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The annual Theory Meeting on Particle Physics Phenomenology (KEK-PH2023) will be held at KEK between Nov 7th -10th. This meeting covers many topics in Particle Physics and Cosmology, from the Standard Model and models beyond the Standard Model to particle cosmology and astrophysics. We plan to discuss recent developments in modeling Physics Beyond the Standard Model with their phenomenological aspects and also learn about the latest results and status of various ongoing and planned experiments.
The meeting includes talks by invited speakers and short talks by participants. All the talks will be given in English. We aim to provide an opportunity, not only for experts but also for master/Ph.D course students, to learn recent developments in particle physics phenomenology and to activate intensive discussions.
(Please go through both KEK and workshop registrations.)
registration fee: 1,000JPY (please pay at the registration desk.)
Invited Speakers:
This workshop is supported by JSPS KAKENHI Grant Numbers JP22K21350, JP21H01086, and JP19H00689.
invited plenary talk
Many collider searches have attempted to detect the Higgs boson decaying to a photon and an invisible massless dark photon. For the branching ratio to this channel to be realistically observable at the LHC, there must exist new mediators that interact with both the standard model and the dark photon. In this talk, we present experimental and theoretical constraints on an extensive set of mediator models. We show that these constraints limit the Higgs branching ratio to a photon and a dark photon to be far smaller than the current sensitivity of collider searches.
The Froggatt-Nielsen (FN) mechanism is a compelling explanation for the hierarchical structures observed in the Yukawa couplings of charged leptons and quark mixing angles. In this mechanism, the above structures are realized by imposing different U(1) charges for each generation of fermions under a new U(1) flavor symmetry. So far, several FN charge assignments have been proposed in the literature where the charge assignments have typically been determined by hand. However, it is difficult to quantitatively determine which FN charge assignment is ``good'' in a systematic way. Besides, only a limited number of FN charge possibilities have been discussed. In this paper, we revisit choice of phenomenologically valid FN charges in the Standard Model with type-I seesaw mechamism and dimension five operator respectively in a Bayesian statistical approach.
Despite the longstanding assumption that neutrinos are massless, oscillation experiments have shown that they are, in fact, massive, and furthermore mix significantly. Constraints from other observations additionally indicate that these masses are very small compared to others in the Standard Model. A possible explanation is provided by the seesaw mechanism, wherein heavy intermediate particles suppress the masses of the Standard Model neutrinos. On the other hand, the unique dimension-five Weinberg-Operator provides a model-independent description of Majorana neutrino masses. Restrictions on its structure, and thus the mixing angles, are often induced via flavor symmetries. Furthermore, radiative running effects can significantly impact neutrino phenomenology due to the different scales involved in mass generation, neutrino creation, and detection mechanisms. In this work, we combine the above-mentioned paradigms, and consider the renormalization group equations (RGEs) of the Weinberg-Operator in flavor-nonuniversal gauge theories, such as the U(1){L\mu - L_\tau} extension of the Standard Model. We find that in such models, the new gauge bosons induce novel terms in the beta-function of the neutrino mass matrix at the one-loop level. These terms can raise the rank of the mass matrix even at the one-loop level, and generate up to three neutrino masses via RGE running only. We then derive the most general RGEs for the Weinberg-Operator and its mass eigenvalues, and discuss their origin. Furthermore, we provide formulae that verify straightforwardly whether the new terms discovered in this work appear in any theory of interest.
In a broad class of theories, the accumulation of ultralight dark matter (ULDM) with particles of mass $10^{-22}~\textrm{eV} < m_{\phi} < 1~\textrm{eV}$ leads to the formation of long-lived bound states known as boson stars. When the ULDM exhibits self-interactions, prodigious bursts of energy carried by relativistic bosons are released from collapsing boson stars in bosenova explosions. I will show the potential reach of terrestrial and space-based experiments for detecting transient signals of emitted relativistic bursts of scalar particles. The ULDM is coupled to photons, electrons, and gluons in an EFT framework, encapsulating a large space of theories. These bursts of relativistic scalars could be detected by a host of different detectors, such as a nuclear clock and space based interferometers.
We present an alternative production mechanism to thermal freeze-out for WIMP dark matter. In this model, GeV mass particles are shepherded into false vacuum pockets during a first order phase transition and trapped by a large mass gap. They form compact remnants that collapse into light primordial black holes, which subsequently regurgitates the initial constituent particles through Hawking evaporation. The WIMP mass density is nearly independent of the cross section and can constitue all of dark matter over a wide swath of parameter space. The dark matter particles in this unique model are responsible for creating the PBHs which later re-emit them.
