1. C.Woody, PHENIX Upgrades, 11/10/00 A TPC for PHENIX ?? No, surely you must mean for STAR…. PHENIX, really …. ??? You must be NUTS !!! Well, wait a minute... Maybe we should think about this ….

2. C.Woody, PHENIX Upgrades, 11/10/00 Many Thanks to a Number of STAR Colleagues for Enlightening and Useful Discussions (and several nice pictures) * H.Wieman * N. Smirnoff J. Thomas T. Hallman M. Messer And several PHENIX Colleagues as well... Y. Akiba A. Drees I. Tserruya E. Kistenev

3. C.Woody, PHENIX Upgrades, 11/10/00 Why a TPC for an inner tracker/electron identifier for PHENIX ? Excellent position resolution (STAR: s r f ~ 500 m m, s z ~ 1mm) Excellent two particle resolution (STAR: ~ few mm) Provides additional tracking information near the vertex Would improve momentum resolution by tracking in field Can naturally provide 2 p tracking coverage Provides electron identification by dE/dx Long drift time can limit rate capabilities Possible space charge limitations at high track densities Diffusion ultimately limits spatial resolution Must have sufficient sampling to do good dE/dx measurement Requires large number of readout channels (=> high cost)

4. C.Woody, PHENIX Upgrades, 11/10/00 PHENIX Central Region 53 47 80 1600 60 40 37.5

5. C.Woody, PHENIX Upgrades, 11/10/00 dE/dx works well for e/ p separation < 1 GeV Requires good sampling ! Dalitz rejection Find soft electron by dE/dx e+e+ e-e- TPC

6. C.Woody, PHENIX Upgrades, 11/10/00 Interaction Rates (PHENIX CDR) 10x Design Luminosity Drift times of 5-10 m s should be ok for most heavy ion running Will certainly have pileup for pp and light ion running How much of a problem is event pileup ? Can PHENIX electronics handle 5-10 m s drift times ?

7. C.Woody, PHENIX Upgrades, 11/10/00 Fast drift gases - CH 4 and CF 4 10 cm / m s 12 cm / m s 40 cm drift => ~ 3-4 m s Requires high drift field CF 4 -Ar CH 4 C 2 H 4 (1 KV/cm) (1 V/cm/Torr)

8. C.Woody, PHENIX Upgrades, 11/10/00 Slower drift gases - He-C 2 H 6 200 m m /  Diffusion Drift velocity ~ 5 cm/ m s 40 cm drift => 8-10 m s Transverse diffusion ~ 1.3 mm

9. C.Woody, PHENIX Upgrades, 11/10/00 Diffusion in STAR P10 Gas

10. C.Woody, PHENIX Upgrades, 11/10/00 Is is Possible to Achieve Good Spatial Resolution and dE/dx Sampling Over a Limited R Range ? MSGC GEM MICROMEGAS... Micropattern Detectors (~ 40-50 m m spatial resolution) Kapton Hole Pattern GEM Cross-Section Avalanche

11. C.Woody, PHENIX Upgrades, 11/10/00 STAR Inner TPC (R&D by H. Wieman & N. Smirnoff) 1 m 2 m Inner TPC (20 cm < R < 60 cm) Radiator UV Sensitive Pad Plane Tracking + Electron ID

12. C.Woody, PHENIX Upgrades, 11/10/00 ~ 1.8 m 4 Longitudinal Segmentations (limiting drift time,space charge) STAR Inner TPC (R&D by H. Wieman & N. Smirnoff)

13. C.Woody, PHENIX Upgrades, 11/10/00 TPC w/4 Longitudinal Segmentations (~ 40 cm drift each) Inner Vertex Detector (Si Pixels) STAR Inner TPC (R&D by H. Wieman & N. Smirnoff) UV Sensitive Pad Plane

14. C.Woody, PHENIX Upgrades, 11/10/00 Should We Really Consider an Inner TPC for PHENIX ? Could provide necessary e/ p separation for Dalitz rejection Could provide 2 p tracking for jet physics Would significantly improve momentum resolution Would provide additional tracking information near the vertex Could be combined with a Si pixel vertex detector Needs significant study, simulation and R&D TPC’s are best built by experts (do we have any in PHENIX ?) Requires significant development in electronics and readout Cost - Not Cheap ! Time scale - Not Short (> 3-5 yrs)