Ferenc Siklér

Measurements of charged pion and kaon production in central Pb+Pb collisions at 40, 80, and 158 A GeV are presented. These are compared with data at lower and higher energies as well as with results from p+p interactions. The mean pion multiplicity per wounded nucleon increases approximately linearly with s1/4NN with a change of slope starting in the region 15–40 A GeV. The change from pion suppression with respect to p+p interactions, as observed at low collision energies, to pion enhancement at high energies occurs at about 40A GeV. A nonmonotonic energy dependence of the ratio of K+ to π+ yields is observed, with a maximum close to 40A GeV and an indication of a nearly constant value at higher energies. The measured dependences may be related to an increase of the entropy production and a decrease of the strangeness to entropy ratio in central Pb+Pb collisions in the low SPS energy range, which is consistent with the hypothesis that a transient state of deconfined matter is created above these energies. Other interpretations of the data are also discussed.Received 6 May 2002DOI:https://doi.org/10.1103/PhysRevC.66.054902©2002 American Physical Society

Results on charged pion and kaon production in central Pb+Pb collisions at 20A and 30A GeV are presented and compared to data at lower and higher energies. A rapid change of the energy dependence is observed around 30A GeV for the yields of pions and kaons as well as for the shape of the transverse mass spectra. The change is compatible with the prediction that the threshold for production of a state of deconfined matter at the early stage of the collisions is located at low SPS energies.

Directed and elliptic flow measurements for charged pions and protons are reported as a function of transverse momentum, rapidity, and centrality for 40 and 158A GeV Pb + Pb collisions as recorded by the NA49 detector. Both the standard method of correlating particles with an event plane, and the cumulant method of studying multiparticle correlations are used. In the standard method the directed flow is corrected for conservation of momentum. In the cumulant method elliptic flow is reconstructed from genuine 4, 6, and 8-particle correlations, showing the first unequivocal evidence for collective motion in A+A collisions at SPS energies.

Results of resonance searches in the Xi(-)pi(-), Xi(-)pi(+), Xi;(+)pi(-), and Xi;(+)pi(+) invariant mass spectra in proton-proton collisions at sqrt[s]=17.2 GeV are presented. Evidence is shown for the existence of a narrow Xi(-)pi(-) baryon resonance with mass of 1.862+/-0.002 GeV/c(2) and width below the detector resolution of about 0.018 GeV/c(2). The significance is estimated to be above 4.2sigma. This state is a candidate for the hypothetical exotic Xi(--)(3/2) baryon with S=-2, I=3 / 2, and a quark content of (dsdsū). At the same mass, a peak is observed in the Xi(-)pi(+) spectrum which is a candidate for the Xi(0)(3/2) member of this isospin quartet with a quark content of (dsus[-]d). The corresponding antibaryon spectra also show enhancements at the same invariant mass.

Net proton and negative hadron spectra for central Pb+Pb collisions at 158 GeV per nucleon at the CERN Super Proton Synchrotron were measured and compared to spectra from lighter systems. Net baryon distributions were derived from those of net protons. Stopping (rapidity shift with respect to the beam) and mean transverse momentum ⟨pT⟩ of net baryons increase with system size. The rapidity density of negative hadrons scales with the number of participant nucleons for nuclear collisions, whereas their ⟨pT⟩ is independent of system size. The ⟨pT⟩ dependence upon particle mass and system size is consistent with larger transverse flow velocity at midrapidity for Pb+Pb compared to S+S central collisions.Received 22 October 1998DOI:https://doi.org/10.1103/PhysRevLett.82.2471©1999 American Physical Society

This report presents the capabilities of the CMS experiment to explore the rich heavy-ion physics programme offered by the CERN Large Hadron Collider (LHC). The collisions of lead nuclei at energies , will probe quark and gluon matter at unprecedented values of energy density. The prime goal of this research is to study the fundamental theory of the strong interaction — Quantum Chromodynamics (QCD) — in extreme conditions of temperature, density and parton momentum fraction (low-x).

The directed and elliptic flow of protons and charged pions has been observed from the semicentral collisions of a 158 GeV͞nucleon Pb beam with a Pb target.The rapidity and transverse momentum dependence of the flow has been measured.The directed flow of the pions is opposite to that of the protons but both exhibit negative flow at low p t .The elliptic flow of both is fairly independent of rapidity but rises with p t .

φ meson production is studied by the NA49 Collaboration in central Pb + Pb collisions at 20A, 30A, 40A, 80A, and 158A GeV beam energy.The data are compared with measurements at lower and higher energies and with microscopic and thermal models.The energy dependence of yields and spectral distributions is compatible with the assumption that partonic degrees of freedom set in at low SPS energies.

Proton-nucleus (p+A) collisions have long been recognized as a crucial component of the physics programme with nuclear beams at high energies, in particular for their reference role to interpret and understand nucleus-nucleus data as well as for their potential to elucidate the partonic structure of matter at low parton fractional momenta (small-x). Here, we summarize the main motivations that make a proton-nucleus run a decisive ingredient for a successful heavy-ion programme at the Large Hadron Collider (LHC) and we present unique scientific opportunities arising from these collisions. We also review the status of ongoing discussions about operation plans for the p+A mode at the LHC.

Yields and phase space distributions of φ-mesons emitted from p+p (minimum bias trigger), p+Pb (at various centralities) and central Pb+Pb collisions are reported (Ebeam=158AGeV). The decay φ→K+K− was used for identification. The φ/π ratio is found to increase by a factor of 3.0±0.7 from inelastic p+p to central Pb+Pb. Significant enhancement in this ratio is also observed in subclasses of p+p events (characterized by high charged-particle multiplicity) as well as in the forward hemisphere of central p+Pb collisions. In Pb+Pb no shift or significant broadening of the φ-peak is seen.

We present first data on event-by-event fluctuations in the average transverse momentum of charged particles produced in Pb+Pb collisions at the CERN SPS. This measurement provides previously unavailable information allowing sensitive tests of microscopic and thermodynamic collision models and to search for fluctuations expected to occur in the vicinity of the predicted QCD phase transition. We find that the observed variance of the event-by-event average transverse momentum is consistent with independent particle production modified by the known two-particle correlations due to quantum statistics and final state interactions and folded with the resolution of the NA49 apparatus. For two specific models of non-statistical fluctuations in transverse momentum limits are derived in terms of fluctuation amplitude. We show that a significant part of the parameter space for a model of isospin fluctuations predicted as a consequence of chiral symmetry restoration in a non-equilibrium scenario is excluded by our measurement.

Measurements of the forward and the transverse energy in 158 GeV per nucleon $^{208}\mathrm{Pb}$ + Pb collisions are presented. A total transverse energy of about 1 TeV is created in central collisions. An energy density of about 3 GeV/${\mathrm{fm}}^{3}$ is estimated for near head-on collisions. Only statistical fluctuations are seen in the ratio of electromagnetic to hadronic transverse energy.

