Lepton Flavour Universality (LFU) is one of the fundamental properties of the Standard Model (SM): the three lepton generations should be identical except for their masses. Flavour changing neutral current processes such as $b\to s\ell^+\ell^-$ are ideal to look for hints of LFU violation: they have small SM amplitudes, allowing sizeable contributions from hypotetical new particles. Clean observables such as the ratio between $B\to X_s\ell\ell$ decays, with $\ell=e,\mu$ and where $X_s$ is a strange meson, have been measured with the LHCb detector hinting at deviations from LFU. Further work on similar decays, such as $B\to K\pi\pi\ell\ell$, will allow to corroborate or disprove these deviations.
The LHCb experiment has a unique sensitivity to studying conventional charmonium production and spectroscopy. Leveraging its precise vertex reconstruction and charged hadron identification, LHCb has, for the first time, measured the production of several charmonium states using hadronic decays. This poster presents measurements of $\eta_c$ production and spectroscopy in proton-antiproton interactions, as well as the production of all $\chi_c$ states using di-$\phi$ final states. These results are of significant interest for the development and testing of Non-Relativistic QCD (NRQCD) phenomenology. Furthermore, the poster compares the experimental measurements with the available theoretical predictions.
The purpose of LHCb is to search for indirect evidence of new physics in decays of heavy hadrons. The LHCb detector is a single-arm forward spectrometer with precise silicon-strip detectors in the regions with highest particle occupancies. The non-uniform exposure of the LHCb sensors makes it an ideal laboratory to study radiation damage effects in silicon detectors. The LHCb Silicon Tracker is composed of an upstream tracker, the TT, and of the inner part of the downstream tracker (IT). Dedicated scans are regularly taken, which allow a precise measurement of the charge collection efficiency (CCE) and the calibration of the operational voltages. The measured evolution of the effective depletion voltage $V_{depl}$ is shown, and compared with the Hamburg model prediction. The magnitudes of the sensor leakage current are also analysed and compared to their expected evolution according to phenomenological models. Our results prove that both the TT and the IT will withstand normal operation until the end of the LHC Run II, after which they will be replaced in the context of the LHCb upgrade.
The LHCb experiment is preparing for an upgrade during the second LHC long shutdown in 2019-2020. In order to fully exploit the LHC flavour physics potential with a five-fold increase in the instantaneous luminosity, a trigger-less readout will be implemented. The RICH detectors will require new photon detectors and a brand new front-end electronics. The status of the integration of the RICH photon detector modules with the MiniDAQ, the prototype of the upgraded LHCb readout architecture, has been reported. The development of the prototype of the RICH Upgrade Experiment Control System, integrating the DCS and DAQ partitions in a single FSM, has been described. The status of the development of the RICH Upgrade Inventory, Bookkeeping and Connectivity database has been reported as well.
Lepton universality tests with rare decays at LHCb
Introducing fast simulation models in the MT simulation framework
The poster reports the first observation of the $B^0_{(s)} \to J/\psi p \overline{p}$ decays and precise $B^0_{(s)}$ mass measurements. The analysis is perfomed using proton-proton collision data corresponding to an integrated luminosity of $5.2{\text{fb}}^{-1}$, collected with the LHCb detector. These decays are suppressed due to limited available phase space, as well as due to OZI or Cabibbo suppression. The measured branching fractions are \begin{align*} \mathcal{B}(B^0 \to J/\psi p \overline{p}) &= (4.51\pm 0.40\; \text{(stat)} \pm 0.44\; \text{(syst)}) \times 10^{-7}, \\ \mathcal{B}(B^0_s \to J/\psi p \overline{p}) &= (3.58\pm 0.19\; \text{(stat)} \pm 0.33\; \text{(syst)}) \times 10^{-6}. \end{align*} For the $B^0_s$ meson the result is much higher than the expected value of $ {\cal O} (10^{-9})$. The small available phase space in these decays also allows for the most precise single measurement of both the $B^0$ mass as ${5279.74 \pm 0.30\; ({\rm stat})\pm 0.10\; ({\rm syst})}$ MeV, and the $B^0_s$ mass as ${5366.85 \pm 0.19\; ({\rm stat})\pm 0.13\; ({\rm syst})}$ MeV.
The measurement of the magnitude of the Vcb element of the Cabibbo-Kobayashi-Maskawa matrix is of great importance in the validation of the Standard Model (SM) of particle physics. The current world averages for the inclusive and exclusive measurements of $|V_{cb}|$ are approximately three standard deviations apart, representing a long-standing puzzle in flavour physics. In this work we present the measurement of $|V_{cb}|$ using semileptonic Bs decays produced in proton-proton collision data collected with the LHCb detector during the Run1 of the LHC. This is the first determination of $|V_{cb}|$ from exclusive decays at a hadron collider and the first using decays of the Bs meson.