Search

We describe the sensitivity of the IceCube Neutrino Observatory to the creation of axions in a Type II core-collapse supernova (SN II) in the Galaxy. Axions are a light dark matter candidate, and their existence is well-motivated as a solution to the strong CP problem. In a supernova, axions behave much like neutrinos, efficiently removing energy from the explosion and cooling the system. As a result, neutrino production in an SN~II is suppressed in the presence of axions, mainly affecting the seconds-long tail of the SN~II neutrino light curve. The IceCube Observatory is sensitive to large numbers of MeV neutrinos from an SN~II, which produce a collective rise in the hit rates of all photomultipliers in the detector. We present a shape analysis that can be used with IceCube data to discriminate the axion production scenario from standard SN II models

There are a number of observational hints from astrophysics which point to the existence of stellar energy losses beyond the ones accounted for by neutrino emission. These excessive energy losses may be explained by the existence of a new sub-keV mass pseudoscalar Nambu--Goldstone boson with tiny couplings to photons, electrons, and nucleons. An attractive possibility is to identify this particle with the axion -- the hypothetical pseudo Nambu--Goldstone boson predicted by the Peccei--Quinn solution to the strong CP problem. We explore this possibility in terms of a DFSZ-type axion and of a KSVZ-type axion/majoron, respectively. Both models allow a good global fit to the data, prefering an axion mass around 10 meV. We show that future axion experiments -- the fifth force experiment ARIADNE and the helioscope IAXO -- can attack the preferred mass range from the lower and higher end, respectively. An axion in this mass range can also be the main constituent of dark matter., 32 pages, 5 figures

We present a Peccei-Quinn (PQ)-symmetric two-Higgs doublet model that naturally predicts a fermionic singlet dark matter in the mass range 10 keV-1 GeV. The origin of the smallness of the mass of this light singlet fermion arises predominantly at the one-loop level, upon soft or spontaneous breakdown of the PQ symmetry via a complex scalar field in a fashion similar to the so-called Dine-Fischler-Sredniki-Zhitnitsky axion model. The mass generation of this fermionic Radiative Light Dark Matter (RLDM) requires the existence of two heavy vector-like SU(2) isodoublets, which are not charged under the PQ symmetry. We show how the RLDM can be produced via the freeze-in mechanism, thus accounting for the missing matter in the Universe. Finally, we briefly discuss possible theoretical and phenomenological implications of the RLDM model for the strong CP problem and the CERN Large Hadron Collider (LHC)., 17 pages, v2: typos corrected, matches published version

The first searches for axions and axionlike particles with the Large Underground Xenon experiment are presented. Under the assumption of an axioelectric interaction in xenon, the coupling constant between axions and electrons g_{Ae} is tested using data collected in 2013 with an exposure totaling 95 live days ×118 kg. A double-sided, profile likelihood ratio statistic test excludes g_{Ae} larger than 3.5×10^{-12} (90% C.L.) for solar axions. Assuming the Dine-Fischler-Srednicki-Zhitnitsky theoretical description, the upper limit in coupling corresponds to an upper limit on axion mass of 0.12 eV/c^{2}, while for the Kim-Shifman-Vainshtein-Zhakharov description masses above 36.6 eV/c^{2} are excluded. For galactic axionlike particles, values of g_{Ae} larger than 4.2×10^{-13} are excluded for particle masses in the range 1-16 keV/c^{2}. These are the most stringent constraints to date for these interactions.

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., Comment: 5 pages, 1 figures

We show that in a Complementary two-Higgs doublet model(C2HDM) the CP violating phase in the CKM matrix can be generated spontaneously, dangerous FCNC can be naturally suppressed and the strong CP problem can also be avoided. The two Higgs doublets in the model are complementary in the sense that none of them is enough to describe masses of a given type of quarks. We find that the strength of FCNC is suppressed by the strength of Yukawa couplings of the first generation quark and the tree-level FCNC is sufficiently small. Using an explicit example, we show that radiative correction to the assumed Yukawa couplings can modify the discussion about the strong $\theta$. The correction to the strong $\theta$ is estimated to be less than around $10^{-12}\sim10^{-10}$ which can be tested in future experiment.

We show that solving the flavor problem of the Standard Model with a simple $U(1)_H$ flavor symmetry naturally leads to an axion that solves the strong CP problem and constitutes a viable Dark Matter candidate. In this framework, the ratio of the axion mass and its coupling to photons is related to the SM fermion masses and predicted within a small range, as a direct result of the observed hierarchies in quark and charged lepton masses. The same hierarchies determine the axion couplings to fermions, making the framework very predictive and experimentally testable by future axion and precision flavor experiments.

