I. On Atmospheric Antiprotons in Cosmic Ray Study II. TeV-band Gamma Rays in RX J1713.7-3946 Ching-Yuan Huang (

黄庆元 ) 20 October 2010 Institute of Theoretical Physics Chinese Academy of Science 1

Section I: Cosmic Rays

2

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: 10 8 eV (100 MeV) to  10 20 eV (100 EeV) - Time scale contained in galaxy: can be as long as 10 10 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 3

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

1 / 10 Solar Modulation (200 TeV) • Cosmic Ray (CR) Spectra

N

(

E

) 

E

  (simple power law) Non-thermal!

4

3 Regimes in Cosmic Ray Spectrum

• regimes in CR spectrum knee  5  10 15

eV

ankle  3  10 18

eV

GZK cutoff  5  10 19

eV p

  2 .

73

K E th



m

    (

m p

 

m



N

/ 2 )  5  10 19     10  3

eV

    1

eV

5

2

h g R

Cosmic Rays in Galaxy

z

halo ⊙

r

disc 2

h h

halo • diffusion process in large scale halo under galactic magnetic irregularities; • physics involved: production, (re)-acceleration, energy loss, decay, interaction, convection, diffusion, escape, fluctuation...

6

Cosmic Rays in Solar System and Earth

Both against low energy cosmic rays!

7

Allowed/Forbidden Regions

(shaded: forbidden; white: allowed) • critical case:

b

(impact parameter) = -1, allowed regions linked • Geomagnetic cutoff arises from Earth magnetic field!

8

Cosmic Rays in Earth Atmosphere

unique technique for detection of cosmic-ray particles with E > 200 TeV, due to detector limitation!

9

Section II: Atmospheric Antiprotons

10

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!

• possible exotic origin: annihilation of SUSY Dark Matter (Neutralino χ)    

p

,

e

 ,   - evaporation of Primordial Black Holes (PBH) 11

Antiproton Spectra from Different Sources

ID window by

p

Peak at 2 GeV (SUSY model for

m

  62 GeV) SUSY DM and PBH identification window exists in window E< 1 GeV!

12

Challenge for Cosmic Antiproton Detection

• measured antiprotons in Earth experiments are actually a composition exp. measured

p

2 nd atmospheric

p

cosmic

p

2 nd Galactic

p

primary

p

Correction of atmospheric antiprotons onto experiments is absolutely required!

SUSY

p

PBH

p

13

Schematics of Simulation Model

1) Cosmic Ray distribution (natural abundance); incoming particle propagation in Earth magnetic field 2) Interaction CR+A→n ± ,p ± +X… 3) Propagation of secondaries 4) Counting when crossing orbit altitude

↑

and

↓

Model of Atmosphere geomagnetic field line 5) End of propagation: escape, collision/slowing down/absorbed… 14

400km

Antiproton Experiments and Altitudes to measure pure cosmic antiproton flux (i.e., no atmospheric component)

Ans: quite doubtful!

(Discovery ST591) AMS 40km 3km

to measure antiproton flux at

Top of Atmosphere (TOA)

mountain level exp.

very unusual (BESS ’99 exp.)!

15

Antiproton Flux at TOA by Balloon Exp.

BESS ’98@38km CAPRICE ’98@36km CR He contribution CR He contribution (Huang ’03 PRD) Good agreement with previous calculations!

16

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?

17 AMS@400km (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!

18 (on AMS acceptance) (Huang ’03 PRD)

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!

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Antiproton Measurement at Mountain Level

400km • Flux magnitude at this level is small but still detectable by current exp. detectors.

• Antiprotons are purely atmospheric at such altitudes.

40km

3km

• good probe to test cosmic-ray transport model!

• Result was confirmed by BESS 1999 experiment! (Sanuki, ’03 PLB) 20

Antiproton Flux at Mountain Level

• discrepancy from data in other models usually used (Bowen ’86; Stephens ’93) • result confirmed by BESS exp.!

(Huang ’03 PRD, Huang ’07 Astropart. Phys.) 21

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

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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 23

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…) 24

γ Induced Air Shower Observed at Ground

25

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) 26

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!

27

Best Fitted Spectrum of RX J1713.7-3946

• HEP event generator to simulate full picture of cosmic-ray hadronic interactions • considered full picture of γ-ray decays  2 min = 22.4 for 22 DOF (-) spectral curvature strongly suggested (with CL > 95%)!

28 (Huang et al., ’07)

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) 29

X-Ray Emission Variability in of RX J1713.7-3946

(2000) (2005) (2006) (Uchiyama et al., ‘07) Chandra Observation • unique information of magnetic field in particle acceleration region!

• Rapid variability implies shorter timescales and amplification of

B

field in SNR shell.

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Synchrotron Radiation of RX J1713.7-3946

• 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! (Huang et al, ’08) 31

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!

32

(      )

Induced μ Rate of HE γ-Ray Sources

• IceCube-like detector assumed  •

ν

e

: full mixing assumed:   :    1 : 2 : 0  1 : 1 : 1 experiment with data accumulation over 5-10 yrs at E μ~ few TeV, or Eν ~ 10 TeV to test hadronic origin of TeV γ-rays!

(Huang et al, ’08) 33

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 34

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 J1713.7-3946 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 J1713.7-3946 • 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 35