S. White, BNL review of ATLAS HI

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ATLAS ZDC Project

• Why we need it
• ATLAS ZDC solution
• Collaboration
• Budget and Schedule

2
Event characterization using forward
detectors gtgtDirection and magnitude of impact
parameter, b
z
Magnitude from complementary parameters Nparticipa
nt2A-Nspectator

• Spectator neutrons
• measure centrality,
• Min_min_bias trigger

(Calorimeter_at_qlt2mr.)
Beam-Beam Counter Mult/1000
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Directed flow, v1, is largest at ZDC location
(Reaction Plane resol. from correlation in
hemispheres
BBC ZDC/SMD both )
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RHIC ZDC as an accelerator tool (in pp)
rate
Measured Beam x(mm)
Vernier bump
5
Led to proposal to LARP to integrate ZDC in
Accelerator Instrumentation
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Probing small x structure in the Nucleus with
gN-gtjets, heavy flavor.
di-jet photoproduction-gt parton
distributions,x2 by g with momentum fraction,
x1 4pt2/sx1x2 ltygt -1/2ln(x1/x2) Signature
rapidity gap in g direction(FCAL veto)
ATLAS coverage to hlt5 units. Pt 2
Gev rapidity gap threshold
Analogous upc interactions and gap structure
diffractive
Non-diffractive
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UPC physics with ATLAS

• Rates and energy beyond HERA
• an order of magnitude
• Lower x for equiv virtuality
• Both nuclear targets and p (pA)
• PHENIX UPC showed effectiveness of rap-gapZDC
  tag
• This is well matched to ATLAS coverage

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ZDC tagging in UPC
Fraction of double tag events

• From prl with MS and RV
• Tagging fraction function of g-energy
• Inclusive dijet and b production have 1-tag
• Here we show 2-tag (needed only for diffract)

9
ATLAS ZDC Solution
Identical modules Installed in the TAN
enclosure _at_140m Share space with
Additional(passive) Absorber and Luminosity
monitors gtOnly LHC ZDC Designed to
withstand pp luminosity
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Individual module (1 of 6 total)
Tungsten Alloy (absorber) Steel structure w. 11
Quartz layers Vendor same as RHIC ZDC fab
12k/module 6 identical modules In total
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Neutron energy resolution adequate with 3 modules
(each side)
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Near term activities

• Produce 1st ZDC module (1 of 6)
• Optical fiber ribbon manufacture
• Evaluate coordinate readout
• integration workshop on TAN(3/06)
• Present ZDC plan to ATLAS proj. man.
• RHIC test beam with Lumi monitor
• LBNL readout for accelerator

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Simulation Tasks

• G3 simulation of response(IHEPYale)
• Rad dose calculations for pp
• Simulation of UPC events (from eRHIC)
• Implement beam fragmentation in ZDC

14
Organization

• Originally A. Denisov and SNW with help from
  P.Kroon, J. Farrell
• After demise of KOPIO M. Zeller and collaborators
  (Issakov,Atoyan and Poblaguev) joined
• Very productive collaboration on radiation
  damage, coordinate readout timing over last 2
  months
• Other Institutions have also expressed interest
• LBNL (Ratti and co.)
• Dubna (Pozdnyakov, Timoshenko,..)
• Alberta
• LHCf

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Organization

• Detector design (BNL Yale)
• Optical system manufacture (IHEP)
• Evaluate HEP role (Yale)
• Integrate into T/DaQ (Yale)
• Support commissioning (Dubna Geneva?)
• Simulation (BNL..)

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Documentation

• White paper
• Project file
• Engineering Spec
• Physics case (PRL..)

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Total project cost (w. burdens) 270k BNL funds
now committed and building 1st module(50k) Comple
tion this Spring Full construction schedule
driven by funding rate.
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Summary

• ATLAS ZDC will make unique contribution to HI and
  pp programs, LHC commissioning
• Particularlyto day-1 physics, event
  characterization and emerging UPC program
• ATLAS is only LHC experiment in which ZDC
  installed for all collider species
• Unique in coordinate measurement (v1, etc)