High Energy Scale Research Articles

Neutrinos: Theoretical Aspects

Neutrino physics is a vibrant field of research, ignited by the experimental discoveries of neutrino masses and mixings, and by the quest to understanding their theoretical implications. We shall cover some theoretical and phenomenological aspects of this field, stemming from both recent and time-honoured research areas. In particular, we shall focus on (1) the status of the standard three-neutrino framework, (2) the nearby theory landscape, (3) neutrinos as a bridge to avor physics and (4) neutrinos as a bridge to high energy and mass scales.

A cosmological Higgs collider

The quantum fluctuations of the Higgs field during inflation could be a source of primordial density perturbations through Higgs-dependent inflaton decay. By measuring primordial non-Gaussianities, this so-called Higgs-modulated reheating scenario provides us a unique chance to probe Higgs interactions at extremely high energy scale, which we call the Cosmological Higgs Collider (CHC). We realize CHC in a simple scenario where the inflaton decays into Higgs-portal scalars, taking account of the decay of the Higgs fluctuation amplitude after inflation. We also calculate the CHC signals of Standard Model particles, namely their imprints in the squeezed bispectrum, which can be naturally large. The concept of CHC can be straightforwardly generalized to cosmological isocurvature colliders with other types of isocurvature perturbations.

Lattice models that realize Zn -1 symmetry-protected topological states for even n

Higher symmetries can emerge at low energies in a topologically ordered state with no symmetry, when some topological excitations have very high-energy scales while other topological excitations have low energies. The low-energy properties of topological orders in this limit, with the emergent higher symmetries, may be described by higher symmetry-protected topological order. This motivates us, as a simplest example, to study a lattice model of ${\mathbb{Z}}_{n}$-1 symmetry-protected topological (1-SPT) states in $3+1$ dimensions for even $n$. We write an exactly solvable lattice model and study its boundary transformation. On the boundary, we show the existence of anyons with nontrivial self-statistics. For the $n=2$ case, where the bulk classification is given by an integer $m$ mod 4, we show that the boundary can be gapped with double-semion topological order for $m=1$ and toric code for $m=2$. The bulk ground-state wave-function amplitude is given in terms of the linking numbers of loops in the dual lattice. Our construction can be generalized to arbitrary 1-SPT protected by finite unitary symmetry.

Producing high intensity muon, antiproton beams and related physical researches in the HIAF accelerators

The high intensity frontier in particle physics would reveal physics beyond standard model, and is one of the most sensitive probing tools for particle physics at very high energy scales. In this paper, the high intensity frontier in particle physics is reviewed from the perspective of muon and antiproton physics and the experiments like charged lepton flavor violation are summarized. The possible utilization of HIAF accelerators in muon electron conversion searching and ultra-high precision measurement of muon anomalous magnetic moment is demonstrated. The preliminary analysis considering solely the signal statistics indicates that the muon and antiproton beams produced by the experimental platform of the HIAF accelerators would be quite competitive compared to the available beams around the world. By employing HIAF accelerators, the upper limit of muon electron conversion branching ratio could be pushed to the order of 10−19, and the measurement of muon anomalous magnetic moment would be potentially improved to the precision of 0.07 ppm.

On the inflationary massive field with a curved field manifold

Massive fields during inflation provide an interesting opportunity to test new physics at very high energy scales. Meanwhile in fundamental realizations, the inflationary field space typically has a curved geometry, which may leave detectable imprints in primordial observables. In this paper we study an extension of quasi-single field inflation where the inflaton and the massive field belong to a curved field manifold. Because of the nontrivial field space curvature, the massive field here can get significant mass corrections of order the Hubble scale, thus the quasi-single field predictions on primordial non-Gaussianity are affected. We derive the same result in an equivalent approach by using the background effective field theory of inflation, where a dimension-6 operator is identified to play an important role and its cutoff scale is associated with the curvature scale of the field space. In addition, due to the slow-roll evolution of the inflaton, this type of mass correction has intrinsic time-dependence. Consequently, the running mass modifies the scaling behaviour in the squeezed limit of the scalar bispectrum, while the resulting running index measures the curvature of the internal field space. Therefore the minimal setup of a massive field within curved field space during inflation may naturally lead to new observational signatures of the field space geometry.

QCD corrections in Standard Model EFT fits to WZ and WW production

We investigate the role of anomalous gauge boson and fermion couplings on the production of $WZ$ and $W^+W^-$ pairs at the LHC to NLO QCD in the Standard Model effective field theory, including dimension-6 operators. Our results are implemented in a publicly available version of the POWHEG-BOX. We combine our $WZ$ results in the leptonic final state $e\nu \mu^+\mu^-$ with previous $W^+W^-$ results to demonstrate the numerical effects of NLO QCD corrections on the limits on effective couplings derived from ATLAS and CMS 8 and 13 TeV differential measurements. Our study demonstrates the importance of including NLO QCD SMEFT corrections in the $WZ$ analysis, while the effects on $WW$ production are smaller. We also show that the $\mathcal{O}(1/\Lambda^4)$ contributions dominate the analysis, where $\Lambda$ is the high energy scale associated with the SMEFT.

