Thu·Feb 17, 2022Thursday·February 17, 2022

1. 01*

   Non-local slicing approaches for NNLO QCD in MCFM

   John M. Campbell🇺🇸 · R. Keith Ellis🇬🇧 · Satyajit Seth🇮🇳

   We present the implementation of several processes at Next-to-Next-to Leading Order (NNLO) accuracy in QCD in the parton-level Monte Carlo program MCFM. The processes treated are $pp\to H$, $W^{\pm }$, $Z$, $W^{\pm }H$, $ZH$, $W^{\pm }\gamma$, $Z\gamma$ and $\gamma \gamma$ and, for the first time in the code, $W^{+}{W}^{-}$, $W^{\pm }Z$ and $ZZ$. Decays of the unstable bosons are fully included, resulting in a flexible fully differential Monte Carlo code. The NNLO corrections have been calculated using two non-local slicing approaches, isolating the doubly unresolved region by cutting on the zero-jettiness, ${\mathcal{T}}_0$, or on $q_T$, the transverse momentum of the colour singlet final-state particles. We find that for most, but not all processes the $q_T$ slicing method leads to smaller power corrections for equal computational burden.

   hep-phJHEP(2022)·19 citations
2. 02*

   Dark Sector as Origin of Light Lepton Mass and Its Phenomenology

   Cheng-Wei Chiang🇹🇼 · Ryomei Obuchi🇯🇵 · Kei Yagyu🇯🇵

   We discuss a model with a dark sector, in which smallness of mass for charged leptons and neutrinos can naturally be explained by one-loop effects mediated by particles in the dark sector. These new particles, including dark matter candidates, also contribute to the anomalous magnetic dipole moment, denoted by $(g-2)$, for charged leptons. We show that our model can explain the muon $(g-2)$ anomaly and observed neutrino oscillations under the constraints from lepton flavor violating decays of charged leptons. We illustrate that the scenario with scalar dark matter is highly constrained by direct searches at the LHC, while that with fermionic dark matter allows for considering dark scalars with masses of order 100 GeV. Our scenario can be tested by a precise measurement of the muon Yukawa coupling as well as the direct production of dark scalar bosons at future electron-positron colliders.

   hep-phJHEP(2022)·11 citations
3. 03*

   An Exploration of Higher Order Flavor Sum Rules

   Saquib Hassan🇬🇧

   We explore the idea of higher-order flavor sum rules, i.e. sum rules that hold to higher orders in the flavor symmetry-breaking parameters. In particular, we consider isospin sum rules based on $B\to n\pi$ decays, and U-spin sum rules based on $B_d$ and $B_s$ decays to $n$ charged pions and/or kaons. We also demonstrate that sum rules exist to arbitrary orders by considering decay modes with increasing number of final state mesons $n$. Finally, we identify various theoretical and practical issues that need to be addressed in utilizing these sum rules.

   hep-ph5 citations
4. 04*

   Decays of Roper-like singly heavy baryons in a chiral model

   Daiki Suenaga🇯🇵 · Atsushi Hosaka🇯🇵

   We present a chiral model describing decays of the Roper-like ${\Lambda }_c(2765)$ and ${\Xi }_c(2970)$ as well as those of the heavy quark spin-doublet $\{{\Sigma }_c(2455),{\Sigma }_c(2520)\}$ and $\{{\Xi }_c^{\prime },{\Xi }_c(2645)\}$, by focusing on chiral representations of diquarks inside the heavy baryons. Based on our chiral model together with the heavy quark spin symmetry, we derive a relation satisfied by axial charges of the heavy baryons that controls magnitude of their one pion (kaon) decays. Besides, it is shown that the large decay widths of the Roper-like ${\Lambda }_c(2765)$ and ${\Xi }_c(2970)$, which cannot be implemented by conventional non-relativistic quark models, are explained by reasonable values of the axial charges. In addition, we apply the chiral model to bottom baryons and predict decay widths of the undiscovered Roper-like ${\Xi }_b$. We expect that our present investigation leads to elucidation of dynamical properties of the excited heavy baryons from the viewpoint of chiral symmetry.

