ams-02 and more: direct measurements of cosmic rays · pdf fileams-02 and more: direct...

AMS-02 and more: Direct Measurements of Cosmic Rays

Andreas Obermeier, AMS Collaboration I. Physics Institute B, RWTH Aachen University, Aachen (Germany)

Astroteilchenphysik in Deutschland – Status und Perspektiven

Karlsruhe, September 30th, 2014

Direct Measurements of CR

A. Obermeier, RWTH Aachen Astroteilchenphysik in D., September 30th 2014

Ø Conducted above the atmosphere

Ø  Balloon or Space Experiments

Ø  Limited: Size, Time, Weight, Power

Ø  But: good Energy resolution, elemental or even isotopic detail

A. Obermeier, RWTH Aachen Astroteilchenphysik in D., September 30th 2014 3 /22

Achievable Exposure


Ø  Record circumpolar flight time (LDB): 52 days (Super-TIGER)

Ø  Total Exposure: ~ 350 m2 sr days

Ø  ULDB Flights might double that

Ø  Expected Exposure for AMS-02 (10 years of operation time): 200 m2 sr days

Ø  To reach 50 TeV/nucleon in energy spectra one needs about 4000 m2 sr days

The recent History: Energy Spectra


Ø  Energy spectra of individual CR elements from H to Fe

Ø  Up to a total energy of 105 GeV Oxygen: 6 TeV/nucleon Iron: 4 TeV/nucleon

Ø  Energy measurement with ECAL, TRD, magnetic Spectrometers, Cherenkov, direct Cherenkov (ICTs)

P. Boyle & D. Müller, Particle Data Book (2011)

The recent History: TIGER/ACE-CRIS: OB origins


Ø  Measured the relative abundance of CR elements/isotopes compared to the Solar System

Ø  Abundances arrange themselves nicely when 20% admixture of heavy star ejecta is assumed

Ø  Possible preferred origin of CR in OB associations

Atomic Mass (A)10 210

GCRS

/(80%

SS

+ 20

% M

SP) (

Fe =

1)

-110

1

NO

Ne

Mg

Al

Si

P

SAr

Ca

Fe Co

Ni

Cu

ZnGa

Ge

Se

SrRefractory (Grains)Volatile (Gas)Mixed

Refractory FitVolatile Fit

B. Rauch et al., ApJ (2009) and W. Binns et al., Space Science Reviews (2007)

The recent History: TRACER: Galactic Propagation


Ø  B/C ratio drops not to zero

Ø  Residual path length or “nested” propagation models are preferred

Ø  Impact on shape of source spectra

kinetic Energy [GeV/amu]210 310 410

]-1

sr s

GeV

/am

u)2

(m2.

65 [(

GeV

/am

u)2.

65 E×

Flux

10

210

TRACER 2003

TRACER 2006

2.37

2.712.56

Oxygen

kinetic Energy [GeV/amu]-110 1 10 210 310 410

B/C

ratio

-210

-110

2=0.69 g/cm0R=0.64, b2=0.38 g/cm0R=0.6, b

2=0.0 g/cm0R=0.6, b

TRACERHEAOCRNAMS-01ATICCREAM

A. Obermeier et al., ApJ (2011) and (2012)

The recent History: CREAM: “Discrepant” Hardening


Ø Different spectral indices for p and He at high energies

Ø  Break in spectra of heavy nuclei at ~200 GeV/nucleon

Ø Hints at complex acceleration process at various sources

H. Ahn et al., ApJ Letters (2010)

The recent History: PAMELA: The Positron Fraction


Ø  The Positron Fraction rises with energy

Ø  Hinted at by previous experiments (e.g. HEAT), but first conclusive measurement by PAMELA

Ø  Very difficult to explain by secondary production

Ø  Possible primary sources: Pulsars or Dark Matter

Ø  Sparked over 1000 citations!

Ø  German contribution to PAMELA from Siegen University

O. Adriani et al., Nature (2009)

AMS-02 and the Positron Fraction


Ø  For its first publication AMS-02 determined the positron fraction

Ø  Now, 3 years of data are analyzed

Ø  Results include: Ø  the Positron Fraction up to

500 GeV,

Ø  the positron flux,

Ø  the electron flux

Ø  the combined flux of positrons and electrons

Ø  German contribution to AMS from RWTH Aachen and KIT Karlsruhe

The AMS Collaboration


USA MIT - CAMBRIDGE NASA GODDARD SPACE FLIGHT CENTER NASA JOHNSON SPACE CENTER UNIV. OF HAWAII UNIV. OF MARYLAND - DEPT OF PHYSICS YALE UNIVERSITY - NEW HAVEN

MEXICO UNAM

FINLAND UNIV. OF TURKU

FRANCE LUPM MONTPELLIER LAPP ANNECY LPSC GRENOBLE

GERMANY RWTH-I.

