1. SMRD Meeting @KEK, 17-18 April 2007 Status of the atmospheric muon studies Piotr Mijakowski OUTLINE: Primary muon spectrum at the sea level Primary muon spectrum at the sea level Atmospheric muons underground@ND280 location Atmospheric muons underground@ND280 location Geant4 simulation Geant4 simulation NTUPLES with atmospheric muon data NTUPLES with atmospheric muon data Some results Some results

2. Motivation GOAL: determine the requirements for cosmic ray trigger GOAL: determine the requirements for cosmic ray trigger SMRD will provide c.r trigger for calibration of inner ND280 detector components SMRD will provide c.r trigger for calibration of inner ND280 detector components No Ecal at the beginning No Ecal at the beginning Calibration data taken between a beam spills Calibration data taken between a beam spills Detector requirements: Detector requirements: not always clear (more communication needed) not always clear (more communication needed) TPC+FGD: various samples – crossing FGD&TPC, crossing cathode; giving the 20cm transverse length TPC+FGD: various samples – crossing FGD&TPC, crossing cathode; giving the 20cm transverse length P0D: horizontal muons, 100k per week per channel P0D: horizontal muons, 100k per week per channel

3. Primary muon spectrum at the sea level So far used the official K2K data file – Oyama spectrum So far used the official K2K data file – Oyama spectrum cosmic ray muon simulation cosmic ray muon simulation 10k events 10k events structure: event# cos(  ) Momentum structure: event# cos(  ) Momentum

4. Oyama spectrum Oyama - cos 2.04  world publ. data - cos 2.16  (*) (different geomagnetic locations) Oyama - cos 2.04  world publ. data - cos 2.16  (*) (different geomagnetic locations) Momentum - zoom FIT: - cos(  )>=0.175 by power factor 2.04 - cos(  ) =0.175 by power factor 2.04 - cos(  )<0.175 linear fit (*) http://www.scifun.ed.ac.uk/pages/pp4ss/pp4ss-hodoscope.html 2006 zenith cos 2.04 

5. Oyama spectrum – P and cos  correlation for vertical muons P and cos  uncorrelated for vertical muons P and cos  uncorrelated for large angles: correlation (LE  decay before reaching the surface, HE  decays mainly contribute) for large angles: correlation (LE  decay before reaching the surface, HE  decays mainly contribute)

6. Simulation of atm. muons underground muons sampled from a square surface and propagated through the rock muons sampled from a square surface and propagated through the rock initial energy, zenith angle - Oyama, azimuthal angle – isotropic initial energy, zenith angle - Oyama, azimuthal angle – isotropic normalization: 70  /(m 2 s) > 1 GeV at surface (PDG) normalization: 70  /(m 2 s) > 1 GeV at surface (PDG) 3 sets of simulations: 3 sets of simulations: 22m x 22m, illumination time = ~36.1 sec. 22m x 22m, illumination time = ~36.1 sec. 200m x 200m, illum. time = ~2.2 sec. 200m x 200m, illum. time = ~2.2 sec. 400m x 400m, illum. time = ~0.27 sec. 400m x 400m, illum. time = ~0.27 sec. suitable only for veritical muon study small statistics so far

7. Geant4 simulation - geometry Geometry visualization 30cm thick cement floor 2m of air below floor side view top view 1m cement wall d = 17.5m DETECTOR BOX - shifted 1m 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 x z

8. Zenith angle cos  of muons entering the detector box cos  of muons entering the detector box entries225517242179348 tot. flux [  /(m 2 s)] 39.8 ±0.8 38.0 ±0.3 23.89 ±0.05 mean0.7920.8010.916 green – 400m x 400m, 0.27 s red – 200m x 200m, 2.2 s blue – 22m x 22m, 36 s all det. sides top surface entries151711993152221 tot. flux [  /(m 2 s)] 128±4126±1.596.9±0.3 mean0.849 0.912 Vertical flux information!

9. Energy spectra kinetic energy of muons entering the detector box kinetic energy of muons entering the detector box green – 400m x 400m, 0.27 s red – 200m x 200m, 2.2 s blue – 22m x 22m, 36 s all det. sides top surface entries225517242179348 tot. flux [  /(m 2 s)] 39.8 ±0.8 38.0 ±0.3 23.89 ±0.05 mean [GeV] 12.8713.055.37 entries151711993152221 tot. flux [  /(m 2 s)] 128±4126±1.596.9±0.3 mean [GeV]7.628.565.29

10. Muons@horizontal walls y coordinate (height) distribution of muons entering the detector box from the sides ( only 2 instrumented sides ) y coordinate (height) distribution of muons entering the detector box from the sides ( only 2 instrumented sides ) green – 400m x 400m, 0.27 s red – 200m x 200m, 2.2 s blue – 22m x 22m, 36 s entries458323117566 tot. flux [  /(m 2 s)] 17.7±0.815.6±0.35.12±0.04 mean [m]0.300.270.43 Horizontal flux information! ONLY 2 sides

11. NTUPLES files can be downloaded from: http://neutrino.fuw.edu.pl/public/samples/t2k/nd280_atm_muons/ - see description of the contents in readme.txt file - you will also find some example macro files to read the ntuples NTUPLE (ROOT format): 1 branch „Event” 1 branch „Event” 11 leaves: 11 leaves: „no_event” (event number) „no_event” (event number) „charge” (values = „+1” for  + or „-1” for  - ) * „charge” (values = „+1” for  + or „-1” for  - ) * „cos_theta” „cos_theta” „E_kin” „E_kin” „x”, „y”, „z” „x”, „y”, „z” „px”, „py”, „pz” „px”, „py”, „pz” „ID” (track ID of muon from G4) „ID” (track ID of muon from G4) ( * ) implemented mu+/mu- ratio from „Precise Measurements of Atmospheric Muon Fluxes with the BESS Spectrometer” – meas.@Tsukuba (arXiv:astro-ph/0205344 )arXiv:astro-ph/0205344