A. Penzo

We observe a signal for the doubly charmed baryon Xi(+)(cc) in the charged decay mode Xi(+)(cc)-->Lambda(+)(c)K-pi(+) in data from SELEX, the charm hadroproduction experiment at Fermilab. We observe an excess of 15.9 events over an expected background of 6.1+/-0.5 events, a statistical significance of 6.3sigma. The observed mass of this state is 3519+/-1 MeV/c(2). The Gaussian mass width of this state is 3 MeV/c(2), consistent with resolution; its lifetime is less than 33 fs at 90% confidence.

The analyzing power in inclusive charged pion production has been measured using the 200 GeV Fermilab polarized proton beam. A striking dependence in xF is observed in which AN increases from 0 to 0.42 with increasing xF for the π+ data and decreases from 0 to −0.38 with increasing xF for π− data. The kinematic range covered is 0.2⩽xF⩽0.9 and 0.2⩽pT⩽2.0 GeV/c. In a simple model our data indicate that at large xF the transverse spin of the proton is correlated with that of its quark constituents.

We have measured the spin-dependent structure function $g_1^p$ of the proton in deep inelastic scattering of polarized muons off polarized protons, in the kinematic range $0.003<x<0.7$ and $1\,\mbox{GeV}^2<Q^2<60\,\mbox{GeV}^2$. Its first moment, $\int_0^1 g_1^p(x) dx $, is found to be $0.136 \pm 0.011\,(\mbox{stat.})\pm 0.011\,(\mbox{syst.})$ at $Q^2=10\,\mbox{GeV}^2$. This value is smaller than the prediction of the Ellis--Jaffe sum rule by two standard deviations, and is consistent with previous measurements. A combined analysis of all available proton, deuteron and neutron data confirms the Bjorken sum rule to within $10\%$ of the theoretical value.

We observe a signal for the doubly charmed baryon Ξcc+ in the decay mode Ξcc+→pD+K− to complement the previous reported decay Ξcc+→Λc+K−π+ in data from SELEX, the charm hadroproduction experiment at Fermilab. In this new decay mode we observe an excess of 5.62 events over a combinatoric background estimated by event mixing to be 1.38±0.13 events. The mixed background has Gaussian statistics, giving a signal significance of 4.8σ. The Poisson probability that a background fluctuation can produce the apparent signal is less than 6.4×10−4. The observed mass of this state is 3518±3MeV/c2, consistent with the published result. Averaging the two results gives a mass of 3518.7±1.7MeV/c2. The observation of this new weak decay mode confirms the previous SELEX suggestion that this state is a double charm baryon. The relative branching ratio for these two modes is 0.36±0.21.

This report describes the physics case, the resulting detector requirements, and the evolving detector concepts for the experimental program at the Electron-Ion Collider (EIC). The EIC will be a powerful new high-luminosity facility in the United States with the capability to collide high-energy electron beams with high-energy proton and ion beams, providing access to those regions in the nucleon and nuclei where their structure is dominated by gluons. Moreover, polarized beams in the EIC will give unprecedented access to the spatial and spin structure of the proton, neutron, and light ions. The studies leading to this document were commissioned and organized by the EIC User Group with the objective of advancing the state and detail of the physics program and developing detector concepts that meet the emerging requirements in preparation for the realization of the EIC. The effort aims to provide the basis for further development of concepts for experimental equipment best suited for the science needs, including the importance of two complementary detectors and interaction regions.This report consists of three volumes. Volume I is an executive summary of our findings and developed concepts. In Volume II we describe studies of a wide range of physics measurements and the emerging requirements on detector acceptance and performance. Volume III discusses general-purpose detector concepts and the underlying technologies to meet the physics requirements. These considerations will form the basis for a world-class experimental program that aims to increase our understanding of the fundamental structure of all visible matter.

A bstract We describe a proposal to add a set of very forward detectors to the CMS experiment for the high-luminosity era of the Large Hadron Collider to search for beyond the standard model long-lived particles, such as dark photons, heavy neutral leptons, axion-like particles, and dark Higgs bosons. The proposed subsystem is called FACET for F orward- A perture C MS E x T ension, and will be sensitive to any particles that can penetrate at least 50 m of magnetized iron and decay in an 18 m long, 1 m diameter vacuum pipe. The decay products will be measured in detectors using identical technology to the planned CMS Phase-2 upgrade.

We present a new measurement of the spin-dependent structure function g1d of the deuteron in deep inelastic scattering of 190 GeV polarised muons on polarised deuterons, in the kinematic range 0.003 < x < 0.7 and 1 GeV2 < Q2 < 60 GeV2. This structure function is found to be negative at small x. The first moment Γ1d=∫01g1ddx evaluated at Q02 = 10 GeV2 is 0.034 ± 0.009 (stat.) ± 0.006 (syst.). This value is below the Ellis-Jaffe sum rule prediction by three standard deviations. Using our earlier determination of Γ1p, we obtain Γ1p − Γ1n = 0.199 ± 0.038 which agrees with the Bjorken sum rule.

The analyzing power AN in inclusive π− and π+ production has been measured with a 200 GeV/c transversely polarized antiproton beam over a wide xF range (0.2≤xF≤0.9) and at moderate pT (0.2≤pT≤1.5GeV/c). The asymmetry AN increases with increasing xF from zero to large positive values for π−'s, and decreases from zero to large negative values for π+'s. A threshold for the onset of the asymmetry is observed about pT∼0.5GeV/c, below which AN is essentially zero and above which AN increases (decreases) with pT for π−'s ( π+'s) in the covered pT range.Received 17 April 1996DOI:https://doi.org/10.1103/PhysRevLett.77.2626©1996 American Physical Society

Hadronic shower development in a copper-based fiber calorimeter is studied by simultaneously measuring the scintillation light and the Cherenkov light generated in this process. By comparing these two signals, the electromagnetic shower fraction can be measured event by event. Fluctuations in this fraction are the dominant contribution to the hadronic energy resolution. They are also responsible for the signal non-linearity and the non-Gaussian response function typical for hadron calorimeters. The dual-readout technique makes it possible to eliminate the effects of these fluctuations.

We present a measurement of semi-inclusive spin asymmetries for positively and negatively charged hadrons from deep inelastic scattering of polarised muons on polarised protons and deuterons in the range 0.003 < x < 0.7. From these asymmetries and the previously published inclusive spin asymmetries we determine, for the first time, the x-dependent spin distributions for up and down valence quarks and for non-strange sea quarks. We find that the first moments of the valence quark spin distributions are Δuv = 1.01 ± 0.19 ± 0.14 and Δdv = −0.57 ± 0.22 ± 0.11. The spin distribution function of non-strange sea quarks is consistent with zero over the measured range of x and the first moment is Δu = Δd = −0.02 ± 0.09 ± 0.03.

