Charm production by weak neutral currents

We discuss quantitatively the production of charm in $\text{v}\text{N and}\text{v}\text{N}$ neutral current interactions, and the anomalous lepton events that follow from semi-leptonic charm decay. Diagonal neutral currents, in the Weinberg-Salam model and similar models, predict associated charm production with small cross sections: e.g. $\text{σ(v}\text{N}\text{→ vcc}{}^{\mathrm{?}}\text{X}\text{)/σ(v}\text{N}\text{→ μ}{}^{\mathrm{?}}\text{X}\text{) ? 10}{}^{\mathrm{?2}}$ at high energy. The meagre data on vN → ve⁺X are consistent with a rate of this order. Non-diagonal neutral currents, if present, could give larger cross sections via valence p → c transitions. It should be possible to distinguish diagonal from non-diagonal contributions by their x- or u-dependences, where u = x(1 ? y). We calculate the expected energy distributions of the leptons in characteristic vN → v?⁺X and vN → v?⁺?^?X charm decay events using simple models, and discuss some practical problems in neutral current measurements.     

Deviation from scaling in the triple-regge region of pp→ pX and fP universality

By generalizing $\text{f}\text{P}$ universality to Regge-particle “scattering” we obtain $\text{s}\text{d}\text{σ}\text{d}\text{t}\text{d}\text{M}{}^2\text{= F(}\text{s}\text{M}{}^2\text{,t)}$$\text{[1 +}\text{M}{}^{\mathrm{?1}}\text{b}{}_{\mathrm{<mtext>f</mtext>}}\text{(0)}\text{b}{}_{\mathrm{<mtext>P</mtext>}}\text{(0)}\text{]}$ for pp → pX, where b_f(t) and b_P(t) are the f and P Regge residues for, say, pp → pp. This agrees with the recent NAL data.     

Neutral pion production by weak neutral currents in neutrino and antineutrino reactions

A study is presented of single π^o production in neutrino and antineutrino interactions in Gargamelle filled with freon CF₃Br. Limits on the neutral to charged current cross-section ratios $\text{R}{}_{\mathrm{v}}\text{=σ(v}\text{N}\text{→v}\text{N}\text{′π}{}^{\mathrm{o}}\text{)/2 σ(v}\text{N}\text{→ μ}{}^{\mathrm{-}}\text{N}\text{′π}{}^{\mathrm{o}}\text{)}$ and $\text{R}{}_{\mathrm{<mtext>\nu </mtext>}}\text{= σ(}\text{ν}\text{N}\text{→}\text{ν}\text{N}\text{′π}{}^{\mathrm{o}}\text{)/2 σ(}\text{ν}\text{N}\text{→ ω}{}^{\mathrm{+}}\text{N}\text{′π}{}^{\mathrm{o}}\text{)}$ are found to be $\text{0.10 < R}{}_{\mathrm{\nu }}\text{< 0.20}\text{and}\text{0.26 < R}{}_{\mathrm{<mtext>\nu </mtext>}}\text{< 0.44}$ at 68% confidence level.     

Theoretical prediction of the vertical electronic spectrum of the C2H radical

The vertical transition energies and oscillator strengths from the $\text{X}\text{?}{}^2\text{Σ}{}^{\mathrm{+}}$ ground and $\text{A}\text{?}{}^2\text{Π}$ excited states of the ethynyl radical C₂H to all higher-lying states resulting from excitation out of π and σ into $\text{π}{}^1$ and $\text{σ}{}^1$ valence-shell MO's, respectively, as well as into 3s and 3p Rydberg species, are calculated by large-scale CI techniques. It is found that the first excited states all result from $\text{π → π}{}^1$ excitations (the lowest three with quartet character), and not from the 4σ → 5σ counterparts favored in the case of isoelectronic CN. This distinction can be explained on the basis of orbital stability differences caused by the effects of hydrogen mixing. The first six states of the C₂H⁺ ion are also treated, and the correspondence with the various associated Rydberg series is discussed. Dipole moments for the $\text{X}\text{?}{}^2\text{Σ}{}^{\mathrm{+}}$ and $\text{A}\text{?}{}^2\text{Π}$ states are also calculated.     

