Ultra high frequency geomagnetic radiation from extensive air showers

Using the ZHAireS Monte Carlo code, we show that the Fourier-spectrum of the radio emission of inclined airshowers can have a sizable intensity up to the GHz frequency range. At these frequencies only a signi¿cantly reducedvolume of the shower around the axis contributes coherently to the signal observed on the ground, which is mainly due to thegeomagnetic and charge excess mechanisms. At ground level, the maximum emission at high frequencies is concentrated in aring-like elliptical region defined by the intersection with the ground of a Cherenkov cone with its vertex at shower maximum.The frequency-spectrum of inclined showers, when observed at positions close to the ring-like maximum emission region, isin broad agreement with the pulses detected by the ANITA experiment, making the interpretation that they are due to ultra-high energy cosmic ray atmospheric showers consistent with our simulations. These results are also relevant for ground-basedradio experiments aiming at detecting molecular bremsstrahlung radiation in the GHz range - an entirelly different emissionmechanism which is not included in ZHAireS simulations - since they present an important background for such experiments.Fil: Alvarez Muñiz, Jaime. Universidad de Santiago de Compostela; EspañaFil: Carvalho, Washington R., Jr.. Universidad de Santiago de Compostela; EspañaFil: Romero Wolf, Andrés. California Institute of Technology; Estados UnidosFil: Tueros, Matias Jorge. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; Argentina. Universidad de Santiago de Compostela; EspañaFil: Zas, Enrique. Universidad de Santiago de Compostela; España5th International Workshop on Acoustic and Radio EeV Neutrino detection ActivitiesErlangenAlemaniaErlangen Centre for Astroparticle Physic

Coherent Radiation from Extensive Air Showers in the Ultra-High Frequency Band

Using detailed Monte Carlo simulations we have characterized the features of the radio emission of inclined air showers in the Ultra-High Frequency band (300 MHz - 3 GHz). The Fourier-spectrum of the radiation is shown to have a sizable intensity well into the GHz frequency range. The emission is mainly due to transverse currents induced by the geomagnetic field and to the excess charge produced by the Askaryan effect. At these frequencies only a significantly reduced volume of the shower around the axis contributes coherently to the signal observed on the ground. The size of the coherently emitting volume depends on frequency, shower geometry and observer position, and is interpreted in terms of the relative time delays. At ground level, the maximum emission at high frequencies is concentrated in an elliptical ring-like region around the intersection of a Cherenkov cone with its vertex at shower maximum and the ground. The frequency spectrum of inclined showers when observed at positions that view shower maximum in the Cherenkov direction, is shown to be in broad agreement with the pulses detected by the Antarctic Impulsive Transient Antenna (ANITA) experiment, making the interpretation that they are due to Ultra-High Energy Cosmic Ray atmospheric showers consistent with our simulations. These results are also of great importance for experiments aiming to detect molecular bremsstrahlung radiation in the GHz range as they present an important background for its detection.Comment: 8 pages, 8 figure

Cherenkov radio pulses from electromagnetic showers in the time-domain

The electric field of the Cherenkov radio pulse produced by a single charged particle track in a dielectric medium is derived from first principles. An algorithm is developed to obtain the pulse in the time domain for numerical calculations. The algorithm is implemented in a Monte Carlo simulation of electromagnetic showers in dense media (specifically designed for coherent radio emission applications) as might be induced by interactions of ultra-high energy neutrinos. The coherent Cherenkov radio emission produced by such showers is obtained simultaneously both in the time and frequency domains. A consistency check performed by Fourier-transforming the pulse in time and comparing it to the frequency spectrum obtained directly in the simulations yields, as expected, fully consistent results. The reversal of the time structure inside the Cherenkov cone and the signs of the corresponding pulses are addressed in detail. The results, besides testing algorithms used for reference calculations in the frequency domain, shed new light into the properties of the radio pulse in the time domain. The shape of the pulse in the time domain is directly related to the depth development of the excess charge in the shower and its width to the observation angle with respect to the Cherenkov direction. This information can be of great practical importance for interpreting actual data.Comment: 10 pages, 4 figure

