$D^{\pm }$ production asymmetry at the LHC from heavy quark recombination

The asymmetry in the forward region production cross section of $D^{\pm }$ is calculated using the heavy quark recombination mechanism for $pp$ collisions at 7 TeV. By suitable choices of four nonperturbative parameters, our calculated results can reproduce those obtained at LHCb. We find $A_p\sim -1\%$ when integrated over $2.0\mathrm{GeV}<p_T<18\mathrm{GeV}$ and $2.2<\eta <4.75$, which agrees with $A_p=-0.96\pm 0.26\pm 0.18\%$ as measured by LHCb. Furthermore, the calculated distributions in $\eta$ and $p_T$ agree reasonably well with those obtained at LHCb.

Figure 1

Diagrams for production of a $\overline{D}$ meson by the heavy quark recombination mechanism for (a) $qg\to (\overline{c}q{)}^n+c$ and (b) $q\overline{c}\to (\overline{c}q{)}^n+g$. Each process has five diagrams. Single lines represent light quarks, double lines heavy quarks, and the shaded blob the $\overline{D}$ meson.

Figure 2

Asymmetry in $D^{\pm }$ production $A_p$ as a function of (a) pseudorapidity $\eta$ and (b) transverse momentum $p_T$ in 7 TeV $pp$ collisions. The data points are from LHCb [4]. The grey band is obtained by varying the $\rho \mathrm{s}$ in the intervals $0.055<{\rho }_1^{sm}<0.065$, $0.65<{\rho }_8^{sm}<0.8$, $0.46<{\rho }_1^{sf}<0.56$ and $0.46<{\rho }_8^{sf}<0.56$ respectively. The dashed lines are from varying $0.055<{\epsilon }_c<0.069$.