We present differential and total cross sections for two reactions: π−p→K0Λ and π−p→K0Σ0. The incident pion momenta were 8, 10.7, and 15.7 GeVc. The results are based on an analysis of approximately 22 600 events of the two reactions where the π+ and π− from the decay of the KS0 were detected in the forward leg of the Double Vee Magnetic Spectrometer. The separation of Λ recoils from Σ0 recoils was accomplished by the missing-mass technique.
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We present the results of an analysis of data for the reaction π−p→KS0K−p at 20.3-GeV/c incident π momentum. We find that the K0K− effective-mass spectrum shows a single peak in the A2 region which is well fitted by a Breit-Wigner shape. The data in the A2-peak region are inconsistent with the split-A2 shape reported earlier. The distribution in t of the A2 events shows a forward dip followed by an exponential falloff. The A2 decay angular distribution is well fitted by a single resonance with quantum numbers JP=2+. The results of an analysis of the density-matrix elements for this reaction are given.
CORRECTED FOR UNSEEN K0 DECAYS AND FOR BREIT-WIGNER RESONANCE TAILS.
INCLUDING THE DENSITY MATRIX ELEMENTS OMITTED FROM THIS FIT GIVES NO SIGNIFICANT IMPROVEMENT AND THE NEW PARAMETERS ARE CLOSE TO ZERO. LIM INDICATES FITTED VALUE LIMITED FROM VARIATION BY PHYSICAL CONSTRAINTS FROM OTHER PARAMETERS.
We present the differential cross sections near u=0 for the reactions π−p→K0Λ and π−p→K*0(890)Λ at incident pion momenta of 8 and 10.7 GeV/c. The differential cross section for the first reaction follows the exponential dependence on u previously observed, while the second shows a dip in the backward direction.
Axis error includes +- 25/25 contribution.
Axis error includes +- 25/25 contribution.
Axis error includes +- 25/25 contribution.
We present differential and total cross sections for the reactions π−p→K0[Σ(1385)Λ(1405)] and π−p→K0Λ(1520) at incident pion momenta of 8.0, 10.7, and 15.7 GeV/c. Pions from the decay of the forward K0s's were detected in the forward leg of the BNL double-vee spectrometer and the recoil Y* 's were identified by the missing-mass technique.
Axis error includes +- 20/20 contribution.
Axis error includes +- 20/20 contribution.
Axis error includes +- 20/20 contribution.
The KS0KS0π0 system has been studied in the exclusive reaction π−p→KS0KS0π0n at 21.4 GeV/c. Evidence for the production of the f1(1285) and the η(1460) is presented. The η(1460) is produced away from minimum momentum transfer in the presence of nonresonant K*K (S-wave) production and phase-space background. The observed mass, width, and decay properties of the η(1460) are consistent with those attributed to the ι(1460) observed in radiative Jψ decay.
A coupled channel analysis has been carried out using a new amplitude analysis of the K 0 s K 0 s system produced in the reaction π − p→K 0 s K 0 s n at 22 GeV/ c , which contained about 40 000 new events in the low- t region (| t − t min |<0.1 GeV 2 ). Here only the I G =0 + , J PC =2 ++ amplitude from this analysis is considered, together with available data from other experiments in channels with the same quantum numbers in order to determine which 2 ++ isoscalar mesons have significant pseudoscalar-pseudoscalar couplings. It is found that four poles, f(1270), f'(1525), θ(1690), and f r (1810), are needed, plus a smooth background in order to fit these data; the need for the θ(1690) depends on the J/ψ radiative decay alone, and the f r (1810) is seen only in hadronic production.
The π−+p→π0+n differential cross section at 180° has been measured for 52 values of π− momentum from 1.8 to 6.0 GeV/c using a constant-geometry detection system. The average statistical uncertainty is ∼5% and the systematic uncertainty is ∼10%. The details of the experiment and the data analysis are discussed. The data are compared with those of other experiments with which they are generally in agreement. One set of data disagrees with those presented here and a possible reason for this is discussed. A five-parameter fit of the predictions of a dual-resonance model to our data gave excellent agreement. The differential cross sections at 180° for π±p elastic scattering have been compiled and the moduli and relative phase of the T=12 and T=32 pion-nucleon s- and u-channel amplitudes (|A12|, |A32|, and cosδ) have a minimum at u=0.4 GeV/c and, in the s channel, a corresponding minimum at s=2.2 GeV/c.
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In a new experiment we have obtained 3006 new events in the reaction π − p → φφ n, approximately doubling the statistics which now total 6658. A refined partial wave analysis of the φφ system again reveals three resonances (g T , g T′ , g T′' ) with I G J PC =0 + 2 ++ . The absence of the OZI suppression, and the observation of only three J PC =2 ++ states (g T , g T′ , g T′' ) which comprise virtually all the cross section are unusual characteristics of the data. The large φφn signal occurs over a mostly structureless and incoherent φK + K − n background. All these unusual characteristics are well explained if these states are produced by 1–3 glueballs (multigluon resonances).
Total cross section plus systematic error supplied by authors.
Absolute cross section based on total cross section of 50 +- 15 nb. Errors quoted in Table are statistical only.