Right-handed sneutrinos are natural components of left-right symmetric supersymmetric models where the gauge sector is extended to include right-handed weak interactions. Unlike in other models where right-handed sneutrinos are gauge singlets, here the right sneutrino is part of a doublet and could be a dark matter candidate whose annihilation proceeds via gauge interactions. We investigate this possibility, and find that relic density, low-energy observable and direct supersymmetry search constraints can be satisfied when the lightest supersymmetric particle is a right-handed sneutrino. We introduce benchmarks for left-right supersymmetric realizations where either a sneutrino or a neutralino is the lightest superpartner. We then study the LHC signals arising through resonant right-handed slepton production via a $W_R$ gauge-boson exchange that lead to final states enriched in leptons, additionally containing a large amount of missing transverse momentum, and featuring a low jet multiplicity. We find that such a resonant production would boost the chances of discovering these weakly interacting supersymmetric particles for a mass range extending beyond 1 TeV already with a luminosity of 100 fb$^{-1}$. Finally, we compare sneutrino versus neutralino scenarios, and comment on differences with other sneutrino dark matter models., Comment: 29 pages, 5 figures, revised version

We discuss the possibility of having a non-minimal scalar sector at the weak scale within the framework of invisible axion models. To frame our discussion we consider an extension of the Dine-Fischler-Srednicki-Zhitnitsky invisible axion model with two additional Higgs doublets blind under the Peccei-Quinn symmetry. Due to mixing effects among the scalar fields, it is possible to obtain a rich scalar sector at the weak scale in certain decoupling limits of the theory. In particular, this framework provides an ultraviolet completion of the so-called aligned two-Higgs-doublet model and solves the strong CP problem. The axion properties and the smallness of active neutrino masses are also discussed., 8 pages, 1 figure. Discussion improved, references added. Matching the journal version

We investigate charge quantization in the Standard Model (SM) through a CP 2 nonlinear sigma model (NLSM), SU ( 3 ) G / ( SU ( 2 ) H × U ( 1 ) H ) , and a CP 3 model, SU ( 4 ) G / ( SU ( 3 ) H × U ( 1 ) H ) . We also generalize to any CP k model. Charge quantization follows from the consistency and dynamics of the NLSM, without a monopole or Grand Unified Theory, as shown in our earlier work on the CP 1 model ( arXiv:1309.0692 ). We find that representations of the matter fields under the unbroken non-abelian subgroup dictate their charge quantization under the U ( 1 ) H factor. In the CP 2 model the unbroken group is identified with the weak and hypercharge groups of the SM, and the Nambu–Goldstone boson (NGB) has the quantum numbers of a SM Higgs. There is the intriguing possibility of a connection with the vanishing of the Higgs self-coupling at the Planck scale. Interestingly, with some minor assumptions (no vector-like matter and minimal representations) and starting with a single quark doublet, anomaly cancellation requires the matter structure of a generation in the SM. Similar analysis holds in the CP 3 model, with the unbroken group identified with QCD and hypercharge, and the NGB having the up quark as a partner in a supersymmetric model. This can motivate solving the strong CP problem with a vanishing up quark mass.

We show that in supersymmetric axion models the axion supermultiplet obtains a sizable F-term due to a non-supersymmetric dynamics and it generally gives the gaugino masses comparable to the anomaly mediation contribution. Thus the gaugino mass relation predicted by the anomaly mediation effect can be significantly modified in the presence of axion to solve the strong CP problem., Comment: 10 pages, 1 figure; added references

The lack of evidence for weak scale supersymmetry from LHC Run-I and Run-II results along with null results from direct/indirect dark matter detection experiment have caused a paradigm shift in expected phenomenology of SUSY models. The SUSY dark matter candidate, neutralino $\widetilde{Z}_1$, can only satisfy the measured dark matter abundance due to resonance- and co-annihilations in cMSSM model. Moreover, viable parameter space is highly fine-tuned in the cMSSM. In models that can still satisfy the naturalness condition such as NUHM2, the neutralino is underproduced due to its higgsino nature. Neutralino combined with axion that solves the strong CP problem can explain the observed dark matter in the universe. Here I briefly discuss implications of the mixed axion-neutralino scenario., 8 pages, 6 figures, to appear in the proceedings of the CETUP* 2016

We explore the origin and Yukawa interactions of the scalars with peculiar $CP$ properties which were recently found in a multi-Higgs model based on an order-4 $CP$ symmetry. We relate the existence of such scalars to the enhanced freedom of defining $CP$, even beyond the well-known generalized $CP$ symmetries, which arises in models with several zero-charge scalar fields. We also show that despite possessing exotic $CP$ quantum numbers, these scalars do not have to be inert: they can have $CP$-conserving Yukawa interactions provided the $CP$ acts on fermions by also mixing generations. This paper focuses on formal aspects---exposed in a pedagogical manner---and includes a brief discussion of possible phenomenological consequences.

