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On Target (November & December 1996)
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    Kaons. Though the word may sound like something sweet to eat, it actually refers to tiny particles, unseen by the naked eye, that have puzzled scientists since their discovery almost 50 years ago.

    Scientists believe that understanding the properties of the kaon will put them one step closer toward understanding the structure of matter.

    Kaon electroproduction was the subject of some of the first experiments at Jefferson Lab that scientists hope will lead to answers about matter and the universe. Many theories and models exist for the kaon, however, none have been proven.

    That is why the nuclear physics community anxiously awaits the results of recent experiments at Jefferson Lab - the electromagnetic production of the kaon (E93-018 and E91-016) which began October 3 and concluded November 6, 1996.

    The completion of the kaon experiments was a feat that has caused many to celebrate.

    "I am thrilled to have been a part of this historic measurement - the first time that it will have been done with this precision," said Keith Baker, a Hampton University professor and physicist who is the spokesman for the team of around 90 experimenters on the E93-018 project. Ben Zeidman, an HU adjunct professor, is the spokesman for the related E91-016 experiment.

    "It was a great accomplishment," said Gabriel Niculescu, the HU doctoral candidate on the experiment. "We were able to prove to ourselves that this experiment could be done. The accomplishment also confirms what we can achieve as human beings."

    Graduate students Niculescu, Jinseok Cha, Wendy Hinton, Ioana Niculescu; and postdoctoral fellows, Ketevi Assamagan and Paul Gueye, all from HU, performed critical roles in the success of the experiment. Baker sings high praise for the effort put forth by the group, adding "they all worked very long hours and were under a lot of stress to pull this off."

    The experiments were some of the first of 80 approved for precious beam time at Jefferson Lab. The kaon experiment was also the first major experiment, of at least four by HU, to be conducted by faculty from a Historically Black College or University at a national lab concentrating in nuclear physics. HU is also collaborating in various other experiments at Jefferson Lab and at other research institutions.

    The complex experimental process for measuring kaons is based on a few scientific principles and the use of Jefferson Lab's unique continuous electron beam accelerator and house-sized experimental equipment.

    "Kaons are produced as a result of scattering high energy electrons electrons traveling at the speed of light] off of protons contained in a certain target," explains Baker. "From this scattering process, both kaons and particles known as hyperons, are detected."

    Jefferson Lab's beam of highly accelerated electrons were used to interact with protons from Hall C's liquid hydrogen target, adds Assamagan. "Liquid hydrogen is a good target for this experiment because it only has one proton in its nucleus," he explains. "The less protons there are, the easier it is to measure the motion of the particles."

    Two detectors, located downstream of the target detect particles as they scattered from the target. One detector measures the momentum and direction of the scattered electrons, while the other detects the momentum and direction of the kaons. These two particles must be detected simultaneously in order to ensure that they are produced in the same interaction process.

    The probability of creating kaons is very low. In fact, one out of every 1,0000 or so kaon events will actually be a kaon. "Jefferson Lab's continuous beam of electrons on a target allows the chances of creating kaons to increase," explains Niculescu. "Others were unable to perform a kaon electroproduction experiment as precise as the one we've completed because the equipment and the continuous beam were not available."

    The resulting data, currently being analyzed, will provide a better understanding of the kaon, as well as form a basis for future experiments at Jefferson Lab, and elsewhere, involving kaons and the associated hypernuclei.

    The immediate impact of the experiment will be felt by four of the HU graduate students who participated, as well as University of Maryland graduate student, Rick Mohring. For them, the data taken during the allotted beam-time provides a basis for their theses required to earn doctoral degrees in Physics.

    As for the immediate impact or benefit to the rest of the world, "We never know... perhaps our children and grandchildren may find some practical use for our understanding of the electromagnetic properties of kaons," says Baker. "Meanwhile, we'll continue doing what we do best -- pursuing knowledge."

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