UNSUPERVISED PROBABILISTIC ANOMALY DETECTION OVER NOMINAL SUBSYSTEM EVENTS THROUGH A HIERARCHICAL VARIATIONAL AUTOENCODER

This work develops a versatile approach to discover anomalies in operational data for nominal (i.e., non-parametric) subsystem event signals using unsupervised Deep Learning techniques. Firstly, it builds a neural convolutional framework to extract both intrasubsystem and intersubsystem patterns. This is done by applying banks of voxel filters on the charted data. Secondly, it generalizes the learned embedded regularity of a Variational Autoencoder manifold by merging latent space-overlapping deviations with non-overlapping synthetic irregularities. Contingencies like novel data, model drift, etc., are therefore seamlessly managed by the proposed data-augmented approach. Finally, it creates a smooth diagnosis probabilistic function on the ensuing low-dimensional distributed representation. The resulting enhanced solution warrants analytically strong tools for a critical industrial environment. It also facilitates its hierarchical integrability, and provides visually interpretable insights of the degraded condition hazard to increase the confidence in its predictions. This strategy has been validated with eight pairwise-interrelated subsystems from high-speed trains. Its outcome also leads to further reliable explainability from a causal perspective

Measurement of CP violation in B-0 -> D+D- decays

The CP violation observables S and C in the decay channel B-0 -> D+D- are determined from a sample of proton-proton collisions at center-of-mass energies of 7 and 8 TeV, collected by the LHCb experiment and corresponding to an integrated luminosity of 3 fb(-1). The observable S describes CP violation in the interference between mixing and the decay amplitude, and C parametrizes direct CP violation in the decay. The following values are obtained from a flavor-tagged, decay-time-dependent analysis: S = -0.54(-0.16)(+0.17) (stat) +/- 0.05(syst) ,C=0.26(-0.17)(+0.18) (stat) +/- 0.02(syst). These values provide evidence for CP violation at a significance level of 4.0 standard deviations. The phase shift due to higher-order standard model corrections is constrained to a small value of Delta phi = -0.16(-0.21)(+0.19) rad

Preliminary Performance Study of an Alternative Calorimeter Clustering Solution for Allen in LHCb

The LHCb experiment has recently started a new period of data taking after a major upgrade in both software and hardware. One of the biggest challenges has been the migration of the first part of the trigger system into a parallel GPU architecture framework called Allen, which performs a partial reconstruction of most of the LHCb sub-detectors. In Allen, the reconstruction of the Electromagnetic Calorimeter (ECAL) sub-detector is used in many selection algorithms, but its efficiency is currently 10% lower than the full reconstruction performed in the second stage of the trigger. In this work, we present a preliminary performance study of an alternative ECAL reconstruction algorithm implemented in Allen that complements the current algorithm to maximise the reconstruction efficiency and also minimise the impact on the throughput rate

Search for the Lepton-Flavor-Violating Decays Bs0 →τ±μâ' and B0 →τ±μâ'

Results are reported from a search for the rare decays Bs0→τ±μâ' and B0→τ±μâ', where the τ lepton is reconstructed in the channel τ-→π-π+π-ντ. These processes are effectively forbidden in the standard model, but they can potentially occur at detectable rates in models of new physics that can induce lepton-flavor-violating decays. The search is based on a data sample corresponding to 3 fb-1 of proton-proton collisions recorded by the LHCb experiment in 2011 and 2012. The event yields observed in the signal regions for both processes are consistent with the expected standard model backgrounds. Because of the limited mass resolution arising from the undetected τ neutrino, the Bs0 and B0 signal regions are highly overlapping. Assuming no contribution from B0→τ±μâ', the upper limit B(Bs0→τ±μâ')<4.2×10-5 is obtained at 95% confidence level. If no contribution from Bs0→τ±μâ' is assumed, a limit of B(B0→τ±μâ')<1.4×10-5 is obtained at 95% confidence level. These results represent the first limit on B(Bs0→τ±μâ') and the most stringent limit on B(B0→τ±μâ')

First Measurement of Charm Production in its Fixed-Target Configuration at the LHC

The first measurement of heavy-flavor production by the LHCb experiment in its fixed-target mode is presented. The production of J / ψ and D 0 mesons is studied with beams of protons of different energies colliding with gaseous targets of helium and argon with nucleon-nucleon center-of-mass energies of √ s NN = 86.6 and 110.4 GeV, respectively. The J / ψ and D 0 production cross sections in p He collisions in the rapidity range [2, 4.6] are found to be σ J / ψ = 652 ± 33 ( stat ) ± 42 ( syst )       nb / nucleon and σ D 0 = 80.8 ± 2.4 ( stat ) ± 6.3 ( syst )     μ b / nucleon , where the first uncertainty is statistical and the second is systematic. No evidence for a substantial intrinsic charm content of the nucleon is observed in the large Bjorken- x region

