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2019-03-15
09:54
Machine Learning approach to boosting neutral particles identification in the LHCb calorimeter
Reference: Poster-2019-685
Keywords:  Electromagnetic Calorimeter  Neutral particles identification  Machine learning
Created: 2019. -1 p
Creator(s): Boldyrev, Alexey

We present a new approach to identification of boosted neutral particles using Electromagnetic Calorimeter (ECAL) of the LHCb detector. The identification of photons and neutral pions is currently based on expected properties of the objects reconstructed in the calorimeter. This allows to distinguish single photons in the electromagnetic calorimeter from overlapping photons produced from high momentum $\pi^0$ decays. The proposed approach is based on applying machine learning techniques to primary calorimeter information, that are energies collected in individual cells around the energy cluster. The machine learning model employs extreme gradient boosting trees approach which is widely used nowadays, and separates $\pi^0$ and photon responses from "first principles". This approach allowed to significantly improve separation performance score on simulated data, reducing primary photons fake rate by factor of four. In this presentation we will present the approach, evaluate its performance obtained on MC samples, and discuss specific issues when transferring discriminative models from simulation to real world.

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2019-03-15
09:51
Tracking performance for long-lived particles at LHCb
Reference: Poster-2019-684
Keywords:  LHCb  Data-driven  Downstream  Tracking  Efficiency
Created: 2019. -1 p
Creator(s): Garcia Martin, Luis Miguel

The LHCb experiment is dedicated to the study of the $c$- and $b$-hadrons decays, including long living particles such as $K_s$ and strange baryons ($\Lambda$, $\Xi$, etc... ). These kind of particles are difficult to reconstruct from LHCb tracking systems since they escape the detection in the first tracker. A new method to evaluate the performance in terms of efficiency and throughput of the different tracking algorithms for long living particles have been developed. Special emphasis is laid on particles hitting only part of the tracking system of the new LHCb upgrade detector.

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ACAT 2019
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2019-03-15
09:11
Physics and computing performance of reconstruction algorithms for the GPU High Level Trigger 1 of LHCb
Reference: Poster-2019-683
Keywords:  CERN LHC  LHCb  HLT1  GPU
Created: 2019. -1 p
Creator(s): Vom Bruch, Dorothea

Beginning in 2021, the upgraded LHCb experiment will use a triggerless readout system collecting data at an event rate of 30 MHz. A software-only High Level Trigger will enable unprecedented flexibility for trigger selections. During the first stage (HLT1), a sub-set of the full offline track reconstruction for charged particles is run to select particles of interest based on single or two-track selections. After this first stage, the event rate is reduced by at least a factor 30. Track reconstruction at 30 MHz represents a significant computing challenge, requiring a renovation of current algorithms and the underlying hardware. In this talk we present work based on an R&D project in the context of the LHCb Upgrade I exploring the approach of executing the full HLT1 chain on GPUs. This includes decoding the raw data, clustering of hits, pattern recognition, as well as track fitting. We will discuss the development of algorithms optimized for many-core architectures. Both the computing and physics performance of the full HLT1 chain will be presented.

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ACAT 2019
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2019-02-28
16:29
Search for the lepton-flavour-violating decays $B^+ \rightarrow K^+ e^{\pm}\mu^{\mp}$
Reference: Poster-2019-682
Keywords:  LHCb
Created: 2019. -1 p
Creator(s): Meier, Gerwin

The lepton flavour quantum number is conserved in all processes of the Standard Model of particle physics, and tests of this prediction form an important part of todays particle physics. A large number of models that describe physics beyond the Standard Model include lepton flavour violating processes. One of these is the decay $B^+ \to K^+e^\pm\mu^\mp$, which some models predicted up top a measurable magnitude of $10^{-8}$. This poster presents the current status of the search for the lepton flavour violating decay $B^+ \to K^+e^\pm\mu^\mp$ with the LHCb Run 1 data corresponding to 3 fb$^{−1}$. The sensitivity of the measurement is expected to enter the interesting territory.

