1,120 research outputs found

    The UHECR dipole and quadrupole in the latest data from the original Auger and TA surface detectors

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    The sources of ultra-high-energy cosmic rays are still unknown, but assuming standard physics, they are expected to lie within a few hundred megaparsecs from us. Indeed, over cosmological distances cosmic rays lose energy to interactions with background photons, at a rate depending on their mass number and energy and properties of photonuclear interactions and photon backgrounds. The universe is not homogeneous at such scales, hence the distribution of the arrival directions of cosmic rays is expected to reflect the inhomogeneities in the distribution of galaxies; the shorter the energy loss lengths, the stronger the expected anisotropies. Galactic and intergalactic magnetic fields can blur and distort the picture, but the magnitudes of the largest-scale anisotropies, namely the dipole and quadrupole moments, are the most robust to their effects. Measuring them with no bias regardless of any higher-order multipoles is not possible except with full-sky coverage. In this work, we achieve this in three energy ranges (approximately 8--16 EeV, 16--32 EeV, and 32--∞ EeV) by combining surface-detector data collected at the Pierre Auger Observatory until 2020 and at the Telescope Array (TA) until 2019, before the completion of the upgrades of the arrays with new scintillator detectors. We find that the full-sky coverage achieved by combining Auger and TA data reduces the uncertainties on the north-south components of the dipole and quadrupole in half compared to Auger-only results

    UHECR arrival directions in the latest data from the original Auger and TA surface detectors and nearby galaxies

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    The distribution of ultra-high-energy cosmic-ray arrival directions appears to be nearly isotropic except for a dipole moment of order 6×(E/10 EeV)6 \times (E/10~\mathrm{EeV}) per cent. Nonetheless, at the highest energies, as the number of possible candidate sources within the propagation horizon and the magnetic deflections both shrink, smaller-scale anisotropies might be expected to emerge. On the other hand, the flux suppression reduces the statistics available for searching for such anisotropies. In this work, we consider two different lists of candidate sources: a sample of nearby starburst galaxies and the 2MRS catalog tracing stellar mass within 250 Mpc. We combine surface-detector data collected at the Pierre Auger Observatory until 2020 and the Telescope Array until 2019, and use them to test models in which UHECRs comprise an isotropic background and a foreground originating from the candidate sources and randomly deflected by magnetic fields. The free parameters of these models are the energy threshold, the signal fraction, and the search angular scale. We find a correlation between the arrival directions of 11.8%3.1%+5.0%11.8\%_{-3.1\%}^{+5.0\%} of cosmic rays detected with E38 EeVE \ge 38~\mathrm{EeV} by Auger or with E49 EeVE \gtrsim 49~\mathrm{EeV} by TA and the position of nearby starburst galaxies on a 15.53.2+5.3{15.5^\circ}_{-3.2^\circ}^{+5.3^\circ} angular scale, with a 4.2σ post-trial significance, as well as a weaker correlation with the overall galaxy distribution

    The UHECR dipole and quadrupole in the latest data from the original Auger and TA surface detectors

    Get PDF
    The sources of ultra-high-energy cosmic rays are still unknown, but assuming standard physics, they are expected to lie within a few hundred megaparsecs from us. Indeed, over cosmological distances cosmic rays lose energy to interactions with background photons, at a rate depending on their mass number and energy and properties of photonuclear interactions and photon backgrounds. The universe is not homogeneous at such scales, hence the distribution of the arrival directions of cosmic rays is expected to reflect the inhomogeneities in the distribution of galaxies; the shorter the energy loss lengths, the stronger the expected anisotropies. Galactic and intergalactic magnetic fields can blur and distort the picture, but the magnitudes of the largest-scale anisotropies, namely the dipole and quadrupole moments, are the most robust to their effects. Measuring them with no bias regardless of any higher-order multipoles is not possible except with full-sky coverage. In this work, we achieve this in three energy ranges (approximately 8--16 EeV, 16--32 EeV, and 32--∞ EeV) by combining surface-detector data collected at the Pierre Auger Observatory until 2020 and at the Telescope Array (TA) until 2019, before the completion of the upgrades of the arrays with new scintillator detectors. We find that the full-sky coverage achieved by combining Auger and TA data reduces the uncertainties on the north-south components of the dipole and quadrupole in half compared to Auger-only results

    Cosmological implications of photon-flux upper limits at ultrahigh energies in scenarios of Planckian-interacting massive particles for dark matter

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    Using the data of the Pierre Auger Observatory, we report on a search for signatures that would be suggestive of super-heavy particles decaying in the Galactic halo. From the lack of signal, we present upper limits for different energy thresholds above ≳108 GeV on the secondary by-product fluxes expected from the decay of the particles. Assuming that the energy density of these super-heavy particles matches that of dark matter observed today, we translate the upper bounds on the particle fluxes into tight constraints on the couplings governing the decay process as a function of the particle mass. Instantons, which are nonperturbative solutions to Yang-Mills equations, can give rise to decay channels otherwise forbidden and transform stable particles into metastable ones. Assuming such instanton-induced decay processes, we derive a bound on the reduced coupling constant of gauge interactions in the dark sector: αX ≲ 0.09, for 109 ≲ MX=GeV < 1019. Conversely, we obtain that, for instance, a reduced coupling constant αX ¼ 0.09 excludes masses MX ≳ 3 × 1013 GeV. In the context of dark matter production from gravitational interactions alone during the reheating epoch, we derive constraints on the parameter space that involves, in addition to MX and αX, the Hubble rate at the end of inflation, the reheating efficiency, and the nonminimal coupling of the Higgs with curvature

