Mon·May 2, 2016Monday·May 2, 2016

1. 01*

   Lepton flavor violating processes in the minimal 3-3-1 model with singlet sterile neutrinos

   A. C. B. Machado🇧🇷 · J. Montaño🇧🇷 · V. Pleitez🇧🇷

   We consider the minimal 3-3-1 model with three sterile neutrinos transforming as singlet under the $SU(3{)}_L\otimes U(1{)}_X$ symmetry. This model, with or without sterile neutrinos, predicts flavor violating interactions in both quark and lepton sectors, since all the charged fermions mass matrices can not be assumed diagonal in any case. Here we accommodate the lepton masses and the Pontecorvo-Maki-Nakawaga-Sakata matrix at the same time, and as consequence the Yukawa couplings and the unitary matrices which diagonalize the mass matrices are not free parameters anymore. We study some phenomenological consequences, i.e., $l_i\to l_j{l}_k{\bar{l}}_k$ and $l_i\to l_j\gamma$ which are induced by neutral and doubly charged particles present in the model. In particular we find that if the decay $\mu \to ee\bar{e}$ is observed in the future, the only particle in the model that could explain this decay is the doubly charged vector bilepton.

   hep-phJ.Phys.G(2019)·21 citations
2. 02*

   Gravitational Origin of Dark Matter

   Eugeny Babichev🇫🇷 · Luca Marzola🇪🇪 · Martti Raidal🇪🇪 · Angnis Schmidt-May🇨🇭 · Federico Urban🇪🇪 · Hardi Veermäe🇪🇪 · Mikael von Strauss🇫🇷

   Observational evidence for the existence of Dark Matter is limited to its gravitational effects. The extensive program for dedicated searches has yielded null results so far, challenging the most popular models. Here we propose that this is the case because the very existence of cold Dark Matter is a manifestation of gravity itself. The consistent bimetric theory of gravity, the only known ghost-free extension of General Relativity involving a massless and a massive spin-2 field, automatically contains a perfect Dark Matter candidate. We demonstrate that the massive spin-2 particle can be heavy, stable on cosmological scales, and that it interacts with matter only through a gravitational type of coupling. Remarkably, these features persist in the same region of parameter space where bimetric theory satisfies the current gravity tests. We show that the observed Dark Matter abundance can be generated via freeze-in and suggest possible particle physics and gravitational signatures of our bimetric Dark Matter model.

   hep-phastro-ph.COgr-qchep-thPRD(2016)·108 citations
3. 03*

   $W^{\pm }Z$ production at hadron colliders in NNLO QCD

   Massimiliano Grazzini (Zurich U.)🇨🇭 · Stefan Kallweit (Mainz U. & Santa Barbara, KITP)🇩🇪 · Dirk Rathlev (DESY)🇩🇪 · Marius Wiesemann (Zurich U.)🇨🇭

   We report on the first computation of the next-to-next-to-leading order (NNLO) QCD corrections to $W^{\pm }Z$ production in proton collisions. We consider both the inclusive production of on-shell $W^{\pm }Z$ pairs at LHC energies and the total $W^{\pm }Z$ rates including off-shell effects of the $W$ and $Z$ bosons. In the off-shell computation, the invariant mass of the lepton pairs from the $Z$ boson decay is required to be in a given mass window, and the results are compared with the corresponding measurements obtained by the ATLAS and CMS collaborations. The NNLO corrections range from 8% at $\sqrt{s}$=7 TeV to 11% at $\sqrt{s}$=14 TeV and significantly improve the agreement with the LHC data at $\sqrt{s}$=7 and 8 TeV.

   hep-phhep-exPLB(2016)·260 citations
4. 04*

   Two-Loop Master Integrals for the mixed EW-QCD virtual corrections to Drell-Yan scattering

   Roberto Bonciani🇮🇹 · Stefano Di Vita🇩🇪 · Pierpaolo Mastrolia🇮🇹 · Ulrich Schubert🇩🇪

