High energy cosmic rays
ROBERTA SPARVOLI
ROME “TOR VERGATA” UNIVERSITY
AND INFN, ITALY
Nijmegen 2012
Lecture # 1 : outline
COSMIC RAY SCIENCE
 DIRECT MEASUREMENTS OF CR’S
 BALLOON EXPERIMENTS

The discovery of cosmic rays
• Victor Hess ascended to 5000 m in a balloon in 1912
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• ... and noticed that his electroscope discharged more rapidly
as altitude increased
• Not expected, as background radiation was thought to be
terrestrial. Extraterrestrial origin, confirming previous hints
by Theodore Wulf and Domenico Pacini
Kolhorster 1914
The CR spectrum
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Structures in the CR spectrum
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Primary and secondary CR’s
Astroparticle physics in space is performed by the detection
and analysis of the properties of Cosmic Rays.
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The primary Cosmic Rays reach the top of the atmosphere,
without interacion.
The atmosphere acts as a convertor: the interaction of the
CR’s with the nuclei in atmosphere produces showers of
secondary particles (secondary Cosmic Rays).
The primary radiation can be studied directly only above
the terrestrial atmosphere.
The primary cosmic radiation is affected by the effect of the
Solar System magnetic fields: the Earth’s magnetic field
and the Solar magnetic field.
Primary cosmic ray
~500 km
Smaller detectors
but long duration.
PAMELA!
Top of atmosphere
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~40 km
Large detectors but
short duration.
Atmospheric
overburden ~5 g/cm2.
Almost all data on
cosmic antiparticles
from here.
~5 km
Ground
0m
The composition of CR’s
 Charged component
Neutral component
 Protons (
Gamma rays
Neutrons
Neutrinos (not “real”
CR)
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85%
)
 Nuclei & isotopes (12%
He, 1% heavy nuclei)
 Electrons (2%)
 Antimatter:
 antiprotons (p/p~10-4)
 positrons (e+/e++e- ~10-1)
 antideuterons ?
 antinuclei ?
The neutral component
points to the source!
How to measure
cosmic rays
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
Directly, E<1014 eV
•
•
•
•

High Z particles
Antiparticles
Light Nuclei and isotopes
Composition below the knee
Indirectly, E>1014 eV
Composition at the knee
• UHECR
(Castellina’s talk)
•
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Measurement of primary and
secondary CR elements
 Fundamental questions remain unsolved:
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 GCR
sources?
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 GCR composition?


GCR acceleration sites?
GCR diffusion in the Galaxy?
 The effective possibility to disentangle exotic signal
from pure secondary production depends strongly on
the precise knowledge of the parameters which
regulate the production and diffusion of cosmic rays in
the Galaxy.
e-
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What do we know up to now?
 GCR material ejected in Supernova explosions
(Remnants), the best candidate for CR sources
from the energetic point of view (not yet the smoking
gun…);
GCR accelerated via DSA (First Order Fermi
acceleration) mechanism at the shock wave front
propagating into the ISM, up to roughly 1015 eV;
Power-law energy spectrum expected (E-a);
GCR diffuse in the Galaxy, lose energy, interact, can
be reaccelerated, escape from the Galaxy …. Powerlaw energy spectrum expected (E-(a+d));
Not much known about extra-Galactic CR.
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



