P. Bloch

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.

We discuss the physics potential and the experimental challenges of an upgraded LHC running at an instantaneous luminosity of 1035 cm-2s-1. The detector R&D needed to operate ATLAS and CMS in a very high radiation environment and the expected detector performance are discussed. A few examples of the increased physics potential are given, ranging from precise measurements within the Standard Model (in particular in the Higgs sector) to the discovery reach for several New Physics processes.

An experiment on the decay ${K}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{e}^{+}\ensuremath{\nu}$ was performed at the CERN proton synchrotron with spark-chamber and counter techniques. The ${K}_{e4}$ branching ratio has been measured relative to the $\ensuremath{\tau}$ decay. The $\ensuremath{\pi}\ensuremath{\pi}$ phase-shift difference ${\ensuremath{\delta}}_{0}^{0} \ensuremath{-} {\ensuremath{\delta}}_{1}^{1}$ and the form factors of the hadronic current have been determined as functions of the $\ensuremath{\pi}\ensuremath{\pi}$ energy. The $\ensuremath{\pi}\ensuremath{\pi}$ scattering length ${a}_{0}^{0}$ has been evaluated from the phase shifts with a phenomenological model. The results are compared with the theoretical predictions of current algebra and other models.

We report on the first observation of time-reversal symmetry violation through a comparison of the probabilities of K0 transforming into K0 and K0 into K0 as a function of the neutral-kaon eigentime t. The comparison is based on the analysis of the neutral-kaon semileptonic decays recorded in the CPLEAR experiment. There, the strangeness of the neutral kaon at time t=0 was tagged by the kaon charge in the reaction pp→K±π∓K0(K0) at rest, whereas the strangeness of the kaon at the decay time t=τ was tagged by the lepton charge in the final state. An average decay-rate asymmetry〈R(K0t=0→e+π−νt=τ)−R(K0t=0→e−π+νt=τ)R(K0t=0→e+π−νt=τ)+R(K0t=0→e−π+νt=τ)〉=(6.6±1.3stat±1.0syst)×10−3was measured over the interval 1τS<τ<20τS, thus leading to evidence for time-reversal non-invariance.

We present results on charged current inclusive neutrino and antineutrino scattering in the neutrino energy range 30–200 GeV. The results include a) total cross-sections; b)y distributions; c) structure functions; and d) scaling violations observed in the structure functions. The results, as well as their comparison with the results of electron and muon inclusive scattering, are in agreement with the expectations of the quark parton model and QCD.

Inclusive charged-current interactions of high-energy neutrinos and antineutrinos have been studied with high statistics in a counter experiment at the CERN Super Proton Synchrotron. The energy dependence of the total cross-sections, the longitudinal structure function, and the nucleon structure functionsF 2,xF 3, and $$\bar q^{\bar v} $$ are determined from these data. The analysis of theQ 2-dependence of the structure functions is used to test quantum chromodynamics, to determine the scale parameter Λ and the gluon distribution in the nucleon.

We report results from a beam dump experiment that has been performed at the CERN SPS neutrino facility using the CDHS neutrino counter detector. Limits on dimuon and trimuon production by new penetrating neutral particles are given. A new source of prompt electron and muon neutrinos has been observed giving (1.2±0.4)× 10−7 νe or νμ per incident proton with neutrino angle smaller than 1.85 mrad and Eν > 20 GeV. If these prompt neutrinos are attributed to charmed meson pair production, the inclusive DD production cross section could be of the order of 30 ωb. If axions are existing their production rate relative to π0 mesons is found to be less than 0.5 × 10−8.

The structure functions F2(x, Q2) and xF3(x, Q2) measured in high-energy neutrino charged-current interactions on nuclei are compared with QCD predictions. Solutions to the moment equations of QCD are found which are in good agreement with the data and yield simple parametrisations of the structure functions. For the scale parameter Λ we find Λ = 0.5 ± 0.2 GeV. The analysis also results in values for the width of the gluon distribution as a function of Q2. We find 〈x〉gluons = 0.16 ± 0.03 for Q2 = 10 GeV2.

On the basis of 315 dimuon events of opposite sign for which the nature (and energy) of the incident neutrino is known, and the momenta and hadronic shower energy are measured, we find a) very similar production by neutrinos and antineutrinos, and therefore confirmation of the GIM model for semileptonic weak interactions, b) energy spectra, excitation functions, angular correlations and transverse momentum distributions which are in remarkable agreement with the hypothesis of charm production and decay, c) evidence against models for which the second muon has a heavy lepton as origin, d) evidence against “bottom” quark production by antineutrinos, e) the amount and the structure function for the strange quark-antiquark sea, and f) an approximate branching ratio, of 0.15 for the muonic decay of the semistable charmed meson.

We describe the design, construction and performance of a large mass detector used at CERN to study high-energy neutrino interactions in iron. This detector combines magnetic spectrometry and hadron calorimetry techniques.

We report on the observation of 41 K+ → π+e+e− decays resulting from a counter experiment on Ke4 decay performed at CERN. The branching ratio assuming a uniform phase space distribution is found to be (2.6 ± 0.5) × 10−7.

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.

We use fits to recent published CPLEAR data on neutral kaon decays to π+π− and πeν to constrain the CPT-violation parameters appearing in a formulation of the neutral kaon system as an open quantum-mechanical system. The obtained upper limits of the CPT-violation parameters are approaching the range suggested by certain ideas concerning quantum gravity.

