The case against factorization with vacuum insertion in quark decay graphs for non-leptonic decays

We show that factorization with vacuum insertion, an assumption often made for quark decay topologies in non-leptonic decays (e.g. by the authors of the annihilation model for $\text{D}\text{→}\text{K}\text{π}$), overestimates the absolute magnitude of ($\text{D}{}^{\mathrm{+}}\text{→}\text{K}{}^0\text{π}{}^{\mathrm{+}}$) by a factor 5. It also fails for $\text{ΔI =}\text{3}\text{2}$ hyperon decays.     

Effects of multiplicity on charm semileptonic decay distributions

We consider the effects of multiplicity in semileptonic decays of charmed D(1.87) mesons, produced near threshold in e⁺e^? collisions. We calculate the decay distributions from uncorrelated D → (nπ)Kev and resonance dominated $\text{D}\text{→}\text{K}{}^1\text{e}\text{v}$ modes. Recent data from DORIS suggest that modes with two or more final hadrons dominate strongly.     

Study of the Kππ system produced in K−p → KππN reactions at 14.3 GeV/c

We have studied the $\text{K}\text{ππ}$ system in the 14.3 GeV/c reactions K^?p → K^?π⁺π^?p, $\text{K}{}^{\mathrm{?}}\text{p}\text{→}\text{K}{}^0\text{π}{}^{\mathrm{?}}\text{π}{}^0\text{and}\text{K}{}^{\mathrm{?}}\text{p}\text{→}\text{K}{}^0\text{π}{}^{\mathrm{+}}\text{π}{}^{\mathrm{?}}\text{n}$. The data have been obtained from a 500 000 picture exposure of the CERN 2m HBC. The first two final states are dominated by Q-production in the Kππ system; there is also an L-signal at M (Kππ) ～ 1.75 GeV. The reaction cross sections are compared to K^?p data at other energies. We discuss the Kππ mass dependence of the diffractive production slope. Evidence is presented for a Q^?p versus Q⁺p differential cross section cross-over around |t| = 0.17 GeV². A t-channel isospin analysis for the $\text{KN}\text{→}\text{K}\text{1(890)π}\text{N}$ channels in the Q-region shows that the I = 1 exchange amplitude is $\text{? 10\%}$ of the dominant I = 0 exchange amplitude. The Kππ decay distributions indicate a predominant J^P = 1⁺ state in the Q-region, and an important J^P = 2^? contribution in the L-region. We find neither s-channel nor t-channel helicity conservation at the meson vertex in the Q- or L-regions. The Kπ angular correlation moments within the Kππ diffractive system are characteristic of Kπ elastic scattering, suggesting a π-exchange Deck-type production mechanism. There is evidence for a Kf⁰ and κπ contribution (where κ is the J^P(Kπ) = 0⁺ state) to the diffractive Kππ system. A fit to the $\text{K}{}^{\mathrm{?}}\text{π}{}^{\mathrm{+}}\text{π}{}^{\mathrm{?}}\text{and}\text{K}{}^0\text{π}{}^{\mathrm{?}}\text{π}{}^0$ Dalitz-plot distributions for the Q-re gion indicates that the ratio of $\text{K}\text{?}\text{to K}{}^1\text{π}$ decay amplitudes decreases with increasing Kππ mass.     

Evidence for double dissociation in K-p interactions at 14.3 GeV/c

We have studied the reaction K^-p → K^-π⁺π^-π⁺π^-p at 14.3 GeV/c to search for evidence of the double dissociation process $\text{K}{}^{\mathrm{-}}\text{p}\text{→}\text{QN}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}{}^1$. In the channel $\text{K}{}^{\mathrm{-}}\text{p}\text{→}\text{K}{}^{10}\text{(890)}$π₁^-π₂^-Δ⁺⁺ (1236) there is evidence for simultaneous production of low-mass enhancements in the $\text{K}{}^{10}\text{π}{}_1{}^{\mathrm{-}}$ and Δ⁺⁺(1236)π₂^- subsystems which correspond to the $\text{Q}\text{→}\text{K}{}^1\text{(890)π}$ and $\text{N}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}{}^1\text{→ Δπ}$ decay modes. In this particular final state the double fragmentation system is produced with a cross section of the order of a few microbarns. Our data are consistent with the factorizable pomeron exchange model of double diffractive dissociation.     

Photoproduction of charged π mesons from protons and neutrons in the energy range between 250 and 790 MeV

The differential cross sections for γp→π⁺n from hydrogen and the $\text{π}{}^{\mathrm{?}}\text{π}{}^{\mathrm{+}}$ ratios from deuterium were measured at nine c.m. angles between 30° and 150° for laboratory photon energies between 260 and 800 MeV. A magnetic spectrometer with three layers of scintillation hodoscope was used to detect charged π mesons. The cross section for γn→π^?p was obtained as a product of $\text{d}\text{σ}\text{d}\text{Ω}\text{(γ}\text{p}\text{→π}{}^{\mathrm{+}}\text{n}\text{)}$ and the $\text{π}{}^{\mathrm{?}}\text{π}{}^{\mathrm{+}}$ ratio. The overall features in the cross sections of the two reactions, γp→π⁺n and γn→π^?p, and in the ratios, $\text{π}{}^{\mathrm{?}}\text{π}{}^{\mathrm{+}}$, agree with predictions by Moorhouse, Oberlack and Rosenfeld, and Metcalf and Walker. An investigation of the possible existence of an isotensor current was made and a negative result was found. In detailed balance comparison with the new results on the inverse reaction π^?p→γn, no apparent violation of time-reversal invariance was observed.     

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 $\text{s}\text{= 3.1}\text{and}\text{3.7}\text{GeV}$.     

Momentum transfer distributions of some diffractive enhancements in K−p interactions at 14.3 GeV/c

We discuss the structure of the momentum transfer distributions for the diffractive dissociation processes p → nπ⁺, p → Δ⁺⁺π^? and $\text{K}{}^{\mathrm{?}}\text{→}\text{K}{}_{890}{}^{10}\text{π}{}^{\mathrm{?}}$. In the near-threshold mass region a clear break of slope is found around t′KK ～ 0.25 GeV² for the two baryonic channels, whereas no comparable structure is seen for the mesonic system. The $\text{K}\text{→}\text{K}{}^1\text{π}$ differential cross section exhibits a nearly exponential behaviour up to t′_pp ～ 0.6 GeV², falling over three orders of magnitude. The slope variations and breaks are strongly correlated both to the mass region considered and to the decay angle of the fragmentation system.     

A measurement of K1 (1420) decay branching ratios

The decay branching ratios of K¹⁰ (1420) into K⁺π^?, K⁰π⁺π^? and K¹⁺(892) π^? are measured in the charge exchange reaction $\text{K}{}^{\mathrm{+}}\text{d}\text{→}\text{K}{}^{10}\text{(1420)}\text{pp}{}_{\mathrm{S}}$ using data from a K⁺d bubble chamber experiment at 4.6 GeV/c incident momentum. For the branching ratio $\text{(}\text{K}{}^1\text{(1420) →}\text{K}{}^1\text{(892)π)/(}\text{K}{}^1\text{(1420) →}\text{K}\text{π)}\text{a value of}\text{(0.54 ± 0.16)}$ is obtained. The results are compared with previous measurements.     

Charmed meson decays and right-handed currents

In the presence of right-handed currents including $\text{(}\text{c}\text{s}\text{)}{}_{\mathrm{<mtext>R</mtext>}}$, it is emphasized that the dominant parity-violating (-conserving) Hamiltonian for nonleptonic decays of charmed hadrons transforms like $\text{45}\text{+}\text{45}{}^1\text{(}\text{20″ +}\text{84}\text{)}$ of SU(4), and leads to distinctive results especially in D⁺ → K_Sπ⁺, F⁺ → μ⁺ν_μ and D⁰ → K^?e⁺ν_e, etc.     

