Search results for "effective Lagrangian"
showing 10 items of 42 documents
R-parity-conserving supersymmetry, neutrino mass, and neutrinoless double beta decay
1997
We consider contributions of R-parity conserving softly broken supersymmetry (SUSY) to neutrinoless double beta ($\znbb$) decay via the (B-L)-violating sneutrino mass term. The latter is a generic ingredient of any weak-scale SUSY model with a Majorana neutrino mass. The new R-parity conserving SUSY contributions to $\znbb$ are realized at the level of box diagrams. We derive the effective Lagrangian describing the SUSY-box mechanism of $\znbb$-decay and the corresponding nuclear matrix elements. The 1-loop sneutrino contribution to the Majorana neutrino mass is also derived. Given the data on the $\znbb$-decay half-life of $^{76}$Ge and the neutrino mass we obtain constraints on the (B-L)-…
Isoscalar Roper(N1440*)excitation in thepp→ppπ0reaction close to threshold
1999
A new mechanism for the $p\stackrel{\ensuremath{\rightarrow}}{p}\mathrm{pp}{\ensuremath{\pi}}^{0}$ reaction close to threshold is suggested coming from the isoscalar excitation of the Roper and its decay into $N(\ensuremath{\pi}\ensuremath{\pi}{)}_{s\ensuremath{-}\mathrm{w}\mathrm{a}\mathrm{v}\mathrm{e}},$ with one of the ${\ensuremath{\pi}}^{0}$ emitted and the other one reabsorbed on the second nucleon. We show that this new mechanism can lead to important interference with other mechanisms suggested so far.
Model independent bounds on the tau lepton electromagnetic and weak magnetic moments
2000
Using LEP1, SLD and LEP2 data, for tau lepton production, and data from CDF, D0 and LEP2, for W decays into tau leptons, we set model independent limits on non-standard electromagnetic and weak magnetic moments of the tau lepton. The most general effective Lagrangian giving rise to tau moments is used without further assumptions. Precise bounds ($2\sigma$) on the non-standard model contributions to tau electromagnetic ($-0.007<a_\gamma< 0.005$), tau Z-magnetic ($-0.0024 <a_Z< 0.0025$) and tau W-magnetic ($-0.003 < \kappa^W < 0.004$) dipole moments are set from the analysis.
Magnetic dipole moment of theΔ+(1232)from theγp→γπ0preaction
2001
The $\ensuremath{\gamma}\stackrel{\ensuremath{\rightarrow}}{p}\ensuremath{\gamma}{\ensuremath{\pi}}^{0}p$ reaction in the $\ensuremath{\Delta}(1232)$-resonance region is investigated as a method to access the ${\ensuremath{\Delta}}^{+}(1232)$ magnetic dipole moment. The calculations are performed within the context of an effective Lagrangian model containing both the $\ensuremath{\Delta}$-resonant mechanism and a background of nonresonant contributions to the $\ensuremath{\gamma}\stackrel{\ensuremath{\rightarrow}}{p}\ensuremath{\gamma}{\ensuremath{\pi}}^{0}p$ reaction. Results are shown both for existing and forthcoming $\ensuremath{\gamma}\stackrel{\ensuremath{\rightarrow}}{p}\ensuremath{\…
An isobar model for eta photo- and electroproduction on the nucleon
2001
Eta photo- and electroproduction on the nucleon is studied using an isobar model. The model contains Born terms, and contributions from vector meson exchanges and nucleon resonances. Our results are compared with recent eta photoproduction data for differential and total cross sections, beam asymmetry, and target asymmetry, as well as electroproduction data. Besides the dominant S11(1535) resonance, we show that the second S11 resonance, S11(1650), is also necessary to be included in order to extract S11(1535) resonance parameters properly. In addition, the beam asymmetry data allow us to extract very small (<0.1%) N* --> eta N decay branching ratios of the D13(1520) and F15(1680) res…
Heavy Resonances in the Electroweak Effective Lagrangian
2015
As a first step towards the construction of a general electroweak effective Lagrangian incorporating heavy states, we present here a simplified version where only vector and axial-vector spin-1 triplets are involved. We adopt an effective field theory formalism, implementing the electroweak chiral symmetry breaking SU(2)L x SU(2)R -> SU(2)L+R, which couples the heavy states to the SM fields. At low energies, the heavy degrees of freedom are integrated out from the action and their effects are hidden in the low-energy couplings of the Electroweak Effective Theory, which can be tested experimentally. Short-distance constraints are also implemented, requiring a proper behaviour in the high-…
Electromagnetism in nonleptonic weak interactions
2000
16 páginas, 1 figura.-- PACS: 11.30.Rd; 13.25.Es; 13.40.Ks.-- arXiv:hep-ph/0006172v2
Strange hadronic physics in electroproduction experiments at the Mainz Microtron
2012
Abstract Present and future research into the electroproduction of strangeness plays an important role at Mainz Microtron MAMI. With the Kaos spectrometer for kaon detection operated in the multi-spectrometer facility first cross section measurements of the exclusive p ( e , e ′ K + ) Λ , Σ 0 reactions at low-momentum transfers have been performed. These measurements have clearly discriminated between effective Lagrangian models for photo- and electroproduction of strangeness. Recently, the Kaos spectrometer was upgraded to a double-arm spectrometer for the measurement of elementary cross sections at very forward scattering angles and for the missing mass spectroscopy of hypernuclear states…
Isospin dependence of the three-nucleon force
2004
We classify $A$--nucleon forces according to their isospin dependence and discuss the most general isospin structure of the three--nucleon force. We derive the leading and subleading isospin--breaking corrections to the three--nucleon force using the framework of chiral effective field theory.
Resonant detection and production of axions with atoms
2018
The axions and axion-like particles can be detected via a resonant atomic or molecular transition induced by axion absorption. The signal obtained in this process is second order in the axion-electron interaction constant and hence small. In this chapter, it is demonstrated that this signal may become first order in the axion-electron interaction constant if we allow the interference between the axion-induced transition amplitude and the transition amplitude induced by the electromagnetic radiation. Additionally, we show that the conventional scheme of producing axions from photons in a magnetic field may be improved if the field is replaced by an atomic medium in which photons scattering …