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Register a new userCurrent Status of Quark Gluon Plasma Signals
حالة الآن لإشارات البلازما الكوارك جلوون
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تم الإثبات بشكل قاطع بشأن خلق شكل جديد من المادة في تصادمات Pb+Pb في SPS. نحن نناقش فريدية العلامات التجريبية المقترحة بشكل متكرر لخلق أجسام الذرة في التصادمات الثقيلة الناقلة النسبية. يتم إثبات أن لا أحد من العلامات المقترحة مثل إنتاج / تخفيض Jpsi meson، تعزيز الغرابة، الديليبتون، والتدفق الموجه حتى الآن يظهر بوضوح أن تم خلق فاعلية من المادة المحررة في تصادمات Pb+Pb في SPS. نؤكد على ضرورة القيام بقياسات نظامية في المستقبل للبحث عن عجزات متزامنة في دوال الانشطار لعدة مراكز البحث للقرب من الإصدار الخاص بخواص المادة الساخنة والناعمة الذي يتم تحديدها من البيانات.
Compelling evidence for the creation of a new form of matter has been claimed to be found in Pb+Pb collisions at SPS. We discuss the uniqueness of often proposed experimental signatures for quark matter formation in relativistic heavy ion collisions. It is demonstrated that so far none of the proposed signals like Jpsi meson production/suppression, strangeness enhancement, dileptons, and directed flow unambigiously show that a phase of deconfined matter has been formed in SPS Pb+Pb collisions. We emphasize the need for systematic future measurements to search for simultaneous irregularities in the excitation functions of several observables in order to come close to pinning the properties of hot, dense QCD matter from data.
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We believe that one can have serious reservations as to whether heavy ion collisions (e.g. 100 GeV/n Au + 100 GeV/n Au) can lead to Thermal and Chemical equilibrium over large regions (particularly if it is assumed this happens whenever QGP is produced at RHIC-that is if it is produced). It is at present not clear that the collision dynamics and times available will lead to this. An alternate scenario proposed by Van Hove where localized in rapidity bubbles of plasma may well be more probable, and may well occur at least some of the time, and some of the time mainly survive to the final state. If this occurs we have developed a series of event generators to extend and describe these phenomena. A Van Hove type[6,7] spherical bubble at eta=0 is embedded in a resonable event generator in qualitative agreement with Hijing etc[12]. The plasma bubble hadronized at a temperature of 170 Mev according to the model developed by Koch, Muller and Rafelski[21]. The amount of available bubble energy is selected by that in a small central circular cross-section of radius approx 1.3fm or 2.5fm in 100 Gev/n Au+AU, central events The results predict Possible Striking Signals for a QGP. We are also applying these techniques to investigating Kharzeev and Pisarski bubbles of metastable vacua with odd CP.
Brief review of the hadronic probes that are used to diagnose the quark-gluon plasma produced in relativistic heavy ion collisions and interrogate its properties. Emphasis is placed on probes that have significantly impacted our understanding of the nature of the quark-gluon plasma and confirmed its formation.
The fast simultaneous hadronization and chemical freeze out of supercooled quark-gluon plasma, created in relativistic heavy ion collisions, leads to the re-heating of the expanding matter and to the change in a collective flow profile. We use the assumption of statistical nature of the hadronization process, and study quantitatively the freeze out in the framework of hydrodynamical Bjorken model with different quark-gluon plasma equations of state.
We study the evolution of the quark-gluon composition of the plasma created in ultra-Relativistic Heavy-Ion Collisions (uRHICs) employing a partonic transport theory that includes both elastic and inelastic collisions plus a mean fields dynamics associated to the widely used quasi-particle model. The latter, able to describe lattice QCD thermodynamics, implies a chemical equilibrium ratio between quarks and gluons strongly increasing as $Trightarrow T_c$, the phase transition temperature. Accordingly we see in realistic simulations of uRHICs a rapid evolution from a gluon dominated initial state to a quark dominated plasma close to $T_c$. The quark to gluon ratio can be modified by about a factor of $sim 20$ in the bulk of the system and appears to be large also in the high $p_T$ region. We discuss how this aspect, often overflown, can be important for a quantitative study of several key issues in the QGP physics: shear viscosity, jet quenching, quarkonia suppression. Furthermore a bulk plasma made by more than $80%$ of quarks plus antiquarks provides a theoretical basis for hadronization via quark coalescence.
Here we present several remarkable irregularities at chemical freeze-out which are found using an advanced version of the hadron resonance gas model. The most prominent of them are the sharp peak of the trace anomaly existing at chemical freeze-out at the center of mass energy 4.9 GeV and two sets of highly correlated quasi-plateaus in the collision energy dependence of the entropy per baryon, total pion number per baryon, and thermal pion number per baryon which we found at the center of mass energies 3.8-4.9 GeV and 7.6-10 GeV. The low energy set of quasi-plateaus was predicted a long time ago. On the basis of the generalized shock-adiabat model we demonstrate that the low energy correlated quasi-plateaus give evidence for the anomalous thermodynamic properties inside the quark-gluon-hadron mixed phase. It is also shown that the trace anomaly sharp peak at chemical freeze-out corresponds to the trace anomaly peak at the boundary between the mixed phase and quark gluon plasma. We argue that the high energy correlated quasi-plateaus may correspond to a second phase transition and discuss its possible origin and location. Besides we suggest two new observables which may serve as clear signals of these phase transformations.
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