Results are presented on event-by-event fluctuations of transverse momenta $p_T$ in central Pb+Pb interactions at 20$A$, 30$A$, 40$A$, 80$A$, and 158$A$ GeV. The analysis was performed for charged particles at forward center-of-mass rapidity ($1.1 < y^{*}_π < 2.6$). Three fluctuation measures were studied: the distribution of average transverse momentum - $M(p_T)$ - in the event, the $Φ_{p_{T}}$ fluctuation measure and two-particle transverse momentum correlations. Fluctuations of $p_T$ 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.
The physics goals, the detector and its performance as well as status and plans of the NA61/SHINE experiment at the CERN SPS accelerator are presented.
This paper is dedicated to the memory of Jozsef Zimanyi one of the founders of the experiment NA49 at the CERN SPS. Firstly, the paper summarizes the main results of NA49 concerning observation of the onset of deconfinement in central Pb+Pb collisions at the low SPS energies. Secondly, it sketches the physics program of NA61 at the CERN SPS, the successor of NA49, which in particular aims to discover the critical point of strongly interacting matter. Finaly, a brief review of the future experimental programs in the CERN SPS energy range is given.
A new experimental program to study hadron production in collisions of nuclei at the CERN SPS is presented. The program will focus on measurements of fluctuations and long correlations with the aim to identify properties of the onset of deconfinement and search for the critical point of strongly interacting matter.
Recent searches at the CERN SPS for evidence of the critical point of strongly interacting matter are discussed. Experimental results on theoretically expected signatures, such as event-to-event fluctuations of the particle multiplicity and the average transverse momentum as well as intermittency in particle production are presented.
Recent searches at the CERN SPS for evidence of the critical point of strongly interacting matter are discussed. Experimental results on theroretically expected signatures, such as event-to-event fluctuations of the particle multiplicity and the average transverse momentum as well as intermittency in particle production are presented.
The paper reviews all experimental results on dileptons with invariant mass m < 3 GeV/c$^2$ and real photons obtained from the CERN SPS heavy-ion program with S and Pb beams, together with the current attempts to understand them.
Recent results on K$^0_{\rm S}$ and hyperon production in Pb-Pb collisions at 40 and 158 $A$ GeV/$c$ beam momentum from the NA57 experiment at CERN SPS are presented. Yields and ratios are compared with those measured by the NA49 experiment, where available. The centrality dependence of the yields and a comparison with the higher collision energy data from RHIC are discussed.
A new heavy-ion experiment on fixed target, NA60+, has been proposed at the CERN SPS for data taking in the next years. Its main goals will be focused on precision studies of thermal dimuons, heavy quark and strangeness production in Pb-Pb collisions at center-of-mass energies ranging from 5 to 17 GeV, which will provide a unique opportunity to investigate the region of the QCD phase diagram at high baryochemical potential ($μ_B \sim 200-400$~MeV). The key points of the NA60+ very broad and ambitious physics program will be described.
Status of the new experimental program to study hadron production in hadron-nucleus and nucleus-nucleus collisions at the CERN SPS will be presented. In particular, a detailed physics motivation and experimental strategy will be given for the part of the program related to the physics of strongly interacting matter: search for the critical point of strongly interacting matter, study properties of the onset of deconfinement, and high p_T measurements in p+p and p+A interactions. The planned measurements for the neutrino T2K and cosmic-ray experiments will also be discussed.
The NA61/SHINE programme on strong interactions covers the study of the onset of deconfinement and aims to discover the critical point of strongly interacting matter by performing an energy and system-size scan over the full CERN SPS momentum range. So far the scans of p+p, $^7$Be+$^9$Be, as well as Ar+Sc have been completed. Results from p+p and Be+Be collisions are now emerging, in particular the energy dependence of hadron spectra and yields. Status and preliminary results from this effort will be presented.
The possible transition of nuclear matter to a deconfined phase in relativistic nucleus-nucleus collisions is explored by a systematic variation of the collision system by means of system size, beam energy and centrality of the collision all measured within the same experiment NA49 at the CERN SPS. The investigation takes advantage of the large number of hadronic observables covered over a wide phase space by the acceptance of the NA49 TPCs.
New experimental results of NA49 on hyperon production in central Pb+Pb collisions at the SPS energies are presented. In particular, measurements of $Λ$ production at 30 A$\cdot$GeV and $Ξ$ and $Ω$ production at 40 A$\cdot$GeV are shown. Transverse mass spectra and rapidity distributions of hyperons at different energies are compared. The energy dependence of the particle yields and ratios is discussed.
The current experimental situation concerning high pt observables at the CERN SPS is reviewed. Recent data from the NA45, NA49 and NA57 collaborations are discussed and compared to earlier measurements by WA98 and NA45 at the same center-of-mass energies, as well as to measurements at the higher energies by the RHIC experiments. The observables include new p+p, A+A spectra, nuclear modification factors (R_AA, R_CP), two particle azimuthal correlations, and baryon to meson ratios at moderately high pt. Generally, the interpretation of the SPS data suffers from the lack of reliable baseline meas…
The NA61/SHINE experiment at the CERN SPS aims to discover the critical point of strongly interacting matter and study properties of the onset of deconfinement. These goals will be reached by measurements of hadron production properties in nucleus-nucleus, proton-proton and proton-lead interactions as a function of collision energy and size of the colliding nuclei. Furthermore, NA61/SHINE will perform numerous precision measurements needed for neutrino (T2K) and cosmic-ray (Pierre Auger Observatory and KASCADE) experiments. This paper summarizes physics arguments for the NA61/SHINE ion program…
We present new results on production of 3He and t obtained by the NA49 experiment in 20A, 30A, 40A and 80A GeV central Pb+Pb collisions at the CERN SPS. Transverse mass spectra and rapidity distributions for clusters measured over a large phase space domain are discussed. We observe a weak dependence of the mid-rapidity t/3He ratio on collision energy at SPS. The energy dependence of the total yield for 3He is remarkably reproduced by a statistical hadron gas model. A gradual decrease of the coalescence parameter B3 for 3He with $\sqrt {s_{NN}}$ is observed.In addition, a measurement of the yi…
Theoretical calculations locate the critical point of strongly interacting matter (CP) at energies accessible at the CERN SPS. Event-by-event transverse momentum and multiplicity fluctuations are considered as one of the most important tools to search for the CP. Pilot studies of the energy dependence and the system size dependence of both $p_T$ and multiplicity fluctuations were performed by the NA49 experiment. The NA61/SHINE ion program is a continuation of these efforts. After briefly recalling the essential NA49 results on fluctuations we will discuss the technical methods (removing Non-T…
New results on the production of Xi and Omega hyperons in Pb+Pb interactions at 40AGeV and Lambda at 30AGeV are presented. Transverse mass spectra as well as rapidity spectra of these hyperons are shown and compared to previously measured data at different beam energies. The energy dependence of hyperon production (4pi yields) is discussed. Additionally, the centrality dependence of Xi^{-} production at 40AGeV is presented.
New preliminary results on kaon and pion production in central 30AGeV Pb+Pb collisions are presented. The data are compared to data at lower and higher energies to examine the energy dependence of the kaon to pion ratios and the inverse slope parameters of kaons. The results are compared to expectations from models with and without a phase transition to the Quark Gluon Plasma.
Electric charge correlations are studied with the Balance Function method for central Pb + Pb collisions at the CERN - SPS. The results on centrality selected Pb + Pb interactions at 40 and 158 AGeV are presented for the first time for two different rapidity intervals. In the mid-rapidity region a decrease of the width with increasing centrality of the collision is observed whereas in the forward rapidity region this effect vanishes. This could suggest a delayed hadronization scenario. In addition, the results from a first attempt to study the energy dependence of the Balance Function througho…
The energy dependence of hadron production in central Pb-Pb collisions at SPS energies is presented and compared with data at lower and higher energies and with results from p-p interactions. It is observed that there is little change in transverse activity in the SPS energy range, that there is a steepening rate of increase of pion production and that the K+/pi+ ratio exhibits a sharp peak located at about 30 AGeV. The Lambda/pi ratio also shows a pronounced maximum which is weaker in Ksi/pi and absent in Omega/pi.
