arXiv subjects

Shinya Matsuzaki

Publications and source records attributed to Shinya Matsuzaki.

At least 55 records · Page 3Linked to original sources

arXiv2020

Dynamic scale anomalous transport in QCD with electromagnetic background

We discuss phenomenological implications of the anomalous transport induced by the scale anomaly in QCD coupled to an electromagnetic (EM) field, based on a dilaton effective theory. The scale anomalous current emerges in a way perfectly analogous to the conformal transport current induced in a curved spacetime background, or the Nernst current in Dirac and Weyl semimetals -- both current forms are equivalent by a "Weyl transformation". We focus on a spatially homogeneous system of QCD hadron phase, which is expected to be created after the QCD phase transition and thermalization. We find that the EM field can induce a dynamic oscillatory dilaton field which in turn induces the scale anomalous current. As the phenomenological applications, we evaluate the dilepton and diphoton productions induced from the dynamic scale anomalous current, and find that those productions include a characteristic peak structure related to the dynamic oscillatory dilaton, which could be tested in heavy ion collisions. We also briefly discuss the out-of-equilibrium particle production created by a nonadiabatic dilaton oscillation, which happens in a way of the so-called tachyonic preheating mechanism.

hep-ph↗

arXiv2020

Unified Interpretation of Scalegenesis in Conformally Extended Standard Models

We present a universal interpretation for a class of conformal extended standard models including Higgs portal interactions realized in low-energy effective theories. The scale generation mechanism in this class (scalegenesis) arises along the (nearly) conformal/flat direction for the scale symmetry breaking, where the electroweak-symmetry breaking structure is achieved in a similar way to the standard model's. A dynamical origin for the Higgs portal coupling can provide the discriminator for the low-energy ``universality class'', to be probed in forthcoming collider experiments.

hep-ph↗

arXiv2020

Inverse Mass Hierarchy of Light Scalar Mesons Driven by Anomaly-Induced Flavor Breaking

We propose a novel mechanism to reproduce the observed mass hierarchy for the scalar mesons lighter than 1 GeV (called the inverse hierarchy) regarding them as mesons made of a quark and an anti-quark ($q\bar{q}$ mesons). The source is provided by the SU(3)-flavor symmetry-breaking induced by U(1) axial anomaly. In particular, the anomaly term including the explicit-chiral symmetry-breaking plays a significant role for the light scalar meson spectrum. To be concrete, we construct a linear sigma model for the scalar mesons of $q\bar{q}$ type together with their pseudoscalar chiral partners, including an anomaly-induced explicit-chiral symmetry-breaking term. We find that, due to the proposed mechanism, the inverse hierarchy, i.e., $m\left[ a_0 (980) \right] \simeq m\left[ f_0 (980) \right] > m \left[ K_0^\ast (700) \right] > m \left[ f_0(500) \right]$ is indeed realized. Consequently, the quark content of $f_0 (500)$ is dominated by the isoscalar $\bar uu+ \bar dd$ component, and $f_0 (980)$ is by the strange quark bilinear's, $s\bar{s}$.

hep-ph↗

arXiv2020

A Walking Dilaton Inflation

We propose an inflationary scenario based on a many-flavor hidden QCD with eight flavors, which realizes the almost scale-invariant (walking) gauge dynamics. The theory predicts two types of composite (pseudo) Nambu-Goldstone bosons, the pions and the lightest scalar (dilaton) associated with the spontaneous chiral symmetry breaking and its simultaneous violation of the approximate scale invariance. The dilaton acts as an inflaton, where the inflaton potential is induced by the nonperturbative-scale anomaly linked with the underlying theory. The inflaton potential parameters are highly constrained by the walking nature, which are evaluated by straightforward nonperturbative analyses including lattice simulations. Due to the pseudo Nambu-Goldstone boson's natures and the intrinsic property for the chiral symmetry breaking in the walking gauge dynamics, the inflaton coupled to the pions naturally undergoes the small field inflation consistently with all the cosmological and astrophysical constraints presently placed by Planck 2018 data. When the theory is vector-likely coupled to the standard model in part in a way to realize a dynamical electroweak symmetry breaking, the reheating temperature is determined by the pion decays to electroweak gauge bosons. The proposed inflationary scenario would provide a dynamical origin for the small field inflation as well as the light pions as a smoking-gun to be probed by future experiments.

