Essential Measurements to be made at RHIC using the PHOBOS Detector

1
Essential Measurements to be made at RHIC using
the PHOBOS Detector

• Mark D. Baker
• Brookhaven National Laboratory
• for the PHOBOS Experiment

BNL 08-SEP-2004 Physics Advisory Committee Meeting
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Collaboration (Oct. 2004)
Birger Back, Mark Baker, Maarten Ballintijn,
Donald Barton, Russell Betts, Abigail Bickley,
Richard Bindel, Wit Busza (Spokesperson), Alan
Carroll, Zhengwei Chai, Patrick Decowski,
Edmundo García, Tomasz Gburek, Nigel George,
Kristjan Gulbrandsen, Clive Halliwell, Joshua
Hamblen, Adam Harrington, Michael Hauer, Conor
Henderson, David Hofman, Richard Hollis, Roman
Holynski, Burt Holzman, Aneta Iordanova, Jay
Kane, Nazim Khan, Piotr Kulinich, Chia Ming Kuo,
Willis Lin, Steven Manly, Alice Mignerey, Gerrit
van Nieuwenhuizen, Rachid Nouicer, Andrzej
Olszewski, Robert Pak, Inkyu Park, Heinz
Pernegger, Corey Reed, Christof Roland, Gunther
Roland, Joe Sagerer, Helen Seals, Iouri Sedykh,
Wojtek Skulski, Chadd Smith, Maciej Stankiewicz,
Peter Steinberg, George Stephans, Andrei
Sukhanov, Marguerite Belt Tonjes, Adam Trzupek,
Carla Vale, Sergei Vaurynovich, Robin Verdier,
Gábor Veres, Peter Walters, Edward Wenger, Frank
Wolfs, Barbara Wosiek, Krzysztof Wozniak, Alan
Wuosmaa, Bolek Wyslouch ARGONNE NATIONAL
LABORATORY BROOKHAVEN NATIONAL LABORATORY INSTITU
TE OF NUCLEAR PHYSICS PAN, KRAKOW MASSACHUSETTS
INSTITUTE OF TECHNOLOGY NATIONAL CENTRAL
UNIVERSITY, TAIWAN UNIVERSITY OF ILLINOIS AT
CHICAGO UNIVERSITY OF MARYLAND UNIVERSITY OF
ROCHESTER
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The PHOBOS Detector (2004)

• 4-p Multiplicity Detector
• Comprehensive centrality measures
• Magnetic Spectrometer ToF
• Extends to very low pT
• Good rejection of weak decays

T0 counter
SpecTrig
TOF
Paddle Trigger Counter
Octagon
Spectrometer
NIM A 499 (2003) 603
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Physics Publications (Sept. 2003)
Phys. Rev. Lett. 85 , 3100 (2000) Phys. Rev.
Lett. 87, 102301 (2001) Phys. Rev. Lett. 87,
102303 (2001) Phys. Rev. C 65 , 31901R
(2002) Phys. Rev. Lett. 88 , 22302 (2002) Phys.
Rev. C 65 , 061901R (2002) Phys. Rev. Lett. 89 ,
222301 (2002) Phys. Rev. C 67, 021901R
(2003) Phys. Rev. Lett. 91, 052303
(2003) nucl-ex/0301017, subm. to
PRL nucl-ex/0302015, subm. to PLB Phys. Rev.
Lett. 91, 072302 (2003) nucl-ex/0309013, subm. to
PRC-RC
    
