This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).
Particle physics stands at the threshold of a new era of discovery as the Large Hadron Collider (LHC) begins colliding-beam operations this fall. With the highest-energy collisions ever created in a laboratory environment, the CMS collaboration (about 1600 physicists world-wide) will study some of the most fundamental questions of our time, such as the origin of mass, the possible existence of supersymmetry, and the hypothetical existence of extra spatial dimensions. The Compact Muon Solenoid (CMS), one of two general-purpose detectors at the LHC (the other detector is called ATLAS and has a similar number of collaborators), has been designed to discover the new physics of this energy scale. At the heart of CMS is the silicon pixel detector. The current device took years to design and build and represents the state-of-the-art for this type detector. However, it is well known that it will eventually fail due to radiation damage and a new device with enhanced characteristics must be designed and built to take its place. This award funds Professor Alice Bean, Professor of Physics at the University of Kansas, and a consortium of six universities (Kansas, Kansas State, Illinois at Chicago, Puerto Rico-Mayaguez, Rice, and Rutgers) to develop a detector that will serve as a research instrument for the design of the phase 1 upgraded silicon pixel detector for CMS.
The broader impacts can be divided into two categories - those related to the development of the research and training infrastructure at collaborating institutions and those related to the impacts on the field of high energy physics as a whole. In particle physics the capability to design and build instrumentation is crucial to the success of any university group in this field. This award provides the means for the collaborators to enhance the prestige and capability of the respective institutions at an international level. In addition, the development activities will allow recruiting undergraduate students, especially women and minorities, to help build this instrument and participate in the physics studies and should help attract more students into physics and engineering.
The CMS experiment at the Large Hadron Collider near Geneva, Switzerland seeks to understand the universe at the basic particle level. With the discovery of the Higgs boson in 2012, there is much work to be done to understand the particle and to search for new physics. The LHC will run at a higher energy and higher data rate starting in 2015. This grant developed the instrumentation for an upgrade to the pixel detector which resides in the innermost portion of CMS. The pixel detector helps to locate charged particle tracks at high precision and also pinpoint where other particles decayed by finding secondary vertices. The new pixel detector has a new digital readout chip that allows one to collect data at the higher rates. This MRI group working with the CMS collaboration, designed a new detector which has twice the number of readout channels and half as much of the material in the active region that will allow us to fully exploit the new dataset. The design work included simulations which showed that the performance of the new detector will be improved in particular with respect to finding the secondary vertices. Physics channels with b-quarks such as those from Higgs decays will be more easily identified. The full detector will be installed into CMS after 2016. This grant built a pilot detector to be installed into CMS during 2014. The pilot detector includes 8 modules made from silicon sensors and new pixel readout chips. Custom silicon sensors were designed and purchased to be bonded to the new readout chips which were designed, fabricated, and tested. The new readout chip is found to have a lower threshold which will allow the detector to operate longer in the high radiation environment. Another new electronics chip was designed and fabricated to controls the signals on the modules. State of the art cables were designed and made to bring signals off of the modules. Several teststands were designed and constructed to test the modules including a temperature cycling electronics burn-in stand, and an X-ray system which used a custom designed readout testboard which was designed and tested. In addition to the modules, the MRI group constructed a full chain electronics system to test the data acquisition system for the upgraded pixel detector. This test system was able to demonstrate that the electronic signals can travel from the modules off of the detector after converting the electrical signals to optical signals, and then be received into the computer readout modules that assemble the data events for analysis. The test system included module simulator electronics, a new hybrid which converted the digital electronics signals to optical ones, fiber optics, fiber optic receivers, and computer readout assembly modules with their control and trigger electronics. The data rate for transfer for the system presented many challenges, which were overcome using custom designed parts at every stage. The instrumentation developed with this grant can be used in other fields of science including materials studies. In addition, U.S. companies were engaged to build the new state of the art components, including low mass aluminum cables and bonding the sensors to the readout chips. One important impact of the project was to train undergraduate and graduate students, as well as postdoctoral researchers in this instrumentation. Five postdoctoral researchers, 9 graduate students, and 17 undergraduates worked on the project.
