1 ZDCs in CMS Michael Murray,U Kansas pp Lum EMHad PMTs Lead/ plastic Fiber 1.5cm tungsten plates 2mm plates Beam LED Spare space for flow upgrade Light guide Copper frame to take heat out

2 The geometry of nuclear collisions Spectators Participant Region The number and orientation of spectator neutrons tells us the geometry of the collision. For low luminosity pp we will help diffractive physics.

3 Scope, Structure and People The scope of the project has been set. For HI runs we will provide centrality (1-50 neutrons) and luminosity measurement while for low luminosity pp we will measure bremstralung photons The structure will be a tungstan quartz sandwich divided into an EM section with 4 equal hadronic sections. The EM section will have 5 horizontal divisions. The project is a collaboration of Iowa, UIC, FNAL and Kansas plus David d’Enterria of CERN.

4 Simulation software ZDC is being integrated into CMSSW framework. We would like to include pp luminosity monitor. Eventually we would like a complete description of the very forward region. Chadd Smith UIC

5 Narrow showers give info on beam angle Narrow showers give info on beam angle Only the high energy core of the shower produces Cerenkov light. This means that we can get horizontal position information. We will bundle the electromagnetic fibers onto 5 different PMTs. This will allow us to measure the the beam crossing angle with a resolution of ~ 10  rad within a minute. FWHM = 5 mm Horizontal Position (mm)

6 Radiation Hardness For first 3 years of heavy ion and low luminosity pp running we expect 6GRad to hit the ZDC. So far we Iowa group has tested quartz/plastic fibers up to 1GRad without significant damage. However we are confident that quartz-quartz can do the job. We plan to use HF phototubes (or similar) since they have been very well characterized.

7 During pp runs detector heats by 20 o C During pp running sycnotron radiation will produce 200W. We measured the effect of this by injecting heat into an insulated plate and measuring the temperature increase. The plate was connected to copper strips for cooling. X Y Heat Time TT 20 o 0o0o 0o0o

8 Front End Electronics In order to minimize radiation problems we are planning to have as little electronics in the tunnel as possible. The PMTs will be connected by short cables to a patch panel where they connect to fast low loss cables. Collaboration of FNAL and KU. 140m signal cable Patch panel CMS electonics PMT by ZDC Tunnel Counting Room Time Voltage reference cable Two cables/PMT 1m cable

9 Schedule, cost and radiation risk To minimize these risks we will maximize the use of elements of HF and minimize mission creep. From HF we will copy light insertion system, albedo protection, light guides, PMTs and readout electronics. We also benefiting from experience of Iowa, FNAL and Boston. To avoid mission creep we differ building a flow detector for now but will leave space for future work. Also we will not work on timing for first runs but will leave option open. Finally since the 1 neutron peak gives a natural physics calibration point we will not use a radioactive source for calibration.

10 Timing useful for clean up. Vertex trigger gives factor of 2 increase in useful data for BRAHMS  = 2.8cm

11 Funding Profile Manpower for ZDC is supported by NSF Career award. We have started work on a prototype using $53K from DOE Nuclear program. Remaining $250k has been secured from DOE this week. This June we will get money for fibers and cables. We will build one detector and calibrate in test beam in August.

12 Conclusions ZDCs have been very useful at RHIC for both AA,dA and pp. For CMS they would make a significant contribution to the heavy ion and diffraction groups. The justification for the detector is accepted by NSF and DOE and we will be able to complete the detector with US nuclear funds. The schedule is very aggressive but the technology choices are conservative and we are gaining considerably from HEP experience.

13 Backup slides

14 Schedule, cost and radiation risk To minimize these risks we will maximize the use of elements of HF and minimize mission creep. From HF we will copy light insertion system, albedo protection, light guides, PMTs and readout electronics. We also benefiting from experience of Iowa, FNAL and Boston. To avoid mission creep we differ building a flow detector for now but will leave space for future work. Also we will not work on timing for first runs but will leave option open. Finally since the 1 neutron peak gives a natural physics calibration point we will not use a radioactive source for calibration.

15 Construction Prototype We have built a prototype that is 1/4 as long as the final module. KU machine shop is able to reach desired tolerances. We are now confident that we can construct a full size ZDC with quartz fibers.

16 Summary This week DOE agreed to cover ZDC development. We now have first design of hadronic section and are ready to purchase fibers, cables and tungsten (PMTs already bought). We hadronic prototype with steal plates to build up experience. EM section will come later.

17 Acceptance is ~100% for gray neutrons Protons will be swept down the beam pipe. Coalesence may remove some neutrons by converting them into deuterons. KE=200MeV RHIC 32GeV RHIC 100GeV CMS 2.7TeV P y MeV neutron proton Beam crossing angle shits Px acceptance away from zero

18 Luminosity & beam tuning at RHIC AuAu ZDC coincdence vs time pp Van de Meer scan

19 Centrality & ultraperipheral collisions

20 Number of Photon Electrons Mean = 347 RMS = 197  ≈ 19% 50GeV photon into EM section Z of Photon Electrons Limit of EM part