The gamma -ray sky can be decomposed into individually detected sources, diffuse emission attributed to the interactions of Galactic cosmic rays with gas and radiation fields, and a residual all-sky ...emission component commonly called the isotropic diffuse gamma -ray background (IGRB). The IGRB comprises all extragalactic emissions too faint or too diffuse to be resolved in a given survey, as well as any residual Galactic foregrounds that are approximately isotropic. The first IGRB measurement with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope (Fermi) used 10 months of sky-survey data and considered an energy range between 200 MeV and 100 GeV. Improvements in event selection and characterization of cosmic-ray backgrounds, better understanding of the diffuse Galactic emission (DGE), and a longer data accumulation of 50 months allow for a refinement and extension of the IGRB measurement with the LAT, now covering the energy range from 100 MeV to 820 GeV. The IGRB spectrum shows a significant high-energy cutoff feature and can be well described over nearly four decades in energy by a power law with exponential cutoff having a spectral index of 2.32 + or - 0.02 and a break energy of (279 + or - 52) GeV using our baseline DGE model. The total intensity attributed to the IGRB is (7.2 + or - 0.6) x 10 super(-6) cm super(-2) s super(-1) sr super(-1) above 100 MeV, with an additional +15%/-30% systematic uncertainty due to the Galactic diffuse foregrounds.
ABSTRACT
The Fermi-LAT DR1 and DR2 4FGL catalogues feature more than 5000 gamma-ray sources of which about one fourth are not associated with already known objects, and approximately one third are ...associated with blazars of uncertain nature. We perform a three-category classification of the 4FGL DR1 and DR2 sources independently, using an ensemble of Artificial Neural Networks (ANNs) to characterize them based on the likelihood of being a Pulsar (PSR), a BL Lac type blazar (BLL) or a Flat Spectrum Radio Quasar (FSRQ). We identify candidate PSR, BLL, and FSRQ among the unassociated sources with approximate equipartition among the three categories and select 10 classification outliers as potentially interesting for follow-up studies.
Current theories predict relativistic hadronic particle populations in clusters of galaxies in addition to the already observed relativistic leptons. In these scenarios hadronic interactions give ...rise to neutral pions which decay into gamma rays that are potentially observable with the Large Area Telescope (LAT) on board the Fermi space telescope. We present a joint likelihood analysis searching for spatially extended gamma-ray emission at the locations of 50 galaxy clusters in four years of Fermi-LAT data under the assumption of the universal cosmic-ray (CR) model proposed by Pinzke & Pfrommer. We find an excess at a significance of 2.7sigma, which upon closer inspection, however, is correlated to individual excess emission toward three galaxy clusters: A400, A1367, and A3112. We discuss these cases in detail and conservatively attribute the emission to unmodeled background systems (for example, radio galaxies within the clusters). Through the combined analysis of 50 clusters, we exclude hadronic injection efficiencies in simple hadronic models above 21% and establish limits on the CR to thermal pressure ratio within the virial radius, R sub(200), to be below 1.25%-1.4% depending on the morphological classification. In addition, we derive new limits on the gamma-ray flux from individual clusters in our sample.
Dark matter particle annihilation or decay can produce monochromatic gamma-ray lines and contribute to the diffuse gamma-ray background. Flux upper limits are presented for gamma-ray spectral lines ...from 7 to 200 GeV and for the diffuse gamma-ray background from 4.8 GeV to 264 GeV obtained from two years of Fermi Large Area Telescope data integrated over most of the sky. We give cross-section upper limits and decay lifetime lower limits for dark matter models that produce gamma-ray lines or contribute to the diffuse spectrum, including models proposed as explanations of the PAMELA and Fermi cosmic-ray data.
Minor Recurrent Aphthous Stomatitis (RAS) represents a disease which is very difficult to prevent. This case-control study focused on possible associations between minor Recurrent Aphthous Stomatitis ...in children, their oral health, and underlying behavioral indexes of children's attitudes and habits pertaining to (home) oral hygiene, with the further goal of enabling the dentist to prevent these specific kind of lesions, both from a clinical and a broader psychosocial perspective.
Four hundred one school-children (5-10 years old) in Milan (Italy) were submitted to an intra-oral examination, and interviewed with the aid of a brief psychosocial questionnaire.
