The new model of $n\bar{n}$ transitions in nuclei based on unitary $S$-matrix is considered. The $|in>$-state of nucleus is described by single-particle shell model. The dynamical process part is calculated by means of field-theoretical approach with finite time interval. The lower limit on the free-space $n\bar{n}$ oscillation time $τ_{\rm min}$ is in the range $10^{16}\; {\rm yr}>τ_{\rm min}>1.2\cdot 10^{9}\; {\rm s}$. \end{abstract}
In a supersymmetric extension of the standard model with local gauged baryon and lepton numbers (BLMSSM), there are new sources for lepton flavor violation, because the right-handed neutrinos, new gauginos and Higgs are introduced. We investigate muon conversion to electron in nuclei within the BLMSSM in detail. The numerical results indicate that the $μ\rightarrow e $ conversion rates in nuclei within the BLMSSM can reach the experimental upper bound, which may be detected in the future experiments.
Electron-muon conversion in nuclei and rare decays induced by LFV dark photon
Bogoliubov Laboratory of Theoretical Physics, JINR（鲍戈留博夫理论物理实验室，俄罗斯联合核子研究所）；Matrosov Institute for System Dynamics and Control Theory SB RAS（马特罗索夫系统动力学与控制理论研究所，俄罗斯科学院西伯利亚分院）；Millennium Institute for Subatomic Physics at the High-Energy Frontier (SAPHIR) of ANID（智利国家研究与创新发展局高能前沿亚原子物理学千年研究所（SAPHIR））；Center for Theoretical and Experimental Particle Physics, Facultad de Ciencias Exactas, Universidad Andres Bello（安德烈斯贝洛大学精确科学学院理论与实验粒子物理中心）；Institut für Theoretische Physik, Universität Tübingen, Kepler Center for Astro and Particle Physics（蒂宾根大学理论物理研究所，开普勒天体与粒子物理中心）
μ-e conversion in nuclei versus μ-->e γ: an effective field theory point of view
使用一个有效的拉格朗日描述，我们分析了可能的新的物理贡献最相关的μ子数违反过程：$μ\to e γ$和$μ$ - $e$转换的核。我们确定了一个通用类的模型，其中这些过程是在一个循环级别生成的，其中$μ$ - $e$转换增强相对于$μ\to e γ$由一个大的$\ln(m^2_μ/Λ^2),$，其中$Λ$是规模负责新的物理。对于这类广泛的模型，$μ$- $e$转换比目前已经存在的$μ\to e γ$更严格地限制了新物理学的规模，并且随着$μ$ - $e$转换实验的预期改进，将把它向上推大约一个数量级。为了说明这一一般性结果，我们给出了一个明确的模型包含一个双电荷标量，并推导出新的界限，其耦合的轻子。
Within the Standard Model Effective Field Theory framework, with operators up to dimension 6, we perform a model-independent analysis of the lepton-flavour-violating processes involving tau leptons. Namely, we study hadronic tau decays and $\ell$--$τ$ conversion in nuclei, with $\ell = e,μ$. Based on available experimental limits, we establish constraints on the Wilson coefficients of the operators contributing to these processes. Our work paves the way to extract the related information from Belle II and foreseen future experiments.
