Thu·Aug 1, 2019Thursday·August 1, 2019

1. 01*

   Novel $B$-decay signatures of light scalars at high energy facilities

   Andrew Blance🇬🇧 · Mikael Chala🇬🇧 · Maria Ramos🇵🇹 · Michael Spannowsky🇬🇧

   We study the phenomenology of light scalars of masses $m_1$ and $m_2$ coupling to heavy flavour-violating vector bosons of mass $m_V$. For $m_{1,2}\lesssim$ few GeV, this scenario triggers the rare $B$ meson decays $B_s^0\to 3{\mu }^{+}3{\mu }^{-}$, $B^0\to 3{\mu }^{+}3{\mu }^{-}$, $B^{+}\to K^{+}3{\mu }^{+}3{\mu }^{-}$ and $B_s^0\to K^{0\ast }3{\mu }^{+}3{\mu }^{-}$; the last two being the most important ones for $m_1\sim m_2$. None of these signals has been studied experimentally; therefore we propose analyses to test these channels at the LHCb. We demonstrate that the reach of this facility extends to branching ratios as small as $6.0\times 10^{-9}$, $1.6\times 10^{-9}$, $5.9\times 10^{-9}$ and $1.8\times 10^{-8}$ for the aforementioned channels, respectively. For $m_{1,2}\gg \mathcal{O}(1)$ GeV, we show that slightly modified versions of current multilepton and multitau searches at the LHC can probe wide regions of the parameter space of this scenario. Altogether, the potential of the searches we propose outperform other constraints such as those from meson mixing.

   hep-phhep-exPRD(2019)·12 citations
2. 02*

   Evaluating two-loop non-planar master integrals for Higgs + jet production with full heavy-quark mass dependence

   R. Bonciani🇮🇹 · V. Del Duca🇨🇭 · H. Frellesvig🇮🇹 · J.M. Henn🇩🇪 · M. Hidding🇮🇪 · L. Maestri🇩🇪 · F. Moriello🇨🇭 · G. Salvatori🇨🇭 · V.A. Smirnov🇷🇺

   We present the analytic computation of a family of non-planar master integrals which contribute to the two-loop scattering amplitudes for Higgs plus one jet production, with full heavy-quark mass dependence. These are relevant for the NNLO corrections to inclusive Higgs production and for the NLO corrections to Higgs production in association with a jet, in QCD. The computation of the integrals is performed with the method of differential equations. We provide a choice of basis for the polylogarithmic sectors, that puts the system of differential equations in canonical form. Solutions up to weight 2 are provided in terms of logarithms and dilogarithms, and 1-fold integral solutions are provided at weight 3 and 4. There are two elliptic sectors in the family, which are computed by solving their associated set of differential equations in terms of generalized power series. The resulting series may be truncated to obtain numerical results with high precision. The series solution renders the analytic continuation to the physical region straightforward. Moreover, we show how the series expansion method can be used to obtain accurate numerical results for all the master integrals of the family in all kinematic regions.

   hep-phhep-thJHEP(2020)·68 citations
3. 03*

   Dijets at Tevatron Cannot Constrain SMEFT Four-Quark Operators

   Eduard Keilmann🇩🇪 · William Shepherd🇺🇸

   We explore the sensitivity of Tevatron data to heavy new physics effects in differential dijet production rates using the SMEFT in light of the fact that consistent and conservative constraints from the LHC cannot cover relatively low cutoff scales in the EFT. In contrast to the results quoted by the experimental collaborations and other groups, we find that, once consistency of the perturbation expansion is enforced and reasonable estimates of theoretical errors induced by the SMEFT series in $\frac{E}{\Lambda }$ are included, there is no potential to constrain four-quark contact interactions using Tevatron data. This shows the general difficulty of constraining physics model-independently using fairly imprecise measurements, limited by low luminosity and/or systematic errors inherent to the precision of the detectors.

