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In 2020, the European Union has established a recast of the 1998 EU Directive on the quality of water intended for human consumption, hereafter called Drinking Water Directive – DWD. One of the most significant innovative point in this recast is the introduction of an innovative “complete risk-based approach to water safety, covering the whole supply chain from the catchment area, abstraction, treatment, storage and distribution to the point of compliance” (article 7). In practice, a 3-level risk assessment and risk management is expected: (1) at the level of the catchment area (article 8), (2) at the level of the water supply systems (article 9) and (3) at the level of the domestic distribution system (article 10). In this context, the CASPER project, funded by SPGE in the Walloon Region of Belgium, aims at developing an integrated approach for the evaluation and management of pollution risks for peri-urban groundwater catchments. The approach, which fully complies with the requirements of the DWD recast, consists of several key components. First, point and diffuse pollution sources are identified in the groundwater catchment area based on a mapping of hazardous activities combined with a specific groundwater monitoring survey aiming at identifying specific tracers of such sources of pollution. In a second step, risks associated to each of the identified source of pollution is estimated based on the measurement of pollutant mass fluxes and mass discharges downgradient these sources. Finally, a groundwater flow and transport model is developed at the scale of the groundwater catchment area, with the aim of evaluating the cumulative effect of the multiple sources on groundwater quality deterioration in the catchment and at the abstraction points. The objective here is to describe the CASPER approach and to illustrate it using ongoing investigations in a peri-urban groundwater catchment exploiting groundwater from a chalk aquifer in Western Belgium.

Groundwater catchment located in peri-urban areas may be impacted by many pollutants coming from different types of point or diffuse sources such as accidental spills, continuous hidden leaks in drainage networks, old landfills, treated/untreated wastewater and watercourses. In the scope of the CASPER project, a new methodological approach has been developed based on field survey and interpretation of the collected data in order to distinguish between the different sources of contamination and mixtures of pollutants. First, the groundwater catchment area corresponding to the land surface perimeter in which abstracted groundwater is recharged is determined and characterised in hydrogeological terms. The possible sources of pollution are identified. In a second step, a groundwater and surface water monitoring survey is established, and water samples are collected focusing on a combination of physicochemical parameters and set of various hydrochemical indicators. In particular, different stable isotopes are considered. The NO3- and Boron stable isotopes are used to distinguish between inputs linked to urban effluents, agricultural fertilisers and manure. Stable isotopes of SO42- are used to distinguish between sulphide minerals oxidation, sulphur-carbon compounds mineralisation, lixiviation and human pollution. Moreover, the occurrence of specific molecules like pharmaceutical and lifestyle products (carbamazepine, caffeine, etc.) are used as effective tracers of anthropogenic contamination. Microbiological analyses are also undertaken to identify microbial populations associated with specific sources of pollution or specific biochemical reactions occurring in soil and groundwater. The resulting hydrochemical dataset is then processed using multivariate and clustering analyses. In this context, the objective here is to describe the rigorous methodological approach to assess pollution sources and to illustrate the first steps of this process using a case study corresponding to a groundwater catchment is a chalk aquifer in Western Belgium.

Branching fraction ratios between the decays $$ {B}_{(s)}^0\\to J/\\psi {\\eta}^{\\left(\\prime \\right)} $$ B s 0 → J / ψ η ′ are measured using proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV, corresponding to an integrated luminosity of 9 fb − 1 . The measured ratios of these branching fractions are $$ {\\displaystyle \\begin{array}{c}\\frac{\\mathcal{B}\\left({B}^0\\to J/{\\psi \\eta}^{\\prime}\\right)}{\\mathcal{B}\\left({B}^0\\to J/\\psi \\eta \\right)}=0.48\\pm 0.06\\pm 0.02\\pm 0.01,\\\ {}\\frac{\\mathcal{B}\\left({B}_s^0\\to J/{\\psi \\eta}^{\\prime}\\right)}{\\mathcal{B}\\left({B}_s^0\\to J/\\psi \\eta \\right)}=0.80\\pm 0.02\\pm 0.02\\pm 0.01,\\end{array}} $$ B B 0 → J / ψη ′ B B 0 → J / ψη = 0.48 ± 0.06 ± 0.02 ± 0.01 , B B s 0 → J / ψη ′ B B s 0 → J / ψη = 0.80 ± 0.02 ± 0.02 ± 0.01 , where the uncertainties are statistical, systematic and related to the precision of the η (′) branching fractions, respectively. They are used to constrain the η/η ′ mixing angle, ϕ P , and to probe the presence of a possible glueball component in the η ′ meson, described by the gluonic mixing angle ϕ G . The obtained results are $$ {\\displaystyle \\begin{array}{c}{\\phi}_{\\textrm{P}}={\\left({41.6}_{-1.2}^{+1.0}\\right)}^{\\circ },\\\ {}{\\phi}_{\\textrm{G}}={\\left({28.1}_{-4.0}^{+3.9}\\right)}^{\\circ },\\end{array}} $$ ϕ P = 41.6 − 1.2 + 1.0 ∘ , ϕ G = 28.1 − 4.0 + 3.9 ∘ , where the uncertainties are statistically dominated. While the value of ϕ P is compatible with existing experimental determinations and theoretical calculations, the angle ϕ G differs from zero by more than four standard deviations, which points to a substantial glueball component in the η ′ meson and/or unexpectedly large contributions from gluon-mediated processes in these decays. The absolute branching fractions are also measured relative to that of the well-established $$ {B}_s^0\\to J/\\psi \\phi $$ B s 0 → J / ψϕ decay, which serves as the normalisation channel. These results supersede the previous LHCb measurements and are the most precise to date.

