Study of quasi-two-body (B_{(s)}ightarrow phi (f_0(980)/f_2(1270)ightarrow )pi pi ) decays in perturbative QCD approach

摘要

In 2017, LHCb collaboration reported their first observation of the rare decays $$B_s ightarrow phi (f_0(980)$$ B s → ? ( f 0 ( 980 ) $$/f_2(1270) ightarrow ) pi ^+pi ^-$$ / f 2 ( 1270 ) → ) π + π - and the evidence of $$B^0 ightarrow phi (f_0(980)/f_2(1270)ightarrow )pi ^+pi ^-$$ B 0 → ? ( f 0 ( 980 ) / f 2 ( 1270 ) → ) π + π - . Motivated by this, we study these quasi-two-body decays in the perturbative QCD approach. The branching fractions, CP asymmetries and the polarization fractions are calculated. We find that within the appropriate two-meson wave functions, the calculated branching fractions are in agreement with the measurements of LHCb. Based on the narrow-width approximation, We also calculate the branching fractions of the quasi-two-body $$B_{d,s}ightarrow phi (f_0(980)/f_2(1270)ightarrow ) pi ^0pi ^0$$ B d , s → ? ( f 0 ( 980 ) / f 2 ( 1270 ) → ) π 0 π 0 and $$B_{d,s}ightarrow phi (f_2(1270)ightarrow ) K^+K^-$$ B d , s → ? ( f 2 ( 1270 ) → ) K + K - , and hope the predictions to be tested in the ongoing LHCb and Belle II experiments. Moreover, the processes $$B_{d,s}ightarrow phi f_2(1270)$$ B d , s → ? f 2 ( 1270 ) are also analyzed under the approximation. We note that the CP asymmetries of these decays are very small, because these decays are either penguin dominant or pure penguin processes.