Search

We have observed production of ∅ and ω mesons in K+p interactions at 6.8 GeV/c in the final states K+∅p, K+ωp, KOπ+∅p, and KOπ+ωp. The first two final states show low-mass enhancements K∅, Kω, and ωp combinations. The third evidences strong Δ++ production. The fourth is produced through a combination of mechanisms, but shows some evidence for K∗ (1660) production, with decay to KOω.

Results are reported based on a study of π − p interactions at 147 GeV/ c in the FERMILAB 30-inch Proportional Wire Hybrid Bubble Chamber System. We have measured the topological cross sections and separated two-prong elastic and inelastic channels. In addition, we have extracted leading particle cross sections using the increased momentum resolution of the downstream proportional wire chambers. We have compared our results with experiments and predictions of a simple fragmentation hyphothesis.

We present data on inclusive and semi-inclusive ϱ 0 production in 147 GeV/ c π − p interactions. We find a total cross section of 7.3 ± 1.3 mb. Most of this cross section is found in the lower topology events (⩽ 10 prongs), and in the central and forward rapidity regions. The P T 2 dependence of ϱ 0 production, 〈: n > ϱ 0 per event, and the ϱ 0 / π + ratios are also discussed.

A study of charged particle production in 147 GeV/c π − p collisions yields no evidence for an electrically neutral central region or corresponding rapidity plateau. The results do indicate that electric charge and transverse momentum may be locally conserved over small intervals on the rapidity axis. These results support a picture in which the observed hadrons are emitted in clusters whose quantum numbers vary as a function of rapidity and reflect the incident channel quantum numbers at the extremes of the rapidity scale.

In this paper we present new data for the reactions π−p→pslow+X− and π−p→πfast− + X+ at 147 GeV/c. This is the first time that experimental information on these two processes has been obtained using the same apparatus at Fermilab energies. The triple-Regge formalism is applied to the differential cross sections dσ/dMx2 of both reactions using all the data at present available in the literature. A good description of the data is obtained when parameters from a triple-Regge fit of the reaction pp → p + X are used, together with the assumption of factorization of the pomeron and the reggeons. The equality of the dσ/dMx2 distributions of the two reactions may be explained in terms of an interesting assumption in the framework of the independent quark model and imposes an additional relation between the triple-Regge terms.

We observe the previously reported K+π−π0 enhancement near 1250 MeV in the final state K+π+π−π0 p in a 6.8 GeV/c K+p exposure. We find that this enhancement decays primarily to uncorrelated Kππ and that production is correlated with forward π+. We see no signal in the K0π+π+π−p final state where statistics are limited.

Diffraction dissociation of both the beam and target particles has been observed in 150-GeV/c ..pi../sup -/p interactions in the Fermilab 30-in.-bubble-chamber--proportional-wire-chamber hybrid spectrometer. The dissociations are observed as recoil systems opposite leading particles, the signals of which are separated from background where appropriate by a variant of the Van Hove sector cut, thus allowing the high-mass portion of the spectrum to be observed. Pion dissociation has a cross section of 1758 +- 105 ..mu..b, divided among two-, four-, and six-prong events; some rho/sup 0/ production is seen and comes primarily from the ..pi../sup -/ ..-->.. 2..pi../sup -/..pi../sup +/ channel. The proton dissociation cross section is 1726 +- 100 ..mu..b, again divided among two-, four-, and six-prong events. The final state contains a neutron more frequently than a proton in the two- and six-prong events, a proton more frequently in the four-prong events. Production of ..delta../sup + +/ is observed in the p ..-->.. p..pi../sup +/..pi../sup -/ dissociations.

The experimentally determined average charged-particle multiplicities, , of the systems, X, produced in the following reactions for 147 GeV/c incident pion momentum are presented as functions of the square of the invariant mass of X, M/sub x//sup 2/, and of *t*: ..pi../sup -/p ..-->.. ..pi../sup -//sub fast/X, ..pi../sup -/p ..-->.. pX, ..pi../sup -/p ..-->.. ..delta../sup + +/X, ..pi../sup -/p ..-->.. (..pi../sup -/..pi../sup +/)/sub rho//sup 0/X, and ..pi../sup -/p ..-->.. ..lambda../sup 0/X. Details of the analysis are discussed. These data can be fit by the expression = A + BlnM/sub X//sup 2/ + C*t* and the coefficients obtained for B are equal within their uncertainties. C is significantly different from zero only for ..pi../sup -/p ..-->.. ..pi../sup -//sub fast/X.

