Search

The Large Scale Polarization Explorer (LSPE) is a cosmology program for the measurement of large scale curl-like features (B-modes) in the polarization of the Cosmic Microwave Background. Its goal is to constrain the background of inflationary gravity waves traveling through the universe at the time of matter-radiation decoupling. The two instruments of LSPE are meant to synergically operate by covering a large portion of the northern microwave sky. LSPE/STRIP is a coherent array of receivers planned to be operated from the Teide Observatory in Tenerife, for the control and characterization of the low-frequency polarized signals of galactic origin; LSPE/SWIPE is a balloon-borne bolometric polarimeter based on 330 large throughput multi-moded detectors, designed to measure the CMB polarization at 150 GHz and to monitor the polarized emission by galactic dust above 200 GHz. The combined performance and the expected level of systematics mitigation will allow LSPE to constrain primordial B-modes down to a tensor/scalar ratio of $10^{-2}$. We here report the status of the STRIP pre-commissioning phase and the progress in the characterization of the key subsystems of the SWIPE payload (namely the cryogenic polarization modulation unit and the multi-moded TES pixels) prior to receiver integration., 8 pages, 5 figures, Accepted for publication in Journal of Low Temperature Physics

International audience; The measurement of neutrino masses is still one of the most compelling issues in modern particle physics. HOLMES is an experiment that aims to measure the effective νe mass using a calorimetric approach. It will measure the spectrum end point of the electron capture (EC) decay of $^{163}$Ho. The very low Q-value (2.8 keV) of the decay and its half life (4570 y) are optimal to reach simultaneously a reasonable activity to have sufficient statistics in the end-point, reducing the pile-up probability and have a small quantity of $^{163}$Ho embedded in the detector not to alter significantly its heat capacity. Holmium will be implanted into a micro calorimeter made by a metallic absorber coupled to transition edge sensor (TES). Each detector will be implanted with around 300 Bq of holmium and the goal of the experiment is implanting ≈500 detectors (8x64 array of detectors) to reach an accuracy of the order of eV. In this contribution, we show the HOLMES experiment with its physics reach and technical challenges, along with its status and perspectives.

We present a detailed description of the electromagnetic filter for the PTOLEMY project to directly detect the Cosmic Neutrino Background (CNB). Starting with an initial estimate for the orbital magnetic moment, the higher-order drift process of E×B is configured to balance the gradient-B drift motion of the electron in such a way as to guide the trajectory into the standing voltage potential along the mid-plane of the filter. As a function of drift distance along the length of the filter, the filter zooms in with exponentially increasing precision on the transverse velocity component of the electron kinetic energy. This yields a linear dimension for the total filter length that is exceptionally compact compared to previous techniques for electromagnetic filtering. The parallel velocity component of the electron kinetic energy oscillates in an electrostatic harmonic trap as the electron drifts along the length of the filter. An analysis of the phase-space volume conservation validates the expected behavior of the filter from the adiabatic invariance of the orbital magnetic moment and energy conservation following Liouville's theorem for Hamiltonian systems., CGT is supported by the Simons Foundation (#377485) and John Templeton Foundation (#58851)

