Axions and other pseudoscalar fields comprise an interesting class of ultralight dark matter candidates, that may independently play a role in solving the strong $CP$ problem. In the presence of $CP$-violating sources, these pseudoscalar fields can develop a coherent non-derivative coupling to nucleons, $\bar g_{aNN}$, thus mediating `mass-mass' and `mass-spin' forces in matter that can be probed experimentally. We revisit the non-perturbative generation of these $CP$-odd axion forces, and refine estimates of $\bar g_{aNN}$ generated by the EDMs and color EDMs of quarks. We also revisit the Standard Model contribution to $CP$-odd axion couplings generated by the phase of the Cabibbo-Kobayashi-Maskawa quark mixing matrix.
We made a search for hadronic axions which could be emitted from the Sun in M1 transitions between the first 14.4 keV thermally excited and the ground state in Fe-57, and absorbed in the HPGe detector by axioelectric effect. An upper limit on hadronic axion mass of 400 eV is obtained at the 95% confidence level.
We show that heavy quark axion is not necessarily a hadronic axion, which manifests in the quark and lepton seesaw mechanism. We introduce a heavy $SU(2)$ singlet fermion for each known fermion in order to unify the axion scale and the seesaw scale. The light quarks and leptons gain their masses by the seesaw mechanism. Even though our axion model gives a kind of heavy quark axion, the axion has tree level lepton--axion coupling suppressed by $F_a$, contrary to a widely known belief that heavy quark axions are hadronic.
Mixed dark matter scenario can reconcile the COBE data and the observed large scale structure. So far the massive neutrino with a mass of a few eV has been the only discussed candidate for the hot dark matter component. We point out that the hadronic axion in the so-called hadronic axion window, f_a \sim 10^6 GeV, is a perfect candidate as hot dark matter within the mixed dark matter scenario. The current limits on the hadronic axion are summarized. The most promising methods to verify the hadronic axion in this window are the resonant absorption of almost-monochromatic solar axions from M1 tr…
We investigate the prospects of an extra global symmetry, added to the Standard Model in the context of baryogenesis. The $PQ$ symmetry is studied as an example. We show that the hadronic axion provides a protection of the B-asymmetry even if $B-L$=0 and that there are no limits on the neutrino masses. It is also shown that there is a crucial difference between the two possible invisible axion models. A connection between the baryon asymmetry and dark matter is also pointed out.
We re-examine the possibility of an astrophysically allowed KSVZ-type axion that has a strongly suppressed coupling to photons. We then investigate the impact of such ''hadronic axions'' on two classes of astrophysical objects: black hole accretion disc (BHAD) based gamma-ray bursts and isolated neutron-stars. Although our results are sensitive to details of the underlying models, we show that hadronic axions could in principle play an important role in the evolution of gamma-ray bursts and in the cooling behaviour of neutron stars.
We propose a model for the QCD axion which is realized through a coupling of the Peccei-Quinn scalar field to magnetically charged fermions at high energies. We show that the axion of this model solves the strong CP problem and then integrate out heavy magnetic monopoles using the Schwinger proper time method. We find that the model discussed yields axion couplings to the Standard Model which are drastically different from the ones calculated within the KSVZ/DFSZ-type models, so that large part of the corresponding parameter space can be probed by various projected experiments. Moreover, the a…
We present models in which axions have large couplings to hadrons while remaining naturally light. By assigning $U(1)_{PQ}$ charges to Standard Model quarks such that $U(1)_{PQ}$ is not anomalous under QCD, the derivative couplings naturally arise while no potential is generated for the axion upon QCD confinement. We present simple models that implement this idea both for an axion-like particle and for the QCD axion. We show that both models lead to sizable flavor violations that could be probed by future experiments. Our construction shows that the axion coupling to hadrons can be essentially…
Hadronic axions with the decay constant $f_a\simeq 10^{6}$ GeV may fulfill all astrophysical and laboratory constraints discussed so far. In this paper, we reexamine the possibility of the hadronic axion window while taking into account the uncertainties of some parameters describing low energy axion dynamics. It is found that $f_a$ in the range from $3\times 10^5$ GeV to $3\times 10^6$ can not be excluded by existing arguments. We then examine the implication of this hadronic axion window for the big-bang nucleosynthesis (NS) by evaluating the energy density of thermal axions at the nucleosyn…
Recently we have proposed a simple hadronic axion model within gauge-mediated supersymmetry breaking. In this paper we discuss various cosmological consequences of the model in great detail. A particular attention is paid to a saxion, a scalar partner of an axion, which is produced as a coherent oscillation in the early universe. We show that our model is cosmologically viable, if the reheating temperature of inflation is sufficiently low. We also discuss the late decay of the saxion which gives a preferable power spectrum of the density fluctuation in the standard cold dark matter model when …
Final-state rescattering effects on the hadronic B decays and their impact on direct CP violation are examined. The phenomenology of the polarization anomaly in $B\toϕK^*$ decays is discussed.
