aps topical group on hadronic physics rhic spin fermilab, october 26 th 2004 rhic spin: experimental...

APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004

RHIC SPIN: Experimental Issues

o Physics Goals

o PDFs from hadron collisions?

o A new experimental technique: Polarized proton-proton collisions at high energies!

o First Results from RHIC

o Upgrades

o Summary

Matthias Grosse Perdekamp, UIUC and RBRC


averagehelicity quark)Qq(x 2,

differencehelicity quark )Qq(x 2,

fliphelicty )Qq(x 2,

(well known)

(moderately well known)

(unknown)

onDistributi Gluon)QxG 2,(

(moderately well known)

onPolarizati Gluon )QxG 2,((unknown)

Nucleon Structure Quark and Gluon (parton) Distribution Functions

What is the origin of the Proton Spin?


Gluon polarization

Flavor separation of quark polarizations

Transverse spin structure of the Nucleon

Proton Spin Structure at Hard Scales

)()(

xGxG

)()(,)(

)(xq

xqxq

xq

Physics Channels

Inclusive jets, hadrons, heavy flavor, direct photons,in STAR and PHENIX

Single lepton asymmetriesAL(e,μ) in W-production inSTAR and PHENIX

AN in STAR, PHENIX andBRAHMSback to back correlations,AT in Collins- and interference fragmentation and ATT in Drell Yan in STAR and PHENIX.

What is unique at RHIC?

o Robust extraction of spin dep. pdfs from pQCD analysiso Broad x-range: 0.001<x<0.3o Multiple channels: good control of of sys. and theor. uncertainties determine G(x) and ∫∆G(x)dx !

o direct and theoretically clean flavor separation of spin dependent pdfso sufficient statistical resolution sea quark spin vs gluon spin

o high precision measurements of multiple single and double spin asymmetries at hard scales aim at a separation of Sivers and Transversity contributions

)()(xq

xq


Can Gluon Distributions be Extractedfrom Hadron Collisions?

I) Let’s take a look at G(x,Q2)

II) NLO pQCD vs RHIC data


Global QCD Analysis for G(x,Q2) and q(x,Q2):J. Pumplin et.al JEHP 0207:012 (2002)

3.16GeVQ at u

3.16GeVQ at d

10-410-3 10-2 10-1 0.5 x

gluon

down

up-quarks

anti-down

Quark and Gluon Distributions

error on G(x,Q2)

error for u(x,Q2)

+/- 10%

+/- 5% +/- 5%

error for d(x,Q2)

10-410-3 10-2 10-1 0.5 x

CTEQ6: use DGLAP Q2-evolution of

quark and gluon distributions to extract q(x,Q2)and G(x,Q2) from global fit to data sets atdifferent scales Q2.

H1 + Zeus F2

CDF + D0 Jets

CTEQ5M1

CTEQ6M

Ra

tio

to

CT

EQ

6

Ra

tio

to

CT

EQ

6R

ati

o t

o C

TE

Q6

1.0

1.0

1.0

2.0

0.5

0.5 0.5

2.0 2.0


G(x,Q2) and q(x,Q2) + pQCD beautifully agree with HERA + Tevatron!

J. Pumplin et.al JEHP 0207:012 (2002)

D0 Jet Cross Section ZEUS F2


and RHIC ? q(x,Q2), G(x,Q2) and D(z,Q2) + pQCD nicely consistent with experiment!

o Good agreement between NLO pQCD calculations and experiment can use a NLO pQCD analysis to extract spin dependent quark and gluon distributions from RHIC data!

PHENIX π0 cross section a |η|<0.35 Phys.Rev.Lett.91:241803,2003

STAR π0 cross section a 3.4<η<4.0 Phys.Rev.Lett.92:171801,2004

gluon fragmentation !?


Direct Photons: NLO pQCD vs RHIC data

• NLO-pQCD calculation– Private communication with

W.Vogelsang

– CTEQ6M PDF.

– direct photon + fragmentation photon

– Set Renormalization scale

and factorization scale pT/2,pT,2pT

The theory calculation shows good agreement with our result.

