I. Evangelou

We use the ultra-relativistic quantum molecular dynamics (UrQMD) model to study the multiplicity correlations and fluctuations of charged hadrons emitted in the forward and backward rapidity hemispheres in 197Au + 197Au collisions at four different incident beam energies, namely Elab=10A,20A, 30A and 40A GeV. Dependence of the correlation and fluctuation parameters on the incident beam energy, collision centrality, rapidity gap and rapidity window size are examined. Both short and long-ranged correlations contribute to our UrQMD simulated results. In the framework of the UrQMD model the short-ranged correlations can be interpreted in terms of resonance decays and/or cluster formation. The long-ranged correlations on the other hand, perhaps originate from multiple rescattering suffered by the hadrons and decay of longitudinally stretched strings in the rapidity space. Our simulation based analysis can be used to set a reference base-line for any future experimental study on the forward-backward multiplicity correlation for the colliding system and collision energies involved in the present case.

New data are presented on charged particle pseudorapidity distributions for inelastic events produced at c.m. energies $$\sqrt s $$ =200 and 900 GeV. The data were obtained at the CERN antiproton-proton Collider operated in a new pulsed mode. The rise of the central density ρ(0) at energies up to $$\sqrt s $$ =900 GeV has been studied. A new form of central region scaling is found involving the densityρ n (0) for charged multiplicityn, namely that the scaled central densityρ n (0)/ρ(0) expressed as a function ofz=n/〈n〉 is independent ofs. Scaling in the fragmentation region holds to 10–20%, and the small amount of scalebreaking observed here could be accommodated within the framework suggested by Wdowcyk and Wolfendale to account for both accelerator and cosmic ray data.

Multiplicity distributions of charged particles produced in non single-diffractive collisions between protons and antiprotons at centre of mass energies of 200 and 900 GeV are presented. The data were recorded in the UA5 streamer chambers at the CERN Collider, which was operated in a pulsed mode between the two energies. A new method to correct for acceptance limitations and inefficiencies based on the principle of maximum entropy has been used. Multiplicity distributions in full phase space and in intervals of pseudorapidity are presented in tabular form. The violation of KNO scaling in full phase space found by the UA5 group at an energy of 546 GeV is confirmed also at 200 and 900 GeV. The shape of the 900 GeV distribution in full phase space is narrower in the peak region than at 200 GeV but exhibits a pronounced high multiplicity tail. The negative binomial distribution fits data at 200 GeV in all pseudorapidity intervals and in small intervals at 900 GeV. In large intervals at 900 GeV, however, the negative binomial distribution. Fits to the partially coherent laser distribution are also presented as well as comparisons with predictions of the Dual Parton, the Fritiof and the Pythia models.

Multiplicity distributions of charged particles for inelastic, non single-diffractive events in proton-antiproton collisions at a centre of mass energy of 540 GeV are presented for various pseudorapidity (Δη) intervals. The widths of the multiplicity distributions, scaled to their means, increase as Δη is made smaller, and the deviation from a Poisson distribution becomes progressively more pronounced. It is found that the data are remarkably well described by a negative binomial distribution. The parameters of the distributions vary smoothly with the size of the acceptance interval.

New data are presented on charged particle multiplicity distributions for non single-diffractive events produced at CM energies s = 200 and 900 GeV. The data were obtained at the CERN antiproton-proton collider operated in a new pulsed mode. The multiplicity distributions are very well described by a negative binomial distribution. The highest energy data show no sign of approaching scaling, confirming our earlier results on the breaking of KNO scaling. The energy variation of the average charged multiplicity can be fitted to a quadratic in ln s or a s0.13 dependence.

New data are presented on the charged multiplicity distribution for non single-diffractive events produced in pp̄ interactions at a CM energy s = 540 GeV. The distribution in the full pseudorapidity range is compared with data from the ISR. Using the scaling variable z = n〈n〉 a change of shape is observed. The effect is manifested as an increase from 2% to 6% in the proportion of high multiplicity (z > 2) events. For the central pseudorapidity range, |η| ⪅ 1.5, scaling is approximately valid up to s = 540 GeV.

