Demythification of electroproduction local duality and precocious scaling

In an effort to develop a quantitative check of asymptotically free color-gauge theories, we analyze the logarithmic corrections to ξ-scaling coming from anomalous dimensions and coefficient functions of twist-two operators and compare with electroproduction data for 1 ? Q² ? 16 GeV². Excellent agreement is obtained using $\text{g}{}^2\text{(2}\text{GeV}\text{)}\text{4π}{}^2\text{= 0.17}$ for the effective quark-gluon coupling in the color-gauge theory. Effects of higher-twist operators are suppressed by powers of $\text{M}{}_0{}^2\text{Q}{}^2$. We use data from the resonance region to show $\text{M}{}_0\text{? 400}\text{MeV}$, in agreement with theoretical expectations. Our fit to νW₂ in the scaling region also describes the resonance region in the sense of Bloom-gilman local duality. We show that local duality is a consequence of the moment predictions obtained from the operator-product expansion in quantum chromodynamics. We resolve a paradox associated with local duality and spin-zero targets. Present measurements of $\text{R =}\text{σ}{}_{\mathrm{L}}\text{σ}{}_{\mathrm{T}}$ at large x and Q² are systematically higher than our predictions.     

Contributions from higher twist effects to the quark fragmentation functions in neutrino data

Quark fragmentation functions are studied with ≈3500 charged current events induced in the bubble chamber Gargamelle by neutrinos of the SPS wide band beam, with 〈E_ν〉 ≈ 25 GeV. The Q² and W² regions covered by this experiment are Q² ≈ 0–40 GeV² and W² ≈ 1–100 GeV², the mean values being 〈Q²〉 = 6.5 GeV², 〈W²〉 = 22GeV². A correlation between the variables $\text{z =}\text{E}{}_{\mathrm{\pi }}\text{E}{}_{\mathrm{<mtext>H</mtext>}}$ and $\text{y =}\text{E}{}_{\mathrm{<mtext>H</mtext>}}\text{E}{}_{\mathrm{v}}$ is found in the data in the region Q² = 1–10 GeV², which can be explained in terms of higher twist effects. These effects reproduce the Q² evolution of the non-singlet moments of the fragmentation function without any need for logarithmic terms.     

Antiproton-proton total elastic cross sections in the T and U regions (0.69−2.43 GeV/c)

Antiproton-proton total elastic cross sections at 21 incident momenta in the range 0.69 to 2.43 GeV/c have been deduced by combining p?p elastic differential cross sections over a c.m. angular range $\text{?0.95 ?}\text{cos}\text{θ}{}^1\text{? 0.93}$ with forward elastic cross sections derived from recent real-part measurements and p?p total cross sections. Two bumps are observed, at $\text{M}{}_1\text{? 2.155}$ and $\text{M}{}_2\text{? 2.345}\text{GeV}\text{/c}{}^2$, having widths of Г₁ ～ 0.135 and $\text{Г}{}_2\text{～ 0.135}\text{GeV}\text{/c}{}^2$. Corresponding structures in other p?p reaction channels are discussed.     

The intermediate weak boson and weak interactions at high energy

The high-energy pire-leptonic weak interaction is investigated based on the assumption of the existence of a charged vector boson which mediates the weak processes. With the aid of the fixed-t dispersion relation the following relation is obtained: The weak boson mass m_W should satisfy $\text{m}{}_{\mathrm{<mtext>W</mtext>}}\text{? G}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>2</mtext>}}$, with G the Fermi coupling constant, if the asymptotic value of the cross section becomes of the order of the strong interaction in the energy region observable in cosmic rays, etc.The scattering processes $\text{e}\text{+ν→}\text{e}\text{+ν}\text{and}\text{e}\text{+}\text{ν}\text{→}\text{e}\text{+}\text{ν}$ are examined by the aid of the N/D method. For a large vector-boson mass $\text{m}{}_{\mathrm{<mtext>W</mtext>}}\text{?100}\text{GeV}$, an S-wave resonance should exist for the process e+ν→e+ν while for $\text{e}\text{+}\text{ν}\text{→}\text{e}\text{+}\text{ν}$ there should exist a P-wave resonance which corresponds to the intermediate weak boson. The neutral current is then estimated. It is shown that the neutral current produced as a higher-order effect is not inconsistent with the present experiments on the pure-leptonic weak interaction if m_W?1 TeV.     

