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

Karen Andeen, SPASE/AMANDA Collaboration 2/46 Outline History of Cosmic Rays Cosmic Rays in Physics Composition with SPASE/AMANDA Composition with IceCube/IceTop

Karen Andeen, SPASE/AMANDA Collaboration 3/46 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 4/46 First… Someone had to figure out the electroscope. Then, they had to make an acute observation about the foils.

Karen Andeen, SPASE/AMANDA Collaboration 5/46 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 6/46 …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 7/46 94 years later we have… Reference: EUSO webpage

Karen Andeen, SPASE/AMANDA Collaboration 8/46 Outline History of Cosmic Rays Cosmic Rays in Physics Composition with SPASE/AMANDA Future Projects

Karen Andeen, SPASE/AMANDA Collaboration 9/46 So what is it… Cosmic Ray Spectrum Flux (or # of CRs passing through a surface) at different energies from 10 9 eV to eV Well established up to high energies “Knee" appears as a turn in the slope of the line of data points around 10 6 GeV. Reference: a talk by Albrecht Karle, who got it from a talk by Tom Gaisser

Karen Andeen, SPASE/AMANDA Collaboration 10/46 …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 11/46 “below” the Knee…(i.e. the Thigh) to 3 PeV, 1 st 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 12/46 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 13/46 The knee and above! Above 10 5 GeV/nucleon, SNRs can no longer accelerate particles up to these energies: –Previously accelerated particles encounter another longer-lived shock. Could accelerate to 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 14/46 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 15/46 Cosmic rays hit the atmosphere (most likely smashing into nitrogen) and produce many particles: p + N 14  π 0  γ + γ  e + + e -  π +/-  µ +/- + υ µ 6 Reference: University of Adelaide Astrophysics webpage Extensive Air Showers

Karen Andeen, SPASE/AMANDA Collaboration 16/46 Previous Results Some reference #s lnA iron = lnA oxygen = lnA carbon = lnA helium = lnA hydrogen = 0 Reference: Hoerandel, Overview on Direct and Indirect Measurements of Cosmic Rays (2005)

Karen Andeen, SPASE/AMANDA Collaboration 17/46 Expected Composition in Various Theories a)Acceleration due to SNRs b)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 18/46 Outline History of Cosmic Rays Cosmic Rays in Physics Composition with SPASE/AMANDA Future Projects

Karen Andeen, SPASE/AMANDA Collaboration 19/46 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 20/46 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 21/46 Amundsen-Scott South Pole Station South Pole Dome Summer camp AMANDA road to work 1500 m 2000 m [not to scale] IceCube ANTARTICA To SPASE

Karen Andeen, SPASE/AMANDA Collaboration 22/46 A Blurry but Pertinent View 12° SPASE AMANDA x= m y= m z= m

Karen Andeen, SPASE/AMANDA Collaboration 23/46 The Surface Array: The South Pole Air Shower Experiment Completed in Stations, 30 m triangular grid 4 scintillators per station (.2 m 2 each) Reconstructs shower direction from arrival times of charged particles in its scintillators. Error depends on shower size…larger = better 320 mm Wooden box 10mm plastic scintillator Lucite Prism 170 mm

Karen Andeen, SPASE/AMANDA Collaboration 24/46 Reference: Pierre Auger Observatory Colloquium by Jim Matthews Timing of shower arrival at stations gives zenith and azimuth angles as well as shower core position. Illustration of an air shower hitting SPASE

Karen Andeen, SPASE/AMANDA Collaboration 25/46 Reference: Pierre Auger Observatory Colloquium by Jim Matthews A Better Illustration…

Karen Andeen, SPASE/AMANDA Collaboration 26/46 Antarctic Muon and Neutrino Detector Array AMANDA-B10 ( ) 302 OMs on 10 strings Ø 120m, 500m tall AMANDA-A (1996) AMANDA-II (2000 – 200x) 677 OMs on 19 strings Ø 200m, 500m tall

Karen Andeen, SPASE/AMANDA Collaboration 27/46 Cherenkov Light β ~ Muons emit Cherenkov radiation as they travel faster than the speed of light in ice.

