暗物质探测和 AMS-02结果的解读 毕效军 中国科学院高能物理研究所 中国科学技术大学 2014/12/12

Outline 暗物质和暗物质探测 暗物质性质 暗物质直接探测 暗物质间接探测 AMS-02实验、结果和解读 小结

Standard cosmology Based on the large number of astronomical observations the standard cosmology has been established, that 73% ……. However, we know almost nothing about the nature of dark matter particles. Dark matter (dark energy) exists in the universe. However, we have to figure out its property.

Nature of dark matter – non-baryonic cold dark matter Not in compact form, such as black holes, neutron stars? (MACHO -MAssive Compact Halo Objects)

Non-baryonic From BBN and CMB, it has Bh2=0.02+-0.002. Therefore, most dark matter should be non-baryonic. DMh2=0.113+-0.009

New physics beyond the SM Non-baryonic cold dark matter dominates the matter contents of the Universe. New particles beyond the standard model are required! New physics!

The universe is the ultimate laboratory to study fundamental physics……. 能标>>LHC能标 发现了新物理 LHC can record almost all information of the reaction; but energy is limited. Big bang has large enough energy. But we are very far from the reaction at the Big Bang. Only the relics (stable missing energy) of the reaction can be observed today. We are lucky if the relics of the early Universe is just the LHC missing energy

Candidates of the cold dark matter－ stable、neutral、weak interacting There are dozens of theoretical models in the literature Weakly Interacting Massive Particles (WIMPs) as thermal relics of Big Bang is a natural candidate of CDM－independently proposed by particle physics. such as neutralinos, KK states, Mirror particles … The WIMP miracle: for typical gauge couplings and masses of order the electroweak scale, Wwimph2  0.1 (within factor of 10 or so) WIMP is the most favored.

Thermal history of the WIMP (thermal production) Thermal equilibrium abundance Thermal history of the WIMP (thermal production) At T >> m, At T < m, At T ~ m/22, ，decoupled, relic density is inversely proportional to the interaction strength For the weak scale interaction and mass scale (non-relativistic dark matter particles) , if and WIMP is a natural dark matter candidate giving correct relic density (proposed trying to solve hierarchy problem).

Outline 暗物质和暗物质探测 暗物质性质 暗物质直接探测 暗物质间接探测 AMS-02实验、结果和解读 小结

直接探测 (暗物质像空气一样充满整个银河系) 探测暗物质粒子与 探测器碰撞所产生 的信号

Worldwide WIMP Searches(slides thanks to Elena Aprile) ICFA Seminar Beijing

DAMA观测到9σ的年调制效应 Total exposure reaches 1.17 ton×yr,13yr

Evidence of light dark matter

Isothermal, Maxwellian, v0=220km/s,vesp=544km/s, ρ0=0.3GeV/cm3

LUX and SuperCDMS

锦屏的最新结果

The WIMP Landscape Today

Outline 暗物质和暗物质探测 暗物质性质 暗物质直接探测 暗物质间接探测 AMS-02实验、结果和解读 小结

间接探测 暗物质并不暗：它们湮灭后发出光，中微子，和带电粒子的宇宙线。

What Tools Do We Use? Auger and HiRes measure the highest energy cosmic ray flux, spectrum, and anisotropy ICECube searches for TeV neutrino sources – the most direct signature of hadronic accelerators Fermi detects thousands of new GeV sources VERITAS, HESS, MAGIC, and CANGAROO image and measure spectra and variability of TeV sources Milagro/HAWC, As/ARGO image large-scale structures and searches for new and transient TeV sources AMS-02 (space-based antimatter search ), PAMELA measure ANTIPROTON, POSITRON PLANCK/SNAP

Indirect detection of dark matter --Gamma rays Monoenergetic spectrum Continuous spectrum Smoking gun of dark matter, while low flux Flux is large, not definitive signal

Fit to the data with line spectra for different DM density profile Weniger, arXiv:1204.2791 Einasto NFW

The line feature (120-140GeV) is clear in the spectrum The line feature (120-140GeV) is clear in the spectrum. Excesses is around the GC. Fit data with two lines gives marginally better result. SU, Finkbeiner, arXiv:1205.

Connection with tree level processes DM annihilate in SM final states，(e, μ), τ, qqbar, WW

Fermi data constraint on the DM annihilation from the GC Huang, Yuan, Yin, Bi, Chen, JCAP1204, 030

Constraints on the line emission From halo, cluster and dwarf

Line search result from Fermi-LAT collaboration

Outline 暗物质和暗物质探测 暗物质性质 暗物质直接探测 暗物质间接探测 AMS-02实验、结果和解读 小结

AMS02

AMS-02（阿尔法磁谱仪） AMS02由丁肇中教授领导，历时近20年，参加实验的科学工作者来自美洲，欧洲和亚洲的16个国家（地区），共有60个大学或研究机构，600多人，目前投资约20亿美元。 中科院电工所 中科院高能所 东南大学 上海交大 中山大学 山东大学 航天部一院 航天部五院 中央研究院 汉翔航空工业公司 中山科学研究院 中央大学 成功大学 交通大学 国家太空中心

