The B factories were constructed with a very specific purpose in mind: to test the Cabibbo-Kobayashi-Maskawa description of quark mixing and CP violation in the Standard Model of particle physics. The goals of testing this part of the Standard Model were achieved, and have been surpassed beyond all expectation. As a result the B factories have revolutionised our understanding of many areas of the Standard Model of particle physics, and also provide a number of stringent limits on possible scenarios of physics beyond the Standard Model. In some cases these limits on new physics effects equal or surpass those achievable at the CERN based Large Hadron Collider.
Integrated Luminosity with 100 ppm Precision, Methods for $\sqrt{s}$ Precision of 1 ppm, and Beyond Standard Model Sensitivity using Photonic Events, at $\mathrm{e^{+}e^{-}}$ Higgs Factories
$B$-meson decays involving radiative and electroweak penguin processes are sensitive probes to new physics beyond the standard model. The Belle experiment recently reported measurements of the inclusive radiative decay $B \to X^{}_{s} γ$, and exclusive radiative decays $B \to K^{\ast} γ$ and $B \to K^{0}_{S} ηγ$. A lepton-flavor dependent measurements of angular observables for the decays $B \to K^{\ast} \ell \ell$ by Belle hinted at possible deviation from lepton-flavor-universality. Any departure from lepton flavor universality is essentially accompanied by lepton flavor violation. Recently,…
Exotic decays of the Standard Model-like Higgs boson into beyond-the-Standard Model particles are predicted in a wide range of well-motivated theories. The enormous samples of Higgs bosons that have been and will be produced at the Large Hadron Collider thus constitute one of the key discovery opportunities at that facility, particularly in the upcoming high-statistics high-luminosity run. Here we review recent theoretical work on models that predict or accommodate exotic Higgs decays, the status of current experimental searches, and look forward to future capabilities at dedicated Higgs facto…
In the past decade, electroweak penguin decays have provided a number of precision measurements, turning into one of the most competitive ways to search for New Physics that describe beyond the Standard Model phenomena. An overview of the measurements made at the $B$ factories and hadron colliders are given and the experimental methods are presented. Experimental measurements required to provide further insight into present indications of New Physics are discussed.
The concept of lepton flavour universality (LFU), according to which the three lepton families are equivalent except for their masses, is a cornerstone prediction of the Standard Model (SM). LFU can be violated in models beyond the SM by new physics particles that couple preferentially to certain generations of leptons. In the last few years, hints of LFU violation have been observed in both tree-level $b\to c\ellν$ and loop-level $b\to s\ell\ell$ transitions. These measurements, combined with the tensions observed in angular observables and branching fractions of rare semileptonic $b$ decays,…
Neutrino factories, neutrino beams produced in the decay of a muon or antimuon beam inside a storage ring, yield cleaner, richer, and more flexible neutrino beams relative to super-beams. We explore the physics case for this type of beam both for standard oscillation as well as new physics searches and present some machine options. We argue that there is a rich program beyond what the current neutrino program can cover and a string synergy with the muon collider program.
$L\,\to\, l\, l'\, l'\, ν_l\, ν_L$ in the SM and beyond
我们研究了$L\to l l' l' ν_l ν_L$衰变（$L=τ,μ$ ; $l,l'=μ,e$）在标准模型（SM）和有效场理论（EFT）描述的弱带电电流在低能量下，无论是极化和非极化$L$，保持$l,l'$质量依赖性。我们澄清了两个以前的SM计算的衰变率之间的差异，提高其精度。最近在$τ\to e γ\barν_eν_τ$中发现的$3.5\,σ$异常可以使用我们对$τ\to e e e \barν_eν_τ$衰变的精确预测来检查，这将通过分析来自第一代B工厂的现有数据来测量。它示出了如何测量的二- $l'$质量分布（适当的削减）和$T$ -不对称性能够揭示相应的轻子味违反（LFV）过程中没有中微子的最终状态。
