An alternative mechanism of Jψ suppression in heavy ion collisions

We argue that $\text{J}\text{ψ}$ suppression observed recently in high energy oxygen-uranium collisions by the NA38 Collaboration at CERN need not imply that the quark-gluon plasma was produced. A considerable part of the effect may be caused by the disintegration of $\text{J}\text{ψ}$'s in collisions with dense hadronic matter (below the phase transition into quark-gluon plasma) produced simultaneously with $\text{J}\text{ψ}$ in heavy ion interactions.     

Vector meson pole dominance in Jψ decays into mesons

The validity of the assumption that $\text{J}\text{ψ}$ decays into mesons proceed via ω, φ and ?⁰ poles followed by cascade decays is examined. $\text{Λ(}\text{J}\text{ψ}\text{→}\text{B}\text{π)}$ is well reproduced by using $\text{Λ(}\text{J}\text{ψ}\text{→ ?π), Λ(ω → ?π), Λ(}\text{B}\text{→ ωπ)}$ and the B → ωπ helicity structure. The structure of OZI-violating $\text{J}\text{ψ}\text{?}\text{V}{}^0$ transitions including the electromagnetic contribution is examined, and compared with the data on inclusive $\text{J}\text{ψ}$ decay.     

Instantons and condensates in supersymmetric CPN−1 models

The partition function in the multi-instanton background for the supersymmetric CP^N?1 model is calculated and is shown to be supersymmetry invariant. This is used to calculate Green's function involving N pairs of $\text{ψ}\text{ψ(x}{}_{\mathrm{i}}\text{)}$, and this turns out to be independent of the positions. A possible interpretation is that the composite field $\text{ψ}\text{ψ}$ acquires a vacuum expectation value. The results are in agreement with those obtained in the 1/N expansion.     

QCD anomaly mediation of ψ′ → ψπ0 and ψ′ → ψη

We comment on various decay processes mediated dominantly by pseudoscalar couplings to the QCD axial-vector anomaly. Using coupling strengths of our earlier calculation, we compute $\text{ψ′ → π}{}^0\text{ψ}\text{ψ′}\text{→ ηψ}$ and obtain good agreement with experiment.     

Radiative decays of the Jψ and evidence for a new heavy resonance

The three photon final state produced in e⁺e^? collisions has been measured at the mass of the $\text{J}\text{ψ}$ resonance using the nonmagnetic part of the double arm spectrometer DASP. The decays $\text{J}\text{ψ}\text{→ ηγ, η'γ}$ and π^oγ were observed and their branching ratios are given. A four standard deviation signal was observed in the γγ mass spectrum at a mass of (2.83 ± 0.03) GeV. An upper limit is given for the direct decay $\text{J}\text{ψ}\text{→ 3γ}$.     

Asymptotic scale invariance in two-dimensional theories: A massive Thirring model with bosons

The exact vanishing of all β functions of the Callan-Symanzik equation is proved in a two-dimensional model with Thirring and gradient couplings: $\text{(}\text{ψ}\text{γ}{}_{\mathrm{\mu }}\text{ψ)}{}^2$, $\text{(}\text{ψ}\text{γ}{}^5\text{γ}{}_{\mathrm{\mu }}\text{ψ)?}{}^{\mathrm{\mu }}\text{π}$ and $\text{(}\text{ψ}\text{γ}{}_{\mathrm{\mu }}\text{ψ)?}{}^{\mathrm{\mu }}\text{σ}$, where ψ, π and σ are fermion, pseudoscalar and scalar massive fields, respectively. The anomalous dimensions of scalar and pseudoscalar fields are also shown to be zero. Then we demonstrate that in two-dimensional models including at most one fermion field, only these three couplings can give asymptotic scale invariance.     

Momentum spectra of charged hadrons from the decays of Jψ and ψ'

Momentum spectra and particle ratios are presented for charged pions, kaons and nucleons emitted in the decays of $\text{J}\text{ψ}$ and ψ'.     

