The first experimental evidence for direct CP violation in charm-quark decays has recently been presented by the LHCb collaboration in the difference between the D -> K+ K- and D -> pi+ pi- time-integrated CP asymmetries. We estimate the size of the effects that can be expected within the Standard Model and find that at leading order in 1/mc they are an order of magnitude smaller. However, tree-level annihilation type amplitudes are known to be large experimentally. This implies that certain formally 1/mc-suppressed penguin amplitudes could plausibly account for the LHCb measurement. Simultaneously, the flavor-breaking parts of these amplitudes could explain the large difference between the D -> K+ K- and D -> pi+ pi- decay rates.
New Physics and CP Violation in Singly Cabibbo Suppressed D Decays
我们分析了单卡比博抑制(SCS)D-介子衰变中CP破坏的各个理论方面,例如$D \to K K,ππ$。特别是,我们探讨的可能性,CP不对称性将被测量接近目前水平的实验灵敏度的$O(10^{-2})$。这样的测量将标志着新的物理学。我们提出以下几点:(1)中性D衰变中起作用的机制可以是间接的或直接的CP破坏(或两者兼有)。(ii)人们可以通过实验来区分这些可能性。(iii)如果主要的CP破坏是间接的,那么对于其他模式有明确的预测。(iv)树级直接CP破坏在各种已知的模型中被约束为比$10^{-2}$小得多。(v)SCS衰变,不像Cabibbo青睐或双Cabibbo抑制衰变,是敏感的QCD企鹅运营商,特别是从色磁偶极运营商的新贡献。这一点说明与超对称的胶子夸克环,它可以产生直接CP破坏$O(10^{-2})$的影响。
The singly charged $SU(2)_L$ singlet scalar, with its necessarily flavour violating couplings to leptons, lends itself particularly well for an explanation of the Cabibbo Angle Anomaly and of hints for lepton flavour universality violation in $τ\to μ\bar νν$. In a setup addressing both anomalies, we predict loop-induced effects in $τ\to eγ$ and in $τ\to eμμ$. A recast of ATLAS selectron and smuon searches allows us to derive a coupling-independent lower limit of $\approx 200$ GeV on the mass of the singly charged singlet scalar. At a future $e^+e^-$ collider, dark matter mono-photon searches c…
We analyze the weak processes of anti-triplet charmed baryons decaying to octet baryons and mesons with the SU(3) flavor symmetry and topological quark diagram scheme. We study the decay branching ratios without neglecting the contributions from ${\cal O}(\overline{15})$ for the first time in the SU(3) flavor symmetry approach. The fitting results for the Cabibbo allowed and suppressed decays of $Λ_{c}^+$ are all consistent with the experimental data. We predict all singly Cabibbo suppressed decays. In particular, we find that ${\cal B}(Λ_c^+\to p π^0)=(1.3\pm0.7)\times 10^{-4}$, which is slig…
基于对$c \to s u \bar d$主导的Cabibbo偏好衰变的分析,利用味拓扑方法研究了夸克子过程$c \to s u \bar s$和$c \to d u \bar d$主导的粲粒子的单Cabibbo抑制衰变.考虑了衰变到$PP$和$PV$的情况,其中$P$是赝标介子,$V$是矢量介子.我们包括生产$η$和$η'$的工艺。
We study singly Cabibbo-suppressed two-body hadronic decays of the charmed baryon $Λ_c^+$, namely, $Λ_c^+\to ΛK^+, pπ^0, pη, nπ^+,Σ^0K^+,Σ^+ K^0$. We use the measured rate of $Λ_c^+\to pϕ$ to fix the effective Wilson coefficient $a_2$ for naive color-suppressed modes and the effective number of color $N_c^{\rm eff}$. We rely on the current-algebra approach to evaluate $W$-exchange and nonfactorizable internal $W$-emission amplitudes, that is, the commutator terms for the $S$-wave and the pole terms for the $P$-wave. Our prediction for $Λ_c^+\to pη$ is in excellent agreement with the BESIII mea…
Cabibbo-suppressed non-leptonic B- and D-decays involving tensor mesons
采用Isgur-Scora-Grinstein-Wise的非相对论夸克模型,在因子分解假设下,计算了B(和D)介子到包含张量介子的末态的Cabibbo抑制的非轻子衰变.我们发现其中一些B衰变模式,如B ->(K^*,D^*)D^*_2,其分支比可达6 x 10^{-5},这似乎是未来B工厂所能达到的。
Final-State Phases in Doubly-Cabibbo-Suppressed Charmed Meson Nonleptonic Decays
Cabibbo偏爱的非轻子粲粒子衰变在$\bar K π$和$\bar K^* π$通道中表现出大的末态相位差,但在$\bar K ρ$通道中没有。我们很有兴趣知道由$c \to d u \bar s$子过程控制的双Cabibbo抑制衰变的末态相的相应模式。通过测量$D \to K^* π$和$K (ρ, ω,ϕ)$通道的速率,以及确定Dalitz图中频带之间的干扰,概述了用于确定这种相位的实验程序。这样的计划在计划中的高强度粲化粒子源是可行的。
Asymmetries from the interference between Cabibbo-favored and doubly-Cabibbo-suppressed D decays
利用现有的实验数据对$D\to Kπ$和$D_s^+\to K K $衰变进行了唯象分析,其中包括Cabibbo有利模和双Cabibbo抑制模.分析中考虑了衰变常数和形状因子对SU(3)对称性破缺的影响。三个不对称,$R(D^0)$,$R(D^+)$,和$R(D_s^+)$,这是通过Cabbibo的青睐和双重Cabibbo抑制衰变之间的干扰产生的,估计。理论计算结果与实测结果吻合较好。
Cabibbo-suppressed non-leptonic decays of Lambda_c and final state interaction
利用Lambda_c的双夸克结构,我们研究了Lambda_c -> n π ^+和p π ^0的分支比.结果表明,在不考虑末态相互作用(FSI)的情况下,Lambda_c -> p π ^+的分支比仅为10^{-6}量级,而考虑FSI效应后,该分支比可达10^{-4}量级,与Lambda_c -> n π ^0量级相同.具体值取决于计算中采用的唯象参数。这些分支比可以在以后的实验中测量。
New Physics Effects in Doubly Cabibbo Suppressed D Decays
