7/6/2005douglas fields for the phenix collaboration 1 spin physics with phenix douglas e. fields...
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7/6/2005 Douglas Fields for the PHENIX collaboration
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Spin Physics With PHENIX
Douglas E. FieldsUniversity of New Mexico/Riken-BNL Research
Center
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Outline
• PHENIX Overview• Status as of Run3 and Run4 data
analysis• Run5 achievements• Expected Run5 results• Future plans• Summary
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Multi-purpose experiment:
•Central Spectrometer•Electrons•Photons•Hadrons
•Forward Spectrometer•Muons
•Very Forward Detectors•Triggering•Centrality•Polarimetry
Detector Overview
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Central Arm Spectrometers• East Arm• tracking:
– DC, PC1, TEC, PC3
• electron & hadron ID:
– RICH,TEC/TRD,
– TOF, EMCal
• photons:– EMCal
• PID– TOF
• West Arm• tracking:
– DC,PC1, PC2, PC3
• electron ID:– RICH, – EMCal
• photons:– EMCal
• PID– Aerogel
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Forward Arm Spectrometers• Muon Tracking
– Radial field magnets– 3 stations of cathode strip
chambers– 100m resolution/plane =
60m resolution/station– J/ mass resolution = 160MeV
• Muon Identification– 5 layers of Irocci tubes– x-y planes between steel
absorber– rejection ~ 10-4
• Zero-Degree Calorimeters
– hadron calorimeter
– neutron sensitive
• Beam-Beam Counters
– QuartzCherenkov radiators
– 3.0 < || < 3.9
• Multiplicity-Vertex Detector
– Silicon strip
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Spin Physics Overview
• Physics– Signal
• Single transverse-spin asymmetry– neutron– 0
– charged hadron– single muon from decay– transversity
• Gluon polarization– jet production/direct
photons– open heavy flavor– J/
• Flavor decomposed quark polarization– W±
• PHENIX can see
•
– neutrons in ZDC/SMD– in EMCal– charged hadron (BBC/Central )– single muons in Muon Arms– AT, ATT Drell-Yan di-muons
• – leading high pt in central arms– e, , e, , and D→K– ee, in Central & Muon Arms
• – high pT ± in Muon Arms
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Spin Physics Overview• Physics
– Signal
• Orbital Angular Momentum– Left-right asymmetry in
single transverse polarization
– Di-jet kT difference in double-longitudinal polarization
• PHENIX can see
• – leading high pt π0 with
correlated h± in central arms
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How Do We Measure…
)21(
)(ˆ
)()(
)()(
)(
),(
212
212
1
21
qgqa
xqxqe
xqxqe
xGG
xxA
LL
aaaa
aaaa
LL
= Gluon polarization
from DIS
from pQCD
L
LR
RNN
RNN
PPALL ,
1
21
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Status of Run3 and Run4 Analysis
• Unpolarized cross-sections• Measured un-
polarized cross section at s=200 GeV well described by NLO pQCD
• non-identified charged hadrons, also measured
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Longitudinal Polarization• Double spin asymmetry in π0 production
Confidence Levels
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Transverse Polarization• Single spin asymmetry in π0 and h±
production
•Run02: 0.15 pb-1 and 15 % polarization
•Run05: 0.16 pb-1 and 50% polarization
•~9X better statistical significance
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Forward Neutron AN
• Spin Rotator Magnets enable longitudinal collisions in IRs• PHENIX discovered at low pT and high xF an analyzing power in
neutron production in pp collisions at 100 GeV• ZDC + Shower Max Detector
~ 1800cm
10cm (±2mrad)
PHENIX Collision Point
Blue beam Yellow beam
Blue Yellow
Blue Yellow
PL/P > 0.99 blue & yellow
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Run 5 Achievements
• RHIC Milestones:– >50% polarization achieved without cold
AGS snake! (also commissioned cold snake)
– Increased longitudinal polarized statistics by factor of >10!
– Accelerated and collided polarized protons to 410GeV!
– 110 bunch mode!– Extremely successful!
