The reactionsπ−p→K0(890) Λ,K0(890)Σ0 andK0(890)Σ0 are studied at an incident momentum of 3.95 GeV/c using data from a high statistics bubble chamber experiment corresponding to ∼90 events/μb. The differential cross sections, density matrix elements of the vector meson and hyperon polarizations are presented. A transversity amplitude analysis is performed for each of the reactions. The results are compared with those obtained for the SU(3) related processesK−p→ϕΔ, ϕΣ0, ϕΣ0(1385) andϱ−Σ+(1385) and with predictions of the additive quark model and SU(6) sum rules.
BREIT-WIGNER FIT WITH BACKGROUND POLYNOMIAL.
BACKWARD CROSS SECTION.
TOTAL CROSS SECTION USING SLICING TECHNIQUE. FORWARD (-TP < 1.2 GEV**2) CROSS SECTION IS 25 +- 2 MUB: DOUBLE MASS CUT GIVES 20 +- 7 PCT BACKGROUND CONTAMINATION.
Cross sections for the $\gamma p \to K^+ \Lambda$ have been measured at backward angles using linearly polarized photons in the range 1.50 to 2.37 GeV. In addition, the beam asymmetry for this reaction has been measured for the first time at backward angles. The $\Lambda$ was detected at forward angles in the LEPS spectrometer via its decay to $p\pi^-$ and the K^+ was inferred using the technique of missing mass. These measurements, corresponding to kaons at far backward angles in the center-of-mass frame, complement similar CLAS data at other angles. Comparison with theoretical models shows that the reactions in these kinematics provide further opportunities to investigate the reaction mechanisms of hadron dynamics.
Differential cross sections as a function of the Mandelstam variable U for photon beam energy 1.5 to 1.8 GeV.
Differential cross sections as a function of the Mandelstam variable U for photon beam energy 1.8 to 2.1 GeV.
Differential cross sections as a function of the Mandelstam variable U for photon beam energy 2.1 to 2.4 GeV.
Differential cross sections and polarizations are presented for the reactions K − p → Λπ 0 , Λη , Λη ′ at 8.25 GeV/ c incident K − momentum. The data, which come from a high statistics experiment in the CERN 2 m bubble chamber, are compared with previous experimental results on the same reactions and with current theoretical ideas.
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The reactions K − p → Ξ 0 − (1320) K 0 + , Ξ − (1320) K + (890), Ξ 0 − (1530) K 0 − and Ξ 0 − (1530) K 0 + (890) are studied at 4.2 GeV/ c incident momentum. The data come from a high-statistics bubble chamber experiment with a sensitivity of ∼ 133 events/ μ b. Total anddifferential cross sections are presented. The results are compared to the SU(3)-related processes K + p → pK + and K + p → pK + (890) in the backward hemisphere. In the forward hemisphere “forbidden” peaks are observed and current ideas about them are discussed.
FULLY CORRECTED FOR ALL CUTS AND UNSEEN DECAY MODES.
TOTAL, FORWARD AND BACKWARD CROSS SECTIONS. FULLY CORRECTED FOR CUTS, K0 AND LAMBDA UNSEEN DECAY MODES AND OTHER K*(892) AND XI(1530P13) DECAYS. IN 3-BODY FINAL STATES, THETA REFERS TO THE PI-K SYSTEM.
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We present results for the reactions K 0 p →Λπ + and K 0 p →∑ 0 π + , for |u'| <0. 05 ( GeV /c) 2 and kaon momenta between 1 and 8 GeV/ c . The experiment was performed ina neutral beam at the PS with a two arm spark chamber spectrometer. The cross sections show strong dependence on beam energy and momentum transfer u ′. Λ polarization is compatible with zero. We compare energy dependence of the backward cross sections with the baryon exchange model from π N scattering.
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The reactions π−p→K0Λ,K0Σ0 are studied at an incident momentum of 3.95 GeV/c using data from a high statistics bubble chamber experiment corresponding to ∼90 events/μb. The differential cross sections and hyperon polarizations are presented and compared with existing data from earlier electronic experiments. The data in the forward hemisphere are used to perform an amplitude analysis of the 0−1/2+→0−1/2+ hypercharge exchange processes.
