J. Tuominiemi

The longitudinal phase-space analysis is applied to various three-body final states of meson-nucleon collisions at 5–16 GeV/c primary momentum. The distributions of the angle ω along the hexagonal phase space plot and the dependence of average transverse momenta on ω are investigated in some detail. From the very rich structure of the ω distributions it is possible to conclude that, whenever allowed, the diffraction mechanism (single Pomeranchuk exchange) dominates the three-body reactions at high energy. The study of the transverse momentum distributions reveals the existence of strong correlations between longitudinal and transverse momenta which cannot be explained by phase-space effects. Some consequences of our analysis for the Regge-exchange models are briefly mentioned.

The NA52 experiment searches for long-lived massive strange quark matter particles, so-called ${\mathit{s}\mathit{t}\mathit{r}\mathit{a}\mathit{n}\mathit{g}\mathit{e}\mathit{l}\mathit{e}\mathit{t}\mathit{s},\phantom{\rule{0ex}{0ex}}\mathrm{p}\mathrm{r}\mathrm{o}\mathrm{d}\mathrm{u}\mathrm{c}\mathrm{e}\mathrm{d}\phantom{\rule{0ex}{0ex}}\mathrm{i}\mathrm{n}\phantom{\rule{0ex}{0ex}}\mathrm{P}\mathrm{b}\ensuremath{-}\mathrm{P}\mathrm{b}\phantom{\rule{0ex}{0ex}}\mathrm{c}\mathrm{o}\mathrm{l}\mathrm{l}\mathrm{i}\mathrm{s}\mathrm{i}\mathrm{o}\mathrm{n}\mathrm{s}\phantom{\rule{0ex}{0ex}}\mathrm{a}\mathrm{t}\phantom{\rule{0ex}{0ex}}\mathrm{a}\phantom{\rule{0ex}{0ex}}\mathrm{b}\mathrm{e}\mathrm{a}\mathrm{m}\phantom{\rule{0ex}{0ex}}\mathrm{m}\mathrm{o}\mathrm{m}\mathrm{e}\mathrm{n}\mathrm{t}\mathrm{u}\mathrm{m}\phantom{\rule{0ex}{0ex}}\mathrm{o}\mathrm{f}\phantom{\rule{0ex}{0ex}}{p}_{\mathrm{lab}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}158\mathrm{A}\mathrm{}\mathrm{GeV}\mathrm{/}\mathit{c}.\phantom{\rule{0ex}{0ex}}\mathrm{U}\mathrm{p}\mathrm{p}\mathrm{e}\mathrm{r}\phantom{\rule{0ex}{0ex}}\mathrm{l}\mathrm{i}\mathrm{m}\mathrm{i}\mathrm{t}\mathrm{s}\phantom{\rule{0ex}{0ex}}\mathrm{f}\mathrm{o}\mathrm{r}\phantom{\rule{0ex}{0ex}}\mathrm{t}\mathrm{h}\mathrm{e}\phantom{\rule{0ex}{0ex}}\mathrm{p}\mathrm{r}\mathrm{o}\mathrm{d}\mathrm{u}\mathrm{c}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}\phantom{\rule{0ex}{0ex}}\mathrm{o}\mathrm{f}\phantom{\rule{0ex}{0ex}}\mathrm{s}\mathrm{t}\mathrm{r}\mathrm{a}\mathrm{n}\mathrm{g}\mathrm{e}\mathrm{l}\mathrm{e}\mathrm{t}\mathrm{s}\phantom{\rule{0ex}{0ex}}\mathrm{a}\mathrm{t}\phantom{\rule{0ex}{0ex}}\mathrm{z}\mathrm{e}\mathrm{r}\mathrm{o}\phantom{\rule{0ex}{0ex}}\mathrm{d}\mathrm{e}\mathrm{g}\mathrm{r}\mathrm{e}\mathrm{e}\phantom{\rule{0ex}{0ex}}\mathrm{p}\mathrm{r}\mathrm{o}\mathrm{d}\mathrm{u}\mathrm{c}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}\phantom{\rule{0ex}{0ex}}\mathrm{a}\mathrm{n}\mathrm{g}\mathrm{l}\mathrm{e}\phantom{\rule{0ex}{0ex}}\mathrm{c}\mathrm{o}\mathrm{v}\mathrm{e}\mathrm{r}\mathrm{i}\mathrm{n}\mathrm{g}\phantom{\rule{0ex}{0ex}}\mathrm{a}\phantom{\rule{0ex}{0ex}}\mathrm{m}\mathrm{a}\mathrm{s}\mathrm{s}\phantom{\rule{0ex}{0ex}}\mathrm{t}\mathrm{o}\phantom{\rule{0ex}{0ex}}\mathrm{c}\mathrm{h}\mathrm{a}\mathrm{r}\mathrm{g}\mathrm{e}\phantom{\rule{0ex}{0ex}}\mathrm{r}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{o}\phantom{\rule{0ex}{0ex}}\mathrm{u}\mathrm{p}\phantom{\rule{0ex}{0ex}}\mathrm{t}\mathrm{o}\phantom{\rule{0ex}{0ex}}120\mathrm{GeV}\mathrm{/}\mathit{c}}^{2}$ and lifetimes ${t}_{\mathrm{lab}}\ensuremath{\gtrsim}1.2$ \ensuremath{\mu}s are given. The data presented here were taken during the 1994 lead beam running period at CERN.

The NA52 experiment measured particle and antiparticle yields at 0° production angle over a wide range in rapidity in lead-lead (Pb-Pb) collisions at 158 A GeV/c with a minimum bias trigger. Besides (106) antiprotons () and (103) antideuterons () a total of five antihelium-3 () were found. The resulting invariant differential production cross sections at pt≃0 GeV/c turn out to be E (d3σ)/(dp3) = (2.5 ± 1.8) × 10-7 bc3 GeV-2 at a rapidity of y = 3.4 in the laboratory system and (5.9 ± 3.4) × 10-8 bc3 GeV-2 at y = 4.0. The results are discussed in the framework of a simple coalescence model.

We have analysed a sample of 2.36 million minimum bias events produced in pp collisions at s=630 GeV in the UA1 experiment at the CERN collider. We have studied the production of charged particles with transverse momenta (pT) up to 25 GeV/c. The results are in agreement with QCD predictions. The rise of 〈pT〉 with charged particle multiplicity may be related to changing production of low pT particles.

Higher order Bose-Einstein correlations up to fifth order, of particles produced in proton-antiproton collisions, are presented using UA1 data at √s=630 and 900 GeV. The results are compared with theoretical calculations to investigate the primary assumptions for the parametrization of the correlation functions.

Simple inclusive cross sections for pp interactions at 12 GeV/c are given. The data cover prong cross sections, V0 production and resonances. Separation has been made into annihilation and non-annihilation modes. Some implications of the data are discussed. It is pointed out that the ratios of cross sections for ϱ0π− production are independent of incident antiproton momentum in pp annihilation processes, and that data at the highest available pp energies (ISR) tend to the same value.

We have studied the reactions K+d→K+π−pp,K+d→Koπopp,K+d→Koπ+pp, obtained from an exposure of the Saclay 81-cm bubble chamber filled with deuterium and exposed at CERN to a separated 3 GeV/c K+ beam. In reactions (1) and (2) there is abundant production of K∗0(892) and some production of K∗(1420). From the density matrix elements, it is found that K∗0(892) is produced mainly by pion exchange. The K∗(892) four-momentum-transfer distribution in reaction (1) agrees with the predictions of the OPE model, as modified by Dürr and Pilkuhn. A marked asymmetry of the decay distribution of the K+π− system is observed and discussed in the framework of a unitarized Veneziano model. In reaction (3), on the other hand, the production of K∗+(892) and N∗+(1236) is found to proceed mainly by vector exchange.

A beam telescope based on the CMS Tracker data acquisition prototype cards has been developed in order to test sensor candidates for S-LHC tracking systems. The telescope consists of up to eight reference silicon microstrip modules and slots for a couple of test modules. Beam tracks, as measured by the reference modules, provide a means of determining the position resolution and efficiency of the test modules. The impact point precision of reference tracks at the location of the test modules is about 4μm. This note presents a detailed description of the silicon beam telescope (SiBT) along with some results from its initial operation in summer 2007 in the CERN H2 beamline.

We report on baryon and antibaryon as well as K+ and K− production cross sections measured in lead-lead collisions at 158GeV/c per nucleon. The presented data were taken at zero degree production angle with a minimum bias trigger. The measurements covered a wide range of rapidity 1.4<y<6.0. Using a simple thermodynamical and a coalescence model the temperature and the chemical potential of the particle source as well as the freeze-out radius of baryons and antibaryons have been deduced.

We have analysed a sample of 2.36 million minimum bias events produced in pp collisions at s=630 GeV in the UA1 experiment at the CERN SppS collider. We have studied the production of KS0, Λ and Λ particles with transverse momenta (pt) up to 7 GeV/c and K± up to 2 GeV/c. The kaon data are compared with a recent QCD prediction and are found to be in good agreement. The <pt> for KS0, Λ and Λ is seen to increase as a function of the charged particle multiplicity and is compared with charged particle production.

Inclusive production of Λ and Λ in K+ p interactions is studied at incident momenta of 8.2 and 16.0 GeV/c. Cross sections and single-particle distributions are presented, the correlation between longitudinal and transverse momentum is investigated, and the dependence of average charge multiplicity on missing mass measured. For Λ production, early scaling is observed in the target fragmentation region when the data are presented in terms of (M2-Mth2)/s and t, where Mth is the threshold value of the missing mass M. Furthermore, a triple-Regge analysis in these variable yields an effective exchange trajectory which passes through the K, Q and L mesons. There is evidence for beam fragmentation in Λ and Λ production, but the contributions seem not to be dominant in the fragmentation region. Nevertheless, the parameter values in a triple-Regge description are estimated, and together with those for target fragmentation in Λ production, provide a complete description of the fragmentation contributions to the two reactions. Integration of the resultant distribution functions over the complete Chew-Low plot yields fragmentation cross sections increasing approximately as log s; in addition the observed features of the x, pL and pT2 projections and of the pL-pT correlation are well-described in the fragmentation regions. Central production contributions are isolated by subtracting the calculated fragmentation distributions

We searched for long-lived strange quark matter particles, so-called strangelets, and studied particle and antiparticle production in Pb + Pb collisions at 158 GeV/c per nucleon at zero degree production angle. We give upper limits for the production of strangelets covering a mass to charge ratio up to 120 GeV/c2 and lifetimes tlab > 1.2μs and plot invariant differential production cross sections as a function of rapidity for a variety of particles.