We have analyzed data taken in the CERN narrow-band neutrino and antineutrino beams with regard to the "high-$y$ anomaly" observed by previous experiments at Fermilab. At neutrino energies between 30 and 200 GeV, the $\overline{\ensuremath{\nu}}$ and $\ensuremath{\nu}$ charged-current cross-section ratios and muon-inelasticity distributions disagree with the earlier results. In particular, there is no evidence for energy-dependent effects in the antineutrino data which constitute an important aspect of the alleged anomaly.

We have calibrated a magnetized iron-scintillator sandwhich calorimeter in a hadron beam, finding an energy resolution equal to 16% fwhm at 140 GeV with 5 cm sampling. The hadron energy resolution (fwhm/mean) improves as E−12 between 15 and 140 GeV. No effect due to the magnetic field was observed. Longitudinal and lateral shower containment were also investigated.

We report on results from a study of hadron-energy distributions for ν and ν inclusive neutral current interactions. There is no significant variation of the neutral to charged current total cross-section ratios Rν and Rν with neutrino energy. The space-time structure of neutral currents is dominated by V−A, with a significant admixture of V+A. The Weinberg-Salam model is in agreement with all data if sin2θw=0.24±0.02.

We present moments (both ordinary and Nachtmann) of the nucleon valence structure function measured in high Q2νFE scattering, supplemented by data from deep inelastic eD scattering. These data seem to agree with QCD predictions for vector gluons. The QCD parameter Λ is found to be of the order 0.5 GeV.

We report on the analysis of inclusive neutral current events produced in neutrino and antineutrino narrow band beams. We find for incident neutrino energies in the range 12–200 GeV and for hadron energies above 12 GeV a neutral to charged current cross-section ratio of Rv = 0.293 ± 0.010 for incident neutrinos, and Rv = 0.35 ± 0.03 for antineutrinos. These ratios are consistent with the Weinberg-Salam model, with sin2θw = 0.24 ± 0.02.

In a search for very rare decays of the K+ meson we observed the K+→μ+νe+e− and K+→e+ν e+e− modes with branching ratios of (10±3) ×10−7 and (2+2−2)×10−7 respectively. We also put new limits on a decay allowed by the alternate scheme of lepton conservation K+→π−μ+e+, on a decay with double charged weak current K+→π− e+e+ and on other forbidden decays K+→μ−νe+e+ and K+→π+μ±e±.

The EPR-type strangeness correlation in the K0K0 system produced in the reaction pp→K0K0 at rest has been tested using the CPLEAR detector. The strangeness was tagged via strong interaction with absorbers away from the creation point. The results are consistent with the QM non-separability of the wave function and exclude a spontaneous wave-function factorisation at creation (CL >99.99%).

The properties of 76 neutrino-initiated μ−μ−μ+ events observed in the CDHS detector in the 350 GeV and 400 GeV wide-band beams at CERN are discussed. For neutrino energies 30 GeV and muon momenta ≳4.5 GeV, the average trimuon rate is (3.0 ± 0.4) × 10−5 of the single-muon event rate. The experimental distributions are compared with predictions from various models. The data cannot be understood in terms of either heavy-lepton or heavy-quark cascades; no evidence is found for such processes and upper limits for the two possibilities are established. The data can be understood in terms of the normal charged-current process with the additional production of a muon pair by both hadronic and electromagnetic processes.

We have improved by two orders of magnitude the limit currently available for the CPT violation parameter Re(δ). To this purpose we have analyzed the full sample of neutral-kaon decays to eπν recorded in the CPLEAR experiment, where the strangeness of the neutral kaons was tagged at production and decay time. An appropriate function of the measured decay rates, including information from the analysis of π+π− decay channel, gives directly Re(δ). The result Re(δ)=(3.0±3.3stat±0.6syst)×10−4 is compatible with zero. Values for the parameters Im(δ), Re(x−) and Im(x+) were also obtained.

The amplitude of the signal collected from the PbWO4 crystals of the CMS electromagnetic calorimeter is reconstructed by a digital filtering technique. The amplitude reconstruction has been studied with test beam data recorded from a fully equipped barrel supermodule. Issues specific to data taken in the test beam are investigated, and the implementation of the method for CMS data taking is discussed.

We report two trimuon events producedin v interactions. Of these, one is of the charge type −++, not previously reported. In an antineutrino exposure, one candidate of the charge type +−− has been observed. This type of event has also not been reported previously. The combined π → μ and K → μ background for the three events are calculated to be ∼ 0.7 events. The rate relative to charged current events corresponding to these three events is of the order of 4 × 10−5.

290 events of the type νFe→μ−μ−X and 53 events from the reaction νFe→μ+μ+X withEν>30GeV and muon momenta pμ>6.5GeV/c have been observed in the CDHS detector. After subtracting the background from charged-current processes with one π or K meson of the hadronic shower decaying into μ−ν(or μ+μ), we obtain for neutrinos a rate of prompt like- sign dimuon production of (3.4±1.8)×10−5 relative to the rate of charged-current events with the same cuts, or (4.1 ± 2.2)% relative to the prompt μ−μ+ rate, and for antineutrinos the corresponding relative rates (4.3±2.3)×10−5 and (4.2 ± 2.3)%. A possible explanation for the events is charm pair production at a level of 10−3 relative to all charged-current reactions.

Using a magnetic spectrometer, we have studied 30 000 π0 → e+e−γ events coming from Kπ2+ decays in flight. We find a positive value for the slope of the neutral-pion electromagnetic form factor: a = +0.10 ± 0.03 (or a = +0.05 ± 0.03 without radiative corrections). This value is higher than the predictions of vector meson models.

We report optical absorption measurements made on thick, highly pure crystals of ${\mathrm{Cu}}_{2}$O at 1.6 K. For the first time direct evidence is provided for a phonon-assisted paraexciton absorption edge. The relative strengths of phonon-assisted paraexciton and orthoexciton absorption edges are discussed.

