1

a

FOrward CALorimeter

Richard SetoWinter Workshop on Nuclear Dynamics

Feb 7, 2009

Overview

2

NSAC milestones – Physics Goals

Year # MileStone FOCAL

2012

DM8 Determine gluon densities at low x in cold nuclei via p+ Au or d + Au collisions.

Required for direct photon

2013

HP12 Utilize polarized proton collisions at center of mass energies of 200 and 500 GeV, in combination with global QCD analyses, to determine if gluons have appreciable polarization over any range of momentum fraction between 1 and 30% of the momentum of a polarized proton.

Low-xDirect

2014

DM10(new)

Measure jet and photon production and their correlations in A≈200 ion+ion collisions at energies from medium RHIC energies to the highest achievable energies at LHC.DM10 captures efforts to measure jet correlations over a span of energies at RHIC and a new program using the CERN Large Hadron Collider and its ALICE, ATLAS and CMS detectors.

Marginal without FOCAL

2015

HP13 (new)

Test unique QCD predictions for relation between single-transverse spin phenomena in p-p scattering and those observed in deep-inelastic lepton scatteringNew Milestone HP13 reflects the intense activity and theoretical breakthroughs of recent years in understanding the parton distribution functions accessed in spin asymmetries for hard-scattering reactions involving a transversely polarized proton. This leads to new experimental opportunities to test all our concepts for analyzing hard scattering with perturbative QCD.

Required

G

-Jet AuAu

transversespin phenomena

pA physics – nuclear gluon pdf

3

pA physics – nuclear gluon pdf

direct jets –x resolutionforward η(low-x)

Nuclear Gluon PDF’s : DM8

Look for saturation effects at low x

Measure initial state of Heavy Ion Collision

measure gluon PDF’s in nuclei! (DM8)

1

2

( )

( )

T Jet

T Jet

px e e

sp

x e es

xSaturation at low x

xG(x)

4

Longitudinal Spin G, g(x) : HP12

What is the gluon contribution to the proton spin. Is it at low-x?Phenix and STAR have put constraints on G

0

LLA

5

g(x) very small at medium x (even compared to GRSV or DNS)

best fit has a node at x ~ 0.1 huge uncertainties at small x

DSSV finds

Current data is sensitive to G for xgluon= 0.020.3

direct jets –x resolutionforward η(low-x)0 0

x RHIC range0.05· x · 0.2

small-x0.001· x · 0.05

Longitudinal Spin G, g(x) : HP12

EXTEND MEASUREMENTS TO LOW x!Forward

Measure x

6

direct -jet0

forward η(low-x)large η coverage

Major new Thrust Transverse Spin Phenomena: HP13

use -jet to measure Sivers

Use 0 in jet to measure Collins

determination of the process dependence of the Sivers effect in +jet events

So what does Sivers tell us about orbital angular momentum?

Sivers

7

EM - showerlarge η coverage

Jet correlations in AuAu

Correlations with jets in heavy Ion collisions: DM10

Study the medium via long range correlations with jets

are these correlations from a response by the medium?

leadingEM shower

?

“ridge”

“jet”

STAR Preliminary

for example

8

To meet these goals we must have a detector that measures:

direct and electromagnetic showers

jet angles to obtain x2

0 s forward to reach low-x has large coverage

now what do we build?

9

Schematic of PHENIX

Central Arms ||<0.3 Tracking PbSc/PbGl(EMC) PID VTX to come

MPC 3<||<4

Muon arms 1.1<||<2.4 magnet tracking -ID FVTX to come

central magnet

calorimetry

10

Perfect space for FOCAL! (but tight!)

