Exploring vector-like $B$-quark pair production at CLIC in fully hadronic final states

TL;DR

This work evaluates the potential of a 3 TeV CLIC to discover a singlet vector-like bottom quark $B$ decaying via $B \to tW$ in the fully hadronic channel $B\bar{B}\to tW\,tW$. It employs large-$R$ Valencia jets with a jet-radius optimization ($R=0.8$) and a merging strategy to reconstruct boosted tops and $W$ bosons, achieving a sensitivity to $m_B \lesssim 1.5~{\rm TeV}$ with ${\cal L}=5~{\rm ab}^{-1}$. A cut-based analysis targets the $(2t+2W)$ topology, with robust background suppression from multi-boson and top-associated processes, yielding a cross-section reach of ${\cal O}(10^{-2})$ fb and a $5\sigma$ discovery potential up to $m_B \approx 1.5$ TeV for ${\rm BR}(B\to tW)=0.5$. The results demonstrate CLIC's unique capability to probe heavy vector-like quarks in high jet-multiplicity environments beyond current hadron-collider reach.

Abstract

We investigate the discovery potential of the 3 TeV Compact Linear Collider (CLIC) for a singlet vector-like bottom partner $B$ decaying via $B \to tW$. Focusing on the fully hadronic final state $B\bar{B} \to tW tW$, we reconstruct boosted top and $W$ candidates using large-$R$ Valencia jets, supplemented by a merging strategy for partially resolved decays. A systematic scan of the jet-radius parameter identifies $R=0.8$ as the optimal choice, balancing boosted-jet containment with jet multiplicity. Using a cut-based analysis optimized for the $(2t+2W)$ topology and an integrated luminosity of $5~{\rm ab}^{-1}$, CLIC can achieve sensitivity to $m_B \lesssim 1.5~{\rm TeV}$. These results highlight CLIC's excellent capability to probe heavy vector-like quarks in high jet multiplicity environments, extending well beyond the reach of current hadron collider searches.

Figures (3)

• Figure 1: Representative diagram for $e^+e^-\to B\bar{B}$ with subsequent decays $B\to tW$, $bZ$, and $bH$.
• Figure 2: The reconstructed invariant mass distributions for the two $B$ candidates after applying Cut-5 and Cut-6. The left panel shows the heavier candidate $m_{B_1}^{{\rm rec}}$ and the right panel the lighter $m_{B_2}^{{\rm rec}}$. Stacked histograms represent the total SM background (solid fill) and its main components, while dashed curves correspond to the benchmark signals with $m_B = 1.2~{\rm TeV}$ (black) and $m_B = 1.45~{\rm TeV}$ (red). Vertical lines indicate the chosen SR mass windows. Both distributions are normalised to $5~{\rm ab}^{-1}$ at $\sqrt{s}=3~{\rm TeV}$.
• Figure 3: Expected exclusion and discovery reach for the process $e^+e^-\!\to\!B\bar{B}\!\to\!tW\,tW$ at $\sqrt{s}=3~{\rm TeV}$ with an integrated luminosity of $5~{\rm ab}^{-1}$. The left panel shows the expected $95\%$ confidence level upper limit on the total cross section (blue dashed) compared with the theoretical prediction for a singlet vector-like $B$ quark (green solid). The right panel displays the corresponding $2\sigma$ exclusion (blue dashed) and $5\sigma$ discovery (red solid) contours in the $(m_B,\,{\rm BR}(B\!\to\!tW))$ plane, together with the current LHC constraint (orange curve, Ref. CMS:2022fck).