EWSBElectroweak Symmetry Breaking (theoretical particle physics)
EWSBEast Winds Symphonic Band (Pittsburgh, PA)
EWSBElite War Shark Battalion
EWSBEternal Words Spelling Bee (California)
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As was the case for the bino, there is no pure higgsino state after EWSB, but one obtains an almost pure higgsino-like neutralino by diagonalizing [M.sub.[chi]] in (1) in the limit [absolute value of ([mu])] [much less than] [M.sub.1], [M.sub.2].
As supersymmetry assigns a Weyl spinor to each complex state in the scalar Higgs doublets one counts four physical higgsino states, which, after EWSB, give rise to two Majorana neutralinos, [[chi].sub.1] (or [chi]) and [[chi].sub.2], and a Dirac chargino, [[chi].sup.[+ or -].
The wino belongs to the adjoint representation of the gauge group (hypercharge Y = 0) and the wino-like neutralino emerges, after EWSB, from the diagonalization of (1) in the limit [absolute value of ([M.sub.2])] [much less than] [M.sub.1], [mu].
The four neutralinos of the MSSM are all Majorana fermions that, after EWSB, remain neutral under [U(1).sub.em] and color.
For tan [beta] sufficiently large to ensure a predominantly SM-like Higgs boson (tan [beta] > 3-4 is a condition often fulfilled, for instance, in scenarios where EWSB is obtained radiatively via the renormalization group evolution of soft SUSY-breaking parameters constrained at some high scale, as it prevents certain soft masses from running tachyonic at the low scale.), the coupling to the nucleon can thus be expressed entirely in terms of the higgsino fraction (or purity), [f.sub.h], which depends on the elements of the unitary matrix, N, diagonalizing (1).
We have chosen to show in Figure 4 the higgsino parameter space under CMSSM boundary conditions, which provide a reasonable ansatz for models with scalar universality inspired by supergravity, and more generally cast in a lean framework scenarios in which supersymmetry breaking is transmitted to the visible sector at some high scale (the GUT scale) and EWSB is obtained radiatively around the minima of the MSSM scalar potential.
In order to keep the Higgs doublet soft mass under control, so as to obtain a higgsino-like LSP after EWSB, and avoid tachyonic physical states, numerical scans are in this situation driven to large negative [A.sub.0] and/or larger soft scalar mass.
There is no apparent lower bound on the scattering cross section if we relax the requirement of radiative EWSB from boundary conditions generated at the GUT scale.
Finally, like all BSM models developed at least in part to deal with the hierarchy problem, after the first two runs of the LHC models with higgsino DM have become marred by a certain amount of EWSB fine tuning.
Much of what makes higgsinos very attractive is the fact that the current constraints are not evaded with specific arrangements of some model parameters, but rather as a consequence only of the higgsino isospin quantum numbers, which lead to a fairly large mass to produce [OMEGA][h.sup.2] in agreement with observations, and of the mass splittings among its neutral and charged components, which stem directly from EWSB. As these are not exotic features, one reasonably expects that the higgsino parameter space will not remain unexplored indefinitely.
The prospects are particularly enticing in supergravity-inspired scenarios with radiative EWSB, where the overall consistency of the theoretical picture requires a lower bound on the spin-independent cross section for higgsinos, determined indirectly but convincingly by the measured value of the Higgs boson mass.