Gerson Goldhaber

Professor in the Graduate School
Astrophysics Experiment

Research Interests

Research work spanned nuclear emulsion, bubble chamber and electronic detector techniques, meson and antiproton interactions, and high-energy e+e- annihilation physics. I worked in particular on the proof for the antiproton annihilation process and on the elucidation of this process; the K+- nucleon interaction process, and meson exchange problems; the observation of the Bose-Einstein nature of pions now leading to a tool for interaction size measurements; the observation of the A resonances. In 1972, I started work with colliding beam machines and electronic particle detectors, first at CERN at the ISR, and then at the e+e- machine, SPEAR, PEP, and later the SLC at SLAC. This collaborative work which started with the construction of the SLAC-LBL Solenoidal Magnetic Detector has led to the discovery of the J/psi (3095) and psi (3685) particles, charmed particles, in particular the D mesons, as well as the tau lepton, and the elucidation of the psion spectroscopy.

Current Projects

Since 1990, I have been working in Particle Astrophysics together with Saul Perlmutter. This work involves the study of distant Supernovae. In 1998 we discovered the most distant Supernova observed so far at a distance of about 9 billion light years. From December 1993 to September 2001, more than 120 additional type Ia supernovae were discovered, some of them the most distant ever observed, out to a redshift of 1.2.

The aim of this experiment is to measure the matter density Omega_M and the vacuum energy density Omega_Lambda (related to the cosmological constant Lambda) of the universe by utilizing type Ia supernovae. The type Ia supernovae are the brightest SNe and also appear to be “Standard candles.” As demonstrated in our experiment, they can be observed at cosmological distances.

We have completed an analysis of 42 supernovae which gave us the information that the expansion of the universe rather than slowing down, as was expected, is actually accelerating! We find for a flat universe, one for which Omega_M + Omega_Lambda = 1, that Omega_M is about 1/3, while the value expected was 1, and that the cosmological constant is about 2/3, when zero was expected. We are continuing these measurements with the aim of finding more distant supernovae with the 10 meter Keck telescope in Hawaii and to make more accurate measurements with the Hubble Space Telescope. There is an opportunity for graduate student participation in this work.

Selected Publications

S. Perlmutter, G. Goldhaber, et al., “A supernova at Z=0.458 and implications for measuring the cosmological deceleration,” Ap. J. 440, L41 (1995).

G. Goldhaber, S. Perlmutter, et al., “Discovery of the most distant supernovae and the quest for omega,” Nucl. Phys. B (Suppl.) 38, 435 (1995).

S. Perlmutter, G. Goldhaber, et al., “Measurements of the cosmological parameters omega and lambda from 42 high-redshift supernovae,” Ap. J. 517, 565 (1998).

G. Goldhaber, D. Groom, et al., “Timescale stretch parameterization of type Ia supernova B-band light curves,” Ap. J., in press (2001).