Simulations of Light Collection Efficiency ( JLab Hall C 12 GeV Kaon Aerogel Detector)

1. Simulations of Light Collection Efficiency(JLab Hall C 12 GeVKaonAerogel Detector) Laura Rothgeb Nuclear Physics Group Catholic University of America August 19, 2011

2. Overview: Additional Flavor Degree of Freedom in K+ Production Generalized Parton Distributions (GPD, model of the momenta of quarks within particle) are used to understand the internal structure of nucleons. Using hard scattering meson electroproduction we can construct the GPD of the proton and find the form factor of the kaon. To construct GPDs these data must conform to the model of hard QCD scattering.

3. Kaon Aerogel Cherenkov Detector • Detects kaon particles via Cherenkov radiation • Uses Photomultiplier Tubes (PMTs) to collect the light and convert to electrical signal via the photoelectric effect • Some design considerations • Ideal refractive index of aerogel • Optimum number/placement of PMTs • Effect of light guides on light collection efficiency

4. SimCherenkov FORTRAN Monte Carlo simulation written to model the Kaon Aerogel Cherenkov Detector for Jefferson Lab to optimize conceptual design components Allows for multiple configurations including options for manipulating detector geometry, placement and sizes of PMTs, variety of reflective surfaces and refractive indices of aerogel Tracks photons emitted by the Cherenkov radiation in the simulated detector and relays the total number of photoelectrons produced based on the characteristics of the detector determined by the user

5. Experimental Setup μ Implements extension volume to study effect of a large, asymmetrical light guide Aerogel Casing Extension Volume γ e- Light Diffusion Box PMT

6. Light Guide Simulations Wrote new loop configuration: EXTENSION • Width, length and height of the extension box can be modified to simulate various light guide geometries • Surface of extension box can be changed to compare effects of various reflective materials PMT Aerogel Casing Extension Box Volume Light Diffusion Box

7. EXTENDH = 11.6 EXTENDL = 11.6 μ γ e- Maximum: EXTENDW = 0cm Experimental Setup: EXTENDW = 11.6cm Efficiency: 23%

8. EXTENDW = 11.6 EXTENDL = 11.6 Maximum: EXTENDH = 15cm Experimental Setup: EXTENDH = 11.6 Efficiency: 90%

9. EXTENDH = 11.6 EXTENDW = 11.6 Maximum: EXTENDL = 12cm Experimental Setup: EXTENDL = 11.6cm Efficiency: 99%

10. Efficiency:Photon Loss Returns to Light Box Light Box PMT Window Initial Light Guide (0cm) Light Box (millipore) Extension Box (mylar) Aerogel Aerogel Extension Box PMT Window Returns to Light Box ~37% of the total photons are absorbed in the extension box

11. Results Geometry of light guides have a drastic effect on the efficiency of Aerogel Cherenkov detectors: light is lost mainly due to increased surface area in which the photons are absorbed Decreased efficiency shown empirically with experimental set-up at JLab, confirms simulation results Next, implementing a model of the detector into a detailed GEANT4 Monte Carlo simulation