Low-energy behaviour of realistic locally-supersymmetric grand unified theories

The recently proposed cosmologically acceptable N=1 supergravity models based on the SU(5) unification group define unambigously the minimal particle content of the theory. This fact allows us to determine quite precisely their low-energy behaviour. The SU(2)×U(1) breaking to U(1)_e.m. is a consequence of radiative corrections of the supergravity induced soft breaking terms. The proposed mechanism (which is model independent) introduces naturally a hierarchy between the M_W and M_X scales. Calculating the low-energy effective potential we shot that a corrects SU(2)×U(1) breaking is obtained without any limit (except the experimental one) on the top-quark mass. The masses of the supersymmetric partners of mater and gauge fermions can be low and consequently accessible experimentally (sleptons, s quarks, gauginos $\text{? 20–50}\text{GeV}$). A neutral Higgs is also predicted wirth a mass $\text{m}{}_{\mathrm{H}}\text{?O(5)}\text{GeV}$. In addition, we show that if m_t?45 GeV, the gravitino and gluino masses are bounded from below by $\text{10}\text{GeV}\text{? m}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{and}\text{15}\text{GeV}\text{? m}{}_{\mathrm{<mtext>gluino</mtext>}}$. The values of sin²θ_W (in the two-loop approximation) and the $\text{m}{}_{\mathrm{<mtext>b</mtext>}}\text{m}{}_{\mathrm{\tau }}$ ratio predicted are in very good agreement with the experimentally measured values.     

Measurement of elastic scattering in antiproton-proton collisions at 52.8 GeV centre-of-mass energy

We measured the differential cross section for p?p and pp elastic scattering in the momentum-transfer range 0.01 <|t| < 1.0 GeV² at the CERN Intersecting Storage Rings with center-of-mass energy $\text{s}\text{= 52.8}\text{GeV}$. Fitting the differential cross section with an exponential [Aexp (bt)], we found $\text{b}\text{p}\text{p = 13.92 ± 0.59}\text{GeV}{}^{\mathrm{?2}}$ for |t| < 0.05 GeV², whilst for |t| > 0.09 GeV², $\text{b}\text{p}\text{p = 10.68 ± 0.26}\text{GeV}{}^{\mathrm{?2}}$. Using the optical theorem, we obtained for the total cross section $\text{σ}{}_{\mathrm{<mtext>tot</mtext>}}\text{(}\text{p}\text{p)= 44.86 ± 0.78}\text{mb}$ and, by integrating the differential cross section, we obtained for the total elastic cross section $\text{σ}{}_{\mathrm{<mtext>el</mtext>}}\text{(}\text{p}\text{p) = 7.89 ± 0.28}\text{mb}$. Calculations of σ_tot combining elastic-rate and total-rate measurements are also given. All of these measurements were also performed for pp scattering at the same energy, and the results for both reactions are compared.     

Observation of a direct low-mass e+e− continuum in π-p interactions at 16 GeV/c

The production of prompt electron-positron pairs in 16 GeV/c π^-p collisions has been measured using the LASS spectrometer at SLAC. An excess of events is observed above the estimated contribution of direct and Dalitz decays of known resonances in the kinematic range defined by $\text{0.1?χ?0.45, 0?p}{}_{\mathrm{T}}\text{?0.8}\text{GeV}\text{c}$ and $\text{0.2?M(e}{}^{\mathrm{+}}\text{e}{}^{\mathrm{?}}\text{)?0.7}\text{GeV}\text{c}{}^2$. The excess signal decreases slowly with increasing M, but exhibits very steep χ and p_T² dependence.     

Comparison of three-jet and two-jet cross sections in pp̄ collisions at the CERN SPS pp̄ collider

Results are presented on two-jet and three-jet cross sections, measured in the UA1 experiment at the CERN Super Proton Synchrotron (SPS) pp? Collider, at the highest available subprocess cms energies ($\text{s}\text{?}\text{>150}\text{GeV}$). Precise measurements of the two-jet angular distribution are consistent with previous results but show significant scale-breaking effects. The three-jet Dalitz plot and the three-jet angular distributions show evidence for final- and initial-state bremsstrahlung processes, in agreement with the leading-order QCD predictions. A comparison of the yield of wide-angle three-jet events with the yield of two-jet events at smaller scattering angles gives for the strong interaction coupling constant: $\text{α}{}_{\mathrm{<mtext>s</mtext>}}\text{(}\text{K}{}_{\mathrm{3J}}\text{K}{}_{\mathrm{2J}}\text{)=0.16±0.02±0.03}$ at Q²≈4000 GeV², where the factor $\text{K}{}_{\mathrm{3J}}\text{K}{}_{\mathrm{2J}}$ may plausibly be assumed to be close to unity.     