At the clinical level, statistically significant associations were observed between the presence of decayed teeth and minor Recurrent Aphthous Stomatitis (Odds Ratio: 3.15; 95% CI: lower limit 1.06; upper limit: 9.36; Z-test: 2.07, p = 0.039; Chi-square = 4.71, p = 0.030), and between the Decayed Missing or Filled Teeth (DMFT) index and minor aphthous stomatitis (Odds Ratio: 3.30; 95% CI: lower limit 1.13; upper limit: 9.67; Z-test = 2.18, p = 0.029; Chi-square = 5.27; p = 0.022), both results pointing to a significant increase-by circa 3 times-in the risk of developing minor Recurrent Aphthous Stomatitis in children exposed to the two above-identified factors (i.e., the presence of decayed teeth and a clearly compromised oral condition, as signaled by the DMFT index), if compared with the risk run by their non-exposed counterparts. At the psychosocial level of analysis, statistically significant associations were observed (1) between children's practice of spontaneously brushing teeth when not at home and a comparatively lower (i.e. better) Decayed Missing or Filled Teeth index (Chi-square: 8.95; p = 0.011), and (2) between receiving parental aid (e.g., proper brushing instructions) while practicing home oral hygiene and a significantly reduced presence of decayed teeth (Chi-square = 5.40; p = .067; Spearman's Rho, p = .038). Further, significant associations were also observed between children's reported severity of dental pain and both (a) the presence of decayed teeth (Chi-square = 10.80; p = 0.011), and (b) children's (poor) oral health condition as expressed by the Decayed Missing or Filled Teeth index (Chi-square = 6.29; p = 0.043). Interestingly, specific lifestyles and social status, showed no systematic association to other clinical or psychological/psychosocial indices.
These systematic relations suggest that, in the presence of Recurrent Aphthous Stomatitis in pediatric patients, the dentist should carefully monitor children for potential carious lesions, implement protocols of prevention to control Recurrent Aphthous Stomatitis disease in children affected by caries, and also be particularly aware of the right or wrong habits children may acquire in the course of continued social exchange with their caregivers and peers.
We report new constraints on the size of large extra dimensions from data collected by the MINOS experiment between 2005 and 2012. Our analysis employs a model in which sterile neutrinos arise as ...Kaluza-Klein states in large extra dimensions and thus modify the neutrino oscillation probabilities due to mixing between active and sterile neutrino states. Using Fermilab’s Neutrinos at the Main Injector beam exposure of 10.56×1020 protons on target, we combine muon neutrino charged current and neutral current data sets from the Near and Far Detectors and observe no evidence for deviations from standard three-flavor neutrino oscillations. The ratios of reconstructed energy spectra in the two detectors constrain the size of large extra dimensions to be smaller than 0.45 μm at 90% C.L. in the limit of a vanishing lightest active neutrino mass. Stronger limits are obtained for nonvanishing masses.
A LYSO calorimeter for the SuperB factory Eigen, G.; Zhou, Z.; Chao, D. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2013, Letnik:
718
Journal Article
Recenzirano
Odprti dostop
The SuperB project is an asymmetric e+e− accelerator of 1036cm−2s−1 design luminosity, capable of collecting a data sample of 50–75ab−1 in five years running. The SuperB electromagnetic calorimeter ...(EMC) provides energy and direction measurement of photons and electrons, and is used for identification of electrons versus other charged particles. In particular we present its design, geometry study and related simulations, as well as R&D on LYSO crystals and developments on readout electronics. A matrix of 25 crystals has been tested at the Beam Test Facility of Frascati (BTF) in May 2011 at energies between 200MeV and 500MeV. Results from this test are presented.
The water at the proposed site of the CHIPS water Cherenkov detector has been studied to measure its attenuation length as a function of filtering time. A 3.2 m vertical column was filled with the ...water from the Wentworth Pit, proposed site of the CHIPS deployment. Results consistent with attenuation lengths of up to 100m have been observed at this wavelength with filtration and UV sterilization alone.
A systematic study of the performance of reflectarrays with different element shapes is presented. The reflection properties of the printed elements versus their geometrical dimensions are calculated ...by using the method of moments (MoM)/boundary integral-resonant mode expansion (BI-RME) method, which permits the analysis of arbitrarily shaped elements. In order to compare the element performance, four parameters are defined as "figures of merit": the range of the reflection phase; the sensitivity to fabrication tolerances; the bandwidth; the cross-polarization level. Both classical (e.g., rectangles and rectangles with tuning stubs) and novel element shapes (e.g., ridge, dogbone) are considered in the case of single-layer structures; the novel proposed shapes exhibit a good tradeoff of all the figures of merit. Double-layer structures are also analyzed, which prove their superior performance at the cost of an increased fabrication complexity.
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