# Measurement of the production of charm jets tagged with D$^{0}$ mesons in pp collisions at $\sqrt{s}$= 7 TeV

The production of charm jets in proton-proton collisions at a center-of-mass energy of $\sqrt{s}=7$ TeV was measured with the ALICE detector at the CERN Large Hadron Collider. The measurement is based on a data sample corresponding to a total integrated luminosity of $6.23$ ${\rm nb}^{-1}$, collected using a minimum-bias trigger. Charm jets are identified by the presence of a D$^0$ meson among their constituents. The D$^0$ mesons are reconstructed from their hadronic decay D$^0\rightarrow$K$^{-}\pi^{+}$. The D$^0$-meson tagged jets are reconstructed using tracks of charged particles (track-based jets) with the anti-$k_{\mathrm{T}}$ algorithm in the jet transverse momentum range $5<~p_{\rm{T,jet}}^{\mathrm{ch}}<~30$ ${\rm GeV/}c$ and pseudorapidity $|\eta_{\rm jet}|<~0.5$. The fraction of charged jets containing a D$^0$-meson increases with $p_{\rm{T,jet}}^{\rm{ch}}$ from $0.042 \pm 0.004\, \mathrm{(stat)} \pm 0.006\, \mathrm{(syst)}$ to $0.080 \pm 0.009\, \rm{(stat)} \pm 0.008\, \rm{(syst)}$. The distribution of D$^0$-meson tagged jets as a function of the jet momentum fraction carried by the D$^0$ meson in the direction of the jet axis ($z_{||}^{\mathrm{ch}}$) is reported for two ranges of jet transverse momenta, $5<~p_{\rm{T,jet}}^{\rm{ch}}<~15$ ${\rm GeV/}c$ and $15<~p_{\rm{T,jet}}^{\rm{ch}}<~30$ ${\rm GeV/}c$ in the intervals $0.2<~z_{||}^{\rm{ch}}<~1.0$ and $0.4<~z_{||}^{\rm{ch}}<~1.0$, respectively. The data are compared with results from Monte Carlo event generators (PYTHIA 6, PYTHIA 8 and Herwig 7) and with a Next-to-Leading-Order perturbative Quantum Chromodynamics calculation, obtained with the POWHEG method and interfaced with PYTHIA 6 for the generation of the parton shower, fragmentation, hadronisation and underlying event.

Figures

## Figure 1

 Top: Invariant mass distribution of \Dzero-meson tagged jet candidates with $5< \ptchjet< 30$~\GeVc\ (left and center) and $15< \ptchjet< 30$~\GeVc\ (right) The \Dzero-meson transverse momenta are required to be in the interval $4< \ptd< 5$~\GeVc\ (left), $6< \ptd< 7$~\GeVc\ (center) and $6< \ptd< 12$~\GeVc\ (right) The blue solid line represents the total fit function; the background component of the fit function is shown with and withoutthe reflection component, as a red dotted line and as a magenta dashed line, respectively The green and red filled areas correspond to the side-band and peak regions. Bottom: Distributions of the \Dzero-meson tagged jet candidates in the peak region (red squares) and the side-band region (green circles) as a function of \ptchjet\ (left and center) and \zpar\ (right). The \ptchjet\ and \ptd\ selections are the same as the corresponding top panels The blue diamonds show the subtracted distributions corresponding to the raw signals.

## Figure 2

 Product of acceptance and efficiency of \Dzero-meson jet reconstruction as a function of \ptd. Left: acceptance $\times$ efficiency for prompt \Dzero-meson jets with $5< \ptchjet< 15$~\GeVc\ (full circles) and $15< \ptchjet< 30$~\GeVc\ (open circles) Right: prompt (circles) and non-prompt (squares) \Dzero-meson jet acceptance $\times$ efficiency for $5< \ptchjet< 30$~\GeVc.

## Figure 3

 b-hadron feed-down fraction of \Dzero-meson tagged jets as a function of \ptchjet\ (left) and \zpar\ (right) in \pp\ collisions at $\s=7$~TeV. On the right, the fraction is shown for $5< \ptchjet< 15$~\GeVc\ (circles) and for $15< \ptchjet< 30$~\GeVc\ (squares) The boxes represent the systematic uncertainties, see Section~\ref{sec:systunc} for details.

## Figure 4

 Probability density distribution of $\Delta_{\pt}$ (left) and $\Delta_{z}$ (right) for \Dzero-meson tagged jets in \pp\ collisions at $\s=7$~TeV. Left: $\Delta_{\pt}$ is shown for $5< \ptchjetgen< 6$~\GeVc\ (circles), $8< \ptchjetgen< 10$~\GeVc\ (squares) and $20< \ptchjetgen< 30$~\GeVc\ (diamonds) Right: $\Delta_{z}$ is shown for $0.8< \zpargen< 1$ (diamonds), $0.6< \zpargen< 0.8$ (squares), $0.2< \zpargen< 0.4$ (circles); solid markers are used for $5< \ptchjetgen< 15$~\GeVc, while open markers represent $15< \ptchjetgen< 30$~\GeVc (the data set for $0.2< \zpargen< 0.4$ is omitted for the latter).

## Figure 5

 \pt-differential cross section of charm jets tagged with \Dzero\ mesons (left) and its ratio to the inclusive jet cross section (right) in \pp\ collisions at $\s=7$~TeV The solid red circles show the ALICE data with their systematic uncertainties represented by the grey boxes. The measurements are compared with \mbox{PYTHIA~6} Perugia 2011 (blue), \mbox{PYTHIA~8} Monash 2013 (green), Herwig 7 \texttt{MEPP2QQ} (magenta) and \texttt{MEQCDMinBias} (orange).

## Figure 6

 \pt-differential cross section of charm jets tagged with \Dzero\ mesons (left) and its ratio to the inclusive jet cross section (right) in \pp\ collisions at $\s=7$~TeV The solid red circles show the data with their systematic uncertainties represented by the grey boxes The measurements are compared with the \mbox{POWHEG} heavy-quark (open circles) and di-jet (open squares) implementations.

## Figure 7

 \zpar-differential cross section of \Dzero-meson tagged track-based jetsin \pp\ collisions at $\s=7$~TeV with $5< \ptchjet< 15$~\GeVc\ (left) and $15< \ptchjet< 30$~\GeVc\ (right) The solid red circles show the data with their systematic uncertainties represented by gray boxes The measurements are compared with the \mbox{POWHEG} heavy-quark implementation (open circles) andwith Herwig 7 \texttt{MEPP2QQ} (dashed-dotted lines).

## Figure 8

 (Colours online) Rate of \Dzero-meson tagged track-based jets as a function of the jet momentum fraction carried by the \Dzero\ mesons in the direction of the jet axisin \pp\ collisions at $\s=7$~TeV with $5< \ptchjet< 15$~\GeVc\ (left) and $15< \ptchjet< 30$~\GeVc\ (right) The solid red circles show the data with their systematic uncertainties represented by gray boxes The measurements are compared with \mbox{PYTHIA~6} Perugia 2011 (blue), \mbox{PYTHIA~8} Monash 2013 (green dashed lines),the \mbox{POWHEG} di-jet implementation (open squares) and Herwig 7 \texttt{MEQCDMinBias} (orange).