   hep-phJHEP(2019)·17 citations
4. 04*

   Global parameterization of $\pi \pi$ scattering up to 2 GeV

   J.R. Pelaez🇪🇸 · A. Rodas🇪🇸 · J. Ruiz de Elvira🇨🇭

   We provide global parameterizations of $\pi \pi$ scattering $S0$ and $P$ partial waves up to roughly 2 GeV for phenomenological use. These parameterizations describe the output and uncertainties of previous partial-wave dispersive analyses of $\pi \pi$, both in the real axis up to 1.12 GeV and in the complex plane within their applicability region, while also fulfilling forward dispersion relations up to 1.43 GeV. Above that energy we just describe the available experimental data. Moreover, the analytic continuations of these global parameterizations also describe accurately the dispersive determinations of the $\sigma /f_0(500)$, $f_0(980)$ and $\rho (770)$ pole parameters.

   hep-phhep-exhep-latnucl-thEPJC(2019)·75 citations
5. 05*

   Di-vector boson production in association with a Higgs boson at hadron colliders

   Pankaj Agrawal🇮🇳 · Debashis Saha🇮🇳 · Ambresh Shivaji🇮🇳

   We consider the production of a Higgs boson in association with two electroweak vector bosons at hadron colliders. In particular, we examine $\gamma \gamma H$, $\gamma ZH$, $ZZH$, and $W^{+}{W}^{-}H$ production at the LHC (14 TeV), HE-LHC (27 TeV), and FCC-hh (100 TeV) colliders. Our main focus is to estimate the gluon-gluon ($gg$) channel ($gg\to V{V}^{\prime }H$) contributions to $pp\to V{V}^{\prime }H(V,V^{\prime }=\gamma ,Z,W)$ and compare them with corresponding contributions arising from the quark-quark ($qq$) channel. Technically, the leading order $gg$ channel contribution to $pp\to V{V}^{\prime }H$ cross section is an NNLO correction in ${\alpha }_s$. In the processes under consideration, we find that in the $gg$ channel, $W^{+}{W}^{-}H$ has the largest cross section. However, relative contribution of the $gg$ channel is more important for the $pp\to ZZH$ production. At the FCC-hh, $gg\to ZZH$ contribution is comparable with the NLO QCD correction to $qq\to ZZH$. We also compute the cross sections when $W$ and $Z$-bosons are polarized. In the production of $W^{+}{W}^{-}H$ and $ZZH$, we find that the $gg$ channel contributes more significantly when the vector bosons are longitudinally polarized. By examining such events, one can increase the fraction of the $gg$ channel contribution to these processes. Further, we have studied beyond-the-standard-model effects in the $\kappa$-framework. We find that the $gg$ channel processes $ZZH$ and $WWH$ have very mild dependence on ${\kappa }_{\lambda }$, but strong dependence on ${\kappa }_t$ and ${\kappa }_V$. The $qq$ channel processes mainly depend on ${\kappa }_V$. Dependence of the $gg$ channel contribution on ${\kappa }_V$ is stronger than that of the $qq$ channel contribution. Therefore focusing on events with longitudinally polarized $W$ and $Z$-bosons, one can find stronger dependence on ${\kappa }_V$ that can help us measure this parameter.

   hep-phPRD(2021)·3 citations
6. 06*

   Some Implications of the Leptonic Annihilation of Dark Matter: Possible Galactic Radio Emission Signatures and the Excess Radio Flux of Extragalactic Origin

   Elaine C. F. S. Fortes🇧🇷 · Oswaldo D. Miranda🇧🇷 · Floyd W. Stecker🇺🇸 · Carlos A. Wuensche🇧🇷

   We give theoretical predictions for the radio emission of a dark matter candidate annihilating into 2-lepton and 4-lepton final states. We then compare our results with the known radio measurements of the sky temperature as a function of the frequency. In particular, we calculate the radio emission for some dark matter candidates annihilating into intermediate bosons that subsequently decay into a 4-lepton channel with a thermal annihilation cross-section. We show that within the range of frequencies from $20\mathrm{MHz}$ to $5\mathrm{GHz}$, this channel can produce a stronger signature than direct annihilation into leptons.

   hep-phastro-ph.HEJCAP(2019)·4 citations
7. 07*

   $B_s\to K^{\ast 0}$ decay form factors from covariant confined quark model

   Aidos Issadykov🇷🇺

   We evaluate $B_s\to K^{\ast 0}$ transition form factors in the full kinematical region within the covariant confined quark model. The calculated form factors can be used to calculate the $B_s\to K^{\ast 0}{\mu }^{+}{\mu }^{-}$ rare decay branching ratio, which was recently measured by LHCb collaboration.

