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PHOBOS Case for 400 GeV p+p

PHOBOS Case for 400 GeV p+p. Peter Steinberg Brookhaven National Laboratory RSC Meeting, 11 March 2005. Recommendation for 400 GeV Run. Counting Particles in PHOBOS. f. Signals in the Si for a single RHIC event!. z. Rings. Octagon. dN/d  in Au+Au. PHOBOS PRL91 (2003). 130 GeV.

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PHOBOS Case for 400 GeV p+p

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  1. PHOBOS Case for 400 GeV p+p Peter Steinberg Brookhaven National Laboratory RSC Meeting, 11 March 2005

  2. Recommendation for 400 GeV Run

  3. Counting Particles in PHOBOS f Signals in the Si for a single RHIC event! z Rings Octagon

  4. dN/d in Au+Au PHOBOS PRL91 (2003) 130 GeV 200 GeV 19.6 GeV dN/dh Most Central h h h Extensive data set:3 CMS Energies, Npart from 65 – 340, ||<5.4 Once again, we just integrate over 4!

  5. dN/d in Au+Au We have better statisticsAND systematics thanUA5 (only existing 4measurements up to now) UA5 had O(1000’s) eventsat every energy We have better coverage,statistics --> systematics PHOBOS p+p Preliminary

  6. Nchvs. s in p+p and A+A Central A+A PHOBOS nucl-ex/0301017 Particle Data Book (2000)

  7. Angular Distributions

  8. A+A vs. p+p Central A+A PHOBOS nucl-ex/0301017 Particle Data Book (2000)

  9. More Comparisons (MLLA pQCD, Mueller 1983) Central A+A PHOBOS nucl-ex/0301017 Particle Data Book (2000)

  10. Au+Au approaches e+e- A+A e+e- pp/pp Central A+A

  11. In p+p collisions, have “leading particles” Flat distribution of independent of energy Only ½ of energy available for particle production What about p+p?

  12. Historical Note Leading particle effectstudied at ISR p+pby comparison to e+e-(Basile et al, 1981-1984)

  13. Three Behaviors… Correct for leading particles

  14. …Down to Two But these pointsdon’t seem to fit Universality of particle production?

  15. PHOBOS Request for 400 GeV

  16. Other Systematics • Multiplicities have been useful systematics for all RHIC systems • We can now add another energy to our systematic plots

  17. Energy Dependence near h=0 (dN/dyT )

  18. “Limiting Fragmentation” 400 GeV ybeam ln(s/Mp)

  19. What do we need? • The 200 GeV p+p data set was a total of ~17M events over 4 days. • We take about 1M events/hr with our current DAQ at max rate • Most of these events are usable (|z|<60cm) • So in 16 hrs (2x8 hr) we can achieve similar statistics and systematics • Sufficient for comparison to 200 GeV • High quality 400 GeV data set

  20. Unintended Consequences Believe it or not,this informationwould be eligibleto add to ParticleData Book…

  21. When do we need it? • We are in our last year as PHOBOS • Not official decision yet, but a very likely outcome of DOE budget • Personnel will be decreasing rapidly after Cu+Cu run • Layoffs • Departures • Shift of efforts of local support to PHENIX & ATLAS • Prefer to take 16 hours of data in 2nd week of May • However, if other experiments will benefit from waiting until end June, this may be optimal for the program • Fixing date is highest priority, to facilitate planning for reviving PHOBOS for 400 GeV

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