The transverse mass m t distributions for antiprotons are measured at midrapidity for minimum bias Pb+Pb collisions at 158A GeV and for central Pb+Pb collisions at 20A, 30A, 40A, and 80A GeV beam energies in the fixed target experiment NA49 at the CERN SPS.The rapidity density dn/dy, inverse slope parameter T, and mean transverse mass m t derived from the m t distributions are studied as a function of the incident energy and the collision centrality and compared to the relevant data on proton production.The shapes of the m t distributions of p and p are very similar.The ratios of the particle yields, p/p and ¯ / p, are also analyzed.The p/p ratio exhibits an increase with decreasing centrality and a steep rise with increasing beam energy.The ¯ / p ratio increases beyond unity with decreasing beam energy.

The transverse mass m t distributions for deuterons and protons are measured in Pb+ Pb reactions near midrapidity and in the range 0 Ͻ m t -m Ͻ 1.0 ͑1.5͒ GeV/ c 2 for minimum bias collisions at 158A GeV and for central collisions at 40 and 80 A GeV beam energies.The rapidity density dn / dy, inverse slope parameter T and mean transverse mass ͗m t ͘ derived from m t distributions as well as the coalescence parameter B 2 are studied as a function of the incident energy and the collision centrality.The deuteron m t spectra are significantly harder than those of protons, especially in central collisions.The coalescence factor B 2 shows three systematic trends.First, it decreases strongly with increasing centrality reflecting an enlargement of the deuteron coalescence volume in central Pb+ Pb collisions.Second, it increases with m t .Finally, B 2 shows an increase with decreasing incident beam energy even within the SPS energy range.The results are discussed and compared to the predictions of models that include the collective expansion of the source created in Pb+ Pb collisions.

With its large acceptance and particle identification coverage the NA49 experiment (Fig. 1) can study hadron production in a wide range of high energy reactions [1]. Originally aimed at examining central Pb+Pb collisions for signatures of quark-gluon plasma formation, the scope of the experiment has been enhanced with a systematic study of impact parameter and projectile size dependence, as well as the inclusion of the more elementary p+p and p+A interactions. The question is: are predicted signals of the quark-gluon plasma observed and are there discontinuities which would support the concept of hadronic phase transition?

Results on $\Lambda$, $\bar{\Lambda}}$, $\Xi^{-}$, and $\bar{\Xi}^{+}$ production in central Pb+Pb reactions at 20A, 30A, 40A, 80A, and 158A GeV are presented. The energy dependence of transverse mass spectra, rapidity spectra, and multiplicities is discussed. Comparisons to string hadronic models (UrQMD and HSD) and statistical hadron gas models are shown. While the latter provide a reasonable description of all particle yields, the first class of models fails to match the $\Xi^{-}$, and $\bar{\Xi}^{+}$ multiplicities.

The production of charged pions in minimum bias p+C interactions is studied using a sample of 377000 inelastic events obtained with the NA49 detector at the CERN SPS at 158 GeV/c beam momentum. The data cover a phase space area ranging from 0 to 1.8 GeV/c in transverse momentum and from -0.1 to 0.5 in Feynman xF. Inclusive invariant cross sections are given on a grid of 270 bins per charge, thus offering for the first time a dense coverage of the projectile hemisphere and of the cross-over region into the target fragmentation zone.

Production of $d$, $t$, and $^3$He nuclei in central Pb+Pb interactions was studied at five collision energies ($\sqrt{s_{NN}}=$ 6.3, 7.6, 8.8, 12.3, and 17.3 GeV) with the NA49 detector at the CERN SPS. Transverse momentum spectra, rapidity distributions, and particle ratios were measured. Yields are compared to predictions of statistical models. Phase-space distributions of light nuclei are discussed and compared to those of protons in the context of a coalescence approach. The coalescence parameters $B_2$ and $B_3$, as well as coalescence radii for $d$ and $^3$He were determined as a function of transverse mass at all energies.

The European Particle Physics Strategy Update (EPPSU) process takes a bottom-up approach, whereby the community is first invited to submit proposals (also called inputs) for projects that it would like to see realised in the near-term, mid-term and longer-term future. National inputs as well as inputs from National Laboratories are also an important element of the process. All these inputs are then reviewed by the Physics Preparatory Group (PPG), whose role is to organize a Symposium around the submitted ideas and to prepare a community discussion on the importance and merits of the various proposals. The results of these discussions are then concisely summarised in this Briefing Book, prepared by the Conveners, assisted by Scientific Secretaries, and with further contributions provided by the Contributors listed on the title page. This constitutes the basis for the considerations of the European Strategy Group (ESG), consisting of scientific delegates from CERN Member States, Associate Member States, directors of major European laboratories, representatives of various European organizations as well as invitees from outside the European Community. The ESG has the mission to formulate the European Strategy Update for the consideration and approval of the CERN Council.

Preliminary inclusive spectra of negative hadrons, net protons and neutral strange particles are presented, measured by the NA49 experiment in central Pb+Pb collisions at 158 GeV per nucleon. Comparison of their yields with those from the lighter S+S system suggests that the yields scale approximately with the number of participating nucleons.

Production of Lambda and Antilambda hyperons was measured in central Pb-Pb collisions at 40, 80, and 158 A$\cdot$GeV beam energy on a fixed target. Transverse mass spectra and rapidity distributions are given for all three energies. The $\Lambda/\pi$ ratio at mid-rapidity and in full phase space shows a pronounced maximum between the highest AGS and 40 A$\cdot$GeV SPS energies, whereas the $\bar{\Lambda}/\pi$ ratio exhibits a monotonic increase.

Results are presented on event-by-event fluctuations in transverse momentum of charged particles, produced at forward rapidities in p+p, C+C, Si+Si and Pb+Pb collisions at 158 AGeV. Three different characteristics are discussed: the average transverse momentum of the event, the Phi_pT fluctuation measure and two-particle transverse momentum correlations. In the kinematic region explored, the dynamical fluctuations are found to be small. However, a significant system size dependence of Phi_pT is observed, with the largest value measured in peripheral Pb+Pb interactions. The data are compared with predictions of several models.

The yields of (anti)protons were measured by the NA49 Collaboration in centrality-selected Pb $+$ Pb collisions at $40A$ and $158A$ GeV. Particle identification was obtained in the laboratory momentum range from 5 to 63 GeV$/c$ by measuring the energy loss $dE/dx$ in the time projection chamber detector gas. The corresponding rapidity coverage extends 1.6 units from midrapidity into the forward hemisphere. Transverse-mass spectra, the rapidity dependences of the average transverse mass, and rapidity density distributions were studied as a function of collision centrality. The values of the average transverse mass as well as the midrapidity yields of protons normalized to the number of wounded nucleons show only modest centrality dependences. In contrast, the shape of the rapidity distribution changes significantly with collision centrality, especially at $40A$ GeV. The experimental results are compared to calculations of the hadron-string dynamics and the ultrarelativistic quantum-molecular-dynamics transport models.

