607 research outputs found
Theoretical Aspects of Higgs Physics at the LHC
The strategies recently developed to study Higgs boson properties at the LHC
are reviewed. It is shown how to obtain model-independent determinations of
couplings to fermions and gauge bosons by exploiting different production and
decay channels. We consider the case of Weak Boson Fusion Higgs production with
H decaying into b anti-bComment: 4 pages, 1 figure. EPSHEP Conference Proceedings, Aachen 200
O'Mega: An Optimizing Matrix Element Generator
We sketch the architecture of O'Mega, a new optimizing compiler for tree
amplitudes in quantum field theory, and briefly describe its usage. O'Mega
generates the most efficient code currently available for scattering amplitudes
for many polarized particles in the Standard Model and its extensions.Comment: 29 pages, LaTe
Electroweak Sudakov Corrections to New Physics Searches at the CERN LHC
We compute the one-loop electroweak Sudakov corrections to the production
process Z (nu bar{nu}) + n jets, with n = 1,2,3, in p p collisions at the LHC.
It represents the main irreducible background to new physics searches at the
energy frontier. The results are obtained at the leading and next-to-leading
logarithmic accuracy by implementing the general algorithm of Denner-Pozzorini
in the event generator for multiparton processes ALPGEN. For the standard
selection cuts used by ATLAS and CMS collaborations, we show that the Sudakov
corrections to the relevant observables can grow up to - 40% at sqrt{s} = 14
TeV. We also include the contribution due to undetected real radiation of
massive gauge bosons, to show to what extent the partial cancellation with the
large negative virtual corrections takes place in realistic event selections.Comment: 5 pages, 3 figures, 1 table. Extended discussion on real radiation
processes. Added references. Results unchanged. Version to appear in Phys.
Rev. Let
The Scuola Normale Superiore of Pisa. Between the French model and autonomous choices (1810-1923)
Der Beitrag konzentriert sich auf das französische Modell am Beispiel der Geschichte der Scuola Normale Superiore in Pisa, die 1810 von Napoleon auf der Asche der Erfahrungen des Jahres III der Revolution (1795) gegründet wurde, die 1813 faktisch eröffnet und 1847 von Habsburg-Lothringen wiedereröffnet wurde, bevor sie 1862 von der italienischen Regierung reorganisiert wurde. Im Fall der Scuola Normale Superiore werden alte und neue Bildungsphänomene (man denke an die Realität des Internats, das Erbe der religiösen Lehrorden, das lange Zeit nicht nur in Bezug auf Frankreich, sondern z.B. auch auf England diskutiert wurde) in den Blickpunkt der Gesetzgeber/innen und der Forscher/innen gerückt. Frankreich und Deutschland bleiben lange die zentralen Bezugspunkte in Italien für den sekundären schulischen und den universitären Bereich. (DIPF/Orig.
Higgs Boson Production in Association with a Photon in Vector Boson Fusion at the LHC
Higgs boson production in association with two forward jets and a central
photon at the CERN Large Hadron Collider is analyzed, for the Higgs boson
decaying into a b bbar pair in the m_H <= 140 GeV mass region. We study both
irreducible and main reducible backgrounds at parton level. Compared to the
Higgs production via vector-boson fusion, the request of a further photon at
moderate rapidities dramatically enhances the signal/background ratio.
Inclusive cross sections for p_T^\gamma >= 20 GeV can reach a few tens of fb's.
After a suitable choice of kinematical cuts, the cross-section ratio for signal
and irreducible-background can be enhanced up to >= ~1/10, with a signal cross
section of the order of a few fb's, for m_H ~ 120 GeV. The request of a central
photon radiation also enhances the relative signal sensitivity to the WWH
coupling with respect to the ZZH coupling. Hence, a determination of the cross
section for the associated production of a Higgs boson decaying into a b bbar
pair plus a central photon in vector-boson fusion could help in constraining
the b bbar H coupling, and the WWH coupling as well. A preliminary study of QCD
showering effects points to a further significant improvement of the signal
detectability over the background.Comment: 30 pages, 8 figures, 8 tables; minor corrections to the text; version
appeared in Nuclear Physics
«Quando in cospetto a l’aquila». Sul Medioevo carducciano
«V’imaginate il levar del sole nel primo giorno dell’anno Mille?». La citazione è in fondo scontata, ed il brano è notissimo; ma l’esordio dei discorsi Dello svolgimento della letteratura nazionale fissava con straordinaria efficacia alcune delle coordinate del complesso discorso carducciano attorno al medioevo – e sarebbe preferibile, del resto, usare al plurale la determinazione epocale, parlando, per Carducci, di diversi tempi, luoghi e volti del medioevo. Le profezie più antiche e più recenti, formulate queste in anni di «disperate ruine», non si erano compiute:Mille, e non più mille – aveva, secondo la tradizione, detto Gesù: dopo mille anni, leggevasi nell’Apocalipsi, Satana sarà disciolto. Di fatto nelle nefandezze del secolo decimo, in quello sfracellarsi della monarchia e della società dei conquistatori nelle infinite unità feudali, in quell’abiettarsi ineffabile del ponteficato cristiano, in quelle scorrerie procellose di barbari nuovi ed orribili, non era egli lecito riconoscere i segni descritti dal veggente di Patmo? Il sole, invece, si era ancora alzato sull’«Italia romana» mortificata e devastata dalle «idee degli ascetici» e dalla «violenza dei barbari» – e la terminologia carducciana è rivelatrice di contatti non occasionali, meditati, con uno dei grandi filoni di indagine storica e di rievocazione letteraria che caratterizzarono l’ottocentesca ricostruzione della légende des siècles europea –:Il sole! V’è dunque ancora una patria? e v’è il mondo? E l’Italia distendeva le membra raggricciate dal gelo della notte, e toglieasi d’intorno al capo il velo dell’ascetismo per guardare all’oriente. Di fatti sin nei primi anni del secolo undecimo sentesi come un brulicare di vita ancor timida e occulta, che poi scoppierà in lampi e tuoni di pensieri e di opere: di qui veramente incomincia la storia del popolo italiano
Convergence of Neural Networks with a Class of Real Memristors with Rectifying Characteristics
