arXiv subjects

D. Calvo

Publications and source records attributed to D. Calvo.

At least 19 recordsLinked to original sources

arXiv2026

Testing Heavy Dark Matter Decay as the Origin of KM3-230213A

This work explores the hypothesis that the ultra-high-energy neutrino event KM3-230213A originates from the decay of a heavy dark matter particle with a mass above PeV scale. The analysis exploits the deposited energy and arrival direction of the event as well as a complete detector Monte Carlo simulation to compute the expected signal distributions for different decay channels and assesses the relative contributions from Galactic and extragalactic dark matter. Assuming a dark matter origin of the event, we find that the preferred mass at 95% C.L. is larger than about 100 PeV in all scenarios considered, with best-fit lifetimes in the range $10^{26}$-$10^{27}$ s. These preferred regions are in tension with existing bounds from other neutrino telescopes and gamma-ray observations.

hep-ex↗

arXiv2026

Atmospheric neutrino constraints on Lorentz invariance violation with the first six detection units of KM3NeT/ORCA

Lorentz invariance is a fundamental symmetry underlying both the Standard Model of particle physics and General Relativity. Testing its validity provides a direct means of searching for new physics emerging near the Planck scale. A search for isotropic Lorentz invariance violation with 1.4 years of atmospheric neutrino data collected by a partial configuration of the KM3NeT/ORCA detector comprising six detection units is presented. No evidence for such violation is found; thus, competitive limits are set on a subset of isotropic Lorentz invariance violating coefficients, which complement and extend existing experimental constraints.

hep-ex↗

arXiv2026

Depletion depth measurements of new large area silicon carbide detectors

The ion beam induced charge technique with proton microprobe is used to characterise newly developed p-n junction large area silicon carbide detectors. They were recently produced as part of the ongoing program to develop a new particle identification wall for the focal plane detector of the MAGNEX magnetic spectrometer at INFN - Laboratori Nazionali del Sud in view of the NUMEN experimental campaigns. Four silicon carbide devices are studied. Proton beams over a 1.26 to 6.00 MeV incident energy range are used to probe the active area and the depletion depth of each device. The energy loss tables for the silicon carbide material are checked, finding an empirical correction that is then used to quantify the depletion depth at the full depletion voltage through energy loss measurements of 3.40 MeV proton beams irradiating the back side of the devices. It is possible to fully deplete the devices provided that the epitaxial layer is grown properly on the substrate.

physics.ins-det↗

arXiv2025

HASPIDE-SPACE: a new concept of a radiation-resistant instrument for solar energetic particles

Galactic cosmic rays and solar energetic particles (SEPs) affect the performance of instruments carried on board space missions and are the source of the absorbed dose to astronauts. Particles above 100 MeV are the most penetrating. The overall particle flux impacting spacecraft increases by several orders of magnitude during the most intense SEP events and gamma-ray bursts, compared to the galactic cosmic-ray background. Unfortunately, most detectors dedicated to the monitoring of solar particles in space do not allow measurements above 200 MeV. Space agencies and the space and heliospheric weather communities are interested in improving this scenario. We propose a new, compact, low-power, and radiation-resistant instrument, intended for long-duration missions to monitor solar X-rays, electrons, and protons up to energies of tens of keV, MeV, and 600 MeV, respectively. Intense long and short gamma-ray bursts would be observed in the absence of solar activity.

hep-ex↗

arXiv2025

Optimizing the potential of KM3NeT in detecting core-collapse supernovae

Core-collapse supernovae mark the end of life of massive stars. However, despite their importance in astrophysics, their underlying mechanisms remain unclear. Neutrinos that emerge from the dense core of the star offer a promising way to study supernova dynamics. A strategy is presented to improve the potential of the KM3NeT neutrino telescope to detect core-collapse supernovae in our Galaxy or the Large Magellanic Cloud by further exploiting the properties of its optical modules equipped with multiple photomultipliers. A supernova burst is expected to produce a sudden hit rate increase in the KM3NeT detectors. New observables have been defined for individual optical modules that exploit the geometry and time distribution of the detected hits, enabling a better discrimination between signal and background signatures. In addition, a thorough investigation of the related systematic uncertainties is presented for the first time. When implemented, this new methodology allowed KM3NeT to probe 46% more Galactic core-collapse supernova candidates than with the previous trigger strategy, reaching the dense Galactic bulge. It is now expected that, once completed, KM3NeT will achieve full Galactic sensitivity to core-collapse supernovae.

