SO(10)对称性下的狄拉克中微子辐射机制与暗物质研究

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本文档探讨的是Scotogenic理论框架中的狄拉克中微子概念，这个理论基于标准模型的扩展，引入了一个额外的尺度对称性U(1)χ，它源自于SO(10)群的自发对称性破缺，进一步分解为SU(5)×U(1)χ。在这个背景下，研究者Ernest Ma关注的是中微子质量的生成机制，特别关注的是通过暗物质的作用来实现。首先，论文的核心议题是辐射诱导的狄拉克中微子质量生成。在两种不同的模型示例中，作者提出了新颖的解释。第一种模型允许存在光狄拉克费米子作为暗物质，这意味着这种暗物质粒子具有狄拉克特性，其质量可能通过量子效应而非传统的Yukawa相互作用得到生成。这在理论上为了解决中微子的性质提供了新的可能性，因为它挑战了传统认为中微子为Majorana粒子的观点。第二种模型则涉及到自相互作用标量暗物质，其媒介粒子是一种轻量级的标量粒子。这种暗物质的独特之处在于，它的衰变过程仅限于两个中微子，这在标准模型中是罕见的。这样的设定对于理解暗物质与基本粒子之间的相互作用以及暗物质的宇宙学行为具有重要意义，因为它可能揭示了暗物质与普通物质之间潜在的非标准相互作用。文章指出，尽管目前实验上还没有直接证据表明中微子是狄拉克而不是Majorana类型，但这类理论研究为未来的实验提供了新的预测和可能的信号。此外，这篇论文发表在《物理快报B》上，并遵循开放获取政策，允许读者免费访问，其版权许可为Creative Commons BY 4.0，这体现了科学共享的精神。总结来说，该研究在理论物理学领域推动了对中微子性质的理解，特别是通过暗物质中介的新颖途径，这对理解宇宙的基本粒子组成和早期宇宙的演化过程具有潜在的深远影响。同时，它也强调了实验验证的重要性，因为中微子性质的最终确定将对现有的理论框架产生重大影响。

Physics Letters B 793 (2019) 411–414

Contents lists available at ScienceDirect

Physics Letters B

www.elsevier.com/locate/physletb

Scotogenic U (1)

Dirac neutrinos

Ernest Ma

Physics and Astronomy Department, University of California, Riverside, CA 92521, USA

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

Article history:

Received

5 February 2019

Received

in revised form 5 April 2019

Accepted

2 May 2019

Available

online 6 May 2019

Editor:

A. Ringwald

The standard model of quarks and leptons is extended to include the gauge symmetry U (1)

which

comes from SO(10) → SU(5) × U (1)

. The radiative generation of Dirac neutrino masses through dark

matter is discussed in two examples. One allows for light Dirac fermion dark matter. The other allows for

self-interacting scalar dark matter with a light scalar mediator which decays only to two neutrinos.

(http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP

1. Introduction

Whereas neutrinos are usually assumed to be Majorana, there

is yet no experimental evidence, i.e. no deﬁnitive measurement

of a nonzero neutrinoless double beta decay. To make a case for

neutrinos to be Dirac, the ﬁrst is to justify the existence of a right-

handed

neutrino ν

, which is not necessary in the standard model

(SM) of quarks and leptons. An obvious choice is to extend the SM

gauge symmetry SU(3)

× SU(2)

× U (1)

to the left-right sym-

metry

SU(3)

× SU(2)

× U (1)

(B−L)/2

. In that case, the

SU(2)

doublet (ν, e )

is required, and the charged W

gauge bo-

son

is predicted along with a neutral Z



gauge boson.

more recent choice is to consider U (1)

which comes from

SO(10) → SU(5) × U (1)

, with SU(5) breaking to the SM. As-

suming

that U (1)

survives to an intermediate scale, the current

experimental bound on the mass of Z

being about 4.1 TeV [1,2],

then ν

must exist for the cancellation of gauge anomalies. Now

is a singlet and W

is not predicted. In this context, new in-

sights

into dark matter [3,4] and Dirac neutrino masses [5]have

emerged. In particular, it helps with the following second issue re-

garding

a Dirac neutrino mass. Since neutrino masses are known

to be very small, the corresponding Yukawa couplings linking ν

to ν

through the SM Higgs boson must be very small. To avoid

using such a small coupling, a Dirac seesaw mechanism [6,7]is

advocated in Ref. [5]. The alternative is to consider radiative mech-

anisms,

especially through dark matter, called scotogenic from the

Greek ‘scotos’ meaning darkness. Whereas the original idea [8]was

applied to Majorana neutrinos, one-loop [9,10] and two-loop [11]

examples

for Dirac neutrinos already exist in the context of the

SM. For a generic discussion of Dirac neutrinos, see Ref. [12], which

is patterned after that for Majorana neutrinos [13]. Here two new

E-mail address: ma@phyun8.ucr.edu.

U (1)

examples are shown. One allows for light Dirac fermion

dark matter. The other allows for self-interacting scalar dark matter

with a light scalar mediator which decays only to two neutrinos.

2. First scotogenic U (1)

model

The particle content follows that of Ref. [5]except for the addi-

tion

of ζ ∼ (1, 15) from the 672 of SO(10). This is used to break

U (1)

without breaking global lepton number. The fermions are

shown in Table 1 and scalars in Table 2.

New fermions N, N

belonging to 126

∗

, 126 respectively are

added per family , as well as a Higgs doublet from 144 and a sin-

glet

from 16. Note that their Q

charges are ﬁxed by the SO(10)

representations from which they come. It should also be clear

that incomplete SO(10) and SU(5) multiplets are considered here

(which is the case for all realistic grand uniﬁed models). Since 

†

transforms exactly like 

, the linear combination  = (v



†





+ v

is the analog of the standard-model Higgs dou-

blet,

where φ

 = v

1,2

. An important Z

discrete symmetry is

imposed so that ν

is odd and all other SM ﬁelds are even, pre-

venting

thus the tree-level Yukawa coupling (νφ

− eφ

)ν

. This

symmetry is respected by all dimension-four terms of the La-

grangian.

It will be broken softly by the dimension-three trilinear

term μσ 

†

η (in cases B and D) or the m

mass term (in

cases A and C). This allows the one-loop diagram of Fig. 1 to

generate a radiative Dirac neutrino mass. Cases C and D allow

the Yukawa coupling ζ ν

which would violate lepton number,

hence only cases A and B will be considered. In case A, the quartic

scalar term ζ σ

is allowed. Hence the would-be dark U(1) sym-

metry

is reduced to Z

, i.e. ω for σ , N

and ω

for η, N, where

ω = exp(2π i/3). In case B, it is forbidden, so the model possesses

a dark U(1) symmetry, i.e. D is 1 for σ , N

and −1for η, N. In

either case, there is still a conserved lepton symmetry, i.e. L = 1

https://doi.org/10.1016/j.physletb.2019.05.006

0370-2693/

SCOAP

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