Articles publicats en revistes (Física Quàntica i Astrofísica)

URI permanent per a aquesta col·leccióhttps://diposit.ub.edu/handle/2445/7504

Estadístiques

Examinar

Mostrant 1 - 20 de 2929

Predictors of long-term survival in patients with a first episode of acute heart failure
(Polskie Towarzystwo Kardiologiczne) Repullo, Daniel; Fuentes, Lidia; Anaya Bustos, Sara; Miñana, Gemma; Llorens Soriano, Pere; Miró i Andreu, Òscar; Romero-Carrete, Carlos Jose; Alquézar Arbé, Aitor; Nuñez, Julio; Gil Espinosa, Victor; Jacob, Javier; Aguirre, Alfons; Villarejo Jimenez, Ana; Borja-Cano, Maria; de la Espriella, Rafael; Santas, Enrique; Sánchez Marcos, Carolina
Introduction: Acute heart failure (AHF) represents a critical event in heart failure progression, but data on long-term outcomes after first hospitalization remain scarce. The aim is to describe long-term survival and evaluate its predictors after the first episode of AHF. Material and methods: Patients from five Spanish hospitals with a confirmed first diagnosis of AHF were categorized based on survival (≥5 or <5 years). Thirteen independent variables were identified. Mortality was assessed using Kaplan-Meier curves after up to 10 years of follow-up. Adjusted odds ratios (OR) with 95% confidence intervals (CI) for mortality were calculated. Additionally, adjusted survival probabilities according to patient age and left ventricular ejection fraction (LVEF) were obtained using restricted cubic splines. Results: A total of 1986 patients were included, with a median age 76 years (range: 68-82), 50% women, and 57% with preserved LVEF. Five-year mortality was 52%. Adjusted analysis showed that age (OR, 0.470 per 10-year increment; 95% CI, 0.421-0.525), New York Heart Association class III-IV vs. I (OR, 0.476; 95% CI, 0.341-0.666) and II vs. I (OR, 0.780; 95% CI, 0.627-0.969), chronic kidney disease (OR, 0.609; 95% CI, 0.452-0.820), coronary artery disease (OR, 0.657; 95% CI, 0.523-0.824), diabetes mellitus (OR, 0.658; 95% CI, 0.534-0.811), and male sex (OR, 0.774; 95% CI, 0.625-0.958) were associated with death within 5 years. LVEF at inclusion was not related to 5-year survival. Conclusions: Survival after a first AHF episode is poor, with age, New York Heart Association class, kidney function, coronary artery disease, diabetes, and sex being key predictors of long-term mortality.
The production of orbitally modulated UHE photons in LS 5039
(EDP Sciences, 2025-08) Bosch i Ramon, Valentí; Khangulyan, Dmitry
Conntext. Gamma-ray binaries present emission that is variable and can reach ultra-high energies. The processes behind the acceleration of the particles that produce this very energetic radiation are yet to be understood. Aims. We probe the properties of the particle accelerator and the ultra-high-energy photon emitter in the gamma-ray binary LS 5039. Methods. From the properties of the binary system and the ultra-high-energy radiation detected by HAWC, we used analytical tools to investigate how these properties constrain the emission and acceleration regions, namely the role of synchrotron losses, particle confinement, and the accelerated particle spectrum, and propose an acceleration scenario that can relax the derived constraints. Results. The modest target densities for hadronic processes and the overall gamma-ray orbital variability favor inverse Compton scattering of ultraviolet photons from the massive companion star by highly relativistic electrons. The acceleration of the highest energy electrons implies a constraint on synchrotron cooling in the acceleration region, which can set an upper limit on its magnetic field. Moreover, the detected variability requires very strong particle confinement in both the acceleration and emission regions, which sets a lower limit on their magnetic fields that is barely consistent with the synchrotron cooling constraint from acceleration. Synchrotron losses may be higher in the emitting region if it is separated from the accelerator, but this requires a very hard particle injection spectrum. An accelerator based on an ultrarelativistic magnetized outflow can alleviate these requirements. Conclusions. A scenario for LS 5039 of the kind proposed by Derishev and collaborators, in which an ultrarelativistic magnetized outflow accelerates leptons injected within the outflow by γγ absorption, provides a viable mechanism to accelerate very energetic electrons. This mechanism relaxes the acceleration and confinement requirements by reducing the impact of synchrotron cooling, and can generate the required particle spectrum.