$m_u=0$ has long been proposed as a solution to the strong CP problem. While this solution is sometimes thought to have been excluded, it is actually still ill-defined. In this work, we study the mass dependence of the physical observable $\chi_t$, the topological susceptibility. Assigning an unphysically large value to the down mass allows to be more sensitive to the non-perturbative effects behind the $m_u=0$ ambiguity. Preliminary results are presented for four masses of clover fermions.

We present a determination of the corrections to Dashen's theorem and of the individual up and down quark masses from a lattice calculation based on quenched QED and $N_f=2+1$ QCD simulations with 5 lattice spacings down to 0.054 fm. The simulations feature lattice sizes up to 6 fm and average up-down quark masses all the way down to their physical value. For the parameter which quantifies violations to Dashens's theorem we obtain $\epsilon=0.73(2)(5)(17)$, where the first error is statistical, the second is systematic, and the third is an estimate of the QED quenching error. For the light quark masses we obtain, $m_u=2.27(6)(5)(4) \, \mbox{MeV}$ and $m_d=4.67(6)(5)(4) \, \mbox{MeV}$ in the $\overline{\mbox{MS}}$ scheme at $2 \, \mbox{GeV}$ and the isospin breaking ratios $m_u/m_d=0.485(11)(8)(14)$, $R=38.2(1.1)(0.8)(1.4)$ and $Q=23.4(0.4)(0.3)(0.4)$. Our results exclude the $m_u=0$ solution to the strong CP problem by more than 24 standard deviations.

The Center for Axion and Precision Physics Research (CAPP) was founded in 2013, with the ambition of shedding light on the strong CP problem and the proposed existence of axions. Much of CAPP's effort focuses on the direct detection of dark matter candidate axions with a series of local haloscope experiments, which endeavour to expand dramatically the coverage on the "invisible axion" mass range. The first two of them plan experimental runs during this year, tapping into ultra-low cryogenics and toroidal cavity geometries. The overall programme builds on cutting-edge technology, including developments in superconducting films, SQUID amplifiers and novel magnets. This article presents the planned advancements and the status of the programme, while it can also be considered a pedagogical introduction to haloscope experiments., 7 pages, 4 figures. Proceedings of the ICFNP 2016 conference

We present first results and future plans for the Oscillating Resonant Group AxioN (ORGAN) experiment, a microwave cavity axion haloscope situated in Perth, Western Australia designed to probe for high mass axions motivated by several theoretical models. The first stage focuses around 26.6 GHz in order to directly test a claimed result, which suggests axions exist at the corresponding mass of $110~\mu$eV. Later stages will move to a wider scan range of 15-50 GHz ($60-210~\mu $eV). We present the results of the pathfinding run, which sets a limit on $g_{a\gamma\gamma}$ of $2.02\times 10^{-12} $eV$^{-1}$ at 26.531 GHz, or 110~$\mu$eV, in a span of 2.5 neV (shaped by the Lorentzian resonance) with $90 \%$ confidence. Furthermore, we outline the current design and future strategies to eventually attain the sensitivity to search for well known axion models over the wider mass range., Comment: 15 pages, 5 figures. V2: As published in Physics of Dark Universe

