Measurement of the branching fraction of the decay B0s→K0SK0S
A measurement of the branching fraction of the decay B0s→K0SK0S is performed using proton–proton collision data corresponding to an integrated luminosity of 5 fb−1 collected by the LHCb experiment between 2011 and 2016. The branching fraction is determined to be B(B0s→K0SK0S)=[8.3±1.6(stat)±0.9(syst)±0.8(norm)±0.3(fs/fd)]×10−6, where the first uncertainty is statistical, the second is systematic, and the third and fourth are due to uncertainties on the branching fraction of the normalization mode B0→ϕK0S and the ratio of hadronization fractions fs/fd. This is the most precise measurement of this branching fraction to date. Furthermore, a measurement of the branching fraction of the decay B0→K0SK0S is performed relative to that of the B0s→K0SK0S channel, and is found to be B(B0→K0SK0S)B(B0s→K0SK0S)=[7.5±3.1(stat)±0.5(syst)±0.3(fs/fd)]×10−2.
One of the most challenging data analysis tasks of modern High Energy Physics experiments is the identification of particles. In this proceedings we review the new approaches used for particle identification at the LHCb experiment. Machine-Learning based techniques are used to identify the species of charged and neutral particles using several observables obtained by the LHCb sub-detectors. We show the performances of various solutions based on Neural Network and Boosted Decision Tree models.
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
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.
A full amplitude analysis of Λ 0 b → J/ψ pπ− decays is performed with a data sample acquired with the LHCb detector from 7 and 8 TeV pp collisions, corresponding to an integrated luminosity of 3 fb−1 . A significantly better description of the data is achieved when, in addition to the previously observed nucleon excitations N → pπ−, either the Pc(4380)+ and Pc(4450)+ → J/ψ p states, previously observed in Λ 0 b → J/ψ pK− decays, or the Zc(4200)− → J/ψ π− state, previously reported in B0 → J/ψ K+π − decays, or all three, are included in the amplitude models. The data support a model containing all three exotic states, with a significance of more than three standard deviations. Within uncertainties, the data are consistent with the Pc(4380)+ and Pc(4450)+ production rates expected from their previous observation taking account of Cabibbo suppression.
The production of W and Z bosons in association with jets is studied in the forward region of proton-proton collisions collected at a centre-of-mass energy of 8 TeV by the LHCb experiment, corresponding to an integrated luminosity of 1.98 ± 0.02 fb−1 . The W boson is identified using its decay to a muon and a neutrino, while the Z boson is identified through its decay to a muon pair. Total cross-sections are measured and combined into charge ratios, asymmetries, and ratios of W+jet and Z+jet production cross-sections. Differential measurements are also performed as a function of both boson and jet kinematic variables. All results are in agreement with Standard Model predictions.
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.