Publications

Order by: publication date number of citations

• Photon-ALP oscillations at CTA energies

  M. Kachelriess, J. Tjemsland

  SciPost Phys. Proc. 12, 043 (2023) · published 4 July 2023 | Toggle abstract · pdf

  Axions and axion-like-particles (ALPs) are well motivated beyond the standard model particles that can explain a variety of unsolved problems in physics, such as the strong CP problem and the nature of dark matter. These particles are characterised by their two-photon coupling, which leads to so-called photon-ALP oscillation as photons propagate through an external magnetic field. Such oscillations lead to characteristic signatures in the energy spectrum of high-energy photons from astrophysical sources, allowing us to probe the existence of ALPs and possibly dark matter. We review the signatures from ALPs in photon spectra and discuss a new method that can be used to directly search for the energy dependence of the oscillations. The focus is on photons at TeV-energies relevant for the upcoming Cherenkov Telescope Array (CTA).

• Pion electronic decay and lepton universality

  D. Počanić

  SciPost Phys. Proc. 5, 025 (2021) · published 6 September 2021 | Toggle abstract · pdf

  In common with a number of simple processes involving elementary particles, charged pion decays are profoundly shaped by applicable Standard Model (SM) symmetries and properties. Given the highly precise SM theoretical description, pion decays are used as selective probes of SM parameters, and of possible SM extensions. The PEN experiment at PSI is studying the π + → e + ν e (γ), or π_ e2(γ) decay. The primary goal is to reach the relative precision of 5 × 10 ^{−4} in Re/μ^π, the branching ratio for π_ e2(γ) decay. We review the PEN research program, its present status, and prospects.

• Probing hadronic interactions with measurements from the Pierre Auger Observatory

  B. Andrada

  SciPost Phys. Proc. 10, 005 (2022) · published 10 August 2022 | Toggle abstract · pdf

  The Pierre Auger Observatory is the largest facility in the world to study ultra-high-energy cosmic rays. It has a hybrid detection technique that combines the observation of the longitudinal development of extensive air showers and the measurement of their particles at the ground. This capability has opened the possibility to probe hadronic interactions taking place at energies well beyond those accessible by human-made accelerators. In this report, we present a selection of the latest results on hadronic interactions with measurements from the Pierre Auger Observatory. These data span over three decades in energy, showing the tension between data from the muon component of air showers and predictions based on the most updated hadronic interaction models.

• Determination of $α_{S}$ beyond $NNLO$ using the event shape averages

  Adam Kardos, Gábor Somogyi, Andrii Verbytskyi

  SciPost Phys. Proc. 10, 014 (2022) · published 10 August 2022 | Toggle abstract · pdf

  In this proceedings we discuss a prescription to extract the QCD strong coupling constant at $N^{3}LO$ precision in perturbative QCD using a combination of ${\cal{O}}(\alpha_{S}^{3})$ calculations in pQCD and estimations of the ${\cal{O}}(\alpha_{S}^{4})$ corrections from the data. The method is applied to a set of event shape averages measured in experiments at the LEP, PETRA, PEP and TRISTAN colliders. In our analysis we account for hadronization effects with models from modern Monte Carlo event generators and analytic hadronization models. We conclude that the precision of the $\alpha_{S}$ extraction cannot be improved significantly only with pQCD predictions of higher orders, and further progress in these studies requires a significant advances in the studies and modeling of hadronization process.

• Muonium-Antimuonium Conversion

  Lorenz Willmann, Klaus Jungmann

  SciPost Phys. Proc. 5, 009 (2021) · published 6 September 2021 | Toggle abstract · pdf

  The MACS experiment performed at PSI in the 1990s provided an yet unchallenged upper bound on the probability for a spontaneous conversion of the muonium atom, ${\rm M=}$($\rm{\mu^+e^-}$) , into its antiatom, antimuonium ${\overline{\rm{M}} = }$($\rm{\mu^-e^+})$. It comprises the culmination of a series of measurements at various accelerator laboratories worldwide. The experimental limits on the process have provided input and steering for the further development of a variety of theoretical models beyond the standard theory, in particular for models which address lepton number violating processes and matter-antimatter oscillations. Several models beyond the standard theory could be strongly disfavored. There is interest in a new measurement and improved sensitivity could be reached by exploiting the time evolution of the conversion process, e.g., at intense pulsed muonium sources.

• Approaching the first any light particle search II science run

  Aaron D. Spector for the ALPS Collaboration

  SciPost Phys. Proc. 12, 039 (2023) · published 4 July 2023 | Toggle abstract · pdf

  The Any Light Particle Search II (ALPS II) is a light-shining-through-a-wall (LSW) experiment based at DESY in Hamburg, Germany, that will search for axions and axion-like particles down to the coupling of the axion to two photons of $g_{a\gamma\gamma}$ >2$\times10^{-11}$ GeV$^{-1}$ for masses below 0.1 meV. ALPS II will use two strings of superconducting dipole magnets that are over one hundred meters in length, as well as optical cavities before and after the wall to boost the effective signal rate of the regenerated photons by more than 12 orders of magnitude when compared to previous generations of LSW experiments. Data taking with a simplified optical system is expected to begin in early 2023.

• Quantized fragmentation of three-dimensional QCD string

  S. Todorova-Nova

  SciPost Phys. Proc. 10, 013 (2022) · published 10 August 2022 | Toggle abstract · pdf

  Recent developments of the model of quantized helical QCD string are presented, notably the baryon production. An overview of the experimental evidence is discussed as well as possible applications.

• Logarithmic corrections for jet production at the LHC

  Emmet P. Byrne

  SciPost Phys. Proc. 10, 010 (2022) · published 10 August 2022 | Toggle abstract · pdf

  Several important processes and analyses at the LHC are sensitive to higher-order perturbative corrections beyond what can currently be calculated at fixed order. One important class of logarithmic corrections are those which appear when the centre-of-mass energy of a QCD collision is much larger than the transverse momenta of the observed jets. We describe the High Energy Jets (HEJ) framework, which includes the dominant high-energy logarithms to provide all-order predictions for several LHC processes including Higgs, $W$, or $Z$ boson production in association with jets. We will summarise some recent developments, in particular the first matching of HEJ to a NLO calculation.

• Intermittency analysis in relativistic heavy-ion collisions

  Zhiming Li, Jin Wu

  SciPost Phys. Proc. 10, 006 (2022) · published 10 August 2022 | Toggle abstract · pdf

  Local density fluctuations near the QCD critical point can be probed by an intermittency analysis of power-law behavior on scaled factorial moments in relativistic heavy-ion collisions. We study the second-order scaled factorial moment in Au + Au collisions at $\sqrt{s_\mathrm{NN}}$ = 7.7-200 GeV from the UrQMD model. Since the background subtraction and efficiency correction are two important aspects in this measurement, we propose a cumulative variable method to remove background contribution and a cell-by-cell method for efficiency correction in the intermittency analysis.

• Colouring the Higgs boson

  Andy Buckley, Giuseppe Callea, Andrew J. Larkowski, Simone Marzani

  SciPost Phys. Proc. 10, 001 (2022) · published 10 August 2022 | Toggle abstract · pdf

  The jet colour ring is a novel colour tagger observable designed to separate the decay of a colour-singlet into two jets from a two-jet background in a different colour configuration. Simulation studies in the case of the production of a boosted Higgs boson decaying in two b-quarks and an associate electroweak boson, showed notable discriminator powers when comparing the jet colour ring performances with other observables. These results are opening a wide scenario for further studies.