Measurement of cosmic-ray proton spectrum with the Dark ... · y /MipE Zx = p PsdEx/MipE ZPSD =(Zy...
Transcript of Measurement of cosmic-ray proton spectrum with the Dark ... · y /MipE Zx = p PsdEx/MipE ZPSD =(Zy...
Measurement of cosmic-ray proton spectrum with the Dark Matter Particle Explorer
Chuan Yue*, Antonio De Benedittis, Mario Nicola Mazziotta, Stefania Vitillo, Zhi-Hui Xu, Yu-Hong Yu
(on behalf of the DAMPE Collaboration)*speaker: [email protected]
2019.07.30 Madison, USA
“WuKong”
DAMPE Collaboration
for collaboration list see PoS(ICRC2019)1177
• CHINA – Purple Mountain Observatory, CAS – University of Science and Technology of China – Institute of High Energy Physics, CAS – Institute of Modern Physics, CAS – National Space Science Center, CAS
• 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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3
DAMPE Instrument
- Charge measurement (dE/dx in PSD, STK and BGO) - Gamma-ray converting and tracking (STK and BGO) - Precise energy measurement (BGO Crystals) - Hadron rejection (BGO and Neutron Detector)
(Chang et al. Astropart.Phys. 95 (2017) 6–24)
Orbit Information:Sun-synchronous Orbit Altitude: ~ 500 km Inclination: ~ 97 deg Launch Date: Dec.17th, 2015
Main Scientific Goals:Origins and Propagations of Cosmic-Rays Dark Matter Indirected Detection High Energy Gamma-ray Astronomy
(~32X0, ~1.6λI)
Interesting Scientific Issues:
Proton Spectral Hardening at ~400 GeV Other structures beyond TeV Range?
Proton spectrum has been measured with high precision up to TeV
Measurements in high energy range (TeV ~ PeV) have large uncertainties
(Y.S. Yoon et al., CREAM, 2017)
AMS02,ATIC-2,PAMELA,CREAM
DAMPE
Introduction
(E. Atkin et al., NUCLEON, 2018)4
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Data Sample: Jan. 1st 2016 to Jun. 30th 2018
Total Events: 4.68 Billion Events
Live Time: 5.9670276 * 10^7 s (75.73%)
Data in SAA region are excluded
Dead Time: Instrument Recovery, On-orbit Calibration, etc
Data during Sep2017 Solar Flare (20170908~20170913) are excluded
On-orbit Data Sample
Date01/01/2016 01/07/2016 31/12/2016 02/07/2017 31/12/2017 02/07/2018
Even
ts S
tatis
tic (M
illion
)0
1000
2000
3000
4000
5000DAMPE DAQ Statistic
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Proton Selections
Cut 0: BgoEnergy > 20 GeV
Cut 1: HE-Trigger
Cut 2: STK Track
Cut 3: Track-PSD Match
Cut 4: Track-BGO Match
Cut 5: PSD pre-selection
Cut 6: BGO pre-selection
Particle Identification
Cut 7: e/p Separation
Cut 8: Charge Selection
Pre-selections Flight-Data Proton (BGO-Energy: 1.2 TeV)
Flight-Data Proton (BGO-Energy: 12.1 TeV)
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210 310 410
HE
Trig
ger E
ffici
ency
0.2
0.4
0.6
0.8
1MC Proton
Flight Data
BGO Energy [GeV]210 310 410
MC
/Dat
a
0.8
0.9
1
1.1
1.2
Unbias Trigger (G0) MIPs Trigger (G1&G2) High Energy Trigger (G3) Low Energy Trigger (G4)
"trigger =Nhe|unb
Nunb
G3 Trigger Efficiency
2.5%
Uncertainty mainly comes from the threshold calibration and the limited statistics of unbias trigger events
(unbias trigger pre-scaled by 1/512 at low latitudes <20deg and 1/2048 at high latitudes)
High-Energy (G3) trigger efficiency can be obtained by applying all other proton selections (“N-1”) to unbias (G0) sample
HE-Trigger Efficiency
Efficiency Validation (“N-1”):
Preliminary
10 210 310 410
Trac
k R
cons
truct
ion
Effic
ienc
y
0.2
0.4
0.6
0.8
1
MC ProtonFlight Data
BGO Energy [GeV]10 210 310 410
MC
/Dat
a
0.8
0.9
1
1.1
1.2
Preliminary
STK Track Efficiency
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"track =Ntrack|BGOtrack
NBGOtrack
STK track Efficiency Validation
Selecting a “pure” proton sample by applying BGO shower-axis based proton selections (“N-1”) to estimate STK track reconstruction efficiency
STK Track Efficiency
?