We look for fluctuations expected for the QCD critical point using an intermittency analysis in the transverse momentum phase space of protons produced around midrapidity in the 12.5 % most central C+C, Si+Si and Pb+Pb collisions at the maximum SPS energy of 158A GeV. We find evidence of power-law fluctuations for the Si+Si data. The fitted power-law exponent $$\phi _{2} = 0.96^{+0.38}_{-0.25}\text { (stat.)}$$ $$\pm $$ $$0.16\text { (syst.)}$$ is consistent with the value expected for critical fluctuations. Power-law fluctuations had previously also been observed in low-mass $$\pi ^+ \pi ^-$$ pairs in the same Si+Si collisions.

We present the first measurement of fluctuations from event to event in the production of strange particles in collisions of heavy nuclei. The ratio of charged kaons to charged pions is determined for individual central Pb+Pb collisions. After accounting for the fluctuations due to detector resolution and finite number statistics we derive an upper limit on genuine nonstatistical fluctuations, which could be related to a first- or second-order QCD phase transition. Such fluctuations are shown to be very small.

Results are presented on Omega production in central Pb+Pb collisions at 40 and 158 AGeV beam energy. Given are transverse-mass spectra, rapidity distributions, and total yields for the sum Omega+Antiomega at 40 AGeV and for Omega and Antiomega separately at 158 AGeV. The yields are strongly under-predicted by the string-hadronic UrQMD model and are in better agreement with predictions from a hadron gas models.

The energy dependence of hadron production in central Pb+Pb collisions is presented and discussed. In particular, midrapidity $m_T$-spectra for $\pi^-$, $K^-$, $K^+$, $p$, $\bar{p}$, $d$, $\phi$, $\Lambda$ and $\bar{\Lambda}$ at 40, 80 and 158 $A$GeV are shown. In addition $\Xi$ and $\Omega$ spectra are available at 158 $A$GeV. The spectra allow to determine the thermal freeze-out temperature $T$ and the transverse flow velocity $\beta_T$ at the three energies. We do not observe a significant energy dependence of these parameters; furthermore there is no indication of early thermal freeze-out of $\Xi$ and $\Omega$ at 158 $A$GeV. Rapidity spectra for $\pi^-$, $K^-$, $K^+$ and $\phi$ at 40, 80 and 158 $A$GeV are shown, as well as first results on $\Omega$ rapidity distributions at 158 $A$GeV. The chemical freeze-out parameters $T$ and $\mu_B$ at the three energies are determined from the total yields. The parameters are close to the expected phase boundary in the SPS energy range and above. Using the total yields of kaons and lambdas, the energy dependence of the strangeness to pion ratio is discussed. A maximum in this ratio is found at 40 $A$GeV. This maximum could indicate the formation of deconfined matter at energies above 40 $A$GeV. A search for open charm in a large sample of 158 $A$GeV events is presented. No signal is observed. This result is compared to several model predictions.

Results of the production of Xi and Xi-bar hyperons in central Pb+Pb interactions at 158 GeV/c per nucleon are presented. This analysis utilises a global reconstruction procedure, which allows a measurement of 4pi integrated yields to be made for the first time. Inverse slope paramters, which are determined from an exponential fit to the transverse mass spectra, are shown. Central rapidity densities are found to be 1.49 +- 0.08 and 0.33 +- 0.04 per event per unit of rapidity for Xi and Xi-bar respectively. Yields integrated to full phase space are 4.12 +- 0.02 and 0.77 +- 0.04 for Xi and Xi-bar. The ratio of Xi-bar/Xi at mid-rapidity is 0.22 +- 0.03.

Results are presented on event-by-event fluctuations of transverse momenta pT in central Pb+Pb interactions at 20A, 30A, 40A, 80A, and 158A GeV. The analysis was performed for charged particles at forward center-of-mass rapidity (1.1<yπ*<2.6). Three fluctuation measures were studied: the distribution of average transverse momentum M(pT) in the event, the ΦpT fluctuation measure, and two-particle transverse momentum correlations. Fluctuations of pT are small and show no significant energy dependence in the energy range of the CERN Super Proton Synchrotron. Results are compared with QCD-inspired predictions for the critical point, and with the UrQMD model. Transverse momentum fluctuations, similar to multiplicity fluctuations, do not show the increase expected for freeze-out near the critical point of QCD.18 MoreReceived 10 November 2008DOI:https://doi.org/10.1103/PhysRevC.79.044904©2009 American Physical Society

Emission of pi+/-, K+/-, phi, and Lambda was measured in near-central C+C and Si+Si collisions at 158 AGeV beam energy. Together with earlier data for p+p, S+S, and Pb+Pb, the system-size dependence of relative strangeness production in nucleus-nucleus collisions is obtained. Its fast rise and the saturation observed at about 60 participating nucleons can be understood as the onset of the formation of coherent systems of increasing size.

The centrality and system size dependence of multiplicity fluctuations of charged particles produced in nuclear collisions at $158A$ GeV was studied by the NA49 Collaboration. Centrality selected Pb+Pb collisions, semicentral C+C and Si+Si collisions as well as inelastic $p$+$p$ interactions were analyzed. The number of projectile participants determined on an event-by-event basis was used to characterize the collision centrality. The scaled variance of the multiplicity distribution obtained in the forward rapidity region ($1.1&lt;{y}_{\mathrm{c.m.}}&lt;2.6$) shows a significant increase toward peripheral collisions. The results are similar for negatively and positively charged particles and about 50% larger for all charged particles. String-hadronic models of nuclear reactions without the fusion process do not reproduce the rise of fluctuations from central toward peripheral collisions. The measured centrality dependence can be reproduced in superposition models with the assumption of contributions from target participants to particle production in the forward hemisphere or in string models with fusion.

Production of the $K^{\ast}(892)^0$ and $\bar{K}^{\ast}(892)^0$ resonances was studied via their $K^+ \pi^-$ and $K^- \pi^+$ decay modes in central Pb+Pb, Si+Si, C+C and inelastic p+p collisions at 158\agev ($\sqrt{s_{NN}}$ = 17.3 GeV) with the NA49 detector at the CERN SPS. Transverse momentum and rapidity distributions were measured and total yields were estimated. The yield of $K^{\ast}$ exceeds that of $\bar{K}^{\ast}$ by about a factor of two in nucleus-nucleus reactions. The total yield ratios $< K^{\ast} >/< K^+ >$ and $< \bar{K}^{\ast} >/< K^->$ are strongly suppressed in central Pb+Pb compared to p+p, C+C and Si+Si collisions in agreement with the expected attenuation of these short-lived resonance states in the hadronic phase of the expanding fireball. The UrQMD model, although incorporating such a scenario, does not provide a quantitative description of the experimental results. The statistical hadron gas model assuming the same freeze-out parameters for stable hadrons and resonances overestimates the $< K^{\ast} >/< K >$ ratios in central Pb+Pb collisions by about a factor of 2.5.