    Antihypertensive treatment changes and related clinical outcomes in older hospitalized patients

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    Background: Hypertension management in older patients represents a challenge, particularly when hospitalized.Objective: The objective of this study is to investigate the determinants and related outcomes of antihypertensive drug prescription in a cohort of older hospitalized patients.Methods: A total of 5671 patients from REPOSI (a prospective multicentre observational register of older Italian in-patients from internal medicine or geriatric wards) were considered; 4377 (77.2%) were hypertensive. Minimum treatment (MT) for hypertension was defined according to the 2018 ESC guidelines [an angiotensin-converting-enzyme-inhibitor (ACE-I) or an angiotensin-receptorblocker (ARB) with a calcium- channel-blocker (CCB) and/or a thiazide diuretic; if > 80 years old, an ACE I or ARB or CCB or thiazide diuretic]. Determinants of MT discontinuation at discharge were assessed. Study outcomes were any cause rehospitalization/all cause death, all cause death, cardiovascular (CV) hospitalization/death, CV death, non CV death, evaluated according to the presence of MT at discharge.Results: Hypertensive patients were older than normotensives, with a more impaired functional status, higher burden of comorbidity and polypharmacy. A total of 2233 patients were on MT at admission, 1766 were on MT at discharge. Discontinuation of MT was associated with the presence of comorbidities (lower odds for diabetes, higher odds for chronic kidney disease and dementia). An adjusted multivariable logistic regression analysis showed that MT for hypertension at discharge was associated with lower risk of all cause death, all cause death/hospitalization, CV death, CV death/hospitalization and non-CV death. Conclusions: Guidelines-suggested MT for hypertension at discharge is associated with a lower risk of adverse clinical outcomes. Nevertheless, changes in anti hypertensive treatment still occur in a significant proportion of older hospitalized patients

    Search for photons above 10 19 eV with the surface detector of the Pierre Auger Observatory

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    We use the surface detector of the Pierre Auger Observatory to search for air showers initiated by photons with an energy above 1019^{19} eV. Photons in the zenith angle range from 30∘ to 60∘ can be identified in the overwhelming background of showers initiated by charged cosmic rays through the broader time structure of the signals induced in the water-Cherenkov detectors of the array and the steeper lateral distribution of shower particles reaching ground. Applying the search method to data collected between January 2004 and June 2020, upper limits at 95% CL are set to an E2^{-2} diffuse flux of ultra-high energy photons above 1019^{19} eV, 2 × 1019^{19} eV and 4 × 1019^{19} eV amounting to 2.11 × 103^{-3}, 3.12 × 104^{-4} and 1.72 × 104^{-4} km2^{-2} sr1^{-1} yr1^{-1}, respectively. While the sensitivity of the present search around 2 × 1019^{19} eV approaches expectations of cosmogenic photon fluxes in the case of a pure-proton composition, it is one order of magnitude above those from more realistic mixed-composition models. The inferred limits have also implications for the search of super-heavy dark matter that are discussed and illustrated

    UHECR arrival directions in the latest data from the original Auger and TA surface detectors and nearby galaxies

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    The distribution of ultra-high-energy cosmic-ray arrival directions appears to be nearly isotropic except for a dipole moment of order 6×(E/10 EeV)6 \times (E/10~\mathrm{EeV}) per cent. Nonetheless, at the highest energies, as the number of possible candidate sources within the propagation horizon and the magnetic deflections both shrink, smaller-scale anisotropies might be expected to emerge. On the other hand, the flux suppression reduces the statistics available for searching for such anisotropies. In this work, we consider two different lists of candidate sources: a sample of nearby starburst galaxies and the 2MRS catalog tracing stellar mass within 250 Mpc. We combine surface-detector data collected at the Pierre Auger Observatory until 2020 and the Telescope Array until 2019, and use them to test models in which UHECRs comprise an isotropic background and a foreground originating from the candidate sources and randomly deflected by magnetic fields. The free parameters of these models are the energy threshold, the signal fraction, and the search angular scale. We find a correlation between the arrival directions of 11.8%3.1%+5.0%11.8\%_{-3.1\%}^{+5.0\%} of cosmic rays detected with E38 EeVE \ge 38~\mathrm{EeV} by Auger or with E49 EeVE \gtrsim 49~\mathrm{EeV} by TA and the position of nearby starburst galaxies on a 15.53.2+5.3{15.5^\circ}_{-3.2^\circ}^{+5.3^\circ} angular scale, with a 4.2σ post-trial significance, as well as a weaker correlation with the overall galaxy distribution

    Twelve-crystal prototype of Li2_2MoO4_4 scintillating bolometers for CUPID and CROSS experiments

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    An array of twelve 0.28 kg lithium molybdate (LMO) low-temperature bolometers equipped with 16 bolometric Ge light detectors, aiming at optimization of detector structure for CROSS and CUPID double-beta decay experiments, was constructed and tested in a low-background pulse-tube-based cryostat at the Canfranc underground laboratory in Spain. Performance of the scintillating bolometers was studied depending on the size of phonon NTD-Ge sensors glued to both LMO and Ge absorbers, shape of the Ge light detectors (circular vs. square, from two suppliers), in different light collection conditions (with and without reflector, with aluminum coated LMO crystal surface). The scintillating bolometer array was operated over 8 months in the low-background conditions that allowed to probe a very low, μ\muBq/kg, level of the LMO crystals radioactive contamination by 228^{228}Th and 226^{226}Ra.Comment: Prepared for submission to JINST; 23 pages, 9 figures, and 4 table

    Search for photons above 1019eV with the surface detector of the Pierre Auger Observatory