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 report the first observation of a charm-strange meson D(+)(sJ)(2632) at a mass of 2632.5+/-1.7 MeV/c(2) in data from SELEX, the charm hadro-production experiment E781 at Fermilab. This state is seen in two decay modes, D(+)(s)eta and D0K+. In the D(+)(s)eta decay mode we observe a peak with 101 events over a combinatoric background of 54.9 events at a mass of 2635.4+/-3.3 MeV/c(2). There is a corresponding peak of 21 events over a background of 6.9 at 2631.5+/-2.0 MeV/c(2) in the decay mode D0K+. The decay width of this state is <17 MeV/c(2) at 90% confidence level. The relative branching ratio Gamma(D0K+)/Gamma(D(+)(s)eta) is 0.14+/-0.06. The mechanism that keeps this state narrow is unclear. Its decay pattern is also unusual, being dominated by the D(+)(s)eta decay mode.

Multi-strange baryon and antibaryon production is expected to be a useful probe in the search for quark-gluon plasma formation. We present the transverse mass distributions of negative particles, Λ's, Λ'sand Ξ−'s produced in sulphur-tungsten interactions at 200 GeV/c per nucleon and give the corrected rations Λ/Λ, Ξ−/Λ andΞ−/Λ. Our ratio Ξ−/Λ appears to be larger than that from pp interactions.

We analyse the proton, deuteron and neutron spin dependent structure functions at fixed Q2 = 5 GeV2. The experimental asymmetries for the proton, neutron and deuteron are compared and found to be consistent. The first moment of the neutron structure function is evaluated using all available data. We find that the Bjorken sum rule is confirmed within an experimental uncertainty of 17%. The quark spin contribution to the nucleon spin is small, and the strange quark spin content is different from zero.

Results from the WA85 Experiment at the CERN Ω Spectrometer are presented. A 200 A GeV/c beam of 32S ions was used with a tungsten target. The apparatus is used to detect V0,s and charged tracks in the range pT > 0.9 GeV/c and 2.3 < Ylab < 3.0. Production of Λ, Λ and negative hadrons all show a linear increase with rapidity density in the range 70–140 as expected from models based on a superposition of independent NN collisions.

The DIRAC experiment at CERN has achieved a sizeable production of π+π− atoms and has significantly improved the precision on its lifetime determination. From a sample of 21 227 atomic pairs, a 4% measurement of the S-wave ππ scattering length difference |a0−a2|=(0.2533−0.0078+0.0080|stat|syst−0.0073+0.0078)Mπ+−1 has been attained, providing an important test of Chiral Perturbation Theory.

Analysing powers and differential cross sections for pp → π−π+ and pp → K− K+ have been measured over the full angular range using a polarised target at LEAR at 20 beam momenta from 360 to 1550 MeV/c. Discrepancies in the normalisation of earlier dσ/dΩ data at low momenta are clarified. Above 1000 MeV/c, A0N results confirm values close to +1 over most of the angular range for both reactions, in excellent agreement with earlier data of lower statistics. Below 1000 MeV/c, where the analysing power is measured for the first time, large variations of A0N with energy and angle are present.

Measurements are reported of p̄p total cross sections from 388 to 599 MeV/c in small momentum steps. Statistical errors are typically ±0.4%and the normalisation uncertainty is ±0.7%. There is no evidence for the “S-meson”.

A new polarized-proton and -antiproton beam with 185 GeV/c momentum has been built at Fermilab. The design uses the parity-nonconserving decays of lambda and antilambda hyperons to produce polarized protons and antiprotons, respectively, a beam-transport system that minimizes depolarization effects, and a set of twelve dipole magnets that rotate the beam-particle spin direction. A beam-tagging system determines the momentum and polarization of individual beam particles. This allows a selection of particles in definite intervals of momentum and polarization. Measurements performed by two different polarimeters showed that the beam is polarized and the determination of polarization by beam-particle tagging is verified. A new measurement of the analyzing power of large-xFπ0 production may lead to another beam polarimeter.

p̄p total cross sections have been measured from 220 to 413 MeV/c in small (⩽ 10 MeV/c) steps of momentum with statistics of ± 0.5 %. There is no evidence for structure in the cross section, and a limit of 8 mb MeV/c2 is set with 90% confidence on the strength of any narrow resonance down to 250 MeV/c.

The Sigma^- mean squared charge radius has been measured in the space-like Q^2 range 0.035-0.105 GeV^2/c^2 by elastic scattering of a Sigma^- beam off atomic electrons. The measurement was performed with the SELEX (E781) spectrometer using the Fermilab hyperon beam at a mean energy of 610 GeV/c. We obtain <r^2> = (0.61 +/- 0.12 (stat.) +/- 0.09 (syst.)) fm^2. The proton and pi^- charge radii were measured as well and are consistent with results of other experiments. Our result agrees with the recently measured strong interaction radius of the Sigma^-.

Electromagnetic shower development in a copper-based fiber calorimeter is studied by simultaneously measuring the scintillation light and the Cherenkov light generated in this process. We report on the energy resolution, the signal linearity and the dependence of the response function on the impact point and the angle of incidence.The electrons range in energy from 8 to 200 GeV. Differences observed between the results from the two types of signals are presented and interpreted.

A beam polarimeter using CH2 and carbon targets has been used to measure proton and neutron beam polarization in the energy range 0.4–2.8 GeV in one of the beam lines at the SATURNE II accelerator. The analyzing power for np-scattering is calibrated against the known analyzing power for pp-scattering by using the polarized deuteron beam to measure simultaneously the asymmetries for scattering of quasifree protons and neutrons in the deuterons. A low level of systematic errors is achieved by pulse to pulse polarization reversal at the ion source of the accelerator, and by measuring left and right scattering simultaneously. The detailed operation procedure and the beam polarizations measured during all experiments from 1981 to 1984 are presented.

As part of a programme to study the spin structure of the pp→nn channel, we have measured the analysing power A0n and the differential cross section at an incident antiproton beam momentum of 704 MeV/c. The analysing power exhibits a remarkable angular dependence, which is poorly reproduced by the existing potential models.

The differential cross-section for π−d elastic scattering has been measured at 9.0, 13.0, and 15.2 GeV/c for t-values up to 2.3 GeV2. The results are analysed by comparison with the Glauber scattering model.

