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CDF Collaboration(Aaltonen, T. et al), & Cabrera, S. (2010). Search for new color-octet vector particle decaying to t(t)over-bar in p(p)over-bar collisions at root s=1.96 TeV. Phys. Lett. B, 691(4), 183–190.
Abstract: We present the result of a search for a massive color-octet vector particle, (e.g. a massive gluon) decaying to a pair of top quarks in proton-antiproton collisions with a center-of-mass energy of 1.96 TeV. This search is based on 1.9 fb(-1) of data collected using the CDF detector during Run II of the Tevatron at Fermilab. We study t (t) over bar events in the lepton + jets channel with at least one b-tagged jet. A massive gluon is characterized by its mass, decay width, and the strength of its coupling to quarks. These parameters are determined according to the observed invariant mass distribution of top quark pairs. We set limits on the massive gluon coupling strength for masses between 400 and 800 GeV/c(2) and width-to-mass ratios between 0.05 and 0.50. The coupling strength of the hypothetical massive gluon to quarks is consistent with zero within the explored parameter space.
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Colonna, N., Belloni, F., Berthoumieux, E., Calviani, M., Domingo-Pardo, C., Guerrero, C., et al. (2010). Advanced nuclear energy systems and the need of accurate nuclear data: the n_TOF project at CERN. Energy Environ. Sci., 3(12), 1910–1917.
Abstract: To satisfy the world's constantly increasing demand for energy, a suitable mix of different energy sources has to be devised. In this scenario, an important role could be played by nuclear energy, provided that major safety, waste and proliferation issues affecting current nuclear reactors are satisfactorily addressed. To this purpose, a large effort has been under way for a few years towards the development of advanced nuclear systems with the aim of closing the fuel cycle. Generation IV reactors, with full or partial waste recycling capability, accelerator driven systems, as well as new fuel cycles are the main options being investigated. The design of advanced systems requires improvements in basic nuclear data, such as cross-sections for neutron-induced reactions on actinides. In this paper, the main concepts of advanced reactor systems are described, together with the related needs of new and accurate nuclear data. The present activity in this field at the neutron facility n_TOF at CERN is discussed.
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Pierre Auger Collaboration(Abreu, P. et al), & Pastor, S. (2010). Update on the correlation of the highest energy cosmic rays with nearby extragalactic matter. Astropart Phys., 34(5), 314–326.
Abstract: Data collected by the Pierre Auger Observatory through 31 August 2007 showed evidence for anisotropy in the arrival directions of cosmic rays above the Greisen-Zatsepin-Kuz'min energy threshold, 6 x 10(19) eV. The anisotropy was measured by the fraction of arrival directions that are less than 3.1 degrees from the position of an active galactic nucleus within 75 Mpc (using the Veron-Cetty and Veron 12th catalog). An updated measurement of this fraction is reported here using the arrival directions of cosmic rays recorded above the same energy threshold through 31 December 2009. The number of arrival directions has increased from 27 to 69, allowing a more precise measurement. The correlating fraction is (38(-6)(+7))%, compared with 21% expected for isotropic cosmic rays. This is down from the early estimate of (69-(+11)(13))%. The enlarged set of arrival directions is examined also in relation to other populations of nearby extragalactic objects: galaxies in the 2 Microns All Sky Survey and active galactic nuclei detected in hard X-rays by the Swift Burst Alert Telescope. A celestial region around the position of the radiogalaxy Cen A has the largest excess of arrival directions relative to isotropic expectations. The 2-point autocorrelation function is shown for the enlarged set of arrival directions and compared to the isotropic expectation.
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CDF Collaboration(Aaltonen, T. et al), & Cabrera, S. (2010). Measurement of W-Boson Polarization in Top-Quark Decay in p(p)over-bar Collisions at root s=1.96 TeV. Phys. Rev. Lett., 105(4), 042002–8pp.
Abstract: We report measurements of the polarization of W bosons from top-quark decays using 2.7 fb(-1) of p (p) over bar collisions collected by the CDF II detector. Assuming a top-quark mass of 175 GeV/c(2), three measurements are performed. A simultaneous measurement of the fraction of longitudinal (f(0)) and right-handed (f(0)) W bosons yields the model- independent results f(0) =0. 88 +/- 0.11(stat) +/- 0.06(syst) and f(+) = 0.15 +/- 0.07(stat) +/- 0.06(syst) with a correlation coefficient of -0.59. A measurement of f(0) [f(+)] constraining f(+) [f(0)] to its standard model value of 0.0 [0.7] yields f(0) 0.70 + 0.07(stat) +/- 0.04(syst) [f(+) – 0.01 +/- 0.02(stat) +/- 0.05(syst)]. All these results are consistent with standard model expectations. We achieve the single most precise measurements of f(0) for both the model- independent and modeldependent determinations.
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Perez-Ramos, R., Mathieu, V., & Sanchis-Lozano, M. A. (2010). Heavy quark flavour dependence of multiparticle production in QCD jets. J. High Energy Phys., 08(8), 047–24pp.
Abstract: After inserting the heavy quark mass dependence into QCD partonic evolution equations, we determine the mean charged hadron multiplicity and second multiplicity correlators of jets produced in high energy collisions. We thereby extend the so-called dead cone effect to the phenomenology of multiparticle production in QCD jets and find that the average multiplicity of heavy-quark initiated jets decreases significantly as compared to the massless case, even taking into account the weak decay products of the leading primary quark. We emphasize the relevance of our study as a complementary check of b-tagging techniques at hadron colliders like the Tevatron and the LHC.
