Mon·Jun 25, 2018Monday·June 25, 2018

1. 01*

   The gluon propagator in linear covariant $R_{\xi }$ gauges

   Fabio Siringo🇮🇹 · Giorgio Comitini🇮🇹

   Explicit analytical expressions are derived for the gluon propagator in a generic linear covariant $R_{\xi }$ gauge, by a screened massive expansion for the exact Faddeev-Popov Lagrangian of pure Yang-Mills theory. At one-loop, if the gauge invariance of the pole structure is enforced, the gluon dressing function is entirely and uniquely determined, without any free parameter or external input. The gluon propagator is found finite in the IR for any $\xi$, with a slight decrease of its limit value when going from the Landau gauge ($\xi =0$) towards the Feynman gauge ($\xi =1$). An excellent agreement is found with the lattice in the range $0<\xi <0.5$ where the data are available.

   hep-phhep-lathep-thPRD(2018)·38 citations
2. 02*

   Things that go bump in the night: From $J/\psi \varphi$ to other mass spectrum

   Kai Yi🇺🇸

   This article summarizes a brief development of exotic mesons with Vector-Vector (VV) final states starting from the $J/\psi \varphi$ mass spectrum, as well as extensions to other final states for strong-interaction physics and physics beyond standard model. These VV final states are very suitable to be studied at CEPC through associate production and two-photon production, as well as a visionary low energy photon collider.

   hep-phInt.J.Mod.Phys.A(2019)·20 citations
3. 03*

   Structure of Pion Photoproduction Amplitudes

   V. Mathieu🇺🇸 · J. Nys🇧🇪 · C. Fernandez-Ramirez🇲🇽 · A. N. Hiller Blin🇩🇪 · A. Jackura🇺🇸 · A. Pilloni🇺🇸 · A. P. Szczepaniak🇺🇸 · G. Fox (JPAC Collaboration)🇺🇸

   We derive and apply the finite energy sum rules to pion photoproduction. We evaluate the low energy part of the sum rules using several state-of-the-art models. We show how the differences in the low energy side of the sum rules might originate from different quantum number assignments of baryon resonances. We interpret the observed features in the low energy side of the sum rules with the expectation from Regge theory. Finally, we present a model, in terms of a Regge-pole expansion, that matches the sum rules and the high-energy observables.

   hep-phPRD(2018)·15 citations
4. 04*

   Electroweak symmetry breaking by a neutral sector: Dynamical relaxation of the little hierarchy problem

   Bumseok Kyae🇰🇷

   We propose a new dynamical relaxation mechanism of the little hierarchy problem, based on a singlet extension of the minimal supersymmetric standard model (MSSM). In this scenario, the small soft mass parameter of an MSSM singlet is responsible for the electroweak symmetry breaking and the non-zero Higgs vacuum expectation value, whereas the effect of the large soft mass parameter of the Higgs boson, -m_{h_u}^2 is dynamically compensated by a flat direction of the MSSM singlets. The small singlet's soft mass and the Z boson mass can be protected, even if the stop mass is heavier than 10 or 20 TeV, since the gravity-mediated supersymmetry breaking effects and the relevant Yukawa couplings are relatively small. A "focus point" of the singlet's soft mass parameter can emerge around the stop mass scale, and so various fine-tuning measures can reduce well below 100. Due to the relatively large gauge-mediated effects, the MSSM superpartners are much heavier than the experimental bounds, and the unwanted flavor changing processes are adequately suppressed.

   hep-ph2 citations
5. 05*

   Doubly-Charged Scalars in the Type-II Seesaw Mechanism: Fundamental Symmetry Tests and High-Energy Searches

