Tijana Prodanovi Tijana Prodanovi ć ć , University of Novi Sad , University of Novi Sad Brian D. Fields, University of Illinois at Urbana Champaign Tijana Prodanović Fundamental Interactions, Serbia - 2007 September 28th, 2007
Tijana ProdanoviTijana Prodanovićć, University of Novi Sad, University of Novi SadBrian D. Fields, University of Illinois at Urbana Champaign
Tijana Prodanović
Fundamental Interactions, Serbia -
2007
September 28th, 2007
Tijana
Prodanović
Fundamental Interactions, Serbia -
2007
High-energy charged particlesAccelerated in astrophysical shocksDiffusive shock accelerationAny shock source is a candidate! (Blandford & Eichler 1987)
SitesSupernova remnants
Structure formation shocks
VLA image of Tycho
SNR Reynolds & Chevalier
Tijana Prodanović
Fundamental Interactions, Serbia -
2007
September 28th, 2007
6Li only made by cosmic rays viafusion and spallation6Li very fragile – all other processes (stars) destroy Li more than they produce itPerfect cosmic ray probe!Standard assumption: measured 66LiLiSolarSolar made by Galactic made by Galactic CRsCRsLow-metallicity galactic halo stars stars (old age; older = lower metals) : 6Li plateau (Asplund et al. 2006) → indicates new lithium-6 source!?
Tijana Prodanović
Fundamental Interactions, Serbia -
2007
September 28th, 2007
Li6→+αα LiCNO, 6→+αp
METALLICITY
Li A
BU
ND
AN
CE
6Li plateauUnexpected!New 6Li source?
Asplund et al. (2006)
Normalized to Sun
6Li only made by cosmic rays viaStandard assumption: 6LiSolar made by Galactic CRsBut new observations indicate a 6LiSolar plateauNeed new source?But Li observations are very difficult...maybe some observational effect
Is Is 66Li really in trouble?Li really in trouble?
Make an independent testMake an independent test
Fundamental Interactions, Serbia -
2007
September 28th, 2007Tijana Prodanović
Li6→+αα
Tijana Prodanović
Fundamental Interactions, Serbia -
2007
September 28th, 2007
Hadronic cosmic-ray interactions make both
Lithium - 6 Pionic Gamma RaysLiCNO, 6→+αp ππγγπ →→+ 0pp
Any cosmic-ray source produces both gamma-rays and lithiumConnected essentially with ratio of reaction rates (Fields and Prodanović 2005)
Li abundance: local CR fluence (time integrated flux)Diffuse extragalactic : CR fluence across Universe
Use gamma rays to learn about Li!πγ
Fundamental Interactions, Serbia –
2007
September 28th, 2007Tijana Prodanović
αα
γ
αα
π
σ
σγ
crism yy ,,
1Li
∝
Pionic gamma-ray fraction Normalized to the Milky Way (blue)~30% of the total EGRB (normal gal.)
6Li production channels includedfusionspallation2-step reactions, eg.
Account for astrationsome gas was processed in stars – some Li was destroyedestimate astration from Deuterium: ~ 25% of gas was processed
Li6→+ααLiCNO, 6→+αp
Fundamental Interactions, Serbia -
2007
September 28th, 2007Tijana Prodanović
LiHBHO 611 →+→+
Prodanović
& Fields (2006)
Only ~ 50% of solar 6Li can be explained by GCRs without overproducing gamma-raysNeed newnew important 66Li sourceLi source
Recent observations in halo stars: 6Li plateau? But at 10% level of solar (Asplund et al. 2006)
Astrophysics to the rescue!Milky Way GCR flux higher than the cosmic mean? Implications for star-formation rateLow-energy CR component? Energetics and LiBeBratio constraints
Physics to the rescue!New, yet unknown production channel? Decaying dark matter? New physics?
Tijana Prodanović
Fundamental Interactions, Serbia -
2007
September 28th, 2007
Tijana Prodanović
Fundamental Interactions, Serbia -
2007
September 28th, 2007
It remains to be seen…
Use Li-gamma connection to check if things add upNumerically
GCR spectrumSolve propagation equation for Leaky Box model
Gamma-ray spectrumNumerically calculate from Dermer (1986) model
Tijana Prodanovic
Fundamental Interactions in Serbia
September 28th, 2007
Pfrommer & Enßlin (2003) fit
Numerical: Dermer (1986) model
Below 3 GeV: isobar model
Above 12 GeV: scaling model based on accelerator data for
cross-sectionsLinearly connected
( ) ( )[ ] δαδπ
δπγ
/00 /2/2~)(
−−+ mEmEEF
Fundamental Interactions in Serbia
September 28th, 2007Tijana Prodanovic
02/3 πppppp →Δ→
0πpppp →
Tijana Prodanovic
Fundamental Interactions in Serbia
September 28th, 2007
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Fundamental Interactions in Serbia
September 28th, 2007Tijana Prodanovic
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Tijana Prodanovic
Fundamental Interactions in Serbia
September 28th, 2007
f –
normalized energy spectrum+ forward moving isobar- backward moving isobarΓ
–
resonance width=0.115/2 GeVB –
Breit-Wigner
distributionγπ’
–
Lorentz
factor in rest frame of isobarγc
–
LF in center of momentum sys.γΔ* -
LF in lab sys
)/(cossintan
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2/)4()(
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cos)(
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max
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⊥
⊥⊥
−
⊥
Tijana Prodanovic
Fundamental Interactions in Serbia
September 28th, 2007
Θ
–
angle of emission
Lorentz
invariant x-section
* is in center of massp –
pion
momentum
Tijana
Prodanović
Fundamental Interactions, Serbia -
2007
High-energy charged particlesAccelerated in astrophysical shocksSpectrum:
Strong shocks (diffusive shock acceleraton): Flux~E-2
Measured at Earth (JACEE 1998) : Flux~E-2.75
Tijana
Prodanović
Fundamental Interactions, Serbia -
2007
Diffusive shock accelerationAny shock source is a candidate! (Blandford & Eichler 1987)
SitesSupernova remnants
Structure formation shocks
VLA image of Tycho
SNR Reynolds & Chevalier
7Li made significantly in the Big Bang Nucleosynthesis (Cyburt, Fields, Schramm) but also in CR interactionsLow-metallicity galactic halo stars (old age; older = lower metals): 7Li plateau (Spite & Spite 1982) →indicates primordial lithium
Tijana Prodanović
Fundamental Interactions, Serbia -
2007
September 28th, 2007
7Li plateau Expected but below theoretical predictions
METALLICITY
Li A
BU
ND
AN
CE
Asplund et al. (2006)
Normalized to Sun
TIME
2−∝ pφ
Fundamental Interactions, Serbia -
2007
September 28th, 2007Tijana Prodanovic
75.2)( −+∝ Empφ
Fundamental Interactions, Serbia -
2007
June, 13th
2007Tijana Prodanović
“Pionic” gamma-rays
Distinctive spectrum – pion “bump”; peaks at mπ/2 (Stecker 1971; Dermer 1986)
But no strong evidence for pion “bump” either in the EGRB or in the MW diffuse gamma-ray spectrumUse the shapeshape of the spectrum (Pfrommer & Enßlin 2003) to find max max ““pionicpionic”” fraction fraction (Prodanović & Fields 2004)
0π+→+ pppp ismcr
γγ
Fundamental Interactions, Serbia -
2007
June, 13th
2007Tijana Prodanović