A simple hadronic axion model is proposed in the framework of gauge-mediated supersymmetry breaking. Dynamics of Peccei-Quinn symmetry breaking is governed by supersymmetry breaking effects and the Peccei-Quinn breaking scale $f_{PQ}$ is inversely proportional to the gravitino mass. The gravitino mass range which corresponds to the axion window $f_{PQ} \simeq 10^{9}$ GeV -- $10^{13}$ GeV lies in the region predicted by gauge-mediated supersymmetry breaking models. The model is also shown to be cosmologically viable.
The addition of the QCD axion to the Minimal Supersymmetric Standard Model (MSSM) not only solves the strong CP problem but also modifies the dark sector with new dark matter candidates. While SUSY axion phenomenology is usually restricted to searches for the axion itself or searches for the ordinary SUSY particles, this work focuses on scenarios where the axion's superpartner, the axino, may be detectable at the Large Hadron Collider (LHC) in the decays of neutralinos displaced from the primary vertex. In particular, we focus on the KSVZ axino within the hadronic axion window. The decay lengt…
We consider hadronic axion models that extend the Standard Model by one complex scalar field and one or more new heavy quarks, i.e. $N_\mathcal{Q} \geq 1$. We review previously suggested selection criteria as well as categorize and catalog all possible models for $N_\mathcal{Q} \leq 9$. In particular, allowing for $N_\mathcal{Q} > 1$ can introduce models that spoil the axion solution of the strong CP problem. Demanding that Landau poles do not appear below some energy scale limits the number of preferred models to a finite number. For our choice of criteria, we find that $N_\mathcal{Q} \leq 28…
We derive two features of axion cosmology that may have cosmological implications, whether or not axions are dark matter: For the full range of allowed axion masses, the evolution of a cosmic axion background allows large CP violation until temperatures as low as $\sim$ 2 GeV, and once the axion field begins to oscillate, the cosmological axion field's relaxation to its ground state can briefly provide a new departure from thermal equilibrium, via time-varying CP violation. During both of these periods, the Strong CP violating parameter $\barθ$ can be as large as O(1).
We compute the CP-violating (CPV) scalar axion coupling to nucleons in the framework of baryon chiral perturbation theory and we apply the results to the case of left-right symmetry. The correlated constraints with other CPV observables show that the predicted axion nucleon coupling is within the reach of present axion-mediated force experiments for $M_{W_R}$ up to $1000$ TeV.
We study charged lepton flavor violation associated with a light leptophilic axion-like particle (ALP), $X$, at the $B$-factory experiment Belle II. We focus on production of the ALP in the tau decays $τ\to X l$ with $l=e,μ$, followed by its decay via $X\to l^- l^+$. The ALP can be either promptly decaying or long-lived. We perform Monte-Carlo simulations, recasting a prompt search at Belle for lepton-flavor-violating $τ$ decays, and propose a displaced-vertex (DV) search. For both types of searches, we derive the Belle~II sensitivity reaches in both the product of branching fractions and the …
In this talk, I present a pedagogical and historical review related to the CP symmetry. It includes the weak CP violation, the strong CP problem, "invisible" axions and cosmology, and Type-II leptogenesis.
These proceedings review direct CP violation in hadronic B decays. The experimental results include those related to the measurement of the unitarity triangle angle gamma using B->D(*)K(*) decays and measurements of charmless hadronic B decays. The results reported have been made by the BABAR, Belle and LHCb collaborations. Theoretical calculations related to these decays are also summarised. The importance of inputs from the charm sector in determining gamma from B->D(*)K(*) decays is discussed. In addition, the future prospects for these measurements will be reviewed.
While the axion was originally introduced to wash out CP violation from strong interactions, new sources of CP violation beyond QCD might manifest themselves via a tiny scalar axion-nucleon component. The latter can be experimentally probed in axion-mediated force experiments, as suggested long ago by J.E. Moody and F. Wilczek. In the present note, I review the physical origin of CP-violating axion couplings and point out the special role of the QCD axion as a low-energy portal to high-energy sources of CP violation.
