B. Ille

We have tested new scintillator modules with silicon photodiode readout for the upgraded Active Lead Rings (ALR) of the L3 detector at LEP II. Results are presented from data recorded in muon and electron test beams with particular emphasis on the light production and collection as a function of the particle impact position on the scintillator modules. The results from the beam test data will be used for the design of the readout and trigger electronics in conjunction with the required ALR performance as an electron tagger and beam background monitor at LEP II.

This experiment has been performed at the CERN Intersecting Storage Rings to study the direct formation of charmonium states in antiproton-proton annihilations. The experimental program has partly been devoted to an inclusive scan for pp → J/ψ + X in the range 3520–3530 MeV/c2. A cluster of five events has been observed in a narrow energy band, centred on the centre of gravity of the 3PJ states where the 1P1 is expected to be. When interpreted as a new resonace, these data yield a mass m = 3525.4±0.8 MeV/c2.

In the framework of its search for new heavy, fast and radiation hard scintillators for calorimetry at future colliders, the Crystal Clear Collaboration performed a systematic investigation of the properties and of the scintillation and radiation damage mechanisms of CeF3 monocrystals. Many samples of various dimensions up to 3 × 3 × 28 cm3 were produced by industry and characterised in the laboratories by different methods such as: optical transmission, light yield and decay time measurements, excitation and emission spectra, gamma and neutron irradiations. The results of these measurements are discussed. The measured light yield is compared to the theoretical expectations. Tests in high energy electron beams on a crystal matrix were also performed. The suitability of CeF3 for calorimetry at high rate machines is confirmed. Production and economical considerations are discussed.

Differential cross sections for π−p and pp elastic scattering have been measured at incident momenta ranging from 30 to 345 GeV and in the t range 0.002 (GeV/c)2 ⩽ |t| ⩽ 0.04 (GeV/c)2. From the analysis of the data, the ratio ϱ (t = 0) of the real to the imaginary parts of the forward scattering amplitude was determined together with the logarithmic slope b of the diffraction cone. The results on the real parts confirm the validity of the forward dispersion relations at high energies. Using the dispersion relations, it was shown that the experimental data on ϱπ−p(t = 0) require a continuous rise of the total πp cross sections, at least up to the energy of 2000 GeV, thus revealing a close similarity in high-energy behaviour of πp and pp interactions. The results on the slope parameters from this experiment together with the analysis of the available world data demonstrate that the existing experimental data are consistent with the hypothesis of a universal shrinkage of the hadronic diffraction cone at high energies. The value of the asymptotic shrinkage parameter αp′ was found to be independent of the kind of the incident hadron and of the momentum transfer in the t range |t| ⩽ 0.2 (GeV/c)2 : 2αp′ = ± 3 (GeV/c)−2.

The result of a search at the LHC for heavy stable charged particles produced in pp collisions at $ \sqrt {s} = 7\;{\text{TeV}} $ is described. The data sample was collected with the CMS detector and corresponds to an integrated luminosity of 3.1 pb−1. Momentum and ionization-energy-loss measurements in the inner tracker detector are used to identify tracks compatible with heavy slow-moving particles. Additionally, tracks passing muon identification requirements are also analyzed for the same signature. In each case, no candidate passes the selection, with an expected background of less than 0.1 events. A lower limit at the 95% confidence level on the mass of a stable gluino is set at 398GeV/c 2, using a conventional model of nuclear interactions that allows charged hadrons containing this particle to reach the muon detectors. A lower limit of 311 GeV/c 2 is also set for a stable gluino in a conservative scenario of complete charge suppression, where any hadron containing this particle becomes neutral before reaching the muon detectors.

Hadronic event shapes have been measured in proton-proton collisions at sqrt(s)=7 TeV, with a data sample collected with the CMS detector at the LHC. The sample corresponds to an integrated luminosity of 3.2 inverse picobarns. Event-shape distributions, corrected for detector response, are compared with five models of QCD multijet production.

A measurement of the top-antitop production cross section in proton-proton collisions at a centre-of-mass energy of 7 TeV has been performed at the LHC with the CMS detector. The analysis uses a data sample corresponding to an integrated luminosity of 36 inverse picobarns and is based on the reconstruction of the final state with one isolated, high transverse-momentum electron or muon and three or more hadronic jets. The kinematic properties of the events are used to separate the top-antitop signal from W+jets and QCD multijet background events. The measured cross section is 173 + 39 - 32 (stat. + syst.) pb, consistent with standard model expectations.