   We present the calculation of the master integrals needed for the two-loop QCDxEW corrections to $q+\bar{q}\to l^{-}+l^{+}$ and $q+{\bar{q}}^{\prime }\to l^{-}+\overline{\nu },$ for massless external particles. We treat W and Z bosons as degenerate in mass. We identify three types of diagrams, according to the presence of massive internal lines: the no-mass type, the one-mass type, and the two-mass type, where all massive propagators, when occurring, contain the same mass value. We find a basis of 49 master integrals and evaluate them with the method of the differential equations. The Magnus exponential is employed to choose a set of master integrals that obeys a canonical system of differential equations. Boundary conditions are found either by matching the solutions onto simpler integrals in special kinematic configurations, or by requiring the regularity of the solution at pseudo-thresholds. The canonical master integrals are finally given as Taylor series around d=4 space-time dimensions, up to order four, with coefficients given in terms of iterated integrals, respectively up to weight four.

   hep-phhep-thJHEP(2016)·86 citations
5. 05*

   The Minimal SUSY $B-L$ Model: Simultaneous Wilson Lines and String Thresholds

   Rehan Deen🇺🇸 · Burt A. Ovrut🇺🇸 · Austin Purves🇺🇸

   In previous work, we presented a statistical scan over the soft supersymmetry breaking parameters of the minimal SUSY $B-L$ model. For specificity of calculation, unification of the gauge parameters was enforced by allowing the two ${\mathbb{Z}}_3\times {\mathbb{Z}}_3$ Wilson lines to have mass scales separated by approximately an order of magnitude. This introduced an additional "left-right" sector below the unification scale. In this paper, for three important reasons, we modify our previous analysis by demanding that the mass scales of the two Wilson lines be simultaneous and equal to an "average unification" mass $⟨M_U⟩$. The present analysis is 1) more "natural" than the previous calculations, which were only valid in a very specific region of the Calabi-Yau moduli space, 2) the theory is conceptually simpler in that the left-right sector has been removed and 3) in the present analysis the lack of gauge unification is due to threshold effects--particularly heavy string thresholds, which we calculate statistically in detail. As in our previous work, the theory is renormalization group evolved from $⟨M_U⟩$ to the electroweak scale--being subjected, sequentially, to the requirement of radiative $B-L$ and electroweak symmetry breaking, the present experimental lower bounds on the $B-L$ vector boson and sparticle masses, as well as the lightest neutral Higgs mass of $\sim$125 GeV. The subspace of soft supersymmetry breaking masses that satisfies all such constraints is presented and shown to be substantial.

   hep-phhep-thJHEP(2016)·23 citations
6. 06*

   How Unequal Fluxes of High Energy Astrophysical Neutrinos and Antineutrinos can Fake New Physics

   Hiroshi Nunokawa🇧🇷 · Boris Panes🇧🇷 · Renata Zukanovich Funchal🇧🇷

   Flavor ratios of very high energy astrophysical neutrinos, which can be studied at the Earth by a neutrino telescope such as IceCube, can serve to diagnose their production mechanism at the astrophysical source. The flavor ratios for neutrinos and antineutrinos can be quite different as we do not know how they are produced in the astrophysical environment. Due to this uncertainty the neutrino and antineutrino flavor ratios at the Earth also could be quite different. Nonetheless, it is generally assumed that flavor ratios for neutrinos and antineutrinos are the same at the Earth, in fitting the high energy astrophysical neutrino data. This is a reasonable assumption for the limited statistics for the data we currently have. However, in the future the fit must be performed allowing for a possible discrepancy in these two fractions in order to be able to disentangle different production mechanisms at the source from new physics in the neutrino sector. To reinforce this issue, in this work we show that a wrong assumption about the distribution of neutrino flavor ratios at the Earth may indeed lead to misleading interpretations of IceCube results.

   hep-phastro-ph.HEJCAP(2016)·23 citations
7. 07*

   Left-Right Symmetry and Lepton Number Violation at the Large Hadron Electron Collider

   Manfred Lindner🇩🇪 · Farinaldo S. Queiroz🇩🇪 · Werner Rodejohann🇩🇪 · Carlos E. Yaguna🇩🇪

   We show that the proposed Large Hadron electron Collider (LHeC) will provide an opportunity to search for left-right symmetry and establish lepton number violation, complementing current and planned searches based on LHC data and neutrinoless double beta decay. We consider several plausible configurations for the LHeC -- including different electron energies and polarizations, as well as distinct values for the charge misidentification rate. Within left-right symmetric theories we determine the values of right-handed neutrino and gauge boson masses that could be tested at the LHeC after one, five and ten years of operation. Our results indicate that this collider might probe, via the $\Delta L=2$ signal $e^{-}p\to e^{+}jjj$, Majorana neutrino masses up to 1 TeV and $W_R$ masses up to 6.5 TeV. Interestingly, part of this parameter space is beyond the expected reach of the LHC and of future neutrinoless double beta decay experiments.

   hep-phhep-exJHEP(2016)·79 citations
8. 08*

   The hot Hagedorn Universe

   Johann Rafelski🇺🇸 · Jeremiah Birrell🇺🇸

   In the context of the half-centenary of Hagedorn temperature and the statistical bootstrap model (SBM) we present a short account of how these insights coincided with the establishment of the hot big-bang model (BBM) and helped resolve some of the early philosophical difficulties. We then turn attention to the present day context and show the dominance of strong interaction quark and gluon degrees of freedom in the early stage, helping to characterize the properties of the hot Universe. We focus attention on the current experimental insights about cosmic microwave background (CMB) temperature fluctuation, and develop a much improved understanding of the neutrino freeze-out, in this way paving the path to the opening of a direct connection of quark-gluon plasma (QGP) physics in the early Universe with the QCD-lattice, and the study of the properties of QGP formed in the laboratory.

   hep-phEPJ Web Conf.(2016)·1 citation
9. 09*

   Calculating four-loop massless propagators with Forcer

   T. Ueda🇳🇱 · B. Ruijl🇳🇱 · J.A.M. Vermaseren🇳🇱

   We present Forcer, a new FORM program for the calculation of four-loop massless propagators. The basic framework is similar to that of the Mincer program for three-loop massless propagators: the program reduces Feynman integrals to a set of master integrals in a parametric way. To overcome an ineludible complexity of the program structure at the four-loop level, most of the code was automatically generated or made with computer-assisted derivations. Correctness of the program has been checked with the recomputation of some quantities in the literature.

   hep-phJ.Phys.Conf.Ser.(2016)·21 citations
10. 10*

    $Z_c(3900)$ as a $D{\bar{D}}^{\ast }$ molecule from the pole counting rule

    Qin-Rong Gong🇨🇳 · Zhi-Hui Guo🇨🇳 · Ce Meng🇨🇳 · Guang-Yi Tang🇨🇳 · Yu-Fei Wang🇨🇳 · Han-Qing Zheng🇨🇳

    A comprehensive study on the nature of the $Z_c(3900)$ resonant structure is carried out in this work. By constructing the pertinent effective Lagrangians and considering the important final-state-interaction effects, we first give a unified description to all the relevant experimental data available, including the $J/\psi \pi$ and $\pi \pi$ invariant mass distributions from the $e^{+}{e}^{-}\to J/\psi \pi \pi$ process, the $h_c\pi$ distribution from $e^{+}{e}^{-}\to h_c\pi \pi$ and also the $D{\bar{D}}^{\ast }$ spectrum in the $e^{+}{e}^{-}\to D{\bar{D}}^{\ast }\pi$ process. After fitting the unknown parameters to the previous data, we search the pole in the complex energy plane and find only one pole in the nearby energy region in different Riemann sheets. Therefore we conclude that $Z_c(3900)$ is of $D{\bar{D}}^{\ast }$ molecular nature, according to the pole counting rule method~[Nucl.~Phys.~A543, 632 (1992); Phys.~Rev.~D 35,~1633 (1987)]. We emphasize that the conclusion based upon the pole counting method is not trivial, since both the $D{\bar{D}}^{\ast }$ contact interactions and the explicit $Z_c$ exchanges are introduced in our analyses and they lead to the same conclusion.

    hep-phhep-exhep-latnucl-thPRD(2016)·47 citations
11. 11*

    Warm Little Inflaton

    Mar Bastero-Gil🇪🇸 · Arjun Berera🇬🇧 · Rudnei O. Ramos🇧🇷 · Joao G. Rosa🇵🇹

    We show that inflation can naturally occur at a finite temperature T>H that is sustained by dissipative effects, when the inflaton field corresponds to a pseudo Nambu-Goldstone boson of a broken gauge symmetry. Similarly to "Little Higgs" scenarios for electroweak symmetry breaking, the flatness of the inflaton potential is protected against both quadratic divergences and the leading thermal corrections. We show that, nevertheless, nonlocal dissipative effects are naturally present and are able to sustain a nearly thermal bath of light particles despite the accelerated expansion of the Universe. As an example, we discuss the dynamics of chaotic warm inflation with a quartic potential and show that the associated observational predictions are in very good agreement with the latest Planck results. This model constitutes the first realization of warm inflation requiring only a small number of fields; in particular, the inflaton is directly coupled to just two light fields.

    hep-phastro-ph.COgr-qcPRL(2016)·219 citations
12. 12*

    Stable lepton mass matrices

    Valerie Domcke🇫🇷 · Andrea Romanino🇮🇹

    We study natural lepton mass matrices, obtained assuming the stability of physical flavour observables with respect to the variations of individual matrix elements. We identify all four possible stable neutrino textures from algebraic conditions on their entries. Two of them turn out to be uniquely associated to specific neutrino mass patterns. We then concentrate on the semi-degenerate pattern, corresponding to an overall neutrino mass scale within the reach of future experiments. In this context we show that i) the neutrino and charged lepton mixings and mass matrices are largely constrained by the requirement of stability, ii) naturalness considerations give a mild preference for the Majorana phase most relevant for neutrinoless double-beta decay, $\alpha \sim \pi /2$, and iii) SU(5) unification allows to extend the implications of stability to the down quark sector. The above considerations would benefit from an experimental determination of the PMNS ratio $|U_{32}/U_{31}|$, i.e. of the Dirac phase $\delta$.

    hep-phJHEP(2016)·7 citations
13. 13*

    Gluon Green functions free of Quantum fluctuations

    A. Athenodorou🇨🇾 · Ph. Boucaud🇫🇷 · F. De Soto🇪🇸 · J. Rodríguez-Quintero🇪🇸 · S. Zafeiropoulos🇩🇪

    This letter reports on how the Wilson flow technique can efficaciously kill the short-distance quantum fluctuations of 2- and 3-gluon Green functions, removes the ${\Lambda }_{\mathrm{QCD}}$ scale and destroys the transition from the confining non-perturbative to the asymptotically-free perturbative sector. After the Wilson flow, the behavior of the Green functions with momenta can be described in terms of the quasi-classical instanton background. The same behavior also occurs, before the Wilson flow, at low-momenta. This last result permits applications as, for instance, the detection of instanton phenomenological properties or a cheap lattice calibration.

