ATLAS ZDC Project Why we need it ATLAS

ATLAS ZDC Project • Why we need it • ATLAS ZDC solution • Collaboration • Budget and Schedule 1

Event characterization using forward detectors >>Direction and magnitude of impact parameter, b Reaction plane zz Magnitude from complementary parameters Nparticipant=2*A-Nspectator y x Spectator neutrons • measure centrality, • Min_min_bias trigger (Calorimeter@q<2 mr. ) Beam-Beam Counter Mult/1000 2

Directed flow, v 1, is largest at ZDC location (Reaction Plane resol. from correlation in hemispheres: BBC ZDC/SMD both 3 )

RHIC ZDC as an accelerator tool (in pp) rate Measured Beam x(mm) 4 Vernier bump

Led to proposal to LARP to integrate ZDC in Accelerator Instrumenta 5

Probing small x structure in the Nucleus with g. N->jets, heavy flavor. di-jet photoproduction-> parton distributions, x 2 by g with momentum fraction, x 1 4 pt 2/s=x 1*x 2 <y>~ -1/2*ln(x 1/x 2) Signature: rapidity gap in g direction(FCAL veto) ATLAS coverage to |h|<5 units. Pt ~2 Gev “rapidity gap” threshold Analogous upc interactions and gap structure diffractive 6 Non-diffractive

UPC physics with ATLAS • Rates and energy beyond HERA “an order of magnitude Lower x for equiv virtuality” • Both nuclear targets and p (p. A) • PHENIX UPC showed effectiveness of rapgap+ZDC tag • This is well matched to ATLAS coverage 7

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) 8

ATLAS ZDC Solution Identical modules Installed in the “TAN” enclosure @140 m Share space with Additional(passive) Absorber and Luminosity monitors =>Only LHC ZDC Designed to withstand pp luminosity 9

Individual module (1 of 6 total) Tungsten Alloy (absorber) Steel structure w. 11 Quartz layers Vendor same as RHIC ZDC fab ~$12 k/module 6 identical modules In total 10

Neutron energy resolution adequate with 3 modules (each side) 11

Near term activities • • Produce 1 st 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 12

Simulation Tasks • G 3 simulation of response(IHEP+Yale) • Rad dose calculations for pp • Simulation of UPC events (from e. RHIC) • Implement beam fragmentation in ZDC 13

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 14

Organization • • • Detector design (BNL +Yale) Optical system manufacture (IHEP) Evaluate HEP role (Yale) Integrate into T/Da. Q (Yale) Support commissioning (+Dubna +Geneva? ) Simulation (BNL+. . ) 15

Documentation • • White paper Project file Engineering Spec Physics case (PRL+. . ) 16

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Total project cost (w. burdens)= $270 k BNL funds now committed and building 1 st module($50 k) Completion this Spring Full construction schedule driven by funding rate. 18

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 (v 1, etc) 19