Theresa Brandt2 June 2007

CREAM: Improving Our Understanding of Cosmic Rays

Great Lakes Cosmology Workshop 8

CREAM I, AntarcticaCREAM Collaboration

Power law in energy:

Change in spectral slope: “Knee” at ~1015 eV From ≈ 2.7 to 3.0

Due to change in acceleration mechanism?

What about propagation conditions?

Gather clues from composition

and primary to secondary ratios.

All-particle CR Spectrum

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dN

dE∝ E−α

S. Swordy

... are good candidates because

➢ they are point-like, stellar objects, as required by abundances.

➢ SN shock lifetime implies Emax

~ Z x 1014 eV, which is a potential source of the knee.

➢ typical SN luminosity at a few % efficiency could supply observed CRs.

➢ multi-wavelength observations imply this efficient acceleration.

Kepler's SNRChandra Telescope

CR Origins: Supernova

Transport Equation:Transport Equation:

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∂Ni

∂E=Qi(E,x,t)+∇⋅Di∇Ni( )−∇⋅uNi−

∂∂E

bi(E)Ni(E)[ ]−piNi+vρm

dσ i,k(E, ′ E )dE∫ Nk( ′ E )

k≥i

∑ d ′ E

CR Propagation

M, S, & M, Prop.

CREAM Science Goals

Determine elemental composition from 1012 up to 1015 eV

Measure secondary to primary ratio (e.g. B/C)

Observe predicted “knee” in proton spectrum

CREAM I Hang Test,Antarctica

CREAM Collaboration

Cosmic Ray Energetics and Mass

4 main subsystems:➢ TCD (Z), TRD (E), SCD (Z), Cal (E)Timing Charge Detector, Transition Radiation Detector,

Silicon Charge Detector, and Calorimeter

Flown on a Long-Duration Balloon over Antarctica

➢ CREAM I: 42 day (16 Dec 04 - 27 Jan 05)

➢ CREAM II: 28 day (16 Dec 05 - 13 Jan 06)CREAM

Particle DetectorCharge and Energy:

➢+1 ≤ Z ≤ 26➢1012 eV <~ E <~1015 eV

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are needed to see this picture.

CREAM, AntarcticaCREAM Collaboration

NASA/CSBF

HEAO

CRN

CREAM TRD

CREAM Cherenkov

PreliminaryPreliminary

S. Swordy, S. Wakely

Total Particle Energy (eV)

Flu

x (m

2 s

sr G

eV)-1 HEAO

CRN

Oxygen Spectrum

HEAO

CRN

S. Swordy, S. Wakely

CREAM TRDCREAM Cherenkov

PreliminaryPreliminary

HEAO

CRN

Total Particle Energy (eV)

Flu

x (m

2 s

sr G

eV)-1

Carbon Spectrum

The CREAM Collaboration: University of MarylandH. S. Ahn, O. Ganel, J.H. Han, K.C. Kim, M. H. Lee, L. Lutz, A. Malinine, E. S. Seo, R. Sina, P. Walpole, J. Wu, Y. S. Yoon, S. Y. Zinn

University of ChicagoP. Boyle, S. Swordy, S. Wakely

Penn State UniversityN. B. Conklin, S. Coutu, S. I. Mognet

Ohio State UniversityP. Allison, J. J. Beatty, T. J. Brandt

University of MinnesotaJ. T. Childers, M. A. DuVernois

University of Sienna & INFN, ItalyM. G. Bagliesi, G. Bigongiari, P. Maestro,

P. S. Marrocchesi, R. ZeiEhwa Womans University, S. Korea

H. J. Hyun, J. A. Jeon, J. K. Lee, S. W. Nam, I. H. Park, N. H. Park, J. YangNorthern Kentucky University

S. NutterKent State University

S. MinnickGoddard Space Flight Center

L. BarbierKyungpook National University, S. Korea

H. ParkLaboratoire de Physique Subatomique et de Cosmologie,Grenoble, France

M. Mangin-Brinet, A. Barrau, O. Bourrion, J. Bouvier, B. Boyer, M. Buenerd, L. Eraud, R. Foglio, L. Gallin-Martel, Y. Sallaz-Damaz, J. P. Scordilis

Centre d’Etude Spatiale des Rayonnements, Toulouse, FranceR. Bazer-Bach, J.N. Perie

Universitad Nacional Auto´noma de Mexico, MexicoA. Menchaca-Rocha

CREAM III assemblyCREAM Collaboration

HEAO (90)

Simon (80)

Lezniak (78)

Juliusson (74)

Caldwell (77)

Orth (78)

Swordy (90)

Dwyer (87)

Mahel (77)

Castellina & Donato

Top bottom:=0.3, 0.46, 0.6, 0.7, 0.8

➢Secondary flux reflects propagation conditions for a given source spectrum. ➢Ratios of s:p at given E reduces source dependence.➢Assume ~ steady state.

€

Ns=Qsτ esc=βc ρ

mσ p→sNp

H2

D ⎛ ⎝ ⎜

⎞ ⎠ ⎟ ⇒ Ns

Np

∝ 1D

~ E−δ

Carbon as primary:➢common stellar process end-product

Boron as secondary:➢stable, rarely stellar-synthesized ➢BBN abundence is rel. well known.➢want properties like selected primary's.

All-particle spectral index goes as the source and propagation energy indices:

➢ ➢2.7 = 1.1+1+0.6

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=γ+1+δ

B:C