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Discussion Paper No. 384 of 2025 on Navigating Kenya's Power Quality Landscape for a Sustainable Energy Future
Get PDFThe economic and social growth of any country heavily relies on energy as a key enabler. Despite there being significant progress to deploy and improve energy access in Africa, energy security and access are still major challenges to the continent’s economic progression. Kenya, like many other African countries, has numerous power interruptions annually that negatively affect key economic sectors such as manufacturing and business operations and profits. This highlights power quality, which is linked to energy security, as a key area of concern. This study assesses the determinants and status of power quality and its relation to power costs in Kenya. The power quality metric, denoting the reliability of electric service and supply, is evaluated using a qualitative and quantitative approach. The analysis delves into power quality issues, including power interruptions and losses, while examining Kenya’s policy, legal and regulatory environments related to power quality. The study’s key findings are as follows. Kenya's power system losses average between 15 and 25 per cent annually, which is above the recommended cap of 10 per cent for efficient power transmission and distribution systems. Power interruptions are above the optimal levels, showcasing that more needs to be done to improve power quality. The average electricity consumption per customer significantly influences power losses and interruptions.....
Girth and groomed radius of jets recoiling against isolated photons in lead-lead and proton-proton collisions at = 5.02 TeV
No full textInternational audienceThis Letter presents the first measurements of the groomed jet radius and the jet girth in events with an isolated photon recoiling against a jet in lead-lead (PbPb) and proton-proton (pp) collisions at the LHC at a nucleon-nucleon center-of-mass energy of 5.02 TeV. The observables and provide a quantitative measure of how narrow or broad a jet is. The analysis uses PbPb and pp data samples with integrated luminosities of 1.7 nb and 301 pb, respectively, collected with the CMS experiment in 2018 and 2017. Events are required to have a photon with transverse momentum 100 GeV and at least one jet back-to-back in azimuth with respect to the photon and with transverse momentum such that 0.4. The measured and distributions are unfolded to the particle level, which facilitates the comparison between the PbPb and pp results and with theoretical predictions. It is found that jets with 0.8, i.e., those that closely balance the photon , are narrower in PbPb than in pp collisions. Relaxing the selection to include jets with 0.4 reduces the narrowing of the angular structure of jets in PbPb relative to the pp reference. This shows that selection bias effects associated with jet energy loss play an important role in the interpretation of jet substructure measurements
Enriching the physics program of the CMS experiment via data scouting and data parking
No full textInternational audienceSpecialized data-taking and data-processing techniques were introduced by the CMS experiment in Run 1 of the CERN LHC to enhance the sensitivity of searches for new physics and the precision of standard model measurements. These techniques, termed data scouting and data parking, extend the data-taking capabilities of CMS beyond the original design specifications. The novel data-scouting strategy trades complete event information for higher event rates, while keeping the data bandwidth within limits. Data parking involves storing a large amount of raw detector data collected by algorithms with low trigger thresholds to be processed when sufficient computational power is available to handle such data. The research program of the CMS Collaboration is greatly expanded with these techniques. The implementation, performance, and physics results obtained with data scouting and data parking in CMS over the last decade are discussed in this Report, along with new developments aimed at further improving low-mass physics sensitivity over the next years of data taking
Magnetic Anti-de Sitter Wormholes as seeds for Higgs Inflation
No full textInternational audienceWe show how certain types of magnetic asymptotically Anti-de Sitter Euclidean wormholes can catalyze the onset of inflation. These wormholes can be embedded as saddle point solutions of General Relativity coupled to the Standard Model, the inflaton being identified with the Higgs particle. Our scenario is based on the assumption that the quantum effective potential for the Higgs turns negative at a certain high energy window, in line with current measured values for the Higgs and Top quark masses. Within our proposal, we can estimate various parameters and physical quantities of interest, in consistency with current observational bounds
Mechanism of Ultrafast Flavin Photoreduction in the Active Site of Flavoenzyme LSD1 Histone Demethylase
