Thu·Nov 23, 2017Thursday·November 23, 2017

1. 01*

   Deviations of exact neutrino textures using radiative neutrino masses

   D. Wegman🇧🇪

   The Weinberg operator allows for the construction of radiative Majorana neutrino masses. In this letter, it will be shown that it is possible to construct a one-loop diagram that will be the principal component of the neutrino mass matrix and that will have an exact mixing matrix with ${\theta }_{13}=0$. The addition of a two-loop diagram, which is naturally suppressed, allows the creation of the correct perturbations that will give a neutrino mixing matrix with entries inside experimental constrains, including the possibility of large CP Dirac phases.

   hep-ph2 citations
2. 02*

   Automated QCD and Electroweak Corrections with Sherpa

   Steffen Schumann🇩🇪

   Precise theoretical predictions are vital for the interpretation of Standard Model measurements and facilitate conclusive searches for New Physics phenomena at the LHC. In this contribution I highlight some of the ongoing efforts in the framework of the Sherpa event generator to provide accurate and realistic simulations of Standard Model production processes. This includes the automated evaluation of NLO QCD and NLO EW corrections and their consistent consideration in the parton-shower evolution of scattering events. Particular emphasis is given to examples and applications involving the production of top quarks.

   hep-phhep-ex1 citation
3. 03*

   Hadron tomography by generalized distribution amplitudes in pion-pair production process ${\gamma }^{\ast }\gamma \to {\pi }^0{\pi }^0$ and gravitational form factors for pion

   S. Kumano🇯🇵 · Qin-Tao Song🇯🇵 · O. V. Teryaev🇷🇺

   Hadron tomography can be investigated by three-dimensional structure functions such as generalized parton distributions (GPDs), transverse-momentum-dependent parton distributions, and generalized distribution amplitudes (GDAs). Here, we extract the GDAs, which are $s$-$t$ crossed quantities of the GPDs, from cross-section measurements of hadron-pair production process ${\gamma }^{\ast }\gamma \to {\pi }^0{\pi }^0$ at KEKB. This work is the first attempt to obtain the GDAs from the actual experimental data. The GDAs are expressed by a number of parameters and they are determined from the data of ${\gamma }^{\ast }\gamma \to {\pi }^0{\pi }^0$ by including intermediate scalar- and tensor-meson contributions to the cross section. Our results indicate that the dependence of parton-momentum fraction $z$ in the GDAs is close to the asymptotic one. The timelike gravitational form factors ${\Theta }_1$ and ${\Theta }_2$ are obtained from our GDAs, and they are converted to the spacelike ones by the dispersion relation.From the spacelike ${\Theta }_1$ and ${\Theta }_2$, gravitational densities of the pion are calculated. Then, we obtained the mass (energy) radius and the mechanical (pressure and shear force) radius from ${\Theta }_2$ and ${\Theta }_1$, respectively. They are calculated as $\sqrt{⟨r^2{⟩}_{\text{mass}}}=0.32\sim 0.39$ fm, whereas the mechanical radius is larger $\sqrt{⟨r^2{⟩}_{\text{mech}}}=0.82\sim 0.88$ fm. This is the first report on the gravitational radius of a hadron from actual experimental measurements. It is interesting to find the possibility that the gravitational mass and mechanical radii could be different from the experimental charge radius $\sqrt{⟨r^2{⟩}_{\text{charge}}}=0.672\pm 0.008$ fm for the charged pion.

   hep-phhep-exhep-latnucl-thPRD(2018)·174 citations
4. 04*

   Momentum transfer dependence of the hadron GPDs and Compton form factors

   O.V. Selyugin🇷🇺

   The generalized parton distributions (GPDs) of the meson and nucleon at small and large values of the momentum transfer were determined on the basis of the comparative analysis of different sets of experimental data of electromagnetic form factors of the proton and neutron, using the different sets of the parton distribution functions (PDFs). As a result, different form factors of the nucleons and meson were calculated. The t-dependence of these form factors was checked up in the description of the nucleon-nucleon and meson-nucleon elastic scattering and the differential cross sections of the real Compton scattering.

