Mon·Dec 10, 2018Monday·December 10, 2018

1. 01*

   Analysing direct photon spectra and elliptic flow from heavy ion collision measurements at the top RHIC energy within the integrated hydrokinetic model

   V. Yu. Naboka🇺🇦 · Yu. M. Sinyukov🇺🇦 · G. M. Zinovjev🇺🇦

   The integrated HydroKinetic Model (iHKM) is applied to analyse the results of direct photon spectra and elliptic flow measurements in 200A GeV Au+Au collisions at RHIC for the three centrality bins. We detect the strong centrality dependence of photon elliptic flow as $v_2(p_T)$-coefficient increases towards peripheral collisions. The photon production in the model is accumulated from the different sources along with the process of relativistic heavy ion collision developing. Those include the primary hard photons from the parton collisions at very early stage of the process, the photons generated at the pre-thermal phase of matter evolution, then thermal photons at equilibrated quark-gluon stage together with radiation displaying a confinement and, finally, from the hadron gas phase. Along the way a hadronic medium evolution is treated in two distinct, in a sense opposite, approaches: chemically equilibrated and chemically frozen system expansion. We find that similar as it was found in iHKM for the LHC energies, a description of the direct photon spectra and elliptic flows is significantly improved if an additional portion of the photon radiation, that is associated with hadronization processes, is included into consideration.

   hep-phnucl-th0 citations
2. 02*

   Non-standard neutrino interactions and low energy experiments

   Wolfgang Altmannshofer🇺🇸 · Michele Tammaro🇺🇸 · Jure Zupan🇺🇸

   We formulate an Effective Field Theory (EFT) for Non Standard neutrino Interactions (NSI) in elastic scattering with light quarks, leptons, gluons and photons, including all possible operators of dimension 5, 6 and 7. We provide the expressions for the cross sections in coherent neutrino-nucleus scattering and in deep inelastic scattering. Assuming single operator dominance we constrain the respective Wilson coefficient using the measurements by the COHERENT and CHARM collaborations. We also point out the constraining power of future elastic neutrino-nucleus scattering experiments. Finally, we explore the implications of the bounds for SMEFT operators above the electroweak breaking scale.

   hep-phhep-exJHEP(2019)·84 citations
3. 03*

   Equations of motion, symmetry currents and EFT below the electroweak scale

   Andreas Helset🇩🇰 · Michael Trott🇩🇰

   The low-energy effective field theory is constructed by integrating out Standard Model states with masses proximate to the electroweak scale. We report the equations of motion for this theory, including corrections due to higher dimensional operators up to mass dimension six. We construct the corresponding symmetry currents, and discuss how the $\mathrm{SU}(2{)}_{\mathrm{L}}\times \mathrm{U}(1{)}_{\mathsf{y}}$ symmetry, and global symmetries, are manifested when Standard Model states are integrated out. Including contributions from higher dimensional operators to the equations of motion modifies the interpretation of conserved currents. We discuss the corrections to the electromagnetic current as an example, showing how modifications to the equation of motion, and corresponding surface terms, have a direct interpretation in terms of multipole charge distributions that act to source gauge fields.

   hep-phPLB(2019)·7 citations
4. 04*

   Spin rotation effects in diffractive electroproduction of heavy quarkonia

   Michal Krelina🇨🇱 · Jan Nemchik🇨🇿 · Roman Pasechnik🇸🇪 · Jan Cepila🇨🇿

   In this work we present for the first time the comprehensive study of the Melosh spin rotation effects in diffractive electroproduction of S-wave heavy quarkonia off a nucleon target. Such a study has been performed within the color dipole approach using, as an example and a reference point, two popular parametrizations of the dipole cross section and two potentials describing the interaction between Q and bar{Q} and entering in the Schroedinger equation based formalism for determination of the quarkonia wave functions. We find a strong onset of spin rotation effects in 1S charmonium photoproduction which is obviously neglected in present calculations of corresponding cross sections. For photoproduction of radially excited Psi'(2S) these effects are even stronger leading to an increase of the photoproduction cross section by a factor of 2-3 depending on the photon energy. Even in production of radially excited Y'(2S) and Y"(3S) they can not be neglected and cause the 20-30% enhancement of the photoproduction cross section. Finally, we predict that the spin effects vanish gradually with photon virtuality Q^2 following universality properties in production of different heavy quarkonia as a function of Q^2 + M_V^2.