Measurement of the polarization parameter for antiproton-proton annihilation into charged pion and kaon pairs between 1.0 and 2.2 GeV/c

The polarization parameter P for the reactions $\text{p}\text{p}\text{→ π}{}^{\mathrm{?}}\text{π}{}^{\mathrm{+}}$ and $\text{p}\text{p}\text{→}\text{K}{}^{\mathrm{?}}\text{K}{}^{\mathrm{+}}$ has been measured over essentially the full angular range at ll laboratory momenta between 1.0 and 2.2. GeV/c, using a proton target polarized perpendicular to the scattering plane. The angles and momenta of both final state particles were determined from wire spark chambers, using the deflection caused by the polarized target magnet. Between 1000 and 5300 π^?π⁺ events, and 140 and 1300 K^?K⁺ events, were measured at each momentum. Differential cross sections for $\text{p}\text{p}\text{→ π}{}^{\mathrm{?}}\text{π}{}^{\mathrm{+}}$ were obtained. These are in excellent agreement with previous results. The polarization parameter for both channels is very close to +1 over much of the angular range. Legendre polynomial fits to the data are presented.     

Rare decay modes of K1(1420) and K1(892)

A 2.5 standard deviation signal is observed for the decay $\text{K}{}^{\mathrm{1?}}\text{(1420) →}\text{K}{}^{\mathrm{1?}}\text{(892)π}{}^{\mathrm{+}}\text{π}{}^{\mathrm{?}}$. From this signal a partial width of 13.0 ± 5.0 MeV for the decay mode $\text{K}{}^1\text{(1420)→}\text{K}{}^1\text{(892)ππ}$ is deduced under the assumption that the ππ system is in an I = 1 state. For the rare decay mode $\text{K}{}^1\text{(892)→}\text{K}\text{ππ}$ no signal is observed. The following upper limits can be given for the decay widths: , , .     

Coherent production of multimeson final states on A ∼ 20 nuclei by K− of 5.5, 10.0, 12.7 GeV

Coherent production of $\text{K}\text{π,}\text{K}\text{2π}\text{and}\text{K}\text{3π}$ final states from A ～ 20 nuclei by K^? beams of 5.5, 10.0 and 12.7 GeV is analyzed. Final states with ? 2π^O are included. Coherent $\text{K}\text{π}$ production occurs (although forbidden via 0⁺ exchange) and is dominated by the $\text{K}$¹ (890). The shape of the t distribution, the alignment of the produced meson and the ratio of the cross section on nuclei to that on hydrogen are consistent with optical model predictions assuming that $\text{K}$¹ (890) are produced on single nucleons by exchange of isoscalar trajectories of natural parity (J^P = 1^?, 2⁺, etc.) and that the $\text{K}$¹ (890) absorption in nuclear matter equals that of the K^?. Coherent $\text{K}\text{ππ}$ production (allowed via 0⁺, 1^?, 2⁺, etc. exchange) is dominated by the Q phenomenon. A Dalitz plot and angular correlation analysis yields values for $\text{K}\text{?/}\text{K}{}^1\text{π}$ fractions, and shows that $\text{J}{}^{\mathrm{P}}\text{= 1}{}^{\mathrm{+}}\text{S-wave}\text{K}{}^1\text{π}$ dominates the coherently produced Q. The helicity of the Q is found to be compatible with 0. The Q^? -nucleaon total cross section is estimated to be 0.98_?0.37⁺⁰²⁴ times the $\text{K}$^? -nucleon total cross section from a comparison of the coherent Q-production cross section with corresponding hydrogen cross sections at 10 and 12.7 GeV. We observe coherent production of $\text{K}$ω. The ration $\text{K}\text{ω/}\text{K}\text{ππ}$ coherently produced in the Q mass region is (4 ± 1)%. Coherent production of $\text{K}{}^{\mathrm{?}}\text{π}{}^{\mathrm{+}}\text{π}{}^{\mathrm{?}}\text{and}\text{K}{}^{\mathrm{<mtext>O</mtext>}}\text{π}{}^{\mathrm{+}}\text{π}{}^{\mathrm{?}}\text{π}{}^{\mathrm{<mtext>O</mtext>}}$ is observed in the L region. Coherent production is not observed in the K4π channels.     

