Search results for "Heavy-ion"
showing 10 items of 119 documents
Investigation of fusion probabilities in the reactions with 52,54Cr, 64Ni, and 68Zn ions leading to the formation of Z = 120 superheavy composite sys…
2020
Background: The formation of superheavy nuclei in fusion reactions is suppressed by a competing quasifission process. The competition between the formation of the compound nucleus and the quasifission depends strongly on the reaction entrance channel. Purpose: The investigation of fission and quasifission processes in the formation of Z=120 superheavy composite systems in the 52,54Cr+248Cm and 68Zn+232Th reactions, and their comparison with the 64Ni+238U reaction at energies in the vicinity of the Coulomb barrier. Methods: Mass-energy distributions of fissionlike fragments formed in the reactions 52,54Cr+248Cm and 68Zn+232Th at energies near the Coulomb barrier were measured using the doubl…
117番元素Ts合成のための48Ca+249Bk融合反応
2019
We have performed an experiment to synthesize the element 117 (Ts) with the $^{48}$Ca+$^{249}$Bk fusion reaction. Four $\alpha$-decay chains attributed to the element 117 were observed. Two of them were long decay chains which can be assigned to the one originating from the $\alpha$ decay of $^{294}$Ts. The other two were short decay chains which are consistent with the one originating from the $\alpha$ decay of $^{293}$Ts. We have compared the present results with the literature data, and found that our present results mostly confirmed the literature data, leading to the firm confirmation of the synthesis of the element 117.
Measurement of emission-angle anisotropy via long-range angular correlations with high-pT hadrons in d+Au and p+p collisions at √sNN = 200 GeV
2018
We present measurements of two-particle angular correlations between high-transverse-momentum (2 < pT < 11 GeV/c) π0 observed at midrapidity (|η| < 0.35) and particles produced either at forward (3.1 <η< 3.9) or backward (−3.7 <η< −3.1) rapidity in d + Au and p + p collisions at √sNN = 200 GeV. The azimuthal angle correlations for particle pairs with this large rapidity gap in the Au-going direction exhibit a characteristic structure that persists up to pT ≈ 6 GeV/c and which strongly depends on collision centrality, which is a similar characteristic to the hydrodynamical particle flow in A + A collisions. The structure is absent in the d-going direction as well as in p + p collisions, in t…
Flow dominance and factorization of transverse momentum correlations in Pb-Pb collisions at the LHC
2017
Physical review letters 118(16), 162302 (2017). doi:10.1103/PhysRevLett.118.162302
First measurement of the |t|-dependence of coherent J/ψ photonuclear production
2021
The first measurement of the dependence on $|t|$, the square of the momentum transferred between the incoming and outgoing target nucleus, of coherent J/ψ photoproduction is presented. The data were measured with the ALICE detector in ultra-peripheral Pb-Pb collisions at a centre-of-mass energy per nucleon pair $\sqrt{s_{\rm NN}} = 5.02$ TeV with the J/$\psi$ produced in the central rapidity region $|y| < 0.8$, which corresponds to the small Bjorken-$x$ range $(0.3 − 1.4) \times 10 ^{−3}$. The measured $|t|$-dependence is not described by computations based only on the Pb nuclear form factor, while the photonuclear cross section is better reproduced by models including shadowing according t…
Event-Shape Engineering for the D-meson elliptic flow in mid-central Pb-Pb collisions at √sNN = 5.02 TeV
2019
The production yield of prompt D mesons and their elliptic flow coefficient v2 were measured with the Event-Shape Engineering (ESE) technique applied to mid-central (10–30% and 30–50% centrality classes) Pb-Pb collisions at the centre-of-mass energy per nucleon pair √ sNN = 5.02 TeV, with the ALICE detector at the LHC. The ESE technique allows the classification of events, belonging to the same centrality, according to the azimuthal anisotropy of soft particle production in the collision. The reported measurements give the opportunity to investigate the dynamics of charm quarks in the Quark-Gluon Plasma and provide information on their participation in the collective expansion of the medium…
Centrality dependence of high-pT D meson suppression in Pb-Pb collisions at √sNN = 2.76 TeV
2015
The nuclear modification factor, RAA, of the prompt charmed mesons D0 , D+ and D∗+, and their antiparticles, was measured with the ALICE detector in Pb-Pb collisions at a centre-of-mass energy √ sNN = 2.76 TeV in two transverse momentum intervals, 5 < pT < 8 GeV/c and 8 < pT < 16 GeV/c, and in six collision centrality classes. The RAA shows a maximum suppression of a factor of 5–6 in the 10% most central collisions. The suppression and its centrality dependence are compatible within uncertainties with those of charged pions. A comparison with the RAA of non-prompt J/ψ from B meson decays, measured by the CMS Collaboration, hints at a larger suppression of D mesons in the most central collis…
Coherent photoproduction of ρ0 vector mesons in ultra-peripheral Pb-Pb collisions at √sNN = 5.02 TeV
2020
Cross sections for the coherent photoproduction of ρ0 vector mesons in ultra-peripheral Pb-Pb collisions at √sNN = 5.02 TeV are reported. The measurements, which rely on the π+π− decay channel, are presented in three regions of rapidity covering the range |y| < 0.8. For each rapidity interval, cross sections are shown for different nuclear-breakup classes defined according to the presence of neutrons measured in the zero-degree calorimeters. The results are compared with predictions based on different models of nuclear shadowing. Finally, the observation of a coherently produced resonance-like structure with a mass around 1.7 GeV/c2 and a width of about 140 MeV/c2 is reported and compared w…
Examination of the influence of transfer channels on the barrier height distribution: Scattering of 20Ne on 58Ni, 60Ni, and 61Ni at near-barrier ener…
2016
Background: It was suggested that the shape of the barrier height distribution can be determined not only by strong reaction channels (collective excitations) but also by weak channels such as transfers and/or noncollective excitations. Purpose: The study of the barrier height distributions for the 20Ne + 58,60,61Ni systems requires information on transfer cross sections at near-barrier energies. Methods: A measurement of the cross sections for various transfer channels at a backward angle (142 degrees), at a near-barrier energy was performed. Identification of products was based on time-of-flight and E-E methods. A measurement of the angular distribution of α stripping in the 20Ne + 61Ni s…
Anisotropic flow in Xe-Xe collisions at √sNN = 5.44 TeV
2018
The first measurements of anisotropic flow coefficients for vn mid-rapidity charged particles in Xe–Xe collisions at √sNN=5.44 TeV are presented. Comparing these measurements to those from Pb–Pb collisions at √sNN=5.02 TeV, v2 is found to be suppressed for mid-central collisions at the same centrality, and enhanced for central collisions. The values of v3 are generally larger in Xe–Xe than in Pb–Pb at a given centrality. These observations are consistent with expectations from hydrodynamic predictions. When both and are divided by their corresponding eccentricities for a variety of initial state models, they generally scale with transverse density when comparing Xe–Xe and Pb–Pb, with some d…