Comparable in the pipeline!
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Physics Publications (Sept. 2004)
Phys. Rev. Lett. 85 , 3100 (2000) Phys. Rev.
Lett. 87, 102301 (2001) Phys. Rev. Lett. 87,
102303 (2001) Phys. Rev. C 65 , 31901R
(2002) Phys. Rev. Lett. 88 , 22302
(2002)  Phys. Rev. C 65 , 061901R (2002) Phys.
Rev. Lett. 89 , 222301 (2002) Phys. Rev. C 67,
021901R (2003) Phys. Rev. Lett. 91, 052303
(2003) nucl-ex/0301017, subm. to PRL Phys. Lett.
B 578, 072302 (2003) Phys. Rev. Lett. 91, 072302
(2003) Phys. Rev. C 70, 011901R (2004) Phys. Rev.
Lett. 93, 082301 (2004) dN/dh for
dAu nucl-ex/0401006, subm. to PRL PID at very
low pT nucl-ex/0405003, subm. to PRL Energy
dependence of R(AA) Phys. Rev. C 70, 021902R
(2004) Geometric dN/dh scaling nucl-ex/0406017,
subm. to PRC-RC R(dAu) vs. h nucl-ex/0406021,
subm. to PRL v2 vs. h at 4 energies
nucl-ex/0407012, subm. to PRC-RC v2
vs. h, centrality, pT nucl-ex/0409001, subm. to
PRC-RC HBT vs pT, y at 62.4, 200
nucl-ex/0409003, subm. to PRC-RC pbar/p for pp
gt700 citations total
20 more in pipeline!
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Physics Publications (Sept. 2004)
Phys. Rev. Lett. 85 , 3100 (2000) Phys. Rev.
Lett. 87, 102301 (2001) Phys. Rev. Lett. 87,
102303 (2001) Phys. Rev. C 65 , 31901R
(2002) Phys. Rev. Lett. 88 , 22302
(2002)  Phys. Rev. C 65 , 061901R (2002) Phys.
Rev. Lett. 89 , 222301 (2002) Phys. Rev. C 67,
021901R (2003) Phys. Rev. Lett. 91, 052303
(2003) nucl-ex/0301017, subm. to PRL Phys. Lett.
B 578, 072302 (2003) Phys. Rev. Lett. 91, 072302
(2003) Phys. Rev. C 70, 011901R (2004) Phys. Rev.
Lett. 93, 082301 (2004) dN/dh for
dAu nucl-ex/0401006, subm. to PRL PID at very
low pT nucl-ex/0405003, subm. to PRL Energy
dependence of R(AA) Phys. Rev. C 70, 021902R
(2004) Geometric dN/dh scaling nucl-ex/0406017,
subm. to PRC-RC R(dAu) vs. h nucl-ex/0406021,
subm. to PRL v2 vs. h at 4 energies
nucl-ex/0407012, subm. to PRC-RC v2
vs. h, centrality, pT nucl-ex/0409001, subm. to
PRC-RC HBT vs pT, y at 62.4, 200
nucl-ex/0409003, subm. to PRC-RC pbar/p for pp

AuAu energies 19.6, 55.9, 62.4 130., 200.
gt700 citations total



(1st Run IV paper)


(2nd Run IV paper)

(3rd Run IV paper)

20 more in pipeline!
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Results from dAu - an update
PRL 91 (2003) 072302-5
RdA(h,pT)?
dN/dh data from nucl-ex/0403033 J.Phys.G30
(2004) S1133
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Results from dAu - an update
RdA(h,pT)!
dN/dh data from nucl-ex/0403033 J.Phys.G30
(2004) S1133
nucl-ex/0406017
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The program vary energy and geometry
Varying the geometry (A,b)

• jet quenching
• vary overall path length
• vary asymmetry
• Elliptic (and directed) flow
• Study A dependence at fixed eccentricity.

Npart
eccentricity
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Surprise from 19.6 62.4 GeV AuAu
nucl-ex/0406021
v2
Longitudinal scaling of elliptic flow
hh-ybeam
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Surprise from 19.6 GeV AuAu
PRC 70 (2004) 021902R
Energy Centrality Dependences Factorize
Where are the minijets?
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RAA ratios at 200 and 62.4 GeV (AuAu)
PHOBOS

• Large variation of RAA with centrality
• ltNpartgt from 61 to 335
• ltNcollgt from 76 to 820
• 0 lt b lt 10.5 fm

