Search

We study the vacuum alignment of the top-mode pseudo-Nambu-Goldstone boson Higgs (TMpNGBH) model, which has recently been proposed as a variant of the top-quark condensate model in light of the 126 GeV Higgs boson discovered at the LHC. It is shown that the vacuum of the model, determined from the one-loop effective potential with all the explicit breaking effects included, realizes the electroweak symmetry breaking with the appropriate breaking scale. Phenomenologies of two characteristic particles in the TMpNGBH model, namely the CP-odd partner of the Higgs (A0t) and the vectorlike partner of the top quark (t'), are also studied based on the newly identified vacuum. [ABSTRACT FROM AUTHOR]

We study the mixing structure of isospin-singlet scalars, the light quarkonium (qq) and glueball (gg) in two-flavor QCD, based on a holographic model of bottom-up hard-wall type. In the model the pure quarkonium and glueball states are unambiguously defined in terms of the different U(1)A charges in the restoration limit of the chiral U(2)L × U(2)R symmetry, in which the quarkonium becomes massless as the chiral partner of the pion. Hence the q¯q−gg mixing arises in the presence of the nonzero chiral condensate or pion decay constant. At the realistic point where the pion decay constant and other hadron masses reach the observed amount, we predict a tiny mixing between the lightest quarkonia and glueball: the smallness of the mixing is understood by the slightly small ratio of the chiral and gluon condensate scales. The low-lying two scalar masses are calculated to be ≃1.25 GeV and ≃1.77 GeV, which are compared with the masses of f0(1370) and f0(1710). Our result implies that f0(1710) predominantly consists of the glueball. [ABSTRACT FROM AUTHOR]

We calculate masses of the technipions in the walking technicolor model with the anomalous dimension γm = 1, based on a holographic model which has a naturally light technidilaton ɸ as a composite Higgs with mass mɸ≃125??GeV. The one-family model (with four weak doublets) is taken as a concrete example in such a framework, with the inputs being Fπ = ν/2 ≃ 123??GeV and mɸ ≃ 125??GeV as well as γm = 1. It is shown that technipion masses are enhanced by the large anomalous dimension to typically O(1)??TeV. We find a correlation between the technipion masses and S(TC), the S parameter arising only from the technicolor sector. The current LHC data on the technipion mass limit thus constrains S(TC) to be not as large as O(1), giving a direct constraint on the technicolor model building. This is a new constraint on the technicolor sector alone, quite independent of other sectors connected by the extended-technicolor-type interactions--in sharp contrast to the conventional S parameter constraint from the precision electroweak measurements. [ABSTRACT FROM AUTHOR]

We formulate a scale-invariant hidden local symmetry (HLS) as a low-energy effective theory of walking technicolor (WTC) which includes the technidilaton, technipions, and technirho mesons as the low-lying spectra. As a benchmark for LHC phenomenology, we in particular focus on the one-family model of WTC having eight technifermion flavors, which can be--at energy scales relevant to the reach of the LHC--described by the scale-invariant HLS based on the manifold [SU(8)L x SU(8)R]global x SU(8)local/SU(8)V, where SU(8)local is the HLS and the global SU(8)L x SU(8)R symmetry is partially gauged by the SU(3) x SU(2)L x U(1)Y of the standard model. Based on the scale-invariant HLS, we evaluate the coupling properties of the technirho mesons and place limits on the masses from the current LHC data. Then, implications for future LHC phenomenology are discussed by focusing on the technirho mesons produced through the Drell-Yan process. We find that the color-octet technirho decaying to the technidilaton along with the gluon is of interest as the discovery channel at the LHC, which would provide a characteristic signature to probe the one-family WTC. [ABSTRACT FROM AUTHOR]

