1

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

PDQ BACHFort Sumner 1998

POD

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.

6

CORSIKA Simulation

• Simulates detailed particle propagation and generates CK photons in the atmosphere

7

Light Pool at 35 km Altitude

8

Idealized Detector Images, 500TeV Fe

Non-Interacting

Interacting

Camera locations in light pool

Cartoon Illustration of a MPBACH Event

10

Deflection in the Earth’s Magnetic Field

* Energy & Charge dependence *

A comparison of the compiled data with potential future observations

Extra slides

15

Pixilated Camera Image

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

The

taC

(de

gree

s)

Altitude (km)

Altitude (km)

Altitude (km)

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.