We present the phenomenology of the charged Higgs boson $\textit{H}$ appearing in a fermionic dark matter model mediated by an additional scalar doublet. In order to couple the dark matter fermion to the scalar doublet, we introduce a U(1) gauge symmetry, which is spontaneously broken at electroweak symmetry breaking, resulting in a massive $\textit{Z′}$ gauge boson. Since $\textit{Z′}$ is generically light, the model is subject to strong constraints from electroweak precision observables. As a result, the charged Higgs boson mass allowed by current experimental bounds is typically light in this model, 110 GeV $\textit{<}$ $$ {m}_{H^{\pm }} $$ $\textit{<}$ 170 GeV. Such a light charged Higgs boson will be produced mainly through top-quark decays at the LHC. Additionally, depending on the mass of the additional neutral Higgs boson $\textit{h}$ and the dark gauge boson $\textit{Z′}$, the direct production channels $\textit{pp}$ → $\textit{H}$ $\textit{Z′}$ and $\textit{pp}$ → $\textit{H}$ $\textit{h}$ can become sizable. We investigate the corresponding signal processes at the LHC to assess the discovery potential for $\textit{H}$ . Current ATLAS and CMS searches for light charged Higgs bosons already impose further constraints on the model. We also discuss the implications of dark matter in relation to the charged Higgs boson phenomenology.

South Korea

Kyu Bae

Jinn-Ouk Gong

Dong-Won Jung

Kang Lee

Chaehyun Yu

Chan Park

Charged Higgs boson phenomenology in the dark $\textit{Z}$ mediated fermionic dark matter model

Realising $\textit{F}$ -term slow-roll inflation in supergravity is non-trivial due to the well-known $\textit{η}$-problem. The common strategy to solve the problem is to impose a shift symmetry on the Kähler potential, but this often leads to a negative potential in the large-field regime. To avoid negative potentials, an additional superfield called the stabiliser is usually added with a desired interaction. An alternative mechanism in supergravity, avoiding the use of a stabiliser superfield, was earlier proposed by two of us in the setup with a single chiral superfield having inflaton and goldstino amongst its field components. In this work, we extend that alternative mechanism to multi-superfield models of inflation, thereby providing a generic framework for embedding a wide class of single- and multi-field inflation models into supergravity. We illustrate our approach by several concrete examples of multi-field inflation and clarify the conditions required to avoid tachyonic instabilities during multi-field evolution. Our proposal significantly broadens the theoretical landscape of $\textit{F}$ -term inflation models in supergravity.

Japan

Russia

Sergei Ketov

Takahiro Terada

$\textit{F}$-term multi-field inflation in supergravity without stabiliser superfields

We show that the general vacuum states that respect the de Sitter symmetry, known as the $\textit{α}$-vacua, can introduce non-vanishing parity-violating tensor non-Gaussianities. This is due to the mixing by the Bogoliubov transformation of the positive and negative frequency modes of the Bunch-Davies vacuum. We calculate explicitly the bispectra of tensor perturbations and show that the amplitude can be exponentially enhanced for certain choices of the squeezing parameter $\textit{α}$ and the phase $\textit{ϕ}$ of the $\textit{α}$-vacua. We find a new shape for the parity-violating tensor bispectrum which peaks in the flattened configuration.

Maria Mylova

Taiwan

Misao Sasaki

New shape of parity-violating graviton non-Gaussianity

We investigate the mass range and the corresponding free-streaming length scale of dark matter produced non-thermally from decay of heavy objects which can be either dominant or sub-dominant at the moment of decay. We show that the resulting dark matter could be very light well below keV scale with a free-streaming length satisfying the Lyman-α constraints. We demonstrate two explicit examples for such light cold dark matter.

Ki-Young Choi

Junghoon Joh

Spain

Wan-Il Park

Osamu Seto

Light cold dark matter from non-thermal decay

We present a novel cosmological scenario that describes both inflation and dark matter. A concrete realization of our scenario is given based on a well-established particle physics model, where an axionlike field drives inflation until a potential barrier, which keeps a waterfall field at the origin, disappears to trigger a waterfall transition. Such a barrier makes the inflaton potential much flatter, improving significantly the naturalness and viability of the otherwise problematic setup adopted previously. The observed spectrum of the cosmic microwave background indicates that the inflationary Hubble scale, which is allowed to span a wide range, uniquely fixes the inflaton mass and decay constant. This raises an intriguing possibility of probing inflation via experimental searches for axionlike particles. Further, our model involves dark matter candidates including the inflaton itself. Also, for a complex waterfall field, we can determine cosmologically the Peccei-Quinn scale associated with the strong <math><mrow><mi>C</mi><mi>P</mi></mrow></math> problem.

