High Energy Physics
About the High Energy Physics Group
The goal of High Energy Physics is to understand the fundamental forces of nature. These forces govern the interaction of matter and energy. The UM high-energy physics group is dedicated to the study of the most fundamental physics phenomena.
High Energy Theory (Datta)
We are interested in various areas of particle phenomenology. We are working mostly in flavor physics but recently we have extended our interests to included topics in non-standard Higgs interactions and dark matter physics.
There is a huge amount of data from flavor experiments. The B factories at BaBar and Belle have made many measurements in Flavor Changing Neutral Current Processes (FCNC) which are known to be very sensitive to new physics effects and new sources of CP violation which is required to explain the matter-antimatter asymmetry observed in nature. Most extensions of the Standard Model (SM) contain new CP violating phases which do not have to be small as CP is not an exact or approximates symmetry of nature. Hence, discovery of non-SM CP violation phases is not unexpected. One of my main research interests is to analyze data from current and future B physics experiments to find evidence for new physics and to find the nature of this new physics.
We also have interests in top quark properties and in the search for beyond the SM effects in top production, top decay, single top production and rare top decays.
In the neutrino sector our interest is in the study of deviations from the tri-bimaximal mixing (TBM) for neutrinos. The purpose behind the study is to understand the symmetry behind the tri-bimaximal mixing and how it is broken to generate deviation from the TBM.
We are interested in the non-standard couplings of the Higgs to SM particles. We are involved in the study of the production and decays of additional Higgs bosons in various extensions of the SM. Finally, we are working on building models of dark matter to explain recent data from dark matter experiments.
Upon its discovery in 1973 as the first heavy quark, the charm quark set off a revolution in contemporary thought in quantum field theories. Mississippi physics faculty have been involved in investigations of the charm quark since 1975. Measurements of charmed particle lifetimes, mixing, rare decays, and charm particle production are continuing in Experiment E791, the latest in a series of high statistics charm experiments performed at Fermilab's Tagged Photon Spectrometer.
We logged more than 20 billion hadronic interactions, the most ever recorded at that time and more than 200,000 charmed decays fully reconstructed from these data. Part of this enormous reconstruction feat took place on one of the first UNIX computing farms, established at The University of Mississippi in the early 1990s. Events were processed in parallel on 80 nodes with distributed software written by members of our research group and sent worldwide for further analysis. More than 30 research papers have been written from these data.
Matter and anti-matter are thought to be created in equal abundance. Yet in the universe, matter is dominant over anti-matter. CP (charge-parity) violating effects within the fundamental forces are thought to have caused this particle over anti-particle asymmetry. The BaBar experiment is dedicated to the study of CP violation in the B-meson system. The goal is to see if beauty quarks decay differently from anti-beauty quarks. Our measurements are expected to be important in explaining why we now have a matter universe.
The experiment has been running since May 1999 at the Stanford Linear Accelerator Center in California. The detector sits at the IR2 interaction region of the PEPII electron/positron storage ring, an asymmetric B factory (that is, it produces B mesons copiously at a high relativistic boost by colliding beams of electrons and positrons of unequal energy). The University of Mississippi group played a prominent role in the construction, commissioning, and calibration of the Cesium Iodide electromagnetic calorimeter for this experiment. We are now engaged in the studies of B-meson decays and CP violation.
The Standard Model now explains all of particle physics phenomena to great detail below 200 GeV. But particle physicists will soon begin studying collisions in the TeV energy regime at CERN's Large Hadron Collider (LHC) to search for violations of the model. The LHC, located at CERN near Geneva, Switzerland, will collide protons on protons at 14 TeV in the center of mass. The CMS detector is one of two large experiments being constructed to investigate the collisions in a search for the Higgs particle, supersymmetric particles, and other non-Standard Model phenomena.
The high-energy physics group at The University of Mississippi, along with other U.S. and international groups, is participating in the design and construction of the CMS experiment. We are working on the hadron calorimeter, which will measure the energy released in the violent collisions, and provide a trigger for rare phenomena. We are also working on a pixel-tracking detector able to determine the precise origin of particles in the interaction to 30 micrometers. This fine-grained tracking is decisive in distinguishing rare events from normal background interactions. The experiment is to begin running in 2005.
New Accelerator — the Muon Collider/Neutrino Factory (Summers, Cremaldi)
The University of Mississippi is working with physicists from two dozen universities and national labs to first design a neutrino factory with a muon storage ring and then a ring to collide muons head on. The neutrino factory can produce the quantity of neutrinos needed to study the puzzling neutrino mass. With muons being about 200 times more massive than electrons, a low energy muon collider will allow direct production of the Higgs boson, the particle responsible for giving mass to all other particles.
Our group is fabricating new types of radio-frequency cavities for muon acceleration and is building ultra-thin containers for liquid hydrogen to provide ionization cooling of muon beams. We are working on magnet designs for a fast-ramping acceleration ring and on alternating gradient magnets with a short-lattice spacing for a dogbone geometry accelerator. We are developing parallel Linux computing code to simulate cooling muons into small bunches making them easier to accelerate and to collide.
In 1995, the top quark was discovered by the DØ and CDF experiments in a sample of about 100 events collected during the Run I data taking at Fermilab's Tevatron collider. The top quark immediately stood out from the other fundamental particles due to the fact that it is much more massive than any of the others. Now DØ is in the midst of Run II, during which the experiment will record thousands of top events. From this data set, many properties of the top quark can be measured which could yield insight to the origins and nature of mass.
DØ is a collaboration of almost 700 physicists from more than 80 institutions in 19 countries. The experiment uses a 5000 ton detector to observe millions of interactions each second at the world’s most powerful particle accelerator. In addition to top quark events, scientists will search through this copious data for many other things such as signs of extra dimensions and the Higgs particle, which could be responsible for mass generation. The University of Mississippi group has been heavily involved in the installation, commissioning, and operation of the Silicon Microstrip Tracker which is used to precisely measure the location of particle interactions and decays. This information is crucial for identifying the secondary decays of b quarks which are characteristic features of top quark events.
Cosmic Rays — the Pierre Auger Observatory (Cremaldi, Cavaglià)
Rare cosmic ray showers of energy more than 1020 eV have been consistently observed in the past decade. The origin of such extremely high-energy cosmic rays is unknown and a mechanism for their production can not be easily imagined. Ultra high-energy cosmic rays provide a natural beam of particles to probe new physics, such as existence of extra dimensions, dark matter or supersymmetry.
The Pierre Auger Group is an international collaboration of particle physicists and astrophysicists set on investigating these rare phenomena. The University of Mississippi high-energy physics group is participating in the construction of the Pierre Auger Observatory, a 50-square-mile array of surface water Cerenkov detectors and atmospheric fluorescence detectors constructed in the U.S. and Argentina. The first arrays are being constructed near Malarque, Argentina, and soon in the United States. Data taking began in 2001.