   hep-phhep-exJ.Phys.Conf.Ser.(2017)·1 citation
5. 05*

   One-loop corrections to light cone wave functions: the dipole picture DIS cross section

   H. Hänninen🇫🇮 · T. Lappi🇫🇮 · R. Paatelainen🇫🇮

   We develop methods needed to perform loop calculations in light cone perturbation theory using a helicity basis, refining the method introduced in our earlier work. In particular this includes implementing a consistent way to contract the four-dimensional tensor structures from the helicity vectors with d-dimensional tensors arising from loop integrals, in a way that can be fully automatized. We demonstrate this explicitly by calculating the one-loop correction to the virtual photon to quark-antiquark dipole light cone wave function. This allows us to calculate the deep inelastic scattering cross section in the dipole formalism to next-to-leading order accuracy. Our results, obtained using the four dimensional helicity scheme, agree with the recent calculation by Beuf using conventional dimensional regularization, confirming the regularization scheme independence of this cross section.

   hep-phnucl-thAnnals Phys.(2018)·92 citations
6. 06*

   Tetraquark mixing framework for isoscalar resonances in light mesons

   Hungchong Kim🇰🇷 · K. S. Kim🇰🇷 · Myung-Ki Cheoun🇰🇷 · Makoto Oka🇯🇵

   Recently, a tetraquark mixing framework has been proposed for light mesons and applied more or less successfully to the isovector resonances, $a_0(980),a_0(1450)$, as well as to the isodoublet resonances, $K_0^{\ast }(800),K_0^{\ast }(1430)$. In this work, we present a more extensive view on the mixing framework and extend this to the isoscalar resonances, $f_0(500)$, $f_0(980)$, $f_0(1370)$, $f_0(1500)$. Tetraquarks in this framework can have two spin configurations containing either spin-0 diquark or spin-1 diquark and each configuration forms a nonet in flavor space. The two spin configurations are found to mix strongly through the color-spin interactions. Their mixtures, which diagonalize the hyperfine masses, can generate the physical resonances constituting the two nonets, which, in fact, coincide roughly with the experimental observation. We identify that $f_0(500)$, $f_0(980)$ are the isoscalar members in the light nonet, and $f_0(1370)$, $f_0(1500)$ are the similar members in the heavy nonet. This means that the spin configuration mixing, as it relates the corresponding members in the two nonets, can generate $f_0(500),f_0(1370)$ among the members in light mass, and $f_0(980),f_0(1500)$ in heavy mass. The complication arises because the isoscalar members of each nonet are subject to an additional flavor mixing known as OZI rule so that $f_0(500),f_0(980)$, and similarly $f_0(1370),f_0(1500)$, are the mixture of two isoscalar members belonging to an octet and a singlet in SU${}_f$(3). The tetraquark mixing framework including the flavor mixing is tested for the isoscalar resonances in terms of the mass splitting and the fall-apart decay modes.

   hep-phhep-exnucl-thPRD(2018)·27 citations
7. 07*

   Generation of Asymmetric Dark Matter and Gravitational Waves

   Iason Baldes🇩🇪

   We consider the possibility of a gravitational wave signal in an asymmetric dark matter model. In this model a generative sector produces both the baryon asymmetry and a dark matter asymmetry in a strong first-order phase transtion. Bubble collisions during the phase transition lead to sound waves in the plasma which are a source of a stochastic gravitational wave background. We consider the prospects of future graviational wave observatories such as LISA and BBO detecting such a signal. Constraints on the model from Halo ellipticity, $\Delta N_{\mathrm{eff}}$ and direct detection experiments are also discussed.

   hep-ph4 citations
8. 08*

   Medium effects on the electrical conductivity of a hot pion gas

   Snigdha Ghosh🇮🇳 · Sukanya Mitra🇮🇳 · Sourav Sarkar🇮🇳

   The electromagnetic response of an interacting system of pions has been studied at finite temperature. The corresponding transport parameter i.e. electrical conductivity has been estimated by solving the relativistic transport equation in presence of a finite electric field employing the Chapman-Enskog technique where the collision term has been treated in the relaxation time approximation. The scattering amplitudes of charged pions modeled by $\rho$ and $\sigma$ meson exchange using an effective Lagrangian have been obtained at finite temperature by introducing self-energy corrections in the thermal propagators in the real time formalism. The temperature behavior of electrical conductivity for a hot pion gas shows significant quantitative enhancement due to the inclusion of medium effects in scattering.

   hep-phnucl-thNPA(2018)·16 citations
9. 09*

   Dynamical electroweak breaking and contributions to supersymmetry breaking through logarithmic operators

   Renata Jora🇷🇴

   We introduce in an arbitrary supersymmetric version of the standard model without elementary scalars a logarithmic operator which is irrelevant in the limit in which all symmetries are respected. However through a dynamical mechanism of the Nambu Jona Lasinio type this operator may produce two fermion vacuum condensates that may account for electroweak and contribute to supersymmetry breaking. Some of the phenomenological consequences of this set-up are discussed.

   hep-ph0 citations
10. 10*

    Natural cliff inflation

    Jinn-Ouk Gong🇰🇷 · Chang Sub Shin🇰🇷

    We propose a novel scenario of inflation, in which the inflaton is identified as the lightest mode of an angular field in a compactified fifth dimension. The periodic effective potential exhibits exponentially flat plateaus, so that a sub-Planckian field excursion without hilltop initial conditions is naturally realized. We can obtain consistent predictions with observations on the spectral index and the tensor-to-scalar ratio.

    hep-phastro-ph.COhep-th3 citations
11. 11*

    Testing a new WISP Model with Laboratory Experiments

    P. D. Alvarez🇨🇱 · Paola Arias🇨🇱 · Carlos Maldonado🇨🇱

    We explore the phenomenological consequences of a model with axion-like particles and hidden photons mixing with photons. In this model, the hidden photon is directly coupled to the photon, while the axion coupling is induced by an external electromagnetic field. We consider vacuum effects on a polarised photon beam, like changes in the ellipticity and rotation angles.

    hep-ph0 citations
12. 12*

    Explicit calculation on two-loop correction to the chiral magnetic effect with NJL model

    Kit-fai Chu🇨🇳 · Peng-hui Huang🇨🇳 · Hui Liu🇨🇳

    Chiral Magnetic Effect(CME) is usually believed not receiving higher order corrections due to the non-renormalization of AVV triangle diagram in the framework of quantum field theory. However, the CME-relevant triangle, which is obtained by expanding the current-current correlation requires zero momentum on the axial vertex, is not equivalent to the general AVV triangle when taking the zero-momentum limit owing to the infrared problem on the axial vertex. Therefore, it is still significant to check if there exists perturbative higher order corrections to the current-current correlation. In this paper, we explicitly calculate the two-loop corrections of CME within NJL model with Chern-Simons term which ensures a consistent ${\mu }_5$. The result shows the two-loop corrections to the CME conductivity are zero, which confirms the non-renomalization of CME conductivity.

    hep-phPRD(2018)·0 citations
13. 13*

    Neutrinoless double beta decay and QCD running at low energy scales

    Marcela González🇨🇱 · Martin Hirsch🇪🇸 · Sergey Kovalenko🇨🇱

    There is a common belief that the main uncertainties in the theoretical analysis of neutrinoless double beta ($0\nu \beta \beta$) decay originate from the nuclear matrix elements. Here, we uncover another previously overlooked source of potentially large uncertainties stemming from non-perturbative QCD effects. Recently perturbative QCD corrections have been calculated for all dimension 6 and 9 effective operators describing $0\nu \beta \beta$-decay and their importance for a reliable treatment of $0\nu \beta \beta$-decay has been demonstrated. However, these perturbative results are valid at energy scales above $\sim 1$ GeV, while the typical $0\nu \beta \beta$-scale is about $\sim 100$ MeV. In view of this fact we examine the possibility of extrapolating the perturbative results towards sub-GeV non-perturbative scales on the basis of the QCD coupling constant "freezing" behavior using Background Perturbation Theory. Our analysis suggests that such an infrared extrapolation does modify the perturbative results for both short-range and long-range mechanisms of $0\nu \beta \beta$-decay in general only moderately. We also discuss that the tensor$\otimes$tensor effective operator can not appear alone in the low-energy limit of any renormalizable high-scale model and then demonstrate that all five linearly independent combinations of the scalar and tensor operators, that can appear in renormalizable models, are infrared stable.

    hep-phPRD(2018)·13 citations
14. 14*

    Light meson gas in the QCD vacuum and oscillating Universe

    George Prokhorov🇷🇺 · Roman Pasechnik🇸🇪

    We have developed a phenomenological effective quantum-field theoretical model describing the "hadron gas" of the lightest pseudoscalar mesons, scalar {\sigma}-meson and {\sigma}-vacuum, i.e. the expectation value of the {\sigma}-field, at finite temperatures. The corresponding thermodynamic approach was formulated in terms of the generating functional derived from the effective Lagrangian providing the basic thermodynamic information about the "meson plasma + QCD condensate" system. This formalism enables us to study the QCD transition from the hadron phase with direct implications for cosmological evolution. Using the hypothesis about a positively-definite QCD vacuum contribution stochastically produced in early universe, we show that the universe could undergo a series of oscillations during the QCD epoch before resuming unbounded expansion.

    hep-phastro-ph.HEJCAP(2018)·1 citation
15. 15*

    Lepton Flavor Violation Induced by a Neutral Scalar at Future Lepton Colliders

    P. S. Bhupal Dev🇺🇸 · Rabindra N. Mohapatra🇺🇸 · Yongchao Zhang🇺🇸

    Many new physics scenarios beyond the Standard Model often necessitate the existence of a (light) neutral scalar $H$, which might couple to the charged leptons in a flavor violating way, while evading all existing constraints. We show that such scalars could be effectively produced at future lepton colliders, either on-shell or off-shell depending on their mass, and induce lepton flavor violating (LFV) signals, i.e. $e^{+}{e}^{-}\to {\ell }_{\alpha }^{\pm }{\ell }_{\beta }^{\mp }(+H)$ with $\alpha \ne \beta$. We find that a large parameter space of the scalar mass and the LFV couplings can be probed, well beyond the current low-energy constraints in the lepton sector. In particular, a scalar-loop induced explanation of the longstanding muon $g-2$ anomaly can be directly tested in the on-shell mode.

    hep-phhep-exPRL(2018)·58 citations
16. 16*

    Clockwork / Linear Dilaton: Structure and Phenomenology

    Gian F. Giudice🇨🇭 · Yevgeny Kats🇮🇱 · Matthew McCullough🇨🇭 · Riccardo Torre🇨🇭 · Alfredo Urbano🇨🇭

    The linear dilaton geometry in five dimensions, rediscovered recently in the continuum limit of the clockwork model, may offer a solution to the hierarchy problem which is qualitatively different from other extra-dimensional scenarios and leads to distinctive signatures at the LHC. We discuss the structure of the theory, in particular aspects of naturalness and UV completion, and then explore its phenomenology, suggesting novel strategies for experimental searches. In particular, we propose to analyze the diphoton and dilepton invariant mass spectra in Fourier space in order to identify an approximately periodic structure of resonant peaks. Among other signals, we highlight displaced decays from resonantly-produced long-lived states and high-multiplicity final states from cascade decays of excited gravitons.

    hep-phJHEP(2018)·90 citations
17. 17*

    N-loop running should be combined with N-loop matching

    Johannes Braathen🇫🇷 · Mark D. Goodsell🇫🇷 · Manuel E. Krauss🇩🇪 · Toby Opferkuch🇩🇪 · Florian Staub🇩🇪

    We investigate the high-scale behaviour of Higgs sectors beyond the Standard Model, pointing out that the proper matching of the quartic couplings before applying the renormalisation group equations (RGEs) is of crucial importance for reliable predictions at larger energy scales. In particular, the common practice of leading-order parameters in the RGE evolution is insufficient to make precise statements on a given model's UV behaviour, typically resulting in uncertainties of many orders of magnitude. We argue that, before applying N-loop RGEs, a matching should even be performed at N-loop order in contrast to common lore. We show both analytical and numerical results where the impact is sizeable for three minimal extensions of the Standard Model: a singlet extension, a second Higgs doublet and finally vector-like quarks. We highlight that the known two-loop RGEs tend to moderate the running of their one-loop counterparts, typically delaying the appearance of Landau poles. For the addition of vector-like quarks we show that the complete two-loop matching and RGE evolution hints at a stabilisation of the electroweak vacuum at high energies, in contrast to results in the literature.