The charge asymmetry in the production of top quark and antiquark pairs is measured in proton-proton collisions at a center-of-mass energy of 8 TeV. The data, corresponding to an integrated luminosity of 19.6 inverse femtobarns, were collected by the CMS experiment at the LHC. Events with a single isolated electron or muon, and four or more jets, at least one of which is likely to have originated from hadronization of a bottom quark, are selected. A template technique is used to measure the asymmetry in the distribution of differences in the top quark and antiquark absolute rapidities. The measured asymmetry is A[c,y] = [0.33 +/- 0.26 (stat) +/- 0.33 (syst)]%, which is the most precise result to date. The results are compared to calculations based on the standard model and on several beyond-the-standard-model scenarios.

A method to calibrate the L3 electromagnetic calorimeter with cosmic muons has been tested on a matrix of 100 tapered BGO crystals. Calibration constants in the energy range of 20–30 MeV were measured at the 2% level collecting about 200 muons per crystal. The results are in agreement with the calibration constant determined using a 10 GeV electron beam.

Differential cross sections for the elastic scattering of protons on 2H, 3H, 3He and 4He have been measured at 600 MeV. Proton-deuterium elastic scattering is investigated in a four-momentum transfer square t-range corresponding to Coulomb-nuclear interference in order to determine the nucleon-nucleon amplitudes at 600 MeV. For the other nuclei, we investigate the t-range corresponding to the first and second maximum, in order to determine the mechanism of the nuclear process. A few physical comments on the results are made.

A systematic investigation of the properties of cerium fluoride monocrystals has been performed by the “Crystal Clear” collaboration in view of a p

In an experiment performed at the CERN-ISR the direct formation is observed of the χ1 and χ2 charmonium states in proton-antiproton annihiliation. A novel technique provided excellent energy resolution together with small background and reduced systematics. The following values for the masses and total widths of the states were obtained: Λχ1 <3 MeV (95% CL); mχ1 = (3511.3±0.4±0.4) MeV; Λχ2=(2.6 +1.4−1.0) MeV; mξ2=(3556.9±0.4±0.5) MeV. First measurements of the partial widths to antiproton-proton are also reported: Λ(χ1→pp)=57+13-11±11) and Λ(χ2→pp)=(233 +51-45±48) eV.

The differential cross section has been measured at 30, 50, 80, 100, 120 and 140 GeV/c for 0.002 < |t| < 0.04 (GeV/c)2. The results show that the π−p real part goes from negative to positive values below 80 GeV/c. The slope parameter in the t-region measured is significantly higher than what has been found −t = 0.2 (GeV/c)2.

As part of the charmonium formation experiment at the CERN Intersecting Storage Rings, we studied the reaction pp→cc→γγ in an antiproton momentum scan through the ηc, χ1, and χ2 regions. We report events observed in the ηc and χ2 regions, whilst no event was observed in the χ1 region, as expected for a spin-1 state.

A prototype of the L3 electromagnetic calorimeter to be used at LEP and consisting of 100 tapered BGO crystals has been tested in an electron beam in the energy range of 2 to 50 GeV. The energy resolution and linearity of response have been measured, and are compared to predictions made with the GEANT Monte Carlo program.

The differential cross section of pp scattering has been measured in the energy region 100–300 GeV and in thet-range 0.002 < |t| < 0.04 (GeV/|c)2. The results on the real part of the scattering amplitude agrees with dispersion relation calculations. We also report on our determination of the slope parameterb together with an analysis of the world data ofb for different hadrons and differentt-values. It is shown that the data are consistent with the hypothesis of a universal shrinkage of the hadronic diffraction cone at high energies.

Experiment R704, the last to be performed at the CERN-ISR, has successfully applied a new method to study (cc) states formed directly in antiproton-proton annihilations. The novelty of the method rests on the capability to build a highly performing annihilation source by letting a cold

Differential cross sections for elastic scattering of pions and protons on helium have been measured at incident momenta ranging from 50 to 300 GeV/c in the t-range 0.008 < | < | < 0.05 (GeV/c)2. Both recoil α-particles and forward particles were detected in this experiment. The experimental method provided an absolute normalization of the cross sections with an estimated precision of 1%. From the analysis of the data, the diffraction slope parameters and total cross sections have been obtained. The results are compared with Glauber model calculations.