   P. S. Bhupal Dev🇺🇸 · Michael J. Ramsey-Musolf🇺🇸 · Yongchao Zhang🇺🇸

   We analyze the sensitivity of low-energy fundamental symmetry tests to interactions mediated by doubly-charged scalars that arise in type-II seesaw models of neutrino mass and their left-right symmetric extensions. We focus on the next generation measurement of the parity-violating asymmetry in Møller scattering planned by the MOLLER collaboration at Jefferson Laboratory. We compare the MOLLER sensitivity to that of searches for charged lepton flavor violation (CLFV) and neutrinoless double beta-decay ($0\nu \beta \beta$-decay) as well as present and possible future high-energy collider probes. We show that for the simplest type-II seesaw scenario, CLFV searches have the greatest sensitivity. However, in a left-right symmetric extension where the scale of parity-breaking is decoupled from the $SU(2{)}_R$-breaking scale, the MOLLER experiment will provide a unique probe of scalar triplet interactions in the right-handed sector for a doubly-charged scalar mass up to $\sim$ 10 TeV and help elucidate the mechanism of $0\nu \beta \beta$-decay.

   hep-phhep-exnucl-exnucl-thPRD(2018)·65 citations
6. 06*

   Supersymmetric Naturalness Beyond MSSM

   Archil Kobakhidze🇦🇺 · Matthew Talia🇦🇺

   The experiments at the Large Hadron Collider (LHC) have pushed the limits on masses of supersymmetric particles beyond the $\sim$TeV scale. This compromises naturalness of the simplest supersymmetric extension of the Standard Model, the minimal supersymmetric Standard Model (MSSM). In this paper we advocate that perhaps the current experimental data are actually hinting towards the physics beyond MSSM. To illustrate this, we treat MSSM as a low energy limit of a more fundamental yet unspecified theory at a scale $\Lambda$, and compute the fine-tuning measure $\Delta$ for generic boundary conditions on soft SUSY breaking parameters and various cut-off scales. As a general trend we observe reduction in fine-tuning together with lowering $\Lambda$. In particular, perfectly natural [$\Delta \lesssim \mathcal{O}(10)$] theories with a multi-TeV spectrum of supersymmetric particles and consistent with all current observations can be obtained for $\Lambda \sim \mathcal{O}(100)$TeV. The lowering of the fine-tuning for large cut-off scales can also be observed in theories exhibiting special quasi-fixed point behaviours of parameters. Our observations call for a more throughout exploration of possible alternative ultraviolet completions of MSSM.

   hep-phJHEP(2019)·10 citations
7. 07*

   Decaying axinolike dark matter: Discriminative solution to small-scale issues

   Kyu Jung Bae🇰🇷 · Ayuki Kamada🇰🇷 · Hee Jung Kim🇰🇷

   The latest Lyman-$\alpha$ forest data severely constrain the conventional warm dark matter solution to small-scale issues in the cold dark matter paradigm. It has been also reported that unconstrained astrophysical processes may address the issues. In response to this situation, we revisit the decaying dark matter solution to the issues, discussing possible signatures to discriminate decaying dark matter from astrophysical processes as a solution to small-scale issues. We consider an axinolike particle (ALPino) decaying into an axionlike particle (ALP) and gravitino with the lifetime around the age of the Universe. The ALPino mass is sub-PeV and slightly ($\Delta m/m\sim 10^{-4}$) larger than the gravitino mass, and thus the dark matter abundance does not alter virtually after the ALPino decays. On the other hand, the gravitino produced from the ALPino decay obtains a kick velocity of $\sim 30km/s$, which is sufficiently larger than a circular velocity of dwarf galaxies to impact their dark matter distributions. The Lyman-$\alpha$ forest constraints are relieved since only a small fraction ($\sim 10$%) of dark matter experiences the decay at that time. Decaying dark matter is thus promoted to a viable solution to small-scale issues. The ALPino relic abundance is determined predominantly by the decay of the lightest ordinary supersymmetric particle. The monochromatic ALP emission from the ALPino decay is converted to $\sim 50\mathrm{GeV}$ photon under the Galactic magnetic field. The morphology of the gamma-ray flux shows a distinctive feature of the model when compared to decaying dark matter that directly decays into photons. Once detected, such distinctive signals discriminate the decaying dark matter solution to small-scale issues from unconstrained astrophysical processes.