   hep-phEPJC(2019)·32 citations
5. 05*

   Flavor and Dark Matter connection

   Avelino Vicente🇪🇸

   In recent years, the LHCb collaboration has published results on the measurement of several observables associated to semileptonic $b\to s$ transitions. Interestingly, various deviations from their expected values in the Standard Model have been found, including some tantalizing hints pointing towards the violation of Lepton Flavor Universality. We discuss New Physics models that address these anomalies and explore their possible connection to the dark matter of the Universe.

   hep-phhep-exSpringer Proc.Phys.(2019)·5 citations
6. 06*

   Evaluating multi-loop Feynman integrals numerically through differential equations

   Manoj K. Mandal🇮🇹 · Xiaoran Zhao🇧🇪

   The computation of Feynman integrals is often the bottleneck of multi-loop calculations. We propose and implement a new method to efficiently evaluate such integrals in the physical region through the numerical integration of a suitable set of differential equations, where the initial conditions are provided in the unphysical region via the sector decomposition method. We present numerical results for a set of two-loop integrals, where the non-planar ones complete the master integrals for $gg\to \gamma \gamma$ and $q\bar{q}\to \gamma \gamma$ scattering mediated by the top quark.

   hep-phJHEP(2019)·44 citations
7. 07*

   Spin-states in multiphoton pair production for circularly polarized light

   Christian Kohlfürst🇩🇪

   Scalar and fermionic particle pair production in rotating electric fields is investigated in the nonperturbative multiphoton regime. Angular momentum distribution functions in above-threshold pair production processes are calculated numerically within quantum kinetic theory and discussed on the basis of a photon absorption model. The particle spectra can be understood if the spin states of the particle-antiparticle pair are taken into account.

   hep-phphysics.atom-phphysics.plasm-phquant-phPRD(2019)·41 citations
8. 08*

   Effective approach to lepton observables: the seesaw case

   Rupert Coy🇫🇷 · Michele Frigerio🇫🇷

   In the absence of direct evidence of new physics, any ultraviolet theory can be reduced to its specific set of low-energy effective operators. As a case study, we derive the effective field theory for the seesaw extension of the Standard Model, with sterile neutrinos of mass $M>m_W$. We systematically compute all Wilson coefficients generated at one loop. Hence, it becomes straightforward to (i) identify the seesaw parameters compatible with the smallness of neutrino masses; (ii) compute precision lepton observables, which may be sensitive to scales as large as $M\sim 10^3$ TeV; and (iii) establish sharp correlations among those observables. We find that the flavour-conserving Wilson coefficients set an upper bound on the flavour-violating ones. The low-energy limits on $\mu \to e$ and $\tau \to e,\mu$ transitions suppress flavour violation in $Z$ and Higgs decays, as well as electric dipole moments, far beyond the experimental reach. The precision measurements of $G_F$, $m_W$, and $Z$ partial decay widths set more stringent bounds than present and future limits on $\tau \to e,\mu$ transitions. We also present a general spurion analysis, to compare the seesaw with different models, thus assessing the discriminating potential of the effective approach.

   hep-phPRD(2019)·41 citations
9. 09*

   Bound States of Pseudo-Dirac Dark Matter

   Arindam Bhattacharya🇺🇸 · Tracy R. Slatyer🇺🇸

   We study the bound-state spectrum in a simple model of pseudo-Dirac dark matter, and examine how the rate of bound-state formation through radiative capture compares to Sommerfeld-enhanced annihilation. We use this model as an example to delineate the new features induced by the presence of a mass splitting between the dark matter and a nearly-degenerate partner, compared to the case where only a single dark-matter-like state is present. We provide a simple analytic prescription for estimating the spectrum of bound states in systems containing a mass splitting, which in turn allows characterization of the resonances due to near-zero-energy bound states, and validate this estimate both for pseudo-Dirac dark matter and for the more complex case of wino dark matter. We demonstrate that for pseudo-Dirac dark matter the capture rate into deeply bound states is, to a good approximation, simply related to the Sommerfeld enhancement factor.

