Form Of Hadronic Matter Research Articles

The Nature of the Λ(1405) from Photoproduction at SPring-8/LEPS

The nature of Λ ( 1405 ) hyperon is yet unresolved for distinction among three-quark state, meson-baryon molecular state, or any other new form of hadronic matter. Recent theoretical works predict its lineshape to be different in terms of the πΣ isospin channels in the context of chiral dynamics. We have measured the lineshape of Λ ( 1405 ) in charged πΣ channels through p ( γ , K + π ) Σ reaction at 1.5–2.4 GeV. The observed lineshapes are different in terms of π − Σ + and π + Σ − channels, and depends largely on the angular coverage for pions from the Λ ( 1405 ) decay. The cross section for Λ ( 1405 ) photoproduction integrated over the angular region 0.8 < cos θ K + ∗ < 1.0 was found to be 0.43 μb in the energy range from 1.5 to 2.0 GeV and 0.072 μb in the energy range from 2.0 to 2.4 GeV.

Nucleon number dependence of the onset of anomalous J/ ψ suppression and the dynamics of nuclear collisions

We point out that the data on the onset of anomalous J/ ψ suppression as a function of nucleon numbers A and B could provide information on the dynamics of nuclear interactions. In particular the models of anomalous J/ ψ suppression by Blaizot and Ollitrault (BO) and by Kharzeev, Lourenço, Nardi and Satz (KLNS) are based on different assumptions on the dynamics of nuclear collisions and lead to different predictions of the dependence of the onset of anomalous J/ ψ suppression on nucleon numbers of colliding nuclei. The data on this onset as function of A and B could become a tool for the study of the dynamics of nuclear collisions and bring further evidence on J/ ψ suppression by new form of hadronic matter, possibly quark–gluon plasma. In particular we propose to study J/ ψ suppression in A+Pb interaction with nucleon number of A between 58 and 73 or a bit higher.

Search for the weak decay of a lightly bound H0 dibaryon

We present results of a search for a new form of hadronic matter, a six-quark, dibaryon state called the H0, a state predicted to exist in several theoretical models. Analyzing data collected by experiment E799-II at Fermilab, we searched for the decay H0-->Lambdappi(-) and found no candidate events. We place an upper limit on [B(H0-->Lambdappi(-))dsigma(H)/dOmega]/(dsigma(Xi)/dOmega) and, in the context of published models, exclude the region of lightly bound mass states just below the LambdaLambda mass threshold, 2.194<M(H)<2.231 GeV/c(2), with lifetimes from approximately 5x10(-10) sec to approximately 1x10(-3) sec.

Photon-photon and photon-hadron interactions at relativistic heavy ion colliders

In central collisions at relativistic heavy ion colliders like the Relativistic Heavy Ion Collider RHIC/Brookhaven and the Large Hadron Collider LHC (in its heavy ion mode) at CERN/Geneva, one aims at detecting a new form of hadronic matter — the Quark Gluon Plasma. We discuss here a complementary aspect of these collisions, the very peripheral ones. Due to coherence, there are strong electromagnetic fields of short duration in such collisions. They give rise to photon-photon and photon-nucleus collisions with high flux up to an invariant mass region hitherto unexplored experimentally. After a general survey photon-photon luminosities in relativistic heavy ion collisions are discussed. Then photon-photon physics at various γγ-invariant mass scales is discussed. The region of several GeV, relevant for RHIC is dominated by QCD phenomena (meson and vector meson pair production). Invariant masses of up to about 100 GeV can be reached at LHC, and the potential for new physics is discussed. Lepton-pair production, especially electron-positron pair production is copious. Due to the strong fields there will be new phenomena, especially multiple e + e − pair production.

Dimuons at Fermilab suggest new form of hadronic matter

Neutrino experiments at Fermilab conducted over the past two years, in which pairs of muons are produced, appear to show the existence of a new form of hadronic matter. The discovery suggests that matter carrying a new quantum number has been observed. This quantum number is often generically referred to as “charm.”