1. Brett Fadem of Muhlenberg College for the PHENIX Collaboration

2. Overview The goal Transverse energy for a new kinematic range Definition Motivation The main tool The Muon Piston Calorimeter (MPC) Kinematic coverage Performance Plans for the Future

3. Definition of Transverse Energy θ i is the polar angle E i is the kinetic energy for nucleons Total energy for all other particles

4. Motivations A new kinematic region for E T at RHIC A necessary first step toward fluctuations Search for critical point See, for example, M. Stephanov, K. Rajagopal, E. Shuryak, Phys.Rev.Lett. 81 (1998) 4816-4819

5. ~220 cm from vertex Location of MPC stations Good coverage!

6. North Location South Location Pre-installation During installation

7. North Station 220 PbWO 4 Crystals 3.1 < |η|< 3.8 South Station 196 PbWO 4 Crystals 3.1 < |η|< 3.7

8. PbWO 4 Crystals and Avalanche Photodiodes Density8.28 g/cm 3 Size2.2 x 2.2 x 18 cm 3 Length20 X 0, 0.92 int. lengths Weight721.3 g Moliere radius2.0 cm Radiation Length0.89 cm Interaction Length22.4 cm Light Yield~10 p.e./MeV @ 20 °C Temp. Coefficient-2% / °C Radiation Hardness1000 Gy ~10 yr cont. at PHENIX Main Emission Lines420-440, 500 nm Refractive Index2.16 PreAmp APD Holder PbWO 4 Crystal

9. Avalanche Photodiodes Hamamatsu S8864-55 5 × 5 mm square, large area Gain ~50

10. New PHENIX Calorimeter Acceptance PbGl PbGl / PbSc FC MPC ZDC FCAL ZDC

11. PHENIX Au+Au √s NN = 130 GeV Phys. Rev. Lett. Volume 87, Number 5, 30 July, 2001 |η| ≤ 0.38

12. STAR Au+Au, √S NN = 200 GeV arXiv:nucl-ex/0407003v1 2 Jul 2004 Phys. Rev. C70 (2004) 054906 0 < η ≤ 1

13. Au+Au, √S NN = 200 GeV, Detector Performance

14. MPC π 0 from Run 6 p+p data Background subtracted All Pairs Mixed Events Photon Pair Cuts Pair Energy > 8 GeV Asymmetry |E 1 -E 2 |/|E 1 +E 2 | < 0.6 Noisy towers Width ~ 20 MeV Shower Reconstruction Using Shower Shape Fits Reconstruction of π 0 in Au+Au data is plausible for peripheral Collisions

15. MPC Minimum Ionizing Peak MIP Peak Energy Scale Set by MIP Confirmed with π 0, η peaks Peak corresponds to ~ 240 MeV

16. Fluctuations in Forward Direction? Event by Event Fluctuations in mean P T and mean E T in √s NN = 130 GeV Au+Au Collisions K. Adcox et al., PHENIX Collaboration, Phys.Rev. C66 (2002) 024901 No significant non-random fluctuations observed at central rapidities Maybe in the forward direction we’ll get a different answer

17. Plans for the Future RHIC 2006/2007 Run 7 Au+Au at 200 GeV/c 2.9 Billion minimum bias events are available Continuing work on π 0 peak, and calibrations Using all towers Tower by tower Systematic study of hadronic contribution

18. Acknowledgements Joshua Adams, Undergraduate at Muhlenberg College Mickey Chiu, BNL Physics National Science Foundation