Onset Of Deconfinement Research Articles

The special point on the hybrid star mass\u2013radius diagram and its multi\u2013messenger implications

We show the existence and investigate the location of the special point (SP) in which hybrid neutron star mass-radius (M-R) curves have to cross each other when they belong to a class of hybrid equation of state (EoS) constructed with generic constant–speed–of–sound (CSS) quark matter models for which the onset deconfinement is varied. We demonstrate that for a three-parameter CSS model the position of the SP in the M-R diagram is largely independent of the choice of the hadronic EoS, but in dependence on the stiffness of the quark matter EoS it spans a region that we identify. We find that the difference between the maximum mass and the SP mass depends on the mass at the onset of deconfinement so that an upper limit of 0.19 M⊙ for this difference is obtained from which a lower limit on the radius of hybrid stars is deduced. Together with a lower limit on the radius of hadronic stars, derived from a class of reasonably soft hadronic EoS including hyperons, we identify a region in the M-R diagram which can be occupied only by hybrid stars. Accordingly, we suggest that a NICER radius measurement on the massive pulsar PSR J0740 + 6620 in the range of 8.6-11.9 km would indicate that this pulsar is a hybrid neutron star with deconfined quark matter in the inner core.

Proton-proton interactions and onset of deconfinement

The NA61/SHINE experiment at the CERN SPS is performing a uniqe study of the phase diagram of strongly interacting matter by varying collision energy and nuclear mass number of colliding nuclei. In central Pb+Pb collisions the NA49 experiment found structures in the energy dependence of several observables in the CERN SPS energy range that had been predicted for the transition to a deconfined phase. New measurements of NA61/SHINE find intriguing similarities in p+p interactions for which no deconfinement transition is expected at SPS energies. Possible implications will be discussed.

Strange particle effective temperatures in relativistic nuclear collisions

The energy dependence of the effective temperatures of charged kaons, [Formula: see text] and [Formula: see text] produced in Au[Formula: see text]Au collisions at the Relativistic Heavy Ion Collider (RHIC) Beam Energy Scan (BES) energies are presented. At energies around [Formula: see text][Formula: see text]GeV, there is a sudden change in the energy dependence of [Formula: see text] and [Formula: see text] effective temperatures, while at higher energies a slower, continuous rise up to [Formula: see text][Formula: see text]TeV is observed. This behavior is similar with previous SPS results and could indicate the onset of deconfinement in this energy range. The [Formula: see text] effective temperatures increase with energy and no plateau-like behavior is evidenced by the data.

Brief History of the Search for Critical Structures in Heavy-ion Collisions

The paper briefly presents history, status, and plans of the search for the critical structures - the onset of fireball, the onset of deconfinement, and the deconfinement critical point - in high energy nucleus-nucleus collisions. First, the basic ideas are introduced, the history of the observation of strongly interacting matter in heavy ion collisions is reviewed, and the path towards the quark-gluon plasma discovery is sketched. Then the status of the search for critical structures is discussed - the discovery of the onset of deconfinement, indications for the onset of fireball, and still inconclusive results concerning the deconfinement critical point. Finally, an attempt to formulate priorities for future measurements - charm quarks vs the onset of deconfinement and detailed study of the onset of fireball - closes the paper.

The onsets of deconfinement and fireball of NA61/SHINE

The NA61/SHINE experiment at the CERN SPS is pursuing a rich programme on strong interactions, covering the study of onset of deconfinement and aims to discover the critical point of strongly interacting matter by performing an energy and system-size scan at the full CERN SPS momentum range. These scans of p+p, p+Pb, Be+Be, Ar+Sc and Pb+Pb have been mostly completed with Xe+La last year (more Pb+Pb to to taken this year). Results from the different reactions are now emerging. As a surprise, some measurements did not scale smoothly. In particular, for the K+/π+ ratio, Be+Be collisions behaved similarly to p+p (as superposition of nucleon collisions), while Ar+Sc was closer to Pb+Pb collisions. This step can not be explained by onset of deconfinement, and may indicate that there is also a onset of fireball in relativistic heavy ion collisions. A review of the results as well as possible interpretation will be presented. The theoretical models (SMES, PHSD) describe onset of deconfinement at the heaviest system relatively well. However, no model describes the behaviour of data at previously unmeasured collisions of light and intermediate size ions. The onset of fireball is not described by any model.

