Charged lepton flavour violation from low scale seesaw neutrinos

In the work presented here, we have studied the impact of right handed neutrinos, which are introduced to account for the evidence of neutrino masses, on charged lepton flavour violating observables. In particular, we have focused on the loop induced decays of the Z boson into two leptons of different flavour. We have performed a numerical study of the rates predicted for these processes within the Inverse Seesaw model, specifically considering scenarios where $\mu -e$ transitions are suppressed. Our conclusion, after comparison with the most relevant experimental constraints, is that branching ratios as large as $10^{-7}$ can be predicted in the $\tau -\mu$ or $\tau -e$ channels, together with heavy neutrinos having masses of the TeV order. Such rates could be accessible at next generation colliders.Comment: 13 pages, 5 figures, 3 tables. Proceedings of the Corfu Summer Institute 2016 "School and Workshops on Elementary Particle Physics and Gravity", 31 August - 23 September 2016, Corfu, Greec

A Method of Mass Measurement in Black Hole Binaries Using Timing and High Resolution X-ray Spectroscopy

In X-ray binaries, several percent of the compact object luminosity is intercepted by the surface of the normal companion and re-radiated through Compton reflection and the K-fluorescence. This reflected emission follows the variability of the compact object with a delay approximately equal to the orbital radius divided by the speed of light. This provides the possibility of measuring the orbital radius and thus substantially refining the compact object mass determination compared to using optical data alone. We demonstrate that it may be feasible to measure the time delay between the direct and reflected emission using cross-correlation of the light curves observed near the Kalpha line and above the K-edge of neutral iron. In the case of Cyg X-1, the time delay measurement is feasible with a 300--1000 ksec observation by a telescope with a 1000 cm^2 effective area near 6.4 keV and with a ~5eV energy resolution. With longer exposures, it may be possible to obtain mass constraints even if an X-ray source in the binary system lacks an optical counterpart.Comment: ApJ Letters, in press. 4 pages, 3 figures, uses emulateapj.st

New accurate measurement of 36ArH+ and 38ArH+ ro-vibrational transitions by high resolution IR absorption spectroscopy

The protonated Argon ion, $^{36}$ArH$^{+}$, has been identified recently in the Crab Nebula (Barlow et al. 2013) from Herschel spectra. Given the atmospheric opacity at the frequency of its $J$=1-0 and $J$=2-1 rotational transitions (617.5 and 1234.6 GHz, respectively), and the current lack of appropriate space observatories after the recent end of the Herschel mission, future studies on this molecule will rely on mid-infrared observations. We report on accurate wavenumber measurements of $^{36}$ArH$^{+}$ and $^{38}$ArH$^{+}$ rotation-vibration transitions in the $v$=1-0 band in the range 4.1-3.7 $\mu$m (2450-2715 cm$^{-1}$). The wavenumbers of the $R$(0) transitions of the $v$=1-0 band are 2612.50135$\pm$0.00033 and 2610.70177$\pm$0.00042 cm$^{-1}$ ($\pm3\sigma$) for $^{36}$ArH$^{+}$ and $^{38}$ArH$^{+}$, respectively. The calculated opacity for a gas thermalized at a temperature of 100 K and a linewidth of 1 km.s$^{-1}$ of the $R$(0) line is $1.6\times10^{-15}\times N$($^{36}$ArH$^+$). For column densities of $^{36}$ArH$^+$ larger than $1\times 10^{13}$ cm$^{-2}$, significant absorption by the $R$(0) line can be expected against bright mid-IR sources

Improved determination of the 1(0)-0(0) rotational frequency of NH3D+ from the high resolution spectrum of the v4 infrared band

The high resolution spectrum of the v4 band of NH3D+ has been measured by difference frequency IR laser spectroscopy in a multipass hollow cathode discharge cell. From the set of molecular constants obtained from the analysis of the spectrum, a value of 262817(6) MHz (3sigma) has been derived for the frequency of the 1(0)-0(0) rotational transition. This value supports the assignment to NH3D+ of lines at 262816.7 MHz recorded in radio astronomy observations in Orion-IRc2 and the cold prestellar core B1-bS.Comment: Accepted for publication in the Astrophysical Journal Letters 04 June 201