We propose new perspective in searching for axionlike particles (ALPs) from quark and lepton flavor physics: measurements of the time-dependent CP asymmetry in B0→K0Sπ0γ and the branching ratio of Bs→e±μ∓ decay possess, along with the anomalous magnetic moment of muon. In the mass range of sub-GeV, accessible by the flavorful ALPs search, the experimental sensitivity for these flavor observables reaches the maximum at around the pion mass scale (called the sweetest spots), where a couple of loopholes (unexplored regions) for the ALP parameter space have heretofore been present, because of an unavoidable contamination with pion background events. The proposed complementary probes can precisely determine the ALP coupling to photon at these sweetest spots/loopholes, and will significantly help cover whole parameter spaces in the ALP search including the present loopholes in the future. [ABSTRACT FROM AUTHOR]

We discuss the violation of quark-flavor symmetry at high temperatures, induced from nonperturbative thermal loop corrections and axial anomaly, based on a three-flavor linear-sigma model including an SU(3) flavor violation induced by U(1)A anomaly which we call an axial-anomaly induced-flavor breaking term. We employ a nonperturbative analysis following the Cornwall-Jackiw-Tomboulis formalism, and show that the model undergoes a chiral crossover with a pseudocritical temperature, consistently with lattice observations. We find following features regarding the flavor breaking eminent around and above the pseudocritical temperature: (i) up-and down-quark condensates drop faster than the strange quark's toward the criticality, but still keep nonzero value even going far above the critical temperature; (ii) the introduced anomaly-related flavor-breaking effect acts as a catalyzer toward the chiral restoration, and reduces the amount of flavor breaking in the up, down and strange quark condensates; (iii) a dramatic deformation for the meson flavor mixing structure is observed, in which the anomaly-induced favor breaking is found to be almost irrelevant; (iv) the meson spectroscopy gets corrected by the net nonperturbative flavor breaking effects, where the scalar meson mass hierarchy (inverse mass hierarchy) is significantly altered by the presence of the anomaly-related flavor breaking; (v) the topological susceptibility significantly gets the contribution from the surviving strange quark condensate, which cannot be dictated by the chiral perturbation theory, and deviates from the dilute instanton gas prediction. There the anomaly-induced flavor breaking plays a role of the destructive interference for the net flavor violation, as in the flavor breaking in the quark condensates; (vi) the U(1)A breaking signaled by nonzero topological susceptibility is enhanced by the nonperturbative strange quark condensate, which may account for the tension in the effective restoration of the U(1)A symmetry currently observed on lattices with two flavors and 2+1 flavors near the chiral limit. Our founding critical natures can be checked in the future lattice simulations, and will give some implications to the thermal history of QCD axion. [ABSTRACT FROM AUTHOR]

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 standard model (SM), like the di-Higgs 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 di-Higgs 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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) candidates and active neutrinos. The standard model (SM) is weakly charged under the U(1)B-L gauge symmetry, in conjunction with newly introduced three right-handed Majorana neutrinos and the U(1)B-L Higgs. The model is built on the classical scale invariance, that is dynamically broken by a new strongly coupled sector, that is called the hypercolor (HC) sector, which is also weakly coupled to the U(1)B-L gauge. At the HC strong scale, the simultaneous breaking of the EW and U(1)B-L gauge symmetries is triggered by dynamically induced multiple seesaw mechanisms, namely bosonic seesaw mechanisms. Thus, all of the origins of masses are provided singly by the HC dynamics: that is what we call the dynamical scalegenesis. We also find that a HC baryon, with a mass on the order of a few TeV, can be stabilized by the HC baryon number and the U(1)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)B-L-gauge boson portal in direct detection experiments. [ABSTRACT FROM AUTHOR]

We explore a new horizon of modified gravity from the viewpoint of particle physics. As a concrete example, we take the F(R) gravity to raise a question: can a scalar particle ("scalaron") derived from the F(R) gravity be a dark matter candidate? We place the limit on the parameter in a class of F(R) gravity model from the constraint on the scalaron as a dark matter. The role of the screening mechanism and compatibility with the dark energy problem are addressed. [ABSTRACT FROM AUTHOR]

