Wed·Jan 15, 2020Wednesday·January 15, 2020

1. 01*

   On dark atoms, massive dark photons and millicharged sub-components

   Felix Kahlhoefer🇩🇪 · Einar Urdshals🇩🇪

   We present a simple model of two dark matter species with opposite millicharge that can form electrically neutral bound states via the exchange of a massive dark photon. If bound state formation is suppressed at low temperatures, a sub-dominant fraction of millicharged particles remains at late times, which can give rise to interesting features in the 21 cm absorption profile at cosmic dawn. The dominant neutral component, on the other hand, can have dipole interactions with ordinary matter, leading to non-standard signals in direct detection experiments. We identify the parameter regions predicting a percent-level ionisation fraction and study constraints from laboratory searches for dark matter scattering and dark photon decays.

   hep-phastro-ph.COPLB(2020)·11 citations
2. 02*

   Sub-femtometer scale color charge correlations in the proton

   Adrian Dumitru🇺🇸 · Vladimir Skokov🇺🇸 · Tomasz Stebel🇵🇱

   Color charge correlations in the proton at moderately small $x\sim 0.1$ are extracted from its light-cone wave function. The charge fluctuations are far from Gaussian and they exhibit interesting dependence on impact parameter and on the relative transverse momentum (or distance) of the gluon probes. We provide initial conditions for small-$x$ Balitsky-Kovchegov evolution of the dipole scattering amplitude with impact parameter and $\hat{r}\cdot \hat{b}$ dependence, and with non-zero $C$-odd component due to three-gluon exchange. Lastly, we compute the (forward) Weizsaecker-Williams gluon distributions, including the distribution of linearly polarized gluons, up to fourth order in $A^{+}$. The correction due to the quartic correlator provides a transverse momentum scale, $q>0.5$ GeV, for nearly maximal polarization.

   hep-phnucl-thPRD(2020)·23 citations
3. 03*

   Two-body weak decays of doubly charmed baryons

   Hai-Yang Cheng🇹🇼 · Guanbao Meng🇨🇳 · Fanrong Xu🇨🇳 · Jinqi Zou🇨🇳

   The hadronic two-body weak decays of the doubly charmed baryons ${\Xi }_{cc}^{++},{\Xi }_{cc}^{+}$ and ${\Omega }_{cc}^{+}$ are studied in this work. To estimate the nonfactorizable contributions, we work in the pole model for the $P$-wave amplitudes and current algebra for $S$-wave ones. For the ${\Xi }_{cc}^{++}\to {\Xi }_c^{+}{\pi }^{+}$ mode, we find a large destructive interference between factorizable and nonfactorizable contributions for both $S$- and $P$-wave amplitudes. Our prediction of $\sim 0.70\%$ for its branching fraction is smaller than the earlier estimates in which nonfactorizable effects were not considered, but agrees nicely with the result based on an entirely different approach, namely, the covariant confined quark model. On the contrary, a large constructive interference was found in the $P$-wave amplitude by Dhir and Sharma, leading to a branching fraction of order $(7-16)\%$. Using the current results for the absolute branching fractions of $({\Lambda }_c^{+},{\Xi }_c^{+})\to p{K}^{-}{\pi }^{+}$ and the LHCb measurement of ${\Xi }_{cc}^{++}\to {\Xi }_c^{+}{\pi }^{+}$ relative to ${\Xi }_{cc}^{++}\to {\Lambda }_c^{+}{K}^{-}{\pi }^{+}{\pi }^{+}$, we obtain $\text{B}({\Xi }_{cc}^{++}\to {\Xi }_c^{+}{\pi }^{+}{)}_{\mathrm{expt}}\approx (1.83\pm 1.01)\%$ after employing the latest prediction of $\text{B}({\Xi }_{cc}^{++}\to {\Sigma }_c^{++}{\overline{K}}^{\ast 0})$. Our prediction of $\mathcal{B}({\Xi }_{cc}^{++}\to {\Xi }_c^{+}{\pi }^{+})\approx 0.7\%$ is thus consistent with the experimental value but in the lower end. It is important to pin down the branching fraction of this mode in future study. Factorizable and nonfactorizable $S$-wave amplitudes interfere constructively in ${\Xi }_{cc}^{+}\to {\Xi }_c^0{\pi }^{+}$. Its large branching fraction of order 4\% may enable experimentalists to search for the ${\Xi }_{cc}^{+}$ through this mode. That is, the ${\Xi }_{cc}^{+}$ is reconstructed through the ${\Xi }_{cc}^{+}\to {\Xi }_c^0{\pi }^{+}$ followed by the decay chain ${\Xi }_c^0\to {\Xi }^{-}{\pi }^{+}\to p{\pi }^{-}{\pi }^{-}{\pi }^{+}$.

   hep-phhep-exPRD(2020)·42 citations
4. 04*

   Gravitational Waves from first-order phase transition and domain wall

   Ruiyu Zhou🇨🇳 · Jing Yang🇨🇳 · Ligong Bian🇨🇳

   In many particle physics models, domain wall can form during the phase transition process after discrete symmetry breaking. We study the scenario within a complex singlet extended Standard Model framework, where a strongly first order phase transition can occur depending on the hidden scalar mass and the mixing between the extra heavy Higgs and the SM Higgs mass. The gravitational wave spectrum is of a typical two-peak shape, the amplitude and the peak from the strongly first order phase transition is able to be probed by the future space-based interferometers, and the one locates around the peak from the domain wall decay is far beyond the capability of the current PTA, and future SKA.

   hep-phastro-ph.COJHEP(2020)·36 citations
5. 05*

   Heavy neutral leptons at ANUBIS

   Martin Hirsch🇪🇸 · Zeren Simon Wang🇰🇷

   Recently Bauer $\text{et al.}$ arXiv:1909.13022 proposed ANUBIS, an auxiliary detector to be installed in one of the shafts above the ATLAS or CMS interaction point, as a tool to search for long-lived particles. Here, we study the sensitivity of this proposal for long-lived heavy neutral leptons (HNLs) in both minimal and extended scenarios. We start with the minimal HNL model where both production and decay of the HNLs are mediated by active-sterile neutrino mixing, before studying the case of right-handed neutrinos in a left-right symmetric model. We then consider a $U(1{)}_{B-L}$ extension of the SM. In this model HNLs are produced from the decays of the mostly SM-like Higgs boson, via mixing in the scalar sector of the theory. In all cases, we find that ANUBIS has sensitivity reach comparable to the proposed MATHUSLA detector. For the minimal HNL scenario, the contributions from $W$'s decaying to HNLs are more important at ANUBIS than at MATHUSLA, extending the sensitivity to slightly larger HNL masses at ANUBIS.

   hep-phPRD(2020)·80 citations
6. 06*

   Big Bounce Baryogenesis

   Neil D. Barrie🇯🇵

   We explore the possibility of an Ekpyrotic contraction phase harbouring a mechanism for Baryogenesis. A Chern-Simons coupling between the fast-rolling Ekpyrotic scalar and the Standard Model Hypercharge gauge field enables the generation of a non-zero helicity during the contraction phase. The baryon number subsequently produced at the Electroweak Phase Transition is consistent with observation for a range of couplings and bounce scales. Simultaneously, the gauge field production during the contraction provides the seeds for galactic magnetic fields and sources gravitational waves, which may provide additional avenues for observational confirmation.

   hep-phgr-qcJCAP(2020)·10 citations
7. 07*

   Theory status and implications of $R_K^{(\ast )}$

   Avelino Vicente🇪🇸

   The LHCb and Belle collaborations have reported on some anomalies in $b\to s$ transitions, with discrepancies with the Standard Model predictions in some angular observables and branching ratios and intriguing hints for lepton universality violation. We will review the current situation and explore the proposed New Physics explanations for these tensions. We will also discuss the possible connection of the $b\to s$ anomalies to other central problems in physics, such as the dark matter of the Universe, the origin of neutrino masses or the strong CP problem.

