Mon·Jul 30, 2018Monday·July 30, 2018

1. 01*

   Signatures of dark Higgs boson in light fermionic dark matter scenarios

   Luc Darmé🇵🇱 · Soumya Rao🇵🇱 · Leszek Roszkowski🇵🇱

   Thermal dark matter scenarios based on light (sub-GeV) fermions typically require the presence of an extra dark sector containing both a massive dark photon along with a dark Higgs boson. The latter generates both the dark photon mass and an additional mass term for the dark sector fermions. This simple setup has both rich phenomenology and bright detection prospects at high-intensity accelerator experiments. We point out that in addition to the well studied pseudo-Dirac regime, this model can achieve the correct relic density in three different scenarios, and examine in details their properties and experimental prospects. We emphasize in particular the effect of the dark Higgs boson on both detection prospects and cosmological bounds.

   hep-phhep-exJHEP(2018)·26 citations
2. 02*

   Quark-antiquark asymmetry of helicity distributions in the nucleon sea

   Mengyun Liu🇨🇳 · Bo-Qiang Ma🇨🇳

   We study the helicity distributions of light flavor quark-antiquark ($q\bar{q}$) pairs in the nucleon sea. The valence quarks are handled by adopting the light-cone SU(6) quark-spectator-diquark model and the sea $q\bar{q}$ pairs are treated from statistical consideration by introducing the helicity suppression factors $l_q(x)$ and ${\bar{l}}_q(x)$ to parametrize the helicity distributions of q-flavor sea quark and antiquark respectively, while $\Delta l_q(x)=l_q(x)-{\bar{l}}_q(x)$ represents a combined effect of helicity contribution due to sea $q\bar{q}$ pairs. From fitting the nucleon polarization asymmetries $A_1^N$ in inclusive deep inelastic scattering processes and the single-spin asymmetries $A_L^{W^{\pm }}$ in Drell-Yan type processes, we find a significant asymmetry between the quark and antiquark helicity distributions of the nucleon sea. Therefore the quark-antiquark asymmetry of helicity distributions of nucleon sea $q\bar{q}$ pairs, i.e., $\Delta q_s(x)\ne \Delta {\bar{q}}_s(x)$, plays an important role for a comprehensive understanding of the nucleon spin content.

   hep-phPRD(2018)·4 citations
3. 03*

   CP in the dark

   Duarte Azevedo🇵🇹 · P. M. Ferreira🇵🇹 · M. Margarete Muhlleitner🇩🇪 · Shruti Patel🇩🇪 · Rui Santos🇵🇹 · Jonas Wittbrodt🇩🇪

   We build a model containing two scalar doublets and a scalar singlet with a specific discrete symmetry. After spontaneous symmetry breaking, the model has Standard Model-like phenomenology, as well as a hidden scalar sector which provides a viable dark matter candidate. We show that CP violation in the scalar sector occurs exclusively in the hidden sector, and consider possible experimental signatures of this CP violation.

   hep-phJHEP(2018)·31 citations
4. 04*

   Forward Elastic Scattering and Pomeron Models

   M. Broilo🇧🇷 · E.G.S. Luna🇧🇷 · M.J. Menon🇧🇷

   Recent data from LHC13 by the TOTEM Collaboration have indicated an unexpected decrease in the value of the $\rho$ parameter and a ${\sigma }_{tot}$ value in agreement with the trend of previous measurements at 7 and 8 TeV. These data at 13 TeV are not simultaneously described by the predictions from Pomeron models selected by the COMPETE Collaboration, but show agreement with the maximal Odderon dominance, as recently demonstrated by Martynov and Nicolescu. Here we present a detailed analysis on the applicability of Pomeron dominance by means of a general class of forward scattering amplitude, consisting of even-under-crossing leading contributions associated with single, double and triple poles in the complex angular momentum plane. We carry out fits to $pp$ and $\bar{p}p$ data in the interval 5 GeV - 13 TeV. The data set comprises all the accelerator data below 7 TeV and we consider two independent ensembles by adding either only the TOTEM data or TOTEM and ATLAS data at the LHC energy region. In the data reductions to each ensemble the uncertainty regions are evaluated with both one and two standard deviation ($\sim$ 68 \% and $\sim$ 95 \% CL, respectively). Besides the general analytic model, we investigate four particular cases of interest, three of them typical of outstanding models in the literature. We conclude that, within the experimental and theoretical uncertainties and both ensembles, the general model and three particular cases are not able to describe the ${\sigma }_{tot}$ and $\rho$ data at 13 TeV simultaneously. However, if the discrepancies between the TOTEM and ATLAS data are not resolved, one Pomeron model, associated with double and triple poles and with only 7 free parameters, seems not to be excluded by the complete set of experimental information presently available.

   hep-phhep-exnucl-thPRD(2018)·23 citations
5. 05*

   The Quark-Gluon Vertex and the QCD Infrared Dynamics

   O. Oliveira🇵🇹 · W. de Paula🇧🇷 · T. Frederico🇧🇷 · J. P. B. C de Melo🇧🇷

   The Dyson-Schwinger quark equation is solved for the quark-gluon vertex using the most recent lattice data available in the Landau gauge for the quark, gluon and ghost propagators, the full set of longitudinal tensor structures in the Ball-Chiu vertex, taking into account a recently derived normalisation for a quark-ghost kernel form factors and the gluon contribution for the tree level quark-gluon vertex identified on a recent study of the lattice soft gluon limit. A solution for the inverse problem is computed after the Tikhonov linear regularisation of the integral equation, that implies solving a modified Dyson-Schwinger equation. We get longitudinal form factors that are strongly enhanced at the infrared region, deviate significantly from the tree level results for quark and gluon momentum below 2 GeV and at higher momentum approach their perturbative values. The computed quark-gluon vertex favours kinematical configurations where the quark momentum $p$ and the gluon momentum $q$ are small and parallel. Further, the quark-gluon vertex is dominated by the form factors associated to the tree level vertex ${\gamma }_{\mu }$ and to the operator $2p_{\mu }+q_{\mu }$. The higher rank tensor structures provide small contributions to the vertex.

   hep-phhep-lathep-thnucl-thEPJC(2019)·35 citations
6. 06*

   Cross Sections for Inelastic 2-to-2 Meson-Meson Scattering in Hadronic Matter

   Ting-Ting Wang🇨🇳 · Xiao-Ming Xu🇨🇳

   With quark-antiquark annihilation and creation in the first Born approximation, we study the reactions: $K\bar{K}\to K{\bar{K}}^{\ast },K\bar{K}\to K^{\ast }\bar{K},\pi K\to \pi K^{\ast },\pi K\to \rho K,\pi \pi \to K{\bar{K}}^{\ast },\pi \pi \to K^{\ast }\bar{K},\pi \pi \to K^{\ast }{\bar{K}}^{\ast },\pi \rho \to K\bar{K},\pi \rho \to K^{\ast }{\bar{K}}^{\ast },\rho \rho \to K^{\ast }{\bar{K}}^{\ast },K{\bar{K}}^{\ast }\to \rho \rho$, and $K^{\ast }\bar{K}\to \rho \rho$. Unpolarized cross sections for the reactions are obtained from transition amplitudes that are composed of mesonic quark-antiquark relative-motion wave functions and the transition potential for quark-antiquark annihilation and creation. From a quark-antiquark potential that is equivalent to the transition potential, we prove that the total spin of the two final mesons may not equal the total spin of the two initial mesons. Based on flavor matrix elements, cross sections for some isospin channels of reactions can be obtained from the other isospin channels of reactions. Remarkable temperature dependence of the cross sections is found.

   hep-phnucl-thCPC(2019)·3 citations
7. 07*

   searches for ud\bar{s}\bar{b} in the chiral quark model

   Xiaoyun Chen🇨🇳 · Jialun Ping🇨🇳

   Inspired by the report of D0 Collaboration on the state $X(5568)$ with four different flavors, a similar state, $ud\bar{s}\bar{b}$ is investigated in the present work. The advantage of looking for this state over the state $X(5568)$ with quark contents, $bu\bar{d}\bar{s}$ or $bd\bar{u}\bar{s}$, is that the $BK$ threshold is 270 MeV higher than that of $B_s\pi$, and it allows a large mass region for $ud\bar{s}\bar{b}$ to be stable. The chiral quark model and Gaussian expansion method are employed to do the calculations of four-quark states $ud\bar{s}\bar{b}$ with quantum numbers $I{J}^P$($I=0,1;J=0,1,2;P=+$). Two structures, diquark-antidiquark and meson-meson, with all possible color configurations are considered. The results indicate that energies of the tetraquark with diquark-antiquark configuration are all higher than the threshold of $BK$, but for the state of $I{J}^P=00^{+}$ in the meson-meson structure, the energies are below the corresponding thresholds, where the color channel coupling plays an important role. The distances between two objects (quark/antiquark) show that the state is a molecular one.

   hep-phPRD(2018)·24 citations
8. 08*

   Semi-Inclusive Deep Inelastic Scattering in Wandzura-Wilczek-type approximation

   S. Bastami🇺🇸 · H. Avakian🇺🇸 · A. V. Efremov🇷🇺 · A. Kotzinian🇦🇲 · B. U. Musch🇩🇪 · B. Parsamyan🇨🇭 · A. Prokudin🇺🇸 · M. Schlegel🇺🇸 · G. Schnell🇪🇸 · P. Schweitzer🇺🇸 · K. Tezgin🇺🇸

   We present the complete cross-section for the production of unpolarized hadrons in semi-inclusive deep-inelastic scattering up to power-suppressed $\mathcal{O}(1/Q^2)$ terms in the Wandzura--Wilczek-type approximation which consists in systematically assuming that $\bar{q}gq$--terms are much smaller than $\bar{q}q$--correlators. We compute all twist-2 and twist-3 structure functions and the corresponding asymmetries, and discuss the applicability of the Wandzura--Wilczek-type approximations on the basis of available data. We make predictions that can be tested by data from Jefferson Lab, COMPASS, HERMES, and the future Electron-Ion Collider. The results of this paper can be readily used for phenomenology and for event generators, and will help to improve our understanding of the TMD theory beyond leading twist.

   hep-phhep-exJHEP(2019)·77 citations
9. 09*

   Global fits in the Georgi-Machacek model

   Cheng-Wei Chiang🇹🇼 · Giovanna Cottin🇹🇼 · Otto Eberhardt🇪🇸

   Off the beaten track of scalar singlet and doublet extensions of the Standard Model, triplets combine an interesting LHC phenomenology with an explanation for neutrino masses. The Georgi-Machacek model falls into this category, but it has never been fully explored in a global fit. We use the {\texttt{HEPfit}} package to combine recent experimental Higgs data with theoretical constraints and obtain strong limits on the mixing angles and mass differences between the heavy new scalars as well as their decay widths. We also find that the current signal strength measurements allow for a Higgs to vector boson coupling with an opposite sign to the Standard Model, but this possibility can be ruled out by the lack of direct evidence for heavy Higgs states. For these hypothetical particles, we identify the dominant decay channels and extract bounds on their branching ratios from the global fit, which can be used to single out the decay patterns relevant for the experimental searches.

   hep-phhep-exPRD(2019)·57 citations
10. 10*

    Measuring the Boiling Point of the Vacuum of Quantum Electrodynamics

    Anthony Hartin🇬🇧 · Andreas Ringwald🇩🇪 · Natalia Tapia🇨🇱

    It is a long-standing non-trivial prediction of quantum electrodynamics that its vacuum is unstable in the background of a static, spatially uniform electric field and, in principle, sparks with spontaneous emission of electron-positron pairs. However, an experimental verification of this prediction seems out of reach because a sizeable rate for spontaneous pair production requires an extraordinarily strong electric field strength $|\mathbf{E}|$ of order the Schwinger critical field, ${\mathrm{E}}_c=m_e^2/e\simeq 1.3\times 10^{18}V/m$, where $m_e$ is the electron mass and $e$ is its charge. Here, we show that the measurement of the rate of pair production due to the decays of high-energy bremsstrahlung photons in a high-intensity laser field allows for the experimental determination of the Schwinger critical field and thus the boiling point of the vacuum of quantum electrodynamics.

    hep-phPRD(2019)·59 citations
11. 11*

    Exploring Sensitivity to NMSSM Signatures with Low Missing Transverse Energy at the LHC

    A. Titterton🇬🇧 · U. Ellwanger🇫🇷 · H.U. Flaecher🇬🇧 · S. Moretti🇬🇧 · C.H. Shepherd-Themistocleous🇬🇧

    We examine scenarios in the Next-to-Minimal Supersymmetric Standard Model (NMSSM), where pair-produced squarks and gluinos decay via two cascades, each ending in a stable neutralino as Lightest Supersymmetric Particle (LSP) and a Standard Model (SM)-like Higgs boson, with mass spectra such that the missing transverse energy, $E_T^{\text{miss}}$, is very small. Performing two-dimensional parameter scans and focusing on the hadronic $H\to b\bar{b}$ decay giving a $b\bar{b}b\bar{b}+E_T^{\text{miss}}$ final state we explore the sensitivity of a current LHC general-purpose jets+$E_T^{\text{miss}}$ analysis to such scenarios.

    hep-phJHEP(2018)·13 citations
12. 12*

    On-the-fly reduction of open loops

    Federico Buccioni🇨🇭 · Jean-Nicolas Lang🇨🇭 · Stefano Pozzorini🇨🇭 · Hantian Zhang🇨🇭 · Max Zoller🇨🇭

    We describe new developments in the OpenLoops framework based on the recently introduced on-the-fly method. The on-the-fly approach exploits the factorisation of one-loop diagrams into segments in order to perform various operations, such as helicity summation, diagram merging and the reduction of Feynman integrands in between the recursion steps for the amplitude construction. This method significantly reduces the complexity of scattering amplitude calculations for multi-particle processes, leading to a major increase in CPU efficiency and numerical stability. The unification of the reduction to scalar integrals with the amplitude construction in a single algorithm, allows to identify problematic kinematical configurations and cure numerical instabilities in single recursion steps. A simple permutation trick in combination with a one-parameter expansion for a single topology, which is now implemented to any order, eliminate rank-two Gram determinant instabilities altogether. Due to this any-order expansion, the numerical accuracy of the algorithm can be determined with a rescaling test. The on-the-fly algorithm is fully implemented for double and quadruple precision, which allows for true quadruple precision benchmarks with up to 32 correct digits as well as a powerful rescue system for unstable points. We present first speed and stability results for these new features. The on-the-fly algorithm is part of the forthcoming release of OpenLoops 2.

    hep-phPoS(2018)·2 citations
13. 13*

    Combined explanations of B-physics anomalies: the sterile neutrino solution

    Aleksandr Azatov🇮🇹 · Daniele Barducci🇮🇹 · Diptimoy Ghosh🇮🇹 · David Marzocca🇮🇹 · Lorenzo Ubaldi🇮🇹

    In this paper we provide a combined explanation of charged- and neutral-current $B$-physics anomalies assuming the presence of a light sterile neutrino $N_R$ which contributes to the $B\to D^{(\ast )}\tau \nu$ processes. We focus in particular on two simplified models, where the mediator of the flavour anomalies is either a vector leptoquark $U_1^{\mu }\sim (3,1,2/3)$ or a scalar leptoquark $S_1\sim (\bar{3},1,1/3)$. We find that $U_1^{\mu }$ can successfully reproduce the required deviations from the Standard Model while being at the same time compatible with all other flavour and precision observables. The scalar leptoquark instead induces a tension between $B_s$ mixing and the neutral-current anomalies. For both states we present the limits and future projections from direct searches at the LHC finding that, while at present both models are perfectly allowed, all the parameter space will be tested with more luminosity. Finally, we study in detail the cosmological constraints on the sterile neutrino $N_R$ and the conditions under which it can be a candidate for dark matter.

    hep-phJHEP(2018)·87 citations
14. 14*

    Power Corrections for N-Jettiness Subtractions at $\mathcal{O}({\alpha }_s)$

    Markus A. Ebert🇺🇸 · Ian Moult🇺🇸 · Iain W. Stewart🇺🇸 · Frank J. Tackmann🇩🇪 · Gherardo Vita🇺🇸 · Hua Xing Zhu🇨🇳

    We continue the study of power corrections for $N$-jettiness subtractions by analytically computing the complete next-to-leading power corrections at $\mathcal{O}({\alpha }_s)$ for color-singlet production. This includes all nonlogarithmic terms and all partonic channels for Drell-Yan and gluon-fusion Higgs production. These terms are important to further improve the numerical performance of the subtractions, and to better understand the structure of power corrections beyond their leading logarithms, in particular their universality. We emphasize the importance of computing the power corrections differential in both the invariant mass, $Q$, and rapidity, $Y$, of the color-singlet system, which is necessary to account for the rapidity dependence in the subtractions. This also clarifies apparent disagreements in the literature. Performing a detailed numerical study, we find excellent agreement of our analytic results with a previous numerical extraction.

