GEP-15 · 2011. 7. 1. · PAC32 August 7, 2007 slide GEP-15 Bogdan Wojtsekhowski, JLab Experiment:...

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GEP-15

Large Acceptance Proton Form FactorRatio Measurement at 13 and 15 GeV2

Using Recoil Polarization Method

C.Perdrisat, L.Pentchev, E.Cisbani, V.Punjabi, B.Wojtsekhowski with more than 100 collaborators from almost 30 institutions

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PAC32 August 7, 2007 GEP-15 Bogdan Wojtsekhowski, JLabslide

Outline of the talk

• Physics goals• Experiment• Method• Analysis• Tracking technology• Budget /Road map• Other applications• Beam time request

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Physics Goals: ratio F2 / F1

• Significantly increase the Q2 range up to 15 GeV2

• Study the spin flip part of thehadron current

• Constrain GPDs at high t• Provide critical test of the FF

models and reaction dynamics

JLab measurements

Plan for GEP-15GEP-I, II, III

BJY(03)

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Theory report

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Experiment: Layout and ParametersBeam: 75 µA, 85% polarizationTarget: 40 cm liquid H2Electron arm at 37o, covers Q2range from 12.5 to 16 GeV2Proton arm at angle 14o,

with Ω = 35 msr ,Spin precession angle is ~ 90o

(it is optimum)

Event rate is 15 times higherthan with standard spectrometer

From 58 days of production timeresulting accuracy ( for each oftwo data points):

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What is new in this experiment?

1. Large solid angle in the proton arm at a small scattering angle achieved with single dipole magnet. Beam line will go througha hole in magnet pole.

2. Gas Electron Multiplier chambers to handle high rate of the background. Similar counting rates handled in COMPASS; rate will be much higher in LHCb.

3. High threshold trigger with hadron calorimeter.

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Method: recoil polarization

ratio method developed by C.F.Perdrisat and V.Punjabi and used at JLab in several experiments

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Method: Focal Plane Polarimeter

p will be ~ 8.5 GeV/c

Track inTrack out

Analyzing power vs. inverse proton momentum

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Challenges in this experiment

Need large statistics → max luminosity and solid angle

Max luminosity → large background Large solid angle → small bend → huge background

Solution is a modern tracking detector based on Gas Electron Multiplier (F.Sauli, 1997)

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Proton Arm

- Magnet: 48D48 - 46 cm gap, 3 Tm field integral, 100 ton- solid angle is 35 msr for GEP, could be ~70 msr at larger angle GEM chambers for tracking with 70 µm resolution- momentum resolution is 0.5% for 8.5 GeV/c proton- angular resolution is 0.3 mrad- trigger threshold is 4 GeV from hadron calorimeter

Calorimeter response for 10 GeV protonsfrom test for Compass experiment

Top view A-A

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Expected trigger rate

Total proton trigger rate is 1.5 MHz ( above threshold of 4 GeV )

Electron arm trigger rate (>85%) - 60 kHz

Two level electronic triggerLevel 1 from Electron arm forms gate for ADC

Level 2 from coincidence between two armswith pre-programmed angular correlationbetween arms. Coincidence time window is 50ns, resolution of 5 ns.

Expected DAQ trigger rate is 500 Hz

FWHMof 8%

SLAC data for γ,π yield at 9-18 GeV,DESY data at 6 GeV, Wiser code

EM calorimeter rate vs. deposited energy

beam

Proton calo Electron calo

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Logic of data analysis

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1. Track selection: start with electron arm → defines 26 cm2 area in the protonarm front chamber (out of 3200 cm2) for proton track search within 50 ns time:30 kHz/cm2×26 cm2 ×50×10-9 → 4% are two-track eventsCut on Ph > 4 GeV/c reduces the fraction of two-track events to less 0.1%.

2. Events rate: 500 Hz of the DAQ has 1/60 of real/accidental, time-of-flight cut leads to 1/10 angular correlation of track-calorimeter leads to 10/1 cut on momentum (or Emiss) with

resolution of 0.5% increases to 100/1 Remaining background due to real

coincidence events of pionphotoproduction, mainly

3. Final sample for FPP: cut on reconstructedmissing energy:Monte Carlo shows less than 3%remaining background within the elastic peak.


Analysis of asymmetry

• Elastic scattering events• Events within PT = 0.1 to 1 GeV/c• Phase shift, δ, of the distribution

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GEP-IIQ2 = 5.6 GeV2

A(φ

)


Tracking Technology

350-70020/250 kapton5-100.2/0.075GEM chamber

2200300 Si150.2/0.045Silicon micro strip

30010/30 mylar10010/0.150.1Drift wire chamber

Cost perdevice, k$

Thickness sensitive/total, µm

Cost,$

Pitch /resolution,

mm

Maxrate,MHz

or wire strip50 cm long for

Tracking device dimensions are 0.4x0.8 m2 and 1x2 m2 withrequired resolution of 0.07 mm and 0.3 mm, respectively.

Expected total hit rate of 150 kHz/cm2

MWDC is 10 times slower than project requirement, Silicon MSD has largest cost,large photon efficiency and multiple scattering, GEM has good margin of factor of30 in max rate and acceptable other parameters.

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GEM concept

FieldChamber structure

500 Volt

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GEM chambers have worked in COMPASS for several years


Study of GEM rate capacity

Gai

n of

trip

le G

EM

cha

mbe

r, a.

u.

