ATLAS Collaboration(Aad, G. et al), Amoros, G., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Escobar, C., et al. (2011). Search for high mass dilepton resonances in pp collisions at root s=7 TeV with the ATLAS experiment. Phys. Lett. B, 700(3-4), 163–180.
Abstract: This Letter presents a search for high mass e(+)e(-) or mu(+)mu(-) resonances in pp collisions at root s = 7 TeV at the LHC. The data were recorded by the ATLAS experiment during 2010 and correspond to a total integrated luminosity of similar to 40 pb(-1). No statistically significant excess above the Standard Model expectation is observed in the search region of dilepton invariant mass above 110 GeV. Upper limits at the 95% confidence level are set on the cross section times branching ratio of Z' resonances decaying to dielectrons and dimuons as a function of the resonance mass. A lower mass limit of 1.048 TeV on the Sequential Standard Model Z' boson is derived, as well as mass limits on Z* and E(6)-motivated Z' models.
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n_TOF Collaboration(Belloni, F. et al), Domingo-Pardo, C., & Tain, J. L. (2011). Measurement of the neutron-induced fission cross-section of Am-243 relative to U-235 from 0.5 to 20 MeV. Eur. Phys. J. A, 47(12), 160–8pp.
Abstract: The ratio of the neutron-induced fission cross-sections of Am-243 and U-235 was measured in the energy range from 0.5 to 20 MeV with uncertainties of approximate to 4%. The experiment was performed at the CERN n_TOF facility using a fast ionization chamber. With the good counting statistics that could be achieved thanks to the high instantaneous flux and the low backgrounds, the present results are useful for resolving discrepancies in previous data sets and are important for future reactors with improved fuel burn-up.
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Nishimura, D., Fujita, Y., Fukuda, M., Ganioglu, E., Ichikawa, Y., Kanazawa, M., et al. (2011). Beta and gamma decays of J(pi)=1(+), Al-24m state beta and gamma branching ratios. Eur. Phys. J. A, 47(12), 155–7pp.
Abstract: A beta-gamma spectroscopy of the J(pi) = 1(+), 426 keV isomeric state of Al-24 ( Al-24m) has been carried out by using a Al-24 secondary beam with high purity and high isomeric ratio. From the absolute gamma-ray and beta-particle intensities observed in the decay of the isomeric state, the branching ratio R-B of the isomeric gamma-decay from Al-24m to the J(pi) = 4(+), ground state of Al-24 have been derived. The obtained R-B value of 69.6(7)% is much smaller than the previously accepted value of 82.5(30)%. The precise half-life for the isomer decay, T-1/2(m) = 130.9(13) ms, has been also determined in this experiment. Accordingly, the M3 gamma-decay strength B(M3) of the Al-24m decay becomes smaller and the total beta-decay branching ratio becomes larger. In particular, the beta-decay branching ratio to the ground state of Mg-24 becomes 24.3(9)%, which is 2.4 times larger than the previous value of 10.1(28)%. By combining the branching ratio and the half-life, the Gamow-Teller (GT) transition strength B(GT) of 0.0194(7) is deduced for the GT transition from Al-24m to the J(pi) = 0(+), ground state of Mg-24. This value is in good agreement with the values derived from charge-exchange reactions.
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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. (2011). Measurement of the inclusive isolated prompt photon cross-section in pp collisions at sqrt(s)=7 TeV using 35 pb(-1) of ATLAS data. Phys. Lett. B, 706(2-3), 150–167.
Abstract: A measurement of the differential cross-section for the inclusive production of isