Mon·Sep 5, 2016Monday·September 5, 2016

1. 01*

   The Higgs boson at high $p_T$

   Tobias Neumann🇺🇸 · Ciaran Williams🇺🇸

   We present a calculation of $H+j$ at NLO including the effect of a finite top-mass. Where possible we include the complete dependence on $m_t$. This includes the leading order amplitude, the infrared poles of the two-loop amplitude and the real radiation amplitude. The remaining finite piece of the virtual correction is considered in an asymptotic expansion in $m_t$, which is accurate to $m_t^{-4}$. By successively including more $m_t$-exact pieces, the dependence on the asymptotic series diminishes and we find convergent behavior for $p_T^H>m_t$ for the first time. Our results justify rescaling by the $m_t$-exact LO cross section to model top-mass effects in EFT results up to $p_T$ of 250 to 300 GeV. We show that the error made by using the LO rescaling becomes comparable to the NNLO scale uncertainty for such large energies. We implement our results into the Monte Carlo code MCFM.

   hep-phhep-exPRD(2017)·59 citations
2. 02*

   Precise Higgs mass calculations in (non-)minimal supersymmetry at both high and low scales

   Peter Athron🇦🇺 · Jae-hyeon Park🇰🇷 · Tom Steudtner🇩🇪 · Dominik Stöckinger🇩🇪 · Alexander Voigt🇩🇪

   We present FlexibleEFTHiggs, a method for calculating the SM-like Higgs pole mass in SUSY (and even non-SUSY) models, which combines an effective field theory approach with a diagrammatic calculation. It thus achieves an all order resummation of leading logarithms together with the inclusion of all non-logarithmic 1-loop contributions. We implement this method into FlexibleSUSY and study its properties in the MSSM, NMSSM, E6SSM and MRSSM. In the MSSM, it correctly interpolates between the known results of effective field theory calculations in the literature for a high SUSY scale and fixed-order calculations in the full theory for a sub-TeV SUSY scale. We compare our MSSM results to those from public codes and identify the origin of the most significant deviations between the DR-bar programs. We then perform a similar comparison in the remaining three non-minimal models. For all four models we estimate the theoretical uncertainty of FlexibleEFTHiggs and the fixed-order DR-bar programs thereby finding that the former becomes more precise than the latter for a SUSY scale above a few TeV. Even for sub-TeV SUSY scales, FlexibleEFTHiggs maintains the uncertainty estimate around 2-3 GeV, remaining a competitive alternative to existing fixed-order computations.

   hep-phJHEP(2017)·130 citations
3. 03*

   Can the relic density of self-interacting dark matter be due to annihilations into Standard Model particles?

   Xiaoyong Chu🇮🇹 · Camilo Garcia-Cely🇧🇪 · Thomas Hambye🇧🇪

   Motivated by the hypothesis that dark matter self-interactions provide a solution to the small-scale structure formation problems, we investigate the possibilities that the relic density of a self-interacting dark matter candidate can proceed from the thermal freeze-out of annihilations into Standard Model particles. We find that scalar and Majorana dark matter in the mass range of $10-500$ MeV, coupled to a slightly heavier massive gauge boson, are the only possible candidates in agreement with multiple current experimental constraints. Here dark matter annihilations take place at a much slower rate than the self-interactions simply because the interaction connecting the Standard Model and the dark matter sectors is small. We also discuss prospects of establishing or excluding these two scenarios in future experiments.

   hep-phJHEP(2016)·32 citations
4. 04*

   On thermal corrections to near-threshold annihilation

   Seyong Kim🇰🇷 · M. Laine🇨🇭

   We consider non-relativistic "dark" particles interacting through gauge boson exchange. At finite temperature, gauge exchange is modified in many ways: virtual corrections lead to Debye screening; real corrections amount to frequent scatterings of the heavy particles on light plasma constituents; mixing angles change. In a certain temperature and energy range, these effects are of order unity. Taking them into account in a resummed form, we estimate the near-threshold spectrum of kinetically equilibrated annihilating TeV scale particles. Weakly bound states are shown to "melt" below freeze-out, whereas with attractive strong interactions, relevant e.g. for gluinos, bound states boost the annihilation rate by a factor 4...80 with respect to the Sommerfeld estimate, thereby perhaps helping to avoid overclosure of the universe. Modestly non-degenerate dark sector masses and a way to combine the contributions of channels with different gauge and spin structures are also discussed.

   hep-phJCAP(2017)·54 citations
5. 05*

   Fast neutrino flavor conversions near the supernova core with realistic flavor-dependent angular distributions

   Basudeb Dasgupta (Tata Inst.)🇮🇳 · Alessandro Mirizzi (Bari Univ. and INFN Bari)🇮🇹 · Manibrata Sen (Tata Inst.)🇮🇳

   It has been recently pointed out that neutrino fluxes from a supernova can show substantial flavor conversions almost immediately above the core. Using linear stability analyses and numerical solutions of the fully nonlinear equations of motion, we perform a detailed study of these fast conversions, focussing on the region just above the supernova core. We carefully specify the instabilities for evolution in space or time, andfind that neutrinos travelling towards the core make fast conversions more generic, i.e., possible for a wider range of flux ratios and angular asymmetries that produce a crossing between the zenith-angle spectra of ${\nu }_e$ and ${\bar{\nu }}_e$. Using fluxes and angular distributions predicted by supernova simulations, we find that fast conversions can occur within tens of nanoseconds, only a few meters away from the putative neutrinospheres. If these fast flavor conversions indeed take place, they would have important implications for the supernova explosion mechanism and nucleosynthesis.

   hep-phastro-ph.HEastro-ph.SRJCAP(2017)·136 citations
6. 06*

   Parton Shower Uncertainties in Jet Substructure Analyses with Deep Neural Networks

   James Barnard🇦🇺 · Edmund Noel Dawe🇦🇺 · Matthew J. Dolan🇦🇺 · Nina Rajcic🇦🇺

   Machine learning methods incorporating deep neural networks have been the subject of recent proposals for new hadronic resonance taggers. These methods require training on a dataset produced by an event generator where the true class labels are known. However, training a network on a specific event generator may bias the network towards learning features associated with the approximations to QCD used in that generator which are not present in real data. We therefore investigate the effects of variations in the modelling of the parton shower on the performance of deep neural network taggers using jet images from hadronic W-bosons at the LHC, including detector-related effects. By investigating network performance on samples from the Pythia, Herwig and Sherpa generators, we find differences of up to fifty percent in background rejection for fixed signal efficiency. We also introduce and study a method, which we dub zooming, for implementing scale-invariance in neural network-based taggers. We find that this leads to an improvement in performance across a wide range of jet transverse momenta. Our results emphasise the importance gaining a detailed understanding what aspects of jet physics these methods are exploiting.

   hep-phhep-exPRD(2017)·139 citations
7. 07*

   Higgs potential from extended Brans-Dicke theory and the time-evolution of the fundamental constants

   Joan Sola🇪🇸 · Elahe Karimkhani🇪🇸 · A. Khodam-Mohammadi🇮🇷

   Despite the enormous significance of the Higgs potential in the context of the Standard Model of electroweak interactions and in Grand Unified Theories, its ultimate origin is fundamentally unknown and must be introduced by hand in accordance with the underlying gauge symmetry and the requirement of renormalizability. Here we propose a more physical motivation for the structure of the Higgs potential, which we link to gravity, and more specifically to an extended Brans-Dicke (BD) theory containing two interacting scalar fields. One of these fields is coupled to curvature as in the BD formulation, whereas the other is coupled to gravity both derivatively and non-derivatively through the curvature scalar and the Ricci tensor. By requiring that the cosmological solutions of the model are consistent with observations, we show that the effective scalar field potential adopts the Higgs potential form with a mildly time-evolving vacuum expectation value. Such residual vacuum dynamics could be responsible for the possible time variation of the fundamental constants. The approach is in part reminiscent of Bjorken's ideas on the cosmological constant problem.

   ↳ gr-qcastro-ph.COhep-phhep-thClass.Quant.Grav.(2017)·27 citations
8. 08*

   Inflation from Nilpotent Kähler Corrections

   Evan McDonough🇨🇦 · Marco Scalisi🇩🇪

   We develop a new class of supergravity cosmological models where inflation is induced by terms in the Kähler potential which mix a nilpotent superfield $S$ with a chiral sector $\Phi$. As the new terms are non-(anti)holomorphic, and hence cannot be removed by a Kähler transformation, these models are intrinsically Kähler potential driven. Such terms could arise for example due to a backreaction of an anti-D3 brane on the string theory bulk geometry. We show that this mechanism is very general and allows for a unified description of inflation and dark energy, with controllable SUSY breaking at the vacuum. When the internal geometry of the bulk field is hyperbolic, we prove that small perturbative Kähler corrections naturally lead to $\alpha$-attractor behaviour, with inflationary predictions in excellent agreement with the latest Planck data

   ↳ hep-thastro-ph.COgr-qchep-phJCAP(2016)·68 citations
9. 09*

   Application of the Feynman-tree theorem together with BCFW recursion relations

   Markos Maniatis🇨🇱

   Recently, it has been shown that on-shell scattering amplitudes can be constructed by the Feynman-tree theorem combined with the BCFW recursion relations. Since the BCFW relations are restricted to tree diagrams, the preceding application of the Feynman-tree theorem is essential. In this way amplitudes can be constructed by on-shell and gauge-invariant tree amplitudes. Here we want to apply this method to the electron-photon vertex correction. We present all the single, double, and triple phase-space tensor integrals explicitly and show that the sum of amplitudes coincides with the result of the conventional calculation of a virtual loop correction.

