We study the effects of holographic renormalisation on an AdS/QCD inspired description of dynamical electroweak symmetry breaking. Our model is a 5D slice of AdS_5 geometry containing a bulk scalar and SU(2) times SU(2) gauge fields. The scalar field obtains a VEV which represents a condensate that triggers electroweak symmetry breaking. Fermion fields are constrained to live on the UV brane and do not propagate in the bulk. The two-point functions are holographically renormalised through the addition of boundary counterterms. Measurable quantities are then expressed in terms of well defined physical parameters, free from any spurious dependence on the UV cut-off. A complete study of the precision parameters is carried out and bounds on physical quantities derived. The large-N scaling of results is discussed.
We compute the one-loop renormalisation group running of the bosonic Standard Model effective operators to order $v^4/Λ^4$, with $v\sim 246$ GeV being the electroweak scale and $Λ$ the unknown new physics threshold. We concentrate on the effects triggered by pairs of the leading dimension-six interactions, namely those that can arise at tree level in weakly-coupled ultraviolet completions of the Standard Model. We highlight some interesting consequences, including the interplay between positivity bounds and the form of the anomalous dimensions; the non renormalisation of the $S$ and $U$ parame…
Higgs Vacuum Stability in a Mass-Dependent Renormalisation Scheme
使用物理重正化方案，我们推导出质量相关的重正化组方程的运行的希格斯四次耦合内的标准模型。随后，我们准确地考虑到弱标度阈值，导致在确定的最大$M_t$的绝对稳定的真空到0.28 GeV所需的误差减少。我们第一次确定了电弱真空的命运，发现在99.98% C. L.时，希格斯真空态的绝对稳定性被排除在外。我们还讨论了这一新的结果与BICEP合作的B-模式极化在宇宙微波背景的最近观察相结合的后果，发现标准模型电弱真空寿命太短，有幸存的通货膨胀。对暴胀和新的物理模型的影响也进行了讨论。
We construct spin-improved holographic light front wavefunctions for the nucleons (viewed as quark-diquark systems) and use them to successfully predict their electromagnetic Sachs form factors, their electromagnetic charge radii, as well as the axial form factor, charge and radius of the proton. The confinement scale is the universal mass scale of light-front holography, previously extracted from spectroscopic data for light hadrons. With the Dirac and Pauli form factors normalized using the quark counting rules and the measured anomalous magnetic moments respectively, the masses of the quark…
Renormalisation-group improved analysis of $μ\to e$ processes in a systematic effective-field-theory approach
本文在电弱对称性破缺标度$m_W$下定义的六维算符有效理论框架下，对三个μ子轻子味破坏过程$μ\to e γ$，$μ\to 3e$和相干核$μ\to e$转换进行了全面的分析.在QCD和QED中，在首阶充分考虑了$m_W$与实验尺度之间Wilson系数的重整化群演化，给出了显式的解析和数值演化矩阵.因此，μ子衰变和转换率被解释为威尔逊系数的函数，在任何规模高达$m_W$。以这些过程的实验极限作为输入，混合效应的现象学进行了研究。结果发现，相当一组威尔逊系数无界的简单的树级方法，而不是严重的约束。此外，运营商之间的相关性进行了研究，根据目前的数据和未来的实验前景。
We continue our study of strongly-coupled, approximately scale-invariant gauge theories with a large number of flavours, which provide a suitable ultraviolet completion of the composite-Higgs scenario. We identify the requisite operators to realise partial compositeness of the Standard-Model fermions. In order to compute the spectrum of composite fermionic states, we extend the bottom-up holographic models, which we previously introduced to capture the main features of the non-perturbative dynamics in the Veneziano limit, by adding fermion fields in the bulk. We identify regions in parameter s…
Institute for Theoretical Physics, Karlsruhe Institute of Technology（卡尔斯鲁厄理工学院理论物理研究所）；Institute for Particle Physics Phenomenology, Durham University（达勒姆大学粒子物理现象学研究所）
Complementarity in lepton-flavour violating muon decay experiments
本文在低能有效场论的框架内分析了轻子味破坏的μ子衰变，该理论包含QED和QCD对称性所允许的高维算子。的衰变模式$μ\to e γ$和$μ\to 3e$的研究低于电弱破介标度，下降到能量，在这种过程中发生，即μ子质量尺度。在树的水平上系统地研究了5维和6维算子的完整类，并充分考虑了对重整化群方程的单圈贡献。目前的实验限制被用来提取的威尔逊系数的一些运营商的界限，并最终，在任何能级以下的电弱破键标度的有效耦合。两个耦合相关的两个过程之间的相关性说明了搜索计划的MEG II和Mu3e实验的互补性。
Neutrino Masses from an A4 Symmetry in Holographic Composite Higgs Models
我们表明，全息复合希格斯模型与离散A4对称性自然预测层次带电轻子质量和近似的三双极大轻子混合与正确的中微子质量的规模。它们还满足电弱精密测试、轻子味破坏和轻子混合在大范围参数空间中的电流约束。在这些模型中出现了两个现象学上相关的特征。首先，对轻子汤川耦合的额外抑制使τ轻子比从其质量天真地预期的更复杂。因此，新的轻轻子共振，质量低至几百GeV，大耦合到τ和一个非常典型的对撞机现象，是很有可能的。其次，离散对称性A4与模型结构一起提供了双层风味保护，其允许将树水平介导的过程保持在当前实验极限以下。然而，违反轻子味道的单圈过程，如mu -> e gamma，可能在未来的实验中观察到。
We investigate nonlinear extensions of the holographic soft wall model proposed by Karch, Katz, Son and Stephanov \cite{Karch:2006pv} with a positive quadratic dilaton. We consider a Higgs potential for the tachyonic field that brings a more natural realisation of chiral symmetry breaking in the infrared regime. Utilising the AdS/CFT dictionary and holographic renormalisation we find the chiral condensate as a function of the quark mass. The nonlinearity of the Higgs potential leads to a nonlinear relation between the chiral condensate and the quark mass. Solving the effective Schrödinger equa…
Uncertainty in Electroweak Symmetry Breaking in Models With High Scale Supersymmetry Breaking and its Impact on Interpretations of Searches For Supersymmetric Particles
We study the simplest viable dark matter (DM) model with a real singlet scalar, vector-like singlet, and doublet fermions. The Yukawa couplings associated with the fermion sector are important in obtaining the current DM relic density through Freeze-out and Freeze-in mechanisms. In addition to the standard model-like high scale minima along the Higgs field, we find other high scale minima along the singlet scalar field direction. The other minima appears due to the renormalisation group evolutions of the couplings involving the gauge sector, Higgs portal, and the new Yukawa sector. A detailed …
We propose a brane-world setup based on gauge/gravity duality that permits the simultaneous realisation of self-tuning of the cosmological constant and a stabilisation of the electroweak hierarchy. The Standard Model dynamics including the Higgs sector is confined to a flat 4-dimensional brane, embedded in a 5-dimensional bulk whose dynamics is governed by Einstein-dilaton-axion gravity. The inclusion of a dynamical bulk axion is new compared to previous implementations of the self-tuning mechanism. Because of the presence of the axion, the model generically exhibits a multitude of static solu…
