Martin A. Pomerantz
Cosmic Rays:
Elementary Particles in Nature
by Thomas K. Gaisser
Public lecture, May 9, 2002
Themes
The atomic view of science
Cosmic rays & particle physics: 3 examples
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Neutrinos
Antiprotons
Air showers
Particle astrophysics in Antarctica
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South Pole Air Shower Experiment (SPASE)
IceCube
2400 years of elementary particles
Democritus c. 460-370 B.C.
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Atomic theory of matter
Not continuous elements (fire, air,
earth and water) but
Indivisible atoms ~ elementary
particles
Their interactions, combinations,
motions explain everything
Epicurus c. 341-271
Lucretius (Rome, c. 99-55)
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de Rerum Natura
“least parts” ~ quarks
Epicurus
Levels of structure
Molecules: combinations of atoms
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6CO2 + 6H2O + light  C6H12O6 + 6O2
Produce wood (C6H10O5) by taking carbon out
of the air and water from the ground
Atoms: compact nucleus with electron cloud
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p + Mn  p + e- + Mn+  p + Mn + x-ray
electron ejected; recombination x-ray emitted
Nuclei: Z protons and (N = A - Z) neutrons
Nucleons: p = [uud]; n = [udd]
Epicurean “atom”
Minimal parts
Beta-decay and the neutrino
Nuclear b-decay
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A(Z,N)  A(Z+1,N-1) + e- + ne
n  p + e- + ne ( n = [udd]  p = [uud] )
d  u + e- + ne
Neutrino (symbol n)
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hypothesized by Pauli (1930) to conserve energy
named by Fermi (1933) “little neutral one”
first detected 1956 (ne from nuclear reactor) by
Cowan and Reines
3 neutrino flavors: ne, nm and nt
Elementary Particle Physics
(a.k.a. High Energy Physics)
Study particles by collisions: p + p  ?
E = mc2:
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When E >> mc2, E  mass on large scale
then ? = many particles
Examples:
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p + p  p + n + p+ followed by (p+  m+ nm)
p + p  p + p + p + p (p = antiproton)
p + 14N  200 p + 20 K + …
Macroscopic collisions
Warning:
This is a flawed analogy
because cars are highly
composite objects
P+PP+P+P+P
+

+
+
+
What are Cosmic Rays?
Naturally occurring particles (protons and
nuclei) having very high energies
From sources far outside the solar system
Discovered nearly a century ago
Studied with detectors on balloons and
spacecraft as well as from the ground
Positron, pion, kaon were all discovered
by observations of cosmic-ray interactions
in the atmosphere
n-mass and flavor oscillations
--a recent discovery about particles using interactions of cosmic rays
Cosmic-ray neutrinos
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p + air  p + particles
p  m + nm
m  e + nm + ne
Atmospheric n anomaly
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nm/ne  1 (instead of 2)
upward nm < downward nm
Explanation: nm  nt
Implies n have mass > 0
Artist’s view of Super-K Detector:
11,000 20” phototubes viewing
40,000 tonnes (10 million gallons)
of water in a mine in Japan
Pictures of Super-K
Top left: Super-K half full (1996)
Right: unpacking the PMTs
Bottom: Super-K after accident (Nov. 2001)
Detector is currently being rebuilt
Cherenkov radiation:
signals in Super-Kamiokande
Sonic boom (from object faster than speed of sound)
is analogous to Cherenkov radiation by a charged
particle moving faster than speed of light in a medium
Solar Neutrinos
Cosmic Gall by John Updike
little
hardly
(Gell-Mann)
They also oscillate: ne  [nm,nt]
Neutrinos, they are very small.
They have no charge and have no mass
And do not interact at all.
The earth is just a silly ball
To them, through which they simply pass,
Like dustmaids through a drafty hall
Or photons through a sheet of glass.
They snub the most exquisite gas,
Ignore the most substantial wall,
Cold-shoulder steel and sounding brass,
Insult the stallion in his stall,
And scorning barriers of class,
Infiltrate you and me! Like tall
And painless guillotines, they fall
Down through our heads into the grass.
At night, they enter at Nepal
And pierce the lover and his lass
From underneath the bed - you call
It wonderful; I call it crass.
from Telephone Poles and Other Poems by John Updike ©
Knopf 1963
Sudbury Neutrino Observatory
Art McDonald gave Swann lecture
at Bartol/DPA in February
High-energy accelerators
Accelerator labs  high energy particles
Cosmic accelerators  cosmic rays
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What are the sources?
