Dr. Perl, who shared the 1995 Nobel Prize in physics, died Sept. 30 at 87. (Linda A. Cicero / Stanford News Service)

Martin L. Perl, a physicist who was credited with unveiling a previously unknown subatomic building block of matter, a discovery for which he shared a Nobel Prize and that broadened the field of physics, died Sept. 30 at a hospital in Palo Alto, Calif. He was 87.

The cause was a heart attack, said his son Jed Perl.

Dr. Perl seemed to embody the image of the undaunted scientist who pursues a question even when the answer appears unreachable, and despite the skeptics who might doubt that it exists at all.

He spent decades as a research professor at Stanford University, where, in the 1960s, he and colleagues at the Stanford Linear Accelerator Center began the work that would be honored with the 1995 Nobel Prize in physics.

At the time, the prevailing belief among scientists was that the physical world included two types of particles known as leptons — electrons and muons — and the associated members of their families. Dr. Perl sensed that there had to be at least one more group.

“Why are there just these two particles?” he asked himself, according to an account in the San Jose Mercury News. “Why does nature just have these two things?”

With his colleagues, Dr. Perl identified the tau lepton. More than 3,000 times heavier than an electron, and highly unstable, it exists for less than a trillionth of a second before breaking into smaller elements. To document its existence, Dr. Perl studied its residue.

The findings, made between 1974 and 1977, were initially doubted by physicists who could not independently detect the particle.

“People didn’t believe for three more years,” Dr. Perl told the San Jose paper. “Those were the three most difficult years of my life. Others couldn’t find it, so I thought I must be doing something wrong. It was a wrenching experience. I kept going over the data, looking for a bias.”

His data later helped lead to the completion of the Standard Model, which is used by physicists to explain the structure of matter.

Dr. Perl shared the Nobel with Frederick Reines, a physicist from the University of California at Irvine who was credited with leading the discovery of the neutrino, another infinitesimally small component of matter.

Together, the Royal Swedish Academy of Sciences declared, the scientists had “discovered two of nature’s most remarkable subatomic particles.”

Martin Lewis Perl, the son of Jewish immigrants from Eastern Europe, was born June 24, 1927, in Brooklyn, N.Y.

His mother was a secretary and bookkeeper, and his father, after working as a clerk and salesman, opened a printing business that allowed the family a degree of financial security during the Depression. His sister, the late Lila Perl, became a noted children’s author.

After serving in the Merchant Marine and the Army during and after World War II, Martin Perl received a bachelor’s degree in chemical engineering in 1948 from what is now the NYU Polytechnic School of Engineering.

He began his career working for General Electric on matters including television picture tubes, a field that required additional studies at Union College in Schenectady, N.Y. There, he wrote in his Nobel biographical sketch, a professor told him, “Martin, what you are interested in is called physics not chemistry!”

In 1955, he received a PhD in physics from Columbia University, where his mentors included I.I. Rabi, a Nobel Prize-wining physicist. Before joining Stanford, Dr. Perl taught and did research at the University of Michigan.

He shared the 1982 Wolf Prize in physics, a $100,000 honor that is bestowed by the Wolf Foundation in Israel. Dr. Perl joined scientists who at times weighed in on public affairs, supporting an atomic test ban in 1999 and opposing the U.S.-led invasion of Iraq in 2003.

His marriage to Teri Hoch Perl ended in divorce. Survivors include four children, Anne Bernard of Palo Alto, Joseph Perl of Oakland, Calif., Matthew Perl of San Diego and Jed Perl of New York; eight grandchildren; and a great-granddaughter.

As a mentor to younger scientists, Dr. Perl encouraged them to think in unconventional ways.

“There are books on how to find the Higgs particle,” he told Science in 1992, two decades before scientists made the sensational announcement that they had discovered the Higgs, or something very much like it. “The thing to do if you are young is not look for the Higgs particle. . . . I would try to look for things other people consider to be trash.”