Prospects for High-Elevation Radio Detection of >100 PeV Tau Neutrinos

Tau neutrinos are expected to comprise roughly one third of both the astrophysical and cosmogenic neutrino flux, but currently the flavor ratio is poorly constrained and the expected flux at energies above $10^{17}$ eV is low. We present a detector concept aimed at measuring the diffuse flux of tau neutrinos in this energy range via a high-elevation mountaintop detector using the radio technique. The detector searches for radio signals from upgoing air showers generated by Earth-skimming tau neutrinos. Signals from several antennas in a compact array are coherently summed at the trigger level, permitting not only directional masking of anthropogenic backgrounds, but also a low trigger threshold. This design takes advantage of both the large viewing area available at high-elevation sites and the nearly full duty cycle available to radio instruments. We present trade studies that consider the station elevation, frequency band, number of antennas in the array, and the trigger threshold to develop a highly efficient station design. Such a mountaintop detector can achieve a factor of ten improvement in acceptance over existing instruments with 100 independent stations. With 1000 stations and three years of observation, it can achieve a sensitivity to an integrated $\mathcal{E}^{-2}$ flux of $<10^{-9}$ GeV cm$^{-2}$ sr$^{-1}$ s$^{-1}$, in the range of the expected flux of all-flavor cosmogenic neutrinos assuming a pure iron cosmic-ray composition.Comment: 26 pages, 11 figure

Practical and accurate calculations of Askaryan radiation

An in-depth characterization of coherent radio Cherenkov pulses from particle showers in dense dielectric media, referred to as the Askaryan effect, is presented. The time-domain calculation developed in this article is based on a form factor to account for the lateral dimensions of the shower. It is computationally efficient and able to reproduce the results of detailed particle shower simulations with high fidelity in most regions of practical interest including Fresnel effects due to the longitudinal development of the shower. In addition, an intuitive interpretation of the characteristics of the Askaryan pulse is provided. We expect our approach to benefit the analysis of radio pulses in experiments exploiting the radio technique.Comment: Replaced with version published Phys. Rev.

Neutrino propagation in the Earth and emerging charged leptons with nuPyProp\texttt{nuPyProp}

Ultra-high-energy neutrinos serve as messengers of some of the highest energy astrophysical environments. Given that neutrinos are neutral and only interact via weak interactions, neutrinos can emerge from sources, traverse astronomical distances, and point back to their origins. Their weak interactions require large target volumes for neutrino detection. Using the Earth as a neutrino converter, terrestrial, sub-orbital, and satellite-based instruments are able to detect signals of neutrino-induced extensive air showers. In this paper, we describe the software code $\texttt{nuPyProp}$ that simulates tau neutrino and muon neutrino interactions in the Earth and predicts the spectrum of the $\tau$-lepton and muons that emerge. The $\texttt{nuPyProp}$ outputs are lookup tables of charged lepton exit probabilities and energies that can be used directly or as inputs to the $\texttt{nuSpaceSim}$ code designed to simulate optical and radio signals from extensive air showers induced by the emerging charged leptons. We describe the inputs to the code, demonstrate its flexibility and show selected results for $\tau$-lepton and muon exit probabilities and energy distributions. The $\texttt{nuPyProp}$ code is open source, available on github.Comment: 42 pages, 21 figures, code available at https://github.com/NuSpaceSim/nupypro

High testosterone levels and sensitivity to acute stress in perpetrators of domestic violence with low cognitive flexibility and impairments in their emotional decoding process: a preliminary study.

Hormonal and neuropsychological impairment in intimate partner violence (IPV) perpetrators could play a role in domestic violence. For characterising whether there is a specific psychobiological response to stress, participants who had previously been jailed for IPV and controls were compared for testosterone and cortisol levels, tested for 2D:4D ratios (as an indicator of masculinisation), and given several trait questionnaires and neuropsychological tests related to executive functions and theory of mind. After performing the Trier Social Stress Test (TSST), IPV perpetrators experienced decreases in salivary testosterone (T) levels, a moderate worsening of mood, slight anxiety, and a salivary cortisol (C) level increase. Moreover, high basal T was related with high levels of anger and anxiety and worse mood. However, that basal mood does not significantly alter T levels in response to stress. Nonetheless, controls experienced smaller changes in T and larger changes in C and psychological mood. With respect to neuropsychological and cognitive empathic features, IPV perpetrators showed poorer executive performance and emotional recognition than controls. In addition, deficits in both neuropsychological domains were positively associated. Regarding emotional empathy, IPV perpetrators showed higher levels of personal distress than controls. The 2D:4D ratio was lower in IPV than in controls. Moreover, in IPV perpetrators a smaller 2D:4D ratio was related to large increases in T in response to stress and poor emotional recognition. Together with social aspects involved in IPV, differences in psychobiological variables and their relationships could play a relevant role in the onset and perpetuation of violent behaviour