Welcome to the webpage of the Electroweak Symmetry Breaking Group within MSU's Theoretical High Energy Physics Group. Our research interests encompass the dynamics of electroweak symmetry breaking, flavor physics, and collider phenomenology. Recent Topics have included: Higgsless models, extended electroweak gauge symmetries, Higgs phenomenology with and without supersymmetry, little higgs models, and interpretation of astronomical evidence for dark energy.
Electroweak Symmetry Breaking:
The modern theory of the fundamental interactions describes electromagnetism (the force responsible for binding electrons to nucleii in atoms) and the weak interactions (the force responsible for radioactive decay of unstable nucleii) through a single unified force - the electroweak force. While these two forces are described symmetrically, they behave quite differently. Electromagnetism is mediated by the photon, a massless particle, and has an infinite range. The weak interaction is mediated by the W and Z particles, which have masses of about 100 times the mass of the proton, and operates only over a very short range. Our group studies how the single fundamental electroweak force comes to be manifest in nature in these two very different ways.
The fundamental particles of nature are the quarks (including the up- and down-quarks, the constituents of protons and neutrons) and the leptons (including the electron and its neutral partner, the electron neutrino). Together, the up- and down-quarks and the electron and electron-neutrino comprise the first "generation" of elementary particles. This pattern of two quarks and two leptons is repeated two more times, yielding second and third generations of heavier particles not found inside ordinary atoms. Our group studies the origin of the various masses of these elementary particles, and the mixings which allow transitions among them.
High-energy physicists study the fundamental particles and forces of nature by colliding beams of protons or electrons and observing the new forms of matter and energy produced. Beginning in 2008, the Large Hadron Collider (the LHC) at CERN (in Geneva, Switzerland) will collide counter-rotating beams of protons each accelerated to an energy of 7 trilliion electron-volts. Our group studies the observable consequences of different theories of electroweak symmetry breaking and flavor physics at current and future colliders, including at the LHC.
|This talk introduces two central mysteries of particle physics that are both related to the origin of mass: Why are the W and Z particles responsible for transmitting the (radioactive) weak force extremely heavy while the photon that transmits the electromagnetic force is massless? What causes the matter particles (e.g., electrons, quarks, neutrinos) to have such a wide range of masses? We examine the Standard Model description of the origin of mass to establish its successes and deficiencies, and conclude that physics beyond the Standard Model's Higgs boson is required. The remainder of the talk examines candidate theories of the origin of mass that do not require the existence of a Higgs boson - technicolor and higgsless models - and discusses how they might be explored at the CERN Large Hadron Collider.|
|An outreach effort can combine an eager audience, a favorite topic, and a preferred medium of expression to achieve a wonderful teaching experience. This talk discusses the whys and hows of educational outreach and presents examples from several fields of physics.|
|This talk reviews the theory and phenomenology of Higgsless models, which break the electroweak symmetry without invoking a scalar Higgs boson. Some of the most popular models of this kind are based on an SU(2)xSU(2)xU(1) gauge theory in a slice of Anti-deSitter space, with electroweak symmetry breaking encoded in the boundary conditions of the gauge fields. The spectrum includes states identified with the photon, W, and Z, and also an infinite tower of additional massive vector bosons (Kaluza-Klein excitations) whose exchange unitarizes the scattering of longitudinal W and Z bosons. The properties of Higgsless models may be studied by using the technique of deconstruction to represent the five-dimensional theory as a set of strongly-coupled four-dimensional gauge theories. In this language, one may readily demonstrate that only Higgsless models with fermions that are delocalized in the 5th dimension are consistent with precision electroweak data. After a brief overview of these general concepts, the talk focuses on a highly-deconstructed Higgsless model (the three-site model) that is complex enough to display the relevant physics, yet simple enough to be encoded into a matrix generator program for use with Monte Carlo simulations of LHC phenomenology. We will discuss current experimental constraints and the exciting prospects for discovery of the new heavy gauge bosons at the LHC.|
|We start by reviewing the motivations for Technicolor as a mechanism of electroweak symmetry breaking, and the challenges of using new strong dynamics to generate the masses of the fermions, especially the large mass of the top quark. Topcolor-assisted Technicolor (TC2) is introduced as a framework within which to meet these challenges. We then explore the structure and phenomenology of the recently-introduced model known as hypercharge-universal Technicolor and find that it agrees with the data far better than other TC2 scenarios.|
|The Standard Model is at best a low-energy effective theory of electroweak symmetry breaking that is valid at a scale characteristic of the underlying physics. This talk explores intriguing candidate theories for the new underlying physics - Technicolor and Higgsless Models - and discusses the LHC signatures of these theories. Following the lecture, a discussion session can be appended in which the (graduate student) members of the audience are encouraged to think through a few phenomenological puzzles.|
|This talk explores the smallest building blocks of matter, their interactions with one another, and their far-reaching implications. Starting with familiar concepts related to atoms, we delve inside to explore the known subatomic particles and forces. Then we examine the mysteries that still puzzle researchers today and talk about how particle accelerators are designed to answer them.|
|This talk explores the properties of atomic nuclei, showing how today's nuclear scientists are realizing some of the dreams of the ancient alchemists.|