The European Particle Physics Strategy Update (EPPSU) process takes a bottom-up approach, whereby the community is first invited to submit proposals (also called inputs) for projects that it would like to see realised in the near-term, mid-term and longer-term future. National inputs as well as inputs from National Laboratories are also an important element of the process. All these inputs are then reviewed by the Physics Preparatory Group (PPG), whose role is to organize a Symposium around the submitted ideas and to prepare a community discussion on the importance and merits of the various proposals. The results of these discussions are then concisely summarised in this Briefing Book, prepared by the Conveners, assisted by Scientific Secretaries, and with further contributions provided by the Contributors listed on the title page. This constitutes the basis for the considerations of the European Strategy Group (ESG), consisting of scientific delegates from CERN Member States, Associate Member States, directors of major European laboratories, representatives of various European organizations as well as invitees from outside the European Community. The ESG has the mission to formulate the European Strategy Update for the consideration and approval of the CERN Council.

Results are presented on event-by-event electric charge fluctuations in central Pb+Pb collisions at 20, 30, 40, 80 and 158 AGeV. The observed fluctuations are close to those expected for a gas of pions correlated by global charge conservation only. These fluctuations are considerably larger than those calculated for an ideal gas of deconfined quarks and gluons. The present measurements do not necessarily exclude reduced fluctuations from a quark-gluon plasma because these might be masked by contributions from resonance decays.

New results from the energy scan programme of NA49, in particular kaon production at 30 AGeV and phi production at 40 and 80 AGeV are presented. The K+/pi+ ratio shows a pronounced maximum at 30 AGeV; the kaon slope parameters are constant at SPS energies. Both findings support the scenario of a phase transition at about 30 AGeV beam energy. The phi/pi ratio increases smoothly with beam energy, showing an energy dependence similar to K-/pi-. The measured particle yields can be reproduced by a hadron gas model, with chemical freeze-out parameters on a smooth curve in the T-muB plane. The transverse spectra can be understood as resulting from a rapidly expanding, locally equilibrated source. No evidence for an earlier kinetic decoupling of heavy hyperons is found.

We report measurements of Ξ− and Ξ+ hyperon absolute yields as a function of rapidity in 158 GeV/c Pb+Pb collisions. At midrapidity, dN/dy=2.29±0.12 for Ξ−, and 0.52±0.05 for Ξ+, leading to the ratio of Ξ+/Ξ−=0.23±0.03. Inverse slope parameters fitted to the measured transverse mass spectra are of the order of T≈300 MeV near mid-rapidity. The estimated total yield of Ξ− particles in Pb+Pb central interactions amounts to 7.4±1.0 per collision. Comparison to Ξ− production in properly scaled p+p reactions at the same energy reveals a dramatic enhancement (about one order of magnitude) of Ξ− production in Pb+Pb central collisions over elementary hadron interactions.

We discuss preliminary data on stopping for central Pb + Pb collisions at 158 GeV/nucleon. The (net) proton rapidity density measured by the NA49 Time Projection Chambers, NA49 Time of Flight and the NA44 spectrometer is presented. Slightly higher stopping is observed relative to S + S at 200 GeV/nucleon. The rapidity density exhibits a plateau around mid-rapidity which is qualitatively different from results at the AGS and BEVALAC/SIS energies. The second part of the paper discusses the azimuthal correlation of the energy flow. Preliminary results reveal that the ‘fireball’ preserves the information of the collision geometry even at SPS energies.

In this review we first outline the basics of transport theory and its recent generalization to off-shell transport. We then present in some detail the main ingredients of any transport method using in particular the Giessen Boltzmann–Uehling–Uhlenbeck (GiBUU) implementation of this theory as an example. We discuss the potentials used, the ground state initialization and the collision term, including the in-medium modifications of the latter. The central part of this review covers applications of GiBUU to a wide class of reactions, starting from pion-induced reactions over proton and antiproton reactions on nuclei to heavy-ion collisions (up to about 30AGeV). A major part concerns also the description of photon-, electron- and neutrino-induced reactions (in the energy range from a few 100MeV to a few 100GeV). For this wide class of reactions GiBUU gives an excellent description with the same physics input and the same code being used. We argue that GiBUU is an indispensable tool for any investigation of nuclear reactions in which final-state interactions play a role. Studies of pion–nucleus interactions, nuclear fragmentation, heavy-ion reactions, hypernucleus formation, hadronization, color transparency, electron–nucleus collisions and neutrino–nucleus interactions are all possible applications of GiBUU and are discussed in this article.

Electric charge correlations were studied for p+p, C+C, Si+Si, and centrality selected Pb+Pb collisions at $\sqrt{{s}_{\mathrm{NN}}}=17.2$ GeV with the NA49 large acceptance detector at the CERN SPS. In particular, long-range pseudorapidity correlations of oppositely charged particles were measured using the balance function method. The width of the balance function decreases with increasing system size and centrality of the reactions. This decrease could be related to an increasing delay of hadronization in central Pb+Pb collisions.

Kaons and protons carry large parts of two conserved quantities, strangeness and baryon number. It is argued that their correlation and thus also fluctuations are sensitive to conditions prevailing at the anticipated parton-hadron phase boundary. Fluctuations of the $(\mathrm{K}^+ + \mathrm{K}^-)/(\mathrm{p}+\bar{\mathrm{p}})$ and $\mathrm{K}^+/\mathrm{p}$ ratios have been measured for the first time by NA49 in central Pb+Pb collisions at 5 SPS energies between $\sqrt{s_{NN}}$= 6.3 GeV and 17.3 GeV. Both ratios exhibit a change of sign in $\sigma_{\mathrm{dyn}}$, a measure of non-statistical fluctuations, around $\sqrt{s_{NN}}$ = 8 GeV. Below this energy, $\sigma_{\mathrm{dyn}}$ is positive, indicating higher fluctuation compared to a mixed event background sample, while for higher energies, $\sigma_{\mathrm{dyn}}$ is negative, indicating correlated emission of kaons and protons. The results are compared to UrQMD calculations which which give a good description at the higher SPS energies, but fail to reproduce the transition to positive values.

A novel approach, the identity method, was used for particle identification and the study of fluctuations of particle yield ratios in Pb + Pb collisions at the CERN Super Proton Synchrotron (SPS).This procedure allows one to measure the moments of the multiplicity distributions of protons (p), kaons (K), pions (π ), and electrons (e) in case of incomplete particle identification.Using these moments the excitation function of the fluctuation measure ν dyn [A,B] was measured, with A and B denoting different particle types.The obtained energy dependence of ν dyn agrees with previously published NA49 results on the related measure σ dyn .However, ν dyn [K,p] and ν dyn [K,π ] were found to depend on the phase-space coverage.This feature most likely explains the reported differences between measurements of NA49 and those of STAR in central Au + Au collisions.

