C. Amsler

The Review summarizes much of particle physics and cosmology. Using data from previous editions, plus 2,873 new measurements from 758 papers, we list, evaluate, and average measured properties of gauge bosons and the recently discovered Higgs boson, leptons, quarks, mesons, and baryons. We summarize searches for hypothetical particles such as supersymmetric particles, heavy bosons, axions, dark photons, etc. Particle properties and search limits are listed in Summary Tables. We give numerous tables, figures, formulae, and reviews of topics such as Higgs Boson Physics, Supersymmetry, Grand Unified Theories, Neutrino Mixing, Dark Energy, Dark Matter, Cosmology, Particle Detectors, Colliders, Probability and Statistics. Among the 118 reviews are many that are new or heavily revised, including a new review on Neutrinos in Cosmology.Starting with this edition, the Review is divided into two volumes. Volume 1 includes the Summary Tables and all review articles. Volume 2 consists of the Particle Listings. Review articles that were previously part of the Listings are now included in volume 1.The complete Review (both volumes) is published online on the website of the Particle Data Group (http://pdg.lbl.gov) and in a journal. Volume 1 is available in print as the PDG Book. A Particle Physics Booklet with the Summary Tables and essential tables, figures, and equations from selected review articles is also available.The 2018 edition of the Review of Particle Physics should be cited as: M. Tanabashi et al. (Particle Data Group), Phys. Rev. D 98, 030001 (2018).

We derive non-flat cosmological models for two cases (i.e., dust and radiation) in the context of Møller’s tetradic theory (MTT) of gravitation using the tetrad that creates the non-flat Friedmann–Robertson–Walker (FRW) metric. These two models are affected by the free dimensional parameter, λ, that characterized MTT, which approaches zero in the flat case for both models. Using standard definitions of thermodynamics, we calculate the radius horizon, Hawking temperature, and entropy of our non-flat models in the framework of cosmology and show the effect of λ on open and closed universes. We then use the first law of thermodynamics to construct non-flat cosmological models via the non-extensive thermodynamic approach. The resulting models are affected by λ and the extensive parameter, δ, which quantifies the effect of non-extensive thermodynamics. When we set, λ=0 and δ=1, we return to Einstein’s general relativity models. We study the evolution of our models in the presence of collisionless non-relativistic matter and describe precise forms of the dark energy density and equation-of-state parameter constraining the non-extensive thermodynamic parameter. We show that insertion of the non-extensive thermodynamic parameter affects the non-flat FRW universe in a manner that noticeably differs from that observed under normal thermodynamics. We also show that the deceleration of the open universe behaves as dark energy in a future epoch, i.e., when the redshift approaches −1, i.e., z≈−1.

This biennial Review summarizes much of particle physics. Using data from previous editions, plus 2658 new measurements from 644 papers, we list, evaluate, and average measured properties of gauge bosons, leptons, quarks, mesons, and baryons. We summarize searches for hypothetical particles such as Higgs bosons, heavy neutrinos, and supersymmetric particles. All the particle properties and search limits are listed in Summary Tables. We also give numerous tables, figures, formulae, and reviews of topics such as the Standard Model, particle detectors, probability, and statistics. Among the 112 reviews are many that are new or heavily revised including those on Heavy-Quark and Soft-Collinear Effective Theory, Neutrino Cross Section Measurements, Monte Carlo Event Generators, Lattice QCD, Heavy Quarkonium Spectroscopy, Top Quark, Dark Matter, Vcb & Vub, Quantum Chromodynamics, High-Energy Collider Parameters, Astrophysical Constants, Cosmological Parameters, and Dark Matter. A booklet is available containing the Summary Tables and abbreviated versions of some of the other sections of this full Review. All tables, listings, and reviews (and errata) are also available on the Particle Data Group website: http://pdg.lbl.gov/. The 2012 edition of Review of Particle Physics is published for the Particle Data Group as article 010001 in volume 86 of Physical Review D. This edition should be cited as: J. Beringer et al. (Particle Data Group), Phys. Rev. D 86, 010001 (2012).Received 18 July 2012DOI:https://doi.org/10.1103/PhysRevD.86.010001© 2012 Regents of the University of California*The publication of the Review of Particle Physics is supported by the Director, Office of Science, Office of High Energy and Nuclear Physics, the Division of High Energy Physics of the U.S. Department of Energy under Contract No. DE–AC02–05CH11231; by the U.S. National Science Foundation under Agreement No. PHY-0652989; by the European Laboratory for Particle Physics (CERN); by an implementing arrangement between the governments of Japan (MEXT: Ministry of Education, Culture, Sports, Science and Technology) and the United States (DOE) on cooperative research and development; and by the Italian National Institute of Nuclear Physics (INFN).

This biennial Review summarizes much of particle physics. Using data from previous editions, plus 2778 new measurements from 645 papers, we list, evaluate, and average measured properties of gauge bosons, leptons, quarks, mesons, and baryons. We also summarize searches for hypothetical particles such as Higgs bosons, heavy neutrinos, and supersymmetric particles. All the particle properties and search limits are listed in Summary Tables. We also give numerous tables, figures, formulae, and reviews of topics such as the Standard Model, particle detectors, probability, and statistics. Among the 108 reviews are many that are new or heavily revised including those on CKM quark-mixing matrix, Vud & Vus, Vcb & Vub, top quark, muon anomalous magnetic moment, extra dimensions, particle detectors, cosmic background radiation, dark matter, cosmological parameters, and big bang cosmology. A booklet is available containing the Summary Tables and abbreviated versions of some of the other sections of this full Review. All tables, listings, and reviews (and errata) are also available on the Particle Data Group website: http://pdg.lbl.gov.

This biennial Review summarizes much of Particle Physics. Using data from previous editions, plus 2205 new measurements from 667 papers, we list, evaluate, and average measured properties of gauge bosons, leptons, quarks, mesons, and baryons. We also summarize searches for hypothetical particles such as Higgs bosons, heavy neutrinos, and supersymmetric particles. All the particle properties and search limits are listed in Summary Tables. We also give numerous tables, figures, formulae, and reviews of topics such as the Standard Model, particle detectors, probability, and statistics. This edition features expanded coverage of CP violation in B mesons and of neutrino oscillations. For the first time we cover searches for evidence of extra dimensions (both in the particle listings and in a new review). Another new review is on Grand Unified Theories. A booklet is available containing the Summary Tables and abbreviated versions of some of the other sections of this full Review. All tables, listings, and reviews (and errata) are also available on the Particle Data Group website: http://pdg.lbl.gov.

Abstract The Review summarizes much of particle physics and cosmology. Using data from previous editions, plus 2,143 new measurements from 709 papers, we list, evaluate, and average measured properties of gauge bosons and the recently discovered Higgs boson, leptons, quarks, mesons, and baryons. We summarize searches for hypothetical particles such as supersymmetric particles, heavy bosons, axions, dark photons, etc. Particle properties and search limits are listed in Summary Tables. We give numerous tables, figures, formulae, and reviews of topics such as Higgs Boson Physics, Supersymmetry, Grand Unified Theories, Neutrino Mixing, Dark Energy, Dark Matter, Cosmology, Particle Detectors, Colliders, Probability and Statistics. Among the 120 reviews are many that are new or heavily revised, including a new review on Machine Learning, and one on Spectroscopy of Light Meson Resonances. The Review is divided into two volumes. Volume 1 includes the Summary Tables and 97 review articles. Volume 2 consists of the Particle Listings and contains also 23 reviews that address specific aspects of the data presented in the Listings. The complete Review (both volumes) is published online on the website of the Particle Data Group (pdg.lbl.gov) and in a journal. Volume 1 is available in print as the PDG Book. A Particle Physics Booklet with the Summary Tables and essential tables, figures, and equations from selected review articles is available in print, as a web version optimized for use on phones, and as an Android app.

This biennial review summarizes much of Particle Physics. Using data from previous editions, plus 1900 new measurements from 700 papers, we list, evaluate, and average measured properties of gauge bosons, leptons, quarks, mesons, and baryons. We also summarize searches for hypothetical particles such as Higgs bosons, heavy neutrinos, and supersymmetric particles. All the particle properties and search limits are listed in Summary Tables. We also give numerous tables, figures, formulae, and reviews of topics such as the Standard Model, particle detectors, probability, and statistics. A booklet is available containing the Summary Tables and abbreviated versions of some of the other sections of this full Review.

