Tue·Sep 19, 2017Tuesday·September 19, 2017

1. 01*

   The Brother Higgs

   Javi Serra🇨🇭 · Riccardo Torre🇮🇹

   We present a version of the twin Higgs mechanism with minimal symmetry structure and particle content. The model is built upon a composite Higgs theory with global $SO(6)/SO(5)$ symmetry breaking. The leading contribution to the Higgs potential, from the top sector, is solely cancelled via the introduction of a Standard Model neutral top partner. We show that the inherent $Z_2$ breaking of this construction is under control and of the right size to achieve electroweak symmetry breaking, with a fine-tuning at the level of $5-10\%$, and compatibly with the observed Higgs mass. We briefly discuss the particular phenomenological features of this scenario.

   hep-phPRD(2018)·47 citations
2. 02*

   Threshold Collision Energy of the QCD Phase Diagram Tricritical Endpoint

   K. A. Bugaev🇺🇦 · R. Emaus🇳🇴 · V. V. Sagun🇺🇦 · A. I. Ivanytskyi🇺🇦 · L. V. Bravina🇳🇴 · D. B. Blaschke🇷🇺 · E. G. Nikonov🇷🇺 · A. V. Taranenko🇷🇺 · E. E. Zabrodin🇳🇴 · G. M. Zinovjev🇺🇦

   Using the most advanced formulation of the hadron resonance gas model we analyze the two sets of irregularities found at chemical freeze-out of central nuclear-nuclear collisions at the center of mass energies 3.8-4.9 GeV and 7.6-9.2 GeV. In addition to previously reported irregularities at the collision energies 4.9 GeV and 9.2 GeV we found sharp peaks of baryonic charge density. Also we analyze the collision energy dependence of the modified Wroblewski factor and the strangeness suppression factor. Based on the thermostatic properties of the mixed phase of a 1-st order phase transition and the ones of the Hagedorn mass spectrum we explain, respectively, the reason of observed chemical equilibration of strangeness at the collision energy 4.9 GeV and above 8.7 GeV. It is argued that the both sets of irregularities possibly evidence for two phase transitions, namely, the 1-st order transition at lower energy range and the 2-nd order transition at higher one. In combination with a recent analysis of the light nuclei number fluctuations we conclude that the center of mass collision energy range 8.8-9.2 GeV may be in the nearest vicinity of the QCD tricritical endpoint. The properties of the phase existing between two phase transitions are revealed and discussed.

   hep-phPhys.Part.Nucl.Lett.(2018)·20 citations
3. 03*

   Primordial black hole dark matter from single field inflation

   Guillermo Ballesteros🇫🇷 · Marco Taoso🇪🇸

   We propose a model of inflation capable of generating a population of light black holes (about $10^{-16}$ - $10^{-14}$ solar masses) that might account for a significant fraction of the dark matter in the Universe. The effective potential of the model features an approximate inflection point arising from two-loop order logarithmic corrections in well-motivated and perturbative particle physics examples. This feature decelerates the inflaton before the end of inflation, enhancing the primordial spectrum of scalar fluctuations and triggering efficient black hole production with a peaked mass distribution. At larger field values, inflation occurs thanks to a generic small coupling between the inflaton and the curvature of spacetime. We compute accurately the peak mass and abundance of the primordial black holes using the Press-Schechter and Mukhanov-Sasaki formalisms, showing that the slow-roll approximation fails to reproduce the correct results by orders of magnitude. We study as well a qualitatively similar implementation of the idea, where the approximate inflection point is due to competing terms in a generic polynomial potential. In both models, requiring a significant part of the dark matter abundance to be in the form of black holes implies a small blue scalar tilt with a sizable negative running and a tensor spectrum that may be detected by the next-generation probes of the cosmic microwave background. We also comment on previous works on the topic.

