Triggered by experimentally driven renewed interest in hyperon properties we address the subject of weak radiative hyperon decays (WRHD). We start with the issue of Hara's theorem and briefly discuss the question of its possible evasion. Then, we give a short review of the story of vector-meson-dominance (VMD) approach to WRHD. We stress the shift from the Hara's-theorem-violating to Hara's-theorem-satisfying version of the VMD approach that did occur over time. Finally, spurred by a recent theoretical paper, we discuss the pole model description of WRHD, putting special attention to the issue of the contributions from the intermediate $Λ(1405)$ state. We point out that the measurement of the $Λ\to n γ$ decay asymmetry could resolve the encountered ambiguities and definitely answer the question of whether Hara's theorem is violated or not.
Radiative corrections to the semileptonic Dalitz plot with angular correlation between polarized decaying and emitted hyperons: effects of the four-body region
Weak Radiative Hyperon Decays in Chiral Perturbation Theory
利用手征微扰理论研究了弱辐射超子衰变的宇称守恒$a$和宇称破坏$b$振幅。使用么正性计算$a$和$b$的虚部。计算得到了$b$的实部由单圈红外发散图支配。$a$的实部具有很大的理论不确定性,不能可靠地计算。使用$CPS$对称性对$a$和$b$振幅的对应项进行分类。衰变宽度和不对称性的实验值与理论一致,除了$Σ^+ \rightarrow p γ$衰变的不对称性参数。
Precise nondivergent analytic formulas for the radiative corrections to the beta energy spectrum in hyperon semileptonic decays over the entire Dalitz plot
We revisit the hyperon weak radiative decays in the framework of the non-relativistic constituent quark model. This study confirms the nonlocal feature of the hyperon weak radiative transition operators which are dominated by the pole terms, and an overall self-consistent description of the available experimental data for the Cabibbo-favored hyperon weak radiative decays is achieved. It provides a natural mechanism for evading the Hara theorem, where sizeable parity-violating contributions can come from the intermediate orbital excitations. Cancellations between pole terms also explain signifi…
Weak radiative hyperon decays, important to test the strong interaction and relevant in searches for beyond the standard model physics, have remained puzzling both experimentally and theoretically for a long time. The recently updated branching fraction and first measurement of the asymmetry parameter of $Λ\to nγ$ by the BESIII Collaboration further exacerbate the issue, as none of the existing predictions can describe the data. We show in this letter that the covariant baryon chiral perturbation theory, with constraints from the latest measurements of hyperon non-leptonic decays, can well des…
In this paper, we summarize the existing methods of solving the evolution equation of the leading-twist $B$-meson LCDA. Then, in the Mellin space, we derive a factorization formula with next-to-leading-logarithmic (NLL) resummation for the form factors $F_{A,V}$ in the $B \to γ\ellν$ decay at leading power in $Λ/m_b$. Furthermore, we investigate the power suppressed local contributions, factorizable non-local contributions (which are suppressed by $1/E_γ$ and $1/m_b$), and soft contributions to the form factors. In the numerical analysis, which employs the two-loop-level hard function and the …
We revisit electroweak radiative corrections to Standard Model Effective Field Theory (SMEFT) operators which are relevant for the $B$-meson semileptonic decays. The one-loop matching formulae onto the low-energy effective field theory are provided without imposing any flavor symmetry. The on-shell conditions are applied especially in dealing with quark-flavor mixings. Also, the gauge independence is shown explicitly in the $R_ξ$ gauge.
Radiative Breaking of Two-Zero Neutrino Mass Minors: Revisiting the $\mathrm{U}(1)_{L_μ-L_τ}$ Model
ICRR, The University of Tokyo(东京大学宇宙射线研究所);Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo Institutes for Advanced Study, The University of Tokyo(东京大学国际高等研究院 Kavli宇宙物理与数学研究所)
Electroweak Transitions of Hyperons and Charmed Baryons: Opportunities and Prospects
Uppsala University(乌普萨拉大学);National Centre for Nuclear Research(国家核研究中心);University of Cyprus(塞浦路斯大学);The Cyprus Institute(塞浦路斯研究所);Institute of High Energy Physics(高能物理研究所);Lund University(隆德大学);École Polytechnique Fédérale de Lausanne(洛桑联邦理工学院);University of Graz(格拉茨大学)
QCD theory predicts the existence of glueballs, but so far all experimental endeavors have failed to identify any such states. To remedy this discrepancy between QCD, which has proven to be a successful theory for strong interactions, and the failure of experimental searches for glueballs, one is tempted to accept the promising interpretation that the glueballs mix with regular $q\bar q$ states of the same quantum numbers. The lattice estimate of the masses of pure $0^{++}$ glueballs ranges from 1 to 2 GeV, which is the region of the $f_0$ family. Thus many authors suggest that the $f_0$ meson…
Photo-excitation of hyperons and exotic baryon in gamma N --> K Anti-K N
我们研究了$γN \to K \bar{K} N$的反应,重点是光生$Λ(1520)$和推定的外来$Θ(1540)$。我们考虑各种背景产生机制,包括矢量介子,张量介子,和其他$Λ$和$Σ$超子的生产。讨论了$Λ(1520)$光生截面的角分布和$Λ(1520)$的辐射衰变。我们还讨论了我们所期望的不变的质量分布,如果$Θ(1540)$是在反应中形成的,与迄今为止研究的参数。我们发现,在$KN$不变质量分布中的峰值,如果得到证实,很难来自运动学反射,特别是,由于张量介子的背景。