Peter Jenni, (born 17 April 1948) is an experimental particle physicist working at CERN. He is best known as one of the "founding fathers" of the ATLAS experiment at the CERN Large Hadron Collider together with a few other colleagues. He acted as spokesperson (project leader) of the ATLAS Collaboration until 2009. ATLAS is a world-wide collaboration which started in 1992 involving roughly 3,000 physicists at 183 institutions in 38 countries. Jenni was directly involved in the experimental work leading to the discoveries of the W and Z bosons in the 1980s and the Higgs boson in 2012. He is (co-)author of about 1000 publications in scientific journals.

Peter Jenni, Swiss, born in 1948, obtained his Diploma for Physics at the University of Bern in 1973 and his Doctorate at the Swiss Federal Institute of Technology in Zürich (ETHZ) in 1976. His thesis examined very small angle elastic scattering in the Coulomb-nuclear interference region. Peter Jenni is married and has two adult children.^{[citation needed]}

Peter Jenni participated in CERN experiments at the Synchro-Cyclotron (1972/3), at the Proton Synchrotron (1974/6), and as ETHZ Research Associate at the Intersecting Storage Rings (ISR) (1976/7), the first high-energy hadron collider. From 1974 to summer 1976 he worked as a CERN Fellow in the group of M. Ferro-Luzzi. The group measured the Coulomb nuclear interference scattering of π±, K± and p± on hydrogen and deuterium in two experiments at the CERN PS. The measured real parts of the forward scattering amplitudes were used in dispersion relations. One of these measurements was the subject of the doctoral thesis (H. Hofer).

From 1976 to 1977 Research Associate at the Swiss Federal Institute of Technology in Zürich (ETHZ) working in the CERN-ETH-Saclay collaboration R702 at the CERN Intersecting Storage Rings (P. Darriulat, B. Richter). The experiment covered studies on electron pair production, on e μ events as a signature for charmed particles, and on very high transverse momentum π0 production in pp reactions.

During 1978 and 1979, Research Associate at the Stanford Linear Accelerator Centre (SLAC), Stanford, USA, in B. Richter's group. Participated in the MARK II SLAC-LBL Berkeley experiment at the e+e– storage ring SPEAR. Mainly involved in the following physics analyses: two-photon reactions, meson form factors, and search for the charmed mesons.

The first measurement of the two-photon widths of the η prime was giving further direct support to the quark model. In SLAC he also worked on operating the liquid-argon calorimeter for the MARK II experiment where his interest in high-performance calorimetry was developed.

He became a CERN staff member in 1980 working with the UA2 experiment at the Super Proton Synchrotron collider (major involvement in the discoveries of jets and the W and Z bosons). Worked on the design for the UA2 upgrade since 1984, with special motivation for missing transverse energy signatures. Project leader of the new end cap calorimeter constructed for the upgraded UA2 experiment. As from March 1987, also group leader of the CERN UA2 group. Coordinated calorimeter and trigger work for the upgraded UA2 experiment.

Already during the UA2 time, strong interest in the physics and instrumentation at future colliders, in particular LHC. Early involvement as convener of the jet study group at the ECFA-CERN LHC workshop 1984 (Lausanne, Geneva), member of the advisory panel on the physics potential and the feasibility of experiments at the multi-TeV energies (La Thuile workshop 1987), and calorimetry overview at the ECFA study week on instrumentation technology for high-luminosity hadron colliders (Barcelona 1989).