La física de partículas está viviendo actualmente una era de exploración que comenzó con la observación en el LHC del bosón de Higgs, proporcionando así al Modelo Estándar de la Física de Partículas la elusiva pieza final que lo completa. Si bien esta teoría es extremadamente exitosa, se acepta comúnmente que no es la teoría final ya que no puede responder a todas las preguntas teóricas ni a ciertas observaciones experimentales. Por lo tanto, se espera que Nueva Física que extienda al Modelo Estándar aparezca pronto, aunque esto bien podría ser sólo una esperanza. Esta tesis recoge algunas de las aventuras en la búsqueda de Nueva Física. Se organiza en tres partes: la Parte I introduce, en inglés, los principales temas de la tesis y establece la notación y marcos teóricos que se utilizan más tarde. Esta parte contiene temas que son de conocimiento general en la literatura y pretende ser una introducción amplia. Por el contrario, la Parte II, también en inglés, se dedica específicamente a compilar la investigación científica que se hizo durante el doctorado y, por tanto, es de naturaleza más técnica que la parte anterior. La Parte III contiene un resumen de la tesis en Español. La Parte I está organizada de la siguiente forma. En el Capítulo 1 se introduce el Modelo Estándar, sus principales características, y varias cuestiones teóricas y experimentales que este marco teórico no puede explicar. El resto de esta parte se dedica al análisis de varias extensiones del Modelo Estándar. En particular, en el Capítulo 2 se presenta el modelo de dos dobletes de Higgs, una extensión mínima del Modelo Estándar donde se añade un doblete de Higgs adicional al sector escalar de la teoría. En este capítulo se hace especial hincapié en el problema del sabor del modelo de dos dobletes de Higgs y se estudian sus soluciones. El Capítulo 3 presenta el problema de violación de CP en el sector fuerte en cierto detalle, junto con una discusión sobre la solución de Peccei-Quinn y su fenomenología asociada. En el Capítulo 4 introducimos el concepto de Teorías Efectivas y mostramos cómo construirlas a partir de un modelo ultravioleta dado usando técnicas funcionales. También mostramos ejemplos de Teorías Efectivas dentro del marco teórico del Modelo Estándar que introducen un enfoque complementario en la búsqueda de Nueva Física. Finalmente, en el Capítulo 5 presentamos las recientes anomalías experimentales en desintegraciones del mesón B y discutimos sus principales implicaciones. Mientras que la Parte I sigue una discusión más lineal, con cada capítulo basado en los anteriores, la Parte II está estructurada en tres capítulos esencialmente independientes. El Capítulo 6 extiende los métodos funcionales para la construcción de Teorías Efectivas introducidos en el Capítulo 4. En el Capítulo 7 presentamos tres modelos construidos para proporcionar una explicación a las anomalías en la física del mesón B. Estos se basan en varias extensiones del sector gauge del Modelo Estándar, cada una de las cuales da lugar a predicciones experimentales características diferentes. En el Capítulo 8 se introducen dos modelos de axión invisible que incluyen propiedades adicionales no presentes en las implementaciones originales. La Parte III contiene un único capítulo que resume en Español los principales objetivos, la metodología y las conclusiones de la presente tesis. Particle Physics is currently living an age of exploration that started with the observation at the LHC of the Higgs boson, providing the Standard Model of strong and electroweak interactions the final eluding piece that completes it. While this theory is extremely successful, it is commonly accepted that it is not the final one since it cannot answer all the theoretical questions and experimental observations. It is thus expected that New Physics that extends the Standard Model will appear soon, though this might well be only a hope. This thesis compiles some of the adventures in the Quest for New Physics. It is organized in three parts: Part I introduces the main subjects of the thesis and sets the notation and frameworks that are used later. This part contains topics that are of common knowledge in the literature and it is intended as a broad introduction. On the contrary, Part II is specifically devoted to compile the scientific research that was done during the Ph.D. and therefore it is more technical than the previous part. Part III contains a comprehensive summary of the thesis in Spanish. Part I is organized as follows. In Chapter 1 we introduce the Standard Model, its main features, and several theoretical and experimental issues that this framework cannot explain. The rest of this part is dedicated to the analysis of various extensions of the Standard Model. In particular, in Chapter 2 we introduce the two-Higgs-doublet model, a minimal extension where an additional Higgs doublet is added to the scalar sector of the theory. In this chapter, special emphasis is placed in the two-Higgs-doublet model flavor problem and its solutions. Chapter 3 presents the Strong CP problem in some detail, together with a discussion on the Peccei--Quinn solution and its associated phenomenology. In Chapter 4 we introduce the concept of Effective Field Theories and show how to construct them from a given ultraviolet model using functional techniques. We also introduce examples of Effective Field Theories within the Standard Model framework that stand for a complementary approach in the search for New Physics. Finally, in Chapter 5 we present the recent experimental anomalies in B-physics data and discuss their main implications. While Part I follows a more linear discussion, with each chapter based on the previous ones, Part II is structured in three, essentially unrelated, chapters. Chapter 6 extends to the one-loop order the functional methods for the construction of Effective Field Theories introduced in Chapter 4. In Chapter 7 we present three models aimed to provide an explanation to the B-physics anomalies. These are based in various extensions of the Standard Model gauge sector, each predicting different characteristic experimental signatures. Chapter 8 introduces two invisible axion models that include additional features which are not present in the original implementations. Part III contains a single chapter that summarizes in Spanish the major goals, procedures and results of the present thesis.

The QCD axion is an hypothetical particle introduced to solve the strong CP problem of standard model of particle physics and is of interest as a possible component of cold dark matter. In the axion scenario, J.E. Moody and F. Wilczek showed that a new macroscopic long-range force, mediated by axion exchange, acts on electron spins, and that such force can be described in terms of an effective magnetic field. The QUAX-g$_p$g$_s$ experiment, carried out at INFN Laboratori Nazionali di Legnaro, is designed to search for the effects on magnetized samples of the effective field produced by unpolarized mass sources. As this field is macroscopic, it can be detected by measuring the change of magnetization of a paramagnetic Gadolinium silicate (GSO) crystal cooled at liquid helium temperature. The axion effective field induced magnetization can be detected with a SQUID magnetometer. By varying the position of the of source masses, the induced GSO magnetization is modulated at acoustic frequencies. Although the full QUAX-g$_p$g$_s$ sensitivity has not been yet exploited, we are able to measure a magnetization of $10^{-17}~$T at few tens of Hz. With this sensitivity we expect to further improve the upper limit of the coupling of the predicted long-range force in the $10^{-3}$ to $1~$m interval., Comment: 19 pages, 6 figures, 1 table. Submitted to Nuclear Instruments and Methods A

