Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: $\bar B^0 \to \pi^+ X$ in the Standard Model   In this paper we investigate the possibility of studying $B\to \pi$ form
factor using the semi-inclusive decays $\bar B^0 \to \pi^+ + X_q$. In general
$B\to PX$ semi-inclusive decays involve several hadronic parameters. But for
$\bar B^0 \to \pi^+ X_q$ decays we find that in the factorization
approximation, the only unknown hadronic parameters are the form factors
$F^{B\to \pi}_{0,1}$. Therefore these form factors can be studied in $\bar B^0
\to \pi^+ X_q$ decays. Using theoretical model calculations for the form
factors the branching ratios for $\bar B^0 \to \pi^+ X_d(\Delta S = 0) $ and
$\bar B^0 \to \pi^+ X_s (\Delta S = -1)$, with the cut $E_{\pi} > 2.1$ GeV, are
estimated to be in the ranges of $(3.1\sim 4.9) \times 10^{-5}(F^{B\to
\pi}_1(0)/0.33)^2$ and $(2.5\sim 4.2)\times 10^{-5}(F_1^{B\to \pi}(0)/0.33)^2$,
respectively, depending on the value of $\gamma$. The combined branching ratio
for $\bar B^0 \to \pi^+ (X_d+ X_s)$ is about $7.4\times 10^{-5} (F^{B\to
\pi}_1(0)/0.33)^2$ and is insensitive to $\gamma$. We also discuss CP
asymmetries in these decay modes.

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The categories of this paper are: math
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The categories of this paper are: math-ph
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The categories of this paper are: adap-org
37
The categories of this paper are: supr-con
34
The categories of this paper are: chem-ph
29
The categories of this paper are: funct-an
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The categories of this paper are: hep-lat
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The categories of this paper are: alg-geom
32
The categories of this paper are: atom-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: nucl-th
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The categories of this paper are: nlin
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The categories of this paper are: plasm-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: hep-th