Mon·Apr 19, 2021Monday·April 19, 2021

1. 01*

   Calculating Four-Loop Corrections in QCD

   S. Moch🇩🇪 · V. Magerya🇩🇪

   We review the current status of perturbative corrections in QCD at four loops for scattering processes with space- and time-like kinematics at colliders, with specific focus on deep-inelastic scattering and electron-positron annihilation. The calculations build on the parametric reduction of loop and phase space integrals up to four-loop order using computer algebra programs such as FORM, designed for large scale computations.

   hep-ph2 citations
2. 02*

   Quasi-Dirac neutrinos in the linear seesaw model

   Carolina Arbeláez🇨🇱 · Claudio Dib🇨🇱 · Kevin Monsálvez-Pozo🇪🇸 · Iván Schmidt🇨🇱

   We implement a minimal linear seesaw model (LSM) for addressing the Quasi-Dirac (QD) behaviour of heavy neutrinos, focusing on the mass regime of $M_N\lesssim M_W$. Here we show that for relatively low neutrino masses, covering the few GeV range, the same-sign to opposite-sign dilepton ratio, $R_{\ell \ell }$, can be anywhere between 0 and 1, thus signaling a Quasi-Dirac regime. Particular values of $R_{\ell \ell }$ are controlled by the width of the QD neutrino and its mass splitting, the latter being equal to the light-neutrino mass $m_{\nu }$ in the LSM scenario. The current upper bound on $m_{{\nu }_1}$ together with the projected sensitivities of current and future $|U_{N\ell }{|}^2$ experimental measurements, set stringent constraints on our low-scale QD mass regime. Some experimental prospects of testing the model by LHC displaced vertex searches are also discussed.

   hep-phhep-exJHEP(2021)·8 citations
3. 03*

   Prospects of light charged scalars in a three Higgs doublet model with $Z_3$ symmetry

   Manimala Chakraborti🇵🇱 · Dipankar Das🇮🇳 · Miguel Levy🇵🇹 · Samadrita Mukherjee🇮🇳 · Ipsita Saha🇯🇵

   The stringent constraints from the direct searches for exotic scalars at the LHC as well as indirect bounds from flavor physics measurements have imposed severe restrictions on the parameter space of new physics models featuring extended Higgs sectors. In the Type-II 2HDM, this implies a lower bound on the charged Higgs masses of $\mathcal{O}$(600 GeV). In this work we analyze the phenomenology of a Z3HDM in the alignment limit focusing on the impact of flavor physics constraints on its parameter space. We show that the couplings of the two charged Higgs bosons in this model feature an additional suppression factor compared to Type-II 2HDM. This gives rise to a significant relaxation of the flavor physics constraints in this model, allowing the charged Higgs masses to be as low as $\mathcal{O}$(200 GeV). We also consider the constraints coming from precision electroweak observables and the observed diphoton decay rate of the 125 GeV Higgs boson at the LHC. The bounds coming from the direct searches of nonstandard Higgs bosons at the LHC, particularly those from resonance searches in the ditau channel, prove to be very effective in constraining this scenario further.

   hep-phPRD(2021)·31 citations
4. 04*

   Spin-2 KK Mode Scattering in Models with a Massive Radion

   R. Sekhar Chivukula🇺🇸 · Dennis Foren🇺🇸 · Kirtimaan A. Mohan🇺🇸 · Dipan Sengupta🇺🇸 · Elizabeth H. Simmons🇺🇸

   We calculate tree-level scattering amplitudes of massive spin-2 KK particles in models of stabilized compact extra-dimensional theories. Naively introducing a mass for the radion in an extra-dimensional model without accounting for the dynamics responsible for stabilizing the extra dimension upsets the cancellations relating the masses and couplings of the spin-2 modes, resulting in KK scattering amplitudes which grow like $E^4$ instead of $E^2$. We therefore investigate scattering of the Kaluza-Klein states in theories incorporating the Goldberger-Wise mechanism to stabilize the size of the extra dimension. We demonstrate that the cancellations occur only when one includes not only the massive radion, but also the massive spin-0 modes arising from the Goldberger-Wise scalar. We compute the revised sum rules which are satisfied in a stabilized model to ensure a consistent high-energy scattering amplitude. We introduce a simple model of a stabilized extra dimension which is a small deformation of a flat (toroidal) five-dimensional model, and demonstrate the cancellations in computations performed to leading nontrivial order in the deformation. These results are the first complete KK scattering computation in an extra-dimensional model with a stabilized extra dimension, with implications for the theory and phenomenology of these models.

