Publications

Order by: publication date number of citations

• Massless Rarita-Schwinger equations: Half and three halves spin solution

  Mauricio Valenzuela, Jorge Zanelli

  SciPost Phys. 16, 065 (2024) · published 4 March 2024 | Toggle abstract · pdf

  Counting the degrees of freedom of the massless Rarita-Schwinger theory is revisited using Behrends-Fronsdal projectors. The identification of the gauge invariant part of the vector-spinor is thus straightforward, consisting of spins 1/2 and 3/2. The validity of this statement is supported by the explicit solution found in the standard gamma-traceless gauge. Since the obtained systems are deterministic -free of arbitrary functions of time- we argue that the often-invoked residual gauge symmetry lacks fundamental grounding and should not be used to enforce new external constraints. The result is verified by the total Hamiltonian dynamics. We conclude that eliminating the spin-1/2 mode via the extended Hamiltonian dynamics would be acceptable if the Dirac conjecture was assumed; however, this framework does not accurately describe the original Lagrangian system.

  2 citations

• Stability and asymptotic interactions of chiral magnetic skyrmions in a tilted magnetic field

  Bruno Barton-Singer, Bernd J. Schroers

  SciPost Phys. 15, 011 (2023) · published 17 July 2023 | Toggle abstract · pdf

  Using a general framework, interaction potentials between chiral magnetic solitons in a planar system with a tilted external magnetic field are calculated analytically in the limit of large separation. The results are compared to previous numerical results for solitons with topological charge $\pm 1$. A key feature of the calculation is the interpretation of Dzyaloshinskii-Moriya interaction (DMI) as a background $SO(3)$ gauge field. In a tilted field, this leads to a $U(1)$-gauged version of the usual equation for spin excitations, leading to a distinctive oscillating interaction profile. We also obtain predictions for skyrmion stability in a tilted field which closely match numerical observations.

  2 citations

• Master integrals contributing to two-loop leading colour QCD helicity amplitudes for top-quark pair production in the gluon fusion channel

  Ekta Chaubey

  SciPost Phys. Proc. 7, 001 (2022) · published 20 June 2022 | Toggle abstract · pdf

  We discuss the analytic structure of the master integrals relevant for computing the com- plete set of leading-colour analytic helicity amplitudes for top-quark pair production via gluon fusion at two loops in QCD. This includes corrections due to massive fermion loops which give rise to integrals involving elliptic curves. We also elaborate on the structure of singularities that play an important role in the numerical evaluation of the iterated integrals and their analytic continuation.

  1 citation

• A new Wilson line-based classical action for gluodynamics

  Hiren Kakkad, Piotr Kotko, Anna Stasto

  SciPost Phys. Proc. 7, 011 (2022) · published 20 June 2022 | Toggle abstract · pdf

  We develop a new classical action that in addition to $\mathrm{MHV}$ vertices contains also $\mathrm{N^kMHV}$ vertices, where $1\leq k \leq n-4$ with $n$ the number of external legs. The lowest order vertex is the four-point MHV vertex -- there is no three point vertex and thus the amplitude calculation involves fewer vertices than in the CSW method. The action is obtained by a canonical transformation of the Yang-Mills action in the light-cone gauge, where the field transformations are based on Wilson line functionals.

  1 citation

• Higher-order $β$-functions in the Standard Model and beyond

  Florian Herren

  SciPost Phys. Proc. 7, 029 (2022) · published 21 June 2022 | Toggle abstract · pdf

  In this contribution we consider the recent computation of the gauge coupling $\beta$-function at four loops and the Yukawa matrix $\beta$-function at three loops in the most general, renormalizable and four-dimensional quantum field theory. Furthermore, we discuss ambiguities and divergences arising in Yukawa matrix $\beta$-functions.

  1 citation

• Centre vortex structure of QCD-vacuum fields and confinement

  Derek Leinweber, James Biddle, Waseem Kamleh

  SciPost Phys. Proc. 6, 004 (2022) · published 31 May 2022 | Toggle abstract · pdf

  The non-trivial ground-state vacuum fields of QCD form the foundation of matter. Using modern visualisation techniques, this presentation examines the microscopic structure of these fields. Of particular interest are the centre vortices identified within the ground-state fields of lattice QCD. Our current focus is on understanding the manner in which dynamical fermions in the QCD vacuum alter the centre-vortex structure. The impact of dynamical fermions is significant and provides new insights into the role of centre vortices in underpinning both confinement and dynamical chiral symmetry breaking in QCD.

  1 citation

• Structure Functions and Parton Densities: a Session Summary

  Benjamin Nachman, Katarzyna Wichmann, Pia Zurita

  SciPost Phys. Proc. 8, 004 (2022) · published 11 July 2022 | Toggle abstract · pdf

  Studies of fragmentation and parton density functions are a core component of researchin high energy particle and nuclear physics. These quantities are inherently interestingas a probe of the quantum nature of the strong force and are also essential ingredients toadditional studies in high energy scattering experiments. These proceedings provide anoverview of the state of the art in this area, as presented at the Deep-Inelastic ScatteringConference in the Spring of 2021.

  1 citation

• Central dileption production in proton-proton collisions with rapidity gap and with forward protons

  Antoni Szczurek, Barbara Linek, Marta Luszczak

  SciPost Phys. Proc. 8, 083 (2022) · published 12 July 2022 | Toggle abstract · pdf

  We discuss photon-photon fusion mechanisms of dilepton production in proton-proton collisions with rapidity gap in the main detector and one forward proton in the forward proton detectors. This is relevant for the LHC measurements by ATLAS+AFP and CMS+PPS. Transverse momenta of the intermediate photons are taken into account and photon fluxes are expressed in terms of proton electromagnetic form factors and structure functions. Both double-elastic and single-dissociative processes are included in the analysis. Different parametrizations of the structure functions are used. Some differential distributions are presented. Some differences with respect to the results without proton measurement are discussed.

  1 citation

• Nuclear matter effects on jet production at electron-ion colliders

  Hai Tao Li, Ze Long Liu, Ivan Vitev

  SciPost Phys. Proc. 8, 134 (2022) · published 14 July 2022 | Toggle abstract · pdf

  In these proceedings we report recent progress on understanding hadron and jet production in electron-nucleus collisions at the future Electron-Ion Collider [1,2]. These processes will play an essential role in the exploration of the partonic structure of nuclei and the study of parton shower evolution in strongly-interacting matter. We employ the framework of soft-collinear effective theory, generalized to include in-medium interactions, to present the first theoretical results for inclusive hadron and jet cross sections, as well as the jet charge modification in deep inelastic scattering on nuclei. We further demonstrate how to separate initial-state and final-state effects.

  1 citation

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

  T. J. Hobbs

  SciPost Phys. Proc. 8, 155 (2022) · published 14 July 2022 | Toggle abstract · pdf

  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.

  1 citation