arXiv subjects

N. Eng

Publications and source records attributed to N. Eng.

8 recordsLinked to original sources

arXiv2026

Probing the Dark Matter EFT with QUEST-DMC: Projected Sensitivities and Attenuation Ceilings

This proceedings contribution summarises projected constraints from the QUEST-DMC concept, a surface-based direct-detection experiment using superfluid $^3$He operated below the millikelvin regime and instrumented with nanomechanical resonators read out by SQUIDs. The low recoil-energy threshold (down to sub-eV for the SQUID configuration) enables sensitivity to sub-GeV dark matter across a wide set of interaction structures beyond the canonical spin-independent and spin-dependent limits. We present projections in the non-relativistic Effective Field Theory (EFT) framework, scanning the standard set of fourteen Galilean-invariant operators and expressing reach in terms of effective dark matter-nucleon (or dark matter-neutron) cross sections. Because QUEST-DMC operates at the surface, we also account for suppression of the incident flux due to scattering in the atmosphere and Earth, which produces an interaction-dependent sensitivity ceiling at large couplings. Finally, we outline how the non-relativistic results map onto representative relativistic EFT dark matter-nucleon bilinears, enabling a compact interpretation of the projected reach in terms of UV-motivated coupling structures.

hep-ph↗

arXiv2025

Characterisation of silicon photomultipliers in a dilution refrigerator down to 9.4 mK towards a cryogenic cosmic-ray muon veto system

We report the characterisation of a FBK NUV-HD-cryo silicon photomultiplier (SiPM) sensor operated in a 9.4 $\pm$ 0.2 mK environment inside a dilution refrigerator, towards the development of a cryogenic cosmic ray muon veto system to be operated internal to a dilution refrigerator required for low background experiments such as the QUEST-DMC dark matter search experiment. We characterise the single photon response and the gain (the charge produced per detected photon), the dark count noise rate, and correlated noise contributions as a function of operating voltage. This paper also reports first proof-of-concept measurements of using a SiPM coupled to scintillator internal to a dilution refrigerator, towards detecting high-energy events consistent with candidate cosmic-ray muon signals.

physics.ins-det↗

arXiv2025

Development of superfluid helium-3 bolometry using nanowire resonators with SQUID readout for the QUEST-DMC experiment

Superfluid helium-3 bolometers can be utilised for dark matter direct detection searches. The extremely low heat capacity of the B phase of the superfluid helium-3 at ultra-low temperatures offers the potential to reach world leading sensitivity to spin dependent interactions of dark matter in the sub-GeV/c$^2$ mass range. Here, we describe the development of bolometry using both micron scale and sub-micron diameter vibrating wire resonators, with a SQUID amplifier-based readout scheme. Characterisation of the resonators and bolometer measurements are shown, including the use of non-linear operation and the corresponding corrections. The bolometer contains two vibrating wire resonators, enabling heat injection calibration and simultaneous bolometer tracking measurements. Coincident events measured on both vibrating wire resonators verify their response. We also demonstrate proof of concept frequency multiplexed readout. Development of these measurement techniques lays the foundations for the use of superfluid helium-3 bolometers, instrumented with vibrating nano-mechanical resonators, for future low threshold dark matter searches.

physics.ins-det↗

arXiv2025

Dark Matter EFT Landscape Probed by QUEST-DMC

We present the projected sensitivity to non-relativistic Effective Field Theory (EFT) operators for Dark Matter (DM) direct detection using the QUEST-DMC experiment. QUEST-DMC employs superfluid Helium-3 as a target medium and measures energy deposition via nanomechanical resonators with SQUID-based readout to probe DM interactions. The experiment aims to explore new parameter space in the sub-GeV mass range, probing light DM and a broad range of interaction models. We analyse the sensitivity to a complete set of fourteen independent non-relativistic EFT operators, each parameterised by a Wilson coefficient that quantifies the strength of DM interactions with Standard Model particles. For each interaction channel, we determine the corresponding sensitivity ceiling due to attenuation of the DM flux incident on the detector, caused by DM scattering in the Earth and atmosphere. As a key component of this analysis, we provide the mapping between the non-relativistic EFT operators and the relativistic bilinear DM-nucleon interactions, and assess the interaction sensitivity to sub-GeV DM in the QUEST-DMC detector. Our findings demonstrate that QUEST-DMC provides a unique probe of DM interactions, particularly in previously unexplored parameter space for momentum- and velocity-dependent interactions, thereby expanding the search for viable DM candidates beyond traditional weakly interacting massive particles.

