Measurement of CP violation in B0→ D∗±D∓ decays
The decay-time-dependent CP asymmetry in B0→D∗±D∓ decays is measured using a data set corresponding to an integrated luminosity of 9fb−1 recorded by the LHCb detector in proton-proton collisions at centre-of-mass energies of 7, 8 and 13 TeV. The CP parameters are measured as
The analysis provides the most precise single measurement of CP violation in this decay channel to date. All parameters are consistent with their current world average values.
Simulation is one of the key components in high energy physics. Historically it relies on the Monte Carlo methods which require a tremendous amount of computation resources. These methods may have difficulties with the expected High Luminosity Large Hadron Collider need, so the experiment is in urgent need of new fast simulation techniques. The application of Generative Adversarial Networks is a promising solution to speed up the simulation while providing the necessary physics performance. In this paper we propose the Self-Attention Generative Adversarial Network as a possible improvement of the network architecture. The application is demonstrated on the performance of generating responses of the LHCb type of the electromagnetic calorimeter.
The 25th International Conference on Computing in High Energy and Nuclear Physics (CHEP), organised by CERN, took place as a virtual event from 17–21 May 2021. The conference attracted 1144 registered participants from 46 different countries. There were 207 scientific presentations made over the 5 days of the conference. These were divided between 30 long talks and 2 keynotes, which were presented in plenary sessions; and 175 short talks, which were presented in parallel sessions.
The production of ϒ(nS) mesons (n = 1, 2, 3) in pPb and Pbp collisions at a centre-of-mass energy per nucleon pair 𝑠NN‾‾‾‾√=8.16sNN=8.16 TeV is measured by the LHCb experiment, using a data sample corresponding to an integrated luminosity of 31.8 nb−1−1. The ϒ(nS) mesons are reconstructed through their decays into two opposite-sign muons. The measurements comprise the differential production cross-sections of the ϒ(1S) and ϒ(2S) states, their forward-to-backward ratios and nuclear modification factors. The measurements are performed as a function of the transverse momentum p𝑇T and rapidity in the nucleon-nucleon centre-of-mass frame y∗∗ of the ϒ(nS) states, in the kinematic range p𝑇T < 25 GeV/c and 1.5 < y∗∗ < 4.0 (−5.0 < y∗∗ < −2.5) for pPb (Pbp) collisions. In addition, production cross-sections for ϒ(3S) are measured integrated over phase space and the production ratios between all three ϒ(nS) states are determined. Suppression for bottomonium in proton-lead collisions is observed, which is particularly visible in the ratios. The results are compared to theoretical models.
During LHC Run 1, the LHCb experiment recorded around 1011 collision events. This paper describes Event Index — an event search system. Its primary function is to quickly select subsets of events from a combination of conditions, such as the estimated decay channel or number of hits in a subdetector. Event Index is essentially Apache Lucene  optimized for read-only indexes distributed over independent shards on independent nodes.
The 𝐵0𝑠⎯⎯⎯⎯⎯⎯⎯→𝜒𝑐2𝐾+𝐾−Bs0¯→χc2K+K− decay mode is observed and its branching fraction relative to the corresponding 𝜒𝑐1χc1decay mode, in a ±15MeV/𝑐2±15MeV/c2 window around the 𝜙ϕ mass, is found to be (𝐵0𝑠⎯⎯⎯⎯⎯⎯⎯→𝜒𝑐2𝐾+𝐾−)(𝐵0𝑠⎯⎯⎯⎯⎯⎯⎯→𝜒𝑐1𝐾+𝐾−)=(17.1±3.1±0.4±0.9)%,B(Bs0¯→χc2K+K−)B(Bs0¯→χc1K+K−)=(17.1±3.1±0.4±0.9)%, where the first uncertainty is statistical, the second systematic and the third due to the knowledge of the branching fractions of radiative 𝜒𝑐χc decays. The decay mode 𝐵0𝑠⎯⎯⎯⎯⎯⎯⎯→𝜒𝑐1𝐾+𝐾−Bs0¯→χc1K+K− allows the 𝐵0𝑠Bs0 mass to be measured as 𝑚(𝐵0𝑠)=5366.83±0.25±0.27MeV/𝑐2,m(Bs0)=5366.83±0.25±0.27MeV/c2,where the first uncertainty is statistical and the second systematic. A combination of this result with other LHCb determinations of the 𝐵0𝑠Bs0 mass is made.
The dynamics of a two-component Davydov-Scott (DS) soliton with a small mismatch of the initial location or velocity of the high-frequency (HF) component was investigated within the framework of the Zakharov-type system of two coupled equations for the HF and low-frequency (LF) fields. In this system, the HF field is described by the linear Schrödinger equation with the potential generated by the LF component varying in time and space. The LF component in this system is described by the Korteweg-de Vries equation with a term of quadratic influence of the HF field on the LF field. The frequency of the DS soliton`s component oscillation was found analytically using the balance equation. The perturbed DS soliton was shown to be stable. The analytical results were confirmed by numerical simulations.
Radiation conditions are described for various space regions, radiation-induced effects in spacecraft materials and equipment components are considered and information on theoretical, computational, and experimental methods for studying radiation effects are presented. The peculiarities of radiation effects on nanostructures and some problems related to modeling and radiation testing of such structures are considered.