The well-known leptonic U(1) symmetry of the standard model of quarks and leptons is extended to include a number of new fermions and scalars. The resulting theory has an invisible QCD axion (thereby solving the strong CP problem), a candidate for weak-scale dark matter, as well as radiative neutrino masses. A possible key connection is a color-triplet scalar, which may be produced and detected at the Large Hadron Collider., Comment: 14 pages, 3 figures

金沢大学理工研究域数物科学系, We propose a model which is a simple extension of the KSVZ invisible axion model with an inert doublet scalar. Peccei–Quinn symmetry forbids tree-level neutrino mass generation and its remnant Z2 symmetry guarantees dark matter stability. The neutrino masses are generated by one-loop effects as a result of the breaking of Peccei–Quinn symmetry through a nonrenormalizable interaction. Although the low energy effective model coincides with an original scotogenic model which contains right-handed neutrinos with large masses, it is free from the strong CP problem. © 2018, The Author(s).

A $SU(N)_L\times SU(N)_R$ gauge theory for a scalar multiplet $Y$ transforming in the bi-fundamental representation $(N,\bar N)$ preserves, for $N>4$, an accidental $U(1)$ symmetry firstly broken at operator dimension $N$. Two configurations are possible for the vacuum expectation value of $Y$, which correspond to the (maximal) little groups $\mathcal{H}_s=SU(N)_{L+R}$ and $\mathcal{H}_h=SU(N-1)_L\times SU(N-1)_R\times U(1)_{L+R}$. In the first case the accidental $U(1)$ gets also broken, yielding a pseudo Nambu-Goldstone boson with mass suppression controlled by $N$, while in the second case a global $U(1)$ remains unbroken. The strong CP problem is solved by coupling $Y$ to new fermions carrying color. The first case allows for a Peccei-Quinn solution with $U(1)_{PQ}$ protected up to order $N$ by the gauge symmetry. In the second case $U(1)$ can get broken by condensates of the new strong dynamics, resulting in a composite axion. By coupling $Y$ to fermions carrying only weak isospin, models for axion-like particles can be constructed., 6 pages 1 figure

Axion like particles (ALPs) are fundamental pseudo scalar particles with properties similar to Axions which are a well-known extension of the standard model to solve the strong CP problem in Quantum Chromodynamics. ALPs can oscillate into photons and vice versa in the presence of an external tranversal magnetic field. This oscillation of photon and ALPs could have important implications for astronomical observations, i.e. a characteristic energy dependent attenuation in Gamma ray spectra for astrophysical sources. Here we have revisited the opportunity to search Photon-ALPs coupling in the disappearance channel. We use eight years of Fermi Pass 8 data of a selection of promising galactic Gamma-ray source candidates and study the modulation in the spectra in accordance with Photon-ALPs mixing and estimate best fit values of the parameters i.e. Photon-ALPs coupling constant$ (g_{\alpha\gamma\gamma} )$ and ALPs mass($m_{\alpha} $). For the magnetic field we use large scale galactic magnetic field models based on Faraday rotation measurements and we have also studied the survival probability of photons in the Galactic plane., Comment: 5 pages, 10 figures, submitted as a proceeding of the XV International Conference on Topics in Astroparticle and Underground Physics for Journal of Physics: Conference Series (JPCS)

In this chapter, we try to solve the naturalness problem based on the principle beyond ordinary field theory, maximum entropy principle and saddle/non analytical point of vacuum energy. In Sect. 4.1, we briefly review the naturalness problem of Higgs boson. In Sect. 4.2, we explain the original idea given by Coleman. In Sect. 4.3, we present a solution to the cosmological constant problem and Higgs mass using maximum entropy principle. In Sect. 4.4, we show a solution to the strong CP problem and cosmological constant problem based on the argument about vacuum energy.

We show that a class of parity based solutions to the strong CP problem predicts new colored particles with mass at the TeV scale, due to constraints from Planck suppressed operators. The new particles are copies of the Standard Model quarks and leptons. The new quarks can be produced at the LHC and are either collider stable or decay into Standard Model quarks through a Higgs, a W or a Z boson. We discuss some simple but generic predictions of the models for the LHC and find signatures not related to the traditional solutions of the hierarchy problem. We thus provide alternative motivation for new physics searches at the weak scale. We also briefly discuss the cosmological history of these models and how to obtain successful baryogenesis., 6 pages, 1 figure