hep-ph↗

arXiv2020

Big Bang Nucleosynthesis Hunts Chameleon Dark Matter

We study the chameleon field dark matter, dubbed \textit{scalaron}, in $F(R)$ gravity in the Big Bang Nucleosynthesis (BBN) epoch. With an $R^{2}$-correction term required to solve the singularity problem for $F(R)$ gravity, we first find that the scalaron dynamics is governed by the $R^{2}$ term and the chameleon mechanism in the early universe, which makes the scalaron physics model-independent regarding the low-energy scale modification. In viable $F(R)$ dark energy models including the $R^{2}$ correction, our analysis suggests the scalaron universally evolves in a way with a bouncing oscillation irrespective of the low-energy modification for the late-time cosmic acceleration. Consequently, we find a universal bound on the scalaron mass in the BBN epoch, to be reflected on the constraint for the coupling strength of the $R^2$ term, which turns out to be more stringent than the one coming from the fifth force experiments. It is then shown that the scalaron naturally develops a small enough fluctuation in the BBN epoch, hence can avoid the current BBN constraint placed by the latest Planck 2018 data, and can also have a large enough sensitivity to be hunted by the BBN, with more accurate measurements for light element abundances as well as the baryon number density fraction.

hep-ph↗

arXiv2019

$F(R)$ gravity in the early Universe: Electroweak phase transition and chameleon mechanism

It is widely believed that the screening mechanism is an essential feature for the modified gravity theory. Although this mechanism has been examined thoroughly in the past decade, their analyses are based on the classical configuration of the matter fields. In this paper, we demonstrate a new formulation of the chameleon mechanism in $F(R)$ gravity theory, to shed light on quantum-field theoretical effects on the chameleon mechanism as well as the related scalaron physics, induced by the matter sector. We show a potential absence of the chameleon mechanism in the cosmic history based on a scale-invariant-extended scenario beyond the standard model of particle physics, in which a realistic electroweak phase transition, possibly yielding the right amount of baryon asymmetry of Universe today, simultaneously breaks the scale invariance in the early Universe. Remarkably enough, the matter sector contribution to the trace of energy-momentum tensor turns out to be on the same order of magnitude as that computed in the classical perfect-fluid approximation, even though the theory involves the nontrivial electroweak-phase transition environment. We also briefly discuss the oscillation of the scalaron field and indirect generation of non-tensorial gravitational waves induced by the electroweak phase transition.

gr-qc↗

arXiv2019

Enhanced diHiggs signal from hidden scalar QCD at leading-order scale-symmetry limit

We develop an effective-model description arising from a recently proposed scale-invariant hidden scalar-QCD, which has been used to explain the dynamical origin of the electroweak scale. In addition to the previous works, our new effective model includes the dynamical scale-anomaly effect from the hidden QCD gluons, to explicitly break the classical-scale invariance at the level of an effective field theory, which is known as the leading-order scale-symmetry (LOSS). In the phenomenological analysis, the proposed model predicts a light composite dilaton composed of hidden scalar quarks and gluons with the mass around electroweak scale (around 280 GeV), and has only one input parameter, which is the mixing angle between the Higgs boson and the composite dilaton. Our result for the dilaton mass is in accord with the lattice simulation for scalar QCD, where the scalar-quark bound states acquire a large effective mass from the hidden gluon contribution. Furthermore, we predict several significant deviations from the SM, like the diHiggs production cross sections (maximally about 10 times larger than the SM prediction), that could be directly tested at the high luminosity LHC. It is also the first study for the diHiggs production signal predicted from a scale(conformal)-invariant hidden sector, even from dark/hidden QCD. Our proposed effective model is thus significantly different than the conventional realization of scale-invariant hidden-scalar QCD without the scale anomaly effect, and can potentially provide a competitive explanation for many exotic phenomena beyond the standard model, such as new dark matter candidates and a strongly first-order electroweak phase transition.