Kensuke Okada’s SPIN 2004 talk


30 years of spin dependent DIS

Helicity difference distribution quarks ∆q(x) : moderately well known gluons ∆G(x) : unknown

Helicity flip (transversity) distribution quarks δq(x) : unknown

Current Experiments onNucleon Structure (as reported at DIS 2004)

Field started with polarized electron sources and targets Yale/SLAC mid 70s

SLAC, CERN, DESY

J. Ashman et al., Phys.Lett.B206:364,1988“Proton Spin Crisis” > 1200 citations on SPIRES


AGSLINACBOOSTER

Polarized Source

Spin RotatorsPartial Snake

Siberian Snakes

200 MeV Polarimeter

AGS Internal Polarimeter

Rf Dipole

RHIC pC Polarimeters Absolute Polarimeter (H jet)

PHENIX

PHOBOS BRAHMS & PP2PP

STAR

Siberian Snakes

Run 04 achieved:1

s2

cm30

106~GeV 200

peakLs ,

Pb~45% , 55 bunchesNew working point with long beam and polarization lifetimes

Run 05 planned:Time to tune accelerator complexMeasure: ALL(jets), ALL(π0)Commission strong supercon-ducting AGS snake

AGS pC Polarimeter

A New Experimental Tool for Proton Spin Structure

High Energy Polarized Proton Beams and Collisions

Helical Partial SnakeStrong Snake

Spin Flipper

Spin 2004: M. Bai, H. Huang, V. Ptitsyn, T. Roser A. Bravar, P. Cameron, D. Sviridia,A. Zelenski, T. Wise, W. McKay


An Example: High Energy Proton Polarimeters for p=20-250 GeV/c

High Energy Polarimeter Requirement for RHIC Spin

Absolute RHIC polarimeter

Fast relative RHIC and AGS polarimeters for monitoring and tuning

Local Polarimeters to confirm spin orientation at collision point

RHIC polarimetery relies on newly observed spin asymmetries:

o Sizeable elastic proton-Carbon spin asymmetries at high energies J. Tojo et al. Phys. Rev. Lett. 89:052302, 2002

o Very forward neutron asymmetries A. Bazilevsky et al. AIP Conf. Proc. 675: 584-588, 2003

o Spin asymmetries in forward multiplicity production as seen by beam-beam counters in STAR J. Kiryluk, AIP Conf. Proc. 675, 424 (2003)


Run 04: The Polarized Jet Target for RHIC

Polarized Hydrogen Gas Jet Target

thickness of > 1012 p/cm2

polarization > 93% (+1 −2)%!

no depolarization from beam wake fields

Silicon recoil spectrometer to measure

• The left-right asymmetry AN in pp elastic

scattering in the CNI region to AN < 10-3

accuracy.

• Transfer this to the beam polarization

• Calibrate the p-Carbon polarimeters

• For 2004 we expect to measure PB to 10%

Courtesy Sandro Bravar, STAR and Yousef Makdisi, CAD


Hor. pos. of Jet 10000 cts. = 2.5 mm

Num

ber

of e

last

ic pp

even

ts Jet profileFWHM ~ 6 mmAs designed

Data collected in this run:

• 100 GeV ~ 700,000 events at the peak of the analyzing power (~ 3 x 106 total useful pp elastic events)• 24 GeV ~ 120,000 events at the peak of the analyzing power (~ 5 x 105 total useful pp elastic events)

TD

C: 1

ct =

1.2

ns

ADC: 1 ct = 40 keVCNI peak AN 1 < E REC < 2 MeV

Recoil protons elastic pp ppscattering

prompt eventsand beam gas

sourcecalibration


Local Polarimetry in PHENIX: Transverse Neutron Asymmetry in ZDC

Yellow

Blue

Rotators on--> radial polarizationRotators on --> vertical polarization


First Results: AN

o Experiments are ready for spin measurements at low luminosity relative luminosity ~ 5x10-4 trigger polarization analysis data analysis

PHENIX AN(π0) and AN(π0) at |η|<0.35

C. Aidala, DIS 2004, to be published

STAR AN(π0) at 3.4<η<4.0 Phys.Rev.Lett.92:171801,2004

Run 02, ∫Ldt ~ 0.2pb-1, P~0.15

o First spin results from RHIC AN sizeable in forward XF

AN compatible with 0 at η~0 (as expected from pQCD)


Run3+4

B.Jager et al., PRD67, 054005 (2003)

First results on longitudinal double spin asymmetries from RHIC

consistent with DIS sample result disfavors large ∆G if ∫Ldt = 3pb-1 and P-0.4 (2005) errors will reduce by factor 8

Experiments are ready for spin measurements at low to moderate luminosities!

relative luminosity ~5x10-4

trigger polarization analysis data analysis

First Results: ALLRun 3 and 4 combined

∆G(x)=G(x)

GRSV ∆G(x)


Schedule for RHIC Spin

2004 2005 2006 2007 2008 2009 ….

example: STAR 32 week scenario all schedules subject to further advances in RHIC operations and/or funding!

pp 5+1 5+10 5+11 0 5+9 156pb-1

√s= ……………………….. 200 GeV ………………….........|

P= 0.45 0.5 0.7 ………………………………………….

