EXOTIC MESON AT BROOKHAVEN? Testing the notable proposition that quarks always bind in groups of two (quark- antiquark objects called mesons) or three (baryons), physicists at BNL send 18-GeV pi mesons into a hydrogen target and then harvest events in which the emergent debris includes eta mesons and pi mesons. In particular, they seek to study the parent particle that decayed into the eta and pi. Most of the time this is the humdrum a2 meson, with a mass of 1320 MeV. But about 3% of the time another particle appears to be the parent, one with a mass of about 1370 MeV. Two things in combination hint that something unusual is happening: first, the relative angle between the outgoing eta's and pi's suggests a rivalry or "interference" between the a2 meson and the mysterious particle, strengthening the argument that the particle exists and is not just a spurious blip in the data. Second, the new particle's quantum numbers (its spin, parity, and charge conjugation number) do not conform to what one would expect for a conventional quark-antiquark meson. Scientists in the Northwestern-Rensselaer-Massachusetts- Notre Dame-BNL-Moscow State-IHEP collaboration (one contact is Neal Cason at Notre Dame, 219-631-6305) speculate that the exotic particle might be either an unprecedented 4-quark state (two quarks and two antiquarks) or a quark-antiquark-gluon state; gluons are the particle-like carriers of the strong nuclear force, but in this case the gluon in question would be an independent particle on an even footing with the quarks. (1 Sept. Physical Review Letters; copies for journalists available from physnews@aip.org.)

FROST HEAVING is a process by which ice columns can grow like plants out of moist soils. In the Arctic structures as big as hundreds of meters wide and 50 m tall ("pingos") can form in this way. Where does the energy come from to thrust ice upwards against the force of gravity? Hisashi Ozawa, now at the Nagaoka Institute for Snow and Ice Studies in Japan (ozawa@nisis.nagaoka.bosai.go.jp) observes frost heaving in the lab. He grows ice columns above a reservoir of supercooled water (water below its freezing point kept in a liquid state). A microporous filter (approximating the role of Arctic soil) between water and ice keeps the ice from intruding into the liquid. Ozawa believes that newly formed ice is able to push against gravity not through any conventional mechanical force but by a thermodynamic tendency by which the system as a whole (water plus ice) gains entropy. In principle, one could build a "frost engine" which could produce a heaving pressure of a megapascal per degree of supercooling. Similarly one might make a "helium frost engine" operating near 0 K and a "metal frost engine" operating at blast-furnace temperatures. One could also purify solutions (separate solvents from solutes) without distillation. (In Physical Review E, September 1997; figures at Physics News Graphics.)

FURTHER DISCUSSION OF COSMIC BIREFRINGENCE . The report by Borge Nodland and John Ralston (Update 317, 17 April) that they had uncovered an anisotropy in the amount of polarization of radio waves from distant galaxies is the subject of three items in an upcoming issue (most likely 8 Sept.) of Physical Review Letters: (1) A paper (J.F.C. Wardle et al.) reporting new radio and optical data that rule out any large anisotropy; (2) a comment by D.J. Eisenstein and E.F. Bunn questioning the statistical analysis of Nodland and Ralston; and (3) Nodland's and Ralston's reply in which they refute Eisenstein and Bunn. (Journalists can obtain copies from physnews@aip.org.)