Looking forward to $B^+\to \tau^+ \nu_\tau$ and $B_c^+\to \tau^+ \nu_\tau$

TL;DR

This study demonstrates, via simulation, that the LHCb experiment can feasibly observe the rare decays $B^+ o au^+ u_ au$ and $B_c^+ o au^+ u_ au$ during Run 3, enabling earlier experimental insights into these channels.

Contribution

The paper introduces a novel analysis method leveraging VELO pixel hits to reduce missing momentum limitations, enabling early measurements of these decay channels at LHCb.

Findings

Feasibility of observing $B^+ o au^+ u_ au$ and $B_c^+ o au^+ u_ au$ at LHCb during Run 3.

Use of VELO pixel hits significantly improves decay identification accuracy.

Potential to provide early experimental constraints on $B_c^+ o au^+ u_ au$ decays.

Abstract

These proceedings present the outcome of a feasibility study using RapidSim simulation software that demonstrates that the LHCb experiment will be capable of observing the decays $B^+\to \tau^+ \nu_\tau$ and $B_c^+\to \tau^+ \nu_\tau$ using the data that is being collecting during Run 3 of the LHC. The proposed analysis exploits the small distance of only 5.1 millimetres between the sensing elements of LHCb's innermost silicon pixel detector, the VELO, and the LHC's proton beams to identify direct pixel hits in the VELO that can be associated with the charged $B^+$, $B_c^+$ or $\tau^+$ particles. By using this extra information, the limitations due to the missing momentum and vertex information will be significantly reduced. This provides enough statistical power to pursue the measurements of these two decay channels at the LHC. In particular for the decay $B_c^+\to \tau^+ \nu_\tau$, which has been identified by the high energy physics community as a key objective for experiments at the planned next-generation particle accelerators, this means we do not need to wait for the 2030s or beyond to get first experimental constraints.