Publications

Order by: publication date number of citations

• Top-quark mass determination in the optimised threshold scan

  Kacper Nowak, Aleksander Filip Zarnecki

  SciPost Phys. Proc. 8, 173 (2022) · published 14 July 2022 | Toggle abstract · pdf

  One of the important goals at the future e$^+$e$^−$ colliders is to measure the top-quark mass and width in a scan of the pair production threshold. Presented in this work is the most general approach to the top-quark mass determination from the threshold scan at CLIC, with all relevant model parameters and selected systematic uncertainties included in the fit procedure. In the baseline scan scenario the top-quark mass can be extracted with precision of the order of 30 to 40 MeV, already for 100 fb$^{−1}$ of data collected at the threshold. We present the optimisation procedure based on the genetic algorithm with which the statistical uncertainty of the mass measurement can be reduced by about 20%.

• Reweighting Monte Carlo predictions and automated fragmentation variations in Pythia 8

  Christan Bierlich, Philip Ilten, Tony Menzo, Stephen Mrenna, Manuel Szewc, Michael K. Wilkinson, Ahmed Youssef, Jure Zupan

  SciPost Phys. 16, 134 (2024) · published 27 May 2024 | Toggle abstract · pdf

  This work reports on a method for uncertainty estimation in simulated collider-event predictions. The method is based on a Monte Carlo-veto algorithm, and extends previous work on uncertainty estimates in parton showers by including uncertainty estimates for the Lund string-fragmentation model. This method is advantageous from the perspective of simulation costs: a single ensemble of generated events can be reinterpreted as though it was obtained using a different set of input parameters, where each event now is accompanied with a corresponding weight. This allows for a robust exploration of the uncertainties arising from the choice of input model parameters, without the need to rerun full simulation pipelines for each input parameter choice. Such explorations are important when determining the sensitivities of precision physics measurements. Accompanying code is available at https://gitlab.com/uchep/mlhad-weights-validation.

• Exact effective action for the O(N) vector model in the large N limit

  Han Ma, Sung-Sik Lee

  SciPost Phys. 15, 111 (2023) · published 22 September 2023 | Toggle abstract · pdf

  We present the Wilsonian effective action as a solution of the exact RG equation for the critical $O(N)$ vector model in the large $N$ limit. Below four dimensions, the exact effective action can be expressed in a closed form as a transcendental function of two leading scaling operators with infinitely many derivatives. From the exact solution that describes the RG flow from a UV theory to the fixed point theory in the IR, we obtain the mapping between UV operators and IR scaling operators. It is shown that IR scaling operators are given by sums of infinitely many UV operators with infinitely many derivatives.

• Conformal boundary conditions for a 4d scalar field

  Lorenzo Di Pietro, Edoardo Lauria, Pierluigi Niro

  SciPost Phys. 16, 090 (2024) · published 3 April 2024 | Toggle abstract · pdf

  We construct unitary, stable, and interacting conformal boundary conditions for a free massless scalar in four dimensions by coupling it to edge modes living on a boundary. The boundary theories we consider are bosonic and fermionic QED$_3$ with $N_f$ flavors and a Chern-Simons term at level $k$, in the large-$N_f$ limit with fixed $k/N_f$. We find that interacting boundary conditions only exist when $k≠ 0$. To obtain this result we compute the $\beta$ functions of the classically marginal couplings at the first non-vanishing order in the large-$N_f$ expansion, and to all orders in $k/N_f$ and in the couplings. To check vacuum stability we also compute the large-$N_f$ effective potential. We compare our results with the the known conformal bootstrap bounds.

• High field magnetism of the triangular lattice antiferromagnet CsFeCl$_3$ under high pressure

  Katsuki Nihongi, Takanori Kida, Yasuo Narumi, Nobuyuki Kurita, Hidekazu Tanaka, Yoshiya Uwatoko, Koichi Kindo, Masayuki Hagiwara

  SciPost Phys. Proc. 11, 012 (2023) · published 5 June 2023 | Toggle abstract · pdf

  Magnetization measurements of the triangular lattice antiferromagnet CsFeCl$_{3}$ at 1.4 K for $H \parallel c$ were performed in pulsed high magnetic fields of up to 51 T under high pressures of up to 0.80 GPa. At ambient pressure, the magnetization below $H_{\rm c1}$ = 4 T is small, and then it changes steeply between $H_{\rm c1}$ and $H_{\rm c2}$ = 12 T, followed by a gradual increase in magnetization up to $H_{\rm m}$ = 33 T where a two-step metamagnetic transition occurs. With increasing pressure, the $H_{\rm c1}$ and $H_{\rm m}$ shifted to the low-field side, while the $H_{\rm c2}$ shifted to the opposite side. The change in $H_{\rm m}$ may depend on the difference in the single-ion anisotropies on pressure in the lowest $J$ = 1 and the excited $J$ = 2 states.

