Region I: stringing 1/3 done on 1st chamber! Reg.1 stringing May 25, 2011 Lead stringer hired; being trained at Jlab Clean-room delivered; being set up Readiness review in August

Region II: 2 built / 4 to go! Installing on the stringing fixture: Feb. 2011 2nd crew hired: full 5-man crew! 2nd chamber strung; ready for testing

Region III – parts in procurement Aluminum endplates; steel stiffeners Carbon-fiber posts Carbon-fiber / foam downstream shell Our quality-control manager !

DC12 status – well underway Drift Chamber Activity % complete: 5/25/2011 Procure Wires, Pins, Feedthroughs 95% Procure Endplates, Frames 83% Build Boxes 17% Outfit Cleanrooms 26% Procure Circuit Boards 11% String Chambers 5/27/11 Report Wires are all in hand except for last 20% of Reg.3 guard wires; need to be stronger than Cu-Be because of higher tension; investigating 316SS RFQ ready to go out for Reg.3 endplates, frames, posts, carbon shells Build boxes as needed; build 3rd Reg.2 box and 2nd Reg.1 box in next 2 weeks ISU cleanroom ordered; will be built in June, July 2011 Many details to be ironed out; orientation of connector, consistent labelling (HV & signal), single contract to clean, populate Reg.2#2 stringing finished, Reg.1#1 guard wires done, ~ 400 field wires done

Physics Impact of (not having a)Vertex Detector CLAS12 may begin operations with no forward vertex detector what is the impact on physics? Show impact on tracking resolution Estimate impact of vertex cuts Estimate impact of broadening of missing-mass distributions small impact on non-strangeness physics small impact on exclusive strangeness production Need collaboration concurrence that these estimates are reasonable.

DC+FST – resolution for protons (protons at  = 15°): Compare DC – alone vs. DC + VTX 3-4 times better 8-10 times better Much better vertex resolution with FST (and  resolution at high p) Simulation & Reconstruction 10/30/2008 S.Procureur

DC+FST – resolution for electrons (electrons at  = 15°, now from GEMC!): 20 times better 5 times better FST largely improves the vertex resolution, ,  and p Simulation & Reconstruction 10/30/2008 S.Procureur

Tracking Resolution with/w.o. vertex detector Electron (5 GeV/c, 15 deg.) Proton (2 GeV/c, 15 deg.) Comments with vtx w/o vtx dp/p 0.5 % 0.75 % 0.6 % Modest changes to momentum and angular resolution;  slight increase in running time to achieve same signal/noise in missing-mass dq 0.6 mrad 0.8 mrad 1.25 mrad df 2.3 mrad 4 mrad 3.5 mrad dz 1 mm 5 mm 2 mm 6.5 mm Substantial changes to vertex resolution; impacts strangeness program, but small impact on exclusive production db .15 mm 0.2 mm 1.8 mm

Physics Impact of (not having a)Vertex Detector The vertex detector improves the pointing resolution of the CLAS12 tracking system at the target position substantially: from ~2mm to ~0.2mm in impact parameter resolution. For semi-inclusive identification of weakly-decaying strange particles, this can cut the non-strange background by a factor of 100 with a modest (~20%) loss of efficiency for the strange particle (e.g. a L baryon). The vertex detector will not have a large impact on exclusive production of strangeness for those channels with a missing L because of the inherent narrowness of the L missing mass peak (mass just above threshold). The vertex detector will afford a modest improvement in resolution for the momentum of charged tracks: ~30% improvement in dp/p for high-energy electrons, negligible improvement for lower-energy protons. Likewise, it will afford similar improvements in angular resolution for high-energy electrons and negligible improvement for protons. This will only marginally improve the ability of CLAS12 to identify particles by missing-mass techniques. small impact on non-strangeness physics small impact on exclusive strangeness production