276 research outputs found
Superposition with Lambdas
We designed a superposition calculus for a clausal fragment of extensional polymorphic higher-order logic that includes anonymous functions but excludes Booleans. The inference rules work on -equivalence classes of -terms and rely on higher-order unification to achieve refutational completeness. We implemented the calculus in the Zipperposition prover and evaluated it on TPTP and Isabelle benchmarks. The results suggest that superposition is a suitable basis for higher-order reasoning
Superposition with Lambdas
We designed a superposition calculus for a clausal fragment of extensional polymorphic higher-order logic that includes anonymous functions but excludes Booleans. The inference rules work on βη-equivalence classes of λ-terms and rely on higher-order unification to achieve refutational completeness. We implemented the calculus in the Zipperposition prover and evaluated it on TPTP and Isabelle benchmarks. The results suggest that superposition is a suitable basis for higher-order reasoning
Will jets reduce the elliptic flow at LHC, while decays of resonances restore the constituent quark scaling?
Formation and evolution of the elliptic flow pattern in Pb+Pb collisions at
sqrt{s}=5.5 ATeV and in Au+Au collisions at sqrt{s}=200 AGeV are analyzed for
different hadron species within the framework of HYDJET++ Monte-Carlo model.
The model contains both hydrodynamic state and jets, thus allowing for a study
of the interplay between the soft and hard processes. It is found that jets are
terminating the rise of the elliptic flow with increasing transverse momentum.
Since jets are more influential at LHC compared to RHIC, the elliptic flow at
LHC should be weaker than that at RHIC. The influence of resonance decays on
particle elliptic flow is investigated also. These final state interactions
enhance the low-p_T part of the v_2 of pions and light baryons, and work
towards the fulfilment of idealized constituent quark scaling.Comment: 8 pages, 9 figures, 3 table
High Transverse Momentum Results from the STAR Collaboration
The STAR collaboration presents new measurements of high p_T hadron
production in Au+Au and p+p collisions at RHIC. We extend the previously
reported suppression of inclusive hadron and large azimuthal anisotropies to
much higher transverse momentum, decisively establishing the existence of
strong medium effects on hadron production well into the perturbative regime.
Near-angle two-particle correlations show directly that hadrons at pT > 4 GeV/c
result from the fragmentation of jets. Additional evidence for the onset of
perturbative QCD in this region comes from the flavor dependence of the
inclusive yields and elliptic flow. Finally, comparison of back-to-back hadron
pairs at high pT in p+p and in Au+Au collisions at various centralities reveals
a striking suppression of high pT back-to-back pairs in the most central Au+Au
collisions. All of these phenomena suggest a picture in which partons or their
hadronic fragments are strongly absorbed in the bulk matter, with the observed
hadrons resulting from jets produced on the periphery of the collision zone and
directed outwards.Comment: Plenary talk at QM2002 in Nantes/France, to be published in the
conference proceedings (Nuc.Phys.), 10 page
Particle Production and Flow at SIS Energies
An overview is given over recent measurements of flow and particle production
in the energy range from 0.1 to 2AGeV. Excitation functions for the directed
sideward and the azimuthally symmetric transverse flow are presented and show
the importance of flow phenomena in this incident energy regime. Rapidity
density distributions are indicative of a system size dependence of the
stopping process. The role of strange particles as a probe for the hot and
dense phase of hadronic matter is discussed with respect to the production and
propagation. The spectra of Kaons indicate an equilibration with the
surrounding baryons during the expansion while their directed flow pattern is
different from that of the nucleons.Comment: 14 pages, LaTeX with 10 included figures; Proceedings of the Quark
Matter 1996 conferenc
Particle-type dependence of azimuthal anisotropy and nuclear modification of particle production in Au + Au collisions at sqrt[sNN]=200 GeV
We present STAR measurements of the azimuthal anisotropy parameter v2 and the binary-collision scaled centrality ratio RCP for kaons and lambdas ( Lambda + Lambda -bar) at midrapidity in Au+Au collisions at sqrt[sNN]=200 GeV. In combination, the v2 and RCP particle-type dependencies contradict expectations from partonic energy loss followed by standard fragmentation in vacuum. We establish pT ~ 5 GeV/c as the value where the centrality dependent baryon enhancement ends. The K0S and Lambda + Lambda -bar v2 values are consistent with expectations of constituent-quark-number scaling from models of hadron formation by parton coalescence or recombination
Particle-type dependence of azimuthal anisotropy and nuclear modification of particle production in Au+Au collisions at s(NN)**(1/2) = 200-GeV
We present STAR measurements of the azimuthal anisotropy parameter and
the binary-collision scaled centrality ratio for kaons and lambdas
() at mid-rapidity in Au+Au collisions at
GeV. In combination, the and
particle-type dependencies contradict expectations from partonic energy loss
followed by standard fragmentation in vacuum. We establish
GeV/c as the value where the centrality dependent baryon enhancement ends. The
and values are consistent with
expectations of constituent-quark-number scaling from models of hadron
fromation by parton coalescence or recombination.Comment: 6 pages, 4 figures, 1 table. As published in PRL on Feb. 2, 2004;
Significant revisions have been made to the text and color has been added to
plot
- …