   hep-phastro-ph.COastro-ph.HEPRD(2019)·11 citations
8. 08*

   Hybrid seesaw neutrino model in SUSY $SU(5)\times {\mathbb{A}}_4$

   R. Ahl Laamara🇲🇦 · M. A. Loualidi🇲🇦 · M. Miskaoui🇲🇦 · E. H. Saidi🇲🇦

   Motivated by recent results from neutrino experiments, we study the neutrino masses and mixing in the framework of a SUSY $SU(5)\times {\mathbb{A}}_4$ model. The hybrid of Type I and Type II seesaw mechanisms leads to the nonzero value of the reactor angle ${\theta }_{13}\ne 0$ and to the recently disfavored maximal atmospheric angle ${\theta }_{23}\ne 45^{\circ }$ by the NOvA experiment. The phenomenological consequences of the model are studied for both normal and inverted mass hierarchies. The obtained ranges for the effective Majorana neutrino mass $m_{\beta \beta }$, the electron neutrino mass $m_{{\nu }_e}$, and the $CP$ violating phase ${\delta }_{CP}$ lie within the current experimental allowed ranges where we find that the normal mass hierarchy is favored over the inverted one.

   hep-phPRD(2018)·5 citations
9. 09*

   Dark Matter from Freeze-In via the Neutrino Portal

   Mathias Becker🇩🇪

   We investigate a minimal neutrino portal dark matter (DM) model where a right-handed neutrino both generates the observed neutrino masses and mediates between the SM and the dark sector, which consists of a fermion and a boson. In contrast to earlier work, we explore regions of the parameter space where DM is produced via freeze-in instead of freeze-out motivated by the small neutrino Yukawa couplings in case of $\mathcal{O}\left(\mathrm{TeV}\right)$ heavy neutrinos. \\ For a non-resonant production of DM, its energy density is independent of the DM mass. Assuming a democratic coupling structure we find $M_N\approx 10\mathrm{TeV}$. For the resonant production of DM, we find that it can be produced via freeze-in or freeze-out even with couplings of $\mathcal{O}\left(10^{-5}\right)$. However, the measurement of the Lyman-$\alpha$ forest rules out the feeble coupled freeze-out case completely, while the resonant freeze-in production is only viable for $m_{DM}\gtrsim 3\mathring{keV}$.

   hep-phEPJC(2019)·53 citations
10. 10*

    Second class currents and T violation in quasielastic neutrino and antineutrino scattering from nucleons

    A. Fatima🇮🇳 · M. Sajjad Athar🇮🇳 · S. K. Singh🇮🇳

    The effect of the second class currents with and without time reversal invariance has been studied in the quasielastic production of nucleons and hyperons induced by neutrinos and antineutrinos from the nucleons. The numerical results are presented for the total scattering cross section~($\sigma$) as well as for the longitudinal, perpendicular and transverse components of the polarization of the final baryons ($p$, $n$, $\Lambda$, ${\Sigma }^{-}$, ${\Sigma }^0$) and muon produced in the quasielastic (anti)neutrino-nucleon scattering induced by the weak charged current. In the case of the production of $\Lambda$ hyperon, which is the most suitable candidate for making the polarization measurements, we have also calculated the $Q^2$ dependence of the polarization observables and the differential scattering cross section ($d\sigma /d{Q}^2$). The measurement of the polarization observables and their $Q^2$ dependence provides an independent way to determine the nucleon-hyperon transition form factors at high $Q^2$ which can provide tests of the symmetries of the weak hadronic currents like G-invariance, T invariance and SU(3) symmetry.

    hep-phPRD(2018)·35 citations
11. 11*

    A framework for the chiral extrapolation of the charmed baryon ground-state masses

    Yonggoo Heo🇹🇭 · Xioa-Yu Guo🇩🇪 · Matthias F.M. Lutz🇩🇪

    We consider the chiral Lagrangian for charmed baryon fields with $J^P={\frac{1}{2}}^{+}$ or $J^P={\frac{3}{2}}^{+}$ quantum numbers. A chiral expansion framework for the baryon ground state masses is worked out to N${}^3$LO as to compute their dependence on the up, down and strange quark masses for finite box QCD lattice simulations. It is formulated in terms of on-shell meson and baryon masses. The convergence of such a scheme is illustrated with physical masses as taken from the PDG. The counter terms relevant at N${}^3$LO are correlated systematically by large-$N_c$ sum rules to leading and subleading order in a manner that keeps the renormalization scale invariance of the approach.

    hep-phhep-latnucl-thPRD(2018)·4 citations
12. 12*

    Bracketing the impact of astrophysical uncertainties on local dark matter searches

    Alejandro Ibarra🇩🇪 · Bradley J. Kavanagh🇳🇱 · Andreas Rappelt🇩🇪

    The theoretical interpretation of dark matter (DM) experiments is hindered by uncertainties on the dark matter density and velocity distribution inside the Solar System. In order to quantify those uncertainties, we present a parameter that characterizes the deviation of the true velocity distribution from the standard Maxwell-Boltzmann form, and we then determine for different values of this parameter the most aggressive and most conservative limits on the dark matter scattering cross section with nuclei; uncertainties in the local dark matter density can be accounted for trivially. This allows us to bracket, in a model independent way, the impact of astrophysical uncertainties on limits from direct detection experiments and/or neutrino telescopes. We find that current limits assuming the Standard Halo Model are at most a factor of $\sim 2$ weaker than the most aggressive possible constraints. In addition, combining neutrino telescope and direct detection constraints (in a statistically meaningful way), we show that limits on DM in the mass range $\sim 10-1000$ GeV cannot be weakened by more than around a factor of 10, for all possible velocity distributions. We finally demonstrate that our approach can also be employed in the event of a DM discovery, allowing us to avoid bias in the reconstruction of the DM properties.

    hep-phastro-ph.COJCAP(2018)·32 citations
13. 13*

    Spin-flavor oscillations of Dirac neutrinos in a plane electromagnetic wave

    Maxim Dvornikov (1, 2, 3) ((1) IZMIRAN, (2) Tomsk State University, (3) Nordita)🇷🇺

    We study spin and spin-flavor oscillations of Dirac neutrinos in a plane electromagnetic wave with circular polarization. The evolution of massive neutrinos with nonzero magnetic moments in the field of an electromagnetic wave is based on the exact solution of the Dirac-Pauli equation. We formulate the initial condition problem to describe spin-flavor oscillations in an electromagnetic wave. The transition probabilities for spin and spin-flavor oscillations are obtained. In case of spin-flavor oscillations, we analyze the transition and survival probabilities for different neutrino magnetic moments and various channels of neutrino oscillations. As an application of the obtained results, we study the possibility of existence of ${\nu }_{e\mathrm{L}}\to {\nu }_{\mu \mathrm{R}}$ oscillations in an electromagnetic wave emitted by a highly magnetized neutron star. Our results are compared with findings of other authors.

    hep-phPRD(2018)·10 citations
14. 14*

    Shadowing Neutrino Mass Hierarchy with Lorentz Invariance Violation

    H. Jurkovich🇧🇷 · Pedro Pasquini🇧🇷 · C. P. Ferreira🇧🇷

    The effects of Lorentz Invariance Violation(LIV) operators up to dimension 6 in long baseline neutrino experiments are discussed, in specific for DUNE and T2K. A phenomenological Lagrangian is proposed followed by a computation of the effective Hamiltonian of neutrino propagation in matter for mass eigenstates. It is shown that the simplest dimension 4 Lorentz violation parameter can decrease DUNE sensitivity to neutrino mass hierarchy. Also, a ${\chi }^2$ analysis is performed to obtain the expected long-baseline constraints to the LIV operators up to dimension 6.

    hep-ph7 citations
15. 15*

    Coherency and incoherency in neutrino-nucleus elastic and inelastic scattering

    Vadim A.Bednyakov🇷🇺 · Dmitry V.Naumov🇷🇺

    Neutrino-nucleus scattering $\nu A\to \nu A$, in which the nucleus conserves its integrity, is considered. We show that elastic interactions keeping the nucleus in the same quantum state lead to a quadratic enhancement of the corresponding cross-section in terms of the number of nucleons. Meanwhile, the cross-section of inelastic processes in which the quantum state of the nucleus is changed, essentially has a linear dependence on the number of nucleons. These two classes of processes are referred to as coherent and incoherent, respectively. The coherent and incoherent cross-sections are driven by factors $|F_{p/n}{|}^2$ and $(1-|F_{p/n}{|}^2)$, where $|F_{p/n}{|}^2$ is a proton/neutron form-factor of the nucleus, averaged over its initial states. The coherent cross-section formula used in the literature is revised and corrections depending on kinematics are estimated. As an illustration of the importance of the incoherent channel we considered three experimental setups with different nuclei. Experiments attempting to measure coherent neutrino scattering by solely detecting the recoiling nucleus, as is typical, might be including an incoherent background that is indistinguishable from the signal if the excitation gamma eludes its detection. However, as is shown here, the incoherent component can be measured directly by searching for photons released by the excited nuclei inherent to the incoherent channel. For a beam experiment these gammas should be correlated in time with the beam, and their higher energies make the corresponding signal easily detectable at a rate governed by the ratio of incoherent to coherent cross-sections. The detection of signals due to the nuclear recoil and excitation gammas provides a more sensitive instrument in studies of nuclear structure and possible signs of new physics.

    hep-phPRD(2018)·63 citations
16. 16*

    Gauge Field and Fermion Production during Axion Inflation

    Valerie Domcke🇩🇪 · Kyohei Mukaida🇩🇪

    We study the dual production of helical Abelian gauge fields and chiral fermions through the Chern-Simons (CS) coupling with a pseudo-scalar inflaton in the presence of a chiral anomaly. Through the CS term, the motion of the inflaton induces a tachyonic instability for one of the two helicities of the gauge field. We show that the resulting helical gauge field necessarily leads to the production of chiral fermions by deforming their Fermi sphere into discrete Landau levels. The population of the lowest Landau level leads to a chiral asymmetry as inferred from the chiral anomaly, while the higher levels are populated symmetrically through pair production. From the backreaction of the fermions on the gauge field production we derive a conservative but stringent upper bound on the magnitude of the gauge fields. Consequently, we find that the scalar perturbations sourced by these helical gauge fields, responsible for enhanced structure formation on small scales, get reduced significantly. We also discuss the fate of the primordial chiral asymmetry and of the helical gauge fields after inflation, and show that the instability in the chiral plasma tends to erase these primordial asymmetries. This result may impact scenarios where the baryon asymmetry of the Universe is connected to primordial magnetic fields.

    hep-phastro-ph.COJCAP(2018)·146 citations
17. 17*

    Exploring $B\to \pi \pi ,\pi K$ Decays at the High-Precision Frontier

    Robert Fleischer🇳🇱 · Ruben Jaarsma🇳🇱 · Eleftheria Malami🇳🇱 · K. Keri Vos🇩🇪

    The $B\to \pi \pi ,\pi K$ system offers a powerful laboratory to probe strong and weak interactions. Using the isospin symmetry, we determine hadronic $B\to \pi \pi$ parameters from data where new measurements of direct CP violation in $B_d^0\to {\pi }^0{\pi }^0$ resolve a discrete ambiguity. With the help of the $SU(3)$ flavour symmetry, the $B\to \pi \pi$ parameters can be converted into their $B\to \pi K$ counterparts, thereby allowing us to make predictions of observables. A particularly interesting decay is $B_d^0\to {\pi }^0{K}_{\mathrm{S}}$ as it exhibits mixing-induced CP violation. Using an isospin relation, complemented with a robust $SU(3)$ input, we calculate correlations between the direct and mixing-induced CP asymmetries of $B_d^0\to {\pi }^0{K}_{\mathrm{S}}$, which are the theoretically cleanest $B\to \pi K$ probes. Interestingly, they show tensions with respect to the Standard Model. Should this $B\to \pi K$ puzzle originate from New Physics, electroweak penguins offer an attractive scenario for new particles to enter. We present a strategy to determine the parameters characterising these topologies and obtain the state-of-the-art picture from current data. In the future, this method will allow us to reveal the $B\to \pi K$ dynamics and to obtain insights into the electroweak penguin sector with unprecedented precision.

