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W physics @ PHENIX. 2009/06/01 Kyoto Univ. / RIKEN Ken’ichi Karatsu. Contents. Proton Spin Structure Probe Proton Spin with W boson W detection @ PHENIX Summary. 1. Proton Spin Structure. Parton polarization function. Proton Spin : ½ = ½Δ ∑ + ΔG + L

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w physics @ phenix

W physics @ PHENIX

2009/06/01

Kyoto Univ. / RIKEN

Ken’ichi Karatsu

2009 RHIC & AGS Annual Users’ Meeting

contents
Contents
  • Proton SpinStructure
  • Probe Proton Spin with W boson
  • W detection @ PHENIX
  • Summary

Contents

1 proton spin structure
1. Proton Spin Structure

1. Proton Spin Structure

parton polarization function
Parton polarization function
  • Proton Spin : ½ = ½Δ∑ + ΔG+ L

< about Δ∑= >

  • The polarization of valence quark (u, d) are well understood but, that of sea quark (anti-u, anti-d, anti-s) are not well constrained
  • This talk is about the extraction of sea quark polarization by W-boson production

DSSV Global Fit (2008)

(DIS+SIDIS+pp)

DNS Global Fit (2005)

1. Proton Spin Structure

2 probe proton spin with w boson
2. Probe Proton Spin with W boson

2. Probe Proton Spin with W boson

probe proton spin with w boson
Probe proton spin with W boson
  • Extract the sea polarization by measuring the Single Spin Asymmetry of W-boson production
  • W is produced through pure V-A

- Chirality is fixed ideal for spin structure studies

  • W couples to weak charge ~ flavor

- Flavor is (almost) fixed ideal for flavor structure studies

  • No fragmentation for the final state
  • Asymmetry of W+ -> Δu, Δd-bar
  • Asymmetry of W- -> Δd, Δu-bar

l+

2. Probe Proton Spin with W boson

3 w detection @ phenix
3. W detection @ PHENIX

3. W detection @ PHENIX

slide8

The PHENIX Experiment

  • Philosophy (initial design):
    • High rate capability & granularity
    • Good mass resolution & particle ID
    • Sacrifice acceptance

Central Arm

e+/-

Muon Arm:

Muon Tracking Detector (MuTr),

Muon Identifier (MuID)

Rapidity: 1.2 < η <2.2 (2.4)

Δφ = 2 π

Muon Arm

Rapidity: |h| < 0.35

Δφ = 2 * (π/2)

μ+/-

Central Arm:

Drift Chamber (DC), Pad Chamber (PC),

Ring Imaging Cherenkov Counter (RICH),

Electromagnetic Calorimeter (Emc),

HBD, TOF, TEC

RPCs

3. W detection @ PHENIX

slide9

Expected Asymmetry of W production in the PHENIX Acceptance

(l- pT>20 GeV)

(l+ pT>20 GeV)

Muon Arms: trigger upgrade is ongoing

 will be ready for next 500 GeV run

Central Arms: ready for W measurement

3. W detection @ PHENIX

w in the phenix muon arms
W in the PHENIX Muon Arms

3. W detection @ PHENIX

slide11

μ+/-

RPCs

W in the PHENIX Muon Arms

Muon pT spectra in the Muon Arms

(2000 [1/pb], from PYTHIA5.7)

recorded luminosity

○ 300[pb-1]

Forward AL μ+

Forward AL μ-

W is dominant

(pT>20 [GeV/c])

W

Backward AL μ+

Backward AL μ-

Right plot:

expected asymmetry of W

(assuming 60 % polarization, backgrounds and detector resolution included)

from RHICBOS

3. W detection @ PHENIX

slide12

W in the PHENIX Muon Arms

Design Luminosity

√s = 500 GeV σ=60mb

L = 2x1032/cm2/s

Muon pT spectra in the Muon Arms

(2000 [1/pb], from PYTHIA5.7)

MuID LL1

pmuon>1.5 [GeV/c]

Total interaction rate= 12MHz

New Trigger

DAQ LIMIT

= 2kHz (for Muon Arm)

W

Required RF

6000

BUT

  • Need Momentum Selectivity in the LVL-1 Trigger!

