COSMIC RAY PHYSICS WITH AMS

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COSMIC RAY PHYSICSWITH AMS

• Joseph Burger MIT
• On behalf of the AMS-02 collaboration
• EPS2003 Aachen
• Particle Astrophysics
• July 17, 2003

Joseph.Burger_at_cern.ch
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• Cosmic Rays p, D, He, C,,e,e-,?
• Direct Search for Cosmic Antimatter
• Other Searches Strangelets,
• Dark matter search in morning session talk
• by Mariusz Sapinski

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Cosmic Ray Flux
AMS-02 is a large acceptance magnetic
spectrometer which will extend high statistics
measurements of cosmic ray properties to high
rigidities.
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AMS-023 years on ISS starting 2005-2006
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Precursor Flight on STS91, June 2-12, 1998
10 days technical checkout also brought physics
results and six publications "Search for
Antihelium in Cosmic Rays", M. Aguilar et al.,
Phys. Lett. B461 ( 2 Sep 1999) 387-396
"Protons in Near Earth Orbit", M. Aguilar et al.,
Phys. Lett. B472 (26 Jan 2000) 215-226
"Leptons in Near Earth Orbit", M. Aguilar et al.,
Phys. Lett. B484 (27 Jun 2000) 10-22 "Cosmic
Protons", M. Aguilar et al., Phys. Lett. B490 (28
Sep 2000) 27-35 "Helium in Near Earth Orbit",
M. Aguilar et al., Phys. Lett. B494 (30 Nov 2000)
193-202 "The Alpha Magnetic Spectrometer (AMS)
on the International Space Station, Part I,
Results from the test flight on the Space
Shuttle", M. Aguilar et al., Physics Reports,
vol. 366/6 (Aug.2002), pp.331-404. on e, p,
antiprotons, D, He, antihelium,
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AMS-02
TRD (Transition Radiation Detector) Separates e
from p, p lt 10-2-10-3 from 10-300 GeV ToF
(Upper Time of Flight) Velocity measurement,
dE/dX, fast trigger Star Tracker (pointing to
lt1) Superconducting Magnet 0.8T field for
momentum, sign of charge Silicon Tracker 8 x-y
planes with 10/30µm resolution,
dE/dX Anticoincidence Counter Vetoes particles
from outside trigger aperture ToF (Lower Time of
Flight) Velocity measurement, dE/dX, fast
trigger RICH (Ring Imaging Cerenkov
Counter) Precision ß measurement - separates
isotopes ECAL (Electromagnetic
Calorimeter) Separates e from p, p lt 10-3-10-4
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Transition Radiation Detector (TRD)
TRD Beam Test
? Highly relativistic charged particle generates
photons at the boundary between media (er1 ?
er2) ? Emission probability small (10-2) ? 20
layers ? Photons detected in 5300 straw tubes ?
Good photon identification gas with high atomic
number Z XeCO2 8020
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Time of Flight Counters
Upper and lower each two layers of crossed
scintillators Time-of flight to 140psec for ß
and direction dE/dx measures Z (?E/E 10 for
MIPs)
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Superconducting Magnet
2500 liters superfluid He planned to last 3 years
without refill Field 1T ? measurement of
rigidity to a few TV
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Silicon Tracker
Eight layers of double sided Si detectors 10µm
in bending direction, 30µm orthogonal
Measures rigidity up to a few TV Measures dE/dx
for determining Z
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Ring Imaging Cherenkov Counter (RICH)
Accurate Velocity Measurements via Opening Angle
of Cerenkov Cone ? ??/? 0.1 ? Isotopic
Separation. Q measurements Additional Particle
Identification capability
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Electromagnetic Calorimeter
16 X0 of lead/scintillating fiber
sandwiches Crossed layers for 3D sampling by 384
4-pixel PMTs ?E/E (120.4)/vE(2.80.1) (E
in GeV) Distinguishes between hadrons and e,? by
shower shape Protons suppressed by 10-3-10-4 from
10 to 300 GeV Together with TRD 10-6 Photon
detector with angular resolution 1
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Nuclei in Space
The distribution of nuclei in cosmic rays is
similar to the distribution in the solar system
with some exceptions. Li (except 7Li), Be and B
were not produced in the primordial
nucleosynthesis, nor made in stars, but by
spallation reactions involving p and a colliding
with C,N,O in supernovas. Measure cosmic ray
confinement time in galaxy and mean density of
interstellar matter.
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AMS-02 Expected Performance1 year 10Be/9Be ratio
measurement
Among all ß-radioactive secondary nuclei in
cosmic rays, 10Be is the lightest isotope having
a half-life comparable with the confinement time
of cosmic rays in the galaxy (2x106 yr). AMS-02
will be able to separate 10Be from stable 9Be in
the range 0.15ltElt10 GeV/n. AMS-02 will collect
105 10Be in 3 years.
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AMS-02 Expected Performance6 months B/C ratio
measurement
In 3 years AMS-02 will collect 105 C and 104 B
with energies above 100 GeV/n, measuring the
ratio of boron to its primary carbon up to 1 TeV/n
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AMS-02 Expected Performance1 day 3He/4He ratio
measurement
AMS-02 can distinguish 3He from 4He in the range
0.1ltElt10 GeV/n
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Search for AntimatterAMS-01 10 day precursor
flight
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Search for AntimatterAMS-01 10 day precursor
flight
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Search for AntimatterAMS-02 sensitivity in 3
years
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Search for AntimatterAMS-02 sensitivity in 3
years
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Dark Matter Search AMS-02 e Flux
Structure in spectrum from SUSY neutralinos
?0 Examples for m? 336 GeV and 130.3 GeV
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AMS-02 Antiproton Flux
AMS-02 will measure the antiproton spectrum with
a few percent energy resolution up to hundreds of
GeV
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Other Exotic Matter Strangelets

• Heavy Particle with Low Charge
• Stable mixtures of u,d,s quarks with many
  different quarks in lowest energy state
• Signature is anomalous Z/A
• (Z0.3A2/3)(nuclei Z/A0.33-0.67)
• ? AMS sensitive to 10ltAlt3000

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AMS-02 Sensitivity to Strangelets
Shaded region from rough estimate of strangelet
creation and absorption in galaxy (Chikanian et
al.)
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Search for doubly charged anomalously heavy
nuclei with AMS-01
More than 4x106 He events collected during 10 day
STS91 flight Searched for anomalously heavy
nuclei (Z/A ß?mproton/Rigidity) Tight quality
cuts on measured rigidity and velocity One
candidate event found, corresponding to flux
5x10-5(m2srsec)-1 Estimate background from
ordinary nuclei lt 10-3 events
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Summary / Conclusions

• COSMIC RAY PROPAGATION
• light isotope abundances
• ANTIMATTER SEARCH
• limit on antihelium/helium 10-9
• STRANGE MATTER SEARCH
• anomalous Z/A
• DARK MATTER
• SOMETHING NEW?