Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Model-independent measurement of the W boson helicity in top quark
  decays   We present the first model-independent measurement of the helicity of $W$
bosons produced in top quark decays, based on a 1 fb$^{-1}$ sample of candidate
$t\bar{t}$ events in the dilepton and lepton plus jets channels collected by
the D0 detector at the Fermilab Tevatron $p\bar{p}$ Collider. We reconstruct
the angle $\theta^*$ between the momenta of the down-type fermion and the top
quark in the $W$ boson rest frame for each top quark decay. A fit of the
resulting \costheta distribution finds that the fraction of longitudinal $W$
bosons $f_0 = 0.425 \pm 0.166 \hbox{(stat.)} \pm 0.102 \hbox{(syst.)}$ and the
fraction of right-handed $W$ bosons $f_+ = 0.119 \pm 0.090 \hbox{(stat.)} \pm
0.053 \hbox{(syst.)}$, which is consistent at the 30% C.L. with the standard
model.

24
The categories of this paper are: dg-ga
31
The categories of this paper are: ao-sci
5
The categories of this paper are: gr-qc
29
The categories of this paper are: funct-an
22
The categories of this paper are: chao-dyn
14
The categories of this paper are: math-ph
10
The categories of this paper are: q-bio
0
The categories of this paper are: hep-ph
23
The categories of this paper are: solv-int
4
The categories of this paper are: cond-mat
35
The categories of this paper are: mtrl-th
26
The categories of this paper are: bayes-an
33
The categories of this paper are: plasm-ph
12
The categories of this paper are: nucl-th
25
The categories of this paper are: patt-sol
3
The categories of this paper are: physics