Spin Physics With PHENIX

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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4

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:

Documents

Spin Physics With PHENIX