63,757 research outputs found
Lepton-pair production in ultraperipheral collisions at AFTER@LHC
We investigate the potentialities offered by the study of lepton-pair
production in ultraperipheral collisions at a fixed-target experiment using the
proton and ion LHC beams. In these collisions, exclusive or semi-exclusive
lepton-pair production can be used as luminosity monitor as well as a check of
the equivalent-photon approximation, via the measurement of the Bethe-Heitler
cross section. It can also serve as a probe of the inner hadron structure via
the measurement of the lepton-pair azimuthal asymmetry which is sensitive to
the timelike virtual Compton scattering. We also briefly discuss the
possibility offered by the study of eta(c) production. Finally, we outline the
possibilities for lepton-pair production by Pomeron-Odderon fusion in exclusive
pp and pA collisions.Comment: 21 pages, 19 figures, uses jheppub.sty (included
Microscopic systems with and without Coulomb interaction, fragmentation and phase transitions in finite nuclei
We test the influence of the Coulomb interaction on the thermodynamic and
cluster generation properties of a system of classical particles described by
different lattice models. Numerical simulations show that the Coulomb
interaction produces essentially a shift in temperature of quantities like the
specific heat but not qualitative changes. We also consider a cellular model.
The thermodynamic properties of the system are qualitatively unaltered.Comment: 8 pages, 9 figures. New comments concerning the effect of the Coulomb
interaction on the caloric curve. Justification of the criterion which
defines bound clusters. Further comments about the identification of the
order of the transition. To be published in Eur. Phys. J.
Comment on ``Spin Dependent Hopping and Colossal Negative Magnetoresistance in Epitaxial Films in Fields up to 50 T''
Recently Wagner et al. [Phys. Rev. Lett. Vol. 81, P. 3980 (1998)] proposed
that Mott's original model be modified to incorporate a hopping barrier which
depends on the misorientation between the spins of electrons at the initial and
the final states in an elementary process. They further claimed that using the
model they can explain the observed scaling behavior--
negative-magnetoresistivity scaling proportional to the Brillouin function
in the ferromagnetic state and to in the paramagnetic
state. In this comment we argue that the modification needed for Mott's
original model is different from that proposed by Wagner et al. and further
show that our picture will successfully explain the observed scaling in the two
regimes.Comment: 1 pag
Fermions in the pseudoparticle approach
The pseudoparticle approach is a numerical technique to compute path
integrals without discretizing spacetime. The basic idea is to integrate over
those field configurations, which can be represented by a sum of a fixed number
of localized building blocks (pseudoparticles). In a couple of previous papers
we have successfully applied the pseudoparticle approach to pure SU(2)
Yang-Mills theory. In this work we discuss how to incorporate fermionic fields
in the pseudoparticle approach. To test our method, we compute the phase
diagram of the 1+1-dimensional Gross-Neveu model in the large-N limit.Comment: 11 pages, 10 figure
Microfluidic detection and analysis by integration of evanescent wave sensing with thermocapillary actuation
An integrated system capable of microfluidic actuation, detection and sensing is described which combines evanescent wave sensing with thermocapillary manipulation. Liquid droplets or streams transported across the beam path of a planar thin film waveguide, which encapsulates the microheater array, induce attenuation of the propagating waveguide modes. The attenuated signal is used to monitor droplet location, dye concentration in aqueous solutions and reaction kinetics for enzymatic hydrolysis of the sugar X-galactose by beta-galactosidase
Phase space characteristics of fragmenting nuclei described as excited disordered systems
We investigate the thermodynamical content of a cellular model which
describes nuclear fragmentation as a process taking place in an excited
disordered system. The model which reproduces very well the size distribution
of fragments does not show the existence of a first order phase transition.Comment: 14 pages, TeX type, 7 figure
Inverter ratio failure detector
A failure detector which detects the failure of a dc to ac inverter is disclosed. The inverter under failureless conditions is characterized by a known linear relationship of its input and output voltages and by a known linear relationship of its input and output currents. The detector includes circuitry which is responsive to the detector's input and output voltages and which provides a failure-indicating signal only when the monitored output voltage is less by a selected factor, than the expected output voltage for the monitored input voltage, based on the known voltages' relationship. Similarly, the detector includes circuitry which is responsive to the input and output currents and provides a failure-indicating signal only when the input current exceeds by a selected factor the expected input current for the monitored output current based on the known currents' relationship
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