The Tufts University Elementary Particles Group joined ATLAS in 1994. Together with Boston University, Brandeis University, Harvard University and Massachusetts Institute of Technology we decided to work as a single group, the Boston Muon Consortium (BMC), on the ATLAS muon system. After the decision to focus on the ATLAS end-cap muon system, the Tufts Group was very active in initial physics simulations and in construction and testing of the first MDT end-cap muon chamber, with Prof. Mann leading the latter effort. The Tufts Group’s high precision computer-controlled machine shop served as a R&D lab for BMC, and later manufactured thousands of small, very precise and custom-designed pieces needed for the MDT chambers and for the entire alignment system. At the same time, the Tufts ATLAS Group was very active in studying and planning the world-wide data analysis and reconstruction, needed for the world-wide collaboration like ATLAS. MONARC, a very successful LHC project created jointly by Tufts and Caltech, provided the first realistic modelling of such a world-wide, distributed computer system.
The Tufts ATLAS Group currently consists of three faculty (Pierre-Hugues Beauchemin – who joined the group recently, Austin Napier and Krzysztof Sliwa), a research-associates (Evelin Meoni), two graduate student (Jeffrey Wetter and Hyungsuk Son) and two part-time consultants (Noah Kurinsky and Benjamin Whitehouse, Tufts former students). The Tufts Group was very active in the analysis of the muon test-beam data, and continued to work on the muon reconstruction software. The Tufts ATLAS Group developed the MuonTrackingGeometry, a completely new description of the entire muon system, including the active and the passive elements, which allows the use of ATLAS common tracking tools in muon reconstruction. The MuonTrackingGeometry is also an essential component of FatRas, a new, fast ATLAS track simulation which models the detector response at the hit level. Tufts ATLAS Group was responsible for simulation of the entire muon system in FatRas. FatRas is now an important part of the Integrated Simulation Framework, a new fast simulation of the entire ATLAS detector.
At the same time, we continue with physics studies. The Tufts ATLAS Group is interested in W+jets and Z+jets physics, top physics, Higgs boson studies, and physics beyond the Standard Model (non-standard Higgs searches, SUSY, extra dimensions et cetera). The main objective of the LHC Run-II analyses is to find out whether the new particle discovered in 2012 is a Minimal Standard Model Higgs, or some other kind. It would be really exciting if the latter were true. There is also a chance that with increased energy of the proton-proton collisions completely new particles will be found. Here, studies of top quarks are extremely important, as top quarks will constitute the most important background for almost any final states due to “new physics” and have to be understood very well.
Prof. Beauchemin, together with Dr Meoni, Mr Son and undergaduate students, is studying the production of W and Z electroweak bosons, accompanied by N jets. They study the ratios of W+jets/Z+jets production rates. When taking the ratios, many of the systematic errors cancel, which leads to reduced uncertainties and allows more significant comparison with theoretical predictions. They also study the production of jets accompanied by large missing transverse energy, which could provide clues about dark matter.
The Tufts ATLAS Group has developed a new analysis technique – an event classifier based on a multidimensional machine learning method – Support Vector Machines (SVM). Although SVM were used in other research areas in the past, Tufts was the first group to apply it in collider physics. The method, originally developed by Dr. Ben Whitehouse when he was a student of Prof. Sliwa’s, allows taking into account simultaneusly many physics variables and correlations between them. We believe that it is the best multidimensional analysis technique in existence. In contrast to most other multivariate methods, it has a sound mathematical foundation (Mercer Theorem). Prof. Sliwa, together with Dr Whitehouse, Mr Wetter and a group of undergraduate students, is currently applying this new analysis technique in measurements of the production rate of top quarks at 7 TeV, 8 TeV and their ratio; and in a measurement of the production rate of Higgs bosons in the difficult to analyse final states involving leptons, jets and missing transverse energy, looking for signatures of the Higgs bosons produced via a WW* fusion mechanism.
Prof. Sliwa is also studying topology, differential geometry and other elements of modern mathematics to gain more insight into the meaning of quantum gauge theories, the origin of mass and the structure of space-time, matter and all interactions, including gravity.
Prof. Sliwa has won Tufts Faculty Research Awards in 2012 and 2013, and Prof. Beauchemin in 2014. The Tufts ATLAS Group has also won in 2014 the Tufts International Research Award, which allowed both faculty and four students to spend 6 weeks at CERN in the summer of 2014.
Research Associates: Evelin Meoni
Students: Jeffrey Wetter, Hyungsuk Son
Contact: Krzysztof Sliwa
Webpage: Tufts High Energy Physics Group
Conference presentations and invited talks: