Thu·Jun 1, 2017Thursday·June 1, 2017

1. 01*

   A minimal scale invariant axion solution to the strong CP-problem

   Anna Tokareva🇷🇺

   We present a scale invariant extension of the Standard model allowing for the Kim-Shifman-Vainstein-Zakharov (KSVZ) axion solution of the strong CP problem in QCD. We add the minimal number of new particles and show that the Peccei-Quinn scalar might be identified with the complex dilaton field. Scale invariance, together with the Peccei-Quinn symmetry, is broken spontaneously near the Planck scale before inflation, which is driven by the Standard Model Higgs field. We present a set of general conditions which makes this scenario viable and an explicit example of an effective theory possessing spontaneous breaking of scale invariance. We show that this description works both for inflation and low-energy physics in the electroweak vacuum. This scenario can provide a self-consistent inflationary stage and, at the same time, successfully avoid the cosmological bounds on the axion. Our general predictions are the existence of coloured TeV mass fermion and the QCD axion. The latter has all the properties of the KSVZ axion but does not contribute to dark matter. This axion can be searched via it's mixing to a photon in an external magnetic field.

   hep-phhep-thEPJC(2018)·11 citations
2. 02*

   Optimized perturbation theory applied to the study of the thermodynamics and BEC-BCS crossover in the three-color Nambu--Jona-Lasinio model

   Dyana C. Duarte🇧🇷 · R. L. S. Farias🇧🇷 · Patrícia H. A. Manso🇧🇷 · Rudnei O. Ramos🇧🇷

   The Nambu--Jona-Lasinio model with two flavors, three colors and diquark interactions is analyzed in the context of optimized perturbation theory (OPT). Corrections to the thermodynamical potential that go beyond the large-$N_c$ (LN) approximation are taken into account, and the region of the phase diagram corresponding to intermediate chemical potentials and very low temperatures is explored. The simultaneous presence of both the quark-antiquark and diquark condensates can cause the system to behave as a fluid composed of a Bose-Einstein condensate (BEC) or a color superconductor one, in the form of a Bardeen-Cooper-Schrieffer (BCS) superfluid. The BEC-BCS crossover is then studied in the nonperturbative OPT scheme. The results obtained in the context of the OPT method are then contrasted with those obtained in the LN approximation. We show that there are values for the coupling constants related to quark-quark and quark-antiquark interactions where the corrections beyond LN brought by the OPT method can influence the behavior of the diquark condensate and the effective quark mass as a function of the baryon chemical potential. These changes in the behavior of the phase structure of the model modify the location of the critical point related to the phase structure as a whole of the model. Also, when we impose the color neutrality condition, our results show that the nature of the phase transition can change as well, shifting the ratio of the quark-antiquark and quark-quark interactions to higher values in the OPT case as compared to the LN approximation.

   hep-phhep-thnucl-thPRD(2017)·10 citations
3. 03*

   Extranatural Inflation Redux

   Mansi Dhuria🇮🇳 · Gaurav Goswami🇮🇳 · Jayanti Prasad🇮🇳

   The success of a given inflationary model crucially depends upon two features: its predictions for observables such as those of the Cosmic Microwave background (CMB) and its insensitivity to the unknown ultraviolet (UV) physics such as quantum gravitational effects. Extranatural inflation is a well motivated scenario which is insensitive to UV physics by construction. In this five dimensional model, the fifth dimension is compactified on a circle and the zero mode of the fifth component of a bulk $U(1)$ gauge field acts as the inflaton. In this work, we study simple variations of the minimal extranatural inflation model in order to improve its CMB predictions while retaining its numerous merits. We find that it is possible to obtain CMB predictions identical to those of e.g. $\mathcal{R}+{\mathcal{R}}^2$ Starobinsky model of inflation and show that this can be done in the most minimal way by having two additional extra light fermionic species in the bulk, with the same $U(1)$ charges. We then find the constraints that CMB observations impose on the parameters of the model.