   hep-phhep-exEPJ Web Conf.(2019)·2 citations
8. 08*

   Semileptonic decays of $B_c$ mesons into charmonium states

   Aidos Issadykov🇷🇺 · Mikhail A. Ivanov🇷🇺 · Guliya Nurbakova🇰🇿

   In this work we study the semileptonic decays of $B_c$ meson. We evaluated $B_c\to D(D^{\ast })$, $B_c\to D_s(D_s^{\ast })$ and $B_c\to {\eta }_c(J/\psi )$ transitions form factors in the full kinematical region within the covariant quark model. The calculated form factors are used to evaluate the semileptonic decays of $B_c$ meson and it was defined ratios ($R_{{\eta }_c}$, $R_{J/\psi }$, $R_D$ ,$R_{D^{\ast }}$) of the branching ratios, which will be hopefully tested on LHC experiments.We compare the obtained results with the results from other theoretical approaches.

   hep-phhep-exEPJ Web Conf.(2017)·27 citations
9. 09*

   Generalised power series expansions for the elliptic planar families of Higgs + jet production at two loops

   Francesco Moriello🇨🇭

   We obtain generalised power series expansions for a family of planar two-loop master integrals relevant for the QCD corrections to Higgs + jet production, with physical heavy-quark mass dependence. This is achieved by defining differential equations along contours connecting two fixed points, and by solving them in terms of one-dimensional generalised power series. The procedure is efficient and can be repeated in order to reach any point of the kinematic regions. The analytic continuation of the series is straightforward and we present new results below and above the physical thresholds. The method we use allows to compute the integrals in all kinematic regions with high precision. Performing a series expansion on a typical contour above the physical threshold takes on average $\mathcal{O}(1\text{ second})$ per integral with worst relative error of $\mathcal{O}(10^{-32})$, on a single CPU core. After the series is found the numerical evaluation of the integrals in any point of the contour is virtually instant. Our approach is general and can be applied to Feynman integrals provided that a set of differential equations is available.

   hep-phhep-thJHEP(2020)·172 citations
10. 10*

    Summary of the NuSTEC Workshop on Shallow- and Deep-Inelastic Scattering

    C. Andreopoulos🇬🇧 · M. Sajjad Athar🇮🇳 · C. Bronner🇯🇵 · S. Dytman🇺🇸 · K. Gallmeister🇩🇪 · H. Haider🇮🇳 · N. Jachowicz🇧🇪 · M. Kabirnezhad🇬🇧 · T. Katori🇬🇧 · S. Kulagin🇷🇺 · A. Kusina🇵🇱 · M. Muether🇺🇸 and 5 other authors

    The NuSTEC workshop (https://indico.cern.ch/event/727283) held at L'Aquila in October 2018 was devoted to neutrino-nucleus scattering in the kinematic region where hadronic systems with invariant masses above the $\Delta (1232)$ resonance are produced: the so-called shallow- and deep-inelastic scattering regime. Not only is the physics in this kinematic region quite intriguing, it is also important for current and future oscillation experiments with accelerator and atmospheric neutrinos. For the benefit of the community, links to the presentations are accompanied by annotations from the speakers.

    hep-phhep-exnucl-th20 citations
11. 11*

    Independent quark/antiquark fragmentation to massive particles in proton-proton collisions

    Rafal Maciula🇵🇱 · Antoni Szczurek🇵🇱

    We critically discuss fragmentation of quark or antiquark to massive particles (mesons or baryons) in proton-proton collisions. Both heavy and light quark/antiquark fragmentations are discussed using universal $z$-dependent fragmentation functions. Different scenarios how to define the $z$ variable are considered: as a fraction of energy, momentum or light-cone momentum of the parent quark/antiquark. Also a choice of the direction of motion of hadron with respect to the parent parton must be made in the simplest approach. Energy and flavour violation is discussed for the region of small $p_t$ and/or center-of-mass $y\sim$ 0. Results of different approaches are compared. We show that at the LHC energies all schemes become consistent for $D$-meson transverse momenta larger than $2$ GeV. Relations to results from the literature are made. We present some examples for production of D mesons from light and charm quarks/antiquarks. Emission with respect to the direction of motion lowers the cross section of $D$ mesons at larger rapidities compared to the traditional approach ($y_D=y_{q/\bar{q}}$). As illustrated here the effect of using different prescriptions is particularly large at low energies (fixed target experiments).

    hep-phJ.Phys.G(2020)·12 citations
12. 12*

    Towards a reliable effective field theory of inflation

    Mar Bastero-Gil🇪🇸 · Arjun Berera🇬🇧 · Rudnei O. Ramos🇧🇷 · João G. Rosa🇵🇹

    We present the first quantum field theory model of inflation that is renormalizable in the matter sector, with a super-Hubble inflaton mass and sub-Planckian field excursions, which is thus technically natural and consistent with a high-energy completion within a theory of quantum gravity. This is done in the framework of warm inflation, where we show, for the first time, that strong dissipation can fully sustain a slow-roll trajectory with slow-roll parameters larger than unity in a way that is both theoretically and observationally consistent. The inflaton field corresponds to the relative phase between two complex scalar fields that collectively break a U(1) gauge symmetry, and dissipates its energy into scalar degrees of freedom in the warm cosmic heat bath. A discrete interchange symmetry protects the inflaton mass from large thermal corrections. We further show that the dissipation coefficient decreases with temperature in certain parametric regimes, which prevents a large growth of thermal inflaton fluctuations. We find, in particular, a very good agreement with the Planck legacy data for a simple quadratic inflaton potential, predicting a low tensor-to-scalar ratio $r\lesssim 10^{-5}$.

    hep-phastro-ph.COgr-qchep-thPLB(2021)·90 citations
13. 13*

    Probing New Physics Signals with Symmetry-Restored Yukawa Textures

    Shao-Ping Li🇨🇳 · Xin-Qiang Li🇨🇳

    We implement a symmetry violation guideline into a two-Higgs-doublet model embedded with three right-handed neutrinos, and exploit the generic Yukawa structures of the model via a hypothetical symmetry restoration of a global $U_Q(1{)}^3\times U_L(1{)}^3$ symmetry. We then apply a mass-powered parametrization to construct the phenomenologically motivated Yukawa interactions, which enables us to incorporate correlatively the neutrino mass, dark matter, as well as the lepton-flavor universality violations in $R_{K^{(\ast )}}$ and $R_{D^{(\ast )}}$. Specifically, two atmospheric-scale neutrino masses are generated by a low-scale seesaw mechanism, while the much lighter one, being of $\mathcal{O}(10^{-6})\mathrm{eV}$, is fixed by a $7.1\mathrm{keV}$ sterile neutrino dark matter produced primordially by the freeze-in mechanism. On the other hand, the neutrino and the charged-lepton mass hierarchies encoded in the mass-powered textures can naturally account for the $R_{K^{(\ast )}}$ and the $R_{D^{(\ast )}}$ anomalies, respectively. As a further application, a milder discrepancy of the muon $g-2$ is observed, which has also been implied by the recently refined lattice results.

    hep-phhep-exEPJC(2020)·13 citations
14. 14*

    Resonant photoproduction of high-energy electron-positron pairs in the field of a nucleus and a plane electromagnetic wave

    Nikita R. Larin🇷🇺 · Victor V. Dubov🇷🇺 · Sergei P. Roshchupkin🇷🇺

    The resonant photoproduction of ultrarelativistic electron-positron pairs (PPP) in a nuclear field and a weak laser field is theoretically studied. Under resonance conditions, the intermediate virtual electron (positron) in the laser field becomes a real particle. As a result, the initial process of the second order in the fine structure constant in the laser field effectively reduces into two successive processes of the first order: single-photon production of electron-positron pair in a laser field (laser-stimulated Breit-Wheeler process) and laser-assisted process of electron (positron) scattering on a nucleus. Resonant kinematics of PPP is studied in details. It is shown that for the considered laser intensities resonance is possible only for the initial photon energies greater than the characteristic threshold energy. At the same time, the ultrarelativistic electron and positron propagate in a narrow cone along the direction of the initial photon momentum. The resonant energy of the positron (electron) can has two values for each radiation angle which varies from zero to some maximum value determined by the energy of the initial photon and the threshold energy. Resonant differential cross section of the studied process was obtained. It is shown that the resonant differential cross section of the PPP can significantly exceed the corresponding cross section of the PPP without an external field. The project calculations may be experimentally verified by the scientific facilities of pulsed laser radiation (SLAC, FAIR, XFEL, ELI, XCELS)