Highlights from the LHCb experiment

We report recent results by the LHCb collaboration in heavy-ion collisions in collider and fixed-target mode at the LHC. A large variety of measurements show the potential of LHCb in nuclear collisions

Measurement of the Ωc0 Baryon Lifetime

We report a measurement of the lifetime of the Ω 0 c baryon using proton-proton collision data at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3.0     fb − 1 collected by the LHCb experiment. The sample consists of about 1000     Ω − b → Ω 0 c μ − ¯ ν μ X signal decays, where the Ω 0 c baryon is detected in the p K − K − π + final state and X represents possible additional undetected particles in the decay. The Ω 0 c lifetime is measured to be τ Ω 0 c = 268 ± 24 ± 10 ± 2     fs , where the uncertainties are statistical, systematic, and from the uncertainty in the D + lifetime, respectively. This value is nearly four times larger than, and inconsistent with, the current world-average value

Measurement of psi (2S) production cross-sections in proton-proton collisions at v s=7 and 13 TeV

The cross-sections of ψ(2S) meson production in proton-proton collisions at √ s = 13 TeV are measured with a data sample collected by the LHCb detector corresponding to an integrated luminosity of 275 pb−1. The production cross-sections for prompt ψ(2S) mesons and those for ψ(2S) mesons from b-hadron decays (ψ(2S)-from-b) are determined as functions of the transverse momentum, pT, and the rapidity, y, of the ψ(2S) meson in the kinematic range 2 < pT < 20 GeV/c and 2.0 < y < 4.5. The production cross-sections integrated over this kinematic region are σ(prompt ψ(2S), 13 TeV) = 1.430 ± 0.005 (stat) ± 0.099 (syst) μb, σ(ψ(2S)-from-b, 13 TeV) = 0.426 ± 0.002 (stat) ± 0.030 (syst) μb. A new measurement of ψ(2S) production cross-sections in pp collisions at √ s = 7 TeV is also performed using data collected in 2011, corresponding to an integrated luminosity of 614 pb−1. The integrated production cross-sections in the kinematic range 3.5 < pT < 14 GeV/c and 2.0 < y < 4.5 are σ(prompt ψ(2S),7 TeV) = 0.471 ± 0.001 (stat) ± 0.025 (syst) μb, σ(ψ(2S)-from-b,7 TeV) = 0.126 ± 0.001 (stat) ± 0.008 (syst) μb. All results show reasonable agreement with theoretical calculations

Measurement of Angular and CP Asymmetries in D0 →π+π-μ+μ- and D0 →k+K-μ+μ- Decays

The first measurements of the forward-backward asymmetry of the dimuon pair ( A FB ), the triple-product asymmetry ( A 2 ϕ ), and the charge-parity-conjugation asymmetry ( A C P ), in D 0 → π + π − μ + μ − and D 0 → K + K − μ + μ − decays are reported. They are performed using data from proton-proton collisions collected with the LHCb experiment from 2011 to 2016, corresponding to a total integrated luminosity of 5     fb − 1 . The asymmetries are measured to be A FB ( D 0 → π + π − μ + μ − ) = ( 3.3 ± 3.7 ± 0.6 ) % , A 2 ϕ ( D 0 → π + π − μ + μ − ) = ( − 0.6 ± 3.7 ± 0.6 ) % , A C P ( D 0 → π + π − μ + μ − ) = ( 4.9 ± 3.8 ± 0.7 ) % , A FB ( D 0 → K + K − μ + μ − ) = ( 0 ± 11 ± 2 ) % , A 2 ϕ ( D 0 → K + K − μ + μ − ) = ( 9 ± 11 ± 1 ) % , A C P ( D 0 → K + K − μ + μ − ) = ( 0 ± 11 ± 2 ) % , where the first uncertainty is statistical and the second systematic. The asymmetries are also measured as a function of the dimuon invariant mass. The results are consistent with the standard model predictions

Measurement of charged hadron production in Z-tagged jets in proton-proton collisions at s√=8 TeV

The production of charged hadrons within jets recoiling against a Z boson is measured in proton-proton collision data at ffiffi s p ¼ 8 TeV recorded by the LHCb experiment. The charged-hadron structure of the jet is studied longitudinally and transverse to the jet axis for jets with transverse momentum pT > 20 GeV and in the pseudorapidity range 2.5 < η < 4. These are the first measurements of jet hadronization at these forward rapidities and also the first where the jet is produced in association with a Z boson. In contrast to previous hadronization measurements at the Large Hadron Collider, which are dominated by gluon jets, these measurements probe predominantly light-quark jets which are found to be more longitudinally and transversely collimated with respect to the jet axis when compared to the previous gluon dominated measurements. Therefore, these results provide valuable information on differences between quarks and gluons regarding nonperturbative hadronization dynamics