Single production of vector-like bottom quark at the LHeC
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Regular Article - Theoretical Physics
Single production of vector-like bottom quark at the LHeC Xue Gonga , Chong-Xing Yueb , Hai-Mei Yuc , Dong Lid Department of Physics, Liaoning Normal University, Dalian 116029, China
Received: 2 May 2020 / Accepted: 1 September 2020 © The Author(s) 2020
Abstract Existences of vector-like quarks (VLQs) are predicted in many new physics scenarios beyond the Standard Model (SM). We study the possibility of detecting the vector-like bottom quark (VLQ-B) being the SU (2) singlet with electric charge −1/3 at Large Hadron electron Collider (LHeC) in a model-independent framework. The decay properties and single production of VLQ-B at the LHeC are explored. Three types of signatures are investigated. By carrying out a fast simulation for the signals and the corresponding backgrounds, the signal significances are obtained. Our numerical results show that detecting of VLQ-B via the semileptonic channel is better than via the fully hadronic or leptonic channel.
1 Introduction With the discovery of a 125 GeV Higgs boson in July 2012 by the ATLAS and CMS collaborations at the CERN Large Hadron Collider (LHC) [1,2], the Standard Model (SM) has acquired remarkably success at explaining most of the available experimental phenomena with great accuracy. As yet, there are still unresolved theoretical issues in the SM, such as the nature of the electroweak symmetry breaking and the hierarchy between the electroweak and the Planck scales. One solution is by introducing new heavy particles called vector-like quarks (VLQs) which regulate the Higgs boson mass-squared divergence [3,4]. Since VLQs can obtain the ¯ directly, they gauge invariant mass terms of the form m ψψ are not subject to the constraints from Higgs production. Therefore, VLQs as a class of interesting particles have not been excluded by precision measurements. a e-mail:
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b e-mail:
[email protected] (corresponding author)
c e-mail:
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d e-mail:
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VLQs are hypothetical spin-1/2 colored fermions and are proposed in many new physics scenarios, for example, little Higgs [5–8], composite Higgs [9–12] and extra dimensions models [13,14]. The left- and right-handed components of VLQs have the same transformation properties under the SM electroweak symmetry group [15,16]. VLQs can be embedded in singlet [T , B], doublets [ (X, T ) , (T, B) or (B, Y )] or triplets [(X, T, B) or (T, B, Y )] for the representations of the SU (2) group. The weak hypercharges of VLQs can be determined by their Yukawa couplings with the SM quarks and the Higgs boson, therefore there are four possible charge assignments: Q T = +2/3, Q B = −1/3, Q X = +5/3, and Q Y = −4/3. In the case of UV complete models, the extra-dimensional models predict a tower of the vector-like top quarks, of which the lightest one has sizable mixing with the third generation quarks [17]. The vector-like bottom quarks are predicted in grand unification theories based on E 6 [18,19]. The doublets (X, T ) and
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