Readiness Review for Jlab Experiment E Hall A and BigBite Collaboration experiment Approved Jan 2004 for 16 days Precision Measurement of the Electroproduction of  0 Near Threshold: A Test of Chiral QCD Dynamics Co-spokespersons J. Annand, D. Higinbotham, R. Lindgren, V. Nelyubin, and B. Norum, Physics Goal: Extract high precision data in a fine grid of Q 2 and W from Q 2 = in steps of 0.01 (GeV/c) 2 and from  W = MeV above threshold in steps of MeV. Complete kinematic coverage from MeV above threshold for proton momentum > 220 MeV/c

Outline Overview Beam Energy and Current Beam Monitoring Targets Electron Arm Spectrometer Proton Arm BigBite Mechanical Hardware Additions Calibrations Run Plan/Commissioning Production Running Milestones People Power Safety

W (MeV) Above Threshold Q2 (GeV/c)(Deg.) p  Vertical +/- 18 deg Horizontal +/_ 5 deg 25 cm 80 cm 117 BigBite Solid Angle ~100msr Proton Cone

Layout of Experiment in Hall A Detect electron in HRS and recoil proton in BigBite. LH2 Target 20 cm Liquid Hydrogen( LH2)  m 6061 Al Luminosity 1-2 x Hz/cm 2 HRS Electron BigBite Beam Dump HRS Luminosity Monitor MWDC(12 Planes) p  E-E Trigger Scintillator Arrays Energy 1.2 GeV Current 1- 2  A e

Beam Conditions Beam Energy GeV –No higher than 1.2 GeV –Need the best energy resolution as possible < 2 x –Energy lock on –ep/arc energy measurement and elastic scattering Beam Current –Production running  a –Rastered beam 2 mm x 4mm Polarization as high as possible Beam Monitoring –BCMs, BPMs, Silver calorimeter, Moller Polarimeter Pulsed beam - Investigate using to calibrate acceptance of BigBite in single arm mode. (Radiation tail method looks sufficient)

Targets Cryo-targets liquid hydrogen –Two different length targets will help disentangle systematic errors. – A 20 cm long, 2 cm wide/hign 200 um thick window thick aluminum cell exist. Production data will be taken on the 20 cm cell. Investigating shielding BB from windows of cell at one kinematics.. Compare to data with software cuts on z position. –A 4 cm pan cake cell with thin Be window will be used for same kinematics above. Small target. Smaller acceptance corrections. Take data on empty cell for background. Can not correct in software. Compare with data above for same kinematics. Multi-foil C12 target, C, Ta,BeO –Solid Target for elastic energy and z position measurements. Targets

Electron Arm Spectrometer Range of electron angles for production running and acceptance calibration –Angular range 12.5 to 80 degrees –Momentum range [GeV/c] 0.3 to 1.2 GeV/c –VDC1 Yes –VDC2 Yes –S1 Yes –S2 Yes Only need to cover about 20 MeV in focal Plane. Excellent intrinsic resolution in W and and Q 2 Rates are high due to radiation tail in the region of pion threshold. Need to turn off high voltages for PMTs outside this range of W Air coupling. Contributes to somewhat degraded energy resolution in W. –Still sufficient to accomplish Physics goal Investigating using smaller and thinner window 10 by 6 cm window for HRS with snout.

Electron Rate In HRS

Proton Arm BigBite Replace Havar with 200  m aluminum (Old slide)

BigBite in- plane range

Proton Arm BigBite The low energy recoil protons will be detected in two of the MWDC chambers commissioned in the GEN Experiment. The Middle chamber will be upgraded at UVa.Three more planes will be added to bring it up to six planes. Mitra will discuss this. The MWDC are followed by two planes of 24 scintillators each. A 3 mm thick  E plane and a 30 mm thick E plane. These were designed and tested by Glasgow and commissioned in the SRC experiment. They will be used for particle ID for protons and time of flight will be used to measure momentum of low momentum protons. Better than wire chambers at low p. The trigger for E will be a coincidence between the E plane and the HRS-L. The hadron package electronics, BigBite trigger for E04-007, readout, and milestones will be discussed by B. Moffit, Plan to use VME. Have Fast bus for back-up. Modifications to BigBite frame are being made to accommodate two wire chambers followed by  E-E scintillator planes. Need to minimize straggling of low energy protons. Transport protons using helium a few mm above atmospheric pressure. Cheaper and more convenient than vacuum. Come back to this later.

