128,181 research outputs found
Higgs-boson-plus-photon production at the CERN Large Hadron Collider: A clean probe of the b-quark parton densities
No full textHiggs boson production in association with a high p(T) photon at the CERN Large Hadron Collider is analyzed, in the framework of the MSSM model, for the heavier neutral Higgs bosons. The request of an additional photon in the exclusive Higgs boson final state selects b-quark pairs among the possible initial partonic states, since gluon-gluon initial states are not allowed by C-parity conservation. Hence, the measurement of cross sections for neutral Higgs boson plus photon production can provide a clean probe of the b-quark density in the proton as well as of the b-quark Yukawa coupling. The suppression of the production rates by the b-quark electromagnetic coupling can be compensated by the enhanced Higgs boson Yukawa coupling to b's in the large tan beta regime. The Higgs boson decay into a tau-lepton pair is considered, and irreducible backgrounds with corresponding signal significances are evaluated
Gravitational decays of heavy particles in large extra dimensions
No full textIn the framework of quantum gravity propagating in large extra dimensions, we analyze the inclusive radiative emission of Kaluza-Klein spin-2 gravitons in the two-fermions decays of massive gauge bosons, heavy quarks, Higgs bosons, and in the two-massive gauge bosons decay of Higgs bosons. We provide analytical expressions for the square modulus of amplitudes summed over polarizations, and numerical results for the widths and branching ratios. The corresponding decays in the , top quark, and Higgs boson sectors of the standard model are analyzed in the light of present and future experiments.In the framework of quantum gravity propagating in large extra dimensions, we analyze the inclusive radiative emission of Kaluza-Klein spin-2 gravitons in the two-fermions decays of massive gauge bosons, heavy quarks, Higgs bosons, and in the two-massive gauge bosons decay of Higgs bosons. We provide analytical expressions for the square modulus of amplitudes summed over polarizations, and numerical results for the widths and branching ratios. The corresponding decays in the Z, top quark, and Higgs boson sectors of the standard model are analyzed in the light of present and future experiments.In the framework of quantum gravity propagating in large extra dimensions, we analyze the inclusive radiative emission of Kaluza–Klein spin-2 gravitons in the two-fermions decays of massive gauge bosons, heavy quarks, Higgs bosons, and in the two-massive gauge bosons decay of Higgs bosons. We provide analytical expressions for the square modulus of amplitudes summed over polarizations, and numerical results for the widths and branching ratios. The corresponding decays in the Z , top quark, and Higgs boson sectors of the standard model are analyzed in the light of present and future experiments
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Testing Effective Yukawa Couplings in Higgs Searches at Tevatron and LHC
No full textWe explore the possibility that, while the Higgs mechanism provides masses to the weak-gauge bosons at the electroweak scale as in the standard model, fermion masses are generated by an unknown mechanism at a higher energy scale. At low energies, the standard model can then be regarded as an effective field theory, where fermion masses explicitly break the electroweak SU(2)_L \times U(1)_Y gauge symmetry. If \Lambda is the renormalization scale where the renormalized Yukawa couplings vanish, at energies lower than \Lambda, effective Yukawa couplings will be radiatively induced by nonzero fermion masses. In this scenario, Higgs-boson decays into photons and weak gauge-bosons pairs are in general quite enhanced for a light Higgs. However, depending on \Lambda, a substantial decay rate into b \bar{b} can arise, that can be of the same order, or larger than, the enhanced H\to gamma gamma rate. A new framework for Higgs searches at hadron colliders is outlined, vector-boson fusion becoming the dominant production mechanism at the CERN LHC. A detailed analysis of the Higgs branching fractions and their implications in Higgs searches is provided, versus the energy scale \Lambda.We explore the possibility that, while the Higgs mechanism provides masses to the weak-gauge bosons at the electroweak scale as in the standard model, fermion masses are generated by an unknown mechanism at a higher energy scale. At low energies, the standard model can then be regarded as an effective field theory, where fermion masses explicitly break the electroweak SU(2)_L \times U(1)_Y gauge symmetry. If \Lambda is the renormalization scale where the renormalized Yukawa couplings vanish, then at energies lower than \Lambda, effective Yukawa couplings will be radiatively induced by nonzero fermion masses. In this scenario, Higgs-boson decays into photons and weak gauge-bosons pairs are in general quite enhanced for a light Higgs. However, depending on \Lambda, a substantial decay rate into b \bar{b} can arise, that can be of the same order as, or larger than, the enhanced H\to gamma gamma rate. A new framework for Higgs searches at hadron colliders is outlined, vector-boson fusion becoming the dominant production mechanism at the CERN LHC, with an important role also played by the WH/ZH associated production. A detailed analysis of the Higgs branching fractions and their implications in Higgs searches is provided, versus the energy scale \Lambda
