**Electroweak and QCD physics**

**Introduction**

I performed **the world’s ﬁrst measurement of the A**, produced in a hadron collider. These are 2 of the significant 4 leading angular coefficients. These angular coefficients are ratios of the helicity cross sections of the W and the total unpolarized cross section.

_{2}and A_{3}angular coefficients of the W boson
Here θ and φ are the angles of the charged lepton from the W decay in the Collins-Soper W rest frame.
(the frame where the z-axis bisects the proton and minus the antiproton directions in the W rest frame).
The quantities q_{T} and η and are the transverse momentum and rapidity of the W in the lab frame.
In this frame, the φ angle is always known, and the ambiguity in the value of the neutrino
longitudinal momentum leads to only a sign ambiguity in the polar angle θ of the lepton.
The following picture shows the transformation from the laboratory frame to the Collins-Soper frame:
The angular coefficients with significan value are A_{0},A_{2},A_{3} and A_{4}, as can be seen in my W Helicity page.
Their value is sensitive to the production of the W boson in association with new
exotic particles or the Higgs boson. The presence of jets balance the transverse momentum of the W , which
is necessary for non-zero A_{2} and A_{3} values. At the same time, they introduce QCD effects that we
would like to also test.

The measurement was performed using CDF W+jets data and by reconstructing the φ angle of the charged lepton as a function of the W boson transverse momentum (4 bins). The result agrees well at low momenta, with a slight high deviation at the higher momenta. The analysis was carried out separately for electrons and muons and the results were combined at the end. The final measurement is consistent with the Standard Model, with a ~1 σ deviation at the higher pT bin:

For more information, please visit the PRD publication (Phys. Rev. D **73**, 052002 (2006)).