42,824 research outputs found
Majorana Dark matter with B+L gauge symmetry
We present a new model that extends the Standard Model (SM) with the local
B+L symmetry, and point out that the lightest new fermion , introduced
to cancel anomalies and stabilized automatically by the B+L symmetry, can serve
as the cold dark matter candidate. We study constraints on the model from Higgs
measurements, electroweak precision measurements as well as the relic density
and direct detections of the dark matter. Numerical results reveal that the
pseudo-vector coupling of with and the Yukawa coupling with the SM
Higgs are highly constrained by the latest results of LUX, while there are
viable parameter space that could satisfy all the constraints and give testable
predictions.Comment: 17 pages, 4 figures, minor revision, more references adde
On Torsion and Nieh-Yan Form
Using the well-known Chern-Weil formula and its generalization, we
systematically construct the Chern-Simons forms and their generalization
induced by torsion as well as the Nieh-Yan (N-Y) forms. We also give an
argument on the vanishing of integration of N-Y form on any compact manifold
without boundary. A systematic construction of N-Y forms in D=4n dimension is
also given.Comment: 7 pages, latex, no figure
Quantum Brownian motion model for the stock market
It is believed by the majority today that the efficient market hypothesis is
imperfect because of market irrationality. Using the physical concepts and
mathematical structures of quantum mechanics, we construct an econophysics
framework for the stock market, based on which we analogously map massive
numbers of single stocks into a reservoir consisting of many quantum harmonic
oscillators and their stock index into a typical quantum open system--a quantum
Brownian particle. In particular, the irrationality of stock transactions is
quantitatively considered as the Planck constant within Heisenberg's
uncertainty relationship of quantum mechanics in an analogous manner. We
analyze real stock data of Shanghai Stock Exchange of China and investigate
fat-tail phenomena and non-Markovian behaviors of the stock index with the
assistance of the quantum Brownian motion model, thereby interpreting and
studying the limitations of the classical Brownian motion model for the
efficient market hypothesis from a new perspective of quantum open system
dynamics
NLO Productions of and with a Global Extraction of the Jet Transport Parameter in Heavy Ion collisions
In this work, we pave the way to calculate the productions of and
mesons at large in p+p and A+A collisions at the RHIC and
the LHC. The meson fragmentation functions (FFs) in vacuum at
next-to-leading order (NLO) are obtained by evolving NLO DGLAP evolution
equations with rescaled FFs at initial scale GeV from
a broken SU(3) model, and the FFs in vacuum are taken from AKK08
parametrization directly. Within the framework of the NLO pQCD improved parton
model, we make good descriptions of the experimental data on and
in p+p both at the RHIC and the LHC. With the higher-twist
approach to take into account the jet quenching effect by medium modified FFs,
the nuclear modification factors for meson and meson at
the RHIC and the LHC are presented with different sets of jet transport
coefficient . Then we make a global extraction of at the
RHIC and the LHC by confronting our model calculations with all available data
on 6 identified mesons: , , , , , and
. The minimum value of the total for productions of
these mesons gives the best value of for Au+Au
collisions with GeV at the RHIC, and for Pb+Pb collisions with TeV at the LHC
respectively, with the QGP spacetime evolution given by an event-by-event
viscous hydrodynamics model IEBE-VISHNU. With these global extracted values of
, the nuclear modification factors of , , ,
, , and in A+A collisions are presented, and
predictions of yield ratios such as and at
large in heavy-ion collisions at the RHIC and the LHC are provided.Comment: 9 pages, 13 figures, 1 tabl
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