Search

Abstract The experimental verification of the Newton law of gravity at small scales has been a longstanding challenge. Recently, torsion balance experiments have successfully measured gravitational force at the millimeter scale. However, testing gravity force on quantum mechanical wave function at small scales remains difficult. In this paper, we propose a novel experiment that utilizes the Josephson effect to detect the different evolution of quantum phase induced from the potential difference caused by gravity. We demonstrate that this experiment can test gravity quantum mechanically at the millimeter scale, and also has a potential to investigate the parity invariance of gravity at small scales.

Abstract In this paper, we revisit the féeton (gauge boson of U(1) B−L symmetry) dark matter scenario, and first point out the U(1) gauge symmetry can be a linear combination of the B – L and the SM hypercharge gauge symmetries. With the redefinition of B – L charge of fermions, the coupling between electron and féeton can be enhanced. After showing the parameter space required from the DM stability and cosmic production, we discuss the potential for verifying them in dark matter direct detection experiments. The results show that future experiments, such as SuperCDMS, have a sensitivity to reach the féeton DM region consistent with its cosmic production.

We propose a new scenario that both the dark matter freeze-out in the early Universe and its possible annihilation for indirect detection around a supermassive black hole are enhanced by a Breit-Wigner resonance. With the mediator mass larger than the total initial dark matter mass, this annihilation is almost forbidden at late times. Thus, the stringent cosmic microwave background and indirect detection constraints do not apply. However, a supermassive black hole can accelerate the dark matter particles to reactivate this resonant annihilation whose subsequent decay to photons leaves a unique signal. The running Fermi-LAT and the future COSI satellites can test this scenario.

A new fifth force between particles carrying B−L charges is well-motivated by the intriguing U(1)B−L extension of the standard model. The gauge boson mediator, Féeton, also serves as a dark matter candidate. In this letter, we propose a novel experimental design to detect the quantum phase difference caused by this fifth force using a superconducting Josephson junction. We find that the experiment has the best sensitivity to the gauge coupling when the gauge boson is within the mass range of 0.01eV to 10eV, which is an interesting mass region for the Féeton dark matter. This opens up a new avenue for the measurement of new physics at small scale below millimeter.

The strong charge-parity (CP) problem has been a long-standing problem in particle physics since 1976, illustrating the small CP-violation phase in quantum chromodynamics (QCD). The axion, based on the Peccei–Quinn mechanism, is the most popular solution to the problem. In this paper, we propose an alternative solution based on the three-zero texture of quark mass matrices without additional heavy quark states, which has been shown to fit data well. We show that the required three-zero texture is naturally constructed in a six-dimensional spacetime with a T2/Z3 orbifold compactification.

It is known that two heavy Majorana right-handed neutrinos are sufficient to generate the baryon asymmetry in the present universe. Thus, it is interesting to identify the third right-handed neutrino N with the dark matter. We impose a new discrete symmetry Z2 on this dark matter neutrino to stabilize it. However, the U(1)B−L gauge boson A′ couples to the right-handed neutrino N. If the B−L breaking scale VB−L is sufficiently low, the dark matter neutrino N can be in the thermal bath. We find that the thermal relic N can explain the dark matter abundance for the B−L breaking scale VB−L∼O(10) TeV. After considering all the constraints from the existing experiments, a narrow mass region of the thermal produced right-handed neutrino dark matter N is still surviving.

Abstract When we impose discrete symmetries in the standard model we have Dai-Freed global anomalies. However, interestingly if we introduce three right-handed neutrinos we can have an anomaly-free discrete Z 4 gauge symmetry. This Z 4 symmetry should be spontaneously broken down to the Z 2 symmetry to generate the heavy Majorana masses for the right-handed neutrinos. We show that this symmetry breaking naturally generates topological inflation, which is consistent with the CMB observations at present and predicts a significant tensor mode with scalar-tensor ratio r > 0.03. The right-handed neutrinos play an important role in reheating processes. The reheating temperature is as high as ∼ 108 GeV, and non-thermal leptogenesis successfully takes place.

Abstract Supersymmetry is still a viable explanation for the muon g – 2 anomaly, if the sleptons and electroweak gauginos are O 100 $$ \mathcal{O}(100) $$ GeV. However, for supersymmetry breaking masses this light, the SUSY flavor and CP-problem are exacerbated. To address this issue, we consider a flavor-safe gauge mediated explanation of the muon g – 2 with additional Higgs soft supersymmetry breaking mass parameters. The setup provides a generic parameter space within minimal gauge mediation. Furthermore, we show that the problematic CP violating phase can be dynamically suppressed. We find that gauge mediation models have large portions of parameter space where the muon g – 2 can be explained at 1 σ level. The interplay between the slepton and the CP-odd Higgs masses also makes the majority of this model’s parameter space testable at the LHC through searches for sleptons or additional Higgs bosons.

