Unleashing the full power of LHCb to probe stealth new physics

Abstract

In this paper, we describe the potential of the LHCb experiment to detect Stealth physics. This refers to dynamics beyond the Standard Model that would elude searches that focus on energetic objects or precision measurements of known processes. Stealth signatures include long-lived particles and light resonances that are produced very rarely or together with overwhelming backgrounds. We will discuss why LHCb is equipped to discover this kind of physics at the Large Hadron Collider and provide examples of well-motivated theoretical models that can be probed with great detail at the experiment.

Displaced or invisible? ALPs from $B$ decays at Belle II

“…The scalar form factor f 0 m 2 a parametrizes hadronic effects in B → K transitions at momentum transfer q 2 = m 2 a . 3 The Wilson coefficient C sb describes the effective ALP interaction with lefthanded bottom and strange quarks below the weak scale…”

“…For simplicity, we express the ALP-fermion couplings in terms of mass eigenstates f in (2.1), but include the full evolution in our numerical analysis. 3 We implement the predictions for the scalar form factor from Ref. [41].…”

“…Particle physics experiments are sensitive to LLPs within a huge range of masses and lifetimes [1,2]. Collider experiments with a small detector coverage around the collision point, like LHCb [3] and FASER [4], mostly rely on displaced decays within the detector. Similarly, fixed-target experiments with a directional source are often designed to detect visible final states [5][6][7], but can also be sensitive to signatures with missing energy [8,9].…”

Near or Far Detectors? Optimizing Long-Lived Particle Searches at Electron-Positron Colliders

“…The ALP production from electrons is strongly suppressed by the small electron mass. 3 Compared to e + e − → aγ, ALP production through weak boson fusion, e + e − → ae + e − or e + e − → aν ν, is smaller by about an order of magnitude. 4 Strictly speaking, for the benchmark scenario built on (2.1) the decay a → µ + µ − dominates over a → γγ for c /cW W 0.002 at ma = 300 MeV.…”

“…Existing particle colliders are found to be sensitive to LLPs with a certain range of masses and couplings, which is determined by the particle source and the detector geometry [1]. For the LHC, new search strategies [2,3], as well as several annex experiments like FASER [4,5], MATHUSLA [6], and CODEX-b [7] have been proposed to optimize and extend the reach for LLPs. 1 For the next high-energy particle collider, it is advisable to explore the discovery potential for LLPs and optimize the detector setup before construction.…”