40,233 research outputs found
Packet loss characteristics of IPTV-like traffic on residential links
Packet loss is one of the principal threats to quality of experience for IPTV systems. However, the packet loss characteristics of the residential access networks which carry IPTV are not widely understood. We present packet level measurements of streaming IPTV-like traffic over four residential access links, and describe the extent and nature of packet loss we encountered. We discuss the likely impact of these losses for IPTV traffic, and outline steps which can ameliorate this
An experimental study of client-side Spotify peering behaviour
Spotify is a popular music-streaming service which has seen widespread use across Europe. While Spotify’s server-side behaviour has previously been studied, little is known about the client-side behaviour. In this paper, we describe an experimental study where we collect packet headers for Spotify traffic over multiple 24-hour time frames at a client host. Two distinct types of behaviour are observed, when tracks are being downloaded, and when the client is only serving requests from other peers. We also note wide variation in connection lifetimes, as seen in other studies of peer-to-peer systems. These findings are relevant for improving Spotify itself, and for the designers of other hybrid peer-to-peer and server-based distribution architectures
CP-Violating MSSM Higgs Bosons in the Light of LEP 2
In the MSSM, the CP parities of the neutral Higgs bosons may be mixed by
radiative effects induced by explicit CP violation in the third generation of
squarks. To allow for this possibility, we argue that the charged Higgs-boson
mass and tan(beta) should be used to parametrize the MSSM Higgs sector. We
introduce a new benchmark scenario of maximal CP violation appropriate for
direct searches of CP-violating MSSM Higgs bosons. We show that the bounds
established by LEP 2 on the MSSM Higgs sector may be substantially relaxed at
low and intermediate values of tan(beta) in the presence of CP violation, and
comment on possible Higgs boson signatures at LEP 2 within this framework.Comment: 16 pages, LaTeX, 4 encapsulated figure
Neutrino Masses, Mixing Angles and the Unification of Couplings in the MSSM
In the light of the gathering evidence for neutrino
oscillations, coming in particular from the Super-Kamiokande data on
atmospheric neutrinos, we re-analyze the unification of gauge and Yukawa
couplings within the minimal supersymmetric extension of the Standard Model
(MSSM). Guided by a range of different grand-unified models, we stress the
relevance of large mixing in the lepton sector for the question of bottom-tau
Yukawa coupling unification. We also discuss the dependence of the favoured
value of on the characteristics of the high-energy quark and lepton
mass matrices. In particular, we find that, in the presence of large lepton
mixing, Yukawa unification can be achieved for intermediate values of
that were previously disfavoured. The renormalization-group
sensitivity to the structures of different mass matrices may enable Yukawa
unification to serve as a useful probe of GUT models.Comment: 29 pages, latex, 5 figure
Renormalization-Group-Improved Effective Potential for the MSSM Higgs Sector with Explicit CP Violation
We perform a systematic study of the one-loop renormalization-group-improved
effective potential of the minimal supersymmetric extension of the Standard
Model (MSSM), including CP violation induced radiatively by soft trilinear
interactions related to squarks of the third generation. We calculate the
charged and neutral Higgs-boson masses and couplings, including the two-loop
logarithmic corrections that arise from QCD effects, as well as those
associated with the top- and bottom-quark Yukawa couplings. We also include the
potentially large two-loop non-logarithmic corrections induced by one-loop
threshold effects on the top- and bottom-quark Yukawa couplings, due to the
decoupling of the third-generation squarks. Within this minimal CP-violating
framework, the charged and neutral Higgs sectors become intimately related to
one another and therefore require a unified treatment. In the limit of a large
charged Higgs-boson mass, M_{H^+} >> M_Z, the lightest neutral Higgs boson
resembles that in the Standard Model (SM), and CP violation occurs only in the
heavy Higgs sector. Our analysis shows that sizeable radiative effects of CP
violation in the Higgs sector of the MSSM may lead to significant modifications
of previous studies for Higgs-boson searches at LEP2, the Tevatron and the LHC.
