Cosmic Ray Composition with SPASE and AMANDA (SP/AM)

1. Cosmic Ray Composition with SPASE and AMANDA (SP/AM) By Karen Andeen

2. Outline • History of Cosmic Rays • Cosmic Rays in Physics • Composition with SPASE/AMANDA • Composition with IceCube/IceTop Karen Andeen, SPASE/AMANDA Collaboration

3. What are Cosmic Rays? • According to NASA, “Cosmic Rays are particles that bombard the Earth from anywhere beyond its atmosphere”. • Though it sounds simple, this definition was a long time in coming… Karen Andeen, SPASE/AMANDA Collaboration

4. First… • Someone had to figure out the electroscope. • Then, they had to make an acute observation about the foils. Karen Andeen, SPASE/AMANDA Collaboration

5. Next… In 1912, Hess went up in a balloon to check and see what was happening… he discovered that CRs were coming from outside the atmosphere, not the surface of the earth. Karen Andeen, SPASE/AMANDA Collaboration

6. …Many Hot Debates Were Had. 1932: According to Robert Millikan, Cosmic Rays were gamma rays from space – he gave them their name, in fact. But evidence from Compton, as well as others, was pointing to Cosmic Rays being mostly energetic particles, instead. Reference: Pierre Auger Observatory Webpage Karen Andeen, SPASE/AMANDA Collaboration

7. 94 years later we have… Reference: EUSO webpage Karen Andeen, SPASE/AMANDA Collaboration

8. Outline • History of Cosmic Rays • Cosmic Rays in Physics • Composition with SPASE/AMANDA • Future Projects Karen Andeen, SPASE/AMANDA Collaboration

9. So what is it… • Cosmic Ray Spectrum • Flux (or # of CRs passing through a surface) at different energies from 109 eV to 1021 eV • Well established up to high energies • “Knee" appears as a turn in the slope of the line of data points around 106 GeV. Reference: a talk by Albrecht Karle, who got it from a talk by Tom Gaisser Karen Andeen, SPASE/AMANDA Collaboration

10. …and why do we care? • Can’t make particles of these energies on earth (yet), would like to know what can…particularly interested in: • Origin • Acceleration • Propagation • The CR Spectrum is important because it constrains our theories: they must account for this spectrum. Karen Andeen, SPASE/AMANDA Collaboration

11. “below” the Knee…(i.e. the Thigh) to 3 PeV, 1st Order Fermi Acceleration from SNR shock fronts • Explains the observed power law spectrum (E-2.7) • Gives the CRs the chemical abundances which are similar to observed cosmic abundances of the elements • The total energy available to accelerate the CRs is consistent with the observed CR energy density • Can use direct measurements of particles using balloons and satellites. Karen Andeen, SPASE/AMANDA Collaboration

12. What do Shock Fronts Look Like?(An excuse to throw in a cool picture: The Rotten Egg Nebula) Rotten Egg Nebula, courtesy of NASA Karen Andeen, SPASE/AMANDA Collaboration

13. The knee and above! Above 105 GeV/nucleon, SNRs can no longer accelerate particles up to these energies: • Previously accelerated particles encounter another longer-lived shock. Could accelerate to 1020 eV • Supernovae extending into unusual interstellar environments • New Sources of CRs: GRBs, black holes, neutron stars and pulsars, binary systems, or extra-galactic Each Theory suggests a different composition, thus a composition study is necessary… Karen Andeen, SPASE/AMANDA Collaboration

14. What’s needed for Composition without direct measurements? • Extensive Air Showers produced when CRs hit the atmosphere: • Hadronic Component • Electromagnetic Component • Combining two parts can give an accurate composition analysis… Karen Andeen, SPASE/AMANDA Collaboration

15. Extensive Air Showers Cosmic rays hit the atmosphere (most likely smashing into nitrogen) and produce many particles: p + N14  π0  γ + γ  e+ + e-  π+/-  µ+/- + υµ Reference: University of Adelaide Astrophysics webpage Karen Andeen, SPASE/AMANDA Collaboration 6

16. Previous Results Some reference #s lnAiron = 4.022 lnAoxygen= 2.772 lnAcarbon= 2.4857 lnAhelium= 1.386 lnAhydrogen= 0 Reference: Hoerandel, Overview on Direct and Indirect Measurements of Cosmic Rays (2005) Karen Andeen, SPASE/AMANDA Collaboration

17. Expected Composition in Various Theories • Acceleration due to SNRs • Acceleration in GRBs • c) Diffusion in Galaxy • d) Propagation Models • as well as interaction • with background • neutrinos and photons Reference: Hoerandel, Overview on Direct and Indirect Measurements of Cosmic Rays (2005) Karen Andeen, SPASE/AMANDA Collaboration

18. Outline • History of Cosmic Rays • Cosmic Rays in Physics • Composition with SPASE/AMANDA • Future Projects Karen Andeen, SPASE/AMANDA Collaboration

19. How we do the Composition Study First, we need funding for a detector and the detector to be built Second, we need a Monte Carlo simulation Next, we need a well-understood Data set Then we combine them all to see what we get. Karen Andeen, SPASE/AMANDA Collaboration

20. Our Detectors We have the perfect site and two detectors • SPASE is the surface array and measures the electromagnetic component • AMANDA is the in-ice array and sees the muonic component Karen Andeen, SPASE/AMANDA Collaboration

21. ANTARTICA Amundsen-Scott South Pole Station IceCube South Pole Dome road to work To SPASE AMANDA Summer camp 1500 m Karen Andeen, SPASE/AMANDA Collaboration 2000 m [not to scale]

22. SPASE 12° x=-114.67m y=-346.12m z=1727.91m AMANDA A Blurry but Pertinent View Karen Andeen, SPASE/AMANDA Collaboration

23. The Surface Array: The South Pole Air Shower Experiment • Completed in 1996 • 30 Stations, 30 m triangular grid • 4 scintillators per station (.2 m2 each) • Reconstructs shower direction from • arrival times of charged particles in • its scintillators. Error depends on • shower size…larger = better 10mm plastic scintillator 320 mm Wooden box Lucite Prism 170 mm Karen Andeen, SPASE/AMANDA Collaboration

24. Illustration of an air shower hitting SPASE Timing of shower arrival at stations gives zenith and azimuth angles as well as shower core position. Reference: Pierre Auger Observatory Colloquium by Jim Matthews Karen Andeen, SPASE/AMANDA Collaboration

25. A Better Illustration… Reference: Pierre Auger Observatory Colloquium by Jim Matthews Karen Andeen, SPASE/AMANDA Collaboration

26. Antarctic Muon andNeutrino Detector Array AMANDA-A (1996) • AMANDA-B10 (1997-1999) • 302 OMs on 10 strings • Ø 120m, 500m tall AMANDA-II (2000 – 200x) • 677 OMs on 19 strings • Ø 200m, 500m tall Karen Andeen, SPASE/AMANDA Collaboration

27. Cherenkov Light β Muons emit Cherenkov radiation as they travel faster than the speed of light in ice. ~ Karen Andeen, SPASE/AMANDA Collaboration

28. What do OMs do? The OMs contain the photomultiplier tubes (PMT) which detect the Cherenkov light emitted by particles that pass through the ice. Karen Andeen, SPASE/AMANDA Collaboration 13

29. Why else do we think our detectors are so cool? We’re at the perfect altitude, which allows for great energy resolution References: (top) Atkins et al, Atmospheric Cherenkov Detectors at Milagro, (bottom) Ralph Engel Karen Andeen, SPASE/AMANDA Collaboration

