Status of Atlas Tile Calorimeter and Study of Muon Interactions L. Price for TileCal community

1. Status of Atlas Tile Calorimeter and Study of Muon Interactions L. Price for TileCal community Short Overview of the TileCal Project mechanics instrumentation electronics TileCal and muons muons for calibration of the TileCal measurement of muon energy losses

2. ATLAS hadron calorimeter TileCal TileCal community = 24 institutions TileCal within the Atlas detector: - measures jets energies and directions - provides ATLAS with LVL1 trigger signals TileCal - Barrel and 2 Extended barrels, each cylinder consists of 64 modules

3. Principle of the TileCal Photomultiplier WLS fiber Plastic scintillator inside steel absorber structure Principle of TileCal is a measurement of scintillation light produced by charged particles in plastic scintillator.

4. TileCal modules production: BARREL - 65% of modules finished in JINR Dubna 564 cm EB A - 50% modules finished in US EB C - 73% modules finished in Spain 292 cm

5. Modularity of the Tile Calorimeter 3 cylinders - barrel and two extended barrels Each cylinder consists of 64 modules (+1 spare) SUBMODULES Total number of submodules needed: 65x19 + 2x65x9 = 1235+1170 = 2405 90% is done and the production of submodules will finish in the spring of 2002. 1. Stacking 3. Painting 2. Welding

6. Monitor of production quality in all 9 plants Barrel = 19 submodules, Extended barrel = 9 submodules + special ITC submodules - more than 50% are finished

7. Instrumentation of modules in 4 different plants Scintillator tiles (100% are produced) wrapped in Tyvek sleeves profiles with inserted fibres (65%)

8. Instrumentation of modules: In total more than 50%modules are ready for calibration and preassembly Cell to cell uniformity 6-7% < 10% (target value) Cells are formed by making fibres bundles

9. Cylinder preassembly will start in April 2002in building 185 at CERN - EB C will be assembled first - Barrel - EB A Installation in the pit is foreseen to start in Dec 2003 with the barrel 564 cm 180 cm

10. Electronics Main goal is to start serial production of drawers containing electronics PMT’s PMT blocks

11. Photomultipliers Quantity: barrel : 45 PMTs/superdrawer * 65*2 = 5850 PMTs Ext. barrel : 32 PMTs/superdrawer * 65*2 = 4160 PMTs; total : =10010 PMTs PMT‘s : 45% of tubes delivered and good quality proved by tests in 6 different labs. PMT test bench

12. Calibration of modules will be done with Cs radioactive source for all modules 8 barrel modules and 16 extended barrel modules will be calibrated using particles.

13. 2001 Tiles Testbeam Program H8 Table Setup 20° Incidence 90° Incidence Response to 180 GeV muons, pions, electrons

14. 180 GeV e at 90° Summary Target Value 1.2 pC/GeV/Cell

15. Interactions of different particles inside the TileCal electron pion 1/50 muon 1/500

16. Calibration of the TileCal using muons • Cells of the first longitudinal sampling are calibrated • with electrons of 20 to 300 GeV • All calorimeter cells are calibrated relatively each • to other using Cs radioactive source. • Precise description of TileCal response to muons • (ATL-TILECAL-97-114). The most probable value • of the muon signal can be used for the calibration. Muon signal can be used also for in situ calibration.

17. Calorimeter light yield measured with muons Signal in each TileCal cell is read out from two sides L and R. Differences of signals are caused by photoelectron statistics L muon R 2 σ (L - R) slope~ 1/ Npe L + R Typical values are 50-60 photoelectrons per 1 GeV of energy deposited in cell.

18. Muon energy losses in iron Muon s with 150, 180 GeV are close to the critical energy • Mechanisms of muon energy losses • Knock-on electrons • Bremsstrahlung • e+e- pair • Photonuclear interactions

19. Physics motivation for muon energy loss measurements • Muon traverses more than 100 radiation lengths of dense calorimeter material before being measured by the muon system. • There is a probability of 60 % that in H-> 4 μ at least one muon loses more than 10% of its energy (P~.002/rl) • It is therefore essential to measure muon energy losses in the calorimeter • Also the highest muon energy losses are dominated by bremsstrahlung and momentum transfer to nucleus is much higher than for electron bremsstrahlung. Consequently nuclear form factor should be taken into account. • Nuclear form factor corrections were not known experimentally and different theoretical predictions exist. • Photonuclear interactions of high energy muons at low momentum transfers are also poorly known experimentally and theoretical predictions implemented in different MC codes vary by an order of magnitude.

20. Measured differential probability of muon energy losses in TileCal prototypes Published in Z. Phys. C 73 (1997) 455. Theory without and with the nuclear formfactor correction to bremsstrahlung

21. Detailed measurements with the TileCal Module 0 μ

22. Nuclear form factor correction to muon bremsstrahlung Eur. Phys. J. C 20 (2001) 3, 487-495 Atomic radius a times the minimal momentum transfer to nucleus δ Screened nucleus Unscreened nucleus (Published calculations give 0.5 to 1.5)

23. Measurement of muon photonuclear interactions Photonuclear interactions: μ+A —>μ+ hadrons Coordinate z Photonuclear int. Background Top modules Coordinate z Central module muon Bottom modules

24. Differential cross section of muon photonuclear interactions (preliminary results) Normalization is proportional to σ(γN) Theory [C.19] Bezrukov, Bugaev, Sov. J. Nucl. Phys. 33 (1981) 635. σ(γN) H1, ZEUS Our measurement E lab

25. Summary • Production of instrumented TileCal modules has passed 50% point and is progressing well. • Production of superdrawers with electronics has started, first production modules have been calibrated at the beam and serial production will continue in the autumn after beam tests. • Detailed studies of muon signal have been done with the TileCal module 0. Different mechanisms of muon energy losses has been studied, nuclear form factor correction to muon bremsstrahlung has been measured. • Preliminary results about muon photonuclear interactions in iron have been presented.