Charged particle multiplicity distributions for the inelastic, non-single-diffractive component of pp reactions at 540 GeV CMS energy and of pp reactions above about 10 GeV are shown to be remarkably well described by a negative binomial distribution at each energy. The two parameters of the distribution depend on energy in a regular manner, which affords the possibility of predicting multiplicity distributions at high energies not yet experimentally available. In this description there is a complete absence of any tendency to approach asymptotic KNO scaling below 540 GeV. The approximate scaling in the CM energy range 10–62 GeV is shown, in this framework, to be accidental.

Results on correlations in charged multiplicity are presented using data from the UA5 detector at the CERN SPS collider. Both short-range and long-range correlations are observed. Our analysis gives no evidence for intrinsic long-range correlations. The observations are consistent with a physical picture in which small clusters are emitted at random along the rapidity axis in the plateau region. This result may indicate that random soft processes play a dominant role in high energy hadronic collisions. The average cluster size is about 2 charged particles, the same as at ISR energies. No variation of cluster size with multiplicity has been observed. The forward-backward long-range correlation and its energy dependence are related to the ratio of the first two moments, variance/mean, of the multiplicity distributions.

The goal of the DIRAC experiment at CERN (PS212) is to measure the $\pi^+\pi^-$ atom lifetime with 10% precision. Such a measurement would yield a precision of 5% on the value of the $S$-wave $\pi\pi$ scattering lengths combination $|a_0-a_2|$. Based on part of the collected data we present a first result on the lifetime, $\tau=[2.91 ^{+0.49}_{-0.62}]\times 10^{-15}$ s, and discuss the major systematic errors. This lifetime corresponds to $|a_0-a_2|=0.264 ^{+0.033}_{-0.020} m_{\pi}^{-1}$.

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 present the charged multiplicity distribution in pp interactions at √s=540 GeV. Moments of the distribution are given, and compared with KNO scaling predictions. An estimate of the particle composition at collider energies is also made.

Data on antiproton-proton cross sections at the c.m. energies 200 and 900 GeV are presented. The data were obtained at the CERN antiproton-proton Collider operated in a new pulsed mode in which the same beams were accelerated and decelerated between beam energies of 450 and 100 GeV. The properties of the machine determine the ratio of the luminosities at the two energies to about 1% and thus an accurate measurement of the ratioR of the inelastic cross sections could be made. We findR (=σ 900/σ 200)=1.20±0.01±0.02, where the first error is statistical and the second systematic. Interpolating existing data to estimateσ ine1(200 GeV) this measurement ofR leads toσ ine1(900 GeV)=50.3+0.4+1.0 mb. Using an extrapolated value ofσ e1/σ tot we estimate the total cross section at 900 GeV to be 65.3±0.7±1.5 mb. Both the inelastic and total cross sections are compatible with a ln2 s dependence. Comparisons are made with different fits to the total cross section energy dependence.

The pseudorapidity distribution of photons produced in pp̄ interactions at s=540GeV has been measured and compared with that of charged particles. The correlation between photon and charged-particle production has been studied. A search amongst high multiplicity events for any having the properties of the Centauro events reported in cosmic-ray experiments has revealed no candidates in a sample of 3600 inelastic events.

Using the UA5 detector, the inclusive central production of Ks0 and K± mesons has been measured in non-single-diffractive interactions at the CERN SPS pp Collider at a c.m. energy of 540 GeV. The average transverse momentum is found to be 〈pT〉 = 0.57±0.03 GeV/c in the rapidity range |y|<2.5, which is an increase of about 30% over the top ISR energy. The K/π ratio has increased from about 8% at ISR energies to 9.5±0.9±0.7% (the last error is systematic) at 540 GeV. The average number of Ks0 per non-single-diffractive event is 1.1±0.1 and the inclusive inelastic cross section is estimated at 49±5 mb.

Cross-sections for diffractive particle production and pseudorapidity distributions of the decay products of diffractive states are presented. The data were obtained with the UA 5 streamer chamber detector at the CERNpp Collider operated in a new pulsed mode yieldingpp interactions at c.m. energies of 900 and 200 GeV. Data recorded with a special trigger designed to select a sample of events enriched in single-diffractive interactions clearly favour ap t -limited fragmentation of diffractive states. The cross-section for single-diffractive particle production ϊ was found to be 7.8±0.5±1.1 mb at 900 GeV and 4.8±0.5±0.8 mb at 200 GeV (first error statistical, second systematic). From the pseudorapidity distribution of diffractive states we deduce the average number of charged particles to be 6.5±1.0 at 900 GeV and 4.1±1.1 at 200 GeV. Furthermore we report on our estimates for the cross-section of double-diffractive particle production at both Collider energies.

