18. Cut statictics jet clustering 17th General Meeting @ KEK

  19. Ideal clustering ideal clustering using color singlet information HH ZZ ｂ H or z ｂ for HH, WW,ZZ not for bbbb as color singlet is not trivial 17th General Meeting @ KEK

  20. Cut statictics 17th General Meeting @ KEK

  21. Summary • We tried to see gg -> HH in a photon collider based on TESLA optimistic parameters. • gg CM energy of 270GeV is optimum for mh =120GeV • It is possible to suppress backgrounds with improved jet clustering technique. • statistical significance of 4.9 with integrated luminosity corresonds to 5 years of PLC run

  22. Backup slide

  23. Ideal clustering 17th General Meeting @ KEK

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