LFV and Dipole Moments in Models with A4 Flavour Symmetry
Luca Merlo
备注:
10 pages, 1 figure. Adapted from a talk given at "DISCRETE'08: Symposium on Prospects in the Physics of Discrete Symmetries", December 11-16 2008, Valencia, Spain
It is presented an analysis on lepton flavour violating transitions, leptonic magnetic dipole moments and electric dipole moments in a class of models characterized by the flavour symmetry A4 x Z3 x U(1)_FN, whose choice is motivated by the approximate Tri-Bimaximal mixing observed in neutrino oscillations. A low-energy effective Lagrangian is constructed, where these effects are dominated by dimension six operators, suppressed by the scale M of new physics. All the flavour breaking effects are universally described by the vacuum expectation values of a set of spurions. Two separate cases, a supersymmetric and a general one, are described. An upper limit on the reactor angle of a few percent is concluded.
在这篇评论文章中,我们强调的影响模型,将味对称性带电轻子味违反(LFV)的过程。味对称性提供了一个自然的方法来解释特殊的质量等级和混合模式的标准模型费米子。新的LFV源通常存在于标准模型之外的新物理中,并且味道对称性可以对LFV观测值做出独特的预测。他们的发现可以为区分味道对称性和新的物理场景提供重要信息。由于它们的高灵敏度,我们将专注于寻找低能LFV过程,如原子核中的μ-> e γ或μ-e转换,但我们也将强调LFV过程在LHC中的潜在影响。如果新的物理学在大型强子对撞机可以达到的尺度上发生,那么它们诱导的味道算子可能会被高度详细地探测。
Lepton flavour violation (LFV) naturally occurs in many new physics models, specifically in those explaining the $B$ anomalies. While LFV has already been studied for mesonic decays, it is important to consider also baryonic decays mediated by the same quark transition. In this paper, we study LFV in the baryonic $Λ_b \to Λ\ell_1 \ell_2$ using for the first time a full basis of New Physics operators. We present expected bounds on the branching ratio in a model-independent framework and using two specific new physics models. Finally, we point out the interplay and orthogonality between the bary…
Upcoming searches for lepton flavour change (LFV) aim to probe New Physics(NP) scales up to $ \sim 10^4$ TeV, implying that they will be sensitive to NP at lower scales that is suppressed by loops or small couplings. We suppose that the NP responsable for LFV is beyond the reach of the LHC and can be parametrised in Effective Field Theory, introduce a small power-counting parameter à la Cabibbo-Wolfenstein, and assess whether the existing dimension six operator basis and one-loop RGEs provide a good approximation for LFV. We find that mu to e flavour-changing observables can be sensitive to a …
We explore possible signatures for charged lepton flavour violation (LFV), sparticle discovery at the LHC and dark matter (DM) searches in grand unified theories (GUTs) based on SU(5), flipped SU(5) (FSU(5)) and SU(4)$_c \times $SU(2)$_L \times $SU(2)$_R$ (4-2-2). We assume that soft supersymmetry-breaking terms preserve the group symmetry at some high input scale, and focus on the non-universal effects on different matter representations generated by gauge interactions at lower scales, as well as the charged LFV induced in Type-1 see-saw models of neutrino masses. We identify the different me…
In this work we analyse a non-minimal Lorentz-violating extension of the electroweak theory in the fermionic sector. Firstly we analyse the relation between the CKM rotation in the quark sector and possible contributions of this new coupling to flavour changing neutral currents (FCNC) processes. In sequel we look for non-diagonal terms through possible leptonic flavour violation (LFV) decays. Strong bounds are presented to the Lorentz violating parameters of both the quark and the leptonic sectors.
