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 (*)

March 2004 CALOR 2004, Perugia, Italy 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

March 2004 CALOR 2004, Perugia, Italy Discovery of the High Pt  0 suppresiion in PHENIX was then confirmed by all RHIC experiments measuring yeilds of charged particles Motivation: discovery of jet quenching

March 2004 CALOR 2004, Perugia, Italy 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 Experimentd + Au Control Experiment Preliminary DataFinal Data Motivation: looking for further clues in dAu

March 2004 CALOR 2004, Perugia, Italy 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

March 2004 CALOR 2004, Perugia, Italy Definition of the Project Goals: Comprehensive experiment to study partonic structure functions in the low-x limit: NCC+FST NCC+MS+FST MS+FST Gluons contribute few % to DY production except at large Q2 Z* Components: NCC - Nose Cone Calorimeter MS - Muon Spectrometer FST - Forward Silicon Tracking

March 2004 CALOR 2004, Perugia, Italy 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

March 2004 CALOR 2004, Perugia, Italy 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

March 2004 CALOR 2004, Perugia, Italy Ultimate solution (~14cm of W absorber + readout!!!!!) High Z, very dense Calorimeter: ~40 L rad / 1.6 L abs ShowerMax: at a depth ~ 5Lrad (two layers of ~2x60 mm 2 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

March 2004 CALOR 2004, Perugia, Italy Few words on energy resolution (sampling fraction and sampling rate) R.Wigmans first ~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 mm r/o gap) + 6 x (1.6 cm W mm r/o gap)

March 2004 CALOR 2004, Perugia, Italy Layout : Nose Cone Calorimeter ParameterValue Starts at Z40 cm Radial coverage50 cm Geometrical depth20 cm AbsorberW ReadoutSi Sampling cells22 Longitudinal segments3 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 at3cm Shower max detectorGap 6 Shower max gran. (mm 2 )2 x 60 Two showers resolved at0.3 cm

March 2004 CALOR 2004, Perugia, Italy Silicon … ParameterValueComment Sensor size (cm)6 x 6to maximize the yield Pixel size (cm)1.5 x 1.5to match molier radius and to reduce channel capacitance Pixels per sensor16 Sensors per sampling layer (max) 216 Sensors in the detector3656 Total area of Silicon (m 2 )13 P/A granularity32 channels Chips / sensor0.5 P/A channels / layer<3500 Readout channels~10000 Dynamic range (MIP’s)100 to 500to cover range of species in PHENIX

March 2004 CALOR 2004, Perugia, Italy Impact on J  measurements in the muon spectrometer Cu Nose ConeW/Si NCC X0(total) Labs(total) dE/dx(total)195 MeV390 MeV  (J/Y) (GEANT) 155 MeV178 MeV Mult. Scattering ( GEANT) 100 MeV Mult. Scattrering (estimate) 106 MeV133 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.

March 2004 CALOR 2004, Perugia, Italy Running conditions (occupancy and pileup from underlying event)

March 2004 CALOR 2004, Perugia, Italy G.Bashindzhagyan Moscow State University June 2002 Si/W layers Internal structure (not in scale). Spacers. ~500 mm long; material: steel(?), titanium (?). Stainless steel plate ~10 mm Tungsten plates mm Spacers glued to W 50 mm 2.5 mm ~0.2 mm ~0.3 mm ~3 mm Stainless steel plate …….. ~1 m How to build the calorimeter this dense

March 2004 CALOR 2004, Perugia, Italy Silicon Moscow State University -More then 12 m2 built; Micron semiconductor: -lot of experience, work with PHENIX, perfect prototype available; Other manufacturers …..

March 2004 CALOR 2004, Perugia, Italy 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 samples per signal per L1 trigger

March 2004 CALOR 2004, Perugia, Italy Prototype preamplifier Medical imaging (ratCAP)

March 2004 CALOR 2004, Perugia, Italy 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.

March 2004 CALOR 2004, Perugia, Italy Backups

March 2004 CALOR 2004, Perugia, Italy Silicon Tungsten EMCal Figure of merit something like BR 2 /  –where  = r pixel  r Moliere Maintain the great Moliere radius of tungsten (9 mm) by minimizing the gaps between ~2.5 mm tungsten plates. Dilution is (1+R gap /R w ) –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!

March 2004 CALOR 2004, Perugia, Italy 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 X 0 (14 cm) Sensitive radius: 6.2 – 14.2 cm from the beam axis Each detector layer divided into 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 m 2 /calorimeter OPAL Collaboration, Eur.Phys.J. C14 (2000) 373

March 2004 CALOR 2004, Perugia, Italy 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 channels Total area of Si 2.0 m 2 Depletion voltage ~ 62 V; Bias voltage set to 80 V A detector wedge (OPAL)

March 2004 CALOR 2004, Perugia, Italy 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

March 2004 CALOR 2004, Perugia, Italy Noise and Muons Assume 300  (  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/mm 2, and amplifier noise of 20e - /pf+200 – get about factor of two safety! (1 MIP = 2 x 10 4 e - )

March 2004 CALOR 2004, Perugia, Italy 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 < Peak finding based on 2 nd derivative of the pad signals sensitive to overlapping showers

March 2004 CALOR 2004, Perugia, Italy A is d and B is Au. Energy and momentum conservation x L = x a - x b =(2M T /√s)sinh y k a + k b = k x a x b = M T 2 /s A solution to this system is: x a = (M T /√s) e y x b = (M T /√s) e -y where y is the rapidity of the (x L,, k) system R.Debbe

March 2004 CALOR 2004, Perugia, Italy We are exploring the possibility of completely determining the kinematic variables x 1, x 2, and Q 2 by measuring the jet as well.