Model-independent bounds on light pseudoscalars from rare B-meson decays

New light pseudoscalars, such as axion-like particles, appear in many well-motivated extensions of the Standard Model and provide an exciting target for present and future experiments. We study the experimental sensitivity for such particles by revising the CHARM exclusion contour, updating bounds from LHCb and presenting prospects for NA62 and SHiP. We first consider a simplified model of a light pseudoscalar $A$ and then propose a model-independent approach applicable to any spin-0 boson light enough to be produced in B-meson decays. As illustration, we provide upper bounds on $\text{BR}(B \to K\,A) \times \text{BR}(A \to \mu^+\mu^-)$ as a function of the boson lifetime and mass for models that satisfy minimal flavour violation. Our results demonstrate the important complementarity between different experiments resulting from their different geometries.Comment: 10 pages, 3 figures; v2: matches version published in PLB; B-meson spectra provided as ancillary fil

On the interplay between astrophysical and laboratory probes of MeV-scale axion-like particles

Studies of axion-like particles (ALPs) commonly focus on a single type of interaction, for example couplings only to photons. Most ALP models however predict correlations between different couplings, which change the phenomenology in important ways. For example, an MeV-scale ALP coupled to Standard Model gauge bosons at high energies will in general interact with photons, $W^\pm$ and $Z$ bosons as well as mesons and nucleons at low energies. We study the implications of such scenarios and point out that astrophysical constraints, in particular from SN1987A, may be substantially relaxed, opening up new regions of parameter space that may be explored with laboratory experiments such as NA62.Comment: 20 pages, 4 figures + appendices; v2: matches published versio

Turn up the volume: Listening to phase transitions in hot dark sectors

Stochastic gravitational wave (GW) backgrounds from first-order phase transitions are an exciting target for future GW observatories and may enable us to study dark sectors with very weak couplings to the Standard Model. In this work we show that such signals may be significantly enhanced for hot dark sectors with a temperature larger than the one of the SM thermal bath. The need to transfer the entropy from the dark sector to the SM after the phase transition can however lead to a substantial dilution of the GW signal. We study this dilution in detail, including the effect of number-changing processes in the dark sector (so-called cannibalism), and show that in large regions of parameter space a net enhancement remains. We apply our findings to a specific example of a dark sector containing a dark Higgs boson and a dark photon and find excellent detection prospects for LISA and the Einstein telescope

Comparison of antimicrobial activity of bio-synthesized silver and zinc oxide nanoparticles using Lavandula stoechas leaf extract

In this study, the extract of Lavandula stoechas for production of silver and zinc oxide nanoparticle without use of any chemical agent was investigated. The silver (AgNPs) and zinc oxide nanoparticles (ZnONPs) showed strong antibacterial activity against both tested Escherichia coli 0157:H7 (Gram negative) and Staphylococcus aureus (Gram positive) bacteria. The antibacterial activity of bio-synthesized nanoparticles against two pathogens was assessed by minimal inhibitory concentration (MIC) assays. The MIC values ofAgNPs and ZnONPs of 10.63 mu g/mL and 12.5 mu g/mL for E.coli 0157:H7 AgNPs and Staphylococcus aureus against ZnONPs were at 3.32 mu g/mL and 6.25 mu g/mL respectively

ALPINIST: Axion-Like Particles In Numerous Interactions Simulated and Tabulated

Proton beam dump experiments are among the most promising strategies to search for light and feebly interacting states such as axion-like particles (ALPs). The interpretation of these experiments is however complicated by the wide range of ALP models and the multitude of different production and decay channels that can induce observable signals. Here we propose a new approach to this problem by separating the calculation of constraints and projected sensitivities into model-independent and model-dependent parts. The former rely on extensive Monte Carlo simulations of ALP production and decays, as well as estimates of the detection efficiencies based on simplified detector geometries. Once these simulations have been performed and tabulated, the latter parts only require simple analytical rescalings that can be performed using the public code ALPINIST released together with this work. We illustrate this approach by considering several ALP models with couplings to Standard Model gauge bosons. For the case of ALPs coupled to gluons we show that the sensitivity of proton beam dump experiments can be extended significantly by considering hadronic ALP decays into three-body final states.Comment: 24 pages + appendices, 7 figures, ALPINIST code available at https://github.com/jjerhot/ALPINIST