We have observed for the first time the very rare π0 → e+e− decay. The tagged π0's come from K+ → π+π0 decays in flight. We find the branching ratio to be (2.23−1.1+2.4) × 10−7 (90% C.L.). This value is well above the QED unitary limit and comes in rough agreement with a second-order electromagnetic process mediated by vector mesons.

Abstract As part of its HL-LHC upgrade program, the CMS collaboration is developing a High Granularity Calorimeter (CE) to replace the existing endcap calorimeters. The CE is a sampling calorimeter with unprecedented transverse and longitudinal readout for both electromagnetic (CE-E) and hadronic (CE-H) compartments. The calorimeter will be built with ∼30,000 hexagonal silicon modules. Prototype modules have been constructed with 6-inch hexagonal silicon sensors with cell areas of 1.1 cm 2 , and the SKIROC2-CMS readout ASIC. Beam tests of different sampling configurations were conducted with the prototype modules at DESY and CERN in 2017 and 2018. This paper describes the construction and commissioning of the CE calorimeter prototype, the silicon modules used in the construction, their basic performance, and the methods used for their calibration.

The CPLEAR collaboration has constructed a detector at CERN for an extensive programme of CP-, T- and CPT-symmetry studies using K0 and K0 produced by the annihilation of p's in a hydrogen gas target. The K0 and K0 are identified by their companion products of the annihilation K±π∓ which are tracked with multiwire proportional chambers, drift chambers and streamer tubes. Particle identification is carried out with a liquid Cherenkov detector for fast separation of pions and kaons and with scintillators which allow the measurement of time of flight and energy loss. Photons are measured with a lead/gas sampling electromagnetic calorimeter. The required antiproton annihilation modes are selected by fast online processors using the tracking chamber and particle identification information. All the detectors are mounted in a 0.44 T uniform field of an axial solenoid of diameter 2 m and length 3.6 m to form a magnetic spectrometer capable of full on-line reconstruction and selection of events. The design, operating parameters and performance of the subdetectors are described.

Data from the CPLEAR experiment, together with the most recent world averages for some of the neutral-kaon parameters, were constrained with the Bell–Steinberger (or unitarity) relation, allowing the T-violation parameter Re(ϵ) and the CPT-violation parameter Im(δ) of the neutral-kaon mixing matrix to be determined with an increased accuracy: Re(ϵ)=(164.9±2.5)×10−5, Im(δ)=(2.4±5.0)×10−5. Moreover, the constraint allows the CPT-violation parameter for the neutral-kaon semileptonic decays, Re(y), to be determined for the first time. The ΔS≠ΔQ parameters Re(x−) and Im(x+) are given with an increased accuracy. The quantity Re(y+x−), which enters the T-violation CPLEAR asymmetry previously published, is determined to be (−0.2±0.3)×10−3. The value obtained for Re(δ) is in agreement with the one resulting from a previous unconstrained fit and has a slightly smaller error.

LEAR offered unique opportunities to study the symmetries which exist between matter and antimatter. At variance with other approaches at this facility, CPLEAR was an experiment devoted to the study of CP, T and CPT symmetries in the neutral-kaon system. A variety of measurements allowed us to determine with high precision the parameters which describe the time evolution of the neutral kaons and their antiparticles, including decay amplitudes, and the related symmetry properties. Limits concerning quantum-mechanical predictions (EPR, coherence of the wave function) or the equivalence principle of general relativity have been obtained. An account of the main features of the experiment and its performances is given here, together with the results achieved.

Performance tests of some aspects of the CMS ECAL were carried out on modules of the "barrel" sub-system in 2002 and 2003. A brief test with high energy electron beams was made in late 2003 to validate prototypes of the new Very Front End electronics. The final versions of the monitoring and cooling systems, and of the high and low voltage regulation were used in these tests. The results are consistent with the performance targets including those for noise and overall energy resolution, required to fulfil the physics programme of CMS at the LHC.

A search has been made for neutrino interactions with a positive (wrong-sign) muon in the final state. All the events found can be attributed to known sources. A cut at a visible energy of 100 GeV leaves one event, giving an upper limit for μ+ production relative to μ- of 1.6 × 10−4 at the 90% confidence level. Upper limits are given for (a) charm-changing neutral currents, (b) positive heavy-lepton production, and (c) neutrino-antineutrino oscillations.

Calibration of the relative response of the individual channels of the barrel electromagnetic calorimeter of the CMS detector was accomplished, before installation, with cosmic ray muons and test beams. One fourth of the calorimeter was exposed to a beam of high energy electrons and the relative calibration of the channels, the intercalibration, was found to be reproducible to a precision of about 0.3%. Additionally, data were collected with cosmic rays for the entire ECAL barrel during the commissioning phase. By comparing the intercalibration constants obtained with the electron beam data with those from the cosmic ray data, it is demonstrated that the latter provide an intercalibration precision of 1.5% over most of the barrel ECAL. The best intercalibration precision is expected to come from the analysis of events collected in situ during the LHC operation. Using data collected with both electrons and pion beams, several aspects of the intercalibration procedures based on electrons or neutral pions were investigated.

Abstract The Compact Muon Solenoid collaboration is designing a new high-granularity endcap calorimeter, HGCAL, to be installed later this decade. As part of this development work, a prototype system was built, with an electromagnetic section consisting of 14 double-sided structures, providing 28 sampling layers. Each sampling layer has an hexagonal module, where a multipad large-area silicon sensor is glued between an electronics circuit board and a metal baseplate. The sensor pads of approximately 1.1 cm 2 are wire-bonded to the circuit board and are readout by custom integrated circuits. The prototype was extensively tested with beams at CERN's Super Proton Synchrotron in 2018. Based on the data collected with beams of positrons, with energies ranging from 20 to 300 GeV, measurements of the energy resolution and linearity, the position and angular resolutions, and the shower shapes are presented and compared to a detailed Geant4 simulation.

We test the Principle of Equivalence for particles and antiparticles, using CPLEAR data on tagged K0 and K0bar decays into pi^+ pi^-. For the first time, we search for possible annual, monthly and diurnal modulations of the observables |eta_{+-}| and phi_{+-}, that could be correlated with variations in astrophysical potentials. Within the accuracy of CPLEAR, the measured values of |eta_{+-}| and phi_{+-} are found not to be correlated with changes of the gravitational potential. We analyze data assuming effective scalar, vector and tensor interactions, and we conclude that the Principle of Equivalence between particles and antiparticles holds to a level of 6.5, 4.3 and 1.8 x 10^{-9}, respectively, for scalar, vector and tensor potentials originating from the Sun with a range much greater than the distance Earth-Sun. We also study energy-dependent effects that might arise from vector or tensor interactions. Finally, we compile upper limits on the gravitational coupling difference between K0 and K0bar as a function of the scalar, vector and tensor interaction range.

The CP violation parameter η+− is determined through the eigentime-dependent asymmetry in the rates of initially tagged K0 and K0 decaying to π+π−. The obtained values are |η+−| = (2.312 ± 0.043stat. ± 0.030syst. ± 0.011τs) × 10−3 and Φ+− = 42.7° ± 0.9stat.° ± 0.6syst.° ± 0.9Δm° with Δ = (527.4 ± 2.9) × 107h̵gs−1 measured in the same experiment using the semileptonic decay channel.

We report a measurement of the CP violation parameter η+− from the time-dependent asymmetry between the decay rates of initially tagged K0 and K0. The results are based on the complete data sample collected by the CPLEAR collaboration. With Δm=(530.1±1.4)×107ℏs−1 and τS=(89.34±0.08) ps, the values obtained are |η+−|=(2.264±0.023stat±0.026syst±0.007τS)×10−3 and φ+−=43.19°±0.53°stat±0.28°syst±0.42°Δm.

We report on a new measurement of the KL–KS mass difference Δm using the CPLEAR full data sample of neutral-kaon decays to eπν. The result is Δm=(0.5295±0.0020stat±0.0003syst)×1010 ℏ/s. It includes earlier data reported in R. Adler et al., CPLEAR Collaboration, Phys. Lett. B 363 (1995) 237. A measurement of the ΔS=ΔQ violating parameter Re(x) is also obtained.

In the interactions of 400 GeV/c protons with copper nuclei, a flux of prompt neutrinos is observed. The reactions produced by these neutrinos in our apparatus appear consistent with those of electron- and muon-neutrinos. The prompt neutrino fluxes are interpreted as being due to associated production and subsequent semileptonic decay of charmed hadrons. The prompt flux ratio $$\bar v_\mu /v_\mu = 0.46_{ - 0.16}^{ + 0.21} $$ suggests a sizeable production of charmed baryons near the forward direction. The ratio of prompte −+e + toµ −+µ + event rates is 0.64 −0.15 +0.22 , where unity is expected frome-μ universality.

We report the first determination of CP violation parameters from parameter from particle—antiparticle asymmetry in the decay of neutral kaons into two charged pions. Observation of such an asymmetry is direct proof of CP violation. A fit to the asymmetry enabled a determination of the parameter η+− to be made, yielding the result |η+−|=[2.32±0.14 (stat.)±0.03 (syst.)]×10−3 and σ+−=42.3°±4.4° (stat.)±0.4° (syst.), with an additional uncertainty of ±1.0° due to the error on the present published value of Δm, the KL0-KS0 mass difference. The magnitudes of both statistical and systematic errors will be significantly reduced in the future.

Ensuring the radiation hardness of PbWO4 crystals was one of the main priorities during the construction of the electromagnetic calorimeter of the CMS experiment at CERN. The production on an industrial scale of radiation hard crystals and their certification over a period of several years represented a difficult challenge both for CMS and for the crystal suppliers. The present article reviews the related scientific and technological problems encountered.

We present a new measurement of the KL-KS mass difference (Δm) using semileptonic decays of neutral kaons. The measurement yields Δm = (0.5274 ± 0.0029stat. ± 0.0005syst.) × 1010ħ/s.

The ratio of the branching fractions for pp→K+K− and pp→π+π− was determined with the CPLEAR detector, by stopping antiprotons in a gaseous hydrogen target at 15 bar pressure. It was found to be BR(K+K−)/BR(π+π−)=0.205± 0.016. The fraction of P-wave annihilation at rest at this target density was deduced to be (38±9)%.

A new measurement of the ratio R = σL/σT of longitudinal and transverse structure functions in neutrino interactions on iron between 30 and 190 GeV neutrino energy is reported. The result is given as a function of the scale parameter x and the inelasticity ν of the interaction. The average value is R = 0.10 ± 0.07 around ν ≈ 50 GeV and is in accordance with a prediction from the QCD theory.

Abstract We describe 14 m 2 hexagonal planar drift chambers designed for the neutrino experiment of the CERN-Dortmund-Heidelberg-Saclay Collaboration. Details on mechanical construction, electronic read-out, results on efficiency and accuracy are presented.