The 1500 MeV and 1700 MeV enhancements observed in the pππ system are analyzed. It is found that the 1500 MeV effect is not a pure angular momentum state. Neither t- nor s-channel helicity is conserved. The 1700 MeV effect gives good fits to J=32 and 52 decaying to pππ. In the decay mode Δ++π−J=52 is preferred over 32. Moment analysis shows consistency with t- rather than s-channel helicity conservation.

We investigate antinuclei production in Pb + Pb interactions at 158 GeV/c per nucleon at zero degree production angle. We quote invariant differential production cross sections for antiprotons and antideuterons. The corresponding antideuteron to antiproton ratio at midrapidity is 4.2 · 10−4. One antihelium-3 nucleus was observed. The results are discussed in the framework of a simple coalescence model.

We report on measurements of correlated $$b\bar b$$ production in $$p\bar p$$ collisions at $$\sqrt s = 630GeV$$ , using dimuon data to tag both theb and $$\bar b$$ quarks. Starting from an inclusive dimuon sample we obtain improved cross-sections for single inclusive beauty production and confirm our earlier results on $$B^0 - \bar B^0$$ mixing. From a study of $$b\bar b$$ correlations we derive explicit cross-sections for semi-differential $$b\bar b$$ production. We compare the measured cross-sections and correlations to $$\mathcal{O}\left( {\alpha _s^3 } \right)$$ QCD predictions and find good quantitative agreement. From the measured angular distributions we establish a size-able contribution from higher order QCD processes with a significance of about seven standard deviations. A large nonperturbative contribution to these higher order corrections is excluded.

The inclusive reaction pp → Λ + X++ at 19 GeV/c beam momentum has been analyzed in terms of the triple-Regge formalism. A good description of the structure function is achieved for events with |t| < 4 (GeV/c)2. The effective trajectory obtained from fits to the M2/s distribution in different t bins is αR (t) = −(0.38 ± 0.11) + (1.15 ± 0.07)t, which holds up to a |t| value of 4 (GeV/c)2. This is consistent with the K trajectory rather than the K∗ trajectory which has been reported from other experiments.

Abstract Data are presented on inclusive single particle distributions in the proton fragmentation region for the reactions K + p → π ± X at 8.2 and 16 GeV/ c and K − p → π ± X at 10 and 16 GeV/ c . The energy dependence is studied and compared with the dual Regge model predictions for approach to scaling. None of the existing models is in full agreement with the data. The model of Chan and his collaborators is consistent with our results under the additional assumption of equality of vector and meson coupling constants in the p π + vertex in the Mueller diagram.

During summer 2006 a fraction of the CMS silicon strip tracker was operated in a comprehensive slice test called the Magnet Test and Cosmic Challenge (MTCC). At the MTCC, cosmic rays detected in the muon chambers were used to trigger the readout of all CMS sub-detectors in the general data acquisition system and in the presence of the 4 T magnetic field produced by the CMS superconducting solenoid. This document describes the operation of the Tracker hardware and software prior, during and after data taking. The performance of the detector as resulting from the MTCC data analysis is also presented.

The influence of Bose-Einstein correlations on the rise of factorial moments is small in the 1-dimensional phase space given by the pseudorapidity η, where the 2-body correlation function is dominated by unlike-sign particle correlations. Contraily, the influence is dominant in the higher dimensional phase space. This is shown by using correlation integrals. They exhibit clear power law dependences on the four-momentum transferQ 2 for all orders investigated (i=2–5). When searching for the origin of this behaviour, we found that the Bose-Einstein ratio itself shows a steep rise forQ 2→0, compatible with a power law.

A search for multifractal structures, in analogy with multifractal theories, is performed on UA1 minimum bias events. A downward concave multifractal spectral function,f(α) (where α is the Lipschitz-Hölder exponent), indicates that there are self-similar cascading processes, governing the evolution from the quark to the hadron level, in the final states of hadronic interactions.f(α) is an accurate measure of the bin to bin fluctuations of any observable. It is shown that the most sensitive comparison between data and the Monte Carlo models, GENCL and PYTHIA 4.8 can be made usingf(α). It is found that these models do not fully reproduce the behaviour of the data.

The inclusive reaction K+p → K0X is studied at 5, 8.2 and 16 GeV/c. The inclusive cross sections as well as the inclusive transverse and longitudinal distributions are given. The energy dependence of the structure function in the proton fragmentation region is found to be consistent with s−1-behaviour indicating the presence of f′ - ϕ exchange in the missing mass channel, with a relative contribution of 50–70%.

We have determined the cross section for elastic K+π−→K+π−, and charge exchange, K+π−→K0π0, scattering using the Chew-Low extrapolation method, for Kπ masses up to 1.35 GeV. This has been achieved by using 3026 events of the type K+p→K+π−N∗ (1236) and 1246events of the type K+p→K0π0N∗ (1236) obtained in bubble chamber exposures at CERN. The cross section exhibits the known K∗ (892) resonance shape. A similar study for the K+π+→K+π+ elastic scattering has been attempted. The partial wave expansion coefficients up to 〈Y40〉 (without off-shell correction) have been studied as a function of the Kπ masses.

We present a study of six- and seven-body final states among the K+p interactions at 5 GeV/c incident K+ momentum. Results on cross sections, resonance and single-particle productions are given. Charge dependent angular correlations for pairs of pions occur as in pp and π+p interactions (the so called GGLP effect). In contrast, no dependence on the charge is observed in the angular correlations between kaons and pions. The influence of the production of K∗ and N∗ resonances on these angular correlations is investigated. The predictions of a multi-Regge Model (CŁA) are compared to the experimental results.

