Collider searches for long-lived particles yield a promising avenue to probe the freeze-in production of Dark Matter via the decay of a parent particle. We analyze the prospects of probing the parameter space of Dark Matter freeze-in from the decay of neutral parent particles at the LHC and beyond, taking as a case study a freeze-in Dark Matter scenario via the Standard Model Higgs. We obtain the projected sensitivity of the proposed MATHUSLA surface detector (for MATHUSLA100 and MATHUSLA200 configurations) for long-lived particle searches to the freeze-in Dark Matter parameter space, and study its complementarity to searches by ATLAS and CMS at HL-LHC, as well as the interplay with constraints from Cosmology: Big-Bang Nucleosynthesis and Lyman-$α$ forest observations. We then analyze the improvement in sensitivity that would come from a forward detector within a future 100 TeV $pp$-collider. In addition, we discuss several technical aspects of the present Dark Matter freeze-in scenario: the role of the electroweak phase transition; the inclusion of thermal masses, which have been previously disregarded in freeze-in from decay studies; the impact of $2\to 2$ scattering processes on the Dark Matter relic abundance; and the interplay between freeze-in and super-WIMP Dark Matter production mechanisms.
In this article, we explore the possibility of displaced Higgs production from the decays of the heavy fermions in the Type-III seesaw extension of the Standard Model at the LHC/FCC and the muon collider. The displaced heavy fermions and the Higgs boson can be traced back by measuring the displaced charged tracks of the charged leptons along with the $b$-jets. A very small Yukawa coupling can lead to two successive displaced decays which makes the phenomenology even more interesting. The prospects of the transverse and longitudinal displaced decay lengths are extensively studied in the context…
We study the pair production of the long-lived mediator particles from the decay of the SM Higgs boson and their subsequent decay into standard model particles. We compute the projected sensitivity, both model-independently and with a minimal model, of using the muon spectrometer of the CMS detector at the HL-LHC experiment for ggF, VBF, and Vh production modes of the Higgs boson and various decay modes of the mediator particle, along with dedicated detectors for LLP searches like CODEX-b and MATHUSLA. Subsequently, we study the improvement with the FCC-hh detector at the 100\,TeV collider exp…
We explore the simplest viable dark matter model with a real singlet scalar, vector-like singlet and doublet fermions. The Yukawa couplings associated with the fermion sector play a crucial role in getting the current relic density through Freeze-in and Freeze-out mechanism. We discuss the constraints from the recent muon anomalous magnetic moment experimental data and relic density. We also perform the collider analysis for the FIMP dark matter in the context of 14 TeV LHC experiments with the MATHUSLA100/200 detector. Our analysis shows that one can get enough events $>3$ for heavy charged f…
We present a novel framework capable of addressing the dark matter problem through freeze-in and freeze-out mechanisms, separately or together, depending on the region of the parameter space considered. In the dark matter dynamics, the model features an interplay of thermal production along with sizeable contribution through feeble decay of associated dark fermionic partner, which finally freezes out to the right relic density for a wide range of masses and couplings. Apart from the fermionic dark matter candidate, the model introduces two charged partners, one fermionic and another scalar, wh…
Axion-like particles (ALPs) are pseudo Nambu-Goldstone bosons of spontaneously broken global symmetries in high-energy extensions of the Standard Model (SM). This makes them a prime target for future experiments aiming to discover new physics which addresses some of the open questions of the SM. While future high-precision experiments can discover ALPs with masses well below the GeV scale, heavier ALPs can be searched for at future high-energy lepton and hadron colliders. We discuss the reach of the different proposed colliders, focusing on resonant ALP production, ALP production in the decay …
Future lepton colliders such as the CEPC and FCC-ee would run as high-luminosity $Z-$boson factories, which offer a unique opportunity to study long-lived particles which couple to Z-bosons. In order to exemplify this particular advantage, in this work we consider one benchmark physics scenario where the long-lived lightest neutralinos pair $(\tildeχ_1^0\tildeχ_1^0)$ is produced from $Z-$decays in the context of the R-parity violating supersymmetry. Our analysis indicates that when assuming BR$(Z\rightarrow \tildeχ_1^0\tildeχ_1^0) = 10^{-3}$ and $m_{\tildeχ_1^0} \sim 40$ GeV, the model paramet…
Detecting dark matter (DM) relic via freeze-in is difficult in laboratories due to smallness of the couplings involved. However, a non-standard cosmological history of the Universe, prior to Big Bang Nucleosynthesis (BBN), can dramatically change this scenario. In this context, we study the freeze-in production of dark matter in classically scale invariant $U(1)_X$ gauge extension of the Standard Model (SM), recently dubbed as the \textit{Scale Invariant FIMP Miracle}. We assume an additional species dominates the energy density of the Universe at early times, causing the expansion rate at a g…
We present an extension of the SM involving three triplet fermions, one triplet scalar and one singlet fermion, which can explain both neutrino masses and dark matter. One triplet of fermions and the singlet are odd under a $Z_2$ symmetry, thus the model features two possible dark matter candidates. The two remaining $Z_2$-even triplet fermions can reproduce the neutrino masses and oscillation parameters consistent with observations. We consider the case where the singlet has feeble couplings while the triplet is weakly interacting and investigate the different possibilities for reproducing th…
At the Large Hadron Collider (LHC), several far detectors such as FASER and MATHUSLA have been proposed to target the long-lived particles (LLPs) featured with displaced vertices. Naturally one question arises as to the feasibility of installing similar far detectors at future lepton colliders like the CEPC and FCC-ee. Because of the different kinematics of final state particles and the freedom to locate both the experiment hall and the detectors, the future lepton collider with an additional far detector may play a unique role in searching for LLPs. In this study, we consider various location…
We investigate a prospect of probing the type-III seesaw neutrino mass generation mechanism at various collider experiments by searching for a disappearing track and a displaced vertex signature originating from the decay of $SU(2)_L$ triplet fermion ($Σ$). Since $Σ$ is primarily produced at colliders through the electroweak gauge interactions, its production rate is uniquely determined by its mass. We find that a $Σ$ particle with a mass of a few hundred GeV produces a disappearing track signature from the decay of its charged component, which can be searched at the HL-LHC. Furthermore, we sh…
A certain class of new physics models includes long-lived particles which are singlet under the Standard Model (SM) gauge group.A displaced vertex is a spectacular signature to probe such particles productions at the high energy colliders, with a negligible SM background. In the context of the minimal gauged $B-L$ extended SM, we consider a pair creation of Majorana right-handed neutrinos (RHNs) at the high energy colliders through the production of the SM and the $B-L$ Higgs bosons and their subsequent decays into RHNs. With parameters reproducing the neutrino oscillation data, we show that t…
In the framework of the scotogenic model, which features radiative generation of neutrino masses, we explore light dark matter scenario. Throughout the paper we chiefly focus on keV-scale dark matter which can be produced either via freeze-in through the decays of the new scalars, or from the decays of next-to-lightest fermionic particle in the spectrum, which is produced through freeze-out. The latter mechanism is required to be suppressed as it typically produces a hot dark matter component. Constraints from BBN are also considered and in combination with the former production mechanism they…
Can LLP detectors probe the reheating temperature? A case study of vector dark matter
Pontificia Universidad Católica de Chile（智利天主教 Pontificia 大学）；Millennium Institute for Subatomic Physics at the High Energy Frontier (SAPHIR)（高能前沿亚原子物理千年研究所 (SAPHIR)）；Hefei University of Technology（合肥工业大学）