We have studied inclusive π − production from π + d interactions at 24 GeV/ c using data obtained from the Brookhaven National Laboratory 80” bubble chamber. Distributions of longitudinal momenta in the laboratory frame and the projectile frame, of x (Feynman's scaling variable), and of rapidity in the center of mass frame are presented and compared with the corresponding distributions from the reaction π + p→ π − + anything. The effect of Fermi momentum of the nucleons has been investigated and is found to be small. We conclude that single particle inclusive π − spectra from proton and from neutron targets are very different in this energy range. The two particle correlations among negative pions in the deuteron experiment have been investigated and the results are presented.

The results of a study of the reaction π-p→π-π-π+p at 2 147 GeV/c carried out at the Fermilab Proportional Wire 30″ Bubble Chamber Hybrid Spectrometer are reported. More than 92% of the cross-section ((670±41) μb) for this reaction is contained in those for proton and pion diffraction dissociation. The cross-sections for pion diffraction events with three-pion invariant mass in given regions are in agreement with values obtained by extrapolation of fits to data at lower incidentpion momenta. ρ0π- events make an important contribution in the A1 and A2 mass regions, and the data are consistent with contributions from f0π- in the A3 mass region. The cross-section for proton diffraction events is in agreement with a smooth extrapolation of the data at lower momentum.

The inclusive production of the ${\ensuremath{\Delta}}^{++}(1232)$ resonance in ${\ensuremath{\pi}}^{\ensuremath{-}}p$ collisions at 147 GeV/c has been studied. The ${\ensuremath{\Delta}}^{++}$ is found to be produced in comparable amounts in four-, six-, eight-, and ten-prong events. The Feynman-$x$, ${t}^{\ensuremath{'}}$, ${{P}_{T}}^{2}$, and the decay angular distributions of the ${\ensuremath{\Delta}}^{++}$ are found to be consistent with the predictions of a one-pion-exchange model with absorption. Essentially all of the ${\ensuremath{\Delta}}^{++}$ are found to be associated with a ${\ensuremath{\Delta}}^{++}$${\ensuremath{\pi}}^{\ensuremath{-}}$ low-mass enhancement. The ${\ensuremath{\Delta}}^{++}$ cross section is approximately constant from 11 to 205 GeV/c, which could indicate that the ${\ensuremath{\Delta}}^{++}$ is a decay product of a target-fragmentation object. While the one-pion-exchange character of the ${\ensuremath{\Delta}}^{++}$ production and the target-fragmentation character of the ${\ensuremath{\Delta}}^{++}{\ensuremath{\pi}}^{\ensuremath{-}}$ low-mass enhancement can both be described in terms of a Deck-type diagram, a Monte Carlo study indicates that any mechanism that produces particles with limited transverse momentum will yield a ${\ensuremath{\Delta}}^{++}{\ensuremath{\pi}}^{\ensuremath{-}}$ low-mass enhancement.

From a 2.5 events gmb K − d exposure of the BNL 80″ bubble chamber we obtained 351 events which successfully fit the reaction K − d → K − π − pp s . The (pπ − ) mass spectrum exhibits a strong enhancement, centered at 1400 MeV and 400 MeV wide, which cannot be clearly resolved into individual resonances. The reaction is analyzed with a diffraction dissociation model and the relevant cross sections are given. From a study of the low K − π − mass region we find that the Kπ elastic scattering cross section in the isospin 3 2 state is of the order of 2 mb.