The central exclusive production of charged hadron pairs in pp collisions at a centre-of-mass energy of 13 TeV is examined, based on data collected in a special high-$\beta^*$ run of the LHC. Events are selected by requiring both scattered protons detected in the TOTEM Roman pots, exactly two oppositely charged identified particles in the CMS silicon tracker, and the energy-momentum balance of these four particles. The nonresonant continuum processes are studied with the invariant mass of the centrally produced two-pion system in the resonance-free region, $m < 0.7~\mathrm{GeV}$ or $m > 1.8~\mathrm{GeV}$. Differential cross sections as functions of the azimuthal angle between the surviving protons, squared four-momenta, and two-hadron invariant mass are measured in a wide region of scattered proton transverse momenta $0.2~\mathrm{GeV} < p_\text{1,T}, p_\text{2,T} < 0.8~\mathrm{GeV}$ and for hadron rapidities $|y| < 2$. A rich structure of interactions related to double pomeron exchange emerges. The parabolic minimum in the distribution of the two-proton azimuthal angle is observed for the first time. It can be understood as an effect of additional pomeron exchanges between the protons from the interference between the bare and the rescattered amplitudes. After model tuning, various physical quantities related to the pomeron cross section, proton-pomeron and hadron-pomeron form factors, trajectory slopes and intercepts, as well as coefficients of diffractive eigenstates of the proton are determined.

The NA49 large-acceptance hadron spectrometer has measured strange and multi-strange hadrons from Pb + Pb and p + p collisions at the CERN SPS. Preliminary results for the transverse mass and rapidity distributions for Ξ- and from central Pb + Pb collisions at 158 GeV c-1/nucleon are presented. Fully integrated yields per event of 4.42 ± 0.31 and 0.74 ± 0.04 are found for Ξ- and , respectively, leading to a 4π /Ξ- ratio of 0.17 ± 0.02. The ratio /Ξ- at mid-rapidity is found to be 0.22 ± 0.04, agreeing with previously published values. In addition, preliminary data on the Λ(1520) and ϕ (1020) resonances are presented. The Λ(1520) multiplicity for p + p collisions is found to be 0.012 ± 0.003. No signal is observed for Pb + Pb collisions and a production upper limit of 1.36 Λ(1520) per event indicates an apparent suppression when comparing with scaled p + p data. Integrated ϕ(1020) yields per event are found to be 7.6 ± 1.1 for Pb + Pb and 0.012 ± 0.0015 for p + p collisions. No significant shift or broadening of the ϕ(1020) invariant mass distribution is observed in central Pb + Pb collisions.

The dependence of the K+ and K− production on the number of nucleons involved in the annihilation process is investigated experimentally in the p¯ annihilation at rest on hydrogen, deuterium, 3He and 4He gas targets. Annihilations with any number of prongs (charged pions and kaons, protons and deuterons) are analyzed. Events with and without production of neutral mesons and with and without emission of fast neutrons (that is neutrons involved in the annihilation process) are recognized. The results are consistent with our previous ones on a more restricted sample of annihilation reactions and put in evidence that the strangeness production is lower or higher depending on the reaction channel. As a general trend, the strangeness production is higher in events without neutral mesons and still higher in events with the involvement of a higher number of nucleons. Both K+ and K− productions increase with the number of involved nucleons, but K+ much more. The maximum K+ production is observed in the reaction K+2π+2π−3n on 4He (with the involvement of 3–4 nucleons); compared with the production on hydrogen in the reaction K+π+2π−, the production on 4He is higher by a factor of 31.7±5.5. In the light of some theoretical speculations, this enhancement factor is too high to be explainable in terms of hadronic interactions and could be interpreted as a signature of quark deconfinement and of formation of a quark–gluon plasma.

In this paper we present recent results from the NA49 experiment for Λ and hyperons produced in central Pb + Pb collisions at 40, 80 and 158 A GeV. Transverse mass spectra and rapidity distributions for Λ are shown for all three energies. The shape of the rapidity distribution becomes flatter with increasing beam energy. The multiplicities at mid-rapidity as well as the total yields are studied as a function of collision energy including AGS measurements. The ratio Λ/π at mid-rapidity and in 4π has a maximum around 40 A GeV. In addition, rapidity distributions have been measured at 40 and 80 A GeV, which allows us to study the /Λ ratio.

The large acceptance and high momentum resolution as well as the significant particle identification capabilities of the NA49 experiment at the CERN SPS allow for a broad study of fluctuations and correlations in hadronic interactions. In the first part recent results on event-by-event charge and p_t fluctuations are presented. Charge fluctuations in central Pb+Pb reactions are investigated at three different beam energies (40, 80, and 158 AGeV), while for the p_t fluctuations the focus is put on the system size dependence at 158 AGeV. In the second part recent results on Bose Einstein correlations of h-h- pairs in minimum bias Pb+Pb reactions at 40 and 158 AGeV, as well as of K+K+ and K-K- pairs in central Pb+Pb collisions at 158 AGeV are shown. Additionally, other types of two particle correlations, namely pi p, Lambda p, and Lambda Lambda correlations, have been measured by the NA49 experiment. Finally, results on the energy and system size dependence of deuteron coalescence are discussed.

Results from the NA49 experiment at the CERN SPS are presented on event-by-event transverse momentum and multiplicity fluctuations of charged particles, produced at forward rapidities in central Pb+Pb interactions at beam momenta 20$A$, 30$A$, 40$A$, 80$A$, and 158$A$ GeV/c, as well as in systems of different size ($p+p$, C+C, Si+Si, and Pb+Pb) at 158$A$ GeV/c. This publication extends the previous NA49 measurements of the strongly intensive measure $\Phi_{p_T}$ by a study of the recently proposed strongly intensive measures of fluctuations $\Delta[P_T, N]$ and $\Sigma[P_T, N]$. In the explored kinematic region transverse momentum and multiplicity fluctuations show no significant energy dependence in the SPS energy range. However, a remarkable system size dependence is observed for both $\Delta[P_T, N]$ and $\Sigma[P_T, N]$, with the largest values measured in peripheral Pb+Pb interactions. The results are compared with NA61/SHINE measurements in $p+p$ collisions, as well as with predictions of the UrQMD and EPOS models.