Probing the detectability of electromagnetic signatures from Galactic isolated black holes
(EDP Sciences, 2025-08) Martinez, Javier Rodrigo; Bosch i Ramon, Valentí; Vieyro, Florencia; del Palacio, Santiago
Context. A large number of isolated stellar-mass black holes (IBHs) are expected to populate the Galaxy. However, only one has been confirmed by the analysis of a microlensing event, and no confirmed emission detection from an IBH has been reported so far. Aims. We analysed the detectability of electromagnetic signatures from IBHs moving in the Galaxy. Methods. We considered accretion from the interstellar medium onto an IBH and assumed the formation of an outflow. We then semi-analytically modelled the accretion process and the interaction of the outflow with the surrounding medium on large scales, including mechanical feedback on the accretion process. Furthermore, we also (semi-)analytically calculated the emission from three different regions: the accretion region, the thermal and the non-thermal radiation from the outflow-medium interaction structure, and the non-thermal emission of relativistic particles that diffuse in the surrounding medium. Results. Our results show that multi-wavelength emission associated with Galactic IBHs can be detected in systems moving through a very dense medium such as the core of a molecular cloud. In particular, thermal emission from accretion could be observed in the mid-infrared and in hard X-rays with current and forthcoming observatories. Thermal and non-thermal emission from the outflowmedium shock could also be detected in the radio and millimetre ranges. Moreover, detection of the emission from particles diffusing in a dense medium could be feasible in γ-rays. Applying our model to the IBH associated with the gravitational microlensing event MOA-2011-BLG-191/OGLE-2011-BLG-0462, we inferred that radio and infrared detection of the IBH is plausible. Also, we derived that IBHs could be modest Galactic cosmic ray contributors, potentially reaching a ∼1% contribution at E >~ 1 PeV. Finally, by extending our model to primordial black holes, we conclude that efficient leptonic acceleration in their outflow-medium interactions would rule them out as a major dark matter component.
Ionization cross section of the Cu shell by electron impact from the threshold to 90 keV, determined on the basis of diagram lines, satellite lines, and the radiative Auger effect
(American Physical Society, 2025) Barros, Suelen F.; Dardengo, Kai L.; Maidana, Nora L.; Mangiarotti, Alessio; Vanin, Vito R.; Fernández Varea, José María
The Cu ionization cross section by electron impact has been measured in the energy range from the -shell threshold to 90keV. To this end, a thin Cu film deposited on a thin C backing has been employed. The x rays emitted by the target have been detected by two silicon drift detectors placed at front and back angles with respect to the direction of the incident beam, which allowed us to better assess the peak fit procedure of the multiplet. A careful analysis of the Cu x-ray spectra generated by electron bombardment has been conducted, including not only the diagram lines but also the satellite lines and the counts that come from the radiative Auger effect. This enabled us to obtain the ⁢ and ⁢ x-ray production cross sections with relative uncertainties of the order of 5%, and the -shell ionization cross section with a precision around 7.5%. We show that, in most cases, the ionization cross sections reported according to current practice cannot be compared with the available theoretical calculations because the latter do not account for multiple-ionization effects. Our results agree with the distorted-wave Born approximation only when the x-ray counts from satellite lines, which amount to about 20% of the total, are excluded.