   hep-phastro-ph.COgr-qchep-thPRD(2017)·1 citation
4. 04*

   Lorentz Structure of Vector Part of Matrix Elements of Transitions n <-> p, Caused by Strong Low-Energy Interactions and Hypothesis of Conservation of Charged Vector Current

   A. N. Ivanov🇦🇹

   We analyse the Lorentz structure of the matrix elements of the transitions "neutron <-->proton", induced by the charged hadronic vector current. We show that the term maintaining conservation of the charged hadronic vector current even for different masses of the neutron and proton (see T. Leitner et al., Phys. Rev. C 73, 065502 (2006) and A. M. Ankowski, arXiv:1601.06169 [hep-ph]) has a dynamical origin, related to the G-even first class current contribution. We show that because of invariance of strong low-energy interactions under the G-parity transformations, the G-odd contribution with the Lorentz structure $q_{\mu }$, where $q_{\mu }$ is a momentum transferred, does not appear in the matrix elements of the ``neutron <-> proton' transitions.

   hep-phhep-exnucl-exnucl-thJ.Phys.G(2018)·9 citations
5. 05*

   Lepton polarization asymmetries in rare semi-tauonic $b\to s$ exclusive decays at FCC-$ee$

   J. F. Kamenik🇸🇮 · S. Monteil🇫🇷 · A. Semkiv🇫🇷 · L. Vale Silva🇸🇮

   We consider measurements of exclusive rare semi-tauonic $b$-hadron decays, mediated by the $b\to s{\tau }^{+}{\tau }^{-}$ transition, at a future high energy circular electron-positron collider (FCC-$ee$). We argue that the high boosts of $b$-hadrons originating from on-shell $Z$ boson decays allow for a full reconstruction of the decay kinematics in hadronic $\tau$ decay modes (up to discrete ambiguities). This, together with the potentially large statistics of $Z\to b\bar{b}$, opens the door for the experimental determination of $\tau$ polarizations in these rare $b$-hadron decays. In light of the current experimental situation on lepton flavor universality in rare semileptonic $B$ decays, we discuss the complementary short-distance physics information carried by the $\tau$ polarizations and suggest suitable theoretically clean observables in the form of single- and double-$\tau$ polarization asymmetries.

   hep-phEPJC(2017)·58 citations
6. 06*

   Stable non-Abelian semi-superfluid vortices in dense QCD

   Chandrasekhar Chatterjee🇯🇵 · Muneto Nitta🇯🇵

   Color superconductivity is expected to be formed in high density quark matter where color symmetry is spontaneously broken in the presence of di-quark condensate. Stable non-Abelian vortices or color magnetic flux tubes exist in the color-flavor locked phase at asymptotically high density. $\mathbb{C}{P}^2$ Nambu-Goldstone(NG) bosons and Majorana fermions belonging to the triplet representation are localized around a non-Abelian vortex. We discuss the zero mode analysis and the low-energy effective world sheet theory of a non-Abelian vortex. We determine the interactions of these bosonic and fermionic modes by using the nonlinear realization method. We also discuss the Aharanov-Bohm (AB) phases of charged particles, such as, electrons, muons, and color-flavor locked mesons made of tetra-quarks encircling around a non-Abelian vortex in the presence of electro-magnetic fields. This is a review based on our recent works arXiv:1602.01677, arXiv:1512.06603, arXiv:1612.09419.

   hep-phJPS Conf.Proc.(2018)·1 citation
7. 07*

   Radiative corrections of heavy scalar decays to gauge bosons in the singlet extension of the Standard Model

   Gabriele Ria🇮🇹 · Davide Meloni🇮🇹

   Assuming the existence of a new real scalar singlet $s^0$ coupled to the Standard Model via a scalar quartic portal interaction, we compute the radiative corrections to the decay rates of the heavy scalar mass eigenstate to a couple of gauge bosons $ZZ$ and $W^{+}{W}^{-}(\gamma )$, showing that they can give a contribution as large as $\mathcal{O}$(5\%) and $\mathcal{O}$(7\%), respectively. We also explicitly analyze in detail their dependence on the heavy mass $m_S$ and on the scalar mixing angle $\alpha$, finding that, especially in the large-mass region, these depend on the sign of $\sin \alpha$.

   hep-phEPJC(2018)·5 citations
8. 08*

   Cosmological stochastic Higgs stabilization

   Jinn-Ouk Gong🇰🇷 · Naoya Kitajima🇯🇵

   We show that the stochastic evolution of an interacting system of the Higgs and a spectator scalar field naturally gives rise to an enhanced probability of settling down at the electroweak vacuum at the end of inflation. Subsequent destabilization due to parametric resonance between the Higgs and the spectator field can be avoided in a wide parameter range. We further argue that the spectator field can play the role of dark matter.

   hep-phastro-ph.COhep-thPRD(2017)·10 citations
9. 09*

   High-scale Supersymmetry, the Higgs Mass and Gauge Unification

   Sebastian A. R. Ellis🇺🇸 · James D. Wells🇺🇸

   Suppressing naturalness concerns, we discuss the compatibility requirements of high-scale supersymmetry breaking with the Higgs boson mass constraint and gauge coupling unification. We find that to accommodate superpartner masses significantly greater than the electroweak scale, one must introduce large non-degeneracy factors. These factors are enumerated, and implications for the allowed forms of supersymmetry breaking are discussed. We find that superpartner masses of arbitrarily high values are allowed for suitable values of $\tan \beta$ and the non-degeneracy factors. We also compute the large, but viable, threshold corrections that would be necessary at the unification scale for exact gauge coupling unification. Whether or not high-scale supersymmetry can be realised in this context is highly sensitive to the precise value of the top quark Yukawa coupling, highlighting the importance of future improvements in the top quark mass measurement.

   hep-phPRD(2017)·37 citations
10. 10*

    Pinning Down the Axial-Vector Coupling Constant in Nuclei and Dense Matter

    Mannque Rho🇫🇷

    The in-medium property of the axial-vector coupling constant $g_A$ in nuclei and dense baryonic matter, a long standing problem in nuclear physics, is reformulated in terms of the recently constructed scale-invariant hidden local symmetric ($bs$HLS) Lagrangian that encompasses the physics of baryon density ranging from nuclear matter $n_0$ to that of massive compact stars, $\sim 6n_0$. It is shown that unlike the pion decay constant $f_{\pi }$ that slides with the vacuum change induced by, and dropping with, increasing density, the axial-current constant $g_A$ should remain more or less unaffected by the decrease of chiral condensate in nuclear Gamow-Teller transitions (involving the space component of the axial current) whereas it gets strongly enhanced in axial-charge transitions (involving the time component of the axial current) as density increases. This phenomenon confirms the "chiral filter hypothesis" inferred from the current algebras in 1970's. These phenomena can be taken as a "nuclear physics proof" of Weinberg's folk theorem on quantum effective field theories. The implications of these predictions on giant Gamow-Teller resonances in nuclei and on first-forbidden beta transitions (relevant to nuclear astrophysical processes) are discussed.

    ↳ nucl-thhep-ph2 citations
11. 11*

    The SU(3) Sextet Model with Wilson Fermions

    Martin Hansen🇩🇰 · Vincent Drach🇬🇧 · Claudio Pica🇩🇰

    We investigate the spectrum and IR properties of the SU(3) "sextet" model with two Dirac fermions in the two-index symmetric representation via lattice simulations. This model is a prime candidate for a realization of Walking Technicolor, which features a minimal matter content and it is expected to be inside or very close to the lower boundary of the conformal window. We use the Wilson discretization for the fermions and map the phase structure of the lattice model. We study several spectral and gradient flow observables both in the bulk and the weak coupling phases. While in the bulk phase we find clear signs of chiral symmetry breaking, in the weak coupling phase there is no clear indication for it, and instead the chiral limit of the model seems compatible with an IR-conformal behavior.

    ↳ hep-lathep-phPRD(2017)·12 citations
12. 12*

    Precision Measurement of Time-Reversal Symmetry Violation with Laser-Cooled Polyatomic Molecules

    Ivan Kozyryev🇺🇸 · Nicholas R. Hutzler🇺🇸

    Precision searches for time-reversal symmetry violating interactions in polar molecules are extremely sensitive probes of high energy physics beyond the Standard Model. To extend the reach of these probes into the PeV regime, long coherence times and large count rates are necessary. Recent advances in laser cooling of polar molecules offer one important tool -- optical trapping. However, the types of molecules that have been laser-cooled so far do not have the highly desirable combination of features for new physics searches, such as the ability to fully polarize and the existence of internal co-magnetometer states. We show that by utilizing the internal degrees of freedom present only in molecules with at least three atoms, these features can be attained simultaneously with molecules that have simple structure and are amenable to laser cooling and trapping.

    ↳ physics.atom-phhep-phphysics.chem-phPRL(2017)·186 citations
13. 13*

    The QCD mass gap and quark deconfinement scales as mass bounds in strong gravity

    Piyabut Burikham🇹🇭 · Tiberiu Harko🇷🇴 · Matthew J. Lake🇹🇭

    Though not a part of mainstream physics, Salam's theory of strong gravity remains a viable effective model for the description of strong interactions in the gauge singlet sector of QCD, capable of producing particle confinement and asymptotic freedom, but not of reproducing interactions involving $SU(3)$ colour charge. It may therefore be used to explore the stability and confinement of gauge singlet hadrons, though not to describe scattering processes that require colour interactions. It is a two-tensor theory of both strong interactions and gravity, in which the strong tensor field is governed by equations formally identical to the Einstein equations, apart from the coupling parameter, which is of order $1\mathrm{Ge}{\mathrm{V}}^{-1}$. We revisit the strong gravity theory and investigate the strong gravity field equations in the presence of a mixing term which induces an effective {\it strong cosmological constant}, ${\Lambda }_f$. This introduces a {\it strong de Sitter radius} for strongly interacting fermions, producing a confining bubble, which allows us to identify ${\Lambda }_f$ with the `bag constant' of the MIT bag model, $B\simeq 2\times 10^{14}\mathrm{gc}{\mathrm{m}}^{-3}$. Assuming a static, spherically symmetric geometry, we derive the strong gravity TOV equation, which describes the equilibrium properties of compact hadronic objects. From this, we determine the generalised Buchdahl inequalities for a strong gravity `particle', giving rise to upper and lower bounds on the mass/radius ratio of stable, compact, strongly interacting objects. We show, explicitly, that the existence of the lower mass bound is induced by the presence of ${\Lambda }_f$, producing a mass gap, and that the upper bound corresponds to a deconfinement phase transition. The physical implications of our results for holographic duality in the context of the AdS/QCD and dS/QCD correspondences are also discussed.

    ↳ hep-thastro-ph.COgr-qchep-phEPJC(2017)·9 citations
14. 14*

    Perturbative Renormalization of quasi-PDFs

    Martha Constantinou🇺🇸 · Haralambos Panagopoulos🇨🇾

    In this paper we present results for the renormalization of gauge invariant nonlocal fermion operators which contain a Wilson line, to one-loop level in lattice perturbation theory. Our calculations have been performed for Wilson/clover fermions and a wide class of Symanzik improved gluon actions. The extended nature of such long-link operators results in a nontrivial renormalization, including contributions which diverge linearly as well as logarithmically with the lattice spacing, along with additional finite factors. On the lattice there is also mixing among certain subsets of these nonlocal operators; we calculate the corresponding finite mixing coefficients, which are necessary in order to disentangle individual matrix elements for each operator from lattice simulation data. Finally, extending our perturbative setup, we present non-perturbative prescriptions to extract the linearly divergent contributions.

    ↳ hep-lathep-phhep-thPRD(2017)·201 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.