Publications

Order by: publication date number of citations

• Electric and magnetic tau dipole moments revisited

  G. A. González-Sprinberg

  SciPost Phys. Proc. 17, 004 (2025) · published 23 July 2025 | Toggle abstract · pdf

  Precise measurements of magnetic and electric dipole moments are important tests of the Standard Model and beyond Standard Model physics, particularly for the electron and the muon. However, the situation presents distinctive challenges when dealing with the tau lepton due to its very short lifetime and relatively high mass. Here, we review the theoretical predictions and experimental measurements of both the anomalous magnetic and electric dipole moments of the tau lepton.

• Precision $e^-$ beam polarimetry at an $e^+e^-$ B factory using tau-pair events

  Caleb Miller

  SciPost Phys. Proc. 17, 011 (2025) · published 23 July 2025 | Toggle abstract · pdf

  A novel technique for measuring the average beam polarization in $e^+e^-$ collisions, known as Tau Polarimetry, has been developed by the BABAR collaboration. This technique makes use of the relationship between the polarization of the beams, the resulting polarization of the $\tau^+\tau^-$ produced, and the kinematics of the decay products. Using this technique BABAR has measured the average $e^-$ beam polarization of PEP-II to be 0.0034 $± 0.0024_{stat} ± 0.0029_{sys}$. This technique is expected to be used at Belle II after a proposed polarization upgrade as the most precise method with which beam polarization can be determined.

• Chiral Belle: e-Beam polarization upgrade of SuperKEKB

  J. Michael Roney

  SciPost Phys. Proc. 17, 012 (2025) · published 23 July 2025 | Toggle abstract · pdf

  Recent R&D work associated with upgrading the SuperKEKB $e^+e^-$ collider with polarized electron beams is presented. The Chiral Belle physics program enables a set of unique precision measurements using the Belle II detector. It includes a set of measurements of $\sin^2\theta_W$ via separate left-right asymmetry ($A_{LR}$) measurements in annihilations to pairs of electrons, muons, taus, charm and b-quarks that yield precisions matching or exceeding those of the current world averages from measurements at the $Z^0$-pole, but at 10GeV, thereby also probing the running of the couplings. Chiral Belle will also probe for new physics via the highest precision measurements of neutral current universality ratios and precision measurements of tau lepton properties, including the tau magnetic moment. After summarizing the physics goals, developments related to provision of the polarized source, the new components of the accelerator lattice that rotate the electron spin from transverse to longitudinal at the interaction point, and polarimetry of the electron beam will be reported.

• Matter effect in $P_{\mu \tau}$ at long baselines

  Srubabati Goswami, Supriya Pan, Animesh Chatterjee

  SciPost Phys. Proc. 17, 017 (2025) · published 23 July 2025 | Toggle abstract · pdf

  In the simple two-generation case, the probability $P_{\mu \tau}$ is not affected by interactions of neutrinos in matter. But for three-generation case, at baselines of the order of 9000 km, matter effects become important for this channel. This is a genuine three-flavour effect. We study how the presence of non-standard interactions (NSI) alters the $P_{\mu \tau}$ at these baselines. We observe large deviations from the standard matter effect. In particular, we find energies and baselines for which the phases governing the NSIs do not play any role. This may facilitate a better determination of NSI parameters if tau neutrinos can be detected.

• FASER experiment and first results from LHC run 3

  Umut Kose, on behalf of FASER collaboration

  SciPost Phys. Proc. 17, 018 (2025) · published 23 July 2025 | Toggle abstract · pdf

  FASER is designed to search for light, extremely weakly interacting and long-lived beyond standard model particles at the CERN Large Hadron Collider. Such particles, e.g., dark photons, may be produced in the high-energy proton-proton collisions at the ATLAS interaction point and then decay to visible particles in FASER, which is placed 480 m downstream and aligned with the collision axis line-of-sight. The detector covers a previously unexplored range of pseudorapidity larger than 8.8, which allows it to have sensitivity to new physics in the far-forward region. FASER also has a sub-detector called FASER$\nu$, which is specifically designed to detect and investigate high-energy collider neutrino interactions in the TeV regime, extending current cross-section measurements. In this proceeding, the FASER detector and present recent results obtained during LHC Run 3 will be introduced.

• TAMBO: Searching for tau neutrinos in the Peruvian Andes

  William G. Thompson, on behalf of the TAMBO collaboration.