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2019-02-28
16:04
Future upgrades at LHCb
Reference: Poster-2019-681
Keywords:  LHCb
Created: 2019. -1 p
Creator(s): Denysenko, Vadym

The LHCb Collaboration is planning an Upgrade II, a flavour physics experiment for the high luminosity era. This will be installed in LS4 (2030) and targets an instantaneous luminosity of 1 to $2x10^{34}$cm$^-2$ $s^{-1}$, and an integrated luminosity of at least 300fb$^{-1}$. Modest consolidation of the current experiment are also planned for LS3 (2025). This talk are presenting an overview of the LHCb plans for Upgrade II.

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2019-02-28
15:59
CompassUT : study of a GPU track reconstruction for LHCb upgrades
Reference: Poster-2019-680
Keywords:  LHCb
Created: 2019. -1 p
Creator(s): Fernandez Declara, Placido

We present a fast, data-oriented GPU tracking algorithm, CompassUT, as a potential option to cope with the expected throughput of 40Tbit/s for LHCb upgrade. We present a parallel version of the raw input decoding, optimized for SIMD architectures. We sort the hits by X and Y into group sectors while decoding, to have a fast sorting and searching of the hits. We implement the tracking by reducing the memory footprint, reducing branching to a minimum and making the algorithm data-oriented for SIMD architectures. We show the achieved throughput in a variety of consumer and server GPUs, and present the impact on both the computing and physics performance for different configurations of the algorithm.

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2019-02-28
15:55
Study of $\eta_c$ (1S) and $\eta_c$ (2S) production via hadronic decays
Reference: Poster-2019-679
Keywords:  LHCb
Created: 2019. -1 p
Creator(s): Zhovkovska, Valeriia

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2019-02-28
15:50
Observation of $B^0_{(s)} \rightarrow J/\psi p\bar{p}$ decays and precision measurements of the $B^0_{(s)}$ masses
Reference: Poster-2019-678
Keywords:  LHCb
Created: 2019. -1 p
Creator(s): Spadaro Norella, Elisabetta

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.

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2019-02-28
15:32
Measurement of CP violating phase $\varphi_s$ in $B^0_s \rightarrow J/\psi h^+h^-$ Decays at LHCb
Reference: Poster-2019-677
Keywords:  LHCb
Created: 2019. -1 p
Creator(s): Zonneveld, Jennifer Brigitta

The measurement of the CP violating phase $\phi_s$ is one of the key goals of the LHCb experiment. A time-dependent amplitude analysis of $B^-0_s \rightarrow J/\psi h^+ h^-$ decays allows the determination of this theoretically precisely predicted phase. New Physics could significantly affect the measured $\phi_s$ value, making it experimentally very interesting. This poster shows the Run 1 analyses results, and a prospect of the precision that can be expected when analysing data from 2015 and 2016, leading to the the World's most precise determination of $\phi_s$.

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2019-02-28
15:07
Study of the decay $B^0 \rightarrow \rho^0K^*(892)^0$
Reference: Poster-2019-676
Keywords:  LHCb
Created: 2019. -1 p
Creator(s): Vieites Diaz, Maria

An amplitude analysis of ${B^0\to (\pi^+\pi^-) (K^+\pi^-)}$ decays is performed in the two-body invariant mass regions ${300 < m(\pi^+\pi^-)<1100}$ MeV/$c^2$, accounting for the $\rho^0$, $\omega$, $f_0(500)$, $f_0(980)$ and $f_0(1370)$ resonances, and ${750 < m(K^+\pi^-)<1200}$ MeV/$c^2$, which is dominated by the $K^{*}(892)^0$ meson. The analysis uses 3 fb$^{-1}$ of proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The $CP$ averages and asymmetries are measured for the magnitudes and phase differences of the contributing amplitudes. The $CP$-averaged longitudinal polarisation fraction of the $B^0\rightarrow \rho K^{*}$ mode is found to be $\tilde{f}^0_{\rho K^{*}} = 0.164 \pm 0.015 \pm 0.022$ and its $CP$ asymmetry $\mathcal{A}^0_{\rho K^{*}} = -0.62 \pm 0.09 \pm 0.09$, where the first uncertainty is statistical and the second systematic.

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