Results from electric charge correlations studied with the Balance Function (BF) method in $A+A$ collisions from $20A$ to $158A$ GeV are presented in two different rapidity intervals: In the midrapidity region we observe a decrease of the width of the BF distribution with increasing centrality of the collision, whereas this effect vanishes in the forward rapidity region. Results from the energy dependence study in central $\mathrm{Pb}+\mathrm{Pb}$ collisions show that the narrowing of the BF expressed by the normalized width parameter $W$ increases with energy toward the highest CERN Super Proton Synchrotron and BNL Relativistic Heavy Ion Collider energies. Finally we compare our experimental data points with the predictions of several models. The hadronic string models Ultra-relativistic Quantum Molecular Dynamics and Heavy Ion Jet INteraction Generator (HIJING) do not reproduce the observed narrowing of the BF. However, A MultiPhase Transport medel (AMPT), which contains a quark-parton transport phase before hadronization, can reproduce the narrowing of the BF's width with centrality. This confirms the proposed sensitivity of the BF analysis to the time of hadronization.

With its large acceptance and particle identification coverage the NA49 experiment (Fig. 1) can study hadron production in a wide range of high energy reactions [1]. Originally aimed at examining central Pb+Pb collisions for signatures of quark-gluon plasma formation, the scope of the experiment has been enhanced with a systematic study of impact parameter and projectile size dependence, as well as the inclusion of the more elementary p+p and p+A interactions. The question is: are predicted signals of the quark-gluon plasma observed and are there discontinuities which would support the concept of hadronic phase transition?

Abstract The two Zero Degree Calorimeters (ZDCs) of the CMS experiment are located at ± 140 m from the collision point and detect neutral particles in the |η| &gt; 8.3 pseudorapidity region. This paper presents a study on the performance of the ZDC in the 2016 pPb run. The response of the detectors to ultrarelativistic neutrons is studied using in-depth Monte Carlo simulations. A method of signal extraction based on template fits is presented, along with a dedicated calibration procedure. A deconvolution technique for the correction of overlapping collision events is discussed.

Experimental results on deuteron emission from central Pb+Pb collisions (Ebeam=158A GeV, fixed target), obtained by NA49 at the CERN SPS accelerator, are presented. The transverse mass mt distribution was measured near mid-rapidity (2.0<y<2.5) in the range of 0<mt−m0<0.9 GeV/c2 (0<pt<2.0 GeV/c) for the 4% most central collisions. An exponential fit gives an inverse slope Td=(450±30) MeV and a yield dNd/dy=0.34±0.03. The coalescence factor B2(mt=m0)=(3.5±1.0)·10−4 GeV2 and its mt-dependence are determined and discussed in terms of a model that includes the collective expansion of the source created in a collision. The derived Gaussian size parameter RG of the emission volume is consistent with earlier HBT results on the source of pion emission.

The two-proton correlation function at midrapidity from Pb+Pb central collisions at 158 A GeV has been measured by the NA49 experiment. The results are compared to model predictions from static thermal Gaussian proton source distributions and transport models rqmd and venus. An effective proton source size is determined by minimizing χ2/ndf between the correlation functions of the data and those calculated for the Gaussian sources, yielding σeff=3.85±0.15(stat.)+0.60−0.25(syst.) fm. Both the rqmd and the venus model are consistent with the data within the error in the correlation peak region.

First results from the NA49 experiment with a 208Pb beam on a Pb target at the CERN SPS with total energy of 33 TeV are presented. Data on transverse energy production, forward energy flow and rapidity density of negative hadrons are shown and discussed. The degree of nuclear stopping and the energy densities achieved are estimated for near head-on collisions.

Bose-Einstein correlations of charged kaons were measured near mid-rapidity in central Pb+Pb collisions at 158 A$\cdot$GeV by the NA49 experiment at the CERN SPS. Source radii were extracted using the Yano-Koonin-Podgoretsky and Bertsch-Pratt parameterizations. The results are compared to published pion data. The measured $m_\perp$ dependence for kaons and pions is consistent with collective transverse expansion of the source and a freeze-out time of about 9.5 $fm$.

New measurements by the NA49 experiment of the centrality dependence of event-by-event fluctuations of the particle yield ratios $({K}^{+}+{K}^{\ensuremath{-}})/({\ensuremath{\pi}}^{+}+{\ensuremath{\pi}}^{\ensuremath{-}})$, $(p+\overline{p})/({\ensuremath{\pi}}^{+}+{\ensuremath{\pi}}^{\ensuremath{-}})$, and $({K}^{+}+{K}^{\ensuremath{-}})/(p+\overline{p})$ are presented for Pb+Pb collisions at 158$A$ GeV. The absolute values of the dynamical fluctuations of these ratios, quantified by the measure ${\ensuremath{\sigma}}_{\text{dyn}}$, increase by about a factor of two from central to semiperipheral collisions. Multiplicity scaling scenarios are tested and found to apply for both the centrality and the previously published energy dependence of the $({K}^{+}+{K}^{\ensuremath{-}})/({\ensuremath{\pi}}^{+}+{\ensuremath{\pi}}^{\ensuremath{-}})$ and $(p+\overline{p})/({\ensuremath{\pi}}^{+}+{\ensuremath{\pi}}^{\ensuremath{-}})$ ratio fluctuations. A description of the centrality and energy dependence of $({K}^{+}+{K}^{\ensuremath{-}})/(p+\overline{p})$ ratio fluctuations by a common scaling prescription is not possible since there is a sign change in the energy dependence.

Primary vertex finding for collider experiments is studied. The efficiency and precision of finding interaction vertices can be improved by advanced clustering and classification methods, such as agglomerative clustering with fast pairwise nearest neighbor search, followed by Gaussian mixture model or k-means clustering.

The energy loss of charged particles in silicon can be approximated by a simple analytical model. With help of measured charge deposits in individual channels of hit clusters their position and energy can be estimated. Deposits below threshold and saturated values are treated properly, resulting in a wider dynamic range. The proposed method gives improvements on both hit position and energy residuals. The model is successfully applied to track differential energy loss estimation and to detector gain calibration tasks.

Source imaging methodology is used to provide a three-dimensional two-pion source function for mid-rapidity pion pairs with $p_T<70$ MeV/c in central ($0-7%$) Pb+Pb collisions at $\sqrt s_{NN}$=17.3 GeV. Prominent non-Gaussian tails are observed in the pion pair transverse momentum (outward) and in the beam (longitudinal) directions. Model calculations reproduce them with the assumption of Bjorken longitudinal boost invariance and transverse flow blast-wave dynamics coupled with "outside-in burning" in the transverse direction; they also yield a proper time for breakup and emission duration for the pion source.

Data on φ-production obtained by the CERN NA49 experiment for central Pb+Pb collisions at 158 GeV/u are presented. Compared with pp interactions the φ-yield shows substantial strangeness enhancement: the φ/π ratio is found to increase by a factor of 2.6 ± 0.6, which is approximately the square of the K/π enhancement.

Abstract The directed and elliptic flow of protons and charged pions has been observed from the semi-central collisions of a 158 GeV/nucleon Pb beam with a Pb target. The rapidity and transverse momentum dependence of the flow has been measured. The directed flow of the pions is opposite to that of the protons at high rapidity but both exhibit negative flow at low p t . The elliptic flow of both is fairly independent of rapidity but rises with p t .

