91̽»¨

Abstract:

The ${\mathrm{Ó\copyright }}_c^{+}{\mathrm{Ï€}}^{−}{\mathrm{Ï€}}^{+}$ spectrum is investigated using proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of $5.4{\mathrm{fb}}^{−1}$ , collected by the LHCb experiment during 2016–2018. Four states are observed with high significance, and their masses and widths are measured to be $m[{\mathrm{Ó\copyright }}_c(2815{)}^{+}]=2816.65Â\pm 0.03Â\pm 0.03Â\pm 0.23\mathrm{MeV}$ , $\mathrm{Γ}[{\mathrm{Ó\copyright }}_c(2815{)}^{+}]=2.07Â\pm 0.08Â\pm 0.12\mathrm{MeV}$ , $m[{\mathrm{Ó\copyright }}_c(2923{)}^{+}]=2922.8Â\pm 0.3Â\pm 0.5Â\pm 0.2\mathrm{MeV}$ , $\mathrm{Γ}[{\mathrm{Ó\copyright }}_c(2923{)}^{+}]=5.3Â\pm 0.9Â\pm 1.4\mathrm{MeV}$ , $m[{\mathrm{Ó\copyright }}_c(2970{)}^{+}]=2968.6Â\pm 0.5Â\pm 0.5Â\pm 0.2\mathrm{MeV}$ , $\mathrm{Γ}[{\mathrm{Ó\copyright }}_c(2970{)}^{+}]=31.7Â\pm 1.7Â\pm 1.9\mathrm{MeV}$ , $[{\mathrm{Ó\copyright }}_c(3080{)}^{+}]=3076.8Â\pm 0.7Â\pm 1.3Â\pm 0.2\mathrm{MeV}$ , $\mathrm{Γ}[{\mathrm{Ó\copyright }}_c(3080{)}^{+}]=6.8Â\pm 2.3Â\pm 0.9\mathrm{MeV}$ , where the uncertainties are statistical, systematic, and due to the limited precision on the ${\mathrm{Ó\copyright }}_c^{+}$ mass, respectively. The ${\mathrm{Ó\copyright }}_c(2923{)}^{+}$ baryon is observed for the first time, and is consistent with being the isospin partner of the previously observed ${\mathrm{Ó\copyright }}_c(2923{)}^0$ state. Most of the measured parameters are more precise than existing world averages.

Abstract:

A search for the doubly-charmed-baryon decay өcc++→өc0π+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 өcc++ baryon is observed in the өc0π+π+ invariant-mass spectrum. Using the өcc++→Λc+K−π+π+ decay as the normalisation channel, the branching fraction ratio, Bөcc++→өc0π+π+Bөcc++→Λc+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.

Abstract:

The elliptic and triangular flow of charged particles are measured using two-particle angular correlations in pPb 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 sNN=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.

Abstract:

Branching fraction ratios between the decays Bs0→J/ψη′ 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 areBB0→J/ψη′BB0→J/ψη=0.48±0.06±0.02±0.01, BBs0→J/ψη′BBs0→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, ϕP, and to probe the presence of a possible glueball component in the η′ meson, described by the gluonic mixing angle ϕG. The obtained results are ϕP=41.6−1.2+1.0∘, ϕG=28.1−4.0+3.9∘, where the uncertainties are statistically dominated. While the value of ϕP is compatible with existing experimental determinations and theoretical calculations, the angle ϕG 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 Bs0→J/ψϕ decay, which serves as the normalisation channel. These results supersede the previous LHCb measurements and are the most precise to date.

Abstract:

Volume 3 of the FCC Feasibility Report presents studies related to civil engineering, the development of a project implementation scenario, and environmental and sustainability aspects. The report details the iterative improvements made to the civil engineering concepts since 2018, taking into account subsurface conditions, accelerator and experiment requirements, and territorial considerations. It outlines a technically feasible and economically viable civil engineering configuration that serves as the baseline for detailed subsurface investigations, construction design, cost estimation, and project implementation planning. Additionally, the report highlights ongoing subsurface investigations in key areas to 91̽»¨ the development of an improved 3D subsurface model of the region. The report describes the development of the project scenario based on the ‘avoid-reduce-compensate’ iterative optimisation approach. The reference scenario balances optimal physics performance with territorial compatibility, implementation risks, and costs. Environmental field investigations covering almost 600 hectares of terrain—including numerous urban, economic, social, and technical aspects—confirmed the project’s technical feasibility and contributed to the preparation of essential input documents for the formal project authorisation phase. The summary also highlights the initiation of public dialogue as part of the authorisation process. The results of a comprehensive socio-economic impact assessment, which included significant environmental effects, are presented. Even under the most conservative and stringent conditions, a positive benefit-cost ratio for the FCC-ee is obtained. Finally, the report provides a summary of the studies conducted to document the current state of the environment.