Recent results on strangeness production from NA49

We present a summary of measurements of strange particles performed by the experiment NA49 in inelastic p+p interactions, as well as semi-central C+C and Si+Si, central Pb+Pb, and minimum bias Pb+Pb collisions in the energy range $\sqrt{s_{NN}}$ = 6.3 - 17.3 GeV. New results on $\pi^{-}$, $K^{+}$ and $K^{-}$ production in minimum bias Pb+Pb collisions at $\sqrt{s_{NN}}$ = 8.7 and 17.3 are shown. Furthermore the strangeness enhancement factor at $\sqrt{s_{NN}}$ = 17.3 GeV is presented and compared to the results from NA57 and STAR. Energy dependence of strange particle yields normalized to pion yields is presented. New data on $$ production are shown at $\sqrt{s_{NN}}$ = 17.3 GeV. Furthermore we present the energy dependence of $K/\pi$ and $K/p$ fluctuations. The data are compared with model predictions.Comment: 9 pages, 7 figures, Submitted to J. Phys. G (Proceedings of the International Conference on Strangeness in Quark Matter, Buzios, Rio de Janeiro, Brazil, September 27 - October 2, 2009

Modified Hagedorn formula including temperature fluctuation - Estimation of temperatures at RHIC experiments -

We have systematically estimated the possible temperatures obtained from an analysis of recent data on $p_t$ distributions observed at RHIC experiments. Using the fact that observed $p_t$ distributions cannot be described by the original Hagedorn formula in the whole range of transverse momenta (in particular above 6 GeV/c), we propose a modified Hagedorn formula including temperature fluctuation. We show that by using it we can fit $p_t$ distributions in the whole range and can estimate consistently the relevant temperatures, including their fluctuations.Comment: Some misprints corrected, references updated. To be published in Eur. Phys. J. C (2006

(Anti)Proton and Pion Source Sizes and Phase Space Densities in Heavy Ion Collisions

NA44 has measured mid-rapidity deuteron spectra from AA collisions at sqrt{s}=18GeV/A at the CERN SPS. Combining these spectra with published proton, antiproton and antideuteron data allows us to calculate, within a coalescence framework, proton and antiproton source sizes and phase space densities. These results are compared to pion source sizes and densities, pA results and to lower energy (AGS) data. The antiproton source is larger than the proton source at sqrt{s}=18GeV/A. The phase space densities of pions and protons are not constant but grow with system size. Both pi+ and proton radii decrease with transverse mass and increase with sqrt{s}. Pions and protons do not freeze-out independently. The nature of their interaction changes as sqrt{s}, and the pion/proton ratio increases.Comment: 4 pages, Latex 2.09, 3 eps figures. Changes for January 2001. The proton source size is now calculated assuming a more realistic Hulthen, rather than Gaussian, wavefunction. A new figure shows the effect of this change which is important for small radii. A second new figure shows the results of RQMD calculations of the proton source size and phase density. Because of correlations between position and momentum coalesence does not show the full proton source size. The paper has been streamlined and readability improve

Flavor Production in Pb(160AGeV) on Pb Collisions: Effect of Color Ropes and Hadronic Rescattering

Collective interactions in the preequilibrium quark matter and hadronic resonance gas stage of ultrarelativistic nucleus-nucleus collisions are studied in the framework of the the transport theoretical approach RQMD. The paper reviews string fusion into color ropes and hadronic rescattering which serve as models for these interactions. Hadron production in central Pb(160AGeV) on Pb collisions has been calculated. The changes of the final flavor composition are more pronounced than in previous RQMD studies of light ion induced reactions at 200AGeV. The ratio of created quark pairs $s\bar{s}$/($u\bar{u}$+$d\bar{d}$) is enhanced by a factor of 2.4 in comparison to $pp$ results. Color rope formation increases the initially produced antibaryons to 3 times the value in the `NN mode', but only one quarter of the produced antibaryons survives because of subsequent strong absorption. The differences in the final particle composition for Pb on Pb collisions compared to S induced reactions are attributed to the hadronic resonance gas stage which is baryon-richer and lasts longer.Comment: 60 pages + 11 postscript figures (uuencoded and included

Azimuthal anisotropy of charged jet production in root s(NN)=2.76 TeV Pb-Pb collisions

We present measurements of the azimuthal dependence of charged jet production in central and semi-central root s(NN) = 2.76 TeV Pb-Pb collisions with respect to the second harmonic event plane, quantified as nu(ch)(2) (jet). Jet finding is performed employing the anti-k(T) algorithm with a resolution parameter R = 0.2 using charged tracks from the ALICE tracking system. The contribution of the azimuthal anisotropy of the underlying event is taken into account event-by-event. The remaining (statistical) region-to-region fluctuations are removed on an ensemble basis by unfolding the jet spectra for different event plane orientations independently. Significant non-zero nu(ch)(2) (jet) is observed in semi-central collisions (30-50% centrality) for 20 <p(T)(ch) (jet) <90 GeV/c. The azimuthal dependence of the charged jet production is similar to the dependence observed for jets comprising both charged and neutral fragments, and compatible with measurements of the nu(2) of single charged particles at high p(T). Good agreement between the data and predictions from JEWEL, an event generator simulating parton shower evolution in the presence of a dense QCD medium, is found in semi-central collisions. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).Peer reviewe

Forward-central two-particle correlations in p-Pb collisions at root s(NN)=5.02 TeV

Two-particle angular correlations between trigger particles in the forward pseudorapidity range (2.5 2GeV/c. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B. V.Peer reviewe

Event-shape engineering for inclusive spectra and elliptic flow in Pb-Pb collisions at root(NN)-N-S=2.76 TeV

Peer reviewe

Production of He-4 and (4) in Pb-Pb collisions at root(NN)-N-S=2.76 TeV at the LHC

Results on the production of He-4 and (4) nuclei in Pb-Pb collisions at root(NN)-N-S = 2.76 TeV in the rapidity range vertical bar y vertical bar <1, using the ALICE detector, are presented in this paper. The rapidity densities corresponding to 0-10% central events are found to be dN/dy4(He) = (0.8 +/- 0.4 (stat) +/- 0.3 (syst)) x 10(-6) and dN/dy4 = (1.1 +/- 0.4 (stat) +/- 0.2 (syst)) x 10(-6), respectively. This is in agreement with the statistical thermal model expectation assuming the same chemical freeze-out temperature (T-chem = 156 MeV) as for light hadrons. The measured ratio of (4)/He-4 is 1.4 +/- 0.8 (stat) +/- 0.5 (syst). (C) 2018 Published by Elsevier B.V.Peer reviewe