   hep-phnucl-thPRD(2022)·13 citations
5. 05*

   Higgsino Dark Matter in Pure Gravity Mediated Supersymmetry

   Jason L. Evans🇨🇳 · Keith A. Olive🇺🇸

   We consider the prospects for the direct detection of dark matter in pure gravity meditation (PGM) models of supersymmetry breaking. Minimal PGM models require only two parameters, the gravitino mass, $m_{3/2}$, which sets the UV mass for all scalar masses, and $\tan \beta$. Gaugino masses are generated through anomaly mediation. Typically the lightest supersymmetric state (the dark matter candidate) is a wino. Here, we consider a one-parameter extension of the minimal model by allowing the Higgs soft masses to deviate from universality. For simplicity, we take these to be equal and use the $\mu$-term as a surrogate. We also consider non-universal stop masses. When $|\mu |\sim 1$ TeV, the Higgsino is a viable dark matter candidate when the gravitino mass is of order $\sim 1$ PeV and $\tan \beta \simeq 2$. We calculate the spin-dependent and spin-independent cross sections for dark matter scattering on protons. For spin-independent scattering, existing experimental limits place constraints on the PGM parameter space. Much of the currently allowed parameter space lies above the irreducible neutrino background. Thus, future direct detection experiments will be able to probe much of the remaining PGM parameter space.

   hep-phPRD(2022)·11 citations
6. 06*

   Phenomenology of $t\bar{t}j+X$ production at the LHC

   Simone Alioli🇮🇹 · Juan Fuster🇪🇸 · Maria Vittoria Garzelli🇩🇪 · Alessandro Gavardi🇮🇹 · Adrian Irles🇪🇸 · Davide Melini🇮🇱 · Sven-Olaf Moch🇩🇪 · Peter Uwer🇩🇪 · Katharina Voß🇩🇪

   We present phenomenological results for $t\bar{t}j+X$ production at the Large Hadron Collider, of interest for designing forthcoming experimental analyses of this process. We focus on those cases where the $t\bar{t}j+X$ process is considered as a signal. We discuss present theoretical uncertainties and the dependence on relevant input parameters entering the computation. For the $\mathcal{R}$ distribution, which depends on the invariant mass of the $t\bar{t}j$-system, we present reference predictions in the on-shell, $\overline{\text{mbox}MS}$ and MSR top-quark mass renormalization schemes, applying the latter scheme to this process for the first time. Our conclusions are particularly interesting for those analyses aiming at extracting the top-quark mass from cross-section measurements.

   hep-phJHEP(2022)·26 citations
7. 07*

   Elastic pion-proton and pion-pion scattering at high energies in holographic QCD

   Zhibo Liu🇨🇳 · Wei Xie🇨🇳 · Fei Sun🇨🇳 · Shuang Li🇨🇳 · Akira Watanabe🇨🇳

   The total and differential cross sections of high energy pion-proton and pion-pion scattering are investigated in a holographic QCD model, focusing on the Regge regime in which the Pomeron exchange gives the dominant contribution to those cross sections. The Pomeron is described by the Reggeized spin-2 particle propagator, and the hadron-Pomeron couplings are given by gravitational form factors of the hadrons, which are obtained from the bottom-up AdS/QCD models. Since the parameters, which characterize the Pomeron trajectory, have been determined in a preceding study of the proton-proton scattering, the pion-proton cross sections can be expressed with a single adjustable parameter. Once this parameter is determined by the experimental data of the pion-proton total cross section, its differential cross section and the pion-pion cross sections can be calculated without any additional parameter. Although the currently available data are limited, it is found that our calculation is consistent with those. Our predictions are explicitly shown, and the present model can be tested at the future experimental facilities.

