52,200 research outputs found

### Formation of \eta'(958)-mesic nuclei and axial U_A(1) anomaly at finite density

We discuss the possibility to produce the bound states of the $\eta'(958)$
meson in nuclei theoretically. We calculate the formation cross sections of the
$\eta'$ bound states with the Green function method for ($\gamma$,p) reaction
and discuss the experimental feasibility at photon facilities like SPring-8. We
conclude that we can expect to observe resonance peaks in ($\gamma$,p) spectra
for the formation of $\eta'$ bound states and we can deduce new information on
$\eta'$ properties at finite density. These observations are believed to be
essential to know the possible mass shift of $\eta'$ and deduce new information
of the effective restoration of the chiral $U_A(1)$ anomaly in the nuclear
medium.Comment: 4 pages, 3 figure

### Determination of polarized parton distribution functions

We study parametrization of polarized parton distribution functions in the
\alpha_s leading order (LO) and in the next-to-leading order (NLO). From \chi^2
fitting to the experimental data on A_1, optimum polarized distribution
functions are determined. The quark spin content \Delta\Sigma is very sensitive
to the small-x behavior of antiquark distributions which suggests that small-x
data are needed for precise determination of \Delta\Sigma. We propose three
sets of distributions and also provide FORTRAN library for our distributions.Comment: 1+5 pages, LATEX, aipproc.sty, 4 eps figures. Talk given at the 14th
International Spin Physics Symposium, Osaka, Japan, October 16-21, 200

### Quantum network coding for quantum repeaters

This paper considers quantum network coding, which is a recent technique that
enables quantum information to be sent on complex networks at higher rates than
by using straightforward routing strategies. Kobayashi et al. have recently
showed the potential of this technique by demonstrating how any classical
network coding protocol gives rise to a quantum network coding protocol. They
nevertheless primarily focused on an abstract model, in which quantum resource
such as quantum registers can be freely introduced at each node. In this work,
we present a protocol for quantum network coding under weaker (and more
practical) assumptions: our new protocol works even for quantum networks where
adjacent nodes initially share one EPR-pair but cannot add any quantum
registers or send any quantum information. A typically example of networks
satisfying this assumption is {\emph{quantum repeater networks}}, which are
promising candidates for the implementation of large scale quantum networks.
Our results thus show, for the first time, that quantum network coding
techniques can increase the transmission rate in such quantum networks as well.Comment: 9 pages, 11figure

### A tight analysis of Kierstead-Trotter algorithm for online unit interval coloring

Kierstead and Trotter (Congressus Numerantium 33, 1981) proved that their
algorithm is an optimal online algorithm for the online interval coloring
problem. In this paper, for online unit interval coloring, we show that the
number of colors used by the Kierstead-Trotter algorithm is at most $3
\omega(G) - 3$, where $\omega(G)$ is the size of the maximum clique in a given
graph $G$, and it is the best possible.Comment: 4 page

### Lepton Energy Asymmetry and Precision SUSY study at Hadron Colliders

We study the distribution of lepton pairs from the second lightest neutralino
decay \tilde{\chi}^0_2-->\tilde{l}l followed by \tilde{l}\to \tilde{\chi}^0_1
l. The distribution of the ratio of lepton transverse momenta A_T shows peak
structure if m_{ll}< m^{max}_{ll}/2 is required. The peak position A_T^{peak}
is described by a simple function of the ino and slepton masses in the
m_{ll}\sim 0 limit. When a moderate m_{ll} cut is applied, A_T^{peak} depends
on the \tilde{\chi}^0_2 velocity distribution, but the dependence would be
corrected by studying the lepton P_T distribution. A_T^{peak} and the edge of
m_{ll} distributions are used to determine the mass parameters involved in the
decay for parameters of interest to LHC experiments. For some cases the ino and
slepton masses may be determined within 10% by the lepton distribution only
independent of model assumptions. Correct combinations of A_{T}^{peak} and
m_{ll}^{edge} would be identified even if different \tilde{\chi}^0_2 decay
chains are co-existing. The analysis could be extended to the Tevatron energy
scale or other cascade decays.Comment: 31 pages, 15 figure

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