    hep-phPRD(2018)·38 citations
18. 18*

    GeV-scale hot sterile neutrino oscillations: a numerical solution

    J. Ghiglieri🇨🇭 · M. Laine🇨🇭

    The scenario of baryogenesis through GeV-scale sterile neutrino oscillations is governed by non-linear differential equations for the time evolution of a sterile neutrino density matrix and Standard Model lepton and baryon asymmetries. By employing up-to-date rate coefficients and a non-perturbatively estimated Chern-Simons diffusion rate, we present a numerical solution of this system, incorporating the full momentum and helicity dependences of the density matrix. The density matrix deviates significantly from kinetic equilibrium, with the IR modes equilibrating much faster than the UV modes. For equivalent input parameters, our final results differ moderately (~50%) from recent benchmarks in the literature. The possibility of producing an observable baryon asymmetry is nevertheless confirmed. We illustrate the dependence of the baryon asymmetry on the sterile neutrino mass splitting and on the CP-violating phase measurable in active neutrino oscillation experiments.

    hep-phJHEP(2018)·42 citations
19. 19*

    Black hole superradiance and polarization-dependent bending of light

    Alexis D. Plascencia🇬🇧 · Alfredo Urbano🇨🇭

    An inhomogeneous pseudo-scalar field configuration behaves like an optically active medium. Consequently, if a light ray passes through an axion cloud surrounding a Kerr black hole, it may experience a polarization-dependent bending. We explore the size and relevance of such effect considering both the QCD axion and a generic axion-like particle.

    ↳ gr-qcastro-ph.HEhep-phJCAP(2018)·47 citations
20. 20*

    Neutrino Mass Priors for Cosmology from Random Matrices

    Andrew J. Long🇺🇸 · Marco Raveri🇺🇸 · Wayne Hu🇺🇸 · Scott Dodelson🇺🇸

    Cosmological measurements of structure are placing increasingly strong constraints on the sum of the neutrino masses, $\Sigma m_{\nu }$, through Bayesian inference. Because these constraints depend on the choice for the prior probability $\pi (\Sigma m_{\nu })$, we argue that this prior should be motivated by fundamental physical principles rather than the ad hoc choices that are common in the literature. The first step in this direction is to specify the prior directly at the level of the neutrino mass matrix $M_{\nu }$, since this is the parameter appearing in the Lagrangian of the particle physics theory. Thus by specifying a probability distribution over $M_{\nu }$, and by including the known squared mass splittings, we predict a theoretical probability distribution over $\Sigma m_{\nu }$ that we interpret as a Bayesian prior probability $\pi (\Sigma m_{\nu })$. We find that $\pi (\Sigma m_{\nu })$ peaks close to the smallest $\Sigma m_{\nu }$ allowed by the measured mass splittings, roughly $0.06\mathrm{eV}$ ($0.1\mathrm{eV}$) for normal (inverted) ordering, due to the phenomenon of eigenvalue repulsion in random matrices. We consider three models for neutrino mass generation: Dirac, Majorana, and Majorana via the seesaw mechanism; differences in the predicted priors $\pi (\Sigma m_{\nu })$ allow for the possibility of having indications about the physical origin of neutrino masses once sufficient experimental sensitivity is achieved. We present fitting functions for $\pi (\Sigma m_{\nu })$, which provide a simple means for applying these priors to cosmological constraints on the neutrino masses or marginalizing over their impact on other cosmological parameters.

