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Physical Society ColloquiumR.E. Bell LectureHow idiosyncratic is the weak force?John HardyTexas A&MOf the four fundamental forces identified in nature, the weak force is the most extraordinary. Unlike gravity - or the electromagnetic and strong forces - it does not merely act between a pair of participants, it actually changes the identity of those participants and is thus responsible for the most common types of radioactive decay. It is also the only force that acts asymmetrically (that is, it violates parity). Since Newton, gravity has been understood to be universal, its strength independent of whether it is measured on Earth or in a remote galaxy. Can we count on the idiosyncratic weak force to be `universal' as well?The atomic nucleus provides an ideal laboratory in which to seek the answer. Very precise measurements in nuclei offer a demanding test of the universality of the weak force and probe its conformity with the Standard Model of Particle Physics. Well over 100 individual precision measurements of `superallowed' nuclear beta decay, when compared with one another and with equivalent data obtained from more exotic particle decays, demonstrate near universality but leave a provocative hint of discrepancy at the 0.1% level. In my talk, I shall survey the current state of world data and describe nuclear experiments now underway to further sharpen the universality test in the future.
Friday, November 14th 2003, 15:30
Ernest Rutherford Physics Building, Keys Auditorium (room 112) |