   hep-phgr-qchep-thPRD(2021)·17 citations
5. 05*

   Collective flow in single-hit QCD kinetic theory

   Aleksi Kurkela🇳🇴 · Aleksas Mazeliauskas🇨🇭 · Robin Törnkvist🇸🇪

   Motivated by recent interest in collectivity in small systems, we calculate the harmonic flow response to initial geometry deformations within weakly coupled QCD kinetic theory using the first correction to the free-streaming background. We derive a parametric scaling formula that relates harmonic flow in systems of different sizes and different generic initial gluon distributions. We comment on similarities and differences between the full QCD effective kinetic theory and the toy models used previously. Finally we calculate the centrality dependence of the integrated elliptic flow $v_2$ in oxygen-oxygen, proton-lead and proton-proton collision systems.

   hep-phnucl-thJHEP(2021)·38 citations
6. 06*

   Neutrino masses in the Standard Model effective field theory

   Mikael Chala🇪🇸 · Arsenii Titov🇪🇸

   We compute the leading-logarithmic correction to the neutrino mass matrix in the Standard Model effective field theory (SMEFT) to dimension seven. In the limit of negligible lepton and down-type quark Yukawa couplings, it receives contributions from the Weinberg dimension-five operator as well as from 11 dimension-six and five dimension-seven independent interactions. Two of the main implications we derive from this result are the following. First, we find dimension-seven operators which, despite violating lepton number, do not renormalise neutrino masses at one loop. And second, we demonstrate that the presence of dimension-six operators around the TeV scale can modify the Standard Model prediction by up to $\mathcal{O}(50\%)$. Our result comprises also one step forward towards the renormalisation of the SMEFT to order $v^3/{\Lambda }^3$.

   hep-phPRD(2021)·42 citations
7. 07*

   Glue-and-Cut at Five Loops

   Alessandro Georgoudis🇫🇷 · Vasco Gonçalves🇧🇷 · Erik Panzer🇬🇧 · Raul Pereira🇮🇪 · Alexander V. Smirnov🇷🇺 · Vladimir A. Smirnov🇷🇺

   We compute epsilon-expansions around 4 dimensions of a complete set of master integrals for momentum space five-loop massless propagator integrals in dimensional regularization, up to and including the first order with contributions of transcendental weight nine. Our method is the glue-and-cut technique from Baikov and Chetyrkin, which proves extremely effective in that it determines all expansion coefficients to this order in terms of recursively one-loop integrals and only one further integral. We observe that our results are compatible with conjectures that predict $\pi$-dependent contributions.

   hep-phhep-thJHEP(2021)·26 citations
8. 08*

   B-modes from Post-inflationary Gravitational Waves Sourced by Axionic Instabilities at Cosmic Reionization

   Michael Geller🇮🇱 · Sida Lu🇮🇱 · Yuhsin Tsai🇺🇸

   We show that axion-like particles that only couple to invisible dark photons can generate visible B-mode signals around the reionization epoch. The axion field starts rolling shortly before reionization, resulting in a tachyonic instability for the dark photons. This generates an exponential growth of the dark photon quanta sourcing both scalar metric modes and gravitational waves that leave an imprint on the reionized baryons. The tensor modes modify the cosmic microwave background (CMB) polarization at reionization, generating visible B-mode signatures for the next generation of CMB experiments for parameter ranges that satisfy the current experimental constraints.

   hep-phastro-ph.COPRD(2021)·9 citations
9. 09*

   Probing QCD dynamics and the standard model with $D_{(s)}\to P^{+}{P}^0\gamma$ decays