    hep-phPRA(2019)·23 citations
15. 15*

    Model independent analysis of $B^{\ast }\to P\ell {\bar{\nu }}_{\ell }$ decay processes

    Atasi Ray🇮🇳 · Suchismita Sahoo🇮🇳 · Rukmani Mohanta🇮🇳

    Very compelling deviations in the recently observed lepton nonuniversality observables $(R_{D^{(\ast )}},R_{K^{(\ast )}},R_{J/\psi })$ of semileptonic $B$ meson decays from their Standard Model predictions hint towards the presence of some kind of new physics beyond it. In this regard, we investigate the effect of new physics in the semileptonic ${\bar{B}}_{d(s)}^{\ast }\to P\ell {\bar{\nu }}_{\ell }$ decay processes, where $P=D,\pi (D_s,K$), in a model independent way. We consider the presence of additional vector and scalar type interactions and constrain the corresponding new couplings by fitting $\mathrm{Br}({\mathrm{B}}_{\mathrm{u}}^{+}\to {\tau }^{+}{\nu }_{\tau })$, $\mathrm{Br}(\mathrm{B}\to \pi \tau {\bar{\nu }}_{\tau })$, $\mathrm{Br}({\mathrm{B}}_{\mathrm{c}}^{+}\to {\tau }^{+}{\nu }_{\tau })$, $R_{\pi }^l$, $R_{D^{(\ast )}}$ and $R_{J/\psi }$ data. Using the constrained new parameters, we estimate the branching ratios, forward-backward asymmetry, lepton-spin asymmetry and lepton non-universality observables of ${\bar{B}}_{d,s}^{\ast }\to P\tau {\bar{\nu }}_{\tau }$ processes. We find that the branching ratios of these decay modes are sizeable and deviate significantly (for vector-type couplings) from their corresponding standard model values, which are expected to be within the reach of Run III of Large Hadron Collider experiment.

    hep-phEPJC(2019)·18 citations
16. 16*

    Gravitational waves triggered by $B-L$ charged hidden scalar and leptogenesis

    Ligong Bian🇨🇳 · Wei Cheng🇨🇳 · Huai-Ke Guo🇺🇸 · Yongchao Zhang🇺🇸

    We study the electroweak symmetry breaking in the framework of a classically conformal $U(1{)}_{B-L}$ theory, where three right-handed neutrinos (RHNs) and a hidden scalar are introduced, with the latter playing the role of dark matter (DM). It is found that the DM and RHN sectors are crucial for the spontaneous symmetry breaking of the $U(1{)}_{B-L}$ symmetry, strong first order phase transition in the conformal theory and the resultant gravitational wave (GW) prospects at future space-based interferometer LISA and other GW experiments. The baryon asymmetry of the Universe is addressed by the resonant leptogenesis mechanism, which is potentially disturbed by the hidden scalar. To make the GW spectra detectable by LISA and resonant leptogenesis work in the conformal $U(1{)}_{B-L}$ theory, the hidden scalar can not fully saturate the observed DM relic density.

    hep-phCPC(2021)·40 citations
17. 17*

    NLO QCD predictions for $t\bar{t}b\bar{b}$ production in association with a light jet at the LHC