A report is made of the study of production and decay properties of the ${\ensuremath{\eta}}^{0}$, ${\ensuremath{\omega}}^{0}$, ${\ensuremath{\rho}}^{0}$, and ${\ensuremath{\pi}}^{0}$ mesons produced in ${\ensuremath{\pi}}^{+}\ensuremath{-}d$ collisions at 1.23 BeV/c in the Berkeley 72-in. bubble chamber. The production processes are analyzed in terms of ${\ensuremath{\pi}}^{+}$-neutron interactions through the use of an impulse model. A clear enhancement due to the ${{N}_{\frac{1}{2}}}^{*} (1688)$ resonance is observed in the ${\ensuremath{\pi}}^{0}$ (charge exchange) production cross section. The mass of the ${\ensuremath{\eta}}^{0}$ meson is found to be (${m}_{\ensuremath{\eta}0}=552\ifmmode\pm\else\textpm\fi{}3$ MeV), with a branching ratio of $\frac{({\ensuremath{\eta}}^{0}\ensuremath{\rightarrow}\mathrm{all}\mathrm{neutrals})}{({\ensuremath{\eta}}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{0})}=3.6\ifmmode\pm\else\textpm\fi{}0.8$, and the partial width $\ensuremath{\Gamma}({{N}_{\frac{1}{2}}}^{*} (1688)\ensuremath{\rightarrow}p+{\ensuremath{\eta}}^{0})l2$ MeV. The central value of the ${\ensuremath{\omega}}^{0}$-meson peak is found to be (${m}_{\ensuremath{\omega}0}=781\ifmmode\pm\else\textpm\fi{}2$ MeV), with a branching ratio $\frac{({\ensuremath{\omega}}^{0}\ensuremath{\rightarrow}\mathrm{all}\mathrm{neutrals})}{({\ensuremath{\omega}}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{0})}=8\ifmmode\pm\else\textpm\fi{}3%$, and an upper limit of 5% for decay into two charged pions. The production of the ${\ensuremath{\omega}}^{0}$ is found to be inconsistent with the single-vector-meson exchange model.

The decay process KLo → πμν has been studied in a wire chamber experiment using the three-degree KLo beam at SLAC. A sample of 26 500 Kμ3 events have been identified to obtain information on the form factors ƒ ± associated with the V-A hypothesis for this decay. Expressing the energy dependence of the form factors as ƒ ± = ƒ ± (0) (1 + λ ± q 2 m 2 ), where q 2 = (p K −p μ ) 2 , the experiment yields the value λ+ = 0.08 ± 0.01 and reveals a strong coupling between λ_ and ζ_(0) = ƒ_(0) ƒ + (0) .

We studied the Kπ scattering from threshold to mKπ = 1200 MeV using the Chew-Low extrapolation method in the reactions K + p → K o ← π o − Δ ++ . In addition to an analysis using only the data at 5.43 GeV/c incident momentum, we also present the results using the world data compiled from experiments with momenta from 3.0 to 12.7 GeV/c. The extrapolated cross section for the elastic K+π−→K+π− scattering exceeds the p-wave isospin - 1 2 unitary limit in the K∗ (890) region. The phase shift δ11 (notation δ l 2I ) shows the expected Breit-Wigner behavior which suggests that δ 1 3 ⋍0 in the mass region studied. Solutions for the s-wave phase shifts δo1 and δo3 are obtained from the extrapolated differential cross sections. We obtain a unique set of solutions for δo1 and δo3 by requiring the calculated cross sections to agree with those extrapolated from K+π− elastic scattering and with those for K−π− scattering obtained in other experiments. We find δo1 increasing slowly from 0° at threshold and approaching 80° at m Kπ ⋍1150 MeV with no evidence of passing through 90° in the mass range studied. The phase shift δo3 decreases slowly from 0° at threshold to ⋍ − 30° at m Kπ ⋍ 1200 MeV .

