arXiv subjects

Cecilia Voena

Publications and source records attributed to Cecilia Voena.

12 recordsLinked to original sources

arXiv2026

On the importance of cosmic-ray background in the Atomki anomaly

We report Geant4-based simulations of cosmic-ray muon backgrounds in models reproducing the geometries of the five-arm and six-arm e+e- pair spectrometers operated by the Atomki group at Debrecen. Full detector geometries are implemented for both setups, including position-sensitive detectors and plastic scintillators. In both configurations, cosmic muons generating two-arm coincidences produce statistically significant excesses in the opening-angle distribution whose positions are determined by the discrete azimuthal arrangement of detector arms and the plastic scintillators dimensions: in the six-arm spectrometer a peak appears near 140 degrees when the scintillator energy sum is selected in the 8Be transition window (16-20 MeV) and is suppressed for energy-asymmetric pairs, while a distinct peak near 120 degrees emerges in the 4He window (18-22 MeV), with no comparable enhancement in the respective background energy region. These angles, asymmetry dependences, and background characteristics show behaviours similar to those reported by the Atomki group as evidence for a 17 MeV boson. For the five-arm setup, a 140-degree excess is also reproduced at 8Be energies, and normalizing internal pair conversion events and cosmic coincidences to typical Atomki running conditions yields a cosmic-to-IPC ratio above unity in the signal window, indicating that the cosmic background is a leading contribution to the event rate at the energies and angles of interest. While they do not settle the question of the origin of the Atomki excesses, these results highlight the critical importance of a robust cosmic-ray treatment in this type of measurements, and call for a detailed description of the beam-off studies supporting the search for anomalies in the opening-angle vs. energy-sum distribution around the signal region.

physics.ins-det↗

arXiv2026

Letter Of Intent for a future $μ^+ \to \mathrm{e}^+ γ$ experiment at the High Intensity Muon Beam facility at PSI

Searches for charged lepton flavor violation in the muon sector stand out among the most sensitive and clean probes for physics beyond the Standard Model. Currently, $μ^+ \to \mathrm{e}^+ γ$ experiments provide the best constraints in this field for a wide range of models while, in the coming years, new experiments investigating the processes of $μ^+ \to \mathrm{e}^+ \mathrm{e}^+ \mathrm{e}^-$ and $μ\to \mathrm{e}$ conversion in the nuclear field are anticipated to reach comparable or higher sensitivities. The High-Intensity Muon Beam (HIMB) facility at PSI, which is expected to deliver muon beam intensities up to two orders of magnitude higher than the existing beam lines, offers a unique opportunity to significantly enhance the sensitivity of $μ^+ \to \mathrm{e}^+ γ$ searches. The discovery potential could be substantially boosted and a sensitivity comparable to that of all the other projects could be reestablished, which is essential for discriminating among competing new-physics scenarios should an observation occur in any of the channels. In this document, we express our interest in developing a $μ^+ \to \mathrm{e}^+ γ$ experimental program at HIMB, with the goal of improving, within the next decade, the sensitivity of the $μ^+ \to \mathrm{e}^+ γ$ search by more than one order of magnitude relative to the expected final result of the current leading experiment, MEG II. This effort would ensure that PSI retains its leadership in this field.

hep-ex↗

arXiv2025

Real-Time Motion Correction in Magnetic Resonance Spectroscopy: AI solution inspired by fundamental science

Magnetic Resonance Spectroscopy (MRS) is a powerful non-invasive tool for metabolic tissue analysis but is often degraded by patient motion, limiting clinical utility. The RECENTRE project (REal-time motion CorrEctioN in magneTic Resonance) presents an AI-driven, real-time motion correction pipeline based on optimized GRU networks, inspired by tagging and fast-trigger algorithms from high-energy physics. Models evaluated on held-out test sets achieve good predictive performance and overall positive framewise displacement (FD) gains. These results demonstrate feasibility for prospective scanner integration; future work will complete in-vivo validation.

physics.med-ph↗

arXiv2024

Influence based explainability of brain tumors segmentation in multimodal Magnetic Resonance Imaging

