Search for new heavy charged gauge bosons

Abstract

Additional gauge bosons are introduced in many theoretical extensions to the Standard Model. A search for a new heavy charged gauge boson W ′ decaying into an electron and a neutrino is presented. The data used in this analysis was taken with the DØ detector at the Fermilab proton-antiproton collider at a center-of-mass energy of 1.96 TeV and corresponds to an integrated luminosity of about 1 fb −1 . Since no significant excess is observed in the data, an upper limit is set on the production cross section times branching fraction σ W ′ ×Br (W ′ → eν). Using this limit, a W ′ boson with mass below ∼1 TeV can be excluded at the 95% confidence level assuming that the new boson has the same couplings to fermions as the Standard Model W boson. Search for New Heavy Charged Gauge BosonsAdditional gauge bosons (including the equivalent to the Z, the Z ′ ) are introduced in many extensions to the Standard Model of particle physics. Assuming the most general case, the new gauge group can comprise a new mixing angle and new couplings. Here, the Altarelli Reference Model is considered which represents a generalization of the Manifest Left-Right Symmetric Model with light right-handed neutrinos. This model makes the assumptions that the new gauge boson W ′ has the same couplings as the Standard Model W boson and that there is no mixing. Hence, the W ′ is a heavy copy of the Standard Model W boson.The clear decay signature (in analogy to the decay of the W ) contains an isolated electron with extreme high energy which is important for triggering. The neutrino can not be detected, but it gives rise to missing energy in the detector. The Jacobian peak in the transverse mass distribution stemming from the W decay is used for calibration, whereas the tail of the transverse mass distribution is searched for a possible W ′ signal.The data agrees with the expectation from background processes. For instance, in the data 37 events are reconstructed with transverse masses above 300 GeV compared to a prediction of 37.1 ± 2.1 (stat) +6.0 −3.7 (sys) background events. Since no significant excess is found in the data, an upper limit is set on the production cross section for heavy charged gauge bosons decaying into electron and neutrino, σ W ′ × Br (W ′ → eν). Using this limit, a lower bound on the mass of the new gauge boson can be derived at the 95% confidence level,

Top-quark physics at the LHC

“…The t-channel exchange of heavy charged bosons X ± is marginal to negligible, as their contribution to the cross section is suppressed by 1/m 2 X . Heavy W bosons with SM couplings and masses below 1 TeV have been excluded by the D0 collaboration at the Tevatron from the search for their leptonic decays W → ν [331]. The CDF experiment has searched for W → tb and excludes a W with a mass below 790 GeV having this decay mode [98].…”

Top quark physics at the LHC

“…The t-channel exchange of heavy charged bosons X ± is marginal to negligible, as their contribution to the cross section is suppressed by 1/m 2 X . Heavy W ′ bosons with SM couplings and masses below 1 TeV have been excluded by the D0 collaboration at the Tevatron from the search for their leptonic decays W ′ → ℓν ℓ [324]. The CDF experiment has searched for W ′ → tb and excludes a W ′ with a mass below 790 GeV having this decay mode [93].…”

Direct search for heavy neutral gauge bosons in the dielectron channel at D0

“…For the region considered in this analysis, the maximum uncertainty of 2.5% per electron is considered as a conservative estimate [70,86].…”