Measurement of Dijet Azimuthal Decorrelations in pp Collisions at sqrt(s)=7 TeV

Abstract

Azimuthal decorrelations between the two central jets with the largest transverse momenta are sensitive to the dynamics of events with multiple jets. We present a measurement of the normalized differential cross section based on the full dataset (L=36/pb) acquired by the ATLAS detector during the 2010 sqrt(s)=7 TeV proton-proton run of the LHC. The measured distributions include jets with transverse momenta up to 1.3 TeV, probing perturbative QCD in a high energy regime.

Figures (4)

• Figure 1: The $\Delta\phi$ distribution for $\geq2$, $\geq3$, $\geq4$, and $\geq5$ jets with $p_{\mathrm{T}} > 100\mathrm{\ Ge V} \textrm{Ge V}$. Overlaid on the calibrated but otherwise uncorrected data (points) are results from PYTHIA processed through the detector simulation (lines). All uncertainties are statistical only.
• Figure 2: The differential cross section $(1/\sigma)(d\sigma/d\Delta\phi)$ binned in nine $p_{\mathrm{T}}^{\mathrm{max}}$ regions. Overlaid on the data (points) are results from the NLO pQCD calculation. The error bars on the data points indicate the statistical (inner error bar) and systematic uncertainties added in quadrature in this and subsequent figures. The theory uncertainties are indicated by the hatched regions. Different bins in $p_{\mathrm{T}}^{\mathrm{max}}$ are scaled by multiplicative factors of ten for display purposes. The region near the divergence at $\Delta\phi\to\pi$ is excluded from the calculation.
• Figure 3: Ratio of the differential cross section $(1/\sigma)(d\sigma/d\Delta\phi)$ measured in data with respect to expectations from NLO pQCD (points). The theory uncertainties are indicated by the hatched regions. The region near the divergence at $\Delta\phi\to\pi$ is excluded from the comparison.
• Figure 4: Ratio of the differential cross section $(1/\sigma)(d\sigma/d\Delta\phi)$ measured in data with respect to the result from SHERPA (points). The shaded region indicates the SHERPA statistical uncertainty. Predictions from PYTHIA and HERWIG, also in ratio to SHERPA, are displayed as lines.