Search for single production of vector-like quarks decaying to a b quark and a Higgs boson

Abstract

A search is presented for single production of heavy vector-like quarks (B) that decay to a Higgs boson and a b quark, with the Higgs boson decaying to a highly boosted bb pair reconstructed as a single collimated jet. The analysis is based on data collected by the CMS experiment in proton-proton collisions at √ s = 13 TeV, corresponding to an integrated luminosity of 35.9 fb −1 . The data are consistent with background expectations, and upper limits at 95% confidence level on the product of the B quark cross section and the branching fraction are obtained in the range 1.28-0.07 pb, for a narrow B quark with a mass between 700 and 1800 GeV. The production of B quarks with widths of 10, 20 and 30% of the resonance mass is also considered, and the sensitivities obtained are similar to those achieved in the narrow width case. This is the first search at the CERN LHC for the single production of a B quark through its fully hadronic decay channel, and the first study considering finite resonance widths of the B quark. We present a search for electroweak production of single vector-like B quarks with electrical charge −1/3 e, with e the proton charge, that decay to a bottom (b) quark and a Higgs boson. The search uses pp events collected by the CMS experiment at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb −1 .-1 -

Single production of vectorlike quarks with large width at the Large Hadron Collider

“…Such parameterisation, when associated with a proper way to interpret experimental results, discussed below, represents a robust model-independent framework for testing any theoretical scenario predicting VLQs with small or large width against experimental limits in a given channel. This approach has been followed in two CMS analyses [42,43], whereσ was used for an interpretation of experimental results for single production of VLQs with large width. The values ofσ S andσ int SB in Eqs.…”

“…In most of these frameworks VLQs appear as partners of the third generation of quarks, having an EW coupling to top and bottom quarks. They are accessible at the LHC detectors in a variety of final states [31][32][33][34][35], some of these already explored by the ATLAS and CMS collaborations [36][37][38][39][40][41][42][43][44].…”

“…Up to now, experimental searches have been designed based on a simplified scenario for modelling the VLQ dynamics, assuming that only one new VLQ is present beyond the SM and parameterising its production, cross-section (σ), and decay, Branching Ratio (BR), rates using the Narrow Width Approximation (NWA) [36][37][38][39][40][41], with the exception of [42,43] where large width scenarios were also considered. In reality, both aspects need not be true.…”

“…A similar approach has been already used in its simplest form in Refs. [42,43]. Such strategy should limit the need of performing numerical recasting for the reinterpretation of results: the possibility of having ways to avoid numerical recasting (when possible) is becoming pressing as experimental searches rely more and more upon numerical frameworks which cannot be easily reproduced in tools for phenomenological analyses, such as boosted decision trees or multi-variate analyses.…”

The LHC potential of vector-like quark doublets

“…Searches targeting single production channels, which are proportional to the mixing angles, are also available within the latest dataset. CMS has published a search for B in the final state Ht [73] and for T in the final state Zt [74], while ATLAS has a search in W b for the 2015 dataset [75]. Only the search in the Zt channel can, in principle, be used to set bounds on the Yukawa-like couplings in our model.…”