Detecting long-lived multi-charged particles in neutrino mass models with MoEDAL

TL;DR

This paper explores the detection prospects of long-lived, multi-charged particles predicted by neutrino mass models at the LHC using the MoEDAL detector, highlighting advantages of large electric charge for detection sensitivity.

Contribution

It demonstrates how multi-charged particles enhance MoEDAL's detection capabilities and provides concrete mass reach estimates for two neutrino mass models at the HL-LHC.

Findings

MoEDAL can detect particles lighter than 600-1430 GeV depending on charge.

Compared to ATLAS and CMS, MoEDAL extends the mass reach for multi-charged particles.

Large electric charge improves detection probability due to lower velocity and increased production cross-section.

Abstract

A certain class of neutrino mass models predicts long-lived particles whose electric charge is four or three times larger than that of protons. Such particles, if they are light enough, may be produced at the LHC and detected. We investigate the possibility of observing those long-lived multi-charged particles with the MoEDAL detector, which is sensitive to long-lived particles with low velocities ($\beta$) and a large electric charge ($Z$) with $\Theta \equiv \beta/Z \lesssim 0.15$. We demonstrate that multi-charged scalar particles with a large $Z$ give three-fold advantage for MoEDAL; reduction of $\Theta$ due to strong interactions with the detector, and enhancement of the photon-fusion process, which not only increases the production cross-section but also lowers the average production velocity, reducing $\Theta$ further. To demonstrate the performance of MoEDAL on multi-charged long-lived particles, two concrete neutrino mass models are studied. In the first model, the new physics sector is non-coloured and contains long-lived particles with electric charges 2, 3 and 4. A model-independent study finds MoEDAL can expect more than 1 signal event at the HL-LHC ($L = 300$ fb$^{-1}$) if these particles are lighter than 600, 1100 and 1430 GeV, respectively. These compare with the current ATLAS limits 650, 780 and 920 GeV for $L = 36$ fb$^{-1}$. The second model has a coloured new physics sector, which possesses long-lived particles with electric charges 4/3, 7/3 and 10/3. The corresponding MoEDAL's mass reaches at the HL-LHC are 1400, 1650 and 1800 GeV, respectively, which compare with the current CMS limits 1450, 1480 and 1510 GeV for $L = 36$ fb$^{-1}$. In a model-specific study we explore the parameter space of neutrino mass generation models and identify the regions that can be probed with MoEDAL at the end of Run-3 and the High-Luminosity LHC.