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We present the first continuous operation in a surface lab of BULLKID, a detector for searches of light Dark Matter and precision measurements of the coherent and elastic neutrino-nucleus scattering. The detector consists of an array of 60 cubic silicon particle absorbers of 0.34 g each, sensed by cryogenic kinetic inductance detectors. The data presented focusses on one of the central elements of the array and on its surrounding elements used as veto. The energy spectrum resulting from an exposure of 39 h to ambient backgrounds, obtained without radiation shields, is flat at the level of ( 2.0 ± 0.1 stat . ± 0.2 syst . ) × 10 6  counts/keV kg days down to the energy threshold of 160 ± 13  eV. The data analysis demonstrates the unique capability of rejecting backgrounds generated from interactions in other sites of the array, stemming from the segmented and monolithic structure of the detector.

BULLKID is a cryogenic, solid-state detector designed for direct searches of particle Dark Matter candidates, with mass ≲ 1 GeV/c 2 , and coherent neutrino-nucleus scattering. It is based on an array of dice carved in 5 mm thick silicon crystal, sensed by phonon-mediated Kinetic Inductance Detectors. In previous works, the array was calibrated with bursts of optical photons, which are absorbed in the first hundreds nanometers of the dice and give rise to surface events. In this work, we present the reconstruction of bulk events through the 59.5 keV γ -ray generated by an 241 Am source, which emulates more closely the interaction of Dark Matter and neutrinos. The peak resolution is 5 % ( σ ) and its position is shifted by less than 10 % with respect to the optical calibration. We observe that the resolution is further improved by a factor 2 combining the signal from neighboring dice. These results confirm the performance of the detector in view of the physics goals of the BULLKID-DM experiment for dark matter search.

We present the calibration and data analysis of BULLKID, a cryogenic, low threshold particle detector for searches of low mass dark matter candidates and coherent neutrino on nucleus scattering (CE ν NS) events. The BULLKID detector is an array of 60 cubic particle absorbers made out of 0.34 g of silicon per cube, each one sensed by a kinetic inductance detector (KID). This paper describes the energy calibration of the detector as well as an evaluation of the background rate of the device when operated in an above-ground unshielded environment. By performing coincidence cuts on a cluster of 3x3 dice, the background rejection power of the design is demonstrated, allowing reach to a flat background down to a threshold of 160 eV.

We present the first continuous operation in a surface lab of BULLKID, a detector for searches of light Dark Matter and precision measurements of the coherent and elastic neutrino-nucleus scattering. The detector consists of an array of 60 cubic silicon particle absorbers of 0.34 g each, sensed by cryogenic kinetic inductance detectors. The data presented focusses on one of the central elements of the array and on its surrounding elements used as veto. The energy spectrum resulting from an exposure of 39 hours to ambient backgrounds, obtained without radiation shields, is flat at the level of \\((2.00.1\\, stat.0.2\\, syst.)10^6\\) counts / keV kg days down to the energy threshold of \\(16013\\) eV. The data analysis demonstrates the unique capability of rejecting backgrounds generated from interactions in other sites of the array, stemming from the segmented and monolithic structure of the detector.

Multiple sclerosis (MS) is a progressive immune- mediated disease caused by demyelination of the central nervous system. Cytokines and their receptors have an important role in the evolution of MS lesions, and pro- and anti-inflammatory cytokine levels have been found to correlate with changes in MS disease activity. The aims of the present study were to evaluate the pro-inflammatory [tumor necrosis factor (TNF)-α and interleukin (IL) -1β, -6 and -12], T helper (Th) 1 [interferon (IFN)-γ], Th17 (IL-17) and Th2 (IL-4 and -10) cytokine serum levels in relapsing-remitting (RR)-MS patients and to evaluate the association between the cytokine profile and the progression and activity of the disease. Serum cytokine levels were assessed using enzyme linked-immunosorbent assays in 169 RR-MS patients in the remission clinical phase and 132 healthy individuals who were age-, gender-, ethnicity- and body mass index-matched. Disability and activity of the disease were evaluated using the Expanded Disability Status Scale and magnetic resonance imaging with gadolinium, respectively. IFN-γ and IL-6, -12 and -4 levels were higher in RR-MS patients compared to controls (P=0.0009, 0.0114, 0.0297 and 0.0004, respectively). IL-1 levels were higher in controls compared with RR-MS patients. IL-4 levels were higher in RR-MS patients with mild disability compared to those with moderate and severe disability (P=0.0375). TNF-α and IL-10 levels were higher in RR-MS patients with inactive disease compared with those with active disease. IL-17 levels showed a trend towards being higher in RR-MS patients with inactive disease compared to those with active disease (P=0.0631). Low TNF-α and high IFN-γ levels were independently associated with RR-MS (P=0.0078 and 0.0056, respectively) and also with the activity of the disease (P=0.0348 and 0.0133, respectively). Results indicated that RR-MS patients, even in the remission clinical phase, exhibit a complex system of inflammatory and anti-inflammatory cytokines that may interact to modulate the progression and activity of the disease.