Inclusive hadrons + Jets Transverse Physics Charm Physics direct photons Bottom physics W-physics

ALL(hadrons, Jets) ALL(charm)

ALL(γ) AL(W)

L= 6x1030cm-2s-1 8x1031cm-2s-1


Gluon Polarization at Low Luminosity:Inclusive Jets and Hadrons: (1pb-1< ∫Ldt < 30pb-1, 0.4<P<0.6)

GRSV standard ∆G(x)

Gluon distribution from NLO pQCD fit to DIS data on A1, Gluck Reya, Stratmann, Vogelsang Phys. Rev. D63:094005, 2001

ALL in inclusive π0 production (PHENIX)

ALL(π0)

∫Ldt=3pb-1

P=0.4

Vogelsang hep-ph/0405069

Input:∆G(x)=G(x)

GRSV: standard ∆G(x)

∆G(x)=0 ∆G(x)= -G(x)

ALL in inclusive jet production (STAR)Jager, Stratmann, Vogelsang hep-ph/0404057

ALL(Jets)

∫Ldt=3pb-1

P=0.4

Input:∆G(x)=G(x)

GRSV: standard ∆G(x)

∆G(x)= -G(x)

∆G(x)=0

pT [GeV/c] pT [GeV/c]

Expected in run 05: ∫Ldt =5pb-1 P =0.5All required instrumentation in STAR and PHENIX is in place!


Gluon Polarization at Moderate Luminosity:Charm Production: ( ∫Ldt > 30pb-1, P>0.6)

ALL for single electrons in PHENIX

from Wei Xie, PHENIX

--- ∫Ldt=32pb-1

--- ∫Ldt=320pb-1

eLLA

GS-A/B/C:

∆G(xg) parametrizationfrom Gehrmann and Stirling Phys.Rev. D53 6100-6109,1996

∫GA(x)dx =1.8∫GB(x)dx =1.6∫GC(x)dx =0.2

Silicon Vertex Detector Upgrade!


Sensitivity to Gluon Polarization at RHIC from Les Bland, STAR

xgluon

Good control of experimental

and theoretical uncertainties!

PHENIX and STAR are sensitive to ∆G through several independent channels:

Inclusive photons, inclusive jets, jet-photon, J/ψ production, heavy flavor production

70 , .PXjetpp b pb 800Ldt , GeV 500

pb 320Ldt , GeV 200

1-

-1

s

s

GS-A/B/C:

∆G(xg) parametrizationfrom Gehrmann and Stirling Phys.Rev. D53 6100-6109,1996

∫GA(x)dx =1.8∫GB(x)dx =1.6∫GC(x)dx =0.2


Sensitivity to Gluon Polarization at RHIC

SMC, B. Adeva et al. hep-ex/0402010

HERMES Phys.Rev.Lett.84:2584-2588,2000 (II) RHIC spans a broad range of xgluon

Determine first moment ∫∆G(x)dx = gluon contribution to the proton spin!

RHIC data at hard scale pQCD applicable for the extraction of polarized pdfs.

(I)

Assumes data sample of 320pb-1 at √s=200 GeV and 800pb-1 at √s=500 GeV; P=0.7. (This is baseline spin!)

Upgrades extending kinematic coverage to low x decrease error on ∫∆G(x)dx (low x behavior has been critical in proton spin structure in the past: SLAC E80/E130 vs EMC spin crisis)

(IV)

(III)

from F.-H. Heinsius, DIS 2004


W

Z

W Production in Polarized

pp Collisions Single Spin Asymmetry in the naive Quark Parton Model

GeV 20

for dominates

Tp

W

2121

21 ,

),(

),(xx

Mxu

MxuA

W

WWL

Experimental Requirements: tracking at high pT

event selection for muons difficult due to hadron decays and beam backgrounds.

Parity violation of the weakinteraction in combination withcontrol over the proton spin orientation gives access to theflavor spin structure in the proton!


Can We Connect Observables: inclusive AL(lepton) with quark polarizations?

