14,648 research outputs found
Rho Meson Properties in the Chiral Theory Framework
We study the mass, width and couplings of the lightest resonance multiplet
with I(J^{PC})=1(1^{--}) quantum numbers. Effective field theories based on
chiral symmetry are employed in order to describe the form factor associated
with the two-pseudoscalar matrix element of the QCD vector current. The bare
poles of the intermediate resonances are regularized through a
Dyson-Schwinger-like summation. We explore the role of the resonance width in
physical observables and make a coupled-channel analysis of final-state
interactions. This provides many interesting properties, as the pole mass
M_rho{pole}= 764.1 +- 2.7 +4.0-2.5 MeV. At energies E~1 GeV, a second 1(1^{--})
resonance multiplet is considered in order to describe the data in a more
consistent way. From the phenomenologically extracted resonance couplings, we
obtain the chiral coupling L_9^r(mu0)= (7.04 +- 0.05 +0.19-0.27)* 10^{-3}, at
mu0=770$ MeV, and show how the running with the scale mu affects the resonance
parameters. A 1/N_C counting is adopted in this work and the consistency of the
large--N_C expansion is tested. Finally, we make an estimation of the
contribution from diagrams with resonances in crossed channels.Comment: 26 pages, 8 figures, Latex fil
Pseudoscalar pole light-by-light contributions to the muon in Resonance Chiral Theory
We have studied the transition form-factors
() within a chiral invariant framework that allows us to
relate the three form-factors and evaluate the corresponding contributions to
the muon anomalous magnetic moment , through pseudoscalar pole
contributions. We use a chiral invariant Lagrangian to describe the
interactions between the pseudo-Goldstones from the spontaneous chiral symmetry
breaking and the massive meson resonances. We will consider just the lightest
vector and pseudoscalar resonance multiplets. Photon interactions and flavor
breaking effects are accounted for in this covariant framework. This article
studies the most general corrections of order within this setting.
Requiring short-distance constraints fixes most of the parameters entering the
form-factors, consistent with previous determinations. The remaining ones are
obtained from a fit of these form-factors to experimental measurements in the
space-like () region of photon momenta. The combination of data,
chiral symmetry relations between form-factors and high-energy constraints
allows us to determine with improved precision the on-shell -pole
contribution to the Hadronic Light-by-Light scattering of the muon anomalous
magnetic moment: we obtain for
our best fit. This result was obtained excluding BaBar data, which our
analysis finds in conflict with the remaining experimental inputs. This study
also allows us to determine the parameters describing the system
in the two-mixing angle scheme and their correlations. Finally, a preliminary
rough estimate of the impact of loop corrections () and higher vector
multiplets (asym) enlarges the uncertainty up to .Comment: 43 pages, 5 figures. Accepted for publication in JHEP. New subsection
involving error analysis and some minor change
Form-factors and current correlators: chiral couplings L_10(mu) and C_87(mu) at NLO in 1/N(C)
Using the resonance chiral theory Lagrangian, we perform a calculation of the
vector and axial-vector two-point functions at the next-to-leading order (NLO)
in the 1/N(C) expansion. We have analyzed these correlators within the
single-resonance approximation and have also investigated the corrections
induced by a second multiplet of vector and axial-vector resonance states.
Imposing the correct QCD short-distance constraints, one determines the
difference of the two correlators Pi(t) = Pi_VV(t)- Pi_AA(t) in terms of the
pion decay constant and resonance masses. Its low momentum expansion fixes then
the low-energy chiral couplings L_10 and C_87 at NLO, keeping full control of
their renormalization scale dependence. At mu_0=0.77 GeV, we obtain L_10(mu_0)
= (-4.4 \pm 0.9)10^{-3} and C_87^r(mu_0)=(3.1 \pm 1.1)10^{-5}
On-chip quantum tomography of mechanical nano-scale oscillators with guided Rydberg atoms
Nano-mechanical oscillators as well as Rydberg-atomic waveguides hosted on
micro-fabricated chip surfaces hold promise to become pillars of future quantum
technologies. In a hybrid platform with both, we show that beams of Rydberg
atoms in waveguides can quantum-coherently interrogate and manipulate
nanomechanical elements, allowing full quantum state tomography. Central to the
tomography are quantum non-demolition measurements using the Rydberg atoms as
probes. Quantum coherent displacement of the oscillator is also made possible,
by driving the atoms with external fields while they interact with the
oscillator. We numerically demonstrate the feasibility of this fully integrated
on-chip control and read-out suite for quantum nano-mechanics, taking into
account noise and error sources.Comment: 11 pages, 5 figures, 1 tabl
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