We explore the prospects for searches at the LHC for sparticle decays that violate $τ$ lepton number, in the light of neutrino oscillation data and the seesaw model for neutrino masses and mixing. We analyse the theoretical and phenomenological conditions required for tau flavour violation to be observable in χ_2 \to χ+ τ^\pm μ^\mp decays, for cosmologically interesting values of the relic neutralino LSP density. We study the relevant supersymmetric parameter space in the context of the Constrained Minimal Supersymmetric Extension of the Standard Model (CMSSM) and in SU(5) extensions of the theory. We pay particular attention to the possible signals from hadronic tau decays, that we analyse using PYTHIA event simulation. We find that a signal for τflavour-violating χ_2 decays may be observable if the branching ratio exceeds about 10%. This may be compatible with the existing upper limit on τ\to μγdecays if there is mixing between right-handed sleptons, as could be induced in non-minimal SU(5) GUTs.
Charged Lepton Flavour Violation in Supersymmetric Low-Scale Seesaw Models
我们研究了最小超引力的低尺度跷跷板模型中的带电轻子味破坏，由于近似轻子数对称性，该模型实现了大的中微子汤川耦合。在这样的模型中有两个主要的轻子味破坏源。第一个来源来自通常的软超对称性破坏部门，而第二个是完全超对称的，来自超对称中微子汤川部门。在最小超引力的框架下，我们考虑了轻子味破坏的软源和超对称源，并计算了一些可能的轻子味破坏跃迁，如μ子和τ子的光子衰变，μ-> e γ，τ-> e γ和τ-> μ γ，它们的无中微子三体衰变，μ-> e e e，τ-> e e e e e，τ-> mu mu，τ-> e e μ和τ-> e μ μ以及核内的相干μ-> e转换。在考虑到目前的轻子味违反实验的排斥界限，我们得出的通用重马约拉纳质量尺度mN和轻到重中微子混合的理论限制。超对称低尺度跷跷板模型提供了不同的相关预测轻子味违反签名，这可能会发现在当前和预计的实验，如MEG，彗星/棱镜，Mu 2 e，超级BELLE和LHCb。
Learning about flavour structure from tau to ell gamma and mu to e gamma?
目前和即将进行的实验应该可以将辐射轻子衰变的灵敏度提高一个数量级。本文假设τ->（e，μ）γ衰变之一被观察到，并探讨了所需的新的风味耦合的结构和后果。在简单的模型（一个低尺度的跷跷板，leptoquarks），它示出的偶极顶点函数是成比例的产品的风味矩阵从拉格朗日（一个“Jarlskog样”不变），只要环粒子弱耦合到希格斯玻色子。其次，如果偶极顶点函数具有分层结构，则这可能意味着由于mu --> e gamma上的界限所暗示的“近似零”，因此只能观察到一些tau -->（e，mu）gamma模式。这种潜在的测试的层次结构的假设进行了讨论。
Sensitivity to the Higgs Sector of SUSY-Seesaw Models in the Lepton Flavour Violating tau-->mu f0(980) decay
本文研究了超对称-跷跷板模型下的轻子味破坏半轻子τ-> mu f0（980）衰变，其中MSSM谱被三个右手中微子及其超对称伴子扩展，并利用跷跷板机制产生中微子质量。我们估计了它通过希格斯介导通道tau--> mu H *--> mu f0（980）时的衰变率，其中H指CP偶MSSM希格斯玻色子玻色子h^0和H^0，轻子味破坏tau mu H顶点通过超对称环辐射产生。为了描述f0（980）介子，我们遵循手征约束的指导方针。作为我们的计算的一个含义，我们探讨了希格斯部门在这种衰变的敏感性，并将其与其他LFV τ衰变通道。我们对BR（tau--> mu f0（980））的预测与其目前非常具有竞争力的实验界的对抗，使我们提取了一些有趣的限制最相关的模型参数，特别是，tanbeta和m_{H^0}。
Motivated by flavour symmetry models, we construct theories based on a low-energy limit featuring lepton flavour triality that have the flavour-violating decays $τ^\pm \to μ^\pm μ^\pm e^\mp$ and $τ^\pm \to e^\pm e^\pm μ^\mp$ as the main phenomenological signatures of physics beyond the standard model. These decay modes are expected to be probed in the near future with increased sensitivity by the Belle II experiment at the SuperKEKB collider. The simple standard model extensions featured have doubly-charged scalars as the mediators of the above decay processes. The phenomenology of these exten…
We first study the hadronic lepton flavor violating tau decays within the littlest Higgs model with T-parity (including one or two pseudoscalars, or a vector resonance). We consider the case where only T-odd particles and partner fermions contribute, and also its extension including Majorana neutrinos coming from an inverse seesaw. In both cases our mean values lie only one order of magnitude below current upper limits, strengthening the case of searching for these decays in the quest for new physics.
