Correlating Lepton Flavour (Universality) Violation in BB Decays with μ→eγ\mu\to e\gamma using Leptoquarks

Motivated by the measurements of $b\to s\ell^+\ell^-$ transitions, including $R(K)$ and $R(K^*)$, we examine lepton flavour (universality) violation in $B$ decays and its connections to $\mu\to e\gamma$ in generic leptoquark models. Considering all 10 representations of scalar and vector leptoquarks under the Standard Model gauge group we compute the tree-level matching for semileptonic $b$-quark operators as well as their loop effects in $\ell\to\ell^\prime\gamma$. In our phenomenological analysis we correlate $R(K)$, $R(K^*)$ and the other $b\to s\mu^+\mu^-$ data to $\mu\to e\gamma$ and $b\to s\mu e$ transitions for the three leptoquark representations that generate left-handed currents in $b\to s\ell^+\ell^-$ transitions and, therefore, provide a good fit to data. We find that while new physics contributions to muons are required by the global fit, also couplings to electrons can be sizeable without violating the stringent bounds from $\mu\to e\gamma$. In fact, if the effect in electrons in $b\to s\ell^+\ell^-$ has opposite sign than the effect in muons the bound from $\mu\to e\gamma$ can always be avoided. However, unavoidable effects in $b\to s\mu e$ transitions (i.e. $B_s\to\mu e$, $B\to K\mu e$, etc.) appear which are within the reach of LHCb and BELLE II.Comment: 17 pages, 2 figures and 5 tables, version accepted for publication in PR

Lepton pair production at NNLO in QED with EW effects

We present a fully differential calculation of lepton pair production, taking into account the dominant next-to-next-to-leading order QED corrections as well as next-to-leading order electroweak and polarisation effects. We include all lepton masses, hard photon emission, as well as non-perturbative hadronic corrections. The corresponding matrix elements are implemented in the Monte Carlo framework McMule. In order to obtain a numerically stable implementation, we extend next-to-soft stabilisation, a universal technique based on a next-to-leading-power expansion, to calculations with polarised leptons. As an example, we show results tailored to the Belle II detector with the current setup as well as a potential future configuration that includes polarised beams.Comment: 17 pages, 4 figures, published versio

Universal structure of radiative QED amplitudes at one loop

We present two novel results about the universal structure of radiative QED amplitudes in the soft and in the collinear limit. On the one hand, we extend the well-known Low-Burnett-Kroll theorem to the one-loop level and give the explicit relation between the radiative and non-radiative amplitude at subleading power in the soft limit. On the other hand, we consider a factorisation formula at leading power in the limit where the emitted photon becomes collinear to a light fermion and provide the corresponding one-loop splitting function. In addition to being interesting in their own right these findings are particularly relevant in the context of fully-differential higher-order QED calculations. One of the main challenges in this regard is the numerical stability of radiative contributions in the soft and collinear regions. The results presented here allow for a stabilisation of real­virtual amplitudes in these delicate phase-space regions by switching to the corresponding approximation without the need of explicit computations

Bhabha scattering at NNLO with next-to-soft stabilisation

A critical subject in fully differential QED calculations originates from numerical instabilities due to small fermion masses that act as regulators of collinear singularities. At next-to-next-to-leading order (NNLO) a major challenge is therefore to find a stable implementation of numerically delicate real-virtual matrix elements. In the case of Bhabha scattering this has so far prevented the development of a fixed-order Monte Carlo at NNLO accuracy. In this paper we present a new method for stabilising the real-virtual matrix element. It is based on the expansion for soft photon energies including the non-universal subleading term calculated with the method of regions. We have applied this method to Bhabha scattering to obtain a stable and efficient implementation within the McMule framework. We therefore present for the first time fully differential results for the photonic NNLO corrections to Bhabha scattering

