Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Bounding the effect of penguin diagrams in $a_{CP}(B^0 \to \pi^+\pi^-)$   A clean determination of the angle $\alpha$ of the unitary triangle from
$B\to \pi\pi$ decays requires an isospin analysis. If the $B \to \pi^0\pi^0$
and $\bar B \to \pi^0\pi^0$ decay rates are small it may be hard to carry out
this analysis. Here we show that an upper bound on the error on $\sin 2\alpha$
due to penguin diagram effects can be obtained using only the measured rate
$\BR(B^\pm \to \pi^\pm \pi^0)$ and an upper bound on the combined rate $\BR(B
\to \pi^0 \pi^0) + \BR(\bar B \to \pi^0 \pi^0)$. Since no b flavor tagging is
needed to measure this combined rate, the bound that can be achieved may be
significantly better than any approach which requires separate flavor-tagged
neutral pion information.

4
The categories of this paper are: cond-mat
1
The categories of this paper are: cs
13
The categories of this paper are: quant-ph
2
The categories of this paper are: math
18
The categories of this paper are: econ
6
The categories of this paper are: astro-ph
10
The categories of this paper are: q-bio
14
The categories of this paper are: math-ph
27
The categories of this paper are: comp-gas
21
The categories of this paper are: adap-org
29
The categories of this paper are: funct-an
16
The categories of this paper are: stat
5
The categories of this paper are: gr-qc
35
The categories of this paper are: mtrl-th
19
The categories of this paper are: eess
22
The categories of this paper are: chao-dyn