1. The 21st International Conference on Ultrarelativistic nucleus-nucleus collisions, March 30 – April 4, Knoxville, TN Results from cosmics and First LHC beam with the ALICE-HMPID detector Giacomo Volpe a,b for the ALICE collaboration a INFN, Sezione di Bari, Italy. b Dipartimento Interateneo di Fisica “M. Merlin”, Bari, Italy.

2. HMPID detector description The ALICE-HMPID (High Momentum Particle Identification Detector) performs charged particle track-by-track identification by means of the measurement of the emission angle of Cherenkov radiation and of the momentum information provided by the tracking devices. It consists of seven identical proximity focusing RICH (Ring Imaging Cherenkov) counters. RADIATOR 15 mm liquid C 6 F 14, n ~ 1.2989 @ 175nm,  th = 0.77 PHOTON CONVERTER Reflective layer of CsI QE ~ 25% @ 175 nm. The largest scale (11 m 2 ) application of CsI photo-cathodes in HE/HI-P! PHOTOELECTRON DETECTOR - MWPC with CH 4 at atmospheric pressure (4 mm gap) HV = 2050 V. - Analogue pad readout

3. HMPID detector description CsI photo-cathode is segmented in 0.8x0.84 cm pads Total number of pads per chamber = 161280 Six photo-cathodes per module QM09, 2 April 2009 G. Volpe MIP mip photons

4. HMPID is installed in the ALICE magnet since September 2006 Since July 2007, fully powered (LV & HV); Since July 2007, HMPID is controlled by remote via the Detector Control System; Since May 2008 the radiator liquid circulation system is completed; HMPID is ready to take data!! QM09, 2 April 2009 G. Volpe

5. HMPID Physics Particle ratios vs. p T (pbar/p, p/ , K/  ); Jet physics: Study jet fragmentation with the identification of particles in the jet; Study the “flavor” of the leading particle; Measurement of resonances production such as  K + K - ; Light nuclei (alpha, deuteron, tritium) production; HMPID performs charged hadrons identification in the intermediate momentum region : 1<p<3 GeV/c  -K, 1.5<p<5 GeV/c K-p at 3  Thus, the HMPID can contribute to:

6. Global Run I: December 2007 (2 weeks) Start system commissioning Global Run II: February/March 2008 (3 weeks) global commissioning, magnet commissioning, cosmics. Global Run III: from May, until 12th of October global commissioning, calibration and alignment with cosmics First beams ALICE data taking QM09, 2 April 2009 G. Volpe

7. 0 1 2 17 16 10 9 8 7 6 TOF TRIGGER CONFIGURATION HMPID recorded interesting data using trigger provided by the TOF detector, which match good with its geometry acceptance!! Tracking in the TPC is available. HMPID Trigger configuration for cosmic data taking QM09, 2 April 2009 G. Volpe Trigger purity ~ 2%

8. Results from cosmics: Event display QM09, 2 April 2009 G. Volpe

9. Results from cosmics Occupancy ~ 0.2%

10. Results from cosmics: Event display

11. Results from cosmics

12. Clusters charge distribution selecting clusters corresponding to a track in the TPC Track matching HMPID-TPC, no alignment QM09, 2 April 2009 G. Volpe Dead zone charge (ADC channels )

13. RICH0 RICH2 RICH1 RICH3RICH4 RICH5RICH6 1800 V 1860 V Results from beam injection test dump on TED Because of the large flux of particle foreseen, to prevent trips in the chambers HV has been set to value lower than the usual. QM09, 2 April 2009 G. Volpe

14. RUN 53712 QM09, 2 April 2009 G. Volpe Occupancy ~ 50%

15. Cluster charge distribution. QM09, 2 April 2009 G. Volpe 1860 V 1800 V Statistic shown corresponds to ~ 80 events entries/1 ADC

16. Results from beam injection test Beam through ALICE RICH0 RICH2 RICH1 RICH3RICH4 RICH5RICH6 2050 V HV has been set to the nominal value. QM09, 2 April 2009 G. Volpe

17. Occupancy ~ 12%

18. In this phase, events from beam gas interaction were expected, so very low particle multiplicity. The high particles multiplicity detected was due to a monitor screen present on the beam path! A good chance to check the detector behavior. QM09, 2 April 2009 G. Volpe Occupancy ~ 12%

19. Cluster charge distribution. QM09, 2 April 2009 G. Volpe Statistic shown corresponds to ~ 80 events entries/1 ADC

20. A 0 = 46.9 ADC A 0 = 41.1 ADC A 0 = 41.2 ADCA 0 = 38.7 ADC A 0 = 36.8 ADC A 0 = 43.5 ADC A 0 = 47.1 ADC QM09, 2 April 2009 G. Volpe A = single electron pulse height 1 ADC = 0.17 fC Statistic shown corresponds to ~ 80 events Cluster charge distribution selecting cluster with cluster size < 3. entries/1 ADC

21. Problem of high voltage boards Analysis of cosmic and beam injection test data revealed some unexpected results. The values of Landau distribution MPV and A 0 retrieved, don’t correspond to the expected one at the HV values used. Investigation has been carried out to find the reason of this discrepancy. Error in the calibration of the HV boards has been detected. V out = V set + V set *2.83*10 -2, that approximately corresponds to a positive bias of 58 V at the nominal HV value of 2050 V. According to this, the results obtained are consistent. QM09, 2 April 2009 G. Volpe

22. Conclusions The results obtained from the cosmics and beam injection test have proven that HMPID works as expected. Nevertheless calibration (chambers gain, Q.E.) and alignment with cosmics are not possible since high track statistics is necessary. Hardware problem has been detected and solved HMPID is waiting for collisions!!! QM09, 2 April 2009 G. Volpe