   hep-phJCAP(2019)·6 citations
10. 10*

    Phenomenology of TeV-scale scalar Leptoquarks in the EFT

    Shaouly Bar-Shalom🇮🇱 · Jonathan Cohen🇮🇱 · Amarjit Soni🇺🇸 · Jose Wudka🇺🇸

    We examine new aspects of leptoquark (LQ) phenomenology using effective field theory (EFT). We construct a complete set of leading effective operators involving SU(2) singlets scalar LQ and the SM fields up to dimension six. We show that, while the renormalizable LQ-lepton-quark interaction Lagrangian can address the persistent hints for physics beyond the Standard Model in the B-decays $\bar{B}\to D^{(\ast )}\tau \bar{\nu }$, $\bar{B}\to \bar{K}{\ell }^{+}{\ell }^{-}$ and in the measured anomalous magnetic moment of the muon, the LQ higher dimensional effective operators may lead to new interesting effects associated with lepton number violation. These include the generation of one-loop sub-eV Majorana neutrino masses, mediation of neutrinoless double-$\beta$ decay and novel LQ collider signals. For the latter, we focus on 3rd generation LQ (${\varphi }_3$) in a framework with an approximate $Z_3$ generation symmetry, and show that one class of the dimension five LQ operators may give rise to a striking asymmetric same-charge ${\varphi }_3{\varphi }_3$ pair-production signal, which leads to low background same-sign leptons signals at the LHC. For example, with $M_{{\varphi }_3}\sim 1$ TeV and a new physics scale of $\Lambda \sim 5$ TeV, we expect about $5000$ positively charged ${\tau }^{+}{\tau }^{+}$ events via $pp\to {\varphi }_3{\varphi }_3\to {\tau }^{+}{\tau }^{+}+2\cdot j_b$ ($j_b$=b-jet) at the 13 TeV LHC with an integrated luminosity of 300 fb${}^{-1}$. It is interesting to note that, in the LQ EFT framework, the expected same-sign lepton signals have a rate which is several times larger than the QCD LQ-mediated opposite-sign leptons signals, $gg,q\bar{q}\to {\varphi }_3{\varphi }_3^{\ast }\to {\ell }^{+}{\ell }^{-}+X$. We also consider the same-sign charged lepton signals in the LQ EFT framework at higher energy hadron colliders such as a 27 TeV HE-LHC and a 100 TeV FCC-hh.

    hep-phhep-exPRD(2019)·17 citations
11. 11*

    Bounds and Prospects for Stable Multiply Charged Particles at the LHC

    Sebastian Jäger🇬🇧 · Sandra Kvedaraitė🇬🇧 · Gilad Perez🇮🇱 · Inbar Savoray🇮🇱

    Colored and colorless particles that are stable on collider scales and carry exotic electric charges, so-called multiply-charged heavy stable particles (MCHSPs), exist in extensions of the Standard Model, and can include the top partner(s) in solutions of the hierarchy problem. To obtain bounds on color-triplets and color-singlets of charges up to |Q|=8, we recast searches for signatures of two production channels: the "open" channel - where the particles are pair-produced above threshold, and are detectable in dedicated LHC searches for stable multiply charged leptons, and the "closed" channel - where a particle-antiparticle pair is produced as a bound state, detectable in searches for a diphoton resonance. We recast the open lepton searches by incorporating the relevant strong-interaction effects for color-triplets. In both open and closed production, we provide a careful assessment of photon-induced processes using the accurate LUXqed PDF, resulting in substantially weaker bounds than previously claimed in the literature for the colorless case. Our bounds for colored MCHSPs are shown for the first time, as the LHC experiments have not searched for them directly. Generally, we obtain nearly charge-independent lower mass limits of around 970 GeV (color-triplet scalar), 1200 GeV (color-triplet fermion), and 880 - 900 GeV (color-singlet fermion) from open production, and strongly charge-dependent limits from closed production. In all cases there is a crossover between dominance by open and closed searches at some charge. We provide prospective bounds for $\sqrt{s}=13$ TeV LHC searches at integrated luminosities of 39.5 fb${}^{-1}$, 100 fb${}^{-1}$, and 300 fb${}^{-1}$. Moreover, we show that a joint observation in the open and the closed channels allows to determine the mass, spin, color, and electric charge of the particle.

