Substrate Release Mechanisms for Gas Metal Arc 3-D Aluminum Metal Printing. 3D Printing &Additive Manufacturing

International audienceLimited material options, prohibitively expensive equipment, and high production costs currently limit the ability of small and medium enterprises to use 3-D printing to prototype and manufacture metallic goods. A low-cost open-source 3-D metal printer that utilizes gas metal arc welding technology has been developed that could make metal printing accessible to the average consumer. Unfortunately, this technology would demand access to expensive cutting tools for part removal from the substrate. This paper investigates several substrate treatments to provide a low-cost method to easily remove 3-D printed 1100 aluminum parts from a reusable substrate. Coatings of aluminum oxide and boron nitride on 1100 aluminum and A36 low carbon steel substrates were tested. Lap shear tests were performed to assess the interlayer adhesion between the printed metal part and the print substrate. No warping of the substrate was observed during printing. It was determined that boron nitride coated low carbon steel provided the lowest adhesion strength. Printing aluminum on uncoated low carbon steel also allowed easy removal of the aluminum part with the benefit of no additional coating steps or costs

Substrate Release Mechanisms for Gas Metal Arc Weld 3D Aluminum Metal Printing

Limited material options, prohibitively expensive equipment, and high production costs currently limit the ability of small and medium enterprises to use 3D printing to prototype and manufacture metallic goods. A low-cost open-source 3D metal printer that utilizes gas metal arc welding technology has been developed that could make metal printing accessible to the average consumer. Unfortunately, this technology would demand access to expensive cutting tools for part removal from the substrate. This article investigates several substrate treatments to provide a low-cost method to easily remove 3D-printed 1100 aluminum parts from a reusable substrate. Coatings of aluminum oxide and boron nitride on 1100 aluminum and A36 low-carbon steel substrates were tested. Lap shear tests were performed to assess the interlayer adhesion between the printed metal part and the print substrate. No warping of the substrate was observed during printing. It was determined that boron nitride-coated low-carbon steel provided the lowest adhesion strength. Printing aluminum on uncoated low-carbon steel also allowed easy removal of the aluminum part with the benefit of no additional coating steps or costs

Improved measurement of CPCP violation parameters in Bs0→J/ψK+K−B_s^0\to J/\psi K^+K^- decays in the vicinity of the ϕ(1020)\phi(1020) resonance

The decay-time-dependent $CP$ asymmetry in $B_s^0\to J/\psi(\to \mu^+\mu^-) K^+ K^-$ decays is measured using proton-proton collision data, corresponding to an integrated luminosity of $6 {\rm fb}^{-1}$, collected with the LHCb detector at a center-of-mass energy of 13 TeV. Using a sample of approximately 349 000 $B_s^0$ signal decays with an invariant $K^+ K^-$ mass in the vicinity of the $\phi(1020)$ resonance, the $CP$-violating phase $\phi_s$ is measured, along with the difference in decay widths of the light and heavy mass eigenstates of the $B_s^0$-$\overline{B}_s^0$ system, $\Delta\Gamma_s$, and the difference of the average $B_s^0$ and $B^0$ meson decay widths, $\Gamma_s-\Gamma_d$. The values obtained are $\phi_s = -0.039 \pm 0.022 \pm 0.006$ rad, $\Delta\Gamma_s = 0.0845 \pm 0.0044 \pm 0.0024 ~{\rm ps}^{-1}$ and $\Gamma_s-\Gamma_d = -0.056^{\:+\:0.0013}_{\:-\:0.0015} \pm 0.0014 ~{\rm ps}^{-1}$, where the first uncertainty is statistical and the second systematic. These are the most precise single measurements to date and are consistent with expectations based on the Standard Model and with the previous LHCb analyses of this decay. These results are combined with previous independent LHCb measurements. The phase $\phi_s$ is also measured independently for each polarization state of the $K^+K^-$ system and shows no evidence for polarization dependence.The decay-time-dependent $CP$ asymmetry in $B^0_s\to J/\psi(\to \mu^{+}\mu^{-}) K^{+}K^{-}$ decays is measured using proton-proton collision data, corresponding to an integrated luminosity of 6 $fb^{-1}$, collected with the LHCb detector at a center-of-mass energy of 13 TeV. Using a sample of approximately 349 000 $B^{0}_{s}$ signal decays with an invariant $K^{+}K^{-}$ mass in the vicinity of the $\phi(1020)$ resonance, the $CP$-violating phase $\phi_s$ is measured, along with the difference in decay widths of the light and heavy mass eigenstates of the $B^0_s$-$\bar{B}^0_s$ system, $\Delta\Gamma_s$, and the difference of the average $B^0_s$ and $B^0$ meson decay widths, $\Gamma_s-\Gamma_d$. The values obtained are $\phi_s = \ -0.039 \pm 0.022 \pm 0.006$ rad, $\Delta\Gamma_s = 0.0845 \pm 0.0044 \pm 0.0024$ ps$^{-1}$ and $\Gamma_s-\Gamma_d = -0.0056 ^{+ 0.0013}_{-0.0015} \pm 0.0014$ ps$^{-1}$, where the first uncertainty is statistical and the second systematic. These are the most precise single measurements to date and are consistent with expectations based on the Standard Model and with the previous LHCb analyses of this decay. These results are combined with previous independent LHCb measurements. The phase $\phi_s$ is also measured independently for each polarization state of the $K^{+}K^{-}$ system and shows no evidence for polarization dependence