A beam telescope providing precision track measurements as reference for other detectors has been upgraded in the CERN H2 test beam. The apparatus was completely rebuilt from the detector wafers and front-end electronics to the data acquisition system. The new detector setup consists of eight 5.6×5.6cm2 sized DC coupled silicon microstrip detectors. Typical position resolution values of about 7.5μm were measured. Details of the setup are described and results from the recent beam tests are reported.

From a sample of 2.36 million minimum bias events produced in pp collisions at s=630GeV in the UA1 experiment and from other published data at the CERN SppS collider we have estimated the relative production of π±, π0, K±, KS0, Λ, Λ, p and p. We obtain a meson over baryon ratio MB= 6.4 ± 1.1. From the KS0π± ratio we measure the strangeness suppression factor λ = 0.29 ± 0.02 ± 0.01 which, combining with other available data provides a new world average of 0.29 ± 0.015. Both the KS0π± ratio and the strangeness suppression factor λ as a function of s are investigated, and an extrapolation to the LHC energy is performed.

We investigate the production mechanisms of p, d, t, 3He, 4He, 6Li, , and in Pb+Pb collisions at 158 A GeV measured near zero transverse momentum with the NA52 experiment at the CERN SPS. We find evidence that nuclei and antinuclei in Pb+Pb collisions are mainly produced via the coalescence mechanism out of a thermalized source of hadrons, at a time close to the thermal freeze-out of hadrons corresponding to a temperature of ~120 MeV.

Strip detectors with an area of 16cm2 were processed on high resistivity n-type magnetic Czochralski silicon. In addition, detectors were processed on high resistivity Float Zone wafers with the same mask set for comparison. The detectors were irradiated to several different fluences up to the fluence of 3×10151MeVneq/cm2 with protons or with mixed protons and neutrons. The detectors were fully characterized with CV- and IV-measurements prior to and after the irradiation. The beam test was carried out at the CERN H2 beam line using a silicon beam telescope that determines the tracks of the incoming particles and hence provides a reference measurement for the detector characterization. The n-type MCz-Si strip detectors have an acceptable S/N at least up to the fluence of 1×1015neq/cm2 and thus, they are a feasible option for the strip detector layers in the SLHC tracking systems.

Pad and strip detectors processed on high resistivity n-type magnetic Czochralski silicon (MCz-Si) were irradiated to several different fluences with protons.The pad detectors were characterized with the Transient Current Technique (TCT) and the full-size strip detectors with a reference beam telescope and a 225 GeV muon beam.The TCT measurements indicate a double junction structure and space charge sign inversion in MCz-Si detectors after 6 × 10 14 1 MeV n eq /cm 2 fluence.In the beam test a S/N of 50 was measured for a non-irradiated MCz-Si sensor, and a S/N of 20 for the sensors irradiated to the fluences of 1 × 10 14 1 MeV n eq /cm 2 , and 5 × 10 14 1 MeV n eq /cm 2 .

The UA1 Collaboration has recently improved its measurement of the beauty production cross-section by including explicit measurements of bb correlations. Using these data we have determined the strong coupling constant αs. The comparison of the measured cross-section for 2-body final states with O(αs3) QCD predictions yields a measurement of αs(20 GeV) = 0.145−0.010 exp −0.016 th+0.012 +0.013, corresponding to αs(Mz) = 0.113−0.006 exp −0.009 th+0.007 +0.008. This is the first theoretically well-defined measurement of αs from a purely hadronic production process. Evaluating αs from cross-sections at different Q2-values we find that the running of αs is needed for internal consistency of the UA1 data.

In March 2007 the assembly of the Silicon Strip Tracker was completed at the Tracker Integration Facility at CERN. Nearly 15% of the detector was instrumented using cables, fiber optics, power supplies, and electronics intended for the operation at the LHC. A local chiller was used to circulate the coolant for low temperature operation. In order to understand the efficiency and alignment of the strip tracker modules, a cosmic ray trigger was implemented. From March through July 4.5 million triggers were recorded. This period, referred to as the Sector Test, provided practical experience with the operation of the Tracker, especially safety, data acquisition, power, and cooling systems. This paper describes the performance of the strip system during the Sector Test, which consisted of five distinct periods defined by the coolant temperature. Significant emphasis is placed on comparisons between the data and results from Monte Carlo studies.

The results of the CMS tracker alignment analysis are presented using the data from cosmic tracks, optical survey information, and the laser alignment system at the Tracker Integration Facility at CERN. During several months of operation in the spring and summer of 2007, about five million cosmic track events were collected with a partially active CMS Tracker. This allowed us to perform first alignment of the active silicon modules with the cosmic tracks using three different statistical approaches; validate the survey and laser alignment system performance; and test the stability of Tracker structures under various stresses and temperatures ranging from +15 °C to −15 °C. Comparison with simulation shows that the achieved alignment precision in the barrel part of the tracker leads to residual distributions similar to those obtained with a random misalignment of 50 (80) μm RMS in the outer (inner) part of the barrel.

We present new results on the centrality and rapidity dependence and on azimuthal anisotropies of particle production in Pb+Pb collisions at 158 GeV per nucleon.

