Options for E906/Drell-Yan with a Solid Iron Magnet (Fe906?) Paul E. Reimer 20 June 2008

1. Options for E906/Drell-Yan with a Solid Iron Magnet(Fe906?)Paul E. Reimer20 June 2008 Solid Iron magnet Target dump separation Chamber rates Resolution—Mass, xF, x1, x2 Acceptance

2. Why a Solid Iron Magnet? • E906 budget is very tight. • We are expecting ≈$2M for DOE/Nuclear Physics. Of this $1.6M will be used to produce coils for an open aperture magnet. The remainder is for spectrometer upgrades. • NSF, Taiwan and Japan are planning contributions to the spectrometer upgrades • Fermilab has requested that we contribute an additional $1.5M for M&S that they need to spend for E906 • Some tasks e.g. flammable gas system (Illinois) and cryotargets may be done by collaborators. • RIKEN may to contribute ≈$600k to “common fund” items • Still short ≈$500k • Solid Iron Magnet • Essentially free—coils and iron exist, Iron must be cut ($100k) • Reprogram DOE/ONP funds to Fermilab (Under discussion with Brad Tippens) • Increased acceptance--larger “aperture” (if you can call it that) • Decreased resolution Paul E. Reimer

3. SM3 coils which were constructed in 1981 for E605 by Sumitomo and supervised by KEK and Kyoto. Supervised by Prof. Miyake, Dr. Maki and Dr. Sakai Magnet Description • Use existing coils from SM3 • 3 coil packs: 191, 163 or 135 inch coils • Iron blocks from SM12 (E866) magnet • Simulations shown for 191” • Suggested by Chuck Brown 191” 135” Paul E. Reimer

4. Magnet Description Field simulation for 189” solid Fe magnet (DFG) • Use existing coils from SM3 • 3 coil packs • 191, 163 or 135 inch coils • Simulations shown for 189” • Issues: • Target/dump separation • Chamber rates • Mass Resolution • x2 resolution • Field simulation • no measurements • Accurately determine saturation curve • Acceptance (i.e. statistical uncertainty at the end of the day) Paul E. Reimer

5. Dump/Target Separation Open aperture in red Solid Fe in Blue • Resolution significantly worse • Trigger and reconstruction cuts allow for clean separation • Remove events with tracks at dump face within 2.25” of beam axis • Remove events with tracks greater than 10” from beam axis at targets • Recall dump starts at 0”. These cuts effectively remove all events from the front of the dump!! Target Dump Target Dump Slight problem from dump J/’s Paul E. Reimer

6. Generated Dump/Target Sep., Solid Fe Magnet Only • Target—solid histograms -70 < z < -50 • Dump—dashed histo. 0<z • Magenta, all events • Green: Magneta and • xF>0 and • M>4.5 GeV • and pz>20 GeV • Blue: Green and • |ytrack|>2.25 in at z=0 (dump face) • Red: Blue and • |ytrack|<10.0 in at z=-60 (target) Reconstructed Paul E. Reimer

7.   Sta. 1 Station 1 Chamber Rates Absorber and B Field Occasionally a muon showers in the absorber • If this happens in the center of the absorber, no effect is seen as shower is also absorbed • If this happens in the last few inches of the absorber, shower can create extremely large rates in Station 1 (of low momentum particles) • Solution is to have an absorber-free region at the end of the field volume and use field as a sweeper • In Solid Iron magnet, there is no absorber-free sweeper region! (Can we find a wide gap sweeper magnet?) • Requires GEANT MC to see magnitude of effect Absorber and B Field Absorber and B Field  B Field only Paul E. Reimer

8. Mass Resolution J/ 450 MeV (and don’t forget about the 0) J/ 470 MeV (and don’t forget about the 0) • Reconstruction of Muon tracks yields virtual photon properties: • M2, xF, pT • Mass resolution dictates J/ cut • Critical for x2 (and x1) resolution Drell-Yan Drell-Yan “Standard” E906 Analysis Mass cut of 4.5 GeV Paul E. Reimer

