Publications

Order by: publication date number of citations

• Recent LHCb results on forward physics and diffraction

  Luke McConnell

  SciPost Phys. Proc. 15, 009 (2024) · published 2 April 2024 | Toggle abstract · pdf

  The LHCb detector at the LHC offers unique coverage of forward rapidities for studies of Central Exclusive Production (CEP) and soft QCD. CEP measurements allow the investigation of the nature of pomerons, and provide constraints on low-x gluon phenomenology, probing potential saturation effects. Moreover LHCb can test phenomenological models of soft QCD processes, by measuring the production of forward hadrons in pp collisions. In this talk the latest results from the LHCb experiment will be presented.

• Forward proton measurements with ATLAS

  Mustafa Schmidt

  SciPost Phys. Proc. 15, 008 (2024) · published 2 April 2024 | Toggle abstract · pdf

  The ALFA subdetector is designed to measure elastic proton-proton scattering from which the total cross section and $\rho$-parameter are determined. In 2016, special runs at a center-of-mass energy of $\sqrt{s}$ = 13 TeV and with $\beta^\star$ = 2.5 km were recorded.

• Geometry and causality for efficient multiloop representations

  German F. R. Sborlini

  SciPost Phys. Proc. 7, 047 (2022) · published 22 June 2022 | Toggle abstract · pdf

  Multi-loop scattering amplitudes constitute a serious bottleneck in current high-energy physics computations. Obtaining new integrand level representations with smooth behaviour is crucial for solving this issue, and surpassing the precision frontier. In this talk, we describe a new technology to rewrite multi-loop Feynman integrands in such a way that non-physical singularities are avoided. The method is inspired by the Loop-Tree Duality (LTD) theorem, and uses geometrical concepts to derive the causal structure of any multi-loop multi-leg scattering amplitude. This representation makes the integrand much more stable, allowing faster numerical simulations, and opens the path for novel re-interpretations of higher-order corrections in QFT.

• New 2- and 3-loop heavy flavor corrections to unpolarized and polarized deep-inelastic scattering

  Jakob Ablinger, Johannes Blümlein, Abilio De Freitas, Marco Saragnese, Carsten Schneider, Kay Schoenwald

  SciPost Phys. Proc. 8, 137 (2022) · published 14 July 2022 | Toggle abstract · pdf

  A survey is given on the new 2– and 3–loop results for the heavy flavor contributions to deep–inelastic scattering in the unpolarized and the polarized case. We also discuss related new mathematical aspects applied in these calculations.

• Towards better discrimination and improved modelling of dark-sector showers

  Andy Buckley, Deepak Kar, Sukanya Sinha

  SciPost Phys. Proc. 15, 006 (2024) · published 2 April 2024 | Toggle abstract · pdf

  As no evidence for classic WIMP-based signatures of dark matter have been found at the LHC, several phenomenological studies have raised the possibility of accessing a strongly-interacting dark sector through new collider-event topologies. If dark mesons exist, their evolution and hadronization procedure are currently little constrained. They could decay promptly and result in QCD-like jet structures, even though the original decaying particles are dark sector ones; they could behave as semi-visible jets; or they could behave as completely detector-stable hadrons, in which case the final state is just the missing transverse momentum. In this contribution we will introduce a study performed to explore use of jet substructure methods to distinguish dark-sector from QCD jets in the first two scenarios, using observables in a IRC-safe linear basis, and discuss ways forward for this approach to dark-matter at the LHC.

• Local investigation of the crystal electric field ground-state in CeCu(Sb,Bi)$_2$ heavy fermions

  Davi Zau, G. S. Freitas, P. G. Pagliuso, R. R. Urbano

  SciPost Phys. Proc. 11, 017 (2023) · published 6 June 2023 | Toggle abstract · pdf

  In this work, we performed systematic Nuclear Magnetic Resonance (NMR) and magnetic susceptibility experiments in CeCuSb$_2$ single-crystals. The main findings were compared to previous report for CeCuBi$_2$. The NMR spectra and transferred hyperfine coupling for the $^{63}$Cu nuclei were obtained aiming to observe their correlation with the crystal electric field (CEF) effects on the Ce$^{3+}$ ($J=5/2$) multiplet. Besides, in an attempt to elucidate the magnetic structure through NMR measurements at different magnetic fields orientations, we observed a magnetic transition at $T\approx 8\,$K higher than the Néel temperature $T_N$ measured by magnetic susceptibility indicating the development of short-range magnetic ordering above T$_N$. In addition, the wipe out of the main NMR resonance line and a persistent spin-echo signal throughout the whole frequency-swept range suggest the possibility of an incommensurate magnetic structure in CeCuSb$_2$. Furthermore, the small transferred hyperfine coupling constant found for CeCuSb$_2$ indicates a scenario with more localized Ce$^{3+}$ 4f electrons than for CeMIn$_5$ (M $=$ Co,Rh,Ir) heavy fermions family. Additionally, subtle changes in the hybridization between the $^{63}$Cu with the 4f$^1$ Ce$^{3+}$ electrons in distinct magnetic field orientations allowed us to provide detailed information and map out the 4f CEF orbital ground-state of CeCu(Sb,Bi)$_2$ via NMR measurements.

• Towards the computation of inclusive decay rates using lattice QCD

  Paolo Gambino, Shoji Hashimoto, Sandro Mächler, Marco Panero, Francesco Sanfilippo, Silvano Simula, Antonio Smecca, Nazario Tantalo

  SciPost Phys. Proc. 15, 004 (2024) · published 2 April 2024 | Toggle abstract · pdf

  We present a non-perturbative computation of inclusive rates of semileptonic decays of heavy mesons from lattice QCD simulations. The calculation is based on the extraction of smeared spectral functions obtained from four-point Euclidean correlation functions computed on configuration ensembles of the JLQCD and ETM collaborations. We compare our results for the inclusive decay rates with analytical predictions from the operator-product expansion, finding a good agreement for the calculation of the inclusive decay rate. This opens the path to the theoretical determination of the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element $V_{cb}$ to a level of precision competitive with the present experimental uncertainty.

• IR-Improved Amplitude-Based Resummation in Quantum Field Theory: New Results and New Issues

  B.F.L. Ward, S. Jadach, W. Placzek, M. Skrzypek, Z. Was, S. A. Yost

  SciPost Phys. Proc. 7, 015 (2022) · published 20 June 2022 | Toggle abstract · pdf

  With the advancement of strategies for the precision physics programs for the HL-LHC, FCC-ee, FCC-hh, ILC, CLIC, CEPC, and CPPC, the need for proper control of the attendant theoretical precision tags is manifest. We discuss the role that amplitude-based resummation may play in this regard with examples from the LHC, the proposed new colliders and quantum gravity.

• Measurements of jet substructure and jet fragmentation using the ATLAS detector

  Javier Llorente Merino

  SciPost Phys. Proc. 8, 080 (2022) · published 12 July 2022 | Toggle abstract · pdf

  Measurements of the internal properties of jets at the LHC interaction scale allow QCD to be studied in a new energy regime. In this talk, we discuss recent measurements of jet substructure and jet fragmentation, which were performed using data collected by the ATLAS experiment at a centre-of-mass energy of $\sqrt{s}=13$ TeV. The fragmentation properties of jets, such as the jet charge and summed fragmentation function, are measured using charged particles. A comprehensive suite of jet substructure observables is also measured for jets reconstructed with the soft-drop algorithm applied. In addition, a measurement of the Lund plane is performed using charged particles. All of the measurements are corrected for detector effects and are compared to the predictions of state-of-the-art Monte Carlo event generators.

• All-order renormalization of electric charge in the Standard Model and beyond

  Stefan Dittmaier

  SciPost Phys. Proc. 7, 048 (2022) · published 22 June 2022 | Toggle abstract · pdf

  Electric charge, as defined in the Thomson limit of the electron--photon interaction vertex, is renormalized to all orders both in the Standard Model and in any spontaneously broken gauge theory with gauge group GxU(1) with a group factor U(1) that mixes with electromagnetic gauge symmetry. In the framework of the background-field method the charge renormalization constant $Z_e$ is directly obtained from the photon wave-function renormalization constant, similar to the situation in QED, which proves charge universality as a byproduct. Exploiting charge universality in arbitrary $R_\xi$ gauge by formulating the charge renormalization condition for a ``fake fermion'' that couples only via an infinitesimal electric charge, $Z_e$ can be expressed in terms of renormalization constants that are obtained solely from gauge-boson self-energies.