arXiv subjects

A. Letessier-Selvon

Publications and source records attributed to A. Letessier-Selvon.

At least 19 recordsLinked to original sources

arXiv2026

Constraints on Sub-MeV Dark Matter from Solar Reflection with DAMIC-M

The Sun acts as a natural dark matter accelerator. Galactic halo particles scattering in the solar plasma emerge with velocities well beyond the Galactic escape speed, providing a boosted flux that extends the kinematic reach of direct detection experiments into the sub-MeV mass regime. We present constraints on solar-reflected dark matter (SRDM) from the DAMIC-M prototype detector using $\sim$1.3~kg-day of data acquired with silicon skipper charge coupled devices (CCDs) at the Modane Underground Laboratory. Exploiting the spatial diffusion signature of low-energy electron recoils, we derive 90% C.L. upper limits on the DM-electron scattering cross section for both heavy- and ultralight-mediator benchmarks, reaching $\barσ_e\sim 3.16 \cdot 10^{-37} \rm{cm^2}$ at $0.1$ MeV. For the ultralight mediator, our limits are competitive with the world-leading constraints, achieved with an integrated exposure of $\sim1.3$~kg-day. These results probe the parameter space between stellar-cooling bounds and terrestrial limits from standard halo searches, a region inaccessible to direct detection experiments relying solely on the standard halo flux.

hep-ex↗

arXiv2025

Daily Modulation Constraints on Light Dark Matter with DAMIC-M

The flux of Hidden Sector particles from the Galactic halo reaching an underground detector can be significantly attenuated by interactions within the Earth for sufficiently large scattering crosssections. This attenuation gives rise to a characteristic daily modulation in the detection rate, due to Earth's rotation. We present results from a search for such a modulation using a 1.257 kg-day dataset collected with the DAMIC-M Low Background Chamber. A model-independent analysis reveals no significant modulation in the 1e- event rate over periods from 1 to 48 h, highlighting the excellent temporal stability of the detector. In a complementary model-dependent analysis, we target the expected daily modulation signature of Hidden Sector particles, with masses in the range [0.53,2] MeV/c2, interacting with electrons via a dark photon mediator. By leveraging the expected temporal evolution of the signal, we set improved constraints on Dark Matter masses below 1.2 MeV/c2, surpassing our previous limits.

hep-ex↗

arXiv2025

Probing Benchmark Models of Hidden-Sector Dark Matter with DAMIC-M

We report on a search for sub-GeV dark matter (DM) particles interacting with electrons using the DAMIC-M prototype detector at the Modane Underground Laboratory. The data feature a significantly lower detector single $e^-$ rate (factor 50) compared to our previous search, while also accumulating a ten times larger exposure of $\sim$1.3 kg-day. DM interactions in the skipper charge-coupled devices (CCDs) are searched for as patterns of two or three consecutive pixels with a total charge between 2 and 4 $e^-$. We find 144 candidates of 2 $e^-$ and 1 candidate of 4 $e^-$, where 141.5 and 0.071, respectively, are expected from background. With no evidence of a DM signal, we place stringent constraints on DM particles with masses between 1 and 1000 MeV/$c^2$ interacting with electrons through an ultra-light or heavy mediator. For large ranges of DM masses below 1 GeV/c$^2$, we exclude theoretically-motivated benchmark scenarios where hidden-sector particles are produced as a major component of DM in the Universe through the freeze-in or freeze-out mechanisms.

hep-ex↗

arXiv2024

First Constraints from DAMIC-M on Sub-GeV Dark-Matter Particles Interacting with Electrons

We report constraints on sub-GeV dark matter particles interacting with electrons from the first underground operation of DAMIC-M detectors. The search is performed with an integrated exposure of 85.23 g days, and exploits the subelectron charge resolution and low level of dark current of DAMIC-M charge-coupled devices (CCDs). Dark-matter-induced ionization signals above the detector dark current are searched for in CCD pixels with charge up to 7e$^-$. With this dataset we place limits on dark matter particles of mass between 0.53 and 1000 MeV/$c^2$, excluding unexplored regions of parameter space in the mass ranges [1.6,1000] MeV/$c^2$ and [1.5,15.1] MeV/$c^2$ for ultralight and heavy mediator interactions, respectively.