Measurement of CP violation in B0→ψ(→ℓ+ℓ−)KS0(→π+π−)B^0\to\psi(\to\ell^+\ell^-)K^0_S(\to\pi^+\pi^-) decays

International audienceA measurement of time-dependent CP violation in the decays of $B^0$ and $\overline{B}^0$ mesons to the final states $J/\psi(\to\mu^+\mu^-)K^0_S$, $\psi(2S)(\to\mu^+\mu^-)K^0_S$ and $J/\psi(\to e^+e^-)K^0_S$ with $K^0_S\to\pi^+\pi^-$ is presented. The data correspond to an integrated luminosity of 6 fb${}^{-1}$ collected at a centre-of-mass energy of $\sqrt{s}=13$ TeV with the LHCb detector. The CP-violation parameters are measured to be \begin{align*} S_{\psi K^0_S} &= 0.717 \pm 0.013 (\text{stat}) \pm 0.008 (\text{syst}), \\ C_{\psi K^0_S} &= 0.008 \pm 0.012 (\text{stat}) \pm 0.003 (\text{syst}). \end{align*} This measurement of $S_{\psi K^0_S}$ represents the most precise single measurement of the CKM angle $\beta$ to date and is more precise than the current world average. In addition, measurements of the CP-violation parameters of the individual channels are reported and a combination with the LHCb Run 1 measurements is performed

Helium identification with LHCb

The identification of helium nuclei at LHCb is achieved using a method based on measurements of ionisation losses in the silicon sensors and timing measurements in the Outer Tracker drift tubes. The background from photon conversions is reduced using the RICH detectors and an isolation requirement. The method is developed using $pp$ collision data at $\sqrt{s}=13\,{\rm TeV}$ recorded by the LHCb experiment in the years 2016 to 2018, corresponding to an integrated luminosity of $5.5\,{\rm fb}^{-1}$. A total of around $10^5$ helium and antihelium candidates are identified with negligible background contamination. The helium identification efficiency is estimated to be approximately $50\%$ with a corresponding background rejection rate of up to $\mathcal O(10^{12})$. These results demonstrate the feasibility of a rich programme of measurements of QCD and astrophysics interest involving light nuclei

Study of Bc+→χcπ+B_c^+ \rightarrow \chi_c \pi^+ decays

International audienceA study of $B_c^+ \rightarrow \chi_c \pi^+$ decays is reported using proton-proton collision data, collected with the LHCb detector at centre-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of 9fb$^{-1}$. The decay $B_c^+ \rightarrow \chi_{c2} \pi^+$ is observed for the first time, with a significance exceeding seven standard deviations. The relative branching fraction with respect to the $B_c^+ \rightarrow J/\psi \pi^+$ decay is measured to be $$\frac{\mathcal{B}_{B_c^+ \rightarrow \chi_{c2} \pi^+}} {\mathcal{B}_{B_c^+ \rightarrow J/\psi \pi^+}} = 0.37 \pm 0.06 \pm 0.02 \pm 0.01 ,$$ where the first uncertainty is statistical, the second is systematic, and the third is due to the knowledge of the $\chi_c \rightarrow J/\psi \gamma$ branching fraction. No significant $B_c^+ \rightarrow \chi_{c1} \pi^+$ signal is observed and an upper limit for the relative branching fraction for the $B_c^+ \rightarrow \chi_{c1} \pi^+$ and $B_c^+ \rightarrow \chi_{c2} \pi^+$ decays of $$\frac{\mathcal{B}_{B_c^+ \rightarrow \chi_{c1} \pi^+}} {\mathcal{B}_{B_c^+ \rightarrow \chi_{c2} \pi^+}} < 0.49$$ is set at the 90% confidence level

