Updates from the Tunka Valley. Mark Stockham KU HEP Seminar 4/25/2012

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1 Updates from the Tunka Valley Mark Stockham KU HEP Seminar 4/25/2012

2 Overview TUNKA Collaboration Paper Methods of reconstruction Results of reconstruction Energy Spectrum KU efforts Current state: angle of incidence reconstruction The future 2 /23

3 TUNKA - Refresher Combined PMT/Radio Antenna CR detector array Came online as Tunka-13 circa 1992 Located Southwest of Lake Baikal, conveniently surrounded by mountains Has slowly expanded, now up to Tunka-133, ~1km 2 KU installed radio antennas in Summer '08 Expanded from 2 to 6 RF channels in Summer '10 3 /23

4 Results Paper The collaboration put up the most recent results paper on the arxiv in January 4 /23

5 Reconstruction Use the light flux density at core distance 175m This relates to the primary energy E 0 =C Q The exponent is 0.95 for pure proton composition and 0.91 for pure iron (CORSIKA sim) g 175 Value used in reconstruction is g = 0.93 Note: absolute sensitivity and atmospheric opacity are needed, but can be avoided by normalizing integrated energy spectrum to a reference, here QUEST 5 /23

6 Ne/E0 vs. P Strong correlation between size to primary energy ratio and the steepness of the lateral distribution, P Independent of primary particle mass as well as hadronic interaction model used in CORSIKA Measure N and P to get E e 0 6 /23

7 Reconstruction of Xmax, LDF and WDF Lateral Distribution Function (LDF), fitting a single variable steepness, P gives H max H max = A B P Holds for all energies, zenith angles, primary masses, and models of nuclear interactions Width-Distance Function (WDF) τ=s /(1.24 A max ) Calculate effective pulse width, Use WDF to get effective width at 400m, Xmax given by Δ X max =C D log ( τ 400 ), τ 400 Δ X max = X 0 /cos(θ) X max 7 /23

8 Xmax from LDF ( ( H0 X max cos(θ) H max = 1 X0 cos(θ) ) ) 8 /23

9 Xmax from WDF 9 /23

10 Results! Xmax vs. E0 from LDF and WDF 10 /23

11 Mean Atomic Weight vs. E0 Can recalculate <ln A> from <Xmax> 11 /23

12 All Particle Energy Spectrum 12 /23

13 What KU is Working On Timing delays between RF channels to look for correlation with incident angle reconstructed from the PMT pairs Requires pulse detection cross-correlation to find maximum likelihood of timing offset Trigonometry to find two possible incident angles The true angle will preferentially stack up while the false angle is different for every timing delay Dr. Besson group working on this now DZB/Jeremy Ims responsible for progress so far 13 /23

14 Example Angle Reconstruction 14 /23

15 Example Angle Reconstruction 15 /23

16 Stability With Respect to Source r, z 16 /23

17 17 /23

18 Timing Correlation of the 2 RF Channels Much better than correlation with PMTs perhaps RF events are not the actual CR signal 18 /23

19 Bad Events Display Stronger Correlation 19 /23

20 Good vs. Bad (data) 20 /23

21 Examples of Bad RF Signals 21 /23

22 Future Plans Install pulser at Tunka to get exact timing difference between channels Distances are currently crudely measured, cable delay estimated Will output in both CW (at 2 simultaneous freq.) and pulse modes German collaborators are installing RF antennas More timing correlation studies 22 /23

23 Thanks For Your Time Questions? Sources The Tunka-133 EAS Cherenkov light array: status of 2011 (arxiv) DZB, unpublished manuscript Jeremy Ims, reconstruction code 23 /23