Evidence for the onset of deconfinement in central Pb+Pb collisions was reported by NA49 in fixed target measurements at beam momentum 30A GeV/c. This observation motivated the NA61/SHINE program started in 2009 at the CERN SPS, which, in particular, aims to study properties of the onset of deconfinement by measurements of hadron production in proton-proton, proton-nucleus and nucleus-nucleus collisions. This contribution presents spectra of charged pions produced in p+p interactions and $^7$Be+$^9$Be collisions at 20A-158A GeV/c beam momentum. The NA61/SHINE results are compared with the corr…
A systematic study of two particle correlations measured by the NA49 experiment is summarized. Radii from Bose Einstein interferometry have been determined separately in different parts of phase space, for different collision systems and at different incident beam energies. Moreover, first results of a new method of accessing space-time asymmetries in the emission of particles by means of non identical particle correlations are presented.
The system size and centrality dependence of multiplicity fluctuations in nuclear collisions at $158A$ GeV as well as the energy dependence for the most central $Pb+Pb$ collisions were studied by the NA49 experiment at CERN SPS. A strong increase of fluctuations was observed with decreasing centrality in $C+C$, $Si+Si$ and $Pb+Pb$ collisions. The string hadronic models (UrQMD, Venus, HIJING, HSD) can not reproduce the observed increase. This may indicate a strong mixing of target and projectile contribution in a broad rapidity range. For the most central collisions at all SPS energies multipli…
The NA49 fixed-target experiment studied high energy-density matter produced in nucleus-nucleus reactions at the CERN SPS. In central Pb+Pb collisions at 158A GeV the energy density at the early stage substantially exceeds the threshold for quark deconfinement predicted by lattice QCD. The produced matter shows strong transverse and longitudinal flow. Ratios of yields of produced particles are approximately consistent with statistical equilibration. An energy scan through the SPS range revealed structure in the energy dependence of pion and kaon yields as well as of the inverse slopes of trans…
The latest NA49 results on fluctuations of multiplicity and average transverse-momentum analyzed on an event-by-event basis are presented for central Pb+Pb interactions over the whole SPS energy range (20A - 158A GeV). The scaled variance of the multiplicity distribution decreases with collision energy whereas the $Φ_{p_{T}}$ measure of $<p_T>$ fluctuations is small and independent of collision energy. Thus in central Pb+Pb collisions these fluctuations do not show an indication of the critical point of strongly interacting matter.
First results on the production of Xi and AntiXi hyperons in Pb+Pb interactions at 40 AGeV are presented. The AntiXi/Xi ratio at midrapidity is studied as a function of collision centrality. The ratio shows no significant centrality dependence within statistical errors; it ranges from 0.07 to 0.15. The AntiXi/Xi ratio for central Pb+Pb collisions increases strongly with the collision energy.
In the recent years the NA49 experiment has collected data on Pb+Pb collisions at beam energies between 20 to 158 AGeV with the objective to cover the critical region of energy densities where the expected phase transition to a deconfined phase might occur in the early stage of the reactions. In this contribution the energy dependence of various hadronic observables is presented. These include m_t- and rapidity- distributions, particle ratio fluctuations, as well as HBT radii.
The NA60 experiment at the CERN SPS has studied low-mass dimuon production in 158A GeV In-In collisions. A significant excess of pairs is observed above the yield expected from neutral meson decays, consistent with a dominant contribution from $ππ\toρ\toμμ$. This paper presents precision results on the mass and transverse momentum spectra of the excess pairs. The space-time averaged rho spectral function associated to the measured mass distribution shows a significant broadening, but essentially no mass shift. The slope parameter $T_{eff}$ extracted from the spectra rises with dimuon mass up t…
The NA61/SHINE experiment aims to discover the critical point of strongly interacting matter and study properties of the onset of deconfinement. It also to performs precise hadron production measurements for the neutrino and cosmic rays experiments. These goals will be achieved by measurements of hadron production properties in nucleus-nucleus, proton-proton and proton-nucleus interactions as a function of collision energy and size of the colliding nuclei, as well as pion-nucleus interactions. This contribution summarises the arguments of the ion program as well as presents the first physics r…
The strong interactions programme of the NA61/SHINE experiment at CERN SPS has been extended through the use of new silicon Vertex Detector which provides precise measurements of exotic particles with short lifetime. The detector was designed to meet the challenges of primary and secondary vertexes reconstruction at high spatial resolution. An initial version of the Vertex Detector called SAVD (Small Acceptance Vertex Detector) was installed last end of 2016, and data was from Pb+Pb collisions was collected in 2016, for Xe+La in 2017, as well as further Pb+Pb collisions this year. First indica…
The high-$μ_{\rm B}$ region of the QCD phase diagram has become the object of several studies, focused on the investigation of the order of the phase transition and the search for the critical point. Accessing rare probes is experimentally challenging as it requires large integrated luminosities, and a fixed-target environment represents an ideal solution for these studies. The CERN SPS covers, with large beam intensity, the collision energy region $5<\sqrt{s_{\rm NN}}<17$ GeV. A future experiment, NA60+, is being proposed to access this region and perform accurate measurements of the dimuon s…
The NA61/SHINE at the CERN SPS is a new experiment to study hadron production in p+p p+A, h+A and A+A interactions. The main goal of the NA61 ion program is to explore the phase diagram (T - mu_B) of strongly interacting matter. In particular, we plan to study the properties of the onset of deconfinement and to search for the signatures of the critical point. A two-dimensional scan of the phase diagram will be performed by varying the energy (13A-158A GeV) and system size (p+p, Be+Be, Ar+Ca, Xe+La) of collisions. This paper summarizes the status and plans of the NA61/SHINE ion program. In part…
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. In this talk new results on chemical (particle ratio), transverse momentum, multiplicity and azimuthal angle fluctuations will be presented. We also discuss their connection to the onset of deconfinement and to the critical endpoint.
