The Latest Results from AMS on the International Space...
Transcript of The Latest Results from AMS on the International Space...
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The Latest Results from AMS on the International Space Station
Hefei, Aug 2016
Zuhao LI IHEP, CASOn behalf of the AMS Collaboration
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USAMIT - CAMBRIDGENASA GODDARD SPACE FLIGHT CENTERNASA JOHNSON SPACE CENTERUNIV. OF HAWAII UNIV. OF MARYLAND - DEPT OF PHYSICSYALE UNIVERSITY - NEW HAVEN
MEXICOUNAM
FINLANDUNIV. OF TURKU
FRANCELUPM MONTPELLIERLAPP ANNECYLPSC GRENOBLE
GERMANYRWTH-I.
KIT - KARLSRUHE
ITALYASIIROE FLORENCEINFN & UNIV. OF BOLOGNAINFN & UNIV. OF MILANO-BICOCCAINFN & UNIV. OF PERUGIAINFN & UNIV. OF PISAINFN & UNIV. OF ROMAINFN & UNIV. OF TRENTO
NETHERLANDSESA-ESTECNIKHEF
RUSSIAITEPKURCHATOV INST.
SPAINCIEMAT - MADRIDI.A.C. CANARIAS.
SWITZERLANDETH-ZURICHUNIV. OF GENEVA
CHINACALT (Beijing)IEE (Beijing)IHEP (Beijing)NLAA (Beijing)SJTU (Shanghai)SEU (Nanjing)SYSU (Guangzhou)SDU (Jinan)
KOREAEWHA
KYUNGPOOK NAT.UNIV.
PORTUGALLAB. OF INSTRUM. LISBON
TAIWAN(CHINA)
TURKEYMETU, ANKARA
BRASILIFSC – SÃO CARLOS INSTITUTE OF PHYSICS
AMS is a large international collaboration
ACAD. SINICA (Taipei)
CSIST (Taipei)NCU (Chung Li)NCKU (Tainan)
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TRD
TOF
Tracke
r
TOFRICH
ECAL
1
2
7-8
3-4
9
5-6
TRD Identify e+, e-
Silicon Tracker Z, P
ECAL E of e+, e-
RICH Z, E
TOF Z, E Particles and nuclei are defined
by their charge (Z) and energy (E ~ P)
Z and P ~ Eare measured independently by the
Tracker, RICH, TOF and ECAL
AMS: A TeV precision, multipurpose spectrometer
Magnet±Z
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Prot
on re
ject
ion
at 9
0% e
+ effi
cien
cy
Typically, 1 in 1,000 protons may be misidentified as a positron
ISS Data
Rigidity (GV)
Transition Radiation Detector
4TRD estimator = -ln(Pe/(Pe+Pp))
20 layers: fleece radiator and proportional tubes pO
ne o
f 20
laye
rs radiator
e±
Protons
Electrons
Measurement with 1 of the 20 TRD Layers
Transition Radiation
ISS Data
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Time of Flight SystemMeasures Velocity and Charge of particles
Velocity [Rigidity>20GV]
Even
ts
Z = 6σ = 48ps
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Inner tracker alignment stability monitored with IR Lasers.
The Outer Tracker is continuously aligned with cosmic rays in a 2 minute window
1
56
34
78
9
2
Laser rays
Tracker9 planes, 200,000 channels
The coordinate resolution is 10 mm.
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Measurement of Nuclear Charge (Z) and its Velocity to 1/1000Particle
Ring Imaging CHerenkov (RICH)
Θ
Intensity ⇒ Z2
⇒ V
Aerogel NaF
7
10,880 photosensors
p = 633 GeV/c p = 203
GeV/c
Aerogel NaFFe Fe
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Electromagnetic CalorimeterProvides a precision, 17 X0, TeV, 3-dimensional measurement of the directions
and energies of electrons and positrons, seperate e± from protons
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Typically, 1 in 10,000 protons may be misidentified as a positron
Proton rejection at 90% e+ efficiency
Momentum (GeV/c)
Test beam result
Boosted Decision Tree (BDT):3D shower shape
protons electrons εe = 90%
ECAL estimator
Frac
tion
of e
vent
s
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Extensive tests and calibration at CERN
AMS27 km
7 km
19 January 2010
Beam
Z X
θ
Φ
p, e+, e-, 20…400 GeV2000 positions
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May 16, 2011
May 16, 2011
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In >5 years on ISS,
AMS has collected ~90 billion cosmic rays.
To match the statistics,
systematic error studies have become important.
