1. Cosmic Rays in ATLAS

2. Muon Trigger

3. Low Pt trigger Uses RPC’s allong BM, 2 doublets in eta and 2 in phi Algorithm runs in both projections 3 Pt cuts can be applied simultaneously by changing cone size 3/4 majority is needed Eta-phi is combined to create Region of Interest (RoI) 0.1*0.1 High Pt trigger = Low Pt trigger + (1/2 majority) RPC in BO

5. What do we learn from Fribourg (McPherson): 100 Hz muons pass LV1 trigger (full simulation) I don’t know how the trigger was simulated though.. How to get an accurate T0? Integrated flux above 20/30 GeV = 2.7/1.3 /(m 2 sr s) 100 Hz --> effective area is about 37/77 m 2 sr ! Lets take 50 m 2 in these evaluations (total area ~ 600 m 2 )

6. Are cosmic muons interesting from a physics point of view? 1)Muon Spectrum 2)Charge Ratio 3)Moon Shadow 4)Point Sources 5)Muon Multiplicity 6)Neutrino’s

8. Muon Spectrum Why? No good data exists between 1 and 5 TeV (L3C measures up to 3 TeV) Requirements Good resolution to very high momenta (T0)! Truly understanding your detector efficiency/DAQ and trigger TDR: 1TeV muons, resolution= 11% (L3C 50 %) Combining 2 towers naively: 8 % at 5 TeV: 40 % Expected amount of data above 1 TeV: 290,000 in10 7 sec

9. Muon Charge Ratio Why? The charge ratio is supposed to increase when the kaon production in the atmosphere becomes more important, this has not yet been seen! Requirements Good resolution (charge separation)to very high momenta! TDR: 1TeV muons, resolution= 11% Combining 2 towers naively: 8 % at 300 GeV: ~3-4 % Expected amount of data above 300 GeV: ~5 Hz

12. Moon Shadow Why? Determining pointing accuracy, and systematic offsets (should you wish to go for point sources this is a must!), matter vs antimatter in HE cosmic rays Requirements good angular resolution (moon size =.25-.28 degrees) decent knowledge of time of datataking (earth rotation = 360 degrees/24hrs = 0.18 degrees/min

13. Point Sources Why? Finding point sources in >TeV gamma rays would be extraordinary. It would provide insight into the accelerator mechanisms especially when combined with neutrino sources Requirements good angular resolution good timing resolution when trying to find pulsars the absolute time needs to be known at the microsecond level (gps should be added)

14. Multiplicity vs Shower Size However, simulations of the muon multiplicity show that the data is not easily interpreted. The simulations underestimate the number of muons in the detector, even for relatively low multiplicities.

15. Higher multiplicities L3+C has problems in counting, and relies on manual scanning.

16. Muon Multiplicity Why? Both L3C and Aleph found a good number of extremely high multiplicity muon events, which cannot easily be explained by air shower simulations Requirements the ability to count and measure large multiplicity events (inner tracker is better suited than muon detector) Physics motivation would be greatly improved by putting a decent air shower array on top of Atlas for the appropriate shower energies ~10 18 eV. (25 HiSparc counters on an area of 1km 2 would be nice)

17. Neutrino Physics Why? Should we be able to measure a lot of neutrino induced muons, we could accurately measure the spectrum of atmospheric neutrinos, and compare to models (solar..) How: Measure upward going muons, the background is low. Expected number of events: MACRO measured 783 upward muons in 5.5 years with an effective area of 912 m 2. We can expect 8 events/year, so forget doing neutrino physics