TeV中微子模型与带电轻子外来体：WW事件的新视角

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"文章探讨了一种TeV中微子质量生成模型，该模型预言存在单电荷的轻子外来体。在当前的WW事件观测中，瘦子WW的测量值高于标准模型预测，这促使研究者考虑可能的新物理信号，这些信号可能模仿了W玻色子的轻子衰变。模型中引入了新的SU（2）L双重态轻子，它们衰变成带电轻子和一个O（MeV）级的轻单重态标量，后者进一步衰变为中微子。这种新粒子的存在可能导致独特的对撞机现象，例如Lell + L−通过Drell-Yan过程产生，然后衰变成一对轻子和未探测到的能量，这与轻子WW搜索相符合。同时，L±L0的衰变完全隐藏在标准模型背景中。通过分析LHC的WW搜索数据，作者得出了这种奇异轻子的质量下限为125 GeV，并且在考虑了希格斯玻色子和轻子W'搜索的限制后，确定了上限在150 GeV至300 GeV之间，具体取决于所采用的搜索策略。" 本文是开放获取的Physics Letters B期刊的一篇文章，作者包括Hui Lu、Ming-xing Lu、Kai Wang、Tao Xu和Guohuai Zhu，分别来自中国浙江大学、意大利帕多瓦大学、意大利帕多瓦国家核物理研究所和意大利国际高等研究院。文章在2014年7月23日提交，9月15日完成修订，9月19日被接受，并于9月26日在线发布，由M. Cvetiˇc担任编辑。文章的核心在于研究一个新的物理模型，该模型解释了在WW事件中观察到的异常高轻子率，即所谓的"瘦子WW"现象。这个模型涉及到TeV能量尺度的中微子质量生成机制，并预测了一类新的带电轻子外来体，它们的衰变模式可以模拟轻子W的衰变，从而逃避了其他标准模型的检测。通过引入这些新粒子，研究人员能够构建一个理论框架，该框架不仅能够解释现有数据，还提出了在未来实验中检验这种新物理的可能途径。通过对LHC数据的分析，他们设定了这些新粒子质量的可能范围，这为未来粒子物理实验提供了重要的指导。

Physics Letters B 738 (2014) 160–165

Contents lists available at ScienceDirect

Physics Letters B

www.elsevier.com/locate/physletb

Neutrino mass generation and singly charged leptonic exotics in

WW events

Hui Luo

a,b,c,d

, Ming-xing Luo

, Kai Wang

a,∗

, Tao Xu

, Guohuai Zhu

Zhejiang Institute of Modern Physics, Department of Physics, Zhejiang University, Hangzhou, Zhejiang 310027, China

Dipartimento di Fisica eAstronomia, Università di Padova, Via Marzolo 8, 35131 Padova, Italy

INFN, Sezione di Padova, Via Marzolo 8, 35131 Padova, Italy

SISSA, Via Bonomea 265, 34136 Trieste, Italy

a r t i c l e i n f o a b s t r a c t

Article history:

Received

23 July 2014

Received

in revised form 15 September

2014

Accepted

19 September 2014

Available

online 26 September 2014

Editor:

M. Cveti

Current measurement of leptonic WW is signiﬁcantly higher than the standard model prediction which

may accommodate new physics signal that mimics the leptonic decaying W . We investigate aTeV

neutrino mass generation model that predicts singly charged leptonic exotics. The collider signature of

this model may mimic the leptonic WW search and evade all other searches. With introduction of new

SU(2)

doublet leptons, singly charged exotic leptons L

decay into L

→ 

φ where φ is a light singlet

scalar of O(MeV) that decays into neutrinos. Drell–Yan production of L

−

→ 



−

+ /E

ﬁts leptonic

WW searches and L

→ 

+/E

is completely buried in SM background. In the case of direct lepton

from L-decay instead of secondary decay from leptonic τ

, we ﬁnd the lower mass bound as 125 GeV

of such exotic leptons that can be accommodated by the current measurements of WW searches at

the LHC. To derive the upper bound, we employ both heavy Higgs boson search of di-lepton plus /E

ﬁnal

state and leptonic W



search of single lepton plus /E

. Even though heavy Higgs is excluded between 260

and

640 GeV, we ﬁnd LHC data can still accommodate L between 150 and 300 GeV after giving up the



cut. Using the single W



search bound, we can obtain an approximate upper bound as 300 GeV.

(http://creativecommons.org/licenses/by/3.0/). Funded by SCOAP

Discovery of a 125 GeV Standard Model (SM)-like Higgs boson

at the CERN Large Hadron Collider has dramatically improved our

knowledge on mass generation for elementary particles in SM [1].

However, clear evidence for physics beyond SM lies in experimen-

tal

conﬁrmation of sub-eV neutrino masses based on distance/en-

ergy

dependence measurements in various neutrino oscillation ex-

periments [2].

Being complete neutral under unbroken gauge sym-

metry

SU(3)

× U (1)

, neutrino can be Majorana fermion. More-

over,

Majorana nature of neutrino also ensures the uniqueness of

hyper-charge assignment predicted by gauge anomaly free condi-

tions [3].

The total mass of neutrino states and upper bound on

neutrino charge

are given in [5].

total



 0.24 eV, q

 10

−15

e. (1)

The most elegant proposal of neutrino mass generation is the “see-

saw”

mechanism [6,7] where the tiny but non-zero neutrino mass

Corresponding author.

Based on charge conservation assumption, the neutrino charge bound is further

constrained as less than 10

−21

e [4].

arises as a consequence of ultra-high scale (O(Λ

GUT

)) physics and

the mechanism can be naturally embedded into grand uniﬁcation

framework [7]. In addition, “see-saw” mechanism can naturally ac-

count

for the observed baryon asymmetry of the universe from

WMAP seven year results [8] through “leptogenesis” [9]

≡

= (8.82 ±0.23) × 10

−11

, (2)

where ρ

is the baryon number density and s is the entropy den-

sity

of the universe.

the other hand, the “see-saw” mechanism is unlikely

to be direct tested experimentally in near future. Heavy sin-

glet

fermion with strong Yukawa coupling to the Higgs boson

leads to huge correction to the Higgs boson mass as δm



/(2π v)

log(q/M

) [10]. Supersymmetry is then inevitable

to stabilize the Higgs boson mass while low energy supersym-

metry

suffers severe direct search bounds at LHC. Thermal lepto-

genesis

also requires lower “see-saw” scale of O(10

GeV) with

smaller Dirac neutrino Yukawa couplings and large hierarchies in

the right-handed neutrino masses [11]. Therefore, there are alter-

native

proposals to generate neutrino masses within TeV.

http://dx.doi.org/10.1016/j.physletb.2014.09.044

0370-2693/

SCOAP

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