    hep-phhep-exJHEP(2019)·14 citations
12. 12*

    Lepton-flavor violation and two loop electroweak corrections to $(g-2{)}_{\mu }$ in the B-L symmetry SSM

    Jin-Lei Yang🇨🇳 · Tai-Fu Feng🇨🇳 · Yu-Li Yan🇨🇳 · Wei Li🇨🇳 · Shu-Min Zhao🇨🇳 · Hai-Bin Zhang🇨🇳

    Charged lepton flavor violating processes are forbidden in the standard model (SM), hence the observation of charged lepton flavor transitions would represent a clear signal of new physics beyond the standard Model. In this work, we investigate some lepton flavor violating processes in the minimal supersymmetric extension of the SM with local $B-L$ gauge symmetry (B-LSSM). And including the corrections from some two loop diagrams to the anomalous dipole moments (MDM) of muon, we discuss the corresponding constraint on the relevant parameter space of the model. Considering the constraints from updated experimental data, the numerical results show that, new contributions in the B-LSSM enhance the MSSM predictions on the rates of $l_j-l_i$ transitions about one order of magnitude, and also enhance the MSSM prediction on the muon MDM. In addition, two loop electroweak corrections can make important contributions to the muon MDM in the B-LSSM.

    hep-phPRD(2019)·37 citations
13. 13*

    The Hierarchy Problem and the Cosmological Constant Problem Revisited -- A new view on the SM of particle physics

    Fred Jegerlehner🇩🇪

    We argue that the Standard Model (SM) in the Higgs phase does not suffer from a "hierarchy problem" and that similarly the "cosmological constant problem" resolves itself if we understand the SM as a low energy effective theory emerging from a cutoff-medium at the Planck scale. We actually take serious Veltman's "The Infrared - Ultraviolet Connection" addressing the issue of quadratic divergences and the related huge radiative correction predicted by the SM in the relationship between the bare and the renormalized theory, usually called "the hierarchy problem" and claimed that this has to be cured. We discuss these issues under the condition of a stable Higgs vacuum, which allows to extend the SM up to the Planck cutoff. The bare Higgs boson mass then changes sign below the Planck scale, such that the SM in the early universe is in the symmetric phase. The cutoff enhanced Higgs mass term as well as the quartically enhanced cosmological constant term provide a large positive dark energy which triggers the inflation of the early universe. Reheating follows via the decays of the four unstable heavy Higgs particles, predominantly into top-antitop pairs, which at this stage are still massless. Preheating is suppressed in SM inflation since in the symmetric phase bosonic decay channels are absent at tree level. The coefficients of the shift between bare and renormalized Higgs mass as well as of the shift between bare and renormalized vacuum energy density exhibit close-by zeros at about $7.7\times 10^{14}$ GeV and $3.1\times 10^{15}$ GeV, respectively. The zero of of the Higgs mass counter term triggers the electroweak phase transition from the low energy Higgs phase and to the symmetric phase above the transition point. The scenario highly favors to understand the SM and its main properties as a natural structure emerging at long distance.

    hep-phFound.Phys.(2019)·23 citations
14. 14*

    Fermi-LAT Observations of Gamma-Ray Emission Towards the Outer Halo of M31

    Chris Karwin🇺🇸 · Simona Murgia🇺🇸 · Sheldon Campbell🇺🇸 · Igor Moskalenko🇺🇸

    The Andromeda Galaxy is the closest spiral galaxy to us and has been the subject of numerous studies. It harbors a massive dark matter (DM) halo which may span up to ~600 kpc across and comprises ~90% of the galaxy's total mass. This halo size translates into a large diameter of 42 degrees on the sky for an M31-Milky Way (MW) distance of 785 kpc, but its presumably low surface brightness makes it challenging to detect with gamma-ray telescopes. Using 7.6 years of Fermi Large Area Telescope (Fermi-LAT) observations, we make a detailed study of the gamma-ray emission between 1-100 GeV towards M31's outer halo, with a total field radius of 60 degrees centered at M31, and perform an in-depth analysis of the systematic uncertainties related to the observations. We use the cosmic ray (CR) propagation code GALPROP to construct specialized interstellar emission models (IEMs) to characterize the foreground gamma-ray emission from the MW, including a self-consistent determination of the isotropic component. We find evidence for an extended excess that appears to be distinct from the conventional MW foreground, having a total radial extension upwards of ~120-200 kpc from the center of M31. We discuss plausible interpretations of the excess emission but emphasize that uncertainties in the MW foreground, and in particular, modeling of the H I-related components, have not been fully explored and may impact the results. This study was first presented in a poster at the 8th International Fermi Symposium. The article describing the full analysis is under preparation and will be published elsewhere.

