Search

Abstract The cylindrical drift chamber is the most innovative part of the MEG II detector, the upgraded version of the MEG experiment. The MEG II chamber differs from the MEG one because it is a single volume cylindrical structure, instead of a segmented one, chosen to improve its resolutions and efficiency in detecting low energy positrons from muon decays at rest. In this paper, we show the characteristics and performances of this fundamental part of the MEG II apparatus and we discuss the impact of its higher resolution and efficiency on the sensitivity of the MEG II experiment. Because of its innovative structure and high quality resolution and efficiency the MEG II cylindrical drift chamber will be a cornerstone in the development of an ideal tracking detector for future positron-electron collider machines.

Abstract The MEG II experiment, based at the Paul Scherrer Institut in Switzerland, reports the result of a search for the decay $$\upmu ^+ \rightarrow {\textrm{e}}^+ \upgamma $$ μ + → e + γ from data taken in the first physics run in 2021. No excess of events over the expected background is observed, yielding an upper limit on the branching ratio of $${\mathcal {B}} (\upmu ^+ \rightarrow {\textrm{e}}^+ \upgamma ) < 7.5 \times 10^{-13}$$ B ( μ + → e + γ ) < 7.5 × 10 - 13 (90% CL). The combination of this result and the limit obtained by MEG gives $${\mathcal {B}} (\upmu ^+ \rightarrow {\textrm{e}}^+ \upgamma ) < 3.1 \times 10^{-13}$$ B ( μ + → e + γ ) < 3.1 × 10 - 13 (90% CL), which is the most stringent limit to date. A ten-fold larger sample of data is being collected during the years 2022–2023, and data-taking will continue in the coming years.

Abstract 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.

Abstract We present the results of a combined analysis of remote sensing and geophysical‐geotechnical data carried out in the Acque Albule Basin, a sinkhole prone area located close to the city of Roma, where a wide travertine wedge is present. We carried out geophysical measurements and borehole drillings over two test areas to image the subsoil where paroxysmal surficial dynamics occur. One site is marked by subsidence occurring at least since the early 2000s, whereas the other site hosts the “La Regina” and “Colonnelle” sinkhole lakes, which discharge sulfur‐carbonated waters. The stability of these two sites threatens highway, railway, and airport facilities, and this study helps to assess the geological hazard. For example, InSAR and LiDAR data helped define wide scale subsidence over the last 20 years and previously undetected small‐scale morphologies. Geophysical measurements of the latter revealed shallow and deep dissolution affecting the travertine and driving surficial paroxysmal events. Both study sites were found to lie inside a large depression located at the junction between Jurassic carbonate and Plio‐Pleistocene units in association with paleo karst morphologies in the travertine deposits and affected by the present‐past spillage of sulfurous waters. Given these elements, multidisciplinary geophysical observations are crucial for assessing and mitigating the geological risk and guiding land use planning and management.

Abstract The MEG experiment, designed to search for the $${\mu ^+ \rightarrow \hbox {e}^+ \gamma }$$ μ+→e+γ decay, completed data-taking in 2013 reaching a sensitivity level of $${5.3\times 10^{-13}}$$ 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 $$6\times 10^{-14}$$ 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.

Abstract An aeromagnetic data set from the island of La Gomera was studied through two inverse modeling approaches that produced complementary views of the inner structure of this volcanic island: (1) a variable magnetization model that identified the main lateral magnetization contrasts and (2) a constant magnetization model that imaged the main magnetic source by assuming that it was a uniformly magnetized body. The modeling reveals intense magnetizations beneath the northern part of La Gomera, which occupy an important portion of the northern submarine edifice, correspond well with outcrops of the submarine volcano (Basal Complex), and confirm that most of the magnetic signal revealed by aeromagnetic mapping in the Canary Islands is due to the intense magnetizations of the intrusive complexes (plutonic bodies and dike complexes) emplaced during the initial stages of growth of the volcanic edifices. The consistency of our models with the results of a previous gravimetric study suggests that these intrusive complexes are denser and more magnetic than the surrounding rocks. The location of the main magnetic source reinforces the interpretation, first suggested by geological evidence, that the submarine and early subaerial growth of La Gomera started to the north of the present island. The elongated shape of these intrusive complexes with a nearly E‐W strike agrees with the orientation of analogous structures on Tenerife and Gran Canaria, suggesting that the initial formation of the central islands of the Canary Archipelago was controlled by a set of regional fractures in a strike‐slip tectonic framework.

