Elliot Smith's Research: International Linear Collider

Calorimeter Studies

I am a graduate student at the University of Colorado. My current work is conducted under the guidance of Dr. Uriel Nauenburg and in collaboration with Keith Drake. Our work is based on detector studies for the International Linear Collider. Our goal is to study the ability/efficiency for our detector's design to be the most optimal to be used in the International Linear Collider when it is built. The building of the International Linear Collider will hopefully lead to effectively testing the validity of the Supersymmetric Theory. For a basic/beginners discussion of Supersymmetry please visit this site created for new-comers in our group. Our work is highly dependent on the ability to separate single photon events which will measure our ability to have highly well measured Pi0's (or Hadrons) from their two photon decays. By "well measured" I mean the energy and direction of PiO's (In an ElectroMagnetic Calorimeter (EMCal)) and Hadrons (in a Hadronic Calorimeter (HCal)) would be well measured. This has been made possible through the use of Silicon Photomultipiers (SiPMs). We currently have very good resolution up to six photon events and are currently working on methods to increase this number.

Current Detector Studies

Spatial Mapping of Scintillation Tile (Sr90 beta source)

The first program we have been doing research on for the past year includes our work with the new and improved 40V bias SiPMs. We have done quite a number of studies involving these newer SiPMs, and a paper is pending. Our goal now is to improve our resolution beyond the seven p.e. peaks which we can currently resolve. This will hopefully be attained through faster data analysis equipment and better data interpolation.

40V bias SiPM studies (photon separation attained)

The other project is looking at Cosmic Rays via reading out hits on scintillating tiles which are in an array with an offset geometry to represent a small mock up of our larger detector design. We have quite a bit of data on cosmic rays including the separation of muon and photon showers. currently though we are building a setup that will allow us to take data with our SiPMs at around minus 40 degrees C (-40 F). These colder temperature lead to lower noise rates and steadier charge outputs per p.e. peak which in turn leads to a higher resolution which is why we are interested in being able to take data at colder temperatures than room temp. Up until now we've taken these cold measurements using dry ice, which works fine when taking data that lasts for less than ten minuets because much longer than that the dry ice will not stay at a steady temperature. With cosmic rays coming in at a rate of eleven a minute for muons (or 2 a minute for photons) it is necessary to take days worth of data. Our new cold testing will involve a thermo-electric device which will allow us to keep our experiment cold for days at a time which is exactly what we need.

Tile Studies for detector: Cosmic Ray Detection

Old Detector Studies

One of our first studies involved looking at SiPMs with a 60V bias. These devices due to noise gave a charge readout which did not show individual photon peaks. Some groups working on the ILC were able to get separation with these devices but they were few and far between. This sort of inconsistency would have made calibrating the detector very difficult, if at all possible. The newer 40V bias SiPMs consistently give us readouts with photon peak separation so we've moved away from these older outdated SiPMs.

60V bias SiPM studies (photon separation not possible)

Our other older study involves the study of the degradation of fiber optics over time. Numerous studies of the Wavelength Shifting Fibers (WLS fibers) that we have decided to use in our detector have been performed, but no study on the strains in which we wish to subject our fibers to has been performed. We plan to have our fibers laid into (5cm)x(5cm) scintillating tiles. In order to cover the largest service area possible in the tile we plane to have our fibers bent into 2cm radii circles. Some problems that can arise with these small radii are lose of light due to the tight curvature, cracking of the fiber, strain on the fiber which over time can lead to a lower light yield. Our studies include a normal which is a fiber bent at 6cm radii (at curvature which has been studied by other groups to have little to no degradation) on 6cm fiber is annealed and thew other is not along with one annealed 2cm and one non annealed in order to see the effects of annealing the fibers as well. (Annealing is discussed in much greater detail in the Longterm paper located in the link below.) We are currently reaching data for the last year which suggests that there is no loss of light over time in any of our fiber tests.

Longterm Studies for the Degradation of Fiber Optics

Old SUSY WORK

A look into the fractional decays of W+ and W- collisions, excluding leptons
A look into the fractional decays of Z0 collisions, excluding leptons

Additional High Energy Physics Links:

University of Colorado High Energy Group
Supersymmetry Studies