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Collisions of Dark Matter (neutralinos, c) will produce a signal of e+, p, …
above the background from the collisions of “ordinary” cosmic rays
The Search for the Origin of Dark Matter
M. Turner and F. Wilczek, Phys. Rev. D42 (1990) 1001;J. Ellis, 26th ICRC Salt Lake City (1999) astro-ph/9911440;…………..
Positrons: c + c e+ + …
mc=800 GeV
Collision of Cosmic RaysI. Cholis et al., JCAP 0912 (2009) 007
mc=400 GeV
e± energy [GeV]
e+ /(
e+ +
e- )
Donato et al., PRL 102, 071301 (2009)
Antiprotons: c + c p + …
Collision of Cosmic Rays
mc= 1 TeV
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Dear Sam,
this is just to let you know that your article the first AMS data has been selected in our 2013 APS Physics Highlights (http://physics.aps.org/articles/v6/139).
Congratulation on this work, which has generated a lot attention among our readers, the press and the scientific community.
Best regards,
Matteo
-- Matteo Rini, PhD Deputy Editor, Physics [email protected] http://physics.aps.org
6.8 million events----------------------------------------------------------------------------------
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10.9 million e+ and e- events
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mc=800 GeV
e+, e- from Collision of Cosmic Rays
mc=400 GeV
e± energy [GeV]
e+ /(
e+ +
e- )
c + c → e+ + …
1. The energy at which it begins to increase.
2. The rate of increase with energy
3. The existence of sharp structures. 4. The energy beyond which it ceases to increase.
6. The rate at which it falls beyond the turning point.
5. Isotropy.
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10.9 million e+, e- events
Posi
tron
Fra
ctio
n
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6. The expected rate at which it falls beyond the turning point.
e± energy [Gev]
Posi
tron
frac
tion
Collision of cosmic rays
Turn over energy
Other astrophysical sources
Dark Mattermc ~ 1 TeV
To be determined in the next 10 years:
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AMS, Electron Flux and the Positron Flux
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9.2 M
0.6 M
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1. The electron flux and the positron flux are different in their magnitude and energy dependence.
2. Both spectra cannot be described by single power laws.3. The spectral indices of electrons and positrons are different. 4. Both change their behavior at ~30GeV. 5. The rise in the positron fraction from 20 GeV is due to an excess of
positrons, not the loss of electrons (the positron flux is harder).
Observations:
The Electron Flux and the Positron Flux
spectral index = d log (Φ)/ d log (E)
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E nergy (G eV )1 10 210 310
)-1
sr sec ]
2 [ m
2 (GeV
F ´ 3
E
0
50100
150200
250
300350
400AMS-02ATICBETS 97&98PPB-BETS 04Fermi-LATHEATH.E.S.S.H.E.S.S. (LE)
AMS Results: (e+ + e-) fluxIndependent of charge sign measurement no charge
confusionSmall systematics on acceptance: 2% @ TeV
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10.6 M events
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Spectral Indices of electrons+positrons
γ=−3.170 ± 0.008 (stat + syst.) ± 0.008 (energy scale) E > 30 GeVΦ(e++e−) = C Eγ
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Collisions of Dark Matter (neutralinos, c) will produce a signal of e+, p, …
above the background from the collisions of “ordinary” cosmic rays
The Search for the Origin of Dark Matter
M. Turner and F. Wilczek, Phys. Rev. D42 (1990) 1001;J. Ellis, 26th ICRC Salt Lake City (1999) astro-ph/9911440;…………..
Positrons: c + c e+ + …
mc=800 GeV
Collision of Cosmic RaysI. Cholis et al., JCAP 0912 (2009) 007
mc=400 GeV
e± energy [GeV]
e+ /(
e+ +
e- )
Donato et al., PRL 102, 071301 (2009)
Antiprotons: c + c p + …
Collision of Cosmic Rays
mc= 1 TeV
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|R igidity| [G V ]0 100 200 300 400 500
ratio
pF/
pF
5-10
4-10
A M S -02
P A M E LA
AMS p/p results
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350,000 p events
K inetic E nergy [G eV ]1 10
ratio
pF/
pF
5-10
4-10A M S -02
P A M E LA
B E S S
0.2 0.4 0.6 2 4 6
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To identify the Dark Matter signal we need
to measure the e+, e− and p signal accurately until 2024.
The Search for the Origin of Dark Matter
Positrons: c + c e+ + …
Collision of Cosmic Rays
mc=400 GeV
e± energy [GeV]
e+ /(
e+ +
e- )
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To understand background, we need precise knowledge of:
1. The cosmic ray fluxes (p, He, C, …)
2. Propagation and Acceleration (Li, B/C, …)
Antiprotons: c + c p + …
mc=800 GeVmc= 1 TeV
Collision of Cosmic Rays
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Trac
ker
TOFRICH
ECAL
1
2
7-8
3-4
9
5-6
TRDTracker Plane 1
RICH
Inner Tracker 2-8
Tracker Plane 9
TRD
Upper TOF
Lower TOF
0.30
0.12
0.32
0.30
0.33
0.16
0.16
AMS: Multiple Measurements of Nuclear ChargeCharge Resolution (Z=6)
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The isotropic protonflux Φi for the i th rigidity bin (Ri , Ri +ΔRi) is:
To match the statistics of 300 million events, extensive systematic errors studies have been made.