   Nico Adolph🇩🇪 · Gudrun Hiller🇩🇪

   We compute 10 radiative three-body decays of charged charmed mesons $D^{+}\to P^{+}{P}^0\gamma$ and $D_s\to P^{+}{P}^0\gamma$, $P=\pi ,K$, in leading order QCDF, HH$\chi$PT and the soft photon approximation. We work out decay distributions and asymmetries in the standard model and with new physics in the electromagnetic dipole operators. The forward-backward asymmetry is suitable to probe the QCD frameworks, in particular the $s$-channel dependent weak annihilation contributions in QCDF against the markedly different resonance structure in HH$\chi$PT. These studies can be performed with Cabibbo-favored modes $D_s\to {\pi }^{+}{\pi }^0\gamma$, $D^{+}\to {\pi }^{+}{\overline{K}}^0\gamma$ and $D_s\to K^{+}{\overline{K}}^0\gamma$ with $\mathcal{O}(10^{-4}-10^{-3})$-level branching ratio, which are standard model-like and induced by different hadronic dynamics. Understanding of the latter can therefore be improved in a data-driven way and sharpens the interpretation of standard model tests. Singly Cabibbo-suppressed modes such as $D^{+}\to {\pi }^{+}{\pi }^0\gamma$, $D_s\to {\pi }^{+}{K}^0\gamma$, $D_s\to K^{+}{\pi }^0\gamma$ with branching ratios within $\sim 10^{-5}-10^{-4}$ are sensitive to new physics that can be signalled in the forward-backward asymmetry and in the CP-asymmetry of the rate, ideally in the Dalitz region but also in single differential distributions. Results complement those with neutral $D^0\to PP\gamma$ decays.

   hep-phJHEP(2021)·5 citations
10. 10*

    A Custodial Symmetry for Muon g-2

    Reuven Balkin🇮🇱 · Cedric Delaunay🇫🇷 · Michael Geller🇮🇱 · Enrique Kajomovitz🇮🇱 · Gilad Perez🇮🇱 · Yogev Shpilman🇮🇱 · Yotam Soreq🇮🇱

    We discuss the recent results on the muon anomalous magnetic moment in the context of new physics models with light scalars. We propose a model in which the one-loop contributions to g-2 of a scalar and a pseudoscalar naturally cancel in the massless limit due to the symmetry structure of the model. This model allows to interpolate between two possible interpretations. In the first interpretation, the results provide a strong evidence of the existence of new physics, dominated by the positive contribution of a CP-even scalar. In the second one, supported by the recent lattice result, the data provides a strong upper bound on new physics, specifically in the case of (negative) pseudoscalar contributions. We emphasize that tree-level signatures of the new degrees of freedom of the model are enhanced relative to conventional explanations of the discrepancy. As a result, this model can be tested in the near future with accelerator-based experiments and possibly also at the precision frontier.

    hep-phhep-exPRD(2021)·20 citations
11. 11*

    Radio Line Properties of Axion Dark Matter Conversion in Neutron Stars

    R. A. Battye🇬🇧 · B. Garbrecht🇩🇪 · J. I. McDonald🇧🇪 · S. Srinivasan🇬🇧

    Axions are well-motivated candidates for dark matter. Recently, much interest has focused on the detection of photons produced by the resonant conversion of axion dark matter in neutron star magnetospheres. Various groups have begun to obtain radio data to search for the signal, however, more work is needed to obtain a robust theory prediction for the corresponding radio lines. In this work we derive detailed properties for the signal, obtaining both the line shape and time-dependence. The principal physical effects are from refraction in the plasma as well as from gravitation which together lead to substantial lensing which varies over the pulse period. The time-dependence from the co-rotation of the plasma with the pulsar distorts the frequencies leading to a Doppler broadened signal whose width varies in time. For our predictions, we trace curvilinear rays to the line of sight using the full set of equations from Hamiltonian optics for a dispersive medium in curved spacetime. Thus, for the first time, we describe the detailed shape of the line signal as well as its time dependence, which is more pronounced compared to earlier results. Our prediction of the features of the signal will be essential for this kind of dark matter search.

    hep-phastro-ph.COJHEP(2021)·69 citations
12. 12*

    Better Latent Spaces for Better Autoencoders

    Barry M. Dillon🇩🇪 · Tilman Plehn🇩🇪 · Christof Sauer🇩🇪 · Peter Sorrenson🇩🇪

    Autoencoders as tools behind anomaly searches at the LHC have the structural problem that they only work in one direction, extracting jets with higher complexity but not the other way around. To address this, we derive classifiers from the latent space of (variational) autoencoders, specifically in Gaussian mixture and Dirichlet latent spaces. In particular, the Dirichlet setup solves the problem and improves both the performance and the interpretability of the networks.

    hep-phcs.LGSciPost Phys.(2021)·68 citations
13. 13*

    Explaining $(g-2{)}_{\mu }$ with Multi-TeV Sleptons

    Wolfgang Altmannshofer🇺🇸 · Sri Aditya Gadam🇺🇸 · Stefania Gori🇺🇸 · Nick Hamer🇺🇸

    We present a supersymmetric extension of the Standard Model in which the new physics contributions to the anomalous magnetic moment of the muon can be more than an order of magnitude larger than in the minimal supersymmetric Standard Model. The extended electroweak symmetry breaking sector of the model can consistently accommodate Higgs bosons and Higgsinos with $O(1)$ couplings to muons. We find that sleptons with masses in the multi-TeV range can comfortably explain the recently confirmed discrepancy in the anomalous magnetic moment of the muon. We discuss additional phenomenological aspects of the model, including its effects on tau flavor changing decays.

