Search

The radiative decay Λ ( 1520 ) → Λ γ was measured directly in the study of the exclusive diffractive-like reaction p + N → Λ ( 1520 ) K + + N , Λ ( 1520 ) → Λ γ with the SPHINX spectrometer. The values of the branching and partial width of this radiative decay were obtained: BR [ Λ ( 1520 ) → Λ γ ] = ( 1.02 ± 0.21 ( stat ) ± 0.15 ( syst ) ) × 10 −2 and Γ [ Λ ( 1520 ) → Λ γ ] = 159 ± 33 ( stat ) ± 26 ( syst ) keV .

We present results on the production of jets and "jetlike" clusters in 800-GeV/c proton-nucleus (pA ) collisions. Events with high values of transverse energy in the central kinematic region were selected for nuclear targets of H, Be, C, Cu, and Pb. A jet-finding algorithm was used in analyzing the data. The A dependence of the jet and dijet cross sections was parametrized as Aα. The values of α for events with "jetlike" cluster pairs found by the algorithm without any additional kinematic cuts reach a plateau of approximately 1.5 at dijet transverse energies > GeV. The collimation of observed "jetlike" clusters decreases with A, and the fragmentation is softer for heavier target nuclei. However, nuclear effects become less pronounced with the increasing cluster or cluster-pair transverse energy. We argue that the observed nuclear enhancement for the production of "jetlike" clusters is due to underlying event or/and soft-scattering contributions to the heavy-nuclei data. We show that the nuclear enhancement becomes consistent with a value of α within 0.10 from unity once the data are corrected for the underlying event or kinematic cuts enhancing clear jet structure are applied.

Invariant mass spectrum of μ + μ − pairs produced by 70 GeV/ c protons in Be target are presented. Distinct enhancements in the mass regions of ϱ, ω mesons, φ meson and J/ψ particle are observed. For J/ψ production x and p ⊥ 2 distributions are given. The total cross section for the reaction p + Be → ( J ψ → μ + μ − ) + … is equal to 9.5 ± 2.5 nb/nucleus .

The reaction π−p→Ks0Ks0n was studied at the incident momentum 40 GeV/c making use of the 6 m magnetic spark spectrometer MSS ITEP. Partial wave analysis was carried out using ∼ 6700 events of this reaction with t′

About 7 × 10 3 events of Compton effect on pion in the reaction π − A → A π − γ st 40 GeV/ c were detected and for the first time the charged pion polarizability was obtained α π = (6.8 ± 1.4) × 10 −43 cm 3 .

The ππ0 production in nuclear Coulomb field at threshold has been studied for the first time experimentally. The cross section of the reaction $$\pi ^ - + (A,Z) \to \pi ^ - + \pi ^0 + (A,Z)$$ at 40 GeV on C, Al, Fe nuclei has been determined for small 4-momentum transferst

The reaction π−A→Aπ− γ at 40 GeV/c was studied on “Sigma” spectrometer on six different nuclear targets in the region of four-momentum transfer |t

The absorption cross sections of antideuterons with the momentum P = 13.3 GeV/c by Li, C, Al, Cu and Pb nuclei have been measured. Antiproton stripping of antideuterons has been registered and its cross section for C, Al and Cu has been defined. The binding energy of antideuteron is found to be ed = 2.4 ± 0.6 MeV by measuring the angular distribution of antiprotons from stripping.

Total cross sections for π − , K − and p on protons and deutrons have been measured in the momentum range 15 to 60 GeV/c. Total cross sections for particle interactions with neutrons have been determined with an energy dependent Glauber correction. Using the positive particle data obtained earlier with the same experimental apparatus, the differences of total cross sections for particles and antiparticles as well as for particles belonging to the same isospin multiplet have been calculated. The differences of total cross sections for particles and antiparticles decrease with momentum following a power law. The differences between the pure isospin state cross sections are either close to zero or continue to decrease. The measured total cross sections and their differences are in agreement with relations predicted by quark and Regge-pole models.

Total cross-section data are presented for negative pions, kaons, and antiprotons on protons and deuterons in the momentum range 20 GeV/c to 65 GeV/c in 5 GeV/c steps.

The paper describes differential Cerenkov counters detecting Cerenkov light at the angles of 23 and 12 mrad. The counter lengths are 5 m (θ = 23 mrad) and 10 m (θ = 12 mrad). The spectrum band of the counters is 2500–6000 A. The counter characteristics have been investigated in 35 to 45 GeV/c beams of the 70 GeV accelerator. The velocity resolutions measured are equal to 2×10−6 for a 10 m counter and 6×10−6 for a 5 m counter. The 10 m counter can separate pions and kaons up to 200 GeV/c and kaons and protons (antiprotons) up to 350 GeV/c.

