Tadeusz Kościuszko University of Technology

Abstract: This article presents a new hybrid model for analysing the dynamics of a railway track subjected to excitations generated by a rail vehicle, taking into account the dynamic forces at the wheel-rail interface. It is demonstrated that combining a multi-body force generator with a continuous multi-layer analytical model of the railway track is feasible and enables the analysis of both time-varying forces generated by the vehicle and the response of the track surface depending on the values of the mechanical parameters of the structure. The model of mechanical vibrations of the track in the vertical direction is solved using a semi- analytical approximation method using wavelet filters. Combined with a force description obtained by modelling the mass system corresponding to the vehicle, this represents a novel approach to the parametric analysis of track response. Keywords: rail track; rail vehicle; wheel-rail contact forces; hybrid model

Searches are presented for B c + → D h + h − decays, where D is a charmed meson and h ± is a charged pion or kaon, using p p collision data collected by the LHCb experiment corresponding to an integrated luminosity of 9 fb − 1 . The decays B c + → D + K + π − , B c + → D * + K + π − , and B c + → D s + K + K − are observed for the first time. Their branching fractions, expressed as ratios relative to that of the B c + → B s 0 π + decay, are determined to be R ( B c + → D + K + π − ) = ( 1.96 ± 0.23 ± 0.08 ± 0.10 ) × 10 − 3 , R ( B c + → D * + K + π − ) = ( 3.67 ± 0.55 ± 0.24 ± 0.20 ) × 10 − 3 , R ( B c + → D s + K + K − ) = ( 1.61 ± 0.35 ± 0.13 ± 0.07 ) × 10 − 3 , where the first uncertainty is statistical, the second is systematic, and the third is due to the limited precision on the D -meson branching fractions. The decay channels proceed primarily through excited K 0 or D 0 resonances or ϕ mesons, and open a new avenue for studies of charge-parity violation in beauty mesons.

This paper presents a study of the charmless three-body decays B_(s)^0→K_S^0h^+h'^- (where h(′) = π, K), using a sample of pp collision data collected by the LHCb experiment during Runs 1 and 2 of the LHC, corresponding to an integrated luminosity of 9 fb−1. The decay B_s^0→K_S^0K^+K^- is observed for the first time, and the following ratios of branching fractions are measured: [ ℬ(B^0→K_S^0K^+K^-)/ℬ(B^0→K_S^0π^+π^-)=0.578± 0.007± 0.017,; ℬ(B^0→K_S^0K^±K^∓)/ℬ(B^0→K_S^0π^+π^-)=0.1363± 0.0035± 0.051,; [ ℬ(B_s^0→K_S^0π^+π^-)/ℬ(B^0→K_S^0π^+π^-)=0.269± 0.011± 0.015± 0.008,; ℬ(B_s^0→K_S^0K^+K^-)/ℬ(B^0→K_S^0π^+π^-)=0.0303± 0.0041± 0.0025± 0.0009,; ℬ(B_s^0→K_S^0K^±π^∓)/ℬ(B^0→K_S^0π^+π^-)=1.818± 0.021± 0.031± 0.056, ] ] where the uncertainties are statistical, systematic, and due to knowledge of the ratio of hadronisation fractions of the B_s^0 and B0 mesons, respectively.

Abstract This paper presents a study of the charmless three-body decays B s 0 → K S 0 h + h ′ − $$ {B}_{(s)}^0\to {K}_{\mathrm{S}}^0{h}^{+}h{\prime}^{-} $$ (where h ( ′ ) = π, K), using a sample of pp collision data collected by the LHCb experiment during Runs 1 and 2 of the LHC, corresponding to an integrated luminosity of 9 fb −1. The decay B s 0 → K S 0 K + K − $$ {B}_s^0\to {K}_{\mathrm{S}}^0{K}^{+}{K}^{-} $$ is observed for the first time, and the following ratios of branching fractions are measured: B B 0 → K S 0 K + K − B B 0 → K S 0 π + π − = 0.578 ± 0.007 ± 0.017 , B B 0 → K S 0 K ± K ∓ B B 0 → K S 0 π + π − = 0.1363 ± 0.0035 ± 0.051 , B B s 0 → K S 0 π + π − B B 0 → K S 0 π + π − = 0.269 ± 0.011 ± 0.015 ± 0.008 , B B s 0 → K S 0 K + K − B B 0 → K S 0 π + π − = 0.0303 ± 0.0041 ± 0.0025 ± 0.0009 , B B s 0 → K S 0 K ± π ∓ B B 0 → K S 0 π + π − = 1.818 ± 0.021 ± 0.031 ± 0.056 , $$ {\displaystyle \begin{array}{l}\frac{\mathcal{B}\left({B}^0\to {K}_{\mathrm{S}}^0{K}^{+}{K}^{-}\right)}{\mathcal{B}\left({B}^0\to {K}_{\mathrm{S}}^0{\pi}^{+}{\pi}^{-}\right)}=0.578\pm 0.007\pm 0.017,\\ {}\frac{\mathcal{B}\left({B}^0\to {K}_{\mathrm{S}}^0{K}^{\pm }{K}^{\mp}\right)}{\mathcal{B}\left({B}^0\to {K}_{\mathrm{S}}^0{\pi}^{+}{\pi}^{-}\right)}=0.1363\pm 0.0035\pm 0.051,\\ {}\begin{array}{l}\frac{\mathcal{B}\left({B}_s^0\to {K}_{\mathrm{S}}^0{\pi}^{+}{\pi}^{-}\right)}{\mathcal{B}\left({B}^0\to {K}_{\mathrm{S}}^0{\pi}^{+}{\pi}^{-}\right)}=0.269\pm 0.011\pm 0.015\pm 0.008,\\ {}\frac{\mathcal{B}\left({B}_s^0\to {K}_{\mathrm{S}}^0{K}^{+}{K}^{-}\right)}{\mathcal{B}\left({B}^0\to {K}_{\mathrm{S}}^0{\pi}^{+}{\pi}^{-}\right)}=0.0303\pm 0.0041\pm 0.0025\pm 0.0009,\\ {}\frac{\mathcal{B}\left({B}_s^0\to {K}_{\mathrm{S}}^0{K}^{\pm }{\pi}^{\mp}\right)}{\mathcal{B}\left({B}^0\to {K}_{\mathrm{S}}^0{\pi}^{+}{\pi}^{-}\right)}=1.818\pm 0.021\pm 0.031\pm 0.056,\end{array}\end{array}} $$ where the uncertainties are statistical, systematic, and due to knowledge of the ratio of hadronisation fractions of the B s 0 $$ {B}_s^0 $$ and B 0 mesons, respectively.

Abstract Charged-hadron distributions in heavy-flavor jets are measured in proton-proton collisions at a center-of-mass energy of s = 13 $$ \sqrt{s}=13 $$ TeV collected by the LHCb experiment. Distributions of the longitudinal momentum fraction, transverse momentum, and radial profile of charged hadrons are measured separately in beauty and charm jets. The distributions are compared to those previously measured by the LHCb collaboration in jets produced back-to-back with a Z boson, which in the forward region are primarily light-quark-initiated, to compare the hadronization mechanisms of heavy and light quarks. The observed differences between the heavy- and light-jet distributions are consistent with the heavy-quark dynamics expected to arise from the dead-cone effect, as well as with a hard fragmentation of the heavy-flavor hadron as previously measured in single-hadron fragmentation functions. This measurement provides additional constraints for the extraction of collinear and transverse-momentum-dependent heavy-flavor fragmentation functions and offers another approach to probing the mechanisms that govern heavy-flavor hadronization.