A time-integrated angular analysis of the decay $$ {B}_s^0\\to J/\\psi {\\overline{K}}^{\\ast }{(892)}^0 $$ B s 0 → J / ψ K ¯ ∗ 892 0 , with J / ψ → μ + μ − and $$ {\\overline{K}}^{\\ast }{(892)}^0\\to {K}^{-}{\\pi}^{+} $$ K ¯ ∗ 892 0 → K − π + , is presented. The analysis employs a sample of proton-proton collision data collected by the LHCb experiment during 2015–2018 at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 6 fb − 1 . A simultaneous maximum-likelihood fit is performed to the angular distributions in bins of the K − π + mass. This fit yields measurements of the CP -averaged polarisation fractions and CP asymmetries for the P-wave component of the K − π + system. The longitudinal and parallel polarisation fractions are determined to be f 0 = 0.534 ± 0.012 ± 0.009 and f || = 0.211 ± 0.014 ± 0.005, respectively, where the first uncertainty is statistical and the second is systematic. The CP asymmetries are measured with 3–7% precision and are found to be consistent with zero. These measurements, along with an updated determination of the branching fraction relative to the B 0 → J / ψK *0 decay, are combined with previous LHCb results, providing the most precise values for these observables to date.

A study of $$ {\\Lambda}_b^0 $$ Λ b 0 and $$ {\\Xi}_b^0 $$ Ξ b 0 baryon decays to the final states $$ p{K}_{\\textrm{S}}^0{\\pi}^{-} $$ p K S 0 π − and $$ p{K}_{\\textrm{S}}^0{K}^{-} $$ p K S 0 K − is performed using pp collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb − 1 . The decays $$ {\\Lambda}_b^0\\to p{K}_{\\textrm{S}}^0{K}^{-} $$ Λ b 0 → p K S 0 K − and $$ {\\Xi}_b^0\\to p{K}_{\\textrm{S}}^0{K}^{-} $$ Ξ b 0 → p K S 0 K − are observed for the first time, with significances reaching eight standard deviations. The branching fractions and integrated CP asymmetries are measured for the $$ {\\Lambda}_b^0\\to p{K}_{\\textrm{S}}^0{\\pi}^{-} $$ Λ b 0 → p K S 0 π − , $$ {\\Lambda}_b^0\\to p{K}_{\\textrm{S}}^0{K}^{-} $$ Λ b 0 → p K S 0 K − , and $$ {\\Xi}_b^0\\to p{K}_{\\textrm{S}}^0{K}^{-} $$ Ξ b 0 → p K S 0 K − decays. For the decay $$ {\\Lambda}_b^0\\to p{K}_{\\textrm{S}}^0{\\pi}^{-} $$ Λ b 0 → p K S 0 π − , the CP asymmetries are measured in different regions of the Dalitz plot. No evidence of CP violation is observed.

A search for the doubly-charmed-baryon decay $$ {\\Xi}_{cc}^{++}\\to {\\Xi}_c^0{\\pi}^{+}{\\pi}^{+} $$ Ξ cc + + → Ξ c 0 π + π + is performed using proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of 13 TeV and corresponding to an integrated luminosity of 5 . 4 fb − 1 . A significant structure consistent with the $$ {\\Xi}_{cc}^{++} $$ Ξ cc + + baryon is observed in the $$ {\\Xi}_c^0{\\pi}^{+}{\\pi}^{+} $$ Ξ c 0 π + π + invariant-mass spectrum. Using the $$ {\\Xi}_{cc}^{++}\\to {\\Lambda}_c^{+}{K}^{-}{\\pi}^{+}{\\pi}^{+} $$ Ξ cc + + → Λ c + K − π + π + decay as the normalisation channel, the branching fraction ratio, $$ \\frac{\\mathcal{B}\\left({\\Xi}_{cc}^{++}\\to {\\Xi}_c^0{\\pi}^{+}{\\pi}^{+}\\right)}{\\mathcal{B}\\left({\\Xi}_{cc}^{++}\\to {\\Lambda}_c^{+}{K}^{-}{\\pi}^{+}{\\pi}^{+}\\right)} $$ B Ξ cc + + → Ξ c 0 π + π + B Ξ cc + + → Λ c + K − π + π + , is measured to be 1 . 37 ± 0 . 18 (stat) ± 0 . 09 (syst) ± 0 . 35 (ext). This measurement provides critical input for testing QCD factorisation methods in the weak decays of doubly-heavy baryons, particularly in quantifying nonperturbative effects such as final-state interactions and resonance contributions to the hadronisation process.

