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

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

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

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

Minimal Gaugino Mediation

We propose Minimal Gaugino Mediation as the simplest known solution to the supersymmetric flavor and CP problems. The framework predicts a very minimal structure for the soft parameters at ultra-high energies: gaugino masses are unified and non-vanishing whereas all other soft supersymmetry breaking parameters vanish. We show that this boundary condition naturally arises from a small extra dimension and present a complete model which includes a new extra-dimensional solution to the mu problem. We briefly discuss the predicted superpartner spectrum as a function of the two parameters of the model. The commonly ignored renormalization group evolution above the GUT scale is crucial to the viability of Minimal Gaugino Mediation but does not introduce new model dependence.Comment: LaTeX, 16 pages, 4 figures, running of the bottom and tau Yukawas included, plots revise

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

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

Pseudo-axions in Little Higgs models

Little Higgs models have an enlarged global symmetry which makes the Higgs boson a pseudo-Goldstone boson. This symmetry typically contains spontaneously broken U(1) subgroups which provide light electroweak-singlet pseudoscalars. Unless such particles are absorbed as the longitudinal component of $Z'$ states, they appear as pseudoscalars in the physical spectrum at the electroweak scale. We outline their significant impact on Little Higgs phenomenology and analyze a few possible signatures at the LHC and other future colliders in detail. In particular, their presence significantly affects the physics of the new heavy quark states predicted in Little Higgs models, and inclusive production at LHC may yield impressive diphoton resonances.Comment: 28 pages, 9 figs., accepted to PRD; footnote added, typos correcte

Collective Quartics from Simple Groups

This article classifies Little Higgs models that have collective quartic couplings. There are two classes of collective quartics: Special Cosets and Special Quartics. After taking into account dangerous singlets, the smallest Special Coset models are SU(5)/SO(5) and SU(6)/Sp(6). The smallest Special Quartic model is SU(5)/SU(3) x SU(2) x U(1) and has not previously been considered as a candidate Little Higgs model.Comment: 22 pages, 2 figure