ABSTRACT
Far-infrared fine-structure transitions of C i and C ii and rotational transitions of CO are used to probe hypothetical variations of the electron-to-proton mass ratio μ = me/mp at the epoch ...of reionization (z > 6). A constraint on Δμ/μ = (μobs − μlab)/μlab = (0.7 ± 1.2) × 10−5 (1σ) obtained at $\bar{z} = 6.31$ is the most stringent up-to-date limit on the variation of μ at such high redshift. For all available estimates of Δμ/μ ranging between z = 0 and z ∼ 1100, the epoch of recombination, a regression curve Δμ/μ = kμ(1 + z)p, with kμ = (1.6 ± 0.3) × 10−8 and p = 2.00 ± 0.03, is deduced. If confirmed, this would imply a dynamical nature of dark matter/dark energy.
During the SN1987A explosion on February 23, 1987, four underground neutrino detectors and two gravitational antennas in Rome and Maryland detected signals associated with the gravitational collapse ...of the star’s core. Because it is impossible to detect direct gravitational radiation from the collapse of SN1987A with antennas, it is still unclear what events were recorded by gravitational antennas. In this work, an amplitude analysis of the signals from gravitational antennas in Rome and Maryland in the vicinity of the signals from neutrino detectors during Supernova SN1987A was carried out. It is shown that the amplitude distributions in all antenna signals are consistent with the distribution of fluctuating energy losses of atmospheric muons crossing the antennas. A conclusion has been made about the muon origin of signals Weber type antennas, aluminized cylinders with a mass of 2–3 t.
ABSTRACT
We estimate limits on non-universal coupling of hypothetical hidden fields to standard matter by evaluating the fractional changes in the electron-to-proton mass ratio, μ = me/mp, based on ...observations of Class I methanol masers distributed in the Milky Way disc over the range of the Galactocentric distances $4 \lesssim R \lesssim 12$ kpc. The velocity offsets ΔV = V44 − V95 measured between the 44- and 95-GHz methanol lines provide, so far, one of the most stringent constraints on the spatial gradient kμ ≡ d(Δμ/μ)/dR < 2 × 10−9 kpc−1 and the upper limit on Δμ/μ <2 × 10−8, where Δμ/μ = $(\mu _{\rm \scriptscriptstyle obs}-\mu _{\rm \scriptscriptstyle lab})/\mu _{\rm \scriptscriptstyle lab}$. We also find that the offsets ΔV are clustered into two groups which are separated by $\delta _{\scriptscriptstyle \Delta V} = 0.022 \pm 0.003$ km s−1 (1σ confidence level). The grouping is most probably due to the dominance of different hyperfine transitions in the 44- and 95-GHz methanol maser emission. Which transition becomes favoured is determined by an alignment (polarization) of the nuclear spins of the four hydrogen atoms in the methanol molecule. This result confirms that there are preferred hyperfine transitions involved in the methanol maser action.
Sources of seasonal temperature variations in the average energy of the muon flux detected in the LVD experiment have been discussed. It has been shown that variations are due to the processes of ...generation of muons in upper layers of the atmosphere and the passage of muons through a thick rock layer.
ABSTRACT
Non-standard fields are assumed to be responsible for phenomena attributed to dark energy and dark matter. Being coupled to ordinary matter, these fields modify the masses and/or charges of ...the elementary particles, thereby violating the weak equivalence principle. Thus, values of fundamental constants such as the proton-to-electron mass ratio, μ, and/or the fine structure constant, α, measured in different environment conditions can be used as probes for this coupling. Here we perform differential measurements of F = μα2 to test a non-standard coupling in the Magellanic Clouds–dwarf galaxies where the overall mass budget is dominated by dark matter. The analysis is based on C i and CO lines observed with the Herschel Space Observatory. Since these lines have different sensitivities to changes in μ and α, the combined α and μ variations can be evaluated through the radial velocity offsets, ΔV, between the CO and C i lines. Averaging over nine positions in the Magellanic Clouds, we obtain 〈ΔV〉 = −0.02 ± 0.07 km s−1, leading to |ΔF/F| < 2 × 10−7 (1σ), where ΔF/F = (Fobs − Flab)/Flab. However, for one position observed with five times higher spectral resolution we find ΔV = −0.05 ± 0.02 km s−1, resulting in ΔF/F = (−1.7 ± 0.7) × 10−7. Whether this offset is due to changes in the fundamental constants, due to chemical segregation in the emitting gas, or merely due to Doppler noise requires further investigations.
