up to 10 gev injector

Bernd Surrow

Bernd SurrowLNS Dean’s Advisory Committee MeetingMIT-BATES, 11/21/2003

Up to 10 GeV injector

5-10 GeV static e-ring

Exploring Exploring the Spin structure and dynamics of the Spin structure and dynamics of

the Proton the Proton in high energy polarized pp in high energy polarized pp

collisionscollisionsat RHICat RHIC

AGS

LINACBOOSTER

PHENIX

PHOBOS BRAHMS & PP2PP

STARSTAR

Pol. Proton Source

RHIC


Summary and Summary and Outlook Outlook

Introduction Introduction

Outline

Future MIT research Future MIT research interests interests

Polarized proton Polarized proton collider RHIC collider RHIC

The STAR detector The STAR detector

2

1J

First results in First results in polarized pp collisions polarized pp collisions

Faculty: R. Milner and B. SurrowFaculty: R. Milner and B. SurrowPostdocs: J. Kiryluk and M. MillerPostdocs: J. Kiryluk and M. MillerGraduate student: W. JangGraduate student: W. Jang

STAR RHIC SPIN membersSTAR RHIC SPIN members


RHIC Spin program (e.g. ΔG) Fundamental question: How is the proton spin

made up?

2

1J

gz

qz LLGJ

2

1

2

1

Where is the spin of the proton then?

22 03.0 03.0 )( GeV1at 38.0

iAB Q

)( and gz

qz LLG

Need: New generation of experiments to explore the spin structure of the proton: polarized proton collisions at RHIC which allows to access directly G in polarized pp collisions!

At present: G is only poorly constrained from scaling violations in fixed target DIS experiments

SMC result: Fraction of proton spin carried by quarks is small:

2217.1 31.0 )( GeV1at 99.0

iAB QG

SMC QCD-fit:

B. Adeva et al., SMC Collaboration, Phys. Rev. D58 (1998) 112002.

RHIC spin RHIC spin programprogram:

RHIC spin RHIC spin programprogram:

Spin structure of the proton (gluon polarization, flavor decomposition, transversity)

Spin dependence of fundamental interactions Spin dependence of fragmentation Spin dependence in elastic polarized pp

collisions

Unique multi-year program which has just started…!

Explore various aspects of the spin structure and dynamics of the proton in a new domain:

Introduction


Asymmetries

Measurement of asymmetries (A): Principle approach to study spin effects

Ultimately at RHIC, any combination of beam polarization (longitudinal (+/-) /transverse (/)) is possible, which allows to access different parts of the proton spin structure

Study helicity dependent structure functions!

Double longitudinal-spin asymmetry:

Double transverse-spin asymmetry:

Single longitudinal-spin asymmetry:

Study transverse dependent structure functions!

Study parity violation effects! Study left/right asymmetries!

Statistical significance (FOM=figure-of-merit):

Single transverse-spin asymmetry:

)()(

)()(

LLA )()(

)()(

TTA

LA

NA

Single spin asymmetry:

LdtP2

Double spin asymmetry:

LdtP4

Introduction


Description of ALL in terms of polarized parton distributions:

Introduction

f1

f2

f

ffff

fXff

ffff

fXffLL

fXff

Xpp

Xpp

LL Ddff

Dadff

ddd

d

A

,,21

,,21

21

21

21

2121

22211

222

2112

,,1

, ,/,,

, ,

21

21

zDzppxpxd

d

xfxfdzdxdxd

d

f

fXff

pp

fff

Xpp

22211

222

2112

,,1

, ,/,,

, ,

21

21

zDzppxpxd

d

xfxfdzdxdxd

d

f

fXff

pp

fff

Xpp

fXfffXfffXff

LL dda 212121 / Spin asymmetry of sub-process:


p()

p

Experimental aspects on asymmetry measurement at RHIC: AN

Measurement of AN for forward π0 production at STAR:

Asymmetry:

Xπpp 0

xF ( E0/Ebeam) 0.2 – 0.6 and pT 1 – 3 GeV

Forward 0 (π0 γγ) production

NRN

NRN

LNLN

LNLNPAN cos

Determination of AN requires three measurements:

1. Spin dependent event yield: N()

2. Relative luminosity: R=L/L

3. Beam polarization: P

AN : DIFFERENCE over SUM – In general quite small Require therefore:

1. Statistical precision

2. Control of systematic effects

π0

Introduction


Polarized proton collider RHIC

AGS

LINAC

BOOSTERPol. Proton Source500 mA, 300 ms

Spin RotatorsPartial Siberian Snake

Siberian Snakes

200 MeV Polarimeter

AGS Internal Polarimeter

Rf Dipoles

Absolute Polarimeter (H jet)

2 1011 Pol. Protons / Bunch = 20 mm mrad

PHENIX

PHOBOS BRAHMS & PP2PP

STARSTAR

Siberian Snakes

FY02 devices

FY03 and beyond

RHIC pC Polarimeter

FY03 devices

AGS pC Polarimeter

Lmax = 2 x 1032 cm-2s-1

70% Beam Polarization

50 < √s < 500 GeV

Overview of RHIC polarized pp collider complex Overview of RHIC polarized pp collider complex


Performance overview

Beam energy: 100 GeV

Inst. luminosity: 5 • 1029 s-1 cm-2

Integrated luminosity: 0.3pb-1

Polarization: 0.2 (transverse)

First trans. spin result!

RHIC performance in FY02:

RHIC performance in FY03: Beam energy: 100 GeV

Inst. luminosity: 2 • 1030 s-1 cm-2

Integrated luminosity: 0.5 pb-1 (trans.) 0.4 pb-1

(long.)

Polarization: 0.3 (transverse and longitudinal)

First ALL measurement!

Polarized proton collider RHIC

0.5

0.4

0.3

0.2

0.1

0.0

Polarization

L = 2 x 1030 cm-2 s-1

BBC MinBiasBackground: Blue beamBackground: Yellow beam P

olar

izat

ion

06:00 08:00 10:00 12:00 Time of Day

300k

200k

100kR

ate

RHIC FY03 store: #3714 (05/15/03)

Siberian snake and spin rotator magnets successfully commissioned

Fast polarimeters in AGS/RHIC demonstrated to work

Spin transfer AGS to RHIC demonstrated to work

Commissioning status: Installation and commissioning of AGS partial snake

magnet

Commissioning of polarized gas jet target ( Absolute polarization measurement)

Commissioning of 250GeV ramp

Adequate time for commissioning and luminosity development

RHIC SPIN effort is in the very

beginning of its multi-

year program!

RHIC SPIN effort is in the very

beginning of its multi-

year program!


The STAR detector

Overview Overview Upgrade program of the STAR experiment for the first polarized proton collisions (FY02/FY03):

Beam-Beam Counter (BBC): (2 < < 5) Relative luminosity measurement

Rejection of beam-gas event in pp collisions

Minimum bias trigger

Beam tuning to make collisions at STAR

Luminosity monitor

Forward-Pion Detector (FPD) (3 < < 4) Electromagnetic calorimeter system:

Prototype setup of 3 Pb-glass arrays and 1 Pb-scintillator calorimeter east side for FY02

Upgrade in FY03: Pb-glass array on EAST/WEST

Energy and shower profile measurement (0 )

Event yield for Forward 0 production

Commissioning of EM-calorimeter modules and trigger (Barrel: -1 < < 1 & Endcap: 1.09 < < 2)

Commissioning of spin scaler system

~7.5m

~7.5m

BBC West

BBC East

FPD West

FPD East


STAR calorimeter system: Endcap and Barrel

The STAR detector

Barrel Calorimeter: -1 < < 1

Lead-scintillator EM calorimeter (~20 X0 )

120 modules with: ΔΦ X Δη = 0.1 X 1.0

40 towers per module: ΔΦ X Δη = 0.05 X 0.05

Shower max. detector (SMD): wire proportional counter (γ/π0 discrimination)

Pre-shower layers

Installed (FY04): 90/120

Instrumented towers: 75/120

Instrumented SMD: 75/120

Endcap calorimeter: -1.09 < < 2

Lead-scintillator calorimeter (~24 X0)

780 towers with: ΔΦ = 0.1, Δη = 0.057 at η = 1.09 to 0.099 at η = 2

Shower max. detector (SMD): scintillator strip layers (γ/π0 discrimination)

Pre-shower and post-shower layers

Complete EEMC installed (FY04 run)

Instrumented: 720 towers and 1/3 (4 sectors) SMD and pre/post shower

Completion and full exploitation of STAR barrel

and endcap calorimeter system crucial for STAR

SPIN program!

Completion and full exploitation of STAR barrel

and endcap calorimeter system crucial for STAR

SPIN program!