Lead and cadmium tungstate, in spite of their close chemical compositions, demonstrate quite different temperature dependencies of their scintillation and structural characteristics. Scintillation light yield (LY) and decay time of lead tungstate (PWO) decrease quickly above 200 K, whereas these scintillation parameters of cadmium tungstate (CWO) are much more stable between 77 and 300 K. On the other hand, the structural behaviour of PWO demonstrates a set of distinct indications on the existence of certain phase transformations starting at 200 K, whereas no structural instabilities in CWO are observed. Analysis of theses data enabled us to assume that the fast temperature quenching of scintillation parameters of PWO above 200 K is connected with a metastability of its tetragonal lattice appearing at this temperature. This metastability induces a new channel of non-radiative recombination of electron excitations initiating local transformations of the atomic lattice to more stable structures. So in order to increase the LY of PWO scintillations at room temperature, stabilisation of PWO crystalline structure should be arranged. Several ways of this stabilisation are discussed.

Abstract Three-body break-up spectra from a kinematically complete measurement of the 2H(p, pn)1H reaction have been analyzed to yield the cross section for the production of d∗ (a neutron and a proton in a S = 0, T = 1 configuration). A 27.5 MeV deuteron and a 13.5 MeV proton beam were used, and proton and neutron were detected in coincidence at the same angle to enhance the detection of 2H(p, d∗)1H or (d, d∗)1H events. The data were analyzed in terms of the Phillips-Griffy-Biedenharn model of final-state interaction. Only the n-p FSI contribution gives a structure in all observed spectra; other processes have essentially the same smooth shape in the region of the peak. An angular distribution of the 2H(p, d∗)1H reaction was obtained between θ d ∗ c.m. = 23° and θ d ∗ c.m. = 155° for the c.m. energy of 9.1 MeV. Other measurements for the 1H(d, d∗)1H reaction were also obtained at forward angles for the deuteron bombarding energy range 19.2, 27.5 MeV (which corresponds to 3He excitation energies between 11.8 and 14.7 MeV): the 1H(d, d∗)1H excitation function shows no structure in this range.

Further tests of lead tungstate crystal matrices made in high-energy electron beams in 1996, using new crystals, new APDs and an improved test setup confirm that an energy resolution of better than 0.6% at 100 GeV can be obtained when the longitudinal uniformity of the struck crystal is adequate. Light loss measurements under low dose irradiation are reported. It is shown that there is no loss of energy resolution after irradiation and it is demonstrated that the calibration change due to light loss can be tracked with a precision monitoring system. Successful tests with a preshower device, equipped with a silicon strip detector readout, are also described.

The characteristics of a hybridized low noise preamplifier are described. Performances of the preamplifier in combination with silicon photodiodes are discussed and results from laboratory tests and test runs with an assembly of large BGO crystals are presented.

CONTENTS: 1. Synopsis, 2. The MSSM Spectrum, 3. The Physical Parameters, 4. Higgs Boson Production and Decays, 5. SUSY Particle Production and Decays, 6. Experimental Bounds on SUSY Particle Masses, 7. References.

The differential cross section ofπ−p scattering has been measured in the energy region 100–345 GeV and in thet-range 0.002<|t|< 0.04 (GeV/c)2. The real part of theπ−p scattering amplitude has been extracted from the data. The results show that the real part continues to increase with energy. The energy dependence of the slope parameter has also been determined. The shrinkage found expressed in terms of the slope of the pomeron trajectory is2α′p=0.23±0.04 (GeV/c)−2. This agrees with the energy dependence found at larger|t|-values.

A calibration study was performed on a prototype of the L3 BGO electromagnetic calorimeter. The accuracy and stability reached is a small fraction of the typical detector resolution.

Using matrices of lead tungstate crystals, energy resolutions better than 0.6% at 100 GeV have been achieved in the test beam in 1995. It has been demonstrated that a lead tungstate electromagnetic calorimeter read out by avalanche photodiodes can consistently achieve the excellent energy resolutions necessary to justify its construction in the CMS detector. The performance achieved has been understood in terms of the properties of the crystals and photodetectors.