31 pags., 7 figs., The PTOLEMY project aims to develop a scalable design for a Cosmic Neutrino Background (CNB) detector, the first of its kind and the only one conceived that can look directly at the image of the Universe encoded in neutrino background produced in the first second after the Big Bang. The scope of the work for the next three years is to complete the conceptual design of this detector and to validate with direct measurements that the non-neutrino backgrounds are below the expected cosmological signal. In this paper we discuss in details the theoretical aspects of the experiment and its physics goals. In particular, we mainly address three issues. First we discuss the sensitivity of PTOLEMY to the standard neutrino mass scale. We then study the perspectives of the experiment to detect the CNB via neutrino capture on tritium as a function of the neutrino mass scale and the energy resolution of the apparatus. Finally, we consider an extra sterile neutrino with mass in the eV range, coupled to the active states via oscillations, which has been advocated in view of neutrino oscillation anomalies. This extra state would contribute to the tritium decay spectrum, and its properties, mass and mixing angle, could be studied by analyzing the features in the beta decay electron spectrum., Work supported by the Italian grant 2017W4HA7S “NAT-NET: Neutrino and Astroparticle Theory Network” (PRIN 2017) funded by the Italian Ministero dell’Istruzione, dell’Università e della Ricerca (MIUR); by the Spanish grants ENE2016-76755-R, SEV-2014-0398 and FPA2017- 85216-P (AEI/FEDER, UE), PROMETEO/2018/165 (Generalitat Valenciana), María de Maeztu Unit of Excellence CIEMAT - Particle Physics (MDM-2015-0509) and the Red Consolider MultiDark FPA2017-90566-REDC; by the Vetenskapsrådet (Swedish Research Council) through contract No. 638-2013-8993; by the Simons Foundation, USA (#377485) and John Templeton Foundation, USA (#58851); and by the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie individual Grant Agreement No. 796941.

We present the first direct search for lepton flavour violating muon decay mediated by a new light particle X, $$\upmu ^+ \rightarrow \mathrm {e}^+\mathrm {X}, \mathrm {X} \rightarrow \upgamma \upgamma \ $$ μ + → e + X , X → γ γ . This search uses a dataset resulting from $$7.5\times 10^{14}$$ 7.5 × 10 14 stopped muons collected by the MEG experiment at the Paul Scherrer Institut in the period 2009–2013. No significant excess is found in the mass region 20–45 MeV/c$$^2$$ 2 for lifetimes below 40 ps, and we set the most stringent branching ratio upper limits in the mass region of 20–40 MeV/c$$^2$$ 2 , down to $${\mathcal {O}}(10^{-11})$$ O ( 10 - 11 ) at 90% confidence level.

The PTOLEMY project is devoted to directly detect the cosmic neutrino background. A key point for the project success is the development of a device which is capable of detecting electrons with an energy resolution lower than 0.05eV. Microcalorimeters based on transition-edge sensors are among the best candidates since they already reach 0.11eV of energy resolution for telecomm photons. To further improve the energy resolution, while maintaining a suitable saturation energy, it is necessary to reduce the transition temperature. This could be achieved by proximity effect of a normal-superconducting bilayer. To this aim, TiAu very thin films are under development to demonstrate the feasibility of reaching 0.05eV energy resolution for light pulses of few eV. Thanks to the high electron stopping power of metals, the penetration depth of low energy incident electrons is limited to few nanometers and, with respect to visible light, we expect a high detection efficiency, while keeping similar dark counts and energy resolution.

HOLMES is an experiment aiming at performing a direct measurement of the neutrino mass from the electron capture (EC) spectrum of $$^{163}\hbox {Ho}$$. In order to reach a sensitivity of the order of $$\sim $$1 eV/c$$^2$$ on the neutrino mass, it is necessary to gather as many as $$10^{13}$$ events in the 3-year projected live time of HOLMES, keeping the pileup fraction as low as $$10^{-4}$$. This is not a trivial matter when it comes to low- temperature calorimeters, which usually have a rather slow time response. At the same time, a large number of detectors need to be operated simultaneously, and hence, in order to avoid an extremely large cryogenic facility, multiplexing is required. In this contribution, I will outline the current status and perspective of HOLMES, with special care devoted to the detectors and readout system, which have currently reached their target performance.

International audience; The absolute neutrino mass is still an unknown parameter in the modern landscape of particle physics. The HOLMES experiment aims at exploiting the calorimetric approach to directly measure the neutrino mass through the kinematic measurement of the decay products of the weak process decay of $^{163}$Ho. This low energy decaying isotope, in fact, undergoes electron capture emitting a neutrino and leaving the daughter atom, $^{163}$Dy$^*$, in an atomic excited state. This, in turn, relaxes by emitting electrons and, to a considerably lesser extent, photons. The high-energy portion of the calorimetric spectrum of this decay is affected by the non-vanishing neutrino mass value. Given the small fraction of events falling within the region of interest, to achieve a high experimental sensitivity on the neutrino mass, it is important to have a high activity combined with a very small undetected pileup contribution. To achieve these targets, the final configuration of HOLMES foresees the deployment of a large number of $^{163}$Ho ion-implanted TESs characterized by an ambitiously high activity of 300 Hz each. In this paper, we outline the status of the major tasks that will bring HOLMES to achieve a statistical sensitivity on the neutrino mass as low as 2 eV/c$^2$.