Karen Andeen, SPASE/AMANDA Collaboration 28/46 What do OMs do? The OMs contain the photomultiplier tubes (PMT) which detect the Cherenkov light emitted by particles that pass through the ice. 13

Karen Andeen, SPASE/AMANDA Collaboration 29/46 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 30/46 Cosmic rays hit the atmosphere (most likely smashing into nitrogen) and produce many particles: p + N 14  π 0  γ + γ  e + + e -  π +/-  µ +/- + υ µ 6 Reference: University of Adelaide Astrophysics webpage Extensive Air Showers

Karen Andeen, SPASE/AMANDA Collaboration 31/46 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 32/46 Monte Carlo MOCCA generated air showers, including iron and proton, with energies from ~10 13 to eV Arrival times and densities computed for each scintillator, noise hits added HE Muons are propagated to depth of AMANDA AMANDA detector simulated using AMASIM Output is in same format and follows same processing chain as data…

Karen Andeen, SPASE/AMANDA Collaboration 33/46 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 34/46 SPASE/AMANDA Data Every SPASE trigger sends signal to AMANDA. AMANDA collects any hits within a certain time window and tags the event as SPASE-triggered for off-line separation Processed offline

Karen Andeen, SPASE/AMANDA Collaboration 35/46 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 36/46 Post-DataCollecting/MC Generating All events are now in f2k format, be they MC or data All are reconstructed independently using both AMANDA and SPASE reconstruction Then matching and calibration happens and we make a combined fit: use the (x,y,z) for the shower core from SPASE as input, and vary θ and φ in AMANDA…this fits with great accuracy

Karen Andeen, SPASE/AMANDA Collaboration 37/46 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 38/46 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 39/46 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/m 2 AMANDA Cuts –Cylinder Size <1 –Reconstructed attenuation length of light in ice < 100 m.

Karen Andeen, SPASE/AMANDA Collaboration 40/46 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 41/46 Why S30? S30 is always estimated prior to fitting. If the estimate is < 5 particles/m 2, 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 42/46 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 AMANDA detector Cylinder of closest approach Track

Karen Andeen, SPASE/AMANDA Collaboration 43/46 So what do the cuts leave us with? Two options: 1) Rotate to new coords, shift to real energy instead of E*, and find, or 2) Make a neural network to find the transformation for you, and find.

Karen Andeen, SPASE/AMANDA Collaboration 44/46 NN Output

Karen Andeen, SPASE/AMANDA Collaboration 45/46 Have a look at results Preliminary

Karen Andeen, SPASE/AMANDA Collaboration 46/46 Coming soon… New Monte Carlo: –Corsika generated showers –Geant 4 simulation of SPASE detector –Many more particles (H, He, O, C, Fe) IceCube/IceTop

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Karen Andeen, SPASE/AMANDA Collaboration 48/46 Various Types of Experiments Depending on Energy Satellites and balloons (i.e. direct measurements): only up to ~ eV Ground-based Detectors: –Scintillators: primarily for EM component, but if shielded with lead can be used for muons –Air Cherenkov telescopes: detect Cherenkov light from charged particles in the atmosphere –Ionization Chambers: detect charged particles –Atmospheric Flourescence Detectors: flourescence emission from N 2 molecules excited by the air shower –Water/Ice Cherenkov Telescopes: Cherenkov light from muons in ice or water

Karen Andeen, SPASE/AMANDA Collaboration 49/46 Inconclusive Previous Results with old SPASE/AMANDA Results Reference: Rawlins, Measuring the Composition of Cosmic Rays With the SPASE and AMANDA Detectors, 2002

Karen Andeen, SPASE/AMANDA Collaboration 50/46 Photomultiplier Tubes Each OM contains a PMT, wherein: A Cherenkov photon hits collecting plate and emits a photoelectron Photoelectron hits first dynode, which emits multiple e - for each received Signal is amplified as it hits each dynode Total amplification: –~109 for AMANDA – ~107 for IceCube Photon Dynode Photoelectron

Karen Andeen, SPASE/AMANDA Collaboration 51/46 Shower Max X max is the location of the shower maximum B is a model-dependent fudge factor X 0 is the radiation length (thickness over which an electron loses 1/(1-e) of its energy by bremsstrahlung Epsilon is the critical energy (at which bremsstrahlung losses dominate over ionization) A is atomic mass, E is energy

SPASE-II - AMANDA B10 : Energy resolution of air shower primary Energy resolution of air shower primary for 1<E/PeV<10: σ E ≈ 7% log(E) (Mass independent; based on MC)

Karen Andeen, SPASE/AMANDA Collaboration 53/46 Outline History of Cosmic Rays Cosmic Rays in Physics The SPASE/AMANDA detectors Future Projects

Karen Andeen, SPASE/AMANDA Collaboration 54/46 More about S30 and K50 K50 is basically a measure of the number of Muons in the shower. S30 is basically a measure of energy of the shower primary, though NOT composition independent. Iron Protons

Karen Andeen, SPASE/AMANDA Collaboration 55/46 Theoretically, we can combine Together, K50 and S30 ought to give us a good composition and energy approximation. If we can only figure out how…

Karen Andeen, SPASE/AMANDA Collaboration 56/46 Why 50m? OMs actually participating in the fit lie between 50 and 120 meters Far distances from the track are good because relative distance errors are smaller Too close and you get saturation issues 50m was the most stable compromise

Karen Andeen, SPASE/AMANDA Collaboration 57/46 Our All Important Variables No cuts have been made for these plots. Logically it will make sense to make some cuts before we use them.

