分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-07-05
摘要： Recent studies of precision electroweak observables have led to the conclusion that a fourth generation is highly constrained. However, we point out that a long-lived fourth generation can reopen a large portion of the parameter space. In addition, it preserves baryon and lepton asymmetries against sphaleron erasure even if B - L = 0. It opens up the possibility of exact B - L symmetry and hence Dirac neutrinos. The fourth generation can be observed at the LHC with unique signatures of long-lived particles in the near future. (C) 2011 Elsevier B.V. All rights reserved.
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-06-24
摘要： We present a new probe of strongly coupled electroweak symmetry breaking at the 14 TeV LHC by measuring a phase shift in the event distribution of the decay azimuthal angles in massive gauge boson scattering. One generically expects a large phase shift in the longitudinal gauge boson scattering amplitude due to the presence of broad resonances. This phase shift is observable as an interference effect between the strongly interacting longitudinal modes and the transverse modes of the gauge bosons. We find that even very broad resonances of masses up to 900 GeV can be probed at 3 sigma significance with a 3000 fb(-1) run of the LHC by using this technique. We also present the estimated reach for a future 50 TeV proton-proton collider.
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