Proton-antiproton annihilations at rest into π0ω, π0η, π0γ, π0π0, and π0η′

Proton-antiproton annihilations at rest in liquid hydrogen were investigated through the inclusive γ spectrum, related to the annihilation. The high-energy part of the spectrum was used to deduce branching ratios for the so far unobserved annihilation channels: $\text{R(}\text{p}\text{p}\text{→π}{}^0\text{ω) = (2.38 ± 0.65)\%}$, $\text{R(}\text{p}\text{p}\text{→ π}{}^0\text{η) = (0.82 ± 0.10\%}$, $\text{R}\text{p}\text{p}\text{→π}{}^{\mathrm{0\gamma )}}\text{= (0.015 ± 0.007)\%}$, and $\text{R(}\text{p}\text{p}\text{→ π}{}^0\text{π}{}^0\text{= (0.06 ± 0.04)\%}$. An upper limit for the π⁰η^′ channel was deduced to be $\text{R(}\text{p}\text{p}\text{→ π}{}^0\text{η}{}^{\mathrm{\prime }}\text{) < 1.1\%}$.     

An experimental investigation of the radiative structure decay K+ → e+υγ

The decay K⁺ → e⁺υγ has been investigated. For the structure-dependent part with positive γ-helicity (SD₊) the branching ratio $\text{Γ(}\text{SD}{}_{\mathrm{+}}\text{)}\text{Γ(}\text{K}{}_{\mathrm{\mu 2}}\text{) = (2.33 ± 0.42) × 10}{}^{\mathrm{?5}}$ is obtained from 51 ± 3 events observed in the kinematical region E_e ? 235 MeV, E_γ > 48 MeV and θ_eγ > 140°. For the corresponding part with negative γ-helicity we obtain an upper limit Γ(SD_?)/Γ(SD₊) < 11 (90% CL) from the sample of electrons with energies 220 MeV ? E_e < 230 MeV and with no γ in the backward direction. This upper limit implies that the ratio of structure-dependent axial vector amplitudes lies outside the region $\text{?1.8 < a}{}_{\mathrm{<mtext>K</mtext>}}\text{υ}{}_{\mathrm{<mtext>K</mtext>}}\text{< ?0.54}$.For the decay $\text{K}{}^{\mathrm{+}}\text{→}\text{e}{}^{\mathrm{+}}\text{νν}\text{ν}$ the limit $\text{Γ(}\text{K}{}^{\mathrm{+}}\text{→}\text{e}{}^{\mathrm{+}}\text{νν}\text{ν}\text{)/Γ(}\text{K}{}_{\mathrm{e2}}\text{) < 3.8}$ 90% confidence level) was found.     

On the decays π0→νν′

Phenomenological aspects of π⁰→νν′ are considered. From the existing experimental information, we deduce an upper limit $\text{Γ(π}{}^0\text{→νν′)}\text{Γ(π}{}^0\text{→}\text{all}\text{)}\text{< 2.4 × 10}{}^{\mathrm{?5}}\text{(90\%}\text{c.l.}\text{)}$. Possible mechanisms which can give rise to this process are discussed. Branching ratios of the order of 10^?6 for decays into the known neutrinos (ν_e, ν_μ) are found possible. Rates comparable to the experimental limit for decays into final states involving additional neutrinos (massive or massless) cannot be ruled out.     

Study of the reaction νp → μ+pπ−

We present data on the reaction $\text{ν}\text{p → μ}{}^{\mathrm{+}}\text{pπ}{}^{\mathrm{?}}$ from an exposure of the Fermilab 15 ft hydrogen bubble chamber. The channel cross section for $\text{5}\text{GeV}\text{< E}{}_{\mathrm{<mtext>\nu </mtext>}}\text{< 70}\text{GeV and}\text{M(}\text{p}\text{π}{}^{\mathrm{?}}\text{) < 1.9}\text{GeV is}\text{σ = (27 ± 5) × 10}{}^{\mathrm{?40}}\text{cm}{}^2$. This cross section is dominated by the $\text{I =}\text{1}\text{2}$ production amplitude.     