A theoretical underpinning of the standard model of fundamental particles and interactions is CPT invariance, which requires that the laws of physics be invariant under the combined discrete operations of charge conjugation, parity and time reversal. Antimatter, the existence of which was predicted by Dirac, can be used to test the CPT theorem-experimental investigations involving comparisons of particles with antiparticles are numerous. Cold atoms and anti-atoms, such as hydrogen and antihydrogen, could form the basis of a new precise test, as CPT invariance implies that they must have the same spectrum. Observations of antihydrogen in small quantities and at high energies have been reported at the European Organization for Nuclear Research (CERN) and at Fermilab, but these experiments were not suited to precision comparison measurements. Here we demonstrate the production of antihydrogen atoms at very low energy by mixing trapped antiprotons and positrons in a cryogenic environment. The neutral anti-atoms have been detected directly when they escape the trap and annihilate, producing a characteristic signature in an imaging particle detector.

DARk matter WImp search with liquid xenoN (DARWIN) will be an experiment for the direct detection of dark matter using a multi-ton liquid xenon time projection chamber at its core. Its primary goal will be to explore the experimentally accessible parameter space for Weakly Interacting Massive Particles (WIMPs) in a wide mass-range, until neutrino interactions with the target become an irreducible background. The prompt scintillation light and the charge signals induced by particle interactions in the xenon will be observed by VUV sensitive, ultra-low background photosensors. Besides its excellent sensitivity to WIMPs above a mass of 5 GeV/c2, such a detector with its large mass, low-energy threshold and ultra-low background level will also be sensitive to other rare interactions. It will search for solar axions, galactic axion-like particles and the neutrinoless double-beta decay of 136Xe, as well as measure the low-energy solar neutrino flux with < 1% precision, observe coherent neutrino-nucleus interactions, and detect galactic supernovae. We present the concept of the DARWIN detector and discuss its physics reach, the main sources of backgrounds and the ongoing detector design and R&D efforts.

We discuss theoretical predictions for the existence of exotic (non-quark-model) mesons and review prominent experimental candidates. These are especially the f0(1500) and f0(1710) mesons for the scalar glueball, fJ(2220) for the tensor glueball, η(1410) for the pseudoscalar glueball, f0(600),f0(980),a0(980), the still to be firmly established κ(800) and the f2(1565) for q2q̄2 or two-meson states, and π1(1400),π1(1600) for hybrid states. We conclude that some of these states exist, offer our views and discuss crucial issues that need to be investigated both theoretically and experimentally.

The crystal Barrel spectrometer used at LEAR, CERN to study the products of pd annihilations is described. A 1380 element array of Csl crystals measures photons from the decay of π0, η, η′ and ω mesons. A segmented drift chamber in a 1.5T magnetic field is used to identify and measure charged particles. A fast on-line trigger on charged and neutral multiplicities and on the invariant mass of secondary particles is available. The performance of the detector is discussed.

Following the discovery of two new scalar mesons ${\mathit{f}}_{0}$(1370) and ${\mathit{f}}_{0}$(1500) at the Low Energy Antiproton Ring at CERN, we argue that the observed properties of this pair are incompatible with them both being QQ\ifmmode\bar\else\textasciimacron\fi{} mesons. We show instead that ${\mathit{f}}_{0}$(1500) is compatible with the ground state glueball expected around 1500 MeV mixed with the nearby states of the ${0}^{++}$QQ\ifmmode\bar\else\textasciimacron\fi{} nonet. Tests of this hypothesis include the prediction of a further scalar state ${\mathit{f}}_{0}^{\ensuremath{'}}$(1500--1800) which couples strongly to KK\ifmmode\bar\else\textasciimacron\fi{}, \ensuremath{\eta}\ensuremath{\eta}, and \ensuremath{\eta}\ensuremath{\eta}\ensuremath{'}. Signatures for a possible tensor glueball at \ensuremath{\sim}2 GeV are also considered. \textcopyright{} 1995 The American Physical Society.

We show that the newly discovered scalar meson f0(1500) at LEAR has properties compatible with the lightest scalar glueball predicted by lattice QCD and incompatible with a QQ state. We suggest that decays of glueballs are into pairs of glueballs (including η, η′ or (ππ)s) or by mixing with nearby QQ states. The partial widths of f0(1500) are in accord with this hypothesis, tests of which include characteristic radiative decays to γφ, γω, γϱ and the prediction of a further scalar state, f′0(1500 – 1800) which couples strongly to KK, ηη and ηη′.

The CMS detector team describes their experiment and observation of decay products from a standard model Higgs boson, allowing its mass to be determined.

Abstract Antihydrogen atoms with K or sub-K temperature are a powerful tool to precisely probe the validity of fundamental physics laws and the design of highly sensitive experiments needs antihydrogen with controllable and well defined conditions. We present here experimental results on the production of antihydrogen in a pulsed mode in which the time when 90% of the atoms are produced is known with an uncertainty of ~250 ns. The pulsed source is generated by the charge-exchange reaction between Rydberg positronium atoms—produced via the injection of a pulsed positron beam into a nanochanneled Si target, and excited by laser pulses—and antiprotons, trapped, cooled and manipulated in electromagnetic traps. The pulsed production enables the control of the antihydrogen temperature, the tunability of the Rydberg states, their de-excitation by pulsed lasers and the manipulation through electric field gradients. The production of pulsed antihydrogen is a major landmark in the AE $$\bar{g}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>ḡ</mml:mi> </mml:math> IS experiment to perform direct measurements of the validity of the Weak Equivalence Principle for antimatter.

This report reviews the achievements of the Crystal Barrel experiment at the Low Energy Antiproton Ring (LEAR) at CERN. During seven years of operation Crystal Barrel has collected very large statistical samples in pbarp annihilation, especially at rest and with emphasis on final states with high neutral multiplicity. The measured rates for annihilation into various two-body channels and for electromagnetic processes have been used to test simple models for the annihilation mechanism based on the quark internal structure of hadrons. From three-body annihilations three scalar mesons, a0(1450), f0(1370) and f0(1500) have been established in various decay modes. One of them, f0(1500), may be identified with the expected ground state scalar glueball.

Following a major shortage of 99Mo in the 2009–2010 period, concern grew that the aging reactor production facilities needed to be replaced. Most producers were using highly enriched 235U (HEU) as the target material. The Organisation for Economic Co-...Read More

We confirm the existence of the two IG(JPC) = 0+(0++) resonances f0(1370) and f0(1500) reported by us in earlier analyses. The analysis presented here couples the final states π0π0π0, π0π0η and π0ηη of pp annihilation at rest. It is based on a 3 × 3 K-matrix. We find masses and widths of M = (1390±30) MeV, Γ = (380±80) MeV; and M = (1500±10) MeV, Γ = (154 ± 30) MeV, respectively. The product branching ratios for the production and decay into π0π0 and ηη of the f0(1500) are (1.27 ± 0.33) · 10−3 and (0.60 ± 0.17) · 10−3, respectively.

A partial-wave analysis of the reaction pp→π0π0π0 has been performed using a high-quality high-statistics data set of 712 000 events. In addition to the f0(975) and f0(1300), the scalar resonance with mass m = (1500 ± 15) MeV and width Γ = (120 ± 25) MeV is necessary to describe the data.

The MUNU detector was designed to study ν¯ee− elastic scattering at low energy. The central component is a Time Projection Chamber filled with CF4 gas, surrounded by an anti-Compton detector. The experiment was carried out at the Bugey (France) nuclear reactor. In this Letter we present the final analysis of the data recorded at 3 bar and 1 bar pressure. Both the energy and the scattering angle of the recoil electron are measured. From the 3 bar data a new upper limit on the neutrino magnetic moment μeshort<9×10−11μB at 90% CL was derived. At 1 bar electron tracks down to 150 keV were reconstructed, demonstrating the potentiality of the experimental technique for future applications in low energy neutrino physics.

A new IG=1− JPC=0++πη resonance is observed in p̄p annihilation at rest into π0π0η. It has a mass M=(1450±40)MeV and a width Γ=(270±40)MeV.

The AEGIS experiment, currently being set up at the Antiproton Decelerator at CERN, has the objective of studying the free fall of antimatter in the Earth's gravitational field by means of a pulsed cold atomic beam of antihydrogen atoms. Both duration of free fall and vertical displacement of the horizontally emitted atoms will be measured, allowing a first test of the WEP with antimatter.

The parameters D, R, R' and P for pp elastic scattering have been measured in the centre-of-mass angular range 13 degrees to 58 degrees with an accuracy of about +or-0.02 at 209, 324, 379, 425 and 515 MeV. These results are incorporated with earlier data into a phase-shift analysis. Phase-shifts are generally in agreement with the theoretical predictions of the Paris group, although the F-wave spin-orbit combination is rather stronger than predicted. The fitted value for the pi 0pp coupling constant in g02=14.06+or-0.65.

The precise measurement of forces is one way to obtain deep insight into the fundamental interactions present in nature. In the context of neutral antimatter, the gravitational interaction is of high interest, potentially revealing new forces that violate the weak equivalence principle. Here we report on a successful extension of a tool from atom optics--the moiré deflectometer--for a measurement of the acceleration of slow antiprotons. The setup consists of two identical transmission gratings and a spatially resolving emulsion detector for antiproton annihilations. Absolute referencing of the observed antimatter pattern with a photon pattern experiencing no deflection allows the direct inference of forces present. The concept is also straightforwardly applicable to antihydrogen measurements as pursued by the AEgIS collaboration. The combination of these very different techniques from high energy and atomic physics opens a very promising route to the direct detection of the gravitational acceleration of neutral antimatter.

We demonstrate the laser excitation of the n = 3 state of positronium (Ps) in vacuum.A combination of a specially designed pulsed slow positron beam and a high-efficiency converter target was used to produce Ps.Its annihilation was recorded by single-shot positronium annihilation lifetime spectroscopy.Pulsed laser excitation of the n = 3 level at a wavelength λ ≈ 205 nm was monitored via Ps photoionization induced by a second intense laser pulse at λ = 1064 nm.About 15% of the overall positronium emitted into vacuum was excited to n = 3 and photoionized.Saturation of both the n = 3 excitation and the following photoionization was observed and explained by a simple rate equation model.The positronium's transverse temperature was extracted by measuring 2469

This biennial Review summarizes much of Particle Physics. Using data from previous editions plus new measurements from papers we list evaluate and average measured properties of gauge bosons leptons quarks mesons and baryons. We also summarize searches for hypothetical particles such as Higgs bosons heavy neutrinos and supersymmetric particles. All the particle properties and search limits are listed in Summary Tables. We also give numerous tables gures formulae and reviews of topics such as the Standard Model particle detectors probability and statistics. Among the reviews are many that are new or heavily revised including those on neutrino mixing CP violation in K D and B mesons Vcb the new exotic  particle extra dimensions grand unified theories cosmic background radiation dark matter cosmological parameters and big bang cosmology. A booklet is available containing the Summary Tables and abbreviated versions of some of the other sections of this full Review. All tables listings and reviews and errata are also available on the Particle Data Group website https://pdg.lbl.gov.

Production of antihydrogen atoms by mixing antiprotons with a cold, confined, positron plasma depends critically on parameters such as the plasma density and temperature. We discuss nondestructive measurements, based on a novel, real-time analysis of excited, low-order plasma modes, that provide comprehensive characterization of the positron plasma in the ATHENA antihydrogen apparatus. The plasma length, radius, density, and total particle number are obtained. Measurement and control of plasma temperature variations, and the application to antihydrogen production experiments are discussed.

We report on measurements of the branching ratios for φ production in pp annihilation at rest in H2 gas. Branching ratios for φπ0, φη, φϱ0, φω and φπ+ π− are determined for two data sets with different contributions of annihilations from S and P states of the pp system. The branching ratios are compared to corresponding annihilation modes where the φ is replaced by an ω meson. We conclude that φ production is in most reactions enhanced with respect to the expectation based on the OZI rule. In annihilations from the spin triplet ground state of antiprotonic hydrogen into φπ the OZI rule is violated dramatically.

Antihydrogen is formed when antiprotons are mixed with cold positrons in a nested Penning trap. We present experimental evidence, obtained using our antihydrogen annihilation detector, that the spatial distribution of the emerging antihydrogen atoms is independent of the positron temperature and axially enhanced. This indicates that antihydrogen is formed before the antiprotons are in thermal equilibrium with the positron plasma. This result has important implications for the trapping and spectroscopy of antihydrogen.

We report on a first measurement of the polarized-target asymmetry of the pion-proton bremsstrahlung cross section (${\ensuremath{\pi}}^{+}p\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}p\ensuremath{\gamma}$). As in previous cross section measurements the pion energy (298 MeV) and the detector geometry for this experiment was chosen to optimize the sensitivity to the radiation from the magnetic dipole moment of the ${\ensuremath{\Delta}}^{++}(1232)$ resonance ${\ensuremath{\mu}}_{\ensuremath{\Delta}}$. Comparison to a recent isobar model for pion-nucleon bremsstrahlung yields ${\ensuremath{\mu}}_{\ensuremath{\Delta}}=(1.62\ifmmode\pm\else\textpm\fi{}0.18) {\ensuremath{\mu}}_{p}$, where ${\ensuremath{\mu}}_{p}$ is the proton magnetic moment. Since the asymmetry depends less than the cross section on the choice of the other input parameters for the model, their uncertainties affect this analysis by less than the experimental error. However the theory fails to represent both the cross section and the asymmetry data at the highest photon energies. Hence further improvements in the calculations are needed before the model dependence of the magnetic moment analysis can be fully assessed. The present result agrees with bag-model corrections to the SU(6) prediction ${\ensuremath{\mu}}_{\ensuremath{\Delta}}=2{\ensuremath{\mu}}_{p}$. As a by-product, the analyzing power for elastic ${\ensuremath{\pi}}^{+}p$ scattering at 415 MeV/c was also measured. This second result is in good agreement with phase shift calculations.

We have obtained the branching ratios for pp annihilation at rest into π+π− and K+K− in a pure pp initial angular momentum state L = 1. A gaseous hydrogen target at normal pressure and temperature was used and events associated with transitions of the antiprotonic atom to the 2p level were selected by detecting the Balmer X-ray series. The branching ratios for pp annihilation into π+π− and K+K− from the 2p state are (4.81 ± 0.49) × 10−3 and (2.87 ± 0.51) × 10−4, respect The pion yield is slightly larger than in liquid hydrogen, where L = 0 annihilation dominates, while the kaon yield is suppressed by a factor of four. Using these and previous data, we derive the branching ratios for pp annihilation into all ππ and KK modes from S and P states. A measurement in gaseous hydrogen, without X-ray requirement, yields the branching ratios (4.30 ± 0.14) × 10−3 and (6.92 ± 0.41) × 10−4. With the known branching ratios of (3.33 ± 0.17) × 10−3 and (1.01 ± 0.05) × 10−3 in liquid hydrogen, we find that (50.3 ± 6.4)% of all annihilations in gas at NTP occur in the initial angular momentum state L = 1.

Nuclear and Particle Physics provides an introductory course on nuclear and particle physics for undergraduate and early-graduate students, which the author has taught for several years at the University of Zurich. It contains fundamentals on both nuclear and particle physics, giving emphasis to the discovery and history of developments in the field, and is experimentally/phenomenologically oriented. It contains detailed derivations of formulae such as 2–3 body phase space, the Weinberg-Salam model, and neutrino scattering. Originally published in German as Kern- und Teilchenphysik, several sections have been added to this new English version to cover modern topics, including updates on neutrinos, the Higgs boson, the top quark and bottom quark physics.

The L-series X-rays transitions of the kaonic helium-4 exotic atom were measured by SIDDHARTINO, the reduced configuration of the SIDDHARTA-2 experiment, at the DAΦNE collider of INFN-LNF, with gaseous 4He targets at densities of 1.90 g/l and 0.82 g/l, corresponding to 1.5% and 0.66%, respectively, of the liquid helium-4 density. The absolute yields for the Lα transition are determined to be 0.15 ±0.03 and 0.12 ±0.03, for the two target densities. The yields for the Lβ and Lγ transitions are presented relatively to that of the Lα transition. These results are compatible with the yields measured by the SIDDHARTA experiment at the densities of 1.65 g/l and 2.15 g/l and contribute to refine the cascade models describing the de-excitation of kaonic atoms as function of density.

