Measurement of CP observables in the process B0 → DK*0 with two- and four-body D decays
Measurements of CP observables in B0 → DK∗0 decays are presented, where D represents a superposition of D0 and 𝐷⎯⎯⎯⎯⎯0D¯0 states. The D meson is reconstructed in the two-body final states K+π−, π+K−, K+K− and π+π−, and, for the first time, in the fourbody final states K+π−π+π−, π+K−π+π− and π+π−π+π−. The analysis uses a sample of neutral B mesons produced in proton-proton collisions, corresponding to an integrated luminosity of 1.0, 2.0 and 1.8 fb−1 collected with the LHCb detector at centre-of-mass energies of 𝑠√=7,8s=7,8 and 13 TeV, respectively. First observations of the decays B0 → D(π+K−)K∗0 and B0 → D(π+π−π+π−)K∗0 are obtained. The measured observables are interpreted in terms of the CP -violating weak phase γ.
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.
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.
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.