We present the first performance results obtained with microwave multiplexed Transition Edge Sensors prototypes specifically designed for the HOLMES experiment, a project aimed at directly measuring the electron neutrino mass through the calorimetric measurement of the $$^{163}$$ Ho electron capture spectrum. The detectors required for such an experiment feature a high energy resolution at the Q–value of the transition, around $$\sim $$ 2.8 keV, and a fast response time combined with the compatibility to be multiplexed in large arrays in order to collect a large statistics while keeping the pile-up contribution as small as possible. In addition, the design has to be suitable for future ion-implantation of $$^{163}$$ Ho. The results obtained in these tests allowed us to identify the optimal detector design among several prototypes. The chosen detector achieved an energy resolution of (4.5 ± 0.3) eV on the chlorine K $$_\alpha $$ line, at $$\sim $$ 2.6 keV, obtained with an exponential rise time of 14 $$\upmu $$ s. The achievements described in this paper pose a milestone for the HOLMES detectors, setting a baseline for the subsequent developments, aiming to the actual ion-implantation of the $$^{163}$$ Ho nuclei. In the first section the HOLMES experiment is outlined along with its physics goal, while in the second section the HOLMES detectors are described; the experimental set-up and the calibration source used for the measurements described in this paper are reported in Sects. 3 and 4, respectively; finally, the details of the data analysis and the results obtained are reported in Sect. 6.

The HOLMES project aims to directly measure the ν mass down to the eV scale using the electron capture decay (EC) of 163Ho. It will perform a precise calorimetric measurement of the end-point of the Ho energy spectrum looking for the deformation caused by a finite ν mass. The choice of 163Ho as source is driven by the very low Q-value of the EC reaction, which allows for high sensitivity with low activities (O(10 2 )Bq/detector), thus reducing the pile-up probability. A large array made by thousands of transition edge sensors based micro-calorimeters will be used. The calorimetric approach eliminates systematic uncertainties arising from the use of an external β source, and minimizes the effect of the atomic de-excitation process. The commissioning of the first implanted sub-array is scheduled for the end of 2018. It will provide useful data about the EC decay of 163Ho together with a first limit on ν mass.

The determination of the neutrino mass is an open issue in modern particle physics and astrophysics. The direct mass measurement is the only theory-unrelated experimental tool capable to probe such quantity. The HOLMES experiment aims to measure the end-point energy of the electron capture (EC) decay of $^{163}$Ho with a statistical sensitivity on the neutrino mass as low as $\sim 1$ eV/c$^2$. In order to acquire the large needed statistics, by keeping the pile-up contribution as low as possible, 1024 transition edge sensors (TESs) with high energy and time resolutions will be employed. Microcalorimeter and bolometer arrays based on transition edge sensor with thousands of pixels are under development for several space-based and ground-based applications, including astrophysics, nuclear and particle physics, and materials science. The common necessary challenge is to develop pratical multiplexing techniques in order to simplify the cryogenics and readout systems. Despite the various multiplexing variants which are being developed have been successful, new approaches are needed to enable scaling to larger pixel counts and faster sensors, as requested for HOLMES, reducing also the cost and complexity of readout. A very novel technique that meets all of these requirements is based on superconducting microwave resonators coupled to radio-frequency Superconducting Quantum Interference Devices, in which the the changes in the TES input current is tranduced to a change in phase of a microwave signal. In this work we introduce the basics of this technique, the design and development of the first two-channel read out system and its performances with the first TES detectors specifically designed for HOLMES. In the last part we explain how to extend this approach scaling to 1024 pixels., Comment: accepted on JINST

