California HIgh school Cosmic ray ObServatory

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California HIgh school Cosmic ray ObServatory
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What are cosmic rays?

• Cosmic rays are charged particles (protons,
  electrons, atomic nuclei) or gamma rays
  (high-energy photons)

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Where do they come from?

• The sun is the primary source of low-energy
  cosmic rays
• Higher-energy cosmic rays come from other stars
  in the Milky Way, for example, supernovae
  (exploding stars).
• Ultra-high energy cosmic rays may come from other
  galaxies, in particular those with energetic
  centers housing supermassive black holes.

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Discovery of Cosmic Rays

• Ambient radiation had been detected in the
  atmosphere people speculated that it came from
  the ground.
• In 1911 Victor Hess measured cosmic rays with an
  electroscope from a hot air balloon.

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Discovery of Cosmic Rays

• Hess found that the flux of radiation increased
  with altitude it was coming from space!
• Awarded the Nobel prize in 1936.

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Energy Spectrum
Sun
Single particles (200 /m2/s)
CHIQUITA showers (Caltech Array)
Supernovae
CHICOS showers (San Gabriel and San
Fernando Arrays)
AGN, GRBs, etc. ?
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The GZK Cutoff 1020 eV
11 super-GZK events observed by AGASA
CHICOS will measure a similar number of events
over 3 year period
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Why do we expect the spectrum to end?
Ultra-high energy nuclei lose energy through
interaction with the Cosmic Microwave Background
p g
p p0
If we see UHECRs at the very highest energies
either they come from close by or they are not
made of what we think!
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The GZK Cutoff
p

• y average energy loss .2
• spg interaction x-section 0.1 mb
• ng number density of
• CMB photons 410 cm-3
• Att. length spgngy 12 Mpc

p0
p
An ultra-high energy cosmic ray proton can travel
for about 40 million light-years.
gCMB
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So where do UHECRs come from?
Entire observable universe 13 billion light
years across. We see most violent activity near
edges.
Andromeda 2.9 million light years away. Visible
with the naked eye.
Local supercluster of galaxies About 50 million
light years across.
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Cosmic Ray Airshower
Primary Particle (e.g., Iron Nucleus)
First Interaction
Pion Decay
Pion-Nucleus Interaction
Second Interaction
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CHICOS LDF Simulations
E 1018.5 eV
Particle density drops to lt1/m2 at 700 m from the
core.
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CHICOS LDF Simulations
E 1019.5 eV
Particle density drops to lt1/m2 at 1700 m from
the core.
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The CHICOS Detector Array
San Fernando Valley 27 sites active
San Gabriel Valley 31 sites active
Los Angeles Area 2 sites in progress others
interested
Total 59 active sites Plus 9 temporary
active sites at Caltech (the CHIQUITA array)
Goal 90 active sites in the CHICOS Array by 2005.
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CHIQUITA Detector Array
PCC
CIT 4001
CIT 2001
Caltech 03
CIT 1001 Array
CIT 3001
Polytechnic
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CHICOS Detectors in Schools

• Each school in the array has two detectors
  (shmoos) on the roof.
• We provide a computer which records the data and
  sends files to Caltech each day.
• A teacher contact in each school helps us keep
  the site running smoothly.

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CHICOS Detector Site Layout
Shmoo Design
PMT
Computer
CEU
light
Scintillator
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GPS Timing

• 24 GPS navigation satellites
• Minimum of 3 required for timing
• 50 ns. resolution

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CHICOS Data Collection
On site
At Caltech

• Triggers from all sites are combined into a
  master file.
• The trigger file is sent back to all sites in the
  array, which check for matching events in the A
  and B data.
• Match files are sent back to Caltech, and
  combined into time-ordered lists of nearly
  simultaneous events across the array.
• These lists are filtered to identify possible
  cosmic ray airshowers.

