73,227 research outputs found
Forward Production of Protons and Pions in Heavy-ion Collisions
The problem of forward production of hadrons in heavy-ion collision at RHIC
is revisited with modification of the theoretical treatment on the one hand and
with the use of new data on the other. The basic formalism for hadronization
remains the same as before, namely, recombination, but the details of momentum
degradation and quark regeneration are improved. Recent data on the p/pi and
pbar/p ratios are used to constrain the value of the degradation parameter. The
p_T spectrum of the average charged particles is well reproduced. A prediction
on the p_T dependence of the pbar/p ratio at eta=3.2 is made.Comment: 17 pages in LaTeX including 5 figures in ep
Soft Gluon Resummation Effects in Single Graviton Production at the CERN Large Hadron Collider in the Randall-Sundrum Model
We study QCD effects in single graviton production at the CERN Large Hadron
Collider (LHC) in the Randall-Sundrum (RS) Model. We present in detail the
complete next-to-leading order (NLO) QCD corrections to the inclusive total
cross sections. The NLO QCD corrections enhance significantly the total cross
sections and decrease efficiently the dependence of the total cross sections on
the factorization and renormalization scales. We also examine the uncertainty
of the total cross sections due to the parton distribution function (PDF)
uncertainties. For the differential cross sections on the transverse momentum
() of the graviton, within the CSS resummation formalism, we resum the
logarithmically-enhanced terms at small to all orders up to NLO
logatithmic accuracy. Combined with the fixed order calculations, we give
consistent predictions for both small and large .Comment: 26 pages, 13 figures; minor changes and misprints corrected; version
to appear in PR
Block-Structured Supermarket Models
Supermarket models are a class of parallel queueing networks with an adaptive
control scheme that play a key role in the study of resource management of,
such as, computer networks, manufacturing systems and transportation networks.
When the arrival processes are non-Poisson and the service times are
non-exponential, analysis of such a supermarket model is always limited,
interesting, and challenging.
This paper describes a supermarket model with non-Poisson inputs: Markovian
Arrival Processes (MAPs) and with non-exponential service times: Phase-type
(PH) distributions, and provides a generalized matrix-analytic method which is
first combined with the operator semigroup and the mean-field limit. When
discussing such a more general supermarket model, this paper makes some new
results and advances as follows: (1) Providing a detailed probability analysis
for setting up an infinite-dimensional system of differential vector equations
satisfied by the expected fraction vector, where "the invariance of environment
factors" is given as an important result. (2) Introducing the phase-type
structure to the operator semigroup and to the mean-field limit, and a
Lipschitz condition can be obtained by means of a unified matrix-differential
algorithm. (3) The matrix-analytic method is used to compute the fixed point
which leads to performance computation of this system. Finally, we use some
numerical examples to illustrate how the performance measures of this
supermarket model depend on the non-Poisson inputs and on the non-exponential
service times. Thus the results of this paper give new highlight on
understanding influence of non-Poisson inputs and of non-exponential service
times on performance measures of more general supermarket models.Comment: 65 pages; 7 figure
Two-Higgs-Doublet-Models and Radiative CP Violation
We discuss the feasibility of spontaneous CP violation being induced by
radiative corrections in 2HDM's. Specifically, we analyze the cases of
gaugino/higgsino effect on MSSM, and a new model with an extra exotic quark
doublet. The new model, while demonstrating well the Georgi-Pais theorem, is
also expected to be phenomenlogically interesting.Comment: 8 pages + cover, 3 figures incoporated, in latex with aipproc.sty
/aipproc.cls, talk given by O.K. at MRST '9
CORE: Augmenting Regenerating-Coding-Based Recovery for Single and Concurrent Failures in Distributed Storage Systems
Data availability is critical in distributed storage systems, especially when
node failures are prevalent in real life. A key requirement is to minimize the
amount of data transferred among nodes when recovering the lost or unavailable
data of failed nodes. This paper explores recovery solutions based on
regenerating codes, which are shown to provide fault-tolerant storage and
minimum recovery bandwidth. Existing optimal regenerating codes are designed
for single node failures. We build a system called CORE, which augments
existing optimal regenerating codes to support a general number of failures
including single and concurrent failures. We theoretically show that CORE
achieves the minimum possible recovery bandwidth for most cases. We implement
CORE and evaluate our prototype atop a Hadoop HDFS cluster testbed with up to
20 storage nodes. We demonstrate that our CORE prototype conforms to our
theoretical findings and achieves recovery bandwidth saving when compared to
the conventional recovery approach based on erasure codes.Comment: 25 page
WASP-12b as a prolate, inflated and disrupting planet from tidal dissipation
The class of exotic Jupiter-mass planets that orbit very close to their
parent stars were not explicitly expected before their discovery. The recently
found transiting planet WASP-12b has a mass Mp = 1.4(+/-0.1) Jupiter masses
(MJ), a mean orbital distance of only 3.1 stellar radii (meaning it is subject
to intense tidal forces), and a period of 1.1 days. Its radius 1.79(+/- 0.09)
RJ is unexpectedly large and its orbital eccentricity 0.049(+/-0:015) is even
more surprising as such close orbits are in general quickly circularized. Here
we report an analysis of its properties, which reveals that the planet is
losing mass to its host star at a rate ~ 10^-7 MJ yr^-1. The planets surface is
distorted by the stars gravity and the light curve produced by its prolate
shape will differ by about ten per cent from that of a spherical planet. We
conclude that dissipation of the stars tidal perturbation in the planets
convective envelope provides the energy source for its large volume. We predict
up to 10mJy CO band-head (2.292 micron) emission from a tenuous disk around the
host star, made up of tidally stripped planetary gas. It may also contain a
detectable resonant super-Earth, as a hypothetical perturber that continually
stirs up WASP-12b's eccentricity.Comment: Accepted to Nature, 14 pages, 1 figur
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Effective video multicast over wireless internet
With the rapid growth of wireless networks and great success of Internet video, wireless video services are expected to be widely deployed in the near future. As different types of wireless networks are converging into all IP networks, i.e., the Internet, it is important to study video delivery over the wireless Internet. This paper proposes a novel end-system based adaptation protocol calledWireless Hybrid Adaptation Layered Multicast (WHALM) protocol for layered video multicast over wireless Internet. In WHALM the sender dynamically collects bandwidth distribution from the receivers and uses an optimal layer rate allocation mechanism to reduce the mismatches between the coarse-grained layer subscription levels and the heterogeneous and dynamic rate requirements from the receivers, thus maximizing the degree of satisfaction of all the receivers in a multicast session. Based on sampling theory and theory of probability, we reduce the required number of bandwidth feedbacks to a reasonable degree and use a scalable feedback mechanism to control the feedback process practically. WHALM is also tuned to perform well in wireless networks by integrating an end-to-end loss differentiation algorithm (LDA) to differentiate error losses from congestion losses at the receiver side. With a series of simulation experiments over NS platform, WHALM has been proved to be able to greatly improve the degree of satisfaction of all the receivers while avoiding congestion collapse on the wireless Internet
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