9. Mass Calibration Drell-Yan (M>4.5 GeV) MC in black J/ MC in red • Track reconstruction apparently skews virtual photon mass • Events with tracks which significantly miss target have poor mass reconstruction • Use known mass (J/) to calibrate this correction • Effect is slightly different, but similar to higher mass Drell-Yan yrtp and yrtn are the reconstructed y offsets of the two tracks at a plane perpendicular to the beam in the center of the target. P and n denote positive and negative. Mass is the difference between generate and reconstructed mass in the Monte Carlo Paul E. Reimer

10. Calibrated mass resolution J/ 298 MeV • Significant improvement near J/ • General improvement at all masses Introduces mass offset in Drell-Yan mass range (4.5 < M<8.5 GeV) but better than uncorrected Drell-Yan Paul E. Reimer

11. xF Resolution • No Known xF point to use for calibration. Paul E. Reimer

12. x1 Resolution • x1 resolution worse with correction Resolution for all x1 Resolution x1≥ 0.75 Paul E. Reimer

13. x2 Resolution • Recall D-Y falls exponentially with x2. • Events may be reconstructed into neighboring bins. • x2 resolution improved by correction. • Resolution significantly worse for high x2—is this a problem? Resolution for all x2 Resolution x2≥ 0.35 Paul E. Reimer

14. x2 resolution—solid iron and miss reconstruction • Red events have reconstructed to the correct x2 bin • For a significant fraction of the events, x2true is one (blue) or two (green) bins lower than x2recon. • Can we live with this misidentification? Or find an additional correction Essentially no data in this bin Paul E. Reimer

15. x2 resolution— Open Aperture and miss reconstruction • Red events have reconstructed to the correct x2 bin • Open aperture design also suffered from misreconstruction, but not as much as solid iron design • Does anyone want to look at this in E866 data? Essentially no data in these bins Paul E. Reimer

16. Statistical Precision Increased statistical precision w/Solid Fe Magnet • Larger transverse “aperture” in Solid Fe Magnet (34” vs. 25”) • Larger Station 3 wire chamber • Needed to take advantage of larger aperture • Note: open aperture would also benefit from larger station 3 • Part of Japanese contribution • Significant gain in large-x2 region • Open Ap. Design may also gain in Stat. as well from larger Station 2 & 3 combination Paul E. Reimer

17. Drell-Yan Ratio Statistical Uncertainty • Better Statistical Uncertainty at high x2 • Crude trigger matrix applied • not used in previous plots • Accounts for fall-off at low x2 in solid iron magnet Paul E. Reimer

18. 126 inch Magnet • Resolution in Mass and x2 not better • Lower acceptance at high-x2 • See relative normalization Mass All x2 x2 for x2 > 0.35 Paul E. Reimer

19. Magnet Polarity:which events do we want? • We really want the high-x2 events • All the other events come for free Paul E. Reimer

20. Magnet polarity 8 GeV Paul E. Reimer

21. Magnet Polarity 6 GeV Paul E. Reimer

22. Magent Polarity 4 GeV Paul E. Reimer

23. Magnet Polarity 3 GeV Conclusion • Running in opposite polarity may allow smaller chambers • Important for Station 3 which is LARGE • Acceptance must be verified with Monte Carlo • Preliminary Monte Carlo shows resolution is the same (expected) Paul E. Reimer

24. Things left to do Independent verification of results • Background rate simulations • See GEANT MC talk—this seems to be in hand • Opposite Polarity MC with reduced Sta. 3 size • I’ve run the MC and could have results next week • Resolution improvements with target retrace? • Angular resolution for cos 2 distributions • Partonic Energy Loss—is x1 resolution good enough? • What is the saturation curve of the SM12 iron—this clearly effects the field • Some data from Chuck et al. that must be analyzed Paul E. Reimer

25. Conclusion: Solid Fe magnet will work (always listen to Chuck) Essentially no data in this bin • Resolution is poorer with Solid iron magnet, but acceptable? • x2 bin resolution • Dump/Target separation is achievable • Larger aperture provides better statistical precision at high x2 • Opposite polarity configuration may allow for smaller Station 3 and 4 chambers Paul E. Reimer