We present a supersymmetric version of a two-field relaxion model that naturalizes tuned versions of supersymmetry. This arises from a relaxion mechanism that does not depend on QCD dynamics and where the relaxion potential barrier height is controlled by a second axion-like field. During the cosmological evolution, the relaxion rolls with a nonzero value that breaks supersymmetry and scans the soft supersymmetric mass terms. Electroweak symmetry is broken after the soft masses become of order the supersymmetric Higgs mass term and causes the relaxion to stop rolling for superpartner masses up to $\sim 10^9$ GeV. This can explain the tuning in supersymmetric models, including split-SUSY models, while preserving the QCD axion solution to the strong CP problem. Besides predicting two very weakly-coupled axion-like particles, the supersymmetric spectrum may contain an extra Goldstino, which could be a viable dark matter candidate., 33 pages, 3 figures; v2: bounds and figures corrected

Quite recently, Grabowska and Kaplan presented a 4-dimensional lattice formulation of chiral gauge theories based on the chiral overlap operator. We study this formulation from the perspective of the fermion number anomaly and possible associated phenomenology. A simple argument shows that the consistency of the formulation implies that the fermion with the opposite chirality to the physical one, the "fluffy mirror fermion" or "fluff", suffers from the fermion number anomaly in the same magnitude (with the opposite sign) as the physical fermion. This immediately shows that if at least one of the fluff quarks is massless, the formulation provides a simple viable solution to the strong CP problem. Also, if the fluff interacts with gravity essentially in the same way as the physical fermion, the formulation can realize the asymmetric dark matter scenario., 10 pages, the final version to appear in PTEP

We investigate origin of three features that are often assumed in analysis of two-Higgs doublet models: (i) softly broken Z2 symmetry, (ii) CP invariant Higgs potential, and (iii) degenerated mass spectra. We extend electroweak gauge symmetry, introducing extra gauge symmetry and extra scalars, and we show that our models effectively derive two-Higgs dou- blet models at low energy which naturally hold the three features. We also find that the models can solve the strong CP problem., Comment: 17 pages, no figures; version published in JHEP

We show how superstring models with simple discrete symmetries may have an approximate Peccei-Quinn symmetry in the low-energy effective lagrangian. The breaking of this symmetry is very small and as a consequence in models with intermediate scale breaking the strong CP violation is reduced to an acceptable level. The resultant “pseudo-axion” has properties indistinguishable from the usual “invisible axion” and the scale of its coupling lies naturally in the acceptable range 108–1012 GeV.

The Strong CP Problem can be resolved by introducing an additional global symmetry known as Peccei-Quinn symmetry. Once PQ symmetry is broken the associated particle, the QCD axion, is a plausible dark matter candidate. Calculating the cosmological energy density of the axion requires nonperturbative QCD input---the high-temperature topological susceptibility. I will show results from a pure-glue calculation and examine the implications for the axion mass and coupling., Comment: Proceedings for the 33rd International Symposium on Lattice Field Theory

We consider using particle production as a friction force by which to implement a "Relaxion" solution to the electroweak hierarchy problem. Using this approach, we are able to avoid superplanckian field excursions and avoid any conflict with the strong CP problem. The relaxation mechanism can work before, during or after inflation allowing for inflationary dynamics to play an important role or to be completely decoupled., 12 pages, 1 figures. v2: expanded discussion and reorganized some sections; fixed discussion about destruction of the condensate; accepted for publication in JHEP

We consider the possibility of an enlarged QCD color group, SU(3+$N^\prime$) spontaneously broken to SU(3)$_c\times$SU($N^\prime$) with extra vector-like quarks transforming in the fundamental representation. When the heavy quarks are integrated out below the PQ-breaking scale, they generate an axion coupling which simultaneously solves the strong CP problem for both gauge groups. However, the axion mass now receives a new nonperturbative contribution from the SU($N^\prime$) confinement scale, which can be substantially larger than the QCD scale. This can increase the axion mass to be at or above the electroweak scale. This visible axion can then decay into gluons and photons giving rise to observable signals at Run-II of the LHC. In particular, if the mass is identified with the 750 GeV diphoton resonance then the new confinement scale is $\sim$ TeV and the PQ-breaking scale is $\sim$ 10 TeV. This predicts vector-like quarks and a PQ scalar resonance in the multi-TeV range, with the possibility that dark matter is an SU($N^\prime$) baryon., 27 pages, 3 figures; v2: minor corrections, an explanatory remark and references added; v3: journal version

The Axion Dark Matter experiment (ADMX) is conducting a search for dark-matter axions trapped in the halo of the Milky Way Galaxy. Axions, originally postulated to solve the strong CP problem in particle physics, would have been created as cold (non-relativistic) very weakly interacting particles in the early stages of the expansion of the universe. If their mass is in the range 2 to 50 microeV, axions could be a significant component of the dark matter in the universe. The discovery of the axion, or placing limits on its abundance, would therefore have very important implications for understanding the nature of dark matter, which is one of the most significant problems in contemporary physics.

