Transcript CO NARUSZA SYMETRIE ELEKTROSLABA? – PYTANIE DO LHC

CO NARUSZA SYMETRIE
ELEKTROSLABA? –
PYTANIE DO LHC
Electroweak symmetry breaking in the
SM by the Higgs potential
(renormalizable theory)
Properties of the Higgs potential crucial for
the electroweak theory:
SU(2)xSU(2) global symmetry of V :
Spontaneously broken to the diagonal subgroup SU(2)
3 Goldstone bosons couple to the three
gauge currents corresponding to the three
spontaneously broken symmetries of SU(2)_LxU(1)_Y.
The Higgs mechanism then ensures that the
Goldstone bosons become the longitudinal
modes of the gauge bosons W,Z which acquire masses.
Renormalizability not crucial for EWSB
One physical Higgs particle h ensures unitarity
In the Standard Model
(with a Higgs particle –renormalizable
theory) from the fits to LEP data we get
In the Standard Model, the EWSB is described but
not explained
Can we understand better the Fermi scale?
The hierarchy problem of the Standard
Model.
The impact of physics beyond the Standard Model on
precision electroweak data can be studied in a model
independent way by adding to the SM lagrangian higher
dimension operators
Moreover, two directions:
• embed electroweak theory as the
renormalizable SM into a deeper one
• embed electroweak theory , not
necessarily the renormalizable SM, into
a deeper one
Renormalizability of an effective theory –
not fundamental but very useful !
All observables can be calculated in any order
of perturbation theory in terms of a finite number
of measured quantities.
Any dependence on the scale M of new physics
is suppressed by inverse powers of M
(corrections to a renormalizable theory)
Important example of non-renormalizable effective
theory: theory of 3 pions as (pseudo)Goldstone
bosons.
Valid below the rho meson mass which enters
logarithmically into perturbative calculations
Renormalizability was a driving force in
constructing electroweak theory but….
Two directions:
• embed electroweak theory as the
renormalizable SM into a deeper one;
SUPERSYMMETRY
• embed electroweak theory , not necessarily
the renormalizable SM, into a deeper one;
Higgs doublet as a (pseudo)Goldstone
boson and „higgless” models
Supersymmetry – elementary scalars
Minimal supersymmetric model –
renormlizable extension of the SM
UV behaviour improved due to fermionboson cancellations;
Superpartner masses- cut off in the SM
Higgs potential
Higgs sector of the MSSM:
Two Higgs doublets;
Fermi scale generated by quantum corrections
to the Higgs potential due to the large top
quark mass;
The lightest physical scalar has similar
properties as the Higgs particle in the SM;
We shall find the answer in experiments
at the LHC
Most likely it will tells us a lot
about the physics beyond the SM