    hep-phJHEP(2018)·105 citations
15. 15*

    Boosting $H\to b\bar{b}$ with Machine Learning

    Joshua Lin🇺🇸 · Marat Freytsis🇺🇸 · Ian Moult🇺🇸 · Benjamin Nachman🇺🇸

    High $p_T$ Higgs production at hadron colliders provides a direct probe of the internal structure of the $gg\to H$ loop with the $H\to b\bar{b}$ decay offering the most statistics due to the large branching ratio. Despite the overwhelming QCD background, recent advances in jet substructure have put the observation of the $gg\to H\to b\bar{b}$ channel at the LHC within the realm of possibility. In order to enhance the sensitivity to this process, we develop a two stream convolutional neural network, with one stream acting on jet information and one using global event properties. The neural network significantly increases the discovery potential of a Higgs signal, both for high $p_T$ Standard Model production as well for possible beyond the Standard Model contributions. Unlike most studies for boosted hadronically decaying massive particles, the boosted Higgs search is unique because double $b$-tagging rejects nearly all background processes that do not have two hard prongs. In this context --- which goes beyond state-of-the-art two-prong tagging --- the network is studied to identify the origin of the additional information leading to the increased significance. The procedures described here are also applicable to related final states where they can be used to identify additional sources of discrimination power that are not being exploited by current techniques.

    hep-phhep-exJHEP(2018)·98 citations
16. 16*

    X-Ray Polarization Signals from Magnetars with Axion-Like-Particles

    Jean-François Fortin🇨🇦 · Kuver Sinha🇺🇸

    Axion-like-particles (ALPs) produced in the core of a magnetar can convert to photons in the magnetosphere, giving rise to novel features in the X-ray spectrum. Since ALPs only mix with the parallel mode of the photon, the polarization of the soft and hard X-ray spectra is predicted to have an O-mode component, in addition to the mainly X-mode component given by most astrophysical models. The relative strength of the O-mode component depends on the intensity of ALPs produced in the core and the probability of conversion. We quantify our results by considering X-ray emission produced both by astrophysical processes and by ALP-photon conversion, in an uncorrelated fashion, and in different relative proportions, which we parametrize by the angle ${\chi }_0$. We then define a normalized astrophysics-subtracted Stokes parameter $R$ which only acquires non-zero values in the presence of ALP-photon conversion. We find, remarkably, that the parameter $R$ factorizes into a product of the ALP-to-photon conversion probability and $\cos (2{\chi }_0)$ and display $R$, as well as the usual Stokes parameter $Q$, as a function of the photon energy and relative fractions of ALP and photon intensities. For benchmark points currently allowed by the CAST experiment, the O-mode prediction can be tested in future X-ray polarimeters and used either to constrain ALPs or find evidence for them.

    hep-phastro-ph.HEJHEP(2019)·36 citations
17. 17*

    Vector Fuzzy Dark Matter, Fifth Forces, and Binary Pulsars

    Diana López Nacir🇦🇷 · Federico R. Urban🇨🇿

    We study the secular effects that an oscillating background ultralight (fuzzy) cosmological vector field has on the dynamics of binary systems; such effects appear when the field and the binary are in resonance. We first consider the gravitational interaction between the field and the systems, and quantify the main differences with an oscillating background scalar field. If the energy density of such a field is sufficiently large, as required if it is supposed to be all of the dark matter, we show that the secular effects could yield potentially observable signatures in high precision time of arrival measurements of binary pulsars. We then analyse the secular effects that arise when the field is directly coupled to the bodies in the binary. We show that this study is particularly relevant for models where fuzzy dark matter mediates a baryonic force $B$ (or $B-L$, with $L$ the lepton number), due to the stellar amount of nucleons present in the stars. The constraints we obtain from current data are already competitive with (or even more constraining than) laboratory tests of the equivalence principle.

    ↳ astro-ph.COhep-phJCAP(2018)·37 citations
18. 18*

    On the low-energy limit of the QED N-photon amplitudes: part 2

    James P. Edwards🇲🇽 · Adolfo Huet🇲🇽 · Christian Schubert🇲🇽

    In recent work, Gies and Karbstein have discovered that the two-loop Euler-Heisenberg Lagrangians for scalar and spinor QED have non-vanishing reducible contributions in addition to the well-studied irreducible ones. This invalidates previous applications of those Lagrangians to the computation of the two-loop $N$-photon amplitudes in the low energy limit. Here we compute the corrections to those amplitudes due to the reducible contributions.

    ↳ hep-thhep-phNPB(2018)·15 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.