We study a level crossing between the QCD axion and an axion-like particle, focusing on the recently found phenomenon, the axion roulette, where the axion-like particle runs along the potential, passing through many crests and troughs, until it gets trapped in one of the potential minima. We perform detailed numerical calculations to determine the parameter space where the axion roulette takes place, and as a result domain walls are likely formed. The domain wall network without cosmic strings is practically stable, and it is nothing but a cosmological disaster. In a certain case, one can make domain walls unstable and decay quickly by introducing an energy bias without spoiling the Peccei-Quinn solution to the strong CP problem.

We propose a novel SU(3)_c\times SU(2)_L\times SU(2)_R\times U(1)_{B-L} left-right symmetric model where the standard model fermion and Higgs fields are SU(2)_L doublets or SU(2) singlets while their mirror partners are SU(2)_R doublets or SU(2) singlets. The scalar fields also include a real singlet for dark matter and two SU(2) triplets for seesaw. The mixing between the standard model and mirror fermions is forbidden by a Z_2\times Z'_2 discrete symmetry. The mirror charged fermions can decay into their standard model partners with the dark-matter scalar while the mirror neutrinos can decay into the mirror charged fermions through the right-handed gauge interactions. Our model can have new implications on the strong CP problem, leptogenesis, collider phenomenology and dark matter detection., Comment: 6 pages, 3 figures. One figure and some references are added

QCD depends on an extra parameter θ ¯ . When θ ¯ ≠ 0 , P and CP are violated. Because the strong interactions conserve P and CP, θ ¯ must be very small, of order 10 − 10 or less. However, within the Standard Model, θ ¯ is expected to be of order one. This puzzle is called the strong CP problem. Possible solutions are briefly described.

CP conservation and violation in neutral kaon decay are considered from a first principles’ theory, recently published as “Scalar Strong Interaction Hadron Theory”. The arbitrary phase angle relating K0 and 0 in current phenomenology is identified to be related to the product of the relative energy to the relative time between the s and d quarks in these kaons. The argument of the CP violating parameter ? is predicted to be 45? without employing measured data. The K0S decay rate is twice the K0L -K0S masss difference, in near agreement with data, and both are proportional to the square of the relative energy 29.44 eV. Any pion from K0L decay will also have a mass shift of ≈1.28 × 10-5 eV. The present first principles’ theory is consistent with CP conservation. To achieve CP violation, the relative time cannot extend to both +∞ and -∞ but is bounded in at least one direction. The values of these bounds lie outside the present theory and it is unknown how they can be brought forth. -B0 mixing is also considered and the relative energy is 663.66 eV.

Despite two decades of experimental e_ort, the elusive axion has yet to be discovered. Nevertheless, it remains a well-motivated solution to the strong CP problem and a promising dark matter candidate. Most searches use the axion-two-photon coupling to probe for axions that are generated in the sun, remnants from the big-bang or created in the laboratory. Using techniques inspired by torsion pendulum based tests of gravity, we have constructed a new torsion pendulum experiment that looks for a macroscopic parity and time-violating force mediated by virtual axions. For an axion mass of 1 meV, we have improved the limit on this force by ten orders of magnitude, and thus, have opened another path to look for very heavy axions.

We reveal a new source of CP-violation in the electroweak sector that is free of any experimental bounds, and we highlight the possible implications for baryogenesis., to appear in Physics Letters B

We investigate a recent solution to the strong CP problem, obtaining a theta-angle of order unity, and show that a smooth trajectory of the massive eigenvector of a rank-one rotating mass matrix is consistent with the experimental data for both fermion masses and mixing angles (except for the masses of the lightest quarks). Using this trajectory we study Higgs decay and find suppression of $\Gamma(H\to c\bar{c})$ compared to the standard model predictions for a range of Higgs masses. We also give limits for flavour violating decays, including a relatively large branching ratio for the $\tau^-\mu^+$ mode., Comment: 15 pages, 6 figures; improvements to introduction and preliminaries

Current upper bounds on the neutron electric dipole moment constrain the physically observable quantum chromodynamic (QCD) vacuum angle $|\overline{\ensuremath{\theta}}|\ensuremath{\lesssim}{10}^{\ensuremath{-}11}$. Since QCD explains a great deal of experimental data from the $100\phantom{\rule{0.3em}{0ex}}\mathrm{MeV}$ to the TeV scale, it is desirable to explain this smallness of $|\overline{\ensuremath{\theta}}|$ in the QCD framework; this is the strong $CP$ problem. There now exist two plausible solutions to this problem, one of which leads to the existence of a very light axion. The axion decay constant window, ${10}^{9}\ensuremath{\lesssim}{F}_{a}\ensuremath{\lesssim}{10}^{12}\phantom{\rule{0.3em}{0ex}}\mathrm{GeV}$ for an $O(1)$ initial misalignment angle ${\ensuremath{\theta}}_{1}$, has been obtained from astrophysical and cosmological data. For ${F}_{a}\ensuremath{\gtrsim}{10}^{12}\phantom{\rule{0.3em}{0ex}}\mathrm{GeV}$ with ${\ensuremath{\theta}}_{1}lO(1)$, axions may constitute a significant fraction of the dark matter of the universe. The supersymmetrized axion solution of the strong $CP$ problem introduces its superpartner the axino, which might have affected the evolution of the Universe significantly. The very light axion (theory, supersymmetrization, and models) using recent particle, astrophysical, and cosmological data, and present prospects for its discovery is reviewed here.