  SciPost Phys. Proc. 17, 021 (2025) · published 23 July 2025 | Toggle abstract · pdf

  TAMBO is a planned next-generation neutrino observatory sensitive to 1-100 PeV Earth-skimming tau neutrinos. This tau neutrino specificity will provide a high-purity sample of astrophysical neutrinos whose locations on the sky can then be used to improve the sensitivities of all-flavor neutrino observatories. The observatory will be located in a deep canyon and will comprise an array of water-Cherenkov and plastic scintillator air-shower detectors. In this proceeding, I will summarize the current status of the updated TAMBO simulation package, which is currently being used for detector optimization and reconstruction studies.

• Universality of closed nested paths in two-dimensional percolation

  Yu-Feng Song, Jesper Lykke Jacobsen, Bernard Nienhuis, Andrea Sportiello, Youjin Deng

  SciPost Phys. 18, 057 (2025) · published 18 February 2025 | Toggle abstract · pdf

  Recent work on percolation in $d=2$ [J. Phys. A: Math. Theor. 55, 204002 (2015)] introduced an operator that gives a weight $k^{\ell}$ to configurations with $\ell$ 'nested paths' (NP), i.e.\ disjoint cycles surrounding the origin, if there exists a cluster that percolates to the boundary of a disc of radius $L$, and weight zero otherwise. It was found that $\mathbb{E}(k^{\ell}) \sim L^{-X_{NP}(k)}$, and a formula for $X_{NP}(k)$ was conjectured. Here we derive an exact result for $X_{NP}(k)$, valid for $k ≥ -1$, replacing the previous conjecture. We find that the probability distribution $\mathbb{P}_\ell (L)$ scales as $ L^{-1/4} (\ln L)^\ell [(1/\ell!) \Lambda^\ell]$ when $\ell ≥ 0$ and $L \gg 1$, with $\Lambda = 1/\sqrt{3} \pi$. Extensive simulations for various critical percolation models confirm our theoretical predictions and support the universality of the NP observables.

• Measurement of the muon magnetic anomaly to 0.20 ppm by the Muon g-2 experiment at Fermilab

  Lorenzo Cotrozzi, on behalf of the Muon g-2 collaboration

  SciPost Phys. Proc. 17, 022 (2025) · published 23 July 2025 | Toggle abstract · pdf

  The Muon $g-2$ experiment at Fermilab aims to measure the muon magnetic moment anomaly, $a_{\mu}=(g-2)/2$, with a final accuracy of 0.14 parts per million (ppm). The experiment’s first result was published in 2021, based on data collected in 2018, and in 2023 a new result was published based on two more years of data taking, 2019 and 2020. The combination of the two results from Fermilab and the previous one from Brookhaven National Laboratory brought the uncertainty on the experimental measurement of $a_{\mu}$ to the unprecedented value of 0.19 ppm. This paper will present details about the improvements of statistical and systematic uncertainties on $a_{\mu}$ since the 2021 result.

• ISAI: Investigating Solar Axion by Iron-57

  Tomonori Ikeda, Toshihiro Fujii, Takeshi Go Tsuru, Yuki Amano, Kazuho Kayama, Masamune Matsuda, Hiromu Iwasaki, Mizuki Uenomachi, Kentaro Miuchi, Yoshiyuki Onuki, Yoshizumi Inoue, Akimichi Taketa

  SciPost Phys. Proc. 12, 041 (2023) · published 4 July 2023 | Toggle abstract · pdf

  The existence of the axion is a unique solution for the strong CP problem, and the axion is one of the most promising candidates of the dark matter. Investigating Solar Axion by Iron-57 (ISAI) is being prepared as a complemented table-top experiment to confirm the solar axion scenario. Probing an X-ray emission from the nuclear transitions associated with the axion-nucleon coupling is a leading approach. ISAI searches for the monochromatic 14.4 keV X-ray from the first excited state of $^{57}$Fe using a state-of-the-art pixelized silicon detector, dubbed XRPIX, under an extremely low-background environment. We highlight scientific objectives, experimental design and the latest status of ISAI.

• An alternative evaluation of the leading-order hadronic contribution to the muon $g-2$ with MUonE

  Riccardo N. Pilato

  SciPost Phys. Proc. 17, 024 (2025) · published 23 July 2025 | Toggle abstract · pdf

  The MUonE experiment proposes a novel approach to determine the hadronic contribution to the muon $g-2$, $a_\mu^\text{HLO}$, based on the measurement of the hadronic running of the QED coupling through the analysis of $\mu-e$ elastic scattering events. This could clarify the tensions in the current evaluations of $a_\mu^\text{HLO}$, which are limiting the comparison between theory and experiment for the muon $g-2$. The measurement will be performed at CERN’s North Area by scattering a 160 GeV muon beam on the atomic electrons of a low-Z target. The status and future plans of the experiment will be presented. Furthermore, an alternative method to extract $a_\mu^\text{HLO}$ from MUonE data will be discussed.