We analyze the lepton flavor violating process $μ-e$ conversion in the framework of the minimal R-symmetric supersymmetric standard model. The theoretical predictions are determined by considering the experimental constraint on parameter $δ^{12}$ from the lepton flavor violating decay $μ\rightarrow e γ$. The numerical results show that $γ$ penguins and Z penguins dominate the predictions on CR($μ-e$,Nucleus), and the contributions from Higgs penguins and box diagrams are insignificant. The theoretical predictions on conversion rate CR($μ-e$,Nucleus) in a Al or Ti target can be enhanced close t…
Improved predictions for $μ\to e$ conversion in nuclei and Higgs-induced lepton flavor violation
与$μ\to e γ$和$μ\to e e e$相比，核中的$μ\to e$转换过程受到Higgs诱导的轻子味破坏的增强贡献.即将进行的$μ\to e$转换实验灵敏度大幅提高，将能够对希格斯介导的$μ\to e$转换施加极其严格的限制。我们指出，与这些希格斯效应，编码在夸克标量算子的核子耦合的理论不确定性，可以准确地评估使用我们最近开发的方法的基础上$SU(2)$手征微扰理论，干净地分离两个和三个味道的观测。我们强调，输入从格点量子色动力学耦合到奇异$f_s^N$，强子的不确定性明显减少相比，传统的方法，其中$f_s^N$是确定从π-核子$σ$ -项通过一个$SU(3)$关系。我们说明了这一点，考虑希格斯介导的轻子味违反补充高维运营商的标准模型，两个希格斯偶极子模型与通用汤川耦合，和最小超对称标准模型。此外，我们比较目前和未来的$μ\to e$转换和$μ\to e γ$实验的界限。
Within the Standard Model Effective Field Theory framework, with operators up to dimension 6, we perform a model-independent analysis of the lepton-flavour-violating processes involving tau leptons. Namely, we study hadronic tau decays and $\ell$-$τ$ conversion in nuclei ($\ell=e,μ$). Based on available experimental limits, we establish constraints on the Wilson coefficients of the operators contributing to these processes. The related information from Belle II and foreseen future experiments can be easily incorporated into the resulting framework.
Lepton-flavor-violating decays of light pseudoscalars, $P=π^0,η,η'\toμe$, are stringently suppressed in the Standard Model up to tiny contributions from neutrino oscillations, so that their observation would be a clear indication for physics beyond the Standard Model. However, in effective field theory such decays proceed via axial-vector, pseudoscalar, or gluonic operators, which are, at the same time, probed in spin-dependent $μ\to e$ conversion in nuclei. We derive master formulae that connect both processes in a model-independent way in terms of Wilson coefficients, and study the implicati…
Within a class of models in which lepton flavor violation is induced dominantly by scalar particle exchanges, we estimate the $μ\to e$ conversion rate in several nuclei. We include next-to-leading order (NLO) terms in the one- and two-nucleon interactions in chiral effective theory, rectifying some incorrect results in the previous literature. We provide an uncertainty budget for the conversion rates and we find that NLO contributions affect the amplitudes at the level of $10\%$, which could be larger than the uncertainty on the leading order couplings, dominated by the strange and non-strange…
In a few years, the COMET experiment at J-PARC and the Mu2e experiment at Fermilab will probe the $μ-e$ conversion rate in the vicinity of $\mathcal{O}(10^{-17})$ for an Al target with high experimental sensitivity. Within the framework of the minimal supersymmetric extension of the Standard Model with local $B-L$ gauge symmetry (B-LSSM), we analyze the lepton flavor violating (LFV) process of $μ-e$ conversion in nuclei. Considering the constraint of the experimental upper limit of the LFV rare decay $μ\rightarrow eγ$, the $μ-e$ conversion rates in nuclei within the B-LSSM can achieve $\mathca…