Polarization pattern at STAR: Spin Up Spin Down Unpolarized

Bunch Crossing

Lu

min

osit

y

BB

C E

•W

cou

nts

STAR BBC luminosity monitoring

First results in polarized pp collisions

Abort gaps beam-gas background!

05/16/03 - 05/30/03

Relative Luminosity

L

L

R

Determine relative luminosity of bunch-crossings with different polarization

Accuracy: δRstat ~ 10-4 – 10-3

and δRsys ~ 3·10-3


First measurement of AN for forward π0 production at RHIC

AN is found to increase with energy similar to E704 result (s = 20 GeV (10 X smaller than at RHIC), 0.5 < pT < 2.0 GeV)

This behavior is also seen by several models which predict non-zero AN values

Sivers: include intrinsic transverse component, k, in initial state (orbital momentum) (before scattering takes place)

Collins: include intrinsic transverse component, k, in final state (transversity) (after scattering took place)

Qiu and Sterman (Initial-state twist-3)/Koike (final-state twist-3): more “complicated QCD calculations” (higher-twist, multi-parton correlations)

Several approaches beyond the basic “naive QCD calculations” yield non-zero AN values at RHIC energies:

First results in polarized pp collisions


Access ΔG in polarized pp collisions

Study helicity dependent structure functions!

Access ΔG: Double longitudinal-spin asymmetry ALL

FOM ( = Figure-Of-Merit):

LLA

AN/AL: LdtP2 ALL/ATT: LdtP4

ΔG sensitivity in polarized pp collisions

Measurement of ALL requires:

High-pT (prompt) photon production Jet production Heavy-flavor production

Xpp

Xspp )(jet

XbbXccpp ,

RNN

RNN

PPALL

21

1

RNN

APP

PPA LLLL

221

21

)(11

1. N+(-) : Spin dependent event yield

2. R: Relative luminosity

3. P: Beam polarization

Theoretical advantage of RHIC:

Smaller scale dependence at RHIC compared to HERMES/COMPASS!

W. Vogelsang, M. Strattmann

Future MIT research interests


The golden channel at RHIC: Quark-Gluon Compton scattering

)(cosˆ)()(

)( )(

1

qqg

LLqp

g

gLL axA

xG

xGA

ALL for QGC scattering interpreted in LO QCD:

Gluon polarization Measured asymmetry

from polarized DIS pQCD result for QGC scattering

Polarized cross-section is strongly peaked when photon is emitted in direction of incident quark

Best determination of ΔG for:

final-state photon || to initial-state quark Note: QGC scattering dominates over

competing background process: gqq

Reconstruction of initial-state partonic kinematics:

Event-by-event determination of pT,γ (photon energy), ηγ (photon direction) and ηjet (jet direction) allows to reconstruct:

jet,)2(1

ees

px T

21

21

,min

,max

xxx

xxxrecong

reconq

Large x quark (large quark polarization) analyzes small-x gluons (gluon-rich)

Asymmetric QGC scattering (forward boost in direction of incident quark)

Background:

π0(η0) γγ: π0(η0)/γ discrimination needed

Isolation cone requirement

ggq

Future MIT research interestsFuture MIT research interests


Quark-Gluon Compton scattering: Prospects at STAR

Simulated ALL at two different RHIC center-of-mass energies::

Combined data sample at 200 GeV and 500 GeV is essential to minimize extrapolation errors in determining ΔG:

1

0

22 ),()( dxQxgQG

Ultimately: Global analysis of various ΔG!

)(cosˆ)()(

)( )(

1

qqg

LLqp

g

gLL axA

xG

xGA

Accuracy: 0.5

Multi year program at RHIC which

requires: 1. High luminosity 2. High polarization3. s = 200 / 500GeV



Prospects on constraining ΔG from inclusive jet production in RUN4 (FY04)

Simulation based on Pythia including trigger and and jet reconstruction efficiencies

Assume: Coverage of EMC (barrel) 0 < Φ < 2π and 0 < η < 1

Jet Trigger: ET > 5 GeV over at least one “patch” (Δη = 1) X (ΔΦ = 1)

Jet reconstruction: Cone algorithm (seed = 1GeV, R = 0.7)

Polarization: 40% - Luminosity: 3pb-1




W production: Flavor dependence W± production in pp collisions probes flavor

structure of QCD sea analogous to deep-inelastic scattering

Polarized proton beams allow the measurement of (the expected large) parity violation in W± production