Boron/Carbon ratio
 Present situation of the B/C critical ratio:
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δ:
0.3
0.45
0.6
0.7
0.85
DIFFERENT diffusion coefficients : K(E)= K R
0
Courtesy of F. Donato
d
Secondaries/primaries
i.e. Boron/ Carbon to constrain propagation parameters
D. Maurin, F. Donato R. Taillet and P.Salati ApJ, 555, 585,
2001 [astro-ph/0101231]
B/C
Ratio
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F. Donato et.al, ApJ, 563, 172, 2001 [astroph/0103150]
Antiproton flux
Astrophysic
B/C
constraints
Nuclear
cross
sections!!
Physics around the knee
• Continuity from direct measurements to extensive
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air showers
• Measurements in the knee region:
•
•
•
Normalization of spectrum
Composition
Energy content
• Transition from galactic to extragalactic spectrum?
A & B galactic components + extra-galactic
Hillas, J.Phys.G 31 (2005) R95-131
High Energy electrons
The study of primary electrons is especially important
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textgive
because
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information on the nearest sources
of cosmic rays.
Electrons with energy above 100 MeV rapidly loss their
energy due to synchrotron radiation and inverse
Compton processes.
The discovery of primary electrons with energy above
1012 eV will evidence the existence of cosmic ray sources
in the nearby interstellar space (r300 pc).
Purposes of Electron Observations
Search
for
the signature
ofelectron
nearby
HE
Search
Precise
for
measurement
anisotropy
in
of HE
electron
spectrum
Observation
of electron
spectrum
influx
sources
(believed
to be
above
aselectron
an effect
10
GeV
of to
the
define
nearby
model
sources.
of SNR)
accele1~10
GeV
for
study
of a
solar
modulation
in theand
electron
spectrum above ~ TeV
ration
propagation.
太陽変調
超新星における衝撃波加速
加速機構と拡散過程
超新星の頻度、分布
・CALET
Possible Nearby
Sources
• T< 105 years
• L< 1 kpc
Vela
10,000 years
820 ly
Chandra
近傍ソースの検出
-エネルギースペクトル
-到来方向の異方性
W=1048 erg/SN
I(E)=I0E-α
N=1/30yr
D=D0(E/TeV)0.3
Anisotropy
Vela
ROSAT
Cygnus Loop
20,000 years
2,500 ly
Monogem
86,000 years
1,000 ly
The antimatter issue
“We must regard it rather an accident that the
Earth and presumably the whole Solar System
contains a preponderance of negative electrons
and positive protons.
It is quite possible that for some of the stars it
is the other way about”
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Dirac Nobel Speech (1933)
Simple Big Bang Model
The early Universe was a hot expanding plasma with equal number
of baryons, antibaryons and photons. In thermal equilibrium the
two-ways
reaction
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text was:
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B + anti-B
g+g
As the Universe expands, the density of particles and antiparticles
falls, annihilation process ceases, effectively freezing the ratio:
- baryon/photon = antibaryon/photon ~ 10-18.
- Annihilation catastrophe.
Instead, in the present real Universe:
Baryon/photon (eqv. to BAU) ~ 6 * 10-10 (from direct observ. of light
elements &
microwave background);
Antibaryon/baryon < 10-4.
Sakharov criteria
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To to
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predominance of matter over antimatter,
Sakharov (1967) pointed out the necessary conditions:
• B violating interactions (otherwise B=0 remains);
• Non-equilibrium situation (otherwise all status remain constant, so B=o
remains);
• CP and C violation
(otherwise baryon aymmetric processes would be
compensated by antibaryon asymmetric ones);
GUT theories ?
(not working)
Bariogenesys
(Leptogenesys) ?
The processes really responsible are not presently understood!
What about the observations?
 Indirect ->
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•
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By measuring the spectrum of the Cosmic
Diffuse Gamma emission
• By searching for distortions of the Cosmic
Microwave Background
 Direct ->
• By searching for Antinuclei
• By measuring anti-p and e+ energy spectra
Gamma Evidence for Cosmic Antimatter?
Steigman 1976, De Rujula 1996, Dolgov 2007
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Osservation
intext
the 100 MeV gamma range
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Leading process:
pp
0+ ………
gg
Other processes:
pp
+………
μ+………
e+e0.511 MeV
e+………
γ 1-10 MeV
Cosmic Diffuse Gamma
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P. Sreekumar et al, astroph/9709257
Indirect searches: antimatter/matter
fraction limits
 On a wide scale, there is no evidence for the
intense g-ray and X-ray emission that would
follow annihilation of matter in distant galaxies
with clouds of antimatter:
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 Antimatter/Matter fraction limit:
In Galactic molecular clouds: f<10-15
-10
 In Galactic Halo: f< 10
-5
 In local clusters of galaxies: f<10