hep-ph↗

arXiv2025

Dark Matter Attenuation Effects: Sensitivity Ceilings for Spin-Dependent and Spin-Independent Interactions

Direct detection experiments aimed at uncovering the elusive nature of dark matter (DM) have made significant progress in probing ever lower cross-sections for DM-nucleon interactions. At the same time, an upper limit in the cross-section sensitivity region is present due to DM scattering in the Earth and atmosphere and as a result never reaching the detector. We investigate the impact of this effect for both spin-dependent and spin-independent interactions. In contrast to previous studies that assume a straight line path for DM scattering we employ a semi-analytic diffusion model that takes into account the impact of potentially large angle deviations prevalent for light DM masses. We find that for sufficiently low energy thresholds, this difference in modelling impacts the DM interaction cross-section sensitivity. This study evaluates the impact in the context of the QUEST-DMC experiment, which utilises surface-based detectors with superfluid Helium-3 bolometers to search for sub-GeV DM exploiting low energy threshold. At masses below 1 GeV$/c^2$ the deviation between the two frameworks becomes pronounced. The ceiling sensitivity limit for QUEST-DMC on spin-dependent DM-neutron cross-sections is $\sim 3 \times 10^{-24}$ cm$^2$ using the diffusive framework and approximately doubles with the straight-line path DM scattering. Similarly, for spin-independent DM-nucleon cross-sections, the ceiling limit is $\sim 7.5 \times 10^{-27}$ cm$^2$ under the diffusive framework and also increases about a factor of two with the straight-line path approximation, within the mass range of 0.025-5 GeV$/c^2$.

hep-ph↗

arXiv2024

QUEST-DMC: Background Modelling and Resulting Heat Deposit for a Superfluid Helium-3 Bolometer

We report the results of radioactivity assays and heat leak calculations for a range of common cryogenic materials, considered for use in the QUEST-DMC superfluid 3He dark matter detector. The bolometer, instrumented with nanomechanical resonators, will be sensitive to energy deposits from dark matter interactions. Events from radioactive decays and cosmic rays constitute a significant background and must be precisely modelled, using a combination of material screening and Monte Carlo simulations. However, the results presented here are of wider interest for experiments and quantum devices sensitive to minute heat leaks and spurious events, thus we present heat leak per unit mass or surface area for every material studied. This can inform material choices for other experiments, especially if underground operation is considered where the radiogenic backgrounds will dominate even at shallow depths.

cond-mat.other↗

arXiv2023

QUEST-DMC superfluid $^3$He detector for sub-GeV dark matter

The focus of dark matter searches to date has been on Weakly Interacting Massive Particles (WIMPs) in the GeV/$c^2$-TeV/$c^2$ mass range. The direct, indirect and collider searches in this mass range have been extensive but ultimately unsuccessful, providing a strong motivation for widening the search outside this range. Here we describe a new concept for a dark matter experiment, employing superfluid $^3$He as a detector for dark matter that is close to the mass of the proton, of order 1 GeV/$c^2$. The QUEST-DMC detector concept is based on quasiparticle detection in a bolometer cell by a nanomechanical resonator. In this paper we develop the energy measurement methodology and detector response model, simulate candidate dark matter signals and expected background interactions, and calculate the sensitivity of such a detector. We project that such a detector can reach sub-eV nuclear recoil energy threshold, opening up new windows on the parameter space of both spin-dependent and spin-independent interactions of light dark matter candidates.

hep-ex↗

arXiv2020

Damping of a micro-electromechanical oscillator in turbulent superfluid $^4$He: A novel probe of quantized vorticity in the ultra-low temperature regime

We report a comprehensive investigation of the effects of quantum turbulence and quantized vorticity in superfluid $^4$He on the motion of a micro-electromechanical systems (MEMS) resonator. We find that the MEMS is uniquely sensitive to quantum turbulence present in the fluid. To generate turbulence in the fluid, a quartz tuning fork (TF) is placed in proximity to the MEMS and driven at large amplitude. We observe that at low velocity, the MEMS is damped by the turbulence, and that above a critical velocity, $v_c \simeq 5\,$mm\,s$^{-1}$, the turbulent damping is greatly reduced. We find that above $v_c$, the damping of the MEMS is reduced further for increasing velocity, indicating a velocity dependent coupling between the surface of the MEMS and the quantized vortices constituting the turbulence. We propose a model of the interaction between vortices in the fluid and the surface of the MEMS. The sensitivity of these devices to a small number of vortices and the almost unlimited customization of MEMS open the door to a more complete understanding of the interaction between quantized vortices and oscillating structures, which in turn provides a new route for the investigation of the dynamics of single vortices.

cond-mat.other↗