Report of the Supersymmetry Theory Subgroup
J. Amundson (Wisconsin), G. Anderson (FNAL), H. Baer (FSU), J. Bagger (Johns Hopkins), R.M. Barnett (LBNL), C.H. Chen (UC Davis), G. Cleaver (OSU), B. Dobrescu (BU), M. Drees (Wisconsin), J.F. Gunion (UC Davis), G.L. Kane (Michigan), B. Kayser (NSF),
C. Kolda (IAS), J. Lykken (FNAL), S.P. Martin (Michigan), T. Moroi (LBNL), S. Mrenna (Argonne), M. Nojiri (KEK), D. Pierce (SLAC), X. Tata (Hawaii), S. Thomas (SLAC), J.D. Wells (SLAC), B. Wright (North Carolina), Y. Yamada (Wisconsin)
ABSTRACT Spacetime supersymmetry appears to be a fundamental in- gredient of superstring theory. We provide a mini-guide to some of the possible manifesta- tions of weak-scale supersymmetry. For each of six scenarios These motivations say nothing about the scale at which nature we provide might be supersymmetric. Indeed, there are additional motiva- tions for weak-scale supersymmetry.
a brief description of the theoretical underpinnings,
Incorporation of supersymmetry into the SM leads to a so-
the adjustable parameters, lution of the gauge hierarchy problem. Namely, quadratic divergences in loop corrections to the Higgs boson mass a qualitative description of the associated phenomenology at future colliders, will cancel between fermionic and bosonic loops. This mechanism works only if the superpartner particle masses
comments on how to simulate each scenario with existing are roughly of order or less than the weak scale. event generators.
There exists an experimental hint: the three gauge cou- plings can unify at the Grand Uni®cation scale if there ex- I. INTRODUCTION ist weak-scale supersymmetric particles, with a desert be-
The Standard Model (SM) is a theory of spin- 1 matter tween the weak scale and the GUT scale. This is not the 2 fermions which interact via the exchange of spin-1 gauge case with the SM. bosons, where the bosons and fermions live in independent rep-
Electroweak symmetry breaking is a derived consequence resentations of the gauge symmetries. Supersymmetry (SUSY) of supersymmetry breaking in many particle physics mod- is a symmetry which establishes a one-to-one correspondence between bosonic and fermionic degrees of freedom, and pro- els with weak-scale supersymmetry, whereas electroweak vides a relation between their couplings [1]. Relativistic quan- symmetry breaking in the SM is put in ªby hand.º The
tum ®eld theory is formulated to be consistent with the symme- SUSY radiative electroweak symmetry-breaking mecha-
m 150 200
nism works best if the top quark has mass t
tries of the Lorentz/PoincarÂe group ± a non-compact Lie alge-
m =
GeV. The recent discovery of the top quark with t
bra. Mathematically, supersymmetry is formulated as a gener-
4:4 176 GeV is consistent with this mechanism. alization of the Lorentz/PoincarÂe group of space-time symme- tries to include spinorial generators which obey speci®c anti-
As a bonus, many particle physics models with weak- commutation relations; such an algebra is known as a graded scale supersymmetry contain an excellent candidate for Lie algebra. Representations of the SUSY algebra include both cold dark matter (CDM): the lightest neutralino. Such a bosonic and fermionic degrees of freedom. CDM particle seems necessary to describe many aspects of The hypothesis that nature is supersymmetric is very com- cosmology. pelling to many particle physicists for several reasons. Finally, there is a historical precedent for supersymmetry. In
It can be shown that the SUSY algebra is the only non- 1928, P. A. M. Dirac incorporated the symmetries of the Lorentz trivial extension of the set of spacetime symmetries which group into quantum mechanics. He found as a natural conse- forms one of the foundations of relativistic quantum ®eld quence that each known particle had to have a partner particle theory. ± namely, antimatter. The matter-anti-matter symmetry wasn't revealed until high enough energy scales were reached to create
If supersymmetry is formulated as a local symmetry, then a positron. In a similar manner, incorporation of supersymme- one is necessarily forced into introducing a massless spin-2 try into particle physics once again predicts partner particles for (graviton) ®eld into the theory. The resulting supergravity all known particles. Will nature prove to be supersymmetric at theory reduces to Einstein's general relativity theory in the the weak scale? In this report, we try to shed light on some of appropriate limit. the many possible ways that weak-scale supersymmetry might
Theory subgroup conveners. be revealed by colliders operating at suf®ciently high energy.
655 masses, (C. Kolda, S. Martin and S. Mrenna) Boson ®elds Fermionic partners
Gauge multiplets models with non-universal GUT-scale soft SUSY-breaking
a a
(3) g g~
SU terms, (G. Anderson, R. M. Barnett, C. H. Chen, J. Gunion,
i i
~
(2) W W
SU J. Lykken, T. Moroi and Y. Yamada)
~
B B U (1)
Matter multiplets two MSSM scenarios which use the large parameter free-