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 ½0.53; 2.7 MeV=c2 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 dataset. This daily modulation search represents the current strongest limit on DM-electron scattering via ultralight mediators for DM masses around 1 MeV=c².I. F. C. A. was supported by Project No. PID2019–109829 GB-I00 funded by MCIN/AEI/10.13039/501100011033. B. J. K. acknowledges funding from the Ramón y Cajal Grant No. RYC2021-034757-I, financed by MCIN/AEI/10.13039/501100011033 and by the European Union “NextGenerationEU”/PRTR

Nuclear Recoil Identification in a Scientific Charge-Coupled Device

International audienceCharge-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$$\%$

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

International audienceWe 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 2–6×10-22  A cm−2. We evaluate the charge distribution of pixels that collect <10e- 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

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

International audienceDark 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 periods in the range 1-48 h. 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$^2$

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

International audienceDark 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 periods in the range 1-48 h. 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$^2$

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

International audienceDark 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 periods in the range 1-48 h. 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$^2$