   ↳ hep-thhep-phInt.J.Mod.Phys.A(2018)·6 citations
10. 10*

    Dynamical Screening of $\alpha$-$\alpha$ Resonant Scattering and Thermal Nuclear Scattering Rate in a Plasma

    Xiaojun Yao🇺🇸 · Thomas Mehen🇺🇸 · Berndt Müller🇺🇸

    We use effective field theory and thermal field theory to study the dynamical screening effect in the QED plasma on the $\alpha$-$\alpha$ scattering at the ${}^8$Be resonance. Dynamical screening leads to an imaginary part of the potential which results in a thermal width for the resonance and dominates over the previously considered static screening effect. As a result, both the resonance energy and width increase with the plasma temperature. Furthermore, dynamical screening can have a huge impact on the $\alpha$-$\alpha$ thermal nuclear scattering rate. For example, when the temperature is around $10$ keV, the rate is suppressed by a factor of about $900$. We expect similar thermal suppressions of nuclear reaction rates to occur in those reactions dominated by an above threshold resonance with a thermal energy. Dynamical screening effects on nuclear reactions can be relevant to cosmology and astrophysics.

    ↳ nucl-thhep-phPRD(2017)·5 citations
11. 11*

    Refining the boundaries of the classical de Sitter landscape

    David Andriot🇩🇪 · Johan Blåbäck🇫🇷

    We derive highly constraining no-go theorems for classical de Sitter backgrounds of string theory, with parallel sources; this should impact the embedding of cosmological models. We study ten-dimensional vacua of type II supergravities with parallel and backreacted orientifold Op-planes and Dp-branes, on four-dimensional de Sitter space-time times a compact manifold. Vacua for p=3, 7 or 8 are completely excluded, and we obtain tight constraints for p=4, 5, 6. This is achieved through the derivation of an enlightening expression for the four-dimensional Ricci scalar. Further interesting expressions and no-go theorems are obtained. The paper is self-contained so technical aspects, including conventions, might be of more general interest.

    ↳ hep-thastro-ph.COgr-qchep-phJHEP(2017)·79 citations
12. 12*

    The role of $a_1(1260)$ in ${\pi }^{-}p\to a_1^{-}(1260)p$ and ${\pi }^{-}p\to {\pi }^{-}{\rho }^{0}p$ reactions near threshold

    Chen Cheng🇨🇳 · Ju-Jun Xie🇨🇳 · Xu Cao🇨🇳

    We report on a theoretical study of the ${\pi }^{-}p\to a_1^{-}(1260)p$ and ${\pi }^{-}p\to {\pi }^{-}{\rho }^{0}p$ reactions near threshold within an effective Lagrangian approach. The production process is described by $t$-channel ${\rho }^0$ meson exchange. For the ${\pi }^{-}p\to {\pi }^{-}{\rho }^{0}p$ reaction, the final ${\pi }^{-}{\rho }^0$ results from the decay of the $a_1(1260)$ resonance which is assumed as a dynamically generated state from the $K^{\ast }\bar{K}$ and $\rho \pi$ coupled channel interactions. We calculate the total cross section of the ${\pi }^{-}p\to a_1^{-}(1260)p$ reaction. It is shown that, with the coupling constant of the $a_1(1260)$ to $\rho \pi$ channel obtained from the chiral unitary theory and a cut off parameter ${\Lambda }_{\rho }\sim 1.5$ GeV in the form factors, the experimental measurement can be reproduced. Furthermore, the total and differential cross sections of ${\pi }^{-}p\to a_1^{-}(1260)p\to {\pi }^{-}{\rho }^{0}p$ reaction are evaluated, and it is expected that our model calculations can be tested by future experiments. These reactions are important for the study of the $a_1(1260)$ resonance and would provide further clue for the nature of $a_1(1260)$ state.