    Federico Buccioni🇨🇭 · Stefan Kallweit🇮🇹 · Stefano Pozzorini🇨🇭 · Max Zoller🇨🇭

    Theoretical predictions for ttbb production are of crucial importance for ttH measurements in the H->bb channel at the LHC. To address the large uncertainties associated with the modelling of extra QCD radiation in ttbb events, in this paper we present a calculation of pp->ttbbj at NLO QCD. The behaviour of NLO corrections is analysed in a variety of observables, and to assess theoretical uncertainties we use factor-two rescalings as well as different dynamic scales. In this context, we propose a systematic alignment of dynamic scales that makes it possible to disentangle normalisation and shape uncertainties in a transparent way. Scale uncertainties at NLO are typically at the level of 20-30% in fiducial cross sections, and below 10% for the shapes of distributions. The kinematics of QCD radiation is investigated in detail, including the effects of its recoil on the objects of the ttbb system. In particular, we discuss various azimuthal correlations that allow one to charaterise the QCD recoil pattern in a precise and transparent way. In general, the calculation at hand provides a variety of precise benchmarks that can be used to validate the modelling of QCD radiation in ttbb generators. Moreover, as we will argue, pp->ttbbj at NLO entails information that can be used to gain insights into the perturbative convergence of the inclusive ttbb cross section beyond NLO. Based on this idea, we address the issue of the large NLO K-factor observed in the ttbb cross section, and we provide evidence that supports the reduction of this K-factor through a mild adjustment of the QCD scales that are conventionally used for this process. The presented 2->5 NLO calculations have been carried out using OpenLoops 2 in combination with Sherpa and Munich.

    hep-phhep-exJHEP(2019)·55 citations
18. 18*

    Implications of BBN Bounds for Cosmic Ray Upscattered Dark Matter

    Gordan Krnjaic🇺🇸 · Samuel D. McDermott🇺🇸

    We consider the Big Bang Nucleosynthesis (BBN) bounds on light dark matter whose cross section off nucleons is sufficiently large to enable acceleration by scattering off of cosmic rays in the local galaxy. Such accelerated DM could then deposit energy in terrestrial detectors. Since this signal involves DM of mass ~ keV - 100 MeV and requires large cross sections > 10^-31 cm^2 in a relativistic kinematic regime, we find that the DM population in this scenario is generically equilibrated with Standard Model particles in the early universe. For sufficiently low DM masses < 10 MeV, corresponding to the bulk of the favored region of many cosmic-ray upscattering studies, this equilibrated DM population adds an additional component to the relativistic energy density around T ~ few MeV and thereby spoils the successful predictions of BBN. In the remaining ~ 10-100 MeV mass range, the large couplings required in this scenario are either currently excluded or within reach of current or future accelerator-based searches.

    hep-phastro-ph.COastro-ph.HEPRD(2020)·77 citations
19. 19*

    Axion-like particles, lepton-flavor violation and a new explanation of $a_{\mu }$ and $a_e$

    Martin Bauer🇬🇧 · Matthias Neubert🇩🇪 · Sophie Renner🇩🇪 · Marvin Schnubel🇩🇪 · Andrea Thamm🇨🇭

    Axion-like particles (ALPs) with lepton-flavor violating couplings can be probed in exotic muon and tau decays. The sensitivity of different experiments depends strongly on the ALP mass and its couplings to leptons and photons. For ALPs that can be resonantly produced, the sensitivity of three-body decays such as $\mu \to 3e$ and $\tau \to 3\mu$ exceeds by many orders of magnitude that of radiative decays like $\mu \to e\gamma$ and $\tau \to \mu \gamma$. Searches for these two types of processes are therefore highly complementary. We discuss experimental constraints on ALPs with a single dominant lepton-flavor violating coupling. Allowing for one or more such couplings offers qualitatively new ways to explain the anomalies related to the magnetic moments of the muon and electron.

    hep-phPRL(2020)·203 citations
20. 20*

    Electron Ionization via Dark Matter-Electron Scattering and the Migdal Effect

    Daniel Baxter🇺🇸 · Yonatan Kahn🇺🇸 · Gordan Krnjaic🇺🇸

    There are currently several existing and proposed experiments designed to probe sub-GeV dark matter (DM) using electron ionization in various materials. The projected signal rates for these experiments assume that this ionization yield arises only from DM scattering directly off electron targets, ignoring secondary ionization contributions from DM scattering off nuclear targets. We investigate the validity of this assumption and show that if sub-GeV DM couples with comparable strength to both protons and electrons, as would be the case for a dark photon mediator, the ionization signal from atomic scattering via the Migdal effect scales with the atomic number $Z$ and 3-momentum transfer $\mathbf{q}$ as $Z^2{\mathbf{q}}^2$. The result is that the Migdal effect is always subdominant to electron scattering when the mediator is light, but that Migdal-induced ionization can dominate over electron scattering for heavy mediators and DM masses in the hundreds of MeV range. We put these two ionization processes on identical theoretical footing, address some theoretical uncertainties in the choice of atomic wavefunctions used to compute rates, and discuss the implications for DM scenarios where the Migdal process dominates, including for XENON10, XENON100, and the recent XENON1T results on light DM scattering.