First results are presented on kaon and lambda yields in pp̄ collisions at s=540 GeV. Our data show an increase in the Kπ ratio and especially in kaon mean transverse momentum relative to results at lower energies.

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.

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.

The DIRAC spectrometer has been commissioned at CERN with the aim of detecting $\pi^+ \pi^-$ atoms produced by a 24 GeV/$c$ high intensity proton beam in thin foil targets. A challenging apparatus is required to cope with the high interaction rates involved, the triggering of pion pairs with very low relative momentum, and the measurement of the latter with resolution around 0.6 MeV/$c$. The general characteristics of the apparatus are explained and each part is described in some detail. The main features of the trigger system, data-acquisition, monitoring and setup performances are also given.

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.

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.

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 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.

A search for the Centauro phenomenon has been made at s = 900 GeV using the UA5 detector at the SPS pp collider operated in a pulsed mode. Possible interpretations of the cosmic ray data are discussed leading to various analyses of our data which exploit the distinctive features of the Centauro events: high multiplicity, high pT and absence of produced photons. No indication of Centauro production is observed. Upper limits on the production of Centauros at the level of a few per thousand inelastic events are obtained.

The goal of the DIRAC experiment at CERN is to measure with high precision the lifetime of the $\pi^+\pi^-$ atom ($A_{2\pi}$), which is of order $3\times10^{-15}$ s, and thus to determine the s-wave $\pi\pi$-scattering lengths difference $|a_{0}-a_{2}|$. $A_{2\pi}$ atoms are detected through the characteristic features of $\pi^+\pi^-$ pairs from the atom break-up (ionization) in the target. We report on a first high statistics atomic data sample obtained from p Ni interactions at 24 GeV/$c$ proton momentum and present the methods to separate the signal from the background.

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.

We have made the first observations of Ξ− production in pp interactions at √s=540 GeV. In a sample of 6964 non single-diffractive events we observe 17 Ξ− decays with an estimated background of less than one event. This corresponds to 0.04 ± 0.01 Ξ− per event in the transverse momentum range pt>1.0 GeV/c and in the pseudorapidity range |η| < 3.5. Assuming an exponential pt distribution, we find 〈pt〉=1.1−0.2+0.3 GeV/c.

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 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 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.

We have developed a 1.5 D CMOS active pixel sensor to be used in conjunction with a scintillator for X-ray imaging. Within the Intelligent Imaging Sensors (I-ImaS) project, multiple sensors will be aligned to form a line-scanning system and its performance evaluated with respect to existing sensors in other digital radiography systems. Each sensor contains a 512×32 array of pixels and the electronics to convert the collected amount of charge to a digital output value. These include programmable gain amplifiers (PGAs) and analogue-to-digital converters (ADCs). The gain of the PGA can be switched between one or two, to increase the sensitivity for smaller collected charge; the ADC is a 14-bit successive approximation with a sampling rate of 1.25 MHz. The ASIC includes a programmable column fixed pattern noise mitigation circuit and a digitally controllable pixel reset mode block. Here we will describe the sensor design and the expected performance.

Abstract We present a mixed-signal, continuously sensitive, self-triggered IC designed for X-ray imaging applications. Both bipolar and CMOS devices were employed in order to achieve the speed and noise requirements associated with the particular application. Phenomena related to the submicron nature of the devices used have been also taken into consideration. The circuit is optimized to operate with a 3 pF Si-microstrip detector and it exhibits an equivalent noise charge of 225e − rms with a slope of 45e − /pF. The peaking time of the pulse at the output of the analog part is 28 ns and the circuit recovers to the baseline within 600 ns. Moreover, it has the ability of handling either positive or negative current pulses originating from the detector. The IC power consumption is 4.5 mW per channel and the chip was fabricated using a 0.8 μm BiCMOS technology.

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.

A search for the decay KS → e+e− was performed within the framework of the CPLEAR experiment. Full event reconstruction together with e/π separation allowed powerful background rejection and high signal acceptance. The analysis of the complete set of data yields the result: BR(KS → e+e−) < 1.4 × 10−7 (90% CL), an improvement on the current experimental limit by a factor of 20.

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.