astro-ph.HE↗

arXiv2025

Deep Learning Framework for Enhanced Neutrino Reconstruction of Single-line Events in the ANTARES Telescope

We present the $N$-fit algorithm designed to improve the reconstruction of neutrino events detected by a single line of the ANTARES underwater telescope, usually associated with low energy neutrino events ($\sim$ 100 GeV). $N$-Fit is a neural network model that relies on deep learning and combines several advanced techniques in machine learning --deep convolutional layers, mixture density output layers, and transfer learning. This framework divides the reconstruction process into two dedicated branches for each neutrino event topology --tracks and showers-- composed of sub-models for spatial estimation --direction and position-- and energy inference, which later on are combined for event classification. Regarding the direction of single-line events, the $N$-Fit algorithm significantly refines the estimation of the zenithal angle, and delivers reliable azimuthal angle predictions that were previously unattainable with traditional $\chi^2$-fit methods. Improving on energy estimation of single-line events is a tall order; $N$-Fit benefits from transfer learning to efficiently integrate key characteristics, such as the estimation of the closest distance from the event to the detector. $N$-Fit also takes advantage from transfer learning in event topology classification by freezing convolutional layers of the pretrained branches. Tests on Monte Carlo simulations and data demonstrate a significant reduction in mean and median absolute errors across all reconstructed parameters. The improvements achieved by $N$-Fit highlight its potential for advancing multimessenger astrophysics and enhancing our ability to probe fundamental physics beyond the Standard Model using single-line events from ANTARES data.

physics.comp-ph↗

arXiv2025

Search for steady and flaring neutrino emission from cosmic sources using the complete ANTARES dataset

ANTARES, a neutrino detector located in the depths of the Mediterranean Sea, operated successfully for over 15 years before being decommissioned in 2022. The telescope offered an ideal vantage view of the Southern Sky and benefited from optimal water properties for enhanced angular resolution. This study makes use of data collected over the entire operational period of ANTARES to search for sources of high-energy cosmic neutrinos, considering both steady and flaring emission scenarios. First, a time-integrated search for high-energy neutrino clustering across the celestial sphere is conducted. The most significant accumulation is found at coordinates $(\alpha, \delta) =(200.5^\circ\, 17.7^\circ)$ with a post-trial p-value equal to 0.38. A dedicated search in the Galactic Plane is also performed for extended sources, yielding no significant excess. Additionally, a list of potential neutrino sources are investigated. The blazar MG3 J225517+2409 is identified as the most significant object, yet the excess remains compatible with background fluctuations. A mild local excess of 2.4$\sigma$ is found for the blazar TXS 0506+056. The full sky is also examined for the presence of flaring neutrino emissions. The most significant excess in this case corresponds to a $\sim$4-day flare from the direction $(\alpha, \delta) = (141.3^\circ\, 9.8^\circ)$, with a post-trial p-value of 0.30. Finally, the directions of sources highlighted in IceCube's time-dependent searches are investigated. Temporal overlaps between ANTARES and IceCube flares are identified for PKS 1502+106 and TXS 0506+056, with an estimated chance probability of about 0.02%, making this observation particularly noteworthy.

astro-ph.HE↗

arXiv2025

Search for an eV-scale sterile neutrino with the first six detection units of KM3NeT/ORCA

The existence of an eV-scale sterile neutrino has been proposed to explain several anomalous experimental results obtained over the course of the past 25 years. The first search for such a sterile neutrino conducted with data from KM3NeT/ORCA -- a water Cherenkov neutrino telescope under construction at the bottom of the Mediterranean Sea -- is reported in this paper. GeV-scale atmospheric neutrino oscillations are measured by reconstructing the energy and arrival direction of up-going neutrinos that have traversed the Earth. This study is based on a data sample containing 5828 neutrino candidates collected with 6 detection units ($5\%$ of the complete detector), corresponding to an exposure of 433 kton-years. From the expected effect of an eV-scale sterile neutrino on the first $\nu_\mu \rightarrow \nu_\tau$ standard oscillation maximum, simultaneous constraints are put on the magnitude of the $U_{\mu 4}$ and $U_{\tau 4}$ mixing elements assuming $\Delta m^2_{41} \geq 1$ eV$^2$. The results are compatible with the absence of mixing between active neutrinos and a sterile state, with $|U_{\mu 4}|^2 < 0.138$ and $|U_{\tau 4}|^2 < 0.076$ at a $90\%$ confidence level. Such constraints are compatible with the results reported by other long-baseline experiments, and indicate that with KM3NeT/ORCA it is possible to bring crucial contributions to sterile neutrino searches in the coming years.

