The W program at PHENIX R. Seidl (University of Illinois and RBRC) for the PHENIX Collaboration Workshop on Parity Violating Spin Asymmetries BNL, April

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


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


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


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


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


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


Limited space for installation

• RPC2


Sideview of PHENIX with RPCs

RPC3 South

RPC2 South

RPC2 North

RPC3 North


New MuTRG Front End Electronics(FEE)

MuTRG-TX

Current FEE

MuTRG-AD

MuTr Chamber


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


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 )


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


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


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


vs HERMES

SIDIS:

•large x-coverage•uncertainties from Fragmentation functions

W-physics:

•limited x-coverage•High Q2 theoretically clean•No FF-info needed


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


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


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


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

Documents

The W program at PHENIX R. Seidl (University of Illinois and RBRC) for the PHENIX Collaboration Workshop on Parity Violating Spin Asymmetries BNL, April