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Test with cosmic rays at LNGS - final results -

Test with cosmic rays at LNGS - final results -. S. Bastianelli, L. Degli Esposti, R.Diotallevi, G. Mandrioli, P. Righini, G. Rosa, M. Sioli. OPERA meeting, LNGS, May 19-22, 2003. What’s new:. Emulsion data completely analysed (Test 1 and Test 2);

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Test with cosmic rays at LNGS - final results -

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  1. Test with cosmic rays at LNGS- final results - S. Bastianelli, L. Degli Esposti, R.Diotallevi, G. Mandrioli, P. Righini, G. Rosa, M. Sioli OPERA meeting, LNGS, May 19-22, 2003

  2. What’s new: • Emulsion data completely analysed (Test 1 and Test 2); • An additional MC production without shielding(hard job: from TeV primaries down to 1 MeV secondaries!); • “Emulsion cuts” reproduced into MC; • Scintillator data recovery of Test 1; • Mutual comparison Scint-Emul-MC; • The inheritance of this test:must we fear exposures to CRs?

  3. 1) Analysis of emulsion data • Eight 3-plate stacks scanned:25-50-75 cm of iron (Test 1=48 days exposure)0-5-40-70-100 cm of iron (Test 2=74 days exp.) • Scanned area in each plated=150-200 mm2; • Base-tracks/plate of the order of 10-20k; • Plate-to-plate connections and efficiency corrections only in “effective scanning areas”, i.e. in common zones of adjacent plates with large enough statistics; • Angular distributions and integral fluxes in the range 20-300 mrad; • Systematic error is taken to be as the relative difference between plate12 and plate23 countings (ranging from 10% at small coverage up to 1% at large coverages).

  4. 2) New MC production up to 1 MeV • Fundamental in order to: • Compare emulsionexposure withoutshielding and with5 cm of iron; • Check the former MCproduction performed withhigher thresholds; Spallation neutrons are the most abundant component Nice agreement between the resulting spectra with the one found in literature Lack of statistics...

  5. 3) Emulsion cuts implemented into MC Dimpact≤ 20 mm Dslope≤ (0.010 + 0.1 slope) rad Effective for low energy particle. An additional cut on the energy loss has been applied dE/dX ≤ 2(dE/dX)mip Effective for non-relativistic protons. Scintillator cuts are unchanged: Released Energy > 20% of the muon signal (to reproduce discriminator thresholds) Emulsion stack

  6. 4) All scintillator data analysed neutron muon 10 cm of Lead Proton recoil Test 1 Test 2

  7. Scintillator counting statistics: Good agreement at the level of 5% (taken as systematic error) due to atmosphere, season ...

  8. Emulsion – MC comparison:zenith angle distributions Emulsion data (corrected for efficiency) MC data (with cuts) Errors only statistical (0 cm – 5 cm – 25 cm – 40 cm)

  9. Emulsion – MC comparison:zenith angle distributions Emulsion data (corrected for efficiency) MC data (with cuts) (50 cm – 70 cm – 75 cm – 100 cm)

  10. Emulsion – MC comparison:integral distribution in zenith MC simulation: 5% systematics on absolute flux knowledge Emulsion data: 10% systematics on efficiency corrections

  11. Details on the integral distribution Original CR e.m. showers Rigeneration phenomena from muon activity in iron 40 cm of iron: minimum e+e- flux

  12. Residual energy spectra after40 cm of iron coverage After 40 cm: Muon flux: 1.78 mm-2 day-1 Median muon energy: 2 GeV e+e- flux: 0.2 mm-2 day-1 Median e+e- energy: 8 MeV e+e- flux with cuts: 0.02 mm-2 day-1 Median e+e- energy: 40 MeV

  13. An interesting by-product of emulsion data analysis: f=0 is the Geomagnetic North Azimuthal distributions of emulsion tracks are strongly asimmetric... Possible interpretations (to be confirmed by MC): very low energy CR components splitted in charge by the Geomagnetic Field (it carries information on charge ratio at very low energies)

  14. Conclusions and future • An native-coarse test allowed us to perform “precision” measurements! • Emulsion-Scintillator-MC data fairly agree at 5-10% level; • We have a reliable and experimentally tested MC code, ready to use for further checks in the future; • We can safely conclude about the best choice for the iron coverage; • Further fine-tuning studies are required, in order to explore a mixed solution for the coverage; • Next obliged step: a whole brick exposure...

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