A characterization of the segal entropy

We study the Segal entropy $\text{S(ψ∣τ) = -τ(}\text{dψ}\text{dτ}\text{ln}\text{dψ}\text{dτ}\text{)}$ of a normal state ψ on a W¹-algebra $\text{M}$ with respect to a faithful normal semi-finite trace τ on $\text{M}$ and we give a unique characterization of this general entropy concept by means of some natural properties.     

Jψ and ψ′ decays into two hadrons

Branching ratios have been determined for the decays of $\text{J}\text{ψ}$ and ψ ′ into π⁺π^?, K⁺K^?, $\text{p}\text{p}$, π^±?^? and $\text{K}{}^{\mathrm{\pm }}\text{K}{}^1\text{(892)}{}^{\mathrm{?}}$. Results on a search for other two body decays of $\text{J}\text{ψ}$ and ψ′ are given. Also presented are values for the π and K from factors at $\text{s}\text{= 3.1}\text{and}\text{3.7}\text{GeV}$.     

Effective lagrangian of mesons and baryons in the strong-coupling expansion of lattice QCD

U(N) and SU(N) lattice QCD are considered. By using a method of the strong-coupling expansion, the effective lagrangian of hadrons is calculated up to the first order in 1/(g²N). For the Susskind lattice fermions, it is shown that chiral symmetry is spontaneously broken and as a result there appears the Nambu-Goldstone boson (pion). The fermion condensation 〈$\text{ψ}\text{ψ}$t>, the masses of hadrons and the pion decay constant are calculated and compared with the results of Monte Carlo (MC) simulations. In the strong-coupling region, our result of the order parameter 〈$\text{ψ}\text{ψ}$〉 coincides very well with that calculated by MC simulations.     

Inclusive Jψ production in e+e− annihilation in the energy range from 4.0 to 5.0 GeV

We report on inclusive production of $\text{J}\text{ψ}$ (3.1)-mesons observed in e⁺e^?-annihilation in the energy range $\text{s}\text{= 4.0–5.0}\text{GeV}$. After substraction of the radiative tail of the ψ(3.7) direct production of the $\text{J}\text{ψ}$ (3.1) is found to be in the order of 0.1% of the total hadronic cross section. No enhancements are seen at $\text{s}\text{= 4.03}\text{GeV}$ and 4.4 GeV. The level is in agreement with expectations from violation of the Zweig-rule.     

The η-η′ mixing angle and the relative radiative decay rates Γ(ψ→ηγ)Γ(ψ→η′γ)

The problem of η-η′ mixing is reexamined within the nonet scheme. It is shown that the mixing angle θ_p is quite sensitive to a small SU(3) violating $\text{27}$ piece. Taking SU(3) violating q$\text{q}$ annihilation terms into account, we obtain a large ratio $\text{Γ(ψ→ηγ)}\text{Γ(ψ→η′γ)}$ which is largely independent of the mixing angle and agrees with the measured value to within 20–30%.     

Monte Carlo calculations with fermions: The Schwinger model

An algorithm for Monte Carlo simulation of lattice gauge theories with fermions is presented. The method is applied to the Schwinger model with two flavors of massless fermions, formulated on a two-dimensional euclidean lattice. Preliminary results of the Monte Carlo iteration of this system are presented, with special emphasis on the behavior of the Wilson loop and bilocal chiral correlation functions such as $\text{〈}\text{ψ}\text{(1 + γ}{}_5\text{)ψ(x)}\text{ψ}\text{(1 ? γ}{}_5\text{)ψ(y)〉}$.     

