Search

The radiative decay Λ(1520) → Λγ was recorded in the exclusive reaction p + N → Λ(1520)K+ + N at the SPHINX facility. The branching ratio for this decay and the corresponding partial width were found to be, respectively, Br[Λ(1520) → Λγ] = (1.02 ± 0.21) × 10−2 and Γ[Λ(1520) → Λγ] = 159 ± 35 keV (the quoted errors are purely statistical, the systematic errors being within 15%).

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 .

The first preliminary results from the upgraded SPHINX spectrometer, working in the proton beam with the energy of 70 GeV of the IHEP accelerator, are presented. The data for the reaction p + N ⊒ [Σ0 K +] + N based on new statistics are in good agreement with our previous data and strongly support the existence of the X (2000) state (with an increase in statistics for this state by a factor of ∼5). We also observed radiative decay of Λ(1520) → Λγ. The significant increase in statistics for many diffractive-production reactions will allow us to study them in great detail.

The design of the drift tubes with flat and with wire field shaping electrodes is described. The physical characteristics of the tubes are studied in the beam of Serpukhov accelerator. The optical measurements of wires displacements are made for a long (7.4 m) drift tube with wire field shaping. The comparison of two drift tube options is presented.

The inclusive cross sections of backward proton production in π − ( K − , p ) -Be, Al, Cu, Pb interactions at 40 GeV/ c are presented. Protons have been detected in the angular range 150°–165° and kinetic energy region 0.1–0.3 GeV. The invariant cross-section ratios for various beam particles are independent of the values of kinetic energy and of the nuclear target type: 〈ƒ K − /ƒ π − 〉= 0.87 ± 0.03 stat ± 0.03 syst , 〈ƒ p /ƒ π − 〉 = 1.82 ± 0.10 stat ± 0.05 syst . The A -dependence of the cross-section slope parameter for A ⩾27 is less than ∼2%.

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.

The pion radiative scattering (π-p → π-pγ) has been studied at 43 GeV in the interval 0.2 < |tp| < 0.4 (GeV/c)2 of the momentum transfer squared to the proton and in the range of photon energy 2 < ω < 40 GeV. Calculations based on Low theorem agree well with measured ω, tp and mπγ (final πγ-invariant mass) differential cross-sections. The results obtained extend the validity of Low approach to the radiative scattering at high energies.

The nuclear ({ital A}) dependence of the event structure in the central and forward (projectile fragmentation) regions has been studied for highly inelastic proton-nucleus ({ital pA}) collisions at an incident momentum of 800 GeV/{ital c}. Events with high values of transverse energy ({ital E}{sub {ital t}}) were selected using the large-acceptance Fermilab multiparticle spectrometer. The multiplicity distributions and energy flows in different regions of phase space are presented for six nuclear targets: H, Be, C, Al, Cu, and Pb. The event structure for highly inelastic {ital pA} collisions is strongly dependent on the transverse energy observed in the central region. However at a fixed {ital E}{sub {ital t}}, there is only a weak nuclear dependence of event structure in the central and forward fragmentation regions. This observation is consistent with a thermodynamical description of inelastic {ital pA} interactions and suggests that the observed {ital E}{sub {ital t}} is a good measure of the inelasticity of the reaction. The nuclear dependence of event structure on the particle density and the energy in the forward fragmentation region is also discussed. In contrast with {ital E}{sub {ital t}} as a variable, the particle density and the forward missing energy provide measures of eventmore » inelasticity that are {ital A} dependent.« less

The $A$ dependence of the cross section for $\frac{J}{\ensuremath{\psi}}$ production was measured in the Feynman-$x$ region $0.1\ensuremath{\le}{x}_{F}\ensuremath{\le}0.8$ with a 530-GeV/c ${\ensuremath{\pi}}^{\ensuremath{-}}$ beam. Thick targets of C, Al, Cu, and Pb were employed. Using the cross-section parametrization $\ensuremath{\sigma}={\ensuremath{\sigma}}_{0}{A}^{\ensuremath{\alpha}}$, we find $\ensuremath{\alpha}=0.85\ifmmode\pm\else\textpm\fi{}0.06$. No statistically significant dependence of $\ensuremath{\alpha}$ on either ${x}_{F}$ or transverse momentum ${p}_{t}$ is observed.

Total and differential cross sections for production of the ρ, ω, φ, and J/ψ vector mesons were measured in the Feynman‐x region 0.1≤xF≤0.8 with a 530 GeV/cπ− beam incident on beryllium and copper targets. Using the cross‐section parametrization Aα, we find α=0.76±0.02, 0.81±0.04, 0.87±0.04, and 0.97±0.06 for the ρ/ω, φ, Jψ and Drell‐Yan continuum, respectively. No statistically significant dependence of α on either xF or transverse momentum pT is observed. We have also studied the relative production rates of vector mesons as a function of the event inelasticity, as measured by transverse energy, ET. ET is defined as the scalar sum of transverse momenta for centrally produced charged particles. The relative rate of J/ψ’s and continuum muon pairs does not change with event inelasticity, contrary to the findings of a heavy‐ion collision experiment. On the other hand, the production rate of φ mesons as compared to ρ/ω increases with ET. We argue that the observed increase reflects a simple momentum conserva...

