Experiments with the CERN SPS hyperon beam

High energy charged hyperons produced in proton collisions at large accelerators have a lifetime long enough to be channelled into beams of particles of appreciable intensity. This has opened up a new domain of research in experimental high energy physics. This article reviews recent works at the CERN SPS using a dedicated charged hyperon beam facility.     

Charmonium production in fixed-target experiments with SPS and LHC beams at CERN

The possibility of measuring cross sections for the production of J/ψ mesons in fixed-target experiments with the proton and ion beams of the Large Hadron Collider (LHC) at CERN (Switzerland) is considered. At the present time, measurements of charmonium production in proton-proton collisions at an energy of 7 TeV have begun at LHC. Previously, the production of J/ψ and ψ′ mesons was studied in the NA38, NA50, and NA60 fixed-target experiments with beams of the CERN synchrotron (SPS) and in the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC, Brookhaven National Laboratory, USA). A normal nuclear absorption of J/ψ mesons in proton-nucleus collisions and an enhanced, anomalous, suppression of the production of charmonium states in central collisions of relativistic nuclei were observed. At the present time, there are no theoretical models that could describe the entire body of experimental data. Measurements over a broad interval of proton and ion energies are required. Measurements of charmonium production using LHC beams with fixed targets in the energy range between the SPS and RHIC energies-a beam of 7-TeV protons (√s = 114.6 GeV) and a beam of 2.75-TeV/nucleon lead ions (√s = 71.8 GeV)-will provide an additional possibility for studying the charmonium-production mechanism. Estimates of the geometric acceptance, luminosity, and counting rate for the production of J/ψ mesons are presented.     

Single diffraction dissociation at the CERN SPS collider

The reaction $\text{p}\text{p}\text{→}\text{p}\text{X}$ was studied at a centre-of-mass energy $\text{s}\text{= 540}\text{GeV}$ by measuring the momentum spectrum of the antiproton. Data are presented in the four-momentum transfer range 05 < ?t < 1.2GeV². The shape of the mass distribution of the system X shows a diffractive component as already observed at lower energies. The differential cross section scales approximately with energy when compared to the ISR data.     

Recent results from CERN SPS experiments and the future heavy ion programme

We describe the important results from the recent experiments using lead beams at the CERN SPS. The results of the WA98 experiment, which has substantial Indian participation along with the photon multiplicity detector is described in some detail. Combining the preliminary results from various experiments looking at different signals of phase transition, one finds enough evidences to suggest that phase transition has taken place in nuclear collisions at the SPS. Future programme of heavy ion physics at the LHC is being greared around the ALICE experiment. This will comprise of detector subsystems capable of studying almost all the signals in the same event. The photon multiplicity detector will be an important component of the ALICE experiment, being a totally Indian contribution to ALICE.     

Kaon interferometry in heavy-ion collisions at the CERN SPS

K⁺K⁺ and K^–K^– correlations from S+Pb collisions at 200 GeV/c per nucleon and K⁺K⁺ correlations from p+Pb collisions at 450 GeV/c per nucleon, are presented as measured by the focusing spectrometer of the NA44 experiment at CERN. Multidimensional fits are performed in order to characterize the kaon-emission volume, which is found to be smaller than the pion-emission volume.     

Search for deconfinement in NA49 at the CERN SPS

Experiment NA49 at the Cern SPS has performed large acceptance measurements of hadron production in pp, pPb, CC, SiSi and PbPb collisions at 40 and 158 A·GeV beam energies. These data allowed a study of particle yields, spectra and correlations as well as event-by-event fluctuations of average event properties of the created hadron system. Results from central PbPb collisions are consistent with the onset of deconfinement during the early stage of the reaction in the lower SPS energy range. A new scaling property of particle production ratios was found which relates collision systems of different size and centrality. Systematics of the evolution of particle production from pp via pPb to PbPb collisions were investigated.     

Search for free quark production at the CERN SPS collider

No experiment has found convincing evidence for free quarks [1, 2]. A possible explanation for this non-observation in accelerator experiments is that their cross-section for interaction with matter is much larger than those of hadrons [3], and hence they are scattered and/or absorbed by material between their production point and the detector. We have examined this possibility by exposing 1/4 mm diameter steel balls near an intersection point of the CERN SPS \(p\bar p\) collider beams. These balls have been subsequently examined for the presence of fractional charge, using the Rutherford Laboratory room temperature magnetic levitation system [4]. None of the 60 balls tested to date shows evidence of fractional charge.     

Kaon decay studies at CERN SPS in the last decades

This review summarizes the kaon experimental results obtained in the last 15 years on the basis of data collected on the SPS in CERN with a participance of JINR physicists. These results contribute essentially into the Standard Model checks and search for its extension, fundamental symmetry violations and low energy strong interactions theory development. A progress in the experimental technique and prospects for the future results are also discussed.     

