239 research outputs found
Effective action for the Kondo lattice model. New approach for S=1/2
In the partition function of the Kondo lattice, spin matrices are exactly
replaced by bilinear combinations of Fermi operators with the purely imaginary
chemical potential lambda=-i.pi.T/2 (Popov representation). This new
representation of spin operators allows one to introduce new Green's functions
with Matsubara frequencies 2.pi.T(n+1/4) for S=1/2. A simple temperature
diagram technique is constructed with the path integral method. This technique
is standard and does not contain the complicated combinatoric rules
characteristic of most of the known variants of the diagram techniques for spin
systems. The effective action for the almost antiferromagnetic Kondo lattice is
derived.Comment: 7 pages, Proceedings of SCES98/Paris; one reference adde
Contribution to muon g-2 from the \pi0\gamma and \eta\gamma intermediate states in the vacuum polarization
Using new experimental data, we have calculated the contribution to the
anomalous magnetic moment of the muon from the \pi0\gamma and \eta\gamma
intermediate states in the vacuum polarization with high precision:
a{\mu}(\pi0\gamma)+a{\mu}(\eta\gamma)=(54.7\pm 1.5)\times 10^{-11}. We have
also found the small contribution from e+e-\pi0, e+e-\eta and \mu+\mu-\pi0
intermediate states equal to 0.5\times 10^{-11}.Comment: 6 pages, 2 figures, revte
Resonance Kondo Tunneling through a Double Quantum Dot at Finite Bias
It is shown that the resonance Kondo tunneling through a double quantum dot
(DQD) with even occupation and singlet ground state may arise at a strong bias,
which compensates the energy of singlet/triplet excitation. Using the
renormalization group technique we derive scaling equations and calculate the
differential conductance as a function of an auxiliary dc-bias for parallel DQD
described by SO(4) symmetry. We analyze the decoherence effects associated with
the triplet/singlet relaxation in DQD and discuss the shape of differential
conductance line as a function of dc-bias and temperature.Comment: 11 pages, 6 eps figures include
The new analysis of the KLOE data on the phi->eta pi0 gamma decay
In this paper we present the fit to the recent high-statistical KLOE data on
the phi -> eta pi^0 gamma decay. This decay mainly goes through the a_0 gamma
intermediate state. The obtained results differ from those of the previous
fits: data prefer a high a_0 mass and a considerably large a_0 coupling to the
K\bar K}.Comment: 11 pages, 2 figure
Ginzburg-Landau functional for nearly antiferromagnetic perfect and disordered Kondo lattices
Interplay between Kondo effect and trends to antiferromagnetic and spin glass
ordering in perfect and disordered bipartite Kondo lattices is considered.
Ginzburg-Landau equation is derived from the microscopic effective action
written in three mode representation (Kondo screening, antiferromagnetic
correlations and spin liquid correlations). The problem of local constraint is
resolved by means of Popov-Fedotov representation for localized spin operators.
It is shown that the Kondo screening enhances the trend to a spin liquid
crossover and suppresses antiferromagnetic ordering in perfect Kondo lattices
and spin glass ordering in doped Kondo lattices. The modified Doniach's diagram
is constructed, and possibilities of going beyond the mean field approximation
are discussed.Comment: 18 pages, RevTeX, 7 EPS figures include
Electronic spin working mechanically (Review Article)
A single-electron tunneling (SET) device with a nanoscale central island that can move with respect to the
bulk source- and drain electrodes allows for a nanoelectromechanical (NEM) coupling between the electrical
current through the device and mechanical vibrations of the island. Although an electromechanical “shuttle” instability
and the associated phenomenon of single-electron shuttling were predicted more than 15 years ago, both
theoretical and experimental studies of NEM-SET structures are still carried out. New functionalities based on
quantum coherence, Coulomb correlations and coherent electron-spin dynamics are of particular current interest.
In this article we present a short review of recent activities in this area
ϒ production in p–Pb collisions at √sNN=8.16 TeV
ϒ production in p–Pb interactions is studied at the centre-of-mass energy per nucleon–nucleon collision √sNN = 8.16 TeV with the ALICE detector at the CERN LHC. The measurement is performed reconstructing bottomonium resonances via their dimuon decay channel, in the centre-of-mass rapidity intervals 2.03 < ycms < 3.53 and −4.46 < ycms < −2.96, down to zero transverse momentum. In this work, results on the ϒ(1S) production cross section as a function of rapidity and transverse momentum are presented. The corresponding nuclear modification factor shows a suppression of the ϒ(1S) yields with respect to pp collisions, both at forward and backward rapidity. This suppression is stronger in the low transverse momentum region and shows no significant dependence on the centrality of the interactions. Furthermore, the ϒ(2S) nuclear modification factor is evaluated, suggesting a suppression similar to that of the ϒ(1S). A first measurement of the ϒ(3S) has also been performed. Finally, results are compared with previous ALICE measurements in p–Pb collisions at √sNN = 5.02 TeV and with theoretical calculations.publishedVersio
(Anti-)deuteron production in pp collisions at 1as=13TeV
The study of (anti-)deuteron production in pp collisions has proven to be a powerful tool to investigate the formation mechanism of loosely bound states in high-energy hadronic collisions. In this paper the production of (anti-)deuterons is studied as a function of the charged particle multiplicity in inelastic pp collisions at s=13 TeV using the ALICE experiment. Thanks to the large number of accumulated minimum bias events, it has been possible to measure (anti-)deuteron production in pp collisions up to the same charged particle multiplicity (d Nch/ d \u3b7 3c 26) as measured in p\u2013Pb collisions at similar centre-of-mass energies. Within the uncertainties, the deuteron yield in pp collisions resembles the one in p\u2013Pb interactions, suggesting a common formation mechanism behind the production of light nuclei in hadronic interactions. In this context the measurements are compared with the expectations of coalescence and statistical hadronisation models (SHM)
Multiplicity dependence of inclusive J/psi production at midrapidity in pp collisions at root s=13 TeV
Measurements of the inclusive J/psi yield as a function of charged-particle pseudorapidity density dN(ch)/d eta in pp collisions at root s = 13 TeV with ALICE at the LHC are reported. The J/psi meson yield is measured at midrapidity (vertical bar y vertical bar <0.9) in the dielectron channel, for events selected based on the charged-particle multiplicity at midrapidity (vertical bar eta vertical bar <1) and at forward rapidity (-3.7 <eta <-1.7 and 2.8 <eta <5.1); both observables are normalized to their corresponding averages in minimum bias events. The increase of the normalized J/psi yield with normalized dN(ch)/d eta is significantly stronger than linear and dependent on the transverse momentum. The data are compared to theoretical predictions, which describe the observed trends well, albeit not always quantitatively. (C) 2020 European Organization for Nuclear Research. Published by Elsevier B.V.Peer reviewe
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