|Abstract: The symmetries of a quantum field theory can be realized in a variety of ways. Symmetries can be realized explicitly, approximately, through spontaneous symmetry breaking or, via an anomaly, quantum effects can dynamically eliminate a symmetry of the theory that was present at the classical level. Quantum Chromodynamics (QCD), the modern theory of the strong interactions, exemplifies each of these possibilities. The interplay of these effects determine the spectrum of particles that we observe and, ultimately, accounts for 99% of the mass of ordinary matter.|
|Abstract: Higgsless models provide electroweak symmetry breaking, including unitarization of the scattering of longitudinal W and Z bosons, without employing a scalar Higgs boson. These theories may be viewed as "dual" to more conventional walking technicolor models. I show that the salient phenomenological features of these theories can be modeled by a simple extended electroweak theory incorporating an SU(2) x SU(2) x U(1) gauge structure: the "Three site model". Using the three site model, I illustrate the electroweak and LHC phenomenology of Higgsless theories in general.|
|Abstract: In theories of dynamical electroweak symmetry breaking, the electroweak interactions are broken to electromagnetism by the vacuum expectation value of a fermion bilinear. These theories may thereby avoid the introduction of fundamental scalar particles, of which we have no examples in nature. In these talks, I describe technicolor, topcolor, Higgsless, and related models, and discuss their theoretical and phenomenological properties. In doing so, I emphasize the techniques of effective field theory and its relevance to electroweak theory and phenomenology.|
|Abstract: Our modern understanding of gravity is based on general relativity, which may be summarized by the statement that "space-time geometry tells matter how to move, and matter tells space-time geometry how to curve" (J. A. Wheeler). In this talk I describe how this understanding arises from the principle of equivalence, what we mean by space-time curvature, how we know general relativity is correct, and what this means for cosmology. The talk can be adapted to various audiences, from elementary school pupils, to general adult audiences, to science teachers.|
Chivukula and Simmons were among the co-organizers of the 2011 Aspen Winter Conference on High-Energy Physics: New Data from the Energy Frontier.
The search for new physics at the TeV scale is entering an exciting era with many new experimental results emerging from the Tevatron's last run and the LHC's first -- as well as from a variety of searches for new astrophysical and cosmological indicators. This conference brought together experimentalists and theorists to present new results and ideas, creating an atmosphere that encouraged the close collaborations and active discussion that are crucial for making progress at the energy frontier.
2011 Aspen Winter Conference on High-Energy Physics
Chivukula was an organizer of the 2010 Aspen Workshop on Strong Dynamics Beyond the Standard Model.
As the experimental program at the Large Hadron Collider (LHC) explores the TeV energy range, there is potential for the discovery of new strong interactions beyond the QCD sector of the standard model. Strong interactions arise in several promising extensions of the standard model, which are being actively explored in the particle theory community. The workshop brought together particle theorists working in (1) lattice field theory and simulation, (2) non-perturbative gauge theory dynamics and (3) string/gauge duality to explore fundamental mechanisms and their generic consequences for phenomenological signatures.
Simmons is a member of the Program Committee of the Rencontres de Blois, an annual high-energy-physics and cosmology summer conference that is held in the Loire Valley. The 2010 conference was entitled First Results from LHC and the 2011 workshop was named Particle Physics and Cosmology.
The workshops draw physicists from Europe, the Americas, Asia, and the Middle East, including many younger physicists and scientists from developing nations. Participants traditionally visit the nearby mansion Clos Luce', home to Leonardo da Vinci during his final years, in order to see the life-size models of many of his most famous inventions and reflect upon his contributions to science.
The LHC Theory Initiative (LHC-TI)
Chivukula is involved in the LHC Theory Initiative. The LHC Theory Initiative is a program to provide national graduate and postdoctoral fellowships to support LHC-related theory. Unlike our European colleagues, the US theory program has not emphasized theory related to collider physics -- this despite the Tevatron's decade plus reign as the energy frontier collider facility. A successful US LHC program must include a substantial theory component, to complement the extensive investments in the LHC experiments. The LHC fellowship program is modeled on the successful SSC fellowship program funded by the state of Texas in the years prior to 1993, and aims to ensure that the US maintains a vibrant and successful program in collider theory over the twenty year lifetime of the LHC.
LHC Theory Initiative
Higgsless EWSB in the LHC Era, Radcliffe Institute for Advanced Study (2007)
Simmons, in collaboration with Chivukula, organized the week-long seminar at the Radcliffe Institute focusing on Higgsless models of electroweak symmetry breaking and their observable consequences at the LHC.
Radcliffe Institute Exploratory Seminars
MSU China Program Development Grant (2006):
Chivukula and Simmons, accompanied by their postdoctoral associate, Neil Christensen, and two of their graduate students, Baradhwaj Coleppa and Stefano Di Chiara, traveled to Beijing, China, from Dec. 10-17, 2006 to visit the Tsinghua University Center for High-Energy Physics. Their hosts at Tsinghua University included Prof. Hong-Jian He, a long-time collaborator of Chivukula and Simmons, and Prof. Yu Ping Kuang, a member of the Chinese Academy of Sciences.
Tsinghua University Center for High-Energy Physics
The Aspen Center for Physics (1994-2014)
Simmons is a general member of the ACP, and has served as a trustee, corporate secretary, and scientific secretary.
Aspen Center for Physics
5. Wu-Ki Tung Symposium, May 12, 2007.
Chivukula, in collaboration with Chip Brock and C.-P. Yuan, organized the Wu-Ki Tung Symposium held on May 12, 2007.
The Electroweak group has close ties and longstanding collaborations with the following research groups and individuals: