Jan Ridky and Petr Travnicek Inst. of Physics, Czech Academy of Sciences, Prague for DELPHI collaboration Muon Bundles from Cosmic Ray Showers Detected by DELPHI at LEP Jan Ridky, ISVHECRI, Pylos, Greece, 6-12 Sept. 2004

Detection of cosmic rays at LEP DELPHI (100 m, E cut = 50 GeV) ALEPH (140 m, E cut = 70 GeV) L3 (30 m, E cut = 15 GeV) Jan Ridky, ISVHECRI, Pylos, Greece, 6-12 Sept. 2004

Simulation and detection Jan Ridky, ISVHECRI, Pylos, Greece, 6-12 Sept. 2004

Description of the overburden 5 layers with proper rock density & experimental cavern description different kinds of molasses Jan Ridky, ISVHECRI, Pylos, Greece, 6-12 Sept. 2004

Detektor DELPHI MUB HCAL TOF TPC Jan Ridky, ISVHECRI, Pylos, Greece, 6-12 Sept. 2004

Hadron calorimeter barrel module Sensitive units - streamer tubes 1 tube has x-section 8  1 cm in (x,y) plane Read-out only YES or NO, length of a tube in barrel part 350 cm Jan Ridky, ISVHECRI, Pylos, Greece, 6-12 Sept. 2004

Typical high multiplicity event RUN , EVT 4731 Jan Ridky, ISVHECRI, Pylos, Greece, 6-12 Sept. 2004

Saturated event … we have 6 such cases Jan Ridky, ISVHECRI, Pylos, Greece, 6-12 Sept. 2004

Data selection - DELPHI cosmic trigger coincidence of 3 sectors in TOF, parasitic data taking to e + e - and several dedicated cosmic runs Duty cycle of LEP  total live time  s N muons > 4 Jan Ridky, ISVHECRI, Pylos, Greece, 6-12 Sept. 2004

Projected angle  background rejection HCAL projected angle Jan Ridky, ISVHECRI, Pylos, Greece, 6-12 Sept. 2004

4 saturated events 2 saturated events (MUB) 1999, 2000 Muon multiplicity Jan Ridky, ISVHECRI, Pylos, Greece, 6-12 Sept. 2004

Track saturation yes/no signals in streamer tubes  track pile up Jan Ridky, ISVHECRI, Pylos, Greece, 6-12 Sept. 2004

Saturated events ● too many hits, reconstruction in HCAL fails ● 6 such events, parallel ‘tracks’ of un-hit tubes -> cosmic ● 2 events in MUB  multiplicity >150 Jan Ridky, ISVHECRI, Pylos, Greece, 6-12 Sept. 2004

MC simulation of cosmic rays ● QGSJET, CORSIKA, GEANT3, DELSIM ● Primary particles: p, Fe ● Primary energies – eV ● Events generated according to E -1 and weighted by E -2.7(3.0) ● Shower smearing within radius R = 200 m at the detector level Jan Ridky, ISVHECRI, Pylos, Greece, 6-12 Sept. 2004

MC comparisons Which model provides more muons? LDF of p > 50 GeV muons => QGSJET > SIBYLL > DPMJET Jan Ridky, ISVHECRI, Pylos, Greece, 6-12 Sept. 2004

HCAL – MC (QGSJET) vs. DATA Jan Ridky, ISVHECRI, Pylos, Greece, 6-12 Sept. 2004

rock density cross-talk Systematic errors – rock density, cross-talk Jan Ridky, ISVHECRI, Pylos, Greece, 6-12 Sept. 2004

Simulations – supposed flux Jan Ridky, ISVHECRI, Pylos, Greece, 6-12 Sept. 2004

HCAL – MC (QGSJET) vs. DATA flux no. 1 Jan Ridky, ISVHECRI, Pylos, Greece, 6-12 Sept. 2004

Comparison – MC vs. DATA flux 1, 2, 3- influence of the flux of primary particles Jan Ridky, ISVHECRI, Pylos, Greece, 6-12 Sept. 2004

Simulations – energy contributions – flux 1 Jan Ridky, ISVHECRI, Pylos, Greece, 6-12 Sept. 2004

Simulations – energy contributions – flux 1 Jan Ridky, ISVHECRI, Pylos, Greece, 6-12 Sept. 2004

TPC sky plot (galactic coordinates), HCAL multiplicity > 15 Jan Ridky, ISVHECRI, Pylos, Greece, 6-12 Sept. 2004

Other LEP results Aleph Delphi multiplicity L3-C

Conclusions DELPHI cosmic data in qualitative agreement with other LEP measurements (L3+C). High energy models fail to describe muon multiplicity Data are sensitive to the dynamics of the high energy interactions (talk of Jörg Hörandel) Cosmic data …. the only measurement at LEP unexplained by theory