Search for deconfinement in NA49 at the CERN SPS

Experiment NA49 at the CERN SPS uses a large acceptance detector for a systematic study of particle yields and correlations in nucleus-nucleus, nucleon-nucleus and nucleon-nucleon collisions. Preliminary results for Pb+Pb collisions at 40, 80 and 158 A⋅GeV beam energy shown and compared to measurements at lower and higher energies.     

Quark-gluon plasma signatures in nucleus-nucleus collisions at CERN SPS

Two signatures of the quark-gluon plasma—strangeness ‘enhancement’ and J/ψ ‘suppression’—in nucleus-nucleus collisions at the SPS energies are critically discussed.     

Tests of the OLVE-HERO Calorimeter Prototype at Heavy-Ion Beams at SPS CERN

Physics of Atomic Nuclei - A project of the OLVE-HERO space detector for measurement of the cosmic rays in the range 1012–1016 eV is proposed. It will include a large ionization-neutron 3D...     

Measuring Displaced muon Pairs in Indium-Indium collisions at the CERN SPS

The NA60 experiment at the CERN-SPS studies dimuon production in proton-nucleus and heavy-ion collisions. We report on the effort towards measuring open charm in Indium-Indium collisions. Although work on the final background subtraction procedure is still under way, we can already demonstrate that the detector performance is adequate to separate prompt dimuous from muon pairs originating in distant $D\bar D$ decays.     

20 years of J/\psi suppression at the CERN SPS

J/ suppression was predicted to be a signature of deconfinement and has been extensively studied at the CERN-SPS in proton, light and heavy ion induced reactions. Indeed, proton, O, S and Pb ion beams, at various incident energies, have been used at CERN on different targets, in order to precisely quantify J/ production as a function of both the colliding nuclei and the centrality of the collision itself. This paper reviews the results obtained so far with a critical discussion of the experimental conditions and successive improvements implemented for the various data samples. It makes a tentative summary of what has been learned on the subject, from the experimental point of view, in the SPS energy range.Arrival of the final proofs: 7 July 2005PACS: 25.75.-q, 25.75.Nq, 13.20.Gd     

On energy densities reached in heavy-ion collisions at the CERN SPS

We present a few estimates of energy densities reached in heavy-ion collisions at the CERN SPS. The estimates are based on data and models of proton-nucleus and nucleus-nucleus interactions. In all of these estimates the maximum energy density in central Pb+Pb interactions is larger than the critical energy density GeV/fm³ following from lattice gauge theory computations. In estimates which we consider as realistic the maximum energy density is about . In this way our analysis gives some support to claims that deconfined matter has been produced at the CERN SPS. Any definite statement requires a deeper understanding of formation times of partons and hadrons in nuclear collisions. We also compare our results with implicit energy estimates contained in earlier models of anomalous suppression in nuclear collisions. Received: 3 February 2003 / Revised version: 5 March 2003 / Published online: 5 May 2003     

Study of neutrino-indiced dimuon events in gargamelle at CERN SPS

This letter reports a study of 117 opposite-sign and 41 like-sign dimuons, in a wide-band neutrino exposure of Gargamelle at CERN SPS. No signal is found in the μ^?μ^? channel. The μ^?μ⁺ channel is found to be dominated by D-meson production and decay. There is evidence in these events for missing energy which may be interpreted as an unseen neutrino. The V⁰ multiplicities, K⁰/event=0.53_?0.20^+0.25and Λ/event=0.03_?0.04^+0.06 show only evidence for charmed meson production. Information on the D-meson fragmentation function is presented. In a specific model, a rate $\text{σ}\text{(μ}{}^{\mathrm{?}}\text{μ}{}^{\mathrm{+}}\text{)}\text{σ(μ}{}^{\mathrm{?}}\text{)}\text{=(0.72±0.14×10}{}^{\mathrm{?2}}$ is found, independent of the energy. An investigation of these events for visible D-decays sets a limit on the life-time τ_D<0.8 ×10^?12s at 90% C.L.     

Signatures of the deconfinement transition in nucleus-nucleus collisions at the CERN SPS

The energy dependence of hadron production in relativistic nucleus-nucleus collisions reveals anomalies-kink, horn, and step. They have been predicted as the signals of the deconfinement phase transition and observed recently by the NA49 Collaboration in Pb + Pb collisions at the CERN SPS. This indicates the onset of deconfinement in nucleus-nucleus collisions at about 30 A GeV. The text was submitted by the author in English.     

New results from fluctuation analysis in NA49 at the CERN SPS

The exploration of the phase diagram of strongly interacting matter, particularly the study of the phase transition from hadronic to partonic matter and the search for a hypothetical critical endpoint of the first order transition line, is one of the most challenging tasks in present heavy ion physics. New results on chemical (particle ratio), transverse momentum, multiplicity and azimuthal angle fluctuations are presented. We also discuss their connection to the onset of deconfinement and to the critical endpoint.