In recent years Artificial Intelligence has emerged as a fundamental tool in medical applications. Despite this rapid development, deep neural networks remain black boxes that are difficult to explain, and this represents a major limitation for their use in clinical practice. We focus on the segmentation of medical images task, where most explainability methods proposed so far provide a visual explanation in terms of an input saliency map. The aim of this work is to extend, implement and test instead an influence-based explainability algorithm, TracIn, proposed originally for classification tasks, in a challenging clinical problem, i.e., multiclass segmentation of tumor brains in multimodal Magnetic Resonance Imaging. We verify the faithfulness of the proposed algorithm linking the similarities of the latent representation of the network to the TracIn output. We further test the capacity of the algorithm to provide local and global explanations, and we suggest that it can be adopted as a tool to select the most relevant features used in the decision process. The method is generalizable for all semantic segmentation tasks where classes are mutually exclusive, which is the standard framework in these cases.

eess.IV↗

arXiv2021

The Search for $μ^+\to e^+ γ$ with 10$^{-14}$ Sensitivity: the Upgrade of the MEG Experiment

The MEG experiment took data at the Paul Scherrer Institute in the years 2009--2013 to test the violation of the lepton flavour conservation law, which originates from an accidental symmetry that the Standard Model of elementary particle physics has, and published the most stringent limit on the charged lepton flavour violating decay $μ^+ \rightarrow {\rm e}^+ γ$: BR($μ^+ \rightarrow {\rm e}^+ γ$) $<4.2 \times 10^{-13}$ at 90% confidence level. The MEG detector has been upgraded in order to reach a sensitivity of $6\times10^{-14}$. The basic principle of MEG II is to achieve the highest possible sensitivity using the full muon beam intensity at the Paul Scherrer Institute ($7\times10^{7}$ muons/s) with an upgraded detector. The main improvements are better rate capability of all sub-detectors and improved resolutions while keeping the same detector concept. In this paper, we present the current status of the preparation, integration and commissioning of the MEG II detector in the recent engineering runs.

hep-ex↗

arXiv2018

The Quest for $μ\to e γ$ and its Experimental Limiting Factors at Future High Intensity Muon Beams

The search for the Lepton Flavor Violating decay $μ\to e γ$ exploits the most intense continuous muon beams, which can currently deliver $\sim 10^8$ muons per second. In the next decade, accelerator upgrades are expected in various facilities, making it feasible to have continuous beams with an intensity of $10^9$ or even $10^{10}$ muons per second. We investigate the experimental limiting factors that will define the ultimate performances, and hence the sensitivity, in the search for $μ\to e γ$ with a continuous beam at these extremely high rates. We then consider some conceptual detector designs and evaluate the corresponding sensitivity as a function of the beam intensity.

hep-ex↗

arXiv2018

Combined readout of a triple-GEM detector

Optical readout of GEM based devices by means of high granularity and low noise CMOS sensors allows to obtain very interesting tracking performance. Space resolution of the order of tens of $μ$m were measured on the GEM plane along with an energy resolution of 20%$÷$30%. The main limitation of CMOS sensors is represented by their poor information about time structure of the event. In this paper, the use of a concurrent light readout by means of a suitable photomultiplier and the acquisition of the electric signal induced on the GEM electrode are exploited to provide the necessary timing informations. The analysis of the PMT waveform allows a 3D reconstruction of each single clusters with a resolution on z of 100 $μ$m. Moreover, from the PMT signals it is possible to obtain a fast reconstruction of the energy released within the detector with a resolution of the order of 25% even in the tens of keV range useful, for example, for triggering purpose.

physics.ins-det↗

arXiv2016

Design of a new tracking device for on-line dose monitor in ion therapy

Charged Particle Therapy is a technique for cancer treatment that exploits hadron beams, mostly protons and carbons. A critical issue is the monitoring of the dose released by the beam to the tumor and to the surrounding tissues. We present the design of a new tracking device for monitoring on-line the dose in ion therapy through the detection of secondary charged particles produced by the beam interactions in the patient tissues. In fact, the charged particle emission shape can be correlated with the spatial dose release and the Bragg peak position. The detector uses the information provided by 12 layers of scintillating fibers followed by a plastic scintillator and a small calorimeter made of a pixelated Lutetium Fine Silicate crystal. Simulations have been performed to evaluate the achievable spatial resolution and a possible application of the device for the monitoring of the dose profile in a real treatment is presented.