We consider the positivity bounds for WIMP scalar dark matter with effective Higgs-portal couplings up to dimension-8 operators. Taking the superposed states for Standard Model Higgs and scalar dark matter, we show that the part of the parameter space for the effective couplings, otherwise unconstrained by phenomenological bounds, is ruled out by the positivity bounds on the dimension-8 derivative operators. We find that dark matter relic density, direct and indirect detection, and LHC constraints are complementary to the positivity bounds in constraining the effective Higgs-portal couplings. We also consider the relic density and positivity bounds for freeze-in scalar dark matter.
We revisit the relic density of Higgs portal dark matter (DM) with taking into account the Higgsplosion effect. We minimally extend the standard model by introducing a fermionic DM, and derive the Boltzmann equation with the DM annihilation channel of high-multiplicity final state. It is shown that the balance of Higgsplosion and Higgspersion effects derives a window function, and the final state multiplicity of DM annihilation is uniquely fixed as a function of Higgs self-coupling. Numerical calculation of the Boltzmann equation demonstrates the enhancement of effective reaction rate at the freeze out regime compared with well-studied DM scenario which annihilates into Higgs-pair.
We study the CP-even neutral Higgs boson decays $h \to c \bar{c}, b \bar{b}, b \bar{s}, \gamma \gamma, g g$ in the Minimal Supersymmetric Standard Model (MSSM) with general quark flavor violation (QFV) due to squark generation mixings, identifying the h as the Higgs boson with a mass of 125 GeV. We compute the widths of the h decays to $c \bar c, b \bar b, b \bar s (s \bar b)$ at full one-loop level. For the h decays to photon photon and gluon gluon we compute the widths at NLO QCD level. {\it For the first time}, we perform a systematic MSSM parameter scan for these widths including Supersymmetric (SUSY) QFV parameters respecting all the relevant constraints, i.e. theoretical constraints from vacuum stability conditions and experimental constraints, such as those from K- and B-meson data, electroweak precision data, and the 125 GeV Higgs boson data from recent LHC experiments, as well as the limits on SUSY particle masses from the LHC experiment. We also take into account the expected SUSY particle mass limits from the future HL-LHC experiment in our analysis. {\it In strong contrast to} the usual studies in the MSSM with quark flavor conservation (i.e. the MSSM with MFV), from the parameter scan we find that the deviations of these MSSM decay widths from the Standard Model (SM) values can be quite sizable and that there are significant correlations among these deviations. From the parameter scan, actually we have found the followings: \item DEV(c) and DEV(b) can be very large simultaneously: DEV(c) can be as large as $\sim \pm60\%$, and DEV(b) can be as large as $\sim \pm20\%$. \item DEV(b/c) can exceed $\sim +100\%$. \item $B(h^0 \to b s)$ can be as sizable as $\sim 0.15\%$ exceeding the ILC250+500+1000 sensitivity of $\sim 0.1\%$ at 4$\sigma$ signal significance. \item DEV($\gamma$) and DEV(g) can be sizable simultaneously: DEV($\gamma$) can be as sizable as $\sim \pm 1\%$, and DEV(g) can be as large as $\sim -7\%$ and $\sim +4\%$. \item DEV($\gamma$/g) can be as large as $\sim +8\%$ and $\sim -4\%$. \item There are significant correlations among these DEVs and BRbs: - There is a very strong correlation between DEV(b/c) and DEV(c). - There are significant correlations between $B(h^0 \to b s)$ and the deviations DEV(b), DEV(c), DEV(b/c). - There is a very strong correlation between DEV($\gamma$) and DEV(g). This correlation is due to the fact that the stop-scharm mixture loop contributions dominate the two DEVs. Here, DEV(X) = Gam(X)_MSSM/Gam(X)_SM - 1, DEV(X/Y) = [(Gam(X)/Gam(Y))_MSSM]/[(Gam(X)/Gam(Y))_SM] - 1 with Gam(X) = Gamma(h -> X X bar). All of these sizable deviations from the SM in the h decays are due to (i) large scharm-stop mixing and large scharm/stop involved trilinear couplings $T_{U23}, T_{U32}, T_{U33}$, (ii) large sstrange-sbottom mixing and large sstrange/sbottom involved trilinear couplings $T_{D23}, T_{D32}, T_{D33}$ and (iii) large bottom Yukawa coupling $Y_b$ for