hep-ph↗

arXiv2019

Simultaneous explanation of $K$ and $B$ anomalies in vectorlike compositeness

We address the presently reported significant flavor anomalies in the $K$ and $B$ meson systems such as the CP violating Kaon decay ($ε'/ε$) and lepton-flavor universality violation in $B$ meson decays ($R_{K^{(*)}},$ and also commenting ${R_{D^{(*)}}}$), by proposing flavorful and chiral vector bosons as the new physics constitution at $\sim 1\,\mathrm{TeV}$. Interestingly, if the new (composite) vector bosons are quite heavier than $\sim 1\,\mathrm{TeV}$, we face a difficulty in addressing the anomaly in $ε'/ε$ consistently with the constraint from the $K^0$-$\overline{K^0}$ mixing. Both of the anomalies can be addressed within $1σ$ confidence levels individually, where the relevant parameter space will be investigated by the NA62 and KOTO experiments, in addition to direct searches at the large hadron collider.

hep-ph↗

arXiv2019

Chiral-Imbalance Density Wave in Baryonic Matters

We propose a new chirality-imbalance phenomenon arising in baryonic/high dense matters under a magnetic field. A locally chiral-imbalanced (parity-odd) domain can be created due to the electromagnetically induced $U(1)_A$ anomaly in high-dense matters. The proposed local-chiral imbalance generically possesses a close relationship to a spacial distribution of an inhomogeneous chiral (pion)-vector current coupled to the magnetic field. To demonstrate such a nontrivial correlation, we take the skyrmion crystal approach to model baryonic/high dense matters. Remarkably enough, we find the chirality-imbalance distribution takes a wave form in a high density region (dobbed ``chiral-imbalance density wave''), when the inhomogeneous chiral condensate develops to form a chiral density wave. This implies the emergence of a nontrivial density wave for the explicitly broken $U(1)_A$ current simultaneously with the chiral density wave for the spontaneously broken chiral-flavor current. We further find that the topological phase transition in the skyrmion crystal model (between skyrmion and half-skyrmion phases) undergoes the deformation of the chiral-imbalance density wave in shape and periodicity. The emergence of this chiral-imbalance density wave could give a crucial contribution to studies on the chiral phase transition, as well as the nuclear matter structure, in compact stars under a magnetic field.

nucl-th↗

arXiv2018

Simultaneous interpretation of $K$ and $B$ anomalies in terms of chiral-flavorful vectors

We address the presently reported significant flavor anomalies in the Kaon and $B$ meson systems such as the CP violating Kaon decay ($ε'/ε$) and lepton-flavor universality violation in $B$ meson decays ($R_{K^{(*)}},{R_{D^{(*)}}}$), by proposing flavorful and chiral vector bosons as the new physics constitution at around TeV scale. The chiral-flavorful vectors (CFVs) are introduced as a 63-plet of the global $SU(8)$ symmetry, identified as the one-family symmetry for left-handed quarks and leptons in the standard model (SM) forming the 8-dimensional vector. Thus the CFVs include massive gluons, vector leptoquarks, and $W',Z'$-type bosons, which are allowed to have flavorful couplings with left-handed quarks and leptons, and flavor-universal couplings to right-handed ones, where the latter arises from mixing with the SM gauge bosons. The flavor texture is assumed to possess a "minimal" structure to be consistent with the current flavor measurements on the $K$ and $B$ systems. Among the presently reported significant flavor anomalies in the Kaon and $B$ meson systems ($ε'/ε$, $R_{K^{(*)}}, {R_{D^{(*)}}}$), the first two $ε'/ε$ and $R_{K^{(*)}}$ anomalies can simultaneously be interpreted by the presence of CFVs, the ${R_{D^{(*)}}}$ anomaly is predicted not to survive, due to the approximate $SU(8)$ flavor symmetry. Remarkably, we find that as long as both of the $ε'/ε$ and $R_{K^{(*)}}$ anomalies persist beyond the SM, the CFVs predict the enhanced $K^+ \to π^+ ν\barν$ and $K_L \to π^0 ν\barν$ decay rates compared to the SM values, which will readily be explored by the NA62 and KOTO experiments, and they will also be explored in new resonance searches at the Large Hadron Collider.