We have studied the decays into lepton pairs of vector mesons ($\ensuremath{\rho},\ensuremath{\varphi},\ensuremath{\omega}$) produced by a beam of $3\ensuremath{-}\frac{\mathrm{BeV}}{c{\ensuremath{\pi}}^{\ensuremath{-}}}$ mesons incident on a liquid-${\mathrm{H}}_{2}$ target at the Brookhaven AGS. The experiment utilized scintillation counters and spark chambers as well as a lead-scintillator "shower chamber" constructed for the identification of electrons and rejection of background. A Monte Carlo technique was used to predict the background and determine the number of real events. For the muon-pair mode, the results are upper limits, with the branching ratio $\frac{(\ensuremath{\rho}\ensuremath{\rightarrow}\ensuremath{\mu}\overline{\ensuremath{\mu}})}{(\ensuremath{\rho}\ensuremath{\rightarrow}\mathrm{all}\mathrm{modes})}l14\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ being the best limit determined. For the electron-pair decays we obtain $\frac{(\ensuremath{\rho}\ensuremath{\rightarrow}e\overline{e})}{(\ensuremath{\rho}\ensuremath{\rightarrow}\mathrm{all}\mathrm{modes})}=({{0.65}_{\ensuremath{-}0.5}}^{+1.1})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ and $(\frac{\ensuremath{\omega}\ensuremath{\rightarrow}e\overline{e}}{\ensuremath{\omega}\ensuremath{\rightarrow}\mathrm{all}\mathrm{modes}})=({{1.0}_{\ensuremath{-}0.75}}^{+1.7})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ for an assumed $\ensuremath{\varphi}\ensuremath{-}\ensuremath{\omega}$ mixing angle of 38\ifmmode^\circ\else\textdegree\fi{}. Because of insufficient knowledge of the production process, we tentatively quote for the $\ensuremath{\varphi}$ meson a result ${\ensuremath{\sigma}}_{\ensuremath{\varphi}}\ifmmode\times\else\texttimes\fi{}\frac{(\ensuremath{\varphi}\ensuremath{\rightarrow}e\overline{e})}{(\ensuremath{\varphi}\ensuremath{\rightarrow}\mathrm{all}\mathrm{modes})}={{0.31}_{\ensuremath{-}0.21}}^{+.34}$ \ensuremath{\mu}b. The results are compared with other experiments.

From a 3.5 ev/μb exposure of the BNL 80 inch chamber filled with deuterium to a 7.0 GeV/cp beam we obtained 664 events in the channel pn → pπ−p. The channel cross section is (1270 ± 11060) μb. The final state is dominated by Δ(1230) production. The experimental data is well described by a one-pion exchange model with off-mass shell corrections.

We have studied the proper time distribution of coherent π+π− decays from a 3 – 10 GeV/c KLo beam incident on a one meter liquid hydrogen target using a wire spark chamber spectrometer in the 30 neutral beam at SLAC. We find ∣(ƒ(0) − ƒ (0))/k∣ = 0.43 ± 0.11 mb , φ(ƒ(0) − ƒ (0)) = -101 0 ± 42 0 .

A search has been made for a baryon of strangeness +1 (the Z+) in the mass range from 940 to 1440 MeV/c2. Three production modes have been considered: K+ + p → Z+ + π+, K+ + p → Z+ + π+ + π0, π+ + d → Z+ +\(\overline {K^0 } \) + p. Candidates for the first two reactions came from a 2.26 GeV/c K+p bubble chamber experiment and were of two types: all 2-prong events in which one track decayed in the chamber and a sample of nondecaying 2-prongs in which there was no apparent neutral production (as determined by the momentum balance at the production vertex). The associated production events were taken from π+d exposures at 1.2 and 2.8 GeV/c. In all cases the data are consistent with the absence of a Z+, although kinematic ambiguities of various types prevent an absolute statement. In the K+-initiated reactions, the production cross-sections are less thean 1 μb for the 2-body production of the decaying Z+, less than 3 μb for the 3-body production of the decaying Z+, and less than 25 μb for a Z+ which does not have a visible decay (with reasonable assumptions on the ambiguities). The associated production cross-section for a Z+ is less than 18 μb.

In a 3.5 event/ub exposure of the BNL 80″ bubble chamber we have observed the following reactions: p d → p d φ + φ − , p d → p pn φ + φ − , p d → p d φ + φ − φ 0 . The incident p momentum was 7.0 GeV/c. We give cross sections for the reactions, as well as for other reactions involving production of Λ We give detailed descriptions of the coherent final states (1) and (3). It is observed that reactions (1)-(3) are dominated by production of Δ −− (1236) . We apply a Deck model, both in Reggeized and non-Reggeized form, to the reaction p d → Δ −− π + d and obtain satisfactory fits to the distributions of all kinematic variables. In particular, the π+d mass spectrum, which shows a prominent peak (the “d∗”) at a mass M(πd) ≈ 2170 MeV, is well reproduced by the predictions of the model without introducing a resonant interpretation for this effect. Modified versions of this model are applied to the reactions p d → Δ −− π + pn , and p d → Δ −− π O π + d , which occur as sub-samples of the final states (2) and (3) respectively. Here also, prominent peaks are observed in the π+pn mass spectrum (in the former reaction) and in the π+d and πOd mass spectrum (in the latter reaction). Again the predictions of the model agree well with the observed distributions of all the kinematic variables.