 Antimatter must be separated from matter at
scales at least as 100 Megaparsec
Direct searches: current status
Antiprotons: DETECTED! secondary production
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PCR+HISM
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PCR+HeISM
antiprotons
aCR+HISM
aCR+HeISM
p + anti-p
secondary
Positrons: DETECTED! secondary production
PCR+ ISM
NCR+ISM
positrons
+ -> m+ -> e+
secondary
Anti-nuclei: never detected !
They would be the real signature of antistars because
their production by “spallation” is negligible
Antiproton/proton ratio: before PAMELA
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Positron/electron ratio before PAMELA
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Antimatter Search
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Dark Matter searches
Evidence for the existence of an unseen, “dark”, component
in the energy density of the Universe comes from several
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independent
observations at different length scales:
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Rotation curves of galaxies
Galaxy clusters
CMB
Lensing
Large Scale Structure
SN Ia
Bertone, Hooper & Silk, hep-ph/0404175, Bergstrom, hep-ph/0002126, Jungman et al, hep-ph/9506380
The “Concordance Model” of cosmology
The “concordance model” of big bang cosmology
attempts
totext
explain cosmic microwave background
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observations,
as well as large scale structure
observations and supernovae observations of the
accelerating expansion of the universe.
tot = 1.0030.010
m ~ 0.22 [b=0.04]
 ~ 0.74
Most of matter of non-baryonic nature
and therefore “dark” !
Different data:
 WD supernovae
• CMB
• Matter surveys
all agree
at one point
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•Kaluza-Klein DM in UED
•Kaluza-Klein DM in RS
•Axion
•Axino
•Gravitino
•Photino
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•SM Neutrino
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•Sterile Neutrino
•Sneutrino
•Light DM
•Little Higgs DM
•Wimpzillas
•Q-balls
•Mirror Matter
•Champs (charged DM)
•D-matter
•Cryptons
•Self-interacting
•Superweakly interacting
•Braneworld DM
•Heavy neutrino
•NEUTRALINO
•Messenger States in GMSB
•Branons
•Chaplygin Gas
•Split SUSY
•Primordial Black Holes
Dark matter candidates
L. Roszkowski
DM candidates: WIMP’s !
SUSY particles ?
Neutralino as the CDM candidate
~
~3
~1
~2
  a1B0 + a2W0 + a3 H 0 + a4 H 0
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Linear combination of the neutral gauge bosons B and W3
and the neutral higgsinos H1 and H2. The neutralino is a
good candidate because:
•
•
•
•
•
•
Stable (if R-parity is conserved)
Mass: m~ 10-1000 GeV
Non-relativistic at decoupling 
CDM
Neutral & colourless
Weakly interacting (WIMP)
Good relic density 
SIGNALS from RELIC WIMPs
For a review, see i.e. Bergstrom hep-ph/0002126
Direct searches:
elastic scattering of a WIMP off detector nuclei
Measure of the recoil energy
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Indirect detection: in cosmic radiation
 signals due to annihilation of accumulated  in the centre of
celestial bodies (Earth and Sun)
 neutrino flux
 signals due to  annihilation in the galactic halo
 neutrinos
 gamma-rays
 antiprotons, positrons, antideuterons
n and g keep directionality
can be detected only if emitted from high  density regions
Charged particles diffuse in the galactic halo
antimatter searched as rare components in cosmic rays
Neutralino annihilation
Production takes place everywhere in the halo!!
The presence of neutralino annihilation will destort the positron,
antiproton and gamma energy spectrum from purely secondary
production
Spectrum deformation
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Another possible scenario:
KK Dark Matter
LIGHTEST KALUZA-KLEIN PARTICLE
( L K P ) : B (1)
Bosonic Dark Matter:
fermionic final states
no longer helicity
suppressed.
e+e- final states
directly produced.
As in the neutralino case
there are 1-loop
processes that produces
monoenergetic
γ γ in the final state.
Kaluza-Klein Dark Matter in
+
e e
Direct annihilation of the Lightest Kaluza-Klein
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particle
(LKP)
into electron-positron pair in the
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Galactic halo (Baltz and Hooper, JCAP 7, 2007, and references
therein)
e- + e+ yield is estimated to be ~20% per
annihilation
Could be a unique opportunity to observe a sharp
feature in the electron spectrum (predicted in some
models)
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DIRECT MEASUREMENTS
OF
HIGH ENERGY COSMIC RAYS
Main physics research lines
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Stratospheric balloons
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The antimatter balloon flights: overview
Aim of the activity is the detection of antimatter and dark matter signals in
CR nei RC (antiprotons, positrons, antinuclei) for energies from hundreds of
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MeV
to about 30 GeV, and measurements of primary CR from hundreds of
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MeV to about 300 GeV.
6 flights from the WIZARD collaboration: MASS89, MASS91, TRAMPSI, CAPRICE 94, 97, 08. The flights started from New Mexico or Canada,
with different geomagnetic cut-offs to optimize the investigation of different
energy regions. The flights lasted about 20 hours.
4 flights from the HEAT collaboration: 2 HEAT-e+, in 1994 and 1995, and 2
HEAT-pbar flights, in 2000 and 2002
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CAPRICE-94
• Charge sign and
momentum
determination;
• Beta selection
• Z selection
• hadron – electron
discrimination
Results from
MASS/TrampSI/CAPRICE/HEAT:
Positrons & antiprotons
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Excess ??
Highest energetic points available from balloons
The BESS program
The BESS program had 11 successful flight campaigns
since
1993
up
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Aim of the program is to search for antimatter (antip,
antiD) and to provide high precision p, He, m spectra.
A modification of the BESS instrument, BESS-Polar, is
similar in design to previous BESS instruments, but is
completely new with an ultra-thin magnet and configured to
minimize the amount of material in the cosmic ray beam, so as
to allow the lowest energy measurements of antiprotons.
BESS-Polar has the largest geometry factor of any balloon-
borne magnet spectrometer currently flying (0.3 m2-sr).
BESS Collaboration
High Energy Accelerator
Research Organization(KEK)
The University
of Tokyo
National Aeronautical and
Space Administration
Goddard Space Flight Center
BESS
Collaboration
University of Maryland
University of Denver
(Since June 2005)
Kobe University
Institute of Space and
Astronautical Science/JAXA
BESS Detector
Rigidity measurement
SC Solenoid (L=1m, B=1T)
•
Min. material (4.7g/cm2)
• Uniform field
TOF
• Large acceptance
b, dE/dx
Central tracker
•
Drift chambers (Jet/IDC)
•
d ~200 mm
Z, m measurement
R,b --> m = ZeR
√ 1/b2-1
dE/dx --> Z
JET/IDC
Rigidity
BESS-Polar I and II
Long duration flights of total 38 days with
two circles around the Pole
52
BESS-Polar II Antiproton Spectrum
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Compared with
BESS’95+’97:
 x 14 statistics at < 1 GeV