The expected particle fluence in the inner part of the CMS Preshower is calculated to be 1.6×1014cm−2 for neutrons and 0.4×1014cm−2 for charged hadrons. Since the error of the calculation is high and/or unexpected accidental beam misalignments might happen we have irradiated Preshower silicon sensors to fluences up to 5×1014n/cm2 to verify that they hold voltages necessary to reach the full charge collection efficiency. All irradiated sensors showed no signs of breakdown up to 1000V, the maximum voltage applied. All but one display a sufficiently stable charge collection efficiency up to 1000V. No noisy channels were observed at the extreme voltages. The measured charge collection efficiency was 71±12% and 59±12% for sensors irradiated to 3×1014 and 5×1014n/cm2, respectively. These values are consistent with the extrapolation from previous measurements made on sensors irradiated to 2.3×1014n/cm2. The work presents the results of static and dynamic measurements and shows that our design and the technology are very robust.

The design and performance of the upgraded CMS Level-1 Trigger Barrel Muon Track Finder (BMTF) is presented. Monte Carlo simulation data as well as cosmic ray data from a CMS muon detector slice test have been used to study in detail the performance of the new track finder. The design architecture is based on twelve MP7 cards each of which uses a Xilinx Virtex-7 FPGA and can receive and transmit data at 10 Gbps from 72 input and 72 output fibers. According to the CMS Trigger Upgrade TDR the BMTF receives trigger primitive data which are computed using both RPC and DT data and transmits data from a number of muon candidates to the upgraded Global Muon Trigger. Results from detailed studies of comparisons between the BMTF algorithm results and the results of a C++ emulator are also presented. The new BMTF will be commissioned for data taking in 2016.

Abstract A central tracking detector based on micro strip gas chambers (MSGC) for the compact muon solenoid (CMS) at LHC is part of a hybrid inner tracking system to be operated in a 4 Tesla magnetic field. Expected performance in terms of momentum resolution, rate capability and long term survivability will be discussed. Considerable efforts in simulation studies have been made, to optimize the tracking system for pattern recognition and track finding efficiencies. A preliminary engineering study on mechanical stability and heat load shows that the detector structures can be made sufficiently stiff to maintain systematic alignment precision within the intrinsic spatial measurement accuracy of the detector.

This paper describes the in situ absolute calibration of the Preshower (ES) detector of CMS. Energy deposited in the lead of the Preshower is measured by silicon sensors, allowing a re-scaling of the energy measured by the endcap crystals. Measurement of the energy deposited in the lead absorbers to 5% accuracy is required over a very large dynamic range (1–400 MIPs equivalent); a maximum accuracy of 1% on the measurement of the charge deposited in the silicon will be sufficient. Radiation damage to the sensors (decrease in charge collection efficiency by up to 17% over 10 years) and the electronics (decrease in gain by up to 2% over 10 years) will need to be assessed by periodic in situ calibrations. A precise in situ absolute calibration using particle signals from physics events is examined. It is shown that sufficient calibration accuracy can be obtained by using muon or pion events, and that the time required for the calibration is of the order of a few days at initial LHC luminosity and at least a factor of two less for nominal LHC luminosity.

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.

Developing silicon strip sensors for the CMS Preshower detector we have noticed that some strips have a noise higher than the average and not correlated to a high leakage current. In order to investigate this effect we have developed a set-up for noise measurement on wafers and diced sensors that does not require bonding. The set-up is based on the DeltaStream chip coupled to a probe card. We have tested 45 sensors and found that the strips with an above average noise have a higher relative current increase as a function of voltage, ΔI/(IΔV). We also observed that, on these strips, the breakdown occurs within about 60V from the voltage at which the noise is observed. We describe our measurement method and present the results.

The CPLEAR experiment at CERN measures the time dependent decay rate asymmetries of initially pure K0 and K0 states to study CP,T and CPT symmetries in the neutral kaon system. The latest results on η+−, Δm and x are reported, as well as direct tests of T violation and CPT violation in K0-K0 oscillations. Our results are consistent with CPT invariance and allow for an improved limit on the K0-K0 mass difference. Further, a possible loss of quantum coherence of the neutral kaon system has been tested to a level near the Planck scale.

