1 / 22

Analysis of Higgs Production and Decay Channels in Particle Physics

This study, presented by Christos Lazaridis in Spring 2007, explores various Higgs production mechanisms, including gluon-gluon fusion and vector boson fusion, highlighting their respective rates and backgrounds. It emphasizes the significance of decay channels for different Higgs masses, particularly for low and high mass scenarios. The study also presents methods for identifying electron candidates and discusses filters to reduce background noise from various processes. The findings demonstrate a promising signal efficiency, underlined by advanced algorithms for data analysis within the CMS detector framework.

gunda
Télécharger la présentation

Analysis of Higgs Production and Decay Channels in Particle Physics

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Christos Lazaridis, Particle Physics 735 A study on... Particle Physics 735 Spring 2007

  2. Christos Lazaridis, Particle Physics 735 Higgs Production • Gluon-gluon fusionhighest Higgs production rate, high QCD background • Vector boson fusion lower rate, lower background

  3. Christos Lazaridis, Particle Physics 735 Higgs Decays • For low Higgs mass is the most important decay • For higher Higgs masses WW is the most important decay (wait for Kira’s talk!) • A Higgs mass of 300 GeV was chosen for this study

  4. ISUB Which? 24 fi fibarZh0 26 fi fjbarW+h0 102 ggh0 123 fifj -> fifjh0 124 fifj -> fkflh0 Signal Characteristics • Higgs→ZZ→e+e-νν • Turned off all Higgs decays except the desired one • Cross section: • 6.60*10-11 mb Pythia parameters: Christos Lazaridis, Particle Physics 735

  5. Christos Lazaridis, Particle Physics 735 ISUB Which? 15 fifibargZ 16 fifjbargZ 30 figfiZ Background Characteristics • 4 Background sets: • Single Z • Total cross section: • 5.35x10-3 mb Pythia parameters:

  6. Christos Lazaridis, Particle Physics 735 ISUB Which? 19 fifibarγZ 22 fifibarZZ 23 fifjbarZW+ 25 fifibarW+W- Background Characteristics • 4 Background sets: • Vector Boson fusion • Total cross section: • 2.35x10-5 mb Pythia parameters:

  7. Christos Lazaridis, Particle Physics 735 ISUB Which? 81 fifibarQkQkbar 82 ggQkQkbar Background Characteristics • 4 Background sets: • Top quark • Total cross section: • 6.88x10-6 mb Pythia parameters:

  8. Christos Lazaridis, Particle Physics 735 ISUB Which? 1 fifibarγ*/ Z Background Characteristics • 4 Background sets: • Drell-Yan • Total cross section: • 3.27x10-3 mb Pythia parameters:

  9. Christos Lazaridis, Particle Physics 735 The CMS Detector

  10. Christos Lazaridis, Particle Physics 735 Procedure to identify electrons • Iterating over all SuperClusters • Ignoring all SCs with very low or very high energy • Comparing each SC with all Jets • If there is no near Jet or the SC has most of the energy then • We compare the SC with all tracks. Tracks of very low Pt are ignored. • If there is a track close enough and the ratio of ESC/Pt,Track is above a certain threshold then we can officially declare that SC as an electron candidate

  11. Christos Lazaridis, Particle Physics 735 Cuts to identify electrons Starting with 2060 Events : 12705 Initial SCs } 10278 Remain (80.9%) • Min SC energy cut = 5.0 GeV • Max SC energy cut = 500.0 GeV • ΔR between SCs & Jets ≥ 0.15 • E ratio between SCs & Jets ≥ 0.85 • Track Pt Cut ≥ 10 GeV • ΔR between Tracks & SCs ≤ 0.15 • E/Pt between Tracks & SCs ≥ 0.7 } 7015 Remain (55.2%) } 3493 Remain (27.5%)

  12. Christos Lazaridis, Particle Physics 735 Jet ΔR Cut ΔR between SCs & Closest Jet

  13. Christos Lazaridis, Particle Physics 735 Track ΔR Cut ΔR between Scs & Closest Track

  14. Generated Electrons Christos Lazaridis, Particle Physics 735

  15. Christos Lazaridis, Particle Physics 735 Electron Candidates Et (GeV)

  16. Christos Lazaridis, Particle Physics 735 Generated vs Reconstructed η Minimal matching: Ereco = 0.8~1.2 Egene

  17. Christos Lazaridis, Particle Physics 735 Generated vs Reconstructed φ Minimal matching: Ereco = 0.8~1.2 Egene

  18. Christos Lazaridis, Particle Physics 735 Variable Selects against... Z mass WW, Top, Drell-Yan Electron Et Fake electron, combinatoric Z Pt Fake Z Missing Et Z bg (maybe not top or W) Higgs Selection Variables • Higgs→ZZ→e+e-νν main backgrounds: • Single Z • Vector Boson fusion • Top • Drell-Yan

  19. Christos Lazaridis, Particle Physics 735 Signal/Bg comparison(only 2 bg sets) Electron Candidates Et (GeV)

  20. Christos Lazaridis, Particle Physics 735 Missing Et(Generated vs. Reconstructed)

  21. Christos Lazaridis, Particle Physics 735 Z Invariant Mass Inv. Mass (GeV/c2)

  22. The end! Summary • Is an interesting Higgs channel to work with • The backgrounds are high, but using the selection variables mentioned, can be significantly reduced • Using our home-made electron finder we’ve had a pretty good yield (84.8% of expected electrons were found and with good agreement to the generated set). Using the advanced algorithms implemented within CMMSW we can do better Christos Lazaridis, Particle Physics 735

More Related