6,093 research outputs found
Planning the Future of U.S. Particle Physics (Snowmass 2013): Chapter 6: Accelerator Capabilities
These reports present the results of the 2013 Community Summer Study of the
APS Division of Particles and Fields ("Snowmass 2013") on the future program of
particle physics in the U.S. Chapter 6, on Accelerator Capabilities, discusses
the future progress of accelerator technology, including issues for high-energy
hadron and lepton colliders, high-intensity beams, electron-ion colliders, and
necessary R&D for future accelerator technologies.Comment: 26 page
Prospects for the Search for a Standard Model Higgs Boson in ATLAS using Vector Boson Fusion
The potential for the discovery of a Standard Model Higgs boson in the mass
range m_H < 2 m_Z in the vector boson fusion mode has been studied for the
ATLAS experiment at the LHC. The characteristic signatures of additional jets
in the forward regions of the detector and of low jet activity in the central
region allow for an efficient background rejection. Analyses for the H -> WW
and H -> tau tau decay modes have been performed using a realistic simulation
of the expected detector performance. The results obtained demonstrate the
large discovery potential in the H -> WW decay channel and the sensitivity to
Higgs boson decays into tau-pairs in the low-mass region around 120 GeV.Comment: 20 pages, 13 ps figures, uses EPJ style fil
Hierarchical Multimodel Ensemble Estimates of Soil Water Retention with Global Coverage
A correct quantification of mass and energy exchange processes among land
surface and atmosphere requires an accurate description of unsaturated soil
hydraulic properties. Soil pedotransfer functions (PTFs) have been widely used
to predict soil hydraulic parameters. Here, 13 PTFs were grouped according to
input data requirements and evaluated against a well-documented soil database
with global coverage. Weighted ensembles (calibrated by four groups and the
full 13-member set of PTFs) were shown to have improved performance over
individual PTFs in terms of root mean square error and other model selection
criteria. Global maps of soil water retention data from the ensemble models as
well as their uncertainty were provided. These maps demonstrate that five PTF
ensembles tend to have different estimates, especially in middle and high
latitudes in the Northern Hemisphere. Our full 13-member ensemble model
provides more accurate estimates than PTFs that are currently being used in
earth system models
Simplified Multistep Outflow Method to Estimate Unsaturated Hydraulic Functions for Coarse-Textured Soils
Although the multistep outfl ow (MSO) method is well suited for the estimation of soil hydraulic properties by
inverse solution techniques, this method has not been widely adopted because it requires advanced instrumentation
and is time consuming. Th e objective of this study was to develop a modifi ed version of the multistep outfl ow
technique that largely simplifi es laboratory procedures and reduces costs and time. Th e numerical inversion
procedures require applying user-friendly HYDRUS soft ware to estimate fi tting parameters for soil water retention
and unsaturated hydraulic conductivity curves. Whereas values of saturated water content and saturated hydraulic
conductivity must be measured independently, the remaining functional parameters are estimated using an inverse
solution of a transient drainage experiment using multiple suction steps and a hanging water column, with drainage
outfl ows measured during drainage. A comparison test showed that the simplifi ed experiment without tensiometric
measurements provided suffi cient information in the parameter identifi cation compared with a traditional pressure
outfl ow experiment with tensiometric measurements for an Oso Flaco sand and a loamy sand fi eld soil in the
suction range of 0 to 17 kPa
The Higgs Working Group: Summary Report (2001)
Report of the Higgs working group for the Workshop `Physics at TeV
Colliders', Les Houches, France, 21 May - 1 June 2001. It contains 7 separate
sections: A. Theoretical Developments B. Higgs Searches at the Tevatron C.
Experimental Observation of an invisible Higgs Boson at LHC D. Search for the
Standard Model Higgs Boson using Vector Boson Fusion at the LHC E. Study of the
MSSM channel at the LHC F. Searching for Higgs Bosons in
Production G. Studies of Charged Higgs Boson Signals for the
Tevatron and the LHCComment: 120 pages, latex, many figures, proceedings of the Workshop `Physics
at TeV Colliders', Les Houches, France, 21 May - 1 June 2001, full Author
list included in paper. Typos corrected, author list and acknowledgements
completed. Convernors: D. Cavalli, A. Djouadi, K. Jakobs, A. Nikitenko, M.