How are the particles accelerated?
How do they get here?
What happens on the way?
Particle accelerators
Fermilab’s Tevatron ring is 4 miles around
CERN site with LEP tunnel & L3
Cosmic accelerators
(some supernova remnants in our galaxy)
SN1987A
Circa 1650
(Cas-A)
SN1054
SN1572
Really Big Cosmic accelerators:
jets in active galaxies
20 TeV gamma rays observed
Higher energies obscured by IR light
but the universe is transparent to n
VLA image of Cygnus A
Primary cosmic-ray antiprotons
p + interstellar gas  p + …
Issues:
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Are there exotic sources?
Probe the heliosphere
Results: p/p ratio
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consistent with origin in
interstellar gas
Predicted change agrees with
Bartol group’s prediction for
2000 solar maximum based on
large-scale structure of solar
wind and its magnetic field
Interactions at ultra-high energy
make air showers
Intensity is very low
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~20 per hour per acre
for E = 2 million x mc2
(~E of biggest accelerator)
~ 1 per sq. km per century
at E = 200 trillion x mc2
(most energetic cosmic ray)
Use large ground arrays
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Several acres …
Several thousand sq. miles
Schematic view of air shower detection:
ground array and Fly’s Eye
Auger detector
Under construction in Argentina
Jim Cronin, Alan Watson, Jim Beatty …
SPASE-AMANDA
SPASE-1, 1987-1996
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Hillas, Pomerantz, Watson
(Leeds-Bartol)
SPASE-2, 1996 –
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Current Bartol experiment
TKG, Watson, Evenson,
Stanev, Tilav, Bai ...
Coincidences with
AMANDA
AMANDA is a neutrino
telescope
McMurdo
Amundsen-Scott South Pole Station
Optical
sensor
Martin A. Pomerantz Observatory (MAPO)
The IceCube Collaboration
Institutions: 11 US and 9 European institutions
(most of them are also AMANDA member institutions)
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Bartol Research Institute, University of Delaware
BUGH Wuppertal, Germany
Universite Libre de Bruxelles, Brussels, Belgium
CTSPS, Clark-Atlanta University, Atlanta USA
DESY-Zeuthen, Zeuthen, Germany
Institute for Advanced Study, Princeton, USA
Dept. of Technology, Kalmar University, Kalmar, Sweden
Lawrence Berkeley National Laboratory, Berkeley, USA
Department of Physics, Southern University and A\&M College, Baton Rouge, LA, USA
Dept. of Physics, UC Berkeley, USA
Institute of Physics, University of Mainz, Mainz, Germany
Dept. of Physics, University of Maryland, USA
University of Mons-Hainaut, Mons, Belgium
Dept. of Physics and Astronomy, University of Pennsylvania, Philadelphia, USA
Dept. of Astronomy, Dept. of Physics, SSEC, PSL, University of Wisconsin, Madison, USA
Physics Department, University of Wisconsin, River Falls, USA
Division of High Energy Physics, Uppsala University, Uppsala, Sweden
Fysikum, Stockholm University, Stockholm, Sweden
University of Alabama, Tuscelosa, USA
Vrije Universiteit Brussel, Brussel, Belgium
IceCube
IceTop
80 Strings
4800 PMT
Instrumented
volume: 1 km3 (1 Gt)
IceCube is designed
to detect neutrinos of
all flavors at energies1400 m
from 107 eV (SN) to
1020 eV
Motivation: weakly
interacting n can
emerge from deep
inside a source
Need BIG detector 2400 m
AMANDA
South Pole
Skiway
Muon Events
Eµ= 6 PeV
Eµ= 10 TeV
Measure energy by counting the number of fired PMT.
(This is a very simple but robust method)
Future prospects
The IceCube neutrino telescope--goals:
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Find high-energy neutrinos: unique probes of
cosmic accelerators--see brochures
Measure primary cosmic rays to > billion mc2
with a three-dimensional air shower detector
A multi-year project (10-15 years)
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Many high-level reviews passed
First year funding in NSF plan for current year
We are working hard to make this happen
South Pole Air Shower Experiment
Sunset, March 21,
2002
Photo of electronics
tower by Katherine
Rawlins