Abstract The CMS experiment at the CERN LHC will be upgraded to accommodate the 5-fold increase in the instantaneous luminosity expected at the High-Luminosity LHC (HL-LHC) [1]. Concomitant with this increase will be an increase in the number of interactions in each bunch crossing and a significant increase in the total ionising dose and fluence. One part of this upgrade is the replacement of the current endcap calorimeters with a high granularity sampling calorimeter equipped with silicon sensors, designed to manage the high collision rates [2]. As part of the development of this calorimeter, a series of beam tests have been conducted with different sampling configurations using prototype segmented silicon detectors. In the most recent of these tests, conducted in late 2018 at the CERN SPS, the performance of a prototype calorimeter equipped with ≈12,000 channels of silicon sensors was studied with beams of high-energy electrons, pions and muons. This paper describes the custom-built scalable data acquisition system that was built with readily available FPGA mezzanines and low-cost Raspberry Pi computers.

The neutral kaon regeneration amplitude in carbon at momenta between 250 and 750 MeV/c was determined by measuring the interference of inherent and coherently regenerated KS amplitudes. This interference appears in the rates of initially pure (tagged) K0 and K0 decaying to π+π− after crossing a carbon absorber.

The CPLEAR experiment measured time-dependent decay-rate asymmetries of K0 and K0 decaying to π+π−π0 in order to study the interference between the decay amplitudes of KS0 — either CP-violating or CP-conserving — and the CP-conserving KL0 decay amplitude. From the analysis of the complete data set we find for the CP-violating parameter η+−0, Re(η+−0) = (−2 ± 7 stat. −1+4 syst.) × 10−3, Im(η+−0) = (−2 ± 9 stat. −1+2 syst.) × 10−3 and for the CP-conserving parameter λ, Re(λ) = (+28 ± 7 stat. ± 3 syst.) × 10−3, Im(λ) = (−10 ± 8 stat. ± 2 syst.) × 10−3. From the latter, the branching ratio of the CP-conserving K0S → π+π−π0 decay is deduced to be B = (2.5−1.0+1.3 stat. −0.6+0.5 syst.) × 10−7.

The CPLEAR experiment measured the eigentime-dependent asymmetry in the rates of initially tagged K0 and K0 decaying to π0π0π0 in order to study the interference between the CP-violating KS and the CP-conserving KL decay amplitudes. Without assuming CPT invariance, we obtain for the CP-violation parameter η000 the values Re(η000)=0.18±0.14stat.±0.06syst. and Im(η000)=0.15±0.20stat.±0.03syst.. Requiring Re(η000) to be equal to Re(ϵ) we obtain Im(η000)=−0.05±0.12stat.±0.05syst.. The corresponding upper limit for the branching ratio of the KS→π0π0π0 decay is deduced to be BKS→π0π0π0<1.9×10−5 at the 90% confidence level.

Neutrinos are elementary particles electrically neutral which belong to the family of leptons. As a consequence and in first approximation they only undergo weak processes. This gives them very special properties. They are ideal tools to study precisely the weak interactions, but there is a price to pay: neutrinos are characterized by extremely low probabilities of interactions, they easily penetrate large amount of matter without being stopped. Consequently, it is hard to perform neutrino physics measurements. In practice the difficulty is twofold: in order to accumulate enough statistics, experiments must rely on huge fluxes traversing huge detectors, the number of interactions being obviously proportional to these two factors. As a corollary, backgrounds are difficult to handle because they appear much more commonly than good events. Nevertheless, neutrino interactions have been detected from a variety of sources, both man-made and natural, from very low to very large energies.The aim of this review is to survey our current knowledge about interaction cross sections of neutrinos with matter across all pertinent energy scales. We will see that neutrino interactions cover a large range of processes: nuclear capture, inverse beta-decay, quasi-elastic scattering, resonant pion production, deep inelastic scattering and ultra-high energy interactions.All the gathered information will be used to study weak properties of matter but it will also allow to explore the properties of the neutrinos themselves. In particular, the known three different flavors of neutrinos have different behaviors inside matter and this will be relevant to give some precious understanding about their intrinsic parameters in particular their masses and mixings.As a second order process, neutrinos can undergo electromagnetic interactions. This will also be discussed. Although the corresponding phenomena are not yet experimentally proven by actual measurements, the theory is able to calculate them and it is useful to discuss the topic since it may become an important issue to test ideas of cosmological relevance.This review will mainly adopt an experimental point of view. Strong emphasis will be placed on important detectors which have illustrated the challenging progresses in neutrino physics; they will be described and their results confronted to theoretical predictions.

The cyclotron resonance of electrons and holes in red HgI2 has been observed below 4.2K using a cross modulation technique at a microwave frequency of 137 GHz. Cold polaron masses of carriers moving within the layer planes were found to be me perpendicular to =(0.37+or-0.02)m0 and mh perpendicular to =(1.03+or-0.10)m0, where m0 is the mass of the free electron. Masses of carriers moving parallel to the crystal c axis were deduced from a combination of cyclotron resonance and mobility measurements, as me//=(0.31+or-0.03)m0 and mh//=(2.06+or-0.51)m0. Polaron effects are discussed and carrier band masses deduced. The masses are found to agree with band structure calculations, and suggest a reinterpretation of the experimental exciton spectra.

Photoexcited electrons and holes in 2H-PbI2 are studied by measurements of the Hall effect magnetoconductivity and cyclotron resonance. Transport by holes is dominant below 20K under long-wavelength illumination. Electron transport is dominant under white light illumination below 20K and under all illumination conditions above 20K. Hole mobility is anisotropic with 2< mu perpendicular to c/ mu /sub //c/<4. The mobility of electrons above 30K, when limited by optical phonon scattering may be fitted by an effective band mass of 0.55 m0 where m0 is the mass of the free electron. Cyclotron resonance at 137 GHz gives a polaron mass m/sub ///mperpendicular to )12/=(0.68+or-0.16)m0, or a band mass (mb//mb perpendicular to )12/=(0.46+or-0.15)m0.

