Measurement of the shape of the boson rapidity distribution for p\bar{p}-> Z/gamma*-> e+e- +X events produced at sqrt(s) of 1.96 TeV

TL;DR

The paper delivers a precise measurement of the Z/gamma* boson rapidity distribution in p-pbar collisions at 1.96 TeV by extracting a normalized differential cross section in rapidity from Z/γ*→ee events in a narrow mass window. It relies on data-driven efficiencies (tag-and-probe) and careful background subtraction, complemented by NNLO QCD predictions for comparison. The results show good agreement with NNLO across the full rapidity range, with notably improved precision in the forward region, enhancing constraints on PDFs at low x and high Q^2. This work demonstrates the value of forward-rapidity measurements in testing perturbative QCD and informing parton distribution fits with Run II data.

Abstract

We present a measurement of the shape of the boson rapidity distribution for p\bar{p}-> Z/gamma*-> e+e- +X events at a center-of-mass energy of 1.96 TeV. The measurement is made for events with electron-positron mass 71< M_ee < 111 GeV and uses 0.4 fb^-1 of data collected at the Fermilab Tevatron collider with the D0 detector. This measurement significantly reduces the uncertainties on the rapidity distribution in the forward region compared with previous measurements. Predictions of NNLO QCD are found to agree well with the data over the full rapidity range.

Figures (5)

• Figure 1: Comparisons of data and Monte Carlo plus background are presented for (a) the vertex $z$ distribution and (b) the electron-positron invariant mass spectrum. The vertex $z$ plot shows data after all selection cuts. The data in the mass plot pass all selection criteria except for the mass cut. Uncertainties shown on the data points are statistical.
• Figure 2: Relative uncertainties plotted against the boson rapidity.
• Figure 3: DØ Run II measurement of $\frac{1}{\sigma} \text{d}\sigma/\text{d}y$ vs $y$. The inner (outer) error bars show the statistical (total) uncertainty.
• Figure 4: DØ Run II measurement of $\frac{1}{\sigma} \text{d}\sigma/\text{d}y$ vs $|y|$. The inner (outer) error bars show the statistical (total) uncertainty. The curve is a NNLO calculation from Anastasiou:2003ds using MRST 2004 PDFs.
• Figure 5: Relative uncertainties from this measurement and from the CDF Run I result. Also shown is the PDF uncertainty on the differential cross section using the CTEQ6M uncertainty PDF sets. The values for the CTEQ6M curve are generated with code from Ref. Anastasiou:2003ds.