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In order to determine the ηNN coupling constant we have measured the two reactions K − p→ Λη and K − p→ Λπ 0 with a magnetic wire chamber spectrometer which contained a gamma counter for the γγ decays of π 0 and η. The Λ polarization and the differential cross sections are given. The latter have quite different u dependences. Their ratio is interpreted, in terms of a nucleon-Regge exchange model, as the effect of a small ηNN coupling constant for which we obtain G η NN 2 = G π NN 2 · (0.26 ± 0.10) as allowed by SU(3). The large value given by Heisenberg's non-linear field theory, G η NN 2 = G π NN 2 · 0.9, is excluded by this measurement if the characteristic u dependence of the Λπ 0 channel is attributed to N α Regge exchange.
Axis error includes +- 10/10 contribution.
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Axis error includes +- 10/10 contribution.
The reactions p¯p→V0+neutrals were studied in a multiparticle spectrometer at 3.0 GeV/c incident momentum, with a sensitivity of about 150 events/μb. Differential cross sections and polarization of the Λ¯ for the final states Λ¯(Λ) and Λ¯(Σ0) are reported and compared with theoretical models. Differential cross sections of the K0 in K0[K*(890)] and the Λ in Λ(Λ¯+Σ¯0) are also measured. Upper limits of a few μb MeV are obtained for the formation of narrow resonances decaying into V0+neutrals in the mass interval 2.74-2.80 GeV/c2.
FORWARD HEMISPHERE TOTAL CROSS SECTIONS NOT INCLUDING CHARGE CONJUGATE REACTIONS. CORRECTED FOR DECAY BRANCHING RATIOS AND FOR BACKGROUNDS.
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A bubble-chamber study is presented of a 10 events/μb experiment using K − mesons of 4.25 GeV/ c incident momentum. Differential and total cross sections are determined for 7 different reactions: K − p → K 0 n ( la ), → π 0 Λ ( lb ), → ηΛ ( lc ), → η′Λ ( ld ), → π − Σ ( le ), → π + Σ − ( lf ), K + Ξ − ( lg ) . The experimental characteristics in d σ /d t of each reaction are described: (la) shows a levelling off at t = 0 (GeV/ c ) 2 , a break at t = −0.6 (GeV/ c ) 2 and no backward events, (lb) d σ /d t has a smooth behaviour and a measurable backward component with an indication of a dip at u = −0.2 (GeV/ c ) 2 , (1c) d σ /d t shows a dip in the region between t ≈ −0.2 and −0.4 (GeV/ c ) 2 , (ld) d σ /d t has a smooth behaviour; neither this reaction nor the preceding one shows a clear evidence for backward events, (le) d σ /d t has a break at t = −0.5 (GeV/ c ) 2 ; there is a significant cross section in the backward region; (lf) and (lg) show mainly backward production. The polarization of the hyperon is measured in the reactions (lb), (lc), (ld) and (le) in the forward production peak. The statistics do not allow the detection of a definite structure in the polarization but the sign and magnitude are determined. An interpretation of the results is given in terms of a dual Regge model, including the effects of absorption as elaborated recently by several authors.
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The vector meson production, hypercharge exchange reactions K − p → ( φ , ω , ϱ ) Λ and ( φ , ϱ ) Σ 0 are studied at 4.2 GeV/ c incident momentum. The data come from a high statistics bubble chamber experiment with a sensitivity of ∼ 120 events/μb. Total and differential cross sections are presented. The vector meson density matrix elements and hyperon polarization are investigated as functions of momentum transfer. Amplitude analyses are performed for all five reactions. The results are compared with duality and quark model predictions, as well as used to test current ideas in two-body phenomenology.
ERRORS INCLUDE THE 5 PCT MODEL ERROR BUT NOT THEORETICAL RESONANCE PARAMETRIZATION ERRORS.
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Final states ηΛ and η ′ Λ were studied in K − p interactions at 3.95 GeV c . Cross sections, angular distributions and Λ polarizations are reported. The coupling ration R T = (η 1 K K ∗∗ (1420) (η 8 K K ∗∗ (1420)) M is found to be independent of the momentum transfer. Backward Λη is compared to K − p → Λπ o , π ± p → pπ ± and π − p → nπ o at the same momentum.