The HOLMES experiment aims to directly measure the ν mass with a calorimetric approach. The choice of 163Ho isotope as source is driven by the very low decay Q-value ( ∼ 2.8 keV), which allows for high sensitivity with low activities (O(10 2 )Hz/detector), thus reducing the pile-up probability. 163 Ho will be produced by neutron irradiation of 162Er 2 O 3 then chemically separated; anyway, traces of others isotopes and contaminants will be still present. In particular 166 m Ho has a beta decay ( τ ∼ 1200y) which can induce background below 5 keV. The removal of the contaminants is critical so a dedicated system has been set up. It is designed to achieve an optimal mass separation @ 163 a.m.u. and consists of two main components: an evaporation chamber and an ion implanter. The first item is used to reduce Ho in metallic form providing a target for the ion implanter source. The implanter is made by the sputter source, an acceleration section, a magnetic dipole, a x–y scanning stage and a focusing electrostatic triplet. In this contribution we will describe the procedures for the Holmium “distillation” process and the status of the machine commissioning.

This paper describes the production and chemical separation of the 163Ho isotope that will be used in several nuclear physics experiments aiming at measuring the neutrino mass as well as the neutron cross section of the 163Ho isotope. For this purpose, several batches of enriched 162Er have been irradiated at the Institut Laue-Langevin high flux reactor to finally produce 6 mg or 100 MBq of the desired 163Ho isotope. A portion of the Er/Ho mixture is then subjected to a sophisticated chemical separation involving ion exchange chromatography to isolate the Ho product from the Er target material. Before irradiation, a thorough analysis of the impurity content was performed and its implication on the produced nuclide inventory will be discussed.

HOLMES is an experiment aimed at directly measuring the neutrino mass through the calorimetric measurement of the 163Ho electron capture decay. The final goal of the project consists in providing a sensitivity on the neutrino mass below 2 eV; in addition, it will establish the potential of this approach to achieve a sub-eV sensitivity. The detectors performances play a crucial role in achieving the desired sensitivity. Indeed, for such an experiment, the following characteristics are required: short response time ( ∼ 1 μ s ) to solve pile-up events, great energy resolution ( ∼ 1 eV @ 2.8 keV) and compatibility to be multiplexed in large detector arrays ( ≳ 1000). HOLMES will deploy 1000 Transition Edge Sensors which will be readout with the microwave multiplexing technique. In this contribution we outline the experimental setup used in the characterization phase of the detectors.

The assessment of neutrino absolute mass scale is still a crucial challenge in today particle physics and cosmology. Beta or electron capture spectrum end-point study is currently the only experimental method which can provide a model independent measurement of the absolute scale of neutrino mass. HOLMES is an experiment funded by the European Research Council to directly measure the neutrino mass. HOLMES will perform a calorimetric measurement of the energy released in the electron capture decay of the artificial isotope $^{163}$Ho. In a calorimetric measurement the energy released in the decay process is entirely contained into the detector, except for the fraction taken away by the neutrino. This approach eliminates both the issues related to the use of an external source and the systematic uncertainties arising from decays on excited final states. The most suitable detectors for this type of measurement are low temperature thermal detectors, where all the energy released into an absorber is converted into a temperature increase that can be measured by a sensitive thermometer directly coupled with the absorber. This measurement was originally proposed in 1982 by A. De Rujula and M. Lusignoli, but only in the last decade the technological progress in detectors development has allowed to design a sensitive experiment. HOLMES plans to deploy a large array of low temperature microcalorimeters with implanted $^{163}$Ho nuclei. In this contribution we outline the HOLMES project with its physics reach and technical challenges, along with its status and perspectives., This is a pre-print of an article published in Journal of Low Temperature Physics. The final authenticated version is available online at: https://doi.org/10.1007/s10909-018-2025-x

