The high-energy physics group focuses on two research areas, the highest energy cosmic rays and neutrino physics. Our research is addressing some of the most exciting puzzles that nature has to offer.
Despite the fact that neutrinos are some of the most abundant particles in the Universe they are also some of the most ghostly particles which require very sophisticated detectors to observe and characterize them. Neutrinos can be studied in underground laboratories or at particle accelerators. The latter is not true for the highest energy cosmic rays which are particles arriving on Earth with energies many orders of magnitude larger than what could be accomplished with man-made particle accelerators.
We are involved in a number of experimental projects to collect data on neutrinos and the highest energy cosmic rays in order to solve the mysteries associated with these particles.
Neutrino Physics (Kutter, Metcalf)
Neutrinos are produced in the fusion reactions that fuel stars. Hence, our Sun is a powerful source of neutrinos. Numerous experiments have observed solar neutrinos but the observed solar neutrino flux was lower than theoretical models predicted; a dilemma that was termed the 'solar neutrino problem'. In recent years the Sudbury Neutrino Observatory (SNO) demonstrated conclusively that the discrepancy between theoretical expectations and data is resolved by the nature of neutrinos themselves. As the neutrinos travel from Sun to Earth they change their type (they 'oscillate') and previous experiments had only been sensitive to one type. The SNO experiment which consists of 1kton of heavy water which is viewed by nearly 10,000 light sensitive photo-sensors is able to distinguish between the different types of neutrinos. The observed flux of all three known types of neutrinos agrees very well with predictions.
Three types of neutrinos are known to exist but results from the 'Liquid Scintillator Neutrino Detector' (LSND) give indications that a fourth and rather mysterious neutrino might exist. The MiniBooNE experiment at Fermilab has been built and is collecting data to address the open question of the existence of a fourth type of neutrino. The experiment studies neutrinos coming from a man-made neutrino beam with a spherical detector which contains mineral oil and which is viewed by 1,500 photo multipliers. If the MiniBooNE experiment confirms the LSND results , it will have profound implications not only for the standard model of particle physics but also for many areas of astrophysics.
The fact that neutrinos have been observed to oscillate, e.g. change from one type into another is merely the beginning of what promises to be an exciting exploration of uncharted physics terrain. Observations to date indicate that the mixing of neutrinos is very different of what has been observed in the quark sector. The next step on this journey is to measure the last unknown neutrino mixing parameter theta-13. The next generation neutrino long baseline experiment T2K (Tokai to Kamiokande) is currently under construction in Japan and directs a muon-neutrino beam through a near detector complex and on to the 295 km distant water Cherenkov detector Super-Kamiokande. A comparison of measurements at the near detector which samples the un-oscillated neutrino beam with observations made with the far detector allows to study neutrino characteristics. In a potential future upgrade of the T2K experiment it might be possible to study the asymmetry of matter over anti-matter and hence the origin of our very own existence.
The experimental neutrino physics group at LSU is heavily involved in the SNO, the MiniBooNE, and the T2K projects.
The Highest Energy Cosmic Rays (Matthews, McNeil)
The highest energy cosmic rays are particles that have been observed on Earth with energies in excess of 1020eV. One of the largest mysteries associated with the highest energy cosmic rays is their origin. Where do they come from ? What astrophysical objects and mechanisms can accelerate particles to energies of 1020eV and above ? What exactly are these particles ?
The Pierre Auger Observatory is a project which is currently taking data to answer the above questions. The observatory is located in Mendoza Province, Argentina. It consists of an array of 1600 regularly spaced water Cherenkov detectors spread out over an area the size of Rhode Island and a series of fluorescence telescopes which monitor the atmosphere above the detector array. The strengths of both detection techniques complement each other and allow to obtain a maximum amount of information on the highest energy cosmic rays. In order to fully study the origin of these particles full sky coverage is mandatory and plans for a second observatory site in the northern hemisphere are currently being pursued.
LSU has been a member of the Auger Project since its inception and continues to be a key contributor to the experiment.
Updated:
Tue, 01-Apr-2008 3:12 PM