hep-ph↗

arXiv2018

Chiral soliton lattice effect on baryonic matter from skyrmion crystal model

The chiral soliton lattice (CSL) has been studied in condensed-matter system such as chiral magnets, which arises as a parity-violating topological soliton. In hadron physics, various attempts have also been made to apply the idea of CSL to baryonic matter. In this work, we explore the CSL effects on the baryonic matter based on the skrymion crystal approach. It is found that the CSL causes an inverse catalysis for the topology change in the dense baryonic matter. Furthermore, we observe that the CSL makes the single-baryon shape deformed to be highly oscillating as the frequency of the CSL gets larger, which leads to the enhancement of a baryon energy. Of interest is that in a high density region, the CSL goes away due to the topology change in the baryonic matter. What we find here might deepen our understanding of dense matter systems as well as compact stars.

nucl-th↗

arXiv2018

Magnetic field effect on nuclear matter from skyrmion crystal model

We explore magnetic field effects on the nuclear matter based on the skrymion crystal approach for the first time. It is found that the magnetic effect plays the role of a catalyzer for the topological phase transition (topological deformation for the skyrmion crystal configuration from the skrymion phase to half-skyrmion phase). Furthermore, we observe that in the presence of the magnetic field, the inhomogeneous chiral condensate persists both in the skyrmion and half-skyrmion phases. Explicitly, as the strength of magnetic field gets larger, the inhomogeneous chiral condensate in the skyrmion phase tends to be drastically localized, while in the half-skyrmion phase the inhomogeneity configuration is hardly affected. It also turns out that a large magnetic effect in a low density region distorts the baryon shape to an elliptic form but the crystal structure is intact. However, in a high density region, the crystal structure is strongly effected by the strong magnetic field. A possible correlation between the chiral inhomogeneity and the deformation of the skrymion configuration is also addressed. The results obtained in this paper might be realized in the deep interior of compact stars.

nucl-th↗

arXiv2017

Cosmic History of Chameleonic Dark Matter in $F(R)$ Gravity

We study the cosmic history of the scalaron in $F(R)$ gravity with constructing the time evolution of the cosmic environment and discuss the chameleonic dark matter based on the chameleon mechanism in the early and current Universe. We then find that the scalaron can be a dark matter. We also propose an interesting possibility that the $F(R)$ gravity can address the coincidence problem.

gr-qc↗

arXiv2017

Bosonic-Seesaw Portal Dark Matter

We discuss a new type of Higgs-portal dark matter (DM)-production mechanism, called bosonic-seesaw portal (BSP) scenario. The BS provides the dynamical origin of the electroweak symmetry breaking, triggered by mixing between the elementary Higgs and a composite Higgs generated by a new-color strong dynamics, hypercolor (HC). At the HC strong coupling scale, the classical-scale invariance assumed in the model is dynamically broken as well as the "chiral" symmetry present in the HC sector. In addition to the composite Higgs, HC baryons emerge to potentially be stable because of the unbroken HC baryon number symmetry. Hence the lightest HC baryon can be a DM candidate. Of interest in the present scenario is that HC pions can be as heavy as the HC baryon due to the possibly enhanced-explicit "chiral"-breaking effect triggered after the BS mechanism, so the HC baryon pair cannot annihilate into HC pions. As in the standard setup of freeze-in scenario, it is assumed that the DM was never in the thermal equilibrium, which ends up with no thermal abundance. It is then the non-thermal BSP process that crucially comes into the game below the HC scale: the HC baryon significantly couples to the standard-model Higgs via the BS mechanism, and can non-thermally be produced from the thermal plasma below the HC scale, which turns out to allow the TeV mass scale for the composite baryonic DM, much smaller than the generic bound placed in the conventional thermal freeze-out scenario, to account for the observed relic abundance. Thus the DM can closely be related to the mechanism of the electroweak symmetry breaking.

