Fri·Jun 22, 2018Friday·June 22, 2018

1. 01*

   Updating and Optimizing Error PDFs in the Hessian Approach

   Carl Schmidt · Jon Pumplin · C.-P. Yuan

   We discuss how to apply the Hessian method (i) to predict the impact of a new data set (or sets) on the parton distribution functions (PDFs) and their errors, by producing an updated best-fit PDF and error PDF sets, such as the CTEQ-TEA PDFs; (ii) to predict directly the effect of a new data set on the PDF errors of any other set of observables, without the need to recalculate using the new error PDFs; and (iii) to transform the original set into a reduced set of error PDFs which is optimized for a specific set of observables to reproduce the PDF-induced uncertainties to any specified precision. We present a software package, {\tt ePump} (error PDF Updating Method Package), that can be used to update or optimize a set of PDFs, including the best-fit PDF set and Hessian eigenvector pairs of PDF sets (i.e., error PDFs), and to update any other set of observables. We demonstrate the potential of the program by presenting selected phenomenological applications relevant to the Large Hadron Collider. Special care is given to discuss the assumptions made and the limitations of this theoretical framework compared to a treatment by the full global analysis program.

   hep-phPRD(2018)·79 citations
2. 02*

   Exploring NSI degeneracies in long-baseline experiments

   L. J. Flores🇲🇽 · E. A. Garcés🇲🇽 · O. G. Miranda🇲🇽

   One of the main purposes of long-baseline neutrino experiments is to unambiguously measure the CP violating phase in the neutrino sector within the three neutrino oscillation picture. In the presence of physics beyond the Standard Model, the determination of the CP phase will be more difficult, due to the already known degeneracy problem. Working in the framework of non-standard interactions (NSI), we compute the appearance probabilities in an exact analytical formulation and analyze the region of parameters where the confusion problem is present. We also discuss some cases where the falsification of the NSI parameters can be done in long-baseline experiments.

   hep-phhep-exPRD(2018)·27 citations
3. 03*

   Hyperspherical-coordinate approach to the spectra and decay widths of hybrid quarkonia

   Tomokazu Miyamoto🇯🇵 · Shigehiro Yasui🇯🇵

   In this paper, we consider the possibility that Y(4260), Y(4360), $\psi (4415)$ or X(4660) is the ground state or the first excited state of a hybrid charmonium and examine whether ${\rm Y}(10860)$ is the ground state or the first excited state of a hybrid bottomonium. Under a constituent quark model, we carry out numerical calculations to obtain the spectra of both electric gluon and magnetic gluon hybrid quarkonia. We see that the ground state of a magnetic gluon hybrid charmonium and the first excited state of an electric gluon hybrid are comparable in energy to $\psi (4415)$ and that the first excited states of an electric gluon hybrid bottomonium and the ground state of a magnetic gluon hybrid appear a few hundred MeV above the mass of ${\rm Y}(10860)$. Also, we evaluate the widths of the decays of a hybrid charmonium into $D^{(\ast )}{\bar{D}}^{(\ast )}$ and those of a hybrid bottomonium into $B^{(\ast )}{\bar{B}}^{(\ast )}$. We show that if the exotic meson candidates are hybrid charmonia, then they are magnetic gluon ones and argue that it seems unlikely that ${\rm Y}(10860)$ is the ground state of an electric gluon hybrid bottomonium.

   hep-phPRD(2018)·5 citations
4. 04*

   Charm-quark pole mass from HERA Combined and LHCb charm production data

   A. Vafaee🇮🇷 · K. Javidan🇮🇷 · S. Atashbar Tehrani🇮🇷

   One of the most popular definition for the charm-quark mass is the charm-quark pole mass $m_c^{\mathrm{pole}}$. In this contribution, we extract the charm-quark pole mass through perturbative Quantum Chromo Dynamics (pQCD) analysis up to the next-to-next-to-leading order (NNLO) corrections from HERA Combined and LHCb charm production recent data sets. Then, we investigate for the first time the charm-quark pole mass $m_c^{\mathrm{pole}}$ pure impact, as an extra pQCD parameter on the proton Parton Distribution Functions (PDFs) at the NNLO corrections.

   hep-ph5 citations
5. 05*

   Minimal QCDF Model for $B\to \pi K$ Puzzle

   Tsung-Wen Yeh🇹🇼

   In this work, we propose a model by combining the parameterization method and the QCD factorization to study the $B\to \pi K$ puzzle. The parameterization introduces twelve parameters, the weak angle $\gamma$ and the other eleven hadronic parameters. These hadronic parameters are calculated by the QCD factorization (QCDF). The calculational accuracy of the QCDF is improved by including the twist-3 three parton tree and one loop corrections. Three additional nonperturbative strong phases from the gluonic penguin, color suppressed, and color favored tree diagrams are required to account for the direct CP asymmetries. The weak angle, three nonperturbative strong phases, and four scale variables are assumed as fitting parameters. These eight parameters are determined by a least squares fit to the eight measurements. The fit shows that the hadronic parameters need to be process-dependent. The process-dependent hadronic parameters break the isospin symmetry `dynamically'. A large negative relative phase associated with the internal up quark gluonic penguin diagram is observed. The weak angle $\gamma$ is found to be $72.1\pm 5.8$ degree, being consistent with the world averaged value, $72.1\pm 5.8$ degree. By a least squares fit to the mixing induced asymmetry $S({\pi }^0{K}_S)=0.58\pm 0.06$, the weak angle $\beta$ is determined to be $22.9\pm 2.1$ degree, which is in a well agreement with the world averaged value, $22.5\pm 4.4\pm 0.6$ degree. The model predicts the ratio $C^{\prime }/T^{\prime }$ (color suppressed/color favored) to be $0.59\pm 0.08$. The above evidences indicate that the model can solve the $B\to \pi K$ puzzle consistently.

   hep-ph0 citations
6. 06*

   Scalar assisted singlet doublet fermion dark matter model and electroweak vacuum stability

   Amit Dutta Banik🇮🇳 · Abhijit Kumar Saha🇮🇳 · Arunansu Sil (IIT Guwahati)🇮🇳

   We extend the so-called singlet doublet dark matter model, where the dark matter is an admixture of a Standard Model singlet and a pair of electroweak doublet fermions, by a singlet scalar field. The new portal coupling of it with the dark sector not only contributes to the dark matter phenomenology (involving relic density and direct detection limits), but also becomes important for generation of dark matter mass through its vacuum expectation value. While the presence of dark sector fermions affects the stability of the electroweak vacuum adversely, we find this additional singlet is capable of making the electroweak vacuum absolutely stable upto the Planck scale. A combined study of dark matter phenomenology and Higgs vacuum stability issue reflects that the scalar sector mixing angle can be significantly constrained in this scenario.

   hep-phPRD(2018)·41 citations
7. 07*

   On spin asymmetry in muon and tau decays

   A.B. Arbuzov🇷🇺 · T.V. Kopylova🇷🇺 · I.K. Sklyarov🇷🇺

   The angular asymmetry in decays of polarized muons and tau leptons is discussed. Both the standard $V-A$ Fermi model and the general parameterization via Michel parameters are considered. Numerical importance of contributions suppressed by charged lepton mass ratio is underlined. Contribution of the second order QED correction is estimated in the leading logarithm approximation.

   hep-phInt.J.Mod.Phys.A(2018)·0 citations
8. 08*

   Scalar Dark Matter, GUT baryogenesis and Radiative neutrino mass

   Wei-Chih Huang🇩🇰 · Heinrich Päs🇩🇪 · Sinan Zeißner🇩🇪

   We investigate an interesting correlation among dark matter phenomenology, neutrino mass generation and GUT baryogenesis, based on the scotogenic model. The model contains additional right-handed neutrinos $N$ and a second Higgs doublet $\Phi$, both of which are odd under an imposed $Z_2$ symmetry. The neutral component of $\Phi$, i.e. the lightest of the $Z_2$-odd particles, is the dark matter candidate. Due to a Yukawa coupling involving $\Phi$, $N$ and the Standard Model leptons, the lepton asymmetry is converted into the dark matter asymmetry so that a non-vanishing $B-L$ asymmetry can arise from $(B-L)$-conserving GUT baryogenesis, leading to a nonzero baryon asymmetry after the sphalerons decouple. On the other hand, $\Phi$ can also generate neutrino masses radiatively. In other words, the existence of $\Phi$ as the dark matter candidate resuscitates GUT baryogenesis and realizes neutrino masses.