A compact, portable PC-based X-ray imaging system has been developed based on a 2D silicon microstrip sensor and particle physics readout electronics. The sensor is housed in a specially built hybrid, which also hosts the front-end electronics. The control and the readout electronics used are based on the standard PCI and PMC architectures and were originally developed for High Energy Physics Experiments. The use of PCI based electronics and the development of the control software for the PC-Linux platform led to a compact, portable, low cost imaging system. The system was initially tested and evaluated with beta particles from a 90Sr radioactive source, gamma rays from an 241Am radioactive source and cosmic rays, and it displayed consistent response. It was then operated using a compact X-ray machine with Mo tube and images of various targets were reconstructed offline using the ROOT data analysis package.

The method for studying semileptonic neutral kaon decays at CPLEAR is presented together with a preliminary data analysis. For the first time a direct determination of T violation is shown to be possible and low statistics results are given. From the same data the KL-KS mass difference, Δm, the CP violation parameter of KS, ϵs, and the parameter x testing the ΔS = ΔQ rule are also obtained.

The I-Imas (Intelligent Imaging Sensors) is an EU project whose objective is to design and develop intelligent imaging sensors and evaluate their use within an adaptive medical imaging system specifically tailored to Mammography and Dental Radiology. The system will employ an in line scanning technology approach and proposes the use of CMOS active pixels sensors. The I-Imas sensor will have the capability of processing the data on every pixel and be able to dynamically respond in real time to changing conditions during imaging recording. The result will be to minimise the radiation exposure to areas of low diagnostic information content while extracting the highest diagnostic information from region of high interest. The first phase of the I-Imas project deals with the characterisation of the key features in a medical image that carry the highest content of diagnostic information. With this objective in mind an End-Users Survey has been carried out. We have been distributed a questionnaire to experts in the field of mammography and dental radiology (the dental radiology results will be presented elsewhere): medical physicists, radiologists, radiographers and dentists. From this survey we have collected information about the most useful specifications to be implemented in the I-Imas imaging system. This paper discusses the results from the End-Users survey and considers design implications for the I-Imas sensors

A measurement of the branching ratio for KS→e+e− decay was performed with the CPLEAR detector at LEAR. Full event reconstruction together with calorimeter e/π separation allowed for powerful background rejection and high signal acceptance. The analysis on the complete set of data yields the result: BR(KS→e+e−)<1.4⋅10−7 (90% CL), an improvement on the current experimental limit by a factor of 20.

Using strangeness tagging at production time, CPLEAR measures K0/K̄0 time-dependent asymmetries in pionic and semileptonic kaon decays. From those, a set of parameters describing CP, T and CPT violation in neutral kaon mixing and decay can be determined. Strangeness tagging at decay time with the lepton charge allows for time-reversal violation to be directly observed with a significance of more than three standard deviations. The precision on each of the CPT violation parameters is discussed. The mass equality of the K0 and K̄0 is tested within 4.×10−19 GeV.

A measurement of the branching ratio for Ks → e+e− decay was performed with the CPLEAR detector at LEAR. Full event reconstruction together with calorimeter e/π separation allowed for powerful background rejection and high signal acceptance. Analysis of data taken up to 1994 yields the result: Br(Ks → e+e−) < 4.2 · 10−7 (90 % CL).

The CPLEAR experiment at CERN uses time-dependent decay-rate asymmetries between K0 and K̄0 to measure η+−. The analysis and the systematic errors are discussed. The preliminary results from all our data are φ+− = 43.50 ± 0.50stat ± 0.5syst ± 0.4Δm and |η+−| = (2.316 ± 0.025stat ± 0.028syst ± 0.009τS) × 10−3. The dominant part in the systematic error of φ+− is due to the regeneration correction. A dedicated experiment was performed to reduce this error considerably.

The CPLEAR experiment at CERN studies theCP, T andCPT symmetries in the neutral-kaon system by measuring the rate asymmetries between the decays of initially pure K0 and $$\overline {K^0 } $$ states. Using data taken between 1990 and mid 1994, precise measurements of |η+-|,φ +- and Δm are reported. The comparison of φ+- the superweak phase gives one of the most sensitive tests ofCPT invariance and leads to a new limit on the $$K^0 - \overline {K^0 } $$ mass difference.

Studies of the practices of the documentalists in the information retrieval on the Web by the means of social navigation (Dourish and Chalmers).