Abstract In this work, we discuss how the use of the symmetries well motivated in physics beyond the Standard model (BSM) can guarantee the high quality axions. We avoid to introduce symmetries only useful for addressing the axion quality problem. Rather, we rely on symmetries well motivated by other issues in BSM: supersymmetry, U(1)B−L and the discrete R-symmetry Z NR . We show that the interplay among these guarantees the high quality of the axion even for the gravitino mass and axion decay constant as large as m 3/2 = O $$ \mathcal{O} $$ (10)TeV and F a = O $$ \mathcal{O} $$ (1015)GeV respectively. The key point of this work relies on the observation that the MSSM contribution to the mixed anomalies Z NR − [SU(2) L ]2 and Z NR − [SU(3) c ]2 is not enough for gauging Z NR for N ≠ 6, which necessitates the introduction of new matter fields. We make the introduction to achieve zero mixed anomalies, which logically supports a desired large enough N for Z NR . This mechanism effectively makes Z NR equal to U(1) R and thus offers a logically complete solution to the axion quality problem.

Abstract It is remarkable that the matter fields in the Standard Model (SM) are apparently unified into the SU(5) representations. A straightforward explanation of this fact is to embed all the SM gauge groups into a simple group containing SU(5), i.e., the grand unified theory (GUT). Recently, however, a new framework “fake GUT” has been proposed. In this new framework, the apparent matter unification can be explained by a chiral gauge group G, G ⊃ SU(5). We emphasize that the SM matter fields are not necessarily embed- ded into the chiral representations to explain the apparent unification. In this paper, we discuss details of concrete realizations of the fake GUT model. We first study the model based on SU(5) × U(2) H , where SU(3) c in the SM is from SU(5) while SU(2) L × U(1) Y are from the diagonal subgroups of SU(5) × U(2) H . We also extend this model to the one based on a semi-simple group, SU(5) × SU(3) H , so that U(2) H is embedded in SU(3) H . We also show that this framework predicts rather different decay patterns of the proton, compared to the conventional GUT.

We consider a scenario where supersymmetry breaking, its mediation, and the cancellation of the theta parameter of SU(3)C are all caused by a single chiral multiplet. The string axion multiplet is a natural candidate of such a superfield. We show that the scenario provides a convincing basis of focus point gaugino mediation, where the electroweak scale is explained with a moderate tuning among the parameters of the theory.

In minimal supersymmetric SU(5) models, the proton can decay through dimension 5 operators. Since this decay depends directly on the supersymmetric soft masses, it will be constrained by other observables which depend on the soft masses, such as the Higgs mass and the dark matter relic density. In this work, we will examine the upper limit on the proton lifetime in minimal supersymmetric SU(5) with constrained minimal supersymmetric (CMSSM) boundary conditions set at the grand unification scale. We perform a random scan over the variables of the (CMSSM), with of order 106 points, and find that the proton lifetime is within reach of JUNO and Hyper-Kamiokande's experiment.

It is known that the recently reported shift of the W boson mass can be easily explained by an SU(2)L triplet Higgs boson with a zero hypercharge if it obtains a vacuum expectation value (VEV) of O(1) GeV. Surprisingly, the addition of a TeV scale complex triplet Higgs boson to the standard model (SM) leads to a precise unification of the gauge couplings at around 1014 GeV. We consider that it is a consequence of SU(5) grand unification and show a possible potential for the Higgs fields yielding a weak scale complex SU(2) triplet scalar boson. Although it seems the proton decay constraint would doom such a low-scale unification, we show that the constraint can be avoided by introducing vector-like fermions which mix with the SM fermions through mass terms involving the VEV of GUT breaking Higgs field. Importantly, the simplest viable model only requires the addition of one pair of vector-like fermions transforming 10 and 10‾.

Abstract By extending a previously proposed conformal gauge mediation model, we construct a gauge-mediated SUSY breaking (GMSB) model where a SUSY-breaking scale, a messenger mass, the μ-parameter and the gravitino mass in a minimal supersymmetric (SUSY) Standard Model (MSSM) are all explained by a single mass scale, a R-symmetry breaking scale. We focus on a low scale SUSY-breaking scenario with the gravitino mass m 3/2 = O 1 eV $$ \mathcal{O}(1)\mathrm{eV} $$ , which is free from the cosmological gravitino problem and relaxes the fine-tuning of the cosmological constant. Both the messenger and SUSY-breaking sectors are subject to a hidden strong dynamics with the conformality above the messenger mass threshold (and hence the name of the model “strongly interacting conformal gauge mediation”). In our model, the Higgs B-term is suppressed and a large tan β is predicted, resulting in the relatively light second CP-even Higgs and the CP-odd Higgs with a sizable production cross section. These Higgs bosons can be tested at future LHC experiments.