   hep-phPRD(2018)·8 citations
9. 09*

   Impact of CMS 5.02 TeV dijet measurements on gluon PDFs - a preliminary view

   Kari J. Eskola🇫🇮 · Petja Paakkinen🇫🇮 · Hannu Paukkunen🇫🇮

   We discuss the implications of the preliminary CMS dijet data from 5.02 TeV pp and pPb collisions for gluon PDFs of the proton and nuclei. The preliminary pp data show a discrepancy with NLO predictions using for example the CT14 PDFs. We find that this difference cannot be accommodated within the associated scale uncertainties and debate the possible changes needed in the gluon PDF. A similar discrepancy is found between the CMS pPb data and NLO predictions e.g. with the EPPS16 nuclear modifications imposed on the CT14 proton PDFs. When a nuclear modification ratio of the pp and pPb data is constructed, the uncertainties in the scale choices and in proton PDFs effectively cancel and a good agreement between the data and EPPS16 is found, except in some bins at backward rapidities corresponding to large x of the nucleus. To assess the impact of these data on the EPPS16 nuclear PDFs, we use a non-quadratic extension of the Hessian PDF reweighting method. A significant reduction in EPPS16 uncertainties is obtained with the fit supporting strong nuclear shadowing and valence-like antishadowing for gluons. We also indicate the possible extensions needed in the EPPS16 parametrization at large x.

   hep-phhep-exPoS(2018)·2 citations
10. 10*

    Re-visiting the bounds on hydrogen-antihydrogen oscillations from diffuse $\gamma$-ray surveys

    Yuval Grossman🇺🇸 · Wee Hao Ng🇺🇸 · Shamayita Ray🇮🇳

    Surveys of diffuse $\gamma$-ray in the interstellar medium (ISM) can be used to probe hydrogen-antihydrogen oscillations, by detecting the $\gamma$-ray emission from antihydrogen annihilation. A bound on the oscillation parameter $\delta$ was originally derived by Feinberg, Goldhaber and Steigman (1978). In this paper, we re-visit the original derivation by performing a more detailed analysis that (1) incorporates suppression effects from additional elastic and inelastic processes, (2) treats the ISM as a multi-phase medium, and (3) utilises more recent $\gamma$-ray data from the Fermi Large Area Telescope. We find that suppression from elastic scattering plays a more important role than previously thought, while the multi-phase nature of the ISM affects how the $\gamma$-ray data should be utilised. We derive a more accurate bound on the oscillation period that is about an order of magnitude weaker than the older bound.

    hep-phPRD(2018)·16 citations
11. 11*

    Analyticity domain of a Quantum Field Theory and Accelero-summation

    Marc P. Bellon🇫🇷 · Pierre J. Clavier🇩🇪

    From 't Hooft's argument, one expects that the analyticity domain of an asymptotically free quantum field theory is horned shaped. In the usual Borel summation, the function is obtained through a Laplace transform and thus has a much larger analyticity domain. However, if the summation process goes through the process called acceleration by Ecalle, one obtains such a horn shaped analyticity domain. We therefore argue that acceleration, which allows to go beyond standard Borel summation, must be an integral part of the toolkit for the study of exactly renormalisable quantum field theories. We sketch how this procedure is working and what are its consequences.

    hep-phhep-thmath-phmath.MPLett.Math.Phys.(2019)·7 citations
12. 12*

    A Closer Study of the Framed Standard Model Yielding Testable New Physics plus a Hidden Sector with Dark Matter Candidates

    Jose Bordes (1)🇪🇸 · H. M. Chan (2)🇬🇧 · S. T. Tsou (3) ((1) Universitat de Valencia (Spain), (2) Rutherford Appleton Laboratory (United Kingdom) (3) Mathematical Institute University of Oxford (United Kingdom))🇬🇧

    This closer study of the FSM: [I] retains the earlier results in offering explanation for the existence of three fermion generations, as well as the hierarchical mass and mixing patterns of leptons and quarks; [II] predicts a vector boson $G$ with mass of order TeV which mixes with $\gamma$ and $Z$ of the standard model. The subsequent deviations from the standard mixing scheme are calculable in terms of the $G$ mass. While these deviations for (i) $m_Z-m_W$, (ii) $\Gamma (Z\to {\ell }^{+}{\ell }^{-})$, and (iii) $\Gamma (Z\to \mathrm{hadrons})$ are all within present experimental errors so long as $m_G>1$ TeV, they should soon be detectable if the $G$ mass is not too much bigger; [III] suggests that in parallel to the standard sector familiar to us, there is another where the roles of flavour and colour are interchanged. Though quite as copiously populated and as vibrant in self-interactions as our own, it communicates but little with the standard sector except via mixing through a couple of known portals, one of which is the $\gamma -Z-G$ complex noted in [II] above, and the other is a scalar complex which includes the standard model Higgs. As a result, the new sector appears hidden to us as we appear hidden to them, and so its lowest members with masses of order 10 MeV, being electrically neutral and seemingly stable, but abundant, may make eligible candidates as constituents of dark matter. A more detailed summary of these results together with some remarks on the model's special theoretical features can be found in the last section of the text.

    hep-phInt.J.Mod.Phys.A(2018)·9 citations
13. 13*

    The $Z$ boson in the Framed Standard Model

    Jose Bordes (1)🇪🇸 · H. M. Chan (2)🇬🇧 · S. T. Tsou (3) ((1) Universitat de Valencia (Spain), (2) Rutherford Appleton Laboratory (United Kingdom), Mathematical Institute University of Oxford (United Kingdom)(3))🇬🇧

    The framed standard model (FSM), constructed initially for explaining the existence of three fermion generations and the hierarchical mass and mixing patterns of quarks and leptons, suggests also a "hidden sector" of particles including some dark matter candidates. It predicts in addition a new vector boson $G$, with mass of order TeV, which mixes with the $\gamma$ and $Z$ of the standard model yielding deviations from the standard mixing scheme, all calculable in terms of a single unknown parameter $m_G$. Given that standard mixing has been tested already to great accuracy by experiment, this could lead to contradictions, but it is shown here that for the three crucial and testable cases so far studied (i) $m_Z-m_W$, (ii) $\Gamma (Z\to {\ell }^{+}{\ell }^{-})$, (iii) $\Gamma (Z\to$ hadrons), the deviations are all within the present stringent experimental bounds provided $m_G>1$ TeV, but should soon be detectable if experimental accuracy improves. This comes about because of some subtle cancellations, which might have a deeper reason that is not yet understood. By virtue of mixing, $G$ can be produced at the LHC and appear as a ${\ell }^{+}{\ell }^{-}$ anomaly. If found, it will be of interest not only for its own sake but serve also as a window on to the "hidden sector" into which it will mostly decay, with dark matter candidates as most likely products.

    hep-phInt.J.Mod.Phys.A(2018)·9 citations
14. 14*

    Probing compressed dark sectors at 100 TeV in the dileptonic mono-Z channel

    Rakhi Mahbubani🇨🇭 · Jose Zurita🇩🇪

    We examine the sensitivity at a future 100 TeV proton-proton collider to compressed dark sectors whose decay products are invisible due to below-threshold energies and/or small couplings to the Standard Model. This scenario could be relevant to models of WIMP dark matter, where the lightest New Physics state is an (isolated) electroweak multiplet whose lowest component is stable on cosmological timescales. We rely on the additional emission of a hard on-shell $Z$-boson decaying to leptons, a channel with low background systematics, and include a careful estimate of the real and fake backgrounds to this process in our analysis. We show that an integrated luminosity of 30 ab${}^{-1}$ would allow exclusion of a TeV-scale compressed dark sector with inclusive production cross section of 0.3 fb, for 1\% background systematic uncertainty and splittings below 5 GeV. This translates to exclusion of a pure higgsino (wino) multiplet with mass of 500 (970) GeV.

    hep-phJHEP(2018)·2 citations
15. 15*

    Decay rate and asymmetries of ${\Sigma }^{+}\to p{\mu }^{+}{\mu }^{-}$

    Xiao-Gang He🇹🇼 · Jusak Tandean🇹🇼 · German Valencia🇦🇺

    The LHCb Collaboration has recently reported evidence for the rare hyperon decay ${\Sigma }^{+}\to p{\mu }^{+}{\mu }^{-}$ that is consistent with the standard model expectation. Motivated by this new result we revisit the calculation of this mode including both long and short distance contributions. In the standard model this mode is completely dominated by long distance physics and thus subject to large uncertainties. We present a range of predictions for the rate, the dimuon invariant mass spectrum, and a muon polarization asymmetry that covers these uncertainties as well as known constraints. We study the interplay between short and long distance contributions which could result in additional asymmetries, but we find that they are negligible within the standard model. We propose a parameterization of these asymmetries in terms of a couple of constants that can arise from new physics.

    hep-phhep-exnucl-thJHEP(2018)·29 citations
16. 16*

    Prospects for discovering a light charged Higgs boson within the NMSSM at the FCC-eh collider