Perhaps scalar neutrinos are the lightest supersymmetric partners

We consider the possibility that the scalar partners of the neutrinos $\text{(}\text{v}\text{)}$ are the least massive supersymmetric partners, and show that this alternative is compatible with cosmological constraints, which put a significant lower bound on photino masses but not on $\text{v}$ masses. Various consequences are examined: the photon counting rate for $\text{e}{}^{\mathrm{+}}\text{e}{}^{\mathrm{-}}\text{→γ}\text{v}$$\text{v}\text{?}\text{?}$ may be large; the rate for $\text{e}{}^{\mathrm{+}}\text{e}{}^{\mathrm{-}}\text{→}\text{W}{}^{\mathrm{+}}\text{a}\text{W}{}^{\mathrm{-}}$ by $\text{v}$ exchange is enhaced; Z⁰→ increases Γ(Z⁰) by about 0.25 GeV; $\text{W}{}^{\mathrm{\pm }}\text{→}\text{?}{}^{\mathrm{+-}}\text{v}$ may be enhanced; the decay $\text{τ→}\text{v}{}_{\mathrm{\tau }}\text{?}{}_{\mathrm{?}}$$\text{v}\text{?}\text{?}$ may be detectable; there can be additional contributions to the rare decay $\text{K}{}^{\mathrm{+}}\text{→π}{}^{\mathrm{+}}\text{v}$$\text{v}\text{?}\text{?}$; restrictions on gluino masses, which depend on photinos interacting before they decay, have to be re-examined; scalar neutrinos have suitable characteristics as candidates for dark matter in the universe. We discuss one currently fashionable class of models that can predicr a light $\text{v}$.     

Observed and calculated interactions between valence states of the NO molecule

No perturbation between two valence states of NO has ever been identified, although many valence-Rydberg and several Rydberg-Rydberg perturbations have been extensively studied. The first valence-valence crossing to be experimentally documented for NO is reported here and occurs between the ¹⁵N¹⁸O B²Π (v = 18) and B′²Δ (v = 1) levels. No level shifts larger than the detection limit of 0.1 cm^?1 are observed at the crossings near $\text{J = 6.5 [B}{}^2\text{Π}\text{(F}{}_1\text{) ～ B′}{}^2\text{Δ}\text{(F}{}_2\text{)]}$ and $\text{J = 12.5 [B}{}^2\text{Π}\text{(F}{}_1\text{) ～ B′}{}^2\text{Δ}\text{(F}{}_1\text{)]}$; two crossings involving higher rotational levels could not be examined. Semi-empirical calculations of spin-orbit and Coriolis perturbation matrix elements indicate that although the electronic part of the $\text{B}{}^2\text{Π}\text{～ B′}{}^2\text{Δ}$ interaction is large, a small vibrational factor renders the ¹⁵N¹⁸O B (v = 18) ? B′ (v = 1) perturbation unobservable. Semi-empirical estimates are given for all perturbation matrix elements of the operators $\text{Σ}{}_{\mathrm{i}}\text{a}\text{?}{}_{\mathrm{i}}\text{l}{}_{\mathrm{i}}\text{·s}{}_{\mathrm{i}}$ and $\text{B(L}{}_{\mathrm{\pm }}\text{S}{}_{\mathrm{?}}\text{? J}{}_{\mathrm{\pm }}\text{L}{}_{\mathrm{?}}\text{)}$ which connect states belonging to the configurations $\text{(σ2p)}{}^2\text{(π2p)}{}^4\text{(π}{}^1\text{2p)}$, $\text{(σ2p)(π2p)}{}^4\text{(π}{}^1\text{2p)}{}^2$, and $\text{(σ2p)}{}^2\text{(π2p)}{}^3\text{(π}{}^1\text{2p)}{}^2$.     

Multiplicity distributions and double-scattering effects in π−d interactions at 360 GeV/c

Double-scattering effects are studied in π^?d interactions at 360 GeV/c. The partial cross sections $\text{σ}{}_{\mathrm{<mtext>N</mtext>}}\text{(π}{}^{\mathrm{?}}\text{d}\text{), σ}{}_{\mathrm{<mtext>N</mtext>}}\text{(“π}{}^{\mathrm{?}}\text{p}\text{”)}\text{and}\text{σ}{}_{\mathrm{<mtext>N</mtext>}}\text{(“π}{}^{\mathrm{?}}\text{n}\text{”)}$ are presented. The double-scattering probability per πd collision is found to be $\text{? = 0.15 ± 0.02}$. We have extracted the partial cross section X_N of the double-scattering plus interference contributions, and find that X_N obeys KNO scaling. The data are compared with various theoretical predictions.     

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.     