   hep-phhep-exPoS(2020)·3 citations
8. 08*

   On the momentum transfer dependence of the phase in elastic scattering

   Vladimir A. Petrov🇷🇺

   The question is discussed: to what extent the often assumed independence of the phase of the elastic scattering amplitude from the momentum transfer \textit{in the region of only small values} of $t$ limits $t$-dependence of the phase generally. Analyticity allows to give a proof that if the phase of a strong interaction scattering amplitude is independent on the transferred momentum $t$ at small values of $t$ then it does so in all physical region. Moreover, if such an independence holds in any physical energy $\sqrt{s}$ region including the values infinitesimally close to the first inelastic threshold from below the whole scattering amplitude vanishes. Relationship of the $t$-dependence of the phase with the size of the interaction range is also discussed.

   hep-phhep-th1 citation
9. 09*

   Lightening Gravity-Mediated Dark Matter

   Yoo-Jin Kang🇰🇷 · Hyun Min Lee🇰🇷

   We revisit the scenario of a massive spin-2 particle as the mediator for communicating between dark matter of arbitrary spin and the Standard Model. Taking the general couplings of the spin-2 particle in the effective theory, we discuss the thermal production mechanisms for dark matter with various channels and the dark matter self-scattering. For WIMP and light dark matter cases, we impose the relic density condition and various experimental constraints from direct and indirect detections, precision measurements as well as collider experiments. We show that it is important to include the annihilation of dark matter into a pair of spin-2 particles in both allowed and forbidden regimes, thus opening up the consistent parameter space for dark matter. The benchmark models of the spin-2 mediator are presented in the context of the warped extra dimension and compared to the simplified models.

   hep-phastro-ph.COhep-thEPJC(2020)·42 citations
10. 10*

    A Potentially Detectable Gamma-Ray Line in the Fermi Galactic Center Excess -- In Light of One-Step Cascade Annihilations of Secluded (Vector) Dark Matter via the Higgs Portal

    Kwei-Chou Yang🇹🇼

    We show the presence of a potentially detectable gamma-ray line in the Fermi Galactic center excess in light of the secluded (vector) dark matter (DM) model in which the hidden scalar, nearly degenerate with DM in mass, mediates the interaction of the secluded DM with the Standard Model (SM) due to its mixing with the SM Higgs. We find that the parameter region $m_X\in [60,132]$ GeV can provide a good fit to the Fermi Galactic center gamma-ray excess spectrum, appearing a prominent gamma-ray line with the energy $\in [30,66]$ GeV. The best fit gives $m_X\simeq m_S\simeq 86$ GeV with a $p$-value$=0.42$, so that the resultant gamma-ray line, arising from the decay of the scalar mediator into $\gamma \gamma$, peaks at 43 GeV. We derive constraints on the annihilation cross section from the Fermi-LAT gamma-ray line search, gamma-ray observations of the Fermi-LAT dwarf spheroidal galaxies, and Planck cosmic microwave background measurement. For the secluded vector DM model, the parameter space constrained by the current XENON1T and future LUX-ZEPLIN is shown. Finally, for the mixing angle between the Higgs sectors, we discuss its lower bound, which is required by the big bang nucleosynthesis constraint and relevant to the hidden sector decoupling temperature.