Abstract A keV-scale gravitino arising from a minimal supersymmetric (SUSY) Standard Model (MSSM) is an interesting possibility since the small scale problems that the ΛCDM model encounters in the modern cosmology could be alleviated with the keV-scale gravitino serving as the warm dark matter (WDM). Such a light gravitino asks for a low scale supersymmetry (SUSY) breaking for which the gauge mediation (GM) is required as a consistent SUSY-breaking mediation mechanism. In this paper, we show upper bounds of the masses of the second CP-even Higgs boson H and the CP-odd Higgs boson A, assuming the keV-scale gravitino to be responsible for the current DM relic abundance: the upper bound on the mass of H/A is found to be ∼ 4 TeV for the gravitino mass of O 10 − 100 $$ \mathcal{O}\left(10-100\right) $$ keV. Interestingly, the mass of H/A can be as small as 2–3 TeV and the predicted tan β is as large as 55–60 for the gravitino mass of O 10 $$ \mathcal{O}(10) $$ keV. This will be tested in the near future Large Hadron Collider (LHC) experiments.

Abstract The extension of the Standard model (SM) with three heavy right handed neutrinos, a complex scalar and the gauged U(1)B−L symmetry (the minimal B − L model) is considered the most compelling minimal one: the presence and the out-of-equilibrium decay of the heavy right handed neutrinos can account for the small masses of the active neutrinos and the baryon asymmetry of the universe. A natural accompanying question concerns whether the minimal B − L model can naturally accommodate an interesting dark matter (DM) candidate. We study the possibility where the current DM population is explained by the gauge boson of U(1)B−L symmetry. We discuss how the minimal set-up originally aimed at the seesaw mechanism and the leptogenesis is connected to conditions making the gauge boson promoted to a DM candidate.

Abstract We present a model describing the dark sector (DS) featured by two interactions remaining efficient until late times in the matter-dominated era after recombination: the interaction among dark radiations (DR), and the interaction between a small fraction of dark matter and dark radiation. The dark sector consists of (1) a dominant component cold collisionless DM (DM1), (2) a sub-dominant cold DM (DM2) and (3) a self-interacting DR. When a sufficient amount of DR is ensured and a few percent of the total DM density is contributed by DM2 interacting with DR, this set-up is known to be able to resolve both the Hubble and σ 8 tension. In light of this, we propose a scenario which is logically natural and has an intriguing theoretical structure with a hidden unbroken gauge group SU(5)X ⊗ U(1)X. Our model of the dark sector does not introduce any new scalar field, but contains only massless chiral fermions and gauge fields in the ultraviolet (UV) regime. As such, it introduces a new scale (DM2 mass, m DM2) based on the confinement resulting from the strong dynamics of SU(5)X. Both DM2-DR and DR-DR interactions are attributed to an identical long range interaction of U(1)X. We show that our model can address the cosmological tensions when it is characterized by g X = O $$ \mathcal{O} $$ (10 −3)– O $$ \mathcal{O} $$ (10 −2), m DM2 = O $$ \mathcal{O} $$ (1)– O $$ \mathcal{O} $$ (100) GeV and T DS /T SM ≃ 0.3–0.4 where g X is the gauge coupling of U(1)X and T DS(T SM) is a temperature of the DS (Standard Model sector). Our model explains candidates of DM2 and DR, and DM1 can be any kind of CDM.

Abstract In this paper, we show that the Peccei-Quinn (PQ) symmetry with a good quality can be realized in a simple B −L extension of the minimal supersymmetric standard model. The PQ symmetry is a remnant of the B − L gauge symmetry at the renormalizable level. Besides, the sufficient quality of the PQ symmetry is preserved by a non anomalous discrete gauged R-symmetry and a small gravitino mass m 3/2 ≪ 100 GeV. A viable mass range is m 3 / 2 = O 1 $$ {m}_{3/2}=\mathcal{O}(1) $$ eV which allows a high reheating temperature and many baryogenesis scenarios typified by the thermal leptogenesis without any astrophysical and cosmological problems. Such a light gravitino may be tested in the future 21cm line observations.