Spectroscopic age estimates for APOGEE red-giant stars: Precise spatial and kinematic trends with age in the Galactic disc
(EDP Sciences, 2023-10) Anders, Friedrich; Gispert, P.; Ratcliffe, Bridget; Chiappini, C.; Minchev, I.; Nepal, Samir; Queiroz, A. B. A.; Amarante, João Antônio Silveira do; Antoja Castelltort, M. Teresa; Casali, Giada; Casamiquela, L.; Khalatyan, A.; Miglio, A.; Perottoni, Helio; Schultheis, M.
Over the last few years, many studies have found an empirical relationship between the abundance of a star and its age. Here we estimate spectroscopic stellar ages for 178 825 red-giant stars observed by the APOGEE survey with a median statistical uncertainty of 17%. To this end, we use the supervised machine learning technique XGBoost, trained on a high-quality dataset of 3060 redgiant and red-clump stars with asteroseismic ages observed by both APOGEE and Kepler. After verifying the obtained age estimates with independent catalogues, we investigate some of the classical chemical, positional, and kinematic relationships of the stars as a function of their age. We find a very clear imprint of the outer-disc flare in the age maps and confirm the recently found split in the local age-metallicity relation. We present new and precise measurements of the Galactic radial metallicity gradient in small age bins between 0.5 and 12 Gyr, confirming a steeper metallicity gradient for ∼2−5 Gyr old populations and a subsequent flattening for older populations mostly produced by radial migration. In addition, we analyse the dispersion about the abundance gradient as a function of age. We find a clear power-law trend (with an exponent β ≈ 0.15) for this relation, indicating a relatively smooth radial migration history in the Galactic disc over the past 7−9 Gyr. Departures from this power law may possibly be related to the Gaia Enceladus merger and passages of the Sagittarius dSph galaxy. Finally, we confirm previous measurements showing a steepening in the agevelocity dispersion relation at around ∼9 Gyr, but now extending it over a large extent of the Galactic disc (5 kpc < RGal < 13 kpc). To establish whether this steepening is the imprint of a Galactic merger event, however, detailed forward modelling work of our data is necessary. Our catalogue of precise stellar ages and the source code to create it are publicly available.
The Beauty of Speed
(European Southern Observatory, 2009-03) Richichi, Andrea; Barbieri, Cesare; Fors Aldrich, Octavi; Mason, Elena; Naletto, Giampiero
The burst mode of ISAAC has been used systematically to record lunar occultations with high time resolution, producing several unique new results that remain unattainable by any other technique. This is not the only possible choice of instrument for high time resolution, and fast time modes of one kind or another have been implemented on several other ESO instruments. We provide a brief overview of the present capabilities and summarise some scientific results. We speculate about the future of high temporal resolution applications, presenting the trail-blazing instrument Iqueye that recently completed its first technical run at La Silla.
Burst or Bust: ISAAC at Antu Sets New Standards with Lunar Occultations
(European Southern Observatory, 2006-12) Richichi, Andrea; Fors Aldrich, Octavi; Mason, Elena; Stegmeier, Jörg
Imagine a car as fast as a Ferrari, and as cheap as a Trabi. Sounds crazy? Maybe it is, but when it comes to high angular resolution in astronomy there is something that comes close to the miracle: lunar occultations. As the Moon moves over a background star, the phenomenon of diffraction causes tenuous, quick fringes to appear in the stellar light just before it vanishes. The fringes carry valuable information on the size of the source, on scales much smaller than possible with even a perfect, extremely large telescope. Paranal is now superbly equipped to perform this kind of observation, and for that matter all sorts of high-speed near-IR photometry. And the results are impressive. Find out more about the ISAAC burst mode, which is now officially supported from Period 79.
Superfluid rings as quantum pendulums
(American Physical Society, 2024-07-31) Muñoz Mateo, Antonio; Astrakharchik, Grigory E.; Juliá-Díaz, Bruno
A nondispersive quantum pendulum is presented. The proposed setup consists of an ultracold atomic cloud, featuring attractive interatomic interactions, loaded into a tilted ring potential. The classical and quantum domains are switched on by tuned interactions, and the classical dynamical stabilization of unstable states, i.e., à la Kapitza, is shown to be driven by quantum phase imprinting. One potential application of this system as a gravimeter is discussed.
