Abstract
In scenarios beyond the Standard Model (BSM) characterised by charged (W′) or neutral (Z′) massive gauge bosons with large width, resonant mass searches are not very effective, so that one has to exploit the tails of the mass distributions measured at the Large Hadron Collider (LHC). In this case, the LHC sensitivity to new physics signals is influenced significantly by systematic uncertainties associated with the Parton Distribution Functions (PDF), particularly in the valence quark sector relevant for the multi-TeV mass region. As a BSM framework featuring such conditions, we consider the 4-Dimensional Composite Higgs Model (4DCHM), in which multiple W′ and Z′ broad resonances are present, with strongly correlated properties. By using the QCD tool xFitter, we study the implications on W′ and Z′ searches in Drell-Yan (DY) lepton decay channels that follow from the reduction of PDF uncertainties obtained through combining high-statistics precision measurements of DY lepton-charge and forward-backward asymmetries. We find that the sensitivity to the BSM states is greatly increased with respect to the case of base PDF sets, thereby enabling one to set more stringent limits on (or indeed discover) such new particles, both independently and in correlated searches.
Highlights
Current (NC) DY asymmetries in the mass region near the Standard Model (SM) vector boson poles
In this work we analyze the impact of improving the Parton Distribution Functions (PDF) systematics with the method of ref. [10] on the experimental sensitivity of forthcoming W and Z searches at the Large Hadron Collider (LHC), focusing on scenarios characterised by multiple W and Z broad resonances and by interference effects of the heavy bosons with each other and with SM gauge bosons in the CC and NC channels, respectively
We have analyzed LHC searches for broad W and Z vector resonances using as theoretical scenario the gauge sector of the 4-Dimensional Composite Higgs Model (4DCHM), a calculable minimal representation of a CHM
Summary
We describe the parameter space of the 4DCHM in terms of two parameters, the compositeness scale f and the gauge coupling gρ of the extra symmetry group [14, 17]. [20] has been used to obtain the chiral couplings to fermions of the heavy gauge bosons, which in turn have been included in a dedicated C++ code for the computation of the invariant and transverse mass distributions used for the analysis in the NC and CC channels, respectively. The invariant mass distributions of the di-lepton spectra have been generated taking 1200 points separated with 40 GeV ≤ M ≤ 13 TeV for each realization of the 4DCHM neutral resonances in the parameter space. The transverse mass distributions of the lepton-neutrino spectra have been produced computing 109 points separated with 100 GeV ≤ MT ≤ 11 TeV for each realization of the 4DCHM charged resonances in the model parameter space. Sensitivity studies in composite Higgs models comparing dilepton with heavy-quark channels in broad resonance searches may be found e.g. in [23, 24]
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