31,840 research outputs found

### Analysis of the antineutrino capture on protons

Corrections to the zeroth-approximation cross-section formula for antineutrino capture on protons at nuclear reactors are evaluated. They include recoil corrections 1/M of three kinds. The true recoil correction to the cross section is negligible. The weak-magnetism—axial-vector interference is sizable, decreasing the cross section by ∼2% for 5-MeV positrons. One also has to include the recoil-neutron energy in relating the positron and antineutrino energies in order to evaluate the antineutrino flux. That effect decreases the positron yield by as much as 6% for 5-MeV positrons. The radiative corrections of order α have been also evaluated; they increase the cross section by ∼1.5% near threshold and by ∼0.7% at 5MeV. Formulas and a table of numerical values of all corrections are presented

### Entanglement in atomic resonance fluorescence

The resonance fluorescence from regular atomic systems is shown to represent
a continuous source of non-Gaussian entangled radiation propagating in two
different directions. For a single atom entanglement occurs under the same
conditions as squeezing. For more atoms, the entanglement can be more robust
against dephasing than squeezing, hence providing a useful continuous source
for various applications of entangled radiation.Comment: 4 pages, 1 figur

### Nuclear structure and double beta decay: Two neutrino mode

The decay rate of the 2ν double beta decay is calculated. The effects of pairing, static quadrupole deformation, spin-isospin polarization, and the Δ_(33) isobar admixtures on the nuclear matrix elements are studied and the relation of the 2ν ββ rate and the β^- and β^+ strength is stressed. In agreement with other calculations, we predict a faster decay rate than has been observed experimentally in ^(82)Se, ^(130)Te, and ^(150)Nd

### Reconstructing $\rho^0$ and $\omega$ mesons from non-leptonic decays in C+C at 2AGeV

We predict transverse and longitudinal momentum spectra and yields of
$\rho^0$ and $\omega$ mesons reconstructed from hadron correlations in C+C
reactions at 2~AGeV. The rapidity and $p_T$ distributions for reconstructable
$\rho^0$ mesons differs strongly from the primary distribution, while the
$\omega$'s distributions are only weakly modified. We discuss the temporal and
spatial distributions of the particles emitted in the hadron channel. Finally,
we report on the mass shift of the $\rho^0$ due to its coupling to the
$N^*(1520)$, which is observable in both the di-lepton and $\pi\pi$ channel.
Our calculations can be tested with the Hades experiment at GSI, Darmstadt

### Optimal Squeezing in Resonance Fluorescence via Atomic-State Purification

Squeezing of atomic resonance fluorescence is shown to be optimized by a
properly designed environment, which can be realized by a quasi-resonant
cavity. Optimal squeezing is achieved if the atomic coherence is maximized,
corresponding to a pure atomic quantum state. The atomic-state purification is
achieved by the backaction of the cavity field on the atom, which increases the
atomic coherence and decreases the atomic excitation. For realistic cavities,
the coupling of the atom to the cavity field yields a purity of the atomic
state of more than 99%. The fragility of squeezing against dephasing is
substantially reduced in this scenario, which may be important for various
applications.Comment: 6 pages including supplemental information, 3 figures. Accepted for
PR

### Persistent inequality when learning requires a minimal standard of living

This paper studies the persistence of wealth and utility inequality in a dynamicmodel of skill acquisition with complete credit markets and rational, perfectly altruistic,dynastic utility-maximization, when efficient learning requires a minimal standardof living. The main result is that, if the minimal standard of living is not triviallysmall, at any stationary equilibrium without intergenerational mobility there are?poor?, unskilled and ?rich?, skilled dynasties. Members of rich dynasties inherit morefrom their parents than members of poor dynasties. The former in general acquireskill, while the latter remain unskilled, and - most importantly - members of rich familiesalso enjoy strictly higher utility than members of poor dynasties. This paper studies the persistence of wealth and utility inequality in a dynamicmodel of skill acquisition with complete credit markets and rational, perfectly altruistic,dynastic utility-maximization, when efficient learning requires a minimal standardof living. The main result is that, if the minimal standard of living is not triviallysmall, at any stationary equilibrium without intergenerational mobility there are?poor?, unskilled and ?rich?, skilled dynasties. Members of rich dynasties inherit morefrom their parents than members of poor dynasties. The former in general acquireskill, while the latter remain unskilled, and - most importantly - members of rich familiesalso enjoy strictly higher utility than members of poor dynasties

### Low-energy neutrino physics and neutrino mass

Among the principal concerns in neutrino physics today are the questions of whether neutrinos are massive and, if so, whether the neutrinos emitted in a weak decay are pure or mixed quantum states. The concept of mixed neutrinos has been with us for more than 20 years, having first been introduced by Maki et al (1) and by Pontecorvo (2) following demonstration in 1962 that more than one type (flavor) of neutrino existed. After having been dormant for some time, the interest in these issues was reborn in recent years with the advent of grand unified theories, which predict nonvanishing neutrino mass and which can accommodate eutrino mixing, in a natural way. Controversial experiments also refueled the excitment (and consternation) of researchers in this endeavor

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