1) σtrig.:trigger efficiency
2) σacc.: a. the acceptance and event selection b. background contamination c. geomagnetic cutoff
3) σunf : a. unfolding b. the rigidity resolution
4) σscale.: the absolute rigidity scale function
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300 million events
AMS proton flux
AMS-02
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Soide curve is the fit to the data above 45 GV: χ2/d.f.= 25 /26Dashed curve uses the same fit values but with Δ set to zero.
Δ = 0
Φ
AMS proton flux two power laws: R, R+Δ with a characteristic transition rigidity R0 and
smoothness s
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AMS proton spectral index variation:Model independent measurement of spectral index
Spec
tral
Inde
x
= d log (Φ)/ d log (R)
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Kinetic Energy (Ek) [GeV]
AMS proton flux
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To measure the flux of nuclei (He, Li, Be, B, C, O, …) accurately, we need to know the interaction cross section of these nuclei with the materials in AMS.
Unfortunately, the interactions of nuclei with
the materials in AMS could not be measured on the ground. This limits the accuracy to which we could measure the fluxes.
On ISS we have now a method to measure these interactions in space accurately.
Accurate measurement of the flux of nuclei on the ISS
A new method:
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Measuring the interactions of nuclei within AMSwhen AMS is flying horizontal
First, we use the seven inner tracker layers, L2-L8, to define beams of nuclei: He, Li, Be, B, …
Second, we use left-to-right particles to measure the nuclear interactions in the lower part of the detector.
Third, we use right-to-left particles to measure the nuclear interactions in the upper part of detector.
L2 - - - L8
L9
L1
L2 - - - L8
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AMS Measurement of He+C Cross Section
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) [G V ]R~
R igidity (
10 2103
10
]1.7
GV
-1sec
-1sr
-2 [m
2.7
R~ ´Flux
0.5
1
1.5
2
2.5
3
3.53
10´
A M S -02 a)
AMS Helium Flux
50 million events
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AMS Helium Flux
Solid curve fit of Φ to the data above 45 GV: χ2/d.f.= 25 /27Dashed curve uses the same fit values but with R0 = infinity.
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R0 = ∞
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) [G eV /n]K
K inetic E nergy (E
1 10 2103
10
]1.7
(GeV/n)
-1sec
-1sr
-2 [m
2.7
K E´
Flux
0
0.2
0.4
0.6
0.8
1
1.23
10´A M S -02
AT IC -2
B E S S -P olar
C R E A M
PA M E LA
b)
AMS Helium Flux
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Φp/ΦHe = C Rγ
proton/He flux ratio
Change of slope at ~45 GV
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R igidity [G V ]10 210 310
]-1
s-1
sr
-2 m
1.7
[ GV
2.7
R´Flux
1
10
• Like B and Be, Li is produced by the spallation of heavier nuclei during their propagation.
• Sensitive to CR propagation parameters (diffusion, convection, reacceleration…).
Lithium in Cosmic Rays
C, N, O,…Fe + ISM Li B, Be + ISM Li
Current data from balloon experiments:
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Orth et al (1978)Juliusson et al (1974)
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AMSOrth et al (1978)Juliusson et al (1974)
AMS Lithium flux – current status
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1.5 M events
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Lithium flux with two power law fit
Slope changes at about the same rigidity as for protons and helium
R0 = ∞
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ZTOF_LOW=5.2
ZTRK_IN=4.8
ZRICH=5.1
ZTRK_L1=6.1
ZTRD=6.0
Z0=9.9Z1=5.3
front view
Carbon Fragmentation to Boron R = 10.6 GV
Precise measurement of the rigidity spectra of B/C provides information on Cosmic Ray Interactions and Propagation
The propagation of cosmic rays and their interactions with the Interstellar Medium (ISM) is measured through the B/C ratio.
AMS
( B )
HALO
DISKC
B
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Boron and Carbon: Sample composition
Tracker L1 Charge (c.u.)
Contamination < 3%Selection efficiency > 96%
BO
C
N
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AMS B/C Ratio
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AMS physics for the lifetime of the Space StationAccurate measurement (~1%) of Cosmic Rays to higher energies including:
a. Continue the study of Dark Matter b. Search for the Existence of Antimatter
c. Search for New Phenomena, …
The latest AMS measurements of the positron fraction, the antiproton/proton ratio, the behavior of the fluxes of electrons, positrons, protons, helium, and other nuclei is providing new, precise, and unexpected information.
The accuracy and characteristics of the data, simultaneously from many different types of cosmic rays, will soon determine the true nature of the new phenomena we observe.
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In the past hundred years, measurements of charged cosmic rays by balloons and satellites have typically contained ~30% accuracy.
AMS is providing cosmic ray information with ~1% accuracy.The improvement in accuracy will provide new insights.
The Space Station is now a unique platform for fundamental physics research.