Møller scattering at NNLO

We present a calculation of the full set of next-to-next-to-leading-order QED corrections to unpolarized Møller scattering. This encompasses photonic, leptonic, and nonperturbative hadronic corrections and includes electron mass effects as well as hard photon radiation. The corresponding matrix elements are implemented in the Monte Carlo framework mcmule allowing for the computation of fully differential observables. As a first application we show results tailored to the kinematics and detector design of the PRad II experiment where a high-precision theory prediction for Møller scattering is required to achieve the targeted precision. We observe that the corrections become essential to reliably calculate the corresponding differential distributions especially in regions where the leading-order contribution is absent

Eco-efficiency of tomato from Rwamagana district in Rwanda: From field constraints to statistical significance

On the request of decision-makers, the Life Cycle Assessment (LCA) framework is increasingly applied in agri-food value chains in developing countries under particularly demanding constraints. Based on the cradle-to-farm-gate LCA results of the tomato in Rwamagana district in Rwanda commissioned by the European Union, the main objectives of the paper were to validate statistically the differences in environmental impacts among expert-based types for this crop based on location and season and identify the key-drivers of these impacts. The study was developed thanks to two intensive field visits and a survey of 15 plots. The functional unit was one kg of tomato at farm-gate. Combining several statistical analyses allowed identifying three groups of plots with contrasting input profile and eco-efficiency. For most impact categories, the first group with mainly plots in marshland during wet season had the lowest impacts and the third group with plots in hillside showed the highest impacts. The yield of tomato being significantly different between marshland and hillside plots was an important driver of these results. The second group composed of plots in marshland during the dry season generally showed intermediate impacts due to the withdrawing of water for irrigation. The second group obtained a higher freshwater ecotoxicity due to a more intensive use of toxic insecticides. The factorial analysis for mixed data (FAMD) confirmed the importance of the location and the season for the eco-efficiency of tomato plots and the hierarchical clustering on principle components (HCPC) separated the tomato plots into three clusters. The generalized linear models (GLMs) validated the differences in the environmental impacts per kg of tomato between the clusters. The principal component analysis (PCA) combined to GLM revealed that only the use of water was significantly different between the three groups. Compared to existing datasets, all groups showed high freshwater ecotoxicity impacts due to the use of toxic insecticides and the excessive use of mancozeb. The third group also showed a high freshwater eutrophication in relation to P losses due to erosion and low yield. From a methodological point of view, we demonstrated in this paper that using expert-based typologies combined with adapted statistical analyses constituted a relevant approach under such circumstances

High-precision muon decay predictions for ALP searches

We present an improved theoretical prediction of the positron energy spectrum for the polarised Michel decay \mu^+\to e^+ \nu_e\bar{\nu}_\mu. In addition to the full next-to-next-to-leading order correction of order \alpha^2 in the electromagnetic coupling, we include logarithmically enhanced terms at even higher orders. Logarithms due to collinear emission are included at next-to-leading accuracy up to order \alpha^4. At the endpoint of the Michel spectrum, soft photon emission results in large logarithms that are resummed up to next-to-next-to-leading logarithmic accuracy. We apply our results in the context of the MEG II and Mu3e experiments to estimate the impact of the theory error on the branching ratio sensitivity for the lepton-flavour-violating decay \mu^+\to e^+ X of a muon into an axion-like particle X

A quantitative analysis of the taxonomy of artistic styles

Classifying artists and their work as distinct art styles has been an important task of scholars in the field of art history. Due to its subjectivity, scholars often contradict one another. Our project investigated differences in aesthetic qualities of seven art styles through quantitative means. This was achieved with state-of-the-art deep-learning paradigms to generate new images resembling the style of an artist or entire era. We conducted psychological experiments to measure the behavior of subjects when viewing these new art images. Two different experiments were used: In an eye-tracking study, subjects viewed art-style-specific generated images. Eye movements were recorded and then compared between art styles. In a visual singleton search study, subjects had to locate a style-outlier image among three images of an alternative style. Reaction time and accuracy were measured and analyzed. These experiments show that there are measurable differences in behavior when viewing images of varying art styles. From these differences, we constructed hierarchical clusterings relating art styles based on the different behaviors of subjects viewing the samples. Our study reveals a novel perspective on the classification of artworks into stylistic eras and motivates future research in the domain of empirical aesthetics through quantitative means