The nuclear modification factor of neutral pions is measured in proton-lead collisions collected at a center-of-mass energy per nucleon of \(8.16~{\rm TeV}\) with the LHCb detector. The \(\pi^0\) ...production cross section is measured differentially in transverse momentum (\(p_{\rm T}\)) for \(1.5<p_{\rm T}<10.0~{\rm GeV}\) and in center-of-mass pseudorapidity (\(\eta_{\rm c.m.}\)) regions \(2.5<\eta_{\rm c.m.}<3.5\) (forward) and \(-4.0<\eta_{\rm c.m.}<-3.0\) (backward) defined relative to the proton beam direction. The forward measurement shows a sizable suppression of \(\pi^0\) production, while the backward measurement shows the first evidence of \(\pi^0\) enhancement in proton-lead collisions at the LHC. Together, these measurements provide precise constraints on models of nuclear structure and particle production in high-energy nuclear collisions.
The first observation of the \(B^0_s\!\to D^{*+}D^{*-}\) decay and the measurement of its branching ratio relative to the \(B^0\!\to D^{*+}D^{*-}\) decay are presented. The data sample used ...corresponds to an integrated luminosity of \(9\,\text{fb}^{-1}\) of proton-proton collisions recorded by the LHCb experiment at centre-of-mass energies of 7, 8 and \(13\,\text{TeV}\) between 2011 and 2018. The decay is observed with more than \(10\) standard deviations and the time-integrated ratio of branching fractions is determined to be \begin{align*} \frac{\mathcal{B}(B^0_s\!\to D^{*+}D^{*-})}{\mathcal{B}(B^0\!\to D^{*+}D^{*-})} = 0.269 \pm 0.032 \pm 0.011 \pm 0.008\, , \end{align*} where the first uncertainty is statistical, the second systematic and the third due to the uncertainty of the fragmentation fraction ratio \(f_s/f_d\). The \(B^0_s\!\to D^{*+}D^{*-}\) branching fraction is calculated to be \begin{align*} \mathcal{B}(B^0_s\!\to D^{*+}D^{*-}) = (2.15 \pm 0.26 \pm 0.09 \pm 0.06 \pm 0.16)\times 10^{-4} \,, \end{align*} where the fourth uncertainty is due to the \(B^0\!\to D^{*+}D^{*-}\)branching fraction. These results are calculated using the average \(B^0_s\) meson lifetime in simulation. Correction factors are reported for scenarios where either a purely heavy or a purely light \(B^0_s\) eigenstate is considered.
The first observation of the \(\Lambda_b^0\to D_s^- p\) decay is presented using proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of \({\sqrt{s}=13 ...\,\textrm{TeV}}\), corresponding to a total integrated luminosity of \(6\,\textrm{fb}^{-1}\). Using the \(\Lambda_b^0\to\Lambda_c^+\pi^-\) decay as the normalisation mode, the branching fraction of the \(\Lambda_b^0\to D_s^- p\) decay is measured to be \({\mathcal{B}(\Lambda_b^0\to D_s^- p)=(12.6 \pm 0.5 \pm 0.3 \pm 1.2 )\times 10^{-6}}\), where the first uncertainty is statistical, the second systematic and the third due to uncertainties in the branching fractions of the \(\Lambda_b^0\to\Lambda_c^+\pi^-\), \(D_s^- \to K^-K^+\pi^-\) and \(\Lambda_c^+\to p K^- \pi^+\) decays.
Resonant structures in the dipion mass spectrum from \(\chi_{c1}(3872)\to\pi^+\pi^- J/\psi\) decays, produced via \(B^+\to K^+\chi_{c1}(3872)\) decays, are analyzed using proton-proton collision data ...collected by the LHCb experiment, corresponding to an integrated luminosity of 9 \(fb^{-1}\). A sizeable contribution from the isospin conserving \(\chi_{c1}(3872)\to\omega J/\psi\) decay is established for the first time, \((21.4\pm2.3\pm2.0)\%\), with a significance of more than \(7.1\sigma\). The amplitude of isospin violating decay, \(\chi_{c1}(3872)\to\rho^0 J/\psi\), relative to isospin conserving decay, \(\chi_{c1}(3872)\to\omega J/\psi\), is properly determined, and it is a factor of six larger than expected for a pure charmonium state.
The ratio of branching fractions of \(B_c^+ \to B_s^0 \pi^+\) and \(B_c^+ \to J/\psi \pi^+\) decays is measured with proton-proton collision data of a centre-of-mass energy of \(13\text{TeV}\). The ...data were collected with the LHCb experiment during 2016--2018, corresponding to an integrated luminosity of \(5.4 \text{fb}^{-1}\). The \(B_s^0\) mesons are reconstructed via the decays \(B_s^0 \to J/\psi \phi\) and \(B_s^0 \to D_s^- \pi^+\). The ratio of branching fractions is measured to be \(\mathcal{B}(B_c^+ \to B_s^0 \pi^+)/\mathcal{B}(B_c^+ \to J/\psi \pi^+) = 91 \pm 10 \pm 8 \pm 3\) where the first uncertainty is statistical, the second is systematic and the third is due to the knowledge of the branching fractions of the intermediate state decays.