The Large Volume Detector, hosted in the INFN Laboratori Nazionali del Gran Sasso, is triggered by atmospheric muons at a rate of ∼0.1 Hz. The data collected over almost a quarter of a century are ...used to study the muon intensity underground. The 5×107 muon series, the longest ever exploited by an underground instrument, allows for the accurate long-term monitoring of the muon intensity underground. This is relevant as a study of the background in the Gran Sasso Laboratory, which hosts a variety of long-duration, low-background detectors. We describe the procedure to select muon-like events as well as the method used to compute the exposure. We report the value of the average muon flux measured from 1994 to 2017: Iμ0=3.35±0.0005stat±0.03sys×10−4 m−2 s−1. We show that the intensity is modulated around this average value due to temperature variations in the stratosphere. We quantify such a correlation by using temperature data from the European Center for Medium-range Weather Forecasts: we find an effective temperature coefficient αT=0.94±0.01stat±0.01sys, in agreement with other measurements at the same depth. We scrutinize the spectral content of the time series of the muon intensity by means of the Lomb-Scargle analysis. This yields the evidence of a 1-year periodicity, as well as the indication of others, both shorter and longer, suggesting that the series is not a pure sinusoidal wave. Consequently, and for the first time, we characterize the observed modulation in terms of amplitude and position of the maximum and minimum on a year-by-year basis.
The Large-Volume scintillation Detector commonly known as LVD and located at the Gran Sasso Laboratory at an average depth of 3650 m w.e. measures muons of intensity
m
s
. The results obtained from ...an analysis of the properties of seasonal variations of the horizontal and vertical muon fluxes are presented in this article. Horizontal muons detected in LVD mostly correspond to rock depths of about 5 km w.e. and zenith angles
of about
, while vertical muons (
) correspond to depths of about 4.6 km w.e.
Context. Absorption-line systems detected in quasar spectra can be used to compare the value of the fine-structure constant, α, measured today on Earth with its value in distant galaxies. In recent ...years, some evidence has emerged of small temporal and also spatial variations in α on cosmological scales. These variations may reach a fractional level of ≈ 10 ppm (parts per million). Aims. To test these claims we are conducting a Large Program of observations with the Very Large Telescope’s Ultraviolet and Visual Echelle Spectrograph (UVES), and are obtaining high-resolution (R ≈ 60 000) and high signal-to-noise ratio (S/N ≈ 100) UVES spectra calibrated specifically for this purpose. Here we analyse the first complete quasar spectrum from this programme, that of HE 2217−2818. Methods. We applied the many multiplet method to measure α in five absorption systems towards this quasar: zabs = 0.7866, 0.9424, 1.5558, 1.6279 , and 1.6919. Results. The most precise result is obtained for the absorber at zabs = 1.6919 where 3 Fe ii transitions and Al ii λ1670 have high S/N and provide a wide range of sensitivities to α. The absorption profile is complex with several very narrow features, and it requires 32 velocity components to be fitted to the data. We also conducted a range of tests to estimate the systematic error budget. Our final result for the relative variation in α in this system is Δα/α = +1.3 ± 2.4stat ± 1.0sys ppm. This is one of the tightest current bounds on α-variation from an individual absorber. A second, separate approach to the data reduction, calibration, and analysis of this system yielded a slightly different result of −3.8 ppm, possibly suggesting a larger systematic error component than our tests indicated. This approach used an additional 3 Fe ii transitions, parts of which were masked due to contamination by telluric features. Restricting this analysis to the Fe ii transitions alone and using a modified absorption profile model gave a result that is consistent with the first approach, Δα/α = +1.1 ± 2.6stat ppm. The four other absorbers have simpler absorption profiles, with fewer and broader features, and offer transitions with a narrower range of sensitivities to α. They therefore provide looser bounds on Δα/α at the ≳10 ppm precision level. Conclusions. The absorbers towards quasar HE 2217−2818 reveal no evidence of any variation in α at the 3-ppm precision level (1σ confidence). If the recently reported 10-ppm dipolar variation in α across the sky is correct, the expectation at this sky position is (3.2−5.4) ± 1.7 ppm depending on dipole model used. Our constraint of Δα/α = +1.3 ± 2.4stat ± 1.0sys ppm is not inconsistent with this expectation.
The spatial and temporal variability of the maximum annual ice thickness on the rivers located north of latitude 60° north in the Asian part of Russia is considered. Ice thickness values of 1% ...exceedance probability were obtained. The possibility of using the conventional method to calculate the ice thickness on unexplored rivers in modern climatic conditions is assessed.
The paper is devoted to the issues in the field of producing radio-absorbing materials in order to solve the problem of electromagnetic compatibility in aircraft. The characteristics of ...radio-absorbing materials of the VRM-1 brand (developed by VIAM) based on semirigid polyurethane foam modified with carburized discrete fiber are given before and after accelerated climatic tests. The following characteristics were chosen as criteria for evaluating the performance of the material under operating conditions: the reflection coefficient of electromagnetic radiation in the microwave range, ultimate tensile strength, and elongation in tension.
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