Abstract Performance of single-sided DC-coupled silicon strip detectors is studied in the CERN H2 test beam. A great emphasis is put on the calibration of the detector response as well as on the geometric alignment of the detector planes. Performance results are presented for different angles of incidence for the particles.

The reaction K+p→Δ++(1236)+ anything is studied at beam momenta 8.2 and 16 GeV/c and compared with other Δ++ producing reactions. We find that the low-mass Δ++π− enhancement affects the shapes of Δ++ inclusive distributions. The triple-Regge formula is found to be consistent with the data. Dual properties of this formula are successfully tested.

Results are presented on the production of K0, K∗+(892) and π± in the interaction K+p → K0 + π± + anything at 8.2 and 16 GeV/c. The π± forward and backward dσdx distributions are of the form exp (−Ax). It is shown that the forward and backward values of A in a quark-quark rest frame change after subtraction of the contributions due to the resonances produced. A comparison is made of dσdx inclusive cross sections for K0's and K∗+(892) with the predictions of a quark model in the fragmentation region. The experimental cross section matches the theoretical predictions for K0's but disagree with those for K∗+(892).

We present new results of the CERN experiment NA52 on the centrality dependence of π±, K±, p, d, and production yields near zero transverse momentum and at several rapidities, from 64% to 4% of the total Pb + Pb cross section. Baryon yields increase nearly linearly and K± yields faster than linearly with the number of participating nucleons Np. The antibaryon yields increase less than linearly with Np, indicating absorption. The centrality and rapidity dependence of the π−/π+ ratio indicates Coulomb interaction of the pions with the projectile spectator protons. Within the framework of a coalescence model the radius of the particle source has been estimated from the ratios d/p2 and /2. The source radii are similar for matter and antimatter and are found to increase with ∼ Np0.30−0.36.

The total punchthrough probability of showers produced by negatively charged pions of momenta 30, 40, 50, 75, 100, 200 and 300 GeV/c, has been measured in the RD5 experiment at CERN using a toroidal spectrometer. The range of the measurement extends to 5.3 m of equivalent iron. Our results have been obtained by two different analysis methods and are compared with the resutls of a previous experiment.

Abstract Single layer honeycomb strip chambers have been constructed for the tracking calorimeter TRACAL. This detector is a component of the RD5 experimental test setup at CERN, where aspects of muon detection in LHC conditions are studied. The construction of the chambers is described and the excellent spatial resolution obtained from strip signals (σ

The NA52 experiment searched for long-lived charged strangelets in 158 A GeV/c Pb+Pb collisions at CERN SPS. We collected 1013 Pb+Pb interactions looking for negatively charged strangelets and 3 × 1011 Pb+Pb interactions for positively charged ones. No evidence for the production of strangelets has been observed. The upper strangelet production limits are discussed. Besides the strangelet searches NA52 was able to identify particles and anti-particles over a wide range in rapidity. Results of the invariant differential particle production cross sections including fragments up to carbon and 5 are presented.

Inelastic nuclear collisions of hadrons incident on silicon sensors can generate secondary highly ionising particles (HIPs) and deposit as much energy within the sensor bulk as several hundred minimum ionising particles. The large signals generated by these ‘HIP events’ can momentarily saturate the APV25 front-end readout chip for the silicon strip tracker (SST) sub-detector of the compact muon solenoid (CMS) experiment, resulting in deadtime in the detector readout system. This paper presents studies of this phenomenon through simulation, laboratory measurements and dedicated beam tests. A proposed change to a front-end component to reduce the APV25 sensitivity to HIP events is also examined. The results are used to infer the expected effect on the performance of the CMS SST at the future large hadron collider. The induced inefficiencies are at the percent level and will have a negligible effect on the physics performance of the SST.

We present results on the analysis of the quasi three-body reaction K+p → K+π−N∗++ obtained from bubble chamber exposures at 5 GeV/c incident K+ momentum. We have applied a method of analysis based on the study of the longitudinal phase space plot recently proposed by Van Hove. Evidence for the existence of π− mesons with a four-momentum transfer peaked at small values is shown. (Events contributing to this peak correspond to the cross section of about 80 μb.) The difficulties in explaining this result in terms of the double-particle exchange model are discussed.

We present the data on the Λ(Σ) events produced in final states of K+p interactions at 8.25 GeV/c. Cross sections for Yo production are given for most final states obtained in this experiment, and the results at other energies are listed for comparison. No significant enhancement is seen in the Yo N mass distributions while there is some indication of the production of Y∗ (1385) and N∗ (1236) in the Λπ and Nπ systems respectively. An attempt at the description of the reaction K+p→Λpp in terms of a five-point Veneziano amplitude is also included.

The experiments at the planned 14 TeV proton-proton collider LHC will need a good identification and measurement of muons with energies of up to about 800 GeV. The production of electromagnetic secondaries by muons of energy from 10 to 300 GeV has been measured at the RD5 experiment at CERN using various detector types proposed for LHC experiments. It is demonstrated that the detectors can recognize the presence of individual hits from em secondaries, and that the muon measurement would be seriously compromised if these hits are not suppressed.

The NA52 experiment searches for long-lived charged strangelets in 158 A GeV c-1 Pb + Pb collisions at CERN SPS. The experiment is able to identify single particles coming from the collisions at pt = 0. We collected 1013 Pb + Pb interactions looking for negatively charged strangelets and 3 × 1011 Pb + Pb interactions for positively charged ones. No evidence for the production of strangelets has been observed. We present here resulting experimental differential and total upper production limits.