The MEG experiment, designed to search for the μ+→e+γ decay, completed data-taking in 2013 reaching a sensitivity level of 5.3×10^−13 for the branching ratio. In order to increase the sensitivity reach of the experiment by an order of magnitude to the level of 6×10^−14, a total upgrade, involving substantial changes to the experiment, has been undertaken, known as MEG II. We present both the motivation for the upgrade and a detailed overview of the design of the experiment and of the expected detector performance

International audience; The assessment of the neutrino absolute mass scale is still a crucial challenge in today particle physics and cosmology. Beta or electron capture spectrum end-point study is currently the only experimental method which can provide a model independent measurement of the absolute scale of neutrino mass. HOLMES is an experiment to directly measure the neutrino mass by performing a calorimetric measurement of the energy released in the electron capture decay of the artificial isotope 163Ho. In a calorimetric measurement the energy released in the decay process is entirely contained into the detector, except for the fraction taken away by the neutrino. This approach eliminates both the issues related to the use of an external source and the systematic uncertainties arising from decays on excited final states. HOLMES will deploy a large array of low temperature microcalorimeters implanted with 163Ho nuclei. The achievable neutrino mass statistical sensitivity is expected in the eV range, thereby making HOLMES an important step forward in the direct neutrino mass measurement with a calorimetric approach as an alternative to spectrometry. HOLMES will also establish the potential of this approach to achieve a sub-eV sensitivity. HOLMES is designed to collect about 3 × 1013 decays with an instrumental energy resolution around 1 eV FWHM and a time resolution around 1 µs. To achieve this in three years of measuring time, HOLMES is going to deploy 16 sub-arrays of TES microcalorimeters. Each sub-array has 64 pixels ion implanted with 163Ho nuclei to give a pixel activity of 300 Bq per pixel. The TES arrays are read out using microwave multiplexed rf-SQUIDs in combination with a Software Designed Radio data acquisition system. The commissioning of the first implanted sub-array is scheduled for 2018 and it will provide first high statistics data about the EC decay of 163Ho together with a preliminary limit on the neutrino mass. In this contribution we outline the HOLMES project with its physics reach and technical challenges, along with its status and perspectives. In particular we will present the status of the HOLMES activities concerning the 163Ho isotope production by neutron irradiation and purification, the TES pixel design and optimization, the multiplexed array read-out characterization, the cryogenic set-up installation, and the setting up of the mass separation and ion implantation system for the isotope embedding in the TES absorbers.

Measuring the neutrino mass is one of the most compelling issues in particle physics. HOLMES is an experiment for a direct measurement of the neutrino mass. HOLMES will perform a precise measurement of the end point of the electron capture decay spectrum of $$^{163}\hbox {Ho}$$ in order to extract information on the neutrino mass with a sensitivity as low as 1 eV. HOLMES, in its final configuration, will deploy a 1000-pixel array of low-temperature microcalorimeters: each calorimeter is made of an absorber, where the Ho atoms will be implanted, coupled to a transition-edge sensor (TES) thermometer. The detectors will be operated at the working temperature of $$100\,\hbox { mK}$$ provided by a dilution refrigerator. In order to read out the 1000-detector array of HOLMES, a multiplexing system is necessary: the choice is to couple the transition-edge sensors to a multiplexed rf-SQUID. In this contribution we outline the progress made towards the final configuration of HOLMES regarding both the performances of the TES detectors and the characteristics of the multiplexing system.

