3,087 research outputs found
Bounds on the anomalous vertex arising from the process
We obtain limits on the anomalous coupling through data published
by the L3 Collaboration on the process . Our
analysis leads to bounds on this coupling of order , for an
intermediate mass Higgs boson , two orders of magnitude
above the Standard Model prediction.Comment: 10 pages, 3 figure
Deep GMRT 150 MHz observations of the LBDS-Lynx region: Ultra-Steep Spectrum Radio Sources
It has been known for nearly three decades that high redshift radio galaxies
exhibit steep radio spectra, and hence ultra-steep spectrum radio sources
provide candidates for high-redshift radio galaxies. Nearly all radio galaxies
with z > 3 have been found using this redshift-spectral index correlation. We
have started a programme with GMRT to exploit this correlation at flux density
levels about 10 to 100 times deeper than the known high-redshift radio galaxies
which were identified primarily using the already available radio catalogues.
In our programme, we have obtained deep, high resolution radio observations at
150 MHz with GMRT for several 'deep' fields which are well studied at higher
radio frequencies and in other bands of the electromagnetic spectrum, with an
aim to detect candidate high redshift radio galaxies. In this paper we present
results from the deep 150 MHz observations of LBDS-Lynx field, which has been
already imaged at 327, 610 and 1412 MHz with the WSRT and at 1400 and 4860 MHz
with the VLA. The 150 MHz image made with GMRT has a rms noise of ~0.7 mJy/beam
and a resolution of ~19" X 15". It is the deepest low frequency image of the
LBDS-Lynx field. The source catalog of this field at 150 MHz has about 765
sources down to ~20% of the primary beam response, covering an area of about 15
degree. Spectral index was estimated by cross correlating each source
detected at 150 MHz with the available observations at 327, 610, 1400 and 4860
MHz and also using available radio surveys such as WENSS at 327 MHz and NVSS
and FIRST at 1400 MHz. We find about 150 radio sources with spectra steeper
than 1. About two-third of these are not detected in SDSS, hence are strong
candidate high-redshift radio galaxies, which need to be further explored with
deep infra-red imaging and spectroscopy to estimate the redshift.Comment: Accepted for publication in MNRAS, 24 pages (including 12 pages
online material), 9 Figures, 5 Table
Chromomagnetic Dipole Moment of the Top Quark Revisited
We study the complete one-loop contributions to the chromagnetic dipole
moment of the top quark in the Standard Model, two Higgs doublet
models, topcolor assited technicolor models (TC2), 331 models and extended
models with a single extra dimension. We find that the SM predicts
and that the predictions of the other models are also
consitent with the constraints imposed on by low-energy
precision measurements.Comment: 20 pages, 5 figures, Updat
SEOM clinical guideline for the management of cutaneous melanoma (2020)
Melanoma affects about 6000 patients a year in Spain. A group of medical oncologists from Spanish Society of Medical Oncology (SEOM) and Spanish Multidisciplinary Melanoma Group (GEM) has designed these guidelines to homogenize the management of these patients. The diagnosis must be histological and determination of BRAF status has to be performed in patients with stage ≥ III. Stage I-III resectable melanomas will be treated surgically. In patients with stage III melanoma, adjuvant treatment with immunotherapy or targeted therapy is also recommended. Patients with unresectable or metastatic melanoma will receive treatment with immunotherapy or targeted therapy, the optimal sequence of these treatments remains unclear. Brain metastases require a separate consideration, since, in addition to systemic treatment, they may require local treatment. Patients must be followed up closely to receive or change treatment as soon as their previous clinical condition changes, since multiple therapeutic options are available
Constraints on the non-linear coupling parameter fnl with the Archeops data
We present a Gaussianity analysis of the Archeops Cosmic Microwave Background
(CMB) temperature anisotropy data maps at high resolution to constrain the
non-linear coupling parameter fnl characterising well motivated non-Gaussian
CMB models. We used the data collected by the most sensitive Archeops bolometer
at 143 GHz. The instrumental noise was carefully characterised for this
bolometer, and for another Archeops bolometer at 143 GHz used for comparison.
Angular scales from 27 arcmin to 1.8 degrees and a large fraction of the sky,
21 %, covering both hemispheres (avoiding pixels with Galactic latitude |b| <
15 degrees) were considered.
The three Minkowski functionals on the sphere evaluated at different
thresholds were used to construct a chi-squared statistics for both the
Gaussian and the non-Gaussian CMB models. The Archeops maps were produced with
the Mirage optimal map-making procedure from processed time ordered data. The
analysis is based on simulations of signal (Gaussian and non-Gaussian fnl CMB
models) and noise which were processed in the time domain using the Archeops
pipeline and projected on the sky using the Mirage optimal map-making
procedure.
