W Production in an Improved Parton-Shower Approach

Abstract

In the description of the production properties of gauge bosons (W+/W-, Z0, gamma) at colliders, the lowest-order graph normally is not sufficient. The contributions of higher orders can be introduced either by an explicit order-by-order matrix-element calculation, by a resummation procedure or by a parton-shower algorithm. Each approach has its advantages and disadvantages. We here introduce a method that allows the parton-shower algorithm to be augmented by higher-order information, thereby offering an economical route to a description of all event properties. It is tested by comparing with the pT spectrum of W bosons at the Tevatron.

Figures (4)

• Figure 1: Schematic picture of an initial-state parton shower, extending from both sides of the event in to the $\mathrm{W}$.
• Figure 2: The $p_{\perp\mathrm{W}}$ distribution in $\mathrm{p}\mathrm{\overline{p}}$ collisions at 1.8 TeV. Parton distributions and $\alpha_{\mathrm{s}}$ are frozen and only one emission at a time is allowed in the shower. Events are classified either as (a) $\mathrm{q}\mathrm{\overline{q}}' \to \mathrm{g}\mathrm{W}$ or (b) $\mathrm{q}\mathrm{g} \to \mathrm{q}'\mathrm{W}$.
• Figure 3: $R(\hat{s},\hat{t})$ distributions in $\mathrm{p}\mathrm{\overline{p}}$ collisions at 1.8 TeV. (a) The inclusive distribution. (b) The average value as a function of $p_{\perp\mathrm{W}}$. Events are classified either as $\mathrm{q}\mathrm{\overline{q}}' \to \mathrm{g}\mathrm{W}$ or $\mathrm{q}\mathrm{g} \to \mathrm{q}'\mathrm{W}$.
• Figure 4: Transverse momentum spectrum of the $\mathrm{W}$; full parton-shower results compared with data from the D0 Collaboration D0data. (The error bars include both statistical and systematic uncertainties.)