forward calorimeter upgrades in phenix: past and future

Forward Calorimeter Upgrades in PHENIX:

Past and Future

Richard Hollis for the PHENIX Collaboration

University of California, Riverside

Winter Workshop on Nuclear Dynamics

8th January 2010

Richard Hollis8th January 2010 ● 2

NUCLEARDYNAMICSWINTER●WORKSHOP

Overview

The next decade at RHIC&PHENIXMotivation and Needs

Calorimeter UpgradesPast: MPC – currently operationalFuture: FoCal – proposal soon

Summary



The next decade at PHENIX

A biased (to Forward Calorimetry) view: Gluon density at low-x in cold nuclear matter Proton spin contribution from Gluon Polarization Measure -jet production, correlations in Au+Au collisions Test predictions for the relation between single-transverse spin in

p+p and those in DIS

For data taking and analysis over the course of the next decade…

First step: measurements at high



Onset of Gluon Saturation

Nuclear modification factor: Increasing suppression with

Consistent with the onset of gluon saturation at small-x in the Au nucleus.

Need to study this in more detail by identifying particles expanding forward coverage

BRAHMS: PRL93 (2009) 242303

d+Au collisions

CentralArms

MuonArms



Proton spin contribution from gluon polarization

p+p collisions

RHIC range0.05 < x < 0.2

xg Spin contribution from gluon

polarization derived from measured ALL

currently over a narrow region of x

Large uncertainty at low-x

Need to measure ALL over a broader region of x forward measure direct photons



Building detectors to suit physics needs

Need:Forward rapiditiesDirect photonsWell defined energy scale for measurements



PHENIX Acceptance

Tracking Central region and forward

muon arms

Calorimetry Very limited acceptance

In and

What do we need for the future? and how can we obtain it?

-3 -2 -1 0 1 2 3

0

c

over

age

2

EMC

-3 -2 -1 0 1 2 3

0

c

over

age

2

Tr Tr

(F)VTX



PHENIX Acceptance

Staged Calorimeter Upgrades

Muon Piston Calorimeter (MPC) 3.1<||<3.9

-3 -2 -1 0 1 2 3

0

c

over

age

2

Tr Tr

(F)VTX

-3 -2 -1 0 1 2 3

0

c

over

age

2

EMCMPC MPC



Muon Piston Calorimeter (MPC)

Lead Scintillator (PbW04)

18cm long ~20X0

2.2x2.2cm transverse 220 (196) Crystals in N (S)

South Arm: -3.7<<-3.1 North Arm: 3.1<< 3.9

Measure 0’s up to 17 GeV pT~1.7 GeV/c

pT>1.7GeV/c – measure single “clusters”

12 < E < 15 GeV

Raw Signal

Mixed-eventBackground

Yield

Cou

nts

MPC(N)



Physics Application

Two-particle correlations Correlation of central arm 0

and h with MPC 0

Measure jet modification in d+Au collisions

Mid-rapidity 0 Trigger

Forward Associates

dNd



Physics Application

Two-particle correlations Correlation of central arm 0

and h with MPC 0

Measure jet modification in d+Au collisions

Probe low-x (0.006<x<0.1)

IdA suppression – a signature of CGC

Mid-rapidity 0 Trigger

Forward Associates



Physics Application

Calorimeters are versatile Measurements using identified

C and are underway

Preliminary results on transverse single-spin asymmetries

• Measurements over a broad phase space will provide quantitative tests for models

How do the calorimeters contribute to G – the gluon contribution to proton spin Would like to measure direct s

3.0<<4.0

p+p0+X at s=62.4 GeV/c2



PHENIX Acceptance

Staged Calorimeter Upgrades

Muon Piston Calorimeter (MPC) 3.1<||<3.9

Forward Calorimeter (FoCal) 1<||<3

-3 -2 -1 0 1 2 3

0

c

over

age

2

Tr Tr

(F)VTX

-3 -2 -1 0 1 2 3

0

c

over

age

2

EMCMPC MPC



Finding space in PHENIX

MPC installed ~ 3<||<4

MPC

FoCal: where could it fit?



