Tracking charged $b$-hadrons: feasibility study of the use of inner trackers to improve $B^{+}_{(c)}$ reconstruction

TL;DR

The paper addresses the challenge of partially reconstructed charged $b$-hadron decays at hadron colliders by proposing to use energy deposits in inner tracking detectors placed near the production vertex to constrain the $B^+$ momentum and decay kinematics. It evaluates multiple VELO-like detector geometries through a simulation study, quantifying the feasibility of obtaining 1–3 deposits and their impact on reconstruction efficiency. The results show that closer proximity to the beam and higher station density can substantially increase multi-hit fractions, enabling sensitivity to rare decays with branching fractions as low as $10^{-7}-10^{-9}$ and single-event sensitivities of $10^{-11}-10^{-12}$. These findings offer a practical route to extend flavour physics reach at hadron colliders and provide concrete guidance for design choices in future inner-tracking systems.

Abstract

A method to improve the reconstruction of charged b-hadron decays is proposed that uses energy deposits left by the hadron in tracking detectors close to the production point. Performances are shown for different detector configurations and different number of deposits reconstructed, as obtained in simulation, for $b$-hadrons produced in high energy proton-proton collisions. It is shown that up to few percent of the $B^+$ mesons could leave two deposits before decaying, depending on the detector configuration. The presented results can inform the design of future inner detectors. This method could increase significantly the physics reach of flavour physics at hadron colliders, opening it to decays with missing particles and vertex information that are otherwise unreconstructable.

Figures (5)

• Figure 1: Examples of the simulated geometries.(Left) Run 1/2 VELO; (Right) Run 3/4 VELO.
• Figure 2: Sample of simulated $B^+$ mesons in proton-proton collisions at 13 TeV traversing at least two detecting stations in the Run 3/4 geometry. Blue lines represent the paths of the mesons before decaying, red dots represent energy deposits.
• Figure 3: Fraction of $B^+$ mesons as a function of the number of hits produced for the different geometry configurations.
• Figure 4: Characteristics of $B^+$ mesons that produce at least two hits in the detector stations for the different geometry configurations: (top left) flight distance from the primary vertex, (top right) $B^+$ meson lifetime and (bottom) momentum.
• Figure 5: Kinematic variables of all the generated particles: pseudorapidity (top left), momentum (top right), and transverse momentum (bottom).