Readiness Review for Jlab Experiment E04 - 007

Hall A and BigBite Collaboration experimentApproved 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 Q2 and W from Q2 = 0.05 - 0.10in steps of 0.01 (GeV/c)2 and from W = 0 - 20 MeV above threshold in steps of 1 - 2 MeV.Complete kinematic coverage from 0 - 4 MeV above threshold for proton momentum > 220 MeV/c

€

• σ T + εLσ L 2 - 4 %

• σ LT 3- 6 %

• σ TT 10 - 20 %

€

H(e,e' p)π 0

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

d 5σdΩe'dEe'dΩ

* =σ

σ =Γv (σ 0 +h 2εL 1−ε( )σ LT '(θ* )sinφ

* )

σ 0 =σ T(θ* ) + εLσ L (θ

* ) + 2εL 1+ ε( )σ LT (θ* )cosφ

* + εσTT (θ* )cos2φ

* )

θcone = 4.5o

W

(MeV)

Above

Threshold

Q2

(GeV/c) (Deg.)

1075 1.7 - 0.05 4.5

1076 2.7 - 0.10 4.5

1095 22 - 0.10 9

θcone

p

Vertical +/- 18 degHorizontal +/_ 5 deg

25 cm

80 cm

117

BigBite Solid Angle ~100msr

Proton Cone

Layout of Experiment in Hall ADetect electron in HRS and recoil proton in BigBite.

LH2

H (re, e'p) π0

Target• 20 cm Liquid Hydrogen( LH2)• 200-175 m 6061 Al

Luminosity• 1-2 x 1037 Hz/cm2

HRS

Electron

BigBite

BeamDump

HRSLuminosityMonitor

MWDC(12 Planes)p

E-E Trigger Scintillator Arrays

Energy 1.2 GeVCurrent 1- 2 A e

Beam Conditions

• Beam Energy 1.1 - 1.2 GeV–No higher than 1.2 GeV–Need the best energy resolution as possible < 2 x 10-4

–Energy lock on–ep/arc energy measurement and elastic scattering

• Beam Current –Production running 0.5 - 20 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 Q2

• 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.

Q Squared vrs Electron Angle for Old and New set of Beam Energies

00.010.020.030.040.050.060.070.080.09

0.10.110.120.130.140.150.160.170.18

0 5 10 15 20

Electron Angle

Q (GeV/c)

2

1200 MeV 12.5 Deg

2400 MeV 6.0 Deg

3200 MeV 6.0 Deg

1200 MeV 14.7 Deg

1200 MeV 16.6 Deg

Electron Rate In HRS

Proton Arm BigBite

Replace Havar with200 m aluminum(Old slide)

1200 Mev Beam ( pi0,p)

200

300

400

500

600

30 40 50 60 70

Proton Lab Angle (Deg.)

Proton Lab Momentum MeV/c

HRS 12.5 Deg

HRS 14.7 Deg

HRS 16.6 Deg

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 E07-004 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.

Pi0 TRIGGER PLANE RATES20 cm LH2 Target 2 ua 1200 MeV beam

Scaled by a factor of 2.0 from SRC 3-10-05 Halog

0

200

400

600

800

1000

1200

1400

1600

1800

2000

1 3 5 7 9 11 13 15 17 19 21 23 25PMT Position

KHz

DEL

DER

EL

ER

• 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 (12.5 - 16.6 Deg.) and elastic calibration data (40 - 80 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 CollimatorSide View

Clamshell and Coffee Can CollimatorTop view

Transport of low energy protons (200-600 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 0.15 - 0.005 “ 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

206.2 cm

44.0 cm

33.1 cm

38.7 cm

Bottom view

2 Deg

5 cm

25.2 cm

18 Deg

18 Deg

Side view

122.9 cm

33.8 cm

157.8 cm

82.3 cm5 cm

Stretch over aluminum support frame and hot glue poly and terminate with 10 m mylar

Stretch over “coffeecan” 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

MediumHRS

Target Cell

Window

Vacuum

Window

σ Miss. Mass)

MeV

σ W)

MeV

σ c.

m.)

Deg.

σ Deg.

σ Q2(GeV/c)2

1.2He

bag

Air

Coupled

190 m

Al

170 m

Al

2.11.0

18.4 Ave

26 Ave 1.7x10-3

1.2He

bag

Vacuum

coupled

190 m

Al

170 m

Al2.0 1.0

Same as

above

Same as

above1.5 x 10-3

1.2He

bag

Air

Coupled

25 m

Havar

25 m

Havar2.0 1.0

15.9 ave

19.4 ave

1.2 x 10-3

2.4He

bagVacuum Coupled

25 m

Havar

25 m

Havar1.1 0.6 11 12.5 0.60x10-3

2.4Vacuum

Chamber

Vacuum

coupled

25 m

Havar

150 m

Kapton1.0 0.6 10 11.0 0.56x10-3

W = 1 - 4 MeVQ2 = - 0.048 to -0.07 (GeV/c)2

σp 2 σz 22 cmB=7 kG at 1.2 GeV

Q2=0.10 (GeV/c)2

Distler PRL 80, 2294 (1998)

LEC’sa3 = - 0.92 and a4 = - 0.99

Q2=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 Q2

Electro- 0 production on the protonσ t

ot

b

σ to

tb

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= 938.5 -1700 MeV

P = 300 - 800 MeV/c, HRS-L 45 - 80 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 40-80 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 40-80 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 40-80 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( 0.005” 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 Plan R. Lindgren, B.E. Norum (UVa)

• GEANT Calculations V. Nelyubin (UVa)

• Target Design and Construction D. Meekins (JLab)

• Design of new Clamshell, Coffee Can

Collimator, Helium Bag system R. Lindgren (UVa)

• CAD Drawings JLab

• Middle Wire-Chamber Upgrade M. Shabestrai (UVa Grad. Student)

N. Liyanaga (UVa)

• Hadron Package for BigBite X. Zhan (MIT) Grad. Student

• Hadron Electronics for BigBite B. Moffit (MIT) Research Associate

• Shifts The 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.