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The W program at PHENIX
R. Seidl (University of Illinois and RBRC)
for the PHENIX Collaboration
Workshop on Parity Violating Spin Asymmetries
BNL, April 26-27th
R.Seidl:The W physics program at PHENIX 2 PVSA, BNL April 27th
Motivation for W physics I: sea polarization
• Parity violating decay selects quark flavor:
• Forward/backward region selects valence/sea quark helicity contribution
• High luminosity and high √s=500 GeV needed
• Only ± detected control of backgrounds important
• High energy muon trigger necessary
W a b a bL
a b a b
u(x )d(x ) d(x )u(x )A
u(x )d(x ) d(x )u(x )
)()(),()( abbaba xdxdxuxuxx
)()(
)()(
ba
baWL
xdxu
xdxuA
Advantages of W as probe:
• Large Scale ( ~mW)
• no Fragmentation functions required
R.Seidl:The W physics program at PHENIX 3 PVSA, BNL April 27th
Motivation for W physics II: asymmetric (unpolarized) sea?
• Asymmetry between
d(x) and u(x) seen at E866,
HERMES and NA51• Test asymmetry in W
production w/o possible
nuclear effects• Also high-x behavior of
u(x)/d(x) can be tested
)()(),()( abbaba xdxdxuxuxx
)()(
)()(
ba
ba
W
W
xuxd
xdxuR
R.Seidl:The W physics program at PHENIX 4 PVSA, BNL April 27th
Philosophy (initial design):Philosophy (initial design): High rate capability & granularityHigh rate capability & granularity Good mass resolution & particle IDGood mass resolution & particle ID Sacrifice acceptanceSacrifice acceptance
The PHENIX Detector
detection• Electromagnetic Calorimeter
• Drift Chamber• Ring Imaging Čerenkov
Counter
• Heavy quarks• Muon Id/Muon Tracker
• Relative Luminosity• Beam Beam Counter (BBC) • Zero Degree
Calorimeter(ZDC)
• Local Polarimetry - ZDC
R.Seidl:The W physics program at PHENIX 5 PVSA, BNL April 27th
Necessity of muon trigger upgrade
• Hadronic decays dominate muon rates
• W dominate only above 20-25 GeV
• DAQ cannot take full rate @500GeV
• Current muon trigger momentum “blind”
Need for a momentum sensitive muon trigger
Add Resistive Plate Counters(RPCs)
Add fast readout electronics for Muon tracker
R.Seidl:The W physics program at PHENIX 6 PVSA, BNL April 27th
PHENIX muon trigger upgrade
RPC1(a+b)
RPC2 RPC3
r=3.40m
MuTr
(I) Three dedicated trigger RPC stations (CMS design):
RPC1(a,b): ~180 segments in , 2 in θ
RPC2: ~360 segments in , 2 in θ
RPC3: ~360 segments in , 2 inθ
(Trigger only – offline segmentation higher)
NSF (Funded)
JSPS (Funded)
(II) MuTr front end electronics
Upgrade to allow LL1 information
R.Seidl:The W physics program at PHENIX 7 PVSA, BNL April 27th
Resistive Plate Counters
Challenges:• Equip large areas
(RPC2 ~22 m2)• Limited space
(smallest ~30cm)• Varying rates from pp to Heavy
Ion Bakkelite RPCs:• Modules can cover larger area• Lower resistivity than glass
higher rate capability• Thickness of a module only
~3cm
-HV
-HV
GND
GND
Readout
Collaborative effort between groups in Korea, China, several American universities and BNL
R.Seidl:The W physics program at PHENIX 8 PVSA, BNL April 27th
Limited space for installation
• RPC2
R.Seidl:The W physics program at PHENIX 9 PVSA, BNL April 27th
Sideview of PHENIX with RPCs
RPC3 South
RPC2 South
RPC2 North
RPC3 North
R.Seidl:The W physics program at PHENIX 10 PVSA, BNL April 27th
New MuTRG Front End Electronics(FEE)
MuTRG-TX
Current FEE
MuTRG-AD
MuTr Chamber
R.Seidl:The W physics program at PHENIX 11 PVSA, BNL April 27th