The single spin asymmetry for inclusive direct-photon production has been measured using a polarized proton beam of 200 GeV/c with an unpolarized proton target at −0.15 < xf < 0.15 and 2.5 < pt < 3.1 GeV/c at Fermilab. The data on the cross section for pp → γX at 2.5 < pt < 3.8 GeV/c are also provided. The measurement was done using lead-glass calorimeters and photon detectors which surrounded the fiducial area of the calorimeters. Background rejection has been done using these surrounding photon detectors. The cross section obtained is consistent with the results of previous measurements assuming a nuclear dependence of A1.0. The single spin asymmetry, AN, for the direct-photon production is consistent with zero within experimental uncertainty.

We present the results of beam tests with high-energy (8–375 GeV) electrons, pions, protons and muons of a sampling calorimeter based on the detection of Cherenkov light produced by shower particles. The detector, a prototype for the very forward calorimeters in the CMS experiment, consists of thin quartz fibers embedded in a copper matrix. Results are given on the light yield of this device, on its energy resolution for electron and hadron detection, and on the signal uniformity and linearity. The signal generation mechanism gives this type of detector unique properties, especially for the detection of hadron showers: narrow, shallow shower profiles and extremely fast signals. These specific properties were measured in detail. The implications for measurements in the high-rate, high-radiation Large Hadron Collider (LHC) environment are discussed.

We present data from Fermilab experiment E781 (SELEX) on the hadroproduction asymmetry for Λ̄c− compared to Λc+ as a function of xF, and on pt2 distributions for Λc+. These data were measured in the same apparatus using incident π−, Σ− beams at 600 GeV/c and proton beam at 540 GeV/c. The asymmetry is studied as a function of xF. In the forward hemisphere with xF⩾0.2 both baryon beams exhibit very strong preference for producing charm baryons rather than charm antibaryons, while the pion beam asymmetry is much smaller. In this energy regime the results show that beam fragments play a major role in the kinematics of Λc formation, as suggested by the leading quark picture.

Production of Ξ− and Ξ− has been observed for the first time in heavy ion interactions by the WA85 Experiment. Multistrange baryon and antibaryon production is expected to be a useful probe in the search for quark-gluon plasma formation. We describe the procedure used to select these cascade candidates and show that Ξ− and Ξ− decays can be identified. The ratio of ΞΞ production, corrected for geometrical acceptances and reconstruction efficiencies, is 0.39 ± 0.07 for sulphur-tungsten interactions in the central rapidity interval 2.3<Ylab<3.0 and pT>1.1 GeV/c.

Asymmetries A0n have been measured at LEAR for s¯s elastic scattering for 15 beam momenta from 497 to 1550 MeV/c.

New scintillation counters have been designed and constructed for the CDF upgrade in order to complete the muon coverage of the central CDF detector, and to extend this coverage to larger pseudorapidity. A novel light collection technique using wavelength shifting fibers, together with high quality polystyrene-based scintillator resulted in compact counters with good and stable light collection efficiency over lengths extending up to 320 cm. Their design and construction is described and results of their initial performance are reported.

The two-spin parameter ALL in inclusive π0 productionby longitudinally-polarized protons and antiprotons on a longitudinally-polarized proton target has been measured at the 200 GeV Fermilab spin physics facility, for π0's at xF=0 with 1⩽pt⩽3 GeV/c. The results exclude, at the 95% confidence level, values of ALL (pp) > 0.1 and < − 0.1 for π0's produced by protons, and values of ALL (pp) > 0.1 and < −0.2 for incident antiprotons. The relevance of ALL (pp) for the gluon spin density is discussed. The data are in good agreement with “conventional”, small or zero, gluon polarization.

Two high statistics measurements of antiproton-proton small-angle elastic scattering, at p = 233 MeV/c and p = 272 MeV/c, are presented. The measurements were carried out at the LEAR facility at CERN. By the Coulomb-nuclear interference method, values are obtained for the real-to-imaginary ratio ρ of the p̄p forward nuclear scattering amplitude and for its exponential slope b: ρ = + 0.041 ± 0.026 and b = 71.5 ± 4.5 (GeV/c)−2 at 233 MeV/c and ρ = −0.014 ± 0.027 and b = 47.7 ± 2.7 (GeV/c)−2 at 272 MeV/c. The method to derive these values is discussed in detail and so are the uncertainties contributing to their systematic error. The results are compared with predictions from forward dispersion relation calculations and with predictions from p̄p potential models.

The total cross section difference ΔαL(pp) for proton-proton scattering with beam and target polarized longitudinally parallel and antiparallel, respectively, has been measured using the polarized proton beam from SATURNE II and a frozen spin polarized proton target. The beam polarization was reversed from pulse to pulse, and at each energy ΔαL was measured for both signs of target polarization. The data below 800 MeV confirm the previously observed structures. The cross section difference is found to change by 8.0 ± 0.5 mb between 520 MeV and 760 MeV. At the higher energies the results show no indication for similar structures or for a change of the sign of ΔαL.

Data are given for the polarization parameter and for the differential cross section in pp elastic scattering at 200 GeV/c, in the range 0.5 ⪕−t ⪕ 4.0GeV2. The polarization changes sign in the dip region, as already observed at 150 GeV/c.

Results are presented of beam tests in which a small electromagnetic calorimeter consisting of lead tungstate crystals was exposed to 50 GeV electrons and pions. This calorimeter was backed up by the DREAM Dual-Readout calorimeter, which measures the scintillation and Cherenkov light produced in the shower development, using two different media. The signals from the crystal calorimeter were analyzed in great detail in an attempt to determine the contributions from these two types of light to the signals, event by event. This information makes it possible to eliminate the dominating source of fluctuations and thus achieve an important improvement in hadronic calorimeter performance.

The differential cross-section for pd elastic scattering has been measured at 9.7, 12.8 and 15.8 GeV/c for t-values up to −2 GeV2. The Glauber multiple scattering model has been used to analyse the data, the main interest being the double scattering region.

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

Total cross sections for Σ− and π− on beryllium, carbon, polyethylene and copper as well as total cross sections for protons on beryllium and carbon have been measured in a broad momentum range around 600GeV/c . These measurements were performed with a transmission technique in the SELEX hyperon-beam experiment at Fermilab. We report on results obtained for hadron–nucleus cross sections and on results for σtot(Σ−N) and σtot(π−N) , which were deduced from nuclear cross sections.