Elastic proton scattering from 4He at 0.58 and 0.72 GeV

The energy spectra of α-particles recoiling from a ⁴He gas target bombarded by 0.58 and 0.72 GeV protons have been measured to obtain the differential cross sections for elastic scattering $\text{d}{}_{\mathrm{\sigma }}\text{d}{}_{\mathrm{t}}$, in the region of four-momentum transfer squared, ?t=0.13 ? 0.55 (GeV/c)². The experiment was designed especially to observe the region between the first and second diffraction maxima.     

Pion production and the higher resonances in pion-nucleon scattering

The reaction π + N → 2π + N has been studied in the vicinity of the higher resonances in the pion-nucleon cross section. The Low equation for the production amplitude is transformed into an integral equation by isolating the true one-meson intermediate states and discarding higher order contributions. The only part kept in the inhomogeneous term corresponds to the collision of a pion in the nucleon cloud with the incident pion in the resonant T = J = 1 state, which is simulated by an unstable vector Boson. Crossed terms are neglected and the 2π-N state is described by the static model. The terms kept in the sum over states describe the rescattering (off the nucleon) of one of the outgoing pions. The required off-the-energy-shell elastic scattering amplitude is approximated by the 3-3 resonance formula of Chew and Low. With these simplifications the Low equation for the production amplitude reduces to an easily soluble linear integral equation. The rescattering amplitude, which dominates the inhomogeneous term in the resonance region, is proportional to the 3-3 scattering amplitude of one of the outgoing pions. Although the result provides some support for the conventional isobar model, it is important to note that the largeness of the rescattering term arises from scattering far off the energy shell, rather than by “real” excitation as in the phenomenological isobar model. Quantitative calculations for the $\text{D}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ channel leading to a p-wave ($\text{J =}\text{3}\text{2}$) and an s-wave pion produce a maximum in the cross section near 600 Mev incident pion lab energy. For a π-π resonance energy squared S = 10, agreement with experiment is obtained with a width about one third that suggested by nucleon electromagnetic structure. In our approximation, the well known 600 Mev $\text{D}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ isospin $\text{1}\text{2}$ resonance occurs at the same energy as the 800 Mev $\text{D}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ isospin $\text{3}\text{2}$ resonance. It is assumed, but not proved, that the neglected terms are responsible for the splitting of the resonance energies. When this splitting is taken into account, the predicted charge state ratios near the second resonance agree well with existing data. The “third” resonance occurs for the state having two p-wave pions, according to the present theory, although no numerical calculations were made for this case. This point of view suggests that the $\text{F}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$, $\text{P}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$, and $\text{P}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ incident channels contribute to the third resonance.     

Evidence for a narrow peak in Ksoπ±π+π- at 2.6 gev in 12 gev/cpp interactions

We report the evidence for a narrow charged peak (5.5 s.d.), which we suggest calling the I, in the 6-prong-V⁰ topology of $\text{p}$p interactions at 12 GeV/c. The mass, widht and the product of cross section σ_I times the branching ratio BR into the final state (K_s^oτ±τ⁺τ^? are found to be: $\text{M}{}_{\mathrm{I}}\text{=2.60 ±}\text{0.01}\text{GeV}\text{/}\text{c}{}^2$, $\text{Γ}{}_{\mathrm{I}}\text{?}\text{0.018}\text{GeV}\text{/}\text{c}{}^2$, σ_I·BR≈20 μbarn     

The size of inelastic diffraction dissociation

It is suggested that the inelastic diffraction dissociation cross section is a constant fraction β of the unitary bound, i.e. $\text{σ}{}_{\mathrm{DIFF}}\text{(s) = β[}\text{1}\text{2}\text{σ}{}_{\mathrm{TOT}}\text{(s) ? σ}{}_{\mathrm{EL}}\text{(s)]}$. Available data from pp collisions for s ? 20 (GeV/c)² are consistent with our hypothesis with $\text{β ～}\text{1}\text{2}$. Consideration of a specific model for diffraction suggests that the value of $\text{β ～}\text{1}\text{2}$ is a consequence of there being no lower mass state than pp with its quantum numbers. Predictions for πp and Kp scattering are presented.     