The best estimation of ϕ+− (the phase of the CP violation parameter η+−) and of Δm (the KL - KS mass difference) is obtained by averaging the results of different experiments, taking into account the different correlation, existing for most of the experiments, between the measurement of ϕ+− and Δm. Including the recent measurements, we obtain the average values 〈Δm〉 = (530.7 ± 1.3) × 107 ħ/s and 〈ϕ+−〉 = 43.82° ± 0.63°. This value of ϕ+− is in good agreement with the superweak phase ϕSW = 43.49° ± 0.08°.

The CPT-violation parameters Re(δ) and Im(δ) determined recently by CPLEAR are used to evaluate the K0–K̄0 mass and decay-width differences, as given by the difference between the diagonal elements of the neutral-kaon mixing matrix (M−iΓ/2). The results – (MK0K0−MK̄0K̄0)=(−1.5±2.0)×10−18 GeV and (ΓK0K0−ΓK̄0K̄0)=(3.9±4.2)×10−18 GeV – are consistent with CPT invariance. The CPT invariance is also shown to hold within a few times 10−3–10−4 for many of the amplitudes describing neutral-kaon decays to different final states.

Neutral-kaon decays to πeν were analysed to determine the q2 dependence of the K0e3 electroweak form factor f+. Based on 365612 events, this form factor was found to have a linear dependence on q2 with a slope λ+=0.0245±0.0012stat±0.0022syst.

The high value of K2 associated with shear horizontal waves launched by an interdigital transducer (IET) on 41' rotated Y-cut Lithium Niobate (an SSBW cut) makes the launching and propagation of these waves of particular interest. Theoretical predictions of the velocity and attenuation of leaky surface waves and surface skimming bulk waves on a free surface and under a metal film and a water film are presented. Experimental results confirm the predicted slowing of the Leaky wave by about 10% under metal and 5% under water. Experiments on propagation under a periodic metal grating reveal that only a single mode propagates if it is fed with a symmetric wave. If fed with an antisymmetric wave severe attenuation occurs. Preliminary results on the behaviour of ininterdigital transducer are presented.

The sample thickness dependence of the absorption coefficient of the yellow exciton 1s line of Cu2O was investigated experimentally using present state of the art crystals. The integrated absorption coefficient increases as the sample thickness decreases and also has an oscillatory component with period 0.053 cm. The experimental results are discussed in terms of the exciton-polariton formalism described by Pekar (1958) and Hopfield (1963).

The time-dependent rate asymmetry of initial K0 and K0 decaying into π+π−π0 was measured in order to reveal the CP-violating amplitude of the KS → π+π−π0 decay. For the real and the imaginary parts of η+−0, we find Re(η+−0) = (6 ± 13stat. ± 1syst.) × 10−3 and Im(η+−0) = (−2 ± 18stat. ± 3syst.) × 10−3 which correspond to |η+−0| < 0.037 with CL.

The interference between CP-conserving Ks and KL → π+π−π0 decay amplitudes was observed by studying the decay rate asymmetries between initial K0 and K0 separately for the phase space regions ECM(π+) > ECM(π−) and ECM(π+) < ECM(π−). For the parameter λ we found Re(λ) = 0.036 ± 0.010(stat.)−0.003+0.002(syst.) and Im(λ) consistent with zero, leading to a branching ratio B = [4.1−1.9+2.5(stat.)−0.6+0.5(syst.)] × 10−7 for the CP-conserving KS → π+π−π0 decay.

The ratio R between the branching fractions of pp → KSKS and pp → KSKL for antiprotons annihilating at rest in gaseous hydrogen at 27 bar pressure was measured with the CPLEAR detector to be R(27 bar) = 0.037 ± 0.002. The fraction of P-wave annihilation at rest at this target density was deduced to be 0.45 ± 0.06. A value of R was also measured at 15 bar, with less statistics, yielding R(15 bar) = 0.041 ± 0.009.

The CPLEAR set-up (modified) has been used to determine the KL–KS mass difference by a method where neutral-kaon strangeness oscillations are monitored through kaon strong interactions, rather than semileptonic decays, thus requiring no assumptions on CPT invariance for the decay amplitudes. The result, Δm=(0.5343±0.0063stat±0.0025syst)×1010ℏ/s, provides a valuable input for CPT tests.

Abstruct-Surface skimming bulk waves may be strongly reflected by the sides of a crystal device structure. The range of angle of incidence over which reflections are strong and over which mode conversion can occur is of interest for the utilization and for the suppression of reflections in devices. Theoretical results are presented for lithium niobate, lithium tantalate, and quartz, giving the amplitude, phase shift, reflection angle, and power reflection angle of reflected waves generated when a surface skimming bulk wave is incident on a free, planar surface at various angles of incidence. In addition, the effect on reflectivity of a thin metal film on the reflecting surface is considered. Some experimental results are presented for lithium niobate. Conclusions are drawn relevant to both the use and suppression of reflected waves.