Mapping the spatial variation of soil moisture at the large scale using GPR for pavement applications
No full textThe characterization of shallow soil moisture spatial variability at the large scale is a crucial issue in many research studies and fields of application ranging from agriculture and geology to civil and environmental engineering. In this framework, this work contributes to the research in the area of pavement engineering for preventing damages and planning effective management. High spatial variations of subsurface water content can lead to unexpected damage of the load-bearing layers; accordingly, both safety and operability of roads become lower, thereby affecting an increase in expected accidents. \ud
A pulsed ground-penetrating radar system with ground-coupled antennas, i.e., 600-MHz and 1600-MHz center frequencies of investigation, was used to collect data in a 16 m × 16 m study site in the Po Valley area in northern Italy. Two ground-penetrating radar techniques were employed to non-destructively retrieve the subsurface moisture spatial profile. The first technique is based on the evalu¬ation of the dielectric permittivity from the attenuation of signal amplitudes. Therefore, dielectrics were converted into moisture values using soil-specific coefficients from Topp’s relationship. Ground-penetrating-radar-derived values of soil moisture were then compared with measurements from eight capacitance probes. The second technique is based on the Rayleigh scattering of the signal from the Fresnel theory, wherein the shifts of the peaks of frequency spectra are assumed comprehensive indi¬cators for characterizing the spatial variability of moisture. Both ground-penetrating radar methods have shown great promise for mapping the spatial variability of soil moisture at the large scale
ZγH Vertex Effects at Future Colliders
No full textWe show that the Higgs production in e gamma collisions, through the one-loop reaction e gamma \to eH at large transverse momentum, can provide a precise determination of the Z gamma H vertex. We concentrate on the analysis of signal rates vs background looking for strategies to improve the ratio S/B. Possible bounds on anomalous contributions to the Z gamma H vertex are derived
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
A Combined Experimental and Theoretical Study on the Stereodynamics of Monoaza[5]helicenes: Solvent-Induced Increase of the Enantiomerization Barrier in 1-Aza-[5]helicene
No full textHelicenes and heterohelicenes are attractive compounds with great potential in materials sciences to be used in optoelectronics as ligand backbones in enantioselective catalysis and as chiral sensors.[1] Synthetic protocols were developed to obtain helicenes with skeletons consisting of ortho-fused benzene rings or analogue structures incorporating a heteroatom, as in thiophene-, furane-, or pyridine-containing helicenes.[2] In recent years, a repertoire of synthetic strategies was developed to access all monoaza[5]helicenes as well as some diaza[ 5]helicenes.[3] The properties of these materials are related to the stereodynamics of these helical chiral compounds. By exploration of the unexpected broad range of physicochemical properties of aza[n]helicenes it was realized that there is an opportunity to modulate a specific property by controlled design of the position of the N atoms in the helical molecular frame. In this contribution, we show a complete stereodynamic characterization of monoaza[5]-helicenes combining enantioselective dynamic HPLC and DFT calculations. At variance with previous theoretical calculations[4], 1-aza[5]helicene shows a surprisingly high enantiomerization barrier, which is triggered by specific solvent interactions. [5]
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[3] a) C. Bazzini, S. Brovelli, T. Caronna, C. Gambarotti, M. Giannone, P. Macchi, F. Meinardi, A. Mele, W. Panzeri, F. Recupero, A. Sironi, Eur. J. Org. Chem. 2005, 1247 – 1257; b) S. Abbate, C. Bazzini, T. Caronna, F. Fontana, C. Gambarotti, F. Gangemi, G. Longhi, A. Mele, I. Natali Sora, W. Panzeri, Tetrahedron 2006, 62,139 –148; c) T. Caronna, F. Fontana, A. Mele, I. Natali Sora, W. Panzeri, L. Vigan_, Synthesis 2008, 413– 416; d) T. Caronna, S. Gabbiadini, A. Mele, F. Recupero, Helv. Chim. Acta 2002, 85, 1 –8; e) T. Caronna, F. Castiglione, F. Fontana, D. Mendola, I. Natali Sora, Molecules 2012, 17, 463 –479.
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[5] T. Caronna, A. Mele, A. Famulari, D. Mendola, F. Fontana, M. Juza, M. Kamuf, K. Zawatzky, and O. Trapp, Chem. Eur. J. 2015, 21, 1–7
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