   hep-phastro-ph.COgr-qchep-thPRD(2018)·417 citations
4. 04*

   Rare weak decays of ${\eta }^{\prime }\to K\pi$

   Dao-Neng Gao🇨🇳

   Rare weak decays of ${\eta }^{\prime }\to K\pi$ have been investigated in the framework of the $U(3)$ chiral perturbation theory at the leading order. Our study shows that the branching ratio $\mathcal{B}({\eta }^{\prime }\to K\pi )$ is of the order of $10^{-11}$, which is far below the present experimental upper bound given by the BESIII Collaboration. By further analysis of ${\eta }^{\prime }\to K^{+}{\pi }^{-}$ and ${\eta }^{\prime }\to K^0{\pi }^0$, the ratio of isospin amplitudes is found that $|A_{1/2}/A_{3/2}|\simeq 35$, which supports that the $\Delta I=1/2$ transition enhancement, namely, the $\Delta I=1/2$ rule, could be functional in ${\eta }^{\prime }$ weak decays.

   hep-phhep-exhep-latPRD(2017)·1 citation
5. 05*

   Functional renormalization group study of the Quark-Meson model with $\omega$ meson

   Hui Zhang🇨🇳 · Defu Hou · Toru Kojo🇨🇳 · Bin Qin🇨🇳

   We study the phase diagram of two-flavor massless QCD at finite baryon density by applying the functional renormalization group (FRG) for a quark-meson model with $\sigma ,\pi$, and $\omega$ mesons. The dynamical fluctuations of quarks, $\sigma$, and $\pi$ are included into the flow equations, while the amplitudes of $\omega$-fields are also allowed to fluctuate. At high temperature the effects of the $\omega$-field on the phase boundary are qualitatively similar to the mean-field calculations; the phase boundary is shifted to the higher chemical potential region. As the temperature is lowered, however, the transition line bends back to the lower chemical potential region, irrespective to the strength of the vector coupling. In our FRG calculations, the driving force of the low temperature first order line is the fluctuations rather the quark density, and the effects of $\omega$-fields have little impact. At low temperature, the effective potential at small $\sigma$ field is very sensitive to the infrared cutoff scale, and this significantly affects our determination of the phase boundaries. The critical chemical potential at the tricritical point is affected by the $\omega$-field effects but its critical temperature stays around the similar value. Some caveats are given in interpreting our model results.

   hep-phhep-thPRD(2017)·53 citations
6. 06*

   Elastic amplitudes studied with the LHC measurements at 7 and 8 TeV

   A. K. Kohara🇧🇷 · E. Ferreira🇧🇷 · T. Kodama🇧🇷 · M. Rangel🇧🇷

   Recent measurements of the differential cross sections in the forward region of pp elastic scattering at 7 and 8 TeV show precise form of the $t$ dependence. We propose a detailed analysis of these measurements including the structures of the real and imaginary parts of the scattering amplitude. A good description is achieved, confirming in all experiments the existence of a zero in the real part in the forward region close to the origin, in agreement with the prediction of a theorem by A. Martin, with important role in the observed form of $d\sigma /dt$. Universal value for the position of this zero and regularity in other features of the amplitudes are found, leading to quantitative predictions for the forward elastic scattering at 13 TeV.

   hep-phEPJC(2017)·16 citations
7. 07*

   Lorentz Invariance and QCD Equation of Motion Relations for Generalized Parton Distributions and the Dynamical Origin of Proton Orbital Angular Momentum

   Abha Rajan🇺🇸 · Michael Engelhardt🇺🇸 · Simonetta Liuti🇺🇸

   We derive new Lorentz Invariance and Equation of Motion Relations between twist-three Generalized Parton Distributions (GPDs) and moments in the parton transverse momentum, $k_T$, of twist-two Generalized Transverse Momentum-Dependent Distributions (GTMDs), as a function of the parton longitudinal momentum fraction $x$. Although GTMDs in principle define the observables for partonic orbital motion, experiments that can unambiguously detect them appear remote at present. The relations presented here provide a solution to this impasse in that, e.g., the orbital angular momentum density is connected to directly measurable twist-three GPDs. Out of 16 possible Equation of Motion relations that can be written in the T-even sector, we focus on three helicity configurations that can be detected analyzing specific spin asymmetries: two correspond to longitudinal proton polarization and are associated with quark orbital angular momentum and spin-orbit correlations; the third, obtained for transverse proton polarization, is a generalization of the relation obeyed by the $g_2$ structure function. We also exhibit an additional relation connecting the off-forward extension of the Sivers function to an off-forward Qiu-Sterman term.

   hep-phPRD(2018)·43 citations
8. 08*

   Automated computations of electroweak corrections using Sherpa+Recola

   Mathieu Pellen🇩🇪

   Given the experimental precision and the multitude of processes that can be measured at the LHC, electroweak (EW) corrections become more and more relevant. This calls for the automatisation of EW corrections and in particular their implementations in multi-purpose Monte Carlo generators in order to allow for a systematic study of such contributions. In these proceedings I present the implementation of the matrix-element generator Recola in the Sherpa Monte Carlo. The combination Sherpa+Recola allows to compute, in principle, any process in the Standard Model at NLO QCD and EW accuracy. In addition to fixed-order NLO computations, all functionalities of Sherpa such as parton shower or hadronisation are still available.

   hep-phhep-ex1 citation
9. 09*

   Joint analysis of Borexino and SNO solar neutrino data and reconstruction of the survival probability

   Francesco Vissani🇮🇹

   Solar neutrino oscillations are supported by KamLAND's antineutrino measurements, but certain solar neutrino data - the observed shape of the ${}^8$B flux and the difference between day and night counting rates measured in Super-Kamiokande - do not fit well with the ensuing oscillation pattern. Interestingly, other solar neutrino data allow independent tests of the survival probability. Thanks to the new measurements of Borexino at low-energies along with the standard solar model and to the results of SNO at high-energies, four values of the neutrino survival probability are known. We build and study a likelihood based only on these solar neutrino data. The results agree well with the standard oscillation pattern and in particular with KamLAND findings. A related and straightforward procedure permits to reconstruct the survival probability of solar neutrinos and to assess its uncertainties, for all solar neutrino energies.

   hep-phNucl.Phys.Atom.Energy(2017)·8 citations
10. 10*

    On non-primitively divergent vertices of Yang-Mills theory

    Markus Q. Huber🇦🇹

    Two correlation functions of Yang-Mills beyond the primitively divergent ones, the two-ghost-two-gluon and the four-ghost vertices, are calculated and their influence on lower vertices is examined. Their full (transverse) tensor structure is taken into account. As input, a solution of the full two-point equations - including two-loop terms - is used that respects the resummed perturbative ultraviolet behavior. A clear hierarchy is found with regard to the color structure that reduces the number of relevant dressing functions. The impact of the two-ghost-two-gluon vertex on the three-gluon vertex is negligible, which is explained by the fact that all non-small dressing functions drop out due to their color factors. Only in the ghost-gluon vertex a small net effect below $2\%$ is seen. The four-ghost vertex is found to be extremely small in general. Since these two four-point functions do not enter into the propagator equations, these findings establish their small overall effect on lower correlation functions.

    hep-phEPJC(2017)·43 citations
11. 11*

    Lepton Electric Dipole Moment and Strong CP Violation

    Diptimoy Ghosh🇮🇱 · Ryosuke Sato🇮🇱

    Contribution of the strong CP angle, $\bar{\theta }$, to the Wilson Coefficients of electron and muon electric dipole moment (EDM) operators are discussed. Previously, $\bar{\theta }$ contribution to the electron EDM operator was calculated by Choi and Hong. However, the effect of CP-violating three meson coupling was missing there. We include this missing contribution for the first time in the literature, and reevaluate the Wilson coefficients of the lepton EDM operator. We obtain $d_e=-(2.2-8.6)\times 10^{-28}\bar{\theta }$ e-cm which is 15 - 70 % of the result obtained in Choi and Hong. We also estimated the muon EDM as $d_{\mu }=-(0.5-1.8)\times 10^{-25}\bar{\theta }$ e-cm. Using $|\bar{\theta }|\lesssim 10^{-10}$ suggested by the neutron EDM measurements, we obtain $|d_e|\lesssim 8.6\times 10^{-38}$ e-cm and $|d_{\mu }|\lesssim 1.8\times 10^{-35}$ e-cm. The $\bar{\theta }$ contribution to the muon EDM is much below the sensitivities of the current and near future experiments. Our result shows that the $\bar{\theta }$ contribution to $d_{e,\mu }$ can be larger than the CKM contributions by many orders of magnitude.

    hep-phhep-exPLB(2018)·26 citations
12. 12*

    Gravitational waves from the first order electroweak phase transition in the $Z_3$ symmetric singlet scalar model

