Searching for long-lived particles: A compact detector for exotics at LHCb

Abstract

We advocate for the construction of a new detector element at the LHCb experiment, designed to search for displaced decays of beyond Standard Model long-lived particles, taking advantage of a large shielded space in the LHCb cavern that is expected to soon become available. We discuss the general features and putative capabilities of such an experiment, as well as its various advantages and complementarities with respect to the existing LHC experiments and proposals such as SHiP and MATHUSLA. For two well-motivated beyond Standard Model benchmark scenarios-Higgs decay to dark photons and B meson decays via a Higgs mixing portal-the reach either complements or exceeds that predicted for other LHC experiments.

Heavy neutral fermions at the high-luminosity LHC

“…Perhaps unsurprisingly, a number of new proposals to search for LLLPs have appeared, all based on the idea to exploit LHC's large luminosity: MATHUSLA [6], CODEX-b [7] and FASER [8]. The physics potential of these three experiments has so far not been fully discussed in the literature and it is the aim of the current paper to estimate, and compare to each other and previous experiments, the sensitivity of these proposals for fermionic LLLPs.…”

“…For more details we refer to the original publications for MATHUSLA [6], CODEX-b [7] and FASER [8]. We then describe our numerical simulation of these proposals.…”

“…Similarly, the authors of CODEXb [7] used a Higgs portal model for LLLPs to investigate the reach of their proposal. They also considered [7] a light neutral scalar, that mixes with the Higgs, produced in B-mesons decays as a LLLP candidate.…”

“…Similarly, the authors of CODEXb [7] used a Higgs portal model for LLLPs to investigate the reach of their proposal. They also considered [7] a light neutral scalar, that mixes with the Higgs, produced in B-mesons decays as a LLLP candidate. The original FASER [8] publication studied dark photons produced in meson decays to estimate the sensitivity of the different FASER setups.…”

“…CODEX-b [7] is a proposal that takes advantage of a relatively large shielded empty space near the location of the LHCb experiment. Being closer to the IP, CODEX-b proposed size is much smaller than that of MATHUSLA.…”