| Abstract |
content_type = "text/plain"
user_agent = "Mozilla/5.0 AppleWebKit/537.36 (KHTML, like Gecko; compatible; ClaudeBot/1.0; +claudebot@anthropic.com)"
moz = "Mozilla/5.0 "
moz_version = "5"
We present a preliminary measurement of R_1, R_2, and rho^2 which
are the three parameters used to characterize the B\to D^*\ell\bar\nu_e
form factors (A_1, V, and A_2). We use 85 \times 10^6 B\bar
B-pairs accumulated on the \Upsilon(4{\rm S}) resonance at PEP-II. In
this analysis we use the decay mode \bar B^0\rar D^{+*}e^-\bar\nu and
its charge conjugate. The D^{*+} is reconstructed in the channel
D^{*+}\to D^0\pi^+ and the D^0 in the channel
D^{0}\rightarrow K^{-}\pi^{+}. We parameterize the form factors in terms
of their ratios (determined by the parameters R_1 and R_2) and the
common slope \rho^2 in the variable w (a quantity related to the
momentum transfer in the decay process). These parameters are determined
via an unbinned maximum likelihood fit to the distributions in four
kinematic variables (three decay angles and w). The results are R_1=
1.328 \pm 0.055\pm 0.025\pm 0.025 and R_2=0.920 \pm 0.044\pm 0.020\pm
0.013 for the ratios and \rho^2= 0.769\pm 0.039 \pm 0.019\pm 0.032
for the slope. The stated errors are the statistical uncertainty from the
data, statistical uncertainty from the size of the Monte Carlo sample and
the systematic uncertainty, respectively.
|
