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For a class of precision CPT-invariance test measurements using antihydrogen, a deficit in the data indicates the presence of the signal. The construction of classical confidence intervals for the properties of the antiatoms from measurements may pose a challenge due to the limited statistics experimentally available. We use the Feldman–Cousins (Feldman and Cousins, Phys. Rev. D , 57 , 3873. ( doi:10.1103/PhysRevD.57.3873 )) method to estimate model parameters for such a low count rate measurement. First, we construct confidence intervals for the Poisson process with a known background and an unknown signal deficit. Then the generalized Monte Carlo version of the method is applied to the use case of the hyperfine transition frequency measurement of the ground-state antihydrogen atom, where the expected double-dip resonance line shape and the mean background is assumed to be known. We find that confidence intervals of the antihydrogen properties could be obtained already from low statistics data. We also discuss how the method may be extended to allow estimation of additional model parameters.

In this work, we report on the sensitivity potential of complementary muon-on-target experiments to new physics using a scalar boson benchmark model associated with charged lepton flavor violation. The NA64 μ experiment at CERN uses a 160-GeV energy muon beam with an active target to search for excess events with missing energy and momentum as a probe of new physics. At the same time, the proton beam at Fermilab, which is used to produce the neutrino beam for the Deep Underground Neutrino Experiment (DUNE), will also produce a high-intensity muon beam dumped in an absorber. Combined with the liquid argon near detector, the system could be used to search for similar scalar boson particles with a lower-energy but higher-intensity beam. We find that both NA64 μ and DUNE could cover new, unexplored parts of the parameter space of the same benchmark model, providing a complementary way to search for new physics.

Antihydrogen, a positron bound to an antiproton, is the simplest antiatom. Its counterpart—hydrogen—is one of the most precisely investigated and best understood systems in physics research. High-resolution comparisons of both systems provide sensitive tests of CPT symmetry, which is the most fundamental symmetry in the Standard Model of elementary particle physics. Any measured difference would point to CPT violation and thus to new physics. Here we report the development of an antihydrogen source using a cusp trap for in-flight spectroscopy. A total of 80 antihydrogen atoms are unambiguously detected 2.7 m downstream of the production region, where perturbing residual magnetic fields are small. This is a major step towards precision spectroscopy of the ground-state hyperfine splitting of antihydrogen using Rabi-like beam spectroscopy. Comparing hydrogen and antihydrogen—its antimatter counterpart—provides important tests of fundamental symmetries in the Standard Model. Kuroda et al . present a source of antihydrogen atoms that may provide high-precision in-flight measurements of their ground-state hyperfine splitting.

A bstract We report on an updated sensitivity for proton decay via p → ν ¯ K + at large, dual phase liquid argon time projection chambers (LAr TPCs). Our work builds on a previous study in which several nucleon decay modes have been simulated and analyzed [1]. At the time several assumptions were needed to be made on the detector and the backgrounds. Since then, the community has made progress in defining these, and the computing power available enables us to fully simulate and reconstruct large samples in order to perform a better estimate of the sensitivity to proton decay. In this work, we examine the benchmark channel p → ν ¯ K + , which was previously found to be one of the cleanest channels. Using an improved neutrino event generator and a fully simulated LAr TPC detector response combined with a dedicated neural network for kaon identification, we demonstrate that a lifetime sensitivity of τ / Br ( p → ν ¯ K + ) > 7 × 10 34 years at 90% confidence level can be reached at an exposure of 1 megaton · year in quasi-background-free conditions, confirming the superiority of the LAr TPC over other technologies to address the challenging proton decay modes.

In this work, we report on the sensitivity potential of complementary muon-on-target experiments to new physics using a scalar boson benchmark model associated with charged lepton flavor violation. The NA64 [Formula omitted] experiment at CERN uses a 160-GeV energy muon beam with an active target to search for excess events with missing energy and momentum as a probe of new physics. At the same time, the proton beam at Fermilab, which is used to produce the neutrino beam for the Deep Underground Neutrino Experiment (DUNE), will also produce a high-intensity muon beam dumped in an absorber. Combined with the liquid argon near detector, the system could be used to search for similar scalar boson particles with a lower-energy but higher-intensity beam. We find that both NA64 [Formula omitted] and DUNE could cover new, unexplored parts of the parameter space of the same benchmark model, providing a complementary way to search for new physics.