    Toshinori Matsui🇰🇷

    Among various scenarios of baryon asymmetry of the Universe, electroweak baryogenesis is directly connected with physics of the Higgs sector. We discuss spectra of gravitational waves which are originated by the strongly first order phase transition at the electroweak symmetry breaking, which is required for a successful scenario of electroweak baryogenesis. In the $Z_3$ symmetric singlet scalar model, the significant gravitational waves are caused by the multi-step phase transition. We show that the model can be tested by measuring the characteristic spectra of the gravitational waves at future interferometers such as LISA and DECIGO.

    hep-phEPJ Web Conf.(2018)·8 citations
13. 13*

    Two Component Feebly Interacting Massive Particle (FIMP) Dark Matter

    Madhurima Pandey🇮🇳 · Debasish Majumdar🇮🇳 · Kamakshya Prasad Modak🇮🇳

    We explore the idea of an alternative candidate for particle dark matter namely Feebly Interacting Massive Particle (FIMP) in the framework of a two component singlet scalar model. Singlet scalar dark matter has already been demonstrated to be a viable candidate for WIMP (Weakly Interacting Massive Particle) dark matter in literature. In the FIMP scenario, dark matter particles are slowly produced via "thermal frreze-in" mechanism in the early Universe and are never abundant enough to reach thermal equilibrium or to undergo pair annihilation inside the Universe's plasma due to their extremely small couplings. We demonstrate that for smaller couplings too, required for freeze-in process, a two component scalar dark matter model considered here could well be a viable candidate for FIMP. In this scenario, the Standard Model of particle physics is extended by two gauge singlet real scalars whose stability is protected by an unbroken $Z_2\times {Z^{\prime }}_2$ symmetry and they are assumed to acquire no VEV after Spontaneous Symmetry Breaking. We explore the viable mass regions in the present two scalar DM model that is in accordance with the FIMP scenario. We also explore the upper limits of masses of the two components from the consideration of their self interactions.

    hep-phJCAP(2018)·32 citations
14. 14*

    SANC: the process $\gamma \gamma \to ZZ$

    D. Bardin🇷🇺 · S. Bondarenko🇷🇺 · P. Christova🇷🇺 · L. Kalinovskaya🇷🇺 · W. von Schlippe🇷🇺 · E. Uglov🇷🇺

    The implementation of the process $\gamma \gamma \to ZZ$ at the one-loop level within {\tt SANC} system multi-channel approach is considered. The derived one-loop scalar form factors can be used for any cross channel after an appropriate permutation of their arguments -- Mandelstam variables $s,t,u$. To check of the correctness of the results we observe the independence of the scalar form factors on the gauge parameters and the validity of Ward identity (external photon transversality). We present the complete analytical results for the covariant and tensor structures and helicity amplitudes for this process. We make an extensive comparison of our analytical and numerical results with those existing in the literature.

    hep-phPhys.Part.Nucl.Lett.(2017)·5 citations
15. 15*

    The low-temperature behavior of the quark-meson model

    Ralf-Arno Tripolt🇮🇹 · Bernd-Jochen Schaefer🇩🇪 · Lorenz von Smekal🇩🇪 · Jochen Wambach🇮🇹

    We revisit the phase diagram of strong-interaction matter for the two-flavor quark-meson model using the Functional Renormalization Group. In contrast to standard mean-field calculations, an unusual phase structure is encountered at low temperatures and large quark chemical potentials. In particular, we identify a regime where the pressure decreases with increasing temperature and discuss possible reasons for this unphysical behavior.

    hep-phhep-thnucl-thPRD(2018)·82 citations
16. 16*

    Determining Dark Matter properties with a XENONnT/LZ signal and LHC-Run3 mono-jet searches

    Sebastian Baum🇸🇪 · Riccardo Catena🇸🇪 · Jan Conrad🇸🇪 · Katherine Freese🇸🇪 · Martin B. Krauss🇸🇪

    We develop a method to forecast the outcome of the LHC Run 3 based on the hypothetical detection of $\mathcal{O}(100)$ signal events at XENONnT. Our method relies on a systematic classification of renormalisable single-mediator models for dark matter-quark interactions, and is valid for dark matter candidates of spin less than or equal to one. Applying our method to simulated data, we find that at the end of the LHC Run 3 only two mutually exclusive scenarios would be compatible with the detection of $\mathcal{O}(100)$ signal events at XENONnT. In a first scenario, the energy distribution of the signal events is featureless, as for canonical spin-independent interactions. In this case, if a mono-jet signal is detected at the LHC, dark matter must have spin 1/2 and interact with nucleons through a unique velocity-dependent operator. If a mono-jet signal is not detected, dark matter interacts with nucleons through canonical spin-independent interactions. In a second scenario, the spectral distribution of the signal events exhibits a bump at non zero recoil energies. In this second case, a mono-jet signal can be detected at the LHC Run 3, dark matter must have spin 1/2 and interact with nucleons through a unique momentum-dependent operator. We therefore conclude that the observation of $\mathcal{O}(100)$ signal events at XENONnT combined with the detection, or the lack of detection, of a mono-jet signal at the LHC Run 3 would significantly narrow the range of possible dark matter-nucleon interactions. As we argued above, it can also provide key information on the dark matter particle spin.

    hep-phastro-ph.COPRD(2018)·25 citations
17. 17*

    High-precision methods for Coulomb, linear confinement and Cornell potentials in momentum space

    Viktor Andreev🇧🇾

    We use special quadrature formulas for singular and hypersingular integral to numerically solve the Schrödinger equation in momentum space with the linear confinement potential, Coulomb and Cornell potentials. It is shown that the eigenvalues of the equation can be calculated with high accuracy, far exceeding other calculation methods. Special methods of solution for states with zero orbital angular momentum are considered.

    hep-ph1 citation
18. 18*

    Experimental Targets for Photon Couplings of the QCD Axion

    Prateek Agrawal🇺🇸 · JiJi Fan🇺🇸 · Matthew Reece🇺🇸 · Lian-Tao Wang🇺🇸

    The QCD axion's coupling to photons is often assumed to lie in a narrow band as a function of the axion mass. We demonstrate that several simple mechanisms, in addition to the photophilic clockwork axion already in the literature, can significantly extend the allowed range of couplings. Some mechanisms we present generalize the KNP alignment scenario, widely studied as a model of inflation, to the phenomenology of a QCD axion. In particular we present KSVZ-like realizations of two-axion KNP alignment and of the clockwork mechanism. Such a "confinement tower" realization of clockwork may prove useful in a variety of model-building contexts. We also show that kinetic mixing of the QCD axion with a lighter axion-like particle can dramatically alter the QCD axion's coupling to photons, differing from the other models we present by allowing non-quantized couplings. The simple models that we present fully cover the range of axion-photon couplings that could be probed by experiments. They motivate growing axion detection efforts over a wide space of masses and couplings.

    hep-phastro-ph.COhep-exJHEP(2018)·131 citations
19. 19*

    Neutrino vs. Antineutrino Oscillation Parameters at DUNE and Hyper-Kamiokande

    André de Gouvêa🇺🇸 · Kevin J. Kelly🇺🇸

    Testing, in a non-trivial, model-independent way, the hypothesis that the three-massive-neutrinos paradigm properly describes nature is among the main goals of the current and the next generation of neutrino oscillation experiments. In the coming decade, the DUNE and Hyper-Kamiokande experiments will be able to study the oscillation of both neutrinos and antineutrinos with unprecedented precision. We explore the ability of these experiments, and combinations of them, to determine whether the parameters that govern these oscillations are the same for neutrinos and antineutrinos, as prescribed by the CPT-theorem. We find that both DUNE and Hyper-Kamiokande will be sensitive to unexplored levels of leptonic CPT-violation. Assuming the parameters for neutrino and antineutrinos are unrelated, we discuss the ability of these experiments to determine the neutrino and antineutrino mass-hierarchies, atmospheric-mixing octants, and CP-odd phases, three key milestones of the experimental neutrino physics program. Additionally, if the CPT-theorem is violated in nature in a way that is consistent with all present neutrino and antineutrino oscillation data, we find that DUNE and Hyper-Kamiokande have the potential to ultimately establish CPT-invariance violation.