hep-ph↗

arXiv2017

Phenomenology of flavorful composite vector bosons in light of $B$ anomalies

We analyze the flavor structure of composite vector bosons arising in a model of vectorlike technicolor, often called hypercolor (HC), with eight flavors that form a one-family content of HC fermions. Dynamics of the composite vector bosons, referred to as HC rho in this paper, are formulated together with HC pions by the hidden local symmetry (HLS), in a way analogous to QCD vector mesons. Then coupling properties to the standard model (SM) fermions, which respect the HLS gauge symmetry, are described in a way that couplings of the HC rhos to the left-handed SM quarks and leptons are given by a well-defined setup as taking the flavor mixing structures into account. Under the present scenario, we discuss significant bounds on the model from electroweak precision tests, flavor physics, and collider physics. We also try to address B anomalies in processes such as B -> K(*) mu+ mu- and B -> D(*) tau nu, recently reported by LHCb, Belle, (ATLAS, and CMS in part.) Then we find that the present model can account for the anomaly in B -> K(*) mu+ mu- consistently with the other constraints while it predicts no significant deviations in B -> D(*) tau nu from the SM, which can be examined in the future Belle II experiment. The former is archived with the form C9 = -C10 of the Wilson coefficients for effective operators of b -> s mu+ mu-, which has been favored by the recent experimental data. We also investigate current and future experimental limits at the Large Hadron Collider (LHC) and see that possible collider signals come from dijet and ditau, or dimuon resonant searches for the present scenario with TeV mass range. To conclude, the present b -> s mu+ mu- anomaly is likely to imply discovery of new vector bosons in the ditau or dimuon channel in the context of the HC rho model. Our model can be considered as a UV completion of conventional U(1)' model.

hep-ph↗

arXiv2017

Charged pions tagged with polarized photons probing strong CP violation in a chiral-imbalance medium

It is expected that in a hot QCD system, a local parity-odd domain can be produced due to nonzero chirality, which is induced from the difference of winding numbers carried by the gluon topological configuration (QCD sphaleron). This local domain is called the chiral-imbalance medium characterized by nonzero chiral chemical potential, which can be interpreted as the time variation of the strong CP phase. We find that the chiral chemical potential generates the parity breaking term in the electromagnetic form factor of charged pions. Heavy ion collision experiments could observe the phenomenological consequence of this parity-odd form factor through the elastic scattering of a pion and a photon in the medium. Then we quantify the asymmetry rate of the parity violation by measuring the polarization of the photon associated with the pion, and discuss how it could be measured in a definite lab frame. We roughly estimate the typical size of the asymmetry, just by picking up the pion resonant process, and find that the signal can be sufficiently larger than possible background events from parity-breaking electroweak process. Our findings might provide a novel possibility to make a manifest detection for the remnant of the strong CP violation.

nucl-th↗

arXiv2017

Dark Side of the Standard Model: Dormant New Physics Awaken

We find that the nonperturbative physics of the standard-model Higgs Lagrangian provides a dark matter candidate, "dormant skyrmion in the standard model", the same type of the skyrmion, a soliton, as in the hadron physics. It is stabilized by another nonperturbative object in the standard model, the dynamical gauge boson of the hidden local symmetry, which is also an analogue of the rho meson.

hep-ph↗

arXiv2017

Scalegenesis via dynamically induced multiple seesaws

We propose a model which accounts for the dynamical origin of the electroweak symmetry breaking (EWSB), directly linking to the mass generation of dark matter (DM) candidate and active neutrinos. The standard model (SM) is weakly charged under the $U(1)_{\rm B-L}$ gauge symmetry, in conjunction with newly introduced three right-handed Majorana neutrinos and the $U(1)_{\rm B-L}$ Higgs. The model is built on the classical scale invariance, that is dynamically broken by a new strongly coupled sector, what is called the hypercolor (HC) sector, which is also weakly coupled to the $U(1)_{\rm B-L}$ gauge. At the HC strong scale, the simultaneous breaking of the EW and $U(1)_{\rm B-L}$ gauge symmetries is triggered by dynamically induced multiple seesaw mechanisms, namely bosonic seesaw mechanisms. Thus, all the origins of masses are provided singly by the HC dynamics: that is what we call the dynamical scalegenesis. We also find that an HC baryon, with mass on the order of a few TeV, can be stabilized by the HC baryon number and the $U(1)_{\rm B-L}$ charge, so identified as a DM candidate. The relic abundance of the HC-baryon DM can be produced dominantly via the bosonic-seesaw portal process, and the HC-baryon DM can be measured through the large magnetic moment coupling generated from the HC dynamics, or the $U(1)_{\rm B-L}$-gauge boson portal in direct detection experiments.

hep-ph↗