Nuclear Physics Seminar

Searches for the intermediate boson, W±, the heavy quantum of the Weak Interaction, via its semi-leptonic decay, W -> e + nu, in the 1970’s instead discovered unexpectedly large hadron production at high pT , notably pi0, which provided a huge background of e± from internal and external conversions. Methods developed at the CERN ISR led to the discovery of direct-single-e± in 1974, later determined to be from the semi-leptonic decay of charm which had not yet been discovered. The same methods i) 10^5 charged hadron rejection; ii) minimum of material in the aperture to avoid external conversions; iii) zero magnetic field on the axis to avoid de-correlating conversion pairs; iv) precision measurement of pi0 and eta, the predominant background source; v) precision background determination in the direct-single-e± signal channel by adding external converter were used at RHIC to make precision measurements of heavy quark production in p-p and Au+Au collisions, leading to the puzzle of apparent equal suppression of light and heavy quarks in the QGP. If the Higgs mechanism gives mass to gauge bosons but not to fermions, then a proposal that all 6 quarks are nearly massless in a QGP, which would resolve the puzzle, cannot be excluded. This proposal can be tested with future measurements.