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Qiang Yuan (袁强)Purple Mountain Observatory
(on behalf of the DAMPE collaboration)
Nov. 27 - 31, 2019, Tsung-Dao Lee Institute, Shanghai
Latest results of the Dark Matter Particle Explorer (DAMPE) experiment
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• CHINA• Purple Mountain Observatory, CAS, Nanjing • Institute of High Energy Physics, CAS, Beijing• National Space Science Center, CAS, Beijing• University of Science and Technology of China, Hefei• Institute of Modern Physics, CAS, Lanzhou
• ITALY• INFN Perugia and University of Perugia• INFN Bari and University of Bari• INFN Lecce and University of Salento• INFN LNGS and Gran Sasso Science Institute
• SWITZERLAND• University of Geneva
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The DAMPE collaboration
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ØIntroduction
ØDAMPE instrument
ØOn-orbit performance
ØPhysical Results
ØSummary
Outline
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PLANCK
Composition of the Universe
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Detection of dark matter
arXiv:0806.29115
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Cosmic raysBraz. J. Phys., 44, 441 (2014)
Ø Precision measurements of cosmic ray spectra: cosmic ray origin, acceleration, and propagation
Ø The spectra above TeV are not well measured due to limited statistics of direct detection experiments
DAMPE coverage
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Fermi
ISS-CREAM
Recent space particle/ detectors
NUCLEONCALET
PAMELA
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Dark matter indirect detection
-ray astronomy
Cosmic ray physics
Three major scientific goalsDAMPE (“Wukong”) lanuched on Dec. 17, 2015
Dark Matter Particle Explorer (DAMPE)
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DAMPE instrument
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Ø PSD: charge measuresument via dE/dx and ACD for photonsØ STK: track, charge, and photon converterØ BGO: energy measurement, particle (e-p) identificationØ NUD: Particle identification
Instrument design
Astropart. Phys., 95, 6 (2017)
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Ø 2 layers (x,y) of 88.4 cm × 2.8 cm × 1 cm
Ø Active area: 82 cm × 82 cm Ø Weight : ~103 kgØ Power: ~ 8.5 W
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PSD charge detectorAstropart. Phys., 94, 1 (2017)
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Silicon tracker
Ø Detection area: 76 cm x 76 cm
Ø Total weight: ~154 kg
Ø Total power consumption: ~ 82W
Ø Three 1 mm tungsten plates for photon conversion (0.86 X0)
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BGO calorimeter
Ø Outer envelop: 100 cm x 100 cm x 50 cm
Ø Detection area: 60 cm x 60 cm
Ø Total weight: ~1052 kg
Ø Total power consumption: ~ 41.6 W
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NUD neutron detector
+ Li+ α → B+ n 710Ø
Ø 4 plastic scintillators
Ø Active area: 60 cm x 60 cm
Ø Total weight: ~12 kg
Ø Total power: ~ 0.5 W
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On-orbit performance
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7 full scans of the sky 5M events/day6.6 billion in total
DAMPE 3.5 year counts map
Observation overview
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PSD pedestal<0.5% STK pedestal<0.7%
BGO pedestal<0.9% NUD pedestal<0.6%
Detector stability
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Ni
Fe
SiNe
C O
H
He
Ca
LiBe
B N
F
NaMg
AlS
ClAr
K TiVCr
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Species Charge Res.P 0.06He 0.10Li 0.14Be 0.21B 0.17C 0.18N 0.21O 0.20
Astropart. Phys., 105, 31 (2019)
PSD charge measurement
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PSF calibrated with bright gamma-ray sources:~0.5 degrees @ 5 GeV
Geminga
AGNs
STK direction measurement
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MIP: minimum ionizing particle
BGO energy calibration
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P vs. N-side
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BGO energy linearity
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P vs. N-side
BGO energy linearity
1.005±0.016
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Total vs. Max bar energy
BGO energy linearity
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electron gamma proton
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Particle identification
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MC protonsMC electronsMC sumFlight data
z = Flast× (SumRms)4 /(8 × 106)
Candidate protonsCandidate electrons
0.5-1.0 TeV
SumRms [mm]
F las
t
Nature, 552, 63 (2017)
Ø We use the lateral (SumRMS) and longitudinal (energy ratio in last layer) developments of the showers to discriminate electrons from protons
Ø For 90% electron efficiency, proton background is ~2% @ TeV, ~5% @ 2 TeV, ~10% @ 5 TeV
e/p separation
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Physical results
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Ø Three different PID methods give very consistent results on event-by-event level
Ø Direct detection of a spectral break at ~1 TeV with 6.6 confidence level
Ø Analysis with new data is on-going
Total e++e- spectrum
(2017)
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Errors of e++e- spectrum
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Ø Cooling time of TeV electrons ~ Myr, effective propagation range ~ kpcØ Assuming a total SN rate of 0.01 per year, the total number of SNRs
within the effective volume and cooling time is O(10)
Astrophys. J., 836, 172 (2017)
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Implication of the spectral softening: discreteness of source distributions?
