Multifragmentation of Agnat and Au197 nuclei induced by 1.8–4.8 GeV He3 ions has been studied with the Indiana Silicon Sphere 4π detector array. Rapidity, moving source, and sphericity-coplanarity analyses are consistent with near-simultaneous emission from a source in approximate kinetic equilibrium. For the most dissipative collisions, the spectral peaks are broadened and shifted to very low energies, indicative of emission from an extended nuclear system with ρ/ρ0∼1/3. Predictions of an intranuclear cascade/expanding, emitting source model compare well with experimental multiplicity distributions and the evolution of fragment spectral shapes. © 1996 The American Physical Society.
No description provided.
No description provided.
We report the measurement of secondary charge and isotopic fragmentation cross sections in a liquid hydrogen target from 30 incident beams of relativistic nuclei ranging from 10B to 55Mn. These individual beams were obtained by initially accelerating 580 MeV/nucleon 40Ar and 630 MeV/nucleon 56Fe nuclei and letting these nuclei interact in a thin CH2 target in the beam line. The fragments of these interactions were then focused according to their A/Z ratios onto a hydrogen target and the charge and isotopic composition of the fragmentation in this target was measured using our standard cosmic ray telescope. Several of these nuclei have had their cross sections measured previously and a comparison with earlier data confirms the estimated precision ∼5% of the new cross section data. The 30 nuclei for which the cross sections were measured doubles the previously reported data for 15 nuclei from several experiments in the charge range from Li to Ni. The systematics of these new cross sections are discussed both with respect to the charge changing and isotopic cross sections. These systematics will lead to improvements in the productive capability of the formulas used to describe the unmeasured cross sections. It should be noted, however, that from the point of view of the propagation of galactic cosmic rays through the interstellar medium, which is one of the main goals of this experiment, the fragmentation cross sections have now been measured at at least one energy for over 98% of the arriving particles with Z=3–28.
No description provided.
No description provided.
The Indiana Silicon Sphere 4π detector has been used to measure light-charged particles and intermediate-mass fragments (IMFs) emitted in the 18–4.8 GeV He3+natAg, Au197 reactions. Ejectile multiplicity and total event kinetic energy distributions scale systematically with projectile energy and target mass, except for the Agnat target at 3.6 and 4.8 GeV. For this system, a saturation in deposition energy is indicated by the data, suggesting the upper projectile energy for stopping has been reached. Maximum deposition energies of ∼950 MeV for the Agnat target and ∼1600 MeV for the Au197 target are inferred from the data. The results also demonstrate the importance of accounting for fast cascade processes in defining the excitation energy of the targetlike residue. Correlations between various observables and the average IMF multiplicity indicate that the total thermal energy and total observed charge provide useful gauges of the excitation energy of the fragmenting system. Comparison of the experimental distributions with intranuclear cascade predictions shows qualitative agreement. © 1996 The American Physical Society.
TARGET IS NATURAL AG.
No description provided.
The cross section for K + meson production in collisions of 36 Ar ions on a 48 Ti target has been measured at an incident energy of 92 MeV per nucleon. A description of the experimental set-up is given. Twelve events attributed to monoenergetic muons following the decay of stopped kaons have been identified. From these events, one infers a production cross section of 240 pb. Data are briefly discussed.
No description provided.
K+ production far below the free nucleon-nucleon threshold has been investigated in collisions of 36Ar on 12C, natTi, and 181Ta targets at an incident energy of 92 MeV per nucleon. The cross sections for K+ production have been inferred from the observed muon decays of positive kaons. The results are discussed in the framework of a participant-spectator model and are compared to proton induced K+ production and to subthreshold pion production experiments.
Three different production modes are assumed: (C=ISOTROPIC) isotropic emmision inthe lab frame with a kinetic energy EKIN(K) = 35 MeV, (C=SPECTRUM) isotropic emmision inthe lab frame with a kinetic energy spectrum from S. Gosh, PR C45,R518, (C=FIREBALL) isotropic emmision in the fireball frame with a kinetic ener gy EKIN(K) = 35 MeV.
The production of neutral pions has been studied in the 16 O+ 27 Al, 58 Ni, 208 Pb reactions at 95 MeV/nucleon. Inclusive pion differential distributions d σ d p t , d σ d T π , and d σ d Ω have been measured by detecting the two-pion decay γ-rays in a setup of 8 lead glass Cherenkov detector telescopes. The data are discussed in the framework of a moving thermal source model. It is shown that the shape of the pion energy spectra is better described if mean field effects on the primary pion-production cross section and pion reabsorption are included in the calculation.
Axis error includes +- 10/10 contribution.
SPECTRA WERE FITTED USING THE FORMULA D3(N)/D3(P)= CONST/(EXP(EKIN(P=3)/T)-1).
Axis error includes +- 10/10 contribution.