large $\tan\beta$ and large top Yukawa coupling $Y_t$. Such sizable deviations from the SM can be observed at high signal significance in future lepton colliders such as ILC, CLIC, CEPC, FCC-ee and MuC {\it even after} the failure of SUSY particle discovery at the HL-LHC. In case the deviation pattern shown here is really observed at the lepton colliders, then it would strongly suggest the discovery of QFV SUSY (the MSSM with general QFV). This work is based on collaboration with H. Eberl and E. Ginina (HEPHY, Vienna). This work is based on the following papers and contains substantial new findings: Phys. Rev. D 91 (2015) 015007 [arXiv:1411.2840 [hep-ph]], JHEP 1606 (2016) 143 [arXiv:1604.02366 [hep-ph]]], IJMP A34 (2019) 1950120 [arXiv:1812.08010 [hep-ph]], PoS(EPS-HEP2021) 594, 2021 [arXiv:2111.02713 [hep-ph], ILC White Paper for Snowmass 2021 [arXiv:2203.07622], PoS(ICHEP2022) 536, 2022 [arXiv:2211.07243 [hep-ph]].
A phenomenological study for determining the chirality structure in lepton-flavor-violating Higgs (hLFV) decays $h \to \tau\mu$ at the LHC is presented. We estimate the effects of the $\tau$ polarization in the analysis. We find that the sensitivity would be generically affected up to $ \pm4-6 \%$ in terms of the BR($h\to\tau\mu$) upper bound. We further study the benchmark scenarios, and demonstrate the sensitivity study for the chirality structure. We find that the two fully polarized cases, the $\tau_R$ and $\tau_L$ scenarios consistent with the recently reported excess, are distinguishable at $2\sigma$ level for 1000 fb$^{-1}$.
We study the quark sector of the universal seesaw model with SU(2)L × SU(2)R × U(1). This model aims to explain the mass hierarchy of the quark sector by introducing the corresponding vector-like quark (VLQ) for each ordinary quark with different hierarchical masses. We integrated out the VLQs one by one within the tree-level matching and also took into account the one-loop renormalization group (RG) effect. Then we aim to examine this quantum correction effect on the ordinary quarks' mass hierarchy.
Recently precise experiments have suggested that there is a discrepancy between theoretical and experimental values of muon g-2 based on the Standard Model (SM). It is known that the $$U(1)_{¥mu-¥tau}$$ gauge model can solve this. There are also studies that describe neutrino physics in terms of this symmetry-based model. For example, an analytical method has been proposed to give predictions for neutrino masses and Majorana phases that have not been experimentally determined based on models with $$U(1)_{¥mu-¥tau}$$ gauge symmetry and three right-handed neutrinos and a scalar field with $$U(1)_{¥mu-¥tau}$$ charge are added to the SM when the models have two zero components in the neutrino mass matrix and its inverse matrix (two zero texture or minor structure). The scalar fields added here take on different neutrino mass matrix structures for each behavior with respect to the $$SU(2)$$ gauge symmetry of the SM. The predictions obtained in the above analysis are subject to change as the neutrino oscillation experiments are refined and the experimental data are updated. We therefore performed the analysis using the latest data (NuFITv5.2) and confirmed the existence of a parameter region that is not excluded in the SM+right-handed neutrino + $$SU(2)$$ doublet scalar model, which was excluded in the previous study. On the other hand, focusing on the newly added $$U(1)_{¥mu-¥tau}$$ gauge symmetry, the simple SM+right-handed neutrino+ $$SU(2)$$ doublet scalar model is excluded due to Atomic Parity Violation, meson decay, and other limitations from cosmological observations. So the simple SM + right-handed neutrino + $$SU(2)$$ doublet scalar model is excluded. We therefore add a $$SU(2)$$ singlet scalar to this model which relaxes the restriction and found to allow us to place a limit on the ratio of the vacuum expectation values of the two types of scalar fields. This talk is based on the collaboration with Kento Asai, Shohei Okawa and Koji Tsumura.
We review recent progress on flavor physics from lattice QCD
Modular symmetry of flavors presents new aspects for mass hierarchy and CP violation. I introduce the general discussions and then present examples. of flavor model. These works are collaborated with S. Petcov.
