91̽»¨

Abstract:

In response to the 2020 Update of the European Strategy for Particle Physics, the Future Circular Collider (FCC) Feasibility Study was launched as an international collaboration hosted by CERN. This report describes the FCC integrated programme, which consists of two stages: an electron-positron collider (FCC-ee) in the first phase, serving as a high-luminosity Higgs, top, and electroweak factory; followed by a proton-proton collider (FCC-hh) at the energy frontier in the second phase. The FCC-ee is designed to operate at four key centre-of-mass energies: the Z pole, the WW pair production threshold, the ZH production peak, and the top/anti-top production threshold—each delivering the highest possible luminosities to four experiments. Over 15 years of operation, FCC-ee will produce more than 6 trillion Z bosons, 200 million WW pairs, nearly 3 million Higgs bosons, and 2 million top anti-top pairs. Precise energy calibration at the Z pole and WW threshold will be achieved through frequent resonant depolarisation of pilot bunches. The sequence of operation modes between the Z, WW, and ZH substages remains flexible. The FCC-hh will operate at a centre-of-mass energy of approximately 85 TeV—nearly an order of magnitude higher than the LHC—and is designed to deliver 5 to 10 times the integrated luminosity of the upcoming High-Luminosity LHC. Its mass reach for direct discovery extends to several tens of TeV. In addition to proton-proton collisions, the FCC-hh is capable of 91̽»¨ing ion-ion, ion-proton, and lepton-hadron collision modes. This second volume of the Feasibility Study Report presents the complete design of the FCC-ee collider, its operation and staging strategy, the full-energy booster and injector complex, required accelerator technologies, safety concepts, and technical infrastructure. It also includes the design of the FCC-hh hadron collider, development of high-field magnets, hadron injector options, and key technical systems for FCC-hh.

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:

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.