Search results for "Observable"
showing 10 items of 634 documents
Decay modes of sigma and lambda hypernuclei
1990
Abstract A review is presented of the problem of Σ and Λ decay in nuclei. By means of handy, yet reliable approximations, an approach to Σ decay is developed which allows a clear insight into the different aspects of the problem. The role of nuclear polarization, due to the spin-isospin ΣN → ΛN interaction, in the reduction of the Σ widths is discussed. Many experimentally observable Σ hypernuclei are predicted by showing that their widths are narrower than the separation energies between levels. The mesonic and non-mesonic decays of Λ hypernuclei are analyzed. The non-mesonic width is fairly well reproduced by simplified models for the ΛN → NN weak transition, but quantities like the ratio…
Dispersion theoretical analysis of the nucleon spin polarizabilities
1999
The spin polarizabilities of the nucleon have been calculated from pion photoproduction data using forward dispersion relations. The feasibility of an experimental determination of these structure constants is discussed by focusing on polarization observables of the reaction \( \vec{\gamma }\vec{p} \to \gamma p \)→ γ p.
The W and Z boson spin observables as messengers of New Physics at LHC
2017
The successful LHC operation suggests going beyond the search of excess of events for the quest of new physics. We demonstrate that the eight multipole parameters describing the spin state of the W or Z bosons are able to disentangle their hidden production mechanism. They can be separately extracted from well defined angular asymmetries in the leptonic distribution of boson decays. The discriminating power of this analysis is well illustrated by: (i) polarised top quark decays, (ii) two body decay of heavy resonances, (iii) Drell-Yan production of Z plus jets, (iv) Z boson plus missing transverse energy.
Recent results from the MAID and Dubna-Mainz-Taipei PWA analysis
2008
The unitary isobar model MAID2007 has been developed to analyze the world data of pion photo- and electroproduction. The model contains both a common background and several resonance terms. The background is unitarized according to the K-matrix prescription, and the 13 four-star resonances with masses below 2 GeV are described by appropriately unitarized Breit-Wigner forms. The data have been analyzed by both single-energy and global fits, and the transverse and longitudinal helicity amplitudes have been extracted for the four-star resonances below 2 GeV. Because of its inherent simplicity, MAID2007 is well adopted for predictions and analysis of the observables in pion photo- and electropr…
Implications of parity violation in atoms for gauge theories
1977
The knowledge to be gained on neutral currents from parity-violating observables in heavy atoms is studied. After isolating the relevant couplings, the major part of the analysis is done within the framework ofSU 2 ⊗U 1 unified gauge theories of weak and electromagnetic interactions. The leptonic and hadronic sectors of these models are studied separately, by means of the available information from neutrino physics, to impose restrictions on the mass of the neutral intermediate boson and on the unification angle. The observable in atoms, which provides a link between the two sectors, is found to be powerful in discriminating among models.
The Demise of Flavour Tagging and its Delta-T Dependence
2007
In this work we discuss how the loss of particle-antiparticle identity due to CPT violation affects the observables in the decay of two neutral EPR-correlated $B$-mesons. We study this possible new effect in the context of equal-sign flavour specific decays and we find a considerable modification in the $\Delta t$-dependence of the equal-sign dilepton charge asymmetry, $A_{sl}$. Although the more important changes occur right outside the $\Dt$ region that has been up-to-the-date effectively explored, we show that a deeper experimental research may be able to distinguish a possible existence of this new CPT violating parameter, $\w$. In any case, using the available data for $A_{sl}$, we put…
General formulae for polarization observables in two-body break-up of deuteron photodisintegration
1988
The formal expressions of all possible polarization observables ind(γ,N)N with polarized photons and oriented deuterons are derived in terms of thet-matrix elements. Furthermore, using the multipole expansion of thet-matrix, all observables are expanded in terms of Legendre polynomials or associated functions, the coefficients of which are given as bilinear forms of the multipole moments and allow a model independent analysis of experimental data.
Probing fast oscillating scalar dark matter with atoms and molecules
2021
Light scalar Dark Matter with scalar couplings to matter is expected within several scenarios to induce variations in the fundamental constants of nature. Such variations can be searched for, among other ways, via atomic spectroscopy. Sensitive atomic observables arise primarily due to possible changes in the fine-structure constant or the electron mass. Most of the searches to date have focused on slow variations of the constants (i.e. modulation frequencies $<$ 1 Hz). In a recent experiment \mbox{[Phys. Rev. Lett. 123, 141102 (2019)]} called WReSL (Weekend Relaxion-Search Laboratory), we reported on a direct search for rapid variations in the radio-frequency band. Such a search is particu…
Nucleon structure observables with PANDA
2017
The PANDA detector will be built as a part of the future FAIR facility in Darmstadt. The availability of an antiproton beam with beam momenta up to 15 GeV/c will make possible a broad nuclear physics program. Topics like hadron spectroscopy in the charmonium mass region, the property of hadrons inside nuclear matter, hypernuclear physics, or nucleon properties using electromagnetic processes are part of the physics program of PANDA. The main part of this contribution concentrates on the feasibility of measurement of nucleon structure observables, such as electromagnetic form factors or transition distribution amplitudes, via experiments using electromagnetic processes in PANDA.
Electronic momentum distribution in the one-dimensional extended Hubbard model: determinantal Monte Carlo study
2002
Abstract The effect of electron–electron (e–e) interaction on trans -polyacetylene ( t -PA) properties is investigated within the framework of an extended Hubbard model in one dimension. For numerical calculation, we use the determinantal version of quantum Monte Carlo approach, which provides a breakthrough to simulate statistical fluctuations in the systems with many degrees of freedom, in order to obtain mean values for observables of physical interest. This allows one to analyze the discrete system of fermions without encountering the numerical instabilities that generally occur from the original problem involving anticommuting fermion operators. We calculate the electronic momentum dis…