A number of 3-oxo and 3-thiosemicarbazono analogues of 1-aryl-1-ethylthio-nonanes and related compounds were synthesized. Solutions of the thiosemicarbazones in deuterochloroform were shown by PMR ...spectroscopy to exist principally in the anti configuration at equilibria except when an ortho-methoxy group was present in the aryl ring. In this case intramolecular hydrogen bonding probably accounts principally for the presence of equal amounts of anti and syn isomers. Evaluation of these compounds for anti-convulsant properties revealed that 1-(2-aminoethylthio)-1-(2-chlorophenyl)nonan-3-one hydrochloride (6a) and sodium 2-(N-acetylamino)-3-1-(2-chlorophenyl)-3-oxononylthiopropionate (6c) were active and thus they could serve as prototype molecules for future development.
The mass difference between the \(\Omega^-_b\) and \(\Xi^-_b\) baryons is measured using proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of ...\(9 \, \text{fb}^{-1}\), and is found to be \begin{equation} m(\Omega^-_b)- m(\Xi^-_b) = 248.54 \pm 0.51 \text{(stat)} \pm 0.38 \text{(syst)} \, \text{MeV}/c^2. \end{equation} The mass of the \(\Omega^-_b\) baryon is measured to be \begin{equation} m(\Omega^-_b)= 6045.9 \pm 0.5 \text{(stat)} \pm 0.6 \text{(syst)} \, \text{MeV}/c^2. \end{equation} This is the most precise determination of the \(\Omega^-_b\) mass to date. In addition, the production rate of \(\Omega^-_b\) baryons relative to that of \(\Xi^-_b\) baryons is measured for the first time in \(pp\) collisions, using an LHCb dataset collected at a center-of-mass energy of \(13 \, \text{TeV}\) and corresponding to an integrated luminosity of \(6\,\text{fb}^{-1}\). Reconstructing beauty baryons in the kinematic region \(2 < \eta < 6\) and \(p_T < 20\,\text{GeV}/c\) with their decays to a \(J/\psi\) meson and a hyperon, the ratio \begin{equation} \frac{f_{\Omega^-_b}}{f_{\Xi^-_b}}\times\frac{\mathcal{B}(\Omega^-_b \to J/\psi \Omega^-)}{\mathcal{B}(\Xi^-_b \to J/\psi \Xi^-)} = 0.120 \pm 0.008 \text{(stat)} \pm 0.008 \text{(syst)}, \end{equation} is obtained, where \(f_{\Omega^-_b}\) and \(f_{\Xi^-_b}\) are the fragmentation fractions of \(b\) quarks into \(\Omega^-_b\) and \(\Xi^-_b\) baryons, respectively, and \(\mathcal{B}\) represents the branching fractions of their respective decays.
For some applications, 3D printed parts usually do not have satisfactory mechanical properties, so to broaden their usage, additive technologies should be combined with the well-known metallurgical ...processes, such as investment and others casting techniques. 3D printing developers persistently introduce new base materials and strengthening fluids which may cause different surface roughness. Therefore, in this paper, the authors have tested the roughness of 3D printed samples strengthened with common, but also with alternative fluids. Measurements proved that fluids do have significant influence on the roughness.
The first observation of the semileptonic \(b\)-baryon decay \( \Lambda_b^0 \rightarrow \Lambda_c^+ \tau^-\overline{\nu}_{\tau}\), with a significance of \(6.1\,\sigma\), is reported using a data ...sample corresponding to 3 fb\(^{-1}\) of integrated luminosity, collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV at the LHC. The \(\tau^-\) lepton is reconstructed in the hadronic decay to three charged pions. The branching fraction \({\mathcal{B}}(\Lambda_b^0 \rightarrow \Lambda_c^+\tau^-\overline{\nu}_{\tau}) = (1.50 \pm 0.16\pm 0.25\pm 0.23)\%\) is obtained, where uncertainties are statistical, systematic and from the external branching fraction of the normalisation channel \(\Lambda_b^0\rightarrow \Lambda_c^+\pi^-\pi^+\pi^-\). The ratio of semileptonic branching fractions \({\mathcal{R}}( \Lambda_c^+)\equiv {\mathcal{B}}( \Lambda_b^0 \rightarrow \Lambda_c^+ \tau^-\overline{\nu}_{\tau})/{\mathcal{B}}( \Lambda_b^0 \rightarrow \Lambda_c^+ \mu^-\overline{\nu}_{\mu})\) is derived to be \(0.242 \pm 0.026 \pm 0.040\pm 0.059\), where the external branching fraction uncertainty from the channel \(\Lambda_b^0\rightarrow \Lambda_c^+\mu^-\overline{\nu}_{\mu}\) contributes to the last term. This result is in agreement with the Standard Model prediction.