Abstract A simple model for the explanation of the muon anomalous magnetic moment was proposed by the present authors within the context of the minimal supersymmetric standard model [1, 2]: Higgs-anomaly mediation. In the setup, squarks, sleptons, and gauginos are massless at tree-level, but the Higgs doublets get large negative soft supersymmetry (SUSY) breaking masses squared m H u 2 ≃ m H d 2 < 0 $$ {m}_{H_u}^2\simeq {m}_{H_d}^2

In this paper, we discuss interesting scenarios resulting from the interplay between the gravitino and the lightest right-handed (s)neutrino. We consider two gravitino mass regimes vastly separated, that is, m3/2=O(100) eV and m3/2≃100 GeV. For the former case, a significant amount of the entropy production in the cosmological history to dilute the gravitino relic abundance is unavoidable for consistency with the number of satellite galaxies in the Milky way. We will show that the right-handed (s)neutrino can play the role of the heavy particle whose late time decay provides such an additional radiation. For the later case, the gravitino of m3/2≃100 GeV may resolve the S8 tension as a decaying dark matter. We will show how the lightest right-handed neutrino and its superpartner can help the gravitino decaying dark matter be equipped with a long enough life time and mass degeneracy with a massive decay product to address the S8 tension.

In this letter, we show that the wino-Higgsino dark matter (DM) is detectable in near future DM direct detection experiments for almost all consistent parameter space in the spontaneously broken supergravity (SUGRA) if the muon g−2 anomaly is explained by the wino-Higgsino loop diagrams. We also point out that the present and future LHC experiments can exclude or confirm this SUGRA explanation of the observed muon g−2 anomaly.

Abstract We study the phenomenological consequences of the supersymmetric (SUSY) E 7 /SU(5) × U(1)3 non-linear sigma model coupled to supergravity, where the three gen- erations of quark and lepton chiral multiplets appear as (pseudo) Nambu Goldstone (NG) multiplets, that is, the origin of the three families is explained. To break SUSY, we intro- duce a SUSY breaking field charged under some symmetry avoiding the Polonyi problem. The gaugino mass spectrum is almost uniquely determined when one requires the electroweak vacuum to be (meta)stable: it would be a miracle that the mass difference between the bino and wino turns out to be within O $$ \mathcal{O} $$ (1)% at the low energy. Thus, a bino-wino coannihilation is naturally predicted, which can explain the correct relic abundance of dark matter. Moreover, we find that the bottom-tau Yukawa couplings and the gauge couplings are unified up to O $$ \mathcal{O} $$ (1)% in most of the viable region. This scenario can be fully tested at the LHC and future collider experiments since the gauginos and some of the pseudo-NG bosons are light. An axion-like multiplet, which can be identified with the QCD axion, is also predicted.

Abstract We explore the possibility that the muon g − 2 anomaly and the nature of dark matter can be simultaneously explained within the framework of gaugino mediation, focusing on bino-like dark matter where the observed abundance is obtained via co-annihilations. The minimal model with non-universal gaugino masses is excluded by stau vacuum instability, although this constraint can be somewhat relaxed via the addition of a universal soft scalar mass (or B − L gaugino mediation). A more promising alternative is gaugino+Higgs mediation, which significantly raises the soft masses of the third generation sfermions leading to a split spectrum. In this framework, the muon g − 2 can be easily explained and the dark matter abundance obtained through either bino-wino or bino-slepton co-annihilations.

Abstract The Split-Family supersymmetry is a model in which the sfermion masses of the first two generations are in $${\mathcal {O}}(100{-}{1000})\,\hbox {GeV}$$ O(100-1000)GeV while that of the third one is in $${\mathcal {O}}(10)$$ O(10) TeV. With such a hierarchical spectrum, the deviation of the muon $$g-2$$ g-2 and the observed Higgs boson mass are explained simultaneously. In this paper, we revisit the Split-Family SUSY model in light of the updated LHC constraints. We also study the flavor changing neutral current problems in the model. As we will show, the problems do not lead to stringent constraints when the Cabibbo-Kobayashi-Maskawa matrix is the only source of the flavor mixing. We also study how large flavor mixing in the supersymmetry breaking parameters is allowed.

Abstract A simple model of dark matter contains a light Dirac field charged under a hidden U(1) gauge symmetry. When a chiral matter content in a strong dynamics satisfies the t’Hooft anomaly matching condition, a massless baryon is a natural candidate of the light Dirac field. One realization is the same matter content as the standard SU(5) × U(1)(B−L) grand unified theory. We propose a chiral [SU(5) × U(1)]4 gauge theory as a unified model of the SM and DM sectors. The low-energy dynamics, which was recently studied, is governed by the hidden U(1)4 gauge interaction and the third-family U 1 B − L 3 $$ \mathrm{U}{(1)}_{{\left(B-L\right)}_3} $$ gauge interaction. This model can realize self-interacting dark matter and alleviate the small-scale crisis of collisionless cold dark matter in the cosmological structure formation. The model can also address the semi-leptonic B-decay anomaly reported by the LHCb experiment.