The experimental sensitivity to $μ\to e$ conversion on nuclei is expected to improve by four orders of magnitude in coming years. We consider the impact of $μ\to e$ flavour-changing tensor and axial-vector four-fermion operators which couple to the spin of nucleons. Such operators, which have not previously been considered, contribute to $μ\to e$ conversion in three ways: in nuclei with spin they mediate a spin-dependent transition; in all nuclei they contribute to the coherent ($A^2$-enhanced) spin-independent conversion via finite recoil effects and via loop mixing with dipole, scalar, and v…
$μ-e$ conversion in nuclei within the CMSSM seesaw: universality versus non-universality
本文在约束最小超对称标准模型中研究了原子核中的$μ-e$转换，该模型由三个右手中微子和它们的超对称伙伴放大，其中中微子质量是通过跷跷板机制产生的。两种不同的情况下，无论是普遍的或非普遍的软超对称破缺希格斯质量的规范耦合统一尺度被认为是。在第一部分中，我们提出了一个完整的一个循环计算的转换率为这个过程中，包括光子，$Z$ -玻色子，希格斯玻色子企鹅，以及框图，并比较它们的大小在两个考虑的情况。然后，在这两种情况下，我们分析的转换率的各种参数的相关性，特别强调的作用所发挥的重中微子质量，$\tan β$，特别是$θ_{13}$。在分级重中微子的情况下，发现了$μ-e$转换率对$θ_{13}$的极高灵敏度，本文的最后一部分致力于研究在非普适情形下$μ-e$转换率与$μ\to e γ$转换率之间有趣的关联丢失。在大$\tan β$和轻$H^0$希格斯玻色子的情况下，$μ-e$与$μ\to e γ$速率的比率相对于普遍情况被发现，这可以用未来的实验灵敏度进行测试。
The experimental sensitivity to $μ\to e$ conversion will improve by four or more orders of magnitude in coming years, making it interesting to consider the "spin-dependent" (SD) contribution to the rate. This process does not benefit from the atomic-number-squared enhancement of the spin-independent (SI) contribution, but probes different operators. We give details of our recent estimate of the spin dependent rate, expressed as a function of operator coefficients at the experimental scale, and explore the prospects for distinguishing coefficients by using different targets. For this purpose, a…
The muon-to-electron conversion in nuclei like aluminum, titanium and gold is studied in the context of a class of mirror fermion model with non-sterile right-handed neutrinos having mass at the electroweak scale. At the limit of zero momentum transfer and large mirror lepton masses, we derive a simple formula to relate the conversion rate with the on-shell radiative decay rate of muon into electron. Current experimental limits (SINDRUM II) and projected sensitivities (Mu2e, COMET and PRISM) for the muon-to-electron conversion rates in various nuclei and latest limit from MEG for the radiative…
The mu - e Conversion in Nuclei, mu --> e gamma, mu --> 3e Decays and TeV Scale See-Saw Scenarios of Neutrino Mass Generation
我们进行了详细的分析，轻子味违反（LFV）内的最小跷跷板型扩展的标准模型（SM），这给出了一个可行的中微子质量产生的机制，并提供新的粒子内容在电弱尺度。我们的重点，主要是预测和约束设置在每一个方案从μ-> e γ，μ-> 3e和μ- e转换的核。在这类模型中，额外的标量和费米子表示与SM轻子之间的汤川耦合的味结构受到中微子振荡测量的高度约束。特别是，我们表明，在某些区域的参数空间的I型和II型跷跷板模型，狄拉克和马约拉纳阶段的中微子混合矩阵，排序和层次的活性中微子质谱以及反应堆混合角theta_{13}的值可能会大大影响LFV观测值的大小。后者的相互作用显然允许区分不同的低能量跷跷板的可能性。
We consider the possibility of neutron-antineutron ($n-\bar n$) conversion, in which the change of a neutron into an antineutron is mediated by an external source, as can occur in a scattering process. We develop the connections between $n-{\bar n}$ conversion and $n-{\bar n}$ oscillation, in which a neutron spontaneously tranforms into an antineutron, noting that if $n-{\bar n}$ oscillation occurs in a theory with B-L violation, then $n-{\bar n}$ conversion can occur also. We show how an experimental limit on $n-{\bar n}$ conversion could connect concretely to a limit on $n-{\bar n}$ oscillat…
Limits on Lepton Flavor Violation from μ-e-conversion
本文从原子核中μ- e -转换的角度重新讨论了轻子味破坏（LFV）μ eqq接触相互作用的现状。我们考虑了它们通过强子水平上的两种机制对LFV过程的贡献：直接核子交换机制和介子交换机制。在前一种情况下，夸克直接嵌入核子中，而在后一种情况下，则嵌入介子中，然后介子与核中的核子相互作用。我们修正并在某些情况下重新估计了与这两种机制有关的强子参数，并计算了上述接触相互作用在各种核的相干μ- e -转换中的贡献。然后我们更新了已有的上界，并从μ- e -转换俘获率的实验极限出发，导出了μe-qq接触相互作用尺度的新上界.我们比较这些限制与文献中来自其他LFV过程和评论的LHC搜索的前景有关的接触μe qq相互作用。
A study of bound states of $η, η^{'}, D^{0}$, $\bar{D^{0}}$, $B^{0}$, $\bar{B^{0}}$, $\bar{K^{0}}$ and $ϕ$ mesons with light and heavy nuclei within chiral SU(3) model
