THE OLYMPUS LUMINOSITY MONITORS Ozgur Ates Hampton University

“THE OLYMPUS LUMINOSITY MONITORS” * Ozgur Ates Hampton University § 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 1

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Luminosity Monitors: Telescopes Luminosity monitors for LEPTON in coincidence with Recoil PROTON detected in the opposite sector, and vice versa. 2 t. GEM telescopes, 1. 2 msr, 12 o, R=187/237/287 cm, d. R=50 cm, 3 tracking planes Forward telescopes PROTON LEPTON 12 o LEPTON PROTON TOF

Control of Systematics 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 counts • • • Ratio of luminosities Ratio of acceptances (phase space integrals) 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 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 Technology MIT prototype: Telescope of 3 Triple GEM prototypes (10 x 10 cm 2) using Tech. Etch foils F. Simon et al. , NIM A 598 (2009) 432

Monte Carlo Studies by using Geant 4 • 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) Te. Tp: Te – Te(Tp) Te. Pe: Te – Te(Pe) Te. Pp: Te – Te(Pp) • Coplanarity: Phe. Php: Phe – Php – 180 • Common vertex: Ze. Zp: Ze – Zp 6

Resolution: generated - reconstructed 100 micron, 50 cm, Lu. Mo+BLAST (Te=0 -80 dg, Phe=+-15 dg) δZp δZe δTp δTe δPhp δPhe δPp δPe 7

Resolution: generated - reconstructed 100 micron, 50 cm, Lu. Mo only (Te=6 -13 dg, Phe=+-5 dg) δZp δZe δTp δTe δPhp δPhe δPp δPe 8

Residuals: Te. Tp=Te-Te. Tp (one sample) 9

Design Parameters: Resolutions Left Sec. Proton RESOLUTIONS Delta. Z Electron Proton Electron Delta. Z Del. Theta Delta. Phi Delta. P 100 mic. /50 cm 1. 70 mm 1. 68 cm 0. 59 Deg. 0. 15 Deg. 0. 55 Deg. 0. 39 Deg. 21 Me. V 78 Me. V Lu. Mo Only 100 mic. /50 cm Lu. Mo + MWPC 1. 80 mm 2. 11 cm 0. 61 Deg. 0. 17 Deg. 0. 56 Deg. 0. 40 Deg. 21 Me. V 106 Me. V Imposed • Many configurations were simulated. • Varied intrinsic res. and distance between tracking planes. • 100 µm intrinsic res. and 50 cm gap between Gem 1/2 and Gem 2/3 show the optimum performance. 10

Conclusions • 10 x 10 cm 2 GEM detector size for active area at 12 degree. • Least distance of first element 187 cm for clearance • The second should sit 237 cm and third gem 287 cm away from the target. • Elastic count rate still sufficient with 50 cm gaps • 100 µm intrinsic resolutions of GEM’s meet the experimental requirement. 13

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 208 Pb 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 ~3 mm= 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