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation R. Adler, T. Alhalel, A. Angelopoulos, A. Apostolakis, E. Aslanides, G. Backenstoss, C. P. Bee, O. Behnke, J. Bennet, V. Bertin, F. Blanc, P. Bloch, Ch. Bula, P. Carlson, M. Carroll, J. Carvalho, E. Cawley, S. Charalambous, M. Chardalas, G. Chardin, M. B. Chertok, M. Danielsson, A. Cody, S. Dedoussis, M. Dejardin, J. Derre, M. Dodgson, J. Duclos, A. Ealet, B. Eckart, C. Eleftheriadis, I. Evangelou, L. Faravel, P. Fassnacht, J. L. Faure, C. Felder, R. Ferreira‐Marques, W. Fetscher, M. Fidecaro, A. Filipc̆ic̆, D. Francis, J. Fry, E. Gabathuler, R. Gamet, D. Garreta, T. Geralis, H.‐J. Gerber, A. Go, P. Gumplinger, C. Guyot, A. Haselden, P. J. Hayman, F. Henry‐Couannier, R. W. Hollander, E. Hubert, K. Jansson, H. U. Johner, K. Jon‐And, P. R. Kettle, C. Kochowski, P. Kokkas, R. Kreuger, T. Lawry, R. Le Gac, F. Leimgruber, A. Liolios, E. Machado, P. Maley, I. Mandić, N. Manthos, G. Marel, M. Mikuž, J. Miller, F. Montanet, T. Nakada, A. Onofre, B. Pagels, P. Pavlopoulos, F. Pelucchi, J. Pinto da Cunha, A. Policarpo, G. Polivka, H. Postma, R. Rickenbach, B. L. Roberts, E. Rozaki, T. Ruf, L. Sacks, L. Sakeliou, P. Sanders, C. Santoni, K. Sarigiannis, M. Schäfer, L. A. Schaller, A. Schopper, P. Schune, A. Soares, L. Tauscher, C. Thibault, F. Touchard, C. Touramanis, F. Triantis, D. A. Tröster, E. Van Beveren, C. W. E. Van Eijk, S. Vlachos, P. Weber, O. Wigger, C. Witzig, M. Wolter, C. Yeche, D. Zavrtanik, D. Zimmerman; CP, T, and CPT tests in neutral Kaon decays using tagged K0, K0at LEAR. AIP Conf. Proc. 10 May 1995; 334 (1): 816–821. https://doi.org/10.1063/1.48110 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAIP Publishing PortfolioAIP Conference Proceedings Search Advanced Search |Citation Search

The CPLEAR experiment is aiming at precise CP violation tests using initially pure K0- andK0 beams from the intense source provided by the annihilation of the LEAR p-beam in hydrogen. The strangeness tagging efficiency and the systematic errors have been studied and found to be in agreement with the design specifications. The measurement of the differential time asymmetry of the π+π− decays allowed the direct observation of differences in the decay rates of particles and antiparticles. The CP violating parameters were determined as |ν±| = (2.32 ± 0.14) · 10−3 and ψ± = 42.3° ± 4.4°. First results in the reconstruction and analysis of the neutral kaon decays into two neutral pions and the Ke3 decay are presented.

The CPLEAR experiment at CERN has been designed to measure CP and T violating effects in the neutral kaon system by observing particle-antiparticle asymmetries. The motivation and the physics program of CPLEAR is presented and first analyses of the K0, k0 to π+π−, π0π0 and π+π−π0 decays are discussed. Special emphasis is given to the recent results of the measurement of the CP violating parameters ϑ+− and η+− based on first data taken in 1990/1991.

We review a phenomenological parametrization of an open quantum-mechanical formalism for CPT violation in the neutral kaon system, and constrain the parameters using fits to recent CPLEAR data.

Abstract The CPLEAR experiment is aiming at precise CP violation tests using initially pure K 0 - and K 0 beams from the intense source provided by the annihilation of the LEAR p - beam in hydrogen. The strangeness tagging efficiency and the systematic errors have been studied and found to be in agreement with the design specifications. The measurement of the differential time asymmetry of the π+π− decays allowed the direct observation of differences in the decay rates of particles and antiparticles. The CP violating parameters were determined as |ν±| = (2.32 ± 0.14) · 10−3 and ψ± = 42.3° ± 4.4°. First results in the reconstruction and analysis of the neutral kaon decays into two neutral pions and the Ke3 decay are presented.