Since the beginning of the ongoing Amatrice seismic sequence on August 24, 2016, initiated by a Mw 6.0 normal faulting earthquake, the EMERGEO Working Group (an INGV team devoted to earthquake aftermath geological survey) set off to investigate any coseismic effects on the natural environment. Up to now, we surveyed about 750 km2 and collected more than 3200 geological observations as differently oriented tectonic fractures together with intermediate- to small- sized landslides, that were mapped in the whole area. The most impressive coseismic evidence was found along the known active Mt. Vettore fault system, where surface ruptures with clear vertical/horizontal offset were observed for more than 5 km, while unclear and discontinuous coseismic features were recorded along the Laga Mts. Fault systems.

This study presents magnetic anomaly data from a new high-resolution, low-altitude helicopter-borne magnetic survey recently collected on and offshore Tenerife in the Canary Archipelago. The Italian Istituto Nazionale di Geofisica e Vulcanologia (INGV) in collaboration with the Museo Nacional de Ciencias Naturales of the CSIC of Spain conducted the survey in 2006. The data for Tenerife and surrounding marine areas were processed into digital total intensity magnetic anomalies for geomagnetic epoch 2006.4. Relative to previously available higher altitude magnetic survey data, the new survey mapped higher resolution anomalies with significantly improved spatial details, especially over the Las Cañadas caldera and Teide-Pico Viejo complex in the central part of the island. A good correlation is evident between known structural geology and the magnetic anomalies, where the new shorter wavelength anomalies facilitate more detailed and comprehensive geologic interpretations.

This paper presents a new method to invert magnetic anomaly data in a variety of non-complex contexts when a priori information about the sources is not available. The region containing magnetic sources is discretized into a set of homogeneously magnetized rectangular prisms, polarized along a common direction. The magnetization distribution is calculated by solving an underdetermined linear system, and is accomplished through the simultaneous minimization of the norm of the solution and the misfit between the observed and the calculated field. Our algorithm makes use of a dipolar approximation to compute the magnetic field of the rectangular blocks. We show how this approximation, in conjunction with other correction factors, presents numerous advantages in terms of computing speed and depth resolution, and does not affect significantly the success of the inversion. The algorithm is tested on both synthetic and real magnetic datasets.

In this paper we present and discuss the results of a geophysical airborne survey carried out in the Somma-Vesuvius volcanic area, Southern Italy, in 1999. The helicopter-borne survey was aimed at giving new detailed insights into the distribution of the magnetization of the area and, therefore, into the volcanological characteristics of the region, enhancing the knowledge given by a previous low resolution survey carried out at a regional scale by Agip. The new survey was carried out by flying on a surface parallel to the topography of the area, along flight lines spaced 600 m apart. The obtained total field map is dominated by a large anomaly related to the Mt. Somma-Vesuvius complex itself and characterized by a roughly elliptical shape. High-frequency anomalies occur in the edifice and in the area east of it, partly produced by cultural noise due to the densely inhabited area. The compilation of the maps of the analytic signal and of the horizontal derivative of the field allowed the location of the lateral boundaries of the magnetic sources of the area and represents a first step toward the interpretation of the maps in terms of geological structures.

Newly acquired high-resolution, low-altitude aeromagnetic data over Vulcano Island and Southwestern Lipari in the Southern Tyrrhenian Sea resolve the major volcanic features in the area associated with the past and present activity. The magnetic character changes in amplitude and frequency from south-east to north-west. The Primordial Vulcano, the Lentia Complex, the Piano Caldera units, the Fossa Caldera deposits, and the currently active La Fossa cone and Vulcanello represent the main volcanic phases on Vulcano Island. They show a distinct magnetic anomaly pattern, whereas prior to this survey, no magnetic signatures of these features were found.

Taking advantage of the measurements undertaken during the Albanian and Italian magnetic repeat station networks since 1990, as well as of a selected set of Ørsted satellite total field measurements, a magnetic reference model for the region comprising the Albanian territory, the southern part of the Italian Peninsula, and the Ionian Sea is presented. The model, designed to model the components of the main geomagnetic field for epochs between 1990 and 2005, has been developed by means of spherical cap harmonic analysis applied to a cap of semiangle 8°, larger than that investigated to take into account the appropriate spatial wavelength content of the main geomagnetic field over the region. The goodness of the fit to the real data suggests that the model can be used as a reference model to reduce magnetic surveys developed in the area during the time of validity of the model.