A bstract The inclusion of an additional U(1) gauge L μ − L τ symmetry would release the tension between the measured and the predicted value of the anomalous muon magnetic moment: this paradigm assumes the existence of a new, light Z ′ vector boson, with dominant coupling to μ and τ leptons and interacting with electrons via a loop mechanism. The L μ − L τ model can also explain the Dark Matter relic abundance, by assuming that the Z ′ boson acts as a “portal” to a new Dark Sector of particles in Nature, not charged under known interactions. In this work we present the results of the Z ′ search performed by the NA64- e experiment at CERN SPS, that collected ~ 9 × 10 11 100 GeV electrons impinging on an active thick target. Despite the suppressed Z ′ production yield with an electron beam, NA64- e provides the first accelerator-based results excluding the g − 2 preferred band of the Z ′ parameter space in the 1 keV < m Z ′ ≲ 2 MeV range, in complementarity with the limits recently obtained by the NA64- μ experiment with a muon beam.

A bstract Thermal light dark matter (LDM) with particle masses in the 1 MeV–1 GeV range could successfully explain the observed dark matter abundance as a relic from the primordial Universe. In this picture, a new feeble interaction acts as a “portal” between the Standard Model and LDM particles, allowing for the exploration of this paradigm at accelerator experiments. In the last years, the “missing energy” experiment NA64 e at CERN SPS (Super Proton Synchrotron) has set world-leading constraints in the vector-mediated LDM parameter space, by exploiting a 100 GeV electron beam impinging on an electromagnetic calorimeter, acting as an active target. In this paper, we report a detailed description of the analysis of a preliminary measurement with a 70 GeV/c positron beam at NA64 e , performed during summer 2023 with an accumulated statistics of 1 . 596 × 10 10 positrons on target (hereafter referred to as e + OT). This data set was analyzed with the primary aim of evaluating the performance of the NA64 e detector with a lower energy positron beam, towards the realization of the post-LS3 program. The analysis results, other than additionally probing unexplored regions in the LDM parameter space, provide valuable information towards the future NA64 e positron campaign.

Impressive growth in Asia, as one of most dynamic regions in the world, sometimes happens at the expense of marginalisation. Individuals who do not fit normative ideals, who are deemed economically unproductive or who do not participate in heterosex-centred reproduction are often regarded as different, even deviant, and come to take on or are given identities that are marginalised. These include, but are not limited to, people with physical or intellectual disabilities, the elderly, gender and sexual minorities, never-married parents or unmarried people. Stigmatisation can be pronounced in homogenous or insular societies and communities that use 'culture' and 'tradition' as a justification to extract conformity. It can also appear where the self-sufficiency of individuals and heterosexual, biological and nuclear families is touted as a moral virtue that aligns with neoliberal and anti-welfare ideologies.

AbstractThe ASACUSA (Atomic Spectroscopy And Collisions Using Slow Antiprotons) collaboration plans to measure the ground-state hyperfine splitting of antihydrogen in a beam at the CERN Antiproton Decelerator with initial relative precision of 10-6 or better, to test the fundamental CPT (combination of charge conjugation, parity transformation and time reversal) symmetry between matter and antimatter. This challenging goal requires a polarised antihydrogen beam with a sufficient number of antihydrogen atoms in the ground state. The first measurement of the quantum state distribution of antihydrogen atoms in a low magnetic field environment of a few mT is described. Furthermore, the data-driven machine learning analysis to identify antihydrogen events is discussed.Graphic Abstract

For a class of precision CPT-invariance test measurements using antihydrogen, a deficit in the data indicates the presence of the signal. The construction of classical confidence intervals for the properties of the antiatoms from measurements may pose a challenge due to the limited statistics experimentally available. We use the Feldman–Cousins (Feldman and Cousins, Phys. Rev. D, 57, 3873. (doi:10.1103/PhysRevD.57.3873)) method to estimate model parameters for such a low count rate measurement. First, we construct confidence intervals for the Poisson process with a known background and an unknown signal deficit. Then the generalized Monte Carlo version of the method is applied to the use case of the hyperfine transition frequency measurement of the ground-state antihydrogen atom, where the expected double-dip resonance line shape and the mean background is assumed to be known. We find that confidence intervals of the antihydrogen properties could be obtained already from low statistics data. We also discuss how the method may be extended to allow estimation of additional model parameters.