COSMIC RAY PHYSICSWITH AMS

Joseph Burger MITOn behalf of the AMS-02 collaboration

EPS2003 AachenParticle Astrophysics

July 17, 2003

Joseph.Burger@cern.ch

• Cosmic Rays: p, D, He, C,…,e+,e-,γ• Direct Search for Cosmic Antimatter• Other Searches: Strangelets,…• Dark matter search in morning session talk by Mariusz Sapinski

Cosmic Ray Flux

AMS-02 is a large acceptance magnetic spectrometer which will extend high statistics measurements of cosmic ray properties to high rigidities.

AMS-023 years on ISS starting 2005-2006

Precursor Flight on STS91, June 2-12, 199810 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,…

AMS-02TRD (Transition Radiation Detector)Separates e± from p, p� < 10-2-10-3 from 10-300 GeV

ToF (Upper Time of Flight)Velocity measurement, dE/dX, fast trigger

Star Tracker (pointing to <1’)Superconducting Magnet0.8T field for momentum, sign of charge

Silicon Tracker8 x-y planes with 10/30μm resolution, dE/dXAnticoincidence CounterVetoes particles from outside trigger aperture

ToF (Lower Time of Flight)Velocity measurement, dE/dX, fast trigger

RICH (Ring Imaging Čerenkov Counter)Precision β measurement - separates isotopes ECAL (Electromagnetic Calorimeter)Separates e± from p, p� < 10-3-10-4

Transition Radiation Detector (TRD)

Highly relativistic charged particle generates photons at the boundary between media (εr1 ≠ εr2) Emission probability small (10-2) 20 layers Photons detected in ~5300 straw tubes Good photon identification: gas with high atomic number Z Xe:CO2 80:20

TRD Beam Test

Time of Flight Counters

Upper and lower each two layers of crossed scintillatorsTime-of flight to ~140psec for β and directiondE/dx measures Z (ΔE/E ~10% for MIPs)

Superconducting Magnet

2500 liters superfluid He planned to last 3 years without refillField ~1T measurement of rigidity to a few TV

Silicon Tracker

Charged particle

Eight layers of double sided Si detectors~10μm in bending direction, ~30μm orthogonal

Measures rigidity up to a few TVMeasures dE/dx for determining Z

Ring Imaging Cherenkov Counter (RICH)

Aerogel Radiator

Mirror

CerenkovCone

Photomultipliers

Accurate Velocity Measurements via OpeningAngle of Čerenkov Cone / ~ 0.1% Isotopic Separation.|Q| measurementsAdditional Particle Identification capability

Electromagnetic Calorimeterp

16 X0 of lead/scintillating fiber sandwichesCrossed layers for 3D sampling by 384 4-pixel PMTsΔE/E ~ (12±0.4)%/√E̅�+(2.8±0.1)% (E̅ in GeV)

Distinguishes between hadrons and e,γ by shower shapeProtons suppressed by 10-3-10-4 from 10 to 300 GeVTogether with TRD ~10-6

Photon detector with angular resolution ~1°

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 α colliding with C,N,O in supernovas.Measure cosmic ray confinement time in galaxy and mean density of interstellar matter.

AMS-02 Expected Performance1 year 10Be/9Be ratio measurement

Among all β-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 0.15<E<10 GeV/n. AMS-02 will collect 105 10Be in 3 years.

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

AMS-02 Expected Performance1 day 3He/4He ratio measurement

AMS-02 can distinguish 3He from 4He in the range 0.1<E<10 GeV/n

Search for AntimatterAMS-01 10 day precursor flight

Search for AntimatterAMS-01 10 day precursor flight

Search for AntimatterAMS-02 sensitivity in 3 years

Search for AntimatterAMS-02 sensitivity in 3 years

Dark Matter Search: AMS-02 e+ Flux

Structure in spectrum from SUSY neutralinos χ0

Examples for mχ 336 GeV and 130.3 GeV

AMS-02 Antiproton Flux

AMS-02 will measure the antiproton spectrum with a few percent energy resolution up to hundreds of GeV

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

(Z~0.3A2/3)(nuclei Z/A=0.33-0.67)

AMS sensitive to ~10<A<3000

AMS-02 Sensitivity to Strangelets

Shaded region from rough estimate of strangelet creation and absorption in galaxy(Chikanian et al.)

Search for doubly charged anomalously heavy nuclei with AMS-01

More than 4x106 He events collected during 10 day STS91 flightSearched for anomalously heavy nuclei (Z/A ~ β·γ·mproton/Rigidity)Tight quality cuts on measured rigidity and velocityOne candidate event found, corresponding to flux 5x10-5(m2·sr·sec)-1

Estimate background from ordinary nuclei < 10-3 events

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?