hep-ex↗

arXiv2025

Constraining gamma-ray burst parameters with the first ultra-high energy neutrino event KM3-230213A

Context: The detection of the highest energy neutrino observed to date by KM3NeT, with an estimated energy of 220 PeV, opens up new possibilities for the study and identification of the astrophysical sources responsible for a diffuse flux of such ultra-high-energy neutrinos, among which gamma-ray bursts are longstanding candidates. Aims: Based on the event KM3-230213A, we derive constraints on the baryon loading and density of the surrounding environment in models of blastwaves in long-duration gamma-ray bursts. Methods: We compute the diffuse flux from gamma-ray burst blastwaves, either expanding in a constant density interstellar medium or developing in a radially decreasing density of a wind-like environment surrounding the gamma-ray burst progenitor star, by taking into account the expected neutrino spectra and luminosity function. We use a Poisson likelihood method to constrain the blastwave model parameters by calculating the expected number of neutrino events within the 90% confidence level energy range of KM3-230213A and by using the joint exposure of KM3NeT/ARCA, IceCube and Pierre Auger. Results: We constrain the baryon loading to be $\leq \{392, 131, 39, 13\}$ at 90% confidence level, which is inversely proportional to a varying interstellar medium particle density of $\{1, 3, 10, 30\}$ cm$^{-3}$. In the wind-like environment case, the baryon loading is $\leq \{20, 50, 100\}$ at 90% confidence level, which is proportional to the sixth power of a varying density parameter of $\{0.05, 0.06, 0.07\}$.

astro-ph.HE↗

arXiv2025

The Online Data Filter for the KM3NeT Neutrino Telescopes

The KM3NeT research infrastructure comprises two neutrino telescopes located in the deep waters of the Mediterranean Sea, namely ORCA and ARCA. KM3NeT/ORCA is designed for the measurement of neutrino properties and KM3NeT/ARCA for the detection of high-energy neutrinos from the cosmos. Neutrinos are indirectly detected using three-dimensional arrays of photo-sensors which detect the Cherenkov light that is produced when relativistic charged particles emerge from a neutrino interaction. The analogue pulses from the photo-sensors are digitised offshore and all digital data are sent to a station on shore where they are processed in real time using a farm of commodity servers and custom software. In this paper, the design and performance of the software that is used to filter the data are presented. The performance of the data filter is evaluated in terms of its efficiency, purity and capacity. The efficiency is measured by the effective volumes of the sensor arrays as a function of the energy of the neutrino. The purity is measured by a comparison of the event rate caused by muons produced by cosmic ray interactions in the Earth's atmosphere with the event rate caused by the background from decays of radioactive elements in the sea water and bioluminescence. The capacity is measured by the minimal number of servers that is needed to sustain the rate of incoming data. The results of these evaluations comply with all specifications. The count rates of all photo-sensors are measured with a sampling frequency of 10 Hz. These data are input to the simulations of the detector response and will also be made available for interdisciplinary research.

astro-ph.IM↗

arXiv2025

Search for Magnetic Monopoles with the Complete ANTARES Dataset

This study presents a novel search for magnetic monopoles using data collected over a 14 year period (2008-2022) by the ANTARES neutrino telescope. The interaction of magnetic monopoles with matter was modeled according to Kazama, Yang, and Goldhaber cross-section. Upper limits on the flux of magnetic monopoles are obtained for velocities both above and below the Cherenkov threshold. No events consistent with the passage of magnetic monopoles were detected, enabling the setting of an upper flux limit for relativistic magnetic monopoles of the order of $10^{-18} \mathrm{cm}^{-2} \mathrm{s}^{-1} \mathrm{sr}^{-1}$.