Karen Andeen, SPASE/AMANDA Collaboration 58/46 Effect of Radius Cut Radius cut has been made… Can you see the difference? It’s in the tails…

Karen Andeen, SPASE/AMANDA Collaboration 59/46 Effect of S30 Cut Radius cut and S30 cut have been made…you can see that the bins with log 10 S30 <.7 have been removed.

Karen Andeen, SPASE/AMANDA Collaboration 60/46 Effect of Cylinder Size Cut All three cuts have now been applied.

Karen Andeen, SPASE/AMANDA Collaboration 61/46 Cuts give good correspondence between MC and DATA!

Karen Andeen, SPASE/AMANDA Collaboration 62/46 Compare!!!!

Karen Andeen, SPASE/AMANDA Collaboration 63/46 Outline History of Cosmic Rays Cosmic Rays in Physics The SPASE/AMANDA detectors What I’ve Accomplished so far Future Project 1) Plot log10(S30) vs log10(K50) overlaid with energy gradient 2) Approximate energy gradient with lines and rotate axes to E* and A* 3) Plot E* against Energy to find a relationship 4) Plot log(Energy) vs ln for my 2003 data. Need to find proper iron/proton mixture to do this 5) (next slide) Compare!!!

Karen Andeen, SPASE/AMANDA Collaboration 64/46 IceCube In-Ice Array: Number of strings:80 (9) Optical Sensors:4800 (540) Depth: m Instr. Volume:0.9 km 3 Angular Resolution:0.6° Construction: (status February 2006)

Karen Andeen, SPASE/AMANDA Collaboration 65/ (32) tanks (2 per in-ice string) 2 DOMs per tank Total 320 DOMs (64) Note: This is ice, not water! Surface Array: IceTop

Karen Andeen, SPASE/AMANDA Collaboration 66/46 Remember this Plot? The below plot you’ve seen before. The one on the right says that at higher energies we have even better resolution!

Karen Andeen, SPASE/AMANDA Collaboration 67/46 Thesis Topic An IceCube/IceTop analysis using 2006 (and maybe 2007) data. This would enable us to look at cosmic rays of much higher energies. In 2007, we are hoping for more strings in the ice for a total of 20-22, as well as many more surface modules.

Karen Andeen, SPASE/AMANDA Collaboration 68/46 Fermi Acceleration Reference: Longair

Karen Andeen, SPASE/AMANDA Collaboration 69/46 Acknowledgements Thanks to Albrecht Karle, Katherine Rawlins, Chihwa Song and all the SPASE people at Bartol for their assistance and advice on this project. Thanks also to my prelim committee for agreeing to help. Thanks to my many friends and family for being there for me when work drives me nuts!

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Karen Andeen, SPASE/AMANDA Collaboration 72/46 Why is this new detector even cooler than the last one? N  from IceCube; N e from IceTop High altitude allows good energy resolution Good mass separation from N  /N e 1/3 km 2 sr (2000 x SPASE-AMANDA) Covers sub-PeV to EeV energies Reference: Ralph Engel

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Karen Andeen, SPASE/AMANDA Collaboration 80/46 Below are Extra Slides

Karen Andeen, SPASE/AMANDA Collaboration 81/46 SPASE/AMANDA ➢ Unique Coincidence between SP/AM ➢ SPASE provides Accurate Shower Position and Direction ➢ Use to measure Energy and Mass of C.R. Primary ➢ AMANDA Calibration 12° SPASE AMANDA x= m y= m z= m

Karen Andeen, SPASE/AMANDA Collaboration 82/46 How you get an E -2 spectrum ? Particles experience Fermi acceleration E= k E o N=P k N o dN/dE ~ E -1 and = ln P / ln After derivation, = -1 dN/dE ~ E -2 E o = Initial energy N o = Number of particles with energy E o P = Probability of crossing shock k = Number of times that the shock is crossed Reference frame.... of the shock of the downstream material of the upstream material v 2 =(1/4)v 1 v 1 = |U| (3/ 4) U The particle gains the same amount of energy every time it crosses the shock, regardless of which direction it is crossing. 8 Reference: Longair (1994)

Karen Andeen, SPASE/AMANDA Collaboration 83/46 Why do we need both? Without both we could not distinguish…Heavier particles are predicted to have more predominant hadronic components than lighter particles. A plot of hadronic particle density in ice vs EM particle density at surface would generally be expected to look like: Heavier particles Lighter Particles EM particle density at surface Hadronic particle density in ice

Karen Andeen, SPASE/AMANDA Collaboration 84/46 main board LED flasher board PMT base 25 cm PMT 33 cm Benthosphere

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