Search results for "yield"
showing 10 items of 1338 documents
Zeptosecond contact times for element Z=120 synthesis
2020
The synthesis of new superheavy elements beyond oganesson (Z=118) requires fusion reactions with projectile nuclei with proton numbers larger than that of $^{48}$Ca (Z=20), which has been successfully employed for the synthesis of elements with Z=112-118. In such reactions, fusion is drastically hindered by fast non-equilibrated dynamical processes. Attempts to produce nuclei with Z=120 using the $^{64}$Ni+$^{238}$U, $^{58}$Fe+$^{244}$Pu, $^{54}$Cr+$^{248}$Cm, and $^{50}$Ti+$^{249}$Cf reactions have been made, which all result in larger Coulomb forces than for $^{48}$Ca-induced reactions, but no discovery has been confirmed to date. In this work, mass and angle distributions of fission frag…
Miss Piggy, a californium-252 fission fragment source as a generator of short-lived radionuclides
2003
Abstract Carrier-free short-lived nuclides are employed in many different fields of modern nuclear chemistry. The two main production strategies are either thermal neutron-induced fission of 235U or 239Pu at nuclear reactors or spallation neutron sources or charged particle-induced nuclear reactions at accelerator facilities. An alternative method is to use a spontaneously fissioning nuclide. A facility applying this technique (“Miss Piggy”) was built at the University of Berne (Switzerland). Californium-252 (252Cf), which has a 3% fission branch and a half-life of 2.645 a, is used for the production of short-lived fission products that are stopped in an adjacent recoil chamber. Short-lived…
Cross section forbb¯production via dielectrons ind+ Au collisions atsNN=200GeV
2015
We report a measurement of e+e− pairs from semileptonic heavy-flavor decays in d+Au collisions at sNN−−−√=200 GeV. By exploring the mass and transverse-momentum dependence of the yield, the bottom decay contribution can be isolated from charm, and quantified by comparison to pythia and mc@nlo simulations. The resulting bb¯-production cross section is σdAubb¯=1.37±0.28(stat)±0.46(syst) mb, which is equivalent to a nucleon-nucleon cross section of σNNbb=3.4±0.8(stat)±1.1(syst)μb.
The12C(γ,NN)reaction studied over a wide kinematic range
2000
The ${}^{12}\mathrm{C}(\ensuremath{\gamma},np)$ and ${}^{12}\mathrm{C}(\ensuremath{\gamma},pp)$ reactions have been studied using the Glasgow photon tagging spectrometer at the Mainz MAMI electron microtron for ${E}_{\ensuremath{\gamma}}=150--700$ MeV over a kinematic range which extends well beyond the approximately back-to-back detector arrangements of previous work. For ${}^{12}\mathrm{C}(\ensuremath{\gamma},np)$ the general trends of the missing energy distributions are reproduced over a wide range of kinematics and photon energies by the theory developed by the Valencia group. The corresponding ${}^{12}\mathrm{C}(\ensuremath{\gamma},pp)$ channel is overestimated by a factor of \ensurem…
Estimation of bounds for left-right mixing from nuclear double beta decay processes
1993
Abstract Nuclear matrix elements, extracted from a systematic calculation of neutrinoless double beta decay rates for 0 + g.s →o + g.s transitions in 76 Ge, 82 Se, 128 Te, 130 Te and 136 Xe, have been used to compute bounds on the left-right mixing angle ζ of the weak currents. The parameters of the nuclear model have been fixed by calculating the corresponding two-neutrino double beta decay half lives. The present analysis favours a mixing of the order of |tanξ| −3 which is to be compared with those obtained in muon decay (|tan ξ | ⩽ 0.035) and in supernova (|tan ξ | ⩽ 10 −5 ) analysis. It shows that nuclear structure calculations yield estimates on ξ which complement the existing data.
Independent Fission Yield Measurements
1986
Various methods to measure independent yields are reviewed and discussed. A survey on actual measurements carried out after 1978 is given.
Manifestations of Clustering in Fission of Excited Actinides
2003
A new, graphical way of extracting important physical information from the total kinetic-energy—mass (TKE—M) distributions of the nuclear reaction products is presented. The resulting images indicate for the first time the presence of the Ni—Mo and Ge—Mo fission modes in the fission of Np nuclei at intermediate excitation energies.
EPPS16 : Bringing nuclear PDFs to the LHC era
2018
We report on EPPS16, the first global analysis of nuclear parton distribution functions (nPDFs) to include LHC data. Also for the first time, a full flavour dependence of nPDFs is allowed. While the included Z and W data are found to have insufficient statistics to yield stringent constraints, the CMS 5.02 TeV proton-lead dijet data prove crucial in setting the shape of nuclear gluon modifications. With these and other observables being measured in proton-lead runs, we are experiencing a shift of nPDFs to the LHC precision era.
J/ψSuppression at Forward Rapidity in Pb-Pb Collisions atsNN=2.76 TeV
2012
The ALICE experiment has measured the inclusive J/psi production in Pb-Pb collisions at root s(NN) = 2.76 TeV down to zero transverse momentum in the rapidity range 2.5 < y < 4. A suppression of the inclusive J/psi yield in Pb-Pb is observed with respect to the one measured in pp collisions scaled by the number of binary nucleon-nucleon collisions. The nuclear modification factor, integrated over the 0%-80% most central collisions, is 0.545 +/- 0.032(stat) +/- 0.083dsyst_ and does not exhibit a significant dependence on the collision centrality. These features appear significantly different from measurements at lower collision energies. Models including J/psi production from charm quarks in…
Microscopic carrier dynamics in quantum wells modulated by high-frequency lateral fields
2002
Abstract We have investigated the dynamics of photogenerated carriers in GaAs quantum wells under the influence of high-frequency fields produced by metal gratings and by surface acoustic waves (SAW's) using spatially and time-resolved photoluminescence (PL). The frequency and phase of the PL oscillations induced by the high-frequency field yield information about the spatial distribution of the carriers and, in the case of SAW's, about the band-gap modulation induced by the SAW strain.