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Status of PSD

A.Ivashkin (INR, Moscow)

• PSD structure.• In-beam performance in Be run.• Performance in Pb test run.• PSD trigger in Be run.• Status of calibration.• Future steps.

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PSD – Projectile Spectator Detector

Precise measurement of the energyof projectile spectators.•Centrality selection (on trigger level)• Measurement of event-by-event fluctuations (to reduce Npart fluctuations)• Reconstruction of the reaction plane

Compensating calorimeter•Pb/scintillator (4/1) 60 sandwiches in one module•Modules 10 x 10 x 120 cm3 – central part• Modules 20 x 20 x 120 cm3- outer part• 10 longitudinal sections with 10 MAPDs readout

PSD in 2011

16 central modules in trigger

PSD modules in 2011 Be-run

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Photo of PSD after full construction (Feb.2012)

Front

Rear side before FEE installation

44 modules

440 MAPDs and readout channels

17 tons

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PSD performance in 2011 7Be run

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Energy in PSD vs Z-detector (Be-run 2011)40 AGeVRun 15258 special, target INtrigger S1

75 AGeVRun 15161, target INTrigger T4

150 AGeVRun 14946, target OUT All triggers

dHe

Be

d

d

He

He

Be

Be

Off-time particles

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Energy in PSD for beam trigger75 AGeVRun 15161, target INTrigger T4

150 AGeVRun 14946, target OUT All triggers

Beam energy (AGeV) 40 75 150 Etotal (GeV) Resol. ( %) Etotal (GeV) Resol. (%) Etotal (GeV) Resol. (%)2H 80 11.8 150 9.2 300 6.6 4He 160 8.1 300 7.0 600 6.77Be 280 6.4 525 6.1 1050 4.1

dd

d

He He

HeBe Be

Be

40 AGeVRun 15258 special, target INtrigger S1

The PSD on-line resolution ~90%/sqrt(E) is about 1.5 times worse of expected one. Further improvement needs the accurate energy calibration.

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PSD spectrum for 150 GeV beam(calibration of scale)

2H-253 GeV

4He- 520 GeV

7Be-1024 GeVE1n(7Be)=150 GeV

But

E1n(4He)=130 GeV

Why?

P1n(4He)x4/2=P1n(7Be)x7/4

P1n(7Be)x7=P1n(4He)x4/2x4=P1n(4He)x8

The reason is rigidity of beam =P/Z=const.

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Runs 15418 - INThe same HV as for Be runs

Pb+Pb@80 AGeV (test runs)

Run 15438 – INHV for 2 beam modules are decreased

T2

T1All triggers

T2

Pb energy peak ~11 TeV Expected -16 TeV (ADC saturation)

ADC saturation is avoided

Minimum bias spectrum Calibration needed after HV changes

For heavy ions the HV adjustment of in-beam modules is required to avoid the ADC saturation

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Deposited energies in PSD modules7Be + 9Be@40 AGeV 7Be + 9Be@75 AGeV

Pb + Pb@80 AGeV

neutrons

Pb-beam position at PSD is not optimized!

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PSD trigger in 2011 7Be run

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PSD trigger - T2 (interaction):deposited energy in PSD is less of some thresholds

Energy of first sections is addedW/o section 1

To avoid the contribution of non-interacting beam ions first section must be in trigger!

Sharp cut according to trigger threshold

7Be + 9Be@75 AGeV

To avoid the contribution from e/m particles first section in each central module was out of trigger

non-interacting beam ions

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40A GeV

Energy in PSD (central part): triggers T1(beam) and T2 (interaction)7Be + 9Be

75A GeV

150A GeV

Significant part of T2 triggers has no interactions because of exclusion of first section from trigger.

Problem is fixed now!

First section is in trigger!

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Future plan: Modification of PSD trigger (faster PSD signal)

60 ns300 ns

MAPD signal M~5x104

integrated signal M~107 ADC signal

At present: the PSD trigger signal comes after integrators with rise time ~60 ns: too slow and too large time-amplitude walk. Needs careful adjustment for each beam energy.

Future plans: trigger signal after MAPD – fast signal, no problem with time walk and delay.

Test of fast trigger to be done in June, 2012. Modification in 2013.

First section is in trigger from Feb.2012!

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Status of PSD calibration

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Matrix method of energy calibration with protons

Aj1-10 – amplitudes of the signals in sections 1-10 for event j

C1-10 – calibration parameters for sections 1–10 (to be found)

EACACAC

EACACAC

EACACAC

beamjjj

beamjjj

beamjjj

109

1029

219

1

101

1021

211

1

10 102 21 1

...

...

...

Ten sequential events are used to find 10 unknown calibration parameters in 10 sections of one PSD module

Calibration was done with p@158 GeV , each module was scanned

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CLUSTER 1: hit module – small module 6

Deposited energy 155.8 GeVResolution 7.6%

CLUSTER 2: hit module – large module 25

Deposited energy 153.7 GeVResolution 7.1%

Deposited energy in clusters reconstructed with final calibration parameters

Module 6

Module 25

MC expected resolution ~6.5%

Beam spots

Cluster 2

Cluster 1

6

25

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Comparison of energy reconstruction with all modules and with clusters

Mean value

Resolution

One needs to understand why 1/3 of modules has significantly worse resolution

ResolutionReconstruction with all modulesReconstruction with clusters

Accuracy of calibration parameters depends on beam spot position at front of PSD module

We see larger mean values and worse resolution for all modules comparing with clusters:

• Larger contribution of electronic noise? - unlikely – see next slide.

• Additional energy from background events ?

According to MC the resolution should be 6.5%

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Reconstruction with all modulesReconstruction with clusters(noise cuts – 5 /7 ch – small/large)

• reconstr. with all modules• reconstr. with clusters(noise cuts – 7/10 ch - small and large)• reconstr. with all modules • reconstr. with clusters (noise cuts – 10/12 ch - small and large)

Dependence of energy resolution on noise cut

Noise is not responsible for worse resolution

E/E=60%/sqrt(E)

E/E~70%/sqrt(E)

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Strategy of PSD calibration in June, 2012

2007 SPS muon beam pedestal

Muon peak

1. Calibration of each module with ~100 GeV muons. - straightforward evaluation of calibration parameters from muon peaks. But… very close to pedestal.

2. Calibration of each module with 158 MeV/c protons. Matrix method of calibration.

One needs accurate beam positioning at the module centers.

Remote control on PSD platform is requested!

Backup option – two web-cameras for X- and Y-axis of PSD platform.

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Future steps on PSD activity

• Calibration of all modules with protons (158 GeV/c) and muons – June, 2012

• Evaluation of new set of calibration parameters for 2012 beam run.

• Improvement of calibration algorithm and energy resolution. Our goal is E/E~60%/sqrt(E).

• Development of cluster algorithm in energy reconstruction. Suppression of contributions from secondaries.

• Test of new fast trigger scheme – June, 2012

• Implementation of fast trigger scheme for all modules – 2013.

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Thank you!

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Energy in PSD: trigger T2 (interaction)

7Be + 9Be@75 AGeV Non-calibrated data Calibrated data

All sections

W/o section 1

First section must be in trigger!