Commissioning the PHENIX RPC Forward Trigger Upgrade

Michael DaugherityAbilene Christian University

for the PHENIX Collaboration

Physics MotivationSources of proton spin:

1 12 2

ΔΣ: quark contribution• valence quarks, well-known (but surprisingly small)• sea quark contribution has large uncertainties

G

ΔG: gluon contribution being studied, likely to be small

DOE Frontier of Nuclear Science

LZ: Orbital angular momentum, largely unknown

zL

3

Physics MotivationW-boson production gives nice access to anti-quark distributions in the proton.

1 2 1 2

1 2 1 2

WL

Δu(x )d(x ) Δd(x )u(x )σ σAσ σ d(x )u(x ) u(x )d(x )

A polarized proton experiment is sensitive to the polarization of the sea quarks

• A very precise and clean measurement, both theoretically and experimentally. • A “cornerstone” of the RHIC spin program and a DOE milestone for 2013.

4

Detecting Forward W’s• We take advantage of PHENIX’s muon arms to look for W decays in

the forward/backward region:– compliments PHENIX and STAR W analyses at mid-rapidity using

electron/positron decay channel

W

W

MuID

New trigger

Challenges in detecting W’s• Cross-section x Luminosity give us an expected interaction rate of 9.6 MHz

• DAQ bandwidth for muon arm is 1-2 KHz

• Need a rejection power of ~ 10,000

We need a new high-pt muon trigger to reduce backgrounds in W signal and maximize data-taking rate.

• Current muon trigger provides pt>2 GeV/c

background

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Resistive Plate ChambersUse established CMS designs of resistive plate

chambers to provide a large area, fast, and efficient high-pt muon trigger

Time resolution 3 nsAverage cluster size ~ cm

Efficiency 95%Rate capability 0.5 kHz/cm2

Cathode

Anodex = 2mm

-10 kV

0 kV

W-trigger requirements

All requirements are exceeded with RPC detectors

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Forward Upgrade OverviewRPC3(2010)

RPC1(2011)

HadronAbsorber

(2010)

MuTRG(2008)

MuTRG(2009)

• 2008/2009 – Muon Trigger FEE upgrade

RPC3(2009)

• 2009 – RPC Station 3 North installed • 2010 – Install RPC Station 3 South and hadron absorber• 2011 – RPC Station 1 planned install

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RPC Station 3 North

RPC3 Frame at UIUC

RPC3N installation completed (2009)

RPC stations consist of 16 half-octants of three modules each

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Commissioning RPC3N• After Run 10 we sampled cosmic rays to study high

momentum tracks in the RPC3N • Each station has (3 modules)*(64 channels/module)*(16 half-

octants) = 3,072 channels to evaluate and monitor

Healthy half-octant

mod

ule

Hit rate (Hz/cm2)uninstrumented

channels

Half-octant with dead and hot channels

Entire Station 3N

Overall good detector performance, some issues with gas distribution leading to loss of HV, some dead or noisy channels to address.

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RPC Station 3 South

Completed on Sep. 22

Installation completed about 6 weeks ago, and is being cabled as we speak.

(Each station requires ~ 2 km of signal cable)

Significant effort underway to integrate this station for Run 11.

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Hadron AbsorberNorth Hadron Absorber

• Hadron (π or K) decaying to muon can produce a fake high-pt track •35 cm of stainless steel (2 interaction lengths) significantly reduces background• Trade-off between our backgrounds and degrading other signals (e.g. J/ψ)• Absorber severely constrains space for station 1 RPC’s

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RPC Station 1 Prototype• With absorbers in place, we have final measurements for

station 1 prototypes• Difficult balance between maximizing acceptance and leaving

enough room for signal cables, HV/LV, gas, etc.• On schedule to be constructed and installed for Run 12

RPC Station 1 Station 1 Prototype

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Conclusions• The W measurements are a cornerstone of the RHIC Spin

program and an important component of the 500 GeV polarized proton collisions in the next few runs

• The Forward Trigger Upgrade is preparing PHENIX to make these important measurements

• Abilene Christian University• University of California, Riverside• CIAE, Beijing• University of Colorado, Boulder• Columbia University and Nevis

Laboratory• Georgia State University• University of Illinois, Urbana• Iowa State University

• KEK• Korea University• Kyoto University• Los Alamos National Laboratory• Muhlenberg College• University of New Mexico• Peking University, Beijing• RIKEN Brookhaven Research Center• RIKEN • Rikkyo University

special thanks to theForward Trigger Upgrade Collaboration