1,296 research outputs found
Top Background Extrapolation for H -> WW Searches at the LHC
A leading order (LO) analysis is presented that demonstrates that key top
backgrounds to H -> W^+W^- -> l^\pm l^\mp \sla{p}_T decays in weak boson fusion
(WBF) and gluon fusion (GF) at the CERN Large Hadron Collider can be
extrapolated from experimental data with an accuracy of order 5% to 10%. If LO
scale variation is accepted as proxy for the theoretical error, parton level
results indicate that the tt~j background to the H -> WW search in WBF can be
determined with a theoretical error of about 5%, while the tt~ background to
the H -> WW search in GF can be determined with a theoretical error of better
than 1%. Uncertainties in the parton distribution functions contribute an
estimated 3% to 10% to the total error.Comment: 17 pages, 9 tables, 4 figures; LO caveat emphasized, version to be
published in Phys. Rev.
Mapping of odor-related neuronal activity in the olfactory bulb by high-resolution 2-deoxyglucose autoradiography.
Magnetocardiography with a modular spin-exchange relaxation free atomic magnetometer array
We present a portable four-channel atomic magnetometer array operating in the
spin exchange relaxation-free regime. The magnetometer array has several design
features intended to maximize its suitability for biomagnetic measurement,
specifically foetal magnetocardiography, such as a compact modular design, and
fibre coupled lasers. The modular design allows the independent positioning and
orientation of each magnetometer, in principle allowing for non-planar array
geometries. Using this array in a magnetically shielded room, we acquire adult
magnetocadiograms. These measurements were taken with a 6-11 fT Hz^(-1/2)
single-channel baseline sensitivity that is consistent with the independently
measured noise level of the magnetically shielded room.Comment: 15 pages, 5 figure
Inadequacy of zero-width approximation for a light Higgs boson signal
In the Higgs search at the LHC, a light Higgs boson (115 GeV <~ M_H <~ 130
GeV) is not excluded by experimental data. In this mass range, the width of the
Standard Model Higgs boson is more than four orders of magnitude smaller than
its mass. The zero-width approximation is hence expected to be an excellent
approximation. We show that this is not always the case. The inclusion of
off-shell contributions is essential to obtain an accurate Higgs signal
normalisation at the 1% precision level. For gg (-> H) -> VV, V= W,Z, O(10%)
corrections occur due to an enhanced Higgs signal in the region M_VV > 2 M_V,
where also sizable Higgs-continuum interference occurs. We discuss how
experimental selection cuts can be used to exclude this region in search
channels where the Higgs invariant mass cannot be reconstructed. We note that
the H -> VV decay modes in weak boson fusion are similarly affected.Comment: 26 pages, 18 figures, 6 tables; added references, expanded
introduction, version to appear in JHE
New one-loop techniques and first applications to LHC phenomenology
In this talk we describe our approach for the computation of multi-leg
one-loop amplitudes and present some first results relevant for LHC
phenomenology.Comment: 5 pages, to appear in the proceedings of the conference "Loops and
Legs", Eisenach, 200
Finite-Width Effects in Top Quark Production at Hadron Colliders
Production cross sections for t\bar{t} and t\bar{t}j events at hadron
colliders are calculated, including finite width effects and off resonance
contributions for the entire decay chain, t --> bW --> b\ell\nu, for both top
quarks. Resulting background rates to Higgs search at the CERN LHC are updated
for inclusive H --> WW studies and for H --> \tau\tau and H --> WW decays in
weak boson fusion events. Finite width effects are large, increasing
t\bar{t}(j) rates by 20% or more, after typical cuts which are employed for
top-background rejection.Comment: 32 pages, 11 figures, 7 tables; minor changes, reference added, to be
published in Phys. Rev.
Higgs Physics at Future Colliders: recent theoretical developments
I review the physics of the Higgs sector in the Standard Model and its
minimal supersymmetric extension, the MSSM. I will discuss the prospects for
discovering the Higgs particles at the upgraded Tevatron, at the Large Hadron
Collider, and at a future high--energy linear collider with
centre--of--mass energy in the 350--800 GeV range, as well as the possibilities
for studying their fundamental properties. Some emphasis will be put on the
theoretical developments which occurred in the last two years.Comment: 20 pages, latex, 12 figures. Talk given at PASCOS 2003 (Bombay,
India
QCD corrections to electroweak l nu_l jj and l^+ l^- jj production
The production of W or Z bosons in association with two jets is an important
background to the Higgs boson search in vector-boson fusion at the LHC. The
purely electroweak component of this background is dominated by vector-boson
fusion, which exhibits kinematic distributions very similar to the Higgs boson
signal. We consider the next-to-leading order QCD corrections to the
electroweak production of l nu_l jj and l^+ l^- jj events at the LHC, within
typical vector-boson fusion cuts. We show that the QCD corrections are modest,
increasing the total cross sections by about 10%. Remaining scale uncertainties
are below 2%. A fully-flexible next-to-leading order partonic Monte Carlo
program allows to demonstrate these features for cross sections within typical
vector-boson-fusion acceptance cuts. Modest corrections are also found for
distributions.Comment: 26 pages, 10 figures. PRD final version. One reference corrected,
introduction expande
Lowering the energy threshold in COSINE-100 dark matter searches
COSINE-100 is a dark matter detection experiment that uses NaI(Tl) crystal
detectors operating at the Yangyang underground laboratory in Korea since
September 2016. Its main goal is to test the annual modulation observed by the
DAMA/LIBRA experiment with the same target medium. Recently DAMA/LIBRA has
released data with an energy threshold lowered to 1 keV, and the persistent
annual modulation behavior is still observed at 9.5. By lowering the
energy threshold for electron recoils to 1 keV, COSINE-100 annual modulation
results can be compared to those of DAMA/LIBRA in a model-independent way.
Additionally, the event selection methods provide an access to a few to sub-GeV
dark matter particles using constant rate studies. In this article, we discuss
the COSINE-100 event selection algorithm, its validation, and efficiencies near
the threshold
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