Бочарников Владимир Олегович

Measurement of the Λ c + Λ c + ​ to D 0 0 production ratio in periphera PbPb collisions at s NN s NN ​ ​ = 5.02 TeV

2024 · ARTICLE · en

We report on a measurement of the Λc+ to D0 production ratio in peripheral PbPb collisions at sNN = 5.02 TeV with the LHCb detector in the forward rapidity region 2 4.5. The Λc+ (D0) hadrons are reconstructed via the decay channel Λc+ → pK−π+ (D0 → K−π+) for 2 T 8 GeV/c and in the centrality range of about 65–90%. The results show no significant dependence on pT, y or the mean number of participating nucleons. They are also consistent with similar measurements obtained by the LHCb collaboration in pPb and Pbp collisions at sNN = 5.02 TeV. The data agree well with predictions from PYTHIA in pp collisions at s = 5 TeV but are in tension with predictions of the Statistical Hadronization model.

Search for the rare hadronic decay Bs0->pp

2023 · ARTICLE · en

A search for the rare hadronic decay B0s→p¯p is performed using proton-proton collision data recorded by the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 6 fb−1. No evidence of the decay is found and an upper limit on its branching fraction is set at B(B0s→p¯p)

Test of lepton flavor universality using B0→D*-τ+ντ decays with hadronic τ channels

2023 · ARTICLE · en

The branching fraction B(B0→D*−τ+ντ) is measured relative to that of the normalization mode B0→D*−π+π−π+ using hadronic τ+→π+π−π+(π0)¯ντ decays in proton-proton collision data at a center-of-mass energy of 13 TeV collected by the LHCb experiment, corresponding to an integrated luminosity of 2 fb−1. The measured ratio is B(B0→D*−τ+ντ)/B(B0→D*−π+π−π+)=1.70±0.10+0.11−0.10, where the first uncertainty is statistical and the second is related to systematic effects. Using established branching fractions for the B0→D*−π+π−π+ and B0→D*−μ+νμ modes, the lepton universality test R(D*−)≡B(B0→D*−τ+ντ)/B(B0→D*−μ+νμ) is calculated, R(D*−)=0.247±0.015±0.015±0.012, where the third uncertainty is due to the uncertainties on the external branching fractions. This result is consistent with the Standard Model prediction and with previous measurements.

Search for D∗(2007)0 → μ+μ− in B− → π−μ+μ− decays

2023 · ARTICLE · en

The very rare D∗(2007)0 ⁣→μ+μ−{{D} ^*} (2007)^0\!\rightarrow {\mu ^+\mu ^-} D∗(2007)0→μ+μ− decay is searched for by analysing B− ⁣→π−μ+μ−{{{B} ^-}} \!\rightarrow {{\pi } ^-} {\mu ^+\mu ^-} B−→π−μ+μ− decays. The analysis uses a sample of beauty mesons produced in proton–proton collisions collected with the LHCb detector between 2011 and 2018, corresponding to an integrated luminosity of 9 fb−1\text {\,fb} ^{-1}fb−1. The signal signature corresponds to simultaneous peaks in the μ+μ−{\mu ^+\mu ^-} μ+μ− and π−μ+μ−{{\pi } ^-} {\mu ^+\mu ^-} π−μ+μ− invariant masses. No evidence for an excess of events over background is observed and an upper limit is set on the branching fraction of the decay at B(D∗(2007)0 ⁣→μ+μ−)

Observation of the B+→Jψη′K+ decay

2023 · ARTICLE · en

The B+ →Jψη′K+ decay is observed for the first time using proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7, 8, and 13 TeV, corresponding to a total integrated luminosity of 9 fb−1. The branching fraction of this decay is measured relative to the known branching fraction of the B+ →ψ(2S)K+ decay and found to beBB+→Jψη′K+BB+→ψ2SK+=4.91±0.47±0.29±0.07×10−2

Neutron reconstruction in the BM@N experiment using machine learning

2023 · CHAPTER · en

At present, new compact highly granular neutron detector is being developed for the BM@N experiment. This detector will be used to identify neutrons, to measure their energies using time-of-flight method, neutron yields and azimuthal flow of neutrons in heavy-ion collisions at beam energies up to 4A GeV. Application of machine learning techniques and preliminary results of neutron identification and energy reconstruction are discussed. First predictions of the anisotropic flow of neutrons using state-of-the-art models of heavy-ion collisions are shown.

Search for CP violation in the phase space of D0 → π−π+π0 decays with the energy test

2023 · ARTICLE · en

A search for CP violation in D0 → π−π+π0 decays is reported, using pp collision data collected by the LHCb experiment from 2015 to 2018 corresponding to an integrated luminosity of 6 fb−1. An unbinned model-independent approach provides sensitivity to local CP violation within the two-dimensional phase space of the decay. The method is validated using the Cabibbo-favoured channel D0 → K−π+π0 and background regions of the signal mode. The results are consistent with CP symmetry in this decay.

Exploring the structure of hadronic showers and the hadronic energy reconstruction with highly granular calorimeters

2022 · CHAPTER · en

Analysis of testbeam data of the highly granular RPC-steel CALICE digital hadron calorimeter and validation of GEANT4 Monte Carlo models

2019 · ARTICLE · en

We present a study of the response of the highly granular Digital Hadronic Calorimeter with steel absorbers, the Fe-DHCAL, to positrons, muons, and pions with momenta ranging from 2 to 60GeV/c. Developed in the context of the CALICE collaboration, this hadron calorimeter utilises Resistive Plate Chambers as active media, interspersed with steel absorber plates. With a transverse granularity of 1×1cm2 and a longitudinal segmentation of 38 layers, the calorimeter counted 350,208 readout channels, each read out with single-bit resolution (digital readout). The data were recorded in the Fermilab test beam in 2010–11. The analysis includes measurements of the calorimeter response and the energy resolution to positrons and muons, as well as detailed studies of various shower shape quantities. The results are compared to simulations based on GEANT4, which utilise different electromagnetic and hadronic physics lists. © 2019 Elsevier B.V.

Characterisation of different stages of hadronic showers using the CALICE Si-W ECAL physics prototype

2019 · ARTICLE · en

A detailed investigation of hadronic interactions is performed using π−-mesons with energies in the range 2–10 GeV incident on a high granularity silicon–tungsten electromagnetic calorimeter. The data were recorded at FNAL in 2008. The region in which the π−-mesons interact with the detector material and the produced secondary particles are characterised using a novel track-finding algorithm that reconstructs tracks within hadronic showers in a calorimeter in the absence of a magnetic field. The principle of carrying out detector monitoring and calibration using secondary tracks is also demonstrated.