   hep-phhep-exnucl-exnucl-thPRD(2022)·13 citations
8. 08*

   1-jettiness with jet axis at $O({\alpha }_s)$ in jeep inelastic scattering

   Zexuan Chu🇨🇳 · Yunlu Wang🇨🇳 · June-Haak Ee🇨🇳 · Jinhui Chen🇨🇳 · Daekyoung Kang🇨🇳

   We present $O({\alpha }_s)$ analytic predictions for event shape 1-jettiness ${\tau }_1$ distribution aiming measurements in deep inelastic scattering process at future Electron Ion Colliders. The result depends on conventional variables $x$ and $Q$ as well as on ${\tau }_1$ and is relatively compact and easy to implement for numerical calculation. Three different choices of axis, with respect to which ${\tau }_1$ is measured are considered in the Breit frame. The first is the one optimally adjusted to minimize ${\tau }_1$ and the second and third are taken from anti-$k_T$ and Centauro jet algorithms defined with a jet radius parameter $R$, respectively. We find that the first and second give the same result at this order and are independent of $R$, while the third depends on the radius. This fixed-order result provides a nonsingular contribution to be combined with a singular log-resummed contribution to give the full spectrum in ${\tau }_1$ space and also shows how fixed-order and resummation regions change as a function of $x$ and $Q$.

   hep-phnucl-exnucl-thJHEP(2022)·10 citations
9. 09*

   Enhanced Next-to-Leading-Order Corrections to Weak Annihilation $B$-Meson Decays

   Cai-Dian Lü🇨🇳 · Yue-Long Shen🇨🇳 · Chao Wang🇨🇳 · Yu-Ming Wang🇨🇳

   We accomplish the analytical computation of the pure weak annihilation non-leptonic $B$-meson decay amplitudes at leading power in the heavy quark expansion. The novel observation regarding such fundamental hadronic quantities is that adding the missing hard-collinear contribution on top of the hard gluon exchange effect eliminates rapidity divergences entering the convolution integrals of factorization formulae. Subsequently we identify the perturbative enhancement mechanism due to the penguin contractions of the current-current operators from the weak effective Hamiltonian, which yields the significant impacts on the CP violating observables.

   hep-phhep-exhep-latNPB(2023)·35 citations
10. 10*

    Rare top-quark decays $t\to cg(g)$ in the aligned two-Higgs-doublet model

    Fang-Min Cai🇨🇳 · Shuichiro Funatsu🇨🇳 · Xin-Qiang Li🇨🇳 · Ya-Dong Yang🇨🇳

    We update the Standard Model (SM) predictions for the branching ratios of the rare top-quark decays $t\to cg(g)$, and evaluate the maximum rates that can be reached in the aligned as well as in the four conventional two-Higgs-doublet models (2HDMs) with ${\mathcal{Z}}_2$ symmetries. Taking into account the relevant constraints on the model parameters resulting from a global fit obtained at the $95.5\%$ confidence level, we find that the branching ratios of $t\to cg$ and $t\to cgg$ decays can reach up to $3.36\times 10^{-9}$ and $2.95\times 10^{-9}$ respectively, being therefore of the same order, in the aligned 2HDM (A2HDM). This is obviously different from the SM case, where the predicted branching ratio of the three-body decay $t\to cgg$ is about two orders of magnitude larger than that of the two-body decay $t\to cg$. On the other hand, compared with the SM predictions, no significant enhancements are observed in the four conventional 2HDMs with ${\mathcal{Z}}_2$ symmetries for the branching ratios of these two decays. Nevertheless, the predicted branching ratios of $t\to cg$ and $t\to cgg$ decays in the A2HDM are still out of the expected sensitivities of the future high-luminosity Large Hadron Collider and the Future Circular Collider in hadron-hadron mode.

    hep-phhep-exEPJC(2022)·9 citations
11. 11*

    Investigation of the MicroBooNE neutrino cross sections on Argon

    M. Martini🇫🇷 · M. Ericson🇫🇷 · G. Chanfray🇫🇷

    Experimental data of charged current inclusive neutrino cross sections on argon as a function of different variables have recently appeared. We have compared them to our theoretical approach. Overall we find an agreement in spite of a tendency of underestimation in some specific regions. A new aspect is the availability of data in terms of the energy transfer to the nucleus, which allows a better separation of the different reaction mechanisms. We explain the deterioration of agreement in specific kinematical conditions by the absence in our model of two-pion production and other inelastic channels, more important for MicroBooNE than for T2K.