Improved π0,η,η′ transition form factors in resonancechiral theory and their aHLbL μ contribution
(Springer Verlag, 2024-12-27) Estrada, Emilio J.; Gonzàlez-Solís, Sergi; Guevara, Adolfo; Roig, Pablo
Working with Resonance Chiral Theory, within the two resonance multiplets saturation scheme, we satisfy leading (and some subleading) chiral and asymptotic QCD constraints and accurately fit simultaneously the π0,η,η′transition form factors, for single and double virtuality. In the latter case, we supplement the few available measurements with lattice data to ensure a faithful description. Mainly due to the new results for the doubly virtual case, we improve over existing descriptions for the η and η′. Our evaluationof the corresponding pole contributions to the hadronic light-by-light piece of the muon g−2 read: aπ0-pole µ=(61.9 ±0.6+2.4−1.5)×10−11, aη-poleµ=(15.2 ±0.5+1.1−0.8)×10−11 and aη′-poleµ=(14.2 ±0.7+1.4−0.9)×10−11, for a total of aπ0+η+η′-poleµ= (91.3 ±1.0+3.0−1.9)×10−11, where the first and second errors are the statistical and systematic uncertainties, respectively.
Anomalous quantum transport in fractal lattices
(Springer Nature, 2024-08-02) Rojo Francàs, Abel; Pansari, Priyanshu; Bhattacharya, Utso; Juliá-Díaz, Bruno; Grass, Tobias
Fractal lattices are self-similar structures with repeated patterns on different scales. Quantum transport through such structures is subtle due to the possible co-existence of localized and extended states. Here, we study the dynamical properties of two fractal lattices, the Sierpiński gasket and the Sierpiński carpet. While the gasket exhibits sub-diffusive behavior, sub-ballistic transport occurs in the carpet. We show that the different dynamical behavior is in line with qualitative differences of the systems’ spectral properties. Specifically, in contrast to the Sierpiński carpet, the Sierpiński gasket exhibits an inverse power-law behavior of the level spacing distribution. As a possible technological application, we discuss a memory effect in the Sierpiński gasket which allows to read off the phase information of an initial state from the spatial distribution after long evolution times. We also show that interpolating between fractal and regular lattices allows for flexible tuning between different transport regimes.
New high-sensitivity, milliarcsecond resolution results from routine observations of lunar occultations at the ESO VLT
(EDP Sciences, 2010-11-04) Richichi, A.; Fors Aldrich, Octavi; Chen, W. -P.; Mason, E.
Context. Lunar occultations (LO) are a very efficient and powerful technique that achieves the best combination of high angular resolution and sensitivity possible today at near-infrared wavelengths. Given that the events are fixed in time, that the sources are occulted randomly, and that the telescope use is minimal, the technique is very well suited for service mode observations.Aims: We have established a program of routine LO observations at the VLT observatory, especially designed to take advantage of short breaks available in-between other programs. We have used the ISAAC instrument in burst mode, capable of producing continuous read-outs at millisecond rates on a suitable subwindow. Given the random nature of the source selection, our aim has been primarily the investigation of a large number of stellar sources at the highest angular resolution in order to detect new binaries. Serendipitous results such as resolved sources and detection of circumstellar components were also anticipated.Methods: We have recorded the signal from background stars for a few seconds, around the predicted time of occultation by the Moon's dark limb. At millisecond time resolution, a characteristic diffraction pattern can be observed. Patterns for two or more sources superimpose linearly, and this property is used for the detection of binary stars. The detailed analysis of the diffraction fringes can be used to measure specific properties such as the stellar angular size and the presence of extended light sources such as a circumstellar shell.Results: We present a list of 191 stars for which LO data could be recorded and analyzed. Results include the detection of 16 binary and 2 triple stars, all but one of which were previously unknown. The projected angular separations are as small as 4 milliarcsec and magnitude differences as high as Δ K = 5.8 mag. Additionally we derive accurate angular diameters for 2 stars and resolve circumstellar emission around another one, also all for the first time. We have established upper limits on the angular size of 177 stars, mostly in the 1 to 5 mas range, and we plan to include them in a future list of sources well suited for the calibration of interferometers.Conclusions: We confirm the performance of the technique already established in our previous work. LO at an 8 m-class telescope can achieve an angular resolution close to 0farcs001 with a sensitivity K ≈ 12 mag.