Scintillator Rates scaled from measured rates in SRC Experiment. Shows why we plan to use the E plane in the trigger and not the  E. We may miss some low energy protons. Needs to be investigated. 3 mm  E Plane 30 mm E Plane

Machining of scattering chamber clamshell flange-right (CS-R) with windows for BigBite and HRS-R(Monitor). Machining of scattering chamber clamshell flange- left (CS-L)for HRS-L with windows for production data ( Deg.) and elastic calibration data ( Deg) “Coffee can” collimator, vacuum window, and flanges Construction of polyurethane “helium containment” balloons for BigBite and coupling to scattering chamber and wire chambers support stand. Helium gas handling system, pressure monitor, venting to outside Hall A. New Mechanical Hardware Additions

Scattering chamber Clamshell flange (not here yet) “Coffee can” collimator 0.005” Polyurethane Balloon (sides only) 10  m Mylar Balloon Front wire chamber Upgraded Rear wire chamber  E Plane E Plane 20 H targetElectron Beam 10  m mylar foil

Coffee Can Collimator

Clamshell and Coffee Can Collimator Side View Clamshell and Coffee Can Collimator Top view

Transport of low energy protons ( MeV/c) from target through BigBite to MWDC Transport protons using helium a few mm above atmospheric pressure. Almost as good as using vacuum. More convenient and cheaper. Use company that makes polyurethane helium filled balloons of all shapes and sizes. Polyurethane skin “ thick. Will lose helium slowly over a few days. Test leakage rate. Flexible enough to have limited angular movement of BigBite. Show sample material. Stretched over circular snout fixed to scattering chamber and hot glued Stretched over rectangular angle aluminum attached to wire chamber frame and hot glued Investigate stability of system and radiation damage of polyurethane and glue.

Shape of Polyurethane Helium Filled Balloon cm 44.0 cm 33.1 cm 38.7 cm Bottom view 2 Deg 5 cm 25.2 cm 18 Deg Side view cm 33.8 cm cm 82.3 cm 5 cm Stretch over aluminum support frame and hot glue poly and terminate with 10  m mylar Stretch over “coffee can” collimator and hot glue

Test on Balloons Need to always keep inflated above atmospheric pressure Monitor during the experiment. This is crucial. Mechanical stability of of joints and seams and leak rates On the polyurethane balloons and mylar balloons Conduct radiation damage test on both types. –Effects on hot glue joints –Effects on seams –Effects on polyurethane

GEANT Results Beam Energy GeV Transport Medium HRS Target Cell Window Vacuum Window  Miss. Mass) MeV  W) MeV  c. m. ) Deg.  Deg.  Q   (GeV/c) He bag Air Coupled 190  m Al 170  m Al Ave 26 Ave1.7x He bag Vacuum coupled 190  m Al 170  m Al Same as above Same as above 1.5 x He bag Air Coupled 25  m Havar 25  m Havar ave 19.4 ave 1.2 x He bag Vacuum Coupled 25  m Havar 25  m Havar x Vacuum Chamber Vacuum coupled 25  m Havar 150  m Kapton x10 -3  W = MeV Q 2 = to (GeV/c) 2  p   z  cm B=7 kG at 1.2 GeV

Q 2 =0.10 (GeV/c) 2 Distler PRL 80, 2294 (1998) LEC’s a 3 = and a 4 = Q 2 =0.05 (GeV/c) 2 Merkel et al. PRL 88, 1230 (2002) ChPT Bernard, et al. NP A607, 379(1996) MAID Large deviations between ChPT and data Need data in a finer grid in Q 2 Electro-  0 production on the proton  tot  b 

