The nature of dark matter is one of the most important research topics in physics today. It pertains to fundamental unanswered questions in particle physics, astrophysics, and cosmology. This award will enable a probe of a very interesting new region of theoretical phase space for viable Weakly Interacting Massive Particle (WIMP) candidates in the search for dark matter in order to improve our understanding of it: what it is, where it is, how it interacts with Standard Model particles, and what its role is in the evolution and fate of the universe.
The research objective is to either measure a dark matter signal or set a limit on the WIMP-nucleon cross-section for a 60 GeV WIMP mass. This will be reached through the PI's work as a member of the Cold Dark Matter Search (CDMS) collaboration. The approach is to improve the efficiency and to reduce the lower energy threshold of their current detectors to obtain a factor of 2 increase in the science reach of the experiment, and to implement new higher-performance, more massive detectors for the next phase of SuperCDMS.
The Broader Impacts of this project include increasing the pool of under-represented minority applicants to graduate programs in physics and astronomy. The approach is to increase the exposure of these students to opportunities in research through a summer program at MIT. The PI will work with HBCUs and HSIs to bring talented students for a summer of research, journal club presentations, networking with MIT minority graduate students, and outreach to local high schools in the Boston community. Research in the physics of high-resolution low-temperature detectors and new analysis techniques have applications in other fields such as astrophysics, nuclear physics, and solid-state physics.
This CAREER Award has focused on the search for dark matter, a misterious substance that makes up 26% of the Universe. We think dark matter is a new type of fundamental particle, one that might be detectable in extremely sensitive detectors designed specifically for this search. We are part of the Cryogenic Dark Matter Search (CDMS), a collaboration that uses germanium and silicon crystals cooled to close to absolute zero and instrumented with current and vibration sensors to attempt to discover the very rare events in which dark matter particles could interact with our detectors. Findings and Science Results of this award: (1) My group led the analysis of the silicon detector of CDMS-II, which found three events with a background expectation of less than one event. This analysis made a major impact in our field, as the three events might be from dark matter. A recent result from our new experiment SuperCDMS Soudan (with germanium detectors) rules out a dark matter interpretation for the simplest model of dark matter interactions, although more complex interactions could be at play and have not yet been ruled out. More data is needed (from SuperCDMS SNOLAB) to settle the fate of this signal. (2) My group led the analysis of the SuperCDMS Low Threshold analysis which was the first results using our new SuperCDMS detector's full background discrimination capabilities at low energies. This analysis placed world-leading limits on the interactions between dark matter and normal matter for models with dark matter particles whose mass is a few times that of the proton. (3) My group lead the annual modulation analysis of the CDMS-II germanium detectors. Annual modulation of a signal is one of the expected properties of dark matter, so seeing it in your data may mean you are seeing dark matter interactions. Our data showed no significant modulation, in dissagreement with the modulation result from another dark matter experiment from the CoGeNT collaboration. (4) We have published several papers breaching the divide between dark matter and neutrino physics. We have studied several applications of our CDMS detectors to neutrino physics and of the implications of solar, atmospheric, and diffuse supernova background neutrinos on future third-generation dark matter searches. Other Experimental, Simulation, and Analysis Techniques results: (1) We developed a CDMS Detector Monte Carlo (DMC), which is a software program which produces synthetic data that can be compared to real data to test our understanding of the underlying detector physics and its response and calibration. (2) We developed several analysis advances for CDMS-II and SuperCDMS Soudan data. (3) We developed a low-temperature detector testing facility at MIT which as been used in R&D and in prototype testing of SuperCDMS SNOLAB detectors. (4) We designed the sensor layout mask for the SuperCDMS Soudan detectors. Intellectual merit and broader impacts: This work has focused on answering one of the most fundamental questions in physics and cosmology today: What is Dark Matter? This question is at the heart of our cosmological understanding of the Universe and its answer may be a Rosetta Stone to allow us to understand the fundamental structure of particle physics. The technology development we work on could have applications in the medical and homeland security fields, and the training we provide our students benefits the general public as they move on to jobs outside of academia and apply what they have learned to other problems facing socitey. We have also worked on increasing diversity in our scientific workforce by participating in several programs bringing students from underrepresented groups to our lab for summer research experiences.