Flux peak consistent at
2 GeV

Spectral shape different
at low energies.
BESS-Polar II results
Ref. for BESS’95+’97:
S. Orito et al. PRL, Vol. 84, No, 6, 2000
ICRC2011. BESS highlight
- generally consistent with
secondary p-bar
- calculations under solar
minimum conditions.
- NO low energy
enhnacement due to PBH
100 times improvement
Limits on antimatter (antiHe and antiD)
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CREAM – Overview
 Aim is the study of CR from 1012 to 5x1014 eV, from proton to Iron,
by means of a series of Ultra Long Duration Balloon (ULDB) flights
from
Antarctica.
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 6 flights up to now: 2004, 2005, 2007, 2008, 2009, 2010.
The instrument is composed by a sampling tungsten/scintillating fibers
calorimeter (20 r.l.), preceded by a graphite target with layers of
scintillating fibers for trigger and track reconstruction, a TRD for
heavy nuclei, and a timing-based segmented charge device.
A fundamental aspect of the instrument is the capability to obtain
simultaneous measurements of energy and charge for a sub-sample of
nuclei by calorimeter and TRD, thus allowing an inter-calibration in
flight of the energy.
The CREAM instrument
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Collecting power: 300 m2-sr-day for proton and helium, 600 m2-sr-day nuclei
Protons and heliums
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Heavier elements: hardening
Advanced Thin Ionization Calorimeter
(ATIC)
ATIC COLLABORATION:
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Institute
Physical
and Technology,
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University
Marshall Space Flight Center, Huntsville, AL,
USA
Skobeltsyn Institute of Nuclear Physics, Moscow
State University, Moscow, Russia
Purple Mountain Observatory, Chinese Academy
of Sciences, China
Max Planck Institute for Solar System Research,
Katlenburg-Lindau, Germany
Department of Physics, Southern University,
Baton Rouge, LA, USA
Department of Physics and Astronomy,
Louisiana State University, Baton Rouge, LA,
USA
Department of Physics, University of Maryland,
College Park, MD, USA
The ATIC balloon flight
program measures the cosmic
ray spectra of nuclei:
1 < Z < 26
between 1011 eV and 1014 eV.
ATIC has had three successful
long-duration balloon (LDB)
flights launched from
McMurdo Station, Antarctica
in 2000, 2002 and 2007.
ATIC Instrument Details
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Protons and heliums
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The ATIC “bump” in the all-electron spectrum
TRACER balloon flights
 TRACER and TIGER
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CR energy spectra
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TRACER 2 flights data:
POWER_LAW fit above 20 GeV/n:
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B/C ratio
GALPROP fit with
reacceleration:
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GALPROP fit without
reacceleration:
Leaky Box:
TIGER and SuperTIGER balloon flights
Super-TIGER builds on the smaller Trans-Iron Galactic Element Recorder (TIGER),
flown twice on balloons in Antarctica in Dec. 2001 and 2003.
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TIGER
a total
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abundances
of the elements 31Ga, 32Ge, and 34Se, and an upper-limit on the
abundance of 33As.
Excellent charge resolution in the 10≤Z≤38 charge range.
SUPERTIGER:
30≤Z≤42
It is known by ACE_CRIS data that the abundance of 22Ne points towards
a contribution from outflow of massive starts (Wolf-Rayet stars).
TIGER and SuperTIGER search for the enrichments of hevy elements
expected from nucleosynthesis in massive stars.
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TIGER 1 and 2 combined results
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