π − p , K − p and p p total cross-sections are measured at momenta up to 65GeV/c with statistical accuracy 0.3 ÷ 0.6% and systematical (scale) error ≈ 0.4%.

Absorption cross sections for pi /sup plus or minus /, K/sup plus or minus mesons, protons andantiprotons on Li, Be, C, Al, Cu, Sn, Pb and V in the momentum range from 6.65 to 60 GeV/c are measured at the 70 GeV IHEP accelerator. The cross sections are compared with calculations using the Glauber multiple- scattering model. Nucleus radii are found to be described by a power dependence on atomic weight R = r/sub o/A/sup 1/3/, where r/sub o/= 1.05 plus or minus 0.02 fm. (auth)

The pion radiative scattering πZ→πZγ at 40 GeV was investigated. Coulomb scattering-i.e. pion Compton-effect-dominates for small fourmomentum transfers in this reaction. In our previous paper we found the pion polarizability to beβ π =(−6.8±1.4)·10−43, cm3, where we assume following the theory that the sum of electrical and magnetic polarizabilities (α π +β π )≃0. More complete analysis of our data is done in order to test this assumption. The result for (α π +β π ) is in agreement with theoretical predictions.

The A -dependence of J/ψ inclusive production by 43 GeV/ c π − -mesons was measured to be σ = (18 ± 6) A (0.92±0.06) nb/nucleus for x > 0.

In the diffraction dissociation of π− into μ+μ−π− on a Cu nucleus at 50 GeV/c, the cross section $$\sigma _{\mu ^ + \mu ^ - \pi ^ - } $$ for the 1+S(ρ0π) wave was measured. The branching ratio of ρ0→μ+μ− could be calculated from the ratio of this and the corresponding cross sections in the diffraction dissociation of π− into π+π−π−. The obtained value $$BR_{\rho ^0 \to \mu ^ + \mu ^ - } = (4.6 \pm 0.2_{stat^ \pm } \pm 0.2_{syst} )10^{ - 5} $$ is in good agreement with the branching ratio $$BR_{\rho ^0 \to e^ + e^ - } $$ , as expected ifeμ universality holds.

Results of the experimental study of inclusive φ meson production off berillium nuclei by 70 GeV/ c protons in the beam fragmentation region x > 0.41 are presented. Fitting of the measured differential cross sections to the forms d σ d x ∼ (1 − x) n x and d σ d p 2 t ∼ exp (−bp 2 t ) gives the parameters n = 6.0 ± 1.7 and b = (2.4 ± 0.7) (GeV/ c ) −2 . In the framework of a quark-parton model the measured φ meson x -distribution suggests that in the region of x > 0.41 nearly 90% of the φ mesons are produced via a strange sea quark fusion. The ratio of the OZI-forbidden and OZI-allowed transition coupling constants has been found to be ten times smaller than the same ratio calculated from the partial decay widths. The total inclusive cross section is estimated to be σ (pN → φ X) = (0.7 ± 0.2) × 10 −27 cm 2 .

d p and p d total cross-sections have been measured at 13.3 and 6.65 GeV/c respectively to check CPT-invariance. The standard transmission technique was used. The difference of d p and p d total cross-sections appeared to be equal 0.2 ± 2.6 mb. In addition d d and p p total cross-sections have been obtained. The experimental data allowed us to derive the total cross-section of antineutrons on protons, neutrons and deutrons.

The yields of pions, kaons, antiprotons and antideuterons, produced by the 70 GeV protons on Al and Be nuclei at the momenta 10 and 13.3 GeV/ c have been measured. Gas Cerenkov counters and time-of-flight spectrometers were used for particle identification.

The E672/E706 Spectrometer, located in the MW beam at Fermilab, was used to collect data on events containing a pair of muons in the final state with large effective mass. The momentum of incident pions and protons was 530 GeV/c. Nuclear targets included Be, C, Al, Cu and Pb. We report on a preliminary measurement of the A‐dependence of the per nucleus cross section for forward J/ψ production. The apparatus also detected charged particles and γ’s produced in association with the muon pair. The expected physics results on the hadroproduction of χ states and beauty particles are discussed.

Data are presented on the yields of π − , K − , and p produced at small angles by 70 GeV proton-aluminium interactions. The momenta of the secondaries studied were greater than 40 GeV/ c . Upper limits have been obtained on the production of antideuterons and possible new particles up to a mass of 2.2 GeV in this new energy region.

The differential cross sections d σ d x and d σ d p t 2 of inclusive J/ψ production by 43 GeV/ c π − off Be, Cu and W nuclei have been measured. Fitting d σ d p t 2 ∼ A α (p t 2 ) we observed the increase of α with p t 2 .