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
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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.
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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