    hep-phhep-exPRD(2017)·32 citations
20. 20*

    Spectroscopy of Exotic Hadrons Formed from Dynamical Diquarks

    Richard F. Lebed🇺🇸

    The dynamical diquark picture asserts that exotic hadrons can be formed from widely separated colored diquark or triquark components. We use the Born-Oppenheimer (BO) approximation to study the spectrum of states thus constructed, both in the basis of diquark spins and in the basis of heavy quark-antiquark spins. We develop a compact notation for naming these states, and use the results of lattice simulations for hybrid mesons to predict the lowest expected BO potentials for both tetraquarks and pentaquarks. We then compare to the set of exotic candidates with experimentally determined quantum numbers, and find that all of them can be accommodated. Once decay modes are also considered, one can develop selection rules of both exact ($J^{PC}$ conservation) and approximate (within the context of the BO approximation) types and test their effectiveness. We find that the most appealing way to satisfy both sets of selection rules requires including additional low-lying BO potentials, a hypothesis that can be checked on the lattice.

    hep-phnucl-thPRD(2017)·50 citations
21. 21*

    Search for single production of the vector-like top partner at the 14 TeV LHC

    Yao-Bei Liu🇨🇳 · Yu-Qi Li🇨🇳

    The new heavy vector-like top partner~($T$) is one of typical features of many new physics models beyond the standard model. In this paper we study the discovery potential of the LHC for the vector-like $T$-quark both in the leptonic $T\to bW$ and $T\to t_{\mathrm{lep}}{Z}_{\mathrm{lep}}$ (trilepton) channels at $\sqrt{s}=14$ TeV in the single production mode. Our analysis is based on a simplified model including a $SU(2{)}_L$ singlet with charge $2/3$ with only two free parameters, namely the $TWb$ coupling parameter $g^{\ast }$ and the top partner mass $m_T$. The $2\sigma$ exclusion limits, $3\sigma$ evidence and the $5\sigma$ discovery reach in the parameter plane of $g^{\ast }-m_T$, are, respectively, obtained for some typical integrated luminosity at the 14 TeV LHC. Finally we analyze the projected sensitivity in terms of the production cross section times branching fraction for two decay channel.

    hep-phEPJC(2017)·30 citations
22. 22*

    Infrared Fixed Point Physics in $\mathrm{SO}(N_c)$ and $\mathrm{Sp}(N_c)$ Gauge Theories

    Thomas A. Ryttov🇩🇰 · Robert Shrock🇺🇸

    We study properties of asymptotically free vectorial gauge theories with gauge groups $G=\mathrm{SO}(N_c)$ and $G=\mathrm{Sp}(N_c)$ and $N_f$ fermions in a representation $R$ of $G$, at an infrared (IR) zero of the beta function, ${\alpha }_{IR}$, in the non-Abelian Coulomb phase. The fundamental, adjoint, and rank-2 symmetric and antisymmetric tensor fermion representations are considered. We present scheme-independent calculations of the anomalous dimensions of (gauge-invariant) fermion bilinear operators ${\gamma }_{\bar{\psi }\psi ,IR}$ to $O({\Delta }_f^4)$ and of the derivative of the beta function at ${\alpha }_{IR}$, denoted ${\beta }_{IR}^{\prime }$, to $O({\Delta }_f^5)$, where ${\Delta }_f$ is an $N_f$-dependent expansion variable. It is shown that all coefficients in the expansion of ${\gamma }_{\bar{\psi }\psi ,IR}$ that we calculate are positive for all representations considered, so that to $O({\Delta }_f^4)$, ${\gamma }_{\bar{\psi }\psi ,IR}$ increases monotonically with decreasing $N_f$ in the non-Abelian Coulomb phase. Using this property, we give a new estimate of the lower end of this phase for some specific realizations of these theories.

    ↳ hep-thhep-lathep-phPRD(2017)·31 citations
23. 23*

    Modeling Smooth Backgrounds and Generic Localized Signals with Gaussian Processes

    Meghan Frate🇺🇸 · Kyle Cranmer🇺🇸 · Saarik Kalia🇺🇸 · Alexander Vandenberg-Rodes · Daniel Whiteson🇺🇸

    We describe a procedure for constructing a model of a smooth data spectrum using Gaussian processes rather than the historical parametric description. This approach considers a fuller space of possible functions, is robust at increasing luminosity, and allows us to incorporate our understanding of the underlying physics. We demonstrate the application of this approach to modeling the background to searches for dijet resonances at the Large Hadron Collider and describe how the approach can be used in the search for generic localized signals.