Angular correlations of high-pT hadrons can serve as a probe of interactions of partons with the dense medium produced in high-energy heavy-ion collisions but other sources of such correlations exist which can be non-negligible SPS energies. In an attempt to determine the primary source, NA49 has performed an energy and system-size scan of two-particle azimuthal correlations in central Pb+Pb, Si+Si and p+p collisions at 158A GeV, as well as central Pb+Pb collisions at 20A, 30A, 40A and 80A GeV. Moreover, results at 158A GeV have been compared to UrQMD simulations.
Event-by-event fluctuations and correlations in azimuthal angle are currently widely investigated in various experiments. In this paper the $Φ$ measure (earlier used in experiments to evaluate fluctuations in transverse momentum) is now applied to azimuthal angle $ϕ$. Properties of this $Φ_ϕ$ function are investigated through fast generators and with complex models such as Pythia, Hijing, and UrQMD. Preliminary results of NA49 on $Φ_ϕ$ are also presented. The system size dependence (p+p, C+C, Si+Si and 6 centralities of Pb+Pb) at the highest SPS energy (158$A$ GeV) is shown, as well as the ene…
Measurements of Bose-Einstein correlations of pion pairs in central Pb+Pb collisions were performed with the NA49 detector at the CERN SPS for beam energies of 20A, 30A, 40A, 80A, and 158A GeV. Correlation functions were measured in the longitudinally co-moving ``out-side-long'' reference frame as a function of rapidity and transverse momentum in the forward hemisphere of the reaction. Radius and correlation strength parameters were obtained from fits of a Gaussian parametrization. The results show a decrease of the radius parameters with increasing transverse momentum characteristic of strong…
The exploration of the QCD phase diagram particularly the search for a phase transition from hadronic to partonic degrees of freedom and possibly a critical endpoint, is one of the most challenging tasks in present heavy-ion physics. As observed by the NA49 experiment, several hadronic observables in central Pb+Pb collisions at the CERN SPS show qualitative changes in their energy dependence. These features are not observed in elementary interactions and indicate the onset of a phase transition in the SPS energy range. The existence of a critical point is expected to result in the increase of …
Rapidity distributions for $Λ$ and $\barΛ$ hyperons in central Pb-Pb collisions at 40, 80 and 158 A$\cdot$GeV and for ${\rm K}_{s}^{0}$ mesons at 158 A$\cdot$GeV are presented. The lambda multiplicities are studied as a function of collision energy together with AGS and RHIC measurements and compared to model predictions. A different energy dependence of the $Λ/π$ and $\barΛ/π$ is observed. The $\barΛ/Λ$ ratio shows a steep increase with collision energy. Evidence for a $\barΛ/\bar{\rm p}$ ratio greater than 1 is found at 40 A$\cdot$GeV.