    ↳ astro-ph.HEhep-ph38 citations
15. 15*

    Covariant chiral nucleon-nucleon contact Lagrangian up to order $\mathcal{O}(q^4)$

    Yang Xiao🇨🇳 · Li-Sheng Geng🇨🇳 · Xiu-Lei Ren🇩🇪

    We adopt a covariant version of the naive dimensional analysis and construct the chiral two-nucleon contact Lagrangian constrained by Lorentz, parity, charge conjugation, hermitian conjugation, and chiral symmetries. We show that at $\mathcal{O}(q^0)$, $\mathcal{O}(q^2)$, $\mathcal{O}(q^4)$, where $q$ denotes a generic small quantity, there are 4, 13, and 23 terms, respectively. We find that by performing $1/m_N$ expansions, the covariant Lagrangian reduces to the conventional non-relativistic one, which includes 2, 7, and 15 terms at each corresponding order.

    ↳ nucl-thhep-lathep-phPRC(2019)·41 citations
16. 16*

    Kaons and antikaons in strong magnetic fields

    Amruta Mishra🇮🇳 · Anuj Kumar Singh🇮🇳 · Neeraj Singh Rawat🇮🇳 · Pratik Aman🇮🇳

    The in-medium masses of the kaons and antikaons in strongly magnetized asymmetric nuclear matter are studied using a chiral SU(3) model. The medium modifications of the masses of these open strange pseudoscalar mesons arise due to their interactions with the nucleons and scalar mesons within the model. The proton, the charged nucleon, has effects from the Landau energy levels in the presence of the magnetic field. The anomalous magnetic moments (AMM) of the nucleons are taken into consideration in the present study and these are seen to be large at high magnetic fields and high densities. The isospin effects are appreciable at high densities. The density effects are observed to be the dominant medium effects, as compared to the effects from magnetic field and isospin asymmetry. ~

    ↳ nucl-thhep-phEPJA(2019)·18 citations
17. 17*

    Black hole formation in the context of dissipative dark matter

    M. A. Latif🇦🇪 · A. Lupi🇮🇹 · D. R. G. Schleicher🇨🇱 · G. D'Amico🇨🇭 · P. Panci🇨🇭 · S. Bovino🇨🇱

    Black holes with masses of $10^6-10^9{\mathrm{M}}_{\odot }$ dwell in the centers of most galaxies, but their formation mechanisms are not well known. A subdominant dissipative component of dark matter with similar properties to the ordinary baryons, known as mirror dark matter, may collapse to form massive black holes during the epoch of first galaxies formation. In this study, we explore the possibility of massive black hole formation via this alternative scenario. We perform three-dimensional cosmological simulations for four distinct halos and compare their thermal, chemical and dynamical evolution in both the ordinary and the mirror sectors. We find that the collapse of halos is significantly delayed in the mirror sector due to the lack of ${\mathrm{H}}_2$ cooling and only halos with masses above $\ge 10^7{\mathrm{M}}_{\odot }$ are formed. Overall, the mass inflow rates are $\ge 10^{-2}{\mathrm{M}}_{\odot }/yr$ and there is less fragmentation. This suggests that the conditions for the formation of massive objects, including black holes, are more favorable in the mirror sector.