Very high frequency deep radio sounding systems for ice thickness measurements are practically the only useful apparatuses for large scale radar flight surveys in polar regions. The morphology of the bottom surface of an Antarctic floating ice tongue, in the Ross Sea area, East Antarctica, was studied using the arrival times of signal echoes of the radio sounding system. The amplitude variations of radar signals from the reflecting surface were analyzed to determine the gain or the loss of the reflectors. Such surfaces show quasi-parabolic geometrical shapes at the ice/water interface with both concave and convex faces towards the sounding system. Electromagnetic analysis performed on radar echoes indicates that amplitude variations detected by the antenna are focusing or defocusing effects only due to the reflector's shape. A factor in the radar equation that represents the surface shape when coherent reflectors are involved is introduced. This factor allows us to determine more precisely the morphology and electromagnetic characteristics of the interface between the media investigated by means of radio echo sounding.

During three Antarctic summer campaigns (1995/97/99) Radio Echo Sounding (RES) system data from some glacier ice tongues in the East Antarctic regions between Victoria Land and George V Land were collected. The morphology and structure of the bottom surfaces deduced from the electromagnetic interpretation of echo signal were observed. The bottom surfaces at the ice/water interface show either irregular or flat contours or both. Some ice tongues are nearly perfectly flat, others show clear signs of irregularities while three of them have good regular spaced rippled bottom surfaces. The latter structures are well-evident in the longitudinal traverse of the tongues, whereas the transversal paths do not show the same features. This particular shape of the bottom surfaces related to the ablation process and detachment mechanism could be interesting especially to determine some physical characteristics and the possible fracture points of the ice tongues.

Within the framework of the GITARA II project an aeromagnetic survey was performed during the GANOVEXVII expedition (1992/1993) over the King Edward VII Peninsula in northwestern Marie Byrd Land (West Antarctica). This region which may represent the eastern flank of the Ross Sea rift system had previously been explored only at reconnaissance level. New total field and upward continued (10 km) magnetic anomaly maps are produced and interpreted here to map and discuss the crustal structure of the Edward VII Peninsula. Tworound-shaped, high-amplitude magnetic anomalies are recognised over the Alexandra Mountains block. The anomalies are difficult to interpret since susceptibility data indicate the prevalence of non-magnetic rocks at the surface. A possible interpretation is that the anomalies are due to Cretaceous mafic intrusives distinct from weakly magnetic Byrd Coast Granite of the adjacent Rockefeller Mountains block. Alternatively the anomalies could be related to buried pluton-sized Devonian Ford Granodiorite intruded by dikes. If Cretaceous in age, the former intrusives revealed from the magnetics could also be responsible for contact metamorphism of the adjacent Alexandra Mountains migmatites. Lower amplitude circular anomalies over the Central Plateau and Prestrud Inlet are likely to be caused by unexposed Devonian Ford Granodiorite which crops out in the Ford Ranges. Elongated high-frequency anomalies of the Sulzberger Bay are similar to those recognised over seismically constrained Cenozoic rift-related volcanics of the Ross Sea. A broad magnetic low over the Sulzberger Ice Shelf may be indicative of a fault bounded graben-like basin with sedimentary infill. Overall recognition of magnetic anomaly patterns and trends reveals segmentation of the Edward VII Peninsula and of the adjacent marine areas in distinct crustal blocks. Faults may separate these blocks and they are interpreted to reflect multiple Cretaceous and maybe Cenozoic crustal extensionuplift phases within this part of the West Antarctic rift system.

Magnetic observations made onshore the Italian Peninsula, and across the adjacent seas, have been compiled in a new digital database that provides the first complete regional scale view of the crustal scale magnetic anomalies of the region at sea level. The offshore data were acquired between 1965-1972 by the Osservatorio Geofisico Sperimentale (OGS) while the ground measurements were performed within the framework of the Progetto Finalizzato Geodinamica of the Consiglio Nazionale delle Ricerche (PFG-CNR) between 1977 and 1981. The new shaded relief magnetic anomaly map of total intensity of the Earth's magnetic field for Italy and the surrounding seas has been produced at sea level, for the geomagnetic epoch 1979.0. The most remarkable result of this new map, with respect to the previous compilations and to the aeromagnetic map of Italy, is an unprecedented view of the magnetic signature of the major tectonic elements in their regional setting. There is good correlation between known structural geology and the magnetic anomalies, and now that the longer wavelength signatures have been corrected, deeper interpretations are possible.

