JHEP05(2017)002
decay φ → ηA
0
, which may receive additional contributions from axial couplings to
quarks because the decay is s-wave [20, 40], but estimating this contribution is beyond
the scope of this work.
• Annihilation or bremsstrahlung: if the A
0
is produced through annihilation, e
+
e
−
→
γA
0
, or bremsstrahlung, e → e + A
0
or p → p + A
0
, the cross section is gener-
ally proportional to c
2
V
+ c
2
A
for relativistic kinematics. Thus the constraints on
a kinetically-mixed dark photon are qualitatively similar to those for a dark pho-
ton, using e →
q
c
2
V
+ c
2
A
to translate between kinetic mixing and axial and
vector couplings.
• Other production mechanisms: a recent proposal [41] suggests exploiting the large
flux of D
∗
mesons at LHCb to search for D
∗
→ D + A
0
, or more generally performing
an inclusive search using data-driven techniques to relate any process with a photon
to the corresponding dark photon process [42]. It is difficult to analyze the effect of
axial couplings for such searches in general terms, since the hadronic matrix elements
may have complicated dependence on axial currents which are not present in the case
of pure kinetic mixing. We leave an analysis of such constraints to future work.
2.4 Above 2m
µ
and below 2m
e
For m
A
0
> 2m
µ
, the possibility of seeing a dimuon resonance in collider experiments or
rare meson decays severely constrains the parameter space for axial couplings to quarks,
c
q
A
. For example, vector meson decays ψ → γA
0
and Υ → γA
0
proceed at tree-level
and are proportional to the axial coupling c
c,b
A
of the heavy quarks [27]. If the A
0
also
couples to muons through either an axial or vector coupling, there are stringent bounds
on Br(Υ → γµ
+
µ
−
) and Br(ψ → γµ
+
µ
−
) through a resonance. Constraints from BaBar,
Belle, and the LHC only depend on the combination c
2
V
+ c
2
A
, and so as mentioned above
are qualitatively similar to a kinetically-mixed dark photon with purely vector couplings.
For m
A
0
< 2m
e
, and assuming no dark sector particles lighter than 2m
A
0
, the A
0
can
only decay into neutrinos or three photons. For a kinetically-mixed A
0
, both processes
have extremely small widths, and the A
0
can be effectively stable on large timescales. This
leads to stringent stellar cooling bounds (see e.g. [43, 44]), where photons in the stellar
plasma can convert to A
0
s which carry away energy. However, an A
0
with axial couplings
has drastically different phenomenology, both because it can naturally have unsuppressed
couplings to neutrinos, and because the dominant source of A
0
production in stars is not
necessarily through kinetic mixing. A detailed survey of the constraints on an ultralight A
0
with axial couplings requires a dedicated analysis which is beyond the scope of this work.
2
2
We note, however, that portions of this parameter space may be of great interest to direct-detection
experiments searching for keV dark matter, since an eV-scale A
0
with c
e
A
∼ c
e
V
can avoid in-medium effects
in superconductors which suppress scattering through a kinetically-mixed A
0
[45, 46]; we discuss this case
further in section 4.
– 6 –
剩余33页未读，继续阅读
weixin_38649356
- 粉丝: 5
- 资源: 951
我的内容管理
展开
最新资源
- 前端面试必问：真实项目经验大揭秘
- 永磁同步电机二阶自抗扰神经网络控制技术与实践
- 基于HAL库的LoRa通讯与SHT30温湿度测量项目
- avaWeb-mast推荐系统开发实战指南
- 慧鱼SolidWorks零件模型库：设计与创新的强大工具
- MATLAB实现稀疏傅里叶变换(SFFT)代码及测试
- ChatGPT联网模式亮相，体验智能压缩技术.zip
- 掌握进程保护的HOOK API技术
- 基于.Net的日用品网站开发：设计、实现与分析
- MyBatis-Spring 1.3.2版本下载指南
- 开源全能媒体播放器：小戴媒体播放器2 5.1-3
- 华为eNSP参考文档：DHCP与VRP操作指南
- SpringMyBatis实现疫苗接种预约系统
- VHDL实现倒车雷达系统源码免费提供
- 掌握软件测评师考试要点：历年真题解析
- 轻松下载微信视频号内容的新工具介绍
资源上传下载、课程学习等过程中有任何疑问或建议，欢迎提出宝贵意见哦~我们会及时处理！
点击此处反馈
