A Proposed FOrward CALorimeter Upgrade in PHENIX

A Proposed

FOrward CALorimeter Upgrade in PHENIX

Richard Hollis for the PHENIX Collaboration

University of California, Riverside

CAARI 2010

12th August 2010

Richard Hollis12th August 2010 ● 2

CAARI2010

Overview

The next decade at RHIC&PHENIXMotivation and Needs

Overview of Current PHENIX DetectorFuture: FOCAL

Event Reconstruction and Expected Impact

Summary


CAARI2010

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


CAARI2010

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 (2004) 242303

d+Au collisions

CentralArms

MuonArms


CAARI2010

Theoretical Guidance

Current theoretical description of nuclear pdfs (at small x) is unconstrained How to reduce the

uncertainty?

We can directly access the gluon pdf from direct-

Direct- is a simple measurement as there is no fragmentation function

Access to low-x at high rapidity

EPS09: NPA830 (2010) 599c


CAARI2010

Building detectors to suit physics needs

Need:Forward rapiditiesDirect photonsWell defined energy scale for measurements

Current PHENIX Detector


CAARI2010

The PHENIX Detector

General features

Central region: E-M Calorimeter

• Electron/photon energy measurements

Tracking• Charged particle momenta

Time of Flight• Charged particle identification

Forward region: Muon Tracker

• Muon identification and momentum

Calorimeter• Very forward photons


CAARI2010

The PHENIX Detector

MPC

Muon TrackerMuon identification and momentum

CalorimeterVery forward photons

TriggerBBC and ZDC

E-M CalorimeterElectron/photon energy measurements

TrackingCharged particle momenta

Time of FlightCharged particle identification


CAARI2010

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


CAARI2010

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


CAARI2010

PHENIX Acceptance

Staged Calorimeter Upgrades

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

Forward Calorimeter (FoCal) 1.6<<2.5 d-going side in d+Au

collisions

-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


CAARI2010

Finding space in PHENIX

MPC installed ~ 3<||<4

MPC

FoCal: where could it fit?


CAARI2010

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


CAARI2010

FoCal

Silicon-Tungsten sampling calorimeter 21 layers ~21X0

d-side Arm: 1.6<<2.5

Expect good resolution in E and / Active readout

~1.5x1.5cm

Distinct 2-shower 0 up to pT~2 GeV/c (~1.6)

Transverse View

Longitudinal View

6.1cm

Instrumented region

S2

S1

S0

1 “brick”


CAARI2010

FOCAL Technology

Tungsten High density for compactness

Silicon Compact Segmentation is easy/versatile

Can be built in stackable blocks

Read-out: 163 pads per brick 12824 strips per brick

Beam S2

S1

S0

Test-beam setup (CERN 2009)


CAARI2010

FoCal x Coverage

Remember: we need low-x

x coverage: Weak pT dependence

p+p collisions

x versus pT (p+p, 200 GeV)(FoCal Acceptance)


CAARI2010

FoCal x Coverage



Strong dependence

p+p collisions

x versus (p+p, 200 GeV)(FoCal Acceptance)


CAARI2010

FoCal x Coverage

p+p collisions

x versus (p+p, 200 GeV)(FoCal & MPC Acceptance)



Strong dependence FoCal complementary to MPC


CAARI2010

FoCal x Coverage

x for bins (p+p, 200 GeV)(FoCal Acceptance)



Strong dependence FoCal complementary to MPC

Selecting region probes a specific x range

1.6<<2.02.0<<2.5


CAARI2010

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

Note: Simulation of fully-instrumented FOCAL


CAARI2010

What about direct identification?

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


CAARI2010

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


CAARI2010

High energy 0 shower

Origin of all shower particles (red) Shown with effective

resolution of pads

Individual tracks not distinguishable

p+p collisions


CAARI2010


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


CAARI2010




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


CAARI2010




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


CAARI2010


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


CAARI2010

High energy 0 reconstruction

Reconstruction of single and 0’s with FOCAL

Observe: good separation of peak and 0 mass peak

Low mass peak from 0’s due to: Large-angle decays One (from 0→) dominating

(asymmetric energy) Only one conversion

Single Particle Simulation


CAARI2010

Understanding the background sources

For each track Found the closest primary

particle Sorted into 4 categories:

0 – is a 0

hit – but not 0, , or dir-Hadron – any

– is an

Full PYTHIA Simulation


CAARI2010

Currently Expected Sensitivity

Lines: nuclear pdf fits based on current data EPS09

Colors represent nuclear pdfs fits with respect to FOCAL uncertainties B lue: within 1 Purple: 2 Cyan: 3


CAARI2010

Summary

PHENIX Forward Calorimeter upgrade (will) provide much extended coverage for a variety of physics topics FoCal complements the existing detectors in terms of additional

phase-space coverage and direct photon identification capabilities at high energies.

Novel design integrates a calorimeter and a tracking device For p+p, d+Au (and Au+Au) collisions

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A Proposed FOrward CALorimeter Upgrade in PHENIX

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