3,080 research outputs found
One-loop Higgs boson production at the Linear Collider within the general two-Higgs-doublet model: e+eâ versus γγ
present an updated overview on the phenomenology of one-loop
Higgs boson production at Linear Colliders within the general Two-Higgs-Doublet Model (2HDM). First we report on the Higgs boson pair production, and associated Higgs-Z boson production, at O(α3ew) from e+eâ collisions. These channels furnish cross-sections in the range of 10â100 fb for âs = 0.5TeV and exhibit potentially large radiative corrections (|ÎŽr| ⌠50%), whose origin can be traced back to the genuine enhancement capabilities of the triple Higgs boson self-interactions. Next we consider the loop-induced production of a single Higgs boson from direct γγ scattering. We single out sizable departures from the expected γγ â h rates in the Standard Model, which are again correlated to trademark dynamical features of the
2HDMânamely the balance of the non-standard Higgs/gauge, Higgs/fermion and Higgs self-interactions, which leads to sizable (destructive) interference effects. This pattern of quantum effects is unmatched in the MSSM, and could hence provide distinctive footprints of non-supersymmetric Higgs boson physics. Both calculations are revisited within a common, brought-to-date framework and include, in particular, the most stringent bounds from unitarity and flavor physics
Quantum effects on Higgs-strahlung events at Linear Colliders within the general 2HDM
The associated production of neutral Higgs bosons with the Z gauge boson is
investigated in the context of the future linear colliders, such as the ILC and
CLIC, within the general two-Higgs-doublet model (2HDM). We compute the
corresponding production cross-sections at one-loop, in full consistency with
the available theoretical and phenomenological constraints. We find that the
wave-function renormalization corrections to the external Higgs fields are the
dominant source of the quantum effects, which turn out to be large and
negative, and located predominantly in the region around \tan\beta=1 and
moderate values of the parameter \lambda_5 (being \lambda_5 < 0). This behavior
can be ultimately traced back to the enhancement potential of the triple Higgs
boson self-couplings, a trademark feature of the 2HDM with no counterpart in
the Higgs sector of the Minimal Supersymmetric Standard Model. The predicted
Higgs-strahlung rates comfortably reach a few tens of femtobarn, which means
barely 10^3 - 10^4 events per 500 inverse femtobarn of integrated luminosity.
Due to their great complementarity, we argue that the combined analysis of the
Higgs-strahlung events and the previously computed one-loop Higgs-pair
production processes could be instrumental to probe the structure of the Higgs
sector at future linac facilities.Comment: LaTeX, 16 pages, 9 Figures, 2 Tables. Extended discussion, references
added, matches published version in Phys. Rev.
Positron detection in silica monoliths for miniaturised quality control of PET radiotracers
We demonstrate the use of the miniaturised Medipix positron sensor for detection of the clinical PET radiotracer, [â¶âžGa]gallium-citrate, on a silica-based monolith, towards microfluidic quality control. The system achieved a far superior signal-to-noise ratio compared to conventional sodium iodide-based radio-HPLC detection and allowed real-time visualisation of positrons in the monolith
High Precision Photometry for K2 Campaign 1
The two reaction wheel K2 mission promises and has delivered new discoveries
in the stellar and exoplanet fields. However, due to the loss of accurate
pointing, it also brings new challenges for the data reduction processes. In
this paper, we describe a new reduction pipeline for extracting high precision
photometry from the K2 dataset, and present public light curves for the K2
Campaign 1 target pixel dataset. Key to our reduction is the derivation of
global astrometric solutions from the target stamps, from which accurate
centroids are passed on for high precision photometry extraction. We extract
target light curves for sources from a combined UCAC4 and EPIC catalogue --
this includes not only primary targets of the K2 campaign 1, but also any other
stars that happen to fall on the pixel stamps. We provide the raw light curves,
and the products of various detrending processes aimed at removing different
types of systematics. Our astrometric solutions achieve a median residual of ~
0.13". For bright stars, our best 6.5 hour precision for raw light curves is
~20 parts per million (ppm). For our detrended light curves, the best 6.5 hour
precisions achieved is ~15 ppm. We show that our detrended light curves have
fewer systematic effects (or trends, or red-noise) than light curves produced
by other groups from the same observations. Example light curves of transiting
planets and a Cepheid variable candidate, are also presented. We make all light
curves public, including the raw and de-trended photometry, at
http://k2.hatsurveys.org.Comment: submitted to MNRA
Seiche- and storm-driven benthic oxygen uptake in a eutrophic freshwater bay determined with aquatic eddy covariance