    hep-phastro-ph.COhep-exPRD(2020)·121 citations
21. 21*

    Minimal signatures of the Standard Model in non-Gaussianities

    Anson Hook🇺🇸 · Junwu Huang🇨🇦 · Davide Racco🇨🇦

    We show that the leading coupling between a shift symmetric inflaton and the Standard Model fermions leads to an induced electroweak symmetry breaking due to particle production during inflation, and as a result, a unique oscillating feature in non-Gaussianities. In this one parameter model, the enhanced production of Standard Model fermions dynamically generates a new electroweak symmetry breaking minimum, where the Higgs field classically rolls into. The production of fermions stops when the Higgs expectation value and hence the fermion masses become too large, suppressing fermion production. The balance between the above-mentioned effects gives the Standard Model fermions masses that are uniquely determined by their couplings to the inflaton. In particular, the heaviest Standard Model fermion, the top quark, can produce a distinct cosmological collider physics signature characterised by a one-to-one relation between amplitude and frequency of the oscillating signal, which is observable at future 21-cm surveys.

    hep-phastro-ph.COhep-thPRD(2020)·80 citations
22. 22*

    A new evaluation of the hadronic vacuum polarisation contributions to the muon anomalous magnetic moment and to $\mathbf{\alpha }({\mathbf{m}}_{\mathbf{Z}}^2)$

    M. Davier🇫🇷 · A. Hoecker🇨🇭 · B. Malaescu🇫🇷 · Z. Zhang🇫🇷

    We reevaluate the hadronic vacuum polarisation contributions to the muon magnetic anomaly and to the running of the electromagnetic coupling constant at the $Z$-boson mass. We include newest $e^{+}{e}^{-}\to$ hadrons cross-section data together with a phenomenological fit of the threshold region in the evaluation of the dispersion integrals. The precision in the individual datasets cannot be fully exploited due to discrepancies that lead to additional systematic uncertainty in particular between BABAR and KLOE data in the dominant ${\pi }^{+}{\pi }^{-}$ channel. For the muon $(g-2)/2$, we find for the lowest-order hadronic contribution $(694.0\pm 4.0)\cdot 10^{-10}$. The full Standard Model prediction differs by $3.3\sigma$ from the experimental value. The five-quark hadronic contribution to $\alpha (m_Z^2)$ is evaluated to be $(276.0\pm 1.0)\cdot 10^{-4}$.

    hep-phhep-exEPJC(2020)·805 citations
23. 23*

    Gravity with explicit spacetime symmetry breaking and the Standard-Model Extension

    Robert Bluhm🇺🇸 · Hannah Bossi🇺🇸 · Yuewei Wen🇺🇸

    The Standard-Model Extension (SME) is the general phenomenological framework used to investigate Lorentz violation at the level of effective field theory. It has been used to obtain stringent experimental bounds on Lorentz violation in a wide range of tests. In the gravity sector of the SME, it is typically assumed that the spacetime symmetry breaking occurs spontaneously in order to avoid potential conflicts with the Bianchi identities. A post-Newtonian limit as well as matter-gravity couplings in the SME have been developed and investigated based on this assumption. In this paper, the possibility of using the SME to also describe gravity theories with explicit spacetime symmetry breaking is investigated. It is found that in a wide range of cases, particularly when matter-gravity couplings are included, consistency with the Bianchi identities can be maintained, and therefore the SME can be used to search for signals of the symmetry breaking. Two examples with explicit breaking are considered. The first is ghost-free massive gravity with an effective metric that couples to matter. The second is Horava gravity coupled with matter in an infrared limit.

    ↳ gr-qchep-phhep-thPRD(2019)·58 citations
24. 24*

    Non-minimally coupled quartic inflation with Coleman-Weinberg one-loop corrections in the Palatini formulation

    Nilay Bostan🇹🇷

    We discuss how the non-minimal coupling $\xi {\varphi }^{2}R$ between the inflaton and the Ricci scalar affects predictions of single field inflation models in Palatini formalism. To transition radiation dominated era, the inflaton field $\varphi$ must interact to matter fields at the end of inflation. Interactions of the inflaton with other fields lead to radiative corrections to the inflationary potential. These radiative corrections can be explained at leading order by Coleman-Weinberg (CW) one-loop corrections. In this work, using two different prescriptions debated in the literature, the effect of radiative corrections to the potential owing to the coupling of the inflaton to bosons in Prescription I and couplings of the inflaton to bosons and fermions in Prescription II have been examined. We analyze the range of these coupling parameter values for which the spectral index $n_s$ and the tensor-to-scalar ratio $r$ are compatible with the data taken into account to the Keck Array/BICEP2 and Planck collaborations. Finally, we also show that for all the considered potentials the running of the spectral index $\alpha =\mathrm{d}{n}_s/\mathrm{d}\ln k$ as a function of $\kappa$ for selected $\xi$ values.

    ↳ gr-qcastro-ph.COhep-phPLB(2020)·37 citations
25. 25*

    Theory of generalized Josephson effects

    Aron J. Beekman🇯🇵

    The DC Josephson effect is the flow of supercurrent across a weak link between two superconductors with a different value of their order parameter, the phase. We generalize this notion to any kind of spontaneous continuous symmetry breaking. The quantity that flows between the two systems is identified as the Noether current associated with the broken symmetry. The AC Josephson effect is identified as the oscillations due to the energy difference between the two systems caused by an imposed asymmetric chemical potential. As an example of novel physics, a Josephson effect is predicted between two crystalline solids, potentially measurable as a force periodic in the separation distance.

    ↳ cond-mat.othercond-mat.supr-conhep-phPTEP(2020)·3 citations
26. 26*

    Resolving the vDVZ and Strong Coupling Problems in Massive Gravity and Bigravity

    Gregory Gabadadze🇺🇸 · Daniel Older🇺🇸 · David Pirtskhalava🇺🇸

    As is well known, both massive gravity and bigravity exhibit the linear van Dam-Veltman-Zakharov (vDVZ) discontinuity that is cured classically by the nonlinear Vainshtein mechanism due to certain low scale strongly coupled interactions. Here we show how both the vDVZ and strong coupling problems can be removed by embedding 4D covariant massive gravity into a certain 5D warped geometry. The 4D theory is a nonlinear strongly coupled massive gravity, that is being coupled to a 5D bulk theory that generates a bulk graviton mass via a one loop diagram. This induced mass leads to an additional 4D kinetic term for the 4D longitudinal mode, even on flat space. Due to this kinetic term the 4D massive theory becomes weakly coupled all the way up to a high energy scale set by the bulk cosmological constant. The same effect leads to a suppression of the interactions of the 4D longitudinal mode with a 4D matter stress-tensor, thus removing the vDVZ discontinuity. The proposed mechanism has a pure 4D holographic interpretation: a 4D nonlinear massive gravity mixes to a non-conserved symmetric tensor of a 4D CFT that has a cutoff; the latter mixing generates a large kinetic term for the longitudinal mode, and this makes the longitudinal mode be weakly coupled to a matter stress-tensor, and weakly self-coupled, all the way up to the scale of the 4D CFT cutoff.

    ↳ hep-thgr-qchep-phPRD(2019)·10 citations
27. 27*

    On the viability of Locked Inflation

    Michael Zantedeschi🇩🇪

    We review locked inflation and we critically address phenomenological and consistency issues thathave appeared in the literature. A natural window of opportunity is found for the original scenario.Moreover, a simple way to enlarge the parameter space is proposed by considering an equivalentlynatural structure for the locking field. Finally, an estimate of the amount of topological defects atthe end of inflation is given; due to the low inflationary scale, it turns out to be negligible.

    ↳ gr-qchep-phhep-th1 citation

* 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.