arXiv subjects

Shu-Ting Cai

Publications and source records attributed to Shu-Ting Cai.

4 recordsLinked to original sources

arXiv2026

$CP$ violation in singly Cabibbo suppressed $D\to πa_0(980)$ decays

The singly Cabibbo suppressed (SCS) decays $D\to πa_0$, with $a_0\equiv a_0(980)$, have been measured with the branching-fraction ratios $r^{+/-}_{\rm ex}\equiv {\cal B}(D^0\toπ^- a_0^+)/{\cal B}(D^0\toπ^+ a_0^-)=7.5^{+2.5}_{-0.8}\pm 1.7$ and $r^{+/0}_{\rm ex}\equiv {\cal B}(D^+\toπ^0 a_0^+)/{\cal B}(D^+\toπ^+ a_0^0)=2.6\pm 0.6\pm 0.3$, deviating significantly from the short-distance expectations $(r^{+/-},r^{+/0})\simeq (0.07,0.2)$. This discrepancy indicates the necessity of long-distance rescattering effects. In particular, the process $D\to K^*K\to a_0π$ generates ${\cal M}_s$ comparable in magnitude to ${\cal M}_d$ in the amplitude ${\cal M}=λ_d{\cal M}_d+λ_s{\cal M}_s$, with $λ_q\equiv V_{cq}^*V_{uq}$, accompanied by nontrivial strong phases essential for $CP$ violation. Consequently, the direct $CP$ asymmetries naturally arise at the ${\cal O}(10^{-3})$ level, for example, ${\cal A}_{CP}(D^0\toπ^- a_0^+)=(-0.7\pm 0.1\pm 0.1\pm 0.1)\times 10^{-3}$, ${\cal A}_{CP}(D^+\toπ^0 a_0^+)=(-1.4\pm 0.1\pm 0.1\pm 0.1)\times 10^{-3}$, and ${\cal A}_{CP}(D^0\toπ^+ a_0^-)=(-2.1\pm 0.9\pm 1.1\pm 0.4)\times 10^{-3}$. These results establish SCS $D\to πa_0$ decays as a new avenue for probing $CP$ violation.

hep-ph↗

arXiv2026

Rescattering-induced $D\to SS$ weak decays

We investigate two-body non-leptonic $D\to SS$ weak decays, where $S$ denotes a light scalar meson such as $a_0/a_0(980)$, $f_0/f_0(980)$, or $σ_0/f_0(500)$. Short-distance topologies from $W$-boson emission and annihilation (exchange) are found to be negligible, while long-distance final-state interactions provide the dominant contributions. In particular, triangle rescattering processes, $D \to πη^{(\prime)} \to σ_0 a_0$ and $D \to a_1(1260)η\to σ_0 a_0$, mediated by pion exchange in $πη^{(\prime)}$ and $a_1(1260)η$ scatterings, respectively, are identified as the leading mechanisms. Our calculations yield branching fractions ${\cal B}(D_s^+ \to σ_0 a_0^+) = (1.0 \pm 0.2^{+0.1}_{-0.2}) \times 10^{-2}$, ${\cal B}(D^+ \to σ_0 a_0^+) = (1.1 \pm 0.2^{+0.1}_{-0.2}) \times 10^{-3}$, and ${\cal B}(D^0 \to σ_0 a_0^0) = (0.9 \pm 0.2^{+0.2}_{-0.3}) \times 10^{-5}$. For the Cabibbo-allowed decay mode $D_s^+ \to f_0 a_0^+$, the near-threshold condition $m_{D_s}\simeq m_{f_0}+m_{a_0}$ limits the phase space, suppressing the branching fraction to $(3.4\pm0.3^{+0.4}_{-0.9})\times 10^{-4}$. These results highlight rescattering-induced $D\to SS$ decays as promising channels for experimental studies at BESIII, Belle(-II), and LHCb.

hep-ph↗

arXiv2025

Hidden charm ${\cal P}_{cs}(4338)^0$ production in baryonic $B^-\to J/ψΛ\bar p$ decay

We investigate the resonant baryonic $B$ decay $B^-\to {\cal P}_{cs}^0\bar p,{\cal P}_{cs}^0\to J/ψΛ$, where ${\cal P}_{cs}^0\equiv {\cal P}_{cs}(4338)^0$ is identified as a hidden charm pentaquark candidate with strangeness. By interpreting ${\cal P}_{cs}^0$ as the $Ξ_c\bar D$ molecule that strongly decays into $J/ψΛ$ and $η_cΛ$, we discover a dominant triangle rescattering effect for $B^-\to {\cal P}_{cs}^0\bar p$, initiated by $B^-\to J/ψK^-$. Through the exchange of a $\bar Λ$ anti-baryon, $J/ψ$ and $K^-$ undergo rescattering, transforming into ${\cal P}_{cs}^0$ and $\bar p$, respectively. Based on this rescattering mechanism, we calculate ${\cal B}(B^-\to {\cal P}_{cs}^0\bar p,{\cal P}_{cs}^0\to J/ψΛ) =(1.4^{+2.1}_{-1.1})\times10^{-6}$, which is consistent with the measured data.

hep-ph↗

arXiv2020

Two-body charmed baryon decays involving decuplet baryon in the quark-diagram scheme

In the quark-diagram scheme, we study the charmed baryon decays of ${\bf B}_c\to {\bf B}^* M$, where ${\bf B}_c$ is $Λ_c^+$ or $Ξ_c^{+(0)}$, together with ${\bf B}^*$ ($M$) the decuplet baryon (pseudoscalar meson). It is found that only two $W$-exchange processes are allowed to contribute to ${\bf B}_c\to {\bf B}^* M$. Particularly, we predict ${\cal B}(Λ_c^+ \to Σ^{*0(+)} π^{+(0)})=(2.8\pm 0.4)\times 10^{-3}$, which respects the isospin symmetry. Besides, we take into account the $SU(3)$ flavor symmetry breaking, in order to explain the observation of ${\cal B}(Λ_c^+\to Σ^{*+}η)$. For the decays involving $Δ^{++}(uuu)$, we predict ${\cal B}(Λ_c^+\to Δ^{++} π^-,Ξ_c^+ \to Δ^{++} K^-) =(7.0\pm 1.4,13.5\pm 2.7)\times 10^{-4}$ as the largest branching fractions in the singly Cabibbo-suppressed $Λ_c^+,Ξ_c^+\to{\bf B}^*M$ decay channels, respectively, which are accessible to the LHCb, BELLEII and BESIII experiments.

hep-ph↗