HEAD 2010 – Mar.3, 2010 :: IVM/Stanford-KIPAC 1IVM/Stanford-KIPAC 1 PAMELA Workshop, Rome/May 12, 2009 Igor V. Moskalenko (stanford/kipac) Leptons in Cosmic Rays:

HEAD 2010 – Mar.3, 2010 :: IVM/Stanford-KIPAC 2 Positron fraction  The excess in the CR positron fraction relative to the predictions of secondary production models is confirmed by Pamela and extended to higher energies (up to ~100 GeV)  Additional positron component?  Charge sign dependence below ~10 GeV is expected Adriani+’08 Solar modulation sec. production (GALPROP)

HEAD 2010 – Mar.3, 2010 :: IVM/Stanford-KIPAC 3 Cosmic ray electrons  A slope the CR electron spectrum can be easily reproduced in propagation models  Most interesting is the fine structure, if confirmed, and the cutoff at ~1 TeV Latronico+’09 What’s here?

HEAD 2010 – Mar.3, 2010 :: IVM/Stanford-KIPAC 4 One good experiment is worth thousand theories…  ATIC electrons: 270+  PPB-BETS electrons: 150+  Fermi LAT electrons: 170+  HESS electrons: 100+  PAMELA positron fraction: 370+ leptons in CRs total: citations in ~1 year!  PAMELA antiprotons: 150+ citations (in <1 yr)  BESS program (only journal papers): citations Of course, most of citations are coming from particle physics ★ using NASA ADS

HEAD 2010 – Mar.3, 2010 :: IVM/Stanford-KIPAC 5 An experiment in nature, like a text in the Bible, is capable of different interpretations. — William Jones,1781  There is no deficit in interpretations of the PAMELA positron excess (Adriani+’08): 370+ papers since Oct 2008! –Various species of the dark matter (most papers) –Pulsars –SNRs –Microquasars –a recent GRB nearby –…  Perhaps we have to discuss a deficit of positrons, not their excess!  Unfortunately, >99.7% of these explanations are wrong  …Because there is only one correct explanation

HEAD 2010 – Mar.3, 2010 :: IVM/Stanford-KIPAC 6 The Goal of This Talk To discuss a place of recent leptonic data in astrophysics of cosmic rays  Some calibration issues  A couple of words about heliospheric modulation  How well do we understand the propagation of CRs?  Lepton-specific issues

HEAD 2010 – Mar.3, 2010 :: IVM/Stanford-KIPAC 7 Calibration Issues

HEAD 2010 – Mar.3, 2010 :: IVM/Stanford-KIPAC 8 Fermi-LAT: the Earth’s albedo A test of on orbit calibration of the LAT can be done using the Earth limb albedo spectrum – produced by CR interactions with the Earth’s atmosphere (Abdo+’09). The spectral index of the albedo is close to the spectral index of ambient CRs.

HEAD 2010 – Mar.3, 2010 :: IVM/Stanford-KIPAC 9 CR measurements and backgrounds  CR protons are the dominant background for positron detection  PAMELA people made a tremendous job by hunting down every proton (see Mirko’s talk)  See Marty’s summary L.Baldini

HEAD 2010 – Mar.3, 2010 :: IVM/Stanford-KIPAC 10 Cosmic rays in the heliosphere

HEAD 2010 – Mar.3, 2010 :: IVM/Stanford-KIPAC 11 Charge-sign dependence The Parker magnetic field has opposite magnetic polarity above and below the helio- equator, but the spiral field lines are mirror images of each other. M.Potgieter Solar min Solar max This antisymmetry produces the drift velocity fields that affect the particles of opposite charge in different ways (converge on heliospheric equator or diverge from it).

HEAD 2010 – Mar.3, 2010 :: IVM/Stanford-KIPAC 12 Probes of propagation in the interstellar medium  nuclei in cosmic rays  diffuse Galactic γ-rays

HEAD 2010 – Mar.3, 2010 :: IVM/Stanford-KIPAC 13 Secondary/primary nuclei ratio & CR propagation Using secondary/primary nuclei ratio (B/C) & flux: Diffusion coefficient and its index Propagation mode and its parameters (e.g., reacceleration V A, convection V z ) Propagation parameters are model-dependent Make sure that the spectrum is fitted as well Radioactive isotopes: Galactic halo size Z h Z h increase Be 10 /Be 9 E k, MeV/nucleon Parameters (model dependent): D~ (ρ/1 GV) α cm2/s α ≈ Z h ~ 4-6 kpc V A ~ 30 km/s Boron/Carbon (B/C) Interstellar E k, MeV/nucleon

HEAD 2010 – Mar.3, 2010 :: IVM/Stanford-KIPAC 14 Radioactive secondaries Different size from different ratios… Z halo,kpc In determination of the propagation parameters one has to take into account:  Errors in CR measurements HE & LE)  Errors in production cross sections  Errors in the lifetime estimates nat Si+p  26 Al W ST T 1/2 = ? W – Webber+ ST – Silberberg & Tsao – measured W – Webber+ ST – Silberberg & Tsao – measured The error bars can be significantly reduced if more accurate cross sections are used Different ratios provide consistent parameters

HEAD 2010 – Mar.3, 2010 :: IVM/Stanford-KIPAC 15 Diffusion coefficient in different models Plain diffusion Diffusive Reacceleration (Kolmogorov) Reacceleration with damping ~R 0.6 ~β -3 extrapolation Ptuskin+’06  The diffusion coefficient is model-dependent and is derived from secondary/primary nuclei ratio below ~100 GV  It is extrapolated above this energy data

HEAD 2010 – Mar.3, 2010 :: IVM/Stanford-KIPAC 16 PAMELA & CREAM: B/C ratio The B/C ratio <30 GeV/n is measured by Pamela (no surprises) Statistical errors only Sparvoli’09 PAMELA Very preliminary! The propagation models’ predictions differ at high energies which will allow to discriminate between them when more accurate data are available (hopefully after CREAM V flight) CREAM Ahn+’08 Launched on Dec. 1, 2009, CREAM-V just finished its 3 rd circle around the South Pole!