    S.P. Das🇨🇴 · J. Hernandez-Sanchez🇲🇽 · S. Moretti🇬🇧 · A. Rosado🇲🇽

    We analyze the prospects of observing relatively light charged Higgs bosons ($h^{\pm }$) in their decays via $h^{-}\to s\bar{c}+s\bar{u}$ at the upcoming Future Circular Collider in hadron-electron mode (FCC-eh) with $\sqrt{s}\approx 3.5$ TeV. Assuming that the intermediate Higgs boson ($h_2$) is Standard Model (SM)-like, we study the production of $e^{-}b\to {\nu }_e{h}^{-}b$ (also $b$ could be $\bar{b}$ in both initial and final states) in the framework of the Next-to-Minimal Supersymmetric Standard Model (NMSSM). We consider constraints from Dark Matter (DM), super-particle and the Higgs boson data. The charged Higgs boson decays into light flavors leads to a three-jets with missing transverse energy signal with one $b$-tagged jet. Our results show that light charged Higgs bosons with mass close to, e.g., 114(121) GeV have the maximal significance of 3.2(1.8)$\sigma$, upon using normal cut based selections and after 1 ab${}^{-1}$ of luminosity. However, we further adopt an optimization technique to enhance the latter to 4.4 (2.2)$\sigma$, respectively.

    hep-phhep-ex6 citations
17. 17*

    Quark spins and Anomalous Ward Identity

    Jian Liang🇺🇸 · Yi-Bo Yang🇺🇸 · Terrence Draper🇺🇸 · Ming Gong🇨🇳 · Keh-Fei Liu🇺🇸

    We calculate the intrinsic quark spin contribution to the total proton spin using overlap valence quarks on three ensembles of $2+1$-flavor RBC/UKQCD domain-wall configurations with different lattice spacings. The lowest pion mass of the ensembles is around 171 MeV which is close to the physical point. With overlap fermions and topological charge derived from the overlap operator, we verify the anomalous Ward identity between nucleon states with momentum transfer. Both the connected and disconnected insertions of the axial-vector current are calculated. For the disconnected-insertion part, the cluster-decomposition error reduction (CDER) technique is utilized for the lattice with the largest volume and the error can be reduced by $10\%\sim 40\%$. Nonperturbative renormalization is carried out and the final results are all reported in the $\overline{\mathrm{MS}}$ scheme at 2 GeV. We determine the total quark spin contribution to the nucleon spin to be $\Delta \Sigma =0.401(25)(37)$, which is consistent with the recent global fitting result of experimental data. The isovector axial coupling we obtain in this study is $g_A^3=1.256(16)(30)$, which agrees well with the experimental value of 1.2723(23).

    hep-phhep-latPRD(2018)·120 citations
18. 18*

    Gauge and Infrared Properties of Hadronic Structure of Nucleon in Neutron Beta Decay to Order O(\alpha/\pi) in Standard V - A Effective Theory with QED and Linear Sigma Model of Strong Low--Energy Interactions

    A. N. Ivanov🇦🇹 · R. Höllwieser🇦🇹 · N. I. Troitskaya🇦🇹 · M. Wellenzohn🇦🇹 · Ya. A. Berdnikov🇷🇺

    Within the standard V - A theory of weak interactions, Quantum Electrodynamics (QED) and the linear sigma-model (LsM) of strong low-energy hadronic interactions we analyse gauge and infrared properties of hadronic structure of the neutron and proton in the neutron beta decay to leading order in the large nucleon mass expansion. We show that the complete set of Feynman diagrams describing radiative corrections of order O(\alpha/\pi), induced by hadronic structure of the nucleon, to the rate of the neutron beta decay is gauge non-invariant and unrenormalisable. We show that a gauge non-invariant contribution does not depend on the electron energy in agreement with Sirlin's analysis of contributions of strong low-energy interactions (Phys. Rev. 164, 1767 (1967)). We show that infrared divergent and dependent on the electron energy contributions from the neutron radiative beta decay and neutron beta decay, caused by hadronic structure of the nucleon, are cancelled in the neutron lifetime. Nevertheless, we find that divergent contributions of virtual photon exchanges to the neutron lifetime, induced by hadronic structure of the nucleon, are unrenormalisable even formally. Such an unrenormalizability can be explained by the fact that the effective V - A vertex of hadron-lepton current-current interactions is not a vertex of the combined quantum field theory including QED and LsM, which are renormalizable theories.

