The Large Hadron Collider (LHC) at CERN, Geneva, is the highest energy collider in the world. LHC collides protons on protons at center-of-mass energy of 13 TeV (13 trillion eV). The Ohio State University is a member of the ATLAS collaboration that built the gargantuan detector to study particles produced in the collisions. ATLAS, together with the other LHC experiment called CMS, discovered the Higgs boson which led to the 2013 Nobel Prize.
ATLAS is a general purpose detector with multiple sub-detectors designed to characterize particles produced in the collisions. We contributed to the fabrication of the pixel detector and diamond beam monitors. This complex instrumentation allows us to search for physics beyond the Standard Model of particle physics, one of the most extensively tested theories in history. The discovery of the Higgs boson was a triumph of the theory, but despite its success, we know that there must be some yet undiscovered "new physics'' that emerges at higher energy scales. For example, the Standard Model cannot explain the observed mass of the Higgs boson, the matter/anti-matter asymmetry in the Universe, or the existence of dark matter, which is measured to be five times more prevalent than ordinary matter. It also provides no insight as to why there are three generations of elementary particles, why the masses of the charged particles span six orders of magnitude, or why parity is only violated in the weak interaction but not in the strong interaction. The mission of ATLAS is to discover new particles and thereby reveal a new theory that would explain some of above puzzling questions.
The OSU group has a diverse physics program in both physics analysis and instrumentation. To search for new physics, we deploy leptons as a tool due to its clean signature, a tool that have been used in the past for several major discoveries, including the discovery of the Higgs boson. We are presently involved in several analysis projects, including searches for (1) diHiggs production, (2) dark matter, and (3) long-lived exotic particles that decay into a lepton pair.
In addition to strong analysis efforts, we are also actively involved in the R&D of the ATLAS detector upgrade to further enhance the discovery potential. We are part of the pixel detector group. The pixel detector is the tracking device closest to the collision point and is designed to improve the charged particle tracking and identification of bottom quarks in hadronic jets, critical in many of the searches for physics beyond the Standard Model. The pixel detector consists of four barrel layers and three forward and backward disks. The OSU group leads the R&D, design, fabrication, and maintenance of the on-detector radiation-hard and high-speed optical communication. For the future, we are actively involved in the R&D of the high-speed and radiation-hard optical links. More info is available at the web site of Prof. K.K. Gan.
The OSU group is also a major contributor to the diamond-based Beam Condition Monitor (BCM), Beam Loss Monitor (BLM), and Diamond Beam Monitor (DBM). These devices exploit the radiation-hardness and fast response of diamond. The devices play a critical role in protecting the ATLAS detector and measuring the luminosity. For the future, we are actively involved in the R&D on the use of diamond based pixel detector and the design and fabrication of a new Beam Condition Monitor (BCM’) for the detector upgrade.