The title of Louis Nosanow was stated incorrectly yesterday. He is acting division director for the division of materials research of the National Science Foundation.

American physics has declined from a position of preeminence in the world a decade ago to a point where leadership in key areas has clearly passed to other countries, according to some leading physicists.

The discovery announced this week of the elusive "W particle," the carrier of one of the four fundamental forces in the universe, was just one sign that America no longer leads the world, said Wolfgang Panofsky, director of the Stanford Linear Accelerator.

The W particle experiment, conducted in Switzerland, was once planned for an American facility, but was turned down for lack of funds.

The best indication that the United States has slipped behind European physics for the first time since the World War II is not so much the discovery of the particle as the performance of Americans at the last International Conference on High Energy Physics in Paris, Panofsky said.

"You have to say that, at that meeting, the U.S. contributions were severely lacking. I can say unequivocally that for the first time, at that meeting, it was clear that the warnings we had sounded finally fit the facts," Panofsky said.

But other scientists dispute the existence of a "physics gap." While there has been "erosion in the budget" over the years, according to Louis Nosanow, head of the physics division of the National Science Foundation, the United States has not slipped back so much as other nations have caught up.

So long as the United States is still capable of research at the forefront of science, it not important to be first, Nosanow said.

Just as there was a time when budgets were constrained in U.S. science, he said, eventually European science budgets will also be cut, and conditions will even out somewhat.

Panofsky and other scientists, however, say that although leadership in physics--and especially the esoteric kind of physics that produces "W particles"--may not seem important to the nation, it nonetheless is.

"Can a nation live off derivative science? My answer is that in the short run, you can, but in the long run that does not work," Panofsky said. The advancement of technology and the training of technicians for industry depends upon leadership in basic science.

Richard Wilson, chairman of the physics department at Harvard University, said that leadership is important because good people at the top of their professions can stimulate many younger ones, who in turn carry on the tradition.

This country's leadership in physics began in the 1930s and 1940s, when Europe's leading physicists emigrated to the United States to stimulate a new generation of researchers, who are now the graying laureates of the field.

"The concern is that we are now going to reverse that flow," Panofsky said, "and send the flow back toward Europe, unless we change what we are doing."

As an example of the decline in physics funding here, Panofsky said that the entire federal budget for high-energy physics and its practitioners is only about half the budget for a single European research machine in Geneva, the one called CERN (the French initials for the European Organization for Nuclear Research).

Federal funds for physics research of all kinds have declined steadily since the Nixon administration, he said.

Over the years, while the Europeans were spending more money and building bigger machines as rapidly as possible to conduct research in high-energy physics, American physics budgets could not support both construction and personnel.

So construction slowed, and the advancement of American instruments fell behind. Researchers, including Americans, began to do more and better work on the European machines.

Besides the new machine that discovered the "W particle," other machines--"ion-colliding" machines that work with charged atoms, and electron-colliding machines--have been built abroad ahead of similar machines in America.

In the last several years, Americans have tried to catch up to the Europeans by putting money into construction. This has forced a severe cutback in funding for experiments.

At one time America's biggest machines were operating at half-capacity. Now, the Fermilab accelerator in Batavia, Ill., has been shut down entirely because of a lack of funds for both construction and experimentation.

In other areas of physics, the United States is also behind.

William Rodney, director of the nuclear program for the National Science Foundation, said that in nuclear physics, which deals with whole atoms and their behavior, rather than with parts of them, we "are behind the Germans and even the French . . . there was erosion all through the 1970s."

George Pake, vice president for research of Xerox Corp., said that while there may be outright decline in some areas of physics, in other areas, such as materials research and other non-atomic research, there has been "stagnation rather than real decline."

Pake also said that even in areas of physics where this country is not yet trailing other nations, "We are now building in a decline for the future if we do not change our approach" and provide better funding of fundamental research.