1. Ching-Yuan Huang (黄庆元) 20 October 2010
On Atmospheric Antiprotons in Cosmic Ray Study
TeV-band Gamma Rays in
RX J
Ching-Yuan Huang (黄庆元)
20 October 2010
Institute of Theoretical Physics
Chinese Academy of Science

2. Section I: Cosmic Rays

3. Something about Cosmic Rays
High energy charged particles arriving at Earth from outer space
Discovered in 1912
Natural source for new particle discovery (until 1953)
Energy: 108 eV (100 MeV) to  1020 eV (100 EeV)
Time scale contained in galaxy: can be as long as 1010 years
- Messenger of non-thermal Universe
Interest:
origin: Supernova Remnants? Black Holes? Dark Matters?
Pulsar? Active Galactic Nuclei?...
- acceleration: B field? shock acceleration?...
- transport/interaction

4. Cosmic Ray Composition and Spectrum
cosmic ray compositions:
- 86% p; 12% α
- 2% e
- 1 % C, N, O,Li, Mg, Si,
Fe nuclei
- small amount of
(~ p)
Solar Modulation
Cosmic Ray (CR) Spectra
(simple power law)
(200 TeV)
Non-thermal!

5. 3 Regimes in Cosmic Ray Spectrum
knee
ankle
GZK cutoff
regimes in CR spectrum

6. Cosmic Rays in Galaxy halo ⊙ discz r
diffusion process in large scale halo under galactic magnetic irregularities;
physics involved: production, (re)-acceleration, energy loss, decay, interaction, convection, diffusion, escape, fluctuation...

7. Cosmic Rays in Solar System and Earth
Both against low energy cosmic rays!

8. Allowed/Forbidden Regions
(shaded: forbidden; white: allowed)
critical case: b (impact parameter) = -1, allowed regions linked
Geomagnetic cutoff arises from Earth magnetic field!

9. Cosmic Rays in Earth Atmosphere
unique technique for detection of cosmic-ray particles
with E > 200 TeV, due to detector limitation!

10. Section II: Atmospheric Antiprotons

11. Why Antiprotons/Atmospheric Antiprotons?
interest of origin (discovered in 1979)
- galactic origin: secondary product from interactions
between cosmic rays and interstellar medium (called
galactic, galactic secondary)
Not abundant enough to explain the exp. detections!
- evaporation of Primordial Black Holes (PBH)
possible exotic origin:
- annihilation of SUSY Dark Matter (Neutralino χ)

12. Antiproton Spectra from Different Sources
SUSY DM and PBH identification window exists in window
E< 1 GeV!
ID window by
Peak at 2 GeV
(SUSY model for
GeV)

13. Challenge for Cosmic Antiproton Detection
measured antiprotons in Earth experiments are actually a composition
Correction of atmospheric antiprotons onto experiments is absolutely required!

14. Schematics of Simulation Model
1) Cosmic Ray distribution (natural abundance); incoming particle propagation in Earth magnetic field
3) Propagation of secondaries
2) Interaction CR+A→n±,p±+X…
4) Counting when crossing orbit altitude ↑and ↓
AMS
orbit
Model of Atmosphere
Pole
geomagnetic field line
Equatorial plane
5) End of propagation: escape, collision/slowing down/absorbed…

15. Antiproton Experiments and Altitudes
to measure pure cosmic antiproton flux (i.e., no atmospheric component)
(Discovery ST591)
AMS
400km
40km
3km
Ans: quite doubtful!
to measure antiproton flux at Top of Atmosphere (TOA)
very unusual (BESS ’99 exp.)!
mountain level exp.

16. Antiproton Flux at TOA by Balloon Exp.
BESS
CAPRICE
(Huang ’03 PRD)
CR He contribution
Good agreement with previous calculations!

17. Antiproton Flux Measured by AMS
(Huang ’03 PRD)
Antiproton Flux Measured by AMS
Atmospheric correction is always needed, even for space experiments!
pure (nearly) measurement possible only in (sub)polar regions!
upward/downward particles compatible. Why?

18. Integrated Antiproton Flux
(on AMS acceptance)
(Huang ’03 PRD)
Integrated Antiproton Flux
At balloon altitudes, only ↓particles can be detected!
(totally detector effect)
At space altitudes, ↓and ↑ charged particles are of the same order, unless in (sub)polar regions.
Existence of trapped/quasi-trapped charged particles in Earth magnetic field!

19. Charged Particle Trajectory in Earth Multipole
(Huang ’03 PRD)
particles in low latitude regions with extremely complicated trajectories, contributing large crossing multiplicity!
Particles at high altitudes or with high kinematics can be trapped by Earth!