First results on hadron production using the 0.9, 2.36 and 7 TeV data are presented. The topics covered include spectra and multiplicity distributions of charged hadrons, spectra of strange hadrons, angular and Bose-Einstein correlations of charged particles. This is just the beginning of a successful physics program at the LHC, with possible future discoveries.

We look for fluctuations expected for the QCD critical point using an intermittency analysis in the transverse momentum phase space of protons produced around midrapidity in the 12.5\% most central C+C, Si+Si and Pb+Pb collisions at the maximum SPS energy of 158$A$~GeV. We find evidence of power-law fluctuations for the Si+Si data. The fitted power-law exponent $\phi_{2} = 0.96^{+0.38}_{-0.25}\text{ (stat.)}$ $\pm 0.16\text{ (syst.)}$ is consistent with the va\-lue expected for critical fluctuations. Power-law fluctuations had previously also been observed in low-mass $\pi^+ \pi^-$ pairs in the same Si+Si collisions.

Results are presented from a search for the decays D0 -> Kmin piplus and D0bar -> Kplus pimin in a sample of 3.8x10^6 central Pb-Pb events collected with a beam energy of 158A GeV by NA49 at the CERN SPS. No signal is observed. An upper limit on D0 production is derived and compared to predictions from several models.

The CMS heavy-ion program will probe QCD matter under extreme conditions.Its capabilities for the study of global observables and soft probes are described.

The study of central collisions of heavy nuclei at CERN SPS energies by NA49 provided evidence for the onset of deconfinement around 30A GeV. Theoretical considerations predict a critical point of strongly interacting matter accessible in the SPS energy range. A search for the expected fluctuations has not yet found convincing signals. The strategy and plans for the continuation of this program at the SPS by NA61 with lighter nuclei is discussed.

Tracker detectors can be used to identify charged particles based on their global chi value obtained during track fitting with the Kalman filter. This approach builds upon the knowledge of detector material and local position resolution, using the known physics of multiple scattering and energy loss. The proposed method is independent of the traditional way of identification using deposited energy. The performance for present LHC experiments is demonstrated.

A novel combination of established data analysis techniques for reconstructing all charged-particle tracks in high energy collisions is proposed. It uses all information available in a collision event while keeping competing choices open as long as possible. Suitable track candidates are selected by transforming measured hits to a binned, three- or four-dimensional, track parameter space. It is accomplished by the use of templates taking advantage of the translational and rotational symmetries of the detectors. Track candidates and their corresponding hits, the nodes, form a usually highly connected network, a bipartite graph, where we allow for multiple hit to track assignments, edges. The graph is cut into very many minigraphs by removing a few of its vulnerable components, edged and nodes. Finally the hits are distributed among the track candidates by exploring a deterministic decision tree. A depth-limited search is performed maximising the number of hits on tracks, and minimising the sum of track-fit $\chi^2$. Simplified models of LHC silicon trackers, as well as the relevant physics processes, are employed to study the performance (efficiency, purity, timing) of the proposed method in the case of single or many simultaneous proton-proton collisions (high pileup), and for single heavy-ion collisions at the highest available energies.

The high time and position resolution grid geometry time-of-flight spectrometer is described. It is used for particle identification as an element of the NA49 hadron detector system at the CERN-SPS. Performance and operational experience in high particle density environment of Pb+Pb collision are discussed.

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.

A novel approach, the identity method, was used for particle identification and the study of fluctuations of particle yield ratios in Pb+Pb collisions at the CERN Super Proton Synchrotron (SPS). This procedure allows to unfold the moments of the unknown multiplicity distributions of protons (p), kaons (K), pions (π) and electrons (e). Using these moments the excitation function of the fluctuation measure ν\text{;dyn};[A, B] was measured, with A and B denoting different particle types. The obtained energy dependence of νdyn agrees with previously published NA49 results on the related measure σdyn. Moreover, νdyn was found to depend on the phase space coverage for [K, p] and [K, π] pairs. This feature most likely explains the reported differences between measurements of NA49 and those of STAR in central Au+Au collisions.

Results on two-particle correlations, deuteron production, event anisotropy and event-by-event fluctuations of 〈pT〉 and K/π were obtained by the NA49 experiment in Pb+Pb collisions at 158 A·GeV beam energy. The interpretation of the measurements is discussed in light of the search for deconfinement.

Short-range correlations of identified charged hadrons in pp ( s = 0.9, 2.76, and 7 TeV), pPb ( s NN = 5.02 TeV), and peripheral PbPb collisions ( s NN = 2.76 TeV) are studied with the CMS detector at the LHC. Charged pions, kaons, and protons at low momentum and in laboratory pseudorapidity | η | &lt; 1 are identified via their energy loss in the silicon tracker. The two-particle correlation functions show effects of quantum statistics, Coulomb interaction, and also indicate the role of multi-body resonance decays and mini-jets. The characteristics of the one-, two-, and three-dimensional correlation functions are studied as a function of transverse pair momentum, k T , and the charged-particle multiplicity of the event. The extracted radii are in the range 1–5 fm, reaching highest values for very high multiplicity pPb, also for similar multiplicity PbPb collisions, and decrease with increasing k T . The dependence of radii on multiplicity and k T largely factorizes and appears to be insensitive to the type of the colliding system and center-of-mass energy.

The NA49 experiment is able to measure the production of neutral strange baryons and mesons along with other hadronic species in Pb + Pb collisions at 158 GeV per nucleon. These strange particles are an important piece of evidence in the search for the quark-gluon plasma. They have been reconstructed from their charged decay products recorded in the experiment's time projection chambers. A new round of data production has been undertaken with improved software, allowing the reconstruction of neutral strange particles over a rapidity interval covering both sides of mid-rapidity. The procedures used to obtain this sample are outlined and a comparison of the phase space coverage with respect to previous measurements is made.

Slow nucleons emitted during a hadron-nucleus interaction can give information on the centrality, impact parameter of the collision. The aim of this note is to provide the reader with the important characteristics of the slow nucleons, focusing on their spectra, correlations. This study tries to build on evidences, hence more weight is put on experimental results than on models.

The CMS experiment will provide good quality measurements of yields and spectra of identified charged and neutral particles, both in p-p and heavy-ion collisions, thus contributing to the study of soft hadronic physics at the LHC energies.

The latest NA49 results on event-by-event transverse momentum fluctuations are presented for central Pb+Pb interactions over the whole SPS energy range (20A - 158A GeV). Two different methods are applied: evaluating the $Φ_{p_{T}}$ fluctuation measure and studying two-particle transverse momentum correlations. The obtained results are compared to predictions of the UrQMD model. The results on the energy dependence are compared to the NA49 data on the system size dependence. The NA61 (SHINE, NA49-future) strategy of searching of the QCD critical end-point is also discussed.

