# The decays $B\to \Psi(2S)\pi(K),\eta_c(2S)\pi(K)$ in the pQCD approach beyond the leading-order

## TL;DR

This paper calculates branching ratios for B meson decays involving excited charmonium states using pQCD, including NLO effects, and compares predictions with experimental data, highlighting areas for future tests and potential new physics signals.

## Contribution

It provides next-to-leading-order pQCD predictions for B decays to excited charmonium states, incorporating vertex corrections and Wilson coefficients, and compares results with experimental data.

## Key findings

- Predicted branching ratios align with current data when including NLO effects.
- Decays involving K mesons have larger predicted branching ratios than those with pions.
- No significant direct CP violation observed in these decay modes.

## Abstract

Two body $B$ meson decays involving the radially excited meson $\psi(2S)/\eta_c(2S)$ in the final states are studied by using the perturbative QCD (pQCD) approach. We find that: (a) The branching ratios for the decays involving $K$ meson are predicted as $Br(B^+\to\psi(2S)K^+)=(5.37^{+1.85}_{-2.22})\times10^{-4}, Br(B^0\to\psi(2S)K^0)=(4.98^{+1.71}_{-2.06})\times10^{-4}, Br(B^+\to\eta_c(2S)K^+)=(3.54^{+3.18}_{-3.09})\times10^{-4}$, which are consistent well with the present data when including the next-to-leading-order (NLO) effects. Here the NLO effects are from the vertex corrections and the NLO Wilson coefficients. The large errors in the decay $B^+\to\eta_c(2S)K^+$ are mainly induced by using the decay constant $f_{\eta_c(2S)}=0.243^{+0.079}_{-0.111}$ GeV with large uncertainties. (b) While there seems to be some room left for other higher order corrections or the non-perturbative long distance contributions in the decays involving $\pi$ meson, $Br(B^+\to\psi(2S)\pi^+)=(1.17^{+0.42}_{-0.50})\times10^{-5}, Br(B^0\to\psi(2S)\pi^0)=0.54^{+0.20}_{-0.23}\times10^{-5}$, which are smaller than the present data. The results for other decays can be tested at the running LHCb and forthcoming Super-B experiments. (c) There is no obvious evidence of the direct CP violation being seen in the decays $B\to \psi(2S)\pi(K), \eta_c(2S)\pi(K)$ in the present experiments, which is supported by our calculations. If a few percent value is confirmed in the future , it would indicate new physics definitely.