In theoretical physics

Theoretical physics

Theoretical physics is a branch of physics which employs mathematical models and abstractions of physics to rationalize, explain and predict natural phenomena...

, soft SUSY breaking is type of supersymmetry breaking

Supersymmetry breaking

In particle physics, supersymmetry breaking is the process to obtain a seemingly non-supersymmetric physics from a supersymmetric theory which is a necessary step to reconcile supersymmetry with actual experiments. It is an example of spontaneous symmetry breaking...

 that does not cause ultraviolet divergence

Ultraviolet divergence

In physics, an ultraviolet divergence is a situation in which an integral, for example a Feynman diagram, diverges because of contributions of objects with very high energy , or, equivalently, because of physical phenomena at very short distances. An infinite answer to a question that should have a...

s to appear in scalar masses. These terms are relevant operators—i.e. operators whose coefficients have a positive dimension of mass—though there are some exceptions.

A model with soft SUSY breaking was proposed in 1981 by Howard Georgi

Howard Georgi

Howard Mason Georgi III, born January 6, 1947 in San Bernardino, California, is Harvard College Professor and Mallinckrodt Professor of Physics at Harvard University...

 and Savas Dimopoulos

Savas Dimopoulos

Savas Dimopoulos is a Greek particle physicist at Stanford University. He was born in Istanbul, Turkey and later moved to Athens due to ethnic tensions in Turkey during the 1950s and 1960s. Dimopoulos studied as an undergraduate at the University of Houston...

. Before this, dynamical models of supersymmetry breaking were being used that suffered from giving rise to color and charge breaking vacua.

Soft SUSY breaking decouples the origin of supersymmetry breaking from its phenomenological consequences. In effect, soft SUSY breaking adds explicit symmetry breaking

Explicit symmetry breaking

Explicit symmetry breaking indicates a situation where the dynamical equations are not manifestly invariant under the symmetry group considered. This means, in the Lagrangian formulation, that the Lagrangian of the system contains one or more terms explicitly breaking the symmetry...

  to the supersymmetric Standard Model Lagrangian. The source of SUSY breaking results from a different sector where supersymmetry

Supersymmetry

In particle physics, supersymmetry is a symmetry that relates elementary particles of one spin to other particles that differ by half a unit of spin and are known as superpartners...

is broken spontaneously. Divorcing the spontaneous supersymmetry breaking from the supersymmetric Standard Model leads to the notion of mediated supersymmetry breaking.