Non-Standard neutrino Interactions (NSI) are vector contact interactions involving two neutrinos and two first generation fermions, which can affect neutrino propagation in matter. SU(2) gauge invariance suggests that NSI should be accompanied by more observable charged lepton contact interactions. However, these can be avoided at tree level in various ways. We focus on lepton flavour-changing NSI, suppose they are generated by New Physics heavier than $m_W$ that does not induce (charged) Lepton Flavour Violation (LFV) at tree level, and show that LFV is generated at one loop in most cases. Th…
尽管在中微子振荡中观察到了大的轻子味破坏(LFV),但在标准模型中,我们确实期望在带电轻子扇区($μ\to e, γ$,$τ\to μ, γ$等)中有任何可见的LFV(\textit{not})。相反,接近电弱尺度的新物理的存在可以增强这些过程的振幅。我们讨论了这一点,在一般情况下,并专注于一个特别有趣的情况下:婚姻的低能超对称性(SUSY)和跷跷板机制中微子质量(SUSY跷跷板)。在这方面提出的几个想法都审查自下而上和自上而下的方法。我们发现,存在有吸引力的模型,LFV过程的速率可以达到值在前LHC实验中进行探测。
Lepton Flavour Violation In Supersymmetric Models with Trilinear R-parity Violation
具有R宇称破坏的超对称性(RPV)为自然容纳小中微子质量提供了一个有趣的框架。在此框架下,我们讨论了原子核中的轻子味破坏(LFV)过程μ-> e γ,μ-> e γ,μ-> e转换。我们详细研究了不同RPV模型中与LFV相关的观测值,并将它们与重右手中微子的R守恒超对称性的预期进行了比较。我们表明,预测是截然不同的,独特的每个模型,从而提供了一个强大的框架,实验区分不同的理论LFV。除了核中mu -> e和mu -> e转换的放大树能级产生的明显可能性之外,我们发现,即使在这些过程出现在单回路水平的情况下,它们的速率也与mu -> e γ的速率相当,与R守恒模型的预测形成鲜明对比。我们的结论是,为了区分不同的模型,这样的所有LFV过程的综合研究是必要的,和测量P-奇数不对称性极化μ-> μ-可以发挥决定性的作用。我们还评论了RPV模型产生一个大的T-奇数不对称性的极化μ-> μ衰变的有趣的可能性。
In this work we assess the potential of discovering new physics by searching for lepton-flavour-violating (LFV) decays of the $Z$ boson, $Z\to \ell_i \ell_j$, at the proposed circular $e^+e^-$ colliders CEPC and FCC-ee. Both projects plan to run at the $Z$-pole as a Tera Z factory, i.e., collecting $\mathcal O\left(10^{12}\right)$ $Z$ decays. In order to discuss the discovery potential in a model-independent way, we revisit the LFV $Z$ decays in the context of the Standard Model effective field theory and study the indirect constraints from LFV $μ$ and $τ$ decays on the operators that can indu…
Neutrino masses, muon g-2, and lepton-flavour violation in the supersymmetric see-saw model
In the light of the recent muon (g_mu-2) result by the E821 experiment at the Brookhaven National Laboratory, we study the event rates of the charged lepton-flavour-violating (LFV) processes in the supersymmetric standard model (SUSY SM) with the heavy right-handed neutrinos (SUSY see-saw model). Since the left-handed sleptons get the LFV masses via the neutrino Yukawa interaction in this model, the event rate of mu->e gamma and the SUSY-SM correction to (g_mu-2)/2 (δa_mu^{SUSY}) are strongly correlated. When the left-handed sleptons have a LFV mass between the first and second generations ((m…
Polytechnic University of the Philippines(菲律宾理工大学)
The discovery of neutrino oscillation, proving that neutrinos do have masses, reveals the misfits of particles in the current Standard Model (SM) theory. In theory, neutrinos having masses could result in lepton flavour not being a symmetry called Lepton Flavour Violation (LFV). While SM theory extensions allowed LFV processes, their branching fractions are too small, making them unobservable even with the strongest equipment up-to-date. With that, scientists in recent years have generated LFV-like processes from the combined LHCb and Monte-Carlo-Simulated data in an attempt to identify LFV us…
Within an effective-field-theory framework, we present a model-independent analysis of the potential of discovering new physics by searching for lepton flavour violation in heavy quarkonium decays and, more in general, we study the phenomenology of lepton-flavour-violating (LFV) 2 quark - 2 lepton ($2q2\ell$) operators with two charm or bottom fields. We compute the constraints from LFV muon and tau decays on the new-physics operators that can induce LFV processes involving $c\bar c$ and $b\bar b$ systems, thus providing a comprehensive list of indirect upper limits on processes such as $J/ψ\t…