3.5%
∆θx,y(deg)-10 -8 -6 -4 -2 0 2 4 6 8 10
Cou
nts
10
210
310
410
510
610Delta Theta in X-directionDelta Theta in Y-direction
MC Proton
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BGO Energy (GeV)210 310 410 510
PSD
Cha
rge
1
2
3
4
5
6
7
8
9
10
1
10
210
310
410
Charge selection
PSD Charge1 1.5 2 2.5 3
Num
ber o
f Eve
nts
0
500
1000
1500
2000
2500
3000
3500
4000
4500/TeV < 0.562dep0.447 < E Flight Data
MC ProtonMC HeliumMC Proton+Helium
Layer-yLayer-x
X
ZBethe-Bloch
Zy =qPsdEy/MipE Z
x
=pPsdE
x
/MipE ZPSD
= (Zy
+ Zx
)/2
PreliminaryPSD Charge
(see more in talk CRD7b by Zhang Y.P.)
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√ Ask the help of the first layer of STK
To Study PSD layer-1 Selection: PSD_L2 && STK_L1
To Study PSD layer-2 Selection: PSD_L1 && STK_L1
PSD Charge Efficiency Validation
10 210 310 410
Cha
rge
Effic
ienc
y0.4
0.6
0.8
1
MC Proton
Flight Data
BGO Energy [GeV]10 210 310 410
MC
/Dat
a
0.9
0.95
1
1.05
1.110 210 310 410
Cha
rge
Effic
ienc
y
0.4
0.6
0.8
1
MC Proton
Flight Data
BGO Energy [GeV]10 210 310 410
MC
/Dat
a
0.9
0.95
1
1.05
1.1
1% 1.5%
PreliminaryPreliminary
Charge selection
PSD layer-y PSD layer-x
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Bayesian Unfolding Method [Giulio D'Agostini, NIM A362(1995), 487]
Energy Unfolding
Ni =nX
j=1
↵ijMj(1� �j)
↵ij =P (Ed,j |E0,i)N̂i
✏iPn
i=1 P (Ed,j |E0,i)N̂i
Deposited Energy [GeV]210 310 410
Con
tam
inat
ion
[%]
-310
-210
-110
1
10Helium ContaminationElectron Contamination
Background
: Unfolded event numberNi
Mj: Measured event number�j : BackgroundP (Ed,j |E0,i): Response Matrix (MC)
N̂i : Prior (E-2.7)
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Incident Energy [GeV]210 310 410 510
sr]
2Ef
fect
ive
Acce
ptan
ce [m
0
0.01
0.02
0.03
0.04
0.05
Preliminary
Effective Acceptance
HE Tigger: ~2.5%
Track Reconstruction: ~3.5%Charge Identification: ~1.8%
G4 FTFP_BERT
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Proton Spectrum
Kinetic Energy [GeV]10 210 310 410 510
]1.
6G
eV-1 s-1
sr-2
[m2.
6 E×
Flux
410
DAMPEATIC-2 (2009)PAMELA (2011)AMS-02 (2015)CREAM-I+III (2017)NUCLEON-KLEM (2018)CALET (2019)
DAMPE Uncertainties (Stat.+Syst.)
Preliminary
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Proton Spectrum
Kinetic Energy [GeV]10 210 310 410 510
]1.
6G
eV-1 s-1
sr-2
[m2.
6 E×
Flux
410
DAMPEATIC-2 (2009)PAMELA (2011)AMS-02 (2015)CREAM-I+III (2017)NUCLEON-KLEM (2018)CALET (2019)
DAMPE Uncertainties (Stat.+Syst.)
Preliminary
Hardening ~400 GeV
Softening ~10 TeV
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Conclusions
Since launch on Dec. 17, 2015, DAMPE (“WuKong”) has been operated for more
than three years.
Thirty months of on-orbit data with live time fraction of 75.73% are analysed
for cosmic-ray proton spectrum.
The analysis of proton spectrum for energy range 40GeV-100TeV is reported.
The DAMPE measurement confirms the spectral hardening around 400 GeV and
gives a strong evidence of spectral softening at ~10 TeV
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Conclusions
Since launch on Dec. 17, 2015, DAMPE (“WuKong”) has been operated for more
than three years.
Thirty months of on-orbit data with live time fraction of 75.73% are analysed
for cosmic-ray proton spectrum.
The analysis of proton spectrum for energy range 40GeV-100TeV is reported.
The DAMPE measurement confirms the spectral hardening around 400 GeV and
gives a strong evidence of spectral softening at ~10 TeV
Thanks for your attentions!