5,662 research outputs found
Observability of MSSM Higgs bosons via sparticle decay modes in CMS
We discuss the possibilities to observe the decays of heavy SUSY Higgs bosons
into supersymmetric particles at the LHC. Such an observation would be of
interest either in a discovery search if sparticle modes are the dominant ones,
or in a study of additional decay modes, bringing information on the SUSY
scenario potentially at work. We will focus on the most promising channel where
the heavy neutral Higgses decay into a pair of next-to-lightest neutralinos,
followed by their decay into two leptons and the LSP, thus leading to four
isolated leptons + missing E_T as the main final state signature. A study with
the CMS detector shows that the background (SM + SUSY) can be sufficiently
suppressed and that in the mass region between m_A = 230 and 450 GeV, for low
and intermediate values of tan beta, the signal would be visible provided
neutralinos and sleptons are light enough.Comment: 14 pages, 20 figure
Search for SUSY in (Leptons +) Jets + E_T^miss final states
We study the observability of the squarks and gluinos in CMS at LHC.
Classical E_T^miss + jets final state as well as a number of additional
multilepton signatures (0 leptons, 1 lepton, 2 leptons of the same sign, 2
leptons of the opposite sign and 3 leptons) are investigated . The detection of
these sparticles relies on the observation of an excess of events over Standard
Model background expectations. The study is made in the framework of a minimal
SU(5) mSUGRA model as a function of m_0, m_1/2 for 4 sets of model parameters :
tan(beta) = 2 or 35 and sign(mu) = +/- 1 and for fixed value of A_0 = 0. The
CMS detector response is modelled using CMSJET 4.51 fast MC code (non-GEANT).
The results obtained are presented as 5 sigma detection contours in the m_0,
m_1/2 planes and with optimized selection cuts in various regions of the
parameter space. The result of these investigations is that with integrated
luminosity L=10^5 pb^-1 the squark and gluino mass reach is about 2.5 TeV and
covers most of the interesting parts of parameter space according to neutralino
relic density expectations. The influence of signal and background
cross-section uncertainties on the reach contours is estimated. The effect of
pile-up on signal and background is also discussed. This effect is found to be
insignificant for E_T^miss and single lepton signatures, whilst only a minor
deterioration is seen for multilepton final states.Comment: 28 pages, 28 figure
Construction optimization of fire sheet of exhaust boilers
В работе представлены результаты натурного эксперимента и численных расчетов по оценке влияния качества сварного соединения на температурный режим огневого листа, используемого в качестве поверхностей нагрева в котлах утилизаторах. Разработанная и верифицированная по результатам эксперимента модель позволяет рассчитать температурное поле при любых размерах и сочетаниях материалов элементов конструкции. Проведено сравнение полученных максимальных температур в огневом листе и в экранах из стандартных плавниковых труб при аналогичных граничных условиях.The work presents results of experiment and numerical simulations of a weld quality influence on fire sheet temperature regime, which used as a heating surface in exhaust boilers. The model designed and verified by the results of experiments allows to calculate the temperature field of fire sheet of any sizes and combinations of construction elements materials. A comparison of the maximum temperature in the firing sheet and heating surfaces of standard fin tubes under similar boundary conditions presented
Forward Jets and Energy Flow in Hadronic Collisions
We observe that at the Large Hadron Collider, using forward + central
detectors, it becomes possible for the first time to carry out calorimetric
measurements of the transverse energy flow due to "minijets" accompanying
production of two jets separated by a large rapidity interval. We present
parton-shower calculations of energy flow observables in a high-energy
factorized Monte Carlo framework, designed to take into account QCD logarithmic
corrections both in the large rapidity interval and in the hard transverse
momentum. Considering events with a forward and a central jet, we examine the
energy flow in the interjet region and in the region away from the jets. We
discuss the role of these observables to analyze multiple parton collision
effects.Comment: 9 pages, 5 figures. Version2: added results on azimuthal
distributions and more discussion of energy flow definition using jet
clusterin
Vegetation of the supralittoral and upper sublittoral zones of the Western German Baltic Sea coast: a phytosociological study
