Person:
Han, Zhenyu

Profile Picture

Email Address

AA Acceptance Date

Birth Date

Research Projects

Organizational Units

Job Title

Last Name

Han

First Name

Zhenyu

Name

Han, Zhenyu

Filters

20112

Settings

Author's Publications: search.filters.isAuthorOfPublication.f3339a84-b02c-4ce0-a47d-9719bb6fa331

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    Publication
    W-Jet Tagging: Optimizing the Identification of Boosted Hadronically-Decaying W Bosons
    (American Physical Society, 2011) Cui, Yanou; Han, Zhenyu; Schwartz, Matthew
    A method is proposed for distinguishing highly boosted hadronically-decaying \(W's\) \((W jets)\) from QCD-jets using jet substructure. Previous methods, such as the filtering/mass-drop method, can give a factor of \(\sim 2\) improvement in \(S/\sqrt{B}\) for jet \(p_T \ge 200  GeV\). In contrast, a multivariate approach including new discriminants such as \(R\) cores, which characterize the shape of the \(W\) jet, subjet planar flow, and grooming-sensitivities is shown to provide a much larger factor of \(\sim 5\) improvement in \(S/\sqrt{B}\). For longitudinally polarized \(W's\), such as those coming from many new physics models, the discrimination is even better. Comparing different Monte Carlo simulations, we observe a sensitivity of some variables to the underlying event; however, even with a conservative estimates, the multivariate approach is very powerful. Applications to semileptonic \(WW\) resonance searches and all-hadronic \(W+jet\) searches at the LHC are also discussed. Code implementing our \(W-je\)t tagging algorithm is publicly available at http://jets.physics.harvard.edu/wtag.
  • Thumbnail Image
    Publication
    Top Condensation as a Motivated Explanation of the Top Forward-Backward Asymmetry
    (Springer Verlag, 2011) Cui, Yanou; Han, Zhenyu; Schwartz, Matthew
    Models of top condensation can provide both a compelling solution to the hierarchy problem as well as an explanation of why the top-quark mass is large. The spectrum of such models, in particular topcolor-assisted technicolor, includes top-pions, top-rhos and the top-Higgs, all of which can easily have large top-charm or top-up couplings. Large top-up couplings in particular would lead to a top forward-backward asymmetry through t-channel exchange, easily consistent with the Tevatron measurements. Intriguingly, there is destructive interference between the top-mesons and the standard model which conspire to make the overall top pair production rate consistent with the standard model. The rate for same-sign top production is also small due to destructive interference between the neutral top-pion and the top-Higgs. Flavor physics is under control because new physics is mostly confined to the top quark. In this way, top condensation can explain the asymmetry and be consistent with all experimental bounds. There are many additional signatures of topcolor with large tu mixing, such as top(s) + jet(s) events, in which a top and a jet reconstruct a resonance mass, which make these models easily testable at the LHC.