487 research outputs found
Resonance production by neutrinos: I. J=3/2 Resonances
The article contains general formulas for the production of J=3/2 resonances
by neutrinos and antineutrinos. It specializes to the P_{33}(1232) resonance
whose form factors are determined by theory and experiment and then are
compared with experimental results at low and high energies. It is shown that
the minimum in the low Q^2 region is a consequence of a combined effect from
the vanishing of the vector form factors, the muon mass and Pauli blocking.
Several improvements for the future investigations are suggested.Comment: 10 pages, LaTeX, misprints corrected, 1 reference adde
Transport study of charged current interactions in neutrino-nucleus reactions
Within a dynamical transport approach we investigate charged current
interactions in neutrino-nucleus reactions for neutrino energies of 0.3 - 1.5
GeV with particular emphasis on resonant pion production channels via the
resonance. The final-state-interactions of the resonance as
well as of the emitted pions are calculated explicitly for and
nuclei and show a dominance of pion suppression at moderate momenta
0.2 GeV/c. A comparison to integrated spectra for reactions with the available (preliminary) data demonstrates a
reasonable agreement.Comment: 13 pages incl. 6 eps-figures; computational error in final state
interactions corrected; to be published in Phys. Lett.
On the probabilistic min spanning tree Problem
We study a probabilistic optimization model for min spanning tree, where any vertex vi of the input-graph G(V,E) has some presence probability pi in the final instance G′ ⊂ G that will effectively be optimized. Suppose that when this “real” instance G′ becomes known, a spanning tree T, called anticipatory or a priori spanning tree, has already been computed in G and one can run a quick algorithm (quicker than one that recomputes from scratch), called modification strategy, that modifies the anticipatory tree T in order to fit G ′. The goal is to compute an anticipatory spanning tree of G such that, its modification for any G ′ ⊆ G is optimal for G ′. This is what we call probabilistic min spanning tree problem. In this paper we study complexity and approximation of probabilistic min spanning tree in complete graphs under two distinct modification strategies leading to different complexity results for the problem. For the first of the strategies developed, we also study two natural subproblems of probabilistic min spanning tree, namely, the probabilistic metric min spanning tree and the probabilistic min spanning tree 1,2 that deal with metric complete graphs and complete graphs with edge-weights either 1, or 2, respectively
Epstein-Barr virus nuclear protein EBNA3C directly induces expression of AID and somatic mutations in B cells
Activation-induced cytidine deaminase (AID), the enzyme responsible for induction of sequence variation in immunoglobulins (Igs) during the process of somatic hypermutation (SHM) and also Ig class switching, can have a potent mutator phenotype in the development of lymphoma. Using various Epstein-Barr virus (EBV) recombinants, we provide definitive evidence that the viral nuclear protein EBNA3C is essential in EBV-infected primary B cells for the induction of AID mRNA and protein. Using lymphoblastoid cell lines (LCLs) established with EBV recombinants conditional for EBNA3C function, this was confirmed, and it was shown that transactivation of the AID gene (AICDA) is associated with EBNA3C binding to highly conserved regulatory elements located proximal to and upstream of the AICDA transcription start site. EBNA3C binding initiated epigenetic changes to chromatin at specific sites across the AICDA locus. Deep sequencing of cDNA corresponding to the IgH V-D-J region from the conditional LCL was used to formally show that SHM is activated by functional EBNA3C and induction of AID. These data, showing the direct targeting and induction of functional AID by EBNA3C, suggest a novel role for EBV in the etiology of B cell cancers, including endemic Burkitt lymphoma
Determination of the CP Violating Phase by a Sum Over Common Decay Modes to and
To help the difficult determination of the angle of the unitarity
triangle, Aleksan, Dunietz and Kayser have proposed the modes of the type
, common to and . We point out that it is possible
to gain in statistics by a sum over all modes with ground state mesons in the
final state, i.e. , , , .
The delicate point is the relative phase of these different contributions to
the dilution factor of the time-dependent asymmetry. Each contribution to
is proportional to a product where
denotes form factors and decay constants. Within a definite phase
convention, lattice calculations do not show any change in sign when
extrapolating to light quarks the form factors and decay constants. Then, we
can show that all modes contribute constructively to the dilution factor,
except the -wave , which is small. Quark model arguments
based on wave function overlaps also confirm this stability in sign. By summing
over all these modes we find a gain of a factor 6 in statistics relatively to
. The dilution factor for the sum is remarkably stable for
theoretical schemes that are not in very strong conflict with data on or extrapolated from semileptonic charm form factors, giving
, always close to .Comment: 22 pages, LPTHE Orsay 94/03, DAPNIA/SPP/94-2
Qubit Analog with Polariton Superfluid in an Annular Trap
We report on the experimental realization and characterization of a qubit
analog with semiconductor exciton-polaritons. In our system, a condensate of
exciton-polaritons is confined by a spatially-patterned pump laser in an
annular trap that supports energy-degenerate circulating currents of the
polariton superfluid. Using temporal interference measurements, we observe
coherent oscillations between a pair of counter-circulating superfluid vortex
states of the polaritons coupled by elastic scattering off the laser-imprinted
potential. The qubit basis states correspond to the symmetric and antisymmetric
superpositions of the two vortex states forming orthogonal double-lobe spatial
wavefunctions. By engineering the potential, we tune the coupling and coherent
oscillations between the two circulating current states, control the energies
of the qubit basis states, and initialize the qubit in the desired state. The
dynamics of the system is accurately reproduced by our theoretical two-state
model, and we discuss potential avenues to achieve complete control over our
polaritonic qubits and realize controllable interactions between such qubits to
implement quantum gates and algorithms analogous to quantum computation with
standard qubits
Progress on a spherical TPC for low energy neutrino detection
The new concept of the spherical TPC aims at relatively large target masses
with low threshold and background, keeping an extremely simple and robust
operation. Such a device would open the way to detect the neutrino-nucleus
interaction, which, although a standard process, remains undetected due to the
low energy of the neutrino-induced nuclear recoils. The progress in the
development of the fist 1 m prototype at Saclay is presented. Other physics
goals of such a device could include supernova detection, low energy neutrino
oscillations and study of non-standard properties of the neutrino, among
others.Comment: 3 pages, talk given at the 9th Workshop on Topics in Astroparticle
and Underground Physics, Zaragoza, September 10-1
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