Within the Standard Model Effective Field Theory framework, with operators up to dimension 6, we perform a model-independent analysis of the lepton-flavour-violating processes involving tau leptons. Namely, we study hadronic tau decays and $\ell$--$τ$ conversion in nuclei, with $\ell = e,μ$. Based on available experimental limits, we establish constraints on the Wilson coefficients of the operators contributing to these processes. Our work paves the way to extract the related information from Belle II and foreseen future experiments.
In this work, we adress the phenomenological consequences of explicit CP violation on direct Higgs-boson searches at high energy colliders. Having a restricted parameter space, we concentrate on the recently proposed gluino-axion model, and investigate the CP violation capability of the model subject to the recent experimental data. It is shown that the Higgs masses as well as their CP compositions are quite sensitive to the supersymmetric CP phases. The lightest Higgs is found to be nearly CP even to a good approximation whilst the remaining two heavy scalars do not have definite CP parities.
There are different approaches for the hadronic B decay calculations, recently. In this paper, we upgrade three of them, namely factorization, QCD factorization and the perturbative QCD approach based on $k_T$ factorization, by using new parameters and full wave functions. Although they get similar results for many of the branching ratios, the direct CP asymmetries predicted by them are different, which can be tested by recent experimental measurements of B factories.
Within the Standard Model Effective Field Theory framework, with operators up to dimension 6, we perform a model-independent analysis of the lepton-flavour-violating processes involving tau leptons. Namely, we study hadronic tau decays and $\ell$-$τ$ conversion in nuclei ($\ell=e,μ$). Based on available experimental limits, we establish constraints on the Wilson coefficients of the operators contributing to these processes. The related information from Belle II and foreseen future experiments can be easily incorporated into the resulting framework.
We discuss the quantitative impact of duality violations on the determination of the strong coupling constant from hadronic tau decays, based on a preliminary analysis of OPAL data.
We show that the rotation of the QCD axion field, aided by $B-L$ violation from supersymmetric $R$-parity violating couplings, can yield the observed baryon abundance. Strong sphaleron processes transfer the angular momentum of the axion field into a quark chiral asymmetry, which $R$-parity violating couplings convert to the baryon asymmetry of the Universe. We focus on the case of dimensionless $R$-parity violating couplings with textures motivated by grand unified theories and comment on more general scenarios. The axion decay constant and mass spectrum of supersymmetric particles are constr…
We present a novel data-driven method for determining the hadronic interaction strengths of axion-like particles (ALPs) with QCD-scale masses. Using our method, it is possible to calculate the hadronic production and decay rates of ALPs, along with many of the largest ALP decay rate to exclusive final states. To illustrate the impact on QCD-scale ALP phenomenology, we consider the scenario where the ALP-gluon coupling is dominant over the ALP coupling to photons, electroweak bosons, and all fermions for $m_π \lesssim m_a \lesssim 3$ GeV. We emphasize, however, that our method can easily be gen…
Quantum gravity introduces a new source of the combined parity (CP) violation in gauge theories. We argue that this new CP violation gets bundled with the strong CP violation through the coloured gravitational instantons. Consequently, the standard axion solution to the strong CP problem is compromised. Further, we argue that the ultimate solution to the strong CP problem must involve at least one additional axion particle.
We study the rare decays $B_s^0\to D^\pm π^\mp$ and $\bar B_s^0\to D^\mp π^\pm$, which can occur only via annihilation type $W$ exchange diagrams in the standard model. The time-dependent decay rates of the four channels can provide four CP parameters, which are experimentally measurable. We show that the CKM angle $ϕ_3=γ$ can be determined from these parameters without any theoretical model dependence. These channels can be measured in future LHCb experiments to provide a clean way for $γ$ measurement.
I propose a variant invisible axion model of spontaneous CP violation at the electroweak scale without CP domain wall and `strong CP' problems. Both large size QCD and small size non-QCD instantons break CP and Peccei-Quinn symmetries, and render cosmologically harmful CP domain walls unstable. The decaying epoch depends on size of small instanton effects, and is around 100 eV if the current neutron electric dipole moment bound is maximally saturated. The model satisfies constraints from primordial D and He photo-dissociation and black hole formation, while producing cosmologically interesting…
The strong CP-violating parameter is small today as indicated by constraints on the neutron electric dipole moment. In the early universe, the QCD axion has not yet relaxed to its QCD-cancelling minimum and it is natural to wonder whether this large CP violation could be responsible for baryogenesis. We show that strong CP violation from the QCD axion can be responsible for the matter antimatter asymmetry of the universe in the context of cold electroweak (EW) baryogenesis if the EW phase transition is delayed below the GeV scale. This can occur naturally if the Higgs couples to a O(100) GeV d…
In the study of CP violation within and beyond the Standard Model of particle physics, pure hadronic B decays are the key players. Improving the determination of the CKM angle $γ$ is one of the important tasks in this endeavour. Besides, the full description of pure hadronic decays due to their strong interaction dynamics remains one of the challenges. In this summary, we discuss the recent results and progress on $γ$ determinations and direct CP violation in pure hadronic B decays as presented at CKM 2018.
