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A Nature paper outlines how TAMBO can use the mountains to unveil hidden cosmic accelerators and probe new physics with high-energy neutrinos.

More than a decade ago, physicists observed the first astrophysical neutrinos from cosmic accelerators, launching a new age in neutrino astronomy. Because they rarely interact with matter, neutrinos provide a lens into otherwise obscured extreme phenomena, carrying information about their sources — and about the physics that governs them. Yet despite major efforts from neutrino observatories worldwide, the majority of cosmic neutrino sources remain elusive.

Even though TAMBO will detect fewer neutrinos than IceCube, the purity of its cosmic sample will be substantially higher. At the energies TAMBO targets, the cosmic neutrino signal prevails over the atmospheric background, meaning that essentially any neutrino TAMBO detects is of cosmic origin. Tau neutrinos are also the least studied particle in the Standard Model, simply because so few have ever been detected; TAMBO will study them at energies never before reached.

Searching for new physics

Those same properties make TAMBO a powerful laboratory for fundamental physics. Cosmic neutrinos travel across billions of light years before skimming through thousands of kilometres of rock on their way to the detector — an exposure no laboratory experiment can reproduce. Tiny effects that are invisible over terrestrial distances can accumulate into observable signatures over cosmic ones.

The group of Prof. Aaron Vincent in the Department of Physics, Engineering Physics and Astronomy at ¾ÅÐãÖ±²¥ will use TAMBO to look for exactly those signatures. Because the observatory measures the arrival directions, energies and flavour composition of the most energetic neutrinos with high purity, deviations from Standard Model expectations become detectable. The ¾ÅÐãÖ±²¥ team will search for new interactions between neutrinos and dark matter or the cosmic neutrino background, for neutrino decay, and for other departures from standard oscillation and propagation — including a first look at the neutrino-nucleon interaction strength at energies far above the reach of any particle collider. TAMBO's sensitivity to tau neutrinos in particular gives a handle that existing telescopes largely lack: many models of new physics alter the ratio of neutrino flavours arriving at Earth, and that ratio is what TAMBO measures best.

A valley, a prototype, and a collaboration

Because TAMBO requires a deep valley with sufficient surface area and width, collaborators are considering the Colca Valley in the Peruvian Andes as a strong possibility. The experiment would give Peru's high-energy physics community the opportunity to develop a major scientific facility in the country, strengthening the national research ecosystem.

Unique to TAMBO is its mission to spearhead an ethical approach to site selection and construction. Working with support from the John Templeton Foundation, collaborators are integrating social science into the project from the outset, partnering with local communities, social scientists and universities in Arequipa to evaluate the environmental and social impacts of building and operating an observatory in a mountain ecosystem, and to strengthen STEM education and pathways to higher education in the region.

The TAMBO collaboration is led by Prof. Carlos Argüelles of Harvard University and brings together 26 institutions across nine countries, spanning particle physics, astrophysics, engineering and the social sciences. Alongside Harvard and ¾ÅÐãÖ±²¥, partners include the Pontificia Universidad Católica del Perú and other Peruvian institutions, whose researchers are central to the siting, construction and scientific programme of the observatory, as well as groups across the Americas, Europe and Asia.

Design and construction of TAMBITO, TAMBO's prototype and first stage, is currently underway, and will serve as a stepping stone to the full TAMBO array, expected to be completed in 2028.

In Quechua, the indigenous language spoken in the Andes, tambo means "inn" — a resting place for messengers traversing the mountains. Soon, TAMBO will serve as a refuge for cosmic messengers carrying information from the farthest reaches of the universe.

The TAMBO Collaboration is made up of 26 institutions in nine different countries (). This work was made possible through the support of Grant 63651 from the John Templeton Foundation. Additional support was provided by several Harvard University funds, including the Milton Family Fund, the Faculty of Arts and Sciences Dean's Fund for Promising Scholarship, the Harvard-UTEC Fund, and the Radcliffe Institute for Advanced Study; and the David & Lucile Packard Foundation, the Alfred P. Sloan Foundation, the Research Corporation for Science Advancement, and the Canadian Institute for Advanced Research (CIFAR).

+info: "Measuring the high-energy neutrino sky using the deep-valley neutrino observatory TAMBO," TAMBO collaboration: Argüelles, C.A. et al., Nature Astronomy (2026).