5,836 research outputs found
Seesaw mechanism and the baryon asymmetry
I review the present understanding of connection between the non-zero
neutrino masses and the baryon asymmetry of the Universe. The state-of-art
results are presented for the standard thermal leptogenesis.Comment: Talk in Seesaw25, Paris, June 10-11, 200
Doubly Charged Higgsino Pair Production and Decays in e+e- Collisions
In supersymmetric grand unified theories, light higgsino multiplets generally
exist in addition to the familiar chargino/neutralino multiplets of the minimal
supersymmetric extension of the Standard Model. The new multiplets may include
doubly charged states and . We
study the properties and the production channels of these novel higgsinos in
and collisions, and investigate how their properties
can be analyzed experimentally.Comment: LATEX, 25 pages, ps figures include
Evolving Planck Mass in Classically Scale-Invariant Theories
We consider classically scale-invariant theories with non-minimally coupled
scalar fields, where the Planck mass and the hierarchy of physical scales are
dynamically generated. The classical theories possess a fixed point, where
scale invariance is spontaneously broken. In these theories, however, the
Planck mass becomes unstable in the presence of explicit sources of scale
invariance breaking, such as non-relativistic matter and cosmological constant
terms. We quantify the constraints on such classical models from Big Bang
Nucleosynthesis that lead to an upper bound on the non-minimal coupling and
require trans-Planckian field values. We show that quantum corrections to the
scalar potential can stabilise the fixed point close to the minimum of the
Coleman-Weinberg potential. The time-averaged motion of the evolving fixed
point is strongly suppressed, thus the limits on the evolving gravitational
constant from Big Bang Nucleosynthesis and other measurements do not presently
constrain this class of theories. Field oscillations around the fixed point, if
not damped, contribute to the dark matter density of the Universe.Comment: 28 pages, 2 figures, version published in JHE
Implications of effective axial-vector coupling of gluon for spin polarizations at the LHC
We analyze the impact of effective axial-vector coupling of the gluon on spin
polarization observables in pair production at the LHC. Working at
leading order in QCD, we compute the spin-correlation and left-right
spin asymmetry coefficients in the helicity basis in the laboratory frame as
functions of the new physics scale associated with this coupling. We
found that the invariant mass dependent asymmetries are more
sensitive to the scale than the corresponding inclusive ones, in
particular when suitable cuts selecting high invariant mass regions
are imposed. In the context of this scenario, we show that the LHC has
potential either to confirm or to rule out the Tevatron FB top asymmetry
anomaly by analyzing the spin-correlation and left-right
polarization asymmetries. On the other hand, stringent lower bound on the new
physics scale can be set in this scenario if no significant
deviations from the SM predictions for those observables will be measured.Comment: 26 pages, 8 figures, same as published version in PRD. Few
modifications in the text and one new reference adde
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