ZEUS Status

1. R. Yoshida ZEUS Status Funding Agencies 4 Nov 2003 Argonne National Laboratory • Physics and analyses • Detector and data taking • Background and running • Summary 23 Oct 2003

2. Physics and analysis • Publications—since the last November we have produced 9 letters and 6 papers. • There already have been 11 publications in 2003. • Number of papers in the editorial process average about 10-14. • ZEUS paper output has been at a steady rate for the past decade, and is still continuing.

3. 2003 to date Pace of paper production has not slacked off—if anything increased in the recent years. Papers with 100+ citations (spires) ZEUS papers are consistently among the most cited papers. A sampling of recent papers 

13. Detector and data taking • Luminosity operation started 2 weeks ago. • Neither ZEUS nor HERA are yet in a stable running mode. • Nevertheless, first data was relatively “clean”. • Report on selected topics: “New detectors” • MVD • STT • LUMI

16. Detector: MVD status • MVD Operation: • Progress in alignment good z-vertex resolution achieved • Bad channels are low (2%) and not increasing. • Reconstruction development steady (part of routine reconstruction procedure) • Radiation damage tolerable up to now

17. Detector: MVD status Accumulated radiation after shutdown using RADFET (surface damage): 1-8 krad • 0.4 - 3 kRad/month accumulated • 08/2001 - 03/2003 average:0.3 kRad - 7 kRad/month Total tolerable dose is ~100 kRad at the detector. (MC studies show actual detector dose ~x3 lower than the RADFET dose.) --also most dose at injection Still ok but keep a close eye

18. Detector: STT status Last year, a variety of problems were reported.These were all repaired in the spring shutdown. The first data look promising STT tracks in Neutral Current event selection.

19. Detector: LUMI status • Two independent measurements: • LUMI photon calorimeter: stable operation since Sept. 2002 • LUMI spectrometer: stable operation since Nov. 2002 Total energy (GeV)

20. Background and future running New C5a Backscattered synchrotron background has been eliminated. ctd drift time spectrum

21. Background and future running p-particle e-particle Absence of synchrotron background allows us to have a reliable break down of the remaining e-particle and p-particle background using monitor counters. “expectation” (mA) (mA) Total Fill 19-20 Oct: Ip ~ 50 mA (mA)

22. Background and future running “expectation” We can run today at 60 mA p and 30 mA e. (~max HERA to end 2003) We are still 30% away from best particle background expectation. Factor 2 improvement in p-particle background would allow us to run at full current— more on this later.

23. Background and future running • ZEUS is able to run presently with the highest beam currents HERA is able to provide to the end of the year. • If the particle background reaches the best level achieved in the 2002-3 running, then we would be able to run at 100 mA p and 30 mA e. • If p-particle background improves by factor of 2 (there are reasons to believe it could—though no quantitative proof) ZEUS can run at highest HERA currents. • What happens if background does not improve substantially in the coming months? 

24. Background and future running • There are ways to effectively increase the CTD limit by a factor or ~2. • Reduce the HV further 95%  90%. High Q2 NC and CC and high ET physics is do-able. (Experience from pre-shutdown. Triggering tested recently). Run “normally” when Ie intensity falls in the fill. • Increase the current limit: Question of life time of the CTD—under study. • Or some combination. ZEUS data taking will not be limited by the background.

25. Final remarks • Physics analyses of HERA I data are proceeding at a good pace. • The detector is ready for data taking. • The background conditions are tolerable to the end of the year, and the prognosis is good. We see no reasons that ZEUS data taking should be limited by the background.