    ↳ astro-ph.COhep-phhep-thPRD(2018)·48 citations
21. 21*

    The Sudakov form factor at four loops in maximal super Yang-Mills theory

    Rutger H. Boels🇩🇪 · Tobias Huber🇩🇪 · Gang Yang🇨🇳

    The four-loop Sudakov form factor in maximal super Yang-Mills theory is analysed in detail. It is shown explicitly how to construct a basis of integrals that have a uniformly transcendental expansion in the dimensional regularisation parameter, further elucidating the number-theoretic properties of Feynman integrals. The physical form factor is expressed in this basis for arbitrary colour factor. In the nonplanar sector the required integrals are integrated numerically using a mix of sector-decomposition and Mellin-Barnes representation methods. Both the cusp as well as the collinear anomalous dimension are computed. The results show explicitly the violation of quadratic Casimir scaling at the four-loop order. A thorough analysis concerning the reliability of reported numerical uncertainties is carried out.

    ↳ hep-thhep-phJHEP(2018)·65 citations
22. 22*

    MagnetoHydrodynamics with chiral anomaly: phases of collective excitations and instabilities

    Koichi Hattori🇨🇳 · Yuji Hirono🇺🇸 · Ho-Ung Yee🇺🇸 · Yi Yin🇺🇸

    We study the relativistic hydrodynamics with chiral anomaly and dynamical electromagnetic fields, namely Chiral MagnetoHydroDynamics (CMHD). We formulate CMHD as a low-energy effective theory based on a generalized derivative expansion. We demonstrate that the modification of ordinary MagnetoHydroDynamics (MHD) due to chiral anomaly can be obtained from the second law of thermodynamics and is tied to chiral magnetic effect. We further study the real-time properties of chiral fluid by solving linearized CMHD equations. We discover a remarkable "transition" at an intermediate axial chemical potential ${\mu }_A$ between a stable Chiral fluid at low ${\mu }_A$ and an unstable Chiral fluid at large ${\mu }_A$. We summarize this transition in a "phase diagram" in terms of ${\mu }_A$ and the angle of the wavevector relative to the magnetic field. In the unstable regime, there are four collective modes carrying both magnetic and fluid helicity, in contrary to MHD waves which are unpolarized. The half of the helical modes grow exponentially in time, indicating the instability, while the other half become dissipative.

    ↳ hep-thcond-mat.mes-hallhep-phnucl-thPRD(2019)·63 citations
23. 23*

    Prospects to verify a possible dark matter hint in cosmic antiprotons with antideuterons and antihelium

    Michael Korsmeier🇩🇪 · Fiorenza Donato🇮🇹 · Nicolao Fornengo🇮🇹

    Cosmic rays are an important tool to study dark matter annihilation in our Galaxy. Recently, a possible hint for dark matter annihilation was found in the antiproton spectrum measured by AMS-02, even though the result might be affected by theoretical uncertainties. A complementary way to test its dark matter interpretation would be the observation of low-energy antinuclei in cosmic rays. We determine the chances to observe antideuterons with GAPS and AMS-02, and the implications for the ongoing AMS-02 antihelium searches. We find that the corresponding antideuteron signal is within the GAPS and AMS-02 detection potential. If, more conservatively, the putative signal was considered as an upper limit on DM annihilation, our results would indicate the highest possible fluxes for antideuterons and antihelium compatible with current antiproton data.

    ↳ astro-ph.HEhep-phPRD(2018)·119 citations
24. 24*

    Minimal constrained superfields and the Fayet-Iliopoulos model

    Karim Benakli🇫🇷 · Yifan Chen🇫🇷 · Mark D. Goodsell🇫🇷

    We show how the necessary constraints to project out all the components of a chiral superfield except for some scalar degrees of freedom originate from simple operators in the microscopic theory. This is in particular useful in constructing the simplest models of a goldstone boson/inflaton; or extracting the Standard Model Higgs doublet from a supersymmetric electroweak sector. We use the Fayet-Iliopoulos model as an example of the origin for the supersymmetry breaking. We consider the regime where both gauge symmetry and supersymmetry are spontaneously broken, leaving (in the decoupling limit) the goldstino as the only light mode in this sector. We show in three different ways, both in components and in superspace language, how the nilpotent goldstino superfield emerges. We then use it to write different effective operators and extract some of the consequences for the low energy spectrum.

    ↳ hep-thhep-phEPJC(2018)·10 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.