The study of open charm meson production provides an efficient tool for detailed investigations of the properties of hot and dense matter formed in nucleus-nucleus collisions. The interpretation of the existing data from the CERN SPS suffers from a lack of knowledge on the total charm production rate. To overcome this limitation the heavy-ion programme of the NA61/SHINE experiment at CERN SPS has been expanded to allow for precise measurements of particles with a short lifetime. A new Small Acceptance Vertex Detector (SAVD) was designed and constructed to meet the challenges of open charm meas…
The aim of the NA61/SHINE strong interaction programme is to explore the phase diagram of strongly interacting matter. The main physics goals are the study of the onset of deconfinement and the search for the critical point of strongly interacting matter. These goals are pursued by performing a beam momentum (13A -- 150/158A GeV/c) and system size (p+p, p+Pb, Be+Be, Ar+Sc, Xe+La, Pb+Pb) scan. This contribution presents new results from NA61/SHINE on fluctuations and correlations which include in particular quantum correlations, as well as multiplicity and net-charge fluctuations, proton densit…
We report on first measurements of low-mass electron pairs in Pb-Au collisions at the lower SPS beam energy of 40 AGeV. The pair yield integrated over the range of invariant masses 0.2<m<1 GeV/c^2 is enhanced by a factor of 5.1+-1.3(stat)+-1.0/1.5(syst data/decays) over the expectation from neutral meson decays, more than previously observed at the higher energy of 158 AGeV. The results are discussed with reference to model calculations based on pi+ pi- -> e+ e- annihilation with a modified rho-propagator. They may be linked to chiral symmetry restoration and support the notion that the in-med…
Recent femtoscopic measurements involving the use of an imaging technique and a newly developed moment analysis are presented and discussed. We show that this new paradigm allows robust investigation of reaction dynamics for which the sound speed $c_s \neq 0$ during an extended hadronization period. Source functions extracted for charged pions produced in Au+Au and Pb+Pb collisions show non-Gaussian tails for a broad selection of collision energies. The ratio of the RMS radii of these source functions in the out and side directions are found to be greater than 1, suggesting a finite emission t…
The measurements of open charm production was proposed as an important tool to investigate the properties of hot and dense matter formed in nucleus-nucleus collisions as well as to provide the means for model independent interpretation of the existing data on $\text{J}/ψ$ suppression. Recently, the experimental setup of the NA61/SHINE experiment was supplemented with a Vertex Detector which was motivated by the importance and the possibility of the first direct measurements of open charm meson production in heavy ion collisions at SPS energies. First test data taken in December 2016 on Pb+Pb c…
This paper presents results and plans of the NA49 and NA61/SHINE experiments at the CERN Super Proton Synchrotron concerning the study of relativistic nucleus-nucleus interactions. First, the NA49 evidence for the energy threshold of creating quark-gluon plasma, the onset of deconfinement, in central lead-lead collisions around 30A GeV is reviewed. Then the status of the NA61/SHINE systematic study of properties of the onset of deconfinement is presented. Second, the search for the critical point of strongly interacting matter undertaken by both experiments is discussed. NA49 measured large fl…
The strong interactions programme of the NA61/SHINE experiment at the CERN SPS has been extended through the use of new silicon Vertex Detector, which allows for reconstructing open charm particles. The detector was designed to identify those particles by means of a precise reconstruction of their primary and secondary vertices. An initial version of the Vertex Detector, called SAVD (Small Acceptance Vertex Detector), was installed end of 2016. It was operated in a Pb+Pb calibration beam time in 2016, and with Xe+La in 2017. A further Pb+Pb beam time is scheduled for late 2018. The first indic…
In this paper we present recent results from the NA49 experiment for $Λ$ and $\barΛ$ hyperons produced in central Pb+Pb collisions at 40, 80 and 158 A$\cdot$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 4$π$ has a maximum around 40 A$\cdot$GeV. In addition, $\barΛ$ rapidity distributions…
The NA61/SHINE experiment aims to discover the critical point of strongly interacting matter and study the properties of the onset of deconfinement. For these goals a scan of the two dimensional phase diagram ($T$-$μ_{B}$) is being performed at the SPS by measurements of hadron production in proton-proton, proton-nucleus and nucleus-nucleus interactions as a function of collision energy and system size. In this contribution preliminary results on transverse momentum and multiplicity fluctuations expressed in terms of strongly intensive quantities from the Ar+Sc energy scan will be presented. T…
