March 2004 CALOR 2004, Perugia, Italy Super-dense W-Si Calorimeter for the Forward Spectrometer...

March 2004 CALOR 2004, Perugia, Italy

Super-dense W-Si Calorimeter for the Forward Spectrometer Upgrade of

PHENIX at RHIC

(*) on behalf of the PHENIX Forward Upgrade Project

E.Kistenev, BNL, USA,

M.Merkin, MSU, Russia,

R.Seto, UCR, USA (*)


Two central arms for measuring hadrons, photons and electrons

Two forward arms for measuring muons

Event characterization detectors in middle

The PHENIX Experiment At RHIC


pp

AuAubinaryAuAuAA Yield

NYieldR

/

Discovery of the High Pt 0 suppresiion in PHENIX was then confirmed by all RHIC experiments measuring yeilds of charged

particles

Motivation: 2001 - discovery of jet quenching


Dramatically different and opposite centrality evolution of Au+Au experiment from d+Au control allows to claim that suppression observed in

central region is clearly a final state effect.

Au + Au Experiment d + Au Control Experiment

Preliminary DataFinal Data

Motivation: 2003 - looking for further clues in dAu


Motivation: are there any role for initial state nuclear effects to play

• Yes. There are solid theoretical arguments that when probed at a very low partonic x-values, gluon field must be saturated resulting in matter being in the “Color (colored gluons) Glass (partons are disoriented) Condensate (density is saturated)”.

• Collisions probing a low-x parton from Au need a high-x parton from d and will be highly forward focussed.

PHENIX needs Forward Spectrometer to reach into saturated Gluon Fields


Definition of the Project Goals: Comprehensive experiment to study partonic structure functions in the low-x limit:

NCC+FST

NCC+MS+FST

NCC+MS+FST

MS+FST

Gluons contribute few % to DY production except at

large Q2

Z*

Components:

NCC - Nose Cone CalorimeterMS - Muon SpectrometerFST - Forward Silicon Tracking


Problems:

-only 40 cm apart from collision point …

-only 20 cm of space is available … and then …3.5

Labs of dead material downstream

Layout: PHENIX forward spectrometers and NoseCone Calorimeters

FST


What kind of calorimeter we need …..

- reasonable resolution for e/m showers;

- &e identification (what’s about e-sign - VTX?);

- – 0 separation (ShowerMax);

- isolation (electrons and muons) (ShowerMax);

- jet measurements (can it be done without tail catcher?);

- e//jet triggers (fast shaping …. system design);

- early muon tracking to retain J/ resolution (ShowerMax);

Specs clearly point to sampling calorimetery !!!

W+Si


Ultimate solution (~14cm of W absorber + readout!!!!!)

High Z, very dense

Calorimeter: ~40 Lrad / 1.6 Labs

ShowerMax: at a depth ~ 5Lrad (two layers of ~2x60 mm2 strips)

-excellent /0 separation;

-excellent position resolution;

-enough depth to do e/h separation locally;

-reasonable jet measurements

-all what we need for triggering

but …..

-needs shower max layers

-will need upstream tracking to recover J/Y resolution in AuAu

High Z, very dense, Tail Catcher downstream of magnet pole (60 cm Fe)

Probably an overkill


Few words on energy resolution (sampling fraction and sampling rate)

R.Wigmansfirst ~10 Lrad will drive the e-resolution;

< 2mm W plates to get reasonable resolution (~20%);

total number of layers must stay reasonable (<25);

16 x (2.5mm W + 2.5 mm r/o gap)

+

6 x (1.6 cm W + 2.5 mm r/o gap)


Layout : Nose Cone Calorimeter

Parameter Value

Starts at Z 40 cm

Radial coverage 50 cm

Geometrical depth 20 cm

Absorber W

Readout Si

Sampling cells 22

Longitudinal segments 3

EM compartment (Lrad) 10

Total depth (Rad length) ~40

Total depth (Abs length) >1.5

Multiple scattering NCC+Magnet (MeV)

133

Expected EM en. Resol. 20%

Tower size (cm) 1.5

Two showers resolved at 3cm

Shower max detector Gap 6

Shower max gran. (mm2) 2 x 60

Two showers resolved at 0.3 cm


Silicon …

Parameter Value Comment

Sensor size (cm) 6 x 6 to maximize the yield

Pixel size (cm) 1.5 x 1.5 to match molier radius and to reduce channel capacitance

Pixels per sensor 16

Sensors per sampling layer (max)

216

Sensors in the detector 3656

Total area of Silicon (m2) 13

P/A granularity 32 channels

Chips / sensor 0.5

P/A channels / layer <3500

Readout channels ~10000

Dynamic range (MIP’s) 100 to 500 to cover range of species in PHENIX


Impact on Jmeasurements in the muon spectrometer

Cu Nose Cone W/Si NCC

X0(total) 13.3 39.2

Labs(total) 1.26 1.5

dE/dx(total) 195 MeV 390 MeV

(J/Y) (GEANT) 155 MeV 178 MeV

Mult. Scattering ( GEANT)

100 MeV

Mult. Scattrering (estimate)

106 MeV 133 MeV

Struggling & measurements

118 MeV ~118 MeV

Compaund effect of all know scatterers

in the system

-Shower max detector is sufficient to nearly remove multiple scattering contribution to J/Y mass resolution in pp enviroment;

-J/Y mass resolution in AuAu will be recovered whenever upstream tracking is built.