Supralittoral and shallow water seaweed communities are particularly exposed to impacts such as climate change and disturbance by humans. Therefore, their classification, the study of composition, and the monitoring of their structural changes are particularly important. A phytosociological survey of the supralittoral and upper sublittoral vegetation of the South West Baltic Sea revealed eight phytobenthos communities with two variants comprising 35 taxa of macrophytes (18 taxa of Chlorophyta, 13 taxa of Rhodophyta and four taxa of Phaeophyceae, Ochrophyta). Five of the eight communities were dominated by Ulvales (Ulva intestinalis, Kornmannia leptoderma, and three Blidingia species), the other three by Fucus vesiculosus. Most Fucus vesiculosus-dominated communities contained U. intestinalis and U. linza as subdominants. Only one of the communities had until now been described as an association ( Ulvetum intestinalis Feldman 1937). The syntaxonomic composition of the investigated vegetation includes both phytocenoses with the domination of green algae ( Ulvetum intestinalis Feldman 1937 and communities of Blidingia marginata, unidentified Blidingia spp. and Kornmannia leptoderma), as well as a number of communities dominated by Fucus vesiculosus. Mainly boreal Atlantic species and cosmopolitans make up the bulk of the species in these associations
Detecting a light Higgs boson at the Fermilab Tevatron through enhanced decays to photon pairs
We analyze the prospects of the Tevatron for finding a Higgs boson in the two
photon decay mode. We conclude that the Standard Model (SM) Higgs boson will
likely not be discovered in this mode. However, we motivate several theories
beyond the SM, including the MSSM, that predict a Higgs boson with enhanced
branching fractions into photons, and calculate the luminosity needed to
discover a general Higgs boson at the Tevatron by a two-photon invariant mass
peak at large transverse momentum. We find that a high luminosity Tevatron will
play a significant role in discovering or constraining these theories.Comment: 20 pages, latex, 5 figure
MSSM Higgs bosons associated with high-pT jets at hadron colliders
The cross section for the production of the lightest neutral Higgs boson in
association with a high-pT hadronic jet, calculated in the framework of the
minimal supersymmetric standard model (MSSM), is presented. The expectations
for the hadronic cross section at the Large Hadron Collider are discussed using
reasonable kinematical cuts. In particular the contributions from superpartner
loops to the cross section and their dependence on the parameters of the MSSM
are investigated and found to be significant. Comparisons show that the
production rate for h0 + jet in the MSSM can differ widely from the
corresponding standard-model prediction.Comment: 20 page
Summary of the SUSY Working Group of the 1999 Les Houches Workshop
The results obtained by the Working Group on Supersymmetry at the 1999 Les
Houches Workshop on Collider Physics are summarized. Separate chapters treat
"general" supersymmetry, R-parity violation, gauge mediated supersymmetry
breaking, and anomaly mediated supersymmetry breaking.Comment: LaTeX, 110 pages with numerous .ps and .eps files. proc.tex is main
tex fil
Giant QCD K-factors beyond NLO
Hadronic observables in Z+jet events can be subject to large NLO corrections
at TeV scales, with K-factors that even reach values of order 50 in some cases.
We develop a method, LoopSim, by which approximate NNLO predictions can be
obtained for such observables, supplementing NLO Z+jet and NLO Z+2-jet results
with a unitarity-based approximation for missing higher loop terms. We first
test the method against known NNLO results for Drell-Yan lepton pt spectra. We
then show our approximate NNLO results for the Z+jet observables. Finally we
examine whether the LoopSim method can provide useful information even in cases
without giant K-factors, with results for observables in dijet events that can
be compared to early LHC data.Comment: 38 pages, 13 figures; v2 includes additional reference
Difficult Scenarios for NMSSM Higgs Discovery at the LHC
We identify scenarios not ruled out by LEP data in which NMSSM Higgs
detection at the LHC will be particularly challenging. We first review the
`no-lose' theorem for Higgs discovery at the LHC that applies if Higgs bosons
do not decay to other Higgs bosons - namely, with L=300 fb^-1, there is always
one or more `standard' Higgs detection channel with at least a 5 sigma signal.
However, we provide examples of no-Higgs-to-Higgs cases for which all the
standard signals are no larger than 7 sigma implying that if the available L is
smaller or the simulations performed by ATLAS and CMS turn out to be overly
optimistic, all standard Higgs signals could fall below 5 sigma even in the
no-Higgs-to-Higgs part of NMSSM parameter space. In the vast bulk of NMSSM
parameter space, there will be Higgs-to-Higgs decays. We show that when such
decays are present it is possible for all the standard detection channels to
have very small significance. In most such cases, the only strongly produced
Higgs boson is one with fairly SM-like couplings that decays to two lighter
Higgs bosons (either a pair of the lightest CP-even Higgs bosons, or, in the
largest part of parameter space, a pair of the lightest CP-odd Higgs bosons). A
number of representative bench-mark scenarios of this type are delineated in
detail and implications for Higgs discovery at various colliders are discussed.Comment: 31 pages, 5 figure
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