Correlations between target fragments were measured in α- and 14 N-induced reactions at 70, 250 and 800 MeV/u incident energies. The reaction mechanism is characterized by the linear momentum transfer and the excitation energy which were deduced from the kinematics and the mass distribution of the fission fragments. By selecting targets lighter than Th (Au and Ho) the yield from peripheral collisions is reduced by the increase in the fission barrier thus allowing events with the highest linear momentum transfer and excitation energy to be favoured. The results show that up to an incident energy of 800 MeV/u hot nuclei are formed which decay via normal binary fission. The linear momentum transfer is essentially constant over the covered energy range, but the excitation energy increases until the total incident energy is greater than 3 GeV. At this energy, independent of the projectile mass the fission probability of the heavy nuclei drops below 50%, while the emission of intermediate-mass fragments increases. The relative velocities between two intermediate-mass fragments exceed strongly the values of binary fission. Monte Carlo calculations show that the relative velocities between these fragments exclude a sequential emission from the recoil nucleus and support a simultaneous breakup mechanism.
SIG IS FISSION CROSS-SECTION CALCULATED WITH THE SOFT-SPHERE MODEL OF REF. PHYS.REV.C11 (1975) 1203.
SIG IS FISSION CROSS-SECTION CALCULATED WITH THE SOFT-SPHERE MODEL OF REF. PHYS.REV.C11 (1975) 1203.
SIG IS FISSION CROSS-SECTION CALCULATED WITH THE SOFT-SPHERE MODEL OF REF. PHYS.REV.C11 (1975) 1203.
The TOTEM experiment has measured the charged particle pseudorapidity density dN_{ch}/deta in pp collisions at sqrt{s} = 7 TeV for 5.3<|eta|<6.4 in events with at least one charged particle with transverse momentum above 40 MeV/c in this pseudorapidity range. This extends the analogous measurement performed by the other LHC experiments to the previously unexplored forward eta region. The measurement refers to more than 99% of non-diffractive processes and to single and double diffractive processes with diffractive masses above ~3.4 GeV/c^2, corresponding to about 95% of the total inelastic cross-section. The dN_{ch}/deta has been found to decrease with |eta|, from 3.84 pm 0.01(stat) pm 0.37(syst) at |eta| = 5.375 to 2.38 pm 0.01(stat) pm 0.21(syst) at |eta| = 6.375. Several MC generators have been compared to data; none of them has been found to fully describe the measurement.
Charged-particle multiplicities in proton-proton collisions at a centre-of mass energy of 7 TeV as a function of pseudorapidity for events with the number of charged particles >=1 having transverse momentum >40 MeV and 5.3< absolute(pseudorapidity) <6.5.
Proton-proton elastic scattering has been measured by the TOTEM experiment at the CERN Large Hadron Collider at {\surd}s = 7 TeV in dedicated runs with the Roman Pot detectors placed as close as seven times the transverse beam size (sbeam) from the outgoing beams. After careful study of the accelerator optics and the detector alignment, |t|, the square of four-momentum transferred in the elastic scattering process, has been determined with an uncertainty of d t = 0.1GeV p|t|. In this letter, first results of the differential cross section are presented covering a |t|-range from 0.36 to 2.5GeV2. The differential cross-section in the range 0.36 < |t| < 0.47 GeV2 is described by an exponential with a slope parameter B = (23.6{\pm}0.5stat {\pm}0.4syst)GeV-2, followed by a significant diffractive minimum at |t| = (0.53{\pm}0.01stat{\pm}0.01syst)GeV2. For |t|-values larger than ~ 1.5GeV2, the cross-section exhibits a power law behaviour with an exponent of -7.8_\pm} 0.3stat{\pm}0.1syst. When compared to predictions based on the different available models, the data show a strong discriminative power despite the small t-range covered.
The measured differential elastic cross section. Data from the tabulation in CERN-PH-EP-2012-239.
The COMPASS Collaboration at CERN has measured the transverse spin azimuthal asymmetry of charged hadrons produced in semi-inclusive deep inelastic scattering using a 160 GeV positive muon beam and a transversely polarised NH_3 target. The Sivers asymmetry of the proton has been extracted in the Bjorken x range 0.003<x<0.7. The new measurements have small statistical and systematic uncertainties of a few percent and confirm with considerably better accuracy the previous COMPASS measurement. The Sivers asymmetry is found to be compatible with zero for negative hadrons and positive for positive hadrons, a clear indication of a spin-orbit coupling of quarks in a transversely polarised proton. As compared to measurements at lower energy, a smaller Sivers asymmetry for positive hadrons is found in the region x > 0.03. The asymmetry is different from zero and positive also in the low x region, where sea-quarks dominate. The kinematic dependence of the asymmetry has also been investigated and results are given for various intervals of hadron and virtual photon fractional energy. In contrast to the case of the Collins asymmetry, the results on the Sivers asymmetry suggest a strong dependence on the four-momentum transfer to the nucleon, in agreement with the most recent calculations.
The Sivers asymmetry, from the 2010 data set, for positive hadrons as a function of X for full range. Also shown are the mean values of other variables plus the correlation with the Collins data measurments.
The Sivers asymmetry, from the 2010 data set, for negative hadrons as a function of X for full range. Also shown are the mean values of other variables plus the correlation with the Collins data measurments.
The Sivers asymmetry, from the 2010 data set, for positive hadrons as a function of PT for full range. Also shown are the mean values of other variables plus the correlation with the Collins data measurments.
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