INTRAMAP (INtegrated Transantarctic Mountains and Ross Sea Area Magnetic Anomaly Project) is an international effort to merge the magnetic data acquired throughout the "Ross Sea Antarctic Sector" (south of 60°S between 135°-255°E) including the Transantarctic Mountains (TAM), the Ross Sea, Marie Byrd Land, and the Pacific coast, and also to begin the compilation efforts for new data over the Wilkes Basin. This project is a component of the continental scale Antarctic Digital Magnetic Anomaly Project (ADMAP). The first stage of INTRAMAP addresses the analysis and merging of GITARA (1991-1994) and GANOVEX (1984) aeromagnetic surveys together with ground magnetic data (1984-1989). The combined data sets cover an area of approximately 30 km2 over Victoria Land and adjacent Ross Sea. Map and profile gridding were implemented to integrate the data sets. These approaches are studied for improving existing strategies to adopt for the whole magnetic compilation effort. The final microlevelled grid that we produce is a new tool for regional interpretation of the main tectonic and geologic features of this sector of Antarctica.

Radio echo sounding is an active remote-sensing method using electromagnetic wave penetration in a particular medium such as ice and permits the measurements of its thickness, the level of the bedrock and inhomogeneities i.e. of the internal layering of glaciers. The Italian Radar Glaciological Group has implemented technical improvements on the system operating during the 1995-1996 Antarctic expeditions, increasing the horizontal and the vertical resolution by means of a new acquisition ensemble. The new system was used during the Antarctic expedition in 1997-1998. The present paper presents the latest improvements of the radar acquisition system and radar profiles extracted from the 1995-1996 and the 1997-1998 Antarctic expeditions are presented.

The properties of the Earth's core magnetic field and its secular variation are poorly known for the Antarctic. The increasing availability of magnetic observations from airborne and satellite surveys, as well as the existence of several magnetic observatories and repeat stations in this region, offer the promise of greatly improving our understanding of the Antarctic core field. We investigate the possible development of a Laplacian reference model of the core field from these observations using spherical cap harmonic analysis. Possible uses and advantages of this approach relative to the implementations of the standard global reference field are also considered.

A helicopter-borne experimental aeromagnetic survey, covering an area of 200 km2, was performed in the Volturno valley area north of the Roccamonfina volcano and south of Venafro in November 1994. Although severe logistical, instrumental and meteorological conditions significantly reduced the planned coverage, the processed magnetic image still shows a remarkable improvement in the description of the geological and structural features of the area in comparison with previous regional aeromagnetic data. A multi-directional shaded relief anomaly map displays two moderately positive NW magnetic bands associated with lavas, pyroclastics and dykes of the Roccamonfina volcanic district together with N-S, NNE-SSW and NE-SW lineations. A comparative magnetic-geologic map allows correlation with known Pleistocene faults and reveals the existence, especially in the area between Sesto Campano and Presenzano, of a larger presence of high susceptibility dykes than seen in the outcrop, which is dominated by non-magnetic carbonatic rocks. We interpret the curvilinear and intricate pattern of magnetic lineaments as suggestive of an extensional setting along the main NW structures with previous strike slip components and of tectonic activity along a N-S fabric; the latter has no superficial evidence and has also been used for magma upwelling. Overall, this local scale investigation shows both the utility and the need for further efforts in high resolution aeromagnetics in Italy both for geological and environmental purposes similar to those successfully carried out in many other countries throughout the world.

An environmental investigation test site for the application of magnetic techniques to detect buried steel drums was performed in Central Italy. A magnetic survey was carried out on the area of the test site, where 12 steel drums had previously been buried. The survey was performed by means of a proton precession magnetometer for total field measurements in single sensor as well as in gradiometer configurations. The experiment has led to the definition of the magnetic signature of vertically oriented drums buried at 4.5 m below ground level. A digitally enhanced magnetic anomaly map was then produced, allowing further modelling procedures. Data reduction, processing procedures and results are presented.