Recent results of strong interaction program from NA61/SHINE experiment at CERN SPS

The NA61/SHINE experiment at the CERN SPS pursues a rich program of strong interactions. The main physics goals of this program are the study of properties of the onset of deconfinement and search for the signatures of the critical point of strongly interacting matter by performing the two-dimensional scan in a broad region of energy (beam momentum 13A-158A GeV/c) and system size (p+p, Be+Be, Ar+Sc and Xe+La). Recent NA61/SHINE results on particle spectra and event-by-event fluctuations in p+p, Be+Be and Ar+Sc collisions are shown with emphasis on the measurements of particle ratios, namely of pion a strangeness production, multiplicity fluctuations versus energy and the system size of colliding nuclei. It will be shown that the hadron production properties in heavy ion collisions which change rapidly in the low SPS energy domain and are interpreted as the beginning of quark-gluon plasma production – onset of deconfinement could be also the case in inelastic p+p interactions and probably in Be+Be collisions. The paper presents a selection of NA61/SHINE results on particle production properties discussed together with existing data from the NA49 collaboration. The evolution of non-monotonic structures in the pion and strangeness production as a function of the system size and energy is addressed. The rapid change of hadron production properties from p+p and Be+Be up to Ar+Sc and Pb+Pb collisions can be interpreted as the beginning of the large clusters formation of strongly interacting matter - the onset of fireball. The NA61/SHINE strong interaction programme is presented including the recent status on proton intermittency analysis and strongly intensive fluctuation observables of particle multiplicity and transverse momentum.

Onset of Deconfinement and the Critical Point at SPS Energies

Onset of Deconfinement and the Critical Point at SPS Energies

NA61/SHINE Experiment—Program beyond 2020

The fixed-target NA61/SHINE experiment (SPS CERN) looks for the critical point (CP) of strongly interacting matter and the properties of the onset of deconfinement. It is a scan of measurements of particle spectra and fluctuations in proton–proton, proton–nucleus, and nucleus–nucleus interactions as a function of collision energy and system size. This gives unique possibilities to researching critical properties of the dense hot hadronic matter created in the collision process. New measurements and their objectives, related to the third stage of the experiment after 2020, are presented and discussed here.

N – N, PT – N and PT – PT Fluctuations in Nucleus–Nucleus Collisions at the NA61/SHINE Experiment

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News from the NA61/SHINE experiment

The main goals of the NA61/SHINE experiment at the CERN SPS are the search for the critical point of strongly interacting matter and the study of the properties of the onset of deconfinement. These aims are pursued by performing a two-dimensional scan of the phase diagram of strongly interacting matter by varying the momentum and size of the colliding nuclei. This contribution summarises the latest results from the NA61/SHINE experiment, in particular, new results on spectra and yields of ϕ meson in p+p interactions at 40, 80 and 158 GeV/c and K+ and K- production in central Be+Be collisions at mid-rapidity. In addition, results on system size dependence of particle yield ratios and fluctuations are presented.

News from the NA61/SHINE experiment

NA61/SHINE is a fixed target experiment operating at the CERN SPS. Its main goals are to search for the critical point of strongly interacting matter and to study the onset of deconfinement. For these goals a scan of the two dimensional phase diagram (T-μB) is being performed at the SPS by measurements of hadron production in proton-proton, proton-nucleus and nucleusnucleus interactions as a function of collision energy. In this paper the status of the NA61/SHINE strong interaction physics programme is presented including recent results on proton intermittency, strongly intensive fluctuation observables of multiplicity and transverse momentum fluctuations. These measurements are expected to be sensitive to the correlation length in the produced matter and, therefore, have the ability to reveal the existence of the critical point via possible non-monotonic behavior. The NA61/SHINE results are compared to the model predictions.

Measurements of pi ^pm , K^pm , p and {bar{text {p}}} spectra in proton-proton interactions at 20, 31, 40, 80 and 158\xa0text{ GeV }/c with the NA61/SHINE spectrometer at the CERN SPS

Measurements of inclusive spectra and mean multiplicities of pi ^pm , K^pm , p and {bar{text {p}}} produced in inelastic p + p interactions at incident projectile momenta of 20, 31, 40, 80 and 158 text{ GeV }/c (sqrt{s} = 6.3, 7.7, 8.8, 12.3 and 17.3 text{ GeV }, respectively) were performed at the CERN Super Proton Synchrotron using the large acceptance NA61/SHINE hadron spectrometer. Spectra are presented as function of rapidity and transverse momentum and are compared to predictions of current models. The measurements serve as the baseline in the NA61/SHINE study of the properties of the onset of deconfinement and search for the critical point of strongly interacting matter.

The Mar(e)k of QGP: Strangeness

Strangeness signature of of quark-gluon plasma (QGP) is central to the exploration of baryon-dense matter: the search for the critical point and onset of deconfinement. I report on the discovery of QGP by means of strangeness: The key historical figures and their roles in this quest are introduced and the experimental results obtained are discussed. The important role of antihyperons is emphasized. The statistical hadronization model, and sudden hadronization are described. Results of present day data analysis: strangeness and entropy content of a large fireball, and the universal hadronization condition describing key features of all explored collision systems are presented.

