517 research outputs found

    A new method for the q2q^2 reconstruction in semileptonic decays at LHCb based on machine learning

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    The neutrino closure method is often used to obtain kinematics of semileptonic decays with one unreconstructed particle. The kinematics of decays can be deducted by a two-fold ambiguity with a quadratic equation. To resolve the two-fold ambiguity, a new method based on Machine Learning (ML) is proposed. We study the effect of different sets of features and regressors on the improvement of reconstructed invariant mass squared of â„“Îœ\ell \nu system~(q2q^2). The result shows that the best performance is obtained by using the flight vector as the features, and the multilayer perceptron (MLP) model as the regressor. Compared with the random choice, the MLP model improves the resolution of reconstructed q2q^2 by ∌\sim40\%. Furthermore, the possibility of using this method on various semileptonic decays is shown

    CPV search in charm sector at LHCb

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    LHCb HLT2: Real-time alignment, calibration, and software quality-assurance

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    LHCb's second level trigger, deployed on a CPU server farm, not only selects events but performs an offline-quality alignment and calibration of the detector and uses this information to allow physics analysts to deploy essentially their full offline analysis level selections (including computing isolation, flavour tagging, etc) at the trigger level. This “real time analysis” concept has also allowed LHCb to fully unify its online and offline software codebases. We cover the design and performance of the system which will be deployed in Run 3, with particular attention to the software engineering aspects, particularly with respect to quality assurance and testing/limiting failure modes

    Recent results on CPCP Violation in Charm sector by LHCb

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    These proceedings present a measurement of the mass difference between neutral charm meson mass eigenstates, a search for time-dependent CP violation in neutral charm meson decays and the first observation of CP violation in charm hadrons decays

    Monitoring reconstruction software in LHCb

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    The LHCb detector at the LHC is currently undergoing a major upgrade to increase its full detector read-out rate to 30 MHz. In addition to the detector hardware modernisation, the new trigger system will be software-only. The code base of the new trigger system must be thoroughly tested for data flow, functionality and physics performance. Currently, the testing procedure is based on a system of nightly builds and continuous integration tests of each new code development. The continuous integration tests are now extended to test and evaluate high-level quantities related to LHCb’s physics program, such as track reconstruction and particle identification, which is described in this paper. Before each merge request, the differences after the change in code are shown and automatically compared using an interactive visualisation tool, allowing easy verification of all relevant quantities. This approach gives an extensive control over the physics performance of the new code resulting into better preparation for data taking with the upgraded LHCb detector at Run 3