Search results for "elementary"
showing 10 items of 863 documents
Deuteron electrodisintegration near threshold with the Bonn potential
1987
Deuteron electrodisintegration near threshold is calculated for the Bonn potential including consistent meson exchange currents. Experimental data can fairly well be described over the whole q-range if GE is used as electromagnetic form factor for the exchange current, whereas F1 leads to a large overestimation at high q.
The probability of prompt and delayed fission of muonic237Np
1991
Fission fragments from the reaction237Np(μ−,γ,f) have been measured in coincidence with muonic X-rays. The efficiency of the fission fragment detector is determined from (μ−,γ,f)-data of the same experiment. The total fission probability perμ-stopPt has been measured as well as the fission probabilities Pf of the non-radiative muonic (3d→1s)- and (2p→1s)-transitions; the latter has been divided into two parts leading to different mean excitation energiesE:P t =(54±17)%,P f (3d→1s)=(41±21)%,P f (2p→1s,E=6.218 MeV)=(61±19)%, andP f (2p→1s,E=6.525 MeV)=(57±18)%. The influence of the muon on the fission barrier is discussed. The fission probability after muon capture is compared with a calculat…
Higher nucleon resonances in exclusive(γ,πN)reactions on nuclei
1998
We report calculations for exclusive pion photoproduction on nuclei beyond the first resonance region in the distorted wave impulse approximation. The elementary operator contains contributions from the resonances $P_{33}(1232)$, $P_{11}(1440)$, $D_{13}(1520)$, $D_{33}(1740)$, $S_{11}(1535)$, $S_{11}(1650)$, and $F_{15}(1680)$, in addition to the usual Born plus vector meson contributions. It gives a good description of single pion photoproduction data up to about 1.1 GeV. Final state interactions are incorporated via optical potentials and are found to be substantial in the coincidence cross sections, but insensitive to the photon asymmetry. Clear signatures of possible medium modification…
Search for superheavy elements in damped collisions betweenU238andCm248
1986
Negative results for the production of superheavy elements in damped collisions between $^{238}\mathrm{U}$ projectiles and $^{248}\mathrm{Cm}$ targets are reported. This reaction was believed to permit a closer and more widespread approach to the predicted island of stability near Z=114 and N=184 than any practical fusion reaction. Aqueous and gas phase chemistry techniques were used to isolate superheavy element fractions. The fractions were counted for spontaneous fission activity, fragment kinetic energies, and neutron multiplicities. Cross-section limits for half-lives from hours to several years are g4\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}35}$ ${\mathrm{cm}}^{…
Search for quarks in proton-proton interactions at √s = 52.5 GeV
1978
The results of an experiment to search for quarks in pp collisions, at a total centre-of-mass energy √s = 52.5 GeV, are reported. The experiment was sensitive to fractionally charged particles with 0.035e ⩽ |Q| ⩽ 0.67e,β =v/c ⩾ 0.1, and masses up to 21 GeV/c2. The 90% confidence level on the ratio «quark flux/charged-particle flux» is 5.11 · 10−11 for |Q| = 1/3e. This value holds true for particles produced with a mean transverse momentum of 0.4 GeV/c.
Resonant enhancement of neutrinoless double-electron capture in 152Gd.
2010
In the search for the nuclide with the largest probability for neutrinoless double-electron capture, we have determined the ${Q}_{ϵϵ}$ value between the ground states of $^{152}\mathrm{Gd}$ and $^{152}\mathrm{Sm}$ by Penning-trap mass-ratio measurements. The new ${Q}_{ϵϵ}$ value of 55.70(18) keV results in a half-life of ${10}^{26}\text{ }\text{ }\mathrm{yr}$ for a 1 eV neutrino mass. With this smallest half-life among known $0\ensuremath{\nu}ϵϵ$ transitions, $^{152}\mathrm{Gd}$ is a promising candidate for the search for neutrinoless double-electron capture.
Elliptic and Hexadecapole Flow of Charged Hadrons inAu+AuCollisions atsNN=200 GeV
2010
Differential measurements of the elliptic (upsilon(2)) and hexadecapole (upsilon(4)) Fourier flow coefficients are reported for charged hadrons as a function of transverse momentum (p(T)) and collision centrality or number of participant nucleons (N-part) for Au + Au collisions at root s(NN) = 200 GeV/ The upsilon(2,4) measurements at pseudorapidity vertical bar eta vertical bar <= 0.35, obtained with four separate reaction-plane detectors positioned in the range 1.0 < vertical bar eta vertical bar < 3.9, show good agreement, indicating the absence of significant Delta eta-dependent nonflow correlations. Sizable values for upsilon(4)(p(T)) are observed with a ratio upsilon(4)(p(T), N-part)/…
Migration of Nuclear Shell Gaps Studied in thed(Ne24,pγ)Ne25Reaction
2010
The transfer of neutrons onto 24Ne has been measured using a reaccelerated radioactive beam of 24Ne to study the (d,p) reaction in inverse kinematics. The unusual raising of the first 3/2+ level in 25Ne and its significance in terms of the migration of the neutron magic number from N=20 to N=16 is put on a firm footing by confirmation of this state's identity. The raised 3/2+ level is observed simultaneously with the intruder negative parity 7/2- and 3/2- levels, providing evidence for the reduction in the N=20 gap. The coincident gamma-ray decays allowed the assignment of spins as well as the transferred orbital angular momentum. The excitation energy of the 3/2+ state shows that the estab…
Interpretation of the High-Energy ProcessesO16(γ,p0)N15andO16(γ,n0)O15
1978
Calculations based on a two-nucleon ($n\ensuremath{-}p$) absorption mechanism show that the form factor of the residual nucleus plays an important role in determining the shape of the photoproduction cross section in a wide energy range $60 \mathrm{MeV}l~{E}_{\ensuremath{\gamma}}l~300 \mathrm{MeV}$.
Proton distortion effects and meson exchange current contributions in the (e,e′p) reaction
1988
It is demonstrated that proton distortion effects could explain the relative enhancement of transverse to longitudinal response in the recent ($e,{e}^{\ensuremath{'}}p$) reactions on $^{12}\mathrm{C}$. The spin-orbit field is essential to bring about this enhancement. The role of the convection current is pointed out. Favorable contributions from pion-pair and isobar-excitation currents are also found.