Design and implementation of an instrumented pedal for cycling biomechanics research

Cycling is a common, low-impact activity used for recreation, exercise, and rehabilitation. Knee joint loading can be predicted using inverse dynamic analyses of pedal load cell and kinematic data measured during cycling biomechanics experiments. Several studies have successfully measured foot loading at the pedals, e.g. by using custom instrumented pedal spindles outfitted with strain gauges and a potentiometer to measure crank angle [1-3]. Such designs are relatively complex, requiring difficult machining and component fabrication, and require post-processing of strain gauge data. The long-term goal of this study is to calculate knee joint loading and, ultimately, cartilage tissue stress to provide evidence-based prescriptions for rehabilitative and fitness sustainment exercises for those who are at high risk for knee osteoarthritis. The objective of this project was to design, fabricate, and implement an instrumented pedal system using existing load cells for use in cycling biomechanics research. Measured data retrieved from the load cells during cycling experiments will be compared to similar studies to verify that this project was successful

Using OpenSim to predict knee joint moments during cycling

Cycling is a relatively low impact activity conventionally recommended as a rehabilitative or fitness sustaining exercise for patients at a high risk for knee osteoarthritis (OA) [1,2]. Expanding our understanding of knee joint loads is necessary to develop and improve evidence-based prescriptions for cycling as a rehabilitative and fitness therapy that limits the risk for knee OA. OpenSim (www.simtk.org) is an open source biomechanical analysis software that can partition predictions of external joint loads (or net muscle moments) into muscle and joint contact loads [3]. Joint contact loads more accurately represent cartilage tissue loading and hence risk for cartilage damage and/or OA [4]. As a first step towards predicting knee joint contact loads during cycling, we hypothesized that OpenSim can predict external knee joint moments that are consistent with published data [5,6]. To address this hypothesis, we conducted cycling experiments and used OpenSim’s scale tool, inverse kinematics (IK) solver, and inverse dynamics (ID) solver to model the recorded activity

Observation of the suppressed Λb0→DpK- decay with D→K+π- and measurement of its CP asymmetry

International audienceA study of Λb0 baryon decays to the DpK- final state is presented based on a proton-proton collision data sample corresponding to an integrated luminosity of 9  fb-1 collected with the LHCb detector. Two Λb0 decays are considered, Λb0→DpK- with D→K-π+ and D→K+π-, where D represents a superposition of D0 and D¯0 states. The latter process is expected to be suppressed relative to the former, and is observed for the first time. The ratio of branching fractions of the two decays is measured, and the CP asymmetry of the suppressed mode, which is sensitive to the Cabibbo-Kobayashi-Maskawa angle γ, is also reported

Angular analysis of the rare decay Bs0 {B}_s^0 → ϕμ+^{+}μ−^{−}

An angular analysis of the rare decay ${B}_s^0$→ ϕμ$^{+}$μ$^{−}$ is presented, 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 8.4 fb$^{−1}$. The observables describing the angular distributions of the decay ${B}_s^0$→ ϕμ$^{+}$μ$^{−}$ are determined in regions of q$^{2}$, the square of the dimuon invariant mass. The results are consistent with Standard Model predictions.[graphic not available: see fulltext

Simultaneous determination of CKM angle γ\gamma and charm mixing parameters

International audienceA combination of measurements sensitive to the CP violation angle γ of the Cabibbo-Kobayashi-Maskawa unitarity triangle and to the charm mixing parameters that describe oscillations between D$^{0}$ and $\overline{D} ^{0}$ mesons is performed. Results from the charm and beauty sectors, based on data collected with the LHCb detector at CERN’s Large Hadron Collider, are combined for the first time. This method provides an improvement on the precision of the charm mixing parameter y by a factor of two with respect to the current world average. The charm mixing parameters are determined to be $x=\left({0.400}_{-0.053}^{+0.052}\right)\%$ and y = $\left({0.630}_{-0.030}^{+0.033}\right)\%$. The angle γ is found to be γ = $\left({65.4}_{-4.2}^{+3.8}\right){}^{\circ}$ and is the most precise determination from a single experiment.[graphic not available: see fulltext