    ↳ physics.data-anhep-exhep-ph74 citations
24. 24*

    Dynamical generation of fermion mass hierarchy in an extra dimension

    Yukihiro Fujimoto🇯🇵 · Takashi Miura🇯🇵 · Kenji Nishiwaki🇰🇷 · Makoto Sakamoto🇯🇵

    We propose a new mechanism to produce a fermion mass hierarchy dynamically in a model with a singlet generation of fermions. A five dimensional gauge theory on an interval with point interactions (zero-width branes) takes responsibility for realizing three generations and each massless zero mode localizes at boundaries of the segments on the extra dimension. An extra-dimension coordinate-dependent vacuum expectation value of a scalar field makes large differences in overlap integrals of the localized zero modes and then an exponential fermion mass hierarchy can appear. The positions of the point interactions control the magnitude of the fermion mass hierarchy and are determined by the minimization condition of the Casimir energy. As a result of the minimization of the Casimir energy, an exponential mass hierarchy appears dynamically. We also discuss the stability of the extra dimension.

    ↳ hep-thhep-phPRD(2018)·15 citations
25. 25*

    Detecting higher spin fields through statistical anisotropy in the CMB and galaxy power spectra

    Nicola Bartolo🇮🇹 · Alex Kehagias🇬🇷 · Michele Liguori🇮🇹 · Antonio Riotto🇨🇭 · Maresuke Shiraishi🇯🇵 · Vittorio Tansella🇨🇭

    Primordial inflation may represent the most powerful collider to test high-energy physics models. In this paper we study the impact on the inflationary power spectrum of the comoving curvature perturbation in the specific model where massive higher spin fields are rendered effectively massless during a de Sitter epoch through suitable couplings to the inflaton field. In particular, we show that such fields with spin $s$ induce a distinctive statistical anisotropic signal on the power spectrum, in such a way that not only the usual $g_{2M}$-statistical anisotropy coefficients, but also higher-order ones (i.e., $g_{4M}$, $g_{6M}$, $\cdots$, $g_{(2s-2)M}$ and $g_{(2s)M}$) are nonvanishing. We examine their imprints in the cosmic microwave background and galaxy power spectra. Our Fisher matrix forecasts indicate that the detectability of $g_{LM}$ depends very weakly on $L$: all coefficients could be detected in near future if their magnitudes are bigger than about $10^{-3}$.

    ↳ astro-ph.COgr-qchep-phhep-thPRD(2018)·58 citations
26. 26*

    Dual Conformal Symmetry, Integration-by-Parts Reduction, Differential Equations and the Nonplanar Sector

    Zvi Bern🇺🇸 · Michael Enciso🇺🇸 · Harald Ita🇩🇪 · Mao Zeng🇺🇸

    We show that dual conformal symmetry, mainly studied in planar $\mathcal{N}=4$ super-Yang-Mills theory, has interesting consequences for Feynman integrals in nonsupersymmetric theories such as QCD, including the nonplanar sector. A simple observation is that dual conformal transformations preserve unitarity cut conditions for any planar integrals, including those without dual conformal symmetry. Such transformations generate differential equations without raised propagator powers, often with the right hand side of the system proportional to the dimensional regularization parameter $ϵ$. A nontrivial subgroup of dual conformal transformations, which leaves all external momenta invariant, generates integration-by-parts relations without raised propagator powers, reproducing, in a simpler form, previous results from computational algebraic geometry for several examples with up to two loops and five legs. By opening up the two-loop three- and four-point nonplanar diagrams into planar ones, we find a nonplanar analog of dual conformal symmetry. As for the planar case this is used to generate integration-by-parts relations and differential equations. This implies that the symmetry is tied to the analytic properties of the nonplanar sector of the two-loop four-point amplitude of $\mathcal{N}=4$ super-Yang-Mills theory.

    ↳ hep-thhep-phPRD(2017)·52 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.