Inclusive production of ϱ0,K *±(892), andf is studied in $$\bar p$$ p interactions at 12 GeV/c. The inclusive cross sections for ϱ0,K *±(892), andf are found to be 6.7±0.3 mb, 1.0±0.2 mb, and 1.4±0.3 mb, respectively. The differential cross sections are presented as a function of c.m. rapidity, Feynmanx and square of the transverse momentump 2 . Comparison with the correspondingpp data shows some interesting differences which can be attributed to the $$\bar p$$ p annihilation. The results are compared with the predictions of the quark fusion model.

Nuclear matter is expected to undergo a phase transition to quark matter in ultrarelativistic heavy-ion collisions, possibly showing up as a discontinuity in the impact parameter dependence of relevant observables. Following this expectation, we have investigated the impact parameter dependence of the invariant yields of K±, p, d, and in the range ~ 2 - 12 fm in fixed-target Pb+Pb collisions at 158 GeV/nucleon incident energy at the CERN SPS. The particles have been measured near zero transverse momentum and in the rapidity range y = 3.1 - 4.4. In addition, the centrality dependence of the baryon chemical potential, the effective temperature and the size of the particle emitting source at freeze-out were studied. No dramatic change in the distribution of any of these variables is observed as a function of the impact parameter. The same is found for the particle yields, with the exception of the yield of charged kaons per number of nucleons participating in the collision (Np), where there is an indication of a threshold behaviour at Np~80.

The inclusive reaction K+p → K0 + X is studied at 5, 8.2 and 16 GeV/c. The energy dependence and the shapes of inclusive spectra in the central region are found to be consistent with double-Regge expansion. With the values obtained for the parameters of the Regge expansion, prediction are made for the behaviour of the cross section at higher energies.

We report on test beam results obtained with a 32.5 cm2 microstrip detector processed on an n-type 380 μm thick magnetic Czochralski (MCZ) grown silicon substrate with 1200 Ωcm effective resistivity. The full depletion voltage of the as-processed detector was 420 V with a leakage current of 2 μA. The AC coupled detector had 1024 p+ strips, 10 μm by width and 6.154 cm by length with a pitch of 50 μm. The detector was irradiated with 10 MeV protons to 1.6×1014 1 MeV neutron equivalent fluence and annealed for 345 days at room temperature. The post-irradiation full depletion voltage of the detector was 225 V. The leakage current at the full depletion measured at −10 °C was 261 μA. The beam tests were carried out at the CERN H2 area using a Silicon Beam Telescope, which consists of pairs of horizontal and vertical position sensitive silicon detectors. This telescope determines the tracks of incoming particles and hence provides a reference measurement for the detector characterization. In the beam test an average signal to noise ratio of 3 with a spatial resolution of 20 μm and a particle detection efficiency of 36% were measured. These results show that the MCZ device detected particles, which encourages further investigations of MCZ silicon as a detector material. The poor performance of the MCZ detector may be explained by the problems observed in the reference telescope.

The NA52 experiment at CERN has investigated lead-lead collisions at 158 A GeV/c and searched for long-lived strange quark matter droplets, so-called strangelets, with a unique signature of a high mass-to-charge ratio. This ratio was measured in a focusing spectrometer equipped with a time-of-flight system. A total of 3×1011 Pb + Pb interactions at positive and 1013 at negative spectrometer polarities have been recorded. No strangelet has been observed, which sets experimental upper limits (90% CL) for the strangelet production at 3×10-9 per interaction for positively charged and at 2×10-10 per interaction for negatively charged strangelets.

The NA52 collaboration searches for a discontinuous behaviour of charged kaons produced in Pb+Pb collisions at 158 A GeV as a function of the impact parameter, which could reveal a hadron to quark-gluon plasma (QGP) phase transition. The K+ yield is found to grow proportional to the number of participating ('wounded') nucleons N, above N=100. Previous NA52 data agree with the above finding and show a discontinuous behaviour in the kaon centrality dependence near N=100, marking the onset of strangeness enhancement -over e.g. p+A data at the same \sqrt{s}- in a chemically equilibrated phase.

We have tested the detection performance of a strip detector processed on silicon wafer grown by magnetic Czochralski (MCZ) method. This is the first time a full size Czochralski detector has been tested in a beam, although the advantages of CZ silicon have been known before. Prior to test beam measurements, the electrical characteristics of the Czochralski silicon detectors were found to be appropriate for particle detection. Using the Helsinki Silicon Beam telescope at CERN H2 test beam, the performance of the Czochralski silicon detector was shown to be comparable with the existing silicon strip detectors.

Abstract We have analyzed the reaction K + p → K + π − N ∗++ at 5 GeV/ c K + primary momentum, from the point of view of the double-peripheral model. The distributions of four-momentum transfers t′ pN ∗ and t′ KK (t′=t t t min ) have been studied as functions of the masses of the N ∗++ π − and K + π − systems. We have found that the observed correlations cannot be explained adequately by the present version of the Chan-oskiewicz-Allison model. The disagreement is particularly striking for the low N ∗++ π − mass region, where the data show peripheral production of the N ∗++ , contrary to the prediction of the model. The implications of the results for the double peripheral model are discussed.