Two-particle azimuthal correlations of high-pT hadrons can serve as a probe of interactions of partons with the dense medium produced in high-energy heavy-ion collisions. First NA49 results on such correlations are presented for central and mid-central Pb+Pb collisions at 158A GeV beam energy, for different centrality bins and charge combinations of trigger and associate particles. These results feature a flattened away-side peak in the most central collisions, which is consistent with expectations of the medium-interaction scenario. A comparison with CERES Pb+Au results at the same energy, as…
The NA61/SHINE strong interaction programme aims to explore the phase diagram of the strongly interacting matter. The main physics goals are the study of the onset of deconfinement and the search for the critical point of the strongly interacting matter. These goals are pursued by performing a scan in beam momentum (13A -- 158A GeV/c) and size of colliding system (p+p, p+Pb, Be+Be, Ar+Sc, Xe+La, Pb+Pb). This contribution presents new results on system size and energy dependence of multiplicity and net-charge fluctuations measured with higher-order moments of these distributions. Also, new resu…
NA61/SHINE is a multipurpose fixed-target facility at the CERN Super Proton Synchrotron. The main goals of the NA61/SHINE strong interactions program are to discover the critical point of strongly interacting matter and study the properties of the onset of deconfinement. To reach these goals, hadron production measurements are performed in the form of a two-dimensional scan by varying collision energy and system size. The Collaboration has recently finished data acquisition for its original program on strong interactions, accumulating broad data samples on hadron production in various systems …
The NA60 experiment at the CERN SPS has studied $ϕ$ meson production in In-In collisions at 158A GeV via both the $K^+K^-$ and the $μ^+μ^-$ decay channels. The yields and inverse slope parameters of the $m_T$ spectra observed in the two channels are compatible within errors, different from the large discrepancies seen in Pb-Pb collisions between the hadronic (NA49) and dimuon (NA50) decay channels. Possible physics implications are discussed.
NA60 is a fixed-target experiment at the CERN SPS which measured dimuon production in nucleus-nucleus and proton-nucleus collisions. In this paper we report on a precision measurement of low-mass muon pairs in 158 AGeV indium-indium collisions. A significant excess of pairs is observed above the yield expected from neutral meson decays. The excess can be isolated by subtraction of expected sources, thanks to the excellent mass resolution and large sample size.
We report a measurement of low-mass electron pairs observed in 158 GeV/nucleon Pb-Au collisions. The pair yield integrated over the range of invariant masses 0.2 < m < 2.0 GeV is enhanced by a factor of 3.5 +/- 0.4 (stat) +/- 0.9 (syst) over the expectation from neutral meson decays. As observed previously in S-Au collisions, the enhancement is most pronounced in the invariant-mass region 300-700 MeV. For Pb-Au we find evidence for a strong increase of the enhancement with centrality. In addition, we show that the enhancement covers a wide range in transverse momentum, but is largest at the lo…
The NA61/SHINE experiment aims to discover the critical point of strongly interacting matter and study the properties of the onset of deconfinement. For these goals a scan of the two dimensional phase diagram ($T$-$μ_{B}$) is being performed at the SPS by measurements of hadron production in proton-proton, proton-nucleus and nucleus-nucleus interactions as a function of collision energy and system size. In this contribution preliminary results on transverse momentum and multiplicity fluctuations expressed in terms of strongly intensive quantities from the Ar+Sc energy scan will be presented. T…
The search for experimental signatures of the critical point (CP) of strongly interacting matter is one of the main objectives of the NA61/SHINE experiment at CERN SPS. In the course of the experiment, a beam momentum and system size scan is performed. Local proton density fluctuations in transverse momentum space represent an order parameter of the chiral phase transition and are expected to scale according to a universal power-law in the vicinity of the CP; we probe their behavior through an intermittency analysis of the proton second scaled factorial moments (SSFMs) in transverse momentum s…
Azimuthal correlations of particles produced in nucleus-nucleus collisions at CERN SPS are discussed. The correlations quantified by the integral measure Phi are shown to be dominated by effects of collective flow.
Multiplicity fluctuations in the forward hemisphere were studied for positively, negatively and all charged hadrons produced in central Pb+Pb collisions at 20A, 30A, 40A, 80A and 158A GeV. The multiplicity distributions and their scaled variances are presented as a function of collision energy, rapidity and transverse momentum. The distributions have a bell-like shape and the scaled variance changes monotonously with energy in the range from 0.8 to 1.2. No indication of the critical point is observed. The string-hadronic model UrQMD reproduces results on the scaled variance. The predictions of…