physics.med-ph↗

arXiv2016

Secondary radiation measurements for particle therapy applications: prompt photons produced by $^{4}$He, $^{12}$C and $^{16}$O ion beams in a PMMA target

Charged particle beams are used in Particle Therapy (PT) to treat oncological patients due to their selective dose deposition in tissues and to their high biological effect in killing cancer cells with respect to photons and electrons used in conventional radiotherapy. Nowadays, protons and carbon ions are used in PT clinical routine but, recently, the interest on the potential application of helium and oxygen beams is growing due to their reduced multiple scattering inside the body and increased linear energy transfer, relative biological effectiveness and oxygen enhancement ratio. The precision of PT demands for online dose monitoring techniques, crucial to improve the quality assurance of treatments. The beam range confined in the irradiated target can be monitored thanks to the neutral or charged secondary radiation emitted by the interactions of hadron beams with matter. Prompt photons are produced by nuclear de-excitation processes and, at present, different dose monitoring and beam range verification techniques based on the prompt γ detection have been proposed. It is hence of importance to perform the γ yield measurement in therapeutical-like conditions. In this paper we report the yields of prompt photons produced by the interaction of helium, carbon and oxygen ion beams with a PMMA target. The measurements were performed at the Heidelberg Ion-beam Therapy center (HIT) with beams of different energies. A LYSO scintillator has been used as photon detector. The obtained γ yields for $^{12}$C ion beams are compared with results from literature, while no other results from $^{4}$He and $^{16}$O beams have been published yet. A discussion on the expected resolution of a slit camera detector is presented, demonstrating the feasibility of a prompt-γ based monitoring technique for PT treatments using helium, carbon and oxygen ion beams.

physics.med-ph↗

arXiv2015

Polycrystalline para-terphenyl scintillator adopted in a $β^-$ detecting probe for radio-guided surgery

A radio-guided surgery technique exploiting $β^-$ emitters is under development. It aims at a higher target-to-background activity ratio implying both a smaller radiopharmaceutical activity and the possibility of extending the technique to cases with a large uptake of surrounding healthy organs. Such technique requires a dedicated intraoperative probe detecting $β^-$ radiation. A first prototype has been developed relying on the low density and high light yield of the diphenylbutadiene doped para-therphenyl organic scintillator. The scintillation light produced in a cylindrical crystal, 5 mm in diameter and 3 mm in height, is guided to a photo-multiplier tube by optical fibres. The custom readout electronics is designed to optimize its usage in terms of feedback to the surgeon, portability and remote monitoring of the signal. Tests show that with a radiotracer activity comparable to those administered for diagnostic purposes the developed probe can detect a 0.1 ml cancerous residual of meningioma in a few seconds.

physics.ins-det↗

arXiv2015

An Intraoperative $β^-$ Detecting Probe For Radio-Guided Surgery in Tumour Resection

The development of the $β^-$ based radio-guided surgery aims to extend the technique to those tumours where surgery is the only possible treatment and the assessment of the resection would most profit from the low background around the lesion, as for brain tumours. Feasibility studies on meningioma, glioma, and neuroendocrine tumors already estimated the potentiality of this new treatment. To validate the technique, prototypes of the intraoperative probe required by the technique to detect $β^-$ radiation have been developed. This paper discusses the design details of the device and the tests performed in laboratory. In such tests particular care has to be taken to reproduce the surgical field conditions. The innovative technique to produce specific phantoms and the dedicated testing protocols is described in detail.

physics.med-ph↗

arXiv2014

Towards a Radio-guided Surgery with $β^{-}$ Decays: Uptake of a somatostatin analogue (DOTATOC) in Meningioma and High Grade Glioma

A novel radio guided surgery (RGS) technique for cerebral tumors using $β^{-}$ radiation is being developed. Checking the availability of a radio-tracer that can deliver a $β^{-}$ emitter to the tumor is a fundamental step in the deployment of such technique. This paper reports a study of the uptake of 90Y labeled (DOTATOC) in the meningioma and the high grade glioma (HGG) and a feasibility study of the RGS technique in these cases.

physics.med-ph↗