Associated production of bottomonia and open charm hadrons in $pp$ collisions at $\sqrt{s}=7$ and $8$TeV is observed using data corresponding to an integrated luminosity of 3$fb^{1}$ accumulated with the LHCb detector. The observation of five combinations, $\Upsilon(1S)D^0$, $\Upsilon(2S)D^0$, $\Upsilon(1S)D^+$, $\Upsilon(2S)D^+$ and $\Upsilon(1S)D^+_{s}$, is reported. Production crosssections are measured for $\Upsilon(1S)D^0$ and $\Upsilon(1S)D^+$ pairs in the forward region. The measured crosssections and the differential distributions indicate the dominance of double parton scattering as the main production mechanism. This allows a precise measurement of the effective crosssection for double parton scattering.
Invariant mass distributions for selected combination of \Upsilon mesons and $\mathsf{C}$ hadrons: a) $\Upsilon D ^0 $, b) $\Upsilon D ^+ $, c) $\Upsilon D ^+_ s $ and d) $\Upsilon\Lambda ^+_ c $. 
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Projections from twodimensional extended unbinned maximum likelihood fits in bands a) $1.844<m_{ K ^ \pi ^+ }<1.887 {\mathrm{ Me V /}c^2} $, b) $9.332<m_{\mu ^+\mu ^ } <9.575 {\mathrm{ Ge V /}c^2} $, c) $9.889<m_{\mu ^+\mu ^ } <10.145 {\mathrm{ Ge V /}c^2} $ and d) $10.216<m_{\mu ^+\mu ^ } <10.481 {\mathrm{ Ge V /}c^2} $. The total fit function is shown by a solid thick (red) curve; three individual $\Upsilon D ^0 $ signal components are shown by solid thin (red) curves; three components describing \Upsilon signals and combinatorial background in $ K ^ \pi ^+ $ mass are shown with shortdashed (blue) curves; the component modelling the true $ D ^0$ signal and combinatorial background in $\mu ^+\mu ^$ mass is shown with a longdashed (green) curve and the component describing combinatorial background is shown with a thin dotted (black) line. 
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Projections from twodimensional extended unbinned maximum likelihood fits in bands a) $1.848<m_{ K ^ \pi ^+ \pi ^+ }<1.891 {\mathrm{ Me V /}c^2} $, b) $9.332<m_{\mu ^+\mu ^ } <9.575 {\mathrm{ Ge V /}c^2} $ , c) $9.889<m_{\mu ^+\mu ^ } <10.145 {\mathrm{ Ge V /}c^2} $ and d) $10.216<m_{\mu ^+\mu ^ } <10.481 {\mathrm{ Ge V /}c^2} $. The total fit function is shown by a solid thick (red) curve; three individual $\Upsilon D ^+ $ signal components are shown by solid thin (red) curves; three components describing \Upsilon signals and combinatorial background in $ K ^ \pi ^+ \pi ^+ $ mass are shown with shortdashed (blue) curves; the component modelling the true $ D ^+$ signal and combinatorial background in $\mu ^+\mu ^$ mass is shown with a longdashed (green) curve and the component describing combinatorial background is shown with a thin dotted (black) line. 
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Projections from twodimensional extended unbinned maximum likelihood fits in bands a) $1.952<m_{\left( K ^ K ^+ \right)_{\phi }\pi ^+ }<1.988 {\mathrm{ Me V /}c^2} $, b) $9.332<m_{\mu ^+\mu ^ } <9.575 {\mathrm{ Ge V /}c^2} $ , c) $9.889<m_{\mu ^+\mu ^ } <10.145 {\mathrm{ Ge V /}c^2} $ and d) $10.216<m_{\mu ^+\mu ^ } <10.481 {\mathrm{ Ge V /}c^2} $. The total fit function is shown by a solid thick (red) curve; three individual $\Upsilon D ^+_ s $ signal components are shown by solid thin (red) curves; three components describing \Upsilon signals and combinatorial background in $\left( K ^ K ^+ \right)_{\phi }\pi ^+ $ mass are shown with shortdashed (blue) curves; the component modelling the true $ D ^+_ s $ signal and combinatorial background in $\mu ^+\mu ^$ mass is shown with a longdashed (green) curve and the component describing combinatorial background is shown with a thin dotted (black) line. 
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Projections from twodimensional extended unbinned maximum likelihood fits in bands a) $2.273<m_{ p K ^ \pi ^+ }<2.304 {\mathrm{ Me V /}c^2} $ , b) $9.332<m_{\mu ^+\mu ^ } <9.575 {\mathrm{ Ge V /}c^2} $ , c) $9.889<m_{\mu ^+\mu ^ } <10.145 {\mathrm{ Ge V /}c^2} $ and d) $10.216<m_{\mu ^+\mu ^ } <10.481 {\mathrm{ Ge V /}c^2} $ . The total fit function is shown by a solid thick (red) curve; three individual $\Upsilon\Lambda ^+_ c $ signal components are shown by solid thin (red) curves; three components describing \Upsilon signals and combinatorial background in $ p K ^ \pi ^+ $ mass are shown with shortdashed (blue) curves; the component modelling the true $\Lambda ^+_ c $ signal and combinatorial background in $\mu ^+\mu ^$ mass is shown with a longdashed green curve and the component describing combinatorial background is shown with a thin dotted (black) line. 
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Backgroundsubtracted distributions of $\chi^2 _{\mathrm{fit}}\left(\mathsf{C} \right)/\mathrm{ndf}$ for a) $\Upsilon D ^0 $, b) $\Upsilon D ^+ $, c) $\Upsilon D ^+_ s $ and d) $\Upsilon\Lambda ^+_ c $ cases. A thin vertical (green) line indicates the requirement $\chi^2 _{\mathrm{fit}}\left(\Upsilon\mathsf{C} \right)/\mathrm{ndf}<5$ used in the analysis. The solid (red) curves indicate a fit to a sum of two components, each described by $\Gamma$distribution shape. The pileup component is shown with a dashed (blue) line. 
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Backgroundsubtracted and efficiencycorrected $ p^{\Upsilon}_{\mathrm{T}}$ (top) and $ p^{\mathsf{C} }_{\mathrm{T}}$ (bottom) distributions for $\Upsilon\mathrm{(1S)} D ^0 $ events (left) and $\Upsilon\mathrm{(1S)} D ^+ $ event (right). The transverse momentum spectra, derived within the DPS mechanism using the measurements from Refs. [41,44], are shown with the open (blue) squares. The SPS predictions [75] for the $ p^{\Upsilon}_{\mathrm{T}}$ spectra are shown with dashed (orange) and longdashdashed (magenta) curves for calculations based on the $ k_{\mathrm{T}} $dashfactorization and the collinear approximation, respectively. All distributions are normalized to unity. 
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Backgroundsubtracted and efficiencycorrected $ y^{\Upsilon}$ (top) and $ y^{\mathsf{C} }$ (bottom) distributions for $\Upsilon\mathrm{(1S)} D ^0 $ (left) and $\Upsilon\mathrm{(1S)} D ^+ $ (right) events. The rapidity spectra, derived within the DPS mechanism using the measurements from Refs. [41,44], are shown with the open (blue) squares. The SPS predictions [75] for the $ y^{\Upsilon}$ spectra are shown with dashed (orange) and longdashdashed (magenta) curves for calculations based on the $ k_{\mathrm{T}} $dashfactorization and the collinear approximation, respectively. All distributions are normalized to unity. 
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Backgroundsubtracted and efficiencycorrected distributions for $\left\Delta\phi\right/\pi$ (top) and $\Delta y$ (bottom) for $\Upsilon\mathrm{(1S)} D ^0 $ (left) and $\Upsilon\mathrm{(1S)} D ^+ $ (right) events. Straight lines in the $\left\Delta\phi\right/\pi$ plots show the result of the fit with a constant function. The SPS predictions [75] for the shapes of $\Delta\phi$ distribution are shown with dashed (orange) and longdashdashed (magenta) curves for calculations based on the $ k_{\mathrm{T}} $dashfactorization and the collinear approximation, respectively. The solid (blue) curves in the $\Delta y$ plots show the spectra obtained using a simplified simulation based on data from Refs. [41,44]. The dashed (green) lines show the triangle function expected for totally uncorrelated production of two particles, uniformly distributed in rapidity. All distributions are normalized to unity. 
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Backgroundsubtracted and efficiencycorrected $p_{\mathrm{T}}^{\Upsilon\mathrm{(1S)} \mathsf{C} }$ (top) and $y^{\Upsilon\mathrm{(1S)} \mathsf{C} }$ (bottom) distributions for $\Upsilon\mathrm{(1S)} D ^0 $ (left) and $\Upsilon\mathrm{(1S)} D ^+ $ (right) events. The blue curves show the spectra obtained using a simplified simulation based on data from Refs. [41,44]. All distributions are normalized to unity. 
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Backgroundsubtracted and efficiencycorrected $\mathscr{A}_{\mathrm{T}}$ (top) and $m^{\Upsilon\mathrm{(1S)} \mathsf{C} }$ (bottom) distributions for $\Upsilon\mathrm{(1S)} D ^0 $ (left) and $\Upsilon\mathrm{(1S)} D ^+ $ (right) events. The blue curves show the spectra obtained using a simplified simulation based on data from Refs. [41,44]. All distributions are normalized to unity. 
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Animated gif made out of all figures. 
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Signal yields $N^{\Upsilon\mathsf{C} }$ for $\Upsilon\mathsf{C} $ production, determined with twodimensional extended unbinned maximum likelihood fits to the candidate $\Upsilon\mathsf{C} $ samples. 
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Statistical significances of the observed $\Upsilon\mathsf{C} $ signals in units of standard deviations determined using pseudoexperiments. The values in parentheses indicate the statistical significance calculated using Wilks' theorem [65]. 
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Summary of relative systematic uncertainties for $\upsigma^{\Upsilon\mathsf{C} }$ (in %). The total systematic uncertainty does not include the systematic uncertainty related to the knowledge of integrated luminosity [67]. The symbol $\oplus$ denotes the sum in quadrature. 
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Summary of relative systematic uncertainties for $\upsigma_{\mathrm{eff}}$ (in %). The reduced uncertainty for $\mathsf{C}$ hadron production crosssection, denoted as $\updelta(\upsigma^{\mathsf{C} })$, is recalculated from Ref. [41] taking into account the cancellation of correlated systematic uncertainties. 
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Summary of relative systematic uncertainties for the ratios $R^{\Upsilon\mathsf{C} }$ and $R^{ D ^0 / D ^+ }$ (in %). 
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Created on 19 February 2021.