Nanopoulos at the Leading Edge of Higgs Boson Search

Submitted by James A. Maxin, postdoctoral researcher, Department of Physics and Astronomy

Dr Dimitri Nanopoulos

COLLEGE STATION — In mid-December at the European Organization for Nuclear Research (CERN) in Geneva, Switzerland, the Compact Muon Solenoid (CMS) and ATLAS (A Toroidal Lhc ApparatuS) experiments delivered a joint status update regarding their ongoing search for the Higgs boson, a hypothetical particle that is believed to give mass to all matter in the early universe.

The gist? Although neither experiment has produced enough conclusive statistical evidence of the particle’s existence, they may have observed hints of its presence.

More than a dozen Texas A&M University physicists — including Distinguished Professor of Physics Dimitri Nanopoulos — are involved in the two experiments, which are powered by two of the world’s largest particle detectors at the Large Hadron Collider (LHC) at CERN. Collectively CMS and ATLAS produce trillions of collisions resulting from smashing together protons accelerated to near the speed of light. From these high-energy impacts, new particles can be created, including that of the Higgs boson.

The leading mechanism by a factor of 10 for production of the hypothetical Higgs boson is what’s called gluon-pair fusion, or producing Higgs bosons from the annihilation of two gluons in a collision of two protons. Gluons are massless particles binding together quarks, which comprise particles such as protons and neutrons.

Nanopoulos, a member of the Texas A&M Department of Physics and Astronomy faculty since 1989 and holder of the Mitchell-Heep Chair in High-Energy Physics since 2002 who also serves as head of the Houston Advanced Research Center (HARC) astroparticle physics group, is known as one of the founders of Grand Unification Theory (GUT), which seeks to combine gravitation, electroweak and strong forces in an explanation for everything in the universe. His years of research in string unified theories have led to advances in similar fields of study, such as cosmology, fundamental quantum theory and quantum-inspired models of brain function.

In 1978 Nanopoulos teamed with Howard Georgi of Harvard University, 1979 Nobel Laureate Sheldon Glashow of Boston University, and Marie E. Machacek of the Harvard-Smithsonian Center for Astrophysics to predict a leading mechanism for the production of Higgs bosons, also referred to as the GGMN Mechanism in homage to the four-person collaboration. Two years earlier, Nanopoulos, in collaboration with John Ellis of King’s College in London and Mary K. Gaillard of the University of California-Berkeley, calculated that the cleanest mode in the gluon-pair fusion diagram will be the process involving two gamma-rays, also known as the EGN Triangle.

The current strategy employed in the LHC’s hunt for the Higgs boson prominently features both breakthrough discoveries. If these hints of Higgs boson detection are validated, then these predictions formulated in 1976 and 1978 — and therefore Nanopolous — will figure extensively in this historic discovery.

The CMS and ATLAS experiments project that enough data to conclusively substantiate or exclude the presence of the Higgs boson should be delivered in 2012. At present, the data thus far collected suggests the Higgs boson mass is in the vicinity of 125 GeV, where 1 GeV is the mass of a proton. While allowing for the possibility that the signals observed near 125 GeV could be a statistical fluctuation, the experiments are confident that if the Higgs boson exists, around 125 GeV is the mass where it will be discovered.

Nanopoulos is currently collaborating with researchers Tianjun Li and James A. Maxin in Texas A&M’s George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy and Joel W. Walker of Sam Houston State University to study a specific model of the universe that can generate a 125 GeV Higgs boson mass. This model, called Flipped SU(5), features additional hypothetical particles, dubbed flippons, that contribute to the mass of the Higgs boson and can give it the precise mass of 125 GeV. Although this model’s ability to engender a 125 GeV Higgs boson mass is not unique, it does so in a very natural manner, unlike most of the other models being researched within the high-energy physics community, where the computation of a 125 GeV Higgs boson is accomplished by severely fine-tuning other parameters.

The Flipped SU(5) model under study also predicts precise masses of additional hypothetical particles, called sparticles, derived from a theory called supersymmetry. These are symmetric partners of the currently known fundamental particles, but of a different spin (intrinsic angular momentum) and mass. This entails the other great search ongoing at the LHC, the hunt for the existence of these superpartner particles, which is accomplished by searching for unique signatures of their existence in the very same trillions of proton collisions used to search for the Higgs boson. The CMS and ATLAS experiments have also observed tantalizing hints of the unique signature predicted by the Flipped SU(5) model. Because the data is thus far statistically insignificant, it is too early to know yet whether the experiments are observing supersymmetry and whether Flipped SU(5) is the high-energy framework for our universe. This question, though, like the existence of the Higgs boson, may receive a definitive answer in 2012.

A conclusive discovery of the Higgs boson at 125 GeV and also of supersymmetry in 2012 conforming to the predictions of the Flipped SU(5) model published by Li, Maxin, Nanopoulos and Walker (LMNW) will carry with it some exciting implications and possibilities since the Flipped SU(5) model is not consistent without these features. Among these are i) the existence of dark matter, which is the primary form of matter in the universe that experiences no electromagnetic interaction, and hence doesn’t shine with light like ordinary matter; ii) higher dimensions beyond the visible 3D+time world we experience in our daily lives, with possibly up to 12 dimensions, though most of these extra dimensions are tiny and curled up, thus unobservable; iii) indirect evidence of string theory, which is the theory that all matter in the universe is composed of tiny one-dimensional vibrating loops and strands of energy; iv) D-Branes, which are higher dimensional spaces where these strings can vibrate into and where our 3D+time universe can exist at the intersection of where two of these D-Branes have collided; and v) the Multiverse, or the conjecture extensively studied by LMNW that there exists a vast landscape of universes, of which our universe is but only a single one.


Maxin James