Alejandro García

Grace-Rupley Professor,
Experimental Nuclear Physics

Measurements of the e,n correlation in beta decay allow sensitive searches for Physics beyond the standard model. But n's are extremely difficult to detect. Our group deviced a smart way of determining the e,n correlation and our experiment provided the most stringent limits to scaler currents. Which are predicted by models of Physics beyond the standard electro-weak model.

On a different front, our group deviced an experiment to determine the v spectrum from the beta decay of ⁸B. It turns out that most solar neutrino detectors on Earth are mainly sensitive to ⁸B neutrinos. The results of our experiment show that the spectrum is harder than previously thought and this has had important consequences for the interpretation solar neutrino data.

Research Interests
A fundamental issue for the physics of the next decade is the search for evidence of physics beyond the Standard Model (SM).

Prof. García's group is working on a variety of experiments:

(1) Experiments to set the most stringent limits on Scalar contributions to the Weak Interaction. Scalar contributions are predicted by extensions of the standard model like supersymmetry, and by models that include leptoquarks.

(2) Experiments to determine the efficiency of existing (³⁷C1) and proposed (⁴⁰Ar and ¹⁷⁶ Yb) neutrino detectors. The "solar neutrino problem" is based on the number of neutrinos observed on Earth being much smaller than expected. This may indicate that neutrinos are massive. But in order to arrive to such conclusions, a crucial element is the efficiency of the neutrino detectors.

(3) Experiments to look for Time Reversal Symmetry Violation in neutron beta decay. The violation of this symmetry is not well understood and could be a hint of physics beyond the SM.

(4) Experiments to understand the nuclear physics related to double-beta decays. These kind of weak decays can be used to put stringent limits on neutrino masses, but these limits can be extracted from experiments only if the relevant nuclear physics is well understood.

Selected Publications:
"Positron-neutrino Correlation in the O⁺Æ O⁺ Decay of ³²Ar," E.G. Adelberger, C. Ortiz, A. García, H.E. Swanson, M. Beck, O. Tengblad, M.T.G. Borge, I. Martel-Bravo, the ISOLDE Collaboration and H. Bichsel, Phys. Rev. Lett., 83, 1299 (1999).

"Shape of the ⁸B alpha and neutrino spectra," C.E. Ortiz, A. García, R. Waltz, M. Bhattacharya, and A. Komives, Phys. Rev. Lett. (in press).

"New Limit on the D Coefficient in Polarized Neutron Decay," L.J. Lising, S.R. Hwang, J.M. Adams, J.M. Anaya, T.J. Bowles, T.E. Chupp, K.P. Coulter, M.S. Dewey, S.J. Freedman, B.K. Fujikawa, A. García, G.L. Greene, G.L. Jones, H.P. Mumm, J.S. Nico, R.G.H. Robertson, T.D. Steiger, W.A. Teasdale, A.K. Thompson, E.G. Wasserman, F.E. Wietfeldt, J.F. Wilkerson, Phys. Rev. C (in press).

"A Measurement of Gamow-Teller Strength for ¹⁷⁶Ybƹ⁷⁶Lu and the Efficiency of a Solar Neutrino Detector," M. Bhattacharya, C.D. Goodman, R.S. Raghavan, A. García, M. Palarczyk, J. Rapaport, I.J. van Heerden, P. Zupranski, Phys. Rev. Lett. (in press).

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