    hep-phhep-exnucl-thPRC(2022)·10 citations
12. 12*

    Nuclear information entropy, gravitational form factor, and glueballs in AdS/QCD

    G. Karapetyan🇧🇷 · R. da Rocha🇧🇷

    The nuclear configurational entropy (NCE) is employed to derive two parameters encoding the Pomeron Regge trajectory and the spectrum of closed strings, which are also related to the glueball mass, precisely matching data of the TOTEM collaboration at the LHC. In the Regge regime of holographic QCD, the (Reggeized) glueball propagator and the gravitational form factor of the proton occupy a relevant spot in AdS/QCD. They are used for deriving the cross-sections for the TeV scale proton-proton scattering process, which are the main ingredient for computing the NCE. The nuclear configurational stability is also addressed.

    hep-phhep-thnucl-thEur.Phys.J.Plus(2022)·5 citations
13. 13*

    Dissipation of oscillating scalar backgrounds in an FLRW universe

    Zi-Liang Wang🇨🇳 · Wen-Yuan Ai🇬🇧

    We study the dissipation of oscillating scalar backgrounds in a spatially flat Friedmann-Lemaître-Robertson-Walker universe using non-equilibrium quantum field theory. To be concrete, a $Z_2$-symmetric two-scalar model with quartic interactions is used. For quasi-harmonic oscillations, we adopt the multi-scale analysis to obtain analytical approximate expressions for the evolution of the scalar background in terms of the retarded self-energy and retarded proper four-vertex function. Different from the case in flat spacetime, we find that in an expanding universe the condensate decay in this model can be complete only if the imaginary part of the retarded self-energy is not negligibly small. The microphysical interpretation of the imaginary parts of the retarded self-energy and retarded proper four-vertex function in terms of particle production is also discussed.

    hep-phgr-qchep-thJHEP(2022)·14 citations
14. 14*

    Probing an MeV-Scale Scalar Boson in Association with a TeV-Scale Top-Quark Partner at the LHC

    Bhaskar Dutta🇺🇸 · Sumit Ghosh🇺🇸 · Alfredo Gurrola🇺🇸 · Dale Julson🇺🇸 · Teruki Kamon🇺🇸 · Jason Kumar🇺🇸

    Searches for new low-mass matter and mediator particles have actively been pursued at fixed target experiments and at $e^{+}{e}^{-}$ colliders. It is challenging at the CERN LHC, but they have been searched for in Higgs boson decays and in $B$ meson decays by the ATLAS and CMS Collaborations, as well as in a low transverse momentum phenomena from forward scattering processes (e.g., FASER). We propose a search for a new scalar particle in association with a heavy vector-like quark. We consider the scenario in which the top quark ($t$) couples to a light scalar ${\varphi }^{\prime }$ and a heavy vector-like top quark $T$. We examine single and pair production of $T$ in $pp$ collisions, resulting in a final state with a top quark that decays purely hadronically, a $T$ which decays semileptonically ($T$ $\to$ $W$ + $b$ $\to$ $\ell$ $\nu$ $b$), and a ${\varphi }^{\prime }$ that is very boosted and decays to a pair of collimated photons which can be identified as a merged photon system. The proposed search is expected to achieve a discovery reach with signal significance greater than 5$\sigma$ (3$\sigma$) for $m(T)$ as large as 1.8 (2) TeV and $m({\varphi }^{\prime })$ as small as 1 MeV, assuming an integrated luminosity of 3000 fb${}^{-1}$. This search can expand the reach of $T$, and demonstrates that the LHC can probe low-mass, MeV-scale particles.