Access to quark polarizations through Access to quark polarizations through

measurements of inclusive measurements of inclusive longitudinal longitudinal

single spin asymmetry?single spin asymmetry?

– Yes! Complete theoretical treatment from first principles by Nadolsky and Yuan at NLO pQCD (Nucl. Phys.B 666(2003) 31).

pTGeV]

Machine and detector requirements:Machine and detector requirements:

– ∫Ldt=800pb-1, P=0.7 at √s=500 GeV

– Upgrades: o Muon trigger in PHENIX

o Forward tracking in STAR

)( TpAL


Quark Polarization: RHIC vs HERMES

– W-production at RHIC• No fragmentation ambiguity• x-range limited

– Semi-inclusive DIS• Wide x-range• Limited sensitivity to sea

flavors• Fragmentation functions

poorly known at low scales (HERMES)

from Naohito Saito, PHENIX


(A) Physics Channels for Low Luminosity

Transverse Spin at RHIC

GeV 200,pb 101 1 sLdt

)( :A Measure N XhppAN

STAR Phys. Rev. Lett. 92:171801, 2004

Boer and Vogelsang (hep-ph/0312320):azimuthal back to back correlation between hadrons in opposite hemisphere jets:

Separation of intrinsic transverse quark spin (transversity) from trans-verse momentum effects (Sivers)?

Clean channel for Sivers effect!

STAR, PHENIX and BRAHMS STAR and PHENIX

(I) (II)


(B) Physics Channels for high L

XppAT

),(

,

:ionFragmentat ceInterferen

Transverse Spin at RHIC

)(

: Jets in EffectCollins

XJetppAT J.C. Collins, Nucl. Phys. B396, 161(1993)

R. Jaffe, X.Jin, J. Tang Phys. Rev. D57 (1999)5920

J. Collins, S. Heppelmann, G. Ladinsky, Nucl.Phys. B420 (1994)565

GeV 200,pb 100-03 1 sLdt

Statistical sensitivity for AT with 32pb-1

HERMES, COMPASS and Jefferson Lab

Separate transverse quark spin (transversity) and transverse momentum contributions (Sivers) in semi-inclusive deep Inelastic scattering:

o low scale leads to significant theoretical ambiguities o Final data set from HERMES available in mid 2005

Brahms AN measurements from 2004and 2005 polarized proton runs!

Brief PHENIX and STAR runs on AN and back-to-backcorrelations as ∫ Ldt/week>1pb-1/week (2006?)

Brief PHENIX and STAR runs on AT as ∫ Ldt/week>10pb-1/week Spin Rotators:

Give flexibility!

STAR and PHENIX

Transverse Spin Physics Elsewhere


Upgrades and RHIC Spin

I) Upgrades required for core spin program flavor separation of spin dependent quark distribution in W-production

STAR: integrated forward tracking

PHENIX: muon trigger

II) Upgrades aimed at a precision measurement of the first moment ∫∆G(x)dx constrain orbital angular mometum?

STAR: micro vertex detector PHENIX: Silicon Vertex Detector, nose cone calorimeter


prompt photon

GS95

x

G x

Measurement of the first moment ∫∆G(x)dx G at low x 0.001

Silicon Tracker +NCC

Upgrades extends the range of xUpgrades extends the range of xGG for for

the prompt-the prompt- measurement down to measurement down to

XXGG~0.001 at~0.001 at s s ==200 GeV200 GeV

Measurement of ∫∆G(x)dx over a wide

x range will be essential in constraining spin sum 1/2∆Σ+ ∆G+Lz

Sensitivity to shape of polarized gluondistribution over a large x range (important input in fixing the shape and extrapolation to low x in global QCD analysis aimed at extracting ∆G)


Summary: Polarized Proton Collisions

o A new experimental method has been successfully developed and we are beginning to exploit a truly novel experimental tool on proton spin structure.

o Fixed target DIS experiments are carried out at comparably soft scales and are subject to various theoretical uncertainties. Leader- ship in the field will shift from DIS experiments to RHIC spin.

o First physics results are available from exploratory runs. 2005 promises to be the first spin physics run at RHIC.

o Integrated forward tracking (STAR) and muon trigger upgrades (PHENIX) are necessary for W-physics.

o Measurement of gluon spin (first moment) contribution to the proton spin requires larger kinematic range eg. nose-cone calorimeter in PHENIX

aps topical group on hadronic physics rhic spin fermilab, october 26 th 2004 rhic spin: experimental...

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