Oxygen depletion in bottom waters of lakes and coastal regions is expanding worldwide. To examine the causes of hypoxia, we quantified the drivers of benthic oxygen uptake in Green Bay, Lake Michigan, USA, using 2 techniques, aquatic eddy covariance and sediment core incubation. We investigated benthic oxygen uptake along a gradient in C deposition, including shallow water near the riverine source of eutrophication and deeper waters of lower Green Bay where high net sediment deposition occurs. Time-averaged eddy covariance oxygen uptake was high near the source of eutrophication (11.5 mmol mâ2 dâ1) and at the shallower of the high deposition sites (9.8 mmol mâ2 dâ1). The eddy covariance technique revealed a decrease in benthic oxygen uptake with depth at the high deposition sites. These patterns were consistent with benthic uptake being driven by the deposition of autochthonous production. Additionally, eddy covariance revealed a nearly proportional relationship between benthic oxygen uptake and current velocity at all sites. Specifically, because of the lake seiche, water velocity typically varied 3Ă at a site and caused a 3Ă variation in benthic oxygen uptake. A summer storm also doubled bottom-water velocities and caused a further doubling of uptake to 28 mmol mâ2 dâ1. This high sensitivity of benthic oxygen uptake to seiche-driven water velocities indicates that redox conditions in surficial cohesive sediments are highly dynamic
Observation of strongly entangled photon pairs from a nanowire quantum dot
A bright photon source that combines high-fidelity entanglement, on-demand
generation, high extraction efficiency, directional and coherent emission, as
well as position control at the nanoscale is required for implementing
ambitious schemes in quantum information processing, such as that of a quantum
repeater. Still, all of these properties have not yet been achieved in a single
device. Semiconductor quantum dots embedded in nanowire waveguides potentially
satisfy all of these requirements; however, although theoretically predicted,
entanglement has not yet been demonstrated for a nanowire quantum dot. Here, we
demonstrate a bright and coherent source of strongly entangled photon pairs
from a position controlled nanowire quantum dot with a fidelity as high as
0.859 +/- 0.006 and concurrence of 0.80 +/- 0.02. The two-photon quantum state
is modified via the nanowire shape. Our new nanoscale entangled photon source
can be integrated at desired positions in a quantum photonic circuit, single
electron devices and light emitting diodes.Comment: Article and Supplementary Information with open access published at:
http://www.nature.com/ncomms/2014/141031/ncomms6298/full/ncomms6298.htm
Compilability of Abduction
Abduction is one of the most important forms of reasoning; it has been
successfully applied to several practical problems such as diagnosis. In this
paper we investigate whether the computational complexity of abduction can be
reduced by an appropriate use of preprocessing. This is motivated by the fact
that part of the data of the problem (namely, the set of all possible
assumptions and the theory relating assumptions and manifestations) are often
known before the rest of the problem. In this paper, we show some complexity
results about abduction when compilation is allowed
Submillimetric spectroscopic observations of volatiles in comet C/2004 Q2 (Machholz)
We aim to determine the production rates of several parent and product
volatiles and the 12C/13C isotopic carbon ratio in the long-period comet C/2004
Q2 (Machholz), which is likely to originate from the Oort Cloud. The line
emission from several molecules in the coma was measured with high
signal-to-noise ratio in January 2005 at heliocentric distance of 1.2 AU by
means of high-resolution spectroscopic observations using the Submillimeter
Telescope (SMT). We have obtained production rates of several volatiles (CH3OH,
HCN, H13CN, HNC, H2CO, CO and CS) by comparing the observed and simulated
line-integrated intensities. Furthermore, multiline observations of the CH3OH
(7-6) series allow us to estimate the rotational temperature using the rotation
diagram technique. We find that the CH3OH population distribution of the levels
sampled by these lines can be described by a rotational temperature of 40 \pm 3
K. Derived mixing ratios relative to hydrogen cyanide are
CO/CH3OH/H2CO/CS/HNC/H13CN/HCN = 30.9/24.6/4.8/0.57/0.031/0.013/1 assuming a
pointing offset of 8" due to the uncertain ephemeris at the time of the
observations and the telescope pointing error. The measured relative molecular
abundances in C/2004 Q2 (Machholz) are between low- to typical values of those
obtained in Oort Cloud comets, suggesting that it has visited the inner solar
system previously and undergone thermal processing. The HNC/HCN abundance ratio
of ~3.1% is comparable to that found in other comets, accounting for the
dependence on the heliocentric distance, and could possibly be explained by
ion-molecule chemical processes in the low-temperature atmosphere. From a
tentative H13CN detection, the measured value of 97 \pm 30 for the H12CN/H13CN
isotopologue pair is consistent with a telluric value.Comment: 14 pages with 11 figures, abridged abstrac
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