“THE OLYMPUS LUMINOSITY MONITORS”

Ozgur Ates

Hampton University

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A Review of the MC Studies of the Lumi Monitors

Some GEM Reports from PREX at JLAB

April 26-27 OLYMPUS MEETING at DESY

* Supported by NSF grant No. 0855473

*

2

Luminosity Monitors: Telescopes

Forward telescopes

12o

2 tGEM telescopes, 1.2msr, 12o,R=187/237/287cm, dR=50cm, 3 tracking planes

TOF

Luminosity monitors for LEPTON in coincidence with Recoil PROTON detected in the opposite sector, and vice versa.

LEPTON

PROTON

LEPTON

PROTON

Control of Systematics

• Forward-angle (high-epsilon, low-Q) elastic scattering (se+ = se-) means there is no two-photon exchange

• Separately determine three super ratios• Left-right symmetry = Redundancy

Triple Super Ratio:Run the Exp. For the “4 different states”i= e- vs e+ j=toroidal magnet polarity(+-) Repeat cycle many times

Ratio of acceptances(phase space integrals)

Ratio of luminosities

Ratio of counts

4

Forward Elastic Luminosity Monitor• Forward angle electron/positron telescopes or trackers

with good angular and vertex resolution• Coincidence with proton in BLAST• High rate capability

• It will be built at Hampton University this year!

GEM TechnologyMIT prototype:

Telescope of 3 Triple GEM prototypes (10 x 10 cm2) using TechEtch foils

F. Simon et al., NIM A598 (2009) 432

Monte Carlo Studies by using Geant4

• Generated and reconstructed variables Theta, Phi, Momentum, Z(vertex)Proton & Electron• Resolutions δZp, δTp, δPhp, δPp, δZe, δTe, δPhe, δPe

• Residuals: Redundancy of variables / elastic scattering• 4 variables: Pe, Pp, Te, Tp• 3 constraints: 3 conservation equations

4 – 3 = 1 (DEGREES OF FREEDOM)

TeTp: Te – Te(Tp)TePe: Te – Te(Pe)TePp: Te – Te(Pp)

• Coplanarity:PhePhp: Phe – Php – 180

• Common vertex:ZeZp: Ze – Zp

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Resolution: generated - reconstructed

100micron, 50cm, LuMo+BLAST (Te=0-80 dg, Phe=+-15 dg)

δZp δZe

δTp δTe

δPhp δPhe

δPp δPe

7

Resolution: generated - reconstructed100micron, 50cm, LuMo only (Te=6-13 dg, Phe=+-5 dg)

δZp δZe

δTp δTe

δPhp δPhe

δPp δPe

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Residuals: TeTp=Te-TeTp (one sample)

• Many configurations were simulated.• Varied intrinsic res. and distance between tracking

planes.• 100 µm intrinsic res. and 50 cm gap between Gem1/2

and Gem2/3 show the optimum performance. 10

Design Parameters: Resolutions

Left Sec. RESOLUTIONS

Proton DeltaZ

Electron DeltaZ

Proton Del.Theta

Electron Del.Theta

Proton DeltaPhi

Electron DeltaPhi

Proton DeltaP

Electron DeltaP

100mic./50cmLuMo Only

1.70 mm 1.68 cm 0.59 Deg. 0.15 Deg. 0.55 Deg. 0.39 Deg. 21 MeV 78 MeV

100mic./50cmLuMo + MWPC

Imposed1.80 mm 2.11 cm 0.61 Deg. 0.17 Deg. 0.56 Deg. 0.40 Deg. 21 MeV 106 MeV

Conclusions

• 10x10 cm2 GEM detector size for active area at 12 degree.

• Least distance of first element 187cm for clearance

• The second should sit 237cm and third gem 287cm away from the target.

• Elastic count rate still sufficient with 50cm gaps

• 100 µm intrinsic resolutions of GEM’s meet the experimental requirement.

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Next Steps

• Simulations of phase space integral(s), acceptance; expected counts

• Study of systematic effects (beam offset, slope, width; etc.) on counts per bin

• Simulation of backgrounds

• Build and test the detectors by end of this year!

• Implement in OLYMPUS in 2011, run in 2012 14

The 208Pb Radius Experiment ("PREX")

The X position of a VDC Track projected onto the GEM

This value is about +/- 0.1 (units are m)

GEM Hit Pos vs Projected VDC Pos

Resolutions ~3mm= GEM Hit Pos – Projected VDC Pos on X & Y(UVA & INFN)

ADC Spectrum (Entry<50000)Pedestal and Noise Suppressed

ADC Correlations UVA and INFN

ADC values vs Strips(=248) are fired event by event(=50000)

The size of the reconstructed clusters in strips(140 micron strip pitch) events=50000