mp bach multipixel balloon-borne air cherenkov detection of iron cosmic rays using direct cherenkov...
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MP BACH MultiPixel Balloon-borne Air CHerenkov
Detection of Iron Cosmic Rays Using Direct Cherenkov Radiation Imaged with a High
Resolution Camera
University of DelawarePaul Evenson, John Clem, Jamie Holder, Katie Mulrey and Dave Seckel
Energy spectrum of Iron cosmic rays multiplied by E2.5 from different observations. JACEE and RUNJOB, emulsion instruments, are a compilation of many balloon flights. CRN was conducted on the space shuttle. CREAM, ATTC and TRACER are balloon payloads flown from Antarctica and Sweden. BACH payload was flown from Ft Sumner. Sood pioneered the BACH technique. KASKADE (two different interaction models) and EAS-TOP (upper and lower limits) are air shower data. HESS data (two different interaction models) are ground level observations of Cerenkov light imaging.
Current knowledge of the iron spectrum
As the particle penetrates into denser air, the Cherenkov angle and intensity increase.
First photons are emitted just on the axis defined by the particle path, but subsequent photons lie further and further from the axis when they reach any given depth in the atmosphere forming a circular spot or “pool” of light .
This trend continues until the particle is roughly two scale heights (15 km) above an observer, when proximity finally wins out.
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CORSIKA Simulation
• Simulates detailed particle propagation and generates CK photons in the atmosphere
εc is the CK emission vector as viewed from Camera 1 and 2
z
y
xθφ
(xo,yo) (x1,0)(x2,0)
θcL
Path
lengt
h to
emiss
ion
poin
t
Sεcb
θcH
εca
Intersection of Plane C1 and C2 forms a line that lies along the particle trajectorycross product of these two normal C1 and C2 vectors gives a vector which is perpendicular to both of them and which is therefore parallel to the line of intersection of the two planes. So this cross product will give a direction vector for the line of intersection.
Set z=0 and solve for x and y
With only the DCs, reconstruct trajectory
Camera 1 event plane
Camera 2 event plane
Directional cosine observations from the camera and camera location on the gondola
z
y
xθφ
(xo,yo) (x1,0)(x2,0)
θc
Path
lengt
h to
emiss
ion
poin
t
Particle trajectory passes through the x,y plane at location xo,yoThe particle incident angle with respect to z is θ and φ is the polar θc = Cerenkov angle which is a function of z (air density)S is the trajectory straight path-length from the x-y plane intersection to the CK emission point as viewed by camera 1
εc is the CK emission vector as viewed from Camera 1 y
x
Camera 2 Camera 1
z
x1
No Magnetic Field
It can be shown that S is related to the other quantities asS
εc
If the steepening at the cosmic ray knee is caused by a magnetic rigidity dependent mechanism, as a result of an acceleration process limited in a rigidity dependent manner or rigidity dependent propagation, there should be systematic changes in the cosmic ray composition through this region.
It is difficult to see how SN could accelerate protons to energies much beyond ~1015eV/particle. Heavier cosmic rays, for example iron nuclei, could reach energies over an order of magnitude higher than this via the same mechanism.
The objective of this project is to improve our knowledge of the Iron Flux from 5x103 to 3x106GeV
z
y
xθφ
(xo,yo) (x1,0)(x2,0)
θcL
Path
lengt
h to
emiss
ion
poin
t
Sεcb
θcH
εca
Explicitly determine the relationship for the x,y crossing point at z=0
Directional cosine observations from the camera and camera location on the gondola
The trajectory vector S has been determine and is then used to calculate the Cerenkov angle at each intersection point
The index of refraction at each intersection altitude point must be determined to calculate the energy
z
y
xθφ
(xo,yo) (x1,0)(x2,0)
θcb
Path
lengt
h to
emiss
ion
poin
t
Sεcb
θca
εca
Results The calculated energy uses only the directional cosines, camera location and atmospheric model
z
y
xθφ
(xo,yo) (x1,0)(x2,0)
Camera 1 Image Camera 2 Image
Example MPBACH Simulated Event Cartoon
degrees
degr
ees
degrees
degr
ees
Non-interacting Vertical Iron, 1PeV
Cherenkov Light Distribution from Interacting and Non-Interacting Primaries
Cherenkov Total Light Output, 1PeV
Peaks indicate the non-interaction events
FeSiOHeH
Altit
ude
(km
)
Distance from Axis (m)
35km
75km
8-8 0
As the particle penetrates into denser air, the Cherenkov angle and intensity increase.
First photons are emitted just on the axis defined by the particle path, but subsequent photons lie further and further from the axis when they reach any given depth in the atmosphere forming a circular spot or “pool” of light .
This trend continues until the particle is roughly two scale heights (15 km) above an observer, when proximity finally wins out.