The elliptic and triangular flow of charged particles are measured using two-particle angular correlations in p Pb collisions in the pseudorapidity range 2.0 < | η | < 4.8. The data sample was collected by the LHCb experiment in 2016 at a centre-of-mass energy per nucleon pair of $$ \\sqrt{s_{\\textrm{NN}}}=8.16 $$ s NN = 8.16 TeV, containing in total approximately 1.5 billion collision events. Non-flow contributions are obtained in low-multiplicity collisions and subtracted to extract the flow harmonics. The results are presented as a function of event multiplicity and hadron transverse momentum. Comparisons with a full (3+1)D dynamic model indicate that it overestimates the measured elliptic flow. A comparison between the forward and backward regions reveals no significant differences in flow parameters, suggesting that final-state effects may dominate over initial-state effects in the origin of flow in small systems.

The lifetimes of the $$ {\\varOmega}_c^0 $$ Ω c 0 and $$ {\\Xi}_c^0 $$ Ξ c 0 baryons are measured using a pp collision dataset collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb − 1 . The charm baryons are produced in the fully reconstructed decay chains $$ {\\varOmega}_b^{-}\\to {\\varOmega}_c^0\\left(\\to p{K}^{-}{K}^{-}{\\pi}^{+}\\right){\\pi}^{-} $$ Ω b − → Ω c 0 → p K − K − π + π − and $$ {\\Xi}_b^{-}\\to {\\Xi}_c^0\\left(\\to p{K}^{-}{K}^{-}{\\pi}^{+}\\right){\\pi}^{-} $$ Ξ b − → Ξ c 0 → p K − K − π + π − . The measurement uses topologically and kinematically similar B − → D 0 (→ K − K + π − π + ) π − decays for normalisation. The measured lifetimes are $$ {\\displaystyle \\begin{array}{c}{\\tau}_{\\varOmega_c^0}=276.3\\pm 19.4\\left(\\textrm{stat}\\right)\\pm 1.8\\left(\\textrm{syst}\\right)\\pm 0.7\\left({\\tau}_{D^0}\\right)\\textrm{fs},\\\ {}{\\tau}_{\\Xi_c^0}=149.2\\pm 2.5\\left(\\textrm{stat}\\right)\\pm 0.9\\left(\\textrm{syst}\\right)\\pm 0.4\\ \\left({\\tau}_{D^0}\\right)\\textrm{fs},\\end{array}} $$ τ Ω c 0 = 276.3 ± 19.4 stat ± 1.8 syst ± 0.7 τ D 0 fs , τ Ξ c 0 = 149.2 ± 2.5 stat ± 0.9 syst ± 0.4 τ D 0 fs , where the first uncertainty is statistical, the second systematic and the third due to the uncertainty of the D 0 lifetime. These results are consistent with previous measurements performed by the LHCb experiment.

A study of the charmless baryonic decays $$ {B}_{(s)}^0\\to {K}^0p\\overline{p} $$ B s 0 → K 0 p p ¯ is presented, where $$ {B}_{(s)}^0 $$ B s 0 denotes either a B 0 or a $$ {B}_s^0 $$ B s 0 meson. The analysis is based on proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of 9 fb − 1 . The decay $$ {B}_s^0\\to {K}^0p\\overline{p} $$ B s 0 → K 0 p p ¯ is observed for the first time, with a measured branching fraction of (9 . 14 ± 1 . 69 ± 0 . 90 ± 0 . 33 ± 0 . 20) × 10 − 7 and a significance of 5.6 σ . The uncertainties respectively account for statistical and systematic contributions, the precision of the branching fraction of the normalisation channel B 0 → K 0 π + π − and the fragmentation fraction ratio f s /f d . The branching fraction determined for $$ {B}^0\\to {K}^0p\\overline{p} $$ B 0 → K 0 p p ¯ is (2 . 82 ± 0 . 08 ± 0 . 12 ± 0 . 10) × 10 − 6 , which is the most precise measurement to date.

An angular analysis of the decay $$ {B}_s^0 $$ B s 0 → ϕe + e − is presented, using proton-proton collision data collected with the LHCb detector between 2011 and 2018 at centre-of-mass energies of 7, 8 and 13 TeV. The combined dataset corresponds to an integrated luminosity of 9 fb − 1 . Observables are determined by fitting time-integrated projections of the angular distribution in three bins of dielectron mass squared, q 2 , corresponding to [0 . 1 , 1 . 1], [1 . 1 , 6 . 0] and [15 . 0 , 19 . 0] GeV 2 /c 4 . The results are compatible with predictions based on the Standard Model of particle physics.