A calorimeter of 25 bismuth germanate (BGO) crystals equipped with silicon photodiode readout has been tested at the CERN SPS in the energy range 1–50 GeV. The response for electrons has been shown to be linear in this energy range and the rms resolution obtained (σEE) is approximately 1%, for E > 4 GeV. The electron/pion separation was found to be better than 1:500 in the energy range 1–20 GeV. Data on lateral and longitudinal shower development were compared with the results of a Monte Carlo simulation using the SLAC-EGS program and found to be in good agreement.

A search is performed for the production of a massive W′ boson decaying to a top and a bottom quark. The data analysed correspond to an integrated luminosity of 19.7 fb−1 collected with the CMS detector at the LHC in proton-proton collisions at $$ \sqrt{s}=8 $$ TeV. The hadronic decay products of the top quark with high Lorentz boost from the W′ boson decay are detected as a single top flavoured jet. The use of jet substructure algorithms allows the top quark jet to be distinguished from standard model QCD background. Limits on the production cross section of a right-handed W′ boson are obtained, together with constraints on the left-handed and right-handed couplings of the W′ boson to quarks. The production of a right-handed W′ boson with a mass below 2.02 TeV decaying to a hadronic final state is excluded at 95% confidence level. This mass limit increases to 2.15 TeV when both hadronic and leptonic decays are considered, and is the most stringent lower mass limit to date in the tb decay mode.

A cerium fluoride matrix composed of nine longitudinally segmented towers, approximately 25X0 long, has been tested in electron, muon and pion beams of momenta ranging from 10 to 150 GeV/c. The results are discussed in terms of light yield, electronic noise, energy and position resolution. In spite of serious imperfections in geometry and quality of some of the crystals, an electron energy resolution of ∼0.5% has been obtained with a silicon photodiode readout, for energies above 50 GeV. The performance of cerium fluoride in a beam, its high density, high light yield and fast response, radiation resistance and ruggedness make it a very good candidate for high-resolution calorimetry at future colliders. The best conditions for production of large high-quality crystals are being studied in several firms over the world. Many CeF3 crystals, 2 × 2 cm2 or 3 × 3 cm2 in cross section and up to 28 cm long, were received in 1994 from four companies, some of them with excellent light yield and radiation hardness.

Angular and energy distributions of electrons and positrons created by 83–133 GeV photons in an aligned crystal (strong field pair creation) have been measured. The experiment exhibits the “blocking” effect for the positron and the difference of energy loss between channeled electron and quasi-channeled positron. The data are well reproduced by a Monte Carlo simulation.

In the experiment R704 at the CERN Intersecting Storage Rings, the two p-wave charmonium states χ1 and χ2 were formed directly in proton-antiproton annihilation, and detected through the decay chain χj→γ+Jψ→ψ+e+e−. The angular d istributions of the events found are studied here. A maximum likehood analysis shows that χ1 radiative transition to the Jψ is compatible with a pure dipole. Indications of a nonzero, positive quadropole contribution to the χ2 radiative transition are found. Finally, it is found that the χ2 data are consistent with the conventional assumption that a single quark radiates the photon in the transition from the χ2 to the Jψ.

Three-body break-up in n-p final-state interaction regions has been investigated through the reactions 2H + d → p + n + [su2H, 4He + d → p + n + 4He, 6Li + d → p3He + d → p + n + 3He. In all cases, the proton and the neutron were detected at the same angle in a kinematically complete experiment for a deuteron bombarding energy of 27.5 MeV. Helium and deuterium gas targets in a small gas cell cooled with liquid nitrogen were used. No indication of any possible contribution from the (isospin-forbidden) 1S0 p-n final-state interaction was observed in the first three reactions. For the 3He + d reaction, the data shown pronounced enhancements due to the p-n final-state interaction. In the forward regions the observed peaks are broader than the predictions of final-state interaction models.

The quasifree process was studied in the 2H(d, dn)1H reaction at 27.5 MeV for three angular conditions. Neutrons and deuterons were detected in coincidence. The charged particle was identified in a ΔE-E telescope; the neutron energy was measured by a time-of-fiight method. The experimental results are interpreted using the modified simple impulse approximation (MSIA).