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Final states π − Σ + , π + Σ − , π o Λ and ηΛ were studied for K − p reactions at 3.95 GeV/ c . Cross sections, angular distributions and polarizations are presented. Data for π − Σ + and π o Λ production are compared to the line-reversed πp reactions at the same beam momentum. Baryon-exchange peaks are presented for the Σ + π − , Σ − π + and Λπ o final states.
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We have measured the differential cross sections for the reactions K − p → K 0 n, K − p → Λπ 0 and K − p → Λη , and the Λ polarization distribution for the second reaction, at K − lab momenta of 3.13, 3.30 and 3.59 GeV/ c . The K − p → Λπ 0 polarization is very large: for the combined data in the interval 0.1 < - t < 0.4 GeV 2 , it is 0.98 ± 0.15. The K − p → Λη forward peak is very steep: for the combined data, the slope b in d/d t = a e bt is 16.2 ± 2.3 GeV −2 , whereas it is about 3 GeV −2 for K − p → K 0 n and 5 GeV −2 for K − p → Λπ 0 . There is a dip near t = −0.5 GeV 2 in the K − p → Λη differential cross section , and another near u = −0.3 GeV 2 in the K − p → Λπ 0 differential cross section. The results are compared with predictions of simple models.
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We have measured the differential cross sections and Λ polarizations in the reactions π−p→ΛK0 and π−p→ΛK*0 (890) near the backward direction, at 3, 4, 5, and 6 GeV/c. Data equal to several times the world's total sample above 2 GeV/c were recorded. Both reactions are characterized by cross sections falling rapidly with beam momentum, and by large positive Λ polarizations for u′ between 0.0 and 0.6 GeV2. Analysis of π−p→ΛK0 yields an effective Regge trajectory consistent with antishrinkage of the backward peak. Separation into amplitudes of definite-parity-naturality exchange shows the reaction to be dominated by unnatural-parity exchange. The energy behavior of this exchange is, however, not consistent with a single linear baryon Regge trajectory or exchange-degenerate pair of trajectories. An apparent normalization discrepancy between data on π−p→ΛK0 of a CERN-ETH group and other high-statistics data including that of this experiment is discussed.
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Results are presented for the quasi two-body hypercharge exchange reactions of the type using data from a high statistics bubble chamber experiment. Total and differential cross sections and the momentum transfer dependence of the meson and hyperon resonance single density matrix elements are discussed. Amplitude analyses are performed for the first two reactions. The results are compared with quark model and duality predictions and with those from other related reactions.
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In a high statistics CERN 2 m bubble chamber experiment the differential cross sections and polarizations of the Λ for the reactions K − p → Λπ 0 , Λη , Λη ′ at 4.2 GeV/ c have been measured. The reaction K − p → Λη exhibits a pronounced dip around − t ∼0.5 ( GeV / c ) 2 and all three reactions show a significant backward peaking (− u < 1.0 (GeV/ c ) 2 ). The Λ polarization in the reaction K − p → Λπ 0 is measured to be significantly different from zero throughout most of the available t -range. Forward cross sections enable a determination of R T , the ratio of singlet/octet coupling η 1 KK ∗∗ η 8 KK ∗∗ . Backward cross sections are utilized to estimate the effective η-nucleon coupling constant g η NN 2 over the − u range 0–1.5 ( GeV /c) 2 .
QUOTED VALUES OF THE KINEMATIC LOWER LIMITS OF -T AND -U.
Axis error includes +- 5/5 contribution.
Axis error includes +- 5/5 contribution.
The reactions K − p→ π − Σ + (1385) and K − p→ π + Σ − (1385) are studied at 4.2 GeV c incident momentum using data from a high statistics bubble chamber experiment corresponding to ∼80 events/μb. The total and differential cross sections are presented. Amplitude analyses are performed and the complete Σ ± (1385) helicity spin density matrices are extracted. The results are compared with the predictions of the additive quark model and exchange degeneracy. A substantial cross section is observed for the reaction K − p→ π + Σ − (1385) in the forward direction, which implies exotic meson quantum numbers in the t -channel. One possible interpretation of this process provides an explanation for the small but significant violations of the additive quark model predictions observed in the reaction K − p→ π − Σ + (1385) at low four-momentum transfer. In the backward direction unnatural parity exchange is shown to give a larger contribution to K − p→ Σ − (1385) π + than natural parity exchange.
Axis error includes +- 5/5 contribution.
Axis error includes +- 5/5 contribution.
Axis error includes +- 5/5 contribution.