Particle hit rate, Hz/cm2

1.2

1.0

0.8

0.6

0.4

0.2

0105 106 107 108

A very good gain stabilityup to 50 MHz/cm2

LHCb maximum rate,which is three timesexpected rate in GEP-15

k

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Budget: non-DOE resources

Magnet - available from BNL with the power supply

Electron arm - calorimeter of 1744 blocks - constructed by GEP-III

Hadron arm - calorimeter for trigger, 242 elements, several calorimetersdetector available at collaboration institutions

- NEW tracking device for momentum analysis - NEW tracking device(s) for FPP

Tracking working group - INFN, Glasgow, US universities(MIT, UVA, NSU, FIU) and JLab. Large non-US contribution. All hardware and non-scientific manpower will be funded from non-DOE sources

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Road map and time line

If this proposal is approved we expect:

• INFN approval ( September 2007) of 5 years grant for the tracking project

• MRI(s) for the FPP tracking electronics, trigger• Collaboration with Glasgow in GEM DAQ

Time line for the construction project:

First telescope GEM tracker in 2008 BNL magnet in Hall A by 2009 First full size tracking device by 2011 FPP tracking devices by 2012 Hadron calorimeter/electronics in 2012

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Other uses of proposed setup

After approval of this proposal we expect several strong proposals will be developed based on the BNL magnet and GEM-based tracking devicesproposed here, among them: • GEN for 7 GeV2• SIDIS - transversity ( factor of 50 gain in rate)• J/Psi photo production from proton ( gain ~ 25) These experiments will use the same detectors

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Beam time request and Summary

1. As we proposed with 11 GeV electron beam the will be measured with accuracy by using new large acceptance set up in Hall A in a 60-days run.2. Collaboration of 100+ scientists from 30 institutions will be able to construct all new equipment (mainly GEM base chambers) with non-DOE funds.3. Experiment has strong support from the theoretical community.

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Backup slides after this


Reply to TAC comments1. Collaboration ..., it will require a large strongly coordinated effort -The 5 PIs represent several large experiments in recent years: GEP-III - large EM calorimeter and a polarimeter for HMS; GEN (E02-013) - BigBite spectrometer, BigHAND neutron detector and new polarized He-3 target - together the largest installation in Hall A since construction of the HRSs; Septa magnets and state-of-the-art RICH detector for HRS.

2. …large installation effort - yes, it is on the level of GEN, where BigHAND weighed 80 tons, BigBite & BigHAND detector plus He-3 target took 2.5 months to set up in Hall A.

3. The target proposed (40 cm long single-loop) requires a special dedicateddesign. Yes, target cell needs redesign, however it fits inside existing scatteringchamber and has a power load similar to that in previous experiments in Hall A.

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Collaboration

The 5 PIs are from W&M, INFN, Norfolk SU, JLab

Presently four working groups are being formed:

Tracking / FPP - INFN+UVA,FIU,MIT,NSU,GU Hadron calor imeter - W&M, NSU, Dubna Trigger elec tron ics - UNH, W&M, SMU Electron calorimeter - GEP-II I

Contributions from other experiments are also expected

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Letter from BNL

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Physics: proton tomography

Fourier transform of GPDs, Burkardt’simpact parameter representation:

Parameterized GPD:

The DIS and form factor data were used inGPDs model development by Diehl et al.,they find an estimate of the quark orbitalangular momentum by using Ji’s SR

Similar result for quark L obtained fromGPD factorization by Guidal et al.

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Physics Goals: F1 and F2

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There are many models and physics ideas about nucleon FFs


Expected background (low energy)From experimental data from Hall A, event analysis From GEANT-3, -4 Monte Carlo studies

Probability averaged over Eγ for photondetection in one GEM chamber < 0.2%

Flux of 100 keV photons is ~ 2-3times higher at 14o than at 52o

Flux in the front detector will be 80 MHz γ/cm2; leads to 120 kHz/cm2 of uncorrelated hits inGEM chamber → less than one extra hit per event in 26 cm2 area of the front GEM chamber

where the proton track of interest is present

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Dealing with background

GEANT MC results and event examples:

Flux in the front detector will be 80 MHz γ/cm2;leads to 120 kHz/cm2 of uncorrelated hits inGEM chamber → less than one extra hit perevent in 26 cm2 area of front GEM chamberwhere the proton track of interest is present

Proton track has:1. very small scattering 4 GeV/c

Photon hit and 4MeVrecoil electron track

8 GeV proton track

Photon hit

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GEN-7

What is plan for GEN-7 ?

resolution σp/p for electron - BNL magnet, GEM He-3 cell in vacuum, lower background in neutron arm Hybrid He-3 cell with narrow pumping laser line

GEN at 7 GeV2 with uncertaintyof 15% Miller value in 30 days run

8.8 GeV beam

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neutron

e


DIS and SIDIS

What is plan for SIDIS ?

- 50 times more statistics - use of the proposed setup instead of HRS-L

• Proposed setup with 50 msr solid angle (FPP GEM device), 100% momentum acceptance for both +/- charged particles, PID with RICH from HERMES.• polarized He-3 cell in vacuum, higher He-3 polarization• Scattered electron detected in the BigBite spectrometer

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Photoroduction of J/Psi from proton

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γp --> J/Ψp --> e+ e- p

Cross section vs Eγ


Dipole and Solenoid in Hall A

There are different advantages in the Dipole and Solenoid approaches.Usual considerations are “cost vs solid angle” and required run time.

Dipole ~ 60 msr to compare with Solenoid ~ 300 msr ( for 20o).For SIDIS experiments forward angle is the most important feature, sothe difference in solid angle is much less.

Very important experiments based on PV technique, such as “u/d” and“g3” need 1-2 years with the Solenoid detector, so could be done onlywith the Solenoid. Transverse target polarization much more efficient with the proposeddipole system, can take “all” needed data in 1-2 thousands hours.

Construction of the dipole system will be a step to Solenoid project.

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GEP-15 · 2011. 7. 1. · PAC32 August 7, 2007 slide GEP-15 Bogdan Wojtsekhowski, JLab Experiment:...

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