Stable Massive Particles at Colliders

TL;DR

The paper surveys Stable Massive Particles (SMPs) as long-lived, heavy states that could be directly detected at colliders, linking theoretical motivations (SUSY, extra dimensions, and exotic BSM scenarios) with collider phenomenology and cosmological constraints. It details how SMP production, hadronisation into R-hadrons, and interactions with detector material shape search strategies, including ionisation, Cherenkov, and time-of-flight techniques, with special treatment of magnetic monopoles. The work synthesises current collider limits across e+e−, lepton-hadron, and hadron-hadron experiments, and assesses the LHC's discovery potential for SMPs such as gluinos, sleptons, fourth-generation fermions, and monopoles, while addressing cosmological bounds from BBN, DM abundance, and inflationary dilution. The discussion emphasizes the necessity of robust modelling of production and interactions, given sizeable theoretical uncertainties, to interpret searches and guide future experiments like MOEDAL and LHC upgrades. Overall, the review maps the landscape of SMP theories, their collider signatures, and cosmological implications, underscoring the potential for groundbreaking discoveries at the LHC and beyond.

Abstract

We review the theoretical motivations and experimental status of searches for stable massive particles (SMPs) which could be sufficiently long-lived as to be directly detected at collider experiments. The discovery of such particles would address a number of important questions in modern physics including the origin and composition of dark matter in the universe and the unification of the fundamental forces. This review describes the techniques used in SMP-searches at collider experiments and the limits so far obtained on the production of SMPs which possess various colour, electric and magnetic charge quantum numbers. We also describe theoretical scenarios which predict SMPs and the phenomenology needed to model their production at colliders and interactions with matter. In addition, the interplay between collider searches and open questions in cosmology is addressed.

Figures (22)

• Figure 1: GMSB: the smallest index number $N$ required to obtain a $\tilde{\tau}_1$ NLSP as a function of $\Lambda$ and $\tan\beta$ for a) light messengers ($M=2\Lambda$) and b) heavy messengers ($M=10^{10}\, \hbox{GeV}$). The colour coding is the same for both plots and corresponds to the legend shown with b).
• Figure 2: The gluino lifetime in split SUSY as a function of the scalar mass parameter $\tilde{m}$ for $\tan\beta=2$, $\mu >0$, and various choices of the gluino mass, as calculated by Gambino:2005eh. The dashed horizontal line indicates the age of the Universe, $\tau_U = 14$ Gyr.
• Figure 3: Constraints upon direct detection of dark matter onlinedmAkerib:2004fqAngloher:2004trBernabei:2000qiAlner:2005pa. The red dashed curve is from CRESST, purple circles are from Edelweiss 1, green crosses are from ZEPLIN 1 and the solid blue curve is from CDMS. The region enclosed by dashes is the claimed detection from the DAMA collaboration which does not seem to be confirmed by the other experiments. The dark green filled region are a set of example SUSY models from Ref. baltzgondolo.
• Figure 4: Constraints upon the gluino mass and SUSY breaking scale parameters in models of split supersymmetry. Shaded regions are ruled out by different cosmological observations. The tightest constraints come from the diffuse gamma ray background for $m_{\tilde{g}}<300$ GeV and from Big Bang nucleosynthesis (BBN) for $m_{\tilde{g}}>300$ GeV. The plot is taken from Ref. arvanitaki.
• Figure 5: Amount of entropy which needs to be produced in order for the unstable stau to be consistent with nucleosynthesis constraints, see Eq. \ref{['entropy']}. Plot taken from Buchmuller0605164.