Differential cross sections and polarizations have been measured for the backward peaks in the reactions π − p →Λ K 0 and π − p →Λ K ∗ (890) at 8 GeV/c. The experiment was performed with a liquid hydrogen target at the ω spectrometer. The cross sections for u′>−2 ( GeV /c) 2 are 0.27 ± 0.03 μ b for π − p →Λ+ K 0 and 0.55±0.07 μ b for π − p →Λ K ∗0 . Large positive Λ polarization was observed in both reactions for u ′>−0.5 (GeV/ c ) 2 . The dominant production mechanism was found to be unnatural baryon exchange.
Axis error includes +- 0.0/0.0 contribution (?////).
Axis error includes +- 0.0/0.0 contribution (?////).
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We present differential cross sections and the Σ + polarization for the reactions K − p → π ∓ Σ ± using data from a high statistics bubble chamber experiment at 4.2 GeV/ c incident momentum. The statistical level allows a detailed analysis of these reactions over the whole t range. Several significant structures are observed. Comparisons are made with SU(3)-related reactions; for backward production of π − Σ + such a comparison shows good evidence for Δ exchange. The exotic forward peak in K − p → π + Σ − is definitely confirmed.
Axis error includes +- 5/5 contribution.
Axis error includes +- 5/5 contribution.
Axis error includes +- 5/5 contribution.
We have measured the differential cross sections for K − p→ Σ + π − and K − p→ Σ − π + scattering, and the polarization distribution of the Σ + in the first reaction, at K − lab momenta of 3.13 and 3.30 GeV/ c . Our K − p→ Σ + π − cross sections are at least 40% larger than interpolations between measurements at nearby momenta. A comparison using isospin conservation of K − p →Σ + π − , K − p →Σ − π + , and K 0 p → Σ 0 π + cross sections favors our results. The K − p→ Σ + π − differential cross sections have about the same shape and are about twice as large as corresponding K − p→ Λπ 0 differential cross sections across the whole forward region. We discuss the results briefly with reference to simple exchange models.
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TMIN = 0.018 GEV**2. TMAX = 4.67 GEV**2.
TMIN = 0.017 GEV**2. TMAX = 4.98 GEV**2.
We present results on three reactions involving neutral final states which were studied in a magnet spark chamber system. These results are: (a) differential cross section with high statistics for K − p → K 0 n at 5 GeV /c (24 000 events) and at 8 GeV/ c (11 000 events) for t′ <2.0 (GeV/ c ) 2 ; (b) differential cross section and polarization for K − p → Λπ 0 (backward peak) at 5 GeV/ c for u ′ < 1.4 GeV/ c ) 2 ; and (c) differential cross section for K − p → K 0 Δ 0 (1232) at 5 GeV /c for t′ < 1.2 ( GeV /c) 2 . We compare our results with existing data and draw some phenomenological conclusions.
Axis error includes +- 0.0/0.0 contribution (?////TP INDEPENDENT CORRECTIONS AT 5 AND 8 GEV ARE 5.143 +- 0.418 AND 4.981 +- 0.436 RESPECTIVELY).
Axis error includes +- 0.0/0.0 contribution (?////TP INDEPENDENT CORRECTIONS AT 5 AND 8 GEV ARE 5.143 +- 0.418 AND 4.981 +- 0.436 RESPECTIVELY).
Axis error includes +- 0.0/0.0 contribution (?////UP INDEPENDENT CORRECTION FACTOR IS 3.840 +- 0.323).
We present measurements for the baryon-exchange reaction π − p→ Λ K 0 at 5 GeV/ c over the range − u <2(GeV/ c ) 2 . The differential cross section is obtained from events produced on a liquid hydrogen target. These data are combined with events produced on a butanol polarized target and the parameters P , A , and R are then determined from an analysis of the decay angular distribution of the forward-going Λ. From our data it is possible to determine the magnitudes and the relative phase of the two invariant amplitudes A ′ and B . The consequences for the ratio B / A ′ are discussed in detail.
No description provided.
THE ERRORS QUOTED IN D(SIG)/DU DO NOT INCLUDE THE ERROR ASSIGNED TO THE OVERALL U-INDEPENDENT CORRECTIONS FACTOR (4.62 +- 0.36), OR OTHER POSSIBLE NORMALIZATION ERRORS.
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