Updates to the p+p and A+A chemical freeze-out lines from the new experimental data

We show that the new data on mean multiplicities measured in p+p and A+A collisions together with the updated list of resonances lead to the significant changes of the obtained freeze-out lines. The new A+A line gives much smaller temperatures at high collision energies and agrees with the values obtained at the LHC. The newly obtained p+p line is much closer to the A+A line than previously expected, and even touches it in the region where the K+/π+ horn appears in the data. It indicates that the temperatures that will be obtained in the beam energy and system size scan by the NA61/SHINE Collaboration might be very close. However, our analysis shows that the chemical potentials could be very different for the same energies in A+A and p+p. It adds more puzzles to the set of surprising coincidences at the energies close to the possible onset of deconfinement.

Polyakov Loop Fluctuations in Terms of Dirac Eigenmodes

Critical Point and Onset of Deconfinement 2016 and Working Group Meeting of COST Action MP1304

Strangeness from SPS to FAIR: Searching for the onset of deconfinement

Since the early days of heavy-ion physics, strangeness has been considered a sensitive probe of the state of matter created in nuclear collisions. This assessment still holds today, where we are witnessing renewed interest in collisions at moderate energies, manifested in the running or projected experimental programmes at RHIC, SPS, FAIR, and NICA. In this article, we will review the current understanding of strangeness production at lower energies and discuss how far future measurement of strange particles can contribute to understanding the properties of dense QCD matter and to the search for the onset of deconfinement.

Rapidity Distribution of Charged Pions From Pb+Pb and Au+Au Central Collisions

Rapidity distributions for charged pions produced from central collisions Pb+Pb and Au+Au at (b ≤ 3.4 fm.) in range of energy 2 GeV up to  = 200 GeV are investigated. The experimental results are studied  in terms of the Ultra-relativistic Quantum Molecular Dynamic Model Ur-QMD. In general, the model can give suitable predictions of rapidity distributions for production of charged pions from interactions with energies below 160 A GeV. This model is supported the assumption that the onset of de-confinement is located at low energies. It treats the initial nucleon-nucleon interactions within a string-hadronic framework. In addition, it includes effects such as string-string interactions and hadronic re-scattering that expected to be relevant in A+A collisions. There is a kind of similarity for mechanism responsible for production of the two charge states of pions and it can extended to other hadrons. Ultra-relativistic quantum molecular dynamic model give good description on energy dependence for charged pion productions and points of maximum rapidity.Â

Statistical Model of the Early Stage of Nucleus--Nucleus Collisions with Exact Strangeness Conservation

The Statistical Model of the Early Stage, SMES, describes a transition between confined and deconfined phases of strongly interacting matter created in nucleus-nucleus collisions. The model was formulated in the late 1990s for central Pb+Pb collisions at the CERN SPS energies. It predicted several signals of the transition (onset of deconfinement) which were later observed by the NA49 experiment. The grand canonical ensemble was used to calculate entropy and strangeness production. This approximation is valid for reactions with mean multiplicities of particles carrying conserved charges being significantly larger than one. Recent results of NA61/SHINE on hadron production in inelastic p+p interactions suggest that the deconfinement may also take place in these reactions. However, in this case mean multiplicity of particles with non-zero strange charge is smaller than one. Thus for the modeling of p+p interactions the exact strangeness conservation has to be implemented in the SMES. This extension of the SMES is presented in the paper.

Dimuon production in PbPb collisions at 20–160 AGeV at the CERN SPS: Mapping the QCD phase diagram in the transition region with a new NA60-like experiment

Abstract The structure of the QCD phase diagram for moderate temperatures and high baryon densities is still almost unexplored. Here, the QGP and hadronic phases should be separated by a first order transition region which is expected to end with a critical point. In this regime, dilepton measurements provide a rich set of observables to shed light on the onset of deconfinement and on the issue of chiral symmetry restoration. The objective of this paper is to present a proposal for a new NA60-like experiment (NA60+) to measure dimuon production with unprecedented precision in a comprehensive low energy scan at the CERN SPS. The CERN SPS is unique for systematic investigations along these lines, because this accelerator will be able to deliver high quality intense beams to perform systematic measurements of electromagnetic radiation over the full energy range from ∼ 20 to 160 AGeV .

Multiplicity fluctuations of identified hadrons in p+p interactions at SPS energies

Study of energy and system size fluctuations of identified hadrons is one of the key goals of NA61/SHINE at the CERN SPS. Results may allow to discover the critical point (CP) of strongly interacting matter as well as to uncover properties of the onset of deconfinement (OD). But fluctuations exhibit numerous other sources starting from most basic ones like volume effects and conservation laws.NA49 seems to observe fluctuations related to CP in collisions of medium size nuclei at top SPS energy. However, this result will remain inconclusive until systematic data on energy and system size dependence will be available. Moreover, fluctuations in p+p as well as in Pb+Pb interactions should be better understood.In this contribution results on multiplicity fluctuations of identified hadrons in p+p interactions at the CERN SPS energies will be presented. The NA61 data will be compared with the corresponding results from central Pb+Pb collisions of NA49 in the common acceptance region of both experiments. Moreover, predictions of models (EPOS, UrQMD and HSD) for both reactions will be tested.