We study the $D-\bar D$ mixing and rare D decays in the Littlest Higgs model. As the new weak singlet quark with the electric charge of 2/3 is introduced to cancel the quadratic divergence induced by the top-quark, the standard unitary $3\times 3$ Cabibbo-Kobayashi-Maskawa matrix is extended to a non-unitary $4\times 3$ matrix in the quark charged currents and Z-mediated flavor changing neutral currents are generated at tree level. In this model, we show that the $D-\bar D$ mixing parameter can be as large as the current experimental value and the decay branching ratio (BR) of $D\to X_u \ga$ is small but its direct CP asymmetry could be $O(10%)$. In addition, we find that the BRs of $D\to X_u \ell^{+} \ell^{-}$, $D\to X_uν\bar ν$ and $D\to μ^{+} μ^{-}$ could be enhanced to be $O(10^{-9})$, $O(10^{-8})$ and $O(10^{-9})$, respectively.
Motivated by the search for flavor-changing neutral current (FCNC) top quark decays at the LHC, we calculate rare Higgs three body decay $H\rightarrow Wbc$ induced by top-Higgs FCNC coupling in the littlest Higgs model with T-parity(LHT). We find that the branching ratios of $H\rightarrow Wbc$ in the LHT model can reach $\mathcal O(10^{-7})$ in the allowed parameter space.
Rare K and B Decays in the Littlest Higgs Model without T-Parity
我们分析了在没有T宇称的Littlest Higgs(LH)模型中的稀有K和B衰变。我们发现Z^0-penguin贡献的最终结果包含一个发散,该发散是由对与动态断开的发生器相对应的电流的单圈辐射校正产生的。包括对这些物理增强项的估计,我们计算了衰变K^+ -> pi^+ nu bar nu,K_L -> pi^0 nu bar nu,B_{s,d} -> mu^+ mu^-和B -> X_{s,d} nu bar nu的分支比。我们发现,对于高能量标度f=O(2-3)TeV,作为所需的电弱精度研究,所有分支比的增强量最多为15%以上的SM值。在技术方面,我们确定了一些错误,在现有的费曼规则的LH模型没有T-奇偶校验,可能会有一些影响,在文献中的其他分析。在幺正规范下计算企鹅图和箱形图,我们发现除了上面提到的发散之外,这两种贡献的发散在和中被抵消。
We study the rare decay $Z_H \rightarrow H^0 γ$ at $\mathcal{O}(α_{\rm ew}^{3}α_s)$ accuracy including two-loop QCD corrections in the context of the littlest Higgs model (LHM) without $T$-parity. We revisit analytically and numerically the leading-order (LO) contributions of the one-loop diagrams induced by massive fermions, scalars and charged gauge bosons in the LHM, and further study the NLO QCD correction to this decay process. We perform the numerical calculation by taking the LHM input parameters $f=3,~4~\text{TeV}$ and $0.1< c <0.6$, and discuss the numerical results of the decay width…
The Littlest Higgs Model with T-parity (LHT) belongs to the simplest new physics scenarios with new sources of flavour and CP violation. We present a new analysis of quark observables in the LHT model in view of the oncoming flavour precision era. We use all available information on the CKM parameters, lattice QCD input and experimental data on quark flavour observables and corresponding theoretical calculations, taking into account new lower bounds on the symmetry breaking scale and the mirror quark masses from the LHC. We investigate by how much the branching ratios for a number of rare $K$ …
The physics motivation and the conceptual design of the PIONEER experiment, a next-generation rare pion decay experiment testing lepton flavor universality and CKM unitarity, are described. Phase I of the PIONEER experiment, which was proposed and approved at Paul Scherrer Institut, aims at measuring the charged-pion branching ratio to electrons vs.\ muons, $R_{e/μ}$, 15 times more precisely than the current experimental result, reaching the precision of the Standard Model (SM) prediction at 1 part in $10^4$. Considering several inconsistencies between the SM predictions and data pointing towa…
这些讲座提供了最新的描述CP破坏和罕见的衰变的K和B介子,包括十章:i)包括CKM矩阵和幺正三角形的场的宏观视图,ii)基于有效弱哈密顿量、算子乘积展开和重整化群的理论框架的一般方面,iii)粒子-反粒子混合和各种类型的CP破坏,iv)幺正三角形的标准分析,v)比值ε '/ε r,vi)稀有衰变K^+ -> pi^+ nu barnu和K_L到pi ^0 nu barnu,vii)其他稀有衰变的快速回顾,viii)B衰变中的CP破坏,ix)标准模型之外的简要展望,特别讨论具有最小味破坏的模型,x)未来几年的展望。
Flavour mixing and CP violation as measured in weak decays and mixing of neutral mesons are a fundamental tool to test the Standard Model (SM) and to search for new physics. New analyses performed at the LHC experiment open an unprecedented insight into the Cabibbo-Kobayashi-Maskawa (CKM) metrology and new evidence for rare decays. Important progress has also been achieved in theoretical calculations of several hadronic quantities with a remarkable reduction of the uncertainties. This improvement is essential since previous studies of the Unitarity Triangle did show that possible contributions…
在列举了标准模型(SM)在味和CP破坏研究中起着关键作用的基本性质之后,我们讨论了以下几个问题:1)CKM矩阵和酉三角形。2)以非技术方式建立理论框架,对标准管理的各种延伸进行分类。3)粒子-反粒子混合和各种类型的CP破坏。4)酉三角形的标准分析。5)在非轻子B衰变中确定α、β和γ角的策略。6)稀有衰变K^+ -> pi^+ nu \bar nu和K_L -> pi ^0 nu \bar nu 7)具有最小味破坏(MFV)的模型。8)具有新的复杂相位的模型,特别是解决B -> pi K数据中新物理学的可能信号及其对稀有K和B衰变的影响。这些讲座的结尾是一份个人购物清单。
We study the exclusive semileptonic rare $B_c^+ \to D^+ ν\barν$ decay in the framework of light-cone quark model. The transition form factors $f_{+}(q^2)$ and $f_{T}(q^2)$ are evaluated in the time-like region using the analytic continuation method in $q^{+} = 0$ frame. The analytic solutions of these form factors are compared with the results obtained from the double pole parametric form. The branching ratio for $B_c^+ \to D^+ ν\barν$ decay is calculated and compared with the other theoretical model predictions. The predicted results in this model can be tested at the LHCb experiments in near…
The phenomenon of $B^0_q-\bar B^0_q$ mixing ($q=d,s$) provides a sensitive probe for physics beyond the Standard Model. We explore the corresponding space for New Physics left through the current data, having a careful look at analyses of the Unitarity Triangle that are needed for the Standard Model predictions of the $B_q$ mixing parameters. In particular, we explore the impact of tensions between inclusive and exclusive determinations of the CKM matrix elements $|V_{ub}|$ and $|V_{cb}|$. Moreover, we focus on the angle $γ$ of the Unitarity Triangle, comparing measurements from $B\to DK$ and …