OLYMPUS Collaboration Meeting DESY April 6 7 2009

OLYMPUS Collaboration Meeting, DESY, April 6 -7, 2009 OLYMPUS Luminosity Monitors Michael Kohl Hampton University, Hampton, VA 23668 Jefferson Laboratory, Newport News, VA 23606

Proposed Experiment • Electrons/positrons (100 m. A) in multi-Ge. V storage ring DORIS at DESY, Hamburg, Germany • Unpolarized internal hydrogen target (buffer system) 3 x 1015 at/cm 2 @ 100 m. A → L = 2 x 1033 / (cm 2 s) • Large acceptance detector for e-p in coincidence BLAST detector from MIT-Bates available • Measure ratio of positron-proton to electron-proton unpolarized elastic scattering to 1% stat. +sys. • Redundant monitoring of luminosity Pressure, temperature, flow, current measurements Small-angle elastic scattering at high epsilon / low Q 2 Moller scattering?

Control of Systematics OLYMPUS: BLAST @ DORIS Luminosity monitors 10 o • • • Change BLAST polarity once a day Change between electrons and positrons regularly, randomly Left-right symmetry = redundancy

Control of Systematics (Naïve) argument in the past (also in proposal etc. ): i = e+ or ej= pos/neg polarity Geometric proton efficiency: Ratio in single polarity j Geometric lepton efficiency:

Control of Systematics (Naïve) argument in the past (also in proposal etc. ): Super ratio: Cycle of four states ij Repeat cycle N times -> reduction of systematics by √N • • • Change between electrons and positrons every other day Change BLAST polarity regularly, randomly Left-right symmetry = redundancy

Cancellation of geometric efficiencies? Proton detection efficiencies Lepton detection efficiencies • Does the “geometric efficiency” for coincidence of p-l really factorize? ε(pp, θp, pl, θl) =? κp(pp, θp) x κl(pl, θl) • Does the coincidence of lepton and proton generate a correlation? What does “geometric efficiency” mean? p and l are kinematically correlated for the elastic process, as knowledge of just one variable (i. e. Q 2) fully determines the elastic reaction kinematics • The “detection efficiency” is independent of the kinematic correlation and hence factorizes for p and l, if detected at different locations in the detector (as is the case) • But the “acceptance” is not! “Geometric efficiency” = “Detection efficiency” x “Acceptance”

Differential cross section Event counts: A(Ω) = Acceptance function Bin-averaged differential cross section: Phase space integral Require acceptance simulation to determine phase space integral numerically!

Control of Systematics MORE REALISTICALLY: i = e+ or ej= pos/neg polarity A = Acceptance function (phase space integral) Proton ”detection” efficiency: Ratio in single polarity j Lepton detection efficiency:

Control of Systematics MORE REALISTICALLY: Super ratio: Cycle of four states ij Repeat cycle many times • • • Ratios of acceptances (phase space integrals) Change between electrons and positrons every other day Change BLAST polarity regularly, randomly Left-right symmetry = redundancy

Luminosity Monitoring (Naïve) argument in the past (also in proposal etc. ): • • Forward-angle (high-epsilon, low-Q) elastic scattering (se+ = se-) Measure Lij relatively (i. e. Nijfwd) and continuously to ~1%/hour At forward angle:

Control of Systematics (Naïve) argument in the past (also in proposal etc. ): Super ratio: Cycle of four states ij Repeat cycle many times • • • Change between electrons and positrons every other day Change BLAST polarity regularly, randomly Left-right symmetry = redundancy

Luminosity Monitoring MORE REALISTICALLY: • • Forward-angle (high-epsilon, low-Q) elastic scattering (se+ = se-) Measure Lij relatively (i. e. Nijfwd) and continuously to ~1%/hour At forward angle:

Control of Systematics MORE REALISTICALLY: Super ratio (“triple ratio”): Cycle of four states ij Repeat cycle N times -> reduction of systematics by √N • • Change between electrons and positrons every other day Change BLAST polarity regularly, randomly Left-right symmetry = redundancy Determine ratios of phase space integrals from Monte-Carlo simulation

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 GEM technology MIT protoype: Telescope of 3 Triple GEM prototypes (10 x 10 cm 2) using Tech. Etch foils F. Simon et al. , NIM A 598 (2009) 432