The Standard Model fermions, quark leptons, have a generational structure with different masses (mass hierarchy) and mixing of generations (flavour mixing). The Standard Model only assigns parameters to these generational structures, but does not provide a theoretical explanation. In this study, we construct a flavour model that reproduces the generational structure of leptons using the S4 symmetry and the 3 Higgs doublet model(3HDM).
We investigate the twelve-dimensional gauge-Higgs unification models with an eight-dimensional coset space. For each model, we apply the coset space dimensional reduction procedure and examine the particle contents of the resulting four-dimensional theory. Then, some twelve-dimensional SO(18) gauge theories lead to models of the SO(10)\times U(1) grand unified theory in four dimensions, where fermions of the Standard Model appear in multiple generations along with scalars that may break the electroweak symmetry. The representations of the obtained scalars and fermions are summarized. (arXiv:2305.01421 [hep-ph])
We show that three open questions in particle physics and cosmology: the origin of neutrino mass, the identity of dark matter, and the origin of the baryon asymmetry of the universe can be explained simultaneously in the three-loop seesaw model proposed by Krauss, Nasri, and Trodden. We discuss the difficulty of successful leptogenesis with three right-handed neutrinos, and we propose a scenario with four right-handed neutrinos that satisfies all observational constraints. This scenario predicts a sleptonlike particle as light as a few hundreds GeV that can be probed by future collider experiments. This talk is based on the paper by O. Seto, T. Shindou, and T. Tsuyuki, Phys. Rev. D 108, 055002.
Discovery of the cancellation of O(Λ_QCD) renormalons in the QCD potential and quark pole masses improved dramatically our understanding of the quark masses, and furthermore, enabled precise determination of the fundamental physical constants, such as alpha_s(Mz), m_b, m_c and Vcb. Here, we aim to extend our understanding to the cancellation of O(Λ_QCD^2) renormalons, whose nature has not been studied so far. This cancellation is expected to occur between the pole quark masses and non-abelian (NA) potential, -CACFalpha_s^2/mr^2. We perform 3 analyses: (i) We calculate the O(Λ_QCD^2) renormalons of the NA potential in the LL approximation; (ii) Beyond LL approx., we confirm the cancellation of the O(Λ_QCD^2) renormalons at the level of 84-98%; (iii) After the cancellation (beyond LL approx.), the convergence and stability of the perturbative prediction in fact improve. These results indicate that the NA potential and pole masses each carry O(Λ_QCD^2) renormalons and that they cancel out in the heavy quarkonium system.
State-of-the-art (SoTA) deep learning models have achieved tremendous improvements in jet classification performance while analyzing low-level inputs, but their decision-making processes have become increasingly opaque. We introduce an analysis model (AM) that combines several phenomenologically motivated neural networks to circumvent the interpretability issue while maintaining high classification performance. Our methodology incorporates networks that scrutinize two-point energy correlations, generalizations of particle multiplicities via Minkowski functionals, and subjet momenta. Regarding top jet tagging at the hadronic calorimeter angular resolution scale, this AM performs comparably to the SoTA models (such as the ParticleTransformer and ParticleNet) in top jet tagging, at the hadronic calorimeter angular resolution scale. Subsequently, we explore the generator systematics of top versus QCD jet classification among event samples generated from different event generators (Pythia , Vincia , and Herwig ) using both SoTA models and our AM. Both models can accurately discern differences between simulations, enabling us to adjust the systematic differences via reweighting using classifier outputs. %classifier output-based reweighting. Furthermore, AMs equipped with partial high-level inputs (AM-PIPs) can identify relevant high-level features; if critical features are omitted from the AM inputs, reweighting is affected adversely. We also visualize our correction method, focusing on important variables in top jet tagging identified by the DisCo method.
We propose a method to explore the flavor structure of quarks and leptons with reinforcement learning, which is a type of machine learning. As a concrete model, we focus on the Froggatt-Nielsen model with U(1) flavor symmetry. By training neural networks on the U(1) charges of quarks and leptons, the agent finds 21 models to be consistent with experimentally measured masses and mixing angles of quarks and leptons. The normal ordering of neutrino masses is well fitted with the current experimental data in contrast to the inverted ordering. The method with reinforcement learning could be a new analytical technique to flavor physics, and we adapt this approach to modular flavor models also. The reference is arXiv:2304.14176 [hep-ph].
