Jan Ridky and Petr TravnicekInst. 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, Ecut

= 50 GeV)ALEPH (140 m, E

cut = 70 GeV)

L3 (30 m, Ecut

= 15 GeV)Jan Ridky, ISVHECRI, Pylos, Greece, 6-12 Sept. 2004

Simulationand detection

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

Description of the overburden5 layers with proper rock density& experimental cavern description

differentkinds of molasses

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

Detektor DELPHIMUB

HCAL

TOF

TPC

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

Typical high multiplicity event

RUN 107634, 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 triggercoincidence of 3 sectors in TOF,parasitic data taking to e+e- and several dedicated cosmic runs

Duty cycle of LEP total live time 1.6 106 s

Nmuons

> 4

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

Projected angle background rejectionHCAL projected angle

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

4 saturated events

2 saturated events (MUB)

#event s Mul . >30 54201 Mul . >30 1065 Mul . >70 78 Mul . >100 21

1999, 2000

Muon multiplicity

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 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 particlesJan 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

AlephDelphi

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