Lunar occultations of 184 stellar sources in two crowded regions toward the Galactic bulge
(EDP Sciences, 2011-08-01) Richichi, A.; Chen, W. P.; Fors Aldrich, Octavi; Wang, P. F.
Context. Lunar occultations (LO) provide a unique combination of high angular resolution and sensitivity at near-infrared wavelenghts. At the ESO Very Large Telescope, it is possible to achieve about 1 milliarcsecond (mas) resolution and detect sources as faint as K ≈ 12 mag.Aims: We have taken advantage of a passage of the Moon over two crowded and reddened regions in the direction of the inner part of the Galactic bulge to obtain a high number of occultation light curves over two half nights. Our goal was to detect and characterize new binary systems, and to investigate highly extincted and relatively unknown infrared sources in search of circumstellar shells and similar peculiarities. Our target list included a significant number of very late-type stars, but the majority of the sources was without spectral classification.Methods: An LO event requires the sampling of the light curve at millisecond rates to permit a detailed study of the diffraction fringes. For this, we used the so-called burst mode of the ISAAC instrument at the Melipal telescope. Our observing efficiency was ultimately limited by overheads for telescope pointing and data storage to about one event every three minutes.Results: We could record useful light curves for 184 sources. Of these, 24 were found to be binaries or multiples, all previously unknown. The projected separations are as small as 7.5 mas, and the magnitude differences as high as ΔK = 6.5 mag. Additionally we could also establish for the first time the resolved nature of at least two more stars, along with an indication of circumstellar emission. We were also able to put upper limits on the angular size of about 165 unresolved stars, an information that combined with previous and future observations will be very helpful in establishing a list of reliable calibrators for long baseline interferometers.Conclusions: Many of the newly detected companions are beyond the present capabilities of other high angular resolution techniques, but some could be followed up by long baseline interferometry or adaptive optics. From estimates of the stellar density we conclude that statistically the influence of chance alignments appears to be negligible. We infer that most cases are probably giant-dwarf pairs.
Optimization of the Pixel Design for Large Gamma Cameras Based on Silicon Photomultipliers
(MDPI, 2024-09-19) Wunderlich, Carolin; Paoletti, Riccardo; Guberman, Daniel
Most single-photon emission computed tomography (SPECT) scanners employ a gamma camera with a large scintillator crystal and 50–100 large photomultiplier tubes (PMTs). In the past, we proposed that the weight, size and cost of a scanner could be reduced by replacing the PMTs with large-area silicon photomultiplier (SiPM) pixels in which commercial SiPMs are summed to reduce the number of readout channels. We studied the feasibility of that solution with a small homemade camera, but the question on how it could be implemented in a large camera remained open. In this work, we try to answer this question by performing Geant4 simulations of a full-body SPECT camera. We studied how the pixel size, shape and noise could affect its energy and spatial resolution. Our results suggest that it would be possible to obtain an intrinsic spatial resolution of a few mm FWHM and an energy resolution at 140 keV close to 10%, even if using pixels more than 20 times larger than standard commercial SiPMs of 6 × 6 mm2. We have also found that if SiPMs are distributed following a honeycomb structure, the spatial resolution is significantly better than if using square pixels distributed in a square grid.