Since the nature of the Higgs boson remains undetermined, extended Higgs models with different Higgs potentials are proposed to explain phenomena beyond the Standard Model. In this presentation, we focus on the discrimination of extended Higgs models such as the Classical Scale Invariance model and the pseudo-Nambu-Goldstone model. By calculating the Higgs trilinear coupling at the 1-loop level, we discuss the feasibility of discriminating these Higgs models at future colliders such as the High-Luminosity LHC and the ILC.
Weakly interacting massive particles (WIMPs) with electroweak charges, such as the wino and the Higgsino, are one of the most natural candidates of the dark matter in the universe. In this paper, we study the search for WIMPs at future multi-TeV $\mu^+\mu^+$ colliders. We examine the direct production search of WIMPs through the mono-muon channel and the indirect search through the quantum correction on the elastic $\mu^+\mu^+$ M{\o}ller scattering. We find that the indirect search has an advantage over the direct search with sufficient luminosities, $\mathcal{O}(\text{ab}^{-1})$, and low systematic uncertainties, $\lesssim 0.3\,\%$, because the mass dependence of the indirect search is weaker than the direct production search. If the initial muon beams are polarized, the advantage becomes more evident. In particular, we show that the thermal mass target for the wino and the higgsino is detectable by the indirect search method for $\sqrt{s} = 6\,\text{TeV}$ and $2\,\text{TeV}$, respectively, with $80\,\%$ polarized beam and $0.1\,\%$ accuracy.
We study the process $\mu^- \mu^+ \to \nu_\mu \bar{\nu}_\mu t \bar{t} H$.
It is believed that QCD can not play major role to account for cosmological matter abundances observed in the Universe today including the baryon asymmetry of the Universe. However, in this talk, I would like to share a new picture of the thermal history called "QCD preheating". The dynamic motion of light quark condensate should have the potential to explosively produce the number densities for nucleon and antinucleon by nonadiabatic processes, similarly to the preheating induced by the nonadiabatic-varying vacuum. And this dynamic aspect of the QCD vacuum opens a new frontier to explore low-scale matter generation such as baryogenesis. Pursuing the QCD reheating era would also help deeply understanding the subatomic-scale physics in the thermal history of the Universe.
Electroweak baryogenesis is realized by the first order electroweak phase transition. In the extended Higgs models, it is caused by the relatively large scalar coupling constants. In such case, it is known that the Landau pole appears at a low scale, which is not compatible to the high energy experiments. By using the mass dependent beta function, in which threshold effects of the mass are naturally included, we will show that the scale of the Landau pole is much higher than that obtained by the previous studies.
In the Standard Model plus one complex scalar field, it is known that the signal of the new physics is suppressed when Higgs boson masses are degenerate. The introduction of higher dimensional operators is necessary to generate the CP symmetry violation associated with the realization of electroweak baryogenesis in this model. In this study, We analyze the contribution to the electron electric dipole moment (eEDM) produced through higher dimensional operators and show that the degenerate Higgs plays an important role in satisfying severe constraints from experiments. In addition, the possibility of baryon number generation in parameter regions consistent with eEDM experiments is evaluated.
We propose a new possibility of using the coherently enhanced neutrino pair emission to probe BSM light-mediator interactions between electron and neutrinos. With typical momentum transfer at the atomic $\mathcal O(1\,{\rm eV})$ scale, this process is extremely sensitive for the mediator mass range $\mathcal O(10^{-3}∼10^4)$\,eV. The sensitivity on the product of couplings with electron ($g_e$ or $y_e$) and neutrinos ($g_v$ or $y_ν$) can touch down to $|y_ey_v|<10^{-9}∼10^{−19}$ for a scalar mediator and $|g_eg_ν|<10^{-15}∼10^{−26}$ for a vector one, with orders of improvement from the existing constraints. Being a massless mediator, the photon can also mediate the atomic transition for non-zero neutrino electromagnetic properties. We show the neutrino pair emission can put competitive bounds on the neutrino magnetic moment and electric dipole operators but, most importantly, it can identifying their individual elements which are not possible by existing observations.