In this paper, we intend to study the problem of CP violation in $D$ meson by $D\to VV$ decay mode in which the T violating triple-product correlation is examined. That would undoubtedly be another excellent probe of New Physics beyond Standard Model. For the neutral $D$, we focus on direct CP violation without considering $D^0-\bar D^0$ oscillation. Experimentally, by a full angular analysis one may obtain such CP violating signals, and particularly it is worth mentioning that the upcoming large $D$ data samples at BES-III in Beijing will provide a great opportunity to perform it., Comment: 5 pages, 2 tables and 1 figure, version to appear in Phys. Lett. B

The permanent electric dipole moment (EDM) of a particle or system is a separation of charge along the total angular momentum and arises from interactions that directly violate parity and time reversal symmetry, and assuming CPT symmetry, violate CP. EDMs thus probe CP violating interactions in the background of the much stronger strong, weak and electromagnetic interactions. CP violation is also an essential component of Sakharov's mechanism of baryogenesis, but the Standard Model does not provide for CP violation strong enough to account for the observered baryon asymmetry. Currently, only upper limits have been set on EDMs of the neutron and of atoms and molecules, and the Standard Model contributions are many orders of magnitude smaller than these limits. This means that the experimental frontier probes new physics beyond the Standard Model, but also that experiments in at least three systems will be necessary to clarify the soures of CP violating EDMs. This review will describe the motivations and discuss current and near-term experimental endeavors to discover EDMs in a variety of systems.

We point out that the long-standing strong CP problem may be resolved by an anthropic argument. The key ideas are: (i) to allow explicit breaking(s) of the Peccei-Quinn symmetry which reduces the strong CP problem to the cosmological constant problem, and (ii) to conjecture that the probability distribution of the vacuum energy has a mild pressure towards higher values. The cosmological problems of the (s)axion with a large Peccei-Quinn scale are absent in our mechanism, since the axion acquires a large mass from the explicit breaking. Subject Index: 129, 430, 442, 444

Motivated by the possibility of the formation of CP-odd domains in heavy ion collisions, we investigate the effects of CP violation on the chiral transition within the linear sigma model with two flavors of quarks. We also study how the CP-odd system is affected by the presence of a strong magnetic field, that is presumably generated in a non-central heavy ion collision. We find that both ingredients play an important role, influencing drastically the nature of the phase transition and the critical temperature., Comment: 4 pages

Non-standard physics which can be described by effective four fermion interactions may be an additional source of CP violation in the neutrino propagation. We discuss the detectability of such a CP violation at a neutrino factory. We assume the current baseline setup of the international design study of a neutrino factory (IDS-NF) for the simulation. We find that the CP violation from certain non-standard interactions is, in principle, detectable significantly below their current bounds -- even if there is no CP violation in the standard oscillation framework. Therefore, a new physics effect might be mis-interpreted as the canonical Dirac CP violation, and a possibly even more exciting effect might be missed., 6 pages, 4 figures. Version to appear in PLB

A review of $\mathit{CP}$ violation from the standard model to strings is given which includes a broad landscape of particle physics models, encompassing the nonsupersymmetric four-dimensional (4D) extensions of the standard model, and models based on supersymmetry, on extra dimensions, on strings, and on branes. The supersymmetric models discussed include complex minimal supergravity unified model and its extensions, while the models based on extra dimensions include five-dimensional models including models based on warped geometry. $\mathit{CP}$ violation beyond the standard model is central to achieving the desired amount of baryon asymmetry in the Universe via baryogenesis and leptogenesis. They also affect a variety of particle physics phenomena: electric dipole moments, $g\ensuremath{-}2$, relic density and detection rates for neutralino dark matter in supersymmetric theories, Yukawa unification in grand unified and string based models, and sparticle production cross sections, and their decay patterns and signatures at hadron colliders. Additionally $\mathit{CP}$ violations can generate $\mathit{CP}$ even--$\mathit{CP}$ odd Higgs mixings, affect the neutral Higgs spectrum, and lead to phenomena detectable at colliders. Prominent among these are the $\mathit{CP}$ violation effects in decays of neutral and charged Higgs bosons. Neutrino masses introduce new sources of $\mathit{CP}$ violation which may be explored in neutrino factories in the future. Such phases can also enter in proton stability in unified models of particle interactions. The current experimental status of $\mathit{CP}$ violation is discussed and possibilities for the future outlined.