30. Extensive Air Showers Cosmic rays hit the atmosphere (most likely smashing into nitrogen) and produce many particles: p + N14  π0  γ + γ  e+ + e-  π+/-  µ+/- + υµ Reference: University of Adelaide Astrophysics webpage Karen Andeen, SPASE/AMANDA Collaboration 6

31. How we do the Composition Study First, we need funding for a detector and the detector to be built Second, we need a Monte Carlo Simulation Next, we need a well-understood Data Set Then we combine them all. Karen Andeen, SPASE/AMANDA Collaboration

32. How we do the Composition Study First, we need funding for a detector and the detector to be built Second, we need a Monte Carlo Simulation Next, we need a well-understood Data Set Then we combine them all. Karen Andeen, SPASE/AMANDA Collaboration

33. How we do the Composition Study First, we need funding for a detector and the detector to be built Second, we need a Monte Carlo Simulation Next, we need a well-understood Data Set Then we combine them all. Karen Andeen, SPASE/AMANDA Collaboration

34. How we do the Composition Study First, we need funding for a detector and the detector to be built Second, we need a Monte Carlo Simulation Next, we need a well-understood Data Set Then we combine them all. Karen Andeen, SPASE/AMANDA Collaboration

35. Electrons and Muons: S30 and K50 • We want to look variables associated with the number of muons and the number of electrons • SPASE has S30 (electron density at 30m from the core of the shower), AMANDA has K50 (muon density at 50m from the core of the shower). • Why 30? A good approximation of energy, though NOT composition independent. • Why 50? A good approximation of the number of muons. Karen Andeen, SPASE/AMANDA Collaboration

36. Quality Cuts Quality cuts are cuts that select the events that will be well reconstructed. • SPASE Cuts • Distance from the center of SPASE < 60m • S30>5 particles/m2 • AMANDA Cuts • Cylinder Size <1 • Reconstructed attenuation length of light in ice < 100 m. Karen Andeen, SPASE/AMANDA Collaboration

37. The Radius Cut Why necessary? • If core falls outside the area of the surface detector my S30 energy estimator is frequently mis-reconstructed • Cut removes all those events Karen Andeen, SPASE/AMANDA Collaboration

38. Why S30? • S30 is always estimated prior to fitting. If the estimate is < 5 particles/m2, the event is deemed useless and is not reconstructed • However, we did not want to throw away events, so they get tossed into the S30 bin where they were estimated to lie • But most of them were never actually reconstructed • We cut them out now Karen Andeen, SPASE/AMANDA Collaboration

39. What is Cylinder Size? • An AMANDA variable • Events fall outside physical volume of AMANDA • These events can be reconstructed, depending on the amount of light they produce, but are not well reconstructed • Cylinder Size = 1 requires the event to pass through the physical volume of AMANDA Cylinder of closest approach AMANDA detector Track Karen Andeen, SPASE/AMANDA Collaboration

40. So what do the cuts leave us with? Two options: 1) Rotate to new coords, shift to real energy instead of E*, and find <lnA>, or 2) Make a neural network to find the transformation for you, and find <lnA>. Karen Andeen, SPASE/AMANDA Collaboration

41. NN Output Karen Andeen, SPASE/AMANDA Collaboration

42. Have a look at results Preliminary Karen Andeen, SPASE/AMANDA Collaboration

43. Coming soon… • New Monte Carlo: • Corsika generated showers • Geant 4 simulation of SPASE detector • Many more particles (H, He, O, C, Fe) • IceCube/IceTop Karen Andeen, SPASE/AMANDA Collaboration

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46. Karen Andeen, SPASE/AMANDA Collaboration

47. Why is this new detector even cooler than the last one? • Nm from IceCube; Ne from IceTop • High altitude allows good energy resolution • Good mass separation from Nm/Ne • 1/3 km2 sr (2000 x SPASE-AMANDA) • Covers sub-PeV to EeV energies Reference: Ralph Engel Karen Andeen, SPASE/AMANDA Collaboration

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