8,389 research outputs found

### Pulsar interpretation of the lepton spectra measured by AMS-02

AMS-02 recently published its lepton spectra measurement. The results show
that the positron fraction no longer increases above $\sim$200 GeV. The aim of
this work is to investigate the possibility that the excess of positron
fraction is due to pulsars. Nearby known pulsars from ATNF catalogue are
considered as a possible primary positron source of the high energy positrons.
We find that the pulsars with age $T\simeq (0.45\sim4.5)\times10^{5}$ yr and
distance $d<0.5$ kpc can explain the behavior of positron fraction of AMS-02 in
the range of high energy. We show that each of the four pulsars --- Geminga,
J1741-2054, Monogem and J0942-5552 --- is able to be a single source satisfying
all considered physical requirements. We also discuss the possibility that
these high energy $e^{\pm}$ are from multiple pulsars. The multiple pulsars
contribution predicts a positron fraction with some structures at higher
energies.Comment: 27 pages, 5 figures, 3 tables, accepted for publication in EPJ

### Momentum polarization: an entanglement measure of topological spin and chiral central charge

Topologically ordered states are quantum states of matter with topological
ground state degeneracy and quasi-particles carrying fractional quantum numbers
and fractional statistics. The topological spin $\theta_a=2\pi h_a$ is an
important property of a topological quasi-particle, which is the Berry phase
obtained in the adiabatic self-rotation of the quasi-particle by $2\pi$. For
chiral topological states with robust chiral edge states, another fundamental
topological property is the edge state chiral central charge $c$. In this paper
we propose a new approach to compute the topological spin and chiral central
charge in lattice models by defining a new quantity named as the momentum
polarization. Momentum polarization is defined on the cylinder geometry as a
universal subleading term in the average value of a "partial translation
operator". We show that the momentum polarization is a quantum entanglement
property which can be computed from the reduced density matrix, and our
analytic derivation based on edge conformal field theory shows that the
momentum polarization measures the combination $h_a-\frac{c}{24}$ of
topological spin and central charge. Numerical results are obtained for two
example systems, the non-Abelian phase of the honeycomb lattice Kitaev model,
and the $\nu=1/2$ Laughlin state of a fractional Chern insulator described by a
variational Monte Carlo wavefunction. The numerical results verifies the
analytic formula with high accuracy, and further suggests that this result
remains robust even when the edge states cannot be described by a conformal
field theory. Our result provides a new efficient approach to characterize and
identify topological states of matter from finite size numerics.Comment: 13 pages, 8 figure

### Resolving the Degeneracy in Single Higgs Production with Higgs Pair Production

The Higgs boson production can be affected by several anomalous couplings,
e.g. $c_t$ and $c_g$ anomalous couplings. Precise measurement of $gg\to h$
production yields two degenerate parameter spaces of $c_t$ and $c_g$; one
parameter space exhibits the SM limit while the other does not. Such a
degeneracy could be resolved by Higgs boson pair production. In this work we
adapt the strategy suggested by the ATLAS collaboration to explore the
potential of distinguishing the degeneracy at the 14 TeV LHC. If the $c_t$
anomalous coupling is induced only by the operator $H^\dag H \bar Q_L \tilde{H}
t_R$, then the non-SM-like band could be excluded with an integrated luminosity
of $\sim 235~{\rm fb}^{-1}$. Making use of the fact that the Higgs boson pair
is mainly produced through an $s$-wave scattering, we propose an analytical
function to describe the fraction of signal events surviving a series of
experimental cuts for a given invariant mass of Higgs boson pair. The function
is model independent and can be applied to estimate the discovery potential of
various NP models

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