The production of $J/\psi$ mesons with rapidity $1.5<y<4.0$ or $5.0<y<2.5$ and transverse momentum $p_\mathrm{T}<14 \mathrm{GeV}/c$ is studied with the LHCb detector in protonlead collisions at a nucleonnucleon centreofmass energy $\sqrt{s_{NN}}=5 \mathrm{TeV}$. The analysis is based on a data sample corresponding to an integrated luminosity of about $1.6 \mathrm{nb}^{1}$. For the first time the nuclear modification factor and forwardbackward production ratio are determined separately for prompt $J/\psi$ mesons and $J/\psi$ from $b$hadron decays. Clear suppression of prompt $J/\psi$ production with respect to protonproton collisions at large rapidity is observed, while the production of $J/\psi$ from $b$hadron decays is less suppressed. These results show good agreement with available theoretical predictions. The measurement shows that cold nuclear matter effects are important for interpretations of the related quarkgluon plasma signatures in heavyion collisions.
Projections of the combined fit on (a, b) dimuon invariant mass and (c, d) $t_z$ in two representative bins in the (a, c) % forward and (b, d) % backward samples. For the mass projections the (red solid curve) total fitted function is shown together with the (blue dotted curve) $ { J \mskip 3mu/\mskip 2mu\psi \mskip 2mu} $ signal and (green dotted curve) background contributions. For the $t_z$ projections the total fitted function is indicated by the solid red curve, the background by the green hatched area, the prompt signal by the blue area and $ { J \mskip 3mu/\mskip 2mu\psi \mskip 2mu} $ from $b$ by the solid black curve. 
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Distributions (normalised to unitary integral) of (a) track multiplicity and the $ { J \mskip 3mu/\mskip 2mu\psi \mskip 2mu} $ (b) transverse momentum $p_\mathrm{T}$, (c) momentum $p$, and (d) rapidity in laboratory frame $y_{\mathrm{lab}}$ in (black dots) forward and (red squares) backward regions of $ p\mathrm{Pb} $ collisions, and in (blue triangles) simulated $pp$ collisions. The distributions are background subtracted using the sPlot technique. 
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Single differential production crosssections for (black dots) prompt $ { J \mskip 3mu/\mskip 2mu\psi \mskip 2mu} $ and (red squares) $ { J \mskip 3mu/\mskip 2mu\psi \mskip 2mu} $ from $b$ as functions of (a, b) $p_\mathrm{T}$ and (c, d) $y$ in the (a, c) forward and (b, d) backward regions. 
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Double differential production crosssections for (a) prompt $ { J \mskip 3mu/\mskip 2mu\psi \mskip 2mu} $ mesons and (b) $ { J \mskip 3mu/\mskip 2mu\psi \mskip 2mu} $ from $b$ in the forward samples. 
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Nuclear modification factor $R_{ p\mathrm{Pb} }$ as a function of $y$ for (a) prompt $ { J \mskip 3mu/\mskip 2mu\psi \mskip 2mu} $ mesons and (b) $ { J \mskip 3mu/\mskip 2mu\psi \mskip 2mu} $ from $b$, together with the theoretical predictions from (yellow dashed line and brown band) Refs. \cite{Ferreiro:2013pua,delValle:2014wha}, (blue band) Ref. \cite{Albacete:2013ei}, and (green solid and blue dashdotted lines) Ref. \cite{Arleo:2012rs}. The inner error bars (delimited by the horizontal lines) show the statistical uncertainties; the outer ones show the statistical and systematic uncertainties added in quadrature. The uncertainty due to the interpolated $ { J \mskip 3mu/\mskip 2mu\psi \mskip 2mu} $ crosssection in $pp$ collisions at $\sqrt{s}=5\mathrm{ Te V} $ is $5.5\%$ ($8.4\%$) for prompt $ { J \mskip 3mu/\mskip 2mu\psi \mskip 2mu} $ mesosns ($ { J \mskip 3mu/\mskip 2mu\psi \mskip 2mu} $ from $b$). 
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Forwardbackward production ratio $R_{ {FB}}$ as a function of $y$ for (a) prompt $ { J \mskip 3mu/\mskip 2mu\psi \mskip 2mu} $ mesons and (b) $ { J \mskip 3mu/\mskip 2mu\psi \mskip 2mu} $ from $b$, together with the theoretical predictions from (yellow dashed line and brown band) Refs. \cite{Ferreiro:2013pua,delValle:2014wha}, (blue band) Ref. \cite{Albacete:2013ei}, and (green solid and blue dashdotted lines) Ref. \cite{Arleo:2012rs}. The inner error bars (delimited by the horizontal lines) show the statistical uncertainties; the outer ones show the statistical and systematic uncertainties added in quadrature. 
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Forwardbackward production ratio $R_{ {FB}}$ for (black dot) prompt $ { J \mskip 3mu/\mskip 2mu\psi \mskip 2mu} $ mesons and (red square) $ { J \mskip 3mu/\mskip 2mu\psi \mskip 2mu} $ from $b$ as a function of $p_\mathrm{T}$ in the rapidity range $2.5<y<4.0$. The theoretical predictions from (blue band) Ref. \cite{Albacete:2013ei} and (green solid and blue dashdotted lines) Ref. \cite{Arleo:2013zua} are for prompt $ { J \mskip 3mu/\mskip 2mu\psi \mskip 2mu} $ mesons. The inner error bars (delimited by the horizontal lines) show the statistical uncertainties; the outer ones show the statistical and systematic uncertainties added in quadrature. 
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Animated gif made out of all figures. 
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Relative systematic uncertainties on the differential production crosssections. The uncertainty due to the radiative tail and branching fraction cancels in both $R_{ p\mathrm{Pb} }$ and $R_{ {FB}}$. The uncertainty due to the tracking efficiency and the luminosity partially cancels for $R_{ {FB}}$. 
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Single differential production crosssections (in $ {\rm \upmu b} /( {\mathrm{ Ge V /}c} )$) for prompt $ { J \mskip 3mu/\mskip 2mu\psi \mskip 2mu}$ mesons and $ { J \mskip 3mu/\mskip 2mu\psi \mskip 2mu}$ from $b$ as functions of transverse momentum. The first uncertainty is statistical, the second is the component of the systematic uncertainty that is uncorrelated between bins, and the third is the correlated component. 
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Single differential production crosssections (in $ {\rm \upmu b}$ ) for prompt $ { J \mskip 3mu/\mskip 2mu\psi \mskip 2mu}$ mesons and $ { J \mskip 3mu/\mskip 2mu\psi \mskip 2mu}$ from $b$ as functions of rapidity. The first uncertainty is statistical, the second is the component of the systematic uncertainty that is uncorrelated between bins, and the third is the correlated component. 
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Nuclear modification factor $R_{ p\mathrm{Pb} }$ as a function of $y$ with $ p_{\rm T} <14 {\mathrm{ Ge V /}c} $. The first uncertainty is statistical, the second is the systematic, and the third is the uncertainty related to the interpolation error. 
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Forwardbackward production ratio $R_{ {FB}}$ as a function of $y$ with $ p_{\rm T} <14 {\mathrm{ Ge V /}c} $. The first uncertainty is statistical, the second is the uncorrelated systematic component, and the third is the systematic uncertainty correlated between bins. 
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Forwardbackward production ratio $R_{ {FB}}$ as a function of $p_\mathrm{T}$ with $2.5<y<4.0$. The first uncertainty is statistical, the second is the uncorrelated systematic component, and the third is the systematic uncertainty correlated between bins. 
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Created on 17 August 2019.Citation count from INSPIRE on 20 August 2019.