The ${\mathrm{\ensuremath{\pi}}}^{0}$ inclusive and semi-inclusive, single-spin asymmetries have been measured using transversely polarized, 200-GeV/c proton and antiproton beams colliding with an unpolarized hydrogen target. The measured asymmetries are consistent with zero within the experimental uncertainties for the kinematic region -0.15${\mathit{x}}_{\mathit{F}}$+0.15 and 1${\mathit{p}}_{\mathit{T}}$4.5 GeV/c. Improvements in the data analysis showed that our earlier large asymmetries at ${\mathit{p}}_{\mathit{T}}$\ensuremath{\gtrsim}3 GeV/c were not correct. These data indicate that PQCD expectations seem confirmed and the higher-twist contribution to the single-spin asymmetry in ${\mathrm{\ensuremath{\pi}}}^{0}$ production at ${\mathit{x}}_{\mathit{F}}$=0 is not large. Additional evidence for such a conclusion comes from the measurement of a semi-inclusive ${\mathrm{\ensuremath{\pi}}}^{0}$ asymmetry, where associated charged particles are detected opposite to the ${\mathrm{\ensuremath{\pi}}}^{0}$ azimuthal direction. This experiment also provides high-statistics data on the inclusive ${\mathrm{\ensuremath{\pi}}}^{0}$ cross sections for pp and p\ifmmode\bar\else\textasciimacron\fi{}p collisions at \ensuremath{\surd}s\ensuremath{\approxeq}19.4 GeV. \textcopyright{} 1996 The American Physical Society.

Multistrange baryon and antibaryon production is suggested to be a useful probe in the search for Quark-Gluon Plasma formation. We report the detection of an Ω− + Ω− signal in central S+W interactions at 200 A GeV/c and measure the ratio Ω−Ω− = 0.57±0.41 at central rapidity and pT>1.6 GeV/c.

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.

The SATURNE II polarized proton beam and the Saclay frozen spin polarized proton target were used to measure the total cross section difference ΔσT = −2σ1 tot at 26 energies between 0.43 and 2.4 GeV. Here ΔσT is the total cross section difference for transverse beam and target spins parallel and antiparallel, respectively, and σ1tot is one of spin-dependent terms in the total cross section σtot. The energy dependence of ΔσT below 1 GeV shows similar structures as for ΔσL. An additional minimum appears at about 1.3 GeV, which involves a structure in singlet spin partial waves.

Measurements have been made of the differential cross section and asymmetry Aon for pp elastic scattering at 15 incident momenta between 497 MeV/c and 1550 MeV/c. The angular range where both particles have enough energy to traverse target and setup has been covered. The results are compared with predictions of various NN potential models. None of these models fully explains the present results, although the general trend of the data is predicted correctly.

The analyzing power AN in inclusive π0 production has been measured with use of the new 185-GeV/c Fermilab polarized proton beam. We obtain the value AN=0.10±0.03 for π0's in the kinematic region 0.2<xF<0.8 and 0.3<pT<1.2 GeV/c. In certain models of particle production this suggests that the spin of the proton is carried by its valence quarks.Received 25 July 1988DOI:https://doi.org/10.1103/PhysRevLett.61.1918©1988 American Physical Society

A rapidity gap program with great potential can be realized at the Large Hadron Collider, LHC, by adding a few simple forward shower counters (FSCs) along the beam line on both sides of the main central detectors, such as CMS. Measurements of single diffractive cross sections down to the lowest masses can be made with an efficient level-1 trigger. Exceptionally, the detectors also make feasible the study of Central Diffractive Excitation, and in particular the reaction g + g to g + g, in the color singlet channel, effectively using the LHC as a gluon-gluon collider.

The fixed-target MIPP experiment, Fermilab E907, was designed to measure the production of hadrons from the collisions of hadrons of momenta ranging from 5 to 120 GeV/c on a variety of nuclei. These data will generally improve the simulation of particle detectors and predictions of particle beam fluxes at accelerators. The spectrometer momentum resolution is between 3 and 4%, and particle identification is performed for particles ranging between 0.3 and 80 GeV/c using $dE/dx$, time-of-flight and Cherenkov radiation measurements. MIPP collected $1.42 \times10^6$ events of 120 GeV Main Injector protons striking a target used in the NuMI facility at Fermilab. The data have been analyzed and we present here charged pion yields per proton-on-target determined in bins of longitudinal and transverse momentum between 0.5 and 80 GeV/c, with combined statistical and systematic relative uncertainties between 5 and 10%.

The RADiCAL Collaboration is conducting R\&D on high performance electromagnetic (EM) calorimetry to address the challenges expected in future collider experiments under conditions of high luminosity and/or high irradiation (FCC-ee, FCC-hh and fixed target and forward physics environments). Under development is a sampling calorimeter approach, known as RADiCAL modules, based on scintillation and wavelength-shifting (WLS) technologies and photosensor, including SiPM and SiPM-like technology. The modules discussed herein consist of alternating layers of very dense (W) absorber and scintillating crystal (LYSO:Ce) plates, assembled to a depth of 25 $X_0$. The scintillation signals produced by the EM showers in the region of EM shower maximum (shower max) are transmitted to SiPM located at the upstream and downstream ends of the modules via quartz capillaries which penetrate the full length of the module. The capillaries contain DSB1 organic plastic WLS filaments positioned within the region of shower max, where the shower energy deposition is greatest, and fused with quartz rod elsewhere. The wavelength shifted light from this spatially-localized shower max region is then propagated to the photosensors. This paper presents the results of an initial measurement of the time resolution of a RADiCAL module over the energy range 25 GeV $\leq$ E $\leq$ 150 GeV using the H2 electron beam at CERN. The data indicate an energy dependence of the time resolution that follows the functional form: $\sigma_{t} = a/\sqrt{E} \oplus b$, where a = 256 $\sqrt{GeV}$~ps and b = 17.5 ps. The time resolution measured at the highest electron beam energy for which data was currently recorded (150 GeV) was found to be $\sigma_{t}$ = 27 ps.

Surprisingly large polarizations in hyperon production by unpolarized protons have been known for a long time. The spin dynamics of the production process can be further investigated with polarized beams. Recently, a negative asymmetry ${A}_{N}$ was found in inclusive ${\ensuremath{\Lambda}}^{0}$ production with a $200\mathrm{GeV}/c$ transversely polarized proton beam. The depolarization ${D}_{\mathrm{NN}}$ in $p\ensuremath{\uparrow}+p\ensuremath{\rightarrow}{\ensuremath{\Lambda}}^{0}+X$ has been measured with the same beam over a wide ${x}_{F}$ range and at moderate ${p}_{T}$. ${D}_{\mathrm{NN}}$ reaches positive values of about 30% at high ${x}_{F}$ and ${p}_{T}\ensuremath{\sim}1.0\mathrm{GeV}/c$. This result shows a sizable spin transfer from the incident polarized proton to the outgoing ${\ensuremath{\Lambda}}^{0}$.