Forward e detection (Asymmetric partonic collisions!) gives direct access to probe the underlying quark (anti-quark) polarization which is dominated at RHIC by u/d quarks

ud W ud W

du W du W

uuppA

ddppAeL

eL

/)(

/)(

uuppA

ddppAeL

eL

/)(

/)(

ddppA

uuppAeL

eL

/)(

/)(

ddppA

uuppAeL

eL

/)(

/)(

)( 2xd )( 1xu

e

e

W

0*

z

EEMC

)( 2xu )( 1xd

e

e

W

0*

z

EEMC


Inner and forward tracking upgrade at STAR

Formulated as long-term goal in STAR Decadal STAR Decadal Upgrade PlansUpgrade Plans to BNL Management

Main physics motivation: W physics (Polarized pp program) and Heavy Quark production (Au-Au and polarized pp program)

MIT kick-off meetingMIT kick-off meeting on inner/forward tracking upgrade: November 7-8, 2003

Overview of physics case, possible tracking layout and technology choices (Pixel/GEM/Silicon)

Discussion on upgrade strategy, staging of various projects and overall organization

Profit from MIT LNS silicon laboratoryMIT LNS silicon laboratory and MIT-MIT-BATESBATES (Proposal of a GEM facility!Proposal of a GEM facility!) to strongly participate in the STAR tracking upgrade

New STAR Working GroupNew STAR Working Group (MIT, LBL, IUCF, Yale,

BNL, CalTech,…) on STAR tracking upgrade: Simulation and design work Aim for a proposal by summer 2005!


Experimental issues for W case:

e+e- charge sign determination (Select W+/W-)

e/h discrimination (Full EEMC capabilities crucial!)

Trigger: High pT single EM-cluster in BEMC/EEMC tower


Timeline (Machine and detector upgrade)


RHIC RUN NEW EQUIPMENT TO STAR/RHIC SPIN

FY04

FY05

FY06+07

FY08+09

New AGS warm snake; H gas jet; RF spin flipper; BEMCBEMC preshower; EEMCEEMC SMD + preshower; completed FPD

New strong AGS cold snake; Completed BEMC, EEMCCompleted BEMC, EEMC (incl. postshower); Evtl. forward hadron calorimeter

Work to achieve full design L and Pbeam ; s = 500 GeV commissioning; STAR TOF barrel

Improved STAR inner/forward Improved STAR inner/forward trackertracker

Test L improvement schemes; calibrate Pbeam to 10%; continue AALLLL(jets)(jets)

Calibrate Pbeam to 5%; improve L; Collins frag. with forward 0’s; more AALLLL(jets)(jets); first look at +jet+jet

AALLLL(( + jet) + jet), transversity measurements at mid-rapidity, at s = 200 GeV

AALLLL(( + jet) + jet), AALL(W(W±±)) at s = 500

GeV


Summary and Outlook

RHIC Spin program at BNL First successful polarized proton collisions everFirst successful polarized proton collisions ever at RHIC

(transverse and longitudinal)

Successful upgrade and commissioningSuccessful upgrade and commissioning of various new STAR components for the first polarized proton run at RHIC

Unique opportunity to explore the spin structure of the proton in a new unexplored regime at RHIC over the next years. Focus on:

Gluon polarizationGluon polarization Flavor decompositionFlavor decomposition

This requires various accelerator, polarimeter and detector components to be completed (High polarization and luminosity Continuous pp running and development Continuous pp running and development crucialcrucial)!

Profit from infra-structure at MIT-LNSMIT-LNS and MIT-BATESMIT-BATES towards STAR tracking upgradeSTAR tracking upgrade

A very exciting time is ahead of us to explore the spin structure of the proton at RHIC and to establish a new ep/eA facility at BNL!

A very exciting time is ahead of us to explore the spin structure of the proton at RHIC and to establish a new ep/eA facility at BNL!

Future eRHIC program at BNLFuture eRHIC program at BNL

Explore new QCD regimenew QCD regime in eAeA (high parton high parton density – saturation phenomenadensity – saturation phenomena) and polarizedpolarized ep scattering ep scattering (complement ongoing RHIC physics activities)

Unique opportunity to establish such a QCD facility at BNL!

Up to 10 GeV injector

5-10 GeV static e-ringBRAHMS & PP2PP

AGS

LINACBOOSTER

PHENIX

PHOBOS

STARSTAR

Pol. Proton Source

RHIC

up to 10 gev injector

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