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AA->HH study ~AA->bbbb background~

AA->HH subgroup -- Experiment. AA->HH study ~AA->bbbb background~. Shin-ichi Kawada (AdSM, Hiroshima University). Outline. Introduction Previous result AA->bbbb background Results Histograms Summary & Next plan. Introduction.

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AA->HH study ~AA->bbbb background~

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  1. AA->HH subgroup -- Experiment AA->HH study~AA->bbbb background~ Shin-ichi Kawada (AdSM, Hiroshima University) 18th General Meeting @ KEK

  2. Outline • Introduction • Previous result • AA->bbbb background • Results • Histograms • Summary & Next plan 18th General Meeting @ KEK

  3. Introduction • PLC (Photon Linear Collider) has been proposed as one of the options of ILC. • It is expected that we can observe the Higgs self-coupling in PLC. • Feasibility study of Higgs pair creation in PLC is needed. 18th General Meeting @ KEK

  4. About PLC Electrons Backward Compton scattering Photon-Photon collision 18th General Meeting @ KEK

  5. Reaction in photon-photon collision • Signal: AA->HH->bbbb • Many backgrounds • AA->WW, ZZ, bbbb, etc... • Analysis of background reduction is necessary. • We assumed that Higgs mass equals to 120GeV In this study. 18th General Meeting @ KEK

  6. Previous results • Main backgrounds • AA->WW (~11.6pb, 1.5*107events/year) • AA->ZZ (~9.42fb, 1.2*104events/year) • Analysis with Neural Network • We can observe Higgs pair creation if we can develop good b-tagging method and jet clustering. 18th General Meeting @ KEK

  7. Today’s topic • AA->bbbb background • It is needed to estimate the cross-section of AA->bbbb background, because we adopted AA->HH->bbbb as a signal. • We calculated the cross-section of AA->bbbb background with using “GRACE” and ”BASES.” 18th General Meeting @ KEK

  8. Result • Total cross-section of AA->bbbb background is 960fb (collision energy = 270GeV). • ~5000 times larger than the total cross-section of signal (0.19fb) • Then we made histograms of physical values and checked the distributions of these. • Invariant mass • Energy • cos_theta 18th General Meeting @ KEK

  9. Definition of characters There are 3 possible combinations. P3 gamma P4 gamma P5 T1=P3+P4 T2=P5+P6 P6 Combination 1 b b-bar T3=P3+P5 T4=P4+P6 b Combination 2 b-bar T5=P3+P6 T6=P4+P5 Combination 3 18th General Meeting @ KEK

  10. Making histograms (1) • 1-D histograms (total: 38) • cos_theta of P3~P6 (total: 4) • Energy of P3~P6 (total: 4) • Invariant mass of T1~T6 (total: 6) • Energy of T1~T6 (total: 6) • cos_theta of T1~T6 (total: 6) • cos_theta (T1&P5, T1&P6, etc..., total: 12) 18th General Meeting @ KEK

  11. Making histograms (2) • 2-D histograms (total: 12) • Invariant mass (T1&T2, T3&T4, T5&T6, total: 3) • cos_theta (T1&T2, T3&T4, T5&T6, total: 3) • cos_theta ((T1&P5)&(T1&P6), (T2&P3)&(T2&P4), etc..., total: 6) 18th General Meeting @ KEK

  12. Example --- Invariant mass Invariant mass (T1, T2) Invariant mass (T3~T6) 0 0 ~10 sharp peak ~80 270 270 GeV GeV 18th General Meeting @ KEK

  13. Example --- Energy Energy (T1, T2) Energy (T3~T6) 0 0 ~135 ~135 sharp peak 270 270 GeV GeV 18th General Meeting @ KEK

  14. Example --- cos_theta cos_theta (T1&P5) cos_theta (T3&P4) -1 -1 sharp peak sharp peak ~0 +1 +1 Backward scattering only Back-to-back 18th General Meeting @ KEK

  15. Features of distribution • Distributions of T1 and T2 are very characteristic. • Invariant mass of T1 and T2: peak at ~10GeV • Energy of T1 and T2: peak at ~130GeV • cos_theta of (T1&P5) etc...: peak at cos_theta~-1 b Main reaction of AA->bbbb is probably like this. b-bar A g* b A b-bar 18th General Meeting @ KEK

  16. Summary • Since we adopted AA->HH->bbbb as a signal, we have to estimate the cross-section of AA->bbbb background. • Total cross-section of AA->bbbb is 960fb (@ 270GeV). • We made these histograms of AA->bbbb. • Invariant mass • Energy • cos_theta 18th General Meeting @ KEK

  17. Next plan • Making histograms of signal • Invariant mass, energy, cos_theta • Decide the cut criteria • Convolute the luminosity distribution • Calculating the cross-section of AA->bbbb background with luminosity distribution • Generating events of AA->bbbb 18th General Meeting @ KEK

  18. Backup 18th General Meeting @ KEK

  19. Before convolute luminosity • We changed the collision energy and calculate the cross-section of AA->bbbb background. • Changed to 20, 25, 30, ... ,270 GeV (total: 51). 18th General Meeting @ KEK

  20. Result 18th General Meeting @ KEK

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