hep-ex↗

arXiv2025

Design and performance of the prototype of the new Particle Identification system for the MAGNEX spectrometer within the NUMEN project

The MAGNEX large acceptance magnetic spectrometer is installed at the Laboratori Nazionali del Sud of the Istituto Nazionale di Fisica Nucleare (INFN-LNS) in Catania. In the past, MAGNEX experimental campaigns were performed using ion beams up to $10^{10}$ pps provided by the Superconducting Cyclotron (SC) accelerator. Nevertheless, in the context of the NUMEN (Nuclear Matrix Elements for Neutrinoless double beta decay) project, which aims to get accurate values of the tiny Double Charge Exchange (DCE) cross-sections for a large number of nuclei of interest for the neutrinoless double beta decay (0$\nu\beta\beta$), the SC is being fully refurbished featuring ion beams with energies from 15 up to 70 MeV/u and intensities up to $10^{13}$ pps. The high rate of incident particles demands a complete upgrade of the MAGNEX detectors, which will consist of a new Particle Identification (PID) system and a new gas tracker detector along with a $\gamma$-calorimeter. The PID system is equipped with a large number (720) of Silicon Carbide-Cesium Iodide (Tallium doped) telescopes. A prototype of the PID wall has been built and studied thanks to an experimental test with an $^{18}$O beam at 275 MeV incident energy performed at INFN-Laboratori Nazionali di Legnaro, Italy. In this manuscript, the design of the new PID system, the in-beam test experimental set-up, and the prototype's performances are presented.

physics.ins-det↗

arXiv2025

The ANTARES detector: two decades of neutrino searches in the Mediterranean Sea

Interest for studying cosmic neutrinos using deep-sea detectors has increase after the discovery of a diffuse flux of cosmic neutrinos by the IceCube collaboration and the possibility of wider multi-messenger studies with the observations of gravitational waves. The ANTARES detector was the first neutrino telescope in seawater, operating successfully in the Mediterranean Sea for more than a decade and a half. All challenges related to the operation in the deep sea were accurately addressed by the collaboration. Deployment and connection operations became smoother over time; data taking and constant re-calibration of the detector due to the variable environmental conditions were fully automated. A wealth of results on the subject of astroparticle physics, particle physics and multi-messenger astronomy have been obtained, despite the relative modest size of the detector, paving the way to a new generation of larger undersea detectors. This review summarizes the efforts by the ANTARES collaboration that made the possibility to operate neutrino telescopes in seawater a reality and the results obtained in this endeavor.

hep-ex↗

arXiv2025

Discovery of lambda Boo stars in open clusters

The origin of lambda Boo stars is currently unknown. After several efforts by many authors, no bona fide lambda Boo stars have been confirmed as members of open clusters. Their detection could provide an important test bed for a detailed study of lambda Boo stars. Results. For the first time, we present the surprising finding of two lambda Boo stars as members of open clusters: HD 28548 belongs to the cluster HSC 1640 and HD 36726 belongs to the cluster Theia 139. This was confirmed using a detailed abundance analysis, while the cluster membership was independently analyzed using Gaia DR3 data and radial velocities. We compared the lambda Boo star HD 36726 with other cluster members and showed that the lambda Boo star was originally born with a near-solar composition. This also implies one of the highest chemical differences detected between two cluster members (0.5 dex). In addition, we suggest that the lambda Boo peculiarity strongly depletes heavier metals, but could also slightly modify lighter abundances such as C and O. We also found that both lambda Boo stars belong to the periphery of their respective clusters. This would suggest that lambda Boo stars avoid the strong photoevaporation by UV radiation from massive stars in the central regions of the cluster. We preliminarily suggest that peripheral location appears to be a necessary, though not sufficient, condition for the development of lambda Boo peculiarity. We also obtained a precise age determination for the lambda Boo stars HD 28548 (26.3 Myr) and HD 36726 (33.1 Myr). Conclusions. We have confirmed, for the first time, that two lambda Boo stars belong to open clusters. This remarkable finding could make open clusters excellent laboratories for studying the origin of lambda Boo stars.