We discuss the scalar meson mixing scenario and present an OZI rule violation mechanism for understanding the scalar productions in charmoium hadronic decays. We stress that the OZI violation could play a key role in disentangling the structure of the scalars: $f_0(1370)$, $f_0(1500)$ and $f_0(1710)$.
Axion-like particles (ALPs) with lepton-flavor violating couplings can be probed in exotic muon and tau decays. The sensitivity of different experiments depends strongly on the ALP mass and its couplings to leptons and photons. For ALPs that can be resonantly produced, the sensitivity of three-body decays such as $μ\to 3e$ and $τ\to 3μ$ exceeds by many orders of magnitude that of radiative decays like $μ\to eγ$ and $τ\toμγ$. Searches for these two types of processes are therefore highly complementary. We discuss experimental constraints on ALPs with a single dominant lepton-flavor violating co…
Motivated by the recent Xenon1T result, we study a leptophilic flavour-dependent anomaly-free axion-like particle (ALP) and its effects on charged-lepton flavour violation (CLFV). We present two representative models. The first one considers that the ALP origins from the flavon that generates the charged-lepton masses. The second model assumes a larger flavour symmetry such that more general mixings in the charged-lepton are possible, while maintaining flavour-dependent ALP couplings. We find that a keV ALP explaining the Xenon1T result is still viable for lepton flavour violation and stellar …
The QCD axion is one of the most compelling solutions of the strong CP problem. There are major current efforts into searching for an ultralight, invisible axion, which is believed to be the only phenomenologically viable realization of the QCD axion. Visible axions with decay constants at or below the electroweak scale are believed to have been long excluded by laboratory searches. Considering the significance of the axion solution of the strong CP problem, we revisit experimental constraints on QCD axions in the O(10 MeV) mass window. In particular, we find a variant axion model that remains…
New Bounds on Heavy QCD Axions from Big Bang Nucleosynthesis
Institute for Basic Science (IBS)（韩国基础科学研究院）；Center for Theoretical Physics of the Universe, Institute for Basic Science (IBS)（韩国基础科学研究院宇宙理论物理中心）；Florida State University（佛罗里达州立大学）；High Energy Accelerator Research Organization (KEK)（高能加速器研究机构）
We review recent results on hadronic B meson decays including rare as well as non-suppressed decays. The main emphasis is on those channels relevant to measurement of CP violation in the coming B factories. After briefly describing flavor-tagged charm counting, we cover B -> DK(*), B -> charmless 2-body decays, inclusive eta' production, and final-state-interaction phases in B -> Psi K* and B -> D* rho.
We revisit the flavor-changing processes involving an axion-like particle (ALP) in the context of generic ALP effective lagrangian with a discussion of possible UV completions providing the origin of the relevant bare ALP couplings. We focus on the minimal scenario that ALP has flavor-conserving couplings at tree level, and the leading flavor-changing couplings arise from the loops involving the Yukawa couplings of the Standard Model fermions. We note that such radiatively generated flavor-changing ALP couplings can be easily suppressed in field theoretic ALP models with sensible UV completion…
The axion solution to the strong CP problem makes use of a global Peccei-Quinn U(1) symmetry which is susceptible to violations from quantum gravitational effects. We show how discrete gauge symmetries can protect the axion from such violations. PQ symmetry emerges as an approximate global symmetry from discrete gauge symmetries. Simple models based on Z_N symmetries with N =11,12, etc are presented realizing the DFSZ axion and the KSVZ axion. The discrete gauge anomalies are cancelled by a discrete version of the Green-Schwarz mechanism. In the supersymmetric extension our models provide a na…
The search for resonant absorption of the Primakoff solar axions by $^{169}$Tm nuclei have been performed. Such an absorption should lead to the excitation of low-lying nuclear energy level: $A+^{169}$Tm $\to ^{169}$Tm$^*$ $\to ^{169}$Tm$ + γ$ (8.41 keV). The Si(Li) detector and $^{169}$Tm target placed inside the low-background setup were used for that purpose. As a result, a new restriction on the axion-photon coupling and axion mass was obtained: $g_{Aγ}({GeV}^{-1})\cdot m_A(eV)\leq1.36\cdot10^{-5}$ (90% c.l.). In model of hadronic axion this restriction corresponds to the upper limit on ax…
Motivated by the recent observation of CP violation in the charm sector by LHCb, we study direct CP asymmetries in the standard model (SM) for the singly Cabibbo-suppressed two-body hadronic decays of charmed mesons using the topological-diagram approach. In this approach, the magnitude and the phase of topological weak annihilation amplitudes which arise mainly from final-state rescattering can be extracted from the data. Consequently, direct CP asymmetry $a_{dir}^{\rm (tree)}$ at tree level can be reliably estimated. In general, it lies in the range $10^{-4}<a_{dir}^{\rm (tree)}<10^{-3}$. Sh…
We study hadronic and leptonic flavor physics in a SUSY SO(10) model proposed by Chang, Masiero, and Murayama, which links b -> s transitions to the observed large atmospheric neutrino mixing angle. We find large effects in B_s-B_s-bar mixing and BR(tau -> mu gamma) and comment on B_d -> phi K_S.
