Professor Emeritus of Physics
About
For the past few years, Professor Longo has worked primarily in astrophysics, in particular, analyzing data from the Sloan Digital Sky Survey (SDSS). This has led to strong evidence for a cosmic parity violation in the Universe, as indicated by a statistically significant excess of left-handed spiral galaxies toward the North Galactic Pole and an excess of right-handed in the opposite direction. This also suggests that our Universe has a preferred axis and a net angular momentum. Since angular momentum is conserved this means the Universe must have been born spinning. We can't see outside of our Universe, so we'd have to assume it is spinning relative to other universes in a higher dimensional space. Presumably the Big Bang was spinning initially, and as it expanded, the net angular momentum was dissipated among the galaxies. Now we still see it through the preferred spin direction. [See, Detection of a Dipole in the Handedness of Spiral Galaxies with Redshifts z ~0.04, (Michael J. Longo), Phys. Lett. B 699, 224-229 (2011).]
Previously, his primary research activities have been experiments at Fermilab, including E871 (HyperCP), an experiment designed to perform a sensitive search for direct CP violation in the decays of Xi and Lambda hyperons by looking for an asymmetry between particle and antiparticle decay parameters. Research Fellow H.K. Park prepared a paper with results on rare decays of kaons involving two muons, which was the first published result from HyperCP (http://ppd.fnal.gov/experiments/e871). Professor Longo analyzed the HyperCP data to search for the so-called Theta(1.54) pentaquark state. The negative result from this search showed that this state, though reported by several previous experiments, did not exist. HyperCP has come up with a fascinating hint of new physics in the form of a possible sighting of a low-mass sgoldstino in the decay Sigma+ -> pmu+ mu-. There are only three events but they are very clean, so there is little doubt they are genuine. The amazing thing is that all 3 events give the same reconstructed dimuon mass to within 1 MeV which is the experimental resolution. The probability of this happening by chance is 0.8%. Another hint of new physics is that the branching ratio appears to be larger than expected in the Standard Model.
Professor Longo is also on the MIPP experiment at Fermilab. This is an experiment to measure cross sections for production of protons, neutrons, pions, kaons etc. by beams of particles with energies up to 100 GeV.
He was part of the MACRO collaboration. This is a large underground detector under the Gran Sasso in Italy. His team built most of the liquid scintillation counters that covered the vertical faces of the detector.
Professor Longo is a Fellow of the American Physical Society.
Selected Publications
Detection of a Dipole in the Handedness of Spiral Galaxies with Redshifts z ~0.04, (Michael J. Longo), Phys. Lett. B 699, 224-229 (2011).
Forward Neutron Production at the Fermilab Main Injector, (MIPP Collaboration- T.S. Nigmanov et al.), Phys. Rev. D 83 012002 (2011).
Evidence for the Decay Sigma+ ---> p mu+ mu-, (HyperCP Collaboration-H.K. Park et al.), Phys. Rev. Lett. 94, 021801 (2005).
High Statistics Search for the Theta+(1.54) Pentaquark. (HyperCP Collaboration- M.J. Longo et al.). Phys. Rev. D 70, 111101 (2004).
Measurement of the Atmospheric Neutrino Induced Upgoing Muon Flux Using MACRO, (MACRO Collaboration), Phys. Lett. B 434, 451 (1998).
Search for Magnetic Monopoles Trapped in Matter, (Hunmoo Jeon, Michael J. Longo), Phys. Rev. Lett. 75, 1443 (1995).
Demonstration of Megavoltage and Diagnostic X-ray Imaging with Hydrogenated Amorphous Silicon Arrays, (L. E. Antonuk, J. Boudry, W. Huang, D. L. McShan, E. J. Morton, J. Yorkston, M. J. Longo, and R. A. Street), Med. Phys. 19, 1455 (1992).
New Precision Tests of the Einstein Equivalence Principle From SN1987A, (Michael J. Longo), Phys. Rev. Lett. 60, 173 (1988).
Tests of Relativity from SN1987A, (Michael J. Longo), Phys. Rev. D 36, 3276 (1987).
A-Dependence of Charm Production, (M.E. Duffy, G.K. Fanourakis, R.J. Loveless, D.D. Reeder, E.S. Smith, S. Childress, C. Castoldi, G. Conforto, R.C. Ball, C.T. Coffin, H.R. Gustafson, L.W. Jones, M.J. Longo, T.J. Roberts, B.P. Roe, E. Wang, M.B. Crisler, J.S. Hoftun, T.Y. Ling, T.A. Romanowski, J.T. Volk), Phys. Rev. Lett. 55, 1816 (1985).
Neutron Total Cross Section on Nuclei at Fermilab Energies, (P.V. Ramana Murthy, Cyril A. Ayre, H. Richard Gustafson, Lawrence W. Jones, Michael J. Longo), Nucl. Phys. B 92, 269-308 (1975).
Field(s) of Study
- Experimental High-Energy Physics
- Astrophysics