14 EM bricks14 HAD bricksHAD behind EM

FOCAL

40 cm from Vertex

20 cm of space

nosecone

11

FOCAL Requirements Ability to measure photons and π0’s to 30

GeV Energy resolution < 25%/E Compact (20 cm depth) Ability to identify EM/hadronic activity Jet angular measurement High granularity ~ similar to central arms small mollier radius ~1.4 cm large acceptance – rapidity coverage x2 ~

0.001 Densest calorimeter -> Si W

We wanted large coveragewhat sort of coverage if we put a detector where the nosecones are?

12

Mu

on

tra

ckin

g

Mu

on

tra

ckin

g

VTX & FVTX MP

C

MP

C

-3 -2 -1 0 1 2 3 rapidity

cove

rage

2

EM

CE

MC

FOCAL a large acceptance calorimeter

FOCALFOCAL

trac

kin

g

trac

kin

g

What’s missing? FORward CALorimetery

13

reach in x2 for g(x) and GA(x)

log(x2)EMC+VTXEMC+VTX+FOCALEMC+VTX+FOCAL+MPC X2 10-3

2~s Q

14

FOCAL Design

15

Overall Detector – stack the bricks

“brick”

85 cm Note thisledge may not bein the final design

supertower

17 cm6cm

6cm

16

Design Tungsten-Silicon

Silicon “pads”4 planes of x-y “strips” (8 physical planes)

ParticleDirection

4 mm W

Supertower

γ/π0 Discriminator=EM0 EM1 EM2segments=

Pads SiliconDesign

Pads: 21 layers 535 m silicon 16 cells:

15.5mmx15.5mmX and Y Strips: 4 layers

x-y high resolution strip planes

128 strips: 6.2cmx0.5mm

6cm

17

Vital statistics ~17 cm in length 22 X0 ~ 0.9 Strips – read out by SVX-4

8 layer *128 strips=1024 strips/super-tower 1024 strips/super-tower*160 super-towers/side = 163,840 strips/side 163840 strips/side (1detector/128 strips) = 1280 Strip

Detectors/side 163,840 strips /(128 channels/chip)= 1280 chips/side

Pads – read out by ADC– 3 longitudinal readouts 160 supertowers/side*21 detectors/supertower=

3360 Si pad detectors/side 3360 detector*16channels/detector= 53760 pads/side

readout channels (pads) 160 supe-rtowers/side *16 pads/tower*3 towers =7680 readouts/side

Bricks 2x4 supertowers: 4 2x6 supertowers: 6 2x7 supertowers: 4

EM0= /0, EM1, EM2 segments

18

Detection – how it works

Some detector performance examples

19

Status of simulations Stand alone done w/ GEANT3/G4 to study

/0 separation, single track 0 (G4) EM shower energy/angle resolutions (G4)

Full PISA jet resolution (G3/PISA) 2 track 0 (G3/PISA)

Several levels Statistical errors, backgrounds, resolutions folded into

Pythia level calculations Full PISA simulation using old configuration

Transverse spin physics – task force formed – simulations in progress (early step is to put models etc into simulations)

*PISA – PHENIX Geant3 simulation

20

It’s a tracking device

vertex

EM0 EM1 EM2A 10 GeV photon “track”

Pixel-like tracking:3 layers + vertex

Each “hit” is the center of gravity of the cluster in the segment

Iterative pattern recognition algorithm uses a parameterization of the shower shape for energy sharing among clusters in a segment and among tracks in the calorimeter.

21

Energy Resolution (Geant4)

Excludes Stripsno sampling fraction correction

0.00+0.20/√E

New Geometry

adequate: we wanted ~ 0.25/√E

22

pt=2.-2.5y=1-1.5 pt=4.-4.5

y=1-1.5

pt=1.-1.5y=1-1.5

/0 identification: pp 2 track 0 pT<5 GeV

E=6-10 GeV

pt=0.5-1.0y=2-2.5pt=0.5-1.0

y=1.5-2.0

pt=1.5-2.0y=1.5-2.0

23

X-view

Y-view

50 GeV pi0

4-x, 2x

4-y, 3y

/0 identification:

