Monte Carlo model for nuclear collisions from SPS to LHC energies

A Monte Carlo model to simulate nuclear collisions in the energy range going from SPS to LHC, is presented. The model includes in its initial stage both soft and semihard components, which lead to the formation of color strings. Collectivity is taken into account considering the possibility of strings in color representations higher than triplet or antitriplet, by means of string fusion. String breaking leads to the production of secondaries. At this point, the model can be used as initial condition for further evolution by a transport model. In order to tune the parameters and see the results in nucleus-nucleus collisions, a naif model for rescattering of secondaries is introduced. Results of the model are compared with experimental data, and predictions for RHIC and LHC are shown.Comment: LaTeX, 48 pages, 6 tables, 15 postscript figures included using epsfi

Synchonisation of Resonances with Thresholds

The mechanism by which a resonance may be attracted to a sharp threshold is described with several examples. It involves a threshold cusp interfering constructively with either or both (i) a resonance produced via confinement, (ii) attractive t- and u-channel exchanges. More generally, it is suggested that resonances are eigenstates generated by mixing between confined states and long-range meson and baryon exchanges.Comment: 8 pages, 4 figures. For Meson08 Proceedings. One important typo correcte

How many of the scaling trends in pppp collisions will be violated at sqrt{s_NN} = 14 TeV ? - Predictions from Monte Carlo quark-gluon string model

Multiplicity, rapidity and transverse momentum distributions of hadrons produced both in inelastic and nondiffractive $pp$ collisions at energies from $\sqrt{s} = 200$\,GeV to 14\,TeV are studied within the Monte Carlo quark-gluon string model (QGSM). Good agreement with the available experimental data up to $\sqrt{s} = 13$\,TeV is obtained, and predictions are made for the collisions at top LHC energy $\sqrt{s} = 14$\,TeV. The model indicates that Feynman scaling and extended longitudinal scaling remain valid in the fragmentation regions, whereas strong violation of Feynman scaling is observed at midrapidity. The Koba-Nielsen-Olesen (KNO) scaling in multiplicity distributions is violated at LHC also. The origin of both maintenance and violation of the scaling trends is traced to short range correlations of particles in the strings and interplay between the multistring processes at ultrarelativistic energies

The initial state of ultra-relativistic heavy ion collision

A model for energy, pressure and flow velocity distributions at the beginning of ultra-relativistic heavy ion collisions is presented, which can be used as an initial condition for hydrodynamic calculations. Our model takes into account baryon recoil for both target and projectile, arising from the acceleration of partons in an effective field, produced in the collision. The typical field strength (string tension) for RHIC energies is about 5-12 GeV/fm, what allows us to talk about "string ropes". The results show that a QGP forms a tilted disk, such that the direction of the largest pressure gradient stays in the reaction plane, but deviates from both the beam and the usual transverse flow directions. Such initial conditions may lead to the creation of "antiflow" or "third flow component".Comment: 28 pages, 9 figures. The presentation has been changed considerably. Some parts of the model have been reformulated, what led to modifications in several equations: (20-38), Apps. A, B. All the figures have been changed from 100 GeV/nucl initial energy to the achieved RHIC energy of 65 GeV/nucl. The last subplots in the Figs. 3, 4, 5, 6 present E=T^{00} in the laboratory frame now, instead of the energy density in the local rest frame, e, shown in the initial version. We also added the App. C to clarify the transformation from space-time to lightcone coordinates and bac

Third flow component as QGP signal

A review of earlier fluid dynamical calculations with QGP show a softening of the directed flow while with hadronic matter this effect is absent. The effect shows up in the reaction plane as enhanced emission which is orthogonal to the directed flow. Thus, it is not shadowed by the deflected projectile and target. As both of these flow components are in the reaction plane these form an enhanced 'elliptic flow' pattern. Recent experimental data at 11 AGeV and above show the same softening, hinting at QGP formation.Comment: 12 pages, Latex, and 3 figures (.eps), 2 style files (.sty

Dropping rho and A_1 Meson Masses at Chiral Phase Transition in the Generalized Hidden Local Symmetry

We study the chiral symmetry restoration using the generalized hidden local symmetry (GHLS) which incorporates the rho and A_1 mesons as the gauge bosons of the GHLS and the pion as the Nambu-Goldstone boson consistently with the chiral symmetry of QCD. We show that a set of parameter relations, which ensures the first and second Weinberg's sum rules, is invariant under the renormalization group evolution. Then, we found that the Weinberg's sum rules together with the matching of the vector and axial-vector current correlators inevitably leads to {\it the dropping masses of both rho and A_1 mesons} at the symmetry restoration point, and that the mass ratio as well as the mixing angle between the pion and A_1 meson flows into one of three fixed points.Comment: 17 pages, 7 figures; references added and discussions expande