    hep-phastro-ph.COastro-ph.GAastro-ph.HEJHEP(2020)·9 citations
11. 11*

    ${\Lambda }_b(6146{)}^0$ state newly observed by LHCb

    K. Azizi🇮🇷 · Y. Sarac🇹🇷 · H. Sundu🇹🇷

    We study the bottom ${\Lambda }_b(6146{)}^0$ baryon, newly discovered by the LHCb Collaboration. By adopting an interpolating current of $(L_{\rho },L_{\lambda })=(0,2)$ type and $D$-wave nature with spin-parity quantum numbers $J^P={\frac{3}{2}}^{+}$ for this heavy bottom baryon, we calculate its mass and residue. Using these spectroscopic parameters, we also investigate its dominant decays ${\Lambda }_b(6146{)}^0\to {\Sigma }_b\pi$ and ${\Lambda }_b(6146{)}^0\to {\Sigma }_b^{\ast }\pi$ and estimate the width of ${\Lambda }_b(6146{)}^0$ obtained via these channels. The obtained mass, $m_{{\Lambda }_b}=(6144\pm 68)$~MeV is in accord nicely with the experimental data. The width obtained via the dominant channels is also consistent with the experimental data of LHCb collaboration. We calculate the spectroscopic parameters and the same decay channels for the $c$-partner of ${\Lambda }_b(6146{)}^0$ state, namely ${\Lambda }_c(2860{)}^{+}$, as well. We compare the obtained results with the existing theoretical predictions as well as experimental data. The results indicate that the state ${\Lambda }_b(6146{)}^0$ and its charmed-partner ${\Lambda }_c(2860{)}^{+}$ can be considered as $1D$-wave baryons with $J^P={\frac{3}{2}}^{+}$.

    hep-phhep-exhep-latPRD(2020)·23 citations
12. 12*

    Why ${\alpha }_s$ Cannot be Determined from Hadronic Processes without Simultaneously Determining the Parton Distributions

    Stefano Forte🇮🇹 · Zahari Kassabov🇬🇧

    We show that any determination of the strong coupling ${\alpha }_s$ from a process which depends on parton distributions, such as hadronic processes or deep-inelastic scattering, generally does not lead to a correct result unless the parton distributions (PDFs) are determined simultaneously along with ${\alpha }_s$. We establish the result by first showing an explicit example, and then arguing that the example is representative of a generic situation which we explain using models for the shape of equal ${\chi }^2$ contours in the joint space of ${\alpha }_s$ and the PDF parameters.

    hep-phhep-exEPJC(2020)·52 citations
13. 13*

    Anomaly Detection with Density Estimation

    Benjamin Nachman🇺🇸 · David Shih🇺🇸

    We leverage recent breakthroughs in neural density estimation to propose a new unsupervised anomaly detection technique (ANODE). By estimating the probability density of the data in a signal region and in sidebands, and interpolating the latter into the signal region, a likelihood ratio of data vs. background can be constructed. This likelihood ratio is broadly sensitive to overdensities in the data that could be due to localized anomalies. In addition, a unique potential benefit of the ANODE method is that the background can be directly estimated using the learned densities. Finally, ANODE is robust against systematic differences between signal region and sidebands, giving it broader applicability than other methods. We demonstrate the power of this new approach using the LHC Olympics 2020 R\&D Dataset. We show how ANODE can enhance the significance of a dijet bump hunt by up to a factor of 7 with a 10\% accuracy on the background prediction. While the LHC is used as the recurring example, the methods developed here have a much broader applicability to anomaly detection in physics and beyond.

    hep-phhep-exphysics.data-anstat.MLPRD(2020)·236 citations
14. 14*

    On the Sudakov form factor, and a factor of two

    Stefano Forte🇮🇹

    I answer a question that Roman Jackiw asked me, and I draw some lessons from the answer. The question is: why is the Sudakov form factor larger by a factor of two, if computed for off-shell fermions, in comparison to the on-shell case? The answer sheds some light on the interplay between infrared and collinear singularities -- and the importance of factors of two.

    hep-phhep-th3 citations
15. 15*

    R-Parity Violation and Direct Stau Pair Production at the LHC

    Herbert K. Dreiner🇩🇪 · Victor Martin Lozano🇩🇪

    We consider pair production of LSP staus at the LHC within R-parity violating supersymmetry. The staus decay into Standard Model leptons through the LLĒ operator. Using CheckMATE we have recast multileptonic searches to test such scenarios. We show for the first time that using these analyses the stau mass can be constrained up to 345 GeV, depending on the stau decay mode, as well as the stau mixing angle. However, there is for all scenarios a significant gap between the lower LEP limit on the stau mass and the onset of the LHC sensitivity. This approach can be used in the future to constrain the stau sector in the context of RPV lepton-number violating models.

