Measurement of the ratio of the $p\bar{p}\to W$+$c$-jet cross section to the inclusive $p\bar{p}\to W$+jets cross section

Abstract

We present a measurement of the fraction of inclusive $W$+jets events produced with net charm quantum number $\pm1$, denoted $W$+$c$-jet, in $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV using approximately 1~fb$^{-1}$ of data collected by the D0 detector at the Fermilab Tevatron Collider. We identify the $W$+jets events via the leptonic $W$ boson decays. Candidate $W$+$c$-jet events are selected by requiring a jet containing a muon in association with a reconstructed $W$ boson and exploiting the charge correlation between this muon and $W$ boson decay lepton to perform a nearly model-independent background subtraction. We measure the fraction of $W$+$c$-jet events in the inclusive $W$+jets sample for jet $p_{T}>20$ GeV and pseudorapidity $|η|<2.5$ to be 0.074$\pm0.019$(stat.)$\pm^{0.012}_{0.014}$(syst.), in agreement with theoretical predictions. The probability that background fluctuations could produce the observed fraction of $W$+$c$-jet events is estimated to be $2.5\times 10^{-4}$, which corresponds to a 3.5 $σ$ statistical significance.

Figures (2)

• Figure 1: Measured ratio $[\sigma(W$+$c$-jet$)/\sigma(W$+jets$)]$ for jet $p_{T}>20$ GeV and $|\eta|<2.5$. The inner error bars around the data points show the statistical only uncertainties and the full bars represent the quadratic sum of statistical and systematic uncertainties. The systematic uncertainty on $W$+$c$-jet fraction includes the uncertainties due to JES, the jet $p_{T}$ resolution, the background correction factor $f_{c}^{\ell}$, and the product of the relative acceptance and efficiencies $\epsilon_{c}^{\ell}$. It also includes the uncertainty due to $K_{T}^{\mu}$ in the muon channel.
• Figure 2: Comparison of the background-subtracted ($N_{\text{OS}}^{\ell}-f_{c}^{\ell}N_{\text{SS}}^{\ell}$) data in the combined electron and muon channels with the simulation. (a) Signed significance in impact parameter of the jet-muon track with respect to the interaction point, (b) jet-muon transverse momentum relative to the jet axis ($p_T^{\text{rel}}$).