Hollow cylindrical samples of indium have been prepared by an extrusion process and equipped with both a center wire and a concentric tube. The critical current has been determined for the case in which the current passes through the sample and returns through the concentric tube. It has been found that this critical current is identical with that of solid samples. The same determination has been made for the case in which the current returns through the center wire. In this case the critical current is about 80 to 90% of that for solid samples. A field was produced by the center wire, the respective current returning through the concentric tube. The resistance of the sample was measured with a small measuring current, also returned through the concentric tube, as a function of the field produced by the center wire. The critical field thus determined depends on the value of the measuring current. These findings can be interpreted in the following way: If the magnetic field of the current through the center wire is dominating, the current in the sample will flow in a very thin layer at the outer surface of the sample. This constitutes a "thin film experiment" which does not require a thin metal film. The resistance measurements have been supplemented by measurements of the circular flux on a sample of larger size.

A sample of 17 000 K0L → πev decays were measured at the Stanford Linear Accelerator Center using a wire chamber magnetic spectrometer. K0e3 decays were separated from other K0L decay modes by using kinematic tests, muon identification by penetration of a Pb wall and electron identification by a shower counter array. We find the data in fixed q2 bands are in reasonable agreement with the V-A theory and we present the unparametrized form factor ƒ + (q 2 ) . Using the usual linear parametrization ƒ + (q 2 ) ∼ 1 + λ + q 2 /m π 2 , we obtained λ+ = 0.05 ± 0.01.

Angular distributions of neutrons corresponding to transitions to the first (1.31 Mev) and second (3.95 Mev) excited states in the reaction C/sup 13/ (d,n)N/sup 14/ were measured at an incident deuteron energy of 1.3 Mew. A time- of-flight technique utilizing the associated gamma ray as a trigger was employed to separate the various neutron groups. Because the data, particularly for the first excited state transition, exhibited a relatively large intensity in the backward direction, a simple deuteron-stripping process is not sufficient to account for the results. An analysis that included the heavy-particle stripping mode was consistent with the data. (auth)

Abundant production of the established $L$ meson and also of the possible $Q$ meson are observed in coherent production, ${K}^{\ensuremath{-}}d\ensuremath{\rightarrow}{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}d$, at 12.6 BeV/c. This is the first observation of $L$-meson production on nuclei. The $Q$ and $L$ isospins are unambiguously determined to be \textonehalf{}. The $L$ is observed to be produced polarized. A striking resemblance between the final states ${K}^{*}(890)\ensuremath{\pi}d$ and ${K}^{*}(1400)\ensuremath{\pi}d$ is observed with these final states being related to the $Q$ and $L$ mesons, respectively.

Data are presented concerning the energy dependence of the inclusive π - production cross section in π + d interactions. A growth of the cross section at large momentum transfers is parametrized and compared to observations at the ISR.

We report on coherent interactions in a 2.5 event/μb K−d exposure. The predominant channel studied is K−d → K−π+gp−d (415 events). We find strong Q- and L-production in the (Kππ) system. The production mechanism determines I = 1 2 for both enhancements and a spin-parity in the series 0−, 1+,2−… . A spin-parity analysis shows the Q to be a 1+ object, while the L is 1+ or 2−, although a higher spin cannot be excluded. The cross sections for Q and L production and other final states are presented.

We have extracted the strong interaction form factors from K o e3 and K o μ3 data of our previously reported K o L experiment in a manner which does not assume an explicit q 2 = ( p K − p π ) 2 dependence. We present the unparameterized form factors ƒ + (q 2 ) from the K o L → πeν and K o L → πμν modes and ƒ o (q 2 ) and ξ ( q 2 ) from the K o L → πμν data. A comparison of these unparameterized results is made with the results of the Dalitz plot analyses.