The paper considers a neural network with a class of real extended memristors obtained via the parallel connection of an ideal memristor and a nonlinear resistor. The resistor has the same rectifying characteristic for the current as that used in relevant models in the literature to account for diode-like effects at the interface between the memristor metal and insulating material. The paper proves some fundamental results on the trajectory convergence of this class of real memristor neural networks under the assumption that the interconnection matrix satisfies some symmetry conditions. First of all, the paper shows that, while in the case of neural networks with ideal memristors, it is possible to explicitly find functions of the state variables that are invariants of motions, the same functions can be used as Lyapunov functions that decrease along the trajectories in the case of real memristors with rectifying characteristics. This fundamental property is then used to study convergence by means of a reduction-of-order technique in combination with a Lyapunov approach. The theoretical predictions are verified via numerical simulations, and the convergence results are illustrated via the applications of real memristor neural networks to the solution of some image processing tasks in real time
Complete Stability of Neural Networks With Extended Memristors
The article considers a large class of delayed neural networks (NNs) with extended memristors obeying the Stanford model. This is a widely used and popular model that accurately describes the switching dynamics of real nonvolatile memristor devices implemented in nanotechnology. The article studies via the Lyapunov method complete stability (CS), i.e., convergence of trajectories in the presence of multiple equilibrium points (EPs), for delayed NNs with Stanford memristors. The obtained conditions for CS are robust with respect to variations of the interconnections and they hold for any value of the concentrated delay. Moreover, they can be checked either numerically, via a linear matrix inequality (LMI), or analytically, via the concept of Lyapunov diagonally stable (LDS) matrices. The conditions ensure that at the end of the transient capacitor voltages and NN power vanish. In turn, this leads to advantages in terms of power consumption. This notwithstanding, the nonvolatile memristors can retain the result of computation in accordance with the in-memory computing principle. The results are verified and illustrated via numerical simulations. From a methodological viewpoint, the article faces new challenges to prove CS since due to the presence of nonvolatile memristors the NNs possess a continuum of nonisolated EPs. Also, for physical reasons, the memristor state variables are constrained to lie in some given intervals so that the dynamics of the NNs need to be modeled via a class of differential inclusions named differential variational inequalities
Laboratory and on-site tests for rapid runway repair
The attention to rapid pavement repair has grown fast in recent decades: this topic is strategic for the airport management process for civil purposes and peacekeeping missions. This work presents the results of laboratory and on-site tests for rapid runway repair, in order to analyse and compare technical and mechanical performances of 12 different materials currently used in airport. The study focuses on site repairs, a technique adopted most frequently than repairs with modular elements. After describing mechanical and physical properties of the examined materials (2 bituminous emulsions, 5 cement mortars, 4 cold bituminous mixtures and 1 expanding resin), the study presents the results of carried out mechanical tests. The results demonstrate that the best performing material is a one-component fast setting and hardening cement mortar with graded aggregates. This material allows the runway reopening 6 h after the work. A cold bituminous mixture (bicomponent premixed cold asphalt with water as catalyst) and the ordinary cement concrete allow the reopening to traffic after 18 h, but both ensure a lower service life (1000 coverages) than the cement mortar (10,000 coverages). The obtained results include important information both laboratory level and field, and they could be used by airport management bodies and road agencies when scheduling and evaluating pavement repairs
The Swift X-ray Telescope Cluster Survey III: Cluster Catalog from 2005-2012 Archival Data
We present the Swift X-ray Cluster Survey (SWXCS) catalog obtained using
archival data from the X-ray telescope (XRT) on board the Swift satellite
acquired from 2005 to 2012, extending the first release of the SWXCS. The
catalog provides positions, soft fluxes, and, when possible, optical
counterparts for a flux-limited sample of X-ray group and cluster candidates.
We consider the fields with Galactic latitude |b| > 20 degree to avoid high HI
column densities. We discard all of the observations targeted at groups or
clusters of galaxies, as well as particular extragalactic fields not suitable
to search for faint extended sources. We finally select ~3000 useful fields
covering a total solid angle of ~400 degree^2. We identify extended source
candidates in the soft-band (0.5-2keV) images of these fields using the
software EXSdetect, which is specifically calibrated for the XRT data.
Extensive simulations are used to evaluate contamination and completeness as a
function of the source signal, allowing us to minimize the number of spurious
detections and to robustly assess the selection function. Our catalog includes
263 candidate galaxy clusters and groups down to a flux limit of 7E-15
erg/cm^2/s in the soft band, and the logN-logS is in very good agreement with
previous deep X-ray surveys. The final list of sources is cross-correlated with
published optical, X-ray, and SZ catalogs of clusters. We find that 137 sources
have been previously identified as clusters, while 126 are new detections.
Currently, we have collected redshift information for 158 sources (60% of the
entire sample). Once the optical follow-up and the X-ray spectral analysis of
the sources are complete, the SWXCS will provide a large and well-defined
catalog of groups and clusters of galaxies to perform statistical studies of
cluster properties and tests of cosmological models.Comment: 41 pages, 16 figures, 3 tables, published on ApJS in Jan 201
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