Models of the geomagnetic field are mathematical expressions able to represent the Earth's magnetic field space and time variations. Time variations on the long term basis are represented by the so-called secular variation. This paper describes and reviews recent activities of the Italian group at the Istituto Nazionale di Geofisica in regional magnetic field modelling. The models are introduced starting from the classical technique of Spherical Harmonic Analysis (SHA) undertaken for the first time by Gauss, the polynomial analysis and the regional harmonic analysis, specifically introduced as a regional analogue of SHA. In this last group the recent techniques of Spherical Cap Harmonic Analysis (SCHA), Translated Origin Spherical Cap Analysis (TOSCA) and Adjusted Spherical Cap Harmonic Analysis (ASHA) are also described and discussed.

Geomagnetic field time variations can be analysed by means of fractal and chaotic techniques. This new kind of analysis can definitely help in studying geophysical signals even when their chaotic and/or fractal aspects are not so obvious. In this short paper some examples of this new kind of analysis are presented in the case of geomagnetic time variation data from L'Aquila Observatory.

Most of the magnetic methods used for investigating planetary interiors are based on the reasonable hypothesis that the mechanism for the origin of the field is an Earth-like hydromagnetic dynamo: in this case the planet has an electrically conducting fluid shell within it as in the case of the Earth's core. The present paper describes several techniques of planetary magnetic investigation which give important clues on the internal constitution of planets. Some considerations on the possible mechanisms for maintaining a dynamo and simple concepts with the help of a few non-dimensional numbers are also introduced and discussed. Then some fundamental relationships are given in order to relate the planetary magnetism to other physical parameters, such as angular rotation, core dimensions etc. It finally summarizes some results available for the planets of the Solar System.

Background: Robot-Assisted Gait Rehabilitation (RAGR) is an established clinical practice to encourage neuroplasticity in patients with neuromotor disorders. Nevertheless, tasks repetition imposed by robots may induce boredom, affecting clinical outcomes. Thus, quantitative assessment of engagement towards rehabilitation using physiological data and subjective evaluations is increasingly becoming vital. This study aimed at methodologically exploring the performance of artificial intelligence (AI) algorithms applied to structured datasets made of heart rate variability (HRV) and electrodermal activity (EDA) features to predict the level of patient engagement during RAGR., Methods: The study recruited 46 subjects (38 underage, 10.3 ± 4.0 years old; 8 adults, 43.0 ± 19.0 years old) with neuromotor impairments, who underwent 15 to 20 RAGR sessions with Lokomat. During 2 or 3 of these sessions, ad hoc questionnaires were administered to both patients and therapists to investigate their perception of a patient's engagement state. Their outcomes were used to build two engagement classification targets: self-perceived and therapist-perceived, both composed of three levels: "Underchallenged", "Minimally Challenged", and "Challenged". Patient's HRV and EDA physiological signals were processed from raw data collected with the Empatica E4 wristband, and 33 features were extracted from the conditioned signals. Performance outcomes of five different AI classifiers were compared for both classification targets. Nested k-fold cross-validation was used to deal with model selection and optimization. Finally, the effects on classifiers performance of three dataset preparation techniques, such as unimodal or bimodal approach, feature reduction, and data augmentation, were also tested., Results: The study found that combining HRV and EDA features into a comprehensive dataset improved the synergistic representation of engagement compared to unimodal datasets. Additionally, feature reduction did not yield any advantages, while data augmentation consistently enhanced classifiers performance. Support Vector Machine and Extreme Gradient Boosting models were found to be the most effective architectures for predicting self-perceived engagement and therapist-perceived engagement, with a macro-averaged F1 score of 95.6% and 95.4%, respectively., Conclusion: The study displayed the effectiveness of psychophysiology-based AI models in predicting rehabilitation engagement, thus promoting their practical application for personalized care and improved clinical health outcomes., Competing Interests: Declarations. Ethics approval and consent to participate: The study was performed in accordance with the Declaration of Helsinki, and the Ethics Committee of Scientific Institute E. Medea approved the observational study protocol (protocol code: Prot. N. 02/22-CE; date of approval: January 27th, 2022). Patients, if adults, or their guardians signed a written informed consent. Consent for publication: All subjects consented for their data to be published. Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)