The rare decay $\bar B_d^0\to J/ψϕ$ can proceed in four distinct mechanisms: (i) production of the $ϕ$ via tri-gluon fusion, (ii) photoproduction of the $J/ψ$ or $ϕ$, (iii) final-state rescattering of $D_s^{(*)}D_s^{(*)}$ produced in the $\bar B_d$ decay to $J/ψϕ$, and (iv) production of the $ϕ$ via $ω-ϕ$ mixing. In this work, we examine the contributions from photoproduction and final-state rescattering to $\bar B_d^0\to J/ψϕ$ and find that the corresponding branching ratios are of order $10^{-11}$ and $10^{-9}$, respectively. Hence, this decay is dominated by the $ω-ϕ$ mixing effect.
Motivated by the reported discrepancies between experimental data and Standard Model predictions for the branching ratios of the color-allowed decays $\overline{B}^0 \to D^{(*)+}K^-$ and $\overline{B}^0_s \to D^{(*)+}_s π^-$, we study final-state rescattering effects on $\overline{B}_{(s)}\to D^{(*)}_{(s)} P$ and $\overline{B}_{(s)}\to D_{(s)} V$, where $P$ ($V$) is a light pseudoscalar (vector) meson. We consider quasi-elastic rescatterings in the framework of $SU(3)$ and $U(3)$ flavor symmetries, and find that the effects cannot explain the measured branching ratios of the color-allowed and …
Understanding the nature of the heavy pentaquarks and searching for them in pion-induced reactions
利用开粲强子再散射图研究了反应$π^- p \to π^- J/ψp$。由于再散射振幅中存在三角形奇异性(TS),TS峰可以模拟$J/ψp$不变质量分布中的类五夸克共振,这可能会给我们对奇异态性质的理解带来模糊性.由于TS机制具有高度的过程依赖性,在不同过程中寻找重五夸克态可以帮助我们澄清这些不确定性。
The branching fraction of the $B_s\to K^0\bar K^0$ decay has been recently measured by the LHCb and Belle experiments. We study the consistency of the measured value with three relations to other decay rates and CP asymmetries which follow from the Standard Model, and from the approximate flavor $SU(3)$ symmetry of the strong interactions. We find that each of these relations is violated at a level of above $3σ$. We argue that various subleading effects -- rescattering, electroweak penguins and $SU(3)$ breaking -- if larger than theoretically expected, can account for some of these puzzles, bu…
Direct CP violation in two-body $D\to PP$ and $D\to V\!P$ decays is studied within the framework of the topological amplitude approach for tree amplitudes and the QCD factorization approach for penguin amplitudes. It is the interference between tree and long-distance penguin and penguin-exchange amplitudes that pushes CP asymmetry difference between $D^0\to K^+K^-$ and $π^+π^-$ modes up to the per mille level. Using the same mechanism, we find that CP asymmetry can also occur at the $10^{-3}$ level in many of the $D\to V\!P$ channels or otherwise be negligibly small. There are six golden modes…
Recent measurements performed by the ATLAS and CMS collaborations on the Run 2 dataset are testing QCD with unprecedented precision. The wealth of data, an ever-improving experimental understanding of jets and photons, and novel measurements of jet substructure enable an improved understanding.
We present a systematic study of the productions and decays of light axial vector mesons with $J^{PC}=1^{+\pm}$ in charmonium decays. In the quark model scenario, the two axial vector nonets are connected with each other by the Gell-Mann-Okubo mass relation through the mixing between two $K_1$ states (i.e. $K_1(1270)$ and $K_1(1400)$) with configurations of $^3P_1$ and $^1P_1$. The mixing angles between $f_1$ and $f_1'$ (i.e. $f_1(1285)$ and $f_1(1420)$), and between $h_1$ and $h_1'$ (i.e. $h_1(1170)$ and $h_1(1415)$) can be reliably constrained. We then introduce the intermediate $K^*\bar{K}+…
We calculate the signal rate of hypothetical heavy neutral leptons (HNL or sterile neutrinos) from kaon decays expected in the framework of the SHiP experiment. The kaons are produced in the hadronic shower initiated in the beam-dump mode by 400 GeV protons from CERN SPS. For a sufficiently light HNL (when the decays are kinematically allowed) we find kaon decays to be a noticeably richer source of HNL as compared to $D$-meson decays adopted in previous studies of the HNL phenomenology at SHiP. In particular, SHiP is capable of fully exploring the central part of the kinematically allowed regi…