1. Commissioning the PHENIX RPC Forward Trigger Upgrade Michael Daugherity Abilene Christian University for the PHENIX Collaboration

2. Physics Motivation Sources of proton spin: ΔΣ: quark contribution valence quarks, well-known (but surprisingly small) sea quark contribution has large uncertainties ΔG: gluon contribution being studied, likely to be small DOE Frontier of Nuclear Science L Z : Orbital angular momentum, largely unknown

3. Physics Motivation W-boson production gives nice access to anti-quark distributions in the proton. 3 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 4 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-p t muon trigger to reduce backgrounds in W signal and maximize data-taking rate. Current muon trigger provides p t >2 GeV/c background

5. Resistive Plate Chambers Use established CMS designs of resistive plate chambers to provide a large area, fast, and efficient high-p t muon trigger 5 Time resolution  3 ns Average cluster size~ cm Efficiency  95% Rate capability0.5 kHz/cm 2 Cathode Anode x = 2mm -10 kV 0 kV W-trigger requirements All requirements are exceeded with RPC detectors

6. Forward Upgrade Overview 6 RPC3 (2010) RPC1 (2011) Hadron Absorber (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

7. RPC Station 3 North 7 RPC3 Frame at UIUC RPC3N installation completed (2009) RPC stations consist of 16 half- octants of three modules each

8. 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 8 Healthy half-octant module Hit rate (Hz/cm 2 ) 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.

9. RPC Station 3 South 9 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.

10. Hadron Absorber 10 North Hadron Absorber Hadron (π or K) decaying to muon can produce a fake high-p t 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

11. 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 11 RPC Station 1 Station 1 Prototype

12. 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 12 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 the Forward Trigger Upgrade Collaboration