Strong interaction physics at the luminosity frontier with 22 GeV electrons at Jefferson Lab
(Società Italiana di Fisica & Springer Verlag, 2024-09-04) Gonzàlez-Solís, Sergi; Mathieu, Vincent; Perry, Robert J.
The purpose of this document is to outline the developing scientific case for pursuing an energy upgrade to 22 GeV of the Continuous Electron Beam Accelerator Facility (CEBAF) at the Thomas Jefferson National Accelerator Facility (TJNAF, or JLab). This document was developed with input from a series of workshops held in the period between March 2022 and April 2023 that were organized by the JLab user community and staff with guidance from JLab management (see Sec. 10). The scientific case for the 22 GeV energy upgrade leverages existing or already planned Hall equipment and world-wide uniqueness of CEBAF high-luminosity operations.CEBAF delivers the world’s highest intensity and high-est precision multi-GeV electron beams and has been do so for more than 25 years. In Fall 2017, with the completion of the 12 GeV upgrade and the start of the 12 GeV science program, a new era at the Laboratory began. The 12 GeV era is now well underway, with many important experimental results already published, and an exciting portfolio Program Advisory Committee approved experiments plannedfor at least the next 8–10 years [1]. At the same time, the CEBAF community is looking toward its future and the science that could be obtained through a future cost-effective upgrade to 22 GeV. The great potential to upgrade CEBAF to higher energies opens a rich and unique experimental nuclear physics program that combines illustrious history with an exciting future, extending the life of the facility well into the 2030s and beyond.JLab at 22 GeV will provide unique, world-leading science with high-precision, high-luminosity experiments elucidating the properties of quantum chromodynamics (QCD) in the valence regime (x ≥ 0.1). JLab at 22 GeV also enables researchers to probe the transition to a region of sea dominance, with access to hadrons of larger mass and different structures. With a fixed-target program at the “luminosity frontier”, large acceptance detection systems, as well as high-precision spectrometers, CEBAF will continue to offer unique opportunities to shed light on the nature of QCD and the emergence of hadron structure for decades to come. In fact, CEBAF today, and with an energy upgrade, will continue to operate with several orders of magnitude higher luminosity than what is planned at the Electron-Ion Collider (EIC). CEBAF’s current and envisioned capabilities enable exciting scientific opportunities that complement the EIC operational reach, thus giving scientists the full suite of tools necessary to comprehensively understand how QCD builds hadronic matter.The physics program laid out in this document spans a broad range of exciting initiatives that focus on a common theme, namely, investigations that explore different facets of the nonperturbative dynamics that manifest in hadron structure and probe the richness of these strongly interacting systems. The central themes of this program are reviewed in Sect. 2 - Introduction. The main components of the research program are highlighted in Sects. 3 through 8, followed by Sect. 9, which provides a brief overview of the 22 GeV CEBAF energy-doubling concept. These sections outline the key measurements in different areas of experimental studies possible at a 22 GeV CEBAF accelerator in the existing JLab experimental end stations. They provide details on the key physics outcomes and unique aspects of the programs not possible at other existing or planned facilities.