Isospin analysis of NN → NNπ reactions at 5.7 GeV/c

A cross-channel isospin analysis has been performed on the channels $\text{p}\text{N}\text{→}\text{N}\text{(}\text{N}\text{π)}\text{and}\text{p}\text{N}\text{→}\text{N}\text{(}\text{N}\text{π)}$ in terms of three isospin amplitudes $\text{M}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}{}^0\text{, M}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}{}^1$, and $\text{M}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}{}^1$ where the upper index is the isospin of the exchanged “object” in the t-channel and the lower index is the isospin of the $\text{(}\text{N}\text{π)}\text{or}\text{(}\text{N}\text{π)}$ system. Enhancements are observed in the low Nπ) invariant mass region for an $\text{I =}\text{1}\text{2}$ final state when the isospin of the exchanged object in cross channel is I_E = 0 and 1.     

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.     

O(18) revived: Splitting the spinor

We propose an O(18) theory which is perturbatively unifiable and which accounts for the absence of right-handed families in the low-energy world. The theory predicts a fourth left-handed family as well as four right-handed families at energies near the weak scale. It also implies the existence of eight light neutrinos, all of which contribute to the width of the Z⁰. Cosmological arguments suggest that four of these neutrinos should have masses between 2 and 35 GeV, and that the other four should be much lighter. They also suggest the existence of a doubly charged scalar φ⁺⁺ and a singly charged scalar φ⁺. Dramatic signatures include the production of four right-handed charged leptons and eight right-handed quarks, $\text{Z}{}^0\text{→ v′}{}_{\mathrm{<mtext>R</mtext>}}\text{+}\text{v}\text{′}{}_{\mathrm{<mtext>R</mtext>}}\text{→ v}{}_{\mathrm{<mtext>R</mtext>}}\text{γ +\_}\text{v}{}_{\mathrm{<mtext>R</mtext>}}\text{γ}$, and e⁺e^? → φ⁺⁺ + φ^??. The lightest right-handed charged quark should be surprinsingly long-lived $\text{(τ?10}{}^{\mathrm{?2}}\text{sec}\text{)}$ for a particle of mass ? 100 GeV.     

Upper bounds on the fine structure constant and on nucleon magnetic moments in terms of Compton scattering cross sections

We derive and compare with experimental data the bound

$\text{α??λm}{}_{\mathrm{<mtext>p</mtext>}}\text{?m}{}_{\mathrm{<mtext>p</mtext>}}\text{ν}{}^2{}_1\text{2π}{}^2\text{∫}\text{ν}{}_0\text{∞}\text{d}\text{ν′σ}{}_{\mathrm{<mtext>tot</mtext>}}\text{(ν′)}\text{(ν′}{}^2\text{+ν}{}^2{}_1\text{)}\text{+2πm}{}_{\mathrm{<mtext>p</mtext>}}\text{∫}\text{ν}{}_0\text{∞}\text{ν′}{}^2\text{d}\text{ν′σ}{}_{\mathrm{<mtext>tot</mtext>}}\text{(ν′)}\text{(ν′}{}^2\text{+ν}{}^2{}_1\text{){ν′}{}^2\text{(}\text{d}\text{σ}\text{d}\text{t)}{}_0\text{+πλ}{}^2\text{+2ν′|λ|}\text{π}\text{(}\text{d}\text{σ}\text{d}\text{t)}{}_0\text{?}\text{σ}{}^2{}_{\mathrm{<mtext>tot</mtext>}}\text{16π}\text{}}{}^{\mathrm{?1}}$

, where α is the fine-structure constant, m_p the proton mass, ν₀ the photo-pion production threshold, σ_tot and $\text{(}\text{d}\text{σ}\text{d}\text{t}\text{)}{}_0$ are the unpolarized total hadronic photo-absorption cross section on protons and the unpolarized forward differential cross section for proton Compton scattering at photon-lab energy ν′, and λ and ν₁ are any real numbers. We derive similar bounds on proton and neutron magnetic moments.     

Study of the photon spectrum in the decay KS0→π+π−γ

The branching ratio $\text{Λ(}\text{K}{}_{\mathrm{<mtext>S</mtext>}}{}^0\text{→π}{}^{\mathrm{+}}\text{π}{}^{\mathrm{?}}\text{γ)}\text{Λ(}\text{K}{}_{\mathrm{<mtext>S</mtext>}}{}^0\text{→π}{}^{\mathrm{+}}\text{π}{}^{\mathrm{?}}\text{)}$ has been determined to be (2.68±0.15)×10^?3 for photon energies $\text{E}{}_{\mathrm{\gamma }}{}^1$ greater than 50 MeV in the K_S⁰ rest frame. The decay K_S⁰→π⁺π^?γ is found to be dominated by the internal bremsstrahlung transition. The branching rato of a possible direct transition is found to be less than 0.06 × 10^?3 at 90% confidence level for $\text{E}{}_{\mathrm{\gamma }}{}^1\text{> 50}\text{MeV}$.     

