521 research outputs found
Little Higgs Model Completed with a Chiral Fermionic Sector
The implementation of the little Higgs mechanism to solve the hierarchy
problem provides an interesting guiding principle to build particle physics
models beyond the electroweak scale. Most model building works, however, pay
not much attention to the fermionic sector. Through a case example, we
illustrate how a complete and consistent fermionic sector of the TeV effective
field theory may actually be largely dictated by the gauge structure of the
model. The completed fermionic sector has specific flavor physics structure,
and many phenomenological constraints on the model can thus be obtained beyond
gauge, Higgs, and top physics. We take a first look on some of the quark sector
constraints.Comment: 14 revtex pages with no figure, largely a re-written version of
hep-ph/0307250 with elaboration on flavor sector FCNC constraints; accepted
for publication in Phys.Rev.
Understanding Pound-Drever-Hall locking using voltage controlled radio-frequency oscillators: An undergraduate experiment
We have developed a senior undergraduate experiment that illustrates
frequency stabilization techniques using radio-frequency electronics. The
primary objective is to frequency stabilize a voltage controlled oscillator to
a cavity resonance at 800 MHz using the Pound-Drever-Hall method. This
technique is commonly applied to stabilize lasers at optical frequencies. By
using only radio-frequency equipment it is possible to systematically study
aspects of the technique more thoroughly, inexpensively, and free from eye
hazards. Students also learn about modular radio-frequency electronics and
basic feedback control loops. By varying the temperature of the resonator,
students can determine the thermal expansion coefficients of copper, aluminum,
and super invar.Comment: 9 pages, 10 figure
The Little Higgs from a Simple Group
We present a model of electroweak symmetry breaking in which the Higgs boson
is a pseudo-Nambu-Goldstone boson. By embedding the standard model SU(2) x U(1)
into an SU(4) x U(1) gauge group, one-loop quadratic divergences to the Higgs
mass from gauge and top loops are canceled automatically with the minimal
particle content. The potential contains a Higgs quartic coupling which does
not introduce one-loop quadratic divergences. Our theory is weakly coupled at
the electroweak scale, it has new weakly coupled particles at the TeV scale and
a cutoff above 10 TeV, all without fine tuning. We discuss the spectrum of the
model and estimate the constraints from electroweak precision measurements.Comment: 29 pages, referencing error corrected after death threats, dude
remove
Vacuum Stability in Split Susy and Little Higgs Models
We study the stability of the effective higgs potential in the split
supersymmetry and Little Higgs models. In particular, we study the effects of
higher dimensional operators in the effective potential on the higgs mass
predictions. We find that the size and sign of the higher dimensional operators
can significantly change the higgs mass required to maintain vacuum stability
in Split Susy models. In the Little Higgs models the effects of higher
dimensional operators can be large because of a relatively lower cut-off scale.
Working with a specific model we find that a contribution from the higher
dimensional operator with coefficient of O(1) can destabilize the vacuum.Comment: Latex 22 pages, 3 figures. Added discussion, published versio
New Physics with earliest LHC data
We investigate which new physics models could be discovered in the first year of the LHC. Such a “Supermodel” is a new physics scenario for which the LHC sensitivity with only 10 pb−1 useful luminosity is greater than that of the
Tevatron with 10 fb−1. The simplest supermodels involve s-channel resonances in the quark-antiquark and especially in the quark-quark channels. We concentrate on easily visible final states with small standard model backgrounds, and suggest simple searches, besides those for Z
states, which could discover new physics in
early LHC data
Phenomenology of the Littlest Higgs with T-Parity
Little Higgs models offer an interesting approach to weakly coupled
electroweak symmetry breaking without fine tuning. The original little Higgs
models were plagued by strong constraints from electroweak precision data which
required a fine tuning to be reintroduced. An economical solution to this
problem is to introduce a discrete symmetry (analogous to R-parity of SUSY)
called T-parity. T-parity not only eliminates most constraints from electroweak
precision data, but it also leads to a promising dark matter candidate. In this
paper we investigate the dark matter candidate in the littlest Higgs model with
T-parity. We find bounds on the symmetry breaking scale f as a function of the
Higgs mass by calculating the relic density. We begin the study of the LHC
phenomenology of the littlest Higgs model with T-parity. We find that the model
offers an interesting collider signature that has a generic missing energy
signal which could "fake" SUSY at the LHC. We also investigate the properties
of the heavy partner of the top quark which is common to all littlest Higgs
models, and how its properties are modified with the introduction of T-parity.
We include an appendix with a list of Feynman rules specific to the littlest
Higgs with T-parity to facilitate further study.Comment: 32 pages, 8 figures; dark matter bounds revised; comphep model files
made publicly available at http://www.lns.cornell.edu/public/theory/tparity
Interpreting gaps: a geoarchaeological point of view on the Gravettian record of Ach and Lone valleys (Swabian Jura, SW Germany)
Unlike other Upper Paleolithic industries, Gravettian assemblages from the Swabian Jura are documented solely
in the Ach Valley (35-30 Kcal BP). On the other hand, traces of contemporaneous occupations in the nearby Lone
Valley are sparse. It is debated whether this gap is due to a phase of human depopulation, or taphonomic issues
related with landscape changes.
In this paper we present ERT, EC-logging and GPR data showing that in both Ach and Lone valleys sediments
and archaeological materials eroded from caves and deposited above river incisions after 37-32 Kcal BP. We
argued that the rate of cave erosion was higher after phases of downcutting, when hillside erosion was more
intensive. To investigate on the causes responsible for the dearth of Gravettian materials in the Lone Valley we
test two alternative hypotheses: i) Gravettian humans occupied less intensively this part of the Swabian Jura. ii)
Erosion of cave deposits did not occur at the same time in the two valleys. We conclude that the second hypothesis
is most likely. Ages from the Lone Valley show increasing multimillennial gaps between 36 and 18 Kcal
BP, while a similar gap is present in the Ach Valley between 28 and 16 Kcal BP. Based on geoarchaeological data
from previous studies and presented in this paper, we interpreted these gaps in radiocarbon data as indicating of
cave erosion. Furthermore, we argued that the time difference across the two valleys show that the erosion of
cave deposits began and terminated earlier in the Lone Valley, resulting in a more intensive removal of
Gravettian-aged deposits. The hypothesis that cave erosion was triggered by regional landscape changes seems to
be supported by geochronological data from the Danube Valley, which show that terrace formation at the end of
the Pleistocene moved westwards throughout southern Germany with a time lag of few millennia.PTDC/HAR-ARQ/27833/2017info:eu-repo/semantics/publishedVersio
Near-brane SU(6) origin Higgs in Scherk-Schwarz breaking of five-dimensional SU(6) GUT
The symmetry breaking of five-dimensional SU(6) GUT is realized by
Scherk-Schwarz mechanisms through trivial and pseudo nontrivial orbifold S1/Z2
breakings to produce dimensional deconstruction 5D SU(6) \rightarrow4D SU(6).
The latter also induces near-brane weakly-coupled SU(6) Baby Higgs to further
break the symmetry into SU(3)C \otimes SU(3)H \otimes U(1)C. The model
successfully provides a scenario of the origin of (Little) Higgs from GUT
scale, produces the (intermediate and light) Higgs boson with the most
preferred range and establishes coupling unification and compactification scale
correctly.Comment: 23 pages, 5 figure
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