Calibrations/Commissioning Beam Current integration - Silver Calorimeter BigBite angle and acceptance in-plane –Elastic scattering from hydrogen and radiative tail –Coincidence between electron in HRS-L and recoil p in BigBite –Cut on W= MeV P = MeV/c, HRS-L degrees. Vertex reconstruction accuracy - multi foil C target –BigBite at 48 Deg Beam energy calibration- – Elastic scattering from Ta, C, H Efficiency of detection system – Measure elastic cross section H HRS-L at 45 Deg, BigBite at 48 Deg Luminosity monitor HRS-R

Run Plan Production running BigBite Calibration Measurements HRS-L at Deg BigBite at 42 Deg –Production Running HRS-L at 12.5 Deg., BigBite at 42 Deg –Production Running HRS-L at 14.7 Deg., BigBite at 42 Deg –Production Running HRS-L at 16.6 Deg., BigBite at 42 Deg BigBite Calibration Measurements HRS-L at Deg., BigBite at 48 Deg –Production Running HRS-L at 12.5 Deg., BigBite at 48 Deg –Production Running HRS-L at 14.7 Deg., BigBite at 48 Deg –Production Running HRS-L at 16.6 Deg., BigBite at 48 Deg BigBite Calibration Measurements HRS-L at Deg., BigBite at 54 Deg –Production Running HRS-L at 12.5 Deg., BigBite at 54 Deg –Production Running HRS-L at 14.7 Deg., BigBite at 54 Deg –Production Running HRS-L at 16.6 Deg., BigBite at 54 Deg HRS-R fixed at 90 Degrees

Milestones March –Design/Draft windows in Clamshell Flanges (2) –Design/Draft Coffee Can Collimator –Design/Draft shape of polyurethane helium containment balloon –Design ways of coupling balloon to chamber –Order sample polyurethane balloon material April –Design Helium gas handling system for balloon –Design 4 cm pancake cell - D. Meekins. –Order prototype polyurethane balloon( ” thick) and prototype 10  m mylar pillow shape balloon. Order two extra balloons for protecting PMTs from helium leaks –Finalize mechanical hardware design (Lindgren) and have CAD drawings made for integration into the system(Jlab). –Middle Wire chamber shipped to UVa for upgrade to 6 wire planes May –Test prototype balloons for helium leak rate and radiation damage

Milestones June –Upgraded wire chamber shipped to JLab for testing July –Install upgraded wire chamber into frame. –Start and complete machining clamshell flanges, collimator, and window components August –Assemble flanges, collimator, window, gas handling system, and balloon for further testing. September –Check out all new hardware, electronics, and hadron package. Make sure it all works. (Need milestones for hadron package) November - December –Review, Check out Run Plan, Check BigBite scintillators and wire planes with Cosmic rays, check discriminator levels and high voltages. Check out trigger electronics with cosmic rays. Jan 2008 –Install pi0 experiment - one month Feb 2008 –Run pi0 (32 days)

People Power Overview and Run PlanR. Lindgren, B.E. Norum (UVa) GEANT Calculations V. Nelyubin (UVa) Target Design and ConstructionD. Meekins (JLab) Design of new Clamshell, Coffee Can Collimator, Helium Bag systemR. Lindgren (UVa) CAD DrawingsJLab Middle Wire-Chamber UpgradeM. Shabestrai (UVa Grad. Student) N. Liyanaga (UVa) Hadron Package for BigBiteX. Zhan (MIT) Grad. Student Hadron Electronics for BigBiteB. Moffit (MIT) Research Associate ShiftsThe BigBite Family

Safety Documentation This research will be conducted in a manner that ensures that environmental, health, and safety (EH&S) and radiation safety (ALARA) concerns receive the highest consideration yet maintain the programmatic goals of the laboratory in producing the highest quality results efficiently. –Conduct of Operations (COO) –Experiment Safety Assessment Document (ESAD) – Radiation Safety Assessment Document.