    hep-ph4 citations
16. 16*

    Simulation Assisted Likelihood-free Anomaly Detection

    Anders Andreassen🇺🇸 · Benjamin Nachman🇺🇸 · David Shih🇺🇸

    Given the lack of evidence for new particle discoveries at the Large Hadron Collider (LHC), it is critical to broaden the search program. A variety of model-independent searches have been proposed, adding sensitivity to unexpected signals. There are generally two types of such searches: those that rely heavily on simulations and those that are entirely based on (unlabeled) data. This paper introduces a hybrid method that makes the best of both approaches. For potential signals that are resonant in one known feature, this new method first learns a parameterized reweighting function to morph a given simulation to match the data in sidebands. This function is then interpolated into the signal region and then the reweighted background-only simulation can be used for supervised learning as well as for background estimation. The background estimation from the reweighted simulation allows for non-trivial correlations between features used for classification and the resonant feature. A dijet search with jet substructure is used to illustrate the new method. Future applications of Simulation Assisted Likelihood-free Anomaly Detection (SALAD) include a variety of final states and potential combinations with other model-independent approaches.

    hep-phhep-exphysics.data-anstat.MLPRD(2020)·147 citations
17. 17*

    Fluid property of QGP in presence of magnetic field

    Souvik Paul🇮🇳 · Ankita Mishra🇮🇳 · Jayanta Dey🇮🇳 · Sarthak Satapathy🇮🇳 · Sabyasachi Ghosh🇮🇳

    Fluidity of quark-gluon plasma (QGP) is studied where interaction between quark and gluon is mapped through fugacity in particle distribution function using lattice quantum chromodynamics (LQCD) results.

    hep-phnucl-thDAE Symp.Nucl.Phys.(2019)·0 citations
18. 18*

    NJL model estimation of anisotropic electrical conductivity for quark matter in presence of magnetic field

    Jayanta Dey🇮🇳 · Sabyasachi Ghosh🇮🇳 · Aritra Bandyopadhyay🇧🇷 · Ricardo L. S. Farias🇧🇷 · Gastao Krein🇧🇷

    We have calculated electrical conductivity in the presence of a magnetic field by using the Nambu-Jona-Lasinio model.

    hep-phnucl-thDAE Symp.Nucl.Phys.(2019)·0 citations
19. 19*

    Role of interaction on electrical conductivity of QGP in presence of magnetic field

    Ankita Mishra🇮🇳 · Souvik Paul🇮🇳 · Jayanta Dey🇮🇳 · Sarthak Satapathy🇮🇳 · Sabyasachi Ghosh🇮🇳

    Effect of quantum chromodynamics (QCD) interaction in quark-gluon plasma on electrical conductivity is studied, where lattice quantum chromodynamics (LQCD) results are mapped through quark and gluon degeneracy.

    hep-phnucl-thDAE Symp.Nucl.Phys.(2019)·0 citations
20. 20*

    Causal aspects of effective QCD models

    Jayanta Dey🇮🇳 · Sabyasachi Ghosh🇮🇳 · Chowdhury Aminul Islam🇮🇳

    Here we studied the possible diffusion speed for relativistic fluid in different effective quantum chromodynamics models: Nambu-Jona-Lasinio (NJL), Polyakov loop extended NJL, entangled PNJL (EPNJL) model.

    hep-phnucl-thDAE Symp.Nucl.Phys.(2019)·0 citations
21. 21*

    Unitarity in Maxwell-Carroll-Field-Jackiw electrodynamics

    Manoel M. Ferreira · Jr. · Jose A. Helayël-Neto · Carlos M. Reyes · Marco Schreck · Pedro D.S. Silva

    In this work we focus on the Carroll-Field-Jackiw (CFJ) modified electrodynamics in combination with a CPT-even Lorentz-violating contribution. We add a photon mass term to the Lagrange density and study the question whether this contribution can render the theory unitary. The analysis is based on the pole structure of the modified photon propagator as well as the validity of the optical theorem. We find, indeed, that the massive CFJ-type modification is unitary at tree-level. This result provides a further example for how a photon mass can mitigate malign behaviors.