Modified fermion tunneling radiation of Demianski–Newman black hole at higher energy scales

It is suggested that the dispersion relation might be corrected at higher energy scales and lead to the deformed Hamilton–Jacobi equation. In this paper, we use the correction to investigate the fermion tunneling radiation for Demianski–Newman black hole spacetime, and the result shows that the corresponding Hawking temperature and the black hole entropy are related to the angular parameters of the black hole coordinates.

Resolving the van Dam-Veltman-Zakharov and strong coupling problems in massive gravity and bigravity

As is well known, both massive gravity and bigravity exhibit the linear van Dam-Veltman-Zakharov (vDVZ) discontinuity that is cured classically by the nonlinear Vainshtein mechanism due to certain low scale strongly coupled interactions. Here we show how both the vDVZ and strong coupling problems can be removed by embedding 4D covariant massive gravity into a certain 5D warped geometry. The 4D theory is a nonlinear strongly coupled massive gravity, that is being coupled to a 5D bulk theory that generates a bulk graviton mass via a one loop diagram. This induced mass leads to an additional 4D kinetic term for the 4D longitudinal mode, even on flat space. Due to this kinetic term the 4D massive theory becomes weakly coupled all the way up to a high energy scale set by the bulk cosmological constant. The same effect leads to a suppression of the interactions of the 4D longitudinal mode with a 4D matter stress-tensor, thus removing the vDVZ discontinuity. The proposed mechanism has a pure 4D holographic interpretation: a 4D nonlinear massive gravity mixes to a non-conserved symmetric tensor of a 4D CFT that has a cutoff; the latter mixing generates a large kinetic term for the longitudinal mode, and this makes the longitudinal mode be weakly coupled to a matter stress-tensor, and weakly self-coupled, all the way up to the scale of the 4D CFT cutoff.

Effects of universal extra dimensions on top-quark electromagnetic interactions

Universal extra dimensions, presumably observable at some high-energy scale, would modify low-energy observables, being particularly relevant for physical processes forbidden at tree level by the Standard Model. We address the Kaluza–Klein contributions from the 5-dimensional Standard Model to the anomalous magnetic moment and to branching ratios of electromagnetic decays of the top quark. In accordance with present bounds on the compactification scale, contributions to both quantities are found to be at least 3 orders of magnitude below Standard-Model predictions.

Dark matter as Planck relics without too exotic hypotheses

The idea that dark matter could be made of stable relics of microscopic black holes is not new. In this article, we revisit this hypothesis, focusing on the creation of black holes by the scattering of trans-Planckian particles in the early Universe. The only new physics required in this approach is an unusually high-energy scale for inflation. We show that dark matter emerges naturally and we study the question of fine-tuning. We finally give some lines of thoughts for a possible detection.

Gravitational waves as a probe of left-right symmetry breaking

Left-right symmetry at high energy scales is a well-motivated extension of the Standard Model. In this paper we consider a typical minimal scenario in which it gets spontaneously broken by scalar triplets. Such a realization has been scrutinized over the past few decades chiefly in the context of collider studies. In this work we take a complementary approach and investigate whether the model can be probed via the search for a stochastic gravitational wave background induced by the phase transition in which SU(3)C × SU(2)L × SU(2)R × U(1)B−L is broken down to the Standard Model gauge symmetry group. A prerequisite for gravitational wave production in this context is a first-order phase transition, the occurrence of which we find in a significant portion of the parameter space. Although the produced gravitational waves are typically too weak for a discovery at any current or future detector, upon investigating correlations between all relevant terms in the scalar potential, we have identified values of parameters leading to observable signals. This indicates that, given a certain moderate fine-tuning, the minimal left-right symmetric model with scalar triplets features another powerful probe which can lead to either novel constraints or remarkable discoveries in the near future. Let us note that some of our results, such as the full set of thermal masses, have to the best of our knowledge not been presented before and might be useful for future studies, in particular in the context of electroweak baryogenesis.