PLB (2004) 578297
arXivnucl-ex/0405003
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RAA ratios at 200 and 62.4 GeV (AuAu)
arXivnucl-ex/0405003
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RAA ratios at 200 and 62.4 GeV (AuAu)
For blt10.5 fm
arXivnucl-ex/0405003
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RAA ratios at 200 and 62.4 GeV (AuAu)
For blt10.5 fm

• Energy-independent
• Weak function of Npart, pT

arXivnucl-ex/0405003
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Another surprise from energy variation
For blt10.5 fm
arXivnucl-ex/0405003
Varying the beam energy changes

• Initial state sNN, Ncoll/Npart, Qs(?)
• System ?, mB, Nch,
• Partonic xT, dE/dx

Why does the energy dependence factorize?
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What Have We Learned? what are the essential
measurements w/ ?
http//www.phobos.bnl.gov/Publications/PublicDocum
ents/PhobosWhitePaper.pdf (or .ps)

• We have discovered a strongly interacting medium
  with extremely high energy density whose
  description in terms of simple hadronic degrees
  of freedom is not appropriate.
• Study the systematics of this medium (vary A
  ?sNN).
• Furthermore, we have discovered that much of the
  data can be expressed in terms of simple scaling
  rules which suggest the existence of strong
  global constraints or some kind of universality
  in the mechanism of the production of hadrons in
  high energy collisions (possible connection to
  ideas of parton saturation).
• Study these simple scaling rules systematically.
• Will they survive further scrutiny?

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Benefits of very light ions (SiSi e.g.)

• Clearly different from AuAu
• study flow, jet quenching
• Extensive low energy comparison data exists
  (CC,SiSi,SiAl,SS...)
• See BUP refs. 3-15 for a partial listing

NA49 (C. Hohne et al.), NPA715 (2003) 474c
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Benefits of intermediate ions (CuCu)

• Npart100 is better determined for central CuCu
  than for AuAu
• Overlaps both AuAu SiSi
• Geometry different.
• study flow, jet quenching

nucl-ex/0301017
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Benefits of a short pp run _at_ 400-500 GeV

• Compare pp_at_400 to AA_at_200.
• Better systematics within a single experiment.
• Better coverage than UA5
• Better statistical power.

J.Phys.G30 (2004) S1133 nucl-ex/0403033
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Proposed scenario (updated)

• Boundary conditions
• Run CuCu as the light ion species this year
• RHIC will run ?7 weeks of pp200 physics
• Phobos does not request any pp _at_ 200 GeV.
• 31 - 10 weeks of setup - 7 weeks pp200
• 14 weeks
• 200 GeV CuCu (10 weeks physics)
• 62.4 GeV CuCu (3 weeks incl. setup)
• 22.5 GeV CuCu (3 days incl. setup)
• 400 GeV pp (4 days incl. setup)

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Fallback Scenario (updated)

• Constrained to 10 weeks
• 27 weeks of cryo., still 7 weeks of pp200
• RHIC becomes RppC
• 31 weeks, but 11 weeks for pp _at_ 200 GeV
• 10 weeks
• 200 GeV CuCu (7 weeks physics)
• 62.4 GeV CuCu (2.5 weeks incl. setup)
• 22.5 GeV CuCu (3 days incl. setup)

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Scenarios at a glance
d2Nch/dhdf d2N/dydpT HBT
d2Nch/dhdf d2N/dydpT HBT
d2Nch/dhdf
dNch/dh
including energy-change setup time
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Run VI ??

• Highest priority SiSi _at_ 3 energies
• Other possibilities depend on results
• Longer 19.6 GeV AuAu
• 200 GeV SiAu
• Au-d(yellow)
• ???

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Summary

• Many new interesting results from Phobos
• Rate of publication growing exponentially.
• Golden opportunity in Run V
• RHIC tuned for Cu ions
• PHOBOS-specific features
• Unique h coverage
• Total Nch event-by-event
• Unique centrality measures
• Run CuCu at 200, 62.4 and 22.5 GeV!
• Run VI
• SiSi at 200, 62.4 and 24 GeV
• base further running on what we learn...