In particular, CP violation could enable a relatively light Higgs boson to
escape detection at LEP2.Comment: 55 pages, LaTeX, 9 eps figures, typo in (A.12) eliminate
Virtual RTCP: A Case Study of Monitoring and Repair for UDP-based IPTV Systems
IPTV systems have seen widespread deployment, but often lack robust mechanisms for monitoring the quality of experience. This makes it difficult for network operators to ensure that their services match the quality of traditional broadcast TV systems, leading to consumer dissatisfaction. We present a case study of virtual RTCP, a new framework for reception quality monitoring and reporting for UDP-encapsulated MPEG video delivered over IP multicast. We show that this allows incremental deployment of reporting infrastructure, coupled with effective retransmission-based packet loss repair
Prospects for Discovering Supersymmetry at the LHC
Supersymmetry is one of the best-motivated candidates for physics beyond the
Standard Model that might be discovered at the LHC. There are many reasons to
expect that it may appear at the TeV scale, in particular because it provides a
natural cold dark matter candidate. The apparent discrepancy between the
experimental measurement of g_mu - 2 and the Standard model value calculated
using low-energy e+ e- data favours relatively light sparticles accessible to
the LHC. A global likelihood analysis including this, other electroweak
precision observables and B-decay observables suggests that the LHC might be
able to discover supersymmetry with 1/fb or less of integrated luminosity. The
LHC should be able to discover supersymmetry via the classic missing-energy
signature, or in alternative phenomenological scenarios. The prospects for
discovering supersymmetry at the LHC look very good.Comment: 8 pages, 11 figure
Collider Probes of the MSSM Higgs Sector with Explicit CP Violation
We investigate the hadron collider phenomenology of the Minimal
Supersymmetric Standard Model (MSSM) with explicit CP violation for Higgs
bosons that can be observed in Standard Model search channels: W/ZH(->b-bbar)
at the Tevatron, and gg->H(->gamma-gamma), t-tbar-H(->b-bbar) and
WW->H(->tau+tau-) at the LHC. Our numerical analysis is based on a benchmark
scenario proposed earlier called CPX, which has been designed to showcase the
effects of CP violation in the MSSM, and on several variant benchmarks. In most
of the CPX parameter space, these hadron colliders will find one of the neutral
MSSM Higgs bosons. However, there are small regions of parameter space in which
none of the neutral Higgs bosons can be detected in the standard channels at
the Tevatron and the LHC. This occurs because the neutral Higgs boson with the
largest coupling to W and Z bosons decays predominantly into either two lighter
Higgs bosons or a Higgs boson and a gauge boson, whilst the lighter Higgs boson
has only small couplings to the W and Z bosons and the top quark. For other
choices of CP-violating parameters, all three neutral Higgs bosons can have
significant couplings to W and Z bosons, producing overlapping signatures:
these may or may not be distinguishable from backgrounds. The existence of
these regions of parameters provides a strong motivation for a detailed
experimental simulation of these channels.Comment: 42 pages, 13 figure
High angular resolution observation of the Sunyaev-Zel'dovich effect in the massive z=0.83 cluster ClJ0152-1357
X-ray observations of galaxy clusters at high redshift (z>0.5) indicate that
they are more morphologically complex and less virialized than those at
low-redshift. We present the first subarcmin resolution at 18 GHz observations
of the Sunyaev-Zel'dovich (SZ) effect for ClJ0152-1357 using the Australia
Telescope Compact Array. ClJ0152-1357 is a massive cluster at redshift z=0.83
and has a complex structure including several merging subclumps which have been
studied at optical, X-ray, and radio wavelengths. Our high-resolution
observations indicate a clear displacement of the maximum SZ effect from the
peak of X-ray emission for the most massive sub-clump. This result shows that
the cluster gas within the cluster substructures is not virialised in
ClJ0152-1357 and we suggest that it is still recovering from a recent merger
event. A similar offset of the SZ effect has been recently seen in the `bullet
cluster' by Malu et al. This non-equilibrium situation implies that high
resolution observations are necessary to investigate galaxy cluster evolution,
and to extract cosmological constraints from a comparison of the SZ effect and
X-ray signals.Comment: 5 pages, 4 figures, submitted to ApJ
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