9 research outputs found
The Origin of Mass
The quark-lepton mass problem and the ideas of mass protection are reviewed.
The hierarchy problem and suggestions for its resolution, including Little
Higgs models, are discussed. The Multiple Point Principle is introduced and
used within the Standard Model to predict the top quark and Higgs particle
masses. Mass matrix ans\"{a}tze are considered; in particular we discuss the
lightest family mass generation model, in which all the quark mixing angles are
successfully expressed in terms of simple expressions involving quark mass
ratios. It is argued that an underlying chiral flavour symmetry is responsible
for the hierarchical texture of the fermion mass matrices. The phenomenology of
neutrino mass matrices is briefly discussed.Comment: 33 pages, 7 figures, to be published in the Proceedings of the XXXI
ITEP Winter School, Moscow, Russia, 18 - 26 February 200
Beautiful Mirrors at the LHC
We explore the "Beautiful Mirrors" model, which aims to explain the measured
value of , discrepant at the level. This scenario
introduces vector-like quarks which mix with the bottom, subtly affecting its
coupling to the . The spectrum of the new particles consists of two
bottom-like quarks and a charge -4/3 quark, all of which have electroweak
interactions with the third generation. We explore the phenomenology and
discovery reach for these new particles at the LHC, exploring single mirror
quark production modes whose rates are proportional to the same mixing
parameters which resolve the anomaly. We find that for mirror quark
masses is required to
reasonably establish the scenario and extract the relevant mixing parameters.Comment: version to be published in JHE
Sparticle mass spectra from SU(5) SUSY GUT models with Yukawa coupling unification
Supersymmetric grand unified models based on the gauge group SU(5) often
require in addition to gauge coupling unification, the unification of b-quark
and -lepton Yukawa couplings. We examine SU(5) SUSY GUT parameter space
under the condition of Yukawa coupling unification using 2-loop MSSM
RGEs including full 1-loop threshold effects. The Yukawa-unified solutions
break down into two classes. Solutions with low tan\beta ~3-11 are
characterized by gluino mass ~1-4 TeV and squark mass ~1-5 TeV. Many of these
solutions would be beyond LHC reach, although they contain a light Higgs scalar
with mass <123 GeV and so may be excluded should the LHC Higgs hint persist.
The second class of solutions occurs at large tan\beta ~35-60, and are a subset
of unified solutions. Constraining only unification to ~5%
favors a rather light gluino with mass ~0.5-2 TeV, which should ultimately be
accessible to LHC searches. While our unified solutions can be
consistent with a picture of neutralino-only cold dark matter, invoking
additional moduli or Peccei-Quinn superfields can allow for all of our
Yukawa-unified solutions to be consistent with the measured dark matter
abundance.Comment: 19 pages, 5 figures, 1 table, PDFLate
A realistic intersecting D6-brane model after the first LHC run
With the Higgs boson mass around 125 GeV and the LHC supersymmetry search
constraints, we revisit a three-family Pati-Salam model from intersecting
D6-branes in Type IIA string theory on the
orientifold which has a realistic phenomenology. We systematically scan the
parameter space for , and find that the gravitino mass is
generically heavier than about 2 TeV for both cases due to the Higgs mass low
bound 123 GeV. In particular, we identify a region of parameter space with the
electroweak fine-tuning as small as 24-32 (3-4). In the
viable parameter space which is consistent with all the current constraints,
the mass ranges for gluino, the first two-generation squarks and sleptons are
respectively TeV, TeV, and TeV. For the
third-generation sfermions, the light stop satisfying WMAP bounds via
neutralino-stop coannihilation has mass from 0.5 to 1.2 TeV, and the light stau
can be as light as 800 GeV. We also show various coannihilation and resonance
scenarios through which the observed dark matter relic density is achieved.
Interestingly, the certain portions of parameter space has excellent
-- and - Yukawa coupling unification. Three regions of
parameter space are highlighted as well where the dominant component of the
lightest neutralino is a bino, wino or higgsino. We discuss various scenarios
in which such solutions may avoid recent astrophysical bounds in case if they
satisfy or above observed relic density bounds. Prospects of finding
higgsino-like neutralino in direct and indirect searches are also studied. And
we display six tables of benchmark points depicting various interesting
features of our model.Comment: 41 pages, 12 figures, 6 table