Reinterpreting the ATLAS bounds on heavy neutral leptons in a realistic neutrino oscillation model

Heavy neutral leptons (HNLs) are hypothetical particles, motivated in the first place by their ability to explain neutrino oscillations. Experimental searches for HNLs are typically conducted under the assumption of a single HNL mixing with a single neutrino flavor. However, the resulting exclusion limits may not directly constrain the corresponding mixing angles in realistic HNL models — those which can explain neutrino oscillations. The reinterpretation of the results of these experimental searches turns out to be a non-trivial task, that requires significant knowledge of the details of the experiment. In this work, we perform a reinterpretation of the latest ATLAS search for HNLs decaying promptly to a tri-lepton final state. We show that in a realistic model with two HNLs, the actual limits can vary by several orders of magnitude depending on the free parameters of the model. Marginalizing over the unknown model parameters leads to an exclusion limit on the total mixing angle which can be up to 3 orders of magnitude weaker than the limits reported in ref. [1]. This demonstrates that the reinterpretation of results from experimental searches is a necessary step to obtain meaningful limits on realistic models. We detail a few steps that can be taken by experimental collaborations in order to simplify the reuse of their results.

First results of the CAST-RADES haloscope search for axions at 34.67 μeV

We present results of the Relic Axion Dark-Matter Exploratory Setup (RADES), a detector which is part of the CERN Axion Solar Telescope (CAST), searching for axion dark matter in the 34.67 μeV mass range. A radio frequency cavity consisting of 5 sub-cavities coupled by inductive irises took physics data inside the CAST dipole magnet for the first time using this filter-like haloscope geometry. An exclusion limit with a 95% credibility level on the axion-photon coupling constant of gaγ ≳ 4 × 10−13 GeV−1 over a mass range of 34.6738 μeV < ma< 34.6771 μeV is set. This constitutes a significant improvement over the current strongest limit set by CAST at this mass and is at the same time one of the most sensitive direct searches for an axion dark matter candidate above the mass of 25 μeV. The results also demonstrate the feasibility of exploring a wider mass range around the value probed by CAST-RADES in this work using similar coherent resonant cavities.

Gravitational wave complementarity and impact of NANOGrav data on gravitational leptogenesis

In seesaw mechanism, if right handed (RH) neutrino masses are generated dynamically by a gauged U(1) symmetry breaking, a stochastic gravitational wave background (SGWB) sourced by a cosmic string network could be a potential probe of leptogenesis. We show that the leptogenesis mechanism that facilitates the dominant production of lepton asymmetry via the quantum effects of right-handed neutrinos in gravitational background, can be probed by GW detectors as well as next-generation neutrinoless double beta decay (0νββ) experiments in a complementary way. We infer that for a successful leptogenesis, an exclusion limit on f − ΩGWh2 plane would correspond to an exclusion on the |mββ| − m1 plane as well. We consider a normal light neutrino mass ordering and discuss how recent NANOGrav pulsar timing data (if interpreted as GW signal) e.g., at 95% CL, would correlate with the potential discovery or null signal in 0νββ decay experiments.

Size-exclusion liquid chromatography for effective purification of amphiphilic trinuclear gold(I) pyrazolate complex

Column gravity chromatography suffered from several drawbacks such as time-consuming and need a large amount of eluents. Herein we reported an efficient technique for effective separation of amphiphilic trinuclear gold(I) pyrazolate complex ([Au3Pz3]C10TEG) with high polarity based on size-exclusion principle of chromatographic technique. Based on the size-exclusion limit, [Au3Pz3]C10TEG having a larger size with molecular weight of 4011.39 Da (4030.40 Da when added Na+) was successfully eluted and collected firstly from its impurities after being recycled for 2 times. In the chromatogram for first cycle, an intense peak upon excitation at 220 nm for [Au3Pz3]C10TEG was observed at retention time of 58 mins, while small peaks due to the presence of impurities was observed in the range between 73 to 85 mins. In the second cycle, the impurities were flushed away before [Au3Pz3]C10TEG was successfully collected at retention time of 170 mins in the third cycle. The columns were a set of polystyrene/divinylbenzene (PS/DVB) JAIGEL-1H and -2.5H connected in series having exclusion limit of 1 X 103 and 2 X 104 in which chloroform was used as the eluent at flow rate of 3.5 mL min-1. As a result, the visual appearance of dark-yellowish [Au3Pz3]C10TEG was successfully purified to give pale-yellowish product. Moreover, differential scanning calorimetry thermogram showed that extra shoulder from impurities at 6.13 °C in the first endothermic peak of [Au3Pz3]C10TEG at 0.76 °C was completely removed. Hence, it can be concluded that size-exclusion chromatography can be used as an effective purification method with much more convenience and small consumption of solvents.

Determining the Size Exclusion for Nanoparticles in Citrus Leaves

Implementation of nanotechnology in agriculture is intimately dependent on the capacity of nanoparticles (NPs) to move within the plant body and reach the targeted cells. Although the fibrillar nature of the plant cell wall permits the movement of molecules through its porous matrix (apoplast), the movement of particles through the aqueous apoplastic milieu has its size limitations given the tightly knitted cellulose/hemicellulose fiber structure. In the present study, we used fluorescent NPs of different composition and sizes, and followed their movement into citrus leaves by fluorescent microscopy. Our results indicate that in citrus leaves, the size exclusion limit for NPs is of ≈5.4 nm. This conclusion was based on the capacity of PAMAM dendrimers G-4 and G-5 (4.5 and 5.4 nm, respectively) to move through the cell wall and into the phloem, but failure of similar PAMAM dendrimers G-6 (6.7 nm) to move through the apoplast. Dendrimer NPs 5.4 nm and smaller were observed to penetrate the leaf tissue, and then taken up and mobilized by the phloem elements. The current study provides evidence on the size limit for NPs use in agriculture.

BRIEF REVIEW OF THE SEARCHES FOR THE RARE DECAYS $B^0_{s}\to\mu^+\mu^-$ and $B^0\to\mu^+\mu^-$

The current experimental status of the searches for the very rare decays [Formula: see text] and [Formula: see text] is discussed. These channels are highly sensitive to various extensions of the Standard Model, especially in the scalar and pseudoscalar sector. The recent, most sensitive measurements from the CDF, ATLAS, CMS and LHCb collaborations are discussed and the combined upper exclusion limit on the branching fractions determined by the LHC experiments is shown to be 4.2×10-9 for [Formula: see text] and 0.8×10-9 for [Formula: see text]. The implications of these tight bounds on a selected set of New Physics models is sketched.