FEPP Final Report DAMPE Indirect Dark Matter Search

FEPP Final Report DAMPE (Indirect Dark Matter Search) Zhibo Wu, USTC 2019. 06. 26 1

Outline • Dark matter signal candidates • The DAMPE instrument • Event reconstruction • Electron/proton discrimination • Physics results 2

Dark Matter Signal Candidates • 3

The DAMPE Instrument Sub-detectors: • PSD • STK • BGO Calorimeter • NUD 4

The DAMPE Instrument Plastic Scintillator Detector Task: Measure |Z| of incident high-energy particles. Structure: • 82 plastic scintillator in two planes • Double dynode readout 5

The DAMPE Instrument Silicon-Tungsten trac. Ker Task: • Measure charges & trajectories • Reconstruct the direction of photons Structure: • 6 double-planes of silicon detectors • Multiple tungsten layers 6

The DAMPE Instrument BGO Calorimeter Task: • Energy deposition • e/P identification Structure: • 14 Layersⅹ 22 BGO bars • Three dynode readout 7

The DAMPE Instrument • 8

Event Reconstruction • Energy: Signals (ADC counts) from proper dynodes are converted into energy. Total deposited energy: summing up the energies of all BGO crystals. • Track: (1) BGO: “Cluster” of fired BGO bars are built according to energy deposit. The positions of bars in the cluster will be fitted linearly. (2) STK: Select strips with high S/N ratio. The Kalman filter is then performed offline on the ground. • Charge By evaluating the path length, the position, the incidence angle and energy values from PSD & STK. 9

Electron/Proton Discrimination • The development of showers in BGO Showers initiated by electrons and protons behave differently in the BGO calorimeter. • NUD can further discriminate EM / hadronic showers 10

Physics Results • Cosmic Ray Electron (CRE) spectrum from 55 Ge. V to 2. 63 Te. V has been fitted: An energy break in the spectrum at around 0. 9 Te. V. • The evidence for a signal around 1. 4 Te. V is not statistically compelling. 11

Electron/Proton Discrimination • Constraints on the DM mass & annihilation cross section for μ+μ- channel 12

Electron/Proton Discrimination • Constraints on DM Favored DM parameter region. Combined with astrophysics observation, the annihilation or decay channels can hardly survive. DM models have to be tuned. • e+e- Channels: excluded by DAMPE+AMS-02; • τ Channels: too many photons; • Other annihilation channels: constraint by astrophysical observation; • Decay channels: severely constraint by EGRB data. 13

Summary DAMPE is a successful space-based experiment. • Well-designed and functioning detector systems; • Powerful reconstruction and identification algorithm; • Important physics results: (1) An energy break in CRE spectrum; (2) No compelling evidence for 1. 4 Te. V CRE signal; (3) Favored DM parameter regions mostly excluded. Thank You! 14

Main References [1] J. Chang, G. Ambrosi et. al. , The Dark Matter Particle Explorer mission, Astroparticle Physics, 95 (2017) 6– 24. [2] T. Bringmann, C. Weniger, Gamma ray signals from dark matter: Concepts, status and prospects, Dark Universe 1 (2012) 194– 217. [3] Yifeng Wei, Yunlong Zhang, Performance of the DAMPE BGO calorimeter on the ion beam test, Nuclear Inst. and Methods in Physics Research, A 922 (2019) 177– 184. [4] Rui Qiao et. al. , Charge reconstruction of the DAMPE Silicon. Tungsten Tracker: A preliminary study with ion beams, Nuclear Inst. and Methods in Physics Research, A 886 (2018) 48 -52. [5] A. Tykhonov et. al. , Interal alignment and position resolution of the silicon tracker of DAMPE determined with orbit data, Nuclear Inst. and Methods in Physics Research, A 893 (2018) 43 -56. 15

Main References [6] Tiekuang Dong, Yapeng Zhang et. al. , Charge measurement of cosmic ray nuclei with the plastic scintillator detector of DAMPE, Astroparticle Physics 105 (2019) 31 -36. [7] DAMPE Collaboration, First data from the DAMPE space mission, Nuclear and Particle Physics Proceedings 291 -293 (2017) 59 -65. [8] DAMPE Collaboration, Direct detection of a break in the teraelectronvolt cosmic-ray spectrum of electrons and positrons, nature, Vol. 552, 7 December 2017, 63 -66. [9] Andrew Fowlie, DAMPE squib? Significance of the 1. 4 Te. V DAMPE excess, Physics Letters B 780 (2018) 181– 184. [10] Q. Yuan, L. Feng et. al. , Interpretations of the DAMPE electron data, Ar. Xiv e-prints (2017), ar. Xiv: 1711. 10989 [astroph. HE]. 16

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