A California physicist may have discovered the basic magnetic force unit, which scientists have sought more than 50 years, Stanford University has announced.

It would be the discovery of the decade in physics and one of the most important this century, if confirmed. It also would be the best confirmation yet of the new theories in physics that unite all the forces operating in the universe, including magnetism, gravity, electricity, radiation and nuclear, under a single "grand unified theory," as physicists call it.

The discovery, not yet officially announced in a scientific publication, is expected to start a rush of new research to confirm or knock down the result.

Blas Cabrera of Stanford made the find, working alone in a basement laboratory with borrowed equipment. On Feb. 14 his equipment registered a sudden change in its electric current.

The change was most likely caused by passage through the machine of the particle physicists call the "magnetic monopole".

Physicists thought it might take years for a monopole to pass through Cabrera's equipment to be recorded. But the result came after 185 days. Cabrera hopes now to get funds to build a larger, more sensitive detector to confirm that the event he recorded was a monopole and not an accidental glitch in his experimental machinery.

Richard Carrigan, a physicist who has studied monopoles at the Fermi National Accelerator Laboratory, said there is a small possibility that the result is not genuine, as apparently was the case in a 1975 report that the monopole was found.

But Cabrera's experiment is more likely to be right, and will be tested quickly, he said.

The particle is extremely rare and difficult to detect, and so physicists have left open the possibility of its existence for the 50 years or so that it has been predicted in theory.

Magnetic force has appeared only to scientists in the ordinary way, as in a magnet with two poles of force, north and south. The poles of magnets are inseparable. If a magnetized bar is cut in half between the two poles, the result does not isolate the poles. Instead it makes two magnets, each with its own north and south poles.

But the magnetic monopole is a particle that carries only one of the two poles, north or south, and so is the basic unit of magnetic force, just as the photon is the basic unit of light.

The monopole far smaller than the nucleus of an atom, but at the same time it is the heaviest particle predicted in physics, so heavy that even though it is trillions of times smaller than a living cell it would weigh as much as an amoeba or paramecium.

Cabrera's equipment consists of a two-inch loop of niobium metal, cooled by liquid helium to a temperature near absolute zero. A current is passed through the loop, and if a monopole intersects the loop its odd single-pole magnetic property should give rise to a special sort of disturbance in the current.