HEAD 2010 – Mar.3, 2010 :: IVM/Stanford-KIPAC 17 CR Protons & He The CR proton and He spectra by Pamela agree well with previous measurements No surprises for production of secondary particles and diffuse gammas protons He PAMELA Picozza’09 H: ±0.071 He: ±0.122 IM+’02

HEAD 2010 – Mar.3, 2010 :: IVM/Stanford-KIPAC 18 Antiprotons  Antiprotons in CRs (BESS, Pamela) <100 GeV are in agreement with secondary production PAMELA Picozza’09 | Ptuskin+’06

HEAD 2010 – Mar.3, 2010 :: IVM/Stanford-KIPAC 19 Fermi-LAT: diffuse gammas  Conventional GALPROP model is in agreement with the Fermi-LAT data at mid-latitudes (mostly local emission)  This means that we understand the basics of cosmic ray propagation and calculate correctly interstellar gas and radiation field, at least, locally model Abdo+’09

HEAD 2010 – Mar.3, 2010 :: IVM/Stanford-KIPAC 20 Spectrum of the Galactic diffuse emission, longitude and latitude profiles CR intensities are adjusted by a factor: protons – 1.3, electrons |b|≤5,°|l|≤30° |b|≤5° |l|≤60° 1.2 GeV ≤ E ≤ 1.6 GeV Loop I Total diffuse Bright sources π 0 -decay Inverse Compton Bremsstrahlung Isotropic component

HEAD 2010 – Mar.3, 2010 :: IVM/Stanford-KIPAC 21 Lepton-specific issues

HEAD 2010 – Mar.3, 2010 :: IVM/Stanford-KIPAC 22 Kobayashi+’03 Interpretation of CR electron data  CR electron spectrum is consistent with a single power-law with index  Can be reproduced well by the propagation models  Multi-component interpretation is also possible –Dark matter contribution –Astrophysical sources (SNR, pulsars) –… The key in understanding of the electron spectrum (local vs global) is the origin of the positron excess and the diffuse gamma-ray emission

HEAD 2010 – Mar.3, 2010 :: IVM/Stanford-KIPAC 23 Geminga pulsar Milagro C3 Pulsar (AGILE/Fermi) MGRO Fermi Pulsar SNR  Cygni Fermi Pulsar HESS, Milagro, Magic Fermi Pulsar Milagro (C4) 3EG Boomerang PWN SNR IC433 MAGIC, VERITAS Radio pulsar (new TeV source) unID (new TeV source) unID (new TeV source) Fermi Pulsar MGRO HESS SNR W51 HESS J G (SNR) Fermi Pulsar (J1958) New TeV sources G.Sinnis’09 Milagro: TeV observations of Fermi sources Many γ -ray sources show extended structures at HE – thus they are also the sources of accelerated particles (CRs)

HEAD 2010 – Mar.3, 2010 :: IVM/Stanford-KIPAC 24 Effective propagation distance  The energy loss time scale (IC) at ~1 GeV – 1 TeV: τ ~ 300 E kyr ~ E cm; E 12 – energy in TeV  The diffusion coefficient: D ~ (0.5-1)x10 30 E 12 1/2 cm 2 /s  Effective propagation distance: ~ √6D τ ~ 5x10 21 E 12 -1/4 cm ~ 1 kpc E 12 -1/4  We do not know the exact energy of the spectral cutoff and electron spectrum at the source, so the distance to the local sources of VHE electrons could be ≥ a few 100 pc.

HEAD 2010 – Mar.3, 2010 :: IVM/Stanford-KIPAC 25 Solar system in the Milky Way The solar system is located in the inter-arm region – a very safe place!

HEAD 2010 – Mar.3, 2010 :: IVM/Stanford-KIPAC 26 (Some) Important questions to answer  How large is the positron fraction at HE (PAMELA)? –Identifies the nature of sources of primary positrons  If SNRs are the sources of primary positrons, this should also affect antiprotons and secondary HE… –Measure pbars and secondary nuclei (PAMELA, CREAM…)  How typical for the local Galactic environment is the observed positron fraction? –If this is the typical fraction, the sources of primary positrons are distributed in the Galaxy (could be pulsars, SNRs, or DM) –If this fraction is peculiar then there is a local source or sources of primary positrons  Fine structure and the TeV cutoff of the electron spectrum –If confirmed, the fine structure may be telling us something –What’s beyond ~1 TeV?  Dark matter vs Astrophysical source –Distribution and spectrum of the diffuse γ-ray emission at HE (Fermi)  To answer these important questions we should consider all relevant astrophysical data (CRs, gamma rays) and particle data (LHC) together

HEAD 2010 – Mar.3, 2010 :: IVM/Stanford-KIPAC 27 Thank you ! You are here