The SIDDHARTA-2 experiment installed at the DA $$\mathrm {\Phi }$$ NE collider of INFN-LNF performed, for the first time, measurements of high-n transitions in intermediate mass kaonic atoms during the data taking campaigns of 2021 and 2022. Kaonic carbon, oxygen, nitrogen and aluminium transitions, which occur in the setup materials, were measured by using the kaons stopped in the gaseous helium target cell with aluminium frames and Kapton walls, and are reported in this paper. These new kaonic atoms measurements add valuable input to the kaonic atoms transitions data base, which is used as a reference for theories and models of the low-energy strong interaction between antikaon and nuclei. Moreover, these results pave the way for future dedicated kaonic atoms measurements through the whole periodic table and to a new era for the antikaon-nuclei studies at low energy.

A partial wave analysis is presented of two high-statistics data samples of protonium annihilation into π0π0η in liquid and 12 atm gaseous hydrogen. The contributions from the 1S0 ,3P1 and 3P2 initial atomic fine structure states to the two data sets are different. The change of their fractional contributions when going from liquid to gaseous H2 as calculated in a cascade model is imposed in fitting the data. Thus the uncertainty in the fraction of S-state and P-state capture is minimized. Both data sets allow a description with a common set of resonances and resonance parameters. The inclusion of a πη P-wave in the fit gives supportive evidence for the ρ̂(1405), with parameters compatible with previous findings.

The ATHENA apparatus that recently produced and detected the first cold antihydrogen atoms is described. Its main features, which are described herein, are: an external positron accumulator, making it possible to accumulate large numbers of positrons; a separate antiproton catching trap, optimizing the catching, cooling and handling of antiprotons; a unique high resolution antihydrogen annihilation detector, allowing an clear determination that antihydrogen has been produced; an open, modular design making variations in the experimental approach possible and a "nested" Penning trap situated in a cryogenic, 3T magnetic field environment used for the mixing of the antiprotons and positrons.

The results of a measurement of p̄p annihilation at rest into ηηπ0 are presented. Assuming a resonance dominated model for the annihilation process an isoscalar JPC=0++ resonance decaying into ηη is observed with a mass of 1560±25 MeV/c2 and a width of 245±50 MeV/c2.

We show that antihydrogen production is the dominant process when mixing antiprotons and positrons in the ATHENA apparatus, and that the initial production rate exceeds 300 Hz, decaying to 30 Hz within 10 s. A fraction of 65% of all observed annihilations is due to antihydrogen.

Antiproton-proton annihilations at rest into 3π0 are analyzed in terms of π0π0 final state interactions. A JPC = 2+ + resonance at a mass of 1515 ± 10 MeV with a width of 120 ± 10 MeV is required to explain the data. This result is supported by previous observations made on the ππ system in pp and pn annihilations which show that the resonance has I = 0. This resonance is practically degenerate in mass with the f′2 (1525) but the two resonances have very different production and decay characteristics.

A new isoscalar ππ resonance AX(1565) has been observed at a mass of 1565±10 MeV/c2 and a width of 170±20 MeV/c2. The resonance is produced in pp annihilation at rest into π+π−π0 from P states of antiprotonic hydrogen atoms formed b y stopping antiprotons in hydrogen gas at normal temperature and pressure. Annihilation from P states is identified by coincident observations of the LX-ray series emitted in the cascade of pp atoms. The resonance is seen as striking peak in the π+π− invariant mass spectrum. The phase of the π+π− D wave shows a resonance-like behaviour. Hence we assign the quantum numbers IG(JPC) = 0+(2++) to the resonance.

The Kα X-rays from pp̄ atoms formed in H2 gas at normal temperature and pressure are unambiguously identified by coincidences with L X-rays populating the 2P level. Background due to inner bremsstrahlung is suppressed by selecting events annihilating into neutral final states only. The Kα line is observed with a significance of more than 25 standard deviations at an energy of 8.67 (15) keV. From fits to the Kα line we obtain a strong-interaction shift and width of the 1S level, averaged over the unresolved spin singlet and triplet contributions, of ΔE + iΓ/2 = [−0.70(15) + i0.80(20)] keV.

In a multivariate regression model relating individual returns to the market return, CAPM implies non-linear restrictions on the parameters. Several asymptotically valid tests of these restrictions have been suggested. The existing Monte Carlo evidence shows that some of these tests are unreliable for reasonable sample sizes, but does not indicate well which tests are reliable. This paper reports the results of an extensive Monte Carlo experiment. Shanken's CSR test and Jobson and Korkie's corrected likelihood ratio test are quite accurate in all cases we consider.

A polarimeter is described having a large solid angle of acceptance and using a carbon analyser combined with 12 multiwire proportional chambers. Its analysing power for protons has been calibrated at TRIUMF with an absolute accuracy reaching ±0.015 ≡ 2% in the angular range 3.5° to 28° laboratory angle and for incident energies between 107 and 462 MeV. A mean analysing power of about 35% and an efficiency of approximately 3% was observed.

The main goal of the AEgIS experiment at CERN is to test the weak equivalence principle for antimatter. We will measure the Earth's gravitational acceleration g¯ with antihydrogen atoms being launched in a horizontal vacuum tube and traversing a moiré deflectometer. We intend to use a position sensitive device made of nuclear emulsions (combined with a time-of-flight detector such as silicon μ-strips) to measure precisely their annihilation points at the end of the tube. The goal is to determine g¯ with a 1% relative accuracy. In 2012 we tested emulsion films in vacuum and at room temperature with low energy antiprotons from the CERN antiproton decelerator. First results on the expected performance for AEgIS are presented.

We describe a system designed to re-bunch positron pulses delivered by an accumulator supplied by a positron source and a Surko-trap. Positron pulses from the accumulator are magnetically guided in a 0.085 T field and are injected into a region free of magnetic fields through a μ-metal field terminator. Here positrons are temporally compressed, electrostatically guided and accelerated towards a porous silicon target for the production and emission of positronium into vacuum. Positrons are focused in a spot of less than 4 mm FWTM in bunches of ∼8 ns FWHM. Emission of positronium into the vacuum is shown by single shot positron annihilation lifetime spectroscopy.

The goal of the ASACUSA-CUSP collaboration at the Antiproton Decelerator of CERN is to measure the ground-state hyperfine splitting of antihydrogen using an atomic spectroscopy beamline. A milestone was achieved in 2012 through the detection of 80 antihydrogen atoms 2.7 m away from their production region. This was the first observation of ‘cold’ antihydrogen in a magnetic field free region. In parallel to the progress on the antihydrogen production, the spectroscopy beamline was tested with a source of hydrogen. This led to a measurement at a relative precision of 2.7×10 −9 which constitutes the most precise measurement of the hydrogen hyperfine splitting in a beam. Further measurements with an upgraded hydrogen apparatus are motivated by CPT and Lorentz violation tests in the framework of the Standard Model Extension. Unlike for hydrogen, the antihydrogen experiment is complicated by the difficulty of synthesizing enough cold antiatoms in the ground state. The first antihydrogen quantum states scan at the entrance of the spectroscopy apparatus was realized in 2016 and is presented here. The prospects for a ppm measurement are also discussed. This article is part of the Theo Murphy meeting issue ‘Antiproton physics in the ELENA era’.

We present a measurement and partial wave analysis of the final state K L K Ϯ ϯ of p ¯p annihilation at rest in liquid hydrogen.This reaction is important for the study of the K ¯K decay mode of scalar resonances, in particular, the isovectors a 0 (980) and a 0 (1450).The determination of the a 0 (1450) production also fixes the K ¯K coupling of the isoscalar f 0 (1500) which is discussed as a glueball.We find B"p ¯p →a 0 (1450);a 0 (1450)→K ¯K…ϭ(8.88Ϯ1.68)ϫ10Ϫ4 and hence B"p ¯p→ f 0 (1500); f 0 (1500)→K ¯K…ϭ(4.52Ϯ0.36)ϫ10 Ϫ4 .The mass and width of a 0 (1450) are mϭ1480Ϯ30 MeV/c 2 and ⌫ϭ265Ϯ15 MeV/c 2 , respectively.For a 0 (980) we determine the relative ratio B(p ¯p→a 0 ;a 0 →K ¯K)/B(p ¯p→a 0 ;a 0 →) ϭ0.23Ϯ0.05 and its relative coupling, K ¯K to , is 1.03Ϯ0.14.͓S0556-2821͑98͒02907-5͔

The MUNU experiment was carried out at the Bugey nuclear power reactor. The aim was the study of ν̄ee− elastic scattering at low energy. The recoil electrons were recorded in a gas time projection chamber, immersed in a tank filled with liquid scintillator serving as veto detector, suppressing in particular Compton electrons. The measured electron recoil spectrum is presented. Upper limits on the neutrino magnetic moment were derived and are discussed.

