Quick viewing(Text Mode)

Super Symmetry

Super Symmetry

M i l e s to n e s

DOI: 10.1038/nphys868

m iles tone 1 3 Super

The way that is woven into the in 1015. However, a form of symmetry very fabric of the is writ between and called large in the of offers a much more . In this model, which elegant solution because the took shape in the 1970s and can fluctuations caused by explain the results of all particle- bosons are naturally cancelled physics experiments to date, out by those caused by fermions and (and ) is made of three vice versa. families of and , which Symmetry plays a central role in are all fermions, whereas the physics. The fact that the laws of electromagnetic, strong physics are, for instance, symmetric in and weak that act on these (that is, they do not change with are carried by other time) to the conservation of particles, such as and , . These laws are also symmetric The ATLAS experiment under construction at the which are all bosons. with respect to , and Large . Image courtesy of CERN. Despite its success, the standard relative motion. Initially explored in model is unsatisfactory for a number the early 1970s, supersymmetry is a of reasons. First, although the less obvious kind of symmetry, which, . Searching for electromagnetic and weak forces if it exists in , would mean that supersymmetric particles will be a have been unified into a single , the laws of physics do not change priority when the Large Hadron a ‘grand unified ’ that brings when bosons are replaced by Collider comes into operation at the strong into the fold fermions, and fermions are replaced CERN, the European particle-physics remains elusive. Second, the origins by bosons. near , in 2008. of are not fully understood. Although it is difficult to explain Peter Rodgers, Chief Editor, Third, is not included. supersymmetry through analogies to Nature Nanotechnology Moreover, there are other, less , its consequences obvious problems with the standard are dramatic — it predicts that every ORIGINAL RESEARCH PAPERS Golfand, Y. A. & Likhtman, E. P. Extension of the algebra of model. The two natural mass scales in fundamental particle has a Poincaré generators and violation of nature are zero and the Planck mass, with half a unit of spin P invariance. JETP Lett. 13, 323–326 (1971) | ~ 1019 GeV c−2. Neither photons nor less. The , for instance, has a Neveu, A. & Schwarz, J. H. Factorizable dual model of . Nucl. Phys. B 31, 86–112 (1971) | gluons (which carry the spin of a half, so its superpartner Ramond, P. Dual theory for free fermions. Phys. electromagnetic and strong forces, (which is known as a selectron) has Rev. D 3, 2415–2418 (1971) | Wess, J. & Zumino, B. Supergauge transformations in four dimen- respectively) have mass, but the W zero spin. This means that the sions. Nucl. Phys. B 70, 39–50 (1974) | Wess, J. & and Z bosons that are responsible for superpartner of a is always a Zumino, B. A Lagrangian model under the weak force have of about and vice versa. supergauge transformations. Phys. Lett. B 49, 52–54 (1974) −2 90 GeV c . Where does this mass Supersymmetry also plays a central further reading Dimopoulos, S., Raby, S. scale come from? role in that attempt to unify & Wilczek, F. Supersymmetry and the scale of This ‘’ can be the forces in the standard model with unification. Phys. Rev. D 24, 1681–1683 (1981) | Almadi, U., de Boar, W. & Furstenau, H. Comparison solved by fine-tuning the model so gravity by treating fundamental of grand unified theories with electroweak and that various quantum fluctuations particles as vibrating strings or strong constants measured at LEP. Phys. Lett. B 260, 447–455 (1991) | Greene, B. cancel out, although many membranes in 10-dimensional or (Vintage, London, 2000) | are uncomfortable with this solution 11-dimensional . In these Kane, G. & Shifman, M. (eds) The Supersymmetric because some parameters must theories the gravitational force is World: The Beginnings of the Theory (World Scientific, Singapore, 2000) be fine-tuned to better than 1 part carried by a spin-two boson called the

nature MILESTONES | Spin march 2008 © 2008 Nature Publishing Group