Three different methods, using $B_d\to J/ψK_S$, $J/ψK_S π^0$, $B_d\to K^-π^+, π^+π^-$ and $B_u\to K^- π^0, \bar K^0 π^-, π^-π^0$, to extract hadronic model independent information about new physics are discussed in this talk.
I present two disparate examples of isospin violation in hadronic B-decays. In the first, the presence of ρ^0-ωmixing in the decay B^\mp\toρ^\mpρ^0(ω)\toρ^\mpπ^+ π^- permits the extraction of sgn(\sin α), where αis the usual angle of the unitarity triangle, with minimal hadronic uncertainty. In the second, the presence of π^0-η,η' mixing can obscure the extraction of \sin 2αfrom an isospin analysis in B\toππdecays.
Weak interactions between quarks give rise to hadronic parity violation which can be observed in nuclear and few-nucleon systems. We study the QCD renormalization of the isotensor component of parity violation at next-to-leading order accuracy. The renormalization group is employed to evolve the interaction down to hadronic scales. As the results are renormalization scheme dependent, we compare various schemes, including 't Hooft-Veltman dimensional regularization, and several regularization independent-momentum subtraction schemes.
CP violating interactions are required to realize the matter abundance of our Universe. It is however known that the standard model of particle physics does not contain sufficient CP violation. The electric dipole moment (EDM) of atomic systems is a very sensitive experimental probe of CP violation beyond the standard model, and it is very actively studied in experiments. The atomic EDM has a significant sensitivity to hadronic CP violation, but its quantification has for long been obstructed by the nonperturbative physics of quantum chromodynamics. Quite recently, the contribution of the Wein…
In this talk I discuss three different methods, using B_d to J/psi K_S, J/psi K_s pi^o, B_d to K^- pi^+, pi^+ pi^- and B_u to K^- pi^0, bar K^0 pi^- pi^- pi^0, to extract hadronic model independent information about new physics.
Axions are introduced to explain the observed smallness of the $\bar θ$ term of QCD. Standard Model extensions typically contain new sources of CP violation, for instance to account for the baryon asymmetry of the universe. In the presence of additional CP-violating sources a Peccei-Quinn mechanism does not remove all CP violation, leading to CP-odd interactions among axions and Standard Model fields. In this work, we use effective field theory to parametrize generic sources of beyond-the-Standard-Model CP violation. We systematically compute the resulting CP-odd couplings of axions to leptons…
We discuss phenomenological criteria for defining "axion windows", namely regions in the parameter space of the axion-photon coupling where realistic models live. Currently, the boundaries of this region depend on somewhat arbitrary criteria, and it would be highly desirable to specify them in terms of precise phenomenological requirements. We first focus on hadronic axion models within post-inflationary scenarios, in which the initial abundance of the new vectorlike quarks $Q$ is thermal. We classify their representations $R_Q$ by requiring that $i)$ the $Q$ are sufficiently short lived to av…
The QCD axion provides an elegant solution to the Strong CP Problem. While the minimal realization is vulnerable to the so-called "Axion Quality Problem", we will consider a more robust realization in the presence of a mirror sector related to the Standard Model by a (softly broken) $\mathbb{Z}_2$ symmetry. We point out that the resulting "heavy" axion, while satisfying all theoretical and observational constraints, has a large and uncharted parameter space which allows it to be probed at the LHC as a Long-Lived Particle (LLP). The small defining axionic coupling to gluons results in a challen…
We discuss a preliminary study of the impact of duality violations on extractions from tau decay data of the D=6 VEVs which determine chiral limit Standard Model K-->pi pi matrix elements of the electroweak penguin operators.