Kwang Sik Jeong

Axion-driven hybrid inflation over a barrier

This exploratory study computes two-photon decay widths of pseudo-scalar (
					) and scalar (
					) charmonium using two ensembles of 
					 twisted mass lattice QCD gauge configurations. The simulation is performed using two lattice ensembles with lattice spacings 
					 fm with size 
					 and 
					 fm with size 
					. The decay widths for the two charmonia are obtained within the expected ballpark, but are however smaller than the experimental ones. Possible reasons for these discrepancies are discussed.
				

China

Ying Chen

Ming Gong

Ning Li

Chuan Liu

Yu-Bin Liu

Zhaofeng Liu

Jian-Ping Ma

Yu Meng

Chao Xiong

Ke-Long Zhang

Lattice study of two-photon decay widths for scalar and pseudo-scalar charmonium This work is supported in part by the National Science Foundation of China (NSFC) (11335001, 11275169, 11405178, 11935017, 11575196, 11875169, 11775229). It is also supported in part by the DFG and the NSFC (11261130311) through funds provided to the Sino-Germen CRC 110 symmetries and the Emergence of Structure in QCD. This work is also funded in part by National Basic Research Program of China (973 Program) (2015CB856700). M. Gong and Z. Liu are partially supported by the Youth Innovation Promotion Association of CAS (2013013). This work is also supported by the Scientific Research Program Funded by Shaanxi Provincial Education Department (19JK0391) andNatural Science Basic Research Plan in Shaanxi Province of China (2019JM-001)

We study the Wigner function for the inflationary tensor perturbation defined in the real phase space. We compute explicitly the Wigner function including the contributions from the cubic self-interaction Hamiltonian of tensor perturbations. Then we argue that it is no longer an appropriate description for the probability distribution in the sense that quantum nature allows negativity around vanishing phase variables. This comes from the non-Gaussian wavefunction in the mixed state as a result of the non-linear interaction between super- and sub-horizon modes. We also show that this is related to the explicit infrared divergence in the Wigner function, in contrast to the trace of the density matrix.

Min-Seok Seo

Quantum nature of Wigner function for inflationary tensor perturbations

We study the quantum mechanical evolution of the tensor perturbations during inflation with non-linear tensor interactions. We first obtain the Lindblad terms generated by non-linear interactions by tracing out unobservable sub-horizon modes. Then we calculate explicitly the reduced density matrix for the super-horizon modes, and show that the probability of maintaining the unitarity of the squeezed state decreases in time. The decreased probability is transferred to other elements of the reduced density matrix including off-diagonal ones, so the evolution of the reduced density matrix describes the quantum-to-classical transition of the tensor perturbations. This is different from the classicality accomplished by the squeezed state, the suppression of the non-commutative effect, which is originated from the quadratic, linear interaction, and also maintains the unitarity. The quantum-to-classical transition occurs within 5–10 e-folds, faster than the curvature perturbation.

Quantum non-linear evolution of inflationary tensor perturbations

We compute for general single-field inflation the intrinsic non-Gaussianity due to the self-interactions of the inflaton field in the squeezed limit. We recover the consistency relation in the context of the δN formalism, and argue that there is a particular field redefinition that makes the intrinsic non-Gaussianity vanishing, thus improving the estimate of the local non-Gaussianity using the δN formalism.

Guillem Domènech

Consistency relation and inflaton field redefinition in the δN formalism

We develop the path integral formalism for studying cosmological perturbations in multi-field inflation, which is particularly well suited to study quantum theories with gauge symmetries such as diffeomorphism invariance. We formulate the gauge fixing conditions based on the Poisson brackets of the constraints, from which we derive two convenient gauges that are appropriate for multi-field inflation. We then adopt the in-in formalism to derive the most general expression for the power spectrum of the curvature perturbation including the corrections from the interactions of the curvature mode with other light degrees of freedom. We also discuss the contributions of the interactions to the bispectrum.

United States

Hong Kong

Gary Shiu

Path integral for multi-field inflation