None
CROSS SECTION WAS ESTIMATED ASSUMING IT'S INDEPENDENCE OF THE ANTIPROTON M OMENTUM.
A study of the reactions p Xe → K + K + X , p Xe → K + H(H → Σ − p)X and p Xe → K + K + H(H → Σ − p)X was performed using the 700-litre xenon bubble chamber DIANA, exposed to the 1 GeV/ c antiproton beam of ITEP (Moscow). From a sample of 7.8 · 10 5 antiproton annihilations at low energy in xenon nuclei 4 events were observed for the reaction p Xe | → K + K + X at rest ( P p ≤ 400 MeV /c ) and 8 for the same reaction in flight ( 400 ≤ P p ≤ 900 MeV /c ). The corresponding probabilities turned out to be 3.1 · 10 −5 and 3.4 · 10 −5 , respectively. No H -event was found in the two semi-inclusive reactions p Xe → K + HX and p Xe → K + K + HX . This lead to the upper limits 6 · 10 −6 and 8 · 10 −6 (90% C.L.), respectively. The corresponding upper limit for the fully inclusive reaction p Xe → HX turned out to be 1.2 · 10 −5 (90% C.L.), which is about one order of magnitude lower than the actual value reported in the literature.
No description provided.
The double strangeness production has been observed in two final states of annihilation of antiprotons at momentum less than 0.9 GeV/ c on Xe nuclei: K + K + X (8 events) and K + K 0 ΛX (6 events). The probabilities of the reaction p Xe → K + K + X vary from 2 · 10 −5 (at rest) up to 7 · 10 −5 (in flight). The reaction p Xe → K + K 0 ΛX is observed only in flight with probability 3 · 10 −4 . The properties of the observed reactions are similar to those resulting from the cascade process with production of Ξ hyperon: p N → K ∗ −K ∗ , K ∗ → Kπ, −K ∗ N → ΞK, ΞN → ΛΛ . The new upper limit on the production probability of the stable H ( S = −2) dibaryon in the reaction Xe → K + K + H(H → Σ − p)X was obtained to be < 2 · 10 − (90% C . L .).
No description provided.
An energy-independent phase-shift analysis ofπ+p-scattering has been carried out at 16 energies in the region 194–600 MeV. The new data on elastic polarization, obtained in LNPI up to 1983, were included.
No description provided.
No description provided.
No description provided.
The differential cross sections for antiproton elastic scattering on 4 He at 192.8 MeV/ c are measured. The annihilation cross section σ a = (377.6 ± 8.0) mb, the elastic cross section σ el = (206.3 ± 6.6) mb and the total p 4 He interaction cross section σ tot = (583.9 ± 10.4) mb are determined. The ratio of the real to imaginary part of the forward p 4 He amplitude is found: π =−0.17± 0.33 0.24 . Partial wave analysis reveals that the S, P and D waves are essential in this energy region.
Charged prong multiplicity distributions in pbar HE annihilation.
Mean charged particle multiplicity in pbar HE4 annihilations.
No description provided.
None
43 EVENTS WITH LAMBDA, 54 EVENTS WITH KS.
43 EVENTS WITH LAMBDA, 54 EVENTS WITH KS.
43 EVENTS WITH LAMBDA, 54 EVENTS WITH KS. D(N)/D(P) WAS FITTED BY P**2*EXP(-SLOPE*EKIN).
None
No description provided.
No description provided.
The measurement of different reactions of p d annihilation at rest in a gaseous target has been performed using the OBELIX spectrometer at LEAR (CERN). A strong deviation from the OZI-rule prediction was found from the measurement of the ratio R = φπ ωπ in two regions of proton momenta, P < 200 MeV/ c and P > 400 MeV/ c : R( φπ − ωπ − ) = (133 ± 26) × 10 −3 and (113 ± 30) × 10 −3 , respectively. These values are about 30 times greater than the theoretical prediction. For the first time the excitation of the †-resonance was observed among the final-state products of p d annihilation. The existence of a broad enhancement in the 4π invariant mass at m ≈ 1480 MeV, seen in previous experiments, was confirmed. A ≈ 100 MeV downward shift of the bump position, when the proton momentum increased up to P > 400 MeV/ c , was also observed, while the positions of ω, ϱ and f 2 (1270) did not change with the proton momentum. The following branching ratios were measured: BR( p d → π − φ p ) = (6.62 ± 0.49) × 10 −4 , for P < 200 MeV/ c ; BR( p d → π − φ p ) = (0.95 ± 0.22) × 10 −4 , for P > 400 MeV/ c ; BR( p d → π − ω p ) = (49.7 ± 8.9) × 10 −4 , for P < 200 MeV/ c ; BR( p d → π − ω p ) = (8.38 ± 1.09) × 10 −4 , for P > 400 MeV/ c ; BR( p d → 2π − π + p ) = (150 ± 6) × 10 −4 , for P < 200 MeV/ c ; BR( p d → 2π − π + p ) = (16.6 ± 0.9) × 10 −4 , for P > 400 MeV/ c ; BR( p d → 3π − 2π + p ) = (326 ± 12) × 10 −4 , for P < 200 MeV/ c ; BR( p d → 3π − 2π + p ) = (44 ± 7) × 10 −4 , for P > 400 MeV/ c ; BR( p d → Λ K + π − ) = (0.96 ± 0.19) × 10 −4 , for P > 400 MeV/ c ; BR( p d → Λ K + π − π 0 ) = (3.5 ± 0.8) × 10 −4 , for P > 400 MeV/ c ; BR( p p → 2π − 2π + ) = (540 ± 20) × 10 −4 ; BR( p p → 3π − 3π + ) = (251 ± 21) × 10 −4 .
No description provided.
No description provided.
No description provided.
The results of a study of the annihilation reactions n p → θπ + and n p → ωπ + are reported; the data were collected by the OBELIX apparatus, with antineutrons annihilating in flight (momenta from ∼ 50 MeV/ c to 405 MeV/ c ). Annihilation frequencies and annihilation cross sections have been deduced, for both channels, as a function of antineutron momentum. From the cross section ratio, a substantial deviation from OZI rule expectations is observed. An s s quark content in the nucleon offers a fairly plausible explanation for such an effect.
No description provided.
No description provided.
Antinucleon-nucleus annihilations into two-body final states containing only one or no meson are unusual annihilations (Pontecorvo reactions), practically unexplored experimentally, with the exception of the channel p d → π − p , for which only two low-statistics measurements exist. Their physical interest lies in the possibility of exploring small-distance nuclear dynamics, in which an important role can be played by non-nucleonic degrees of freedom. A new measurement of the p d → π − p reaction rate at rest, performed with the OBELIX spectrometer at LEAR, with the best statistics up to now and a careful evaluation of systematic effects is reported, together with a critical analysis of the existing theoretical models. The measured branching ratio, which confirms the previous results, can represent a reference point for the studies in the field.
No description provided.
Forum