We present a cosmic rack, the FinnCRack. This device is a silicon strip detector-based telescope that measures tracks of cosmic particles. The FinnCRack is constructed using components of the Tracker Outer Barrel (TOB) of the CMS experiment at the CERN LHC. The device is part of the TOB integration and verification effort together with its sister telescope, the CERN CRack. Both CRacks mimick a six degree slice of the TOB barrel structure. The FinnCRack is intended to (a) serve as a platform for TOB software development, both analysis and online software such as run control; (b) be used for noise and cluster shape studies; (c) act as a reference tracker in detector studies; and (d) provide a testbed for track-based alignment testing and development. The construction and setup of the FinnCRack have been documented in detail—the entire chain from connecting cables to physics data analysis—and the operation guide was tested in practice. Both these actions serve the purpose of training and attracting future HEP students. We also showed that we were able to measure cosmic muon tracks.

We have searched for strange matter particles, so-called strangelets, in PbPb interactions at plab = 157.7 GeV/c per nucleon. The NA52 apparatus is also ideally suited to measure production yields and rapidity distributions of π±, K±, p, p, d, d, … near 0° production angle. Some preliminary results are shown.

The average charged particle multiplicity, 〈nch(MX2)〉, in the reaction K+p→KoX++ is studied as a function of the mass squared, MX2, of the recoil system X and also as a function of the Ko transverse momentum, pT, at incident momenta of 5.0, 8.2 and 16.0 GeV/c. The complete data samples yield distributions which are not independent of c.m. energy squared, s, They exhibit a linear dependence on log (MX2X/Mo2)[Mo2=1 GeV2] with a change in slope occurring for MX2≈s/2, and do not agree with the corresponding distributions of 〈nch〉 as a function of s for K+ p inelastic scattering. Sub-samples of the data for which Ko production via beam fragmentation, central production and target fragmentation are expected to be the dominant mechanisms show that, within error, the distribution of 〈nch(MX2)〉 versus MX2 is independent of incident momentum for each sub-sample separately. In particular in the beam fragmentation region the 〈nch(MX2)〉 versus MX2 distribution agrees rather well with that of 〈nch〉 versus s for inelastic K+p interactions. The latter result agrees with recent results on the reactions pp → pX and π−p → pX in the NAL energy range. Evidence is presented for the presence of different production mechanisms in these separate regions.

The reaction K+p → Δ++(1236) + anything is studied at beam momentum 8.2 GeV/c. The spin density matrix of the Δ++ shows than one-pion exchange is dominant at low-momentum transfer. The total and topological K+π− cross sections have been determined by a Chew-Low extrapolation in the cm energy range from threshold to 1.8 GeV, using three different methods of extrapolation.

Besides the dedicated search for strangelets NA52 measures light (anti)particle and (anti)nuclei production over a wide range of rapidity. Compared to previous runs the statistics has been increased in the 1998 run by more than one order of magnitude for negatively charged objects at different spectrometer rigidities. At a rigidity of −20 GeV/c we measured 106 p, 103 d and one 3He without any centrality requirements. These preliminary results together with previous measurements near central rapidity are discussed in the framework of a thermodynamical and a coalescence model.

A test of factorization is made using data on the inclusive reactions pp → Λ + X++ at 19 GeV/c and K+p → Λ + X++ at 16 GeV/c incident momentum. In these reactions Λ production occurs dominantly via proton fragmentation and, in addition, abc is exotic in both cases. The comparison of the structure functions on the Chew-Low plot shows that the factorization hypothesis is satisfied at the ∼10% level when the momentum transfer from the proton to the Λ is less than 1 (GeV/c)2.

In a study of 12 GeV/c pp interactions in the CERN 2 m HBC, we have searched for a narrow K3π state. Contrary to an investigation of 12 GeV/c pp interactions in the CERN BEBC, we find no support for such a state.

We have searched for strange matter particles, so‐called strangelets, in Pb‐Pb interactions at plab=157.7 GeV/c per nucleon. The NA52 apparatus is also ideally suited to measure production yields and rapidity distribution of π±, K±, p, p̄, d, d̄, ... near 00 production angle. Some preliminary results are shown.

The impact parameter dependence of π±, K±, p, p, d and d yields produced in fixed target lead+lead collisions at 158 A GeV incident energy is presented. The particle yields are measured near zero transverse momentum and in the forward rapidity region.

We have developed a novel data acquisition system for measuring tracking parameters of a silicon detector in a particle beam. The system is based on a commercial Analog-to-Digital VME module and a PC Linux based Data Acquisition System. This DAQ is realized with C++ code using object-oriented techniques. Track parameters for the beam particles were reconstructed using off-line analysis code and automatic detector position alignment algorithm. The new DAQ was used to test novel Czochralski type silicon detectors. The important silicon detector parameters, including signal size distributions and signal to noise distributions, were successfully extracted from the detector under study. The efficiency of the detector was measured to be 95 %, the resolution about 10 micrometers, and the signal to noise ratio about 10.

Longitudinal phase space plots in arbitrary frames are considered. In any frame moving with constant velocity relative to the target or beam system, these plots, when scaled by the incident momentum, approach regular hypertetrahedrons when s increases. Plots in target and beam system longitudinal momenta are useful for investigating beam and target fragmentation, respectively.

The momentum and angular distributions of punchthrough muons have been measured after a 10 λ calorimeter using an iron toroid magnet with 1.5 T as spectrometer. The calorimeter was inside a variable magnetic field of 0 to 3 T. The incident momentum of the π− beam ranged from 20 to 300 GeV/c. Measurements were also done at some beam momenta for π+, K+ and p. The results are compared with Monte Carlo predictions. A parameterization for the momentum spectrum of punchthrough muons was derived from the data.