The Archeops data were found to be compatible with Gaussianity after removal
of highly noisy pixels at high resolution. The non-linear coupling parameter
was constrained to -400 < fnl < 590 at 68% CL and -920 < fnl < 1075 at 95% CL,
for realistic non-Gaussian CMB simulations.Comment: 10 pages, 7 figures, 3 tables. Accepted for publication in A&
P-P Total Cross Sections at VHE from Accelerator Data
Comparison of P-P total cross-sections estimations at very high energies -
from accelerators and cosmic rays - shows a disagreement amounting to more than
10 %, a discrepancy which is beyond statistical errors. Here we use a
phenomenological model based on the Multiple-Diffraction approach to
successfully describe data at accelerator energies. The predictions of the
model are compared with data On the basis of regression analysis we determine
confident error bands, analyzing the sensitivity of our predictions to the
employed data for extrapolation. : using data at 546 and 1.8 TeV, our
extrapolations for p-p total cross-sections are only compatible with the Akeno
cosmic ray data, predicting a slower rise with energy than other cosmic ray
results and other extrapolation methods. We discuss our results within the
context of constraints in the light of future accelerator and cosmic ray
experimental results.Comment: 26 pages aqnd 11 figure
Effective Lagrangian description of the lepton flavor violating decays Z-->li lj
A comprehensive analysis of the lepton flavor violating (LFV) decays Z-->li
lj is presented within the effective Lagrangian approach. Both the decoupling
and nondecoupling scenarios are explored. The experimental constraints from li
--> lj lk \bar{lk} and li -->lj gamma as well as some relationships arising
from the gauge invariance of the effective Lagrangian are used to put
constraints on Z-->li lj. It is found that while current experimental data
impose very strong constraints on Z-->mu e, the channel Z --> tau mu (e)still
may be at the reach of the planned TESLA collider.Comment: References added, final version to appear in Physical Review
Secondary organic aerosol origin in an urban environment: Influence of biogenic and fuel combustion precursors
Source contributions of organic aerosol (OA) are still not fully understood, especially in terms of quantitative distinction between secondary OA formed from anthropogenic precursors vs. that formed from natural precursors. In order to investigate the OA origin, a field campaign was carried out in Barcelona in summer 2013, including two periods characterized by low and high traffic conditions. Volatile organic compound (VOC) concentrations were higher during the second period, especially aromatic hydrocarbons related to traffic emissions, which showed a marked daily cycle peaking during traffic rush hours, similarly to black carbon (BC) concentrations. Biogenic VOC (BVOC) concentrations showed only minor changes from the low to the high traffic period, and their intra-day variability was related to temperature and solar radiation cycles, although a decrease was observed for monoterpenes during the day. The organic carbon (OC) concentrations increased from the first to the second period, and the fraction of non-fossil OC as determined by C analysis increased from 43% to 54% of the total OC. The combination of C analysis and Aerosol Chemical Speciation Monitor (ACSM) OA source apportionment showed that the fossil OC was mainly secondary (>70%) except for the last sample, when the fossil secondary OC only represented 51% of the total fossil OC. The fraction of non-fossil secondary OC increased from 37% of total secondary OC for the first sample to 60% for the last sample. This enhanced formation of non-fossil secondary OA (SOA) could be attributed to the reaction of BVOC precursors with NO emitted from road traffic (or from its nocturnal derivative nitrate that enhances night-time semi-volatile oxygenated OA (SV-OOA)), since NO concentrations increased from 19 to 42 μg m from the first to the last sample
Homochirality and the need of energy
The mechanisms for explaining how a stable asymmetric chemical system can be
formed from a symmetric chemical system, in the absence of any asymmetric
influence other than statistical fluctuations, have been developed during the
last decades, focusing on the non-linear kinetic aspects. Besides the absolute
necessity of self-amplification processes, the importance of energetic aspects
is often underestimated. Going down to the most fundamental aspects, the
distinction between a single object -- that can be intrinsically asymmetric --
and a collection of objects -- whose racemic state is the more stable one --
must be emphasized. A system of strongly interacting objects can be described
as one single object retaining its individuality and a single asymmetry; weakly
or non-interacting objects keep their own individuality, and are prone to
racemize towards the equilibrium state. In the presence of energy fluxes,
systems can be maintained in an asymmetric non-equilibrium steady-state. Such
dynamical systems can retain their asymmetry for times longer than their
racemization time.Comment: 8 pages, 7 figures, submitted to Origins of Life and Evolution of
Biosphere
Evolution of ocean circulation and water masses in the Guaymas Basin (Gulf of California) during the last 31,000Â years revealed by radiolarians and silicoflagellates in IODP expedition 385 sediment cores
The high-resolution analysis of radiolarians and silicoflagellates in sediments from Holes U1545A and U1549A drilled during IODP Expedition 385 in the Guaymas Basin, in the Gulf of California provides detailed insights into the evolution of ocean circulation and water masses, and its relation to Eastern Tropical Pacific Ocean climate conditions, over the past 31,000 cal years BP (based on AMS radiocarbon dates). In the pre-Last Glacial Maximum, the Guaymas Basin experienced alternating circulation patterns of California Current Water (CCW) and Gulf of California Water (GCW), with an extended presence of the Pacific Intermediate Water (PIW) owing to: amplified jet streams; southern movement of the California Current System (CCS) and the incursion of CCW into the gulf; and increased North Pacific Intermediate Water (NPIW) formation. The Last Glacial Maximum witnessed the incursion of CCW due to the stronger CCS. The dominance of the PIW indicates the expansion and formation of NPIW. The Heinrich-I event as manifested in the core record, displays two distinct patterns, one suggesting GCW-like dominance and the other, the occurrence of CCW. The Bølling-Ållerød interstadial featured the entry of Tropical Surface Water (TSW), GCW, and CCW, linked with the northward migration of the Intertropical Convergence Zone. In the Younger Dryas, CCW dominated, transitioning to GCW as colder climatic conditions and more intense CCS. The Holocene displayed alternating periods of TSW and GCW, with a modern monsoon regime from 7,600 to 1,000 cal years BP. From 1,000 cal years BP to the present the ITCZ shifted to the south
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