Single track /0

for pt>5 GeV showers overlap use x/y + vertex

to get opening angle

Energy from Calorimeter

Energy Asymmetry – assume 50-50 split as a first algorithm

invariant mass

24

10 GeV ~1.65 (Geant4-pp events)

Fake reconstruction: 20%Real 0 reconstruction: 50-60%

Real reconstruction: ~ 60%Fake 0 reconstruction ~ 5%

Assumed 0 region Assumed region

0

/0 identification: single track /0tested at various energies and angles, so far at pp multiplicities

25

Longitudinal Spin G, g(x) : HP12

150/pb, P=0.7

GSC, Response + Background

FOCAL Direct Gamma ALLnext step: use -jet to constrain x

RHICregion

ALL

26

DSSV

GSC

Selecting x with rapidity cuts 0

0

Use 0 as a stand in for jets and do a correlation require 1st 0 pT>2.5 GeV, =1-3 (into focal) Choose 2nd 0 to be opposite side in and to go to low

x2

Longitudinal Spin Goal

log(x2)

(2nd 0)

0

LLA

27

“Direct” Constraint of G(x) in Nuclei:DM8

q

qg

q

q g

Compton

Annihilation

•G(x) in nuclei almost unconstrained at low x•Proposal: Measure -jet in d+Au collisions to extract G(x) in nuclei

unknown

Eskola et al, JHEP0807:102,2008 hep-ph/0802.0139

( )

( )Pb

p

G x

G x

GluonSeaValence

28

Resolutions EM shower

energy – 20%/E angular – 6mr

Jet angular resolution 60 mr @ pt=20 GeV

pT

jet angularresolution

( )JetTgluon

px e e

s

x2~ resolution 15%

2 2/x x

29

Expected Error for GA(x)/Gp(x) :DM8

G(x)Au/G(x)p

Log(x2)

d+Au: Ldt = 0.45 pb -1 x 0.25 effp+p: Ldt = 240 pb-1 x 0.25 eff

pT jet>4 GeV, ptgamma>2

Current uncertainty

•Possibility for a dramatic improvement in understanding of G(x) in nuclei•Impact is widespread•Errors are statistical only

30

hadrons

q

q

hadrons leading particle suppressed

leading particle suppressed

Studying the medium through jet “tomography” DM10

hadrons

q

q

hadrons

leadingparticle

leading particle

“ridge”

“jet”

STAR Preliminary

ridgejet

pTtrig>2.5 GeV/c, pT

assoc > 20 MeV/c, Au+Au 0-30%

E. Wenger (PHOBOS), QM2008

31

Jet correlation studies with the FoCal DM10

Need higher-pT triggers, Extended reach large

How: trigger on high-energy in FoCal study associated particles in central and muon arms

What: Extended reach and range (~6) Study particle composition of correlated particles using

central/muon arm PID detectors including photons Heavy-quark studies via leptons in central/muon arms

32

backgroundassumingpp high ptrates

/0 trigger eff, AuAu b=3.2 fm =[1.,1.5] Ecut> ~15 GeV

S:B~10:1

Parameterize background by studying average energy deposited in the detector (E) and its fluctuations (RMS)

Study efficiency and contamination for set values of Nσ

Strategy:

2

measE EN

RMS

E

ERMS

/0

tri

gg

er

eff

high pT em showerembedded inhijing

33

Conclusion

We want to address the following NSAC milestones measure G at low-x to see if the gluon contributes to the

proton spin measure the nuclear gluon pdf’s to study the effects of transverse spin and its connection to

the orbital angular momentum of the constituents of the proton

Study long range correlations between jets and secondary particles as a means to understand the medium created in heavy ion collisions at RHIC

These goals can addressed by calorimeter which can identify and measure s and 0

can measure the jet angular resolution and together with the information from the can lead to a reasonable measurement of x2

has large rapidity coverage and can probe x2 10-3

We now have a have design Prototype in April