astro-ph.SR↗

arXiv2025

Searching for lambda Boo stars in binary systems

Our goal is to find new candidate lambda Boo stars that belong to binary systems. A detailed abundance determination of some candidates could confirm their true lambda Boo nature, while the composition of eventual late-type companions could be used as a proxy for the initial composition of the lambda Boo stars. Results. We obtained a group of 19 newly identified binary systems which contain a candidate lambda Boo star, allowing to duplicate the number of lambda Boo stars currently known in multiple systems. This important group could be used in further studies of lambda Boo stars. For the first time, we performed a detailed abundance analysis of three of these binary systems which includes a candidate lambda Boo star and a late-type companion. We confirmed the true lambda Boo nature of the three early-type stars (HD 87304, HD 98069 and HD 153747), and obtained mostly a solar-like composition for their late-type components. Adopting as a proxy the late-type stars, we showed that the three lambda Boo stars were initially born with a solar-like composition. This is an important constraint for any scenario trying to explain the origin of lambda Boo stars. Also, the solar-like composition of the late-type stars supports the idea that lambda Boo stars are Population I objects, however, we caution that other explanations are also possible. Conclusions. We performed, for the first time, a detailed abundance analysis of binary systems including a lambda Boo star and a late-type companion. We obtained a solid indication that lambda Boo stars born from a solar-like composition and established an important constraint to test formation models of lambda Boo stars.[abridged]

astro-ph.SR↗

arXiv2025

KM3NeT Constraint on Lorentz-Violating Superluminal Neutrino Velocity

Lorentz invariance is a fundamental symmetry of spacetime and foundational to modern physics. One of its most important consequences is the constancy of the speed of light. This invariance, together with the geometry of spacetime, implies that no particle can move faster than the speed of light. In this article, we present the most stringent neutrino-based test of this prediction, using the highest energy neutrino ever detected to date, KM3-230213A. The arrival of this event, with an energy of $220^{+570}_{-110}\,\text{PeV}$, sets a constraint on $\delta \equiv c_\nu^2-1 < 4\times10^{-22}$.

astro-ph.HE↗

arXiv2025

The ultra-high-energy event KM3-230213A within the global neutrino landscape

On February 13th, 2023, the KM3NeT/ARCA telescope detected a neutrino candidate with an estimated energy in the hundreds of PeVs. In this article, the observation of this ultra-high-energy neutrino is discussed in light of null observations above tens of PeV from the IceCube and Pierre Auger observatories. Performing a joint fit of all experiments under the assumption of an isotropic $E^{-2}$ flux, the best-fit single-flavour flux normalisation is $E^2 \Phi^{\rm 1f}_{\nu + \bar \nu} = 7.5 \times 10^{-10}~{\rm GeV cm^{-2} s^{-1} sr^{-1}}$ in the 90% energy range of the KM3NeT event. Furthermore, the ultra-high-energy data are then fit together with the IceCube measurements at lower energies, either with a single power law or with a broken power law, allowing for the presence of a new component in the spectrum. The joint fit including non-observations by other experiments in the ultra-high-energy region shows a slight preference for a break in the PeV regime if the ``High-Energy Starting Events'' sample is included, and no such preference for the other two IceCube samples investigated. A stronger preference for a break appears if only the KM3NeT data is considered in the ultra-high-energy region, though the flux resulting from such a fit would be inconsistent with null observations from IceCube and Pierre Auger. In all cases, the observed tension between KM3NeT and other datasets is of the order of $2.5\sigma-3\sigma$, and increased statistics are required to resolve this apparent tension and better characterise the neutrino landscape at ultra-high energies.

astro-ph.HE↗

arXiv2025

On the Potential Galactic Origin of the Ultra-High-Energy Event KM3-230213A

The KM3NeT observatory detected the most energetic neutrino candidate ever observed, with an energy between 72 PeV and 2.6 EeV at the 90% confidence level. The observed neutrino is likely of cosmic origin. In this article, it is investigated if the neutrino could have been produced within the Milky Way. Considering the low fluxes of the Galactic diffuse emission at these energies, the lack of a nearby potential Galactic particle accelerator in the direction of the event and the difficulty to accelerate particles to such high energies in Galactic systems, we conclude that if the event is indeed cosmic, it is most likely of extragalactic origin.

astro-ph.HE↗