We report measurements of branching ratios for production of a series of two meson final states in $$\bar p$$ p annihilations at rest in liquid hydrogen. We find: $$\begin{gathered} BR(\bar pp \to \pi ^ + \pi ^ - ) = (3.07 \pm 0.13) \cdot 10^{ - 3} \hfill \\ BR(\bar pp \to K^ + K^ - ) = (0.99 \pm 0.05) \cdot 10^{ - 3} \hfill \\ BR(\bar pp \to \pi ^0 \pi ^0 ) = (6.93 \pm 0.43) \cdot 10^{ - 4} \hfill \\ BR(\bar pp \to \pi ^0 \eta ) = (2.12 \pm 0.12) \cdot 10^{ - 4} \hfill \\ BR(\bar pp \to \pi ^0 \omega ) = (5.73 \pm 0.47) \cdot 10^{ - 3} \hfill \\ BR(\bar pp \to \pi ^0 \eta ') = (1.23 \pm 0.13) \cdot 10^{ - 4} \hfill \\ BR(\bar pp \to \eta \eta ) = (1.64 \pm 0.10) \cdot 10^{ - 4} \hfill \\ BR(\bar pp \to \eta \omega ) = (1.51 \pm 0.12) \cdot 10^{ - 2} \hfill \\ BR(\bar pp \to \eta \eta ') = (2.16 \pm 0.25) \cdot 10^{ - 4} \hfill \\ BR(\bar pp \to \omega \omega ) = (3.32 \pm 0.34) \cdot 10^{ - 2} \hfill \\ BR(\bar pp \to \omega \eta ') = (0.78 \pm 0.08) \cdot 10^{ - 2} \hfill \\ \end{gathered}$$ These are the first measurements of the channels ηη′ and ωη′ and in almost all the other channels are more precise than previous results. We also obtain, in a more precise fashion, the following ratios of branching ratios:K + K −/π+π−=0.323±0.013, π0η′/π0η=0.548±0.056, ηη′/ηη=0.31±0.15, ωη′/ωη=0.515±0.040, π0η/π0π0=0.303±0.010, ηη/π0π0=0.232±0.011 and π0ω/ηω=0.377±0.12. The measurements are made for different η and η′ decays, and we thus obtain Γη→3π 0/Γη→γγ=0.841±0.034, and $$\Gamma _{\eta ' \to \gamma \gamma } /\Gamma _{\eta ' \to \pi ^0 \pi ^0 \eta } = 0.091 \pm 0.009$$ .

The temperature dependence of the light emission for pure CsI crystals has been measured with photomultipliers, and photodiodes with wavelength shifters from 80–300K. The light yield at 80K is Nγ=50,000±5000 photons/MeV. This number was deduced from the number of electron–hole pairs produced in the photodiode, Neh=39,600±1200. The light yield at room temperature is lower by a factor of 15.8±1.0, giving 3200±400 photons/MeV. Decay times were measured with a photomultiplier. At room temperature two fast decay components were observed with decay times of 6±1 and 28±2ns. Below 180K only one component is observed and at 80K the decay time is 1015±17ns.

We have determined ratios of branching ratios for pp annihilations at rest into π0η and π0η′, into ηη and ηη′, and into ωη and ωη′. All reactins are observed in two different all-neutral final states. The ratios permit a determination of the pseudoscalar mixing angle. We find ΘPS = −(17.3±1.8)°.

Cold antihydrogen atoms were produced by mixing cold samples of antiprotons and positrons. The temperature of the positron plasma was increased by controlled radio-frequency (RF) heating, and the antihydrogen production was measured. Formation is observed to decrease with increased temperature but a simple power law scaling is not observed. Significant production is still present at room temperature.

We report on the observation of an ηη′ threshold enhancement produced in p̄p annihilations at rest into π0ηη′, which we identify with the recently discovered ƒ0(1500).

K and L series X-rays have been observed from pp atoms formed in hydrogen gas at NTP in association with annihilations into neutral particles. The total K X-ray yield is (6.5 ± 3.2) × 10−3 per stopped antiproton. A model-dependent fit of the K X-ray spectrum gives a Kα energy of 8.9±0.3 keV, corresponding to a strong interaction shift of (−0.5±0.3) keV.

The CMS experiment at the (LHC) includes a hybrid silicon pixel detector for the reconstruction of charged tracks and of the interaction vertices. The barrel region consists of n-in-n sensors with 100×150μm2 cell size processed on diffusion oxygenated float zone silicon. A biasing grid is implemented and pixel isolation is achieved with the moderated p-spray technique. An extensive test program was carried out on the H2 beam line of the CERN-SPS. In this paper we describe the sensor layout, the beam test setup and the results obtained with both irradiated and non-irradiated prototype devices. Measurements of charge collection, hit detection efficiency, Lorentz angle and spatial resolution are presented.

The main goal of the AEgIS experiment at CERN is to test the weak equivalence principle for antimatter. AEgIS will measure the free-fall of an antihydrogen beam traversing a moir&apos;e deflectometer. The goal is to determine the gravitational acceleration with an initial relative accuracy of 1% by using an emulsion detector combined with a silicon μ-strip detector to measure the time of flight. Nuclear emulsions can measure the annihilation vertex of antihydrogen atoms with a precision of ∼ 1–2 μm r.m.s. We present here results for emulsion detectors operated in vacuum using low energy antiprotons from the CERN antiproton decelerator. We compare with Monte Carlo simulations, and discuss the impact on the AEgIS project.

This graduate-level text is a modern primer on the subject matter specifically developed for a new generation of experiments and high-energy physicists. it offers course-tested material, comparison between theory and up-to-date data, and includes problems and solutions.

Abstract A partial wave analysis of antiproton–proton annihilation data in flight at 900 $$\mathrm {MeV/}c$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mrow><mml:mi>MeV</mml:mi><mml:mo>/</mml:mo></mml:mrow><mml:mi>c</mml:mi></mml:mrow></mml:math> into $${\pi ^0\pi ^0\eta }$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mi>π</mml:mi><mml:mn>0</mml:mn></mml:msup><mml:msup><mml:mi>π</mml:mi><mml:mn>0</mml:mn></mml:msup><mml:mi>η</mml:mi></mml:mrow></mml:math> , $${\pi ^0\eta \eta }$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mi>π</mml:mi><mml:mn>0</mml:mn></mml:msup><mml:mi>η</mml:mi><mml:mi>η</mml:mi></mml:mrow></mml:math> and $${K^+K^-\pi ^0}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mi>K</mml:mi><mml:mo>+</mml:mo></mml:msup><mml:msup><mml:mi>K</mml:mi><mml:mo>-</mml:mo></mml:msup><mml:msup><mml:mi>π</mml:mi><mml:mn>0</mml:mn></mml:msup></mml:mrow></mml:math> is presented. The data were taken at LEAR by the Crystal Barrel experiment in 1996. The three channels have been coupled together with $$\pi \pi $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>π</mml:mi><mml:mi>π</mml:mi></mml:mrow></mml:math> -scattering isospin I = 0 S- and D-wave as well as I = 1 P-wave data utilizing the K-matrix approach. Analyticity is treated using Chew–Mandelstam functions. In the fit all ingredients of the K-matrix, including resonance masses and widths, were treated as free parameters. In spite of the large number of parameters, the fit results are in the ballpark of the values published by the Particle Data Group. In the channel $${\pi ^0\pi ^0\eta }$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mi>π</mml:mi><mml:mn>0</mml:mn></mml:msup><mml:msup><mml:mi>π</mml:mi><mml:mn>0</mml:mn></mml:msup><mml:mi>η</mml:mi></mml:mrow></mml:math> a significant contribution of the spin exotic $$I^G=1^-$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mi>I</mml:mi><mml:mi>G</mml:mi></mml:msup><mml:mo>=</mml:mo><mml:msup><mml:mn>1</mml:mn><mml:mo>-</mml:mo></mml:msup></mml:mrow></mml:math> $$J^{PC}=1^{-+}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mi>J</mml:mi><mml:mrow><mml:mi>PC</mml:mi></mml:mrow></mml:msup><mml:mo>=</mml:mo><mml:msup><mml:mn>1</mml:mn><mml:mrow><mml:mo>-</mml:mo><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math> $$\pi _1$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>π</mml:mi><mml:mn>1</mml:mn></mml:msub></mml:math> -wave with a coupling to $$\pi ^0 \eta $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mi>π</mml:mi><mml:mn>0</mml:mn></mml:msup><mml:mi>η</mml:mi></mml:mrow></mml:math> is observed. Furthermore the contributions of $$\phi (1020) \pi ^0$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>ϕ</mml:mi><mml:mrow><mml:mo>(</mml:mo><mml:mn>1020</mml:mn><mml:mo>)</mml:mo></mml:mrow><mml:msup><mml:mi>π</mml:mi><mml:mn>0</mml:mn></mml:msup></mml:mrow></mml:math> and $$K^*(892)^\pm K^\mp $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mi>K</mml:mi><mml:mo>∗</mml:mo></mml:msup><mml:msup><mml:mrow><mml:mo>(</mml:mo><mml:mn>892</mml:mn><mml:mo>)</mml:mo></mml:mrow><mml:mo>±</mml:mo></mml:msup><mml:msup><mml:mi>K</mml:mi><mml:mo>∓</mml:mo></mml:msup></mml:mrow></mml:math> in the channel $${K^+K^-\pi ^0}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mi>K</mml:mi><mml:mo>+</mml:mo></mml:msup><mml:msup><mml:mi>K</mml:mi><mml:mo>-</mml:mo></mml:msup><mml:msup><mml:mi>π</mml:mi><mml:mn>0</mml:mn></mml:msup></mml:mrow></mml:math> have been studied in detail. The differential production cross section for the two reactions and the spin-density-matrix elements for the $$\phi (1020)$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>ϕ</mml:mi><mml:mo>(</mml:mo><mml:mn>1020</mml:mn><mml:mo>)</mml:mo></mml:mrow></mml:math> and $$K^*(892)^\pm $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mi>K</mml:mi><mml:mo>∗</mml:mo></mml:msup><mml:msup><mml:mrow><mml:mo>(</mml:mo><mml:mn>892</mml:mn><mml:mo>)</mml:mo></mml:mrow><mml:mo>±</mml:mo></mml:msup></mml:mrow></mml:math> have been extracted. No spin-alignment is observed for both vector mesons. The spin density matrix elements have been also determined for the spin exotic wave.