    hep-phJHEP(2023)·6 citations
15. 15*

    Higgs boson decay to charmonia via $c$-quark fragmentation

    Tao Han🇺🇸 · Adam K. Leibovich🇺🇸 · Yang Ma🇺🇸 · Xiao-Ze Tan🇺🇸

    We calculate the decay branching fractions of the Higgs boson to $J/\psi$ and ${\eta }_c$ via the charm-quark fragmentation mechanism for the color-singlet and color-octet states in the framework of non-relativistic QCD. The decay rates are governed by the charm-quark Yukawa coupling, unlike the decay $H\to J/\psi +\gamma$, which is dominated by the ${\gamma }^{\ast }$-$J/\psi$ mixing. We find that the decay branching fractions can be about $2\times 10^{-5}$ for $H\to c\bar{c}+J/\psi$, and $6\times 10^{-5}$ for $H\to c\bar{c}+{\eta }_c$. We comment on the perspective of searching for the Higgs boson to $J/\psi$ transition at the High-Luminosity LHC for testing the charm-quark Yukawa coupling.

    hep-phhep-exJHEP(2022)·10 citations
16. 16*

    Baryon Asymmetric Universe from Spontaneous CP Violation

    Kohei Fujikura🇯🇵 · Yuichiro Nakai🇨🇳 · Ryosuke Sato🇯🇵 · Masaki Yamada🇯🇵

    Spontaneous CP violation, such as the Nelson-Barr (NB) mechanism, is an attractive scenario for addressing the strong CP problem while realizing the observed phase of the Cabibbo-Kobayashi-Maskawa (CKM) quark-mixing matrix. However, not only the CKM phase but also the baryon asymmetric Universe requires sources of CP violation. In this study, we show that a supersymmetric NB mechanism can naturally accommodate the Affleck-Dine (AD) baryogenesis within a CP-invariant Lagrangian. The model provides flat directions associated with new heavy quarks. Focusing on one of the directions, we find that the correct baryon asymmetry is obtained with a sufficiently low reheating temperature which does not cause the gravitino problem. Some parameter space is consistent with the gravitino dark matter. We assess radiative corrections to the strong CP phase induced by gauge-mediated supersymmetry breaking and CP-violating heavy fields and show that the strong CP problem is solved in a viable parameter space where the visible sector supersymmetric particles must be lighter than O(100) TeV. Even in the case that they are heavier than the TeV scale, our model predicts the neutron electric dipole moment within the reach of the near future experiments. Our model addresses the electroweak naturalness problem, strong CP problem, baryon asymmetric Universe, and dark matter. Then, the model may give a new compelling paradigm of physics beyond the Standard Model.

    hep-phastro-ph.COJHEP(2022)·17 citations
17. 17*

    DIS physics at the EIC and LHeC and connections to the future LHC and $\nu$A programs

    T. J. Hobbs🇺🇸

    Deeply-inelastic scattering (DIS) stands to enter a golden age with the prospect of precision programs at the Electron-Ion Collider (EIC) and Large Hadron-electron Collider (LHeC). While these programs will be of considerable importance to resolving longstanding issues in (non)perturbative QCD as well as hadronic and nuclear structure, they will also have valuable implications for a wider range of physics at the Energy and Intensity Frontiers, including at the High-Luminosity LHC (HL-LHC) and future $\nu A$ facilities. In this plenary contribution, we highlight a number of salient examples of the potential HEP impact from the complementary EIC and LHeC programs drawn from their respective Yellow Report and Whitepaper. Interested readers are encouraged to consult the extensive studies and literature from which these examples are taken for more detail.

    hep-phhep-thnucl-thSciPost Phys.Proc.(2022)·2 citations
18. 18*

    Triple-leptoquark interactions for tree- and loop-level proton decays

    Ilja Doršner🇭🇷 · Svjetlana Fajfer🇸🇮 · Olcyr Sumensari🇫🇷

    We study the impact of triple-leptoquark interactions on matter stability for two specific proton decay topologies that arise at the tree- and one-loop level if and when they coexist. We demonstrate that the one-loop level topology is much more relevant than the tree-level one when it comes to the proton decay signatures despite the usual loop-suppression factor. We subsequently present detailed analysis of the triple-leptoquark interaction effects on the proton stability within one representative scenario to support our claim, where the scenario in question simultaneously features a tree-level topology that yields three-body proton decay $p\to e^{+}{e}^{+}{e}^{-}$ and a one-loop level topology that induces two-body proton decays $p\to {\pi }^0{e}^{+}$ and $p\to {\pi }^{+}\bar{\nu }$. We also provide a comprehensive list of the leading-order proton decay channels for all non-trivial cubic and quartic contractions involving three scalar leptoquark multiplets that generate triple-leptoquark interactions of our interest, where in the latter case one of the scalar multiplets is the Standard Model Higgs doublet.