Photino-photino-photon production in e+e− annihilation

The cross section for production of single photons in the process $\text{e}{}^{\mathrm{+}}\text{e}{}^{\mathrm{?}}\text{→ γ}\text{γ}\text{γ}$ is calculated including selectron propagator and photino mass effects and is found to be significantly smaller than the local limit for selectron masses ? 35 GeV/c². Numerical results for the cross section are obtained as a function of selectron masses for photino masses $\text{m}{}_{\mathrm{<mtext>\gamma </mtext>}}\text{? 10}\text{GeV}\text{/c}{}^2$ and electron beam energies E = 14.5, 25, and 35 GeV appropriate to PEP, PETRA, and TRISTAN, respectively.     

Some thoughts on the mass of the top quark

We propose a new mechanism for up-down symmetry breaking within the context of a technicolor scenario. The experimentally determined ratio $\text{M}{}_{\mathrm{<mtext>W</mtext>}}\text{M}{}_{\mathrm{<mtext>Z</mtext>}}\text{cos}\text{θ}{}_{\mathrm{<mtext>W</mtext>}}\text{? 1}$ is in addition preserved at the technicolor scale. If we assume that the mechanism works at the level of the heaviest generation we find $\text{m}{}_{\mathrm{<mtext>t</mtext>}}\text{= (?}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>2</mtext>}}\text{)38}\text{GeV}$. The parameter ? depends on strong technicolor dynamics and can in principle be determined. Via a crude estimate we find ? to be a number of order 1.     

Cosmological bounds on a left-right symmetric model

The right-handed neutrino cross sections of the processes ν_L + ? → ν_R + ? and ν_R + ? → ν_R + ?, where ? is a relativistic lepton, are calculated in the SU(2)_L × SU(2)_R × U(1) model. According to a cosmological criterion the parameters of the model are bounded. In particular we obtain the bound $\text{M}{}_{\mathrm{<mtext>W</mtext>}}{}_{\mathrm{<mtext>R</mtext>}}\text{? 30 M}{}_{\mathrm{<mtext>W</mtext>}}{}_{\mathrm{<mtext>L</mtext>}}$, assuming the neutrinos are Dirac four-component particles.     

An upper limit to the cross section for the reaction νμe−→νμe− at SPS energies

Candidates for the purely leptonic process $\text{ν}{}_{\mathrm{\mu }}\text{e}{}^{\mathrm{?}}\text{→}\text{ν}{}_{\mathrm{\mu }}\text{e}{}^{\mathrm{?}}$ have been searched for in the bubble chamber Gargamelle exposed to the CERN-SPS antineutrino wide-band beam. No single e^?, of energy greater than 1 GeV, was found in a total of 230 000 pictures, corresponding to 7400 charged current events. This leads to an upper limit for the observed cross section of $\text{σ}{}_{\mathrm{<mtext>obs</mtext>}}\text{< 1.6 × 10}{}^{\mathrm{?42}}\text{(}\text{E}{}_{\mathrm{\nu }}{}^{\mathrm{?}}\text{GeV}\text{)}$ cm² (90% C.L.). Interpretation of this value in terms of the standard W Weinberg-Salam model yields an upper limit to the mixing parameter sin²θ_W < 0.39 at 90% C.L.     

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.     

Analysis of topological cross sections in pp interactions at 22.4 GeVc

The multiplicity distribution for 11558 events in $\text{p}\text{p}$ interactions at 22.4 $\text{GeV}\text{c}$ was analyzed. The average charged multiplicity 〈n_ch〉 for inelastic events was found to be 4.69 ±0.05 and $\text{〈n}{}_{\mathrm{ch}}\text{〉}\text{D=2.04 ± 0.05}$. The early KNO scaling of normalized topological cross sections has been tested.     

Scale breaking in inclusive charged particle production by e+e− annihilation

The scale cross section $\text{s}\text{d}\text{σ}\text{d}\text{x}{}_{\mathrm{<mtext>p</mtext>}}$ for inclusive charged-particle production in e⁺e^? annihilation has been studied for c.m. energies W between 12.0 and 36.7 GeV. Scale breaking is observed. For x_p>0.2 the cross section decreases by ≈20% when W increases from 14 to 35 GeV. The production angular distribution was used to separate the longitudinal and transverse cross-section contributions and to determine the ratio of the structure functions $\text{m}\text{W}{}_1$ and $\text{v}\text{W}{}_2$.