Boosted Event Topologies from TeV Scale Light Quark Composite Partners

We propose a new search strategy for quark partners which decay into a boosted Higgs and a light quark. As an example, we consider phenomenologically viable right handed up-type quark partners of mass $\sim 1$ TeV in composite pseudo-Nambu-Goldstone-boson Higgs models within the context of flavorful naturalness. Our results show that $S/B > 1$ and signal significance of $\sim 7\sigma$ is achievable at $\sqrt{s} = 14$ TeV LHC with 35 $fb^{-1}$ of integrated luminosity, sufficient to claim discovery of a new particle. A combination of a multi-dimensional boosted Higgs tagging technique, kinematics of pair produced heavy objects and $b$-tagging serves to efficiently diminish the large QCD backgrounds while maintaining adequate levels of signal efficiency. We present the analysis in the context of effective field theory, such that our results can be applied to any future search for pair produced vector-like quarks with decay modes to Higgs and a light jet.Comment: 18 pages, 7 figures, 5 tables, v2: short discussion added in Sec. 2, references added, corresponds to version published in JHE

Light Non-degenerate Composite Partners at the LHC

We study the implications of a large degree of compositeness for the light generation quarks in composite pseudo-Nambu-Goldstone-boson Higgs models. We focus in particular on viable scenarios where the right-handed up-type quarks have a sizable mixing with the strong dynamics. For concreteness we assume the latter to be characterized by an SO(5)/SO(4) symmetry with fermionic resonances in the SO(4) singlet and fourplet representations. Singlet partners dominantly decay to a Higgs boson and jets. As no dedicated searches are currently looking for these final states, singlet partners can still be rather light. Conversely, some fourplet partners dominantly decay to an electroweak gauge boson and a jet, a signature which has been analyzed at the LHC. To constrain the parameter space of this scenario we have reinterpreted various LHC analyses. In the limit of first two generation degeneracy, as in minimal flavor violation or U(2)-symmetric flavor models, fourplet partners need to be relatively heavy, with masses above 1.8 TeV, or the level of compositeness needs to be rather small. The situation is rather different in models that deviate from the first two generation degeneracy paradigm, as the charm parton distribution functions are suppressed relative to the up quark ones. The right-handed charm quark can be composite and its partners being as light as 600 GeV, while the right-handed up quark needs either to be mostly elementary or to have its partners as heavy as 2 TeV. Models with fully composite singlet fermions are also analyzed, leading to similar conclusions. Finally, we consider the case where both the fourplet and the singlet states are present. In this case the bounds could be significantly weaken due to a combination of smaller production rates and the opening of new channels including cascade processes.Comment: 49 pages, 18 figure

Anarchic Yukawas and top partial compositeness: the flavour of a successful marriage

The top quark can be naturally singled out from other fermions in the Standard Model due to its large mass, of the order of the electroweak scale. We follow this reasoning in models of pseudo Nambu Goldstone Boson composite Higgs, which may derive from an underlying confining dynamics. We consider a new class of flavour models, where the top quark obtains its mass via partial compositeness, while the lighter fermions acquire their masses by a deformation of the dynamics generated at a high flavour scale. One interesting feature of such scenario is that it can avoid all the flavour constraints without the need of flavour symmetries, since the flavour scale can be pushed high enough. We show that both flavour conserving and violating constraints can be satisfied with top partial compositeness without invoking any flavour symmetry for the up-type sector, in the case of the minimal SO(5)/SO(4) coset with top partners in the four-plet and singlet of SO(4). In the down-type sector, some degree of alignment is required if all down-type quarks are elementary. We show that taking the bottom quark partially composite provides a dynamical explanation for the hierarchy causing this alignment. We present explicit realisations of this mechanism which do not require to include additional bottom partner fields. Finally, these conclusions are generalised to scenarios with non-minimal cosets and top partners in larger representations.Comment: 37 pages, 1 figure, v2: typos fixed, Eq. (3.44) added, version corresponds to published article in JHE

Aspects of Axion Phenomenology in a slice of AdS_5

Motivated by multi-throat considerations, we study the phenomenological implications of a bulk axion in a slice of AdS_5 with a large extra dimension: k~0.01 eV, kR > 1. In particular, we compare axion physics with a warped geometry to axions in flat compactifications. As in flat compactification scenarios, we find that the mass of the axion can become independent from the underlying Peccei-Quinn scale. Surprisingly, we find that in warped extra dimensions the axion's invisibility, cosmological viability, and basic phenomenology remain essentially unaltered in comparison to axions in flat compactifications.Comment: 25 pages, 9 figure

Indirect Detection of Kaluza-Klein Dark Matter from Latticized Universal Dimensions

We consider Kaluza-Klein dark matter from latticized universal dimensions. We motivate and investigate two different lattice models, where the models differ in the choice of boundary conditions. The models reproduce relevant features of the continuum model for Kaluza-Klein dark matter. For the model with simple boundary conditions, this is the case even for a model with only a few lattice sites. We study the effects of the latticization on the differential flux of positrons from Kaluza-Klein dark matter annihilation in the galactic halo. We find that for different choices of the compactification radius, the differential positron flux rapidly converges to the continuum model results as a function of the number of lattice sites. In addition, we consider the prospects for upcoming space-based experiments such as PAMELA and AMS-02 to probe the latticization effect.Comment: 25 pages, 9 figures, LaTeX. Final version published in JCA

High Spin-Wave Propagation Length Consistent with Low Damping in a Metallic Ferromagnet

We report ultra-low intrinsic magnetic damping in Co$_{\text{25}}$Fe$_{\text{75}}$ heterostructures, reaching the low $10^{-4}$ regime at room temperature. By using a broadband ferromagnetic resonance technique, we extracted the dynamic magnetic properties of several Co$_{\text{25}}$Fe$_{\text{75}}$-based heterostructures with varying ferromagnetic layer thickness. By estimating the eddy current contribution to damping, measuring radiative damping and spin pumping effects, we found the intrinsic damping of a 26\,nm thick sample to be $$\alpha_{\mathrm{0}} \lesssim 3.18\times10^{-4}$. Furthermore, using Brillouin light scattering microscopy we measured spin-wave propagation lengths of up to$(21\pm1)\,\mathrm{\mu m}$in a 26 nm thick Co$_{\text{25}}$Fe$_{\text{75}}$ heterostructure at room temperature, which is in excellent agreement with the measured damping.Comment: Updated Versio

String compactification, QCD axion and axion-photon-photon coupling

It is pointed out that there exist a few problems to be overcome toward an observable sub-eV QCD axion in superstring compactification. We give a general expression for the axion decay constant. For a large domain wall number $N_{DW}$, the axion decay constant can be substantially lowered from a generic value of a scalar singlet VEV. The Yukawa coupling structure in the recent $Z_{12-I}$ model is studied completely, including the needed nonrenormalizable terms toward realistic quark and lepton masses. In this model we find an approximate global symmetry and vacuum so that a QCD axion results but its decay constant is at the GUT scale. The axion-photon-photon coupling is calculated for a realistic vacuum satisfying the quark and lepton mass matrix conditions. It is the first time calculation of $c_{a\gamma\gamma}$ in realistic string compactifications: $c_{a\gamma\gamma}={5/3}-1.93\simeq -0.26$.Comment: 33 pages, 2 figures, JHEP format, some errors in the superpotential couplings are corrected and the following discussions are changed correspondingl