Search results for "SCALAR"
showing 10 items of 1002 documents
Scalar ΛN and ΛΛ interactions within a chiral unitary approach
2008
We study the central part of the ΛN potential by considering the correlated and uncorrelated two-meson exchange besides the ω exchange contribution. The correlated two-meson is evaluated in a chiral unitary approach. We find that a short range repulsion is generated by the correlated two-meson potential which also produces an attraction in the intermediate distance region. The uncorrelated two-meson exchange produces a sizable attraction in all cases which is counterbalanced by ω exchange contribution.
Measurement of K-e3(0) form factors
2004
The semi-leptonic decay of the neutral K meson $K^{0}_{L} \to \pi^{\pm}e^{\mp}\nu (K_{e3})$, was used to study the strangeness-changing weak interaction of hadrons. A sample of 5.6 million reconstructed events recorded by the NA48 experiment was used to measure the Dalitz plot density. Admitting all possible Lorentz-covariant couplings, the form factors for vector $(f_{+}(q^{2}))$, scalar $(f_{S})$ and tensor $(f_{T})$ interactions were measured. The linear slope of the vector form factor $\lambda_{+} = 0.0284 \pm 0.0007 \pm 0.0013$ and values for the ratios $|f_{S}/f_{+}(0)|=0.015^{+0.007}_{-0.010} \pm 0.012$ and $|f_{T}/f_{+}(0)|=0.05^{+0.03}_{-0.04} \pm 0.03$ were obtained. The values fo…
Nuclear matrix elements for0νββdecays with light or heavy Majorana-neutrino exchange
2015
We compute the nuclear matrix elements (NMEs) corresponding to the neutrinoless double beta ($0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$) decays of nuclei which attract current experimental interest. We concentrate on ground-state-to-ground-state decay transitions mediated by light (l-NMEs) or heavy (h-NMEs) Majorana neutrinos. The computations are done in realistic single-particle model spaces using the proton-neutron quasiparticle random-phase approximation (pnQRPA) with two-nucleon interactions based on the Bonn one-boson-exchange $G$ matrix. Both the l-NMEs and the h-NMEs include the appropriate short-range correlations, nucleon form factors, and higher-order nucleonic weak …
R-summed form of adiabatic expansions in curved spacetime
2020
The Feynman propagator in curved spacetime admits an asymptotic (Schwinger-DeWitt) series expansion in derivatives of the metric. Remarkably, all terms in the series containing the Ricci scalar R can be summed exactly. We show that this (non-perturbative) property of the Schwinger-DeWitt series has a natural and equivalent counterpart in the adiabatic (Parker-Fulling) series expansion of the scalar modes in an homogeneous cosmological spacetime. The equivalence between both R-summed adiabatic expansions can be further extended when a background scalar field is also present.
Impact of neutrino properties on the estimation of inflationary parameters from current and future observations
2016
We study the impact of assumptions about neutrino properties on the estimation of inflationary parameters from cosmological data, with a specific focus on the allowed contours in the $n_s/r$ plane. We study the following neutrino properties: (i) the total neutrino mass $ M_\nu =\sum_i m_i$; (ii) the number of relativistic degrees of freedom $N_{eff}$; and (iii) the neutrino hierarchy: whereas previous literature assumed 3 degenerate neutrino masses or two massless neutrino species (that do not match neutrino oscillation data), we study the cases of normal and inverted hierarchy. Our basic result is that these three neutrino properties induce $< 1 \sigma$ shift of the probability contours in…
Correlations between Rabi oscillations and atomic translational dynamics
1998
We analyze some aspects of the internal and translational dynamics of a two-level atom interacting with a resonant standing wave of an ideal cavity. We show that the cavity vacuum field can split the incoming wave packet of the excited two-level atom into two parts, whose scalar product in the Hilbert space determines the behavior of the Rabi oscillations. The state of the whole system is derived and allows us to study the correlations between the internal and the translational atomic dynamics. We find that these correlations become negligible when the two parts are sufficiently away from each other in the space.
On the ambiguities of sign determination of the S-matrix from energy levels in a finite box
2013
In a recent paper the authors make a study on the determination of the S-matrix elements for scattering of particles in the infinite volume from the energy levels in a finite box for the case of multiple channels. The study is done with a toy model in 1+1 dimension and the authors find that there is some ambiguity in the sign of nondiagonal matrix elements, casting doubts on whether the needed observables in the infinite volume can be obtained from the energy levels of the box. In this paper I present an easy derivation, confirming the ambiguity of the sign and argue that this, however, does not put restrictions in the determination of observables.
Unraveling the nature of universal dynamics in $O(N)$ theories
2020
Many-body quantum systems far from equilibrium can exhibit universal scaling dynamics which defy standard classification schemes. Here, we disentangle the dominant excitations in the universal dynamics of highly-occupied $N$-component scalar systems using unequal-time correlators. While previous equal-time studies have conjectured the infrared properties to be universal for all $N$, we clearly identify for the first time two fundamentally different phenomena relevant at different $N$. We find all $N\geq3$ to be indeed dominated by the same Lorentzian ``large-$N$'' peak, whereas $N=1$ is characterized instead by a non-Lorentzian peak with different properties, and for $N=2$ we see a mixture …
Systematic derivation of hydrodynamic equations for viscoelastic phase separation
2021
(abridged) We present a detailed derivation of a simple hydrodynamic two-fluid model, which aims at the description of the phase separation of non-entangled polymer solutions, where viscoelastic effects play a role. It is directly based upon the coarse-graining of a well-defined molecular model, such that all degrees of freedom have a clear and unambiguous molecular interpretation. The considerations are based upon a free-energy functional, and the dynamics is split into a conservative and a dissipative part, where the latter satisfies the Onsager relations and the Second Law of thermodynamics. The model is therefore fully consistent with both equilibrium and non-equilibrium thermodynamics.…
A high statistics lattice calculation of the B-meson binding energy
1996
We present a high statistics lattice calculation of the B--meson binding energy $\overline{\Lambda}$ of the heavy--quark inside the pseudoscalar B--meson. Our numerical results have been obtained from several independent numerical simulations at $\beta=6.0$, $6.2$ and $6.4$, and using, for the meson correlators, the results obtained by the APE group at the same values of $\beta$. Our best estimate, obtained by combining results at different values of $\beta$, is $\overline{\Lambda}=180^{+30}_{-20}$ MeV. For the $\overline{MS}$ running mass, we obtain $\overline{m}_{b}(\overline{m}_{b})=4.15 \pm 0.05 \pm 0.20$ GeV, in reasonable agreement with previous determinations. The systematic error is…