Rapidity distributions in exclusive $Z\mathbf{+}\mathrm{\text{jet}}$ and $\gamma \mathbf{+}\mathrm{\text{jet}}$ events in $pp$ collisions at $\sqrt{s}\mathbf{=}7\mathrm{TeV}$

Rapidity distributions are presented for events containing either a $Z$ boson or a photon with a single jet in proton-proton collisions produced at the CERN LHC. The data, collected with the CMS detector at $\sqrt{s}=7\mathrm{TeV}$, correspond to an integrated luminosity of $5.0{\mathrm{fb}}^{-1}$. The individual rapidity distributions of the boson and the jet are consistent within 5% with expectations from perturbative QCD. However, QCD predictions for the sum and the difference in rapidities of the two final-state objects show discrepancies with CMS data. In particular, next-to-leading-order QCD calculations, and two common Monte Carlo event generators using different methods to match matrix-element partons with parton showers, appear inconsistent with the data as well as with each other.

Figure 1

Distributions in absolute values of rapidities for (a) the $Z$ boson, (b) the jet, (c) their sums, and (d) their differences, normalized to unity. The data are shown after correcting for efficiency and resolution, and displayed with statistical and systematic uncertainties combined in quadrature. The lower panel of each figure gives ratios of the data and simulations to the NLO calculation of MCFM. The ratio error bars include MCFM statistical uncertainties folded with data statistical and systematic uncertainties. Theoretical uncertainties in the MCFM calculations are shown as shaded areas representing variations of ${\mu }_{\mathrm{R}}$, ${\mu }_{\mathrm{F}}$, and PDF. Statistical uncertainties for the MadGraph and SHERPA predictions are displayed as bands around the central values. The central value for MADGRAPH simulations using LO PDF is depicted by a line. All other calculations use NLO versions of PDF.

Figure 2

Distributions in absolute values of rapidities for (a) the photon, (b) the jet, (c) their sums, and (d) their differences, normalized to unity. The data are shown after correcting for efficiency and resolution, and displayed with statistical and systematic uncertainties combined in quadrature. The lower panel of each figure gives ratios of the data and simulations to the NLO calculation of Owens. The ratio error bars include Owens statistical uncertainties folded with data statistical and systematic uncertainties. Theoretical uncertainties in the Owens calculations are shown as shaded areas representing variations of ${\mu }_{\mathrm{R}}$, ${\mu }_{\mathrm{F}}$, and PDF. Statistical uncertainties for the MADGRAPH and SHERPA predictions are displayed as bands around the central values. The central value for MADGRAPH simulations using LO PDF is depicted by a line. All other calculations use NLO versions of PDF.