Analysis of π N → K Λ and KN → π Λ using fixed-t dispersion relations,fesr and duality

A simultaneous analysis of low-energy (W ? 2 GeV) data for the reactions π^?p→ K^OΛ and K^?p → π^OΛ has been made using the hypothesis of two-component duality combined with fixed-t dispersion relations. Results are presented for the $\text{?}{}^1\text{Λπ}$ and $\text{N}{}^1\text{Λ}\text{K}$ couplings. The low-energy amplitudes are used to evaluate FESR integrals and lead to large EXD breaking for the $\text{K}{}_{\mathrm{<mtext>V</mtext>}}{}^1\text{?}\text{K}{}_{\mathrm{<mtext>T</mtext>}}{}^1$ helicity flip amplitudes.     

The low-mass Kπ system in K−p → KπN reactions at 14.3 GeV/c

We present experimental results and a partial-wave analysis of the low-mass $\text{(}\text{K}\text{π)}{}^{\mathrm{<mtext>0</mtext>}}$ systems produced in the reactions $\text{K}{}^{\mathrm{?}}\text{p}\text{→}\text{K}\text{π}\text{N}$ at 14.3 GeV/c. The main results concern the production mechanisms of the $\text{K}{}^1\text{(890)}\text{and}\text{K}{}^1\text{(1420)}$. We also extract the s-wave component of the $\text{K}\text{π}$ system as a function of mass.     

Some observations on the differential cross-sections for pp → K−K+

We present Legendre coefficients from fits to the differential cross-sections for $\text{p}\text{p→ K}{}^{\mathrm{?}}\text{K}{}^{\mathrm{+}}$ in the momentum range 0.8 to 2.4 GeV/c. The s-dependence of the cross-sections at small angles is examined for evidence of Reggeized baryon exchange, and a fit made to this channel and backward K⁺p elastic scattering. Comparisons are made with $\text{p}\text{p→ π}{}^{\mathrm{?}}\text{π}{}^{\mathrm{+}}$.     

Symmetry breaking schemes and radiative decays of vector mesons

We have studied a hierarchy of SU(3) breaking schemes for the radiative decays of the vector mesons. In all of the four models we examine in detail, we find it hard to reconcile the newly measured radiative widths of ? → πγ, $\text{K}{}^{01}\text{→ K}{}^0\text{γ}$, φ → πγ, and φ → ηγ with the older measurements and upper bounds on other radiative rates. In particular we have difficulty in understanding the narrow radiative width of ?. A possible extension to an SU(4) symmetry breaking scheme is also suggested.     

New data on the reaction K−n → (Σπ)− and a partial wave analysis of KN → Σπ in the energy range 1520–1745 MeV

Differential cross sections for $\text{K}{}^{\mathrm{?}}\text{n}\text{→ Σ}{}^{\mathrm{<mtext>o</mtext>}}\text{π}{}^{\mathrm{<mtext>o</mtext>}}$ have been measured at K^? momenta between 680 and 840 MeV/c in a bubble chamber experiment. For K^?n → Σ^oπ^? the Σ^o polarization was also determined. The measurements were combined with the available data on K^?p → Σπ in an energy-dependent partial wave analysis in the center of mass energy range from 1520 to 1745 MeV. An acceptable fit was obtained with the well established resonances.     

Investigation of rare non-strange decay modes of the f meson in Π+p interactions at 5GeVc

Rare decay modes of the f meson are studied in the final states Δ⁺⁺π⁺π^?π⁺π^?, Δ⁺⁺π⁺π^?MM and Δ⁺⁺π⁺π^?π⁺π^?MM. The ratio $\text{Γ (f → π}{}^{\mathrm{+}}\text{π}{}^{\mathrm{?}}\text{π}{}^0\text{π}{}^0\text{)}\text{Γ(f → π}{}^{\mathrm{+}}\text{π}{}^{\mathrm{?}}\text{)}$ is 0.23 ± 0.09 and Γ(f → 4 π) saturates the f inelasticity. A 2 s.d. upper limit of 0.09 is found for the branching ratio $\text{(f → ηη)}\text{(f → 2π)}$.