The 21st International Conference on Ultrarelativistic nucleus-nucleus collisions, March 30 – April 4, Knoxville, TN

Results from cosmics and First LHC beam with Results from cosmics and First LHC beam with the ALICE-HMPID detectorthe ALICE-HMPID detector

Giacomo Volpea,b

for the ALICE collaboration

aINFN, Sezione di Bari, Italy.b Dipartimento Interateneo di Fisica “M. Merlin”, Bari, Italy.

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 C6F14, n ~ 1.2989 @ 175nm, th = 0.77

PHOTON CONVERTER

Reflective layer of CsI QE ~ 25% @ 175 nm. The largest scale (11 m2) application of CsI photo-cathodes in HE/HI-P!

PHOTOELECTRON DETECTOR

- MWPC with CH4 at atmospheric pressure (4 mm gap) HV = 2050 V.

- Analogue pad readout

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

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MIP

mip

photons

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!!

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HMPID Physics

Particle ratios vs. pT (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 3Thus, the HMPID can contribute to:

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

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0

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17

1610

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6TOF 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

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Trigger purity ~ 2%

Results from cosmics: Event display

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Results from cosmics

• Occupancy ~ 0.2%

Results from cosmics: Event display

Results from cosmics

Results from cosmics

Clusters charge distribution selecting clusters corresponding to a track in the TPC

Track matching HMPID-TPC, no alignment

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Dead zone Dead zone

charge (ADC channels)

RICH0

RICH2

RICH1

RICH3RICH4

RICH5RICH6

1800 V 1800 V

1800 V 1800 V 1860 V

1860 V 1860 V

Results from beam injection testdump 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.

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RUN 53712

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• Occupancy ~ 50%

Cluster charge distribution.

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1860 V

1860 V

1860 V1860 V1860 V

1860 V1860 V1800 V

1800 V1800 V

Statistic shown corresponds to ~ 80 events

entr

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Results from beam injection testBeam through ALICE

RICH0

RICH2

RICH1

RICH3RICH4

RICH5RICH6

2050 V 2050 V

2050 V 2050 V 2050 V

2050 V 2050 V

HV has been set to the nominal value.

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• Occupancy ~ 12%

• 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.

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• Occupancy ~ 12%

Cluster charge distribution.

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Statistic shown corresponds to ~ 80 events

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A0 = 46.9 ADCA0 = 41.1 ADC

A0 = 41.2 ADCA0 = 38.7 ADC

A0 = 36.8 ADC

A0 = 43.5 ADC

A0 = 47.1 ADC

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1)( A

A

eA

AP

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.

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Problem of high voltage boards

• Analysis of cosmic and beam injection test data revealed some unexpected results.

• The values of Landau distribution MPV and A0 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.

• Vout = Vset + Vset*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.

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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!!!

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