No full textInternational audiencePhotoreduction of oxidized flavins has a functional role in photocatalytic and photoreceptor flavoproteins. In flavoproteins without light-dependent physiological functions, ultrafast, reversible flavin photoreduction is supposedly photoprotective by nature, and holds potential for nonnatural photocatalytic applications. In this work, we combine protein mutagenesis, ultrafast spectroscopy, molecular dynamics simulations and quantum mechanics calculations to investigate the nonfunctional flavin photoreduction in a flavoenzyme, lysine-specific demethylase 1 (LSD1) which is pivotal in DNA transcription. LSD1 harbors an oxidized flavin adenine dinucleotide (FAD) cofactor and multiple electron-donating residues in the active site. Upon photoexcitation, the FAD cofactor is photoreduced in < 200 fs by electron transfer (ET) from nearby residue(s), and the charge pairs recombine in ca. 2 ps. Site-directed mutagenesis pinpoints a specific tryptophan residue, W751, as the primary electron donor, whereas a tyrosine residue, Y761, despite being located closer to the flavin ring, does not effectively contribute to the process. Based on a hybrid quantum–classical computational approach, we characterize the W751–FAD and Y761–FAD charge-transfer states (CTW751 and CTY761, respectively), as well as the FAD locally excited state (LEFAD), and demonstrate that the coupling between LEFAD and CTW751 is larger than those involving CTY761 by an order of magnitude, rationalizing the experimental observations. More generally, this work highlights the role of the intrinsic protein environment and details of donor–acceptor molecular configurations on the dynamics of short-range ET involving a flavin cofactor and amino acid residue(s)
Optimal control under unknown intensity with Bayesian learning
No full textWe consider an optimal control problem inspired by neuroscience, where the dynamics is driven by a Poisson process with a controlled stochastic intensity and an uncertain parameter. Given a prior distribution for the unknown parameter, we describe its evolution according to Bayes' rule. We reformulate the optimization problem using Girsanov's theorem and establish a dynamic programming principle. Finally, we characterize the value function as the unique viscosity solution to a finite-dimensional Hamilton-Jacobi-Bellman equation, which can be solved numerically
First evidence for direct CP violation in beauty to charmonium decays
No full textInternational audienceThe asymmetry and branching fraction of the CKM-suppressed decay are precisely measured relative to the favoured decay , using a sample of proton-proton collision data corresponding to an integrated luminosity of recorded at center-of-mass energy of during 2016--2018. The results of the asymmetry difference and branching fraction ratio are \begin{align*} \Delta\mathcal{A}^{C\!P} &\equiv \mathcal{A}^{C\!P}(B^+ \to J\mskip -3mu/\mskip -2mu\psi\,\pi^+) - \mathcal{A}^{C\!P}(B^+ \to J\mskip -3mu/\mskip -2mu\psi\,K^+) = (1.29 \pm 0.49 \pm 0.08) \times 10^{-2}, \end{align*}\begin{equation*} \mathcal{R}_{\pi/K} \equiv \frac{\mathcal{B}(B^+ \!\to J\mskip -3mu/\mskip -2mu\psi\,\pi^+)}{\mathcal{B}(B^+ \!\to J\mskip -3mu/\mskip -2mu\psi\,K^+)} = (3.852 \pm 0.022 \pm 0.018) \times 10^{-2}. \end{equation*} where the first uncertainties are statistical and the second systematic. A combination with previous LHCb results based on data collected at and in 2011 and 2012 yields and . The combined value deviates from zero by 3.2 standard deviations, providing the first evidence for direct violation in the amplitudes of beauty decays to charmonium final states
Constraints on the photon polarisation in transitions using decays
No full textInternational audienceAn angular analysis of the decay is performed using the proton-proton collision dataset collected between 2011 and 2018 by the LHCb experiment, corresponding to an integrated luminosity of at centre-of-mass energies of 7, 8 and . The analysis is performed in the very low dielectron invariant mass-squared region between and . The longitudinal polarisation fraction of the meson is measured to be less than at confidence level. The observable, which is related to the lepton forward-backward asymmetry, is measured to be , where the first uncertainty is statistical and the second systematic. The transverse asymmetries, and , which are sensitive to the virtual photon polarisation, are found to be and , respectively. The results are consistent with Standard Model predictions
Measurement of the to cross-section ratio as a function of centrality in PbPb collisions at = 5.02 TeV
No full textInternational audienceThe dissociation of quarkonium states with different binding energies produced in heavy-ion collisions is a powerful probe for investigating the formation and properties of the quark-gluon plasma. The ratio of production cross-sections of and mesons times the ratio of their branching fractions into the dimuon final state is measured as a function of centrality using data collected by the LHCb detector in PbPb collisions at = 5.02 TeV. The measured ratio shows no dependence on the collision centrality, and is compared to the latest theory predictions and to the recent measurements in literature
Learning extreme Expected Shortfall and Conditional Tail Moments with neural networks. Application to cryptocurrency data
No full textInternational audienceWe propose a neural networks method to estimate extreme Expected Shortfall, and even more generally, extreme conditional tail moments as functions of confidence levels, in heavy-tailed settings. The convergence rate of the uniform error between the log-conditional tail moment and its neural network approximation is established leveraging extreme-value theory (in particular the high-order condition on the distribution tails) and using critically two activation functions (eLU and ReLU) for neural networks. The finite sample performance of the neural network estimator is compared to bias-reduced extreme-value competitors using synthetic heavy-tailed data. The experiments reveal that our method largely outperforms others. In addition, the selection of the anchor point appears to be much easier and stabler than for other methods. Finally, the neural network estimator is tested on real data related to extreme loss returns in cryptocurrencies: here again, the accuracy obtained by cross-validation is excellent, and is much better compared with competitors