The annihilation pp → Φγ has been investigated with the Crystal Barrel detector at LEAR for antiprotons stopped in liquid hydrogen. The observed branching ratio BR(pp → Φγ = (1.7 ± 0.4) · 10−5 is almost two orders of magnitude higher than expected from the OZI-rule. As a by-product, the branching ratios BR(pp → KLKS) = (9.0 ± 0.6) · 10−4 and BR(pp → Φπ0) = (5.5 ± 0.7) · 10−4 have been measured.

We are building a low background detector based on a gas time projection chamber surrounded by an active anti-Compton shielding. The detector will be installed near a nuclear reactor in Bugey for the experimental study of νee− scattering. We give here a general description of the experiment, and an estimate of the expected counting rate and background. The construction of the time projection chamber is described in details. Results of first test measurements concerning the attenuation length and the spatial as well as energy resolution in the CF4 fill gas are reported.

A partial wave analysis of the reaction pp→πoηη has been performed, using a high quality, high statistics data set of 198,000 events. In addition to the ƒ0(1370), a second scalar resonance decaying into ηη, the ƒ0(1500), with mass m = (1505 ± 15) MeV and width Γ = (120 ± 30) MeV has to be introduced to describe the data.

We report an analysis of pp annihilation at rest into ϱ+ϱ−π0 leading to the final state π+π−3π 0. A strong signal is observed for a scalar resonance with mass 1374 ± 38 MeV/c2 and width 375 ± 61 MeV/c2, decaying to ϱ+ϱ−. The resonance in ϱ+ϱ− represents 2.0 ± 0.3% of all pp annihilation at rest. It is also observed to decay into two S-wave dipions (π+π−) (π0π0)). Under the assumption of isospin 0, this is probably ƒ0(1400), seen for the first time in its 4π decay mode.

The annihilation channels pp→KsKs and KsKL at rest have been observed in hydrogen gas at normal temperature and pressure. The channel KsKs has also been observed from the atomic 2p orbital. The branching fraction for pp→K0K0 from initial L = 1 angular momentum pp states is (8.8±2.3)×10−5 and is suppressed by one order of magnitude compared to L = 0 states.

Results on antiproton absorption at rest in gaseous nitrogen and deuterium are presented from an analysis of approximately ${10}^{6}$ events each taken with a magnetic spectrometer. Inclusive features such as pion and proton multiplicities and spectra are presented. Data relating to absorption modes requiring more than one nucleon, such as the \ensuremath{\Lambda} yield, the \ensuremath{\Lambda} spectrum, and the exclusive deuterium channels p\ifmmode\bar\else\textasciimacron\fi{}d\ensuremath{\rightarrow}${\ensuremath{\pi}}^{\mathrm{\ensuremath{-}}}$p, \ensuremath{\Lambda}${K}^{+}$${\ensuremath{\pi}}^{\mathrm{\ensuremath{-}}}$ are discussed. The fully reconstructable channels p\ifmmode\bar\else\textasciimacron\fi{}d\ensuremath{\rightarrow}${\mathrm{\ensuremath{\pi}}}^{+}$${\mathrm{\ensuremath{\pi}}}^{\mathrm{\ensuremath{-}}}$${\mathrm{\ensuremath{\pi}}}^{\mathrm{\ensuremath{-}}}$p,${\mathrm{\ensuremath{\pi}}}^{+}$${\mathrm{\ensuremath{\pi}}}^{+}$ ${\mathrm{\ensuremath{\pi}}}^{\mathrm{\ensuremath{-}}}$${\mathrm{\ensuremath{\pi}}}^{\mathrm{\ensuremath{-}}}$${\mathrm{\ensuremath{\pi}}}^{\mathrm{\ensuremath{-}}}$p also show a high-energy proton tail unaccounted for by single nucleon rescattering mechanisms.

Data on ${D}_{t}$, ${R}_{t}$, ${A}_{t}$, and $P$ lead to unique and accurate $\mathrm{np}$ phase shift solutions at 210, 325, 425, and 515 MeV. The $I=O, D, \mathrm{and} G$ waves show large systematic deviations from current theoretical models.NUCLEAR REACTIONS $p(n,n)p$, $E=210, 325, 425, \mathrm{and} 515$ MeV; phase shift analysis.

The influence of air contamination on the VUV scintillation yield in gaseous argon at atmospheric pressure is investigated. We determine with a radioactive α-source the photon yield for various partial air pressures and different reflectors and wavelength shifters. We find that the time constant of the slow scintillation component depends on gas purity and is a good indicator for the total VUV light yield, while the fast component is not affected. This dependence is attributed to impurities destroying the long-lived triplet argon excimer state. The population ratio between the slow and the fast decaying excimer states is determined for α-particles to be 5.5 ± 0.6 in argon gas at 1100 mbar and room temperature. The measured decay time constant of the slow component is 3.140 ± 0.067 μs at a partial air pressure of 2 × 10−6 mbar.

The Argon Dark Matter (ArDM-1t) experiment is a ton-scale liquid argon (LAr) double-phase time projection chamber designed for direct Dark Matter searches. Such a device allows to explore the low energy frontier in LAr with a charge imaging detector. The ionization charge is extracted from the liquid into the gas phase and there amplified by the use of a Large Electron Multiplier in order to reduce the detection threshold. Direct detection of the ionization charge with fine spatial granularity, combined with a measurement of the amplitude and time evolution of the associated primary scintillation light, provide powerful tools for the identification of WIMP interactions against the background due to electrons, photons and possibly neutrons if scattering more than once. A one ton LAr detector is presently installed on surface at CERN to fully test all functionalities and it will be soon moved to an underground location. We will emphasize here the lessons learned from such a device for the design of a large LAr TPC for neutrino oscillation, proton decay and astrophysical neutrinos searches.

We propose to build and operate a detector based on the emulsion film technology for the measurement of the gravitational acceleration on antimatter, to be performed by the AEgIS experiment (AD6) at CERN. The goal of AEgIS is to test the weak equivalence principle with a precision of 1% on the gravitational acceleration g by measuring the vertical position of the annihilation vertex of antihydrogen atoms after their free fall while moving horizontally in a vacuum pipe. With the emulsion technology developed at the University of Bern we propose to improve the performance of AEgIS by exploiting the superior position resolution of emulsion films over other particle detectors. The idea is to use a new type of emulsion films, especially developed for applications in vacuum, to yield a spatial resolution of the order of one micron in the measurement of the sag of the antihydrogen atoms in the gravitational field. This is an order of magnitude better than what was planned in the original AEgIS proposal.

