Search results for "Coupling"
showing 10 items of 1862 documents
Evidence for prolate structure in light Pb isotopes from in-beamγ-ray spectroscopy ofPb185
2009
For the first time, excited states in {sup 185}Pb have been observed in in-beam {gamma}-ray spectroscopic measurements using the recoil-decay tagging method. The resulting level scheme reveals a strongly coupled yrast band structure that originates from coupling of the i{sub 13/2} quasineutron to a prolate deformed core. The band is also observed to de-excite via the spherical {alpha}-decaying 13/2{sup +}isomeric state.
Constraints on anomalous QGC's in $e^{+}e^{-}$ interactions from 183 to 209 GeV
2004
The acoplanar photon pairs produced in the reaction e+ e- --> nu nubar gamma gamma are analysed in the 700 inverse nanobarns of data collected by the ALEPH detector at centre-of-mass energies between 183 and 209 GeV. No deviation from the Standard Model predictions is seen in any of the distributions examined. The resulting 95% C.L. limits set on the anomalous QGC's, az_0, az_c, aw_0 and aw_c, are -0.012 GeV**-2 < az_0/Lambda**2 < +0.019 GeV**-2, -0.041 GeV**-2 < az_c/Lambda**2 < +0.044 GeV**-2, -0.060 GeV**-2 < aw_0/Lambda**2 < +0.055 GeV**-2, -0.099 GeV**-2 < aw_c/Lambda**2 < +0.093 GeV**-2, where Lambda is the energy scale of the new Physics responsible for the anomalous couplings.
Nonperturbative effective model for the Higgs sector of the standard model
2010
A nonperturbative effective model is derived for the Higgs sector of the Standard Model which is described by a simple scalar theory. The renormalized couplings are determined by the derivatives of the Gaussian effective potential that are known to be the sum of infinite bubble graphs contributing to the vertex functions. A good agreement has been found with strong coupling lattice simulations when a comparison can be made.
Triangle mechanism in τ → f1(1285)πντ decay
2018
Abstract We show that the τ − decay into f 1 ( 1285 ) π − ν τ is dominated by a triangle loop mechanism with K ⁎ , K ¯ ⁎ and K (or K ¯ ) as internal lines, which manifests a strong enhancement reminiscent of a nearby singularity present in the narrow K ⁎ limit and the near K ¯ ⁎ K ⁎ threshold of the internal K ⁎ propagators. The f 1 ( 1285 ) is then produced by its coupling to the K ⁎ K ¯ and K ¯ ⁎ K which is obtained from a previous model where this resonance was dynamically generated as a molecular K ⁎ K ¯ (or K ¯ ⁎ K ) state using the techniques of the chiral unitary approach. We make predictions for the f 1 π mass distribution which significantly deviates from the phase-space shape, due…
The role of f0(1710) in the ϕω threshold peak of J/Ψ→γϕω
2013
Abstract We study the process J / Ψ → γ ϕ ω , measured by the BES experiment, where a neat peak close to the ϕω threshold is observed and is associated to a scalar meson resonance around 1800 MeV. We make the observation that a scalar resonance coupling to ϕω unavoidably couples strongly to K K ¯ , but no trace of a peak is seen in the K K ¯ spectrum of the J / Ψ → γ K K ¯ at this energy. This serves us to rule out the interpretation of the observed peak as a signal of a new resonance. After this is done, a thorough study is performed on the production of a pair of vector mesons and how its interaction leads necessarily to a peak in the J / Ψ → γ ϕ ω reaction close to the ϕω threshold, due …
Temperatures and chemical potentials at kinetic freeze-out in relativistic heavy ion collisions from coarse grained transport simulations
2019
Using the UrQMD/coarse graining approach we explore the kinetic freeze-out stage in central Au + Au collisions at various energies. These studies allow us to obtain detailed information on the thermodynamic properties (e.g. temperature and chemical potential) of the system during the kinetic decoupling stage. We explore five relevant collision energies in detail, ranging from $\sqrt{s_{NN}}=2.4\,\mathrm{GeV}$ (GSI-SIS) to $\sqrt{s_{NN}}=200\,\mathrm{GeV}$ (RHIC). By adopting a standard Hadron Resonance Gas equation of state, we determine the average temperature $\langle T \rangle$ and the average baryon chemical potential $\langle\mu_{\mathrm{B}}\rangle$ on the space-time hyper-surface of l…
Second-forbidden nonunique $$\beta ^-$$ decays of $$^{59,60}$$Fe:possible candidates for $$g_{\mathrm{A}}$$ sensitive electron spectral-shape measure…
2021
In this work, we present a theoretical study of the electron spectral shapes for the second-forbidden nonunique $\beta^-$-decay transitions $^{59}\textrm{Fe}(3/2^-)\to\,^{59}\textrm{Co}(7/2^-)$ and $^{60}\textrm{Fe}(0^+)\to\,^{60}\textrm{Co}(2^+)$ in the framework of the nuclear shell model. We have computed the involved wave functions by carrying out a complete $0\hbar\omega$ calculation in the full $fp$ model space using the KB3G and GXPF1A effective interactions. When compared with the available data, these interactions predict the low-energy spectra and electromagnetic properties of the involved nuclei quite successfully. This success paves the way for the computations of the $\beta$-de…
From quark-gluon plasma to hadron spectra
2001
Results on initial transverse energy production based on NLO perturbative QCD calculation with final state saturation of produced minijets are used to fix the initial energy density of produced matter. Assuming rapid thermalization, this provides the initial conditions for a hydrodynamic description of the expansion of final matter. Given a prescription of the the decoupling of particles from the thermal system to free particles, final transverse spectra of hadrons and integrated quantities like multiplicity and transverse energy can be calculated in the central rapidity region. Results are reported and compared with measurements.
Charged current weak production of the Delta resonance
1999
The charge changing weak production of Delta in nucleons and nuclei is studied. The reactions e^{-} p -> Delta^{0} ��_{e} and e^{+} p -> Delta^{++} \bar��_{e} are considered as a possible source of information about the weak N-Delta transition form factors. The low q^2 BNL data on neutrino production of Delta are used to extract the axial vector N-Delta coupling, taking into account the deuteron structure and the Delta width. Finally, pion production induced by neutrinos in ^{16}O in the Delta region, relevant to atmospheric neutrino experiments, is investigated.
NUCLEAR EFFECTS IN NEUTRINO INDUCED REACTIONS
2008
We discuss the relevance of nuclear medium effects in the analysis of some low and medium energy neutrino reactions of current interest. In particular, we study the Quasi-Elastic (QE) process, where RPA correlations and Final State Interactions (FSI) are shown to play a crucial role. We have also investigated the neutrino induced coherent pion production. We find a strong reduction of the cross section due to the distortion of the pion wave function and the modification of the production mechanisms in the nucleus. The sensitivity of the results to the axial $N\Delta$ coupling $C_5^A(0)$ has been also investigated.