We have carried out an amplitude analysis of the KS0KS0 system produced in the reaction π−p→KS0KS0n at 23 GeV/c, based on about 15 000 events in the low-t region (|t−tmin|<0.1 GeV2). Below 1.6 GeV/c2, our favored solution is very similar to those from previous analyses. For higher masses, we observe the KS0KS0 decay of the h(2040) meson. In addition, the l=0 partial wave contains a new state, strongly coupled to KS0KS0, with parameters M=1.771−0.053+0.077 GeV/c2 and Γ=0.200−0.009+0.156 GeV/c2. Since this state is most probably I=0, we call it the S*′(1770). We find an f′f production ratio of 0.23−0.13+0.14, and branching ratios for f-meson and h(2040)-meson decays into KK¯ of (3.1−1.7+0.7)% and (0.67−0.15+0.41)%, respectively. We find, in a detailed comparison of our results with those from other experiments, that our solution is compatible with all known features of both charged and neutral KK¯ systems.
No description provided.
Approximately 60 000 events have been collected in a spark chamber experiment at the CERN Proton Synchrotron which studied elastic diffraction scattering of π--p and p-p at incident momenta of 8.5, 12.4 and 18.4 GeV/c and of π+-p at 8.5 and 12.4 GeV/c. Magnetic analysis of the incoming and diffraction scattered particle, together with measurement of all angles, permitted each event to be determined as elastic subject to three constraints, so that the inelastic background was rejected with. high efficiency, even at the larger momentum, transfers. Much of the data have been processed by the CERN Automatic Flying-Spot DigitizerHPD. A detailed description of the experimental technique and of the methods of analysis is given. The results, together with data from lower energies, confirm the remarkable energy-independence of the shape of the pion-proton diffraction scattering peak up to |t| = 1.5 (GeV/c)2, wheret is the square of the four-momentum transfer, over a range of pion energies from 2 to 18 GeV. Proton-proton scattering does however appear to show a shrinking diffraction peak. In general, the data agree with other experiments using both counter and bubble chamber techniques, but some differences do appear. During the experiment, data were taken which set an upper limit of 2·102 μb/(GeV/c)2 on the differential elastic cross-section dσ/dt over a range of |t| from 20.9 to 23.4 (GeV/c)2 at 13.4 GeV/c incident pion momentum.
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Exotic exchange processes observed in K − p and π − p scattering in the neighbourhoood of 4 GeV/ c are analysed in terms of standard models. Some new data on π − p induced processes are presented and used in the analysis. Regge-Regge cut predictions are found to be smaller than the data up to these energies. Baryonium exchange models are shown to be indistindistinguishable from Regge cut models as regards their phenomenological predictions. The double scattering quark model of Białas and Zalewski is compatible with data on the exotic exchange production of Σ and Y ∗ (1385), but fails for Ξ and Ξ ∗ (1530) production. Modifications of this model are discussed.
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FORWARD (SMALL -T) CROSS SECTIONS. THE K- P CROSS SECTIONS ARE COMPUTED FROM THE ACNO DATA AT 4.2 GEV/C, M. MAZZUCATO ET AL., NP B178, 1 (1981).
BACKWARD (SMALL -U) CROSS SECTIONS.
We present the results of an experiment to study the reaction π−p→A2−p, A2−→KS0K− at 22.4 and 23.9 GeV/c. We have 3346 KS0K− events in the effective mass region 1.1 to 1.5 GeV, and covering the |t′| interval 0.0 to 1.0 (GeV/c)2. Because of the low background in this channel, we are able to study various |t′| regions, including the region 0.2 to 0.29 (GeV/c)2 in which the original split A2 peak was observed. We find no substructure in any region. We have also derived differential and total cross sections. The differential cross sections are well fitted by the form dσdt′=At′ebt′ with b≈7.0 (GeV/c)−2. The total cross section is in good agreement with the value derived from other experiments that measure the A2−→ρ0π− decay mode.
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We present data on 3652 analyzed events of the reaction π - p → φφn at 22 GeV/ c . A partial wave analysis has been performed on the φφ system. The results are well represented by three resonances all with quantum numbers I G J PC = 0 + 2 ++ . The absence of the Okubo-Zweig-Iizuka suppression observed in this reaction, the selection of only three J PC =2 ++ states ( g T , g T′ , and g T ″ ) which comprise virtually all of the cross section, and the large φφn signal over a very different φK + K - n background are all well explained if these states are produced by 1–3 glueballs (i.e. multigluon resonances).
Slope indicates pion exchange process.
Decay correlation data for π − p → K ∗ Λ at 3.9 GeV /c are analyzed to determine the amplitude structure. We emphasize combinations of observables invariant under rotations between s and t channel frames.
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We report the results of the investigation of 18 500 frames of π+p interactions in the Brookhaven 20-in. bubble chamber at an incident energy of 900 MeV. It is found that single-pion production proceeds almost entirely through formation of the N33* isobar. The production mechanism of the N33* is analyzed in terms of its spin density matrix. Comparison is made with Stodolsky and Sakurai's ρ-exchange model and with the absorptive peripheral model.
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