The scotogenic model is the Standard Model (SM) with Z2 symmetry and the addition of Z2 odd right-handed Majorana neutrinos and SU(2)L doublet scalar fields. We have extended the original scotogenic model by an additional Z2 odd singlet scalar field that plays a role in dark matter. In our model, the asymmetries of the lepton and Z2 odd doublet scalar are simultaneously produced through CP-violating right-handed neutrino decays. While the former is converted into baryon asymmetry through the sphaleron process, the latter is relaid to the DM density through the decay of SU(2)L doublet scalar that is named “asymmetric mediator”. In this way, we provide an extended scotogenic model that predicts the energy densities of baryon and dark matter being in the same order of magnitude, and also explains the lowenergy neutrino masses and mixing angles.
We propose an SU(5) GUT model extended with two additional pairs of 10 representation vector-like fermions. The CDF collaboration W boson mass anomaly is explained by using the VEV of a real SU(2)L triplet scalar coming from the 24 representation Higgs. The vector-like fermions are decomposed partly into vector-like quark doublets. Those vector-like quark doublets acquire mass from two sources; through the Yukawa interaction with the real SU(2)L triplet via a type-Ⅱ seesaw-like mechanism. And, they acquire mass from the 24 representation Higgs. We assume that the mass for the vector-like quark doublets is expressed in terms of the real triplets mass. By combining the constraints on the vector-like quark masses with those on the heavy Higgs boson masses, we can obtain the narrow allowed mass ranges for the vector-like quark doublet and the real triplet. Therefore, our model can be tested in searches for these particles in the near future. In addition, the two additional pairs of vector-like fermions allow the SM gauge couplings to unify successfully at MGUT ≈5.1×10^15 GeV. Our model is also testable by the future Hyper-Kamiokande experiment via the proton decay lifetime τ_p (p⟶π^0 e^+)<1.0×10^35 years.
We present a finite Landscape of Type IIB flux compactifications on toroidal orientifolds with h^{2, 1} = 1. Due to the S-duality and a duality in the complex-structure modulus space, the flux Landscape where we consider SUSY Minkowski solutions becomes finite with a fixed D3-brane charge of the three-form fluxes. Thus, we can define the probability associated with the modulus VEVs. In the context of modular flavor symmetry, the VEVs for the complex-structure modulus controls the flavor symmetry and its breaking. In our previous study, we only presented a finite Landscape on $T^6/(Z2 \times Z2')$. In this talk, we extend the previous discussion to other toroidal orientifolds that have h^{2, 1} = 1. The duality in the complex-structure modulus may not be the usual SL(2, Z) owing to the orbifold lattice. Indeed, we find a different Landscape with a certain congruence subgroup of SL(2, Z) is obtained, and the Landscape does not predict the usual elliptic points (fixed points that are elements of the fundamental region).
Light hypothetical particles can be produced in the core of supernovae. Their subsequent decays to neutrinos can produce a flux component with higher energies than the standard flux. We discuss limits on light particles decaying to neutrinos flavor-dependently from supernovae using this flux modification. In particular, we will obtain limits on heavy neutral leptons (HNLs) and ${\rm U(1)}_{L_\mu-L_\tau}$ gauge bosons from SN 1987A and future galactic supernovae.
Dark matter particles captured in neutron stars deposit their energy as heat. This DM heating effect can be observed only if it dominates over other internal heating effects in NSs. In this work, as an example of such an internal heating source, we consider the frictional heating caused by the creep motion of neutron superfluid vortex lines in the NS crust. The luminosity of this heating effect is controlled by the strength of the interaction between the vortex lines and nuclei in the crust, which can be estimated from the many-body calculation of a high-density nuclear system as well as through the temperature observation of old NSs. We show that both the temperature observation and theoretical calculation suggest that the vortex creep heating dominates over the DM heating. The vortex-nuclei interaction must be smaller than the estimated values by several orders of magnitude to overturn this.
The recently reported data from NANOGrav, EPTA, PPTA, and CPTA suggest the presence of stochastic gravitational waves in the nHz range. Here, we demonstrate that these can be explained by axion domain walls coupled to QCD. In this scenario, temperature-dependent biases, induced by non-perturbative effects of QCD, act on axion domain walls, causing them to collapse and emit gravitational waves. This study conducts lattice simulations of domain walls, considering the temperature dependence of the bias, to estimate the gravitational waves produced. Additionally, we discuss future prospects, such as accelerator searches for axions, predicted by this scenario.
