Measuring the Sterile Neutrino CP Phase at DUNE and T2HK

The CP phases associated with the sterile neutrino cannot be measured in the dedicated short-baseline experiments being built to test the sterile neutrino hypothesis. On the other hand, these phases can be measured in long-baseline experiments, even though the main goal of these experiments is not to test or measure sterile neutrino parameters. In particular, the sterile neutrino phase $\delta_{24}$ affects the charged-current electron appearance data in long-baseline experiment. In this paper we show for the first time how well the sterile neutrino phase $\delta_{24}$ can be measured by the next-generation long-baseline experiments DUNE, T2HK (and T2HKK). We also show the expected precision with which this sterile phase can be measured by combining the DUNE data with data from T2HK or T2HKK. We also present the sensitivity of these experiments to the sterile mixing angles, both by themselves, as well as when DUNE is combined with T2HK or T2HKK.Comment: Published in EPJ C with minor correction

Exploring fake solutions in the sterile neutrino sector at long-baseline experiments

Active-sterile neutrino mixing is known to affect the neutrino oscillation probabilities at both short as well as long-baselines. In particular, constraints on active-sterile neutrino oscillation parameters can be obtained from long-baseline experiments such as T2HK and DUNE. We present here existence of fake solution in the appearance channel for the 3+1 scenario at long-baseline experiments. We show that the appearance probability is same for values of $\Delta m_{41}^2$ for which the fast oscillations are averaged out and for $\Delta m_{41}^2=(1/2)\Delta m_{31}^2$. The fake solution does not appear for the disappearance channel.Comment: 17 pages, 6 figures, accepted with some modification

Sterile Neutrinos: Propagation in Matter and Sensitivity to Sterile Mass Ordering

We analytically calculate the neutrino conversion probability $P_{\mu e}$ in the presence of sterile neutrinos, with exact dependence on $\Delta m^2_{41}$ and with matter effects explicitly included. Using perturbative expansion in small parameters, the terms involving the small mixing angles $\theta_{24}$ and $\theta_{34}$ can be separated out, with $\theta_{34}$ dependence only arising due to matter effects. We express $P_{\mu e}$ in terms of the quantities of the form $\sin(x)/x$, which helps in elucidating its dependence on matter effects and a wide range of $\Delta m^2_{41}$ values. Our analytic expressions allow us to predict the effects of the sign of $\Delta m^2_{41}$ at a long baseline experiment like DUNE. We numerically calculate the sensitivity of DUNE to the sterile mass ordering and find that this sensitivity can be significant in the range $|\Delta m^2_{41}| \sim (10^{-4} - 10^{-2})$ eV$^2$, for either mass ordering of active neutrinos. The dependence of this sensitivity on the value of $\Delta m^2_{41}$ for all mass ordering combinations can be explained by investigating the resonance-like terms appearing due to the interplay between the sterile sector and matter effects.Comment: 25 pages, 5 figure

Apomyoglobin Sequesters Heme from Heme Bound Aβ Peptides

A combination of absorption, electron paramagnetic resonance (EPR), and resonance Raman (rR) spectroscopy has been used to study the interaction of heme-Aβ and apomyoglobin (apoMb). The absorption spectrum of oxidized heme bound Aβ, characterized by a split Soret band at 364 and 394 nm, shifts to 408 nm on incubation with apoMb, characteristic of Myoglobin (Mb). The ν₄, ν₃, and ν₂ bands in the rR spectrum of heme-Aβ are observed at 1376, 1495, and 1570 cm^–1, which shift to 1371, 1482, and 1563 cm^–1, respectively on incubating with apoMb, implying formation of Mb. Similarly, heme transfer from reduced heme-Aβ to apoMb resulting in the formation of deoxyMb was also observed. Thus, spectroscopic data show that apoMb can sequester heme from heme-Aβ complexes both in oxidized and in reduced forms. Heme uptake by apoMb from native heme-Aβ(1–40) and Aβ(1–16) in both oxidized and reduced forms follow a biphasic reaction kinetics likely representing heme transfer from two dominating conformers of heme-Aβ in solution. The rate constants for the two steps involved in heme uptake by apoMb from heme-Aβ(1–40) are 11.5 × 10⁴ M^–1 s^–1 and 7.5 × 10³ M^–1 s^–1 while from heme-Aβ(1–16) are 6.0 × 10⁴ M^–1 s^–1 and 7.5 × 10³ M^–1 s^–1. The rate constants for heme uptake by apoMb from reduced heme-Aβ(1–40) are 3.7 × 10⁴ M^–1 s^–1 and 6.8 × 10³ M^–1 s^–1 while for reduced heme-Aβ(1–16) are 2.0 × 10⁴ M^–1 s^–1 and 6.0 × 10³ M^–1 s^–1. The heme uptake from heme-Aβ by apoMb leads to a dramatic reduction of PROS generation by the reduced heme-Aβ complexes

Interaction of NO with Cu and Heme-Bound Aβ Peptides Associated with Alzheimer’s Disease

Reduced Cu and heme has been invoked to be involved in Alzheimer’s disease (AD). Recently the Aβ peptides have been demonstrated to bind heme and Cu simultaneously, and this complex produces significantly more toxic partially reduced oxygen species (PROS) than the Cu or heme-bound Aβ peptides. Here a combination of absorption, EPR, and resonance Raman spectroscopy along with kinetic assays are used to investigate the interaction of nitric oxide (NO) with the physiologically relevant form of Cu and heme-bound Aβ peptides, since a down-regulation of nitric oxide synthase activity is observed in patients suffering from AD. The data indicate that NO oxidizes the Cu­(I) sites, making them less toxic toward PROS generation and releases heme from the Aβ peptides ameliorating the effects of heme binding to Aβ peptides associated with AD. This process involves a tyrosine-mediated electron transfer between the Cu and heme sites. These results provide a mechanistic pathway for the possible protective role of NO in AD

Artificial maturation of [FeFe] hydrogenase in a redox polymer film

International audienceWe demonstrate that the insertion of the dinuclear active site of [FeFe] hydrogenase into the apo-enzyme can occur when the enzyme is embedded in a film of redox polymer, under conditions of mediated electron transfer. The maturation can be monitored by electrochemistry, and is as fast as under conditions of direct electron transfer. This new approach clears further the way to the implementation of hydrogenases in large scale real life processes