43,426 research outputs found
A phenomenological interpretation of open charm production at HERA in terms of the semi-hard approach
In the framework of the semi-hard (k_t-factorization) approach, we analyze
the various charm production processes in the kinematic region covered by the
HERA experiments.Comment: DESY 02-017, LUNFD6/(NFFL--7209) 200
A one-dimensional tunable magnetic metamaterial
We present experimental data on a one-dimensional superconducting
metamaterial that is tunable over a broad frequency band. The basic building
block of this magnetic thin-film medium is a single-junction (rf-)
superconducting quantum interference device (SQUID). Due to the nonlinear
inductance of such an element, its resonance frequency is tunable in situ by
applying a dc magnetic field. We demonstrate that this results in tunable
effective parameters of our metamaterial consisting of 54 SQUIDs. In order to
obtain the effective magnetic permeability from the measured data, we employ a
technique that uses only the complex transmission coefficient S21
Charmonia production from -hadron decays at LHC with -factorization: , and
We consider the production of and mesons originating from
the decays of -flavored hadrons at the LHC using the -factorization
approach. Our analysis covers both inclusive charmonia production and
production of mesons in association with bosons. We apply the
transverse momentum dependent (or unintegrated) gluon density in a proton
derived from Catani-Ciafaloni-Fiorani-Marchesini (CCFM) evolution equation and
adopt fragmentation functions based on the non-relativistic QCD factorization
to describe the inclusive -hadron decays into the different charmonium
states. Our predictions agree well with latest experimental data taken by the
CMS, ATLAS and LHCb Collaborations at , and ~TeV. The
contributions from double parton scattering to the associated non-prompt
production are estimated and found to be small.Comment: 12 pages, 5 figure
Testing the parton evolution with the use of two-body final states
We consider the production of quarks and Drell-Yan lepton pairs at
LHC conditions focusing attention on the total transverse momentum of the
produced pair and on the azimuthal angle between the momenta of the outgoing
particles. Plotting the corresponding distributions in bins of the final state
invariant mass, one can reconstruct the full map of the transverse momentum
dependent parton densities in a proton. We give examples of how can these
distributions can look like at the LHC energies.Comment: 8 pages, 7 figure
Wigner crystallization in the quantum 1D jellium at all densities
The jellium is a model, introduced by Wigner (Phys Rev 46(11):1002, 1934), for a gas of electrons moving in a uniform neutralizing background of positive charge. Wigner suggested that the repulsion between electrons might lead to a broken translational symmetry. For classical one-dimensional systems this fact was proven by Kunz (Ann Phys 85(2):303–335, 1974), while in the quantum setting, Brascamp and Lieb (Functional integration and its applications. Clarendon Press, Oxford, 1975) proved translation symmetry breaking at low densities. Here, we prove translation symmetry breaking for the quantum one-dimensional jellium at all densities
Neutrino oscillation signatures of oxygen-neon-magnesium supernovae
We discuss the flavor conversion of neutrinos from core collapse supernovae
that have oxygen-neon-magnesium (ONeMg) cores. Using the numerically calculated
evolution of the star up to 650 ms post bounce, we find that, for the normal
mass hierarchy, the electron neutrino flux in a detector shows signatures of
two typical features of an ONeMg-core supernova: a sharp step in the density
profile at the base of the He shell and a faster shock wave propagation
compared to iron core supernovae. Before the shock hits the density step (t ~
150 ms), the survival probability of electron neutrinos is about 0.68, in
contrast to values of 0.32 or less for an iron core supernova. The passage of
the shock through the step and its subsequent propagation cause a decrease of
the survival probability and a decrease of the amplitude of oscillations in the
Earth, reflecting the transition to a more adiabatic propagation inside the
star. These changes affect the lower energy neutrinos first; they are faster
and more sizable for larger theta_13. They are unique of ONeMg-core supernovae,
and give the possibility to test the speed of the shock wave. The time
modulation of the Earth effect and its negative sign at the neutronization peak
are the most robust signatures in a detector.Comment: 14 pages, 10 figures (16 figure files). Text and graphics added for
illustration and clarification; Results unchanged. Version accepted for
publication in Physical Review
Spinor Dynamics in an Antiferromagnetic Spin-1 Condensate
We observe coherent spin oscillations in an antiferromagnetic spin-1
Bose-Einstein condensate of sodium. The variation of the spin oscillations with
magnetic field shows a clear signature of nonlinearity, in agreement with
theory, which also predicts anharmonic oscillations near a critical magnetic
field. Measurements of the magnetic phase diagram agree with predictions made
in the approximation of a single spatial mode. The oscillation period yields
the best measurement to date of the sodium spin-dependent interaction
coefficient, determining that the difference between the sodium spin-dependent
s-wave scattering lengths is Bohr radii.Comment: 5 pages, 2 figures. Changes: added reference, minor correction
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