The novel PQ mechanism replaces the strong CP problem with some challenges in a model building. In particular, the challenges arise regarding i) the origin of an anomalous global symmetry called a PQ symmetry, ii) the scale of the PQ symmetry breaking, and iii) the quality of the PQ symmetry. In this letter, we provide a natural and simple UV completed model that addresses these challenges. Extra quarks and anti-quarks are separated by two branes in the Randall-Sundrum R4×S1/Z2 spacetime while a hidden SU(NH) gauge field condensates in the bulk. The brane separation is the origin of the PQ symmetry and its breaking scale is given by the dynamical scale of the SU(NH) gauge interaction. The (generalized) Casimir force of SU(NH) condensation stabilizes the 5th dimension, which guarantees the quality of the PQ symmetry.

An excess in the electronic recoil data was observed in the XENON1T detector. One of plausible explanations for the excess is absorption of a vector bosonic particle with the mass of 2−3keV. For this, the kinetic mixing κ∼10−15 of the dark photon with the photon is required if the dark photon explains the current DM abundance. We recently proposed a model where the main component DM today is a decaying warm dark matter (WDM) with the life time comparable to the age of the current universe. The WDM decays to a massless fermion and a massive dark photon. This model was originally designed for addressing both the small scale problems which ΛCDM suffers from and the H0 tension. In this letter, we show that the massive dark photon produced by the WDM decay can be identified with the vector boson inducing the anomalous excess in the XENON1T experiment. Depending on a lifetime of the parent decaying WDM, the dark photon could be either the main component or the sub-component of DM population today.

The recent observation of an excess in the electronic recoil data by the XENON1T detector has drawn many attentions as a potential hint for an extension of the Standard Model (SM). Absorption of a vector boson with the mass of mA′∈(2keV,3keV) is one of the feasible explanations to the excess. In the case where the vector boson explains the dark matter (DM) population today, it is highly probable that the vector boson belongs to a class of the warm dark matter (WDM) due to its suspected mass regime. In such a scenario, providing a good fit for the excess, the kinetic mixing κ∼10−15 asks for a non-thermal origin of the vector DM. In this letter, we consider a scenario where the gauge boson is nothing but the U(1)B−L gauge boson and its non-thermal origin is attributed to the decay of the coherently oscillating scalar of which condensation induces the spontaneous breaking of U(1)B−L. We discuss implications for the early universe physics when the warm nature of the vector DM serves as a resolution to both the small scale problems that ΛCDM model encounters and the XENON1T anomaly.

We discuss formation of dark matter (DM) mini-halos around primordial black holes (PBHs) and its implication on DM direct detection experiments, including axion searches. Motivated by LIGO observations, we consider fDM≃0.01 as the fraction of DM in PBHs with masses 10M⊙−70M⊙. In this case, we expect the presence of dressed PBHs after Milky Way halo formation with mini-halo masses peaked around Mhalo∼(50−55)MPBH. We analyze the effect of tidal forces acting on dressed PBHs within the Milky Way galaxy. In the solar neighborhood, the mini-halos are resistant against tidal disruption from the mean-field potential of the galaxy and encounters with stars, but they undergo a small level of disruption caused by disk shocking. The presence of mini-halos around LIGO-motivated PBHs today could reduce by half the local dark matter background. High-resolution simulations are encouraged. If the proposed scenario is realized, chances of direct detection of DM would decrease.

Abstract A spontaneously broken hidden U(1) h gauge symmetry can explain both the dark matter stability and the observed relic abundance. In this framework, the light gauge boson can mediate the strong dark matter self-interaction, which addresses astrophysical observations that are hard to explain in collisionless cold dark matter. Motivated by flavoured grand unified theories, we introduce right-handed neutrinos and a flavoured B − L gauge symmetry for the third family U 1 B − L 3 $$ \mathrm{U}{(1)}_{{\left(B-L\right)}_3} $$ . The unwanted relic of the U(1) h gauge boson decays into neutrinos via the kinetic mixing with the U 1 B − L 3 $$ \mathrm{U}{(1)}_{{\left(B-L\right)}_3} $$ gauge boson. Indirect detection bounds on dark matter are systematically weakened, since dark matter annihilation results in neutrinos. However, the kinetic mixing between U 1 B − L 3 $$ \mathrm{U}{(1)}_{{\left(B-L\right)}_3} $$ and U(1) Y gauge bosons are induced by quantum corrections and leads to an observable signal in direct and indirect detection experiments of dark matter. This model can also explain the baryon asymmetry of the Universe via the thermal leptogenesis. In addition, we discuss the possibility of explaining the lepton flavour universality violation in semi-leptonic B meson decays that is recently found in the LHCb experiment.

