LHC探索的强耦合模式：新动力学与高能物理信号

122 浏览量更新于2024-07-16 收藏 690KB PDF 举报

本文主要探讨了在标准模型（SM）之外可能存在的强耦合模式，尤其是在多太瓦特（TeV）能量范围内。尽管SM在费米尺度上表现为弱耦合，但研究者们设想存在一种新的、涉及SM自由度的强相互作用理论，这种理论可能隐藏在更高的能量层次。作者们利用近似对称性构建了一个结构稳健的框架，其中SM的耦合在低能描述中显得微弱，而新强动力学则主要通过高阶导数的相互作用显现。文章以有效场论的形式系统地分类这些情景，特别关注了新型模型的构建，这些模型围绕希格斯玻色子、SM规范玻色子和费米子展开。新动力学的红外（IR）软性使得其对LEP（大型电子正负离子对撞机）能量水平的影响被抑制，但在LHC（大型强子对撞机）这样的高能平台上，即使在未达到产生新物理状态阈值的情况下，仍有可能观察到与之相关的偏差。作者们的分析着重于那些由对称性调控的弱耦合、强耦合与导数之间的相互作用，这超越了单纯考虑六维运算符的传统分析。他们发现，这种相互作用模式能够提供一个维度8支配维度6的实例，这一现象恰好处于当前低能量有效理论的适用范围内。这一结果揭示了现有分析方法的局限性，即对于维数扩展的处理可能过于简化，强调了在理解这类强耦合模式时需要更为全面的视角。这篇发表于《Journal of High Energy Physics》（JHEP）的文章对于LHC上的实验搜索策略具有重要指导意义，特别是在希格斯物理学、地核过程以及W玻色子对撞等领域。它提示着在探索超越标准模型的新物理时，必须考虑到非传统耦合和相互作用的可能，以期在复杂且精细的粒子碰撞数据中捕捉到这些潜在的强耦合模式的迹象。

JHEP11(2016)141

2.3 The eﬀective lagrangian at the electroweak scale

Putting together the concepts presented above, it is straightforward to derive the general

structure of the eﬀective Lagrangian for a strongly-interacting light Higgs. This corresponds

to reduce the general scenario of the previous section to the simplest case in which the set

of light states from the CFT contains just the Higgs doublet. In this case, the L in eq. (2.4)

is given by

L =



∗

16π



, (2.9)

≡ L

∗



µν

∗



3/2

∗

, (2.10)

with

H indicating the non-canonically normalized Higgs doublet ﬁeld. In the leading term

the SM (fermion and gauge) ﬁelds appear only as external spectators. Instead, the one-

loop term L

can be written as the sum of a pure CFT contributions, L

(0)

, and contributions

arising from the exchange of one virtual SM state 

(1)

that depends implicitly on :

= L

(0)

+ 

(1)

. (2.11)

The above structure generalizes in the obvious way at the higher loop order.

In the simplest and well motivated situation where the Higgs H spans the SO(5)/SO(4)

coset, the above Lagrangian will respect the symmetry and the selection rules it imposes.

The H dependence will arise via the Goldstone matrix U = e

iΠ

and will be determined by

the CCWZ construction [24, 25], while the dependence on the symmetry-breaking mixings

’s will be constrained by the SO(5) selection rules (see ref. [26] for a thorough discussion).

Within our assumptions, the estimate of the operator coeﬃcients in the eﬀective La-

grangian is a simple matter of power counting. Using the deﬁnition of the dimension-6

operators O

in table 1, we illustrate the leading results for three diﬀerent scenarios in

table 2. The coeﬃcients c

are deﬁned by

∗

. (2.12)

The ﬁrst scenario in table 2 corresponds to an ALH that happens to be lighter than

the other resonances just because of some accidental cancellation, and not because of a

symmetry –see appendix B. The second scenario we consider is that of a general PNGB

strongly-interacting light Higgs (GSILH), deﬁned by the most general L satisfying the

SO(5) selection rules. The third scenario is the slightly more speciﬁc case of the SILH

considered in [12], where L

is not completely generic because of restricted properties

of the dynamics at the scale m

∗

. This third class describes, for instance, Little Higgs

models [27] and Holographic composite Higgs models [10, 11].

