COSMIC RAY PHYSICS WITH AMS Joseph Burger MIT On behalf of the AMS-02 collaboration EPS2003 Aachen Particle Astrophysics July 17, 2003

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-02 3 years on ISS starting

Precursor Flight on STS91, June 2-12, 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) "Protons in Near Earth Orbit", M. Aguilar et al., Phys. Lett. B472 (26 Jan 2000) "Leptons in Near Earth Orbit", M. Aguilar et al., Phys. Lett. B484 (27 Jun 2000) "Cosmic Protons", M. Aguilar et al., Phys. Lett. B490 (28 Sep 2000) "Helium in Near Earth Orbit", M. Aguilar et al., Phys. Lett. B494 (30 Nov 2000) "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 on e ±, p, antiprotons, D, He, antihelium,…

AMS-02 TRD (Transition Radiation Detector) Separates e ± from p, p̅ < from GeV ToF (Upper Time of Flight) Velocity measurement, dE/dX, fast trigger Star Tracker (pointing to <1’) 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 Čerenkov Counter) Precision β measurement - separates isotopes ECAL (Electromagnetic Calorimeter) Separates e ± from p, p̅ <

Transition Radiation Detector (TRD)  Highly relativistic charged particle generates photons at the boundary between media (ε r1 ≠ ε r2 )  Emission probability small (10 -2 )  20 layers  Photons detected in ~5300 straw tubes  Good photon identification: gas with high atomic number Z Xe:CO 2 80:20 TRD Beam Test

Time of Flight Counters Upper and lower each two layers of crossed scintillators Time-of flight to ~140psec for β and direction dE/dx measures Z (ΔE/E ~10% for MIPs)

Superconducting Magnet 2500 liters superfluid He planned to last 3 years without refill Field ~1T  measurement of rigidity to a few TV

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

Ring Imaging Cherenkov Counter (RICH) Accurate Velocity Measurements via Opening Angle of Čerenkov Cone   /  ~ 0.1%  Isotopic Separation. |Q| measurements Additional Particle Identification capability

Electromagnetic Calorimeter 16 X 0 of lead/scintillating fiber sandwiches Crossed layers for 3D sampling by pixel PMTs ΔE/E ~ (12±0.4)%/√ E̅+(2.8±0.1)% (E in GeV) Distinguishes between hadrons and e,γ by shower shape Protons suppressed by from 10 to 300 GeV Together 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 7 Li), 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 Performance 1 year 10 Be/ 9 Be ratio measurement Among all β-radioactive secondary nuclei in cosmic rays, 10 Be is the lightest isotope having a half-life comparable with the confinement time of cosmic rays in the galaxy (~2x10 6 yr). AMS-02 will be able to separate 10 Be from stable 9 Be in the range 0.15<E<10 GeV/n. AMS- 02 will collect Be in 3 years.

AMS-02 Expected Performance 6 months B/C ratio measurement In 3 years AMS-02 will collect 10 5 C and 10 4 B with energies above 100 GeV/n, measuring the ratio of boron to its primary carbon up to 1 TeV/n

AMS-02 Expected Performance 1 day 3 He/ 4 He ratio measurement AMS-02 can distinguish 3 He from 4 He in the range 0.1<E<10 GeV/n

Search for Antimatter AMS day precursor flight

Search for Antimatter AMS-02 sensitivity in 3 years

Dark Matter Search: AMS-02 e + Flux Structure in spectrum from SUSY neutralinos χ 0 Examples for m χ 336 GeV and 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~0.3A 2/3 )(nuclei Z/A= )  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 4x10 6 He events collected during 10 day STS91 flight Searched for anomalously heavy nuclei (Z/A ~ β·γ·m proton /Rigidity) Tight quality cuts on measured rigidity and velocity One candidate event found, corresponding to flux 5x10 -5 (m 2 ·sr·sec) -1 Estimate background from ordinary nuclei < events

Summary / Conclusions COSMIC RAY PROPAGATION light isotope abundances ANTIMATTER SEARCH limit on antihelium/helium STRANGE MATTER SEARCH anomalous Z/A DARK MATTER SOMETHING NEW?