Search results for "quantum field"
showing 10 items of 492 documents
Progress in three-particle scattering from LQCD
2017
We present the status of our formalism for extracting three-particle scattering observables from lattice QCD (LQCD). The method relies on relating the discrete finite-volume spectrum of a quantum field theory with its scattering amplitudes. As the finite-volume spectrum can be directly determined in LQCD, this provides a method for determining scattering observables, and associated resonance properties, from the underlying theory. In a pair of papers published over the last two years, two of us have extended this approach to apply to relativistic three-particle scattering states. In this talk we summarize recent progress in checking and further extending this result. We describe an extensio…
Correlations between a Hawking particle and its partner in a 1+1D Bose-Einstein condensate analog black hole
2020
The Fourier transform of the density-density correlation function in a Bose-Einstein condensate (BEC) analog black hole is a useful tool to investigate correlations between the Hawking particles and their partners. It can be expressed in terms of $⟨{^{\mathrm{out}}\stackrel{^}{a}}_{\mathrm{up}}^{\mathrm{ext}}\text{ }\text{ }{^{\mathrm{out}}\stackrel{^}{a}}_{\mathrm{up}}^{\mathrm{int}}⟩$, where ${^{\mathrm{out}}\stackrel{^}{a}}_{\mathrm{up}}^{\mathrm{ext}}$ is the annihilation operator for the Hawking particle and ${^{\mathrm{out}}\stackrel{^}{a}}_{\mathrm{up}}^{\mathrm{int}}$ is the corresponding one for the partner. This basic quantity is calculated for three different models for the BEC f…
A measurement of |Vcb| from
1995
Abstract From approximately 3 million hadronic decays of Z bosons recorded with the aleph detector at lep , a sample of 410 ± 32 B 0 → D ∗+ l − ν l candidates is selected, where l is either an electron or a muon. The differential decay rate dΓ ( B 0 → D ∗+ l − ν l ) dω from this sample is fitted, yielding a value for the product of the CKM matrix element |Vcb| and the normalisation of the decay form factor at the point of zero recoil of the D∗+ meson F (ω = 1)|Vcb| = (31.4 ± 2.3stat ± 2.5syst) × 10−3. A value for |Vcb| is extracted using theoretical calculations of the form factor normalisation, with the result |Vcb| = (34.5 ± 2.5stat ± 2.7syst ± 1.5theory) × 10−3. From the integrated s the…
Updated determination of chiral couplings and vacuum condensates from hadronic tau decay data
2016
We analyze the lowest spectral moments of the left-right two-point correlation function, using all known short-distance constraints and the recently updated ALEPH V-A spectral function from tau decays. This information is used to determine the low-energy couplings L10 and C87 of chiral perturbation theory and the lowest-dimensional contributions to the Operator Product Expansion of the left-right correlator. A detailed statistical analysis is implemented to assess the theoretical uncertainties, including violations of quark-hadron duality.
Classical form factor for nlm→n′l′m transitions in the hydrogen atom
2000
Abstract The form factor for nlm → n ′ l ′ m transitions in the hydrogen atom is deduced on the basis of kinematics of the classical mechanics. The consistency of this approach is verified by derivation of the known result for the transition probability averaged over m . The classical transition probability as a function of the final state energy and angular momentum is investigated comprehensively in the case of l = m =0.
Line shape and D(*)D¯(*) probabilities of ψ(3770) from the e+e−→DD¯ reaction
2019
We have performed a calculation of the DD¯, DD¯*, D*D¯, D*D¯* components in the wave function of the ψ(3770). For this we make use of the P03 model to find the coupling of ψ(3770) to these components, that with an elaborate angular momentum algebra can be obtained with only one parameter. Then we use data for the e+e-→DD¯ reaction, from where we determine a form factor needed in the theoretical framework, as well as other parameters needed to evaluate the meson-meson self-energy of the ψ(3770). Once this is done we determine the Z probability to still have a vector core and the probability to have the different meson components. We find Z about 80%–85%, and the individual meson-meson compon…
Reply to "Comment on 'Insensitivity of Hawking radiation to an invariant Planck-scale cutoff' "
2010
We clarify the relationship between the conclusions of the previous Comment of A. Helfer and that of our Brief Report.
Baryon Properties with Three-Quark Forces
1987
The Constituent Quark Model (CQM) is very useful for the description of many baryon properties, leading to a fair agreement with the experimental data, especially in the case of the baryon spectrum 1) and of the electromagnetic processes involving baryons2,3). The model is based on a non relativistic QCD-inspired dynamics, which includes a confinement potential and a spin-dependent short-range part, the so called hyperfine interaction4,1). The confinement potential contains as its major part a harmonic oscillator (h.o.) interaction, which has however a too degenerate spectrum with respect to the experimental one and leads to an unreasonable damping of the form factors even at moderate momen…
Analytical and numerical analysis of the atom–field dynamics in non-stationary cavity QED
2011
We study analytically and numerically the dynamics of the quantum non-stationary system composed of a two-level atom interacting with a single mode cavity field whose frequency is rapidly modulated in time (with a small amplitude). We identify modulation laws resulting in qualitatively different dynamical regimes and we present analytical solutions in some simple cases. In particular, we analyse minutely the influence of the field–atom coupling on the photon generation from vacuum via the dynamical Casimir effect.
η−η′(−glue) Mixing from the Chiral Lagrangian
2010
The η − η ′ mixing from the chiral Lagrangian is reviewed. It is shown how the Feldman-Kroll-Stech ansazt can be derived from the chiral Lagrangian. The inclusion of the glueball is also discussed.