Gravitational waves from first-order phase transition in a simple axion-like particle model

We consider a gauge-singlet complex scalar field Φ with a global U(1) symmetry that is spontaneously broken at some high energy scale fa. As a result, the angular part of the Φ-field becomes an axion-like particle (ALP) . We show that if the Φ-field has a non-zero coupling κ to the Standard Model Higgs boson, there exists a certain region in the parameter space where the global U(1) symmetry-breaking induces a strongly first order phase transition, thereby producing stochastic gravitational waves that are potentially observable in current and future gravitational-wave detectors. In particular, we find that future gravitational-wave experiments such as TianQin, BBO and Cosmic Explorer could probe a broad range of the energy scale 103 GeV ≲ fa ≲ 108 GeV, independent of the ALP mass. Since all the ALP couplings to the Standard Model particles are proportional to inverse powers of the energy scale fa (up to model-dependent \U0001d4aa(1) coefficients), the gravitational-wave detection prospects are largely complementary to the current laboratory, astrophysical and cosmological probes of the ALP scenarios.

Flash evaporation intensified by microwave energy and performance analysis

A novel microwave flash evaporation (MFE) system is presented in this paper for the first time, which is expected to solve the inherent problems of conventional flash evaporation (CFE) system, such as high energy consumption, scaling, and long stages etc. In order to demonstrate the performance of such a novel system, some single factor experiments have been carried out by using water as experimental material, and the influence of parameters such as microwave power, initial temperature, and liquid flow rate have been studied. The results show that the evaporation quantity increases with the increase of microwave power, flow rate, and initial temperature. Under experimental conditions, the better operation condition is achieved at flow-rate of 40 L/h, initial liquid temperature of 50 °C, and microwave power of 1.35 kW, the evaporation quantity in the case of MFE is as high as 1.35 L in 20 min, but it is only 0.74 L in 20 min for CFE. The enhanced performance of MFE system is shown by comparing with the CFE system under the same conditions. Moreover, the energy efficiency is calculated and represented by a dimensionless parameter Gain Output Ratio (GOR), and the maximum energy efficiency for MSF system is about 79.38% at the better operation condition.

Holographic inflation

We apply the holographic principle at the early universe, obtaining an inflation realization of holographic origin. Such a consideration has equal footing with its well-studied late-time application, and moreover the decrease of the horizons at early times naturally increases holographic energy density at inflationary scales. Taking as Infrared cutoff the particle or future event horizons, and adding a simple correction due to the Ultraviolet cutoff, whose role is non-negligible at the high energy scales of inflation, we result in a holographic inflation scenario that is very efficient in incorporating inflationary requirements and predictions. We first extract analytically the solution of the Hubble function in an implicit form, which gives a scale factor evolution of the desired e-foldings. Furthermore, we analytically calculate the Hubble slow-roll parameters and then the inflation-related observables, such as the scalar spectral index and its running, the tensor-to-scalar ratio, and the tensor spectral index. Confronting the predictions with Planck 2018 observations we show that the agreement is perfect and in particular deep inside the 1σ region.

Implementing the inverse type-II seesaw mechanism into the 3-3-1 model

After the LHC is turning on and accumulating more data low scale seesaw mechanisms for small neutrino masses with signature manifesting at TeV scale are gaining more and more attention once they provide neutrino masses at sub-eV scale and can be probed at the LHC. In this regard inverse seesaw mechanism arises as an interesting candidate for performing such proposal. This mechanism is a kind of counterpart of canonical mechanism which requires lepton number be violated explicitly at high energy scale while the inverse one requires the contrary, that lepton number be violated explicitly at low energy scale. There are three ways of performing canonical seesaw mechanism. For each one of it there is its inverse counterpart. Here we restrict our investigation to the study of the inverse type II seesaw mechanism. Our main goal is to implement the mechanism into the 3-3-1 model with right-handed neutrinos, but first we revisit the main ideas and consequences of the inverse type I and II seesaw mechanisms when incorporated into the standard model. In regard to the 3-3-1 model, as interesting result, we show that the mechanism may provide small masses to both the standard neutrinos as well as to the right-handed ones. As phenomenological aspect, its best signature are the doubly charged scalars which are sextet by the 3-3-1 symmetry. We investigate their production at the LHC through the process σ(pp→Z⁎,γ⁎,Z′→Δ++Δ−−) and their signal through four leptons final state decay channel.

Nuclear dipole response in the finite-temperature relativistic time-blocking approximation