KIT - KARLSRUHE

ITALY ASI IROE FLORENCE INFN & UNIV. OF BOLOGNA INFN & UNIV. OF MILANO-BICOCCA INFN & UNIV. OF PERUGIA INFN & UNIV. OF PISA INFN & UNIV. OF ROMA INFN & UNIV. OF TRENTO

NETHERLANDS ESA-ESTEC NIKHEF

RUSSIA ITEP KURCHATOV INST.

SPAIN CIEMAT - MADRID I.A.C. CANARIAS.

SWITZERLAND ETH-ZURICH UNIV. OF GENEVA

CHINA CALT (Beijing) IEE (Beijing) IHEP (Beijing) NLAA (Beijing) SJTU (Shanghai) SEU (Nanjing) SYSU (Guangzhou) SDU (Jinan)

KOREA EWHA

KYUNGPOOK NAT.UNIV.

PORTUGAL LAB. OF INSTRUM. LISBON

ACAD. SINICA (Taipei) CSIST (Taipei)

NCU (Chung Li)

TAIWAN

TURKEY METU, ANKARA

The AMS-02 Detector

Ø  ToF Ø  Trigger, Velocity, Charge

Ø  TRD Ø  Heavy/light separation

Ø  Tracker Ø  precision Tracking,

Charge, Charge-sign, Rigidity

Ø  RICH Ø  Velocity, Charge

Ø  ECAL Ø  Energy, heavy/light

separation

A. Obermeier, RWTH Aachen 40th COSPAR, Moscow, August 3rd 2014 12 /22

ECAL

upper ToF

TRD

Tracker L1

RICH

Inner Tracker

lower ToF

Tracker L9

Proton Rejection of AMS-02


Ø At 90% electron efficiency

Ø Combined: Above 106 up to 500 GeV

ECAL TRD

Most important systematic: Charge Confusion


Ø Only the tracker determines the charge sign

Ø  Electrons incorrectly identified as positrons

Ø Due to: Ø  Elastic or inelastic

scattering Ø  Tracker resolution

Ø  Largest systematic uncertainty at high energies Energy [GeV]

10 210

Char

ge C

onfu

sion

-410

-310

-210

-110

1

AMS dataMC predictions

Analysis based on Template Fits


Ø  2D Template Fits in ECAL Estimator and TRD Estimator space

Ø  Projection onto TRD Estimator is shown

Ø  Charge Confusion fixed

Ø  Efficient and background free determination of the number of positrons/electrons

Even

ts

TRD Estimator (173 – 206 GeV)

positrons protons

15

The Positron Fraction


M. Aguilar et al., PRL (2013) with already more than 200 citations; And L. Accardo et al., PRL (2014)

Ø  Positron Fraction measured up to 500 GeV

Ø  Increase confirmed

Ø  Hint at an end to the increase

The Electron and Positron Flux


M. Aguilar et al., PRL (2014)

Ø  Individual Fluxes measured up to 200 GeV

Ø  Smooth development with energy

Ø  Different shape for electrons and positrons

The Electron + Positron Flux


Energy (GeV)1 10 210 310

)-1

sr s

ec ]

2 [

m2

(GeV

\ × 3 E

050

100150200250300350400 AMS-02

ATICBETS 97&98PPB-BETS 04Fermi-LATHEATH.E.S.S.H.E.S.S. (LE)

M. Aguilar et al., PRL (2014), submitted

Ø Combined Flux measured up to 1 TeV with more than 10 million events!

Ø  No small scale features

Fitting a minimal Model to Positron Fraction and Combined Flux


Diffuse Flux Source Flux

e++e-

Courtesy of A. Kounine

The Fit Result in the individual Fluxes


Courtesy of A. Kounine

e-

e+

Outlook


Ø  Energy spectra of protons and helium

Ø  Spectra of heavy nuclei

Ø  B/C ratio

Ø  Anti-protons, anti-helium

Ø  Isotopes at low-energies

Ø  Anisotropies, time dependent fluxes

Ø  Strange unexpected things…

Future AMS-02 Science Program

Ø  Super-TIGER: Balloon-borne, 52 day Antarctic flight; Measurement of ultra-heavy CR

Ø  ISS-Cream: Planned for installation on ISS for 3 years; Measurement of elemental spectra

Ø  Calet: Designed for ISS to explore highest energies electrons

Ø  GAPS: Balloon-borne, will be flown to search for anti-deuterons

Other Experiments: Active and Planned

Conclusion


Ø  Direct measurement of cosmic radiation is a vital component of cosmic ray research.

Ø  It provides elemental information and can even resolve isotopes. This has led to important insights in the past and will continue to do so.

Ø  The challenge to reach higher exposure factors needs new ideas. This is exciting!

Ø  In Germany only few institutes take part in direct measurements, although the cost of ballooning is small and it is a great opportunity to train young scientists.

Ø  Future Experiments will need to focus on areas not covered by AMS-02. E.g. Isotopes and beyond 1 TeV/nucleon

Ø  Vernon Jones at COSPAR 2014: “There is enough ballooning capacity for more and new astropyhsics payloads.”

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