We study the impact of renormalization group effects on QCD axion phenomenology. Focusing on the DFSZ model, we argue that the relevance of running effects for the axion couplings crucially depends on the scale where the heavier Higgs doublet, charged under the Peccei-Quinn symmetry, is integrated out. We study the impact of these effects on astrophysical and cosmological bounds as well as on the sensitivity of helioscopes experiments such as IAXO and XENONnT, showing that they can be sizable even in the most conservative case in which the two Higgs doublets remain as light as the TeV scale. We provide simple analytical expressions that accurately fit the numerical solutions of the renormalization group equations as a function of the mass scale of the heavy scalars.
We propose to use the nuclear spin excitation in the ferromagnetic A1 phase of the superfluid 3He for the axion dark matter detection. This approach is striking in that it is sensitive to the axion-nucleon coupling, one of the most important features of the QCD axion introduced to solve the strong CP problem. We also show that the combination of the squeezing of the final state with the Josephson parametric amplifier and the homodyne measurement can enhance the sensitivity. It turns out that this approach gives good sensitivity to the axion dark matter with the mass of 10^{-6} eV. We estimate the parameters of experimental setups, e.g., the detector volume and the amplitude of squeezing, required to reach the QCD axion parameter space.
Recent cosmological observations have pointed to the existence of ultralight axions. The introduction of at least three ultralight axions could mitigate the Hubble tension and S8 tensions and explain cosmic birefringence. Furthermore, dark energy and dark matter could also be ultralight axions. These multiple axions challenge string theory, especially the swampland conjecture, which is negative for these axions.
Massive fields can leave an imprint on primordial correlation functions or inflationary correlators with specific oscillatory features, which is dubbed the cosmological collider sig- nal. In this work, we analytically investigate effects of a time-dependent mass of a scalar field on inflationary correlators, extending previous numerical studies and implementing techniques developed in the cosmological bootstrap program. The time-dependent mass is in general induced by couplings to the slow-roll inflaton background and gives sizable effects especially in the case with non-derivative couplings. Approximating the time- dependence at the linear order, we obtain an analytic expression for mode functions of the massive scalar, based on which we derive analytic formulae for two-, three-, and four-point correlators with the tree-level exchange of the massive scalar. The obtained formulae are used to discuss phenomenological impacts on the power spectrum and bispectrum. In particular, we find that the scaling behavior of the bispectrum in the squeezed configu- ration, i.e., the cosmological collider signal, is modified by a time-dependent Bolzmann suppression and couplings between inflaton and the massive particle can be distinguished in principle by investigating the scaling behavior in detail.
The small field inflation (SFI) of Coleman-Weinberg (CW) type suffers from precise tuning of the initial inflaton field value to be away from the true vacuum one. We propose a dynamical trapping mechanism to solve this problem: an ultra-supercooling caused by an almost scale-invariant CW potential traps the inflaton at the false vacuum, far away from the true vacuum dominantly created by the quantum scale anomaly, and allows the inflaton to dynamically start the slow-roll down due to a classical explicit-scale breaking effect. To be concrete, we employ a successful CW-SFI model and show that the proposed mechanism works consistently with the observed bounds on the inflation parameters. The proposed new mechanism thus provides new insights for developing small field inflation models.
When the inflaton is coupled to the gluon Chern-Simons term for successful reheating, mixing between the inflaton and the QCD axion is generally expected given the solution of the strong CP problem by the QCD axion. This is particularly natural if the inflaton is a different, heavier axion. We propose a scenario in which the QCD axion plays the role of the inflaton by mixing with heavy axions. In particular, if the energy scale of inflation is lower than the QCD scale, a hybrid inflation is realized where the QCD axion plays the role of the inflaton in early stages. We perform detailed numerical calculations to take account of the mixing effects. Interestingly, the initial misalignment angle of the QCD axion, which is usually a free parameter, is determined by the inflaton dynamics. It is found to be close to π in simple models. This is the realization of the pi-shift inflation proposed in previous literature, and it shows that QCD axion dark matter and inflation can be closely related. The heavy axion may be probed by future accelerator experiments.
The T2K experiment is one of the most powerful long-baseline experiments to investigate neutrino oscillations. The off-axis near detector called ND280 is installed 280m downstream from the neutrino production target to measure the neutrino energy spectrum. In this paper, we study the capability of the ND280 detector to search for the dark photon produced through the meson rare decay and proton bremsstrahlung processes at the proton beam dump. We find that the ten-year operation of T2K with the ND280 detector excludes the unexplored parameter region for the dark photon mass and kinetic mixing. We also show that a broader parameter region can be searched by the ND280 in the future T2K operation for dark photon as well as U(1)_{B-L} gauge boson.