    hep-phJHEP(2022)·21 citations
19. 19*

    Direct Estimate of the Post-Newtonian Parameter and Cosmic Curvature from Galaxy-scale Strong Gravitational Lensing

    Jun-Jie Wei🇨🇳 · Yun Chen🇨🇳 · Shuo Cao🇨🇳 · Xue-Feng Wu🇨🇳

    Einstein's theory of general relativity (GR) has been precisely tested on solar system scales, but extragalactic tests are still poorly performed. In this work, we use a newly compiled sample of galaxy-scale strong gravitational lenses to test the validity of GR on kiloparsec scales. In order to solve the circularity problem caused by the preassumption of a specific cosmological model based on GR, we employ the distance sum rule in the Friedmann-Lema\^ıtre-Robertson-Walker metric to directly estimate the parameterized post-Newtonian (PPN) parameter ${\gamma }_{\mathrm{PPN}}$ and the cosmic curvature ${\Omega }_k$ by combining observations of strong lensing and Type Ia supernovae. This is the first simultaneous measurement of ${\gamma }_{\mathrm{PPN}}$ and ${\Omega }_k$ without any assumptions about the contents of the universe or the theory of gravity. Our results show that ${\gamma }_{\mathrm{PPN}}=1.11_{-0.09}^{+0.11}$ and ${\Omega }_k=0.48_{-0.71}^{+1.09}$, indicating a strong degeneracy between the two quantities. The measured ${\gamma }_{\mathrm{PPN}}$, which is consistent with the prediction of 1 from GR, provides a precise extragalactic test of GR with a fractional accuracy better than 9.0\%. If a prior of the spatial flatness (i.e., ${\Omega }_k=0$) is adopted, the PPN parameter constraint can be further improved to ${\gamma }_{\mathrm{PPN}}=1.07_{-0.07}^{+0.07}$, representing a precision of 6.5\%. On the other hand, in the framework of GR (i.e., ${\gamma }_{\mathrm{PPN}}=1$), our results are still marginally compatible with zero curvature (${\Omega }_k=-0.12_{-0.36}^{+0.48}$), supporting no significant deviation from a flat universe.

    ↳ astro-ph.COgr-qchep-phApJL(2022)·17 citations
20. 20*

    Magnetic field induced hair structure in charmonium gluon-dissociation

    Jin Hu🇨🇳 · Shuzhe Shi🇨🇦 · Zhe Xu🇨🇳 · Jiaxing Zhao🇨🇳 · Pengfei Zhuang🇨🇳

    We study electromagnetic field effect on charmonium gluon-dissociation in quark-gluon plasma. With the effective Hamiltonian derived from QCD multipole expansion under an external electromagnetic field, we first solve the two-body Schrödinger equation for a pair of charm quarks with mean field potentials for color and electromagnetic interactions and obtain the charmonium binding energies and wave functions, and then calculate the gluon-dissociation cross-section and decay width by taking the color electric and magnetic dipole interactions as perturbations above the mean field and employing Fermi's Golden Rule. Considering the charmonium deformation in magnetic field, the discrete Landau energy levels make the dissociation cross-section grow hair, and the electric dipole channel is significantly changed, especially for the $P-$wave states ${\chi }_{c0}$ and ${\chi }_{c\pm }$. From our numerical calculation, the magnetic field strength $eB=5m_{\pi }^2$ already changes the gluon dissociation strongly, which may indicate measurable effects in high-energy nuclear collisions.

    ↳ nucl-thhep-phPRD(2022)·12 citations
21. 21*

    Baikov representations, intersection theory, and canonical Feynman integrals

    Jiaqi Chen🇨🇳 · Xuhang Jiang🇨🇳 · Chichuan Ma🇨🇳 · Xiaofeng Xu🇨🇳 · Li Lin Yang🇨🇳

    The method of canonical differential equations is an important tool in the calculation of Feynman integrals in quantum field theories. It has been realized that the canonical bases are closely related to $d$-dimensional $d\log$-form integrands. In this work, we introduce the concept of generalized loop-by-loop Baikov representation, and clarify its relation and difference with Feynman integrals using the language of intersection theory. We then utilize the generalized Baikov representation to construct $d$-dimensional $d\log$-form integrands, and discuss how to convert them to Feynman integrals. We describe the technical details of our method, in particular how to deal with the difficulties encountered in the construction procedure. Our method provides a constructive approach to the problem of finding canonical bases of Feynman integrals, and we demonstrate its applicability to complicated scattering amplitudes involving multiple physical scales.

    ↳ hep-thhep-phJHEP(2022)·75 citations
22. 22*

    Quantum Off-Shell Recursion Relation

    Kanghoon Lee🇰🇷

    We construct off-shell recursion relations for arbitrary loop-level scattering amplitudes beyond the conventional tree-level recursion relations for ${\varphi }^4$-theory and the Yang-Mills theory. We define a quantum perturbiner expansion that includes loop corrections from the quantum effective action formalism by identifying the external source. Our method clearly shows how the perturbiner expansion becomes an off-shell current generating function. Instead of using the classical equations of motion in the conventional perturbiner method, we exploit the Dyson-Schwinger equation to derive the quantum off-shell recursion relation to arbitrary order of loop-level scattering amplitudes. We solve the recursion relation and reproduce the results which agree up to one-loop six-point scattering amplitudes for ${\varphi }^4$-theory. Furthermore, we construct the recursions for computing loop-level correlation functions by replacing the choice of the external source.

    ↳ hep-thhep-phJHEP(2022)·35 citations
23. 23*

    Extraterrestrial Axion Search with the Breakthrough Listen Galactic Center Survey

    Joshua W. Foster🇺🇸 · Samuel J. Witte🇳🇱 · Matthew Lawson🇸🇪 · Tim Linden🇸🇪 · Vishal Gajjar🇺🇸 · Christoph Weniger🇳🇱 · Benjamin R. Safdi🇺🇸

    Axion dark matter (DM) may efficiently convert to photons in the magnetospheres of neutron stars (NSs), producing nearly monochromatic radio emission. This process is resonantly triggered when the plasma frequency induced by the underlying charge distribution approximately matches the axion mass. We search for evidence of this process using archival Green Bank Telescope data collected in a survey of the Galactic Center in the C-Band by the Breakthrough Listen project. While Breakthrough Listen aims to find signatures of extraterrestrial life in the radio band, we show that their high-frequency resolution spectral data of the Galactic Center region is ideal for searching for axion-photon transitions generated by the population of NSs in the inner pc of the Galaxy. We use data-driven models to capture the distributions and properties of NSs in the inner Galaxy and compute the expected radio flux from each NS using state-of-the-art ray tracing simulations. We find no evidence for axion DM and set leading constraints on the axion-photon coupling, excluding values down to the level $g_{a\gamma \gamma }\sim 10^{-11}$ GeV${}^{-1}$ for DM axions for masses between 15 and 35 $\mu$eV.

    ↳ astro-ph.COastro-ph.HEhep-phPRL(2022)·95 citations
24. 24*

    Gravitational Regge bounds

    Kelian Häring🇨🇭 · Alexander Zhiboedov🇨🇭

    We review the basic assumptions and spell out the detailed arguments that lead to the bound on the Regge growth of gravitational scattering amplitudes. The minimal extra ingredient compared to the gapped case - in addition to unitarity, analyticity, subexponentiality, and crossing - is the assumption that scattering at large impact parameters is controlled by known semi-classical physics. We bound the Regge growth of amplitudes both with the fixed transferred momentum and smeared over it. Our basic conclusion is that gravitational scattering amplitudes admit dispersion relations with two subtractions. For a sub-class of smeared amplitudes, black hole formation reduces the number of subtractions to one. Finally, using dispersion relations with two subtractions we derive bounds on the local growth of relativistic scattering amplitudes. Schematically, the local bound states that the amplitude cannot grow faster than $s^2$.

