17,315 research outputs found
Constraints on Supersymmetry from Relic Density compared with future Higgs Searches at the LHC
Among the theories beyond the Standard Model (SM) of particle physics
Supersymmetry (SUSY) provides an excellent dark matter (DM) candidate, the
neutralino. One clear prediction of cosmology is the annihilation cross section
of DM particles, assuming them to be a thermal relic from the early universe.
In most of the parameter space of Supersymmetry the annihilation cross section
is too small compared with the prediction of cosmology. However, for large
values of the tan beta parameter the annihilation through s-channel
pseudoscalar Higgs exchange yields the correct relic density in practically the
whole range of possible SUSY masses up to the few TeV range. The required
values of tan beta are typically around 50, i.e. of the order of top and bottom
mass ratio, which happens to be also the range allowing for Yukawa unification
in a Grand Unified Theory with gauge coupling unification. For such large
values of tan beta the associated production of the heavier Higgses, which is
enhanced by tan beta squared, becomes three orders of magnitude larger than the
production of a simlar SM-like Higgs and could be observable as one of the
first hints of new physics at the LHC.Comment: 12 pages, 5 figures, Published version in Phys. Lett. B with updated
references and minor correction
Particle Physics and Cosmology
Today, both particle physics and cosmology are described by few parameter
Standard Models, i.e. it is possible to deduce consequence of particle physics
in cosmology and vice verse. The former is examined in this lecture, in light
of the recent systematic exploration of the electroweak scale by the LHC
experiments. The two main results of the first phase of the LHC, the discovery
of a Higgs-like particle and the absence so far of new particles predicted by
"natural" theories beyond the Standard Model (supersymmetry, extra-dimension
and composite Higgs) are put in a historical context to enlighten their
importance and then presented extensively. To be complete, a short review from
the neutrino physics, which can not be probed at LHC, is also given. The
ability of all these results to resolve the 3 fundamental questions of
cosmology about the nature of dark energy and dark matter as well as the origin
of matter-antimatter asymmetry is discussed in each case.Comment: 32 pages, 47 figures, Proceeding from the 100th Les Houches Summer
School on Post-Planck Cosmology, July 8th - Aug 2nd 2013. Update with
recently published ATLAS/CMS 8 TeV result
What are the Building Blocks of Our Universe?
We are told that we are living in a Golden Age of Astronomy. Cosmological
Parameters are found with un precedented accuracy. Yet, the known form of
matter forms only a small fraction of the total energy density of the universe.
Also, a mysterious dark energy dominates the universe and causes acceleration
in the rate of expansion.Comment: To be published in the Proceedings of the Interantional Conference on
COSMOLOGY;Facts and Problems (College de France, Paris, June 8-11, 2004
Some Aspects of String Cosmology and the LHC
I discuss some (unconventional) aspects of String Cosmology of relevance to
supersymmetric dark matter searches at the Large Hadron Collider (LHC) at CERN.
In particular, I analyse the role of time-dependent dilaton fields in relaxing
some of the stringent constraints that characterise minimal supersymmetric
models in standard cosmology. I also study briefly CPT-violating aspects of
brane Universe models with space-time brane defects at early epochs and their
potential relevance to the observed Baryon Asymmetry.Comment: 12 pages pdflatex, uses special macros.Plenary talk at the 1st
International Conference on New Frontiers in Physics 2012, Kolymbari (Crete,
Greece), June 10-16 2012, to appear in the Proc. EPJ WEB of Conferences,
updated reference
Gravity and axions from a random UV QFT
It is postulated that the UV QFT is enormous and random. The coupling of the
Standard Model to such QFT is analyzed. It is argued that massless 4d gravity
and axions are general avatars of the postulate. The equivalence principle
emerges naturally as well as a concrete set of sources for its breaking. The
axion scale is related to the 4d Planck scale as , where is the
"number of colors" of the (almost) hidden UV CFT.Comment: Latex, 39 page
Noncommutative Spectral Geometry: A Short Review
We review the noncommutative spectral geometry, a gravitational model that
combines noncommutative geometry with the spectral action principle, in an
attempt to unify General Relativity and the Standard Model of electroweak and
strong interactions. Despite the phenomenological successes of the model, the
discrepancy between the predicted Higgs mass and the current experimental data
indicate that one may have to go beyond the simple model considered at first.
We review the current status of the phenomenological consequences and their
implications. Since this model lives by construction at high energy scales,
namely at the Grand Unified Theories scale, it provides a natural framework to
investigate early universe cosmology. We briefly review some of its
cosmological consequences.Comment: 11 pages. Invited talk in the Sixth International Workshop DICE2012,
Castello Pasquini/Castiglioncello (Tuscany), September 17-21, 201
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