CONTENTS: 1. Synopsis, 2. The MSSM Spectrum, 3. The Physical Parameters, 4. Higgs Boson Production and Decays, 5. SUSY Particle Production and Decays, 6. Experimental Bounds on SUSY Particle Masses, 7. References.

In a small-angle elastic scattering experiment (NA8) in the H8 beam of the CERN Super Proton Synchrotron, the absolute momentum of the incident beam particles has been determined from data on hadron—4He elastic scattering. Measurements were performed at beam momenta ranging from 100 GeV/c to 300 GeV/c, and the average absolute momentum was determined with a precision of 0.15%. This method can be applied also at higher energies.

From the measurement of e+e- pairs from the reaction p̄p→e+e- at the CERN-ISR, using an antiproton beam and a hydrogen jet target, we derived upper limits for the proton magnetic form factor in the time-like region at Q2⋍8.9(GeVc)2 and Q2⋍12.5(GeVc)2.

We describe a search for a light neutral object X0 possibly produced by ≈ 100 GeV photons interacting with the QED strong field encountered along the <110 > axis of a cooled Ge crystal. We look at the e+e− decay mode, in short (10−18−10−12 s) as well as long (10−13−10−8 s) lifetime detection conditions. For a mass of 1.8 ±0.2MeV/c2 (“Darmstadton” mass) we find no evidence for X0 production. The upper limit for the ratio between e+e− decay rate and pair creation is given as a function of the X0 lifetime. It reaches ≈ 5 × 10−4 and ≈ 2 × 10−5 in the short and long lifetime mode, respectively, including the crystal absorption contribution. However, for the long-lifetime mode and 108 incident photons, 9 events are compatible with neutral objects having masses ranging from 2.1 to 3.5 MeVc2. A Monte Carlo simulation of the background gives only 1 event in the same energy range.

In an experiment performed at the CERN Intersecting Storage Rings as a part of an energy scan to detect the ηc formation in pp annihilation, we studied the reaction pp→φφ→K+K−K+K−. The total cross section has been determined to be 25.0± 7.4±3.8 nb.

Using both recoil and fast-particle spectrometers, the reaction ${\ensuremath{\pi}}^{\ensuremath{-}}+^{4}\mathrm{He}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}+^{3}\mathrm{H}+x$ has been measured for triton momenta in the region 0.24-0.60 GeV/c. The experimental spectra are presented as functions of triton momentum and angle and of mass of the unmeasured object. In the theoretical analysis it is assumed that the final state can be reached via quasielastic scattering from ${N}^{*}^{3}\mathrm{H}$ states and via ${N}^{*}$ productions from the $p^{3}\mathrm{H}$ state of helium. The most credible of three investigated $p^{3}\mathrm{H}$ wave functions requires one percent of ${N}^{*}^{3}\mathrm{H}$ states in the mass range 1.08-1.80 GeV/${\mathit{c}}^{2}$.NUCLEAR REACTIONS $^{4}\mathrm{He}({\ensuremath{\pi}}^{\ensuremath{-}},{\ensuremath{\pi}}^{\ensuremath{-}}x)t$, $E=5$ GeV, ${E}_{t}&gt;10$ MeV measured $\ensuremath{\sigma}({\ensuremath{\theta}}_{t},{m}_{x})$, $\ensuremath{\sigma}({m}_{x},{E}_{t})$, $\ensuremath{\sigma}({m}_{x},{\ensuremath{\theta}}_{t})$; deduced $p\ensuremath{-}t$ wave-$f$, $x\ensuremath{-}t$ prob. $1.1&lt;{m}_{x}&lt;1.8$ GeV. $p({\ensuremath{\pi}}^{\ensuremath{-}},{\ensuremath{\pi}}^{\ensuremath{-}})x$, $E=5$ GeV, measured $\ensuremath{\sigma}({m}_{x})$.

We report on a precise measurement of the energy loss through ionization by pions in bismuth germanate performed at several values of the incident particles momentum with a prototype of the L3 electromagnetic calorimeter. The experimental results are in good agreement with theoretical predictions showing the relativistic rise modified by density effect.