Observation of Λb0→Λc+Dˉ(∗)0K−\Lambda_{b}^{0} \to \Lambda_{c}^{+} \bar{D}^{(*)0} K^{-} and Λb0→Λc+Ds∗−\Lambda_{b}^{0} \to \Lambda_{c}^{+} D_{s}^{*-} decays

International audienceThe decays $\Lambda_b^0 \to \Lambda_c^+\bar{D}^{(*)0}K^-$ and $\Lambda_b^0 \to \Lambda_c^+ D_s^{*-}$ are observed for the first time, in proton-proton collision data at $\sqrt{s}=13$TeV corresponding to an integrated luminosity of 5.4 fb${}^{-1}$ collected with the LHCb detector. Their ratios of branching fractions with respect to the $\Lambda_b^0\!\to\Lambda_c^+\mathrm{D}_s^-$ mode are measured to be \begin{align*} \begin{split} \frac{\mathcal{B}(\Lambda_b^0 \to \Lambda_c^+\bar{D}^0 K^-)}{\mathcal{B}(\Lambda_b^0 \to \Lambda_c^+ D_s^-)} & = 0.1908 {}_{-0.0034}^{+0.0036} {}_{-0.0018}^{+0.0016} \pm 0.0038 \\ \frac{\mathcal{B}(\Lambda_b^0 \to \Lambda_c^+\bar{D}^{*0} K^-)}{\mathcal{B}(\Lambda_b^0 \to \Lambda_c^+ D_s^-)} & = 0.589 {}_{-0.017}^{+0.018} {}_{-0.018}^{+0.017} \pm 0.012 \\ \frac{\mathcal{B}(\Lambda_b^0 \to \Lambda_c^+ D_s^{*-})}{\mathcal{B}(\Lambda_b^0 \to \Lambda_c^+ D_s^-)} & = 1.668 \pm 0.022 {}_{-0.055}^{+0.061}\ , \end{split} \end{align*} where the first uncertainties are statistical, the second systematic, and the third, for the $\Lambda_b^0 \to \Lambda_c^+ \bar{D}^{(*)0} K^-$ decays, are due to the uncertainties on the branching fractions of the $D_s^- \to K^- K^+ \pi^-$ and $\bar{D}^0 \to K^+\pi^-$ decay modes. The measured branching fractions probe factorization assumptions in effective theories and provide the normalization for future pentaquark searches in $\Lambda_b^0 \to \Lambda_c^+ \bar{D}^{(*)0}K^-$ decay channels

Determination of short- and long-distance contributions in B0→K∗0μ+μ−B^{0}\to K^{*0}\mu^+\mu^- decays

International audienceAn amplitude analysis of the $B^0 \to K^{*0} \mu^+\mu^-$ decay is presented. The analysis is based on data collected by the LHCb experiment from proton-proton collisions at $\sqrt{s} = 7,\,8$ and $13$ TeV, corresponding to an integrated luminosity of $4.7$ fb$^{-1}$. For the first time, Wilson coefficients and non-local hadronic contributions are accessed directly from the unbinned data, where the latter are parameterised as a function of $q^2$ with a polynomial expansion. Wilson coefficients and non-local hadronic parameters are determined under two alternative hypotheses: the first relies on experimental information alone, while the second one includes information from theoretical predictions for the non-local contributions. Both models obtain similar results for the parameters of interest. The overall level of compatibility with the Standard Model is evaluated to be between 1.8 and 1.9 standard deviations when looking at the $\mathcal{C}_9$ Wilson coefficient alone, and between 1.3 and 1.4 standard deviations when considering the full set of $\mathcal{C}_9, \, \mathcal{C}_{10}, \, \mathcal{C}_9^\prime$ and $\mathcal{C}_{10}^\prime$ Wilson coefficients. The ranges reflect the theoretical assumptions made in the analysis