    ↳ hep-thhep-phSciPost Phys.(2024)·102 citations
25. 25*

    Gluonic evanescent operators: classification and one-loop renormalization

    Qingjun Jin🇨🇳 · Ke Ren🇨🇳 · Gang Yang🇨🇳 · Rui Yu🇨🇳

    Evanescent operators are a special class of operators that vanish classically in four-dimensional spacetime, while in general dimensions they are non-zero and are expected to have non-trivial physical effects at the quantum loop level in dimensional regularization. In this paper we initiate the study of evanescent operators in pure Yang-Mills theory. We develop a systematic method for classifying and constructing the $d$-dimensional Lorentz invariant evanescent operators, which start to appear at mass dimension ten. We also compute one-loop form factors for the dimension-ten operators via the $d$-dimensional unitarity method and obtain their one-loop anomalous dimensions. These operators are necessary ingredients in the study of high dimensional operators in effective field theories involving a Yang-Mills sector.

    ↳ hep-thhep-phJHEP(2022)·8 citations
26. 26*

    Microphysics of Early Dark Energy

    Vivian I. Sabla🇺🇸 · Robert R. Caldwell🇺🇸

    Early Dark Energy (EDE) relies on scalar field dynamics to resolve the Hubble tension, by boosting the pre-recombination length scales and thereby raising the CMB-inferred value of the Hubble constant into agreement with late universe probes. However, the collateral effect of scalar field microphysics on the linear perturbation spectra appears to preclude a fully satisfactory solution. $H_0$ is not raised without the inclusion of a late universe prior, and the "$S_8$-tension", a discrepancy between early- and late-universe measurements of the structure growth parameter, is exacerbated. What if EDE is not a scalar field? Here, we investigate whether different microphysics, encoded in the constitutive relationships between pressure and energy density fluctuations, can relieve these tensions. We show that EDE with an anisotropic sound speed can soften both the $H_0$ and $S_8$ tensions while still providing a quality fit to CMB data. Future observations from the CMB-S4 experiment may be able to distinguish the underlying microphysics at the $4\sigma$ level, and thereby test whether a scalar field or some richer physics is at work.

    ↳ astro-ph.COgr-qchep-phPRD(2022)·48 citations
27. 27*

    The deepest problem: some perspectives on quantum gravity

    Steven B. Giddings🇺🇸

    Quantum gravity is likely the deepest problem facing current physics. While traditionally associated with short distance nonrenormalizability, it is evident that the long distance problem of unitarity, arising at high energies with black hole formation, is more profound. This reveals a conflict between foundational principles of quantum field theory: those of quantum mechanics, relativity, and locality. Difficulties modifying quantum mechanics suggest a "quantum-first" approach, with other principles as mathematical properties of a quantum space of states. A challenge is how to describe locality, in terms of Hilbert space structure. Perturbative gravity gives clues, with structure apparently different than in field theory. The mathematical structure of subsystems plausibly supplants conventional locality and plays a foundational role in the theory. This view differs from one of spacetime "emerging" from another quantum system. If a black hole behaves as a subsystem, a "black hole theorem" says that unitarity requires interactions with its environment depending on its state, or more drastic phenomena. Minimal interactions can be parameterized, in an effective approach; they could arise from wormholes or other fundamental dynamics. These or other near-horizon modifications potentially alter electromagnetic or gravitational signatures of this strong gravity region, now being probed in a new era of observation; it is important to seek observational clues for or constraints on such scenarios. One may also investigate quantum gravity via its S-matrix. New perturbative structure has been discovered there, but the harder question again goes beyond to the nonperturbative regime. Long-distance behavior of amplitudes indicates novel analytic behavior; further exploration may provide important clues. Other key questions regard quantum description of cosmologies, and of associated observables.

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