Spira, C.E.M. Wagner, W.-M. Ya
A search for W bb and W Higgs production in ppbar collisions at sqrt(s)=1.96 TeV
We present a search for W b \bar{b} production in p \bar{p} collisions at
sqrt{s}=1.96 TeV in events containing one electron, an imbalance in transverse
momentum, and two b-tagged jets. Using 174 pb-1 of integrated luminosity
accumulated by the D0 experiment at the Fermilab Tevatron collider, and the
standard-model description of such events, we set a 95% C.L. upper limit on W b
\bar{b}WH--$135
GeV.Comment: 7 pages, 4 figures, 1 table, submitted to Physical Review Letter
Excess Higgs Production in Neutralino Decays
The ATLAS and CMS experiments have recently claimed discovery of a Higgs
boson-like particle at ~5 sigma confidence and are beginning to test the
Standard Model predictions for its production and decay. In a variety of
supersymmetric models, a neutralino NLSP can decay dominantly to the Higgs and
the LSP. In natural SUSY models, a light third generation squark decaying
through this chain can lead to large excess Higgs production while evading
existing BSM searches. Such models can be observed at the 8 TeV LHC in channels
exploiting the rare diphoton decays of the Higgs produced in the cascade decay.
Identifying a diphoton resonance in association with missing energy, a lepton,
or b-tagged jets is a promising search strategy for discovery of these models,
and would immediately signal new physics involving production of a Higgs boson.
We also discuss the possibility that excess Higgs production in these SUSY
decays can be responsible for enhancements of up to 50% over the SM prediction
for the observed rate in the existing inclusive diphoton searches, a scenario
which would likely by the end of the 8 TeV run be accompanied by excesses in
the diphoton + lepton/MET and SUSY multi-lepton/b searches and a potential
discovery in a diphoton + 2b search.Comment: 42 pages, 19 figure
Measurement of the Ratio of B+ and B0 Meson Lifetimes
The ratio of B+ and B0 meson lifetimes was measured using data collected in
2002-2004 by the D0 experiment in Run II of the Fermilab Tevatron Collider.
These mesons were reconstructed in B -> mu+ nu D*- X decays, which are
dominated by B0, and B ->mu+ nu D0bar X decays, which are dominated by B+. The
ratio of lifetimes is measured to be t+/t0 = 1.080 +- 0.016(stat) +-
0.014(syst).Comment: 7 pages, 2 figures, LaTeX, to be submitted to Physical Review Letter
A Search for the Flavor-Changing Neutral Current Decay B0_s -> mu^+mu^- in pp(bar) Collisions at \sqrt{s} = 1.96 TeV with the D0 Detector
We present the results of a search for the flavor-changing neutral current
decay B0_s -> mu+ mu- using a data set with integrated luminosity of 240
pb^{-1} of pp(bar) collisions at sqrt{s}=1.96 TeV collected with the D0
detector in Run II of the Fermilab Tevatron collider. We find the upper limit
on the branching fraction to be Br(B0_s -> mu+ mu-) \leq 5.0 x 10^{-7} at the
95% C.L. assuming no contributions from the decay B0_d -> mu+ mu- in the signal
region. This limit is the most stringent upper bound on the branching fraction
B0_s -> mu+ mu- to date.Comment: 7 pages, 3 figures, LaTeX, to be submitted to Physical Review
Letters, minor changes to text, reference adde
Study of events and limits on anomalous and couplings in ppbar collisions at TeV
We present a measurement of the Z\gamma production cross section and limits
on anomalous ZZ\gamma and Z\gamma\gamma couplings for form-factor scales of
Lambda = 750 and 1000 GeV. The measurement is based on 138 (152) candidate
events in the ee\gamma (\mu\mu\gamma) final state using 320 (290) pb^{-1} of
ppbar collisions at \sqrt{s} = 1.96 TeV. The 95% C.L. limits on real and
imaginary parts of individual anomalous couplings are |h_{10,30}^{Z}|<0.23,
|h_{20,40}^{Z}|<0.020, |h_{10,30}^{\gamma}|<0.23, and
|h_{20,40}^{\gamma}|<0.019 for Lambda = 1000 GeV.Comment: submitted to Phys. Rev. Letter
- …