Dark matter search at HERD X.-J. Bi Institute of High Energy Physics 3 nd Workshop of Herd. Xi’an,

DM existence has compelling proofs. We know little about the properties of DM. 1, stable; 2, neutral; 3, cold, non-relativistic to behave like gravitational seed of the structure formation; 4, non-baryonic and ~27%, production process MAY require weak interaction with the SM particles (WIMPs).

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

Gamma rays from DM

Gamma ray excess from the GC a

Constraint from dwarf galaxies

The GC excess due to DM annihilaiton seems be disfavored

HESS results

Future prospects

133GeV gamma ray line from GC q Ackermann et al

New limit on monochromatic gamma

New di-photon resonance at ATLAS

Taking all the SM particle final states into account, the decay width is much smaller than 45GeV. There must be an invisible channel to have such large width. DM must have large coupling with S.

Constraints on the DM interaction DM couples with S, which couples with gluon. The elastic cross section can be calculated. Bi, Xiang, Yin, Yu,

a Line sensitivity of HERD Huang et al

AMS-02

AMS-02 pbar/p preliminary results Lin, Bi, Yin, Yu,

Conclusions of the quantitative study I Both astrophysical sources, like pulsars, and dark matter can give good fit the AMS-02 data. AMS02 data can not distinguish the two scenarios.

Electron spectrum expected in 3 yrs

Constraints from gamma Yuan, Bi, Chen, Guo, Lin, Zhang, See also, Jin, Wu, Zhou, Cholis, Hooper,

Relax the constraints from dSphs If p-wave process is important, the annihilation is velocity dependent. Therefore annihilation in dSphs is suppressed and the constraints are relaxed. So the DM explanation to AMS02 is still viable. Zhao, Bi et al,

Relax the constraints from dSphs The Breit-Wigner annihilation formula can also relax the constraint from the dSphs Zhao, Bi et al,

Conclusions of the quantitative study II There is a new break at the primary electron spectrum Comments: 1 ， This is exactly similar to the case of proton spectrum measured by AMS2. The electron break is at ~60GeV with Δγ ≈ , again precise fit! without second break a wrong background is adopted! （ Without a sufficient understanding of background, we can never understand the signal correctly. ） 3, subtle effect is hid behind the precise data, only by quantitative study can it be revealed.

"Advances in Cosmic Ray Science" Waseda University Electrons can provide additional information about the GCR source High energy electrons have a high energy loss rate  E 2 – Lifetime of ~10 5 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 DAMPE and HERD to detect the nearby souces

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

DM vs pulsar: flux anisotropy vs spectrum wiggles

Summary A recent LHC 750 GeV diphoton resonance signal may have close relation with DM. Especially it predicts large monochromatic gamma ray flux, which can be probed at HERD. AMS-02 provided very precise measurement of electron/positron spectrum. Both DM and pulsars give good fit to data. DM scenario is severely constrained by Fermi dwarf galaxy data. But in a velocity-dependent scenario the constraints are relaxed greatly. DM is still a viable interpretation for the positron excess. DAMPE and HERD can give discrimination of the positron origin if a sharp cutoff is measured. Features at the electron spectrum if detected will prefer the astrophysical origin and nearby CR sources.

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

It seems pulsar can fit data roughly. However, the χ 2 /dof=1.8; 6σ deviates from expectaion. Fermi data is not consistent with the AMS02 data. We fit without including the Fermi data. χ 2 /dof=52/80; perfect fit to data! Yuan, Bi, Chen, Guo, Lin, Zhang,

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

Propagation uncertainties

Low energy data

Strong interaction models

质子谱有（无）拐折

Different Galprop versions

Interpret data with pulsars Yin et al Index ~ 2, softer than before to fit PAMELA. Therefore larger total injection power.

We consider contributions from nearby pulsars and add contributions from all pulsars.

DM vs pulsar: flux anisotropy vs spectrum wiggles

summary AMS-02 opens a new era of cosmic ray study. We need precise quantitative study now. Fermi electron spectrum shows inconsistence with AMS-02 positron ratio, by our fitting program. DM interpretation of AMS-02 positron ratio meets challenges from Fermi gamma observations. In several cases, electron spectrum (with wiggle), B/C, proton spectrum, higher energy and more precise measurement beyond the AMS-02 is required.

宇宙线的产生和传播