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Aguilar-Saavedra, J. A., Bernabeu, J., Mitsou, V. A., & Segarra, A. (2017). The Z boson spin observables as messengers of new physics. Eur. Phys. J. C, 77(4), 234–6pp.
Abstract: We demonstrate that the eight multipole parameters describing the spin state of the Z boson are able to disentangle known Z production mechanisms and signals from new physics at the LHC. They can be extracted from appropriate asymmetries in the angular distribution of lepton pairs from the Z boson decay. The power of this analysis is illustrated by (1) the production of Z boson plus jets; (2) Z boson plus missing transverse energy; (3) W and Z bosons originating from the two-body decay of a heavy resonance.
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Albiol, A., Corbi, A., & Albiol, F. (2017). Automatic intensity windowing of mammographic images based on a perceptual metric. Med. Phys., 44(4), 1369–1378.
Abstract: Purpose: Initial auto-adjustment of the window level WL and width WW applied to mammographic images. The proposed intensity windowing (IW) method is based on the maximization of the mutual information (MI) between a perceptual decomposition of the original 12-bit sources and their screen displayed 8-bit version. Besides zoom, color inversion and panning operations, IW is the most commonly performed task in daily screening and has a direct impact on diagnosis and the time involved in the process. Methods: The authors present a human visual system and perception-based algorithm named GRAIL (Gabor-relying adjustment of image levels). GRAIL initially measures a mammogram's quality based on the MI between the original instance and its Gabor-filtered derivations. From this point on, the algorithm performs an automatic intensity windowing process that outputs the WL/WW that best displays each mammogram for screening. GRAIL starts with the default, high contrast, wide dynamic range 12-bit data, and then maximizes the graphical information presented in ordinary 8-bit displays. Tests have been carried out with several mammogram databases. They comprise correlations and an ANOVA analysis with the manual IW levels established by a group of radiologists. A complete MATLAB implementation of GRAIL is available at . Results: Auto-leveled images show superior quality both perceptually and objectively compared to their full intensity range and compared to the application of other common methods like global contrast stretching (GCS). The correlations between the human determined intensity values and the ones estimated by our method surpass that of GCS. The ANOVA analysis with the upper intensity thresholds also reveals a similar outcome. GRAIL has also proven to specially perform better with images that contain micro-calcifications and/or foreign X-ray-opaque elements and with healthy BI-RADS A-type mammograms. It can also speed up the initial screening time by a mean of 4.5 s per image. Conclusions: A novel methodology is introduced that enables a quality-driven balancing of the WL/WW of mammographic images. This correction seeks the representation that maximizes the amount of graphical information contained in each image. The presented technique can contribute to the diagnosis and the overall efficiency of the breast screening session by suggesting, at the beginning, an optimal and customized windowing setting for each mammogram.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Barranco Navarro, L., Cabrera Urban, S., Castillo Gimenez, V., Cerda Alberich, L., et al. (2017). Measurement of charged-particle distributions sensitive to the underlying event in root s=13 TeV proton-proton collisions with the ATLAS detector at the LHC. J. High Energy Phys., 03(3), 157–42pp.
Abstract: We present charged-particle distributions sensitive to the underlying event, measured by the ATLAS detector in proton-proton collisions at a centre-of-mass energy of 13 TeV, in low-luminosity Large Hadron Collider fills corresponding to an integrated luminosity of 1.6 nb-1. The distributions were constructed using charged particles with absolute pseudorapidity less than 2.5 and with transverse momentum greater than 500 MeV, in events with at least one such charged particle with transverse momentum above 1 GeV. These distributions characterise the angular distribution of energy and particle flows with respect to the charged particle with highest transverse momentum, as a function of both that momentum and of charged-particle multiplicity. The results have been corrected for detector effects and are compared to the predictions of various Monte Carlo event generators, experimentally establishing the level of underlying-event activity at LHC Run 2 energies and providing inputs for the development of event generator modelling. The current models in use for UE modelling typically describe this data to 5% accuracy, compared with data uncertainties of less than 1%.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., Ruiz Valls, P., et al. (2017). Observation of B-c(+) -> J/psi D-(*()) K-(*()) decays. Phys. Rev. D, 95(3), 032005–12pp.
