Evidence for the decay BS0→K‾∗0μ+μ− {B}_S^0\to {\overline{K}}^{\ast 0}{\mu}^{+}{\mu}^{-}

International audienceA search for the decay ${B}_S^0\to {\overline{K}}^{\ast 0}{\mu}^{+}{\mu}^{-}$ is presented using data sets corresponding to 1.0, 2.0 and 1.6 fb$^{−1}$ of integrated luminosity collected during pp collisions with the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV, respectively. An excess is found over the background-only hypothesis with a significance of 3.4 standard deviations. The branching fraction of the ${B}_S^0\to {\overline{K}}^{\ast 0}{\mu}^{+}{\mu}^{-}$ decay is determined to be $\mathrm{\mathcal{B}}\left({B}_s^0\to {\overline{K}}^{\ast 0}{\mu}^{+}{\mu}^{-}\right)=\left[2.9\pm 1.0\left(\mathrm{stat}\right)\pm 0.2\left(\mathrm{syst}\right)\pm 0.3\left(\mathrm{norm}\right)\right]\times {10}^{-8}$ , where the first and second uncertainties are statistical and systematic, respectively. The third uncertainty is due to limited knowledge of external parameters used to normalise the branching fraction measurement

QCD and strongly coupled gauge theories : challenges and perspectives

We highlight the progress, current status, and open challenges of QCD-driven physics, in theory and in experiment. We discuss how the strong interaction is intimately connected to a broad sweep of physical problems, in settings ranging from astrophysics and cosmology to strongly coupled, complex systems in particle and condensed-matter physics, as well as to searches for physics beyond the Standard Model. We also discuss how success in describing the strong interaction impacts other fields, and, in turn, how such subjects can impact studies of the strong interaction. In the course of the work we offer a perspective on the many research streams which flow into and out of QCD, as well as a vision for future developments.Peer reviewe

International Geomagnetic Reference Field: the thirteenth generation

In December 2019, the International Association of Geomagnetism and Aeronomy (IAGA) Division V Working Group (V-MOD) adopted the thirteenth generation of the International Geomagnetic Reference Field (IGRF). This IGRF updates the previous generation with a definitive main field model for epoch 2015.0, a main field model for epoch 2020.0, and a predictive linear secular variation for 2020.0 to 2025.0. This letter provides the equations defining the IGRF, the spherical harmonic coefficients for this thirteenth generation model, maps of magnetic declination, inclination and total field intensity for the epoch 2020.0, and maps of their predicted rate of change for the 2020.0 to 2025.0 time period

Apparatus to study crystal channeling and volume reflection phenomena at the SPS H8 beamline

none52A high performance apparatus has been designed and built by the H8-RD22 collaboration for the study of channeling and volume reflection phenomena in the interaction of 400 GeV/c protons with bent silicon crystals, during the 2006 data taking in the external beamline H8 of the CERN SPS. High-quality silicon short crystals were bent by either anticlastic or quasimosaic effects. Alignment with the highly parallel (8 µrad divergence) proton beam was guaranteed through a submicroradian goniometric system equipped with both rotational and translational stages. Particle tracking was possible by a series of silicon microstrip detectors with high-resolution and a parallel plate gas chamber, triggered by various scintillating detectors located along the beamline. Experimental observation of volume reflection with 400 GeV/c protons proved true with a deflection angle of (10.4±0.5) µrad with respect to the unperturbed beam, with a silicon crystal whose (111) planes were parallel to the beam.noneW. Scandale; I. Efthymiopoulos; D. A. Still; A. Carnera; G. Della Mea; D. De Salvador; R. Milan; A. Vomiero; S. Baricordi; S. Chiozzi; P. Dalpiaz; C. Damiani; M. Fiorini; V. Guidi;G. Martinelli; A. Mazzolari; E. Milan; G. Ambrosi; P. Azzarello; R. Battiston; B. Bertucci; W. J. Burger; M. Ionica; P. Zuccon; G. Cavoto; R. Santacesaria; P. Valente; E. Vallazza;A. G. Afonin; V. T. Baranov; Y. A. Chesnokov; V. I. Kotov; V. A. Maisheev; I. A. Yazynin; S. V. Afanasiev; A. D. Kovalenko; A. M. Taratin; N. F. Bondar; A S. Denisov; Y. A. Gavrikov; Y. M. Ivanov; V. G. Ivochkin; S. V. Kosyanenko; L. P. Lapina; P. M. Levtchenko; A. A. Petrunin; V. V. Skorobogatov; V. M. Suvorov; D. Bolognini; L. Foggetta; S. Hasan; M. PrestW., Scandale; I., Efthymiopoulos; D. A., Still; A., Carnera; G., Della Mea; D., De Salvador; R., Milan; A., Vomiero; Baricordi, Stefano; S., Chiozzi; Dalpiaz, Pietro; Damiani, Chiara; Fiorini, Massimiliano; Guidi, Vincenzo; Martinelli, Giuliano; Mazzolari, Andrea; Milan, Emiliano; G., Ambrosi; P., Azzarello; R., Battiston; B., Bertucci; W. J., Burger; M., Ionica; P., Zuccon; G., Cavoto; R., Santacesaria; P., Valente; E., Vallazza; A. G., Afonin; V. T., Baranov; Y. A., Chesnokov; V. I., Kotov; V. A., Maisheev; I. A., Yazynin; S. V., Afanasiev; A. D., Kovalenko; A. M., Taratin; N. F., Bondar; A. S., Denisov; Y. A., Gavrikov; Y. M., Ivanov; V. G., Ivochkin; S. V., Kosyanenko; L. P., Lapina; P. M., Levtchenko; A. A., Petrunin; V. V., Skorobogatov; V. M., Suvorov; D., Bolognini; L., Foggetta; S., Hasan; M., Pres