The calculation of electroweak corrections to processes with jets in the final state involves contributions of low-virtuality photons leading to jets in the final state via the singular splitting $γ^* \to q\bar q$. These singularities can be absorbed into a photon-to-jet "fragmentation function", better called "conversion function", since the physical final state is any hadronic activity rather than an identified hadron. Using unitarity and a dispersion relation, we relate this $γ^* \to q\bar q$ conversion contribution to an integral over the imaginary part of the hadronic vacuum polarization …
We propose a new approach based on the Lindblad and Bloch equations for the density matrix to the problem of a neutron into an antineutron conversion. We consider three strategies to search for conversion: experiments with trapped neutrons, oscillations in nuclei, and quasi-free propagation. We draw a distinction between $n\bar{n}$ oscillations in which the probability that a neutron transforms into an antineutron depends on time according to the sine-square law and the non-oscillatory overdamped $n\bar{n}$ conversion. We show that in all three cases decoherence due to the interaction with the…
We study the inclusive photoproduction of $T_{{\bar c}{\bar c}}(3875)^-$ mesons (which are the antiparticles of the doubly charmed tetraquarks $T_{cc}(3875)^+$ discovered recently by the LHCb Collaboration) from nuclei in the near-threshold energy region within the nuclear spectral function approach by considering incoherent direct ($γp(n) \to D^+(D^0){T_{{\bar c}{\bar c}}(3875)^-}Λ^+_c$) photon--nucleon $T_{{\bar c}{\bar c}}(3875)^-$ creation processes as well as five possible different scenarios for their internal structure with the main goal of clarifying the possibility to decipher this st…
We investigate charged lepton flavor violating processes $μ\rightarrow e γ$, $μ\rightarrow e e \overline{e}$ and $μ-e$ conversion in nuclei for a class of three-loop radiative neutrino mass generation models with electroweak multiplets of increasing order. We find that, because of certain cancellations among various one-loop diagrams which give the dipole and non-dipole contributions in effective $μe γ$ vertex and Z-penguin contribution in effective $μe Z$ vertex, the flavor violating processes $μ\rightarrow eγ$ and $μ-e$ conversion in nuclei become highly suppressed compared to $μ\rightarrow …
Collective pair conversion $ν_e\barν_e\leftrightarrow ν_{x}\barν_{x}$ by forward scattering, where $x=μ$ or $τ$, may be generic for supernova neutrino transport. Depending on the local angular intensity of the electron lepton number carried by neutrinos, the conversion rate is "fast," i.e., of the order of $\sqrt{2}G_{\rm{F}}(n_{ν_e}{-}\,n_{\barν_e})\ggΔm^2_{\rm atm}/2E$. We present a novel approach to understand these phenomena: A dispersion relation for the frequency and wave number $(Ω,\bf{K})$ of disturbances in the mean field of $ν_eν_x$ flavor coherence. Run-away solutions occur in "disp…
We carry out an exhaustive analysis of lepton flavor violating processes within the Simplest Little Higgs model. Its discovery could be expected from either $μ\to e$ conversion in nuclei, $μ\to eγ$ or $μ\to3e$ decays. Then, the tau sector could help discriminating this model not only via $τ\to\ellγ$ ($\ell=μ,e$) and $τ\to3\ell$ decays, but also by means of $\ell\toτ$ conversion in nuclei, which is promising in this respect. Although the model violates slightly custodial symmetry, acommodating the recent CDF $M_W$ measurement is in tension with electroweak precision data.
