3,543 research outputs found
ATLAS discovery potential for a heavy charged Higgs boson
The sensitivity of the ATLAS detector to the discovery of a heavy charged
Higgs boson is presented. Assuming a heavy SUSY spectrum, the most promising
channels above the top quark mass are and
which provide coverage in the low and high
regions up to GeV. The achievable precisions on the
charged Higgs mass and determination are also discussed. The
channel, though restricted to a small MSSM parameter
space, shows a viable signal in NMSSM where the parameter space is less
constrained. The observation of the channel may
constitute a distinctive evidence for models with singlet neutrinos in large
extra dimensions.Comment: 18 page
Performance improvement of the multicell cavity prototype for proton Linac projects
The CEA-Saclay / IPN-Orsay collaboration allowed to manufacture a multicell superconducting RF cavity prototype for proton linac. Since the first experimental results [1], obtained in a vertical cryostat and the horizontal cryostat CryHoLab, the accelerating field Eacc has been recently increased up to 19 MV/m with a quality factor Q0 = 9.109 and a limitation by quench. However some improvements are still needed, in particular to suppress the field emission above 16 MV/m
The Hydration Structure at Yttria-Stabilized Cubic Zirconia (110)-Water Interface with Sub-Angstrom Resolution
The interfacial hydration structure of yttria-stabilized cubic zirconia (110) surface in contact with water was determined with ~0.5 Å resolution by high-resolution X-ray reflectivity measurement. The terminal layer shows a reduced electron density compared to the following substrate lattice layers, which indicates there are additional defects generated by metal depletion as well as intrinsic oxygen vacancies, both of which are apparently filled by water species. Above this top surface layer, two additional adsorbed layers are observed forming a characteristic interfacial hydration structure. The first adsorbed layer shows abnormally high density as pure water and likely includes metal species, whereas the second layer consists of pure water. The observed interfacial hydration structure seems responsible for local equilibration of the defective surface in water and eventually regulating the long-term degradation processes. The multitude of water interactions with the zirconia surface results in the complex but highly ordered interfacial structure constituting the reaction front.ope
Bottom Production
We review the prospects for bottom production physics at the LHC.Comment: 74 pages, Latex, 71 figures, to appear in the Report of the ``1999
CERN Workshop on SM physics (and more) at the LHC'', P. Nason, G. Ridolfi, O.
Schneider G.F. Tartarelli, P. Vikas (conveners
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
Low energy electron/recoil discrimination for directional Dark Matter detection
Directional detection is a promising Dark Matter search strategy. Even though
it could accommodate to a sizeable background contamination, electron/recoil
discrimination remains a key and challenging issue as for direction-insensitive
detectors. The measurement of the 3D track may be used to discriminate
electrons from nuclear recoils. While a high rejection power is expected above
20 keV ionization, a dedicated data analysis is needed at low energy. After
identifying discriminant observables, a multivariate analysis, namely a Boosted
Decision Tree, is proposed, enabling an efficient event tagging for Dark Matter
search. We show that it allows us to optimize rejection while keeping a rather
high efficiency which is compulsory for rare event search.With respect to a
sequential analysis, the rejection is about 20 times higher with a multivariate
analysis, for the same Dark Matter exclusion limit.Comment: 20 pages, 20 figure
Measurement of the t-channel single top quark production cross section
The D0 collaboration reports direct evidence for electroweak production of
single top quarks through the t-channel exchange of a virtual W boson. This is
the first analysis to isolate an individual single top quark production
channel. We select events containing an isolated electron or muon, missing
transverse energy, and two, three or four jets from 2.3 fb^-1 of ppbar
collisions at the Fermilab Tevatron Collider. One or two of the jets are
identified as containing a b hadron. We combine three multivariate techniques
optimized for the t-channel process to measure the t- and s-channel cross
sections simultaneously. We measure cross sections of 3.14 +0.94 -0.80 pb for
the t-channel and 1.05 +-0.81 pb for the s-channel. The measured t-channel
result is found to have a significance of 4.8 standard deviations and is
consistent with the standard model prediction.Comment: 7 pages, 6 figure
Measurement of the B0_s semileptonic branching ratio to an orbitally excited D_s** state, Br(B0_s -> Ds1(2536) mu nu)
In a data sample of approximately 1.3 fb-1 collected with the D0 detector
between 2002 and 2006, the orbitally excited charm state D_s1(2536) has been
observed with a measured mass of 2535.7 +/- 0.6 (stat) +/- 0.5 (syst) MeV via
the decay mode B0_s -> D_s1(2536) mu nu X. A first measurement is made of the
branching ratio product Br(b(bar) -> D_s1(2536) mu nu X).Br(D_s1(2536)->D*
K0_S). Assuming that D_s1(2536) production in semileptonic decay is entirely
from B0_s, an extraction of the semileptonic branching ratio Br(B0_s ->
D_s1(2536) mu nu X) is made.Comment: 7 pages, 2 figures, LaTeX, version with minor changes as accepted by
Phys. Rev. Let
Simultaneous measurement of the ratio B(t->Wb)/B(t->Wq) and the top quark pair production cross section with the D0 detector at sqrt(s)=1.96 TeV
We present the first simultaneous measurement of the ratio of branching
fractions, R=B(t->Wb)/B(t->Wq), with q being a d, s, or b quark, and the top
quark pair production cross section sigma_ttbar in the lepton plus jets channel
using 0.9 fb-1 of ppbar collision data at sqrt(s)=1.96 TeV collected with the
D0 detector. We extract R and sigma_ttbar by analyzing samples of events with
0, 1 and >= 2 identified b jets. We measure R = 0.97 +0.09-0.08 (stat+syst) and
sigma_ttbar = 8.18 +0.90-0.84 (stat+syst)} +/-0.50 (lumi) pb, in agreement with
the standard model prediction.Comment: submitted to Phys.Rev.Letter
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