PMTs and three Nobel Prizes in Physics

How PMTs help reveal neutrinos

A faint flash of light can reveal something profound about the universe. In neutrino research, detecting that light has helped scientists observe a distant supernova, establish that neutrinos have mass, and investigate powerful events in deep space.

Our photomultiplier tubes, or PMTs, were used in experiments that contributed to discoveries recognized by the Nobel Prizes in Physics in 2002, 2015, and 2026. This connection spans decades of research, from massive underground observatories in Japan and Canada to an enormous detector embedded in the Antarctic ice.

How a faint flash becomes a scientific signal

Super-Kamiokande inner detector

Inside Super-Kamiokande, 20-inch PMTs line the water tank to detect faint Cherenkov light.

Neutrinos rarely interact with matter, making them exceptionally difficult to observe. Vast numbers pass through Earth without leaving a trace. Occasionally, however, a neutrino interacts inside a detector and produces charged particles that emit Cherenkov light as they move through water or ice.

PMTs capture this faint light and convert it into amplified electrical signals. Measurements of the light’s timing, intensity, and distribution help researchers reconstruct the interaction and learn about the neutrino that caused it. Detecting a few photons can become the first step toward answering a fundamental scientific question.

Three Nobel milestones in neutrino research

2002: Detecting neutrinos from a supernova

In 2002, Masatoshi Koshiba received a share of the Nobel Prize in Physics for pioneering contributions to astrophysics, particularly the detection of cosmic neutrinos. His work at Japan’s Kamiokande Observatory helped establish neutrinos as a way to study the universe.

One defining moment came in February 1987, when Kamiokande recorded 11 neutrino events in approximately 13 seconds from supernova SN 1987A. The exploding star was about 160,000 light-years away, yet these rare interactions provided direct evidence of processes occurring deep within the collapsing star. ¹

We developed large, 20-inch PMTs for Kamiokande, delivering 1,050 tubes in 1982. The technology helped researchers detect the faint light associated with neutrino interactions in the observatory’s water tank.

The 2002 prize also recognized Raymond Davis Jr. for pioneering neutrino-detection research, particularly his work on solar neutrinos, and Riccardo Giacconi for pioneering contributions to X-ray astronomy. Our direct PMT connection to this award was through Koshiba’s work at Kamiokande.²

Photomultiplier tubes mounted at Kamiokande. (Courtesy of ICRR, University of Tokyo)

Photomultiplier tubes mounted at Kamiokande.
(Courtesy of ICRR, University of Tokyo)

2015: Evidence that neutrinos have mass

Hamamatsu’s 20-inch PMTs were used in Super-Kamiokande.

In 2015, Takaaki Kajita and Arthur B. McDonald shared the Nobel Prize in Physics for the discovery of neutrino oscillations, which showed that neutrinos have mass.

Neutrinos come in three types, known as flavors, and can change flavor as they travel. This behavior helped resolve a longstanding puzzle: why experiments observed fewer neutrinos of a specific flavor from the Sun than scientists expected.

Kajita’s research at Super-Kamiokande in Japan examined neutrinos produced in Earth’s atmosphere. McDonald’s research at the Sudbury Neutrino Observatory (SNO) in Canada studied solar neutrinos. Their findings demonstrated that neutrinos have mass, showing that the original Standard Model of particle physics was incomplete. ³

Both experiments used PMTs. Thousands of 20-inch photomultiplier tubes detected light inside Super-Kamiokande, while thousands of smaller tubes viewed SNO’s heavy-water target. In each observatory, sensitive light detection helped provide the evidence for a major advance in particle physics. More on the development of 20-inch PMTs.

More on Exploring neutinos

Learn more on Kamiokande and Super-Kamiokande

2026: Tracing high-energy neutrinos to the cosmos

In 2026, Francis Halzen received the Nobel Prize in Physics for his contributions to the IceCube Neutrino Observatory and the discovery of high-energy neutrinos of astrophysical origin. ⁴

At the South Pole, IceCube uses a cubic kilometer of Antarctic ice as a detection medium.⁵ Sensors embedded deep in the ice record light produced by charged particles from neutrino interactions. We developed a dedicated PMT for IceCube and supplied more than 5,000 units.

In 2013, IceCube announced compelling evidence for a flux of high-energy neutrinos of astrophysical origin, opening a new route to studying the universe. These particles carry information about cosmic accelerators, complementing what researchers can learn through observations of light.⁶

An mDOM containing Hamamatu's PMTs gets lowered beneath the ice.
Photo by: Yuya Makino, IceCube/NSF

A shared theme: Detecting faint light

The three Nobel Prize milestones addressed different questions: how stars behave, whether neutrinos have mass, and where high-energy cosmic particles originate. All required researchers to detect extraordinarily faint light and interpret what it revealed.

Behind these discoveries are decades of scientific vision, engineering, and international collaboration. At Hamamatsu, our role has been to develop and supply the light detectors that have supported researchers in turning ambitious ideas into observations.

From water deep underground to ice at the South Pole, a few photons can carry the evidence for a new understanding of the universe.

Contributed by: Ardavan Ghassemi

¹K. Hirata et al., “Observation of a neutrino burst from the supernova SN1987A,” Physical Review Letters 58, no. 14 (1987): 1490–1493
NASA, “Supernova 1987A"

²Nobel Prize Outreach, “The Nobel Prize in Physics 2002"

³Nobel Prize Outreach, “The Nobel Prize in Physics 2015: Press release,” October 6, 2015

⁴IceCube Collaboration, “Francis Halzen, IceCube principal investigator, wins 2026 Physics Nobel Prize,” October 6, 2026

⁵IceCube, “IceCube,” detector overview

⁶IceCube Collaboration, “IceCube pushes neutrinos to the forefront of astronomy,” November 21, 2013