We have measured the cross section for π− + 4He→ π− + 3H+p at 5 GeV/c incident pion momentum. The momentum transfer to the pion was in the region 0.005≦|tππ|≦0.15 (GeV/c)2 and the triton recoil momentum in the region 0.24 ≦ pt ≦ 0.60 GeV/c. A theoretical model including final-state interactions has also been developed. Strong final-state interactions prohibit a direct extraction of the relative proton-triton bound-state wave function. Nevertheless, we are able to conclude that the wave function remains positive for relative proton-triton momenta up to at least 0.6 GeV/c. This result questions the relevance of wave functions derived from the helium electromagnetic form factor.

The high antiproton-proton luminosity obtained by using a target system consisting of a hydrogen gas-jet crossing a coasting beam of cooled antiproton circulating in one of the rings of CERN's ISR provides the possibility to measure low cross section reactions with very high precision. We present measurements of the antiproton-proton elastic cross section at 90° CM at incident momenta between 3.5 GeV/c and 5.7 GeV/c. The precision of these measurements is much higher than previously reported results. The data show that the cross section of this reaction decreases faster than s−12 over this momentum range.

The Electromagnetic Calorimeter of the CMS detector for the CERN Large Hadron Collider (LHC) is designed to allow the detection of a standard model Higgs boson of mass below 150 GeV. An overview is given of this homogeneous calorimeter made of almost 80 000 lead tungstate (PbWO4) 26X0 long crystals. This includes a description of the engineering design and a review of the different components of the calorimeter. The most recent results obtained in particle beams with realistic crystal prototypes are also presented.

Unusual decrease of the light yield of scintillations in lead tungstate (PWO) proportional to the logarithm of the length of the crystals is explained by the excitation of the localized surface light waves during the internal total reflection at PWO faces. These light waves are excited due to partial transfer of the light flow from the ordinary normal wave to the extraordinary one with less refractive index. The absorption and scattering of the surface waves by the subsurface defects induce the total losses of the emitted light.

An apparatus, used to search for nucleon isobars, x, in π4 He → πtx or π4 He → π3 Hex reactions, is described. The nuclear fragment and the scattered fast pion were measured in a recoil spectrometer and a fast-particle spectrometer, respectively. The recoil spectrometer has multiwire proportional chambers (MWPC) for the measurement of direction and semiconductor detectors and scintillation counters for the measurement of energy. The identification of the recoil is accomplished by means of the E, ΔE method. The target is gaseous to allow the measurement of low-energy recoils and it can hold pressures up to 150 atm. The spectrometer for the scattered pion consists of a magnet and MWPC's.

The Compact Muon Solenoid is one of two generic detectors currently being constructed for the Large Hadron Collider at CERN foreseen to begin data taking in 2007. The electromagnetic calorimeter consists of a barrel and endcaps made of PbWO4 scintillating crystals. In the barrel, the scintillation signal is read out by Hamamatsu avalanche photodiodes, connected in parallel in a structure called a “capsule”, one for each of the 61 200 channels. We present the calibration results and performance statistics obtained for more than 5000 production capsules.

We give upper bounds on the photoproduction in overcritical electric fields of a neutral light boson which could explain the correlated e+e- production seen at GSI-Darmstadt in heavy-ion-atom collisions.

During 1991 two cosmic rays runs took place for the calibration of the L3 electromagnetic calorimeter. In this paper we present the results of the first high statistics cosmic ray calibration of the calorimeter in situ, including the end caps. Results show that the accuracy on the measurement of the calibration constants that can be achieved in one month of data taking is of 1.3%.

A Cerium Fluoride matrix of 3 × 3 towers with Silicon photodiode readout has been tested in electron and pion beams from 10 to 150 GeV energy. The matrix was assembled with a selection of crystals out of a total of over 40 large crystals (up to 20 cm long and 3 cm × 3 cm in cross section) from various producers. Despite less than optimal geometry and crystal quality, an energy resolution of 0.5% for energies ≥ 50 GeV has been obtained. Fast shaping amplifier prototypes were tested and their performance was found to be appropriate for operation in an LHC-like environment.

We have measured the ionization loss of highly relativistic protons and pions passing through an ionization chamber filled with hydrogen at 10 atm pressure. The Lorentz factor of the particles ranged from γ = 100 toγ = 1800. The ionization loss was found our results disagree with the theoretical predictions of Tsytovich, according to which radiative corrections lead to a decrease in the ionization loss at higher energies.