• Anomalous coupling studies with intact protons at the LHC

  Cristophe Royon

  SciPost Phys. Proc. 15, 029 (2024) · published 3 April 2024 | Toggle abstract · pdf

  We describe the reaches on quartic $\gamma \gamma \gamma \gamma$, $\gamma \gamma WW$, $\gamma \gamma ZZ$, $\gamma \gamma \gamma Z$, $\gamma \gamma t \bar{t}$ anomalous couplings at the LHC using intact protons in the final state measured in AFP in ATLAS or PPS in CMS-TOTEM.

• $tW$ and $tZ'$ production at hadron colliders

  Nikolaos Kidonakis, Marco Guzzi, Nodoka Yamanaka

  SciPost Phys. Proc. 8, 064 (2022) · published 12 July 2022 | Toggle abstract · pdf

  We present theoretical results with soft-gluon corrections for two separate processes: (1) the production of a single top quark in association with a $W$ boson in the Standard Model; and (2) the production of a single top quark in association with a heavy $Z'$ boson in new physics models with or without anomalous couplings. We show that the higher-order corrections from soft-gluon emission are dominant for a wide range of collider energies. Results are shown for the total cross sections and top-quark transverse-momentum and rapidity distributions for $tW$ and $tZ'$ production at LHC and future collider energies up to 100 TeV. The uncertainties from scale dependence and parton distribution functions are also analyzed.

• An overview of lattice results for parton distribution functions

  Luigi Del Debbio

  SciPost Phys. Proc. 15, 028 (2024) · published 3 April 2024 | Toggle abstract · pdf

  Following a ground-breaking proposal by Ji [Phys. Rev. Lett. 110, 262002 (2013)], numerical simulations of Quantum Chromo Dynamics (QCD) on a Euclidean lattice have provided new, valuable information on the structure of hadrons. In this talk, we briefly review the lattice approach to the reconstruction of parton densities, highlighting the connection between lattice observables and parton densities, with a focus on theoretical issues. Since parton distributions are extracted from lattice data by solving an inverse problem, we discuss some of the difficulties that affect these determinations and how they can be formulated in a Bayesian framework.

• Hyperon physics at BESIII

  Viktor Thorén

  SciPost Phys. Proc. 15, 026 (2024) · published 3 April 2024 | Toggle abstract · pdf

  Spin polarization and entanglement are utilized by the BESIII experiment to learn more about the production and decay properties of hyperon-antihyperon pairs in a series of recent analyses of its unprecedented datasets at the $J/\psi$ and $\psi'$ resonances. This has lead to the observation of significant transverse polarisation in decays of $J/\psi$ or $\psi'$ into $\Lambda \bar{\Lambda}$, $\Sigma \bar{\Sigma}$, $\Xi \bar{\Xi}$, and $\Omega \bar{\Omega}$. Because of the non-zero polarization, the decay parameters for the most common hadronic weak decays of both hyperons and antihyperons could be determined independently for the first time. Comparing these to each other yields precise tests of direct, $\Delta S = 1$ CP-violation that complement measurements of kaon decays.

• Proton reconstruction with the Precision Proton Spectrometer (PPS) in Run 2 and the PPS at HL-LHC

  Fabrizio Ferro

  SciPost Phys. Proc. 8, 062 (2022) · published 12 July 2022 | Toggle abstract · pdf

  The Precision Proton Spectrometer (PPS) started operating in 2016 and has collected more than 110 fb$^{-1}$ of data over the course of the LHC Run 2, now fully available for physics analysis. This contribution covers the key features of the PPS alignment and optics calibration, which have been developed from scratch. The reconstructed proton distributions, the performance of the PPS simulation and finally the validation of the full reconstruction chain with physics data (dilepton events) are also illustrated.