We report Hall effect, magnetoconductivity and cyclotron resonance measurements on photoexcited electrons and holes in red HgI2, grown from the vapour phase. At low temperatures, and with optical-excitation energies below the band gap, conduction by holes is predominant. Above 40 K both electrons and holes are always present irrespective of excitation wave-length. Pure electronic conduction could not be achieved. Hole mobilities of up to 60 000 cm2 V−1s−1 have been observed at 4 K. The Hall mobility of holes is greater when the carriers are propagating within the layer planes than when propagating perpendicularly to them. Preliminary measurements of cyclotron resonance of holes give an average effective mass √m h⊥ m h▮ of (0.58±0.2)m 0, wherem 0 is the mass of the free electron. The measured mobility anisotropy, then indicates hole masses ofm h▮=(0.4 ±0.2)m 0 for motion parallel toc andm h⊥=(0.8 ±0.3)m 0 for motion perpendicular toc. The electron mass, evaluated from the excition reduced mass, is (0.17±0.03)m 0.

The temperature dependence of the width of spectral holes burned in the 4f6A1g→4f55d A1u absorption line (6958 Å) of CaF2:Sm2+ has been measured and used to determine the phonon coupling which controls nonradiative relaxation between the A1u and Eu levels. We confirm an assertion made by Akimov and Kaplyanskii that the phonon coupling among the lowest three 4f55d levels of CaF2:Sm2+ exhibits strong selection rules. In particular, the “deformational” Eg phonons are two orders of magnitude more effective than “rotational” T1g phonons in inducing nonradiative relaxation.

After a brief introduction to the CMS crystal calorimeter, we focus on the challenges linked to the lead tungstate crystals and avalanche photodiode production.

Two-charged-pion correlations were studied in $$\bar p$$ p(→2π*2π− nπ0,n≥0) annihilations at rest with the CPLEAR detector at the Low-Energy Antiproton Ring (LEAR). A strong enhancement was found in the production of pairs of like-sign pions with a small value of the relative fourmomentumQ, with respect to pairs of unlike-sign pions. The observed enhancement was interpreted as a consequence of the Bose-Einstein symmetrization of the two-pion wave function. The data are well represented by a correlation function parametrized as a double-Gaussian; an exponential parametrization is also statistically acceptable. The value of the correlation strength is found to be >1. The high-quality large data samples together with the ability for K± identification and final-state separation allowed the study of systematic effects impacting on theQ dependence of the correlation function and on the extracted space parameters of the pion sources.

The CP-violation parameter η00 is determined through the eigentime-dependent asymmetry in the rates of initially tagged K0 and K0 decaying to π0 π0. From the analysis of the complete data set we obtain the values |η00|=[2.47±0.31stat.±0.24syst.]×10−3 and φ00=42.00±5.6stat.0±1.9syst.0.

Abstract Eight μ + μ + μ − events have been observed in the CDHS detector during the 330 GeV and 350 GeV antineutrino wide-band beam exposures at CERN. The corresponding average trimuon rate relative to the single-muon rate is (1.8 ± 0.6) × 10 −5 for visible energy ⩾ 30 GeV and muon momenta ⩾ 4.5 GeV c . Some characteristics of these antineutrino trimuon events are compared with μ − μ − μ + events produced by neutrinos.

Having meaningful social roles and full community participation have been examined as a central tenet of the recovery paradigm. We undertook this study to test a new multimodal, peer-led intervention, which we have developed with the aim of fostering the self-efficacy of individuals with psychiatric disabilities to pursue involvement in community activities of their choice.We evaluated the effectiveness of the 6-month manualized peer-delivered "Bridging Community Gaps Photovoice (BCGP)" program with a multisite randomized trial (N = 185), with recipients of services at five community mental health programs. Mixed-effects regression models were used to examine the impact of the program on community participation, loneliness, personal stigma, psychosocial functioning, and personal growth and recovery when compared to services as usual. Individuals who were randomized to the BCGP intervention were also invited to participate in exit focus groups, exploring the program's perceived active ingredients of mechanisms of impact.Participation in the BCGP program facilitated ongoing involvement in community activities and contributed to a decreased sense of alienation from other members of the community due to internalized stigma of mental illness. In addition, greater attendance of group BCGP sessions had a significant impact on participants' sense of self-efficacy in pursuing desired community activities.This study provided initial evidence about the promise of the BCGP program in enhancing community participation. Its implementation in community mental health agencies can further expand the recovery-oriented services provided to people with psychiatric disabilities. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

As part of its HL-LHC upgrade program, the CMS collaboration is replacing its existing endcap calorimeters with a high-granularity calorimeter (CE). The new calorimeter is a sampling calorimeter with unprecedented transverse and longitudinal readout for both electromagnetic and hadronic compartments. Due to its compactness, intrinsic time resolution, and radiation hardness, silicon has been chosen as active material for the regions exposed to higher radiation levels. The silicon sensors are fabricated as 20 cm (8") wide hexagonal wafers and are segmented into several hundred pads which are read out individually. As part of the sensor qualification strategy, 8" sensor irradiation with neutrons has been conducted at the Rhode Island Nuclear Science Center (RINSC) and followed by their electrical characterisation in 2020-21. The completion of this important milestone in the CE's R&D program is documented in this paper and it provides detailed account of the associated infrastructure and procedures. The results on the electrical properties of the irradiated CE silicon sensors are presented.

Bose-Einstein (BE) correlations between like-sign charged pions were studied in pp annihilations at rest into four-prong events, using data taken with the CPLEAR detector at LEAR (CERN). A strong enhancement was found in the production of pairs of like-sign pions of similar momenta, with respect to the pairs of unlike-sign pions. The observed BE- enhancement was used to extract the values for the strength λ of the effect and the radius r of the pion emitting source. The extracted value of λ >l is of relevant importance and clearly does not depend on the assumed parametrization of the correlation function. The influence of the normalization and fitting procedure, the detector resolution, the resonances production and decay and the neutral-pion multiplicity cuts, on the size of the pion source and the strength of the effect was investigated.

