Search

We study a class of models in which the particle that constitutes dark matter arises as a composite state of a strongly coupled hidden sector. The hidden sector interacts with the Standard Model through the neutrino portal, allowing the relic abundance of dark matter to be set by annihilation into final states containing neutrinos. The coupling to the hidden sector also leads to the generation of neutrino masses through the inverse seesaw mechanism, with composite hidden sector states playing the role of the singlet neutrinos. We focus on the scenario in which the hidden sector is conformal in the ultraviolet, and the compositeness scale lies at or below the weak scale. We construct a holographic realization of this framework based on the Randall-Sundrum setup and explore the implications for experiments. We determine the current constraints on this scenario from direct and indirect detection, lepton flavor violation and collider experiments and explore the reach of future searches. We show that in the near future, direct detection experiments and searches for $\mu \rightarrow e$ conversion will be able to probe new parameter space. At colliders, dark matter can be produced in association with composite singlet neutrinos via Drell Yan processes or in weak decays of hadrons. We show that current searches at the Large Hadron Collider have only limited sensitivity to this new production channel and we comment on how the reconstruction of the singlet neutrinos can potentially expand the reach., Comment: 53 pages, 21 figures, 4 tables; v2: references added

We introduce the Anarchic Axion, a class of axion models which solves the Strong CP problem within current nEDM constraints with a lighter than usual QCD axion, thus populating new parameter space that ongoing and future experiments target. The Anarchic Axion is driven light by a soft breaking of the Peccei-Quinn symmetry, which also predicts a residual neutron electric dipole moment. We introduce a novel measure to quantify the tuning required for large deviations from the usual QCD axion band. In addition to motivating searches for unusually light axions, this work establishes a new target for axion effective field theory., Comment: 5+2 pages. 3 figures. 1 table. v2: minor comments added, version published in Phys. Rev. D Letters

We study a class of models in which the Standard Model (SM) and dark matter (DM) belong to a conformal/scale-invariant theory at high energies. Scale invariance is spontaneously broken at scale $f$, giving rise to a dilaton as the corresponding Goldstone boson. In the low energy theory, we assume that DM interacts with the SM solely through the dilaton portal, which is suppressed by the conformal breaking scale $f$. For $f\gg{\rm TeV}$, the portal interactions are extremely weak, resulting in DM not being in thermal equilibrium with the SM. Thus, ultraviolet freeze-in production of DM occurs through the dilaton portal, being most effective at the maximum temperature of the SM bath. The temperature evolution is greatly impacted by the reheating dynamics, which we parametrize using a general equation of state $w$ and temperature at the end of reheating $T_{\rm rh}$. We analyze the implications of the reheating dynamics for DM production in this framework and identify regions of parameter space that result in the observed DM relic abundance for a wide range of DM masses and reheating temperatures for scalar, vector, or fermion DM., Comment: v2: 13 pages and 7 figures, matches the published version in PRD

We outline a scenario where both the Higgs and a complex scalar dark matter candidate arise as the pseudo-Nambu-Goldstone bosons of breaking a global $SO(7)$ symmetry to $SO(6)$. The novelty of our construction is that the symmetry partners of the Standard Model top-quark are charged under a hidden color group and not the usual $SU(3)_c$. Consequently, the scale of spontaneous symmetry breaking and the masses of the top partners can be significantly lower than those with colored top partners. Taking these scales to be lower at once makes the model more natural and also reduces the induced non-derivative coupling between the Higgs and the dark matter. Indeed, natural realizations of this construction describe simple thermal WIMP dark matter which is stable under a global $U(1)_D$ symmetry. We show how the Large Hadron Collider along with current and next generation dark matter experiments will explore the most natural manifestations of this framework., Comment: 33 pages, 14 figures and 1 table; v2 Minor updates to indirect detection analysis, published version