Finding space in PHENIX

Small space in front of nosecone 40 cm from vertex 20 cm deep

Calorimeter needs to be high density Silicon-Tungsten sampling

calorimeter



FoCal

Silicon-Tungsten sampling calorimeter 21 layers ~21X0

Each Arm: 1<|<3

Expect good resolution in E and / Active readout

~1.5x1.5cm

Distinct 2-shower 0 up to pT~3 GeV/c (~1)

Transverse View

Longitudinal View

6.1cm



FoCal x Coverage

x coverage: Weak pT dependence

p+p collisions

x versus pT (p+p, 500 GeV)(FoCal Acceptance)



FoCal x Coverage


Strong dependence

p+p collisions

x versus (p+p, 500 GeV)(FoCal Acceptance)



FoCal x Coverage

p+p collisions

x versus (p+p, 500 GeV)(FoCal & MPC Acceptance)


Strong dependence FoCal complementary to MPC



FoCal x Coverage

x for bins (p+p, 500 GeV)(FoCal Acceptance)


Strong dependence FoCal complementary to MPC

Selecting region probes a specific x range



FoCal (Expected) Performance

Can one see jets over the background Sufficiently isolated? Average background

• Units are measured energy (~2% of total)

Single-event background• ~20 times higher

30GeV embedded jet• Visible over the

background

d+Au collisions



What about direct identification?

Important for our measurements in the next decade in Spin d+Au Au+Au



Identifying 0 and

First: use physics Direct typically are alone Whilst 0 are produced as part

of a hadronic jet Measurement of accompanying

energy can reduce background at minimal expense to

Still, this does not provide full decontamination Need direct 0 identification

Ratio of background/signal(NLO calculation)

p+p collisions



High energy 0 shower

Origin of all shower particles (red) Shown with effective

resolution of pads

Individual tracks not distinguishable

p+p collisions




Finer resolution could “see” individual tracks from 0 Up to ~50GeV

Make the whole detector with finer resolution!! Not realistic → what can be

designed?

p+p collisions






designed?

Add highly segmented layers of x/y strips into first segment. Measure the development of the

shower at its infancy With a resolution to distinguish

individual tracks

EM0 EM1 EM2

x y x y x y x y

~2 tow

ers

~70 strips

p+p collisions






designed?

Add highly segmented layers of x/y strips into first segment. Measure the development of the

shower at its infancy With a resolution to distinguish

individual tracksCatch the shower, before it’s too late

Tracks are visiblySeparable

Track showersMerge




Using a Hough Transform, Transverse/longitudinal

coordinate Find the best track as most

frequently occurring Hough-slope

Use each track vector, full track energy → calculate invariant mass



Performance of FoCal Reconstruction

Reconstruction of 0 (p+p 500 GeV minimum bias pythia)

Signal reconstruction(d+Au 200 GeV minimum bias + embedded pythia +jet signal)



Summary

PHENIX Calorimeter upgrades (will) provide much extended coverage for a variety of physics topics Proven 0 reconstruction in the MPC further our understanding of

forward jet production in d+Au collisions FoCal complements the MPC in terms of additional phase-space

coverage and direct photon identification capabilities at high energies.

For p+p, d+Au (and Au+Au) collisions



An energy scale for jet suppression

h-h correlations exhibit interesting features … but have limitations: may be subject to surface bias may not reveal the jet energy

scale

-h or -jet could provide an energy scale

• (assuming) the is not [energy] suppressed

Reduced surface bias• as the trigger probe is not

modified

STAR: NPA830 (2009) 685CSTAR: PRL103 (2009) 172301

A+A collisions



MPC x Coverage

x versus (p+p, 500 GeV)(MPC Acceptance)



Correlation of central arm 0 and h with MPC 0

Measured associate yields relative to pp

Systematic suppression with centrality No appreciable trigger

dependence

Probe low-x (0.006<x<0.1)

d+Au collisions

forward calorimeter upgrades in phenix: past and future

Documents

gluon density

forward calorimeter

au nucleus

au collisionstest predictions

singletransverse spin

nuclear dynamics8th

energy scale

increasing suppression