hep-ex↗

arXiv2024

Search for Daily Modulation of MeV Dark Matter Signals with DAMIC-M

Dark Matter (DM) particles with sufficiently large cross sections may scatter as they travel through Earth's bulk. The corresponding changes in the DM flux give rise to a characteristic daily modulation signal in detectors sensitive to DM-electron interactions. Here, we report results obtained from the first underground operation of the DAMIC-M prototype detector searching for such a signal from DM with MeV-scale mass. A model-independent analysis finds no modulation in the rate of 1$e^-$ events with sidereal period, where a DM signal would appear. We then use these data to place exclusion limits on DM in the mass range [0.53, 2.7] MeV/c$^2$ interacting with electrons via a dark photon mediator. Taking advantage of the time-dependent signal we improve by $\sim$2 orders of magnitude on our previous limit obtained from the total rate of 1$e^-$ events, using the same data set. This daily modulation search represents the current strongest limit on DM-electron scattering via ultralight mediators for DM masses around 1 MeV/c$^2$.

hep-ex↗

arXiv2024

Nuclear Recoil Identification in a Scientific Charge-Coupled Device

Charge-coupled devices (CCDs) are a leading technology in direct dark matter searches because of their eV-scale energy threshold and high spatial resolution. The sensitivity of future CCD experiments could be enhanced by distinguishing nuclear recoil signals from electronic recoil backgrounds in the CCD silicon target. We present a technique for event-by-event identification of nuclear recoils based on the spatial correlation between the primary ionization event and the lattice defect left behind by the recoiling atom, later identified as a localized excess of leakage current under thermal stimulation. By irradiating a CCD with an $^{241}$Am$^{9}$Be neutron source, we demonstrate $>93\%$ identification efficiency for nuclear recoils with energies $>150$ keV, where the ionization events were confirmed to be nuclear recoils from topology. The technique remains fully efficient down to 90 keV, decreasing to 50$\%$ at 8 keV, and reaching ($6\pm2$)$\%$ at 1.5--3.5 keV. Irradiation with a $^{24}$Na $γ$-ray source shows no evidence of defect generation by electronic recoils, with the fraction of electronic recoils with energies $<85$ keV that are spatially correlated with defects $<0.1$$\%$.

physics.ins-det↗

arXiv2024

Confirmation of the spectral excess in DAMIC at SNOLAB with skipper CCDs

We present results from a 3.25 kg-day target exposure of two silicon charge-coupled devices (CCDs), each with 24 megapixels and skipper readout, deployed in the DAMIC setup at SNOLAB. With a reduction in pixel readout noise of a factor of 10 relative to the previous detector, we investigate the excess population of low-energy events in the CCD bulk previously observed above expected backgrounds. We address the dominant systematic uncertainty of the previous analysis through a depth fiducialization designed to reject surface backgrounds on the CCDs. The measured bulk ionization spectrum confirms the presence of an excess population of low-energy events in the CCD target with characteristic rate of ${\sim}7$ events per kg-day and electron-equivalent energies of ${\sim}80~$eV, whose origin remains unknown.

astro-ph.CO↗

arXiv2022

The DAMIC-M Experiment: Status and First Results

The DAMIC-M (DArk Matter In CCDs at Modane) experiment employs thick, fully depleted silicon charged-coupled devices (CCDs) to search for dark matter particles with a target exposure of 1 kg-year. A novel skipper readout implemented in the CCDs provides single electron resolution through multiple non-destructive measurements of the individual pixel charge, pushing the detection threshold to the eV-scale. DAMIC-M will advance by several orders of magnitude the exploration of the dark matter particle hypothesis, in particular of candidates pertaining to the so-called "hidden sector." A prototype, the Low Background Chamber (LBC), with 20g of low background Skipper CCDs, has been recently installed at Laboratoire Souterrain de Modane and is currently taking data. We will report the status of the DAMIC-M experiment and first results obtained with LBC commissioning data.

hep-ex↗

arXiv2022

Precision measurement of Compton scattering in silicon with a skipper CCD for dark matter detection

Experiments aiming to directly detect dark matter through particle recoils can achieve energy thresholds of $\mathcal{O}(1\,\mathrm{eV})$. In this regime, ionization signals from small-angle Compton scatters of environmental $γ$-rays constitute a significant background. Monte Carlo simulations used to build background models have not been experimentally validated at these low energies. We report a precision measurement of Compton scattering on silicon atomic shell electrons down to 23$\,$eV. A skipper charge-coupled device (CCD) with single-electron resolution, developed for the DAMIC-M experiment, was exposed to a $^{241}$Am $γ$-ray source over several months. Features associated with the silicon K, L$_{1}$, and L$_{2,3}$-shells are clearly identified, and scattering on valence electrons is detected for the first time below 100$\,$eV. We find that the relativistic impulse approximation for Compton scattering, which is implemented in Monte Carlo simulations commonly used by direct detection experiments, does not reproduce the measured spectrum below 0.5$\,$keV. The data are in better agreement with $ab$ $initio$ calculations originally developed for X-ray absorption spectroscopy.

