Status of the atmospheric muon studies Piotr Mijakowski

Status of the atmospheric muon studies Piotr Mijakowski OUTLINE: • Primary muon spectrum at the sea level • Atmospheric muons underground@ND 280 location • Geant 4 simulation • NTUPLES with atmospheric muon data • Some results SMRD Meeting @KEK, 17 -18 April 2007

Motivation n n GOAL: determine the requirements for cosmic ray trigger SMRD will provide c. r trigger for calibration of inner ND 280 detector components n n n No Ecal at the beginning Calibration data taken between a beam spills Detector requirements: n not always clear (more communication needed) TPC+FGD: various samples – crossing FGD&TPC, crossing cathode; giving the 20 cm transverse length P 0 D: horizontal muons, 100 k per week per channel

Primary muon spectrum at the sea level n So far used the official K 2 K data file – Oyama spectrum n n n cosmic ray muon simulation 10 k events structure: event# cos(q) Momentum

Oyama spectrum Momentum - zoom FIT: - cos(q)>=0. 175 by power factor 2. 04 - cos(q)<0. 175 linear fit cos 2. 04 q zenith n Oyama - cos 2. 04 q; world publ. data - cos 2. 16 q (*) (different geomagnetic locations) (*) http: //www. scifun. ed. ac. uk/pages/pp 4 ss-hodoscope. html 2006

Oyama spectrum – P and cosq correlation n n for vertical muons P and cosq uncorrelated for large angles: correlation (LE m decay before reaching the surface, HE p decays mainly contribute)

Simulation of atm. muons underground n n muons sampled from a square surface and propagated through the rock initial energy, zenith angle - Oyama, azimuthal angle – isotropic normalization: 70 m/(m 2 s) > 1 Ge. V at surface (PDG) 3 sets of simulations: suitable only for veritical muon study n n n 22 m x 22 m, illumination time = ~36. 1 sec. 200 m x 200 m, illum. time = ~2. 2 sec. 400 m x 400 m, illum. time = ~0. 27 sec. small statistics so far

Geant 4 simulation - geometry Geometry visualization top view side view x z d = 17. 5 m 30 cm thick cement floor 2 m of air below floor 1 m cement wall DETECTOR BOX - shifted 1 m along z axis from the pit center length (z axis) = 7. 723 m, width (x axis) = 5. 63 m, height (y axis)= 6. 150 m

Zenith angle n cosq of muons entering the detector box green – 400 m x 400 m, 0. 27 s red – 200 m x 200 m, 2. 2 s blue – 22 m x 22 m, 36 s top surface all det. sides entries 2255 17242 179348 tot. flux [m/(m 2 s)] 39. 8 ± 0. 8 38. 0 ± 0. 3 23. 89 ± 0. 05 mean 0. 792 0. 801 0. 916 entries 1517 11993 152221 tot. flux [m/(m 2 s)] 128± 4 126± 1. 5 96. 9± 0. 3 mean 0. 849 0. 912 Vertical flux information!

Energy spectra n kinetic energy of muons entering the detector box green – 400 m x 400 m, 0. 27 s red – 200 m x 200 m, 2. 2 s blue – 22 m x 22 m, 36 s top surface all det. sides entries 2255 17242 179348 tot. flux [m/(m 2 s)] 39. 8 ± 0. 8 38. 0 ± 0. 3 23. 89 ± 0. 05 mean [Ge. V] 12. 87 13. 05 5. 37 entries 1517 11993 152221 tot. flux [m/(m 2 s)] 128± 4 126± 1. 5 96. 9± 0. 3 mean [Ge. V] 7. 62 8. 56 5. 29

Muons@horizontal walls n y coordinate (height) distribution of muons entering the detector box from the sides (only 2 instrumented sides) green – 400 m x 400 m, 0. 27 s red – 200 m x 200 m, 2. 2 s blue – 22 m x 22 m, 36 s entries 458 tot. flux [m/(m 2 s)] 17. 7± 0. 8 mean [m] 0. 30 3231 17566 ONLY 2 sides 15. 6± 0. 3 5. 12± 0. 04 0. 27 Horizontal flux information! 0. 43

NTUPLES NTUPLE (ROOT format): n 1 branch „Event” n 11 leaves: n n n n „no_event” (event number) „charge” (values = „+1” for m+ or „-1” for m-)* „cos_theta” „E_kin” „x”, „y”, „z” „px”, „py”, „pz” „ID” (track ID of muon from G 4) files can be downloaded from: http: //neutrino. fuw. edu. pl/public/samples/t 2 k/nd 280_atm_muons/ - see description of the contents in readme. txt file - you will also find some example macro files to read the ntuples (*) implemented mu+/mu- ratio from „Precise Measurements of Atmospheric Muon Fluxes with the BESS Spectrometer” – meas. @Tsukuba (ar. Xiv: astro-ph/0205344 )