The radiative neutron capture reaction rates of the r-process nucleosynthesis are immensely affected by the microscopic structure of the low-energy spectra of compound nuclei. The relativistic (quasiparticle) time blocking approximation (R(Q)TBA) has successfully provided a good description of the low-energy strength, in particular, the strength associated with pygmy dipole resonance, describing transitions from and to the nuclear ground state. The finite-temperature generalization of this method is designed for thermally excited compound nuclei and has the potential to enrich the fine structure of the dipole strength, especially in the low-energy region. The finite-temperature RTBA equations are derived using the Matsubara Green's function formalism. We show that with the help of a temperature-dependent projection operator on the subspace of the imaginary time it is possible to reduce the Bethe-Salpeter equation for the nuclear response function to a single frequency variable equation also at finite temperatures. The approach is implemented self-consistently in the framework of quantum hadrodynamics and keeps the ability of connecting the high-energy scale of heavy mesons and the low-energy domain of nuclear medium polarization effects in a parameter-free way. The presented calculations of the dipole response within a self-consistent relativistic framework reveal that, although the Landau damping plays the leading role in the temperature evolution of the strength distribution, (i) at moderate temperatures the PVC effects remain almost as strong as at $T=0$ and (ii) at high temperatures they are tremendously reinforced because of the formation of the new collective low-energy modes. In the dipole channel, the latter effect is responsible for the "disappearance" of the high-frequency GDR or, in other words, brings the GDR to the low-energy domain.

Toy models of holographic duality between local Hamiltonians

Holographic quantum error correcting codes (HQECC) have been proposed as toy models for the AdS/CFT correspondence, and exhibit many of the features of the duality. HQECC give a mapping of states and observables. However, they do not map local bulk Hamiltonians to local Hamiltonians on the boundary. In this work, we combine HQECC with Hamiltonian simulation theory to construct a bulk-boundary mapping between local Hamiltonians, whilst retaining all the features of the HQECC duality. This allows us to construct a duality between models, encompassing the relationship between bulk and boundary energy scales and time dynamics.It also allows us to construct a map in the reverse direction: from local boundary Hamiltonians to the corresponding local Hamiltonian in the bulk. Under this boundary-to-bulk mapping, the bulk geometry emerges as an approximate, low-energy, effective theory living in the code-space of an (approximate) HQECC on the boundary. At higher energy scales, this emergent bulk geometry is modified in a way that matches the toy models of black holes proposed previously for HQECC. Moreover, the duality on the level of dynamics shows how these toy-model black holes can form dynamically.

50 mm-aperture Nd:LuAG ceramic nanosecond laser amplifier producing 10 J at 10 Hz.

The growth and laser amplifier performance of a large-aperture Nd:LuAG ceramic are reported. Using the vacuum sintering and high-temperature insostatic pressing (HIP) methods, three pieces of a 50 mm-aperture Nd:LuAG ceramic are fabricated and used as the gain medium in a diode-pumped nanosecond distributed active mirror amplifier chain (DAMAC). The energy storage capacity of large-aperture Nd:LuAG is investigated and compared with that of Nd:YAG. Energy amplification up to 10.3 J at 10 Hz is achieved, which, to the best of our knowledge, produces the highest peak power (1 GW) using Nd:LuAG. The excellent energy storage and extraction performance confirm the great potential of Nd:LuAG in high-energy scaling.

Strong- vs. weak-coupling pictures of jet quenching: a dry run using QED

High-energy partons (E ≫ T ) traveling through a quark-gluon plasma lose energy by splitting via bremsstrahlung and pair production. Regardless of whether or not the quark-gluon plasma itself is strongly coupled, an important question lying at the heart of philosophically different approaches to energy loss is whether the high-energy partons of an in-medium shower can be thought of as a collection of individual particles, or whether their coupling to each other is also so strong that a description as high-energy “particles” is inappropriate. We discuss some possible theorists’ tests of this question for simple situations (e.g. an infinite, non-expanding plasma) using thought experiments and first-principles quantum field theory calculations (with some simplifying approximations). The physics of in-medium showers is substantially affected by the Landau-Pomeranchuk-Midgal (LPM) effect, and our proposed tests require use of what might be called “next-to-leading order” LPM results, which account for quantum interference between consecutive splittings. The complete set of such results is not yet available for QCD but is already available for the theory of large-Nf QED. We therefore use large-Nf QED as an example, presenting numerical results as a function of Nfα, where α is the strength of the coupling at the relevant high-energy scale characterizing splittings of the high-energy particles.

Cosmological Probes of Supersymmetric Field Theory Models at Superhigh Energy Scales

The lack of positive results in searches for supersymmetric (SUSY) particles at the Large Hadron Collider (LHC) and in direct searches for Weakly Interacting Massive Particles (WIMPs) in the underground experiments may hint to a super-high energy scale of SUSY phenomena beyond the reach of direct experimental probes. At such scales the supergravity models based on Starobinsky inflation can provide the mechanisms for both inflation and superheavy dark matter. However, it makes the indirect methods the only way of testing the SUSY models, so that cosmological probes acquire the special role in this context. Such probes can rely on the nontrivial effects of SUSY physics in the early Universe, which are all model-dependent and thus can provide discrimination of the models and their parameters. The nonstandard cosmological features like Primordial Black Holes (PBHs) or antimatter domains in a baryon-asymmetric universe are discussed as possible probes for high energy scale SUSY physics.