Calculation of baryon masses in quantum chromodynamics

The polarization operator of quark currents with baryon quantum numbers is considered in quantum chromodynamics. The non-zero mean vacuum values of the field operator products are taken into account. The sum rules are obtained assuming that in the virtuality region ～1 GeV, among the mean vacuum values violating the chiral invariance, the most important is $\text{〈0|}\text{ψ}\text{ψ|0〉}$. Saturating these sum rules by the lowest baryonic states one is able to calculate the masses of the isobar Δ and nucleon N, M_Δ = 1.4 GeV, M_N = 1 GeV, up to 15% through the known value $\text{〈0|}\text{ψ}\text{ψ|0〉}$. The mass splitting in the baryonic decuplet $\text{M}{}_{\mathrm{\Sigma 1}}\text{?M}{}_{\mathrm{\Delta }}\text{= 125}\text{MeV}$ is calculated in first order in the current strange quark mass m_s = 150 MeV. Certain results for other baryonic resonances have also been obtained.     

The mixing and decays of isoscalar mesons

The predictions of a linear mass mixing model for pseudoscalar and vector mesons, which incorporates the effects of radial excitations, are examined. Several analyses are made fitting in each case to a different experimental value of $\text{Γ(ψ →η'γ)}\text{Γ(ψ→ηγ)}$ upon which the η-η′ mixing pattern is very sensitive. Predictions for radiative transitions among the mesons and for the ratio of production amplitudes $\text{σ}\text{(π}{}^{\mathrm{?}}\text{p→η′n)}\text{σ}\text{(π}{}^{\mathrm{?}}\text{p→ηn)}$ are compared with experiments. Results indicate a preferred value of 3.1 for $\text{Γ(ψ→η′γ)}\text{Γ(ψ→ηγ)}$.     

Symmetry properties of fermionic bilinears in lattice QCD

The 256 fermionic bilinears $\text{ψ}\text{γTψ}$ appearing in the Kogut-Susskind/Kähler-Dirac theory are classified into representations of the hypercubic rotation reflection group; charge conjugation and U(1)_A are also considered. Applications to the study of the normalization of lattice currents are suggested.     

Chiral phase transition in lattice QCD with dynamical quarks

The effect of virtual light quark loops on the chiral phase transition in lattice QCD with staggered fermions is investigated by employing the pseudo-fermion Monte Carlo method on a 6³ × 2 lattice. The variation in the order parameter $\text{〈}\text{ψ}\text{ψ〉}$ is found to become less sharp than the quenched case, indicating a second order chiral phase transitioon in the full theory.     

Generalized Bargmann inequalities

An extensive set of inequalities is derived for (ψ,?ψ) in $\text{L}{}^2\text{(}\text{R}{}^{\mathrm{n}}\text{)}$ which contains the Bargmann inequalities as a special case.     

Author index to volume 68B

The decay of J/ψ (3.1) into final states containing no charged particles has been studied experimentally. The partial decay width for the observed neutral decays is (470 ± 160) eV. The decay modes J/ψ → γη → 3γ and J/ψγη′ → 3γ are identified and the branching ratios

$\text{J}\text{ψ}\text{→ γη}\text{J}\text{ψ}\text{→}\text{all}\text{= (1.3 ±0.4) × 10}{}^{\mathrm{?3}}\text{,}\text{and}\text{J}\text{ψ}\text{→ γη′}\text{J}\text{ψ}\text{→ γη}\text{= 1.8 ±0.8}$

, are derived. Upper limits for the decay modes J/ψ → γπ⁰ and J/ψ → γγ are given.     

Experimental comparison of Jψ production by π±, K±, p and p̄ beams at 39.5 GeV/c

Measurements have been made of relative production cross sections of the $\text{J}\text{ψ}$ by π^±, K^±, p and p? at 39.5 GeV/c incident on copper. $\text{J}\text{ψ}$ production rates from π^?, K^? and p? are similar. The $\text{J}\text{ψ}$ relative particle/anti-particle production cross sections for x>0 are $\text{σ(π}{}^{\mathrm{+}}\text{)}\text{σ(π}{}^{\mathrm{?}}\text{)=(0.87±0.14)}$, σ(K⁺)/σ(K^?)=(0.85±0.5) and $\text{σ(}\text{p}\text{)}\text{σ(}\text{p}\text{?}\text{)=(0.15 ±0.08)}$. The small p/p? cross section ratio disagrees with models of J/ψ production by gluon amalgamation.