Observation of Diffractive<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi mathvariant="italic">W</mml:mi></mml:math>-Boson Production at the Fermilab Tevatron

Abstract

We report the first observation of diffractively produced $W$ bosons. In a sample of $W\ensuremath{\rightarrow}e\ensuremath{\nu}$ events produced in $p\overline{p}$ collisions at $\sqrt{s}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.8\phantom{\rule{0ex}{0ex}}\mathrm{TeV}$, we find an excess of events with a forward rapidity gap, which is attributed to diffraction. The probability that this excess is consistent with nondiffractive production is $1.1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ $(3.8\ensuremath{\sigma})$. The relatively low fraction of $W+\mathrm{jet}$ events observed within this excess implies that mainly quarks from the Pomeron, which mediates diffraction, participate in $W$ production. The diffractive to nondiffractive $W$ production ratio is found to be ${R}_{W}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}(1.15\ifmmode\pm\else\textpm\fi{}0.55)%$.