    ↳ hep-thhep-phPLB(2020)·24 citations
22. 22*

    Indications for extra scalars at LHC? -- BSM physics at future $e^{+}{e}^{-}$ colliders

    François Richard🇫🇷

    This paper intends to collect available data on searches for scalar resonances at LHC. It is suggested that, in the absence of SUSY, the most compelling picture is the composite framework, with the idea that the lightest particles are composite scalars of the pseudo-Nambu-Goldstone type, emerging from a broken symmetry at a higher scale, the h(125) boson being one of them. Searches in two-photons, Z-photon, ZZ into 4 leptons, top, h and W pairs are reviewed. A recent search based on lepton tagging from a spectator W/Z is also discussed. Aside from the already well-known scalar observed by CMS and LEP2 at 96 GeV, I discuss the evidence and the interpretation for a possible resonance observed in ZZ around 700 GeV by CMS and ATLAS and some evidence for a CP-odd scalar at ~400 GeV. Future searches at HL-LHC and at $e^{+}{e}^{-}$ colliders are briefly sketched.

    ↳ hep-exhep-ph14 citations
23. 23*

    Open string QED meson description of the X17 particle and dark matter

    Cheuk-Yin Wong🇺🇸

    As a quark and an antiquark cannot be isolated, the intrinsic motion of a composite $q\bar{q}$ system in its lowest-energy states lies predominantly in 1+1 dimensions, as in an open string with the quark and the antiquark at its two ends. Accordingly, we study the lowest-energy states of an open string $q\bar{q}$ system in QCD and QED in 1+1 dimensions. We show that ${\pi }^0,\eta$, and ${\eta }^{\prime }$ can be adequately described as open string $q\bar{q}$ QCD mesons. By extrapolating into the $q\bar{q}$ QED sector in which a quark and an antiquark interact with the QED interaction, we find an open string isoscalar $I(J^{\pi })$=$0(0^{-})$ QED meson state at 17.9$\pm$1.5 MeV and an isovector $(I(J^{\pi })$=$1(0^{-}),I_3$=0) QED meson state at 36.4$\pm$3.8 MeV. The predicted masses of the isoscalar and isovector QED mesons are close to the masses of the hypothetical X17 and E38 particles observed recently, making them good candidates for these particles. The decay products of QED mesons may show up as excess $e^{+}{e}^{-}$ and $\gamma \gamma$ pairs in the anomalous soft photon phenomenon associated with hadron productions in high-energy hadron-proton collisions and $e^{+}$-$e^{-}$ annihilations. Measurements of the invariant masses of excess $e^{+}{e}^{-}$ and $\gamma \gamma$ pairs will provide tests for the existence of the open string $q\bar{q}$ QED mesons. An assembly of gravitating QED mesons are expected to emit electron-positron pairs and/or gamma rays and their decay energies and lifetimes will be modified by their gravitational binding energies. Consequently, a self-gravitating isoscalar QED meson assembly whose mass $M$ and radius $R$ satisfy $(M/M_{\odot })/(R/R_{\odot })\gtrsim 4.71\times 10^5$ will not produce electron-positron pairs nor gamma rays and may be a good candidate for the primordial dark matter.

