Transcript Document

Implication of recent cosmic ray data
Qiang Yuan
Institute of High Energy Physics
Collaborated with Xiaojun Bi, Hong Li, Jie Liu, Bing
Zhang & Xinmin Zhang
Lorentz & CPT Violation workshop, Beijing
2011-05-10
Outline
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•
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Introduction to the newest observational data
On the electron/positron data
On the hardening of the nuclei spectra
Summary
Introduction
PAMELA discovery of the positron excess
PAMELA, 2009, Nature, 458, 607
Introduction
PAMELA observation of the antiproton flux
PAMELA, 2010, PRL, 105, 121101
Introduction
PAMELA observation of the electron spectrum
PAMELA, 2011, arXiv:1103.2880
Introduction
ATIC observation of the electron+positron spectra
ATIC, 2008, Nature, 456, 362
Introduction
Fermi observation of the electron+positron spectra
Fermi, 2010, PRD, 82, 092004
Introduction
HESS observation of the electron+positron spectra
HESS, 2008, PRL, 101, 261104
2009, A&A, 508, 561
Introduction
CREAM measurement of the CR nuclei spectra
CREAM, 2010, ApJ, 714, L89
Introduction
PAMELA measurement of the proton and Helium spectra
PAMELA, 2011, Science, 332, 69
Introduction
Short summary of the data
• We have many new CR data with very high quality
recently, which may imply something new in
astrophysics
• In the electron/positron data, strong evidence shows
excesses in addition to the background model
• The hardening of CR nuclei spectra also challenge the
conventional understanding of the acceleration and
propagation of CR particles
Outline
•
•
•
•
Introduction to the newest observational data
On the electron/positron data
On the hardening of the nuclei spectra
Summary
e+/- excess
Really excesses?
To explain simultaneously positron and electron data, we need
exotic electron/positron sources.
e+/- excess
Derived absolute positron flux
The observed positron spectrum is as hard as E-2.7 (before
propagation is ~E-2.0), which is much harder than expected from
background model
Models
Dark Matter
 Annihilation or decay
 Leptonic, quark or gauge
bosonic final states
 Smooth or subhalo
…
Many can work but some
general conclusions:
 TeV scale DM
 Lepton dominated
 Large annihilation or
decay rate
e+/- excess
Astrophysical
 Pulsar, SNR, microquasar
GRB
 Hadronic or leptonic
 Single or population
 Burst or continuous
injection
 Propagation model
…
e+/- excess
Whatever the real physics is, it is possible to parameterize the
exotic source component and derive the model parameters
• Pulsar like scenario
• Dark matter scenario
e+/- excess
Pulsar like scenario
e+/- excess
Pulsar like scenario
e+/- excess
Dark matter scenario
Preliminary!
e+/- excess
Dark matter scenario: antiprotons
Preliminary!
The quark branching ratio is strongly suppressed
e+/- excess
What can we know from the fit?
• The data are precise enough to encourage us to do the
global fitting to extract the underlying physics
• Both the background and source parameters can be
determined
• However, we do not know whether the excesses come
from astrophysical sources or dark matter
• The current fit may suffer from systematical
uncertainties from e.g., CR propagation, hadronic
interaction models
Outline
•
•
•
•
Introduction to the newest observational data
On the electron/positron data
On the hardening of the nuclei spectra
Summary
CR hardening
Basic picture: superposition of sources with a dispersion in
the source injection spectra
CR hardening
Fermi data indeed show the dispersion of the photon
spectrum (hence CR spectrum) of SNRs
YQ, Yin & Bi, arXiv:1010.1901
Fit the CR
data
CR hardening
YQ, Zhang & Bi, arXiv:1104.3357
CR hardening
Implication on secondary particles
YQ, Zhang & Bi, arXiv:1104.3357
CR hardening
An alternative explanation of the ankle-GZK structure?
YQ, Zhang & Bi, arXiv:1104.3357
Summary
• It is an era of discoveries in CR field
• Using the global fitting method we can determine both the
background and source parameters from the electron/positron
data, although we do not know what the sources are
• A simple scenario with dispersion of the source injection
spectra is proposed to explain the CR nuclei hardening
Future
AMS02: scheduled to be launched on May 16th
Thank you