The analyzing power AN of proton-proton elastic scattering in the Coulomb-nuclear interference region has been measured using the 200-GeV/c Fermilab polarized proton beam. A theoretically predicted interference between the hadronic non-spin-flip amplitude and the electromagnetic spin-flip amplitude is shown for the first time to be present at high energies in the region of 1.5 × 10−3 to 5.0 × 10−2 (GeV/c)2 four-momentum transfer squared, and our results are analyzed in connection with theoretical calculations. In addition, the role of possible contributions of the hadronic spin-flip amplitude is discussed.Received 6 April 1993DOI:https://doi.org/10.1103/PhysRevD.48.3026©1993 American Physical Society

We present the results of experimental studies of hadron showers in a copper/quartz-fiber calorimeter, based on the detection of Cherenkov light. These studies show that there are very significant differences between the signals from protons and pions at the same energies. In the energy range between 200 and 375 GeV, where these studies were performed, the calorimeter's response to protons was typically 10% smaller than the response to pions. On the other hand, the energy resolution was about 25% better for protons. In addition, the protons had a Gaussian line shape, whereas the pion response curve was asymmetric. These differences can be understood from the requirements of baryon number conservation in the shower development. They are expected to be present in any non-compensating calorimeter, to a degree determined by the e/h value.

A measurement of the single-spin asymmetry AN in p↑ + p→π0 + X at 200 GeV with xF = 0 shows a transition in the production process from a “low-xT” regime with AN = 0, through an intermediate region of negative asymmetry, to a “high-xT” regime with AN > 0.3. This transition occurs at xT ≈ 0.4 and is consistent with xT-scaling of AN in pion production using polarized beams or targets from √−s=5.2 to 19.4 GeV. Results for AN in η production by polarized protons and in π0 production by polarized antiprotons are also presented.

The accelerated polarized deuteron beam of Saturn II was used to measure the analyzing power for np elastic scattering at five energies. The left-right asymmetries ε = (L + R)/(L + R) for np and for pp elastic scattering were measured simultaneously by CH2− carbon subtraction using one of the beam-line polarimeters. The analyzing power A00n0(np) is given by the ratio εnpd/εppd multiplied by the known analyzing power for pp elastic scattering. Experimental evidence is consistent with the underlying assumption that in the kinetmatic region of the experiment the ratio of the np to pp analyzing powers for scattering of quasifree nucleons in deuterons is the same as for scattering of free neutrons and protons, respectively.

The polarization parameter in pp elastic scattering at 150 GeV/c, and in the momentum transfer interval 0.4 ⩽ −t ⩽ 3.0 GeV2, has been measured in an MWPC and scintillation counter experiment at the CERN SPS using a polarized proton target. The polarization is decreasing steadily from zero to ≈ − 10% in the range 0.4 < −t < 1.3 GeV2; for higher |t| the data suggests a change of sign. Results are also given for the differential cross section, which exhibits a small dip at −t = (1.46 ± 0.01) GeV.

Proton elastic scattering off a polarized proton target has been measured at 150 GeV/c, in the |;t|-range 0.2–3.0 GeV2. The results on polarization and differential cross section are presented.

Results are presented of detailed measurements of the signals generated by high-energy electrons and muons in lead tungstate crystals. A significant fraction of the light produced in these crystals and detected by photomultiplier tubes is the result of the Cherenkov mechanism. This is concluded from the angular dependence of the signals and from their time structure. Depending on the orientation of the crystals and on the particle type, Cherenkov light may account for up to 15% of the total signals.

A selection of recent data referring to Pb + Pb collisions at the SPS CERN energy of 158 GeV per nucleon is presented which might describe the state of highly-excited strongly-interacting matter both above and below the deconfinement-to-hadronization (phase) transition predicted by lattice QCD. A tentative picture emerges in which a partonic state is indeed formed in central Pb + Pb collisions which hadronizes at about T = 185 MeV, and expands its volume more than tenfold, cooling to about 120 MeV, before hadronic collisions cease.

The considerable polarization of hyperons produced at high xF has been known for a long time and has been interpreted with various theoretical models in terms of the constituents' spin. Recently, the analyzing power in inclusive Λ0 hyperon production has also been measured using the 200GeV/c Fermilab polarized proton beam. The covered kinematic range is 0.2≤xF≤1.0 and 0.1≤pT≤1.5GeV/c. The data indicate a negative asymmetry at large xF and moderate pT. These results can further test the current ideas on the underlying mechanisms for hyperon polarization.Received 5 December 1994DOI:https://doi.org/10.1103/PhysRevLett.75.3073©1995 American Physical Society

We report new precision measurements of the lifetimes of the ${\ensuremath{\Lambda}}_{c}^{+}$ and ${D}^{0}$ from SELEX, the charm hadroproduction experiment at Fermilab. Based upon 1630 ${\ensuremath{\Lambda}}_{c}^{+}$ and 10 210 ${D}^{0}$ decays we observe lifetimes of $\ensuremath{\tau}[{\ensuremath{\Lambda}}_{c}^{+}]\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}198.1\ifmmode\pm\else\textpm\fi{}7.0\ifmmode\pm\else\textpm\fi{}5.6\mathrm{fs}$ and $\ensuremath{\tau}[{D}^{0}]\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}407.9\ifmmode\pm\else\textpm\fi{}6.0\ifmmode\pm\else\textpm\fi{}4.3\mathrm{fs}$.

The spin correlation parameter A00kk (pp) has been measured in the angular region 45°<θCM<90° at 0.719, 0.834, 0.874, 0.934, 0.995 and 1.095 GeV using the SATURNE II polarized proton beam incident on a polarized target. The parameters A00nn(pp and A00sk(pp) were measured at 0.874 in the same angular region.

The pp analyzing power was measured using the SATURNE II polarized proton beam and the Saclay frozen spin polarized target. The measurements at 0.88 and 1.1 GeV were carried out in the angular region θCM from 28° to ≅50° and complete our previous measurements from 45 ° to 90°. Above 1.1 GeV the measurements presented here cover both regions, extending from θCM = 28° (at the lower energies) or θCM = 18° (at the higher energies) to θCM > 90°. The shape of the angular distribution Aoono(pp) = ƒ(θCM) changes considerably with increasing energy. The new data show the onset of a characteristic t-dependence of the analyzing power, with a minimum at −t ≅ 1.0 (GeV/c)2 followed by a second maximum at −t ≅ 1.5 (GeV/c)2. This structure is present at all energies, from kinematic threshold to 200 GeV.

