731 research outputs found
New Method to Reveal the Conflict Between Local Realism and Quantum Mechanics
We formulate the expectation value of the Bell-Zukowski operator acting on
qubit states of a two-particle Bell experiment. By using the equivalence
between a set of N copies of a two-qubit experiment and a standard two-setting
Bell experiment in an entangled 2N-particle state, we obtain an inequality,
which we may call the Bell-Zukowski inequality. It determines whether the
measured correlation functions of two-particle states can be modeled locally
and realistically. In this Bell experiment of two particles, the conflict
between local realism and quantum mechanics is discussed in conjunction with
the violation of the Bell-Zukowski inequality. The main point of the result is
that the Bell-Zukowski operator can be represented by the Bell-Mermin operator.
The threshold visibility of two-particle interference analyzed in this scheme
shows good agreement with the value to cause a violation of the Bell-Zukowski
inequality.Comment: To appear in Journal of the Korean Physical Society. We have
introduced an additional assumption that the detector efficiency is perfect
(i.e., 100%). We thank Professor Douglas G. Danforth for valuable comment
Direct Detection of Dark Matter Degenerate with Colored Particles in Mass
In this Letter we explore the direct detection of the dark matter in the
universe, assuming the dark matter particles are degenerate in mass with new
colored particles below TeV scale. The scenario with such a mass spectrum is
difficult to be confirmed or excluded by the present analysis at the LHC
experiments because the QCD jets in the cascade decay of the new particles
produced in the proton-proton collision are too soft to be triggered in the
event selection. It is shown that both of the spin-independent and
spin-dependent couplings of the dark matter with a nucleon are enhanced and the
scattering cross section may reach even the current bound of the direct
detection experiments. Then such a degenerate scenario may be tested in the
direct detection experiments.Comment: 11 pages, 4 figures. Version accepted for publication in Phys. Lett.
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