Spectrum and structure of the He2 molecule: Characterization of the singlet and triplet states associated with the UAO's 4s, 4dσ, 4dπ, and 4dδ

The emission spectrum of the He₂ molecule has been rephotographed in the ～4000–～5700 Å region and the $\text{4d(}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{,}{}^3\text{Π}{}_{\mathrm{u}}\text{,}{}^3\text{Δ}{}_{\mathrm{u}}\text{) → 2pπ}{}^3\text{Π}{}_{\mathrm{g}}$, $\text{4d(}{}^1\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{,}{}^1\text{Π}{}_{\mathrm{u}}\text{,}{}^1\text{Δ}{}_{\mathrm{u}}\text{) → 2pπ}{}^1\text{Π}{}_{\mathrm{g}}$, $\text{4s}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{→ 2pπ}{}^3\text{Π}{}_{\mathrm{g}}$ and $\text{4s}{}^1\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{→ 2pπ}{}^1\text{Π}{}_{\mathrm{g}}$ transitions analyzed. The 4dδj³Δ_u, 4dπj³Π_u, $\text{4dσj}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}$ and $\text{4sh}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}$ states have been characterized through v = 2 and the 4dδJ¹Δ_u, 4dπJ¹Π_u, $\text{4dσJ}{}^1\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}$, and $\text{4sH}{}^1\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}$ states for v = 0. The term levels for these perturbed and l-uncoupled states have been confirmed (a) by analyses of bands with common levels from Δv = 0, ±1 sequences and (b) by analyses of the transitions between the above states from 4d and 4s and the $\text{c}{}^3\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{+}}$ and $\text{C}{}^1\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{+}}$ states associated with 3pσ. Molecular constants are reported which have been partially corrected for the effects of l-uncoupling and the homogeneous perturbations between the state pairs J, H and j, h.     

Nonrelativistic distorted wave born approximation predictions for 500 MeV (p, p') spin-rotation observables

We discuss couplings of scalar gluonium σ on the basis of the low energy theorems of broken chiral symmetry and the anomalous trace of the energy—momentum tensor, implemented using a phenomenological lagrangian. Taking the ITEP value of the gluon consensate as input, we find $\text{Γ(σ → ππ) ? 0.6}\text{GeV}\text{× (}\text{m}{}_{\mathrm{\sigma }}\text{1}\text{GeV}\text{)}{}^5$ and $\text{Γ(σ → γγ) ? 90}\text{eV}\text{× (}\text{m}{}_{\mathrm{\sigma }}\text{1}\text{GeV}\text{)}{}^5$, while m_σ is undetermined. These results suggest that if the scalar gluonium mass is above 1 GeV, it is probably unobservably wide, while production in γγ collisions is probably too small to be detectable if m_σ < 1.5 GeV. We comment on the observability of J/ψ → σ + γ and on the relevance of our results to other gluonia.     

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 $\text{Γ(ψ→η′γ)}\text{Γ(ψ→ηγ)}$.     

On the semileptonic decay of charmed hadrons

The semileptonic and leptonic decay modes of charmed hadrons produced in e⁺e^? collisions above 4 GeV in the cm have been investigated by selecting events with a single electron plus at least two charged tracks. The electron momentum spectrum peaks near 0.5 GeV/c with few events above 0.7 GeV/c. The spectrum excludes large rates for the decays $\text{D}\text{→}\text{e}\text{v}{}_{\mathrm{<mtext>e</mtext>}}$ and $\text{D}\text{→}\text{e}\text{v}{}_{\mathrm{<mtext>e</mtext>}}\text{π}$, but is compatible with $\text{D}\text{→}\text{e}\text{v}{}_{\mathrm{<mtext>e</mtext>}}\text{K}{}^1\text{(892)}$, $\text{D}\text{→}\text{e}\text{v}{}_{\mathrm{<mtext>e</mtext>}}\text{K}$ or a mixture of both. The semileptonic branching ratio is obtained both by comparing the inclusive electron cross section with the total cross section attributable to charm, and by studying the fraction of events containing a second electron. The semileptonic charm branching ratios obtained are 0.11 ± 0.03 and 0.16 ± 0.06 respectively. A single event with three electrons and hadrons is found, consistent with the estimated background. The 90% confidence upper limit for σ(e⁺e^? → 3e + hadrons) is 0.1 nb.     

Proton-proton inelastic scattering at 0.5 TeV

We have measured at 500 GeV the cross section $\text{d}{}^2\text{σ}\text{dt dM}{}_{\mathrm{X}}{}^2$ for the inclusive reaction p + p → + X. We determine the mass spectrum of the diffractive peak to be $\text{1}\text{M}{}^{\mathrm{3.8\pm 0.2}}$ and the scaling part of the cross section to be dσ/dM_X² = (15.7±1.1)/smb/GeV².     

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.     

Elastic scattering and ω meson production near the threshold of π−p→ω+n

Measurements are reported of the differential cross section for the reaction π^?+p→ω+n from threshold to a final-state c.m. momentum $\text{P}{}^1\text{of}\text{200}\text{MeV}\text{/c}$. The previously reported fall in total cross section $\text{σ/P}{}^1$ below about 100 MeV/c is again seen. The differential cross section remains close to isotropic over the entire range. A paralle experiment on the variation in the elastic differential cross section across the threshold shows evidence of this threshold. The elastic data cover a range of incident moments from 1010 to 1180 MeV/c in steps of 5 MeV/c.     