Detector A 200 hits/sec
Detector B 200 hits/sec
Coincidences 25 per minute
Triggers 0-5 per min
Caltech Master File
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Screen Capture of CHICOS software
Coincidences and Triggers
Single Hits
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Parameters of a cosmic ray airshower
Incoming Path
Spread in Shower Front
Curvature Delay
Particle Intensity
Arrival Time Delay
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Lateral Distribution Function

• The Lateral Distribution Function (LDF) describes
  the particle intensity r as a function of
  distance from the corer(r)
  C(r/RM)-a(1r/RM)-(h-a)1(r/1000)2d
• Where h 3.97-1.79 sec q a 1.2
  d 0.6for the fit to AGASA simulated
  air showers.

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Air Shower Development
Shower Maximum
AGASA (altitude 900 m)
CHICOS (altitude 225 m)
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Shower data Trigger Westridge
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Angle
Energy
Reconstruction Log10E 18.31/- 0.6
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Previous Results
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The Milky Way Galaxy
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Anisotropy at E 1018 eV
AGASA
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Hubble Deep Field
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AGASA Clustering Data
1 triplet
5 pairs
super-GZK events
Data set of 59 events with resolution 2.5
CHICOS will observe 100 events with resolution
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Indication of point sources of UHECRS?
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What kind of point sources?

• Charged particles are accelerated by electric and
  magnetic fields.
• A magnetic field makes the particle move in a
  circular shape until it is going fast enough to
  escape.

Radius of source R
Magnetic Field B
Charge Ze
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Hillas Diagram Astrophysical Sources of UHECR
protons
Neutron Stars
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White Dwarfs
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1024 eV
1021 eV
6
1018 eV
AGN
EMAX ZeBR
Log(B/Gauss)
Magnetic Stars
GRBs
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Sunspots
Blazar Jets
1015 eV
0
Radio Galaxy Lobes
Clusters of Galaxies
Supernovae
-3
Interstellar Medium
Galactic Disk
-6
Galactic Halo
Intergalactic Medium
-9
-4
1
Log(R/pc)
-14
-9
-6
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Begin Extra Slides
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CHICOS Hardware
CEU
High Voltage Supply
Photo- Multiplier Tube

• The shmoos were donated by Los Alamos National
  Laboratory.
• Other hardware is made and assembled at Caltech.

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Measuring the Energy

• The measured intensity is related to the LDF by a
  proportionality constantS(r)
  C(r/RM)-a(1r/RM)-(h-a)1(r/1000)2d
• The energy of the primary particle is related to
  the intensity measured 600 m from the core
• E0 2.03 x 1017 eV x S(600)1.0

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Time Delay and Time Spread

• The delay in arrival time due to the curvature of
  the shower front isTd(r) 2.6(1r/30)1.5 ns
• The time spread due to the width of the shower
  front isTs(r,r) 2.6(1r/30)1.5p(r)-0.5 ns

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Reconstruction Method

• Make initial estimates of x,y,z,t,E,q,f.
• Estimate direction of propagation by c2
  minimization of td(r) and ts(r).
• Estimate the energy by c2 minimization of
  intensities given by r(r).
• Simultaneously fit the core location and the
  energy with r(r).
• Repeat steps 2-4 until the fit converges, up to a
  maximum of 10 iterations.

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CHIQUITA Data (300 events)
logE (eV)
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CHIQUITA Aperture
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CHIQUITA Energy Spectrum
x10
x2.5
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Other UHECR flux measurements

• low statistics
• significant disagreement above 1020 eV
• CHICOS will fill in the upper energy range

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90 success rate for data transfer since March
2004
Network problems at Pasadena Unified School
District and LAUSD.
Upgrade Period
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Reconstruction of simulated showers E 5 x 1016
overestimated
within x2
underestimated
detector site
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Reconstructor Bias
Log E (eV)
Reconstructed energy vs. Input energy of
simulated showers
Overestimated at low energies
Underestimated at high energies
Log E (eV)
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CHIQUITA Energy Spectrum
Reconstructor bias accounts for the shallower
slope
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Flys Eye
AGASA
A100
A1
Haverah Park
SIBYLL
QGSJET
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Histograms of hit intensity (Ramona Elementary)
The peak corresponds to 1 vertical muon.
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Depth of first interaction
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Estimates of CHICOS Angular Resolution
Angle errors on 10000 simulated showers.
Integral of angular resolution plot.
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