The condition for obtaining the linear response of a calorimeter to hadronic showers and an energy resolution improving as the incident energy increases is the equalization between the electromagnetic and the hadronic signals. This equalization is obtained within a new approach exploiting a local hardening effect that is realized by inserting low-Z absorbers next to the silicon readout detectors. In this way, the calorimeter response to the electromagnetic component of the hadronic shower is reduced. A systematic investigation of the visible energy response for electromagnetic showers in Si/U and Si/W calorimeters has been carried out for incoming electron energies of 2, 4, and 6 GeV. The insertion of low-Z material (G10 plates) in front or at the rear of the silicon detectors allows a fine tuning of the calorimeter response.

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.

Abstract The elastic scattering cross-section of π - on deuterium at 895 MeV/ c measured with counters and wire spark chambers is given in a region of momentum transfer between 0.16 and 0.96 (GeV/ c ) 2 .

The observation of hydrogenlike πK atoms, consisting of π^{-}K^{+} or π^{+}K^{-} mesons, is presented. The atoms are produced by 24 GeV/c protons from the CERN PS accelerator, interacting with platinum or nickel foil targets. The breakup (ionization) of πK atoms in the same targets yields characteristic πK pairs, called "atomic pairs," with small relative momenta Q in the pair center-of-mass system. The upgraded DIRAC experiment observed 349±62 such atomic πK pairs, corresponding to a signal of 5.6 standard deviations. This is the first statistically significant observation of the strange dimesonic πK atom.

The invariant double-differential cross section, E1E2d6σ / dp31dp32, and the double-spin asymmetry, A LL, for inclusive multi-γ pair production in which γ-rays came from neutral mesons were measured with a 200 GeV/c longitudinally-polarized proton beam and a longitudinally-polarized proton target. Most of the multi-γ pairs comes from two-jet type events which are sensitive to partonic interaction. The ALL values were found to be consistent with zero. The invariant double-differential cross section for inclusive π0π0 production was also measured. These measured cross sections are consistent with LUND Monte Carlo simulations. Using the LUND Monte Carlo simulation package with the Carlitz-Kaur model of spin dependent distribution functions of valence quarks, the ALL values have been compared with theoretical predictions of gluon polarization, ΔG/G. The results put restrictions on the size of ΔG/G in the region of 0.05 ⪅ x ⪅ 0.35.

Results are given for the analysing power of the p̄p→n̄n charge-exchange reaction at four incident beam momenta. The measurement is part of an experimental programme to study the spin structure of this reaction at LEAR. The analyzing power shows strong angular and energy dependence, which at present is not reproduced by the existing meson-exchange potential models.

A double-scattering experiment of antiprotons on carbon has been carried out at the Low-Energy Antiproton Ring (LEAR) at CERN, to measure the polarization parameter ApC in antiproton-carbon elastic scattering at small angles. The polarization parameter has been inferred from the azimuthal distribution of the antiprotons after the second scattering. Data have also been collected with a liquid-hydrogen target as the second scatterer, thus allowing the sign of ApC to be determined. The experiment has been performed at two momenta of the extracted antiproton beam, 800 and 1100 MeV/c. A small positive value of the polarization has been observed, compatible with energy independence and a linear increase with the momentum transfer q. Parametrizing ApC as acq, we get ac = +0.72 0.10+0.09(GeV/c)−1. This result is compared with potential model predictions for N̄N amplitudes through a Glauber theory calculation.

The spin correlation parameter Aoonn(pp) and the analyzing power Aoono(pp) have been measured in the angular region 45°<θCM<90° at 0.834, 0.874, 0.934, 0.995 and 1.095 GeV beam kinetic energy using the SATURNE II polarized proton beam incident on the polarized proton target.

Muon detection in a copper-based fiber calorimeter is studied by simultaneously measuring the scintillation light and the Cherenkov light generated in the detector. We report on the calorimeter response to muons ranging in energy from 20–300 GeV. Muons penetrate the full depth of a calorimeter and therefore can pass through the readout structure (in this case, bundled fibers, ferrules and PMT windows) generating signals not associated with the calorimeter proper. The availability of two physically separate readout signals makes it possible to recognize and eliminate these effects. A comparison of the scintillator and Cherenkov signals make it also possible to measure, for the first time, the separate contributions from ionization and radiation processes by muons in a massive medium.

Simultaneous measurement of the scintillation and the Cherenkov light produced in hadronic shower development makes it possible to eliminate the effects of fluctuations in the electromagnetic shower fraction, which dominate and spoil the performance of non-compensating calorimeters. In this paper, we report on a study to separate the light signal produced by an optical calorimeter into its scintillation and Cherenkov components. To this effect, we use differences in the time structure of these two signals, as well as differences in the angular distribution of these two types of light. Both methods give useful results, especially when the numbers of scintillation and Cherenkov photons are comparable.

Data on polarization in backward elastic π+p scattering at 2.0, 3.5 and 4.0 GeV/c are presented. The data at 2.0 GeV/c are compared with the result of a recent phase-shift analysis. Our data at 3.5 and 4.0 GeV/c, and existing data above 3 GeV/c, show no significant energy dependence of the polarization over the measured u-range. A comparison with Regge models and with results from amplitude analysis is made.

After observing and investigating the double-exotic (a double-exotic atom is a bound system, in which both oppositely charged components are unstable particles like μ,π,K,…) π+π− atom with the ground state lifetime τ of about 3×10−15 s, the upgraded DIRAC experiment at the CERN PS accelerator observes for the first time long-lived states of the same atom with lifetimes of about 10−11 s and more. The number of characteristic pion pairs resulting from the breakup (ionisation) of long-lived π+π− atoms amounts to 436±61, corresponding to a signal-to-error ratio of better than 7 standard deviations. This observation opens a new possibility to measure energy differences between p and s atomic states and so to determine ππ scattering lengths.

Along with recent progress in the scintillating-fibre technique, the readout device is also gaining increasing importance in the field of detector research and development. In this article we present a prototype scintillating-fibre hodoscope read out with a position-sensitive photomultiplier, which demonstrates a good performance for a variety of applications such as particle physics and biological imaging. A new method of handling, in real time, the space information coming from such types of modern photomultiplier tubes, is also presented.

Results are reported on the azimuthal asymmetry of antiprotons of ∼550 MeV / c, doubly scattered at small angles from protons and carbon. The measured asymmetries are small, statistically compatible with zero, and give polarization parameters smaller than those foreseen by some NN potential models.

The SICAPO Collaboration project to build a perfectly compensating hadron calorimeter using silicon as the active medium, is described. The insertion of low-Z material (G10 plates) in front or at the rear of the silicon detectors allows fine tuning of the calorimeter response to electromagnetic showers. This is a new approach to obtaining compensation. The tuning can be exploited to obtain e/π = 1 (compensation condition). The expected performance ranks this calorimeter among the best candidates to face the severe constraints requested by the next generation of colliders.