对$D-\bar D$混合的最灵敏的实验搜索使用$D^0 \to K^+ π^-$衰变。人们通常认为新物理学的效应,特别是CP破坏,可以通过混合出现,而$c \to d u \bar s$衰变振幅不能有新物理学的显著贡献,因此,CP守恒到一个很好的近似。我们从两个方面来检验这个假设。首先,我们计算了新物理学的各种相关模型对衰变的贡献:无R宇称的超对称性,多标量模型,左右对称模型和额外夸克模型。我们发现,唯象约束意味着新物理学的贡献确实是小的相比,标准模型的双重Cabibbo抑制振幅。其次,我们表明,我们的许多约束模型独立。然而,我们发现,在一种情况下,模型无关的约束是相当弱的CP违反贡献的顺序30%不排除。
Combined analysis of the singly-Cabbibo-suppressed decays of $D^{0} \to VP$
Institute of High Energy Physics, Chinese Academy of Sciences(中国科学院高能物理研究所);University of Chinese Academy of Sciences(中国科学院大学);Center for High Energy Physics, Henan Academy of Sciences(河南省科学院高能物理中心)
Taking into account that the scalar $a_0(980)$ can be dynamically generated from the pseudoscalar-pseudoscalar interaction within the chiral unitary approach, we have studied the single Cabibbo-suppressed process $D^+\to π^+π^0η$. We find clear peaks of $a_0(980)^+$ and $a_0(980)^0$ in the $π^+η$ and $π^0η$ invariant mass distributions, respectively. The predicted Dalitz plots of $D^+\to π^+π^0η$ also manifest the significant signals for $a_0(980)^+$ and $a_0(980)^0$ states. The uncertainties of the results due to the free parameters are also discussed. Our study shows that the process $D^+\to…
In this work we study the $Σπ$ and $Λπ$ production off free nucleons driven by the strangeness-changing weak charged current. We calculate the total cross sections for all possible channels and estimate the flux-averaged total cross sections for experiments like MiniBooNE, SciBooNE, T2K, and Minerva. The model is based on the lowest order effective SU(3) chiral Lagrangians in the presence of an external weak charged current and contains Born and the lowest-lying decuplet resonant mechanisms that can contribute to these reaction channels. We also compare and discuss our results with others foll…
Singly Cabibbo-suppressed hadronic weak decays of the $Ω^-$ hyperon
Southern Center for Nuclear-Science Theory (SCNT), Institute of Modern Physics, Chinese Academy of Sciences(中国科学院近代物理研究所);School of Physics and Mechatronic Engineering, Guizhou Minzu University(贵州民族大学);Heavy Ion Science and Technology Key Laboratory, Institute of Modern Physics, Chinese Academy of Sciences(中国科学院近代物理研究所);School of Nuclear Sciences and Technology, University of Chinese Academy of Sciences(中国科学院大学);Institute of High Energy Physics, Chinese Academy of Sciences(中国科学院高能物理研究所);University of Chinese Academy of Sciences(中国科学院大学);Center for High Energy Physics, Henan Academy of Sciences(河南省科学院)
Doubly Cabibbo-suppressed (DCS) nonleptonic weak decays of antitriplet charmed baryons are studied systematically in this work. The factorizable and nonfactorizable contributions can be classified explicitly in the topological-diagram approach and treated separately. In particular, the evaluation of nonfactorizable terms is based on the pole model in conjunction with current algebra. All three types of relevant non-perturbative parameters contributing factorizable and nonfactorizable terms are estimated in the MIT bag model. Branching fractions of all the DCS decays are predicted to be of orde…
We study the $K^0_S-K^0_L$ asymmetries and $CP$ violations in charm-baryon decays with neutral kaons in the final state. The $K^0_S-K^0_L$ asymmetry can be used to search for two-body doubly Cabibbo-suppressed amplitudes of charm-baryon decays, with the one in $Λ^+_c\to pK^0_{S,L}$ as a promising observable. Besides, it is studied for a new $CP$-violation effect in these processes, induced by the interference between the Cabibbo-favored and doubly Cabibbo-suppressed amplitudes with the neutral kaon mixing. Once the new CP-violation effect is determined by experiments, the direct $CP$ asymmetry…
In the chiral unitary approach, we have studied the single Cabibbo-suppressed decays $Λ_c\to pK^+K^-$ and $Λ_c \to p π^+π^-$ by taking into account the $s$-wave meson-meson interaction as well as the contributions from the intermediate vectors $ϕ$ and $ρ^0$. Our theoretical results for the ratios of the branching fractions of $Λ_c\to p \bar{K}^{*0}$ and $Λ_c\to p ω$ with respect to the one of $Λ_c\to p ϕ$ are in agreement with the experimental data. Within the picture that the scalar resonances $f_0(500)$, $f_0(980)$, and $a_0(980)$ are dynamically generated from the pseudoscalar-pseudoscalar …