AMS02于2011年5月16日发射升空，5月19日安装到空间站上开始物理取数。 STS-134 launch May 16, 2011 @ 08:56 AM

AMS02是国际空间站上唯一大型科学实验，将长期在轨运行 TRD TOF Tracker RICH ECAL e+ p AMS AMS物理目标：暗物质寻找 AMS物理目标：寻找反物质 AMS物理目标：带电宇宙线的精确测量 42 42

2013年4月发布第一个物理结果，既正电子比例的测量结果

Updated positron fraction and electron/positron spectra are published in Sep. 2014. We have precise CR data Quantitatively study of physics behind

宇宙线的产生和传播 观测=注入+传播

传播参数  e+ 射 线 Sec/prim 将敏感地依赖于传播模型， 所以常被用于决定模型参量．B/C, 10Be/9Be 是目前测量得最好的． 传播参数 宇宙线粒子传播  射 线 e+

Anti-proton ratio Also show the pbar/p data which is consistent with background.

Galactic diffuse gamma-rays

DM can explain both the positron excesses and total spectrum; but it is not better than astrophysical explanation. To clarify the situation more precise data are necessary. J.Liu, Q. Yuan, X-J Bi, H. Li, and X. Zhang, PRD85, 043507, 2012

怎么理解实验观察到的正电子超出呢？ （since PAMELA 2008) Astrophysical sources Exotic sources Nearby pulsars，SNRs, Propagation effects Early SN stage interaction of CRs …… Dark matter annihilation Dark matter decay e+/(e-+e+) = (e+bkg+e+extra)/(e-bkg+e-extra +e+bkg+e+extra)

Bkg+pulsar (or DM) to fit the data 1，propagation of charged particles is treated by Galprop. We fit the parameters to data by MCMC 2, Note: propagation parameters are the best value to fit B/C, 10Be/9Be (later we discuss the uncertainties from astrophysics)

Both pulsar and DM give good fit Lin, Yuan, Bi, 1409.6248

It seems pulsar can fit data roughly. However, the χ2/dof=1 It seems pulsar can fit data roughly. However, the χ2/dof=1.8; 6σ deviates from expectaion. Fermi data is not consistent with the AMS02 data. We fit without including the Fermi data. χ2/dof=52/80; perfect fit to data! Yuan, Bi, Chen, Guo, Lin, Zhang, 1304.1482 定量研究宇宙线的重要性。

宇宙线中的电子加正电子能谱 与以往实验的比较 AMS-02重要结果： 以前的实验结果是错误的 流量 x E3 (s sr m2 GeV)-1 能量(GeV)

其他一些有意义的结果 电子谱本底有“结构” 宇宙线的传播模型不倾向于“重加速”模型

Electrons can provide additional information about the GCR source High energy electrons have a high energy loss rate  E2 Lifetime of ~105 years for >1 TeV electrons Transport of GCR through interstellar space is a diffusive process Implies that source of high energy electrons are < 1 kpc away Electrons are accelerated in SNR Only a handful of SNR meet the lifetime & distance criteria Kobayashi et al (2004) calculations show structure in electron spectrum at high energy "Advances in Cosmic Ray Science" Waseda University

We consider contributions from nearby pulsars and add contributions from all pulsars. Yin et al.,1304. 4128

DM vs pulsar: flux anisotropy vs spectrum wiggles

Systematic study of uncertainties of astrophysics Propagation Treatment of low energy data Models of strong interaction Galprop version

Propagation uncertainties

Low energy data

总结 暗物质研究在世界各国迅速发展，人们寄希望暗物质寻找成为新物理发现的突破口。 直接探测灵敏度迅速提高，不同实验间竞争尤其激烈，过去的一些疑似信号似乎已经被排除。 间接探测方面，Fermi和AMS-02都有些“异常”的迹象。但如何解释这些“异常”目前仍没有定论。 我国在暗物质研究方面进步非常快，建立锦屏地下实验室。有卫星和空间站实验在进行。

Strong interaction models

暗物质间接探测最新重要的进展一点启示 及DAMPE在国际竞争中的一些优势 启示：暗物质的空间间接探测(尤其是伽玛射线、电子)的探测的确是颇具前景的一个国际重大前沿领域，有望取得突破性的成果 Detector 能量范围(GeV) 能量分辨率 质子电子分辨能力 Key Instrument (Thickness of CAL) 电子/接受度 （m２srday) FERMI-LAT 20-1,000 5-20 % (20-1000 GeV) 103-104 (20-1000GeV) Energy dep. GF Tracker+ACD + Thin Seg. CAL (W:1.5X0+CsI:8.6X0) 60@TeV (1 year) AMS 1-1,000 (Due to Magnet) ～1％ ＠100 GeV 104 (x 102 by TRD) Magnet+IMC +TRD+RICH (Lead: 17Xo) ~50@TeV (1year) CALET 1-10,000 ~2-3% (>100 GeV) ～105 IMC+CAL (W: 3 Xo+ PWO : 27 Xo) 44 (1years) DAMPE ~1% ～106 IMC+CAL+Neutron (W: 2 Xo+ BGO: 32 Xo) 180 (1 years) DAMPE最主要的探测对像正是伽玛射线和电子，在100GeV处的“接受度”小于Fermi但数倍于AMS-02，能量分辨显著优于Fermi, 这对于探测暗物质湮灭线谱信号非常关键。DAMPE可探测能量范围为10TeV，将开辟TeV能段的空间电子能谱测量新窗口

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