MuID LL1 (trigger)

RF < 200

3.W detection @ PHENIX

slide13

RPC

B

PHENIX Muon Trigger Upgrade

Rapidity: 1.2 < h <2.2 (2.4)

New MuTr FEE (MuTRG)

Installed & operated

at 2009 RHIC Run

Prototype RPC

Installed & operated

at 2009 RHIC Run

  • New MuTr FEE was installed fully in North Arm and partially in South Arm
  • Prototype RPC was installed in South Arm
  • Prototype Pb absorber was installed in South Arm
  • -> part of South Arm has the full configuration (MuTRG+RPC+Pb) in 2009 RHIC Run!
  • -> Evaluate the performance with beam of s=500 GeV @ 2009 RHIC Run

Prototype Pb absorber

Installed at 2009 RHIC Run

  • MuTRG
  • use highly segmented
  • Muon Tracker (good
  • momentum selectivity)
  • poor time resolution..
  • (> 1 beam crossing)
  • <Muon Trigger Upgrade>
  • MuTr FEE Upgrade (MuTRG)
  • Install RPC (Resistive Plate Chamber)
  • Install additional Pb absorber
  • MuID
  • - only existing trigger
  • no momentum selectivity..

Basic Idea:

Measure Δstrip in online level

-> more momentum selective trigger

  • RPC
  • add better timing!
  • less background sensitivity
  • Pb absorber
  • reject hadron background

3. W detection @ PHENIX

current status muon arms

MuTr St3

MuTr St2

MuTr St1

Current Status - Muon Arms
  • Performance of New MuTr FEE (MuTRG)
  • Turn on Point of Efficiency Curve ~ 4 (arb. unit)
  • Most Probable Value of MIP ~ 20 (arb. unit)
  • MuTRG and MuTr have matching properly
  • Efficiency for MIP is 97.5%(Yellow / Blue)
  • Study of rejection factor is ongoing

Trigger Emulation (offline analysis)

Blue : MIP dist.

Yellow : MIP x Eff.

Collision

Point

Red : MuTRG Hit, Blue : Accepted Track

3. W detection @ PHENIX

current status muon arms1

RPC3

(Prototype)

RPC2

(Prototype)

Peak(>0)

Peak (<0)

Current Status - Muon Arms
  • Performance of Prototype RPC

From collision or

out going beam

From beam

background

Peak (<0) : Tracks coming from collision or outgoing beam

Peak (>0) : Background by incoming beam

Width of each peak : 3 [ns] -> good timing resolution!

3. W detection @ PHENIX

w in the phenix central arms
W in the PHENIX Central Arms

3. W detection @ PHENIX

slide17

e+/-

W in the PHENIX Central Arms

pions: NLO pQCD calculation from W. Vogelsang

W: RHICBOS (Nadolsky, Yuan)

pi+

Upper plot:

cross section of e+/- from W & π+/- in the PHENIX acceptance

Rapidity: |h| < 0.35

pi+

<Charged hadron rejection>

EMCal intrinsic: 50-150

Shower profile: 2-4

Isolation cut: ~10

Total: 1000-6000

e+

e-

Lower plot:

expected asymmetry of W

(assuming 70 % polarization, no background or detector resolution included)

recorded luminosity

● 300 [pb-1]

○ 70 [pb-1]

3. W detection @ PHENIX

current status central arms
Current Status - Central Arms

pi+

pi+

  • Brief summary of 2009 RHIC Run (Run9)
  • Polarization: ~35[%]

(from RHIC pol-group)

  • recorded luminosity @ PHENIX: ~10 [pb-1]

(with vertex cut)

  • The aim of Run9 analysis

-> measure cross section of W boson!

(W+e+& W-e-)

e+

e-

3. W detection @ PHENIX

current status central arms1

e+/-

Current Status - Central Arms

Energy v.s. Inclination of the track

pi+

Emc Energy calibration -> Done

Invariant mass v.s. total energy of 2 photons

negative charge

pi+

  • <To do>
  • estimate detector eff. & acceptance
  • estimate backgrounds
  • isolation cut
  • estimate charge contamination
  • etc..
  • ->lots of things are work in progress now

alpha [rad.] ~ 0.1/ mom [GeV/c]

“energy / mom < 3” cut applied

e+

e-

positive charge

eta

Energy dist. (Black: +, Red: -)

Inclination angle

(alpha)

Only analyzed part of data set

pi0

3. W detection @ PHENIX

event display of high energy events
Event Display of High energy events

Energy v.s. Inclination of the track

Found W candidates.

Analysis is under way!

Energy dist. (Black: +, Red: -)

3. W detection @ PHENIX

4 summary
4. Summary
  • W bosons provide possibilities for flavor separated measurements -> sensitive to the polarization of sea quark!
  • Upgrades are ongoing to measure W boson in the PHENIX Muon Arms. They have been partially installed & tested at 2009 RHIC Run

-> Ready for the next 500 GeV run!

  • W boson measurements in the PHENIX Central Arms is possible and analysis is under way on 2009 RHIC data

-> W candidates are seen!

4. Summary

w production

Pol. Proton

proton

  • Flavor is almost fixed
W production
  • We can extract the sea polarization from Single Spin Asymmetry of W production!!
  • No fragmentaion for the final state!
  • W is produced from left-handed q and right-handed q-bar
    • No W founded to coupled to right-handed current