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The Air Microwave Yield (AMY) project aims to measure the emission in the GHz regime from test-beam induced air-shower. The experiment is using the Beam Test Facility (BTF) of the Frascati INFN National Laboratories in Italy. The final purpose is to characterize a process to be used in a next generation of ultra-high energy cosmic rays (UHECRs) detectors. We describe the experimental apparatus and the first test performed in November 2011.

The DAMIC-M (DArk Matter In CCDs at Modane) experiment will use skipper CCDs to search for low mass (sub-GeV) dark matter underground at the Laboratoire Souterrain de Modane (LSM) in France. With about 1 kg of silicon target mass and sub-electron energy resolution, the detector will surpass the exposure and threshold (eV-scale) of previous experiments. Thus, DAMIC-M will have world-leading sensitivity to a variety of \"hidden sector\" candidates. In this talk, we will report on science results from a prototype detector, test performance of CCD modules, and the status of the detector construction at LSM.

Radio emission from air showers enables measurements of cosmic particle kinematics and identity. The radio signals are detected in broadband Megahertz antennas among continuous background noise. We present two deep learning concepts and their performance when applied to simulated data. The first network classifies time traces as signal or background. We achieve a true positive rate of about 90% for signal-to-noise ratios larger than three with a false positive rate below 0.2%. The other network is used to clean the time trace from background and to recover the radio time trace originating from an air shower. Here we achieve a resolution in the energy contained in the trace of about 20% without a bias for \\(80\\%\\) of the traces with a signal. The obtained frequency spectrum is cleaned from signals of radio frequency interference and shows the expected shape.

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.

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 \\(\\gamma\\)-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$$\\%$.

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.

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 \\(\\)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\\).

The DArk Matter In CCDs at Modane (DAMIC-M) experiment is designed to search for light dark matter (m\\(_\\)<10\\,GeV/c\\(^2\\)) at the Laboratoire Souterrain de Modane (LSM) in France. DAMIC-M will use skipper charge-coupled devices (CCDs) as a kg-scale active detector target. Its single-electron resolution will enable eV-scale energy thresholds and thus world-leading sensitivity to a range of hidden sector dark matter candidates. A DAMIC-M prototype, the Low Background Chamber (LBC), has been taking data at LSM since 2022. The LBC provides a low-background environment, which has been used to characterize skipper CCDs, study dark current, and measure radiopurity of materials planned for DAMIC-M. It also allows testing of various subsystems like readout electronics, data acquisition software, and slow control. This paper describes the technical design and performance of the LBC.

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.

Photomultiplier tubes (PMTs) are widely used in astroparticle physics experiments to detect light flashes (e.g. fluorescence or Cherenkov light) from extensive air showers (EASs) initiated by statistically rare very high energy cosmic particles when travelling through the atmosphere. Their high amplification factor (gain) allows the detection of very low photon fluxes down to single photons. At the same time this sensitivity causes the gain and signal-to-noise ratio to decrease with collected charge over the lifetime of the PMT (referred to as \"ageing\"). To avoid fast ageing, many experiments limit the PMT operation to reasonably low night sky background (NSB) conditions. However, in order to collect more event statistics at the highest energies, it is desirable to extend the measurement cycle into (part of) nights with higher NSB levels. In case the signal-to-noise ratio remains large enough in the subsequent reconstruction of the EAS events, lowering the PMT gain in such conditions can be an option to avoid faster ageing. In this paper, performance studies under high NSB with Photonis XP3062 PMTs, as used in the fluorescence detector of the Pierre Auger Observatory, are presented. The results suggest that lowering the PMT gain by a factor of 10 while increasing the NSB level by a similar factor does not significantly affect the PMT performance and ageing behaviour so that detection and offline reconstruction of EASs are still possible. Adjusting the PMT gain according to a changing NSB level throughout a night has been shown to be possible and it follows a predictable behaviour. This allows to extend the measurement cycles of experiments, based on PMTs of type Photonis XP3062 or comparable and exposed to the NSB, to enhance the sensitivity especially at the highest energies where events are very rare.