Experimental Study of Heavy Flavor and CP Violation with the LHCb Experiment at the CERN LHC Collider

University Of Maryland, College Park, College Park MD

Investigators

Abstract

One of the major intellectual achievements of the 20th century was the development of the Standard Model (SM) of particle physics. This model succeeded in classifying all of the elementary particles known at the time into a hierarchy of groups having similar quantum properties. The validity of this model to date was confirmed by the discovery of the Higgs boson at the Large Hadron Collider at CERN. However, the Standard Model as it currently exists, leaves open many questions about the universe. These include why matter dominates over anti-matter in the Universe (CP violation), the values of the masses of the fundamental constituents, the quarks and the leptons, the size of the mixings among the quarks, and separately among the leptons, and the properties of dark matter. Most explanations require the presence of new particles, symmetries or forces, which we call Beyond the Standard Model Physics (BSM). This project is designed to pursue searches for BSM physics. The LHC is the premier High Energy Physics particle accelerator in the world and is currently operating at the CERN laboratory near Geneva Switzerland, one of the foremost facilities for answering these BSM questions. The Maryland group is a collaboration member of LHCb, an experiment designed specifically to study the decays of hadrons containing b or c quarks at the LHC. The goal of LHCb is to identify new physics in nature by examining the properties of hadrons containing these quarks. New physics, or new forces, can be manifest by particles, as yet to be discovered, whose presence would modify decay rates and CP violating asymmetries of hadrons containing the b and c quarks, and thus allow new phenomena to be observed indirectly. Analytically, the Maryland program is focused on measurements related to two of the current anomalies in the decays of B mesons: hints of departure from Lepton Flavor Universality in semi-leptonic B decays and the long-standing so-called K-pi puzzle where the measured CP asymmetries in the family of B decays into the K-pi final state deviate from the expected simple predictions. These anomalies, if confirmed, could be due to the imprints of BSM physics. Technically, the Maryland group leads the development and construction of the off-detector electronics for the new upstream tracker (UT) in the LHCb upgrade and participation in the installation and commissioning of the tracker. The UT represents a major US contribution to the upgrade of the experiment to improve event reconstruction overall and particularly for rare events of the type under study by the Maryland team. The group works closely with an outreach program run by the physics and astronomy departments at the University of Maryland, called GRAD-MAP, which is aimed at providing research and training opportunities for undergraduates from underrepresented groups in the Maryland and Washington area community colleges. The LHCb experiment, with its technical challenges and exciting physics program, serves as a major attractor for student participation. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.