Qausi-elastic ω production by ep scattering in the kinematic region 0.3. < Q 2 < 1.4 GeV 2 and 1.7 < W < 2.8 GeV was studied using a streamer chamber at DESY. The production angular distribution for γ V p → ω p has a strong non-peripheral component for W < 2 GeV. The ω production cross section falls by a factor of 4 as W changes from 1.7 to 2.8 GeV. In contrast the cross section for ω production with | t | < 0.5 GeV 2 is W independent between 1.7 and 2.8 GeV and for W > 2.0 GeV consistent in both W and Q 2 dependence with the predictions of a model based on one-pion exchange and diffraction.
FOR ALL T-VALUES. THE GAMMA* P TOTAL CROSS SECTION WAS TAKEN FROM A FIT TO THE DATA OF S. STEIN ET AL., PR D12, 1884 (1975). 'PPD'.
'PPD'. PERIPHERAL OMEGA PRODUCTION.
No description provided.
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 (?////).
No description provided.
An enhancement in the (K − π + ) mass distribution at 1871 ± 10 MeV with full width of 285 ± 40 MeV is observed in the charge-exchange reaction K − p → K − π + n at 10 and 16 GeV/ c . The energy dependence of its cross section, the shape of the differential cross section d σ /d t and the decay angular distributions are consistent with a production mechanism by pion exchange. No significant enhancement at the same mass is seen in the non-charge exchange reaction K − p → (K π ) − p. The experimental evidence is reviewed and it is suggested that there may be more than one K ∗ enhancement in the 1700–1900 mass region.
FOR ALL EVENTS WITH 1.7 < M(K- PI+) < 2 GEV. NO FORWARD DIP. 'THETA CUT'.
THE 14.3 GEV/C POINT IS FROM ANALYSING THE DATA OF M. SPIRO ET AL., PL 60B, 389 (1976) IN THE SAME WAY. 'THETA-CUT'.
A partial-wave analysis of the low-mass ( π + π − p) system produced in the reaction K − p → K − ( π + π − p) at 4.2 GeV/ c incident momentum is performed in order to study the two ( π + π − p) enhancements around 1500 and 1700 MeV. It is found that the low-mass ( π + π − p) system can be described using the spin-parity states J P = 1 2 + , 3 2 − and 5 2 + only. In the 1500 MeV region contributions are observed from the 1 2 + wave decaying into pϵ and the 3 2 − wave decaying into Δ ++ π − ; in the 1700 MeV region contributions are found from the 1 2 + wave decaying into Δ ++ π − , the 3 2 − wave decaying into pϵ, and the 5 2 + wave decaying into pϵ.
No description provided.
None
No description provided.
No description provided.
Pion production on a CD2 target has been measured using the high-resolution magnetic spectrometer SPES I. Differential cross sections for the reaction D(p, π+)T have been determed at Tp=410, 605, and 809 MeV. The present data, together with previous results establish a complete angular distribution of the reaction D(p, π+)T at ∼ 600 MeV and the energy dependence of the differential cross section for this reaction at several constant momentum transfers.
No description provided.
No description provided.
Using a secondary pion beam from the Argonne Zero Gradient Synchrotron we have studied the process π−p→φn in the region of the cross-section enhancement near kinematic threshold. For incident momenta between 1.6 and 2 GeV/c, we have determined production and decay angular distributions and extrapolated total cross sections from a sample of about 160 φ's above background. The production and decay distributions are consistent with isotropy over this entire incident-momentum range. The extrapolated total cross section varies between 19 and 25 μb.
Axis error includes +- 16/16 contribution (RES-DEF(RES=PHI,BACK=CORRECTED)).
Axis error includes +- 16/16 contribution (RES-DEF(RES=PHI,BACK=CORRECTED)).
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.
No description provided.
No description provided.
No description provided.
Three- and four-body final states with strange particles are studied in π + p and π − p interactions at 16 GeV/ c . We present cross sections and investigate their energy dependence. Production mechanism, resonance production and quantum number transfer are discussed. Strong Y ∗ (1385) production is found in the reaction π + p → Λ K + π + , while the corresponding π − p reaction is dominated by production of K ∗ (890). In the NK K π channels, the K and K are produced mainly at the same vertex, i.e. non-strangeness exchange ΔS = 0 is dominant (about 75% of the cases), whereas in the Λ K ππ channels, the Λ and K are more frequently produced at opposite vertices, i.e. | ΔS | = 1 exchange is important (about 60% of the cases). Results on the polarization of the lambdas produced in the π + p reactions are given.
No description provided.
The reactions π + p giving π 0 Δ ++ (1236), η (549) Δ ++ (1236) and η ′(958) Δ ++ (1236) are studied at 16 GeV/ c . Cross sections, differential cross sections and Δ ++ (1236) spin density matrix elements are presented. The π 0 Δ ++ (1236) differential cross section d σ d t′ indicates a dip towards t ′ = 0 and has a minimum at t ′ ≅ 0.6 GeV 2 . The Δ ++ (1236) spin density matrix elements are consistent with the predictions of the Stodolsky-Sakurai model, except perhaps near the forward direction. For ηΔ ++ (1236), the differential cross section d σ d t′ turns over in the forward direction and presents no further structure. SU(3) sum rules are tested and found to be approximately satisfied. The data agree with factorization of ϱ exchange. The effective A 2 trajectory is calculated and found to be consistent with that reported from the reaction π − p → η n.
No description provided.
NORMALIZED TO THE TOTAL CROSS SECTION OF 49 MUB.
No description provided.
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