    ↳ nucl-thastro-ph.HEhep-phnucl-exJHEP(2020)·31 citations
24. 24*

    Pion valence quark distribution from current-current correlation in lattice QCD

    Raza Sabbir Sufian🇺🇸 · Colin Egerer🇺🇸 · Joseph Karpie🇺🇸 · Robert G. Edwards🇺🇸 · Bálint Joó🇺🇸 · Yan-Qing Ma🇨🇳 · Kostas Orginos🇺🇸 · Jian-Wei Qiu🇺🇸 · David G. Richards🇺🇸

    We extract the pion valence quark distribution $q_{\mathrm{v}}^{\pi }(x)$ from lattice QCD (LQCD) calculated matrix elements of spacelike correlations of one vector and one axial vector current analyzed in terms of QCD collinear factorization, using a new short-distance matching coefficient calculated to one-loop accuracy. We derive the Ioffe time distribution of the two-current correlations in the physical limit by investigating the finite lattice spacing, volume, quark mass, and higher-twist dependencies in a simultaneous fit of matrix elements computed on four gauge ensembles. We find remarkable consistency between our extracted $q_{\mathrm{v}}^{\pi }(x)$ and that obtained from experimental data across the entire $x$-range. Further, we demonstrate that the one-loop matching coefficient relating the LQCD matrix computed in position space to the $q_{\mathrm{v}}^{\pi }(x)$ in momentum space has well-controlled behavior with Ioffe time. This justifies that LQCD calculated current-current correlations are good observables for extracting partonic structures by using QCD factorization, which complements to the global effort to extract partonic structure from experimental data.

    ↳ hep-lathep-exhep-phnucl-ex+1PRD(2020)·125 citations
25. 25*

    Degenerate Bogdanov-Takens bifurcations in a bulk viscous cosmology

    Asmaa Abdel Azim🇪🇬 · Adel Awad🇪🇬 · E. I. Lashin🇪🇬

    Using the dynamical system theory we show that the Friedmann-Robertson-Walker (FRW) cosmological model with bulk viscous fluid in the presence of cosmological constant is equivalent to a degenerate two dimensional Bogdanov-Takens normal form. The equation of state parameter, $\omega$, the bulk viscosity coefficient, $\xi$, and the cosmological constant, $\Lambda$, define the necessary parameters for unfolding the degenerate Bogdanov-Takens system. The fixed points of the system are discussed together with the variation of their stability properties upon changing the relevant parameters $\omega$, $\Lambda$ and $\xi$. The variation of the stability properties are visualized by the appropriate bifurcation diagrams. Phase portrait for finite domain and global phase portrait are displayed and the issue of the structural stability is discussed. Typical issues such as late acceleration or inflation that can be induced by viscosity and could have relevance to observational cosmology are also discussed.

    ↳ gr-qchep-phhep-thEPJC(2020)·3 citations
26. 26*

    Bounds on secret neutrino interactions from high-energy astrophysical neutrinos

    Mauricio Bustamante🇩🇰 · Charlotte Amalie Rosenstroem🇩🇰 · Shashank Shalgar🇩🇰 · Irene Tamborra (Bohr Inst. & U. Copenhagen (main) & DARK)🇩🇰

    Neutrinos offer a window to physics beyond the Standard Model. In particular, high-energy astrophysical neutrinos, with TeV-PeV energies, may provide evidence of new, "secret" neutrino-neutrino interactions that are stronger than ordinary weak interactions. During their propagation over cosmological distances, high-energy neutrinos could interact with the cosmic neutrino background via secret interactions, developing characteristic energy-dependent features in their observed energy distribution. For the first time, we look for signatures of secret neutrino interactions in the diffuse flux of high-energy astrophysical neutrinos, using 6 years of publicly available IceCube High Energy Starting Events (HESE). We find no significant evidence for secret neutrino interactions, but place competitive upper limits on the coupling strength of the new mediator through which they occur, in the mediator mass range of 1-100 MeV.

    ↳ astro-ph.HEhep-phPRD(2020)·86 citations
27. 27*

    Aspects of Conformal Supergravity

    Sergio Ferrara🇨🇭 · Alex Kehagias🇬🇷 · Dieter Lust🇩🇪

    In these lectures we discuss N-extended conformal supergravity and its spectrum in four dimensions. These theories can be considered as the massless limit of Einstein-Weyl supergravity and by taking into account their enhanced gauge symmetries, we derive their massless spectrum, which in general contains a dipole-ghost graviton multiplet and an N-fold tripole-ghost gravitino multiplet.

    ↳ hep-thhep-ph12 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.