Бочарников Владимир Олегович

Neutron Reconstruction in the BM@N Experiment Using Machine Learning

2024 · CHAPTER · en

Observation of muonic Dalitz decays of chib mesons and precise spectroscopy of hidden-beauty states

2024 · ARTICLE · en

The decays of the χb1(1P), χb2(1P), χb1(2P) and χb2(2P) mesons into the Υ(1S)μ+μ− final state are observed with a high significance using proton-proton collision data collected with the LHCb detector and corresponding to an integrated luminosity of 9 fb−1. The newly observed decays together with the Υ(2S) → Υ(1S)π+π− and Υ(3S) → Υ(2S)π+π− decay modes are used for precision measurements of the mass and mass splittings for the hidden-beauty states.

Search for the rare decay of charmed baryon Λ c + into the p μ + μ - final state

2024 · ARTICLE · en

A search for the nonresonant Λc+→pμ+μ- decay is performed using proton-proton collision data recorded at a center-of-mass energy of 13 TeV by the LHCb experiment, corresponding to an integrated luminosity of 5.4 fb-1. No evidence for the decay is found in the dimuon invariant-mass regions where the expected contributions of resonances is subdominant. The upper limit on the branching fraction of the Λc+→pμ+μ- decay is determined to be 2.9(3.2)×10-8 at 90%(95%) confidence level. The branching fractions in the dimuon invariant-mass regions dominated by the η, ρ and ω resonances are also determined.

Precision measurement of the Ξ− 𝑏 baryon lifetime

2024 · ARTICLE · en

A sample of 𝑝⁢𝑝 collision data, corresponding to an integrated luminosity of 5.5 fb−1 and collected by the LHCb experiment during LHC Run 2, is used to measure the ratio of the lifetime of the Ξ−𝑏 baryon to that of the Λ0𝑏 baryon, 𝑟𝜏 ≡𝜏Ξ−𝑏/𝜏Λ0𝑏. The value 𝑟𝜏 =1.076 ±0.013 ±0.006 is obtained, where the first uncertainty is statistical and the second systematic. This value is averaged with the corresponding value from Run 1 to obtain 𝑟Run 1,2𝜏 =1.078 ±0.012 ±0.007. Multiplying by the world-average value of the Λ0𝑏 lifetime yields 𝜏Run 1,2Ξ−𝑏=1.578±0.018±0.010±0.011 ps, where the uncertainties are statistical, systematic, and due to the limited knowledge of the Λ0𝑏 lifetime. This measurement improves the precision of the current world average of the Ξ−𝑏 lifetime by about a factor of 2, and is in good agreement with the most recent theoretical predictions.

Observation of New Charmonium or Charmoniumlike States in Decays

2024 · ARTICLE · en

A study of resonant structures in and 𝐵+→𝐷*−⁢𝐷+⁢𝐾+ decays is performed, using proton-proton collision data at center-of-mass energies of √𝑠 =7, 8, and 13 TeV recorded by the LHCb experiment, corresponding to an integrated luminosity of 9 fb−1. A simultaneous amplitude fit is performed to the two channels with contributions from resonances decaying to 𝐷*−⁢𝐷+ and 𝐷*+⁢𝐷− states linked by 𝐶 parity. This procedure allows the 𝐶 parities of resonances in the 𝐷*±⁢𝐷∓ mass spectra to be determined. Four charmonium or charmoniumlike states are observed decaying into 𝐷*±⁢𝐷∓: 𝜂𝑐⁡(3945), ℎ𝑐⁡(4000), 𝜒𝑐⁢1⁡(4010), and ℎ𝑐⁡(4300), with quantum numbers 𝐽𝑃⁢𝐶 equal to 0−+, 1+−, 1++, and 1+−, respectively. At least three of these states have not been observed previously. In addition, the existence of the 𝑇*¯𝑐⁢¯𝑠⁢0⁢(2870)0 and 𝑇*¯𝑐⁢¯𝑠⁢1⁢(2900)0 resonances in the 𝐷−⁢𝐾+ mass spectrum, already observed in the 𝐵+→𝐷+⁢𝐷−⁢𝐾+ decay, is confirmed in a different production channel.

Amplitude analysis of the radiative decay B s 0 B s 0 ​ → K + + K − − γ

2024 · ARTICLE · en

A search for radiative decay of Bs0 mesons to orbitally excited K+K− states is performed using proton proton collisions recorded by the LHCb experiment, corresponding to an integrated luminosity of 9 fb−1. The dikaon spectrum in the mass range mKK c2 is dominated by the ϕ(1020) resonance that accounts for almost 70% of the decay rate. Considering the possible contributions of f2(1270), f2′(1525) and f2(2010) meson states, the overall tensor contribution to the amplitude is measured to be F{f2}=16.8±0.5(stat.)±0.7(syst.)%, mostly dominated by the f2′(1525) state. Several statistically equivalent solutions are obtained for the detailed resonant structure depending on whether the smaller amplitudes interfere destructively or constructively with the dominant amplitude. The preferred solution that corresponds to the lowest values of the fit fractions along with constructive interference leads to the relative branching ratio measurement B(Bs0→f2′γ)B(Bs0→ϕγ)=19.4−0.8+0.9(stat.)−0.5+1.4(syst.)±0.5(B)%, where the last uncertainty is due to the ratio of measured branching fractions to the K+K− final state. This result represents the first observation of the radiative Bs0→f2′(1525)γ decay, which is the second radiative transition observed in the Bs0 sector.

Search for the lepton-flavor violating decay 𝐵0𝑠 →𝜙⁢𝜇±⁢𝜏∓

2024 · ARTICLE · en

A search for the lepton-flavor violating decays is presented, using a sample of proton-proton collisions at center-of-mass energies of 7, 8, and 13 TeV, collected with the LHCb detector and corresponding to a total integrated luminosity of 9 fb−1. The 𝜏 leptons are selected using decays with three charged pions. No significant excess is observed, and an upper limit on the branching fraction is determined to be ℬ⁡(𝐵0𝑠→𝜙⁢𝜇±⁢𝜏∓)

Transverse polarization measurement of Λ hyperons in pNe collisions at = 68.4 GeV with the LHCb detector

2024 · ARTICLE · en

A measurement of the transverse polarization of the Λ and Λ¯ hyperons in pNe fixed-target collisions at sNN = 68.4 GeV is presented using data collected by the LHCb detector. The polarization is studied using the decay Λ → pπ− together with its charge conjugated process, the integrated values measured are PΛ=0.029±0.019(stat)±0.012(syst),PΛ¯=0.003±0.023(stat)±0.014(syst). Furthermore, the results are shown as a function of the Feynman x variable, transverse momentum, pseudorapidity and rapidity of the hyperons, and are compared with previous measurements.

Measurement of the longitudinal polarization in decays

2024 · ARTICLE · en

The longitudinal polarization fraction of the meson is measured in decays, where the lepton decays to three charged pions and a neutrino, using proton-proton collision data collected by the LHCb experiment at center-of-mass energies of 7, 8 and 13 TeV and corresponding to an integrated luminosity of . The polarization fraction is measured in two regions, below and above , where is defined as the squared invariant mass of the system. The values are measured to be and for the lower and higher regions, respectively. The first uncertainties are statistical and the second systematic. The average value over the whole range is . These results are compatible with the Standard Model predictions.

Test of lepton flavor universality using decays with hadronic 𝜏 channels

2024 · 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 ±0.1⁢0+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.