Offline backgrounds in W analysis
• Cosmic muons– Reliable rates not available– First tests suggest a small
rate
• Muons from Z/ decays– Z have small x-section– Z sensitive to quark helicities
• Fake high PT muons from low PT hadron decays
R.Seidl:The W physics program at PHENIX 12 PVSA, BNL April 27th
How to address fake high PT hadrons I: Absorber
• At early stage (2009-2010) additional absorber instead of RPC1 to reduce rate
• Maybe already install Tungsten instead of Cu in the nosecone ( needed for Nose Cone Calorimeter )
R.Seidl:The W physics program at PHENIX 13 PVSA, BNL April 27th
How to address fake high PT hadronsII:The PHENIX NoseCone Calorimeter (NCC)
• +e identification• – 0 separation• e/ isolation • jet identification•dE/dx• e//jet triggers
NCC
Hadronic
ElectromagneticPreshower
andShower-Max
Fake hadron reduction
R.Seidl:The W physics program at PHENIX 14 PVSA, BNL April 27th
How to address fake high PT hadrons III:The forward Vertex detector
• Baseline:– 4 layers– Vertical planes – 75 m radial pitch, 7.5° phi
segmentation (2 – 13 mm)– Maximize z and r extent to give good
resolution and ≥3 hits/track as much as possible
– 2*600K channels• Scope
– Recently favorably reviewed for FY08 start
– Bootstrapped by LANL LDRD funds to construct one octant prototype
– Submitted proposal to DOE for FY08 funding start
• New Idea on hadron suppression for W physics:
– Average dE/dx in 3 planes can distinguish low energetic hadrons and high energetic muons
R.Seidl:The W physics program at PHENIX 15 PVSA, BNL April 27th
PHENIX ALW+/- Sensitivity
Machine and detector requirements::
– ∫Ldt=800pb-1, P=0.7 at √s=500 GeV
– Muon trigger upgrade!
Expected Sensitivity withW measurement
2009 to 2012 running at √s=500 GeVis projected to deliver ∫Ldt ~980pb-1
R.Seidl:The W physics program at PHENIX 16 PVSA, BNL April 27th
vs HERMES
SIDIS:
•large x-coverage•uncertainties from Fragmentation functions
W-physics:
•limited x-coverage•High Q2 theoretically clean•No FF-info needed
R.Seidl:The W physics program at PHENIX 17 PVSA, BNL April 27th
Upgrade Schedule
2002 2003 2004 2005 2006 2007 2008 2009 2010 2011
MPC
VTX (barrel)
FVTX
NCC
MuTrigger
R&D Phase Construction Phase Ready for Data
R.Seidl:The W physics program at PHENIX 18 PVSA, BNL April 27th
Physics Timeline
2005 2006 2007 2008 2009 …. 2012 (RHIC II)
10 pb-1 …………………………………… 275pb-1 …….. 980pb-1
√s= ……………………….. 200 GeV …………………......... 500 GeV|
P= 0.5 0.6 0.7 ……………………………………
Inclusive hadrons + Jets ~ 25% Transverse Physics Charm Physics direct photons bottom physics W-physics
ALL(hadrons, Jets)
ALL(charm) ALL(γ)AL(W)
L= 1x1031cm-2s-1 6x1031cm-2s-1 1.6x1032cm-2s-1 see Spin report to DOE http://spin.riken.bnl.gov/rsc/
@ 200GeV @ 500GeV
R.Seidl:The W physics program at PHENIX 19 PVSA, BNL April 27th
Outlook: strange polarization with RHICII luminosities
• At high luminosities possibility to tag strangeness:– Detect muon from W decay
(Muon Trigger)– Detect displaced vertex of D
meson decay (VTX and FVTX detectors)
• Charge of selects strange/antistrange
• More in Yokoya-san’s talk
P1
P2
R.Seidl:The W physics program at PHENIX 20 PVSA, BNL April 27th
Summary
• Muon Trigger upgrade funded and progressing well
• First Test Octant of FEE upgrade will be ready for RUN8
• First new muon Trigger available for run 10• Additional upgrades will improve offline W
analysis