Current Data from CHICOS Elina Brobeck

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Current Data from CHICOSElina Brobeck
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Energy Spectrum
Sun
CHIQUITA showers (Caltech Array)
Supernovae
Single particle hits in CHICOS detectors (200
per sec.)
CHICOS showers (San Gabriel and San
Fernando Arrays)
AGN, GRBs, etc. ?
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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 800 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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Parameters of a cosmic ray airshower
Incoming Path
Spread in Shower Front
Curvature Delay
Particle Intensity
Arrival Time Delay
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CHICOS Lateral Distribution
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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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Time Delay and Time Spread

• The arrival time is the curvature delay plus the
  time spread due to the width of the front
• T(r) Td(r) Ts(r,r)

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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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CHICOS LDF Simulations
E 1019.5 eV
Particle density is 100/m2 at 600 m from the
core.
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Reconstructing an Airshower

• Input the data location (x,y,z), time (t), and
  intensity (r) for each hit.

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Reconstructing an Airshower

• Estimate the core location as 200 m from the
  trigger site.

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Reconstructing an Airshower

• Estimate incoming angle from the hit time at each
  location.
• Estimate the energy of the original particle from
  the hit intensities.

trajectory of primary particle
time delay
estimated shower plane
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Reconstructing an Airshower

• Fit core location and energy together by
  performing a c2 minimization on the intensities
  given by the LDF.

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CHIQUITA Detector Array
PCC
CIT 4001
CIT 2001
Caltech 03
CIT 1001 Array
CIT 3001
Polytechnic
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CHIQUITA Data (300 events)
logE (eV)
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CHIQUITA Aperture (m2 sr)
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CHIQUITA Energy Spectrum
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CHIQUITA Simulations Iron
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Future work High-E Spectrum
11 super-GZK events observed by AGASA
CHICOS will measure a similar number of events
over 3 year period
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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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Shower data Trigger Westridge
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Angle
Energy
Reconstruction Log10E 18.31/- 0.6
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Anisotropy at E 1018 eV
AGASA
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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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Hillas Diagram Astrophysical Sources of UHECR
protons
Neutron Stars
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White Dwarfs
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1024 eV
1021 eV
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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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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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Estimates of CHICOS Angular Resolution
Angle errors on 10000 simulated showers.
Integral of angular resolution plot.