We explore a model based on the classically scale-invariant standard model (SM) with a strongly coupled vectorlike dynamics, which is called hypercolor (HC). The scale symmetry is dynamically broken by the vectorlike condensation at the TeV scale, so that the SM Higgs acquires the negative mass squared by the bosonic seesaw mechanism to realize the electroweak symmetry breaking. An elementary pseudoscalar S is introduced to give masses for the composite Nambu-Goldstone bosons (HC pions): The HC pion can be a good target to explore through a diphoton channel at the LHC. As a consequence of the bosonic seesaw, the fluctuating mode of S, which we call s, develops tiny couplings to the SM particles and is predicted to be very light. The s predominantly decays to a diphoton and can behave as invisible axionlike dark matter. The mass of the s dark matter is constrained by currently available cosmological and astrophysical limits to be 10-4 eV≲ms≲1 eV. We find that a sufficient amount of relic abundance for the s dark matter can be accumulated via the coherent oscillation. The detection potential in microwave cavity experiments is also addressed. [ABSTRACT FROM AUTHOR]

In the spirit of the top-quark condensation, we propose a model which has a naturally light composite Higgs boson, "tHiggs" (hto) to be identified with the 126 GeV Higgs discovered at the LHC. The tHiggs, a bound state of the top quark and its flavor (vectorhke) partner, emerges as a pseudo-Nambu-Goldstone boson (NGB), "top-mode pseudo-Nambu-Goldstone boson," together with the exact NGBs to be absorbed into the W and Z bosons as well as another (heavier) top-mode pseudo-Nambu-Goldstone bosons (CP-odd composite scalar, A0t). Those five composite (exact/pseudo-) NGBs are dynamically produced simultaneously by a single supercritical four-fermion interaction having U(3) x U(1) symmetry which includes the electroweak symmetry, where the vacuum is aligned by a small explicit breaking term so as to break the symmetry down to a subgroup, U(2) x U(l)', in a way not to retain the electroweak symmetry, in sharp contrast to the little Higgs models. The explicit breaking term for the vacuum alignment gives rise to a mass of the tHiggs, which is protected by the symmetry and hence naturally controlled against radiative corrections. Realistic top-quark mass is easily realized similarly to the top-seesaw mechanism by introducing an extra (subcritical) four-fermion coupling which explicitly breaks the residual U(2)' x U(l)' symmetry with U(2)' being an extra symmetry besides the above U(3)L x U(1). We present a phenomenological Lagrangian of the top-mode pseudo-Nambu-Goldstone bosons along with the Standard Model particles, which will be useful for the study of the collider phenomenology. The coupling property of the tHiggs is shown to be consistent with the currently available data reported from the LHC. Several phenomenological consequences and constraints from experiments are also addressed. [ABSTRACT FROM AUTHOR]

We develop a method for integrating out the heavy Kaluza-Klein modes of scalar type as well as those of vector and axial-vector types, in a class of hard-wall bottom-up approaches of holographic QCD models, including the Dirac-Born-Infeld and Chern-Simons parts. By keeping only the lowest-lying vector mesons, we first obtain an effective chiral Lagrangian of the vector mesons based on the hidden local symmetry, and all the low-energy constants in the HLS Lagrangian are expressed in terms of holographic integrals and, consequently, are fully determined by the holographic geometry and a few constants of mesons. We find that the Gell-Mann-Oakes-Renner relation is manifestly reproduced at the lowest order of derivative expansion. We also explicitly show that a naive inclusion of the Chern-Simons term cannot reproduce the desired chiral anomaly in QCD, and hence, some counterterms should be provided: This implies that the holographic QCD models of hard-wall type cannot give definite predictions for the intrinsic parity-odd vertices involving vector and axial-vector mesons. After integrating out the vector mesons from the HLS Lagrangian, we further obtain the Lagrangian of chiral perturbation theory for pseudoscalar mesons with all the low-energy constants fully determined. [ABSTRACT FROM AUTHOR]