AMS-02反质子数据揭示简化的暗物质模型参数
53 浏览量
更新于2024-07-16
收藏 1.5MB PDF 举报
本文主要探讨了"根据AMS-02反质子数据简化暗物质模型"这一主题，它发表在2017年的《Journal of High Energy Physics》(JHEP04)上，是Springer出版社为SISSA（国际理论物理中心）发布的开放存取文章。研究者Tong Li来自澳大利亚莫纳什大学的粒子物理和天文学学院，专注于ARCC（太级尺度粒子物理卓越中心）的研究。
研究的核心内容是基于最近AMS-02（阿尔法磁谱仪-02）实验的反质子流量和反质子与质子比的数据，这些数据提供了关于暗物质粒子性质的重要线索。研究者假设暗物质是一种狄拉克费米子，其特性包括与标准模型中的夸克和暗物质粒子耦合的 leptophobic（不亲电子的）伪标量或轴向矢量媒介。这种模型简化了暗物质的复杂性，使得理论预测更具可操作性。
通过利用已观察到的核通量来确定传播和注入参数，研究团队分析了这些模型在解释AMS-02观测结果时的表现。他们的研究结果显示，AMS-02的测量数据与这个简化暗物质框架在不确定性范围内的预测相符合。具体来说，对于伪标量媒介的暗物质，数据倾向于一个媒介质量范围在700 GeV至5 TeV之间，而轴向矢量媒介的情况则要求更高的质量界限，即大于700 GeV，这在大约68%的置信水平下成立。
此外，该研究还讨论了LHC（大型强子对撞机）和Fermi-LAT（费米伽马空间望远镜）实验对暗物质模型的现有约束。这意味着研究者不仅关注AMS-02的数据，还考虑了其他实验的独立验证结果，以确保模型的一致性和可靠性。
结论部分指出，对于这两种媒介类型的简化暗物质模型，有效的暗物质湮灭截面需要在1×10^-25 至1×10^-24 cm^3/s（对于伪标量）和1×10^-25 至4×10^-24 cm^3/s（对于轴向矢量）的范围内。这一研究不仅提供了对暗物质性质的新见解，也为未来的暗物质探测实验和理论发展奠定了基础。
JHEP04(2017)112
with the level of the interstellar turbulence parameter w being 1. The spatial diffusion
coefficient is usually written in this form
D
xx
= βD
0
(R/R
0
)
δ
, (2.3)
with R and β being the rigidity and particle velocity divided by light speed respectively.
This transport equation is numerically solved based on given boundary conditions, that
is, the cosmic ray density ψ vanishes at the radius R
h
and the height z
0
of the cylindrical
diffusion halo.
The above key propagation parameters can be constrained by fitting the latest ratios
of nuclei, that is the Boron-to-Carbon ratio (B/C) and the Beryllium ratio (
10
Be/
9
Be).
We adopt the values of propagation parameters shown in table 1, determined by the B/C
and
10
Be/
9
Be data [6]. The benchmark model of the propagation we use is diffusion
reacceleration model. The
10
Be/
9
Be ratio data are sensitive to the diffusion halo size
z
0
. For a given halo size the diffusion coefficient as a function of momentum and the
reacceleration parameter are determined by B/C ratio data. The values in table 1 are
the best fit results. The diffusion reacceleration scenario is found to be best consistent
with the data compared with other propagation scenarios, such as the diffusion convection
model [27].
In eq. (2.1), the source term of cosmic ray species i can be described by the product
of the spatial distribution and the injection spectrum function
Q
i
(~r, p) = f(r, z)q
i
(p). (2.4)
For the spatial distribution of the primary cosmic rays we use the following supernova
remnants distribution
f(r, z) = f
0
r
r
a
exp
−b
r − r
r
exp
−
|z|
z
s
, (2.5)
where r
= 8.5 kpc is the distance between the Sun and the Galactic center, the height of
the Galactic disk is z
s
= 0.2 kpc, and the two parameters a and b are chosen to be 1.25 and
3.56, respectively [27]. We assume the following power law with one break for the injection
spectrum of various nuclei
q
i
∝
R/R
p
br
−ν
1
, R ≤ R
p
br
R/R
p
br
−ν
2
, R > R
p
br
. (2.6)
The corresponding injection parameters in eq. (2.6), i.e. rigidity break R
p
br
and power law
indexes ν
1
, ν
2
, can be determined by fitting the latest AMS-02 proton data [1]. We adopt
injection parameters obtained by performing such a fit in ref. [6]. The values of these
injection parameters are shown in table 1, together with the Fisk potential φ
i
(i = p, ¯p)
for solar modulation effect. The values of Fisk potential come from ref. [6]. They are the
approximate constants of the time-varying modulation form employed in the reference.
– 3 –
剩余16页未读，继续阅读
120 浏览量
点击了解资源详情
189 浏览量
189 浏览量
2020-03-21 上传
104 浏览量
120 浏览量
137 浏览量
2020-03-25 上传