    ↳ astro-ph.COastro-ph.GAhep-phMNRAS(2019)·30 citations
18. 18*

    Study of warm inflationary models and their parameter estimation from CMB

    Richa Arya🇮🇳 · Raghavan Rangarajan🇮🇳

    Observations of the temperature anisotropies in the Cosmic Microwave Background (CMB) radiation show that the models of inflation with the monomial potentials are inconsistent with the allowed $n_s-r$ bounds. However certain monomial potentials of inflation are allowed in the context of \textit{Warm Inflation}, where the inflaton's coupling with other fields are significant both \textit{during and after} the inflationary phase. In our study, we consider $\lambda {\varphi }^4$ and $\lambda {\varphi }^6$ models of warm inflation with different forms of the inflaton dissipation coefficient. We parameterize the primordial power spectrum in terms of the model parameters, namely, the inflaton self coupling, $\lambda$, and the dissipation parameter, $Q_P$, due to inflaton's interaction with the other fields. Then we obtain the joint and marginal distributions of these parameters by carrying out a Markov Chain Monte Carlo (MCMC) analysis using the {\tt CosmoMC} numerical code. An estimation of these physical parameters is essential for model building. We also obtain the $n_s$ and $r$ values for the mean values of the parameters and find them to be consistent with the observational bounds, confirming that these simple models are viable models for describing inflation.

    ↳ astro-ph.COhep-phInt.J.Mod.Phys.D(2020)·24 citations
19. 19*

    Lattice formulation of axion inflation. Application to preheating

    Jose Roberto Canivete Cuissa🇨🇭 · Daniel G. Figueroa🇨🇭

    We present a lattice formulation of an interaction $\frac{\varphi }{\Lambda }F\tilde{F}$ between an axion and some $U(1)$ gauge sector with the following properties: it reproduces the continuum theory up to $\mathcal{O}(d{x}_{\mu }^2)$ corrections, it preserves exact gauge invariance and shift symmetry on the lattice, and it is suitable for self-consistent expansion of the Universe. The lattice equations of motion can no longer be solved by explicit methods, but we propose an implicit method to overcome this difficulty, which preserves the relevant system constraints down to arbitrary (tunable) precision. As a first application we study, in a comoving grid in $(3+1)$ dimensions, the last efolds of axion-inflation with quadratic potential and the preheating stage following afterwards. We fully account for the inhomogeneity and non-linearity of the system, including the gauge field contribution to the expansion rate of the Universe and its backreaction into the axion dynamics. We characterize in detail, as a function of the coupling, the energy transfer from the axion to the gauge field. Two coupling regimes are identified, sub- and super-critical, depending on whether the final energy fraction stored in the gauge field is below or above $\sim 50\%$ of the total energy. The Universe is very efficiently reheated for super-critical couplings, rapidly entering in a radiation dominated stage. Our results on preheating confirm previously published results.

    ↳ astro-ph.COhep-phJCAP(2019)·109 citations
20. 20*

    Entanglement Suppression and Emergent Symmetries of Strong Interactions

    Silas R. Beane🇺🇸 · David B. Kaplan🇺🇸 · Natalie Klco🇺🇸 · Martin J. Savage🇺🇸

    Entanglement suppression in the strong interaction $S$-matrix is shown to be correlated with approximate spin-flavor symmetries that are observed in low-energy baryon interactions, the Wigner $SU(4)$ symmetry for two flavors and an $SU(16)$ symmetry for three flavors. We conjecture that dynamical entanglement suppression is a property of the strong interactions in the infrared, giving rise to these emergent symmetries and providing powerful constraints on the nature of nuclear and hypernuclear forces in dense matter.

    ↳ nucl-thhep-lathep-phhep-th+1PRL(2019)·184 citations
21. 21*

    Infrared massive gluon propagator from a BRST-invariant Gribov horizon in a family of covariant gauges

    Bruno W. Mintz🇧🇷 · Leticia F. Palhares🇧🇷 · Giovani Peruzzo🇧🇷 · Silvio P. Sorella🇧🇷

    A distinctive feature observed in lattice simulations of confining nonabelian gauge theories, such as Quantum Chromodynamics, is the presence of a dynamical mass for the gauge field in the low energy regime of the theory. In the Gribov-Zwanziger framework in the Landau gauge, such mass is a consequence of the generation of the dimension two condensates $⟨A_{\mu }^a{A}_{\mu }^a⟩$ and $⟨{\bar{\phi }}_{\mu }^{ab}{\phi }_{\mu }^{ab}-{\bar{\omega }}_{\mu }^{ab}{\omega }_{\mu }^{ab}⟩$, where $A$ is the gluon field and the fields $\bar{\phi }$, $\phi$, $\bar{\omega }$, and $\omega$ are Zwanziger's auxiliary fields. In this work, we show that, in the recently developed BRST-invariant version of the Refined Gribov-Zwanziger theory, these condensates can be introduced in a BRST-invariant way for a family of $R_{\xi }$ gauges. Their values are explicitly computed to first order and turn out to be independent of the gauge parameters contained in the gauge-fixing condition, as expected from the BRST invariance of the formulation. This fact supports the possibility of a gauge-parameter independent nonzero infrared gluon mass, whose value is the same as the one in the Landau gauge.