The Strong Decay Patterns of the 1−+1^{-+} Exotic Hybrid Mesons

We calculate the coupling constants of the decay modes $1^{-+}\rightarrow\rho\pi, f_1\pi, b_1\pi, \eta\pi, \eta'\pi, a_1\pi, f_1\eta$ within the framework of the light-cone QCD sum rule. Then we calculate the partial width of these decay channels, which differ greatly from the existing calculations using phenomenological models. For the isovector $1^{-+}$ state, the dominant decay modes are $\rho\pi, f_1\pi$. For its isoscalar partner, its dominant decay mode is $a_1\pi$. We also discuss the possible search of the $1^{-+}$ state at BESIII, for example through the decay chains $J/\psi (\psi')\to \pi_1 +\gamma$ or $J/\psi (\psi')\to \pi_1 +\rho$ where $\pi_1$ can be reconstructed through the decay modes $\pi_1\to \rho\pi\to \pi^+\pi^-\pi^0$ or $\pi_1\to f_1(1285)\pi^0$. Hopefully the present work will be helpful to the experimental establishment of the $1^{-+}$ hybrid meson.Comment: 14 pages, 10 figure

Effective String Rope Model for the initial stages of Ultra-Relativistic Heavy Ion Collisions

Different approaches to describe initial stages of relativistic heavy ion collisions are discussed qualitatively and quantitatively. An Effective String Rope Model is presented for heavy ion collisions at RHIC energies. Our model takes into account baryon recoil for both target and projectile, arising from the acceleration of partons in an effective field, produced in the collision. The typical field strength (string tension) for RHIC energies is about 5-12 GeV/fm, what allows us to talk about ``string ropes''. The results show that a QGP forms a tilted disk, such that the direction of the largest pressure gradient stays in the reaction plane, but deviates from both the beam and the usual transverse flow directions. The produced initial state can be used as an initial condition for further hydrodynamical calculations. Such initial conditions lead to the creation of third flow component.Comment: 47 pages, 14 figures. Minor changes were made, style was changed to "elsart". Paper is accepted to Nucl. Phys.

Hf isotopes in zircon from the western Superior province, Canada: Implications for Archean crustal development and evolution of the depleted mantle reservoir

U-Pb and Hf isotopic measurements on zircons from the western Superior province confirm that the area contains at least three distinct terrane types. Juvenile terranes that formed mostly within the time span 2.75-2.68 Ga occupy much of the western Wabigoon subprovince as well as granite-greenstone belts to the south. Juvenile 3.0 Ga terranes that were reworked over the time span 2.7-3.0 Ga occupy the south-central part of the Wabigoon subprovince and the North Caribou block in the Sachigo subprovince. Rocks with mantle extraction ages as old as 3.5 Ga and zircon U-Pb ages extending to 3.3 Ga characterize a third type of terrane represented by the Winnipeg River subprovince. This terrane was strongly reworked during the late Archean. Arc-related magmatism was ongoing at 2.71-2.75 Ga in the different terranes, which probably accreted over the time span 2.71-2.68 Ga. Enriched Hf and high O isotopic signatures in late sanukitoid-suite plutons appear to be correlated, which suggests that assimilation of Mesoarchean crust was an important factor in their magmatic evolution. Enriched Hf isotopic signatures in detrital and igneous zircon from parts of the north-central Wabigoon subprovince support previous suggestions that the Winnipeg River terrane extends eastward beyond the Winnipeg River subprovince. The Winnipeg River subprovince was probably being uplifted and eroded into the Quetico sedimentary basin shortly after 2700 Ma, as shown by detrital zircons with enriched Hf isotopic signatures and Meso- to Paleoarchean ages. The pattern of ages and isotopic signatures from the North Caribou block and the south-central Wabigoon subprovince are similar, suggesting that these terranes are correlative. If so, the south-central Wabigoon terrane may have been tectonically transported from the north. Hf isotopic compositions of zircon from juvenile Archean sources are remarkably consistent and define an average εHf value of +3.5 ± 0.2 for samples with an average age of 2724 Ma and a best estimate of +2.7 ± 0.4 at 3000 Ma. Thus, the Neaoarchean depleted mantle reservoir beneath the Superior province appears to have been isotopically well mixed. εHf values were calculated using a value of 1.865 × 10-5 Ma-1 [Scherer, E., Munker, C., Mezger, K., 2001. Calibration of the Lutetium-Hafnium clock. Science 293, 683-687] for the 176Lu decay constant, which is thus far the best reproduced estimate and the one most consistent with depleted mantle evolution results based on Nd isotopes and Nb/Th ratios. A linear Hf mantle growth curve defined by these values and recent MORB intersects the chondritic Hf growth curve during the early Archean (3.4-4.0 Ga). This could indicate that the earliest formation of significant amounts of enriched crust coincides with ages of the oldest preserved rocks, but such a conclusion is contradicted by evidence from 142Nd and 143Nd in early Archean rocks for significant mantle depletion during the Hadean eon (>4.0 Ga). Both lines of evidence might be reconciled if Hadean enriched crust were largely remixed with its depleted mantle source near the beginning of the Archean, leaving only fragmentary evidence of its existence in the oldest rocks