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Automatic Detection of Clear-Sky Periods From Irradiance Data
Recent degradation studies have highlighted the importance of considering cloud cover when calculating degradation rates, finding more reliable values when the data are restricted to clear sky periods. Several automated methods of determining clear sky periods have been previously developed, but parameterizing and testing the models has been difficult. In this paper, we use clear sky classifications determined from satellite data to develop an algorithm that determines clear sky periods using only measured irradiance values and modeled clear sky irradiance as inputs. This method is tested on global horizontal irradiance (GHI) data from ground collectors at six sites across the United States and compared against independent satellite-based classifications. First, 30 separate models were optimized on each individual site at GHI data intervals of 1, 5, 10, 15, and 30 min (sampled on the first minute of the interval). The models had an average F0.5 score of 0.949 ± 0.035 on a holdout test set. Next, optimizations were performed by aggregating data from different locations at the same interval, yielding one model per data interval. This paper yielded an average F0.5 of 0.946 ± 0.037. A final, 'universal' optimization that was trained on data from all sites at all intervals provided an F0.5 score of 0.943 ± 0.040. The optimizations all provide improvements on a prior, unoptimized clear sky detection algorithm that produces F0.5 scores that average to 0.903 ± 0.067. Our paper indicates that a single algorithm can accurately classify clear sky periods across locations and data sampling intervals
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
Shift in the LHC Higgs diphoton mass peak from interference with background
The Higgs diphoton amplitude from gluon fusion at the LHC interferes with the
continuum background induced by quark loops. I investigate the effect of this
interference on the position of the diphoton invariant mass peak used to help
determine the Higgs mass. At leading order, the interference shifts the peak
towards lower mass by an amount of order 150 MeV or more, with the precise
value dependent on the methods used to analyze and fit the data.Comment: 10 pages. v2: comments on scale variation added, reference adde
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
Charged-Lepton-Flavour Violation in Kaon Decays in Supersymmetric Theories
We discuss rare kaon decays that violate charged-lepton flavour conservation
in supersymmetric theories with and without R parity, in view of possible
experiments using an intense proton source as envisaged for a neutrino factory.
In the Minimal Supersymmetric Standard Model, such decays are generated by box
diagrams involving charginos and neutralinos, but the limits from \mu -> e
\gamma, \mu-e conversion and \Delta m_K constrain the branching ratios to
challengingly small values. However, this is no longer the case in R-violating
theories, where such decays may occur at tree level at rates close to the
present experimental limits. Within this framework, we obtain bounds on
products of LL\bar{E} and LQ\bar{D} operators from the experimental upper
limits on K^0 -> \mu^\pm e^\mp and K^{\pm,0} -> \pi^{\pm,0} \mu^\pm e^\mp
decays. We also note the possibility of like-sign lepton decays K^\pm ->
\pi^\mp \ell^\pm \ell^\pm in the presence of non-zero \tilde{b}_L-\tilde{b}_R
mixing. We conclude that rare kaon decays violating charged-lepton flavour
conservation could be an interesting signature of R violation.Comment: 25 pages, 6 figures, Prepared for the Kaon Physics Working Group as
part of the ECFA/CERN study of Neutrino Factory & Muon Storage Rings At CERN.
Referencies added, constraints update
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
Quantum Decoherence in a D-Foam Background
Within the general framework of Liouville string theory, we construct a model
for quantum D-brane fluctuations in the space-time background through which
light closed-string states propagate. The model is based on monopole and vortex
defects on the world sheet, which have been discussed previously in a treatment
of 1+1-dimensional black-hole fluctuations in the space-time background, and
makes use of a T-duality transformation to relate formulations with Neumann and
Dirichlet boundary conditions. In accordance with previous general arguments,
we derive an open quantum-mechanical description of this D-brane foam which
embodies momentum and energy conservation and small mean energy fluctuations.
Quantum decoherence effects appear at a rate consistent with previous
estimates.Comment: 16 pages, Latex, two eps figures include
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