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Cosmic Rays measured atthe ISS
Dorottya Szécsi
BUW WS 2011/12.
GETA Seminar, 19th January 2012.
Cosmic Rays measured at the ISS BUW WS 2011/12.
IntroductionI Space instruments, primordial
particles created in the earlyUniverse – background freeenvironment
I Cosmology: baryon asymmetry,mass density composition
I Understanding of Dark Matter,Antimatter, the origin of CR etc.
I Strong demand for precisionmeasurements of cosmic rays: largedeviation of the e+/(e+ + e−) ratiopredicted by our model (withordinary cosmic ray collisions)
I International Space Station (ISS) –AMS launched 16 May 2011
Cosmic Rays measured at the ISS BUW WS 2011/12.
ContentsI PART 1. Overview of the AMS
I Instruments on-boardI How they workI What they measure
I PART 2. AMS Physics PotencialI Anti-MatterI Dark MatterI and all the rest
Cosmic Rays measured at the ISS BUW WS 2011/12.
PART 1. Overview of the AMS
Cosmic Rays measured at the ISS BUW WS 2011/12.
PM – Permanent Magnet
Charged particles in magnetic field:Lorentz force
I made of matter: curve one wayI made of antimatter (opposite charge):
the opposite way
I B = 1.4 kG
Cosmic Rays measured at the ISS BUW WS 2011/12.
Silicon TrackerI detects the trajectory of the
incoming particlesI identifies:
I magnitudeI polarity
of particles’ electrical chargeI the higher the particle’s
momentum, the straighter thearc
I Accuracy: 10 µmI ∼ 200000 readout channelsI charge separation of nuclei
up to Z = 26I anticoincidence counter
Cosmic Rays measured at the ISS BUW WS 2011/12.
TOF – Time of Flight Counters
I distinguish between upwardand downward travelingparticles
I scintillator: flashes of lightwhen struck by particles orphotons
I measures the transit time ofparticles between two layers
Cosmic Rays measured at the ISS BUW WS 2011/12.
RICH – Ring Imaging Cherenkov detector
He Li C O Ca
I velocity of the charged cosmic particlesI by measuring vertex angle of the cone of
Cherenkov lightI particle passes through a tile of silica aerogel (n=1.05) or NaF (n=1.33)I photomultiplier tubes
Cosmic Rays measured at the ISS BUW WS 2011/12.
ECAL – Electromagnetic Calorimeter
I electromagnetic particleidentification:
I electrons, positrons, and gamma raysI up to 1 TeVI angular resolution around 1◦I e/p separation: ∼ 104 > 200 GeV
I 9 modules made of layers of lead andscintillating fibers
I function: completely stop particles→ measuring energy
I electromagnetic showersI lead scintillating fiber sandwichI reading out: 4 PMTs
Cosmic Rays measured at the ISS BUW WS 2011/12.
TRD – Transition Radiation DetectorI Transition radiation:
I soft X-rays emitted by chargedparticles traverse the boundarybetween two media with differentdielectric constants
I electrons and positrons: higherprobability of emitting TR photonsthan heavy particles
I used in conjunction with ECAL →distinguish between light and heavyparticles of equal charge and momentum(positron, proton)
I Xenon/CO2 gas mixture:I Xe captures the TRI leak rate: 6 µg/s → 24 ys in space
Cosmic Rays measured at the ISS BUW WS 2011/12.
Conclusion of Part 1.
I AMS can measuresimultaneously:
I photonI electronsI protonsI nucleiI + anti
Cosmic Rays measured at the ISS BUW WS 2011/12.
PART 2. AMS Physics Potencial – Anti-Matter I.I Experimental evidence: our galaxy is
made of matter. BUT:I more than 100 hundred million
galaxies in the universeI theories trying to explain
matter-antimatter asymmetry: notcompatible with measurements
I → fundamental question in modernastroparticle physics and cosmology
I just one antihelium nucleus!I AMS-02: sensitivity of 109
I 3 orders of magnitude better thanAMS-01 in 1998
I extending the volume of theUniverse tested for the existence ofprimordial antimatter
Cosmic Rays measured at the ISS BUW WS 2011/12.
Anti-Matter II.
Sensitivity of AMS withthe permanent magnet onISS for 18 yearscompared with the otherearlier measurements.
Cosmic Rays measured at the ISS BUW WS 2011/12.
Dark Matter I.
I neither emits nor scatters light or other electromagnetic radiation→ cannot be directly seen with telescopes
I postulated by Fritz Zwicky in 1933I observations of the rotational speeds of galaxiesI believed to be composed of a new type of subatomic particle
I AMS: spectra for nuclei in the energy range [0.5 GeV/nucl ; 2TeV/nucl]
I with 1% accuracyI it can prove or disprove our theories
Cosmic Rays measured at the ISS BUW WS 2011/12.
Dark Matter II.
I Candidate: neutralinoI generic ingredient of
SUSY modelsI supersymmetricI AMS: neutralino
annihilation based on finalstate particles
I Picture: Accuracy ofAMS-02 measurements
I p̄/p spectrumI 10 years on ISS with the
permanent magnet
Cosmic Rays measured at the ISS BUW WS 2011/12.
Dark Matter III.
I Dependence of the measured positron spectrum shape on theneutralino mass.
Cosmic Rays measured at the ISS BUW WS 2011/12.
Strangelets (?)
I fragmet of "strange matter":up, down, strange quarks
I dark matter candidateI higher size: more stableI "quark star" (strange nucleus
interacting with neutronstar)I early Universe or cosmic-ray
collisionsI heavy-ion colliders: we don’t
see them...
Cosmic Rays measured at the ISS BUW WS 2011/12.
Discussion
I Alpha Magnetic Spectrometer 02 (AMS-02) is a particle physicsdetector on board of the ISS
I We had overviewed the instrument and the measuring basics.I AMS-02 uses the unique environment of space to advance
knowledge of the universe and lead to the understanding of theuniverse’s origin by searching for antimatter, dark matter andmeasuring cosmic rays.
I "The most sophisticated particle detector ever sent into space."
Cosmic Rays measured at the ISS BUW WS 2011/12.
References
I A.Kounine, 2010, XVI International Symposium on Very HighEnergy Cosmic Ray Interactions ISVHECRI 2010
I Diego Casadei, 2004, Talk given at Lake Louise Winter InstituteI http://www.ams02.org/ams-and-iss/I WikipediaI http://events.eoportal.org/presentations/10001154/10002501.html
Cosmic Rays measured at the ISS BUW WS 2011/12.
Thank you for your attention!