3He-Rich Solar Energetic Particles in Helical Jets on the Sun

Particle acceleration in stellar flares is ubiquitous in the Universe, however, our Sun is the only astrophysical object where energetic particles and their source flares can both be observed. The acceleration mechanism in solar flares, tremendously enhancing (up to a factor of ten thousand) rare elements like 3He and ultra-heavy nuclei, has been puzzling for almost 50 years. Here we present some of the most intense 3He- and Fe-rich solar energetic particle events ever reported. The events were accompanied by non-relativistic electron events and type III radio bursts. The corresponding high-resolution, extreme-ultraviolet imaging observations have revealed for the first time a helical structure in the source flare with a jet-like shape. The helical jets originated in relatively small, compact active regions, located at the coronal hole boundary. A mini-filament at the base of the jet appears to trigger these events. The events were observed with the two Solar Terrestrial Relations Observatories STEREO on the backside of the Sun, during the period of increased solar activity in 2014. The helical jets may be a distinct feature of these intense events that is related to the production of high 3He and Fe enrichments.Comment: accepted for publication in The Astrophysical Journa

Effects of the anion adsorption and pH on the formic acid oxidation reaction on Pt(111) electrodes

The effects of solution pH and anion adsorption for the formic acid oxidation reaction on the Pt(111) electrode have been examined using electrochemical techniques. Regarding the pH effects, it has been found that oxidation currents for this reaction increase with pH, which indicates that solution formate is involved in the reaction mechanism. Unexpectedly, the adsorption of sulfate on the Pt(111) electrode has a positive effect on the oxidation of formic acid, which also suggests that adsorbed anions are also involved in the mechanism. The activation energy calculated from temperature dependent measurements diminishes with the solution pH and also in the presence of adsorbed sulfate. These measurements corroborate the involvement of solution formate and anions in the oxidation mechanism. Using these results, a rate equation for the oxidation of formic acid is proposed. The current values calculated from this equation are in very good agreement with the experimental currents in perchloric acid solutions.This work has been financially supported by the MICINN (Spain)(project CTQ2010-16271) and Generalitat Valenciana (project PROMETEO/2009/045, FEDER)

On the activation energy of the formic acid oxidation reaction on platinum electrodes

A temperature dependent study on the formic acid oxidation reaction has been carried out in order to determine the activation energy of this reaction on different platinum single crystal electrodes, namely Pt(1 0 0), Pt(1 1 1), Pt(5 5 4) and Pt(5 4 4) surfaces. The chronoamperometric transients obtained with pulsed voltammetry have been analyzed to determine the current densities through the active intermediate and the CO formation rate. From the temperature dependency of those parameters, the activation energy for the direct reaction and the CO formation step have been calculated. For the active intermediate path, the activation energy are in the range of 50–60 kJ/mol. On the other hand, a large dependence on the electrode potential is found for the activation energy of the CO formation reaction on the Pt(1 0 0) electrode, and the activation energy values for this process range between 20 and 100 kJ/mol. These results have been explained using a reaction mechanism in which the oxidation of formic acid requires the presence of a pre-adsorbed anion on the electrode surface

Iterated Nonlinear Control of Ship's Manoeuvring Models

This paper addresses the control design for a nonlinear vessel manoeuvring model. The authors consider a highly nonlinear vessel 4 DOF model. The proposed control algorithm consists of a combination of an iteration technique that approximates the original nonlinear model by a sequence of linear time varying (LTV) equations whose solution converge to the solution of the original nonlinear problem and, a lead compensation design in which for each of the iterated linear time varying systems, the controller is optimized at each time on the interval. The control designed for the last iteration is then applied to the original nonlinear problem. Simulations results show good performance of this approximation methodology and accurate tracking for certain manoeuvring cases under the control of the designed lead controller. The main characteristic of the nonlinear system's response are the reduction of the settling time and the elimination of the steady state error and overshoot