Cosmic strings and monopoles may arise from hidden symmetries. Their interactions and potential observational signatures will be discussed.
We revisit the constraints for the dark photon with the existence of an axion-like particle. We focus on the constraints from the laboratories, including beam dump and colliders. We found that the stringent bounds on the larger mass will be released.
We study axion-like particle contributions to the Higgs boson decays. The particle is assumed to couple with the standard model electroweak gauge bosons. Although direct productions of axion-like particles have often been discussed, we investigate indirect contributions to the Higgs boson decays into fermions, photons, W W, and Z Z bosons at the one-loop level. We found that the corrections to the fermions are suppressed, whereas precise measurements of the di-photon channel of the Higgs boson decay can provide a significant probe of the model especially when the axion-like particle is heavy and its coupling to di-photon is suppressed.
The brief review of NLSGR, the phenomenological meanings, higher-spin SUSY, and superHiggs mechanism, etc are presented.ussed.
We show that the topological charge of nonabelian gauge theory is not observable, which immediately leads to the resolution of the Strong CP problem. We then inspect the phenomenological consequences to particle physics physics. The most notable implication is the prohibition of the 't Hooft vertex and the sphaleron induced baryogenesis.
We demonstrate a universal mechanism of a class of instabilities in infrared regions for massless Abelian p-form gauge theories with topological interactions, which we call generalized chiral instabilities. Such instabilities occur in the presence of initial electric fields for the p-form gauge fields. We show that the dynamically generated magnetic fields tend to decrease the initial electric fields and result in configurations with linking numbers, which can be characterized by non-invertible global symmetries. The so-called chiral plasma instability and instabilities of the axion electrodynamics and (4+1)-dimensional Maxwell-Chern-Simons theory in electric fields can be described by the generalized chiral instabilities in a unified manner. We also illustrate this mechanism in the (2+1)-dimensional Goldstone-Maxwell model in electric field.
We examine symmetries of chiral four-dimensional vacua of Type IIB flux compactifications with vanishing superpotential W=0. We find that the N=1 supersymmetric MSSM-like and Pati-Salam vacua possess enhanced discrete symmetries in the effective action below the mass scale of stabilized complex structure moduli and dilaton. Furthermore, a generation number of quarks/leptons is small on these vacua where the flavor, CP and metaplectic modular symmetries are described in the framework of eclectic flavor symmetry.
The first-order nature of the chiral phase transition in QCD-like theories can play crucial roles in addressing a dark side of the Universe, where the created out-of equilibrium is essential to serve as cosmological and astrophysical probes such as gravitational wave productions, which have extensively been explored. We find that such a first order feature may not hold when ordinary or dark quarks are externally coupled to a weak enough background field of photon or dark photon (which we collectively call a “magnetic” field). We assume that a weak magnetic background field could be originated from some “magnetogenesis” in the early Universe. We work on a Nambu-Jona-Lasinio model which can describe the chiral phase transition in a wide class of QCD-like theories. We show that in the case with massless (light) three flavors, the firstorder feature goes away when the magnetic field is greater than the critical value.
The LHC lifetime frontier will probe a dark sector in the near future, and the visible decay searches at fixed-target experiments have been exploring the dark sector. Dark strong dynamics provides rich structure in the dark sector: dark baryons and dark mesons. Dark photons are also introduced to alleviate cosmological problems. Meanwhile, dark photons make dark hadrons long-lived in terrestrial experiments. Moreover, the dark hadrons are produced through the very same dark photon. In this study, we discuss the visible decay searches for composite asymmetric dark matter and dark pion dark matter. The LHC lifetime frontier (MATHUSLA, FASER, and FACET) has a potential to discover the transition and decay of dark hadrons for a specific spectrum. For composite asymmetric dark matter models, the visible signals arise from dark nucleon transition and dark pion decay. These projected sensitivities to dark hadrons in dark photon parameter space are comparable with the future sensitivities of dark photon searches, such as Belle-II and LHCb. Meanwhile, for the dark pion dark matter model, the visible signals arise from dark vector-meson decay. Depending on the mass spectrum, these sensitivities are comparable with the dark photon searches such as DarkQuest, Belle-II, LHCb, and HPS.
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