    hep-phhep-lathep-thPLB(2016)·21 citations
14. 14*

    Properties of Mesons in a Strong Magnetic Field

    Rui Zhang🇨🇳 · Wei-jie Fu🇩🇪 · Yu-xin Liu🇨🇳

    By extending the $\Phi$-derivable approach in Nambu-Jona-Lasinio model to finite magnetic field we calculate the properties of pion, $\sigma$ and $\rho$ mesons in a magnetic field at finite temperature in not only the quark-antiquark bound state scheme but also the pion-pion scattering resonant state scenario. Our calculation results manifest that the masses of ${\pi }^0$ and $\sigma$ meson can be nearly degenerate at the pseudo-critical temperature which increases with increasing the magnetic field strength, and the ${\pi }^{\pm }$ mass ascends suddenly at almost the same critical temperature. While the $\rho$ mesons' masses decrease with the temperature but increase with the magnetic field strength. We also check the Gell-Mann-Oakes-Renner relation and find that the relation can be violated obviously with increasing the temperature, and the effect of the magnetic field becomes pronounced around the critical temperature. With different criteria, we analyze the effect of the magnetic field on the chiral phase transition and find that the pseudo-critical temperature of the chiral phase cross, $T_c^{\chi }$, is always enhanced by the magnetic field. Moreover our calculations indicate that the $\rho$ mesons will get melted as the chiral symmetry has not yet been restored, but the $\sigma$ meson does not disassociate even at very high temperature. Particularly, it is the first to show that there does not exist vector meson condensate in the QCD vacuum in the pion-pion scattering scheme.

    hep-phnucl-thEPJC(2016)·72 citations
15. 15*

    Gravitational Particle Production in Oscillating Background and Its Cosmological Implications

    Yohei Ema🇯🇵 · Ryusuke Jinno🇯🇵 · Kyohei Mukaida🇯🇵 · Kazunori Nakayama🇯🇵

    We study production of light particles due to oscillation of the Hubble parameter or the scale factor. Any coherently oscillating scalar field, irrespective of its energy fraction in the universe, imprints such an oscillating feature on them. Not only the Einstein gravity but extended gravity models, such as models with non-minimal (derivative) coupling to gravity and $f(R)$ gravity, lead to oscillation of the scale factor. We present a convenient way to estimate the gravitational particle production rate in these circumstances. Cosmological implications of gravitational particle production, such as dark matter/radiation and moduli problem, are discussed. For example, if the theory is described solely by the standard model plus the Peccei-Quinn sector, the Starobinsky $R^2$ inflation may lead to observable amount of axion dark radiation.

    hep-phastro-ph.COgr-qcPRD(2016)·176 citations
16. 16*

    Universal symmetry energy contribution to the neutron star equation of state

    D. Blaschke🇷🇺 · D. E. Alvarez-Castillo🇷🇺 · T. Klahn🇵🇱

    We discuss the observation that under neutron star conditions of charge neutrality and $\beta -$equilibrium the contribution from the symmetry energy to the equation of state (EoS) follows a universal behaviour. We call this behaviour the conjecture of a Universal Symmetry Energy Contribution (USEC). We find that an USEC holds provided the density dependence of the symmetry energy $E_s(n)$ follows a behaviour that limits the proton fraction $x(n)$ to values below the threshold for the direct Urca (DU) cooling process. The absence of DU cooling in typical mass neutron stars appears to be supported by the phenomenology of neutron star cooling data and allows to constrain the behaviour of $E_s(n)$ at high densities. Two classes of symmetry energy functions are investigated more in detail to elucidate the USEC. We derive an analytic formula for the USEC to the neutron star EoS based on the result for the symmetry energy extracted from isobaric analog states of nuclei.

    ↳ nucl-thastro-ph.HEhep-ph17 citations
17. 17*

    A New Target for Cosmic Axion Searches

    Daniel Baumann🇬🇧 · Daniel Green🇺🇸 · Benjamin Wallisch🇬🇧

    Future CMB experiments have the potential to probe the density of relativistic species at the sub-percent level. Sensitivity at this level allows light thermal relics to be detected up to arbitrarily high decoupling temperatures. Conversely, the absence of a detection would require extra light species never to have been in equilibrium with the Standard Model. In this paper, we exploit this feature to demonstrate the sensitivity of future cosmological observations to the couplings of axions to all of the Standard Model degrees of freedom. In many cases, the constraints achievable from cosmology will surpass existing bounds from laboratory experiments and astrophysical observations by orders of magnitude.

