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t / u -channel dark matter

t / u -channel dark matter. Amelia Brennan , Kenji Hamano. CoEPP / The University of Melbourne 11 April 2013. The model. Model proposed by Bell et al, emailed round last week (arxiv.org/abs/1209.0231) χ is gauge-singlet Majorana fermion

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t / u -channel dark matter

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  1. t/u-channel dark matter Amelia Brennan,Kenji Hamano CoEPP / The University of Melbourne 11 April 2013

  2. The model • Model proposed by Bell et al, emailed round last week (arxiv.org/abs/1209.0231) • χ is gauge-singlet Majoranafermion •  is a scalar field, transforms as (3,2,1/3), ie charged under SU(3)C Need to have all three diagrams to have a gauge invariant result

  3. Used FeynRules and MadGraph5 to produce LHE files for 6 mass points: • Don’t use m_eta < 700GeV, as this model is very similar to a SUSY model where m_eta is equivalent to a squark, and we know the squark mass is constrained around this region (though these constraints haven’t been examined in great detail) • Modelled the parton shower using Pythia8

  4. We chose to compare our mass point (200, 700) with the effective operator samples, as this should be far enough away from the regime where the EFT technique is valid • Downloaded following samples to compare: • MC12.158939.MadGraphPythia8_AU2MSTW2008LO_WimpPair_D1_DM200 • MC12.158939.MadGraphPythia8_AU2MSTW2008LO_WimpPair_D5_DM200 • MC12.158939.MadGraphPythia8_AU2MSTW2008LO_WimpPair_D9_DM200 • MC12.158939.MadGraphPythia8_AU2MSTW2008LO_WimpPair_ZZxx_DM200

  5. Selections • Use mc_pt, mc_eta, mc_phi, mc_m and mc_charge variables, where first we require mc_pgdId==+/-13 or +/-11 (iemuon or electron) • These variables should be truth level • Fill histograms with mc_pt, mc_eta and mc_phi • Select the leading and subleading leptons, and reconstruct the di-lepton invariant mass

  6. Lepton pT Generally lower pT for leptons in the Ma model (Problems with examining the lepton pt of ZZxx sample, so not shown here)

  7. Lepton phi

  8. Lepton eta More broadly distributed eta

  9. Invariant mass of leading lepton pair More sharply peaked at Z mass – maybe would change using original LHE files?

  10. A better comparison would be using the original EFT operator LHE files and showering with Pythia8 the same way we have showered our own samples • We downloaded these from Chase’s afs public directory, but Pythia doesn’t recognise the anti-particle ID number – any suggestions?

  11. We plan to request official MC production • All mass points FastSim • 2 mass points FullSim also for comparison

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