Equalization between the electromagnetic and the hadronic signals is the condition for obtaining the linear response of a calorimeter to hadronic showers and an energy resolution that improves as the incident energy increases. In a calorimeter with silicon readout, the use of a combination of low-Z and high-Z materials as absorbers allows the transformation of the electron energy distribution of the incident showers in two media with different critical energies. As a result, the response of the calorimeter to incoming showers is modified to achieve the compensation condition (eπ=1).

Results are presented of detailed measurements of high-energy electromagnetic shower profiles measured in a copper-based fiber calorimeter. The calorimeter was equipped with a mixture of scintillating fibers and undoped (quartz or clear plastic) fibers. The latter measured Cherenkov light generated in the shower development process, whereas the scintillating fibers measured the energy deposit profile. Both lateral and longitudinal profiles were measured for electrons in the energy range 8–200 GeV. The scintillator and Cherenkov profiles exhibit some very striking differences, which are discussed and compared with results of Monte Carlo simulations.

We present evidence for the first observation of electromagnetically bound π±K∓-pairs (πK-atoms) with the DIRAC experiment at the CERN-PS. The πK-atoms are produced by the 24GeV/c proton beam in a thin Pt-target and the π± and K∓-mesons from the atom dissociation are analyzed in a two-arm magnetic spectrometer. The observed enhancement at low relative momentum corresponds to the production of 173±54 πK-atoms. The mean life of πK-atoms is related to the s-wave πK-scattering lengths, the measurement of which is the goal of the experiment. From these first data we derive a lower limit for the mean life of 0.8 fs at 90% confidence level.

The contributions of neutrons to hadronic signals from the DREAM calorimeter are measured by analyzing the time structure of these signals. The neutrons, which mainly originate from the evaporation stage of nuclear breakup in the hadronic shower development process, contribute through elastic scattering off protons in the plastic scintillating fibers which provide the dE/dx information in this calorimeter. This contribution is characterized by an exponential tail in the pulse shape, with a time constant of ∼25ns. The relative contribution of neutrons to the signals increases with the distance from the shower axis. As expected, the neutrons do not contribute to the DREAM Cherenkov signals.

Silicon PhotoMultipliers (SiPMs) are a recently developed type of silicon photodetector characterized by high gain and insensitivity to magnetic fields, which make them a suitable detector for the next generation high energy and space physics experiments. This paper presents the performance of a readout system for SiPMs based on the MAROC3 ASIC. The ASIC consists of 64 channels working in parallel, each one with a variable gain pre-amplifier, a tunable slow shaper with a sample & hold circuit for the analog readout and a tunable fast shaper for the digital one. In the tests described in this paper, only the analog part of the ASIC has been used. A frontend board based on the MAROC3 ASIC has been tested at CERN coupled to a scintillator-lead shashlik calorimeter, readout with 36 large area SiPMs. The performance of the system has been characterized in terms of linearity and energy resolution on the CERN PS-T9 and SPS-H2 beamlines, using different configurations of the ASIC parameters.

The highest-energy measurement of ΔσL(pp) and the first ever measurement of ΔσL(p¯p), the differences between proton-proton and antiproton-proton total cross sections for pure longitudinal spin states, are described. Data were taken using 200-GeV/c polarized beams incident on a polarized-proton target. The results are measured to be ΔσL(pp)=−42±48(stat)±53(syst) μb and ΔσL(p¯p)=−256±124(stat)±109(syst) μb. Many tests of systematic effects were investigated and are described, and a comparison to theoretical predictions is also given. Measurements of parity nonconservation at 200 GeV/c in proton scattering and the first ever of antiproton scattering have also been derived from these data. The values are consistent with zero at the 10−5 level. Received 3 May 1996DOI:https://doi.org/10.1103/PhysRevD.55.1159©1997 American Physical Society

In a hadronic calorimeter with silicon readout, a combination of thin plates oflow-Z andhigh-Z materials used as absorbers enables the reduction of the calorimeter response to the electromagnetic component of the incoming hadronic showers (the “local hardening effect”). As a result, a ratio varying from e/π> 1 toe/π>is obtained as a function of thelow-Z material thickness, demonstrating the possibility of achieving the compensation condition(e/π= 1)by exploiting the local hardening effect.

The ratio of the analysing powers for quasi-elastic pp scattering in carbon and for elastic scattering on free protons was measured fromT = 0.52 to 2.8 GeV by scattering of the SATURNE II polarized proton beam on carbon and CH2. It was found to have a maximum at about 0.8 GeV. The energy dependence for quasielastic scattering on carbon had not been measured before above 1 GeV. The observed effect was not expected from simple models.

Coherent Λπ− production on Pb of 600 GeV Σ− hyperons has been studied with the SELEX facility at Fermilab. Using the Primakoff formalism, we set a 90% CL upper limit on the radiative decay width Γ[Σ(1385)−→Σ−γ]<9.5 keV, and estimate the cross section for γΣ−→Λπ− at s≈1.385 GeV to be 56±16 μb.

The two most recent and precise measurements of the charged kaon mass use X-rays from kaonic atoms and report uncertainties of 14 and 22 ppm yet differ from each other by 122 ppm. We describe the possibility of an independent mass measurement using the measurement of Cherenkov light from a narrow-band beam of kaons, pions, and protons. This technique was demonstrated using data taken opportunistically by the Main Injector Particle Production experiment at Fermi National Accelerator Laboratory which recorded beams of protons, kaons, and pions ranging in momentum from +37 to +63GeV/c. The measured value is 491.3±1.7MeV/c2, which is within 1.4σ of the world average. An improvement of two orders of magnitude in precision would make this technique useful for resolving the ambiguity in the X-ray data and may be achievable in a dedicated experiment.

Silicon photomultipliers are silicon devices that in recent times have been proposed as candidates for the replacement of photomultiplier tubes in many experimental situations. In this article we describe the performance of SiPMs as a readout system of a shashlik calorimeter composed of 41 8×8 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , 3.27-mm-thick tiles of scintillator and 40 8×8 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , 3.27-mm-thick tiles of lead, for a total of ~24 radiation lengths; the light is collected by 64 0.8-mm wave-length-shifter (WLS) fibers grouped in bundles of four for, a total of 16 channels. The SiPMs are manufactured by FBK-irst and have a sensitive area of 1 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The calorimeter has been tested at CERN using both a low (PS T10 beamline) and high (SPS H4 beamline) energy beam during the summer 2009 data taking.