Kaonic atoms are an extremely efficient tool to investigate the strong interaction at the low energy Frontier, since they provide direct access to the K − N interaction at threshold, eliminating the necessity for extrapolation, unlike in the case of scattering experiments. During the 1970s and 1980s, extensive studies were performed on kaonic atoms spanning across a broad spectrum of elements in the periodic table, ranging from lithium to uranium. These measurements provided inputs and constraints for the theoretical description of the antikaon-nuclei interaction potential. Nevertheless, the existing data suffer from significant experimental uncertainties, and numerous measurements have been found to be inconsistent with more recent measurements that utilize advanced detector technology. Furthermore, there remain numerous transitions of kaonic atoms that have yet to be measured. For these reasons, a new era of kaonic atoms studies is mandatory. The DAΦNE electron-positron collider at the INFN Laboratory of Frascati (INFN-LNF) stands out as a unique source of low-energy kaons, having been utilized by Collaborations such as DEAR, SIDDHARTA, and AMADEUS for groundbreaking measurements of kaonic atoms and kaon-nuclei interactions. Presently, the SIDDHARTA-2 experiment is installed at DAΦNE, aiming to perform the first-ever measurement of the 2p → 1s x-ray transition in kaonic deuterium, a crucial step towards determining the isospin-dependent antikaon-nucleon scattering lengths. Based on the experience gained with the SIDDHARTA experiment, which performed the most precise measurement of the kaonic hydrogen 2p → 1s x-ray transition, the SIDDHARTA-2 setup is now fully equipped for the challenging kaonic deuterium measurement. In this paper, we present a comprehensive description of the SIDDHARTA-2 setup and of the first kaonic atoms measurements performed during the commissioning phase of the DAΦNE collider. We also outline a proposal for future measurements of kaonic atoms at DAΦNE beyond SIDDHARTA-2, which is intended to stimulate discussions within the broad scientific community performing research, directly or indirectly, related to this field.

We have observed the ηπ+π− and ηπ0π0 decay modes of the E meson in pp annihilation at rest into π+π−π0π0η. The mass and width of the E meson are 1409 ± 3 and 86 ± 10 MeV. The production and decay branching ratio is B(pp → Eππ)B(E → ηππ) = (3.3 ± 1.0) × 10−3. With a spin-parity analysis we determine that JP = 0−. The observation of the ηπ0π0 decay mode establishes that E is isoscalar (C = +1). We find that E decays to η(ππ)s (where (ππ)s is an S-wave dipion) and πa0(980)(→ πη) with a relative branching ratio of (78 ± 16) %. Using the KKπ production and decay branching ratio measured earlier we determine that B[E → KKπ]B[E → ηππ] = 0.61 ± 0.19. A comparison with observations in radiative JΨ decays suggests that E and ιη(1416) are identical.

The f0(1500) is observed in its KK decay mode in an amplitude analysis of high statistics data in pp annihilation at rest into π0KLKL. The mass and width is found to be (m, Γ) = (1515 ± 20, 105 ± 15) MeV. A comparison of the decay rate into 2π0 shows that this state cannot be dominantly ss. The f′2(1525) has been observed for the first time in pp annihilation and its production rate is consistent with the expectation from the OZI rule.

Crystal Barrel data on pp → 5π0 at rest are presented. Mass spectra for 2π0 combinations, 3π0 and 4π0 and decay angular distributions all differ significantly from phase space. We present several ways of fitting the data. All agree on the definite presence of the f0(1500), observed in its 4π0 decay mode. It can decay into ππ(1300) and into σσ where σ stands for the full ππ S-wave amplitude.

We demonstrate cooling of 104 antiprotons in a dense, cold plasma of ∼108 positrons, confined in a nested cylindrical Penning trap at about 15 K. The time evolution of the cooling process has been studied in detail, and several distinct types of behavior identified. We propose explanations for these observations and discuss the consequences for antihydrogen production. We contrast these results with observations of interactions between antiprotons and “hot” positrons at about 3000 K, where antihydrogen production is strongly suppressed.

We present evidence showing how antiprotonic hydrogen, the quasistable antiproton (p)-proton bound system, has been synthesized following the interaction of antiprotons with the molecular ion H2+ in a nested Penning trap environment. From a careful analysis of the spatial distributions of antiproton annihilation events, evidence is presented for antiprotonic hydrogen production with sub-eV kinetic energies in states around n=70, and with low angular momenta. The slow antiprotonic hydrogen may be studied using laser spectroscopic techniques.

Measurements over an extensive angular range of the ${D}_{t}$ and $P$ parameters in free neutron-proton elastic scattering at laboratory energies of 220, 325, 425, and 495 MeV are reported. Experimental and analytical details are given.NUCLEAR REACTIONS $p(\stackrel{\ensuremath{\rightarrow}}{n}, \stackrel{\ensuremath{\rightarrow}}{p})n$, $E=220, 325, 425, \mathrm{and} 495$ MeV; measured ${D}_{t}(\ensuremath{\theta})$, $P(\ensuremath{\theta})$.

High precision proton-proton analyzing power measurements have been made at incident proton energies of 225, 327, and 520 MeV for θlab = 17°, and at 205, 308, and 499 MeV for θlab = 24°. The relative uncertainty is ± 1% for the results at 17° and ± 3% for the data at 24°. The p-4He analyzing power at θlab = 15° was measured with ± 1–2% errors at 222, 325, and 518 MeV. These results can be used as accurate calibration standards for polarized proton beams and provide accurate polarization normalizations for phase shift analyses.

To optimise the design of the light readout in the ArDM 1-ton liquid argon dark matter detector, a range of reflector and WLS coating combinations were investigated in several small setups, where argon scintillation light was generated by radioactive sources in gas at normal temperature and pressure and shifted into the blue region by tetraphenyl butadiene (TPB). Various thicknesses of TPB were deposited by spraying and vacuum evaporation onto specular 3MTM-foil and diffuse Tetratex® (TTX) substrates. Light yields of each reflector and TPB coating combination were compared. Reflection coefficients of TPB coated reflectors were independently measured using a spectroradiometer in a wavelength range between 200 and 650 nm. WLS coating on the PMT window was also studied. These measurements were used to define the parameters of the light reflectors of the ArDM experiment. Fifteen large 120 × 25 cm2 TTX sheets were coated and assembled in the detector. Measurements in argon gas are reported providing good evidence of fulfilling the light collection requirements of the experiment.

The results of a search for hydrogen-like atoms consisting of π∓K± mesons are presented. Evidence for πK atom production by 24 GeV/c protons from CERN PS interacting with a nickel target has been seen in terms of characteristic πK pairs from their breakup in the same target (178±49) as well as in terms of produced πK atoms (653±42). Using these results, the analysis yields a first value for the πK atom lifetime of τ=(2.5−1.8+3.0)fs and a first measurement of the S-wave isospin-odd πK scattering length |a0−|=13|a1/2−a3/2|=(0.11−0.04+0.09)Mπ−1 (aI for isospin I).

Producing positronium (Ps) in the metastable 2 3 S state is of interest for various applications in fundamental physics.We report here on an experiment in which Ps atoms are produced in this long-lived state by spontaneous radiative decay of Ps excited to the 3 3 P level manifold.The Ps cloud excitation is obtained with a UV laser pulse in an experimental vacuum chamber in presence of guiding magnetic field of 25 mT and an average electric field of 300 V cm -1 .The evidence of the 2 3 S state production is obtained to the 3.6σ level of statistical significance using a novel analysis technique of the single-shot positronium annihilation lifetime spectra.The dynamic of the Ps population on the involved levels has been studied with a rate equation model.

We present a Rabi-type measurement of two ground-state hydrogen hyperfine transitions performed in two opposite external magnetic field directions. This puts first constraints at the level of 2.3 10^-21 GeV on a set of coefficients of the Standard Model Extension, which were not measured by previous experiments. Moreover, we introduce a novel method, applicable to antihydrogen hyperfine spectroscopy in a beam, that determines the zero-field hyperfine transition frequency from the two transitions measured at the same magnetic field. Our value, nu_0 = 1.420 405 751 63(63) GHz, is in agreement with literature at a relative precision of 0.44 ppb. This is the highest precision achieved on hydrogen in a beam, improving over previous results by a factor of 6.