We are presenting new results on K± and π± production in minimum bias lead-lead collisions at 158 A GeV/c. The measurements were performed at zero degree production angle and for a wide rapidity range. The analysis method used the full particle identification capabilities (time of flight, Cerenkov counters and hadronic calorimeter) of the spectrometer. We show K/π and π−/π+ ratios as a function of rapidity, as well as invariant particle production cross sections. As a particularity we observe near projectile rapidity an enhancement in the number of π− with respect to π+.

We present recent results of the NA52 experiment on the strangelet search and on particle, antiparticle, light nuclei and antinuclei production in minimum bias Pb + Pb collisions at 158 A GeV and zero production angle. Upper limits for the production of strangelets are given and one candidate found using less stringent lifetime cuts is discussed. The rapidity dependence of K+(K−), p(), d(), t and as well as first results on 4He, 6Li and 7Be at forward rapidities are presented. First results on the centrality dependence of the /p ratio are reported. Within the framework of a thermodynamical and a coalescence model, the temperature, the baryon- and strangeness-chemical potentials and the radius of the particle source at midrapidity have been estimated.

We present results of the CERN experiment NA52 which measures Pb+Pb collisions at 158 A GeV.The topics we address are: 1. strangelet search, 2. nuclei and antinuclei production and 3. strangeness production.No strangelets have been found.We set upper limits which stretch down to the minimal values of ∼ 2 10 -10 for negatively and 3 10 -9 for positively charged strangelets.We observed 5 3 He near midrapidity.Nuclei and antinuclei cross sections suggest production mainly through coalescence, out of a thermalised particle source, at the time of the thermal freeze-out as witnessed by their temperature of 100-120 MeV.Charged kaons per participant nucleon (N p ) show an onset of enhancement followed by saturation at N p ∼ 80, corresponding approximately to an initial energy density of i ∼ 1.3 GeV/fm 3 .This onset may be connected to the onset of the QCD phase transition.

The NA52 collaboration searches for a discontinuous behaviour of charged kaons produced in Pb+Pb collisions at 158 A GeV as a function of the impact parameter, which could reveal a hadron to quark-gluon plasma (QGP) phase transition. The K+ yield is found to grow proportional to the number of participating ('wounded') nucleons N, above N=100. Previous NA52 data agree with the above finding and show a discontinuous behaviour in the kaon centrality dependence near N=100, marking the onset of strangeness enhancement -over e.g. p+A data at the same \sqrt{s}- in a chemically equilibrated phase.

We propose a way to describe three body final state reactions by one essential invariant variable. As an example we discuss the application of the method to the reaction pp → pπ+n.

We present an analysis of the reaction K+p → K0 + anything at incident momenta of 5, 8.2 and 16 GeV/c in terms of the Björken variables gw and x. Assuming dominance of ϱ exchange, we derive the structure function F2(x, y) which is found similar to the one obtained in deep inelastic electroproduction.

The coherent reactions pd → pdπ+π-, pd → pdπ+π-π0 and pd → ndπ+π+π- are studied at 19 GeV/c. In the two first reactions strong production of Δ2+(1236) is observed. Some ρ and ω production is seen in the second reaction. Production of d*0 and d*+ is observed in the first and second reactions respectively. Clear enhancements are seen at 1500 and 1700 MeV in the pπ+π- mass spectrum of the pd → pdπ+π- channel. From an analysis of the moments of the decay angular distributions of the pπ+π- system we find that the most important contributions to the 1450 and 1700 MeV structures come from spin 3/2 and spin 5/2 states respectively. We find evidence against s-channel helicity conservation and some evidence against t-channel helicity conservation.

Abstract Data on the density of charged particles in rapidity space for annihilation and non-annihilation pp interactions at 7.3 and 12 GeV/c are reported. It is shown that the central rapidity density for non-annihilation processes is a simple linear function of ln ( s ) from these low energies up to pp collider energies ( s =540 GeV ). Significant differences in density distributions for pp and e−e+ annihilations at comparable energies are found.

Search for the top quark in the UA1 experiment in 1988--89 is discussed and preliminary results are given. The analysis is based on 4.6 pb$^{-1}$ integrated luminosity at the CERN SPS p$\bar {\rm p}$ collider. The properties of isolated muons produced in association with jets are found to be consistent with the predictions of the minimal Standard Model but no signal for the top quark is observed. An upper limit for the production cross section is determined. From this a lower limit of 61 GeV/$c^2$ (95\% CL) is obtained for the mass of the top quark in a statistical analysis of all data. A similar analysis gives a lower limit of 41 GeV/$c^2$ for the mass of a fourth generation quark with charge-1/3 (b$'$ quark). The UA2 experiment has obtained in a similar analysis of electron data corresponding to an integrated luminosity of 7.1 pb$^{-1}$ preliminarily a lower limit of 67 GeV/$c^2$ for the top mass and 53 GeV/$c^2$ for the b$'$ quark mass. The CDF experiment at the Fermilab p$\bar {\rm p}$ collider gives as the result of similar analysis of electron data of integrated luminosity of 4.7 pb$^{-1}$ a preliminary lower limit of 77 GeV/$c^2$ for the mass of the top quark.