    hep-phJHEP(2021)·43 citations
14. 14*

    Peccei-Quinn-like symmetries for nonabelian axions

    Debashis Chatterjee🇮🇳 · P. Mitra🇮🇳

    Axions were first introduced in connection with chiral symmetry but are now being looked for mainly as dark matter. In this paper we introduce a nonabelian analogue of axions which can also be potential candidates for dark matter. Their nonabelian symmetries, which are generalizations of the Peccei-Quinn symmetry, are interesting in their own right. Detailed analysis, using fermion measure and zeta function approaches shows that these symmetries are not anomalous.

    hep-phhep-thJ.Phys.Comm.(2021)·0 citations
15. 15*

    Fundamental Landau Levels in a Strongly Coupled Plasma

    Uriel Elinos🇲🇽 · Leonardo Patino🇲🇽

    We use the gauge/gravity correspondence to show that in its context there appear Landau levels when studying the excitations of the fundamental degrees of freedom of a strongly coupled plasma subject to a magnetic field of arbitrary intensity. We work in the phase where mesons are melted by embedding a D7-brane in the 10D uplift that we construct for the 5D background associated to a magnetic brane. By studying the dependence of the lowest quasinormal frequency on both, the intensity of the magnetic field and the Landau level, we corroborate that the energy behaves as expected for dissociating Landau levels. The reconstruction of the impact of the magnetic field on the stability of the quasinormal modes allows us to identify inverse magnetic catalysis for intensities of the field bellow a certain value, and magnetic catalysis for those above it.

    ↳ hep-thgr-qchep-phPRD(2022)·1 citation
16. 16*

    Tidal deformability of strange stars and the GW170817 event

    Odilon Lourenço🇧🇷 · César H. Lenzi🇧🇷 · Mariana Dutra🇧🇷 · Efrain J. Ferrer🇺🇸 · Vivian de la Incera🇺🇸 · Laura Paulucci🇧🇷 · J. E. Horvath🇧🇷

    In this work we consider strange stars formed by quark matter in the color-flavor-locked (CFL) phase of color superconductivity. The CFL phase is described by a Nambu-Jona-Lasinio model with four-fermion vector and diquark interaction channels. The effect of the color superconducting medium on the gluons are incorporated into the model by including the gluon self-energy in the thermodynamic potential. We construct parametrizations of the model by varying the vector coupling $G_V$ and comparing the results to the data on tidal deformability from the GW170817 event, the observational data on maximum masses from massive pulsars such as the MSP J0740+6620, and the mass/radius fits to NICER data for PSR J003+0451. Our results points out to windows for the $G_V$ parameter space of the model, with and without gluon effects included, that are compatible with all these astrophysical constraints, namely, $0.21<G_V/G_S<0.4$, and $0.02<G_V/G_S<0.1$, respectively. We also observe a strong correlation between the tidal deformabilites of the GW170817 event and $G_V$. Our results indicate that strange stars cannot be ruled out in collisions of compact binaries from the structural point of view.

    ↳ astro-ph.HEhep-phPRD(2021)·32 citations
17. 17*

    The Gravitino and the Swampland

    Niccolò Cribiori🇦🇹 · Dieter Lust🇩🇪 · Marco Scalisi🇩🇪

    We propose a new swampland conjecture stating that the limit of vanishing gravitino mass corresponds to the massless limit of an infinite tower of states and to the consequent breakdown of the effective field theory. We test our proposal in large classes of models coming from compactification of string theory to four dimensions, where we identify the Kaluza-Klein nature of the tower of states becoming light. We point out a general relation between the gravitino mass and abelian gauge coupling in models with extended supersymmetry, which can survive also in examples with minimal supersymmetry. This allows us to connect our conjecture to other well established swampland conjectures, such as the weak gravity conjecture or the absence of global symmetries in quantum gravity. We discuss phenomenological implications of our conjecture in (quasi-)de Sitter backgrounds and extract a lower bound for the gravitino mass in terms of the Hubble parameter.

    ↳ hep-thastro-ph.COgr-qchep-phJHEP(2021)·74 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.