Fang et al. (2017)Di Mauro et al. (2017)Manconi et al. (2019)...
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AMS-02, 2017, ICRC
CREAM, 2017, ApJNUCLEON, 2018, JETPL
CALET, 2019, PRLPAMELA, 2011, Science
Spectral structures of nuclei
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Ø Confirms the hundreds GeV hardening
Ø Detecting a softening at ~14 TeV with high significance
DAMPE proton spectrum
~14 TeV break
DAMPE coll. 2019, Sci. Adv., 5, eaax3793 + CALET (2019)
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Implications: source population(?) Nearby source(?)
Liu et al., 1812.09673Gaisser et al. (2013)
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DAMPE helium spectrum
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Cosmic ray anisotropies
95% UL of dipole amplitude for 1-yr data (>~300 GeV): 6.7×10-3
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Solar modulation of e++e-
Ø Anti-correlation with sunspot numbers
Ø Monthly variation may be related to occasional solar activities
Ø Possible time delay between sunspot numbers and CR modulation
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Electron Forbush decrease
Ø Clear flux decreases after 2017/09/07 flare
Ø Decreasing behavior of recovery time versus energy
Amplitude
Recovery time
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DAMPE 3 yearsE > 2 GeV
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-ray skymap
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Preliminary
1%
-ray line searches
DAMPE 3 yrs compared with Fermi 5.8 yrs
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Ø 143 sources with TS > 20Ø Most are AGNs and pulsars
Preliminary
-ray point sources
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-ray pulsars
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(Yuan et al. PoS (ICRC2017) 617)41
• DAMPE detected outbursts of several AGNs• Consistent with multi-wavelength observations
MM potential: AGNs
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• DAMPE works in a survey mode, its data can be used for MM studies• No clear variabilities of TXS 0506+056 were detected due to limited
statistics
Preliminary
IceCube's nuSep. 22, 2017
MM potential: TXS 0506+056
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Ø DAMPE detector is working extremely stably for nearly 4 years since launch
Ø Very precise measurements of the e++e- spectrum from 25 GeV to 4.6 TeV have been obtained, showing a spectral break at ~TeV energies
Ø Precise measurements of proton spectrum from 40 GeV to 100 TeV have been obtained, revealing interesting softening features at ~10 TeV
Ø Variable gamma-rays from AGNs are detected. DAMPE is expected to play an important role in the MM campaign!
Ø More results are coming
Summary
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Thank You!
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Backup
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Raw count spectra
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Energy measurement
BGO calorimeter 308 BGO bars 616 PMTs
Ø Thick calorimeter (32 X0): high-resolution
Ø Two-side readouts
Ø Three dynode outputs enable a >106 dynamic range
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Laser experiment
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Electrons: 0.5 - 243 GeV Raw Energy Corrected Energy
Test beam validation
Astropart. Phys., 95, 6 (2017) 48
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Preliminary
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1 13.0123 0.1640lbindataC GeV
1 1/ 1.0121 0.0126lbin lbindata tracerC C
Absolute energy scale
Ø An energy scale higher by (1.2+/-1.3)% from the geomagnetic cutoffØ Cutoff energy is stable with time (a slight decrease due to solar
modulation)
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400 GeV proton beam
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243 GeV electron beam
Protons
Electrons
γ -rays
Validation of e/p separation
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e/p separation at higher energies
1-2 TeV 2-5 TeV
For 90% electron efficiency, proton background is ~2% @ TeV, ~5% @ 2 TeV, ~10% @ 5 TeV.
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DAMPE IRFs for -raysAstropart. Phys., 95, 6 (2017)Res. Astron. Astrophys., 18, 027 (2018)
Acceptance
Effective area
Point spread Energy response
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Three-component e+e- model
Ø Primary e- accelerated together with ions (in e.g., supernova remnants)Ø Secondary e- and e+ from hadronic interaction of cosmic ray nucleiØ Additional e- and e+ from extra sources (e.g., pulsars, ...)