    ↳ nucl-thhep-phnucl-exCommun.Theor.Phys.(2016)·10 citations
13. 13*

    Possible explanations for fine-tuning of the universe

    Kiyoharu Kawana🇯🇵

    The Froggatt-Nielsen mechanism and the multi-local field theory are interesting and promising candidates for solving the naturalness problem in the universe. These theories are based on the different physical principles: The former assumes the micro-canonical partition function $\int \mathcal{D}\varphi {\prod }_i\delta (S_i^{}-I_i^{})$, and the latter assumes the partition function $\int \mathcal{D}\varphi \exp \left(i{S}_M^{}\right)$ where $S_M^{}$ is the multi-local action ${\sum }_i{c}_i^{}{S}_i^{}+{\sum }_{i,j}{c}_{i,j}^{}{S}_i^{}{S}_j^{}+\cdots$. Our main purpose is to show that they are equivalent in the sense that they predict the same fine-tuning mechanism. In order to clarify our argument, we first study (review) the similarity between the Froggatt-Nielsen mechanism and statistical mechanics in detail, and show that the dynamical fine-tuning in the former picture can be understood completely in the same way as the determination of the temperature in the latter picture. Afterward, we discuss the multi-local theory and the equivalence between it and the the Froggatt-Nielsen mechanism. Because the multi-local field theory can be obtained from physics at the Planck/String scale, this equivalence indicates that the micro-canonical picture can also originate in such physics. As a concrete example, we also review the IIB matrix model as an origin of the multi-local theory.

    ↳ hep-thhep-phInt.J.Mod.Phys.A(2017)·8 citations
14. 14*

    Including heavy spin effects in a lattice QCD study of static-static-light-light tetraquarks

    Pedro Bicudo🇵🇹 · Jonas Scheunert🇩🇪 · Marc Wagner🇩🇪

    In previous works we predicted the existence of a $\bar{b}\bar{b}ud$ tetraquark with quantum numbers $I(J^P)=0(1^{+})$ using the static approximation for the $\bar{b}$ quarks and neglecting heavy spin effects. Since the binding energy is of the same order as expected for these heavy spin effects, it is essential to include them in the computation. Here we present a corresponding method and show evidence that binding is only slightly weakened and that the $\bar{b}\bar{b}ud$ tetraquark persists.

    ↳ hep-lathep-phPoS(2016)·6 citations
15. 15*

    Conformal Bootstrap in Mellin Space

    Rajesh Gopakumar🇮🇳 · Apratim Kaviraj🇮🇳 · Kallol Sen🇮🇳 · Aninda Sinha🇮🇳

    We propose a new approach towards analytically solving for the dynamical content of Conformal Field Theories (CFTs) using the bootstrap philosophy. This combines the original bootstrap idea of Polyakov with the modern technology of the Mellin representation of CFT amplitudes. We employ exchange Witten diagrams with built in crossing symmetry as our basic building blocks rather than the conventional conformal blocks in a particular channel. Demanding consistency with the operator product expansion (OPE) implies an infinite set of constraints on operator dimensions and OPE coefficients. We illustrate the power of this method in the epsilon expansion of the Wilson-Fisher fixed point by reproducing anomalous dimensions and, strikingly, obtaining OPE coefficients to higher orders in epsilon than currently available using other analytic techniques (including Feynman diagram calculations). Our results enable us to get a somewhat better agreement of certain observables in the 3d Ising model, with the precise numerical values that have been recently obtained.

    ↳ hep-thcond-mat.stat-mechcond-mat.str-elhep-phPRL(2017)·186 citations
16. 16*

    (Almost) Closing the $\nu$MSM Sterile Neutrino Dark Matter Window with NuSTAR

    Kerstin Perez🇺🇸 · Kenny C. Y. Ng🇺🇸 · John F. Beacom🇺🇸 · Cora Hersh🇺🇸 · Shunsaku Horiuchi🇺🇸 · Roman Krivonos🇷🇺

    We use NuSTAR observations of the Galactic Center to search for X-ray lines from the radiative decay of sterile neutrino dark matter. Finding no evidence of unknown lines, we set limits on the sterile neutrino mass and mixing angle. In most of the mass range 10-50 keV, these are now the strongest limits, at some masses improving upon previous limits by a factor of ~10. In the neutrino minimal standard model framework, where additional constraints from dark matter production and structure formation apply, the allowed parameter space is reduced by more than half. Future NuSTAR observations may be able to cover much of the remaining parameter space.

    ↳ astro-ph.HEastro-ph.COhep-phPRD(2017)·200 citations
17. 17*

    Bootstrapping a Five-Loop Amplitude Using Steinmann Relations

    Simon Caron-Huot🇩🇰 · Lance J. Dixon🇺🇸 · Andrew McLeod🇺🇸 · Matt von Hippel🇨🇦

    The analytic structure of scattering amplitudes is restricted by Steinmann relations, which enforce the vanishing of certain discontinuities of discontinuities. We show that these relations dramatically simplify the function space for the hexagon function bootstrap in planar maximally supersymmetric Yang-Mills theory. Armed with this simplification, along with the constraints of dual conformal symmetry and Regge exponentiation, we obtain the complete five-loop six-particle amplitude.

    ↳ hep-thhep-phPRL(2016)·263 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.