In this paper, we explore the possibility that a light dilaton can be the first sign of new physics at the LHC. The dilaton could emerge in approximate scale invariant UV completions of the SM as the Goldstone boson associated with the spontaneous breaking of the scale invariance. We study in detail the phenomenology of the dilaton at the LHC in the mass range of [$10-300$] GeV including the case where the dilaton can mix with the SM Higgs boson, leading to an interesting interplay between direct and indirect constraints. A possibility that the dilaton acts as a portal to a dark sector is also considered. As a minimal realization, the dark sector includes a dark photon lighter than the dilaton implying sizeable missing energy signatures. Several simplified benchmark models that can encode different UV completions are discussed, for which we scrutinize the current and future LHC reach., Comment: 32 pages, 7 figures and 3 tables; v2 matches JHEP published version

We consider a strongly interacting twin Higgs (SITH) model where an ultraviolet completion of twin Higgs mechanism is realized by a strongly coupled approximately scale invariant theory. Besides the Standard Model (SM) and twin sectors, the low energy effective theory contains a relatively light scalar called a dilaton --- the pseudo Goldstone boson of spontaneously broken scale invariance. The dilaton provides a unique portal between the SM and twin sectors whose phenomenology could provide an important probe of the twin Higgs mechanism. As a concrete example, we consider a holographic twin Higgs model where the role of the dilaton is played by the radion. The phenomenology of this model is fully determined by a few parameters and our analysis concludes that at the HL-LHC (14 TeV) and HE-LHC (27 TeV) with 3000/fb most of the natural parameter space can be probed., Comment: 29 pages, 8 figures

We consider the collider signals arising from kinetic mixing between the hypercharge gauge boson of the Standard Model and its twin counterpart in the Mirror Twin Higgs model, in the framework in which the twin photon is massive. Through the mixing, the Standard Model fermions acquire charges under the mirror photon and the mirror Z boson. We determine the current experimental bounds on this scenario, and show that the mixing can be large enough to discover both the twin photon and the twin Z at the LHC, or at a future 100 TeV hadron collider, with dilepton resonances being a particularly conspicuous signal. We show that, in simple models, measuring the masses of both the mirror photon and mirror Z, along with the corresponding event rates in the dilepton channel, overdetermines the system, and can be used to test these theories., Comment: 28 pages, 9 figures; Updated to published version

The Twin Higgs mechanism keeps the scalar sector of the Standard Model (SM) natural while remaining consistent with the non-observation of new colored particles at the Large Hadron Collider (LHC). In this construction the heavy twin Higgs boson provides a portal between the SM particles and the twin sector, but is quite challenging to discover at colliders. In the Fraternal Twin Higgs setup, where light twin quarks are absent, we study a novel discovery channel for the heavy twin Higgs boson by considering its decay to a pair of light Higgs bosons, one of which subsequently decays to glueball states in the twin sector, leading to displaced vertex signatures. We estimate the sensitivity of existing LHC searches in this channel, and assess the discovery potential of the high luminosity (HL) LHC. We show that the glueballs probed by these searches are outside the sensitivity of existing searches for exotic decays of the light Higgs boson. In addition, we demonstrate that the displaced signals we consider probe a region of heavy Higgs masses beyond the reach of prompt signals. We also comment on the possibility of probing the input parameters of the microscopic physics and providing a way to test the Twin Higgs mechanism with this channel., Comment: 27 pages, 9 figures, v2: references updated, minor changes

We consider Mirror Twin Higgs models in which the breaking of the global symmetry is realized linearly. In this scenario, the radial mode in the Higgs potential is present in the spectrum, and constitutes a second portal between the twin and SM sectors. We show that a study of the properties of this particle at colliders, when combined with precision measurements of the light Higgs, can be used to overdetermine the form of the scalar potential, thereby confirming that it possesses an enhanced global symmetry as dictated by the Twin Higgs mechanism. We find that, although the reach of the LHC for this state is limited, future linear colliders will be able to explore a significant part of the preferred parameter space, allowing the possibility of directly testing the Twin Higgs framework., Comment: 20 pages plus references and appendix