A search for massive resonances decaying to a Z boson and a photon is performed in events with a hadronically decaying Z boson candidate, separately in light-quark and b quark decay modes, identified using jet substructure and advanced b tagging techniques. Results are based on samples of proton-proton collisions collected with the CMS detector at the LHC at center-of-mass energies of 8 and 13 TeV, corresponding to integrated luminosities of 19.7 and 2.7 inverse femtobarns, respectively. The results of the search are combined with those of a similar search in the leptonic decay modes of the Z boson, based on the same data sets. Spin-0 resonances with various widths and with masses in a range between 0.2 and 3.0 TeV are considered. No significant excess is observed either in the individual analyses or the combination. The results are presented in terms of upper limits on the production cross section of such resonances and constitute the most stringent limits to date for a wide range of masses.

The inelastic hadronic cross section in proton-lead collisions at a centre-of-mass energy per nucleon pair of 5.02 TeV is measured with the CMS detector at the LHC. The data sample, corresponding to an integrated luminosity of 12.6 +/- 0.4 inverse nanobarns, has been collected with an unbiased trigger for inclusive particle production. The cross section is obtained from the measured number of proton-lead collisions with hadronic activity produced in the pseudorapidity ranges 3<abs(eta)<5 and/or -5<abs(eta)<-3, corrected for photon-induced contributions, experimental acceptance, and other instrumental effects. The inelastic cross section is measured to be sigma[inel,pPb]=2061 +/- 3 (stat) +/- 34 (syst) +/- 72 (lum) mb. Various Monte Carlo generators, commonly used in heavy ion and cosmic ray physics, are found to reproduce the data within uncertainties. The value of sigma[inel,pPb] is compatible with that expected from the proton-proton cross section at 5.02 TeV scaled up within a simple Glauber approach to account for multiple scatterings in the lead nucleus, indicating that further net nuclear corrections are small.

Data collected in the experiment R704 at the CERN ISR are used to study the annihilation process pp → π0π0 at several centre-of-mass energies between 2.97 and 3.56 GeV. A total sample of 7359 events has been identified, from which cross sections and angular distributions in the interval 0 < |cosθ∗| < 0.5 have been measured.

A measurement of the ttbar production cross section at sqrt(s)=13 TeV is presented using proton-proton collisions, corresponding to an integrated luminosity of 2.3 inverse femtobarns, collected with the CMS detector at the LHC. Final states with one isolated charged lepton (electron or muon) and at least one jet are selected and categorized according to the accompanying jet multiplicity. From a likelihood fit to the invariant mass distribution of the isolated lepton and a jet identified as coming from the hadronization of a bottom quark, the cross section is measured to be sigma(ttbar)= 835 +/- 3 (stat) +/- 23 (syst) +/- 23 (lum) pb, in agreement with the standard model prediction. Using the expected dependence of the cross section on the pole mass of the top quark (m[t]), the value of m[t] is found to be 172.7+2.4-2.7 GeV.

Missing mass spectra from the reactions πp → πx and πα → πtx have been measured and found to be significantly different. Neglecting all background processes an analysis with the impulse approximation yields a 0.24 percent presence of the isobar-triton state in helium in the triton momentum range 0.32–0.70 GeVc and the mass range 1.30–1.86 GeVc2.

The Compact Muon Solenoid is one of two generic detectors currently being constructed for the Large Hadron Collider at CERN foreseen to begin data taking in 2007. The electromagnetic calorimeter consists of a barrel and endcaps. These are made of PbWO4 scintillating crystals. In the barrel, the scintillation signal is read out by Hamamatsu avalanche photodiodes, connected in parallel in a structure called a “capsule”. Each of the 61,200 channels must be equipped with a capsule, the reliability of which must be assured since they will be inaccessible during the life of the experiment. The capsule production is now finished. We present the final calibration and performance statistics.

Recent measurements of masses, total widths and branching ratios to pp̄ of χ1 and χ2 charmonium states are reported: a novel experimental technique (circulating p̄ beams+gas jet target) has provided excellent energy resolution, together with small background and reduced systematics.