Prospects for γ-ray observations of the Perseus galaxy cluster with the Cherenkov Telescope Array
(Institute of Physics (IOP), 2024-10-01) The CTA Consortium; Aguasca Cabot, Arnau; Bordas Coma, Pol; Paredes i Poy, Josep Maria; Ribó Gomis, Marc; Sanuy Charles, Andreu
Galaxy clusters are expected to be both dark matter (DM) reservoirs and storage rooms for the cosmic-ray protons (CRp) that accumulate along the cluster's formation history. Accordingly, they are excellent targets to search for signals of DM annihilation and decay at γ-ray energies and are predicted to be sources of large-scale γ-ray emission due to hadronic interactions in the intracluster medium (ICM). In this paper, we estimate the sensitivity of the Cherenkov Telescope Array (CTA) to detect diffuse γ-ray emission from the Perseus galaxy cluster. We first perform a detailed spatial and spectral modelling of the expected signal for both the DM and the CRp components. For each case, we compute the expected CTA sensitivity accounting for the CTA instrument response functions. The CTA observing strategy of the Perseus cluster is also discussed. In the absence of a diffuse signal (non-detection), CTA should constrain the CRp to thermal energy ratio X ₅₀₀ within the characteristic radius R ₅₀₀ down to about X ₅₀₀ < 3 × 10^-3, for a spatial CRp distribution that follows the thermal gas and a CRp spectral index α_CRp = 2.3. Under the optimistic assumption of a pure hadronic origin of the Perseus radio mini-halo and depending on the assumed magnetic field profile, CTA should measure α_CRp down to about Δα_CRp ≃ 0.1 and the CRp spatial distribution with 10% precision, respectively. Regarding DM, CTA should improve the current ground-based γ-ray DM limits from clusters observations on the velocity-averaged annihilation cross-section by a factor of up to ∼ 5, depending on the modelling of DM halo substructure. In the case of decay of DM particles, CTA will explore a new region of the parameter space, reaching models with τ _χ > 10²⁷ s for DM masses above 1 TeV. These constraints will provide unprecedented sensitivity to the physics of both CRp acceleration and transport at cluster scale and to TeV DM particle models, especially in the decay scenario.
Introducing tools to test Higgs boson interactions via WW scattering. II. the coupled-channel formalism and scalar resonances
(American Physical Society, 2023) Asiáin, Iñigo; Espriu, D. (Domènec); Mescia, F. (Federico)
In this work, we explore in detail the presence of scalar resonances in the ⁢ fusion process in the context of the LHC experiments working in the theoretical framework provided by Higgs effective field theories (HEFTs). While the phenomenology of vector resonances is reasonably understood in the framework of Weinberg sum-rules and unitarization studies, scalar resonances are a lot less constrained and, more importantly, do depend on HEFT low-energy effective couplings different from the ones of vector resonances that are difficult to constrain experimentally. More specifically, unitarization techniques combined with the requirement of causality allows us to set nontrivial bounds on Higgs self-interactions. This is due to the need for considering coupled channels in the scalar case along the unitarization process. As a byproduct, we can gain some relevant information on the Higgs sector from ⁢ → ⁢ elastic processes without needing to consider two-Higgs production.
Limits on dark matter compact objects implied by supermagnified stars in lensing clusters
(Royal Astronomical Society, 2024-12-17) Vall Müller, Claudi; Miralda Escudé, Jordi
Supermagnified stars are gravitationally lensed individual stars that are located close to a caustic of a lensing galaxy cluster, and have their flux magnified by a large enough factor (typically ⁠) to make them detectable with present telescopes. The maximum magnification is limited by microlensing caused by intracluster stars or other compact objects, which create a network of corrugated critical lines with an angular width proportional to the surface density of microlenses. We consider a set of nine cases of supermagnified stars reported in the literature, and derive an upper limit on the surface density of compact objects, such as primordial black holes, that might be present as a fraction of the dark matter in addition to known intracluster stars. Any such additional compact objects would widen the corrugated critical line network and therefore the width of the distribution of supermagnified stars around the modelled critical lines of the lens. We find that any compact objects, including primordial black holes, with masses above (below which the microcaustics are closer together than the typical angular size of supermagnified stars) cannot account for more than per cent of the dark matter.
QCD constraints on isospin-dense matter and the nuclear equation of state
(American Physical Society, 2025-01-10) NPLQCD Collaboration; Abbott, Ryan; Detmold, William; Illa, Marc; Parreño García, Assumpta; Perry, Robert J.; Romero-López, Fernando; Shanahan, Phiala E.; Wagman, Michael L.