The distribution of m(π+π−) in the decay η′ → π+π−γ has been measured with the Crystal Barrel detector. The results are based on a total of 7392 observed η′ decays. The box anomaly constant is extracted from this and its value is found to agree well with theoretical expectations. The pseudoscalar nonet parameters (f1, f8 and θPS) are determined. Finally, we find that there is a problem of consistency between QCD and the standard VDM assumption.

The annihilation pp→π0π0 was measured for antiprotons stopped in liquid hydrogen (LH2). This reaction is only allowed from odd angular momentum states of the pp-atom. The resulting branching ratio BR(pp→π0π0)LH2=(6.93±0.22stat±0.37syst)×10−4, combined with a previous measurement of the branching ratio BR(pp→π+π−)2P in gas from the 2P-state of pp suggests a fraction of P-wave annihilation in LH2 of (28.8±3.5)%, much larger than the values obtained from other annihilation channels. A method of reconciling the contradictory results is discussed.

We argue that the experimental decay rates of the f0(1500) meson into two pseudoscalar mesons and into two photons are incompatible with a quark–antiquark state and that the f0(1710) meson is dominantly an ss̄ state.

Antihydrogen can be synthesized by mixing antiprotons and positrons in a Penning trap environment. Here an experiment to stimulate the formation of antihydrogen in the n=11 quantum state by the introduction of light from a CO2 continuous wave laser is described. An overall upper limit of 0.8% with 90% C.L. on the laser-induced enhancement of the recombination has been found. This result strongly suggests that radiative recombination contributes negligibly to the antihydrogen formed in the experimental conditions used by the ATHENA Collaboration.Received 14 July 2006DOI:https://doi.org/10.1103/PhysRevLett.97.213401©2006 American Physical Society

We demonstrate temporally controlled modulation of cold antihydrogen production by periodic RF heating of a positron plasma during antiproton-positron mixing in a Penning trap. Our observations have established a pulsed source of atomic antimatter, with a rise time of about 1 s, and a pulse length ranging from 3 to 100 s. Time-sensitive antihydrogen detection and positron plasma diagnostics, both capabilities of the ATHENA apparatus, allowed detailed studies of the pulsing behavior, which in turn gave information on the dependence of the antihydrogen production process on the positron temperature T. Our data are consistent with power law scaling T−1.1±0.5 for the production rate in the high temperature regime from ∼100 meV up to 1.5 eV. This is not in accord with the behavior accepted for conventional three-body recombination.Received 2 October 2007DOI:https://doi.org/10.1103/PhysRevLett.101.053401©2008 American Physical Society

The AEgIS experiment is presently almost completely installed at CERN. It is currently taking data with antiprotons, electrons and positrons. The apparatus is designed to form a cold, pulsed beam of antihydrogen to measure the Earth's gravitational acceleration g on antimatter and to perform spectroscopy measurements. This paper describes the main features of the apparatus and shows a selected review of some achieved results.

Abstract We describe a multi-step “rotating wall” compression of a mixed cold antiproton–electron non-neutral plasma in a 4.46 T Penning–Malmberg trap developed in the context of the AEḡIS experiment at CERN. Such traps are routinely used for the preparation of cold antiprotons suitable for antihydrogen production. A tenfold antiproton radius compression has been achieved, with a minimum antiproton radius of only 0.17 mm. We describe the experimental conditions necessary to perform such a compression: minimizing the tails of the electron density distribution is paramount to ensure that the antiproton density distribution follows that of the electrons. Such electron density tails are remnants of rotating wall compression and in many cases can remain unnoticed. We observe that the compression dynamics for a pure electron plasma behaves the same way as that of a mixed antiproton and electron plasma. Thanks to this optimized compression method and the high single shot antiproton catching efficiency, we observe for the first time cold and dense non-neutral antiproton plasmas with particle densities n ≥ 10 13 m −3 , which pave the way for an efficient pulsed antihydrogen production in AEḡIS. Graphical abstract

Positronium in the 2 3 S metastable state exhibits a low electrical polarizability and a long lifetime (1140 ns), making it a promising candidate for interferometry experiments with a neutral matter-antimatter system.In the present work, 2 3 S positronium is produced, in the absence of an electric field, via spontaneous radiative decay from the 3 3 P level populated with a 205-nm UV laser pulse.Thanks to the short temporal length of the pulse, 1.5 ns full width at half maximum, different velocity populations of a positronium cloud emitted from a nanochanneled positron-positronium converter were selected by delaying the excitation pulse with respect to the production instant. 2 3 S positronium atoms with velocity tuned between 7 × 10 4 ms -1 and 10 × 10 4 ms -1 were thus produced.Depending on the selected velocity, a 2 3 S production efficiency ranging from ∼0.8% to ∼1.7%, with respect to the total amount of emitted positronium, was obtained.The observed results give a branching ratio for the 3 3 P-2 3 S spontaneous decay of (9.7 ± 2.7)%.The present velocity selection technique could allow

The ASACUSA collaboration at the Antiproton Decelerator of CERN aims at a precise measurement of the antihydrogen ground-state hyperfine structure as a test of the fundamental CPT symmetry. A beam of antihydrogen atoms is formed in a CUSP trap, undergoes Rabi-type spectroscopy and is detected downstream in a dedicated antihydrogen detector. In parallel measurements using a polarized hydrogen beam are being performed to commission the spectroscopy apparatus and to perform measurements of parameters of the Standard Model Extension (SME). The current status of antihydrogen spectroscopy is reviewed and progress of ASACUSA is presented.

The Antiproton Decelerator (AD) at CERN provides antiproton bunches with a kinetic energy of 5.3 MeV. The Extra-Low ENergy Antiproton ring at CERN, commissioned at the AD in 2018, now supplies a bunch of electron-cooled antiprotons at a fixed energy of 100 keV. The MUSASHI antiproton trap was upgraded by replacing the radio-frequency quadrupole decelerator with a pulsed drift tube to re-accelerate antiprotons and optimize the injection energy into the degrader foils. By increasing the beam energy to 119 keV, a cooled antiproton accumulation efficiency of (26 +- 6)% was achieved.

Antiproton-proton annihilation at rest in a gaseous H2 target at NTP into the final state π+ π− K ± π∓ (K 0) with an undetectedK 0 or $$\bar K^0 $$ has been investigated. We observe theE(1420) resonance in the invariant mass spectrum (K 0)miss K ± π∓ with massM E =1413±8 MeV/c2 and widthГ E =62 ± 16MeV/c2 and find evidence for the production of thef 1(1285). The absolute branching ratio of $$\bar p$$ p → π+ π− E 0,E 0 →K 0 K ± π ∓ at (61±6)%P wave annihilation is (3.0±0.9)·10−4 of all annihilations. The observed suppression of theE production fromP wave with respect to theS wave together with some simple selection rules suggest that the quantum numbers of theE(1420) areJ pc=0−+ and not I++.

The absolute normalisation of the polarisation in pp elastic scattering at 24 degrees lab has been determined by means of a double-scattering experiment to an accuracy of +or-1.5% at five energies between 200 and 520 MeV.

ArDM-1t is the prototype for a next generation WIMP detector measuring both the scintillation light and the ionization charge from nuclear recoils in a 1-ton liquid argon target. The goal is to reach a minimum recoil energy of 30 keVr to detect recoiling nuclei. In this paper we describe the experimental concept and present results on the light detection system, tested for the first time in ArDM on the surface at CERN. With a preliminary and incomplete set of PMTs, the light yield at zero electric field is found to be between 0.3-0.5 phe/keVee depending on the position within the detector volume, confirming our expectations based on smaller detector setups.

The AEgIS Experiment is an international collaboration based at CERN whose aim is to perform the first direct measurement of the gravitational acceleration g of antihydrogen in the gravitational field of the Earth. Cold antihydrogen will be produced with a pulsed charge exchange reaction in a cylindrical Penning trap where antiprotons will be cooled to 100mK. The cold antihydrogen will be produced in an excited Rydberg state and subsequently formed into a beam. The deflection of the antihydrogen beam will be measured by using Moiré deflectometer gratings. After being approved in late 2008, AEgIS started taking data in a commissioning phase early 2012. This report presents an overview of the AEgIS experiment, describes its current status and shows the first measurements on antiproton catching and cooling in the 5 T Penning catching trap. We will also present details on the techniques needed for the 100mK antihydrogen production, such as pulsed positronium production and its excitation with lasers.