1. Slide 1 of 40 Brovko, Haag, Cebra January 06, 2011 LF Spectra Phone Conference STAR as a Fixed Target Experiment? Sam Brovko, Brooke Haag, Daniel Cebra Abstract for APS meeting: Analysis of fixed target collisions between gold ions in the beam and aluminum nuclei in the beam pipe using the STAR detector at RHIC will be presented. These fixed target collisions allow us to study a region of collision energy below the lowest energy scheduled for the RHIC beam energy scan. This might extend the region baryon chemical potential available for discovery of the critical point in the hadronic gas to quark-gluon plasma boundary in the nuclear matter phase diagram. In this talk, we will show preliminary results of pion, proton and light nuclei spectra as well as dN/dy distributions for pions and protons. Comparisons will be made to results from the AGS heavy ion program and to UrQMD simulations.

2. Slide 2 of 40 Low Energy Reach of Fixed Target Collision Energy (GeV) Single Beam Energy Single Beam Pz (GeV/c) Fixed Target Root S Single Beam Rapidity Center of Mass Rapidity 20010099.99613.75.412.70 643231.987.724.232.11 3919.519.486.173.931.97 2713.513.475.193.371.68 189.08.954.302.961.48 11.55.755.673.532.481.24 7.73.853.732.982.071.04 6.13.052.902.731.840.92 Beam Energy Scan

3. Slide 3 of 40 Beam Energy Scan 64 GeV Fixed Target points What if the critical point is here? Or here?

4. Slide 4 of 40 Be Beam Pipe Al Beam Pipe  =1.0  =1.5  =2.0  =1.0  =1.5  =2.0

5. Slide 5 of 40 Required Steps: 1)Demonstrate that we can select Al target events 2)Demonstrate that we can demonstrate that we have am Au projectile 3)Demonstrate that we know that collision energy 3 AGeV 197 Au + 27 Al

6. Slide 6 of 40 Selecting Aluminum Target “7.7 GeV” Data set: Select Events with 100 < |V z | < 200 and 2 < V r < 5 cm VzVz VxVx VyVy Counts Al Be FTPCSVT Support Au+AuBeam pipe

7. Slide 7 of 40 Determining the Collision Energy Challenge – We have “oriented” the target parallel to the beam axis  The target is infinitely “thick”. The initial projectile energy is 2.94 AGeV. How much energy is lost prior to the Au+Al nuclear collision? Range of 3 AGeV Au in Al is 64.8 cm due to dE/dx The Au+Al nuclear interaction length is 3.63 cm.  The Au ion travels only 5% of its range before experiencing a nuclear collision, therefore it will lose only 5% of its energy.  Collision Energy is 2.8 +/- 0.2 AGeV

8. Slide 8 of 40 Data to Support Collision Energy Note, protons show a narrow distribution around mid-rapidity.  + contamination

9. Slide 9 of 40 Daniel Cebra October 6, 2009 STAR Collaboration Meeting LBNL Determining that the projection is Au 7.7 GeV Au+AuProjectile + 27 Al From E895 Au+Au M max at 2 AGeV is ~200 M max at 4 AGeV is ~300 N part ~380 M max ~50 For Au+Al: Npart ~70 Expect M max ~45 from extrapolation of E895

10. Slide 10 of 40 Determining that the projection is Au Glauber Prediction for 3 AGeV Au+Al STAR 3 AGeV Au+Al data

11. Slide 11 of 40 Daniel Cebra October 6, 2009 STAR Collaboration Meeting LBNL

12. Slide 12 of 40 Pion Spectra from 3.85 AGeV Au+Al

13. Slide 13 of 40 Acceptance for Fixed Target  = 1.8

14. Slide 14 of 40 Conclusions We can select fixed target Au+Al events The collision energy is fairly well defined Fixed target geometry is adequate to RHIC sub- injection energy beams. We will focus on charged particle spectra.

15. Slide 15 of 40 Backup Slides

16. Slide 16 of 40 Daniel Cebra October 6, 2009 STAR Collaboration Meeting LBNL

17. Slide 17 of 40 Daniel Cebra October 6, 2009 STAR Collaboration Meeting LBNL

18. Slide 18 of 40 Daniel Cebra October 6, 2009 STAR Collaboration Meeting LBNL

19. Slide 19 of 40 Daniel Cebra October 6, 2009 STAR Collaboration Meeting LBNL

20. Slide 20 of 40 Daniel Cebra October 6, 2009 STAR Collaboration Meeting LBNL

21. Slide 21 of 40 Daniel Cebra October 6, 2009 STAR Collaboration Meeting LBNL

22. Slide 22 of 40 Daniel Cebra October 6, 2009 STAR Collaboration Meeting LBNL

23. Slide 23 of 40 Daniel Cebra October 6, 2009 STAR Collaboration Meeting LBNL

24. Slide 24 of 40 Daniel Cebra October 6, 2009 STAR Collaboration Meeting LBNL

25. Slide 25 of 40 STAR Beam Pipe Location A description of the STAR beam pipe can be found at arXiv:nucl-ex/0205008v1 Features: Diameter of the central region of the beam pipe is 7.62 cm There is/was a support disk for the SVT at 54.8 cm with OD 128 mm and ID 89 mm From 0 to 76 cm => pipe is made of 1.0 mm thick beryllium At 76 cm there is a weld to an 1.24 mm thick aluminum pipe At 130 cm there is an Al to Al weld, no change in pipe diameter or thickness. From 76 to 402 cm => the pipe is 1.24 mm thick aluminum There is a flange and bellows at 4 meters, the pipe diameter goes to 12.7 cm There is another flange and bellows at 7.12 meters.

26. Slide 26 of 40 Schematic Diagram of the beam pipe profile

27. Slide 27 of 40 Daniel Cebra April 26, 2010 19.6 GeV Au+Au 20019.2 GeV Au+Au 2008 Vxy Vz (r>2) Vz (r>2) Al Be 6733 Au+Au 4150 Beam pipe 100863 Au+Au 2882 Beam pipe ~3000 Au+Al ~1000 Au+Be 2241 Au+Al 641 Au+Be Au+Al |Vz|>75 Au+Be |Vz|<75 Au+Au r<2 Au+pipe r>2 Beam Pipe Locations

28. Slide 28 of 40 22.4 GeV Cu+Cu 20057.7 GeV Au+Au 2010 Vxy Vz (r>2) Al Be Au+Au Beam pipe Au+Al |Vz|>75 Au+Be |Vz|<75 Au+Au r<2 Au+pipe r>2 Vxy Vz (r>2) Al Be C u+Cu Beam pipe Beam pipe supports

29. Slide 29 of 40 Beam-on-Pipe Collisions