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RHIC Status as of Run 5
BRAHMS & PP2PP
STARPHENIX
AGS
LINACBOOSTER
Pol. Proton Source
Spin Rotators
20% Snake
Siberian Snakes
200 MeV polarimeter Rf Dipoles
RHIC pC “CNI” polarimeters
PHOBOS
RHIC
absolute pHpolarimeter
SiberianSnakes
AGS pC “CNI” polarimeter
5% Snake
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Run 5 Achievements
• PHENIX Milestones:– Increased our longitudinal FOM by >200x– Increased our transverse FOM by ~9x– Measured a phi asymmetry at 410GeV– Took scaler data with our new scaler
boards.– Transferred data on-the-fly to CCJ for
reconstruction.– Extremely successful!
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PHENIX Run 5 Integrated L
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PHENIX Run 5 Integrated FOM
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410 GeV Transverse Polarization
blue : ~33%yellow : ~49%
M. Togawa
Polarization
•Analyzing power of PHENIX Local Polarimeter roughly the same despite doubling of energy
•Local Polarimeter can be used at higher s
•Demonstrates that RHIC is capable of accelerating to higher s without losing all polarization•Will provide first look at AN for higher s
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PHENIX scaler boards
-VME based-4 pcs.-25 inputs (24 channels + 1 RHIC-clock) PECL-signals-40 bits deep-80 MB histogram memory-Zero suppression-coarse and vernier delay registers-streaming mode-preparation for high luminosity running
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Data Transfer to CCJ
• 5+ kHz DAQ Rate• International cooperation with RIKEN for data transfer and production• Central Arm production started on June 16, 2005• Muon Arm production to follow
60 MB/s (100 MB/s)
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Expected Run 5 Results
•Run03+Run04 •distinguished between GRSV-max and GRSV-std
•Run05•will distinguish between GRSV-std and G = 0.
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Relative Luminosity Measurement
For double spin asymmetry measurements,relative luminosity error R works as
A systematic uncertainty is checked by consistency between BBC and ZDC counts
YBLL PP
RA
2~
Scalers
BBC
ZDC
ZDC/BBC for each crossing (run171595)
The vertex width fluctuation appears to be small unlike in the past runs.Analysis is on going.
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Sivers di-Hadron AnalysisBoer and Vogelsang, Phys.Rev.D69:094025,2004, hep-ph/0312320
0
2
h
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Orbital From Jet kTLike Helicity
(Positive on Positive Helicity)
Measure jet 2Tk2Tk
Central Collisions
Smaller
Integrate over b, left with some residual kT
Peripheral Collisions
Larger 2Tk
2Tk
Un-like Helicity(Positive On Negative Helicity)
Peripheral Collisions
Smaller
Central Collisions
Larger
Integrate over b, leftwith some differentresidual kT
2Tk
2Tk
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Future Plans: q/q via WNuclear Physics B666(2003)31-55
GS-A,B
GRSV valence
•At s=500 GeV, high rates from heavy flavor and jets overwhelm existing muon trigger
•Requires Muon Trigger Upgrade
AL()
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W Trigger Upgrade
Intended RPC Locations
RPC2
•Resistive Plate Chambers technology chosen by PHENIX forward upgrade group•Cheap – wide coverage possible•Can leverage existing RPC R&D from CMS•Timing information to reject backgrounds and track association with correction bunch•3-dim space point for enhanced pattern recognition
•Two small prototypes successfully tested in Run05•Recently approved NSF-MRI – Full installation expected in Run09
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Silicon Vertex Tracker
Mechanical Specifications:
4-layer Cones at forward rapidity:inner radius 2.5 cmouter radius 18 cmz position (at r
= 2.5cm) 20, 26, 32, 38 cm
mini strips 50 µm x 2.2-13 mmtotal sensor elements ~2.0Mazimuthal coverage 360 deg
4-layer Barrel at central rapidity:layer radius 2.5, 5, 10,14 cmlayer length 24, 24, 30, 36 cmpixels (layers 1+2) 10+20 modules, ~3.9 M pixelspixel size 50 µm x 425 µmstrip-pixels (layers 3+4) 18+26 modules, ~378 K r/o ch. strip-pixel size 80 µm x 1 mm (3 cm)
azimuthal coverage ~320 deg
40 cm0 10 20 30
0
10
20 cm
beam pipe radius: 2 cm
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Summary• RHIC is steadily making progress
towards luminosity and polarization goals.