    ↳ hep-thhep-phPRD(2019)·19 citations
22. 22*

    Elasticity tetrads, mixed axial-gravitational anomalies, and 3+1d quantum Hall effect

    J. Nissinen🇫🇮 · G.E. Volovik🇫🇮

    For two-dimensional topological insulators, the integer and intrinsic (without external magnetic field) quantum Hall effect is described by the gauge anomalous (2+1)-dimensional [2+1d] Chern-Simons (CS) response for the background gauge potential of the electromagnetic U(1) field. The Hall conductance is given by the quantized prefactor of the CS term, which is a momentum-space topological invariant. Here, we show that three-dimensional crystalline topological insulators with no other symmetries are described by a topological (3+1)-dimensional [3+1d] mixed CS term. In addition to the electromagnetic U(1) gauge field, this term contains elasticity tetrad fields $E_{\mu }^a(\mathbf{r},t)={\partial }_{\mu }{X}^a(\mathbf{r},t)$ which are gradients of crystalline U(1) phase fields $X^a(\mathbf{r},t)$ and describe the deformations of the crystal. For a crystal in three spatial dimensions $a=1,2,3$ and the mixed axial-gravitational response contains three parameters protected by crystalline symmetries: the weak momentum-space topological invariants. The response of the Hall conductance to the deformations of the crystal is quantized in terms of these invariants. In the presence of dislocations, the anomalous 3+1d CS term describes the Callan-Harvey anomaly inflow mechanism. The response can be extended to all odd spatial dimensions. The elasticity tetrads, being the gradients of the lattice U(1) fields, have canonical dimension of inverse length. Similarly, if such tetrad fields enter general relativity, the metric becomes dimensionful, but the physical parameters, such as Newton's constant, the cosmological constant, and masses of particles, become dimensionless.

    ↳ cond-mat.mes-hallgr-qchep-phPRResearch(2019)·56 citations
23. 23*

    Simulating dynamically assisted production of Dirac pairs in gapped graphene monolayers

    Ibrahim Akal🇩🇪 · Reinhold Egger🇩🇪 · Carsten Müller🇩🇪 · Selym Villalba-Chávez🇩🇪

    In a vicinity of the Fermi surface, graphene layers with bandgaps allow for closely simulating the vacuum of quantum electrodynamics and, thus, its yet unverified strong-field phenomenology with accessible field strengths. This striking feature is exploited to investigate a plausible materialization of dynamically assisted pair production through the analog production of light but massive pairs of Dirac quasiparticles. The process is considered in a field configuration combining a weak high-frequency electric mode and a strong low-frequency electric field oscillating in time. Its theoretical study is carried out from a quantum kinetic approach, similar to the one governing the spontaneous production of pairs in QED. We show that the presence of the weak assisting mode can strongly increase the number of produced massive Dirac pairs as compared with a setup driven by the strong field only. The efficiency of the process is contrasted, moreover, with the case of gapless graphene to highlight the role played by the quasiparticle mass.

    ↳ cond-mat.mes-hallhep-phPRD(2019)·22 citations
24. 24*

    Sensitivity of the elastic electron-proton cross section to the proton radius

    Simone Pacetti🇮🇹 · Egle Tomasi-Gustafsson🇫🇷

    The precise determination of the proton radius from recent elastic scattering electron-proton data is discussed. The necessary precision on the elastic cross section to discriminate among the values coming from atomic spectroscopy is scrutinized in terms of the relevant quantity, i.e., the derivative of the form factor. It is shown that such precision is two orders of magnitude higher than the precision on the cross section, that is the measured observable. Different fits on the available data and of their discrete derivative, with analytical constraints are shown. The systematic error associated to the radius is evaluated taking into account the uncertainties from different sources, as the extrapolation to the static point, the choice of the class of fitting functions and the range of the data sample. This error is shown to be even orders of magnitude larger than commonly assumed.

    ↳ nucl-thhep-phEPJA(2020)·10 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.