physics.ins-det↗

arXiv2022

Characterization of the background spectrum in DAMIC at SNOLAB

We construct the first comprehensive radioactive background model for a dark matter search with charge-coupled devices (CCDs). We leverage the well-characterized depth and energy resolution of the DAMIC at SNOLAB detector and a detailed GEANT4-based particle-transport simulation to model both bulk and surface backgrounds from natural radioactivity down to 50 eV$_{\text{ee}}$. We fit to the energy and depth distributions of the observed ionization events to differentiate and constrain possible background sources, for example, bulk $^{3}$H from silicon cosmogenic activation and surface $^{210}$Pb from radon plate-out. We observe the bulk background rate of the DAMIC at SNOLAB CCDs to be as low as $3.1 \pm 0.6$ counts kg$^{-1}$ day$^{-1}$ keV$_{\text{ee}}^{-1}$, making it the most sensitive silicon dark matter detector. Finally, we discuss the properties of a statistically significant excess of events over the background model with energies below 200 eV$_{\text{ee}}$.

hep-ex↗

arXiv2021

Measurement of the bulk radioactive contamination of detector-grade silicon with DAMIC at SNOLAB

We present measurements of bulk radiocontaminants in the high-resistivity silicon CCDs from the DAMIC at SNOLAB experiment. We utilize the exquisite spatial resolution of CCDs to discriminate between $α$ and $β$ decays, and to search with high efficiency for the spatially-correlated decays of various radioisotope sequences. Using spatially-correlated $β$ decays, we measure a bulk radioactive contamination of $^{32}$Si in the CCDs of $140 \pm 30$ $μ$Bq/kg, and place an upper limit on bulk $^{210}$Pb of $< 160~μ$Bq/kg. Using similar analyses of spatially-correlated bulk $α$ decays, we set limits of $< 11$ $μ$Bq/kg (0.9 ppt) on $^{238}$U and of $< 7.3$ $μ$Bq/kg (1.8 ppt) on $^{232}$Th. The ability of DAMIC CCDs to identify and reject spatially-coincident backgrounds, particularly from $^{32}$Si, has significant implications for the next generation of silicon-based dark matter experiments, where $β$'s from $^{32}$Si decay will likely be a dominant background. This capability demonstrates the readiness of the CCD technology to achieve kg-scale dark matter sensitivity.

physics.ins-det↗

arXiv2020

Results on Low-Mass Weakly Interacting Massive Particles from an 11 kg-day Target Exposure of DAMIC at SNOLAB

We present constraints on the existence of weakly interacting massive particles (WIMPs) from an 11 kg-day target exposure of the DAMIC experiment at the SNOLAB underground laboratory. The observed energy spectrum and spatial distribution of ionization events with electron-equivalent energies $>$200 eV$_{\rm ee}$ in the DAMIC CCDs are consistent with backgrounds from natural radioactivity. An excess of ionization events is observed above the analysis threshold of 50 eV$_{\rm ee}$. While the origin of this low-energy excess requires further investigation, our data exclude spin-independent WIMP-nucleon scattering cross sections $σ_{χ-n}$ as low as $3\times 10^{-41}$ cm$^2$ for WIMPs with masses $m_χ$ from 7 to 10 GeV$c^{-2}$ . These results are the strongest constraints from a silicon target on the existence of WIMPs with $m_χ$$<$9 GeV$c^{-2}$ and are directly relevant to any dark matter interpretation of the excess of nuclear-recoil events observed by the CDMS silicon experiment in 2013.

astro-ph.CO↗

arXiv2020

Constraints on Light Dark Matter Particles Interacting with Electrons from DAMIC at SNOLAB

We report direct-detection constraints on light dark matter particles interacting with electrons. The results are based on a method that exploits the extremely low levels of leakage current of the DAMIC detector at SNOLAB of 2-6$\times$10$^{-22}$ A cm$^{-2}$. We evaluate the charge distribution of pixels that collect $<10~\rm{e^-}$ for contributions beyond the leakage current that may be attributed to dark matter interactions. Constraints are placed on so-far unexplored parameter space for dark matter masses between 0.6 and 100 MeV$c^{-2}$. We also present new constraints on hidden-photon dark matter with masses in the range $1.2$-$30$ eV$c^{-2}$.

astro-ph.CO↗

arXiv2019

LPNHE scientific perspectives for the European Strategy for Particle Physics

This note summarizes the activities and the scientific and technical perspectives of the Laboratoire de Physique Nucleaire et de Hautes Energies (LPNHE) at Sorbonne University, Paris. Although the ESPP is specifically aimed at particle physics, we discuss in this note in parallel the three scientific lines developed at LPNHE (Particle Physics, Astroparticles, Cosmology), first with the current scientific activities, then for the future activities. However, our conclusions and recommendations are focused on the particle physics strategy.

hep-ph↗

arXiv2018

The AMY (Air Microwave Yield) experiment to measure the GHz emission from air shower plasma

The aim of the Air Microwave Yield (AMY) experiment is to investigate the Molecular Bremsstrahlung Radiation (MBR) emitted from an electron beam induced air-shower. The measurements have been performed with a 510 MeV electron beam at the Beam Test Facility (BTF) of Frascati INFN National Laboratories in a wide frequency range between 1 and 20 GHz. We present the experimental apparatus and the first results of the measurements. Contrary to what have been reported in a previous similar experiment~\cite{Gorham-SLAC}, we have found that the intensity of the emission is strongly influenced by the particular time structure of the accelerator beam. This makes very difficult the interpretation of the emission process and a realistic extrapolation of the emission yield to the plasma generated during the development of an atmospheric shower.

astro-ph.IM↗

arXiv2017

First Direct-Detection Constraints on eV-Scale Hidden-Photon Dark Matter with DAMIC at SNOLAB

We present direct detection constraints on the absorption of hidden-photon dark matter with particle masses in the range 1.2-30 eV$c^{-2}$ with the DAMIC experiment at SNOLAB. Under the assumption that the local dark matter is entirely constituted of hidden photons, the sensitivity to the kinetic mixing parameter $κ$ is competitive with constraints from solar emission, reaching a minimum value of 2.2$\times$$10^{-14}$ at 17 eV$c^{-2}$. These results are the most stringent direct detection constraints on hidden-photon dark matter in the galactic halo with masses 3-12 eV$c^{-2}$ and the first demonstration of direct experimental sensitivity to ionization signals $<$12 eV from dark matter interactions.

astro-ph.CO↗

arXiv2016

Search for low-mass WIMPs in a 0.6 kg day exposure of the DAMIC experiment at SNOLAB

We present results of a dark matter search performed with a 0.6 kg day exposure of the DAMIC experiment at the SNOLAB underground laboratory. We measure the energy spectrum of ionization events in the bulk silicon of charge-coupled devices down to a signal of 60 eV electron equivalent. The data are consistent with radiogenic backgrounds, and constraints on the spin-independent WIMP-nucleon elastic-scattering cross section are accordingly placed. A region of parameter space relevant to the potential signal from the CDMS-II Si experiment is excluded using the same target for the first time. This result obtained with a limited exposure demonstrates the potential to explore the low-mass WIMP region (<10 GeV/$c^{2}$) of the upcoming DAMIC100, a 100 g detector currently being installed in SNOLAB.

astro-ph.CO↗

arXiv2016

Molecular Bremsstrahlung Radiation at GHz Frequencies in Air

A detection technique for ultra-high energy cosmic rays, complementary to the fluorescence technique, would be the use of the molecular Bremsstrahlung radiation emitted by low-energy ionization electrons left after the passage of the showers in the atmosphere. In this article, a detailed estimate of the spectral intensity of photons at ground level originating from this radiation is presented. The spectral intensity expected from the passage of the high-energy electrons of the cascade is also estimated. The absorption of the photons in the plasma of electrons/neutral molecules is shown to be negligible. The obtained spectral intensity is shown to be $2\times10^{-21} $W cm$^{-2}$ GHz$^{-1}$ at 10 km from the shower core for a vertical shower induced by a proton of $10^{17.5}$ eV. In addition, a recent measurement of Bremsstrahlung radiation in air at gigahertz frequencies from a beam of electrons produced at 95 keV by an electron gun is also discussed and reasonably reproduced by the model.

astro-ph.IM↗