Running conditions (occupancy and pileup from underlying event)

J et measurements in NCC (pp collisions)

0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

80.00

90.00

0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00

Rapidi ty

J et energy in NCC (Pt = 4

Under lying event

March 2004 CALOR 2004, Perugia, Italy G.Bashindzhagyan Moscow State University

June 2002

Si/

W la

yers

Internal structure (not in scale).

Spacers. ~500 mm long; material: steel(?), titanium (?).

Stainless steel plate ~10 mmTungsten plates

1.4 - 4.2 mmSpacers glued to W

50 mm 50 mm2.5 mm

~0.2 mm

~0.3 mm~3 mm

Stainless steelplate

……..

~1 m

~1 m

How to build the calorimeter this dense


Silicon

Moscow State University

-More then 12 m2 built;

Micron semiconductor:

-lot of experience, work with PHENIX, perfect prototype available;

Other manufacturers …..


Readout

Preamp/shaper mounted on the pad plane. Signal will be driven to the edge of detector. We would like to measure T0 plus total charge. The longer shaping time will allow us to have several samples at the rising edge of the pulse. We will get 10-20 samples per signal per L1 trigger


Prototype preamplifier

Medical imaging (ratCAP)


Summary

-physics is very interesting;

-no one in heavy-ion community was able to predict the future at a time of RHIC inception. All four RHIC experiments had something to say about CGC this last QM2004, neither can study the details;

-signatures are plenty, but ……what’s required are precision measurements;

-“comprehensive experiment” would require data from “nearly exclusive” partonic channels;

-going step further involves hardware upgrade: for PHENIX this means

Forward Spectrometer:

Forward Silicon Pixels,

W/Si Nose Cone Calorimeter,

Upgraded Muon Spectrometer.


Backups


Silicon Tungsten EMCal• Figure of merit something like BR2/

– where = rpixel rMoliere

• Maintain the great Moliere radius of tungsten (9 mm) by minimizing the gaps between ~2.5 mm tungsten plates. Dilution is (1+Rgap/Rw)

– Could a layer of silicon/support/readout etc. fit in a 2.5 mm gap? (Very Likely)

– Even less?? 1.5 mm goal?? (Dubious)

• Requires aggressive electronic-mechanical integration!


Close relatives …..

The OPAL Si-W luminometer

2 cylindrical calorimeters encircling the beam pipe at ± 2.5 m from the Interaction Point

19 Silicon layers

18 Tungsten layers

Total Depth 22 X0 (14 cm)

Sensitive radius: 6.2 – 14.2 cm from the beam axis

Each detector layer dividedinto 16 overlapping wedges

Even and odd layers staggered in

Cooling pipes as close as possible to the FE chips to remove 340 W dissipated in each calorimeter

Total area of Si 1.0 m2/calorimeter

OPAL Collaboration, Eur.Phys.J. C14 (2000) 373


Shower Maximum layers

Silicon wafer 300 m thick with R- pad geometry (32 x 2 pads)

Pitch R : 2.5 mm ; : 11.25°

Glued to a thick-film ceramic hybrid carrying the FE electronics

Readout with 4 DC-coupled AMPLEX chips (16 channels in a given column each)

The complete luminometer has in total 608 wedges 38,912 channelsTotal area of Si 2.0 m2

Depletion voltage ~ 62 V; Bias voltage set to 80 V

A detector wedge (OPAL)


• TC assumed to be 1.5 thick, with 4 layers 5 cm thick alternating with ~1.5 cm gaps.

• Prefer “non-PMT-based” detectors, probably equivalent of PHENIX pad-chambers (nothing heavy, only mesons).

• TC absorber - non-magnetic metal – probably copper to minimize mult. scattering;

Tail Catcher


Noise and Muons

• Assume 300 (400-500 possible) effective e- collection at 80 e-/. s=0.6%. So S/N=5 seems rational goal.

• 1 SD noise would be 4800 e-. Assuming diode capacitance of 1 pf/mm2, and amplifier noise of 20e-/pf+200 – get about factor of two safety! (1 MIP = 2 x 104 e-)

Noise & Muon Distributions

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

0 2 4 6 8 10 12

Amplitude, SD Units

0

10

20

30

40

50

60

70

80

90

100

Noise

Noise,cum

Signal, cum

Mu Signal

Noise+Sig


Transverse shower profiles

Dense absorber (W) and compact longitudinal size

Sharp shower core (FWHM <1 pad = 2.5 mm)Broad tails to almost 10 pads

Inefficiency of cluster finding < 10-5

Peak finding based on 2nd derivativeof the pad signals sensitive to overlapping showers


A is d and B is Au.

Energy and momentum conservation

xL = xa - xb =(2MT/√s)sinh y

ka + kb = k

xaxb = MT2/s

A solution to this system is:

xa = (MT/√s) ey

xb = (MT/√s) e-y

where y is the rapidity of the (xL,, k) system

R.Debbe


E>10 GeV

E>10GeV

We are exploring the possibility of completely determining the kinematic variables x1, x2, and Q2 by measuring the jet as well.

March 2004 CALOR 2004, Perugia, Italy Super-dense W-Si Calorimeter for the Forward Spectrometer...

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