1 / 14

Discovery of a standard model Higgs boson using vector boson fusion at the LHC

Discovery of a standard model Higgs boson using vector boson fusion at the LHC. Craig Buttar University of Sheffield Collaborators: G.Azuelos, V.Cavasinni, D.Costanzo, R.Harper, K.Jakobs, M.Klute, R.Mazini, E.Richter-Was, I.Vivarelli. 10 5. 10 4. 10 3. Leading order. 10. Higgs production.

ursula
Download Presentation

Discovery of a standard model Higgs boson using vector boson fusion at the LHC

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. Discovery of a standard model Higgs boson using vector boson fusion at the LHC Craig Buttar University of Sheffield Collaborators: G.Azuelos, V.Cavasinni, D.Costanzo, R.Harper, K.Jakobs, M.Klute, R.Mazini, E.Richter-Was, I.Vivarelli

  2. 105 104 103 Leadingorder 10 Higgs production Events for 10 fb-1 Standard channels MH<2MZ: ttHlbb+X, H H ZZ* 4l, H WW(*) ll MH>2MZ: H ZZ 4l qqH ZZ ll, lljj qqHWW  ljj

  3. Tagging jet W Z/W H Z/W W Tagging jet VBF Signal (HWWll) • Cross section ~20% of gg-production BUT clear signature • forward tagging jets • correlated leptons • low hadronic activity in central region • central Higgs production Based on parton level study by Zeppenfeld and Rainwater hep-ph/9906218 Conclusion: >5 observation with 5fb-1 at LHC in the mass range 130-200 GeV

  4. Backgrounds • tt+jets • tWb • jets produced centrally • Use tagging, b-veto, central-jet veto • QCD WW+jets, +jets • Does not have lepton correlation • Reduced using central-jet veto • Low tag-jet invariant mass • -veto • EW WWjj+jj • Signal-like difficult to reduce

  5. Analysis • Signal, tt+jets and QCD backgrounds generated using PYTHIA 6.1 (with ISR, FSR, MI), CTEQ5L structure functions • EW backgrounds generated using Zeppenfeld and Rainwater parton level and interfaced to PYTHIA for PS (with ISR and FSR) and hadronization • tt-background, Z+jet and Z generated using ME and PYTHIA interface for comparison with PYTHIA tt-generation • TAUOLA is used for tau-decays • Detector simulation with ATLFAST

  6. Jet tagging and reconstruction Tag jets defined as jets with highest pT in each hemisphere Fake jet rate in the central region has been studied. 20 GeV threshold at low luminosity Must be raised at higher luminosity. Comparison of jet construction with ATLFAST and full-simulation

  7. Analysis of em channel • Two isolated leptons • pT1 >20GeV, pT2 >15GeV ||  2.5 • leptons observed in the rapidity gap spanned by the tag jets • Two tag jets • pTj1  40GeV; pTj2  20GeV • tags  3.8 • Reject tag jets identifiedas b-jets ||  2.5 • Lepton cuts • ll  1.05 • cosqll  0.2 • Rll  1.8 • Mll 85GeV • pT(l1,l2)  120GeV e pT 

  8. signal +jets • Real tau rejection • xt1, xt2  0.0 for real s • MZ-25  Mtt  MZ+25GeV • Mjj > 550GeV • Transverse momentum balance: |PT| < 30GeV • PT=pTl1+pTl2+pTmiss+pTj1+pTj2 • Jet veto: no jets with pT>20GeV in the region ||  3.2 • Z/* rejection: mT(ll)>30GeV

  9. Results Lepton pT +tag jets Lepton angular MH=160GeV Tau rejection, PT, Jet veto Drell-Yan rejection

  10. Results MT bound MT bound (σ in fb) For 5fb-1, >5σ for 155<MH<180GeV in e channel alone For 30fb-1, >5σ for 125<MH<190GeV in e+ee/ channels PYTHIA and ME background calculations have been compared, ME~2.1xPYTHIA Use ME and assign an additional systematic uncertainty of 10% Experimentally background can be measured using tt-events outside signal region

  11. Tau analysis • Look at   ll+pT-miss and   lhad+pT-miss channels • Similar analysis to WW(*) channel • ll+pT-miss, e final state analysis • Two isolated leptons with pT(e)>15 GeV, pT()>10GeV, |l|<2.5 • 2 tag jets with pTj1  50GeV; pTj2  20GeV (||  5.0 R < 0.7)---???tags  4.4, leptons are found in the rapidity gap between the tag jets • pT-miss > 50GeV • Invariant mass of tag jets, Mjj > 700GeV • Central jet veto, no jets with pT>20GeV in the region tagmin  j  tagmax • Azimuthal separation between tag jet jj<2.2 – reduces Zjj background • Re < 2.6 • Real tau reconstruction: xt1, xt2 > 0, xt12+xt22 < 1 • Mass window around Higgs boson mass: mH-10GeV<m <mH+15GeV

  12. Tau results for 30fb-1 5σ discovery in the region 110<MH<135GeV For 30fb-1

  13. Significance

  14. Summary • A light Higgs can be discovered with ≥5σ significance in the VBF channels: • qqH  WW(*)  ll+pT-miss: 10fb-1, 135GeV<MH<190GeV • qqH    ll+pT-miss and lhad+pT-miss: 30fb-1, 110GeV<MH<135GeV • Combined with other channels ATLAS can discover a Higgs with 5σ significance with 10fb-1 of data in the mass range: 120GeV<MH<190GeV • The measurement in VBF of WW and  decays allows a measurement of: in the mass range 120-150GeV at level of ~10%

More Related