42 research outputs found
Resonance structure in the {\gamma}{\gamma} and systems in dC interactions
Along with and {\eta} mesons, a resonance structure in the invariant
mass spectrum of two photons at M{\gamma}{\gamma} = 360 \pm 7 \pm 9 MeV is
observed in the reaction d + C \rightarrow {\gamma} + {\gamma} + X at momentum
2.75 GeV/c per nucleon. Estimates of its width and production cross section are
{\Gamma} = 64 \pm 18 MeV and = 98 \pm 24 {\mu}b,
respectively. The collected statistics amount to 2339 \pm 340 events of 1.5
\cdot 10^6 triggered interactions of a total number ~ 10^12 of dC-interactions.
The results on observation of the resonance in the invariant mass spectra of
two mesons are presented: the data obtained in the d + C \rightarrow
{\gamma} + {\gamma} reaction is confirmed by the d + C \rightarrow +
reaction: = 359.2 \pm 1.9 MeV, {\Gamma} = 48.9 \pm 4.9
MeV; the ratio of Br(R\rightarrow{\gamma}{\gamma}) /
Br(R\rightarrow) = (1.8 {\div} 3.7)\cdot10^-3.Comment: 10 pages, 11 figure
π
We report on measurements of neutral pion production in the inclusive reactions d + C → π0 + x and d + Cu → π0 + x at an incident momentum of 4.5 GeV/c per nucleon. The experiments were performed on the LHE 90-channel lead glass γ-spectrometer. The cross sections were measured over the kinematical region specified by the inequalities θπ ≤ 16° and Eπ ≥ 2 GeV (in the laboratory frame). The cumulative number and transverse momentum dependencies of the exponent n in the invariant cross section parameterization Ed3 σ / d3 p ~ Atn are investigated by comparing of the observed cross sections for π0 production on carbon and copper targets in the intervals 0.6 ≤ X ≤ 1.8 and 0.04 ≤ pT2 ≤ 0.40 (GeV/c)2. The double differential cross section for the reaction d + C → π0 + x is measured using statistics of about 4.5 · 104π0 mesons. On the basis of these data we verified the so-called cluster mechanism of π0 production. We have compared our data for the reaction d + C → π0 + x, extrapolated to θπ = 0°, with the data from another experiments on π− production: d + C → π−(0°) + x (P = 1.75 and 2.88 GeV/c per nucleon) [1]; p + d → π−(180°) + x and p + d → π+(180°) + x (P = 8.9 GeV/c per nucleon) [2]; d + p → π−(0°) + x (P = 8.9 GeV/c per nucleon) [3]. The invariant cross sections were approximated by an exponential function Ed3 σ / d3 p ~ exp(−X / X0). The slope parameter X0 at different kinetic energies of the projectiles in the range of 1.05÷8.0 GeV per nucleon is determined
Observation of structures at and MeV/c in the invariant mass spectra in pC, dC, and dCu collisions at of a few GeV/c per nucleon
The results of an analysis of the invariant mass spectra of photon pairs
produced in dC, pC and dCu interactions at momenta of 2.75, 5.5 and 3.83 GeV/c
per nucleon respectively, are presented. Signals in the form of enhanced
structures at invariant masses of about 17 and 38 MeV/c2 are observed. The
results of testing of the observed signals, including the results of the Monte
Carlo simulation are presented. The test results support the conclusion that
the observed signals are the consequence of detection of the particles with
masses of about 17 and 38 MeV/c2 decaying into a pair of photons.Comment: arXiv admin note: text overlap with arXiv:0806.279
Experimental and theoretical evidences for an intermediate -dressed dibaryon in the NN interaction
Numerous theoretical and experimental arguments are presented in favor of the
generation of intermediate -dressed dibaryon in interaction at
intermediate and short distances. We argue that this intermediate dibaryon can
be responsible for the strong intermediate-range attraction and the short-range
repulsion in the interaction, and also for the short-range correlations in
nuclei. The suggested mechanism for the -dressing of the dibaryon is
identical to that which explains the Roper resonance structure, its dominant
decay modes and its extraordinary low mass. A similar transformation mechanism
from the glue to the scalar field was discovered in decays. The new
experimental data on 2-production in the scalar-isoscalar channel produced
in - and -collisions and in particular the very recent data on
correlations in C and C scattering in the GeV region seems
to corroborate the existence of the -dressed dibaryon in two- and three
nucleon interactions.Comment: 14 pages,4 figure
Digamma diagnostics for the mixed-phase generation at NICA
A novel type of diagnostics for dense and/or hot nuclear matter produced in heavy-ion collisions at NICA and similar future colliders (FAIR, etc.) is suggested. The diagnostics is based on an assumption (confirmed in many experiments worldwide) about intensive generation of light scalar mesons (σ) the consequent decay of which produces γγ pairs with the mass and width dependent upon density and temperature of the fireball produced in the collision process. Thus, measurements of the absolute yield, mass and width of the γγ signal carry valuable information about the state of fireball generated during the high-energy nuclear collision
INCLUSIVE FORMATION OF NEUTRAL PIONS IN NUCLEON-NUCLEAR AND NUCLEUS-NUCLEAR INTERACTIONS AT THE 4,5 HeV/c ON NUCLEON
Atomic nuclei are considered in the paper aiming at the mechanism investigation of the neutral pion formation in nucleus-nuclear interactions. As a result methods for the measurement of energies of charged particles and gamma -quantums have been suggested. Differential cross sections of the pi degrees -meson formation at the 4,5 HeV on nucleon have been measured. The results have their value for the development of models for a nucleus and nuclear collisons and will be used for the new experiment formulation. The paper results may find their field of application in experimental nuclear physicsAvailable from VNTIC / VNTIC - Scientific & Technical Information Centre of RussiaSIGLERURussian Federatio