We introduce BULLKID, an innovative phonon detector consisting of an array of dices acting as particle absorbers sensed by multiplexed Kinetic Inductance Detectors (KIDs). The dices are carved in a thick crystalline wafer and form a monolithic structure. The carvings leave a thin common disk intact in the wafer, acting both as holder for the dices and as substrate for the KID lithography. The prototype presented consists of an array of 64 dices of 5.4x5.4x5 mm\\(^3\\) carved in a 3\" diameter, 5 mm thick silicon wafer, with a common disk 0.5 mm thick hosting a 60 nm patterned aluminum layer. The resulting array is highly segmented but avoids the use of dedicated holding structures for each unit. Despite the fact that the uniformity of the KID electrical response across the array needs optimization, the operation of 8 units with similar features shows, on average, a baseline energy resolution of \\(26\\pm7\\) eV. This makes it a suitable detector for low-energy processes such as direct interactions of dark matter and coherent elastic neutrino-nucleus scattering.

Cryogenic phonon detectors are adopted in experiments searching for dark matter interactions or coherent elastic neutrino-nucleus scattering, thanks to the low energy threshold they can achieve. The phonon-mediated sensing of particle interactions in passive silicon absorbers has been demonstrated with Kinetic Inductance Detectors (KIDs). Targets with neutron number larger than silicon, however, feature higher cross section to neutrinos while multi-target absorbers in dark matter experiments would provide a stronger evidence of a possible signal. In this work we present the design, fabrication and operation of KIDs coupled to a germanium absorber, achieving phonon-sensing performance comparable to silicon absorbers. The device introduced in this work is a proof of concept for a scalable neutrino detector and for a multi-target dark matter experiment.

BULLKID-DM is an experiment designed for the direct searches of particle dark matter candidates with mass around 1 GeV, or below, and cross-section with nucleons smaller than \\(10^{-40}\\) cm\\(^2\\). The detector consists of a stack of diced silicon wafers, acting as arrays of particle absorbers, sensed by multiplexed Kinetic Inductance Detectors. The target will amount to 800 g subdivided in more than 2000 silicon dice, with the aim of controlling the background from natural radioactivity by creating a fully active structure and by applying fiducialization techniques. In this work we present the projected sensitivity of BULLKID-DM to light WIMP-like particles considering also the other future experiments in the field.

The BULLKID-DM experiment aims to detect WIMP-like potential Dark Matter particles with masses below 1 GeV/c^2. Sensing these particles is challenging, as it requires nuclear recoil detectors characterized by high exposure and an energy threshold in the order of 100 eV, thus exceeding the capabilities of conventional semiconductor detectors. BULLKID-DM intends to tackle this challenge by using cryogenic Kinetic Inductance Detectors (MKIDs) with exceptional energy thresholds to sense a target with a total mass of 800 g across 16 wafers, divided into over 2000 individually instrumented silicon dice. The MKIDs on each wafer are coupled to a single transmission line and read using a frequency division multiplexing approach by the room-temperature data acquisition. In this contribution, we describe and assess the design of the room-temperature readout electronics system, including the selected hardware components and the FPGA firmware which contains the real-time signal processing stages for tone generation, frequency demultiplexing, and event triggering. We evaluate the system on the ZCU216 board, a commercial evaluation card built around a Radio-Frequency System-on-Chip (RFSoC) with integrated high-speed DACs and ADCs, and connected it to a custom-designed analog front-end for signal conditioning.

BULLKID is a cryogenic, solid-state detector designed for direct searches of particle Dark Matter candidates, with mass \\( 1\\) GeV/c\\(^2\\), and coherent neutrino-nucleus scattering. It is based on an array of dice carved in 5 mm thick silicon crystal, sensed by phonon-mediated Kinetic Inductance Detectors. In previous works, the array was calibrated with bursts of optical photons, which are absorbed in the first hundreds nanometers of the dice and give rise to surface events. In this work, we present the reconstruction of bulk events through the 59.5 keV \\(\\)-ray generated by an \\(^241\\)Am source, which emulates more closely the interaction of Dark Matter and neutrinos. The peak resolution is \\(5\\%~()\\) and its position is shifted by less than \\(10\\%\\) with respect to the optical calibration. We observe that the resolution is further improved by a factor \\(2\\) combining the signal from neighboring dice. These results confirm the performance of the detector in view of the physics goals of the BULLKID-DM experiment for dark matter search.