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Decoster, S., Cottenier, S., Wahl, U., Correia, J. G., Pereira, L. M. C., Lacasta, C., et al. (2010). Diluted manganese on the bond-centered site in germanium. Appl. Phys. Lett., 97(15), 151914–3pp.
Abstract: The functional properties of Mn-doped Ge depend to large extent on the lattice location of the Mn impurities. Here, we present a lattice location study of implanted diluted Mn by means of electron emission channeling. Surprisingly, in addition to the expected substitutional lattice position, a large fraction of the Mn impurities occupies the bond-centered site. Corroborated by ab initio calculations, the bond-centered Mn is related to Mn-vacancy complexes. These unexpected results call for a reassessment of the theoretical studies on the electrical and magnetic behavior of Mn-doped Ge, hereby including the possible role of Mn-vacancy complexes.
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ATLAS Collaboration(Aad, G. et al), Amoros, G., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Escobar, C., et al. (2010). Search for New Particles in Two-Jet Final States in 7 TeV Proton-Proton Collisions with the ATLAS Detector at the LHC. Phys. Rev. Lett., 105(16), 161801–19pp.
Abstract: A search for new heavy particles manifested as resonances in two-jet final states is presented. The data were produced in 7 TeV proton-proton collisions by the LHC and correspond to an integrated luminosity of 315 nb(-1) collected by the ATLAS detector. No resonances were observed. Upper limits were set on the product of cross section and signal acceptance for excited-quark (q*) production as a function of q* mass. These exclude at the 95% C. L. the q* mass interval 0: 30< m(q)*< 1:26 TeV, extending the reach of previous experiments.
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BABAR Collaboration(del Amo Sanchez, P. et al), Lopez-March, N., Martinez-Vidal, F., Milanes, D. A., & Oyanguren, A. (2010). Search for b -> u transitions in B- -> DK- and D*K- decays. Phys. Rev. D, 82(7), 072006–18pp.
Abstract: We report results from an updated study of the suppressed decays We report results from an updated study of the suppressed decays B- -> DK- and B- -> D*K- followed by D -> K+ pi(-), where D-(*()0) indicates a D-(*()0)or a (D) over bar (()*()0) meson, and D* -> D pi(0) or D* -> D gamma. These decays are sensitive to the Cabibbo-Kobayashi-Maskawa unitarity triangle angle gamma due to interference between the b -> c transition B- -> D-(*K-)0(-) followed by the doubly Cabibbo-suppressed decay D-0 -> K+ pi(-), and the b -> u transition B- -> (D) over bar (()*()0) K- followed by the Cabibbo-favored decay (D) over bar (0) -> K+ pi(-). We also report an analysis of the decay B- -> D-(*())pi(-) with the D decaying into the doubly Cabibbo-suppressed mode D -> K+ pi(-). Our results are based on 467 x 10(6) Gamma(4S) -> BB- decays collected with the BABAR detector at SLAC. We measure the ratios R-(*()) of the suppressed ([K+ pi(-)](D)K- / pi(-)) to favored ([K+ pi(-)](D)K- / pi(-)) branching fractions as well as the CP asymmetries A(()*()) of those modes. We see indications of signals for the B- -> DK- and B- -> D-D pi 0(()*()) K- suppressed modes, with statistical significances of 2.1 and 2.2 sigma, respectively, and we measure: R-DK = (1.1 +/- 0: 6 +/- 0.2) x 10(-2); A(DK) = -0.86 +/- 0: 47(-0.16)(+0.12), R-(D pi 0)K* = (1.8 +/- 0: 9 +/- 0: 4) x 10(-2); A ((D pi 0)K)* = +0.77 +/- 0: 35 +/- 0.12; R-(D gamma)K* = (1.3 +/- 1.4 +/- 0.8) x 10(-2); A((D gamma)K)* = +0.36 +/- 0: 94(-0.41)(+0.25), where the first uncertainty is statistical and the second is systematic. We use a frequentist approach to obtain the magnitude of the ratio r(B) equivalent to vertical bar A(B- -> (D) over bar 0K(-))/A(B- -> (DK-)-K-0)vertical bar = (9.5(-4.1)(+5.1))%, with r(B) < 16: 7% at 90% confidence level. In the case of B- -> D*K- we find r(B) equivalent to vertical bar A(B- -> <(D)over bar>0K(-))/A(B- -> (DK-)-K-0)vertical bar = (9.6(-5.1)(+3.5))%, with r(B)* < 15.0% at 90% confidence level.
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CDF Collaboration(Aaltonen, T. et al), Cabrera, S., & Cuenca Almenar, C. (2010). Study of multi-muon events produced in p (p)over-bar interactions at root s=1.96 TeV. Eur. Phys. J. C, 68(1-2), 109–118.
Abstract: We report the results of a study of multi-muon events produced at the Fermilab Tevatron collider and acquired with the CDF II detector using a dedicated dimuon trigger. The production cross section and kinematics of events in which both muon candidates are produced inside the beam pipe of radius 1.5 cm are successfully modeled by known processes which include heavy flavor production. In contrast, we are presently unable to fully account for the number and properties of the remaining events, in which at least one muon candidate is produced outside of the beam pipe, in terms of the same understanding of the CDF II detector, trigger, and event reconstruction.
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Gavela, M. B., Lopez Honorez, L., Mena, O., & Rigolin, S. (2010). Dark coupling and gauge invariance. J. Cosmol. Astropart. Phys., 11(11), 044–15pp.
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