Abstract: A search for the decays B-c(+) -> J/psi D-(*()0) Kappa(+) and B-c(+) -> J/psi D-(*K)+*(0) is performed with data collected at the LHCb experiment corresponding to an integrated luminosity of 3 fb(-1). The decays B-c(+) -> J/psi(DK+)-K-0 and B-c(+) -> J/psi D*K-0(+) are observed for the first time, while first evidence is reported for the B-c(broken vertical bar) -> J/psi D*K-broken vertical bar(*0) and B-c(broken vertical bar) -> J/psi(DK)-K-broken vertical bar*(0) decays. The branching fractions of these decays are determined relative to the B-c(+) -> J/psi pi(+) decay. The B-c(+) mass is measured, using the J/psi(DK+)-K-0 final state, to be 6274.28 +/- 1.40(stat) +/- 0.32(syst) MeV/c(2). This is the most precise single measurement of the B-c(+) mass to date.
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Wuensch, W., Degiovanni, A., Calatroni, S., Korsback, A., Djurabekova, F., Rajamaki, R., et al. (2017). Statistics of vacuum breakdown in the high-gradient and low-rate regime. Phys. Rev. Accel. Beams, 20(1), 011007–11pp.
Abstract: In an increasing number of high-gradient linear accelerator applications, accelerating structures must operate with both high surface electric fields and low breakdown rates. Understanding the statistical properties of breakdown occurrence in such a regime is of practical importance for optimizing accelerator conditioning and operation algorithms, as well as of interest for efforts to understand the physical processes which underlie the breakdown phenomenon. Experimental data of breakdown has been collected in two distinct high-gradient experimental set-ups: A prototype linear accelerating structure operated in the Compact Linear Collider Xbox 12GHz test stands, and a parallel plate electrode system operated with pulsed DC in the kV range. Collected data is presented, analyzed and compared. The two systems show similar, distinctive, two-part distributions of number of pulses between breakdowns, with each part corresponding to a specific, constant event rate. The correlation between distance and number of pulses between breakdown indicates that the two parts of the distribution, and their corresponding event rates, represent independent primary and induced follow-up breakdowns. The similarity of results from pulsed DCto 12GHz rf indicates a similar vacuum arc triggering mechanism over the range of conditions covered by the experiments.
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Pakarinen, J. et al, & Algora, A. (2017). Collectivity in Pb-196, Pb-198 isotopes probed in Coulomb-excitation experiments at REX-ISOLDE. J. Phys. G, 44(6), 064009–10pp.
Abstract: The neutron-deficient Pb-196,Pb-198 isotopes have been studied in Coulomb-excitation experiments employing the Miniball gamma-ray spectrometer and radioactive ion beams from the REX-ISOLDE post-accelerator at CERN. The reduced transition probabilities of the first excited 2(+) states in Pb-196 and Pb-198 nuclei have been measured for the first time. Values of B (E2) = 18.2(-4.1)(+4.8) W. u. and B (E2) = 13.1(-3.5)(+4.9) W. u., were obtained, respectively. The experiment sheds light on the development of collectivity when moving from the regime governed by the generalised seniority scheme to a region, where intruding structures, associated with different deformed shapes, start to come down in energy and approach the spherical ground state.
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del Rio, A., Ferreiro, A., Navarro-Salas, J., & Torrenti, F. (2017). Adiabatic regularization with a Yukawa interaction. Phys. Rev. D, 95(10), 105003–19pp.
Abstract: We extend the adiabatic regularization method for an expanding universe to include the Yukawa interaction between quantized Dirac fermions and a homogeneous background scalar field. We give explicit expressions for the renormalized expectation values of the stress-energy tensor < T-mu nu > and the bilinear <(psi) over bar psi > in a spatially flat Friedmann-Lemaitre-Robertson-Walker (FLRW) spacetime. These are basic ingredients in the semiclassical field equations of fermionic matter in curved spacetime interacting with a background scalar field. The ultraviolet subtracting terms of the adiabatic regularization can be naturally interpreted as coming from appropriate counterterms of the background fields. We fix the required covariant counterterms. To test our approach we determine the contribution of the Yukawa interaction to the conformal anomaly in the massless limit and show its consistency with the heat-kernel method using the effective action.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2017). Measurement of the B-s(0)-> mu(+) mu(-) Branching Fraction and Effective Lifetime and Search for B-0 ->mu(+) mu(-) Decays. Phys. Rev. Lett., 118(19), 191801–11pp.
Abstract: A search for the rare decays B-s(0)->mu(+)mu(-) and B-0 -> mu(+)mu(-) is performed at the LHCb experiment using data collected in pp collisions corresponding to a total integrated luminosity of 4.4 fb(-1). An excess of B-s(0) -> mu(+)mu- decays is observed with a significance of 7.8 standard deviations, representing the first observation of this decay in a single experiment. The branching fraction is measured to be B(B-s(0) -> mu(+)mu(-)) = (3.0 +/- 0.6(-0.2)(+)(0.3)) x 10(-9), where the first uncertainty is statistical and the second systematic. The first measurement of the B-s(0) -> mu(+)mu(-) effective lifetime, tau(B-s(0)-> mu(+) mu(-)) = 2.04 +/- 0.44 +/- 0.05 ps, is reported. No significant excess of B-0 -> mu(+)mu(-) decays is found, and a 95% confidence level upper limit, B(B-0 -> mu(+)mu(-) ) < 3.4 x 10(-10), is determined. All results are in agreement with the standard model expectations.
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Guerrero, C., Domingo-Pardo, C., Kappeler, F., Lerendegui-Marco, J., Palomo, F. R., Quesada, J. M., et al. (2017). Prospects for direct neutron capture measurements on s-process branching point isotopes. Eur. Phys. J. A, 53(5), 87–5pp.
Abstract: The neutron capture cross sections of several unstable key isotopes acting as branching points in the s-process are crucial for stellar nucleosynthesis studies, but they are very challenging to measure directly due to the difficult production of sufficient sample material, the high activity of the resulting samples, and the actual (n, gamma) measurement, where high neutron fluxes and effective background rejection capabilities are required. At present there are about 21 relevant s-process branching point isotopes whose cross section could not be measured yet over the neutron energy range of interest for astrophysics. However, the situation is changing with some very recent developments and upcoming technologies. This work introduces three techniques that will change the current paradigm in the field: the use of gamma-ray imaging techniques in (n,gamma) experiments, the production of moderated neutron beams using high-power lasers, and double capture experiments in Maxwellian neutron beams.
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KM3NeT Collaboration(Adrian-Martinez, S. et al), Barrios-Marti, J., Calvo, D., Hernandez-Rey, J. J., Illuminati, G., Lotze, M., et al. (2017). Intrinsic limits on resolutions in muon- and electron-neutrino charged-current events in the KM3NeT/ORCA detector. J. High Energy Phys., 05(5), 008–39pp.
Abstract: Studying atmospheric neutrino oscillations in the few-GeV range with a multimegaton detector promises to determine the neutrino mass hierarchy. This is the main science goal pursued by the future KM3NeT/ORCA water Cherenkov detector in the Mediterranean Sea. In this paper, the processes that limit the obtainable resolution in both energy and direction in charged-current neutrino events in the ORCA detector are investigated. These processes include the composition of the hadronic fragmentation products, the subsequent particle propagation and the photon-sampling fraction of the detector. GEANT simulations of neutrino interactions in seawater produced by GENIE are used to study the effects in the 1-20 GeV range. It is found that fluctuations in the hadronic cascade in conjunction with the variation of the inelasticity y are most detrimental to the resolutions. The effect of limited photon sampling in the detector is of significantly less importance. These results will therefore also be applicable to similar detectors/media, such as those in ice.
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