    ↳ astro-ph.COhep-phhep-thPRL(2016)·180 citations
18. 18*

    Hawking Radiation Spectra for Scalar Fields by a Higher-Dimensional Schwarzschild-de-Sitter Black Hole

    T. Pappas🇬🇷 · P. Kanti🇬🇷 · N. Pappas🇬🇷

    In this work, we study the propagation of scalar fields in the gravitational background of a higher-dimensional Schwarzschild-de-Sitter black hole as well as on the projected-on-the-brane 4-dimensional background. The scalar fields have also a non-minimal coupling to the corresponding, bulk or brane, scalar curvature. We perform a comprehensive study by deriving exact numerical results for the greybody factors, and study their profile in terms of particle and spacetime properties. We then proceed to derive the Hawking radiation spectra for a higher-dimensional Schwarzschild-de-Sitter black hole, and we study both bulk and brane channels. We demonstrate that the non-minimal field coupling, that creates an effective mass term for the fields, suppresses the energy emission rates while the cosmological constant assumes a dual role. By computing the relative energy rates and the total emissivity ratio for bulk and brane emission, we demonstrate that the combined effect of a large number of extra dimensions and value of the field coupling gives to the bulk channel the clear domination in the bulk-brane energy balance.

    ↳ hep-thastro-ph.COgr-qchep-phPRD(2016)·64 citations
19. 19*

    Probing QED Vacuum with Heavy Ions

    Johann Rafelski🇺🇸 · Johannes Kirsch🇩🇪 · Berndt Müller🇺🇸 · Joachim Reinhardt🇩🇪 · Walter Greiner🇩🇪

    We recall how nearly half a century ago the proposal was made to explore the structure of the quantum vacuum using slow heavy-ion collisions. Pursuing this topic we review the foundational concept of spontaneous vacuum decay accompanied by observable positron emission in heavy-ion collisions and describe the related theoretical developments in strong fields QED.

    ↳ nucl-thhep-phphysics.atom-phFIAS Interdisc.Sci.Ser.(2017)·21 citations
20. 20*

    Neutrino Mass Ordering Studies with PINGU and IceCube/DeepCore

    Steven Wren🇬🇧

    The Precision IceCube Next Generation Upgrade (PINGU) is a proposed extension to the IceCube detector. The design of PINGU would augment the existing 86 strings with an additional 40 with the main goal of determining the neutrino mass ordering (NMO). Preliminary studies of the NMO can start with IceCube/DeepCore, a sub-array of more densely- packed strings in operation since 2011. This detector has a neutrino energy threshold of roughly 10 GeV and allows for high-statistics datasets of atmospheric neutrinos to be collected. This data provides a unique opportunity to better understand the systematic effects involved in making the NMO measurement by comparing the simulation studies to real data. These proceedings will present the current status of these studies in Monte Carlo simulations with projected DeepCore sensitivity for the NMO.

    ↳ physics.ins-dethep-exhep-ph2 citations
21. 21*

    Interplay between Symmetry Energy and Excluded Volume Corrections under the Direct Urca Cooling Constraint in Neutron Stars

    David E. Alvarez-Castillo🇷🇺 · David Blaschke🇷🇺

    Both the symmetry energy part and excluded volume corrections to the equation of state play an important role for the neutron star interior structure and composition, namely for the profile of the baryon density and the proton fraction. While the symmetry energy uniquely determines the proton fraction, excluded volume effects control the maximum density values inside neutron stars. Observations of cooling neutron stars indicate that the fast direct Urca cooling is not operative for the typical, low mass stars, pointing at proton fractions that lie below the threshold for the onset of direct Urca cooling process. This in turn, restricts the density range admissible in neutron star interiors and may require an excluded volume correction. In this contribution we discuss the interplay between fast cooling, symmetry energy and excluded volume corrections to the equation of state that would be required to fulfil the direct Urca cooling constraint.

    ↳ nucl-thastro-ph.HEhep-phPoS(2016)·5 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.