Search results for "Amplitude"
showing 10 items of 1169 documents
Active spike responses of analog electrical neuron: Theory and experiments
2010
Using an analog electrical FitzHugh-Nagumo neuron including complex threshold excitation (CTE) properties, we analyze its spiking responses under pulse stimulation corresponding to oscillating threshold manifold. The system is subjected to outside pulse stimulus and can generate nonlinear integrate-and-flre and resonant responses which are typical for excitable neuronal cells ("all-or-none"). The answer of the neuron strongly depends on the number and the characteristics of incoming impulses (amplitude, width, strength and frequency). For certain parameters range, there is a possibility to trigger a spiking sequence with a finite number of spikes in response of a single short stimulus pulse…
Study of thee+e−→K+K−reaction in the energy range from 2.6 to 8.0 GeV
2015
The e^+e^− → K^+K^− cross section and charged-kaon electromagnetic form factor are measured in the e^+e^− center-of-mass energy range (E) from 2.6 to 8.0 GeV using the initial-state radiation technique with an undetected photon. The study is performed using 469 fb^(−1) of data collected with the BABAR detector at the PEP-II2 e^+e^− collider at center-of-mass energies near 10.6 GeV. The form factor is found to decrease with energy faster than 1/E^2 and approaches the asymptotic QCD prediction. Production of the K^+K^− final state through the J/ψ and ψ(2S) intermediate states is observed. The results for the kaon form factor are used together with data from other experiments to perform a mod…
Wide Angle Compton Scattering within the SCET factorization Framework
2016
Existing data for the electromagnetic proton form factors and for the cross section of the wide angle Compton scattering (WACS) show that the hard two-gluon exchange mechanism (collinear factorization) is still not applicable in the kinematical region where Mandelstam variables s ~ −t ~ −u are about few GeV2 . On the other hand these observables can be described in phenomenological models where spectator quarks are soft which assumes a large contribution due to the soft-overlap mechanism. It turns out that the simple QCD factorization picture is not complete and must also include the soft-overlap contribution which can be described as a certain matrix element in the soft collinear effective…
Observation of an Anomalous Line Shape of theη′π+π−Mass Spectrum near thepp¯Mass Threshold inJ/ψ→γη′π+π−
2016
Using 1.09 x 10(9) J/psi events collected by the BESIII experiment in 2012, we study the J / psi -> gamma eta'pi(+)pi(-) process and observe a significant abrupt change in the slope of the eta'pi(+)pi(-) invariant mass distribution at the proton-antiproton (p (p) over bar) mass threshold. We use two models to characterize the eta'pi(+)pi(-) line shape around 1.85 GeV/c(2): one that explicitly incorporates the opening of a decay threshold in the mass spectrum (Flatte formula), and another that is the coherent sum of two resonant amplitudes. Both fits show almost equally good agreement with data, and suggest the existence of either a broad state around 1.85 GeV/c(2) with strong couplings to t…
Odderon Exchange from Elastic Scattering Differences between pp and pp¯ Data at 1.96 TeV and from pp Forward Scattering Measurements
2021
We describe an analysis comparing the p p ¯ elastic cross section as measured by the D0 Collaboration at a center-of-mass energy of 1.96 TeV to that in p p collisions as measured by the TOTEM Collaboration at 2.76, 7, 8, and 13 TeV using a model-independent approach. The TOTEM cross sections, extrapolated to a center-of-mass energy of s = 1.96 TeV , are compared with the D0 measurement in the region of the diffractive minimum and the second maximum of the p p cross section. The two data sets disagree at the 3.4 σ level and thus provide evidence for the t -channel exchange of a colorless, C -odd gluonic compound, also known as the odderon. We combine these results with a TOTEM analysis of th…
Determination of resonance parameters in QCD by functional analysis methods
1988
A mathematically rigorous method based on functional analysis is used to determine resonance parameters of an amplitude from its given asymptotic expression in the space-like region. This method is checked on a model amplitude where both the asymptotic expression and the exact function are known. This method is then applied to the determination of the mass and the width of the ρ-meson from the corresponding space-like asymptotic QCD expression.
Determination of s - and p -wave I = 1/2 Kπ scattering amplitudes in N f = 2 + 1 lattice QCD
2018
Nuclear physics 932, 29 - 51 (2018). doi:10.1016/j.nuclphysb.2018.05.008
Linear Wave Equations and Effective Lagrangians for Wigner Supermultiplets
1995
The relevance of the contracted SU(4) group as a symmetry group of the pion nucleon scattering amplitudes in the large $N_c$ limit of QCD raises the problem on the construction of effective Lagrangians for SU(4) supermultiplets. In the present study we suggest effective Lagrangians for selfconjugate representations of SU(4) in exploiting isomorphism between so(6) and ist universal covering su(4). The model can be viewed as an extension of the linear $\sigma$ model with SO(6) symmetry in place of SO(4) and generalizes the concept of the linear wave equations for particles with arbitrary spin. We show that the vector representation of SU(4) reduces on the SO(4) level to a complexified quatern…
A simple formula for the infrared singular part of the integrand of one-loop QCD amplitudes
2010
We show that a well-known simple formula for the explicit infrared poles of one-loop QCD amplitudes has a corresponding simple counterpart in unintegrated form. The unintegrated formula approximates the integrand of one-loop QCD amplitudes in all soft and collinear singular regions. It thus defines a local counter-term for the infrared singularities and can be used as an ingredient for the numerical calculation of one-loop amplitudes.
Gauge invariance of the deeply virtual Compton scattering amplitude
2000
We analyze in detail the problem of gauge invariance of the deeply virtual Compton scattering (DVCS) amplitude. Using twist-3 one-gluon exchange diagram contributions and the QCD equations of motion, we derive the general gauge invariant expression of the DVCS amplitude on a (pseudo)scalar particle (pion, ${\mathrm{He}}^{4}).$ Similarly to the case of deep inelastic scattering, the amplitude does not depend on the twist-3 quark-gluon correlations at the Born level. The contribution of the derived amplitude to the single-spin asymmetry with longitudinally polarized lepton is calculated.