• PHENIX has set the baseline for RHIC Spin Physics in previous runs.
• Run 5 was a tremendous success!• PHENIX has many pots in the analysis
fire - next stop: Waco.• Future is even brighter, with a rich
assortment of interesting new physics in the coming years!
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Backup
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π± ALL MeasurementStratmann Lecture, BNL 1st Spin School
•5-15 GeV identified by RICH and EMC hadronic shower•Not yet possible to determine sign of g
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Jet ALL
Even with a limited acceptance in PHENIX central arm, we can capture most of a Jet.→ Tag one photon, sum all energy in one arm.
Question : 1. Are those really jets? (agreement much worse at low pT) 2. How much fraction (Z) do we catch? How much is its ambiguity (Z)?Compared to pi0:― More statistics, but Systematic uncertainty in interpretation
By K.Nakano
One whole armTheoretical curve is scaled by Z~0.85 to match with our observable.
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•Run02: 0.15 pb-1 and 15 % polarization
h-
AN for both charged hadrons and neutral pions consistent with zero at midrapidity.
process contribution to 0
More statistics needed to map out pT x g/q dependence
•Run05: 0.16 pb-1 and 50% polarization•~9X better statistical significance
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Polarization DirectionBLUE (AN = 6.24%) YELLOW (AN = 5.27%) (LR)
(TB)
(LR)
(TB)
PHYSICS Period
SL
ST
Commisioning Period
)(~~2
2222
TTT
LLTTTLLLraw APol
polAPolApolApolA
=A
Blue : 10.3% 3.9%Yellow : 21.5% 5.3%
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Transverse Spin Asymmetries
• Neutron asymmetry observed in IP12 while testing a local polarimeter designed to look for 0, asymmetries:
• “Left-Right” asymmetry measured for different slices in phi:
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Phi Asymmetry
• Successful measurement of forward neutron asymmetry.
• Understood (?) in terms of single pion exchange.
• Large asymmetry gives good figure of merit for local (PHENIX) polarimetry. Y. Fukao et al., "Proceedings of the 15th
International Spin Physics Symposium (SPIN2002)
Run-02
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Local Polarimeter at PHENIX
Spin Rotators OFF
Blue YellowYellow
Spin Rotators ON, Current Reversed
YellowYellowBlue
BlueBlue
YellowYellow
YellowYellow
Spin Rotators ON, Almost…Spin Rotators ON, Correct!
|P|=30%, PT=0% PL=30%) |P|=37%, PT=24% PL=28%)
PB=35.5% PB=37%
Run-03
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Transverse Spin Asymmetries
• Charged hadron asymmetry– Measured using BBC– Hadrons in central arms– Decay muons in Muon
Arms
Nor
mal
ized
Yie
ld
PYTHIA+Decay
Real Data
Distance from Absorber [cm]
80 cm
/K
Beam Beam
AbsorberL : Distance from Absorber
Event Vertex
AN from quark polarization
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Longitudinal Double Spin Asymmetries
proton beam
proton beam
or
or
gluon
photon
jet
• Want to measure inclusive photon production (NLO calculations available).
• Need higher luminosity.• Instead, (for now) measure
leading 0 as a jet tag.
G(x
)
x
prompt photon
GS95
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Longitudinal Double Spin Asymmetries
• To determine G, look at ALL:
• R is the relative luminosity, and can be measured (to some accuracy) at PHENIX.
• Our Goal: R/R < 1×10-3 for each fill ALL < 2×10-3
(expected ALL for pions ~ 3×10-3 @PT=3 GeV/c)
L
LR
RNN
RNN
PPALL ,
1
21
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Relative Luminosity• In order to investigate our ability
to measure the relative (++ vs. +-) luminosity:
– look at ratio of 2 detector scalers crossing-by-crossing:
• a(i) = NA(i)/NB(i)– Ratio should be the same for all
crossings (constant) if:• NA(i) = L * ε and NB(i) = L *
ε– B is always the counts from the
beam-beam counter (BBCLL1), A is one of the other scalers.