An experimental study of the form factor in the decay K+ → πoe+ν

The q² variation of the factor $\text{?}{}_{\mathrm{+}}\text{(q}{}^2\text{)}$ in the decay K⁺→π⁰e⁺ν has been studied using a sample of even detected in the CERN 1.1 m³ heavy-liquid bubble chamber. The data are consistent with a linear development $\text{?}{}_{\mathrm{+}}\text{(q}{}^2\text{)=?}{}_{\mathrm{+}}\text{(0) (1+λ}{}_{\mathrm{+}}\text{q/m}{}^2{}_{\mathrm{\pi }}\text{)}$ with λ₊=0.027±0.008.     

Dual parton model and the photoproduction of pseudoscalar and vector mesons in the high energy region

On the basis of the dynamical dual model of strong interactions followed from the parton model of hadrons as discussed in an earlier paper, we study here the photo-production of pseudoscalar and vector mesons in the high energy region. To incorporate the concept of duality, it is taken that any two spin $\text{1}\text{2}$ pointlike constituents (partons) can form a π-meson cluster in the structure of a nucleon and the basic interaction involved in MB scattering is the interaction of the incident meson with the π meson in the structure of the nucleon. In this scheme, the amplitudes for the photoproduction of mesons such as γN → Nπ, γN → N?, and γN → Nω in the high energy region can be related with the amplitudes for the process γπ → ππ, γπ → π?, and γπ → πω, respectively. To calculate the amplitudes for the relevant process we also consider a factor corresponding to the structural rearrangement of partons involved in duality diagrams. To obtain the cross sections, we take into account the photon-vector meson analogy, though the naive form of the vector dominance model (VDM) has not been considered here. From a knowledge of the coupling constants $\text{γ?}{}^2\text{4π}$, $\text{γω}{}^2\text{?π}$, , and we obtain the differential cross sections which are in excellent agreement with experimental results. Also we obtain a good fit for the scattering process γN → Nπ at backward angles. For the vector meson production processes, we have contributions from the diffraction mechanism also apart from the amplitudes considered here. In the region where the contribution from the diffraction part is negligible, we obtain the relation

which is in nice agreement with experiments. Finally, it is shown that, though the vector meson dominance is not considered here, the universality of the vector meson coupling with hadrons follows directly from the present model.     

Features of diffractive scattering and the nature of the N1(1400) observed in NN→N(Nπ) reactions at 5.7 GeV/c

The results for the diffractive scattering contribution ($\text{F}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}{}^0$) obtained in a cross channel isospin analysis of the $\text{N}\text{N}\text{→}\text{N}\text{(}\text{N}\text{π)}$ reactions at 5.7 GeV/c are compared with those obtained for other ZN → Z′(Nπ) reactions where Z stands for N, π and the carbon nucleus. The dependence of the diffractive scattering on the mass M_πN and the momentum transfer t seems very weakly related to the nature of Z and the incident momentum.A comparison between amplitudes of the isospin exchange I_ex = 0 and I_ex = 1 leading to $\text{N}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ production shows that $\text{N}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(1492)}$ and $\text{N}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(1670)}$ are produced essentialy through I_ex = 1.     

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.     

Measurement of the isospin amplitude ∣M012∣ in the reaction γn → ϱ0(pπ−) at 7.5 GeV

The cross-channel isospin amplitude $\text{∣M}{}_0{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{∣}$ is measured in the single reaction γn → ?⁰(pπ^?) at 7.5 GeV assuming the ?⁰ dominance model. A low-mass enhancement is found for $\text{∣M}{}_0{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{∣}{}^2$ in the range of m(pπ^?) of ～1.2 to ～1.7 GeV. The reaction strongly violates s-channel helicity conservation but is consistent with t-channel helicity conservation. The $\text{∣M}{}_0{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{∣}$ features are found to be very similar to those obtained in previous analyses of πp → π(Nπ) reactions.     

New upper limit for μ− → e+ conversion

An upper limit for μ^? → e⁺ conversion has been established by searching for specific decay properties of the expected final state nucleus. We obtain $\text{R}{}_{\mathrm{<mtext>coh</mtext>}}\text{= (μ}{}^{\mathrm{?}}\text{+}{}^{127}\text{I →}\text{e}{}^{\mathrm{+}}{}^{127}\text{Sb}{}^1\text{)/(μ}{}^{\mathrm{?}}\text{→ v}{}_{\mathrm{\mu }}\text{) < 3 × 10}{}^{\mathrm{?10}}$ with 90% c.l.