We have measured cross sections for forward neutron production from a variety of targets using proton beams from the Fermilab Main Injector. Measurements were performed for proton beam momenta of 58, 84, and $120\text{ }\text{ }\mathrm{GeV}/c$. The cross section dependence on the atomic weight ($A$) of the targets was found to vary as ${A}^{\ensuremath{\alpha}}$, where $\ensuremath{\alpha}$ is $0.46\ifmmode\pm\else\textpm\fi{}0.06$ for a beam momentum of $58\text{ }\text{ }\mathrm{GeV}/c$ and $0.54\ifmmode\pm\else\textpm\fi{}0.05$ for $120\text{ }\text{ }\mathrm{GeV}/c$. The cross sections show reasonable agreement with FLUKA and DPMJET Monte Carlos. Comparisons have also been made with the LAQGSM Monte Carlo.

The LHC detectors have incomplete angular coverage in the forward direction, for example in the region 6 ≲ |η| ≲ 8, which can be improved with the addition of simple scintillation counters around the beam pipes about 50 m to 120 m from the intersection point. These counters detect showers created by particles hitting the beam pipes and nearby material. The absence of signals in these counters in low pileup conditions is an indication of a forward rapidity gap as a signature of diffraction. In addition, they can be used to detect hadrons from low mass diffractive excitations of the proton, not accompanied by a leading proton but adjacent to a rapidity gap over (e.g.) 3 ≲ |η| ≲ 6. Such a set of forward shower counters, originally used at CDF, was used in CMS (FSC) for high-β* running with TOTEM during LHC Run-1. During LS1 the CMS FSC system is being upgraded for future low pileup runs. A similar system, called HERSCHEL is being installed in LHCb. ALICE is implementing scintillation counters, ADA and ADC, with 4.5 ≲ |η| ≲ 6.4.

After having announced the statistically significant observation ($5.6\ensuremath{\sigma}$) of the new exotic $\ensuremath{\pi}K$ atom, the DIRAC experiment at the CERN proton synchrotron presents the measurement of the corresponding atom lifetime, based on the full $\ensuremath{\pi}K$ data sample: $\ensuremath{\tau}=(5.{5}_{\ensuremath{-}2.8}^{+5.0})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}15}\text{ }\text{ }\mathrm{s}$. By means of a precise relation ($\ensuremath{\approx}1%$) between atom lifetime and scattering length, the following value for the $S$-wave isospin-odd $\ensuremath{\pi}K$ scattering length ${a}_{0}^{\ensuremath{-}}=\frac{1}{3}({a}_{1/2}\ensuremath{-}{a}_{3/2})$ has been derived: $|{a}_{0}^{\ensuremath{-}}|=(0.07{2}_{\ensuremath{-}0.020}^{+0.031}){M}_{\ensuremath{\pi}}^{\ensuremath{-}1}$.

The WA94 experiment is designed to study the production of strange and multistrange baryons and antibaryons at central rapidity in sulphur-sulphur interactions at 200 GeV/c per nucleon. Particle production ratios have been obtained in the kinematic region 1.2 ≤ pT ≤ 3.0 GeV/c and 2.5 ≤ ylab ≤ 3.0, and mT spectra for Λ, Λ, Ξ− and Ξ− particles are presented. Preliminary results on charged kaon production are also discussed, together with the status of charged particle identification using the Omega RICH.

Abstract The spin correlation parameter A oonn for pp elastic scattering was measured at 0.88, 1.1, 1.3, 1.6, 1.8, 2.1, 2.4 and 2.7 GeV using the SATURNE II polarized proton beam and the Saclay frozen spin polarized target. At the first two energies, the new measurements at θ CM 90°. At all energies above 1.3 GeV the angular distribution shows a dip at fixed four-momentum transfer − t ∼ 0.90 (GeV/ c ) 2 . The value of A oonn ( θ CM = 90°) decreases from A oonn (90°) ≅ 0.57 at 0.88 GeV to A oonn (90°) ≅ 0.35 at 2.7 GeV. However, the large value found at 1.8 GeV indicates that the energy dependence is not monotonic.

The analyzing power (spin-dependent azimuthal asymmetry) has been observed for the first time in the nuclear Coulomb coherent production process, the ``Primakoff process,'' with the use of the newly constructed 185-GeV/c Fermilab polarized proton beam. We have observed a large asymmetry of this process in the regions of \ensuremath{\Vert}t'\ensuremath{\Vert}0.001 (GeV/c${)}^{2}$ and 1.36(${\ensuremath{\pi}}^{0}$p)1.52 GeV/${c}^{2}$, where the Coulomb process is predominant. The measured asymmetry is consistent with the analyzing power of the existing low-energy \ensuremath{\gamma}+p\ensuremath{\rightarrow}${\ensuremath{\pi}}^{0}$+p data.

The analyzing power AN of proton-proton, proton-hydrocarbon, and antiproton-hydrocarbon, scattering in the Coulomb-nuclear interference region has been measured using thhe 185 GeV/c Fermilab polarized-proton and -antiproton beams. The results are found to be consistent with theoretical predictions within statistical uncertainties.

The polarization parameter has been measured for π−p elastic scattering in the backward region at 3.5 GeV/c incident momentum. The experimental set-up consisted of a polarized target in a spectrometer magnet, hodoscopes and wire spark chambers. Data are presented for the range −0.95<u⩽−0.19 GeV2. An isospin analysis has been carried out to separate the Iu=12and Iu=32 contributions.

The results of a series of experiments on π−d and pd elastic scattering in the 10 GeV region are compared with the prediction of the Glauber multiple scattering model. A disagreement is found in the double scattering region, which does not seem to be explainable in terms of the uncertainty in our current knowledge of the individual hadron-nucleon differential cross section. A way of restoring agreement could be that of reducing the usually quoted amount of screening between the two nucleons in the deuteron.

Two hadronic forward (HF) calorimeters extend the acceptance of CMS at large rapidities and are built with radiation-hard components (steel absorbers and quartz fibers) to resist the severe radiation levels in the forward regions. Very high energy jets can be measured in HF, by detecting Cherenkov light emitted by shower particles in the quartz fibers. The HF calorimeters are now installed in the underground CMS cavern; after commissioning, the detectors are being prepared for beam. Progress in calibration work and current plans for the HF calorimeters during the initial LHC runs are summarized.

Abstract The differential p p → n n charge-exchange cross section has been measured at the CERN Low Energy Antiproton Ring (LEAR), at two incident p momenta, 601 and 1202 MeV/c. features of the differential cross-section near the forward direction, i.e. a sharp peak at 0° scattering angle followed by an energy dependent dip-bump structure, are confirmed and measured with good precision and high statistical accuracy. The data show very clearly that the shape of the cross-section is a manifestation of the pion-exchange amplitude, and a simple extrapolation to the pion pole already indicates that the pion-nucleon coupling constant f c 2 can be determined with good precision.