We study inclusive $B$-meson production in $pp$ collisions at the LHC and compare experimental data with predictions of the general-mass variable-flavour-number scheme at next-to-leading order of perturbative QCD. We find almost perfect agreement provided that the factorization scale parameters and the parton distribution functions are chosen appropriately.
The production of the $W$ and $Z$ bosons in single diffractive processes at the LHC is investigated taking into account the ATLAS, CMS and LHCb acceptances and considering different assumptions for the flavour content of the Pomeron. The total cross sections and pseudorapidity distributions are estimated for $pp$ collisions at $\sqrt{s} = 13$ TeV. Our results indicate that a future experimental analysis of the ratio between the $W$ and $Z$ cross sections can be used to probe the flavour content of the Pomeron.
Lepton Flavour Violation in a Supersymmetric Model with A4 Flavour Symmetry
在味对称群A4 XZ 3 XU（1）_{FN}下的超对称不变量模型中，计算了mu-> e γ，tau-> mu γ和tau -> e γ的分支比，其中近三双峰轻子混合是自然预言的.在小对称性破缺参数u（与反应器混合角theta_{13}同阶）的主导阶，我们发现分支比一般按u ^2标度。对mu -> e γ的分支比应用电流约束表明，对于小于1000 GeV的质量参数m_{SUSY}和m_{1/2}，在模型中u或tan（β）的小值是优选的。从正在进行的MEG实验预期的约束将提供一个严格的约束的参数空间的模型要么强制u约0.01和小tan（β）或m_{SUSY}和m_{1/2}以上1000 GeV。在flavon扇区中的普适软超对称破缺项的特殊情况下，振幅和分支比标度为u^4发生抵消，从而允许较小的slepton质量。预测tau -> mu γ和tau -> e γ的分支比与mu -> e γ的数量级相同，这排除了在不久的将来观察到这些tau衰变的可能性。
Flavourful baryon and lepton number violation at the LHC
我们观察到，味对称性的标准模型规范部门，打破，因为他们是在标准模型汤川拉格朗日，自然抑制重子和轻子数违反在低能量，同时，使其可在大型强子对撞机通过共振过程涉及至少6个费米子从所有三代。我们建立了一个模型独立的分类，这样的过渡，并确定两个类，产生特别干净的LHC签名，即$\bar t μ^+ e^+$和$\bar t \bar t$ +喷流。
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.
Effective operators provide a model-independent description of physics beyond the stan- dard model that is particularly useful given the absence of any signs of new physics at the Large Hadron Collider (LHC). We recast previous LHC analyses to set limits on lepton-flavour-violating gluonic effective operators of dimension 8 and compare our results to existing limits from low-energy precision experiments. Current LHC data constrains the scale $Λ$ of the effective operators to be larger than $Λ\gtrsim 0.5 - 1.6$ TeV depending on the flavour and thus provides the most stringent limit for all oper…
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.
We apply the recently proposed flavoured anti-$k_{\text{T}}$ jet algorithm to $Wb\bar{b}$ production at the Large Hadron Collider at $\sqrt{s}=8$ TeV. We present results for the total cross section and differential distributions at the next-to-next-to-leading order (NNLO) in QCD. We discuss the effects of the remaining parametric freedom in the flavoured anti-$k_{\text{T}}$ prescription, and compare it against the standard flavour-$k_{\text{T}}$ algorithm. We compare the total cross section results against the CMS data, finding good agreement. The NNLO QCD corrections are significant, and thei…
We study inclusive b-hadron production in pp collisions at the LHC at different center-of-mass energies and compare with experimental data from the LHCb and CMS collaborations. Our predictions for cross sections differential in the transverse momentum and (pseudo-)rapidity agree with data within uncertainties due to renormalization scale variations. A small tension is found if data and theory predictions are compared for cross section ratios at different center-of-mass energies.