We present the results of an experimental investigation of the production in the nuclear Coulomb field of low-invariant-mass pions pairs by the reaction ..pi../sup -/Z..--> pi../sup -/..pi../sup 0/Z at 40 GeV. We have obtained for the first time the experimental value of the ..gamma -->..3..pi.. coupling constant F/sup 3pi/(0) = 13.0 +- 0.9 +- 1.3 GeV/sup -3/, where the first (second) error is statistical (systematic). This result is in agreement with calculations based on the theory of chiral anomalies.

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 vertex ..gamma -->..3..pi.. has been investigated in the reaction of pion pair production by pions in the nuclear Coulomb field, ..pi../sup -/+(Z,A)..--> pi../sup -/+..pi../sup 0/+(Z,A), in the region of low-invariant-mass ..pi../sup -/..pi../sup 0/ pairs. The experiment has been carried out in the 40-GeV pion beam of the IHEP accelerator (Serpukhov) with the SIGMA spectrometer. We have measured for the first time the cross section of the reaction in the region of momentum transfer squared q/sup 2/ ..3..pi.. coupling constant F/sup 3//sup ..pi../ = 12.9 +- 0.9 +- 0.5 GeV/sup -3/, where the first (second) error is statistical (systematic). The obtained result agrees with the calculations based on the Wess-Zumino-Witten effective Lagrangian. The hypothesis of chiral anomalies and the color-SU(3) quark symmetry are confirmed.

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.

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′

The paper presents the results on differential cross sections for elastic scattering of 7+-, K+-mesons and protons on protons in the 4-momentum transfer squared range 0·08 ≦¦t¦≦ ≦1·0 (GeV/c)2 and incident particle momentum of 29 and 43 GeV/c for pions and kaons and 29, 43, 50 and 65 GeV/c for protons. The measurements were taken with the spectrometer Sigma, installed in the positive beam of the IHEP accelerator.

The performances of the TOF scintillation counters used in the SIGMA-AIAKS spectrometer are presented. The counters, made of NE110, are 150, 65 and 10 cm long, 10 cm wide and 1.5 cm thick. The time resolutions for minimum ionizing particles have been measured to be σ t = 0.18 ns, 0.14 ns and 0.11 ns respectively. The main contribution to the resolution is given by the photoe collection statistics determined by the decay time of the scintillator and the difference of the optical paths in the counter. The scintillation counters, assembled into hodoscopes of 1.5 × 3.2 m 2 and 0.65 × 0.8 m 2 are used for identification of particles through the TOF. The algorithms of off-line data processing are also presented.

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 .

Propertiea of eventa produced with high values of transverse energy (Et) in 800 GeV/c proton-nucleus collieions are presented. Both full-arimuth and limited aperture high Et triggers were wed to melect event6 from six targets (H, Be, C, Al, Cu, and Pb). The events were collected using the large acceptance Fermilab multiparticle spectrometer that recorded almost 95% of the incoming beam energy. The A dependence of the crow sectiona at a given Rt W(UI parameterixed M Aa . The value of a increases from 0.7 at low Et to a plateau at high Et of approximately 1.6. The high Et value of a is slightly amaller for the limited aperture triggers. A strong dependence of (1 on the event structure was observed; yet-like” events exhibit an A dependence consistent with a-1.0, while for more isotropic events a ia much larger. This observation is consistent with the expected behavior for jet production in pA colliaione. (a) Present address: Dept. of Physics, University of Michigan-Flint, Flint, MI 48502 (*) Present address: Inst. of Nucl. Physics, Novi Sad, Yugoslavia cc) Present address: Dept. of Physics, Univ. of Ariaona, Tucson AZ 85721 cd) Present address: A T & T Bell Laboratories, Naperville, IL, 80540 cc) Present address: Fermi National laboratory, Batavia, IL 60510 (f) Present address: Dept. of Physics, Univ. of Roeheater, NY 14267 (g) Present address: Tata Inst. of Fundamental Research, Bombay, India 400005

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

In the reaction of π- dissociation into a μ+μ-π- system on a Cu nucleus, a clear enhancement in the ρ0π- effective-mass distribution has been observed in the π2(1680) region. Partial-wave analysis shows that this enhancement is due to the P-wave and has a resonant nature. Coherent and incoherent cross-sections for this enhancement have been measured.

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-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%.

This paper describes a 5 m gas Cerenkov threshold counter with a velocity resolution δ = 6.5 × 10 −6 . Resolution of δ = = 3.6 × 10 −6 has been achieved as the result of summarizing the signals from two counters. High velocity resolution has been obtained due to the effective registration of Cerenkov light in the short-wave region (counter spectral range: 1800–6000 A). The threshold counter characteristics have been investigated in 5 to 60 GeV/c beams of the 70 GeV accelerator. The particle registration efficiency on the plateau is more than 99.99994%. The probability of the particle registration below the threshold is less than 3 × 10 −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.

A Fe-scintillator hodoscopic hadron calorimeter is described. It consists of independent sections, each containing four total absorption counters 20×20 cm 2 in cross section. The energy resolution for hadrons in the energy range E = 4–40 GeV is σ E / E = 0.02 + 0.52/√ E and the mean space resolution is ∼ 2 cm at 40 GeV.

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 .