Upload
mauve
View
53
Download
0
Embed Size (px)
DESCRIPTION
RHIC SPIN: Experimental Issues. Matthias Grosse Perdekamp, UIUC and RBRC. Physics Goals PDFs from hadron collisions? A new experimental technique: Polarized proton-proton collisions at high energies! First Results from RHIC Upgrades Summary. Nucleon Structure. - PowerPoint PPT Presentation
Citation preview
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
APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004
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?
APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004
Gluon polarization
Flavor separation of quark polarizations
Transverse spin struc- ture 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
APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004
Can Gluon Distributions be Extractedfrom Hadron Collisions?
I) Let’s take a look at G(x,Q2)
II) NLO pQCD vs RHIC data
APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004
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
APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004
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
APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004
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 !?
APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004
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
APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004
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
APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004
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
APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004
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)
APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004
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
APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004
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
APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004
Local Polarimetry in PHENIX: Transverse Neutron Asymmetry in ZDC
Yellow
Blue
Rotators on--> radial polarizationRotators on --> vertical polarization
APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004
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)
APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004
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)
APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004
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
APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004
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!
APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004
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!
APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004
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
APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004
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
APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 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!
APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004
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
APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004
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
APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004
(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)
APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004
(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
APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004
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
APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004
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)
APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004
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