A few explanations of the results of table 2 are in order. First of all, we should give a

motivation for our choice of operators. Our choice singles out O

W,B

and O

2W,2B,2G

as the

only operators involving vectors that can be generated at tree level by the exchange of mas-

sive vectors, in a theory where the two derivative terms involve the minimal power of the

– 6 –

JHEP11(2016)141

(∂

|H|

)



†

↔



= |H|



†

↔



µν



†

↔



∂

µν

= i(D

†

H)W

µν

= i(D

†

H)B

µν

= |H|

µν

= |H|

µν

Aµν

= |H|

Hψ

= −

(∂

µν

)

= −

µν

)

= −

µν

)



abc

a ν

νρ

c ρµ

ABC

A ν

νρ

C ρµ

L,R

= (iH

†

↔

H)(

L,R

)

(3) ψ

= (iH

†

↔

H)(

)

4ψ

ψγ

Table 1. Dimension-6 operators used in our analysis. Notice that our normalization diﬀers from

previous literature.

|H|

V V

ALH m

∗

GSILH

16π

∗

16π

∗

16π

∗

16π

∗

SILH

16π

∗

16π

∗

16π

∗

16π

∗

16π

∗

Table 2. Estimated coeﬃcients (c

) of diﬀerent operators appearing in the eﬀective Lagrangian

for a strongly interacting Higgs, under diﬀerent hypotheses: an accidentally small electroweak scale

and accidentally light Higgs (ALH), a general SILH (GSILH) scenario, and the proper SILH of [12]

where the additional assumption of MC is considered (see appendix A). The subscript V can denote

W, B, G according to the basis deﬁned in table 1. For the ALH scenario the entries in the ﬁrst two

columns emphasize the need for tuning, w.r.t. the NDA estimate (see appendix B).

ﬁelds which is compatible with symmetry. In particular that is the case for a renormalizable

theory. Now, as it turns out, the simplest incarnations of the Little Higgs and holographic

Higgs models, are to a good approximation described at the scale m

∗

by theories in the

above mentioned class.

That property is essentially a corollary of the mechanism of collec-

tive breaking [27] enforced in these models: the scale of the resonances m

∗

is parametrically

smaller than the genuine cut-oﬀ Λ of the theory, at which no weakly coupled description is

tenable. In such models, apart from O

W,B

and O

2W,2B,2G

, all operators involving vectors

can only be generated via loops. Such a structure was dubbed in ref. [12], for somewhat

obvious reasons, Minimal Coupling (MC). In appendix A we give a detailed discussion of

Notice that these models are not precisely renormalizable at the scale m

∗

as the breakdown G → H at

a higher scale, implies the existence of scalars in a non-linear σ-model.

– 7 –

剩余38页未读，继续阅读

weixin_38580759

粉丝: 4
资源: 971

LHC探索的强耦合模式：新动力学与高能物理信号

LHC的spin-2介体简化了暗物质模型

在HE-LHC和FCC-hh处通过h→γγ通道探测顶部希格斯玻色子FCNC耦合

在14 TeV LHC上搜索类似载体的最佳伴侣的单一生产

从14 TeV LHC的tZ相关产物的三态信号中搜索异常tqZ偶联

LHC的多彩扭曲顶级合作伙伴和Partnerium

Di-Higgs最终状态augMT2ed –选择高光度LHC的hh事件

高质量双光子共振对夸克搜索的影响

LHC搜索标准模型类似希格斯玻色子在μ+μ-和e+e-衰变

多重扭曲几何：解决LHC引力子搜索的困境

LHC中的轻带电希格斯搜索：II型两希格斯模型扩展

最新资源