HOLMES is a new experiment aiming at directly measuring the neutrino mass with a sensitivity below 2 eV. HOLMES will perform a calorimetric measurement of the energy released in the decay of $^{163}$Ho. The calorimetric measurement eliminates systematic uncertainties arising from the use of external beta sources, as in experiments with spectrometers. This measurement was proposed in 1982 by A. De Rujula and M. Lusignoli, but only recently the detector technological progress has allowed to design a sensitive experiment. HOLMES will deploy a large array of low temperature microcalorimeters with implanted $^{163}$Ho nuclei. HOLMES, besides being an important step forward in the direct neutrino mass measurement with a calorimetric approach, will also establish the potential of this approach to extend the sensitivity down to 0.1 eV and lower. In its final configuration HOLMES will collect about $3\cdot 10^{13}$ decays with 1000 detectors characterized by an instrumental energy resolution of the order of few eV and a time resolution of few microseconds. To embed the $^{163}$Ho into the gold absorbers a custom mass separator ion implanter is being developed. The detectors used for the HOLMES experiment will be Mo/Cu bilayers TESs (Transition Edge Sensors) on SiN$_x$ membrane with gold absorbers. Microwave multiplexed rf-SQUIDs are the best available technique to read out large array of such detectors. An extensive R&D activity is in progress in order to maximize the multiplexing factor while preserving the performances of the individual detectors. The current activities are focused on the the single detector performances optimization and on the $^{163}$Ho isotope production and embedding. A preliminary measurement of a sub-array of $4\times 16$ detectors is planned late in 2017. In this contribution we present the HOLMES project with its technical challenges, its status and perspectives.

HOLMES is a new experiment to directly measure the neutrino mass with a sensitivity as low as 0.4 eV. HOLMES will perform a calorimetric measurement of the energy released in the electron capture decay of 163 Ho. HOLMES will deploy a large array of low temperature microcalorimeters with implanted 163 Ho nuclei. HOLMES baseline detector is an array of 1000 microcalorimeters each with an implanted 163 Ho activity of about 300 Bq, an energy resolution FWHM of about 1 eV at the spectrum end-point ( Q ≈ 2.5 keV), and a time resolution of about 1 μs. Matching these performances requires a careful optimization of all components, from the microcalorimeters to the signal processing algorithms. We outline here the project technical challenges and the present status of the development.

The main goal in the HOLMES experiment is the neutrino mass measurement using an array of 1000 micro-calorimeters with standard metallic absorber. A good isotope for such measurement is the 163 Ho, those isotopes embedded in the metallic absorber will be 10 11 –10 13 . Since 163 Ho is not available in nature, a dedicated process must be set up to produce the amount needed for this neutrino mass experiment. The process with the highest born-up cross-section is the neutron irradiation of Er 2 O 3 enriched in 162 Er: 162 Er(n,γ) 163 Er → 163 Ho+ν e , where the decay is an EC with half-life of about 75 min and the (n,γ) is about 20 barns for thermal neutron. After the neutron irradiation in the oxide powder there are several radioactive isotopes which are potentially disturbing because of the background that they cause below 5 keV. The chemical separation of holmium from the irradiation enriched Er 2 O 3 powder is therefore mandatory and will be performed by means of ion exchange chromatography. On the end of those processes the oxide powder enriched in 162 Er will have the 163 Ho isotope number required. The holmium chemical state influences the end point of the EC spectrum, in order to avoid such effect it is necessary to embed in the absorber only the metallic isotope. Reduction and distillation technique allowed us to obtain a pure metallic holmium, starting from natural oxide holmium. This technique will be applied on the irradiated oxide powder to obtain the metallic 163 Ho, ready to be embedded in the micro-calorimeter absorber.

We studied the radiative muon decay $\mu^+ \to e^+\nu\bar{\nu}\gamma$ by using for the first time an almost fully polarized muon source. We identified a large sample (~13000) of these decays in a total sample of 1.8x10^14 positive muon decays collected in the MEG experiment in the years 2009--2010 and measured the branching ratio B($\mu^+ \to e^+\nu\bar{\nu}\gamma$) = (6.03+-0.14(stat.)+-0.53(sys.))x10^-8 for E_e > 45 MeV and E_{\gamma} > 40 MeV, consistent with the Standard Model prediction. The precise measurement of this decay mode provides a basic tool for the timing calibration, a normalization channel, and a strong quality check of the complete MEG experiment in the search for $\mu^+ \to e^+\gamma$ process., Comment: 8 pages, 7 figures. Added an introduction to NLO calculation which was recently calculated. Published version