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 $\text{(σ2p)}{}^2\text{(π2p)}{}^3\text{(π}{}^1\text{2p)}{}^2$.     

Limits on the couplings of ϱ′ (1300 Me) and rhov;″ (1700 MeV) to the photon and to the (ππ) system

The analysis of the reaction e⁺e^?→π⁺π^? measured at the e⁺e^? colliding beam machine ADONE shows that, if ?′ and ?″ exist, the cross sections compare as follows (taking the ? as the reference point): $\text{σ(}\text{e}{}^{\mathrm{+}}\text{e}{}^{\mathrm{?}}\text{→ ? → π}{}^{\mathrm{+}}\text{π}{}^{\mathrm{?}}\text{)}$: σ(e⁺e^? → ?′ → π⁺π^?): σ(e⁺e^? → ?″ → π⁺π^?) = 1: (7 ± 4) × 10^?3: (1 ± 5) × 10^?4. The square of the product of their couplings to the photon (γ_?) and the γγ system (g_?ππ) are derived.     

e+e− annihilation into hadrons and the nature of the hadronic fixpoint

It is shown that the experimental behaviour of the ratio $\text{R =}\text{σ(}\text{e}{}^{\mathrm{+}}\text{e}{}^{\mathrm{?}}\text{→}\text{hadrons}\text{)}\text{σ(}\text{e}{}^{\mathrm{+}}\text{e}{}^{\mathrm{?}}\text{→ >}{}^{\mathrm{+}}\text{>}{}^{\mathrm{?}}\text{)}$ has a natural explanation if hadron interactions at short distances are described by an infrared stable fixpoint of the renormalization group. Experimental estimates of the limiting value of R, the 90% saturation point and of the anomalous dimension dθ of the trace of the energy momentum tensor are given.     

The reactions K−p → K1− + nucleon at 3.13 and 3.3 GeV/c

Results are presented of a 12 event/μb bubble-chamber experiment; the reactions discussed in detail are $\text{K}{}^{\mathrm{?}}\text{p}\text{→}\text{K}{}^1\text{(890)}{}^{\mathrm{?}}\text{p, K}{}^1\text{(1420)}{}^{\mathrm{?}}\text{p and K}{}^1\text{(890)}{}^{\mathrm{?}}\text{Δ}{}^{\mathrm{+}}$.The K¹ (890)^?p channel is dominated by the forward peak. The suggestion of flattering at cos θ = 1 is more pronounced in $\text{(?}{}_{11}\text{+ ?}{}_{\mathrm{1?1}}\text{)}\text{d}\text{σ}\text{d}\text{t}$; which is mainly natural-parity exchange. Pseudoscalar exchange contributes to $\text{?}{}_{00}{}^{\mathrm{J}}\text{d}\text{σ}\text{d}\text{t}$; this is more sharply peaked in t. The value of $\text{(?}{}_{11}\text{? ?}{}_{\mathrm{1?1}}\text{)}\text{d}\text{σ}\text{d}\text{t}$ is somewhat larger than the upper limit from the dominant natural-parity exchange. There is significant structure in $\text{?}{}_{00}{}^{\mathrm{H}}\text{d}\text{σ}\text{d}\text{t}\text{at}\text{t ≈ ?0.6 (}\text{GeV}\text{/c)}{}^2$.The K¹ (1420)^?p channel is much more pronounced at 3.3 GeV/c than at 3.13 GeV/c, but is not markedly peripheral. The width of the K¹ (1420) in the 3.3 GeV/c data is 42 ± 12 MeV/c².The cross section for $\text{K}{}^{\mathrm{1?}}\text{Δ}{}^{\mathrm{+}}$ agrees with that expected from $\text{K}{}^{\mathrm{+}}\text{p}\text{→}\text{K}{}^1\text{Δ}$, assuming a single t-channel exchange. Our measured density matrix elements are consistent with a strong pseudoscalar exchange.     

On the ratio Σ0/Λ in electroproduction off protons

Recent experimental results on electroproduction off protons show that the ratio σ(ep → eK⁺Σ⁰)/σ(ep → eK⁺Λ) decreases strongly with increasing Q². A simple argument is given in the framework of the quark parton model which could provide a qualitative understanding of this fact. The decrease of the Σ⁰/Λ ratio is related to the decrease of the ratio $\text{F}{}_1{}^{\mathrm{<mtext>\gamma </mtext><mtext>n</mtext>}}\text{/F}{}_1{}^{\mathrm{<mtext>\gamma </mtext><mtext>p</mtext>}}$ as Q² increases, where $\text{F}{}_1{}^{\mathrm{<mtext>\gamma </mtext><mtext>p</mtext>}}\text{and F}{}_1{}^{\mathrm{<mtext>\gamma </mtext><mtext>n</mtext>}}$ are the usual structure functions for deep inelastic electron-nucleon scattering.     

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 $\text{v}$.     

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.     

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.