Principle of GEM Detectors • GEM = Gas Electron Multiplier introduced by F. Sauli in mid 90’s, F. Sauli et al. , NIMA 386 (1997) 531 • Copper layer-sandwiched kapton foil with chemically etched micro-hole pattern gas amplification in the hole

GEM foils 70 µm 140 µm Typically 5 mm Cu on 50 mm kapton ~104 holes/cm 2 5 µm 70 µm Chemical etching • R. De Oliveira (CERN-EST) • Tech. Etch (MIT, Bo. Nu. S) • 3 M Corporation Laser drilling • Tamagawa (RIKEN) 55 µm 50 µm``

Multi-GEM Detectors • GEMs can be cascaded for higher gain • Gain of 104 needed for efficient MIP detection Double GEM C. Buettner et al. , Nucl. Instr. and Meth. A 409(1998)79 S. Bachmann et al. , Nucl. Instr. and Meth. A 443(1999)464 Triple GEM

Luminosity Monitors (I): Telescopes Proposed version included in OLYMPUS proposal Sept. 2008 2 t. GEM telescopes, 3. 9 msr, 10 o, R=160 cm, d. R=10 cm, 3 tracking planes Forward telescopes 10 o

Luminosity Monitors (I): Telescopes Proposed version included in OLYMPUS proposal Sept. 2008 • • • Two symmetric GEM telescopes at 10 o Two-photon effect negligible at high-ε / low-Q 2 Sub-percent (relative) luminosity measurement per hour for all energies • • 3. 9 msr = 10 x 10 cm 2 at ~160 cm distance Three GEM layers with ~0. 1 mm resolution with ~10 cm gap → Vertex resolution (z) of ~1 cm at 10 o to match that of proton in BLAST Same readout pitch as in MIT prototype (635 mm), read every other channel Number of electronics channels per telescope: 3 x(100+100)/0. 635 ~= 1000 • •

Luminosity Monitors (I): Telescopes Proposed version included in OLYMPUS proposal Sept. 2008

Luminosity Monitors (II): Trackers Version presented at OLYMPUS meeting in July 2008 2 t. GEM trackers, 30 msr, 10 o, R=160/230/300 cm, d. R=70 cm, 3 tracking planes Forward trackers 10 o

Luminosity Monitors (II): Trackers Version presented at OLYMPUS meeting in July 2008 • Extension of BLAST acceptance at ~5 o-15 o and ± 5 o out of plane • • 30 msr = 28 x 28 cm 2 at 160 cm distance, 40 x 40 at 230, 52 x 52 at 300 cm Three GEM layers with ~0. 1 mm resolution with ~70 cm gap, like WC Same readout pitch as in MIT prototype (635 mm) Number of electronics channels per tracker: 2 x(280+400+520)/0. 635 ~= 3800

Providing GEM technology • Collaboration HU-MIT • Goal: Establish HU/Jlab GEM R&D Center – Thia Keppel / Medical physics applications: Hampton University Proton Therapy Institute (HUPTI) under construction (2010) – Howard Fenker / Jlab / Bonus collaboration – Luminosity monitors for OLYMPUS (2009 -2010) – C 0 cylindrical and C 1 planar GEM trackers for Time Reversal Experiment with Kaons (TREK) at J-PARC (~2012) – Augment 12 Ge. V program at Jlab (~2014) • Funding Requests (regular grant incl. postdoc+students) – – NSF Nuclear Physics (September 24, 2008) DOE OJI Program (December 1, 2008) Included 115 k$ in equipment money for monitors in both requests Decisions awaited

Next steps and timeline • Start GEANT 4 simulation (can use one graduate student of HU nuclear physics group) -> design parameters: size, location, resolution • Start simulations of phase space integral(s) • Finalize design parameters and specifications until end of summer (at MIT visit in July) • • • New research building at HU to be ready for move-in in fall 2009 Expect grant this or next year: equipment, postdoc, students Purchase of parts within first year of grant Assembling/testing with sources and cosmics starting summer 2010 Implementation into OLYMPUS in summer 2011 • Development of analysis software / integration into BLAST analysis by 2011