Abstract Transmission electron microscopy with energy dispersive X-ray fluorescence and selected area electron diffraction has been used for the identification of individual particles in the emissions of an antimony refining plant. Systematic microscopical analysis of 4 distinct Sb-containing particle types can be used to trace sources within the factory and estimate the relative importance of each at distinct sites around the plant. Fugitive emissions appear to be the most important source up to 1.5 km from the factory.

The luminescence spectrum of AgBr at 1.6K reveals a number of sharp lines which are associated with excitons bound to residual impurities and crystalline defects. Two lines are identified as excitons bound to iodine ( epsilon b=43 meV) and cadmium ( epsilon b=8 meV). Several lines are observed in the neighbourhood of the phonon-assisted free-exciton emission, two of them corresponding to excitons bound to unidentified centres with energies of 1 meV and 0.25 meV. Electron-hole exchange coupling is found to be weak for excitons bound to the isoelectronic centres and their Zeeman spectra are described quite adequately by a simple L-S coupling scheme. The Zeeman spectra of the unidentified shallow states are found to be qualitatively similar to those of the isoelectronic traps. The g-values obtained decrease with increasing binding energy from ge=2.29 and gh=0.76 for the shallow states to ge=1.97 and gh=0.66 for the iodine trap.

▪ Abstract We discuss the neutral-kaon system and demonstrate the advantage of strangeness tagging as performed by the CPLEAR experiment. The main results of CPLEAR on tests of discrete symmetries are reviewed.

We present device responses due to fast shear and longitudinal waves, which propagate between a pair of IDTs on an upper surface via a reflection from the lower surface of a parallel-sided plate of 41°-rotated Y-cut lithium niobate. Single-mode response can be obtained by removing unwanted modes using saw cuts in the crystal substrate. Centre-frequency and bandwidth enhancement of a factor of two or more are achievable compared with the SAW response of the same IDTs.

A problem which has inhibited the widespread use of sur- face skimming bulk waves (SSBW) in device structures is that a SSBW is strongly reflected from crystal edges and such reflections can give rise to spurious responses. In this paper we outline design considerations, based on a theoretical model (I) of reflection in an anisotropic, piezo- electric medium, for suppressing such spurious reflection effects. An experimental demonstration of the use of these design considerations is given with a television intermediate frequency (TV IF) fdter as an example. In mass produced acoustoelectronic devices, such as the sur- face acoustic wave (SAW) TV IF filter, the cost of packaging makes up a significant proportion of the total cost of the device. We show that since SSBW ilIe much less sensitive than SAW to surface conditions it is possible to encapsulate SSBW devices in cheap potting materials, thereby reducing the cost of packaging. Our results throw new light on the behavior of the multistrip coupler (MSC) in SSBW devices.

A large-acceptance lead/gas sampling electromagnetic calorimeter (ECAL) was constructed for the CPLEAR experiment to detect photons from decays of π0s with momentum pπ0 ≤ 800 MeV/c. The main purpose of the ECAL is to determine the decay vertex of neutral-kaon decays K0 → π0π0 → 4γ and K0 → π0π0π0 → 6γ. This requires a position-sensitive photon detector with high spatial granularity in r−, ϕ−, and z−coordinates. The ECAL - a barrel without end-caps located inside a magnetic field of 0.44 T - consists of 18 identical concentric layers. Each layer of 13 radiation length (X0) contains a converter plate followed by small cross-section high-gain tubes of 2640 mm active length which are sandwiched by passive pick-up strip plates. The ECAL, with a total of 6X0 has an energy resolution of α(E)E ≈ 13%(E(GeV)and a position resolution of 4.5 mm for the shower foot. The shower topology allows separation of electrons from pions. The design, construction, read-out electronics, and performance of the detector are described.

In the analysis of a new Ke4 experiment with 30 000 events, we obtain an improved upper limit for the branching ratio of the decay which violates the ΔS = ΔQ rule: Γ(K+→ π+π+e−ν)Γ(K+→ π+π−e+ν)< 3.6 × 10su−4(95%CL).

Antiproton annihilation at rest in gaseous hydrogen (16 bar pressure) to the final states ρ(770)X andf 2(1270)X, whereX stands for one or more neutral mesons, has been studied at LEAR using the CPLEAR detector. Relative branching ratios are given forX =π 0,2π 0, 3π 0 ω in the ρ case, and forX =π 0, η in thef 2 case. The annihilation channel $$\bar pp \to \rho 3\pi ^0 $$ has not been measured before. The fraction of P-wave annihilation is deduced from the ratiof 2 π 0/ρπ 0 to be 0.38±0.07, in good agreement with the result previously obtained by CPLEAR from the ratioK + K -/π + π -.

The CPLEAR experiment uses tagged K0 and K0 produced in pp annihilation at rest to measure CP-, T- and CPT-violation parameters in the neutral kaon system. The results of these measurements and some implications are reported.

The CPLEAR experiment uses tagged K0 and K̄0 produced in pp̄ annihilation at rest to measure CP-, T- and CPT-violation parameters in the neutral kaon system. The results of these measurements and some implications are reported.

Abstract Recent results obtained in proton-proton collisions at the Large Hadron Collider at CERN are presented, with some emphasis on the measurements relevant for Astroparticles and High Energy Cosmic Rays experiments.

A small scale prototype of a Cherenkov detector to study νμe scattering using water as an active target has been constructed and tested with electron, muon, photon, and pion beams. We find an angular resolution for electrons of 6 mrad√E[GeV] and good discrimination between electrons, photons, and hadrons.

Recent results obtained in proton-proton collisions at the Large Hadron Collider at CERN are presented, with some emphasis on the measurements relevant for Astroparticles and High Energy Cosmic Rays experiments.