In this work we investigate the observability of Inert Doublet Model scalars at the LHC operating at the center of mass energy of 14 TeV. The signal production process is $pp \to AH^\pm \to ZHW^{\pm}H$ leading to two different final states of $\ell^+\ell^-Hjj H$ and $\ell^+\ell^-H\ell^\pm\nu H$ based on the hadronic and leptonic decay channels of the W boson. All the relevant background processes are considered and an event selection is designed to distinguish the signal from the large Standard Model background. We found that signals of the selected search channels are well observable at the LHC with integrated luminosity of 300 fb$^{-1}$., Comment: v2: 10 pages, 9 figures and 9 tables

We investigate the phenomenology of the light charged and neutral scalars in Inert Doublet Model at future $e^+ e^-$ colliders with center of mass energies of 0.5 and 1 TeV, and integrated luminosity of 500~fb$^{-1}$. The analysis covers two production processes, $e^{+}e^{-} \rightarrow H^{+}H^{-}$ and $e^{+}e^{-}\rightarrow AH$, and consists of signal selections, cross section determinations as well as dark matter mass measurements. Several benchmark points are studied with focus on $H^{\pm} \rightarrow W^{\pm}H$ and $A \rightarrow ZH$ decays. It is concluded that the signal will be well observable in different final states allowing for mass determination of all new scalars with statistical precision of the order of few hundred MeV., Comment: 29 pages, 12 figures and 21 tables. v2: title is modified, some discussion and references added. v3: few minor changes and matches the version to appear in JHEP

We investigate Lepton Flavor Violation (LFV) in the general extension of the Standard Model parametrized by the gauge invariant operators of dimension-6. We discuss 3-body charged lepton decays and decay of $Z$ boson to lepton pair and compare the obtained analytical expression with the current experimental results. We derive the numerical bounds on the size of the Wilson coefficients parameterizing the allowed size of New Physics effects., Comment: Contribution to Rencontres de Moriond EW 2014 proceedings

We study lepton flavor observables in the Standard Model (SM) extended with all dimension-$6$ operators which are invariant under the SM gauge group. We calculate the complete one-loop predictions to the radiative lepton decays $\mu\to e\gamma$, $\tau \to \mu \gamma$ and $\tau\to e\gamma$ as well as to the closely related anomalous magnetic moments and electric dipole moments of charged leptons, taking into account all dimension-$6$ operators which can generate lepton flavor violation. Also the 3-body flavor violating charged lepton decays $\tau^\pm \to \mu^\pm \mu^+ \mu^-$, $\tau^\pm\to e^\pm e^+ e^- $, $\tau^\pm \to e^\pm \mu^+ \mu^- $, $\tau^\pm \to \mu^\pm e^+ e^- $, $\tau^\pm \to e^\mp \mu^\pm \mu^\pm$, $\tau^\pm \to \mu^\mp e^\pm e^\pm $ and $\mu^\pm \to e^\pm e^+ e^-$ and the $Z^0$ decays $Z^0\to\ell_i^+\ell_j^-$ are considered, taking into account all tree-level contributions., Comment: 33 pages, 7 figures, misprints corrected, references added

We investigate the possibility of lepton flavor violation in the decays $\mu\to e\gamma$, $\tau \to \mu\gamma$ and $\tau \to e\gamma$ as well as electric dipole moment and anomalous magnetic moment of charged leptons in the extension of the Standard Model with the most general set of gauge-invariant operators up to dimension 6., Comment: Contribution to Rencontres de Moriond EW 2013 proceedings

It has recently been shown that by measuring the transverse polarizations of the final particles in $\mu^- \to e^- e^+ e^-$, it is possible to extract information on the phases of the effective couplings leading to this decay. We examine this possibility within the context of R-parity violating Minimal Supersymmetric Standard Model (MSSM) in which the $\mu^- \to e^- e^+e^-$ process can take place at a tree level. We demonstrate how a combined analysis of the angular distribution of the emitted positrons and their transverse polarization can determine the CP-violating phases of the trilinear R-parity violating Yukawa couplings., Comment: 21 pages, 2 figures; v2: A discussion on the feasibility of measuring the transverse polarization added