We revisit the number-theory dark matter scenario where one of the light chiral fermions required by the anomaly cancellation conditions of U(1)B-L explains dark matter. Focusing on some of the integer B-L charge assignments, we explore a new region of the parameter space where there appear two light fermions and the heavier one becomes a dark matter of mass ≲O(10)keV or O(10)MeV. The dark matter radiatively decays into neutrino and photon, which can explain the tantalizing hint of the 3.55keV X-ray line excess. Interestingly, the other light fermion can erase the AdS vacuum around the neutrino mass scale in a compactification of the standard model to 3D. This will make the standard model consistent with the AdS-WGC statement that stable non-supersymmetric AdS vacua should be absent.

We present a model in which the question about a nature of the dark energy and the recently raised Hubble tension can be addressed at once. We consider the electroweak axion in the minimal supersymmetric standard model where the axion energy density is identified with the observed dark energy. Along with this, imposing a gauged Z10 symmetry makes it possible to have a gravitino dark matter whose mass amounts to ∼O(1) GeV. We find that the gravitino with mass ∼O(1) GeV can be a good candidate of a decaying dark matter of which decay after recombination can reconcile discrepancy in local measurements of the Hubble expansion rate H0 and that inferred from the cosmic microwave background observation.

A novel idea of the direct detection to search for a ultralight dark matter based on the interaction between the dark matter and a nucleon is proposed. Solar system bodies feel the dark matter wind and it acts as a resistant force opposing their motions. The astronomical ephemeris of solar system bodies is so precise that it has a strong capability to detect a dark matter whose mass is much lighter than O(1)eV. We have estimated the resistant force based on the calculation of the elastic scattering cross section between the dark matter and the bodies beyond the Born approximation, and show that the astronomical ephemeris indeed put a very strong constraint on the interaction between the dark matter and a nucleon, depending on how smoothly the ultralight dark matter is distributed at the scale smaller than the celestial bodies in our solar system.

Abstract A low-energy effective theory is said to be in the swampland if it does not have any consistent UV completion inside a theory of quantum gravity. The natural question is if the standard model of particle physics, possibly with some minimal extensions, are in the swampland — we are in trouble if the answer to this question is yes. We discuss this question in view of the recent swampland conjectures. We prove a no-go theorem concerning the modification of the Higgs sector. Moreover, we find that QCD axion is incompatible with the recent swampland conjectures, unless some sophisticated possibilities are considered. We discuss the implications of this result for spontaneous breaking of CP symmetry. We comment on dynamical supersymmetry breaking as well as the issue of multi-valuedness of the potential. We also propose a refinement of the de Sitter swampland conjecture.

Flavor democracy broken in the fermion mass matrix by means of small perturbations can give rise to hierarchical fermion masses. We study the breaking of the S3L×S3R symmetry associated with democratic mass matrices to a smaller exchange symmetry S2L×S2R in the charged lepton, up and down quark sectors. An additional breaking of the S2L×S2R symmetry is necessary for the down quark mass matrix, which yields arbitrary perturbations in that sector. On the other hand, we require the neutrino mass matrix to be diagonal at the leading order, with the perturbations left arbitrary due to the absence of any guiding symmetry. We show that the interplay between these two kinds of perturbations reproduces the quark and lepton mass and mixing observables for either hierarchy of neutrino masses.

Abstract We consider focus point gauge mediation within the framework of the next-to-minimal supersymmetric standard model, which substantially reduces the degree of finetuning for the electroweak symmetry breaking. The milder fine-tuning is realized by a messenger field in the adjoint representation of SU(5) gauge group with SU(3) c octet being heavy. Our model has a simple ultraviolet completion. The fine-tuning measure Δ can be as small as 40-50 without any contradiction with LHC constraints.

It is increasingly becoming difficult, within a broad class of supersymmetric models, to satisfactorily explain the discrepancy between the measured (g−2)μ and its standard model prediction, and at the same time satisfy all the other constraints. In this paper we propose a new scheme of gauge mediation by introducing new soft supersymmetry breaking mass parameters for the Higgs sector in a minimal setup containing only a pair of (5+5¯) messenger fields of SU(5). This enables us to explain the (g−2)μ discrepancy while avoiding all the existing constraints. We also provide possible dynamical origin of the new soft mass parameters. The wino and higgsino weighing below 500 GeV constitute the smoking gun signal at the (high luminosity) LHC.

Abstract The gauged Peccei-Quinn (PQ) mechanism provides a simple prescription to embed the global PQ symmetry into a gauged U(1) symmetry. As it originates from the gauged PQ symmetry, the global PQ symmetry can be protected from explicit breaking by quantum gravitational effects once appropriate charge assignment is given. In this paper, we identify the gauged PQ symmetry with the B − L symmetry, which is obviously attractive as the B − L gauge symmetry is the most authentic extension of the Standard Model. As we will show, a natural B − L charge assignment can be found in a model motivated by the seesaw mechanism in the SU(5) Grand Unified Theory. As a notable feature of this model, it does not require extra SU(5) singlet matter fields other than the right-handed neutrinos to cancel the self and the gravitational anomalies.

Abstract Recently, a simple prescription to embed the global Peccei-Quinn (PQ) symmetry into a gauged U(1) symmetry has been proposed. There, explicit breaking of the global PQ symmetry expected in quantum gravity are highly suppressed due to the gauged PQ symmetry. In this paper, we apply the gauged PQ mechanism to models where the global PQ symmetry and supersymmetry (SUSY) are simultaneously broken at around O1011−12 $$ \mathcal{O}\left(1{0}^{11-12}\right) $$ GeV. Such scenario is motivated by an intriguing coincidence between the supersymmetry breaking scale which explains the observed Higgs boson mass by the gravity mediated sfermion masses, and the PQ breaking scale which evades all the astrophysical and the cosmological constraints. As a concrete example, we construct a model which consists of a simultaneous supersymmetry/PQ symmetry breaking sector based on SU(2) dynamics and an additional PQ symmetry breaking sector based on SU(N) dynamics. We also show that new vector-like particles are predicted in the TeV range in the minimum model, which can be tested by the LHC experiments.

If the Peccei–Quinn symmetry is already broken during inflation, the decay constant Fa of the axion can be in a wide region from 1011GeV to 1018GeV for the axion being the dominant dark matter. In this case, however, the axion causes the serious cosmological problem, isocurvature perturbation problem, which severely constrains the Hubble parameter during inflation. The constraint is relaxed when Peccei–Quinn scalar field takes a large value ∼Mp (Planck scale) during inflation. In this letter, we point out that the allowed region of the decay constant Fa is reduced to a rather narrow region for a given tensor-to-scalar ratio r when Peccei–Quinn scalar field takes ∼Mp during inflation. For example, if the ratio r is determined as r≳10−3 in future measurements, we can predict Fa≃(0.1–1.4)×1012GeV for domain wall number NDW=6.

A large value of the leptonic Dirac CP phase can arise from broken democracy, where the mass matrices are democratic up to small random perturbations. Such perturbations are a natural consequence of broken residual S3 symmetries that dictate the democratic mass matrices at leading order. With random perturbations, the leptonic Dirac CP phase has a higher probability to attain a value around ±π/2. Comparing with the anarchy model, broken democracy can benefit from residual S3 symmetries, and it can produce much better, realistic predictions for the mass hierarchy, mixing angles, and Dirac CP phase in both quark and lepton sectors. Our approach provides a general framework for a class of models in which a residual symmetry determines the general features at leading order, and where, in the absence of other fundamental principles, the symmetry breaking appears in the form of random perturbations.

Abstract We consider a simple setup with light squarks which is free from the gravitino and SUSY flavor problems. In our setup, a SUSY breaking sector is sequestered from the matter and gauge sectors, and it only couples to the Higgs sector directly with O100 $$ \mathcal{O}(100) $$ TeV gravitino. Resulting mass spectra of sfermions are split: the first and second generation sfermions are light as O1 $$ \mathcal{O}(1) $$ TeV while the third generation sfermions are heavy as O10 $$ \mathcal{O}(10) $$ TeV. The light squarks of O1 $$ \mathcal{O}(1) $$ TeV can be searched at the (high-luminosity) LHC and future collider experiments. Our scenario can naturally avoid too large flavor-changing neutral currents and it is consistent with the ϵ K constraint. Moreover, there are regions explaining the muon g − 2 anomaly and bottom-tau/top-bottom-tau Yukawa coupling unification simultaneously.

We consider a version of the low-scale type I seesaw mechanism for generating small neutrino masses, as an alternative to the standard seesaw scenario. It involves two right-handed (RH) neutrinos ν1R and ν2R having a Majorana mass term with mass M, which conserves the lepton charge L. The RH neutrino ν2R has lepton-charge conserving Yukawa couplings gℓ2 to the lepton and Higgs doublet fields, while small lepton-charge breaking effects are assumed to induce tiny lepton-charge violating Yukawa couplings gℓ1 for ν1R, l=e,μ,τ. In this approach the smallness of neutrino masses is related to the smallness of the Yukawa coupling of ν1R and not to the large value of M: the RH neutrinos can have masses in the few GeV to a few TeV range. The Yukawa couplings |gℓ2| can be much larger than |gℓ1|, of the order |gℓ2|∼10−4–10−2, leading to interesting low-energy phenomenology. We consider a specific realisation of this scenario within the Froggatt–Nielsen approach to fermion masses. In this model the Dirac CP violation phase δ is predicted to have approximately one of the values δ≃π/4,3π/4, or 5π/4,7π/4, or to lie in a narrow interval around one of these values. The low-energy phenomenology of the considered low-scale seesaw scenario of neutrino mass generation is also briefly discussed.

Abstract We consider right-handed neutrino pair production in generic Z ′ models. We propose a new, model-independent analysis using final states containing a pair of same-sign muons. A key aspect of this analysis is the reconstruction of the RH neutrino mass, which leads to a significantly improved sensitivity. Within the U1B−L3 $$ \mathrm{U}{(1)_{\left(B-L\right)}}_{{}_3} $$ model, we find that at the HL-LHC it will be possible to probe RH neutrino masses in the range 0.2≲MNR≲1.1 $$ 0.2\lesssim {M}_{N_R}\lesssim 1.1 $$ TeV.

We consider a flavoured B−L gauge symmetry under which only the third generation fermions are charged. Such a symmetry can survive at low energies (∼TeV) while still allowing for two superheavy right-handed neutrinos, consistent with neutrino masses via see-saw and leptogenesis. We describe a mechanism for generating Yukawa couplings in this model and also discuss the low-energy phenomenology. Interestingly, the new gauge boson could explain the recent hints of lepton universality violation at LHCb, with a gauge coupling that remains perturbative up to the Planck scale. Finally, we discuss more general U(1) symmetries and show that there exist only two classes of vectorial U(1) that are both consistent with leptogenesis and remain phenomenologically viable at low-energies.

We study if the minimal sneutrino chaotic inflation is consistent with a flavor symmetry of the Froggatt–Nielsen type, to derive testable predictions on the Dirac and Majorana CP violating phases, δ and α. For successful inflation, the two right-handed neutrinos, i.e., the inflaton and stabilizer fields, must be degenerate in mass. First we find that the lepton flavor symmetry structure becomes less manifest in the light neutrino masses in the seesaw mechanism, and this tendency becomes most prominent when right-handed neutrinos are degenerate. Secondly, the Dirac CP phase turns out to be sensitive to whether the shift symmetry breaking depends on the lepton flavor symmetry. When the flavor symmetry is imposed only on the stabilizer Yukawa couplings, distributions of the CP phases are peaked at δ≃±π/4,±3π/4 and α=0, while the vanishing and maximal Dirac CP phases are disfavored. On the other hand, when the flavor symmetry is imposed on both the inflaton and stabilizer Yukawa couplings, it is rather difficult to explain the observed neutrino data, and those parameters consistent with the observation prefer the vanishing CP phases δ=0,π and α=0.

The Higgs boson of 125 GeV requires large stop masses, leading to the large μ-parameter in most cases of gauge mediation. On the other hand, the explanation for the muon g−2 anomaly needs small slepton and neutralino/chargino masses. Such disparity in masses may be obtained from a mass splitting of colored and non-colored messenger fields. However, even if the required small slepton and neutralino/chargino masses are realized, all parameter regions consistent with the muon g−2 are excluded by the recent updated ATLAS result on the wino search in the case that the messenger fields are in 5+5¯ representations of SU(5). It is also revealed that the messenger fields in 10+10‾ or 24 representation can not explain the muon g−2 anomaly. We show, giving a simple example model, that the above confliction is solved if there is an additional contribution to the Higgs soft mass which makes the μ-parameter small. We also show that the required Higgs B-term for the electroweak symmetry breaking is consistently generated by radiative corrections from gaugino loops.

The Peccei–Quinn (PQ) solution to the strong CP problem requires an anomalous global U(1) symmetry, the PQ symmetry. The origin of such a convenient global symmetry is quite puzzling from the theoretical point of view in many aspects. In this paper, we propose a simple prescription which provides an origin of the PQ symmetry. There, the global U(1) PQ symmetry is virtually embedded in a gauged U(1) PQ symmetry. Due to its simplicity, this mechanism can be implemented in many conventional models with the PQ symmetry.

We discuss the Dirac CP violating phase δCP in the Froggatt–Nielsen model for a neutrino mass matrix Mν imposing a condition det[Mν]=0. This additional condition restricts the CP violating phase δCP drastically. We find that the phase δCP is predicted in the region of ±(0.4–2.9) radian, which is consistent with the recent T2K and NOνA data. There is a remarkable correlation between δCP and sin2⁡θ23. The phase δCP converges to ∼±π/2 if sin2⁡θ23 is larger than 0.5. Thus, the accurate measurement of sin2⁡θ23 is important for a test of our model. The effective mass mee for the neutrinoless double beta decay is predicted in the rage 3.3–4.0 meV.

Recently ATLAS reported a 3.3σ excess in the stop search with ℓ+jets+E̸Tmiss channel. We try to interpret the signal by a light stop pair production in the MSSM. We find: (1) simple models where stop decays into a higgsino or a bino are not favored. (2) an extension of them can explain the data at 2σ level without conflicting with the other search channels. A surviving possibility includes a light stop and a light higgsino, which is expected in a natural SUSY scenario.