– Fit this by the expected pattern:• a(i) = C[1+ALLP1(i)P2(i)]• C, ALL are the fitting parameters.
– Precision of relative luminosity can be estimated by:
• C/C – If 2 of the fitting is bad, look for
other factors in N(i).
Ratio of Zero-Degree Counter scalars to Beam-Beam Counter scalers, sorted by bunch crossing and fit to a constant.
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Correction factors• What other factors could
play a role in the determination of the scaler rate besides the luminosity?– Vertex width
• Vertex width also measured crossing by crossing.
• Look for a correlation of the scalers ratio with the vertex width:– Good correlation
• Can correct ratio for this factor.
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Limit on Relative Luminosity Measurement
• After correction for (measured) vertex width, the ratio of counts in the two detectors is consistent with constant up to our level of statistics
• This means that if we apply correction for this the precision on R goes from:0.11% 0.06%
(syst. limited) (stat. limited)
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Gluon Polarization
• Next step: Measure cross-section as a test for perturbative QCD at
• In Run-02, precise measure of 0 cross-section.
• Agreement with pQCD indicates we can extend ALL analysis to lower pT, important for increasing statistical precision with Run-3 data set.
submitted to PRL, hep-ex/0304038
.200GeVs
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Gluon Polarization
• Next step: Measure ALL at • In Run-02, had 150nb-1
with polarization ~15%.• In Run-03, we have
~350nb-1 with polarization ~30% (ALL goes as P4).
• Expect that we can make a differentiation with maximal G:
.200GeVs
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Gluon Polarization
• PHENIX can measure J/ → e+e,
• Can also measure open heavy quark decay to single and di-leptons (e±, ±, e+, e.
• Future upgrades to detect offset vertex.
G(x
)
x
cceX
bbeXJ/
GS95
)(ˆ)()(),( 2121 qqggaxGGx
GGxxA LLLL
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Open Charm • Single muons or electrons• e- coincidence• Better:
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Spin Physics with VTX Upgrade
• Jet-axis for photon+jet-axis constraint on x• ce, displaced vertex low-x S/B, DKhigh-x• bdisplaced J/low/high-x, be, displaced
vertexhigh -x
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Flavor Decomposed Quark Polarization
• At = 500GeV/c2, PHENIX can measure W± decay to single, high pt muons.
• W-production sensitive to polarized anti-quark and quark distributions– interpretation of asymmetry
theoretically well established– insensitive to fragmentation
functions– insensitive to higher twist
• Experimental challenge– acceptance for W X– 1 nb cross-section at 500 GeV– at 2*1032 cm-2s-1 10000 W in
10 weeks– reduce interaction rate ~12
MHz to few kHz
s
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Muon Cherenkov Trigger Upgrade
• Possible solutions for an enhanced muon trigger:– forward hodoscopes– anode readout – cherenkov detector– nosecone calorimeter
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Summary• PHENIX is well suited to the study of spin physics
with a wide variety of probes.• Run-02 gave us a baseline for transverse spin
asymmetry and cross-sections.• So far, in Run-03, we have commissioned with
longitudinal polarized protons (successful spin rotators) and are taking data for an ALL measurement using 0.
• We have studied our relative luminosity systematics and can make an ALL measurement that is statistics limited.
• We have an upgrade plan that will give us the triggers and vertex information that we need for precise future measurements of G, q and new physics at higher luminosity and energy.
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Additional Material
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Other Topics
• Transversity structure function g2 in Drell-Yan
A x xe q x q x
e q x q xTTDY a a
Ta
T
a
a a aa
( , )sin cos
cos
( ) ( ) ( )
( ) ( ) ( )1 2
2
2
21 2
21 2
2
1 2
2 1
2 1
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Vertical polarization profile (scan with horizontal target)
Raw
asy
mm
etry
(x1
0-3)
L-R asymmetry
Count rate(beam size profile)
2mm
In BLUE ring at flattop
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Current J/ From Run-02• Using like-sign subtraction from lepton pairs: