http://www.infn.it/pubblicazioni it-IT INFN - Dataweb 199,31 (2012)

We present the second catalog of high-energy gamma-ray sources detected by the Large Area Telescope (LAT), the primary science instrument on the Fermi Gamma-ray Space Telescope (Fermi), derived from data taken during the first 24 months of the science phase of the mission, which began on 2008 August 4. Source detection is based on the average flux over the 24 month period. The second Fermi-LAT catalog (2FGL) includes source location regions, defined in terms of elliptical fits to the 95% confidence regions and spectral fits in terms of power-law, exponentially cutoff power-law, or log-normal forms. Also included are flux measurements in five energy bands and light curves on monthly intervals for each source. Twelve sources in the catalog are modeled as spatially extended. We provide a detailed comparison of the results from this catalog with those from the first Fermi-LAT catalog (1FGL). Although the diffuse Galactic and isotropic models used in the 2FGL analysis are improved compared to the 1FGL catalog, we attach caution flags to 162 of the sources to indicate possible confusion with residual imperfections in the diffuse model. The 2FGL catalog contains 1873 sources detected and characterized in the 100 MeV to 100 GeV range of which we consider 127 as being firmly identified and 1171 as being reliably associated with counterparts of known or likely gamma-ray-producing source classes.]]> Sat, 25 May 2013 13:30:17 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000303105400007 199,25 (2012)

The Cluster Lensing And Supernova survey with Hubble (CLASH) is a 524-orbit Multi-Cycle Treasury Program to use the gravitational lensing properties of 25 galaxy clusters to accurately constrain their mass distributions. The survey, described in detail in this paper, will definitively establish the degree of concentration of dark matter in the cluster cores, a key prediction of structure formation models. The CLASH cluster sample is larger and less biased than current samples of space-based imaging studies of clusters to similar depth, as we have minimized lensing-based selection that favors systems with overly dense cores. Specifically, 20 CLASH clusters are solely X-ray selected. The X-ray-selected clusters are massive (kT > 5 keV) and, in most cases, dynamically relaxed. Five additional clusters are included for their lensing strength (theta(Ein) > 35 '' at z(s) = 2) to optimize the likelihood of finding highly magnified high-z (z > 7) galaxies. A total of 16 broadband filters, spanning the near-UV to near-IR, are employed for each 20-orbit campaign on each cluster. These data are used to measure precise (sigma(z) similar to 0.02(1 + z)) photometric redshifts for newly discovered arcs. Observations of each cluster are spread over eight epochs to enable a search for Type Ia supernovae at z > 1 to improve constraints on the time dependence of the dark energy equation of state and the evolution of supernovae. We present newly re-derived X-ray luminosities, temperatures, and Fe abundances for the CLASH clusters as well as a representative source list for MACS1149.6 + 2223 (z = 0.544).]]> Sat, 25 May 2013 13:30:17 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000303105400001 98,16005 (2012)

The classical hexagonal honeycomb theory for the uniaxial loading case, developed by Gibson and Ashby, considers buckling of the cell walls parallel to one symmetry axis. In general, buckling may also occur in the cell walls inclined with respect to the two symmetry axes. Therefore, in this letter, under the uniaxial loading conditions, we derive the critical stresses of buckling and bending collapses of nanohoneycombs, for which the surface effect is included. Furthermore, the competition between the two failure modes is studied. The present theory could be used to design new nanoporous materials, e.g., scaffolds for the regenerative medicine or energy-absorption materials. Copyright (C) EPLA, 2012]]> Sat, 25 May 2013 13:30:17 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000302932900028 72,1965 (2012)

New metastable massive particles with electric and colour charge are features of many theories beyond the Standard Model. A search is performed for long-lived gluino-based R-hadrons with the ATLAS detector at the LHC using a data sample corresponding to an integrated luminosity of 31 pb(-1). We search for evidence of particles that have come to rest in the ATLAS detector and decay at some later time during the periods in the LHC bunch structure without proton-proton collisions. No significant deviations from the expected backgrounds are observed, and a cross-section limit is set. It can be interpreted as excluding gluino-based R-hadrons with masses less than 341 GeV at the 95 % C.L., for lifetimes from 10(-5) to 10(3) seconds and a neutralino mass of 100 GeV.]]> Sat, 25 May 2013 13:29:13 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000304013800011 72,1947 (2012)

Charged particle production in proton-proton collisions is studied with the LHCb detector at a centre-of-mass energy of root s = 7 TeV in different intervals of pseudorapidity eta. Charged particles are reconstructed close to the interaction region in the vertex detector, which provides high reconstruction efficiency in the eta ranges -2.5 < eta < -2.0 and 2.0 < eta < 4.5. The data were taken with a minimum bias trigger, only requiring one or more reconstructed tracks in the vertex detector. By selecting an event sample with at least one track with a transverse momentum greater than 1 GeV/c a hard QCD subsample is investigated. Several event generators are compared with the data; none are able to describe fully the multiplicity distributions or the charged particle density distribution as a function of eta. In general, the models underestimate charged particle production.]]> Sat, 25 May 2013 13:29:13 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000304013800013 72,1970 (2012)

The cross section of diffractive deep-inelastic scattering ep -> eXp is measured, where the system X contains at least two jets and the leading final state proton is detected in the H1 Forward Proton Spectrometer. The measurement is performed for fractional proton longitudinal momentum loss x(P) < 0.1 and covers the range 0.1 < vertical bar t vertical bar < 0.7 GeV2 in squared four-momentum transfer at the proton vertex and 4 < Q(2) < 110 GeV2 in photon virtuality. The differential cross sections extrapolated to vertical bar t vertical bar < 1 GeV2 are in agreement with next-to-leading order QCD predictions based on diffractive parton distribution functions extracted from measurements of inclusive and dijet cross sections in diffractive deep-inelastic scattering. The data are also compared with leading order Monte Carlo models.]]> Sat, 25 May 2013 13:29:13 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000304013800015 72,1971 (2012)

The CRESST-II cryogenic Dark Matter search, aiming at detection of WIMPs via elastic scattering off nuclei in CaWO4 crystals, completed 730 kg days of data taking in 2011. We present the data collected with eight detector modules, each with a two-channel readout; one for a phonon signal and the other for coincidently produced scintillation light. The former provides a precise measure of the energy deposited by an interaction, and the ratio of scintillation light to deposited energy can be used to discriminate different types of interacting particles and thus to distinguish possible signal events from the dominant backgrounds. Sixty-seven events are found in the acceptance region where a WIMP signal in the form of low energy nuclear recoils would be expected. We estimate background contributions to this observation from four sources: (1) "leakage" from the e/gamma-band (2) "leakage" from the alpha-particle band (3) neutrons and (4) Pb-206 recoils from Po-210 decay. Using a maximum likelihood analysis, we find, at a statistical significance of more than 4 sigma, that these sources alone are not sufficient to explain the data. The addition of a signal due to scattering of relatively light WIMPs could account for this discrepancy, and we determine the associated WIMP parameters.]]> Sat, 25 May 2013 13:29:13 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000304013800024 72,1966 (2012)

Recent improvements to OPUCEM, the tool for calculation of the contributions of various models to oblique parameters, are presented. OPUCEM is used to calculate the available parameter space for the four family Standard Model given the current electroweak precision data. It is shown that even with the restrictions on Higgs boson and new quark masses presented in the 2011 Autumn conferences, there is still enough space to allow a fourth generation with Dirac type neutrinos. For Majorana type neutrinos, the allowed parameter space is even larger. The electroweak precision data also appear to favor non-zero mixing between light and fourth generations, thus effectively reducing the current experimental limits on the masses of the new quarks, which assume that the mixing with the third generation is dominant. Additionally, disregarding the lack of a clear Higgs signal from the LHC and focusing only an electroweak precision data comptability, calculations with OPUCEM show that, the existing electroweak data are compatible with the presence of a 5th and also a 6th generation in certain regions of the parameter space.]]> Sat, 25 May 2013 13:29:13 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000304013800030 72,1974 (2012)

Present experiments do not exclude that the neutron n oscillates, with an appreciable probability, into its invisible degenerate twin from a parallel world, the so-called mirror neutron n'. These oscillations were searched experimentally by monitoring the neutron losses in ultra-cold neutron traps, where they can be revealed by the magnetic field dependence of n-n' transition probability. In this work we reanalyze the experimental data acquired by the group of A.P. Serebrov at Institute Laue-Langevin, and find a dependence at more than 5 sigma away from the null hypothesis. This anomaly can be interpreted as oscillation of neutrons to mirror neutrons with a timescale of few seconds, in the presence of a mirror magnetic field order 0.1 G at the Earth. This result, if confirmed by future experiments, will have deepest consequences for fundamental particle physics, astrophysics and cosmology.]]> Sat, 25 May 2013 13:29:13 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000304013800026 7,P04002 (2012)

Multiple volume reflection has been recognized as an efficient method to steer high-energy particle beams for beam extraction or collimation. A multistrip silicon crystal has been designed, consisting in an array of mutually aligned 16 silicon strips to cause multiple volume reflection. The multistrip was fabricated from one individual wafer and given the shape of a topologically connected crystal, which proved to be the best configuration for alignment. Full characterization of such a crystal has been carried out. The crystal was extensively tested at the H8 CERN line with 400 GeV/c protons. Record deflection efficiency of (96.0 +/- 0.5)% for a mean deflection angle of (112.2 +/- 0.1) mu rad was obtained. Since the performance of volume reflection is energy dependent, a specific emulation code has been developed to predict multistrip behavior at various energies.]]> Sat, 25 May 2013 13:29:13 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000304012800026 7,P04004 (2012)

Interventional radiologists and staff members are frequently exposed to protracted and fractionated low doses of ionizing radiation due to diffused X-ray radiation. The authors propose a novel approach to monitor on line staff during their interventions by using a device based on an Active Pixel Sensor developed for tracking applications. Two different photodiode configurations have been tested in standard Interventional Radiology working conditions. Both options have demonstrated the capability to measure the photon flux and the energy flux to a sufficient degree of uncertainty.]]> Sat, 25 May 2013 13:29:13 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000304012800028 98,20003 (2012)

We derive exact relations between the Renyi entanglement entropies and the particle-number fluctuations of (connected and disjoint) spatial regions in systems of N non-interacting fermions in arbitrary dimension. We prove that the asymptotic large-N behavior of the entanglement entropies is proportional to the variance of the particle number. We also consider 1D Fermi gases with a localized impurity, where all particle cumulants contribute to the asymptotic large-N behavior of the entanglement entropies. The particle cumulant expansion turns out to be convergent for all integer-order Renyi entropies (except for the von Neumann entropy) and the first few cumulants provide already a good approximation. Since the particle cumulants are accessible to experiments, these relations may provide a measure of entanglement in these systems. Copyright (C) EPLA, 2012]]> Sat, 25 May 2013 13:29:13 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000303754100003 50, (2012)

The ground-state wave function Psi for a given force constant k = 1/4 a.u. of the two-electron Hookean atom is known in exact analytical form. Here the corresponding first-order density matrix gamma (r, r') is studied, particular attention being focussed on its equation of motion. The exact form which results from the known Psi is displayed, and given a physical interpretation. Harmonic confined model two-electron atoms with arbitrary interaction u(r(12)) are also briefly referred to in the present context.]]> Sat, 25 May 2013 13:29:13 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000303891200018 14, (2012)

We study the non equilibrium statistical properties of a one dimensional hard-rod fluid undergoing collisions and subject to a spatially non uniform Gaussian heat-bath and periodic potential. The system is able to sustain finite currents when the spatially inhomogeneous heat-bath and the periodic potential profile display an appropriate relative phase shift, phi. By comparison with the collisionless limit, we determine the conditions for the most efficient transport among inelastic, elastic and non interacting rods. We show that the situation is complex as, depending on shape of the temperature profile, the current of one system may outperform the others.]]> Sat, 25 May 2013 13:29:13 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000303882900007 14, (2012)

We discuss molecular dynamics simulations of a granular suspension driven in a channel by an embedding fluid. The flow has three different regimes: it is disordered at small packing fractions, phi; above a transition point, phi(m), flows becomes ordered in layers, but only in a fraction of samples; at higher phi, if ordering is avoided, jamming is also encountered. In the disordered flow regime the velocity profile is power law, consistent with an Ostwald-de Waele constitutive relation. In the ordered regime, flow is concentrated in the bulk in a nearly solid plug having a flat velocity profile, with narrow shear regions at the boundaries. Interestingly, velocity fluctuations are approximately linear in the velocity in all regimes.]]> Sat, 25 May 2013 13:29:13 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000303882900018 ,040 (2012)

Observations of cosmic rays arrival directions made with the Pierre Auger Observatory have previously provided evidence of anisotropy at the 99% CL using the correlation of ultra high energy cosmic rays (UHECRs) with objects drawn from the Veron-Cetty Veron catalog. In this paper we report on the use of three catalog independent methods to search for anisotropy. The 2pt-L, 2pt+ and 3pt methods, each giving a different measure of self-clustering in arrival directions, were tested on mock cosmic ray data sets to study the impacts of sample size and magnetic smearing on their results, accounting for both angular and energy resolutions. If the sources of UHECRs follow the same large scale structure as ordinary galaxies in the local Universe and if UHECRs are deflected no more than a few degrees, a study of mock maps suggests that these three method can efficiently respond to the resulting anisotropy with a P-value = 1.0% or smaller with data sets as few as 100 events. using data taken from January 1, 2004 to July 31, 2010 we examined the 20, 30, ... , 110 highest energy events with a corresponding minimum energy threshold of about 49.3 EeV. The minimum P-values found were 13.5% using the 2pt-L method, 1.0% using the 2pt+ method and 1.1% using the 3pt method for the highest 100 energy events. In view of the multiple (correlated) scans performed on the data set, these catalog-independent methods do not yield strong evidence of anisotropy in the highest energy cosmic rays.]]> Sat, 25 May 2013 13:29:13 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000303665000040 ,010 (2012)

We study the impact of semi-annihilations x(i)x(j) <-> x(k)X and dark matter conversion x(i)x(j) <-> x(k)x(l), where x(i) is any dark matter and X is any standard model particle, on dark matter phenomenology. We formulate minimal scalar dark matter models with an extra doublet and a complex singlet that predict non-trivial dark matter phenomenology with semi-annihilation processes for different discrete Abelian symmetries Z(N), N > 2. We implement two such example models with Z(3) and Z(4) symmetry in micrOMEGAs and work out their phenomenology. We show that both semi-annihilations and dark matter conversion significantly modify the dark matter relic abundance in this type of models. In the Z(4) model, there are two stable neutral particles and therefore multi-component dark matter. We also study the possibility of dark matter direct detection in XENON100 in those models.]]> Sat, 25 May 2013 13:29:13 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000303665000010 ,036 (2012)

Using a recently proposed gauge invariant formulation of light-cone averaging, together with adapted "geodesic light-cone" coordinates, we show how an "induced backreaction" effect emerges, in general, from correlated fluctuations in the luminosity distance and co-variant integration measure. Considering a realistic stochastic spectrum of inhomogeneities of primordial (inflationary) origin we find that both the induced backreaction on the luminosity-redshift relation and the dispersion are larger than naively expected. On the other hand the former, at least to leading order and in the linear perturbative regime, cannot account by itself for the observed effects of dark energy at large-redshifts. A full second-order calculation, or even better a reliable estimate of contributions from the non-linear regime, appears to be necessary before firm conclusions on the correct interpretation of the data can be drawn.]]> Sat, 25 May 2013 13:29:13 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000303665000036 540,A69 (2012)

We use 73 h of stereoscopic data taken with the MAGIC telescopes to investigate the very high-energy (VHE) gamma-ray emission of the Crab pulsar. Our data show a highly significant pulsed signal in the energy range from 50 to 400 GeV in both the main pulse (P1) and the interpulse (P2) phase regions. We provide the widest spectra to date of the VHE components of both peaks, and these spectra extend to the energy range of satellite-borne observatories. The good resolution and background rejection of the stereoscopic MAGIC system allows us to cross-check the correctness of each spectral point of the pulsar by comparison with the corresponding (strong and well-known) Crab nebula flux. The spectra of both P1 and P2 are compatible with power laws with photon indices of 4.0 +/- 0.8 (P1) and 3.42 +/- 0.26 (P2), respectively, and the ratio P1/P2 between the photon counts of the two pulses is 0.54 +/- 0.12. The VHE emission can be understood as an additional component produced by the inverse Compton scattering of secondary and tertiary e(+/-) pairs on IR-UV photons.]]> Sat, 25 May 2013 13:29:13 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000303315400083 540,A26 (2012)

Context. The last decade showed an impressive observational effort from the photometric and spectroscopic point of view for ancient stellar clusters in our Galaxy and beyond, leading to important and sometimes surprising results. Aims. The theoretical interpretation of these new observational results requires updated evolutionary models and isochrones spanning a wide range of chemical composition so that the possibility of multipopulations inside a stellar cluster is also taken also into account. Methods. With this aim we built the new "Pisa Stellar Evolution Database" of stellar models and isochrones by adopting a well-tested evolutionary code (FRANEC) implemented with updated physical and chemical inputs. In particular, our code adopts realistic atmosphere models and an updated equation of state, nuclear reaction rates and opacities calculated with recent solar elements mixture. Results. A total of 32 646 models have been computed in the range of initial masses 0.30 / 1.10 M-circle dot for a grid of 216 chemical compositions with the fractional metal abundance in mass, Z, ranging from 0.0001 to 0.01, and the original helium content, Y, from 0.25 to 0.42. Models were computed for both solar-scaled and alpha-enhanced abundances with different external convection efficiencies. Correspondingly, 9720 isochrones were computed in the age range 8/15 Gyr, in time steps of 0.5 Gyr. The whole database is available to the scientific community on the web. Models and isochrones were compared with recent calculations available in the literature and with the color-magnitude diagram of selected Galactic globular clusters. The dependence of relevant evolutionary quantities, namely turn-off and horizontal branch luminosities, on the chemical composition and convection efficiency were analyzed in a quantitative statistical way and analytical formulations were made available for reader's convenience. These relations can be useful in several fields of stellar evolution, e.g. evolutionary properties of binary systems, synthetic models for simple stellar populations and for star counts in galaxies, and chemical evolution models of galaxies.]]> Sat, 25 May 2013 13:29:13 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000303315400040 540,A23 (2012)

Context. There is mounting evidence that a significant fraction of black holes (BHs) today live in late-type galaxies, including bulge-less galaxies and those hosting pseudobulges, and are significantly undermassive with respect to the scaling relations followed by their counterpart BHs in classical bulges of similar stellar (or even bulge) mass. Aims. Here we discuss the predictions of two state-of-the-art hierarchical galaxy formation models in which BHs grow via mergers and, in one, also via disc instability. Our aim is to understand if the wealth of new data on local BH demography is consistent with standard models. Methods. We follow the merger trees of representative subsamples of BHs and compute the fractional contributions of different processes to the final BH mass. Results. We show that the model in which BHs always closely follow the growth of their host bulges, also during late disk instabilities (i.e., bars), produces too narrow a distribution of BHs at fixed stellar mass to account for the numerous low-mass BHs now detected in later-type galaxies. Models with a looser connection between BH growth and bar instability instead predict the existence of a larger number of undermassive BHs, in better agreement with the observations. Conclusions. The scatter in the updated local BH-bulge mass relation (with no restriction on galaxy type) appears to be quite large when including later-type systems, but it can still be managed to be reproduced within current hierarchical models. However, the fuelling of BHs during the late bar-instability mode needs to be better quantified/improved to properly fit the data. We conclude discussing how the possibly large number of BHs in later type galaxies demands for an in-depth revision of the local BH mass function and its modelling.]]> Sat, 25 May 2013 13:29:13 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000303315400037 540,A55 (2012)

Context. The nova outburst of V407 Cyg in 2010 Mar. 10 was the first observed for this star but its close resemblance to the well known symbiotic-like recurrent nova RS Oph suggests that it is also a member of this rare type of Galactic novae. The nova was the first detected at.-ray energies and is the first known nova explosion for this system. The extensive multiwavelength coverage of this outburst makes it an ideal comparison with the few other outbursts known for similar systems. Aims. We extend our previous analysis of the Mira and the expanding shock from the explosion to detail the time development of the photoionized Mira wind, circumstellar medium, and shocked circumstellar environment to derive their physical parameters and how they relate to large scale structure of the environment, extending the previous coverage to more than 500 days after outburst. Methods. We use optical spectra obtained at high resolution with the Nordic Optical Telescope (NOT) (R approximate to 45 000 to 65 000) and medium resolution Ondrejov Observatory (R approximate to 12 000) data and compare the line variations with publicly available archival measurements at 30 GHz OVNR and at X-rays with Swift during the first four months of the outburst, through the end of the epoch of strong XR emission. We use nebular diagnostics and high resolution profile variations to derive the densities and locations of the extended emission. Results. We find that the higher the ionization and/or the higher the excitation energy, the more closely the profiles resemble the He II/Ca V-type high velocity shock profile discussed in Paper I. This also accounts for the comparative development of the [N II] and [O III] isoelectronic transitions: the [O III] 4363 angstrom profile does not show the low velocity peaks while the excited [N II] 5754 angstrom does. If nitrogen is mainly N+3 or higher in the shock, the upper state of the [N II] nebular lines will contribute but if the oxygen is O+2 then this line is formed by recombination, masking the nebular contributor, and the lower states are collisionally quenched but emit from the low density surroundings. Absorption lines of Fe-peak ions formed in the Mira wind were visible as P Cyg profiles at low velocity before Day 69, around the time of the X-ray peak and we identified many absorption transitions without accompanying emission for metal lines. The H Balmer lines showed strong P Cyg absorption troughs that weakened during the 2010 observing period, through Day 128. The Fe-peak line profiles and flux variations were different for permitted and forbidden transitions: the E1 transitions were not visible after Day 128 but had shown a narrow peak superimposed on an extended (200 km s(-1)) blue wing, while the M1 and E2 transitions persisted to Day 529, the last observation, and showed extended redshifted wings up of the same velocity. We distinguish the components from the shock, the photoionized environment, and the chromosphere and inner Mira wind using spectra taken more than one year after outburst. The multiple shells and radiative excitation phenomenology are similar to those recently cited for GRBs and SNIa.]]> Sat, 25 May 2013 13:29:13 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000303315400069 85,136 (2012)

We study transport properties in a Tomonaga-Luttinger liquid in the presence of two time-dependent point like weak impurities, taking into account finite-length effects. By employing analytical methods and performing a perturbation theory, we compute the backscattering pumping current (I-bs) in different regimes which can be established in relation to the oscillatory frequency of the impurities and to the frequency related to the length and the renormalized velocity (by the electron-electron interactions) of the charge density modes. We investigate the role played by the spatial position of the impurity potentials. We also show how the previous infinite length results for I-bs are modified by the finite size of the system.]]> Sat, 25 May 2013 13:29:13 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000303545400007 53,043701 (2012)

We investigate one particular prototypical system of evolution equations in 1+1 dimensions, which models the (nonlocal) interaction of two waves in quadratic nonlinear media. These equations are integrable as they possess a Lax pair. We consider the spectral method of solving the associated initial value problem and, as recently pointed out, we show that generically the associated initial value problem cannot be linearized. We further elaborate on the integrability issue for this model by displaying the corresponding conservation laws and the motion of a particular soliton. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3699358]]]> Sat, 25 May 2013 13:29:13 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000303416700031 ,L04002 (2012)

In dissipative dynamical systems phase space volumes contract, on average. Therefore, the invariant measure on the attractor is singular with respect to the Lebesgue measure. As noted by Ruelle, a generic perturbation pushes the state out of the attractor, hence the statistical features of the perturbation and, in particular, of the relaxation cannot be understood solely in terms of the unperturbed dynamics on the attractor. This remark seems to seriously limit the applicability of the standard fluctuation-dissipation procedure in the statistical mechanics of nonequilibrium (dissipative) systems. In this letter we show that the singular character of the steady state does not constitute a serious limitation in the case of systems with many degrees of freedom. The reason is that one typically deals with projected dynamics, and these are associated with regular probability distributions in the corresponding lower dimensional spaces.]]> Sat, 25 May 2013 13:29:13 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000303545700002 43, (2012)

A general overview of the results obtained by the ALICE experiment from the analysis of the Pb-Pb data sample collected at the end of 2010 during the first heavy-ion run at the LHC is presented.]]> Sat, 25 May 2013 13:29:12 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000304429400001 43, (2012)

Thanks to its unique capabilities the ALICE experiment can measure the production of identified particles and resonances over a wide momentum range both in pp and Pb-Pb collisions at the LHC. In this report, particle-identification detectors and techniques, as well as achieved performance, are shortly reviewed. The current results on hadron transverse momentum spectra measured in pp collisions at root s = 0.9 TeV and 7 TeV, and in Pb-Pb collisions at root s(NN) = 2.76 TeV are shown. In particular, proton-proton results on particle production yields, spectral shapes and particle ratios are presented as a function of the collision energy and compared to previous experiments and commonly-used Monte Carlo models. Particle spectra, yields and ratios in Pb-Pb are measured as a function of the collision centrality and the results are compared with published RHIC data in Au-Au collisions at root s(NN) = 0.2 TeV and predictions for the LHC.]]> Sat, 25 May 2013 13:29:12 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000304429400007 43, (2012)

We present a systematic analysis of exclusive hadronic channels in e(+)e(-) collisions at centre-of-mass energies between 2.1 and 2.6 GeV within the statistical hadronization model. Because of the low multiplicities involved, calculations have been carried out in the full microcanonical ensemble, including conservation of energy-momentum, angular momentum, parity, isospin, and all relevant charges. We show that the data is in an overall good agreement with the model for an energy density of about 0.5 GeV/fm(3) and an extra strangeness suppression parameter gamma(S) similar to 0.7, essentially the same values found with fits to inclusive multiplicities at higher energy.]]> Sat, 25 May 2013 13:29:12 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000304429400009 43, (2012)

We discuss the possible impact of strange quark matter on the evolution of core-collapse supernovae with emphasis on low critical densities for the quark-hadron phase transition. For such cases the hot proto-neutron star can collapse to a more compact hybrid star configuration hundreds of milliseconds after core-bounce. The collapse triggers the formation of a second shock wave. The latter leads to a successful supernova explosion and leaves an imprint on the neutrino signal. These dynamical features are discussed. with respect to their compatibility with recent neutron star mass measurements which indicate a stiff high density nuclear matter equation of state.]]> Sat, 25 May 2013 13:29:12 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000304429400028 72,1993 (2012)

In models of anomaly-mediated supersymmetry breaking (AMSB), the lightest chargino is predicted to have a lifetime long enough to be detected in collider experiments. This letter explores AMSB scenarios in pp collisions at root s = 7 TeV by attempting to identify decaying charginos which result in tracks that appear to have few associated hits in the outer region of the tracking system. The search was based on data corresponding to an integrated luminosity of 1.02 fb(-1) collected with the ATLAS detector in 2011. The p(T) spectrum of candidate tracks is found to be consistent with the expectation from Standard Model background processes and constraints on the lifetime and the production cross section were obtained. In the minimal AMSB framework with m(3/2) < 32 TeV, m(0) < 1.5 TeV, tan beta = 5 and mu > 0, a chargino having mass below 92 GeV and a lifetime between 0.5 ns and 2 ns is excluded at 95 % confidence level.]]> Sat, 25 May 2013 13:29:12 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000304013800004 111,07E109 (2012)

The field-induced dynamics of artificial spin ice are determined in part by interactions between magnetic islands and the switching characteristics of each island. Disorder in either of these affects the response to applied fields. Numerical simulations are used to show that disorder effects are determined primarily by the strength of disorder relative to inter-island interactions, rather than by the type of disorder. Weak and strong disorder regimes exist and can be defined in a quantitative way. (C) 2012 American Institute of Physics. [doi:10.1063/1.3671434]]]> Sat, 25 May 2013 13:29:12 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000303282401222 ,029 (2012)

In this work we construct an infinite class of four-point functions for massless higher-spin fields in flat space that are consistent with the gauge symmetry. In the Lagrangian picture, these reflect themselves in a peculiar non-local nature of the corresponding non-abelian higher-spin couplings implied by the Noether procedure that starts from the fourth order. We also comment on the nature of the colored spin-2 excitation present both in the open string spectrum and in the Vasiliev system, highlighting how some aspects of String Theory appear to reflect key properties of Field Theory that go beyond its low energy limit. A generalization of these results to n-point functions, fermions and mixed-symmetry fields is also addressed.]]> Sat, 25 May 2013 13:29:12 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000304146600029 ,084 (2012)

The inclusive b-jet production cross section in pp collisions at a center-of-mass energy of 7TeV is measured using data collected by the CMS experiment at the LHC. The cross section is presented as a function of the jet transverse momentum in the range 18 < p(T) < 200 GeV for several rapidity intervals. The results are also given as the ratio of the b-jet production cross section to the inclusive jet production cross section. The measurement is performed with two different analyses, which differ in their trigger selection and b-jet identification: a jet analysis that selects events with a b jet using a sample corresponding to an integrated luminosity of 34 pb(-1), and a muon analysis requiring a b jet with a muon based on an integrated luminosity of 3 pb(-1). In both approaches the b jets are identified by requiring a secondary vertex. The results from the two methods are in agreement with each other and with next-to-leading order calculations, as well as with predictions based on the PYTHIA event generator.]]> Sat, 25 May 2013 13:29:12 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000304148100010 ,061 (2012)

A search for microscopic black holes in pp collisions at a center-of-mass energy of 7TeV is presented. The data sample corresponds to an integrated luminosity of 4.7 fb(-1) recorded by the CMS experiment at the LHC in 2011. Events with large total transverse energy have been analyzed for the presence of multiple energetic jets, leptons, and photons, which are typical signals of evaporating semiclassical and quantum black holes, and string balls. Agreement with the expected standard model backgrounds, which are dominated by QCD multijet production, has been observed for various combined multiplicities of jets and other reconstructed objects in the final state. Model-independent limits are set on new physics processes producing high-multiplicity, energetic final states. In addition, new model-specific indicative limits are set excluding semiclassical and quantum black holes with masses below 3.8 to 5.3TeV and string balls with masses below 4.6 to 4.8TeV. The analysis has a substantially increased sensitivity compared to previous searches.]]> Sat, 25 May 2013 13:29:12 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000304146600061 ,033 (2012)

A search for the rare decays B-S(0) -> mu(+)mu(-) and B-0 -> mu(+)mu(-) performed in pp collisions at root s = 7 TeV, with a data sample corresponding to an integrated luminosity of 5 fb(-1) collected by the CMS experiment at the LHC. In both decays, the number of events observed after all selection requirements is consistent with the expectation from background plus standard model signal predictions. The resulting upper limits on the branching fractions are B(B-S(0) -> mu(+)mu(-)) < 7.7 x 10(-9) and B(B-0 -> mu(+)mu(-) ) < 1.8 x 10(-9) at 95% confidence level.]]> Sat, 25 May 2013 13:29:12 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000304146600033 ,042 (2012)

We propose a four dimensional description of Composite Higgs Models which represents a complete framework for the physics of the Higgs as a pseudo-Nambu-Goldstone boson. Our setup captures all the relevant features of 5D models and more in general of composite Higgs models with partial compositeness. We focus on the minimal scenario where we include a single multiplet of resonances of the composite sector, as these will be the only degrees of freedom which might be accessible at the LHC. This turns out to be sufficient to compute the effective potential and derive phenomenological consequences of the theory. Moreover our simplified approach is well adapted to simulate these models at the LHC. We also consider the impact of non-minimal terms in the effective lagrangian which do not descend from a 5D theory and could be of phenomenological relevance, for example contributing to the S-parameter.]]> Sat, 25 May 2013 13:29:12 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000304146600042 ,124 (2012)

We present a new method to evaluate with high precision isospin breaking effects due to the small mass difference between the up and down quarks using lattice QCD. Our proposal is applicable in principle to any hadronic observable which can be computed on the lattice. It is based on the expansion of the path-integral in powers of the small parameter m(d) - m(u). In this paper, we apply this method to compute the leading isospin breaking effects for several physical quantities of interest: the kaon meson masses, the kaon decay constant, the form factors of semileptonic K-l3 decays and the neutron-proton mass splitting]]> Sat, 25 May 2013 13:29:12 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000304148100050 ,107 (2012)

We show that any pair of classical solutions of open string field theory can be related by a formal gauge transformation defined by a gauge parameter U without an inverse. We investigate how this observation can be used to construct new solutions. We find that a choice of gauge parameter consistently generates a new solution only if the BRST charge maps the image of U into itself. When this occurs, we argue that U naturally defines a star algebra projector which describes a surface of string connecting the boundary conformal field theories of the classical solutions related by U. We also note that singular gauge transformations give the solution space of open string field theory the structure of a category, and we comment on the physical interpretation of this observation.]]> Sat, 25 May 2013 13:29:12 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000304148100033 ,015 (2012)

In this paper we apply in a systematic way a previously developed integration algorithm of the relevant Lax equation to the construction of spherical symmetric, asymptotically flat black hole solutions of N = 2 supergravities with symmetric Special Geometry. Our main goal is the classification of these black-holes according to the H-star-orbits in which the space of possible Lax operators decomposes. By H-star one denotes the isotropy group of the coset U-D=3/H-star which appears in the time-like dimensional reduction of supergravity from D = 4 to D = 3 dimensions. The main result of our investigation is the construction of three universal tensors, extracted from quadratic and quartic powers of the Lax operator, that are capable of classifying both regular and nilpotent H-star-orbits of Lax operators. Our tensor based classification is compared, in the case of the simple one-field model S-3, to the algebraic classification of nilpotent orbits and it is shown to provide a simple discriminating method. In particular we present a detailed analysis of the S-3 model, constructing explicitly its solutions and discussing the Liouville integrability of the corresponding dynamical system. By means of the Kostant-representation of a generic Lie algebra element, we were able to develop an algorithm which produces the necessary number of hamiltonians in involution required by Liouville integrability of generic orbits. The degenerate orbits correspond to extremal black-holes and are nilpotent. We present an in depth discussion of their identification and of the construction of the corresponding supergravity solutions. We dwell on the relation between H-star orbits and critical points of the geodesic potential showing that there is correspondence yet not one-to-one.]]> Sat, 25 May 2013 13:29:12 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000304146600015 ,060 (2012)

We analyze possible interpretations of the recent LHCb evidence for CP violation in D meson decays in terms of physics beyond the Standard Model. On general grounds, models in which the primary source of flavor violation is linked to the breaking of chiral symmetry (left-right flavor mixing) are natural candidates to explain this effect, via enhanced chromomagnetic operators. In the case of supersymmetric models, we identify two motivated scenarios: disoriented A-terms and split families. These structures predict other non-standard signals, such as nuclear EDMs close to their present bounds and, possibly, tiny but visible deviations in K and B physics, or even sizable flavor-violating processes involving the top quark or the stops. Some of these connections, especially the one with nuclear EDMs, hold beyond supersymmetry, as illustrated with the help of prototype non-supersymmetric models.]]> Sat, 25 May 2013 13:29:12 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000304146600060 ,135 (2012)

We study the magnetic response of holographic superconductors exhibiting an insulating 'normal' phase. These materials can be realized as a CFT compactified on a circle, which is dual to the AdS Soliton geometry. We study the response under i) magnetic fields and ii) a Wilson line on the circle. Magnetic fields lead to formation of vortices and allows one to infer that the superconductor is of type II. The response to a Wilson line is in the form of Aharonov-Bohm-like effects. These are suppressed in the holographic conductor/superconductor transition but, instead, they are unsuppressed for the insulator case. Holography, thus, predicts that generically insulators display stronger Aharonov-Bohm effects than conductors. In the fluid-mechanical limit the AdS Soliton is interpreted as a supersolid. Our results imply that supersolids display unsuppressed Aharonov-Bohm (or 'Sagnac') effects - stronger than in superfluids.]]> Sat, 25 May 2013 13:29:12 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000304148100061 ,069 (2012)

A search is preseritecl for same-sign top-quark production and down-type heavy quarks of charge -1/3 in events with two isolated leptons (c or mu) that have the same electric charge, at least two jets and large missing transverse momentum. The data are selected from pp collisions at root s = 7 TeV recorded by the ATLAS detector and correspond to an integrated luminosity of 1.04 fb(-1). The observed data are consistent with expectations from Standard Model processes. Upper limits are set at 95% confidence level on the cross section of new sources of same-sign top-quark pair production of 1.4-2.0 pb depending on the assumed mediator mass. Upper limits are also set on the pair-production cross-section for new heavy down-type quarks; a lower limit of 450 GeV is set at 95% confidence level on the mass of heavy down-type quarks under the assumption that they decay 100% of the time to Wt.]]> Sat, 25 May 2013 13:29:11 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000304146600069 ,129 (2012)

A study of mixing and indirect CP violation in D-0 mesons through the determination of the parameters y(CP) and A(Gamma) is presented. The parameter y(CP) is the deviation from unity of the ratio of effective lifetimes measured in D-0 decays to the CP eigenstate K+K- with respect to decays to the Cabibbo favoured mode K-pi(+). The result measured using data collected by LHCb in 2010, corresponding to an integrated luminosity of 29 pb(-1), is y(CP) = (5.5 +/- 6.3(stat) +/- 4.1(syst)) x 10(-3). The parameter A(Gamma) is the asymmetry of effective lifetimes measured in decays of D-0 and (D) over bar (0) mesons to K+K-. The result is A = (-5.9 +/- 5.9(stat) +/- 2.1(syst)) x 10(-3). A data-driven technique is used to correct for lifetime-biasing effects.]]> Sat, 25 May 2013 13:29:11 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000304148100055 ,093 (2012)

The production of B-+/- mesons in proton-proton collisions at root s = 7 TeV is studied using 35 pb(-1) of data collected by the LHCb detector. The B-+/- mesons are reconstructed exclusively in the B-+/- -> J/(sic)K-+/- mode, with J/(sic) -> mu(+)mu(-). The differential production cross-section is measured as a function of the B-+/- transverse momentum in the fiducial region 0 < p(T) < 40 GeV/c and with rapidity 2.0 < y < 4.5. The total cross-section, summing up B+ and B-, is measured to be sigma(pp -> B-+/- X, 0 < p(T) < 40 GeV/c, 2.0 < y < 4.5) = 41.4 +/- 1.5 (stat.) +/- 3.1 (syst.) mu b.]]> Sat, 25 May 2013 13:29:11 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000304148100019 ,008 (2012)

We provide a comprehensive model-independent analysis of rare decays involving the b -> s transition to put constraints on dimension-six Delta F = 1 effective operators. The constraints are derived from all the available up-to-date experimental data from the B-factories, CDF and LHCb. The implications and future prospects for observables in b -> sl(+)l(-) and b -> sv (v) over bar transitions in view of improved measurements are also investigated. The present work updates and generalises previous studies providing, at the same time, a useful tool to test the flavour structure of any theory beyond the SM.]]> Sat, 25 May 2013 13:29:11 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000304146600008 ,005 (2012)

We compute the first curvature corrections to the spectrum of light-cone gauge type IIA string theory that arise in the expansion of AdS(4) x CP3 about a plane-wave limit. The resulting spectrum is shown to match precisely, both in magnitude and degeneration that of the corresponding solutions of the all-loop Gromov-Vieira Bethe Ansatz. The one-loop dispersion relation correction is calculated for all the single oscillator states of the theory, with the level matching condition lifted. It is shown to have all logarithmic divergences cancelled and to leave only a finite exponentially suppressed contribution, as shown earlier for light bosons. We argue that there is no ambiguity in the choice of the regularization for the self-energy sum, since the regularization applied is the only one preserving unitarity. Interaction matrices in the full degenerate two-oscillator sector are calculated and the spectrum of all two light magnon oscillators is completely determined. The same finite-size corrections, at the order 1/J, where J is the length of the chain, in the two-magnon sector are calculated from the all loop Bethe Ansatz. The corrections obtained by the two completely different methods coincide up to the fourth order in lambda' lambda/J(2.) We conjecture that the equivalence extends to all orders in lambda' and to higher orders in 1/J.]]> Sat, 25 May 2013 13:29:11 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000304146600005 ,127 (2012)

We present up-to-date constraints on a generic Higgs parameter space. An accurate assessment of these exclusions must take into account statistical, and potentially signal, fluctuations in the data currently taken at the LHC. For this, we have constructed a straightforward statistical method for making full use of the data that is publicly available. We show that, using the expected and observed exclusions which are quoted for each search channel, we can fully reconstruct likelihood profiles under very reasonable and simple assumptions. Even working with this somewhat limited information, we show that our method is sufficiently accurate to warrant its study and advocate its use over more naive prescriptions. Using this method, we can begin to narrow in on the remaining viable parameter space for a Higgs-like scalar state, and to ascertain the nature of any hints of new physics - Higgs or otherwise - appearing in the data.]]> Sat, 25 May 2013 13:29:11 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000304148100053 ,105 (2012)

In this article we explore the duality between the low energy effective theory of five-dimensional N = 1 SU(N)(M-1) and SU(M)(N-1) linear quiver gauge theories compactified on S-1. The theories we study are the five-dimensional uplifts of four-dimensional superconformal linear quivers. We study this duality by comparing the Seiberg-Witten curves and the Nekrasov partition functions of the two dual theories. The Seiberg-Witten curves are obtained by minimizing the worldvolume of an M5-brane with nontrivial geometry. Nekrasov partition functions are computed using topological string theory. The result of our study is a map between the gauge theory parameters, i.e., Coulomb moduli, masses and UV coupling constants, of the two dual theories. Apart from the obvious physical interest, this duality also leads to compelling mathematical identities. Through the AGTW conjecture these five-dimentional gauge theories are related to q-deformed Liouville and Toda SCFTs in two-dimensions. The duality we study implies the relations between Liouville and Toda correlation functions through the map we derive.]]> Sat, 25 May 2013 13:29:11 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000304148100031 ,037 (2012)

We present a fully consistent implementation of electroweak and strong radiative corrections to single W hadroproduction in the POWHEG BOX framework, treating soft and collinear photon emissions on the same ground as coloured parton emissions. This framework can be easily extended to more complex electroweak processes. We describe how next-to-leading order (NLO) electroweak corrections are combined with the NLO QCD calculation, and show how they are interfaced to QCD and QED shower Monte Carlo. The resulting tool fills a gap in the literature and allows to study comprehensively the interplay of QCD and electroweak effects to W production using a single computational framework. Numerical comparisons with the predictions of the electroweak generator HORACE, as well as with existing results on the combination of electroweak and QCD corrections to W production, are shown for the LHC energies, to validate the reliability and accuracy of the approach.]]> Sat, 25 May 2013 13:29:11 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000304146600037 ,045 (2012)

We derive an exact algebraic identity between the two-loop four-point amplitude in ABJM theory and the corresponding one-loop amplitude in N = 4 SYM theory. This identity generalizes previous partial results to an exact relation valid at all orders in the IR regulator. Moreover, it allows to conjecture an exact iterative expression for the complete three dimensional amplitude in terms of the BDS ansatz for the four dimensional one, indicating that the strict relation between the two amplitudes experimented at two loops might propagate to all orders. In particular, an almost complete expression for the ABJM amplitude at four loops is derived.]]> Sat, 25 May 2013 13:29:11 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000304146600045 ,117 (2012)

We study theta-vacua in the 2-d lattice O(3) model using the standard action and an optimized constraint action with very small cut-off effects, combined with the geometric topological charge. Remarkably, dislocation lattice artifacts do not spoil the non-trivial continuum limit at theta not equal 0, and there are different continuum theories for each value 0 <= theta <= pi. A very precise Monte Carlo study of the step scaling function indirectly confirms the exact S-matrix of the 2-d O(3) model at theta = pi.]]> Sat, 25 May 2013 13:29:11 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000304148100043 ,001 (2012)

]]> Sat, 25 May 2013 13:29:11 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000304146600001 ,036 (2012)

A search for the standard model Higgs boson decaying into two Z bosons with subsequent decay into a final state containing two quark jets and two leptons, H -> ZZ((*)) -> q (q) over barl(-)l(+) is presented. Results are based on data corresponding to an integrated luminosity of 4.6 fb(-1) of proton-proton collisions at root s = 7TeV, collected with the CMS detector at the LHC. In order to discriminate between signal and background events, kinematic and topological quantities, including the angular spin correlations of the decay products, are employed. Events are further classified according to the probability of the jets to originate from quarks of light or heavy flavor or from gluons. No evidence for the Higgs boson is found, and upper limits on its production cross section are determined for a Higgs boson of mass between 130 and 600 GeV]]> Sat, 25 May 2013 13:29:11 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000304146600036 710, (2012)

A search for the standard model Higgs boson (H) decaying to (b) over barb when produced in association with weak vector bosons (V) is reported for the following modes: W(mu nu)H, W(e nu)H, Z(mu mu)H, Z(ee)H and Z(nu nu)H. The search is performed in a data sample corresponding to an integrated luminosity of 4.7 fb(-1), recorded by the CMS detector in proton-proton collisions at the LHC with a center-of-mass energy of 7 TeV. No significant excess of events above the expectation from background is observed. Upper limits on the VH production cross section times the H -> b (b) over bar branching ratio, with respect to the expectations for a standard model Higgs boson, are derived for a Higgs boson in the mass range 110-135 GeV. In this range, the observed 95% confidence level upper limits vary from 3.4 to 7.5 times the standard model prediction; the corresponding expected limits vary from 2.7 to 6.7 times the standard model prediction. (C) 2012 CERN. Published by Elsevier B.V. All rights reserved.]]> Sat, 25 May 2013 13:27:50 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000302838100005 710, (2012)

The search for neutrinoless double beta decay probes lepton number conservation with high sensitivity and investigates the neutrino nature and mass scale. Experiments presently in preparation will cover the quasi-degeneracy region of the neutrino mass pattern. Probing the inverted hierarchy region requires improved sensitivities and next-generation experiments, based either on large expansions of the present searches or on new ideas. We examine here a novel technology relying on ZnMoO4 scintillating bolometers, which can provide an experiment with background close to zero in the ton x year exposure scale. The promising performance of a pilot detector is presented, both in terms of energy resolution and background control. A preliminary study of the sensitivities of future experiments shows that the inverted hierarchy region is within the reach of the technique here proposed. A realistic phased approach program towards a next-generation search is presented and briefly discussed. (C) 2012 Elsevier B.V. All rights reserved.]]> Sat, 25 May 2013 13:27:50 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000302838100007 85,045802 (2012)

Proton resonant states in P-27 were studied by the resonant elastic scattering of Si-26 + p with a Si-26 radioactive ion beam bombarding a thick H-2 gas target with the inverse kinematics method. The properties of these resonance states are important to better constrain the production rates of the Si-26( p, gamma)P-27 reaction. This is one of the astrophysically important reactions needed to understand proton-rich nucleosynthesis such as the galactic production of Al-26 and energy generation in explosive stellar environments. Although there are recent studies on the resonant structure in P-27, large uncertainties remain, and only a few levels are known. In this work, resonant states were observed over the excitation energies range of 2.3 to 3.8 MeV with high statistics and without background contamination within the target. The resonance parameters were extracted by an R-matrix analysis of the excitation function. The Si-26( p,gamma)P-27 stellar reaction rate has been evaluated, including high-lying resonances found in this work.]]> Sat, 25 May 2013 13:27:50 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000302292000007 85,086002 (2012)

We study both the large and small U-duality charge orbits of extremal black holes appearing in D = 5 and D = 4 Maxwell-Einstein supergravity theories with symmetric scalar manifolds. We exploit a formalism based on cubic Jordan algebras and their associated Freudenthal triple systems, in order to derive the minimal charge representatives, their stabilizers and the associated "moduli spaces." After recalling N = 8 maximal supergravity, we consider N = 2 and N = 4 theories coupled to an arbitrary number of vector multiplets, as well as N = 2 magic, STU, ST2 and T-3 models. While the STU model may be considered as part of the general N = 2 sequence, albeit with an additional triality symmetry, the ST2 and T-3 models demand a separate treatment, since their representative Jordan algebras are Euclidean or only admit nonzero elements of rank 3, respectively. Finally, we also consider minimally coupled N = 2, matter-coupled N = 3, and pure N = 5 theories.]]> Sat, 25 May 2013 13:27:50 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000302293000007 85,086001 (2012)

We investigate static, planar solutions of Einstein-scalar gravity admitting an anti-de Sitter (AdS) vacuum. When the squared mass of the scalar field is positive and the scalar potential can be derived from a superpotential, minimum energy theorems indicate the existence of a scalar soliton. On the other hand, for these models, no-hair theorems forbid the existence of hairy black brane solutions with AdS asymptotics. By considering a specific example (an exact integrable model which has the form of a Toda molecule) and by deriving explicit exact solution, we show that these models allow for hairy black brane solutions with non-AdS domain wall asymptotics, whose extremal limit is a scalar soliton. The soliton smoothly interpolates between a non-AdS domain wall solution at r = infinity and an AdS solution near r = 0.]]> Sat, 25 May 2013 13:27:50 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000302293000006 85,072001 (2012)

This paper presents a search for standard model Higgs boson production in association with a W boson using events recorded by the CDF experiment in a data set corresponding to an integrated luminosity of 5.6 fb(-1). The search is performed using a matrix element technique in which the signal and background hypotheses are used to create a powerful discriminator. The discriminant output distributions for signal and background are fit to the observed events using a binned likelihood approach to search for the Higgs boson signal. We find no evidence for a Higgs boson, and 95% confidence level (C.L.) upper limits are set on sigma(p (p) over bar -> WH) X B(H -> b (b) over bar). The observed limits range from 3.5 to 37.6 relative to the standard model expectation for Higgs boson masses between m(H) = 100 GeV/c(2) and m(H) 150 GeV/c(2). The 95% C.L. expected limit is estimated from the median of an ensemble of simulated experiments and varies between 2.9 and 32.7 relative to the production rate predicted by the standard model over the Higgs boson mass range studied.]]> Sat, 25 May 2013 13:27:50 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000302238000001 85,042102 (2012)

We generalize Bell's hidden-variable model describing the singlet state of a two-qubit system by extending it to arbitrary states and observables. As in the original work, we assume a uniform, state-independent probability distribution for the hidden variables which are identified with the unit vectors of a three-dimensional real space. By slightly modifying our model, we provide also a minimal hidden variable description of the two-qubit system, relying on a single hidden variable. We discuss the main features and the implications of the model.]]> Sat, 25 May 2013 13:27:50 +0200 http://www.infn.it/pubblicazioni/dettaglio.php?UT=WOS%3A000302234800002