Discovery of a New Albatross Isted in the Theory

181 _NA_ru_~__ v_o_L_~ __ ,s_s_EYm __ M_B_ER __ I~------NNfEW~S~AVN~O~V~IE~W~S~------~ that while the positive discrepancy had Ornithology disappeared, a small negative discrepancy of about 1.5 per cent remained. This dis crepancy could only be explained if 'very heavy intermediate bosons' of mass M ex Discovery of a new albatross isted in the theory. Then the radiative cor from P. Jouventin and J-P. Roux rections to {J decay not present in muon decay gave rise to a term A NEW species of albatross has been discovered on Amsterdam Island, situated -(3aln) ln(Mim ) (2) p in the southern Indian Ocean midway bet where m is the proton mass, which re ween South Africa and Australia, and moved the 1.5 per cent discrepancy for named Amsterdam Albatross, Diomedea M ~ el0112 ~ 90 GeV typical of electro amsterdamensis. weak theories. This result was for many Several 'great albatrosses', presumed to Qexu/ans years the only experimental evidence for belong to the species Diomedea exulans the existence of the mass scale associated (Wandering Albatross), had occasionally with the W and Z as Bailin and I have been reported on the island. However, dur pointed out9. Bailin concluded that only ing a recent study it was realized that the when experiments can be made sensitive to population differed from the Wandering effects of order a - 1 per cent can the Albatross in several ways (see the figure). standard model be verified; this in itself The weight of the adult is nearly 3 kg less demands a theory that can make definite than in D. exulans; the breeding plumage is D epomophora predictions to this accuracy. dark; the eyelid white instead of blue as in L. Baulieu (Ecole Normale Superieure) D. exulans; there is a decorative black then presented a paper which was a stripe on the beak, as in the Royal Alba technical tour de force: he proved the tross (D. epomophora), and a black patch renormalizability of the standard model on at the tip; and finally, the breeding cycle of one transparency. He then showed the im D. amsterdamensis starts 2 months later portant result that for the measurable than in populations of D. exulans. quantities (the so-called S-matrix elements) The family Diomedea has been thought in the theory to be gauge invariant, the to comprise 13 species. Ernst Mayr (per D amsterdamensis renormalization scheme used must define sonal communication) believes the albatros all its parameters on-shell. This property on Amsterdam Island is an allospecies in The three largest representatives of the family the standard model shares with QED where the superspecies D. exulans, that has Diomedea: the Wandering Albatross (D. exulans), the Royal Albatross (D. all S-matrix elements can be expressed in adapted to subtropical conditions. epomophora) and the new species (D. amster- terms of the fine structure constant and the The total population including non damensis). masses of the particles in the theory; it is breeding adults and immature birds has unlike the situation in quantum chromo been estimated at 30-50 individuals, and that the breeding site (400 ha) be made a dynamics (the present theory of strong Amsterdam Island is certainly its only conservation area. D interactions) in which all mass scales are ar breeding site. Such a tiny and slow P. Jouventin and J-P. Roux are at the Institut bitrary and renormalization is performed breeding bird population is very suscepti des Sciences de /'Evolution, USTL, Place off-shell. ble to disturbance, so we would propose Bataillon, 34060 Montpellier. This result led directly to the appropriate definition of the electroweak mixing angle wide range for the unknown Higgs mass obtained which is about double its actual 8\\/. Experimental papers take 8w to be the and the top-quark mass, there are strict value. Using the central value Mz = 95 mixing angle between the electromagnetic limits on M given Mw, regardless of the GeV of the UA1 report11 still gives a muon and weak neutral currents. This is a per value taken For sinew. The variation of Mz lifetime about 50 per cent too long. fectly proper definition but one that leads with Mw was almost linear in this mass The primary test then of the success of to difficulties in a renormalization scheme region and for a given Mw, Mz was deter the standard model quantitatively lies in since the weak current is normally defined mined with error of less than 0.5 GeV. the precise determination of the masses of at mass Mz while the electromagnetic cur Sirlin stressed that it is preferable to W and Z to better than 1 per cent to see rent is detmed at zero mass. A. Sirlin of eliminate ew altogether from this analysis, whether they are consistent with the muon New York University (who first especially as sinew is determined in ex lifetime using equation (4). If not, the calculated 10 a radiative correction to a periments where there are strong interac model can be patched up- another Higgs weak process back in 1956 and who has tion corrections which are hard to quan can be introduced for example- but advo been the leading advocate of the impor tify. He preferred to write down the direct cates of the view that the standard model tance of radiative corrections since unified relationship between Mw and Mz in the simply provides an effective theory rather electroweak theories were introduced) sug standard model. This is than the basic quantum field theory of gested with little dissent that Baulieu's on Mz = Mw I ( 1-(A I Mw)2)v' (4) elementary particles will be on stronger shell approach required the natural defini where A depends only on G(determined ground. D tion of ew in the standard model to be from the muon lifetime) and a. At tree level Norman Dombey is in the Division of Physics, A = 37.28 GeV, but including radiative University of Sussex, Fa/mer, Brighton BNI cos8w = Mw I Mz (3) correctionsA = 38.66GeV. 9RF. I. Se< Close, F. Na1Ure302, 148 (1873). using equation (1). The argument can also be reversed. 2. SccCiose,F.Nature303,280(1983) Salam was very keen that the workshop From the experimental measurements of 3 Dombcy, N. Nature282, 131 (1979). consider the question of the range of values 4. Salam, A. Nud. Phys. 18, 681 (1960). Mw and Mz, A and hence the muon 5. Glashow, S.l.. Nud. Phys. 22,579 (1%1). of Mw and Mz allowed in the standard lifetime can be calculated; so if the 6. Weinberg, S. Phys. Rev. Le{{. 19, 1264 (1967). model since he had just received a telex standard model is correct, this procedure 7. Cabibbo, N. Phys. Re.·. Lett. 10,531 (1%3). 8. Blin-Stoylc, R.J. & Freeman, J.M. Nud. Phys. AlSO, from CERN announcing the discovery of should be self-consistent. This is a very 369 (1970). the Z of mass around 97 Ge V. The question stringent requirement on the vector boson 9. Bailin, D. & Dombey, N. Nature 271, 20 (1978). 10. Behrends, R.E .. Finkd.stdn, R.J., & Sirlin, A. Phys. was answered by M. Consoli (Catania) and masses: for example, takingMw = 81 GeV Rev. 333, 866 ( 1956). Sirlin who showed that even allowing a and Mz = 97 GeV, a muon lifetime is II. Arnison eta/. CERN Rep. (June 1983).