20. Antiproton Measurement at Mountain Level
Flux magnitude at this level is small but still detectable by current exp. detectors.
Antiprotons are purely atmospheric at such altitudes.
400km
good probe to test cosmic-ray transport model!
Result was confirmed by BESS 1999 experiment! (Sanuki, ’03 PLB)
40km
3km

21. Antiproton Flux at Mountain Level
(Huang ’03 PRD, Huang ’07 Astropart. Phys.)
discrepancy from data in other models usually used
(Bowen ’86; Stephens ’93)
result confirmed by BESS exp.!

22. Section II: TeV-band Gamma Rays of RX J1713.7-3946

23. Gamma-Ray Astrophysics
probe of the non-thermal Universe
neutral in charge, high penetrating nature of emissions, as a powerful tool to study cosmic-ray sources in γ-ray domain
Broad waveband γ-ray observation presents clear physical characters:
- Synchrotron
- Bremsstrahlung
- hadronic interactions (and decays)
- Inverse Compton Scattering

24. Gamma-Ray Astrophysics
(Ultimate Purpose)
understand cosmic-ray origin, acceleration, propagation…
understand the γ-ray background (Big Bang, DM, CMB…)
Need to unmask the γ-ray foreground!
(γ-ray foreground: cosmic-ray source emissions, diffuse radiation in transport…)

25. γ Induced Air Shower Observed at Ground

26. RX J1713.7-3946 Observation young shell-type SNR
→ study cosmic-ray time evolution near source
dense molecular gas along line of sight
→ test for hadronic/leptonic model for cosmic-ray acceleration
X-ray time variability
→ study SNR magnetic field strength
(HESS ’06)

27. TeV-Band Spectrum of RX J1713.7-3946
Leptonic models (bremsstrahlung or Inverse Compton) requires unusually weak magnetic field!
Data with E ~ MeV to 10 TeV is needed for the puzzle!

28. Best Fitted Spectrum of RX J1713.7-3946
(Huang et al., ’07)
HEP event generator to simulate full picture of cosmic-ray hadronic interactions
considered full picture of γ-ray decays
(-) spectral curvature strongly suggested (with CL > 95%)!
= 22.4 for 22 DOF

29. Shock Modification for Cosmic Rays
non-linear shock modification arises due to the dynamical reactions of accelerated particles on the shocks
Models predict continuous hardening spectra with a (+) spectral curvature!
(Amato & Blasi ’06)
(Ellison et al., ’00)

30. X-Ray Emission Variability in of RX J1713.7-3946
(Uchiyama et al., ‘07)
(2000)
(2006)
(2005)
Chandra Observation
unique information of magnetic field in particle acceleration region!
Rapid variability implies shorter timescales and amplification of B field in SNR shell.

31. Synchrotron Radiation of RX J1713.7-3946
(Huang et al, ’08)
Synchrotron Radiation of RX J
full picture of e-/e+ production and decays in CR interactions
more severe limits on B, α;
The non-thermal X-ray emission must originate from primary e-/e+!
multi-mG field only possible with very limited fraction!

32. Cosmic-Ray Neutrinos background for ν Astrophysics
tool to study on CP-violation (neutrino oscillations) in Standard Model (atmospheric ν anomaly…)
accompanied product of hadronic γ-rays
Neutrinos as the supplement tool to study hadronic and leptonic scenario in cosmic-ray particle origin/acceleration!

33. -Induced μ Rate of HE γ-Ray Sources
(Huang et al, ’08)
IceCube-like detector assumed
ν full mixing assumed:
experiment with data accumulation over 5-10 yrs at Eμ~ few TeV, or Eν ~ 10 TeV to test hadronic origin of TeV γ-rays!

34. Summary on Atmospheric Antiprotons
a tool allowing to calculate the proton and atmospheric antiproton flux in the Earth environment:
- developed antiproton production cross section in pp and pA collisions;
- shown the atmospheric antiproton correction is always required;
- model agreed with proton flux from sea level to TOA
Antiprotons at low altitudes provides a tool to verify models and calculations.
approved understanding of particle dynamics in Earth environment

35. Summary of TeV Gamma Rays
easy-to-use production matrices for cosmic ray interactions and decays;
favored in hadronic model for SNR such as RX J
no evidence for standard models of CR modified shock accelerations;
γ-ray data with energy E: GeV~ TeV is needed to test cosmic-ray acceleration model;
the multi-mG magnetic field proposed for X-ray flux variations is very limited in RX J
proposed a promising experiment with data accumulation over 5-10 years at E(μ)~ few TeV, or E(ν) ~ 10 TeV, to test origin of TeV γ-rays