    hep-phEPJC(2018)·52 citations
18. 18*

    The Hierarchion, a Relaxion Addressing the Standard Model's Hierarchies

    Oz Davidi🇮🇱 · Rick S. Gupta🇬🇧 · Gilad Perez🇮🇱 · Diego Redigolo🇮🇱 · Aviv Shalit🇮🇱

    We present a mechanism that addresses the electroweak, the strong CP, and the flavor hierarchies of the Standard Model (including neutrino masses) in a unified way. The naturalness of the electroweak scale is solved together with the strong CP problem by the Nelson-Barr relaxion: the relaxion field is identified with the pseudo-Nambu-Goldstone boson of an abelian symmetry with no QCD anomaly. The Nelson-Barr sector generates the "rolling" potential and the relaxion vacuum expectation value at the stopping point is mapped to the Cabibbo-Kobayashi-Maskawa phase. An abelian symmetry accounts for the Standard Model's mass hierarchies and flavor textures through the Froggatt-Nielsen mechanism. We show how the "backreaction" potential of the relaxion can be induced by a sterile neutrino sector, without any extra state with electroweak quantum numbers. The same construction successfully explains neutrino masses and mixings. The only light field in our construction is the relaxion, which we call the hierarchion because it is essentially linked to our construct that accounts for all the Standard Model hierarchies. Given its interplay with flavor symmetries, the hierarchion can be probed in flavor-violating decays of the Standard Model fermions, motivating a further experimental effort in looking for new physics in rare decays of leptons and mesons.

    hep-phJHEP(2018)·38 citations
19. 19*

    In-medium loop corrections and longitudinally polarized gauge bosons in high-energy showers

    Peter Arnold🇺🇸 · Shahin Iqbal🇵🇰

    The splitting processes of bremsstrahlung and pair production in a medium are coherent over large distances in the very high energy limit, which leads to a suppression known as the Landau-Pomeranchuk-Migdal (LPM) effect. We continue study of the case when the coherence lengths of two consecutive splitting processes overlap (which is important for understanding corrections to standard treatments of the LPM effect in QCD), avoiding soft-emission approximations. In this particular paper, we show (i) how the "instantaneous" interactions of Light-Cone Perturbation Theory must be included in the calculation to account for effects of longitudinally-polarized gauge bosons in intermediate states, and (ii) how to compute virtual corrections to LPM emission rates, which will be necessary in order to make infrared-safe calculations of the characteristics of in-medium QCD showering of high-energy partons. In order to develop these topics in as simple a context as possible, we will focus in the current paper not on QCD but on large-$N_f$ QED, where $N_f$ is the number of electron flavors.

    hep-phnucl-thJHEP(2018)·22 citations
20. 20*

    Novel constraints on non-cold (non-thermal) Dark Matter from Lyman-$\alpha$ forest data

    Riccardo Murgia🇮🇹 · Vid Iršič🇺🇸 · Matteo Viel🇮🇹

    In this paper we present an efficient method for constraining both thermal and non-thermal Dark Matter (DM) scenarios with the Lyman-$\alpha$ forest, based on a simple and flexible parametrisation capable to reproduce the small scale clustering signal of a large set of non-cold DM (nCDM) models. We extract new limits on the fundamental DM properties, through an extensive analysis of the high resolution, high redshift data obtained by the MIKE/HIRES spectrographs. By using a large suite of hydrodynamical simulations, we determine constraints on both astrophysical, cosmological, and nCDM parameters by performing a full Monte Carlo Markov Chain (MCMC) analysis. We obtain a marginalised upper limit on the largest possible scale at which a power suppression induced by nearly any nCDM scenario can occur, i.e. $\alpha <0.03\mathrm{Mpc}/h$ (2$\sigma$ C.L.). We explicitly describe how to test several of the most viable nCDM scenarios without the need to run any specific numerical simulations, due to the novel parametrisation proposed, and due to a new scheme that interpolates between the cosmological models explored. The shape of the linear matter power spectrum for standard thermal warm DM models appear to be in mild tension ($\sim 2\sigma$ C.L.) with the data, compared to non-thermal scenarios. We show that a DM fluid composed by both a warm (thermal) and a cold component is also in tension with the Lyman-$\alpha$ forest, at least for large $\alpha$ values. This is the first study that allows to probe the linear small scale shape of the DM power spectrum for a large set of nCDM models.

    ↳ astro-ph.COhep-phPRD(2018)·128 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.