An iron/gas parallel plate volume calorimeter prototype, working in the avalanche mode, has been tested using electrons of 20 to 150 GeV/c momentum with high voltages varying from 5400 to 5600 V (electric fields ranging from 36.0 to 37.3 kV/ cm), and a gas mixture of CF4/ CO2 (80%/20%). The collected charge has been measured as a function of the high voltage and of the electron energy. The energy resolution has also been measured. Comparisons have been made with Monte Carlo predictions. Agreement between data and simulation allows the calculation of the expected performance of a full size calorimeter.

Spectra of identified charged hadrons in pPb collisions measured with the CMS detector at the LHC at s NN = 5.02 TeV are presented. Charged pions, kaons, and protons in the transverse-momentum range p T ≈ 0.1 – 1.7 GeV / c and laboratory rapidity | y | < 1 are identified via their energy loss in the silicon tracker. The average p T increases with particle mass and the charged multiplicity of the event. The increase of the average p T with charged multiplicity is greater for heavier hadrons. Comparisons with Monte Carlo event generators reveal that epos lhc , which incorporates additional hydrodynamic evolution of the created system, is able to reproduce most of the data features, unlike hijing and ampt . The average transverse momentum and particle ratio measurements indicate that characteristics of particle production at LHC energies are strongly correlated with event particle multiplicity.

An overview of the first 13 TeV results from CMS is presented, including measurements of pseudorapidity-density of charged hadrons, two-particle angular correlations, inclusive t\bar t and single top production, as well as exotica

Short range correlations of identified charged hadrons in pp (sqrt(s) = 0.9, 2.76, and 7 TeV), pPb (sqrt(sNN) = 5.02 TeV), and peripheral PbPb collisions (sqrt(sNN) = 2.76 TeV) are studied with the CMS detector at the LHC. Charged pions, kaons, and protons at low pT and in laboratory pseudorapidity |eta| &lt; 1 are identified via their energy loss in the silicon tracker. The two-particle correlation functions show effects of quantum statistics, Coulomb interaction, and also indicate the role of multi-body resonance decays and mini-jets. The characteristics of the one-, two-, and three-dimensional correlation functions are studied as a function of pair momentum and the charged-particle multiplicity of the event. The extracted radii are in the range 1-5 fm, reaching highest values for very high multiplicity pPb, also for similar multiplicity PbPb collisions, and decrease with increasing kT. The dependence of radii on multiplicity and kT largely factorizes and appears to be insensitive to the type of the colliding system and center-of-mass energy.

The estimation of differential energy loss for charged particles in tracker detectors is studied. The robust truncated mean method can be generalized to the linear combination of the energy deposit measurements. The optimized weights in case of arithmetic and geometric means are obtained using a detailed simulation. The results show better particle separation power for both semiconductor and gaseous detectors.

We look for fluctuations expected for the QCD critical point using an intermittency analysis in the transverse momentum phase space of protons produced around midrapidity in the 12.5\% most central C+C, Si+Si and Pb+Pb collisions at the maximum SPS energy of 158$A$~GeV. We find evidence of power-law fluctuations for the Si+Si data. The fitted power-law exponent $\phi_{2} = 0.96^{+0.38}_{-0.25}\text{ (stat.)}$ $\pm 0.16\text{ (syst.)}$ is consistent with the va\-lue expected for critical fluctuations. Power-law fluctuations had previously also been observed in low-mass $\pi^+ \pi^-$ pairs in the same Si+Si collisions.

Tracker detectors can be used to identify charged particles based on their global χ value obtained during track fitting with the Kalman filter. This approach builds upon the knowledge of detector material and local position resolution, using the known physics of multiple scattering and energy loss. The proposed method is independent of the traditional way of identification using deposited energy. The performance for present LHC experiments is demonstrated.

A CMS kiserlet kereteben reszt vettem az első 0,9 es 2.36 TeV tomegkozepponti energiaju proton-proton utkozesek kiertekeleseben es a publikacio megirasaban. Meghataroztam a keletkező toltott hadronok pszeudo-rapiditas es transzverz impulzus eloszlasat, amely egy egyszerű fizikai modellel leirhato. A kapott eredmenyek 0,9 TeV-en osszhangban vannak korabbi meresekkel es megerősitik, hogy a proton-antiproton es a proton-proton utkozesekben kozel azonos mennyisegű hadron keletkezik. A 2,36-TeV-en kapott hadronsűrűseg a modellek altal josoltnal meredekebb energiafuggesre utal. A LHC kesői indulasa folytan uj adatkiertekelesi modszerekkel is foglalkoztam: javitott kolcsonhatasi pont kereses utkozőnyalabos detektorokra, szilicium alapu detektor beuteseinek javitott kiertekelese, toltott reszecskek fajlagos energiaveszteseg-becslesenek javitasa, kis impulzusu toltott reszecskek azonositasa a track-illesztes chi^2 ertekevel. | In the CMS collaboration I took part in the analysis and publication of the first proton-proton collision data at 0.9 and 2.36 center-of-mass energies. I have determined the pseudo-rapidity and transverse momentum distribution of created charged hadrons. The latter is well described by a simple physical model. The obtained results confirm that proton-antiproton and proton-proton collisions produce nearly equal amount of hadrons. The measured particle density at 2.36 TeV points to a steeper-than-predicted increase with energy. Due to the late start of the LHC I had the possibility to work on new data analysis methods, such as: improved vertex finding for collider detectors; improved estimation of cluster properties for silicon detectors; optimized estimation of energy loss for charged particles; identification of low momentum charged particles with track fit chi^2.

The early data from LHC will allow the first look at minimum bias p-p collisions initially at the center-of-mass energies of 10 and later 14 TeV.The measurements of the basic observables will also serve as an important tool for calibrating and understanding the CMS detector at start-up.We present the plans of the CMS collaboration to measure cross sections and differential yields of charged particles (unidentified or identified pions, kaons and protons) and neutrals (K 0 S , lambdas and anti-lambdas) produced in inelastic p-p collisions at 14 TeV, as well as their multiplicity distributions.The tracking of charged particles is possible down to about 100 MeV/c, with good efficiency and negligible fake rate.The yield of charged kaons and protons can be extracted for total momenta below 0.8 and 1.5 GeV/c, respectively.Comparisons of the results to theoretical models are discussed.Studies of the underlying event at CMS are presented by examining charged particle and momentum densities in the transverse region in charged particle jet production.The possibility of discriminating among models is shown.

The CMS experiment and its detector systems show an excellent performance.Many aspects, physics objects, are already commissioned.The collaboration produced pioneering results from a small data sample: the first publications using the 0.9 and 2.36 TeV data are already available.This is just the beginning of a successful physics program at the LHC, with possible future discoveries.