    hep-phgr-qcnucl-exInt.J.Mod.Phys.A(2019)·6 citations
19. 19*

    The scalar and pseudoscalar hidden-charm tetraquark states with QCD sum rules

    Zun-Yan Di🇨🇳 · Zhi-Gang Wang🇨🇳

    Based on the diquark configuration, we construct the diquark-antidiquark interpolating tetraquark currents with $J^{PC}=1^{-\pm }$ and $1^{+\pm }$, which can couple to the scalar and pseudoscalar tetraquark states respectively, since they are not conserved currents. Then we investigate their two-point correlation functions including the contributions of the vacuum condensates up to dimension-10 and extract the masses and pole residues of the tetraquark states with $J^{PC}=0^{+\pm }$ and $0^{-\pm }$ through the QCD sum rule approach. The predicted masses can be confronted with the experimental data in the future. Moreover, we briefly discuss the possible decay patterns of the tetraquark states.

    hep-phInt.J.Mod.Phys.A(2018)·1 citation
20. 20*

    Non-Gaussian Features of Primordial Gravitational Waves

    Abhishek Naskar🇮🇳 · Supratik Pal🇮🇳

    We explore possible non-Gaussian features of primordial gravitational waves by constructing model-independent templates for nonlinearity parameters of tensor bispectrum. Our analysis is based on Effective Field Theory of inflation that relies on no particular model as such and thus the results are quite generic. The analysis further reveals that chances of detecting squeezed limit tensor bispectrum are fairly higher than equilateral limit. We also discuss prospects of detectability in upcoming CMB missions.

    ↳ astro-ph.COgr-qchep-phPRD(2018)·8 citations
21. 21*

    On the quantum equivalence of an antisymmetric tensor field with spontaneous Lorentz violation

    Sandeep Aashish🇮🇳 · Sukanta Panda🇮🇳

    We present an explicit proof that a minimal model of rank-2 antisymmetric field with spontaneous Lorentz violation and a classically equivalent vector field model are also quantum equivalent, by calculating quantum effective actions of both theories. We comment on the issues encountered while checking quantum equivalence in curved spacetime.

    ↳ gr-qchep-phhep-thMod.Phys.Lett.A(2020)·10 citations
22. 22*

    Lorentz-violating dimension-five operator contribution to the black body radiation

    M. A. Anacleto🇧🇷 · F. A. Brito🇧🇷 · E. Maciel🇧🇷 · A. Mohammadi🇧🇷 · E. Passos🇧🇷 · W. O. Santos🇧🇷 · J. R. L. Santos🇧🇷

    We investigate the thermodynamics of a photon gas in an effective field theory model that describes Lorentz violations through dimension-five operators and Horava-Lifshitz theory. We explore the electrodynamics of the model which includes higher order derivatives in the Lagrangian that can modify the dispersion relation for the propagation of the photons. We shall focus on the deformed black body radiation spectrum and modified Stefan-Boltzmann law to address the allowed bounds on the Lorentz-violating parameter.

    ↳ hep-thhep-phPLB(2018)·38 citations
23. 23*

    Nonlinear perturbations from the coupling of the inflaton to a non-Abelian gauge field, with a focus on Chromo-Natural Inflation

    Alexandros Papageorgiou🇺🇸 · Marco Peloso🇺🇸 · Caner Unal🇺🇸

    Several models of inflation employing a triplet of SU(2) vectors with spatially orthogonal vacuum expectation values (VEVs) have been recently proposed. One (tensor) combination $t$ of the vector modes is amplified in some momentum range during inflation. Due to the vector VEVs, this combination mixes with gravitational waves (GW) at the linear level, resulting in a GW amplification that has been well studied in the literature. Scalar perturbations in this class of models have been so far studied only at the linear level. We perform a first step toward the nonlinear computation using as an example the original model of Chromo-Natural Inflation. We compute the contribution to the scalar power spectrum arising from the coupling of the combination $t$ to the inflaton. This contribution is mostly controlled by a single parameter of the model (namely, the ratio between the mass of the fluctuations of the vector field and the Hubble rate), and, for a wide range of this parameter, it can significantly affect the phenomenology obtained from the linear theory. This nonlinear contribution is significantly blue, improving the comparison between the two-point function and the Cosmic Microwave Background (CMB) data. This growth can be also relevant for smaller scale phenomenology, such as large scale structure, CMB distortions, and primordial black holes.

    ↳ astro-ph.COgr-qchep-phhep-thJCAP(2018)·56 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.