125,766 research outputs found
Two Recent Results on B Physics from CDF
Preliminary results from two recent CDF b physics analysis are presented. The
first obtains sin(2beta) = 0.79 + 0.41 -0.44 from a measurement of the
asymmetry in B0, B0bar to J/psi K_short decays, providing the best direct
indication so far that CP invariance is violated in the b sector. The second
obtains new results on the parity even (A_0 and A_par) and odd (A_perp)
polarization amplitudes from full angular analyses of B0 to J/psi K*0 and B_s
to J/psi phi decays.Comment: 8 pages, 4 figures; presented at the 34th Recontres de Moriond, Les
Arcs, 1800, France, 13-20 March 199
Electromagnetic Pulse from Final Gravitational Stellar Collapse
We employ an effective gravitational stellar final collapse model which
contains the relevant physics involved in this complex phenomena: spherical
radical infall in the Schwarzschild metric of the homogeneous core of an
advanced star, giant magnetic dipole moment, magnetohydrodynamic material
response and realistic equations of state (EOS). The electromagnetic pulse is
computed both for medium size cores undergoing hydrodynamic bounce and large
size cores undergoing black hole formation. We clearly show that there must
exist two classes of neutron stars, separated by maximum allowable masses:
those that collapsed as solitary stars (dynamical mass limit) and those that
collapsed in binary systems allowing mass accretion (static neutron star mass).
Our results show that the electromagnetic pulse spectrum associated with black
hole formation is a universal signature, independent of the nuclear EOS. Our
results also predict that there must exist black holes whose masses are less
than the static neutron star stability limit.Comment: 9 pages, 8 figures, to be published in Astronomy and Astrophysic
Shadowing and Antishadowing in Neutrino Deep Inelastic Scattering
The coherence of multiscattering quark nuclear processes leads to shadowing
and antishadowing of the electromagnetic nuclear structure functions in
agreement with measurements. This picture leads to substantially different
antishadowing for charged and neutral current processes, particularly in
anti-neutrino reactions, thus affecting the extraction of the weak-mixing angle
.Comment: 4 pages, 1 figure, Prepared for the International Conference on QCD
and Hadronic Physics, Beijing, China, June 16-20 200
Family of exactly solvable models with an ultimative quantum paramagnetic ground state
We present a family of two-dimensional frustrated quantum magnets solely
based on pure nearest-neighbor Heisenberg interactions which can be solved
quasi-exactly. All lattices are constructed in terms of frustrated quantum
cages containing a chiral degree of freedom protected by frustration. The
ground states of these models are dubbed ultimate quantum paramagnets and
exhibit an extensive entropy at zero temperature. We discuss the unusual and
extensively degenerate excitations in such phases. Implications for
thermodynamic properties as well as for decoherence free quantum computation
are discussed
Unifying Magnons and Triplons in Stripe-Ordered Cuprate Superconductors
Based on a two-dimensional model of coupled two-leg spin ladders, we derive a
unified picture of recent neutron scattering data of stripe-ordered
La_(15/8)Ba_(1/8)CuO_4, namely of the low-energy magnons around the
superstructure satellites and of the triplon excitations at higher energies.
The resonance peak at the antiferromagnetic wave vector Q_AF in the
stripe-ordered phase corresponds to a saddle point in the dispersion of the
magnetic excitations. Quantitative agreement with the neutron data is obtained
for J= 130-160 meV and J_cyc/J = 0.2-0.25.Comment: 4 pages, 4 figures included updated version taking new data into
account; factor in spectral weight corrected; Figs. 2 and 4 change
Do Stops Slow Down Electroweak Bubble Walls?
We compute the wall velocity in the MSSM. We therefore generalize the SM
equations of motion for bubble walls moving through a hot plasma at the
electroweak phase transition and calculate the friction terms which describe
the viscosity of the plasma. We give the general expressions and apply them to
a simple model where stops, tops and W bosons contribute to the friction. In a
wide range of parameters including those which fulfil the requirements of
baryogenesis we find a wall velocity of order v = 0.05-0.1 much below the SM
value.Comment: Numerical error corrected, result qualitatively unchange
The mobile Sousy-Doppler radar: Technical design and first results
A mobile VHF Doppler system was developed. The electronic part is installed in a 20 ft container and tested using a special log periodic aerial to illuminate the 300 m dish. The system was extended by designing a mobile phased antenna array with finally 576 Yagi elements. The grouping of the single Yagis, the system of transmission lines, the phase shifters, the power splitters and the T/R switch are described. Results from the first two campaigns and a survey of future programs demonstrating the flexibility of this mobile system are summarized
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