Understanding the behavior of dense hadronic matter is a central goal in nuclear physics as it governs the nature and dynamics of astrophysical objects such as supernovae and neutron stars. Because of the nonperturbative nature of quantum chromodynamics (QCD), little is known rigorously about hadronic matter in these extreme conditions. Here, lattice QCD calculations are used to compute thermodynamic quantities and the equation of state of QCD over a wide range of isospin chemical potentials with controlled systematic uncertainties. Agreement is seen with chiral perturbation theory when the chemical potential is small. Comparison to perturbative QCD at large chemical potential allows for an estimate of the gap in the superconducting phase, and this quantity is seen to agree with perturbative determinations. Since the partition function for an isospin chemical potential bounds the partition function for a baryon chemical potential, these calculations also provide rigorous nonperturbative QCD bounds on the symmetric nuclear matter equation of state over a wide range of baryon densities for the first time.
Toward Sub-100 ps TOF-PET Systems Employing the FastIC ASIC With Analog SiPMs
(Institute of Electrical and Electronics Engineers (IEEE), 2024-09-01) Mariscal-Castilla, Antonio; Gomez Fernandez, Sergio; Manera Escalero, Rafel; Fernandez-Tenllado, José María; Mauricio Ferre, Joan; Kratochwil, Nicolaus; Alozy, J.; Piller, Markus; Portero, Sara; Sanuy Charles, Andreu; Guberman, Daniel; Silva, J. J.; Auffray, Etiennette; Ballabriga, Rafael; Ariño Estrada, Gerard; Campbell, Michael; Gascón Fora, David
Time of Flight positron emission tomography (TOFPET) scanners demand electronics that are power-efficient, low-noise, cost-effective, and possess a large bandwidth. Recent developments have demonstrated sub-100 ps time resolution with elevated power consumption per channel, rendering this unfeasible to build a scanner. In this work, we evaluate the performance for the TOF-PET of the FastIC front-end using different scintillators and silicon photomultipliers (SiPMs). FastIC is an eight-channel application specific integrated circuit developed in CMOS 65 nm capable of measuring the energy and the arrival time of a detected pulse with 12 mW per channel. Using Hamamatsu SiPMs (S13360-3050PE) coupled to LSO:Ce:0.2%Ca crystals of 2 × 2 × 3 mm3 and LYSO:Ce:0.2%Ca of 3.13 × 3.13 × 20 mm3, we measured a coincidence time resolution (CTR) of (95 ± 3) and 156 ± 4) ps full width half maximum (FWHM), respectively. With Fondazione Bruno Kessler NUV-HD LF2 M0 SiPMs coupled to the same crystals, we obtained a CTR of (76 ± 2) and (127 ± 3) ps FWHM. We employed FastIC with a TlCl pure Cherenkov emitter, demonstrating time resolutions comparable to those achieved with the high-power-consuming electronics. These findings shows that the FastIC represents a cost-effective alternative that can significantly enhance the time resolution of the current TOF-PET systems while maintaining low power consumption. Index Terms—Fast front-end electronics, photo-detector technology, positron emission tomography, scintillator, silicon photomultipliers (SiPMs), Time of Flight positron emission tomography (TOF-PET).
Final state rescattering effects in axio-hadronic η and η' decays
(Springer Verlag, 2024-07-30) Alves, Daniele S.M.; Gonzàlez-Solís, Sergi
It has been long-understood that final state rescattering effects provide O(1) corrections to hadronic meson decays rates, such as η →πππ and η′→ηππ. Hence, one would expect that such effects would be just as important in axio-hadronic η and η′decays, such as η(′) →ππa, where a is an axion or axion-like particle (ALP). And indeed they are, as we show in this paper by using the treatment of dispersion relations to include the effects of strong final state interactions in several axio-hadronic processes, namely, η(′) →π0π0a, η(′) →π+π−a, and η′→ηπ0a. We also compute the perturbative, leading order decay rates for multiple ALP emission, such as in η(′) →π0aa, η′ →ηaa and η(′) →aaa, and briefly discuss the expected corrections from strong interactions and the processes that must be considered for an accurate rate estimation of these multi-ALP decay channels.

Examinar

Enviaments recents