Verifying the frequency ratios in the musical scale of just intonation with "hear-and-see" learning tools

In engineering colleges, Acoustics often includes the musical scale topic, which is not very popular with most engineering students. In order to face this situation, this paper presents two alternative or complementary “hear-and-see” learning tools for the musical scale of just intonation. The first one combines the hearing of musical notes from an electric organ with the display on an oscilloscope from which the frequency ratios are inferred. Alternatively, the frequencies are computed in advance on the basis of the theoretical frequency ratios, and an audio editor allows to hear the resulting notes, while the PC screen can display similar graphs to those on the oscilloscope.Postprint (author's final draft

Chiral fermions and gauge-fixing in five-dimensional theories

We study in detail the issue of gauge-fixing in theories with one universal extra dimension, i.e. theories where both bosons and fermions display Kaluza-Klein (KK) excitations. The extra dimension is compactified using the standard orbifold construction for a massless chiral fermion. We carry out the gauge-fixing procedure at the level of the five-dimensional theory and determine the tree-level propagators and interaction vertices needed for performing perturbative calculations with the effective four-dimensional theory resulting after the compactification. The gauge-independence of the tree-level S-matrix involving massive KK modes is verified using specific examples. In order to obtain massive fermionic zero modes one has to enlarge the theory by introducing a set of mirror fermions, a construction which is carried out in detail. Finally, the gauge-independence of the tree-level S-matrix involving the resulting new mass-eigenstates is proved by resorting to generalized current conservation equations.Comment: 10 pages, 5 figures, revtex and axodra

Dark Matter Phenomenology of SM and Enlarged Higgs Sectors Extended with Vector Like Leptons

We will investigate the scenario in which the Standard Model (SM) Higgs sector and its 2-doublet extension (called the Two Higgs Doublet Model or 2HDM) are the "portal" for the interactions between the Standard Model and a fermionic Dark Matter (DM) candidate. The latter is the lightest stable neutral particle of a family of vector-like leptons (VLLs). We will provide an extensive overview of this scenario combining the constraints purely coming from DM phenomenology with more general constraints like Electro-weak Precision Tests (EWPT) as well as with collider searches. In the case that the new fermionic sector interacts with the SM Higgs sector, constraints from DM phenomenology force the new states to lie above the TeV scale. This requirement is relaxed in the case of 2HDM. Nevertheless, strong constraints coming from Electroweak Precision Tests (EWPT) and the Renormalization Group Equations (RGEs) limit the impact of VLFs on collider phenomenology.Comment: 32 pages, 12 figure

Impact of Dark Matter Direct and Indirect Detection on Simplified Dark Matter Models

We discuss simple extensions of the Standard Model featuring a (fermionic) stable DM candidate interacting with SM fermions through a $Z^{'}$ mediator. These kind of models offer a wide phenomenology but result, at the same time, particularly manageable, given the limited number of free-parameters, and offer a broad LHC phenomenology. We will discuss the impact Direct and Indirect Dark Matter searches, assuming the latter to be thermal WIMPs. We will show in particular that the combinations of the limits on the DM Spin Independent and Spin Dependent scattering cross-section on nuclei already exclude large portions of the parameter space favored by DM relic density, in particular if, in addition, a DM Indirect signal, like the Galactic Center gamma-ray excess is required.Comment: 7 pages, 2 figures. To appear as proceeding of the conference HEP-EPS 2015, Wien (Austria

Accurate estimate of the relic density and the kinetic decoupling in non-thermal dark matter models

Non-thermal dark matter generation is an appealing alternative to the standard paradigm of thermal WIMP dark matter. We reconsider non-thermal production mechanisms in a systematic way, and develop a numerical code for accurate computations of the dark matter relic density. We discuss in particular scenarios with long-lived massive states decaying into dark matter particles, appearing naturally in several beyond the standard model theories, such as supergravity and superstring frameworks. Since non-thermal production favors dark matter candidates with large pair annihilation rates, we analyze the possible connection with the anomalies detected in the lepton cosmic-ray flux by Pamela and Fermi. Concentrating on supersymmetric models, we consider the effect of these non-standard cosmologies in selecting a preferred mass scale for the lightest supersymmetric particle as dark matter candidate, and the consequent impact on the interpretation of new physics discovered or excluded at the LHC. Finally, we examine a rather predictive model, the G2-MSSM, investigating some of the standard assumptions usually implemented in the solution of the Boltzmann equation for the dark matter component, including coannihilations. We question the hypothesis that kinetic equilibrium holds along the whole phase of dark matter generation, and the validity of the factorization usually implemented to rewrite the system of coupled Boltzmann equation for each coannihilating species as a single equation for the sum of all the number densities. As a byproduct we develop here a formalism to compute the kinetic decoupling temperature in case of coannihilating particles, which can be applied also to other particle physics frameworks, and also to standard thermal relics within a standard cosmology

The Semi-Hooperon: Gamma-ray and anti-proton excesses in the Galactic Center

A puzzling excess in gamma-rays at GeV energies has been observed in the center of our galaxy using Fermi-LAT data. Its origin is still unknown, but it is well fitted by Weakly Interacting Massive Particles (WIMPs) annihilations into quarks with a cross section around $10^{-26}{\rm cm^3 s^{-1}}$ with masses of $20-50$~GeV, scenario which is promptly revisited. An excess favoring similar WIMP properties has also been seen in anti-protons with AMS-02 data potentially coming from the Galactic Center as well. In this work, we explore the possibility of fitting these excesses in terms of semi-annihilating dark matter, dubbed as semi-Hooperon, with the process ${\rm WIMP\, WIMP \rightarrow WIMP\, X}$ being responsible for the gamma-ray excess, where X=h,Z. An interesting feature of semi-annihilations is the change in the relic density prediction compared to the standard case, and the possibility to alleviate stringent limits stemming from direct detection searches. Moreover, we discuss which models might give rise to a successful semi-Hooperon setup in the context of $\mathcal{Z}_3$,$\mathcal{Z}_4$ and extra "dark" gauge symmetries.Comment: 8 pages, 3 figures, version published in Phys. Lett.

"Secret" neutrino interactions

We review the information about a potentially strong non-standard four-neutrino interaction that can be obtained from available experimental data. By using LEP results and nucleosynthesis data we find that a contact four-fermion neutrino interaction that involve only left-handed neutrinos or both left-handed and right-handed neutrinos cannot be stronger than the standard weak interactions. A much stronger interaction involving only right-handed neutrinos is still allowed.Comment: 12 pages, 2 figures, latex with ws-p8-50x6-00.cls, Talk presented in "Neutrino Mixing", in honour of Samoil Bilenky's 70th Birthday, Torino, March 199

Re-opening dark matter windows compatible with a diphoton excess

We investigate a simple setup in which an excess in the di-photon invariant mass distribution around $750$ GeV, as seen by the ATLAS and CMS collaborations, is originated through a pair of collimated photon pairs. In this framework a scalar state $s$ decays into two light pseudo-Goldstone bosons $a$, each of which subsequently decays into a pair of collimated photons which are misidentified as a single photon. In a minimal context of spontaneous symmetry breaking, we show that coupling a complex scalar field $\Phi=(s+ia)/\sqrt{2}$ to a fermionic dark matter candidate $\chi$, also responsible for generating its mass, allows for the correct relic density in a large region of the parameter space, while not being excluded by the direct or indirect detection experiments. Moreover, the correct relic abundance can naturally co-exist with a relatively large width for the resonant field $s$.Comment: 29 pages, 11 figures, new references adde