Simultaneous determination of CKM angle γ\gamma and charm mixing parameters

A combination of measurements sensitive to the CP violation angle γ of the Cabibbo-Kobayashi-Maskawa unitarity triangle and to the charm mixing parameters that describe oscillations between D$^{0}$ and $\overline{D} ^{0}$ mesons is performed. Results from the charm and beauty sectors, based on data collected with the LHCb detector at CERN’s Large Hadron Collider, are combined for the first time. This method provides an improvement on the precision of the charm mixing parameter y by a factor of two with respect to the current world average. The charm mixing parameters are determined to be $x=\left({0.400}_{-0.053}^{+0.052}\right)\%$ and y = $\left({0.630}_{-0.030}^{+0.033}\right)\%$. The angle γ is found to be γ = $\left({65.4}_{-4.2}^{+3.8}\right){}^{\circ}$ and is the most precise determination from a single experiment.[graphic not available: see fulltext

Observation of a Λb0−Λ‾b0\Lambda_b^0-\overline{\Lambda}_b^0 production asymmetry in proton-proton collisions at s=7 and 8 TeV\sqrt{s} = 7 \textrm{ and } 8\,\textrm{TeV}

International audienceThis article presents differential measurements of the asymmetry between ${\varLambda}_b^0$ and ${\overline{\varLambda}}_b^0$ baryon production rates in proton-proton collisions at centre-of-mass energies of $\sqrt{s}$ = 7 and 8 TeV collected with the LHCb experiment, corresponding to an integrated luminosity of 3 fb$^{−1}$. The ${\varLambda}_b^0$ baryons are reconstructed through the inclusive semileptonic decay ${\varLambda}_b^0$ → ${\varLambda}_c^{+}$μ$^{−} \overline{\nu} _{μ}$X. The production asymmetry is measured both in intervals of rapidity in the range 2.15 < y < 4.10 and transverse momentum in 2 < p$_{T}$< 27 GeV/c. The results are found to be incompatible with symmetric production with a significance of 5.8 standard deviations for both $\sqrt{s}$ = 7 and 8 TeV data, assuming no CP violation in the decay. There is evidence for a trend as a function of rapidity with a significance of 4 standard deviations. Comparisons to predictions from hadronisation models in Pythia and heavy-quark recombination are provided. This result constitutes the first observation of a particle-antiparticle asymmetry in b-hadron production at LHC energies.[graphic not available: see fulltext

Angular analysis of the rare decay Bs0 {B}_s^0 → ϕμ+^{+}μ−^{−}

International audienceAn angular analysis of the rare decay ${B}_s^0$→ ϕμ$^{+}$μ$^{−}$ is presented, 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 8.4 fb$^{−1}$. The observables describing the angular distributions of the decay ${B}_s^0$→ ϕμ$^{+}$μ$^{−}$ are determined in regions of q$^{2}$, the square of the dimuon invariant mass. The results are consistent with Standard Model predictions.[graphic not available: see fulltext

The LHCb upgrade I

International audienceThe LHCb upgrade represents a major change of the experiment. The detectors have been almost completely renewed to allow running at an instantaneous luminosity five times larger than that of the previous running periods. Readout of all detectors into an all-software trigger is central to the new design, facilitating the reconstruction of events at the maximum LHC interaction rate, and their selection in real time. The experiment's tracking system has been completely upgraded with a new pixel vertex detector, a silicon tracker upstream of the dipole magnet and three scintillating fibre tracking stations downstream of the magnet. The whole photon detection system of the RICH detectors has been renewed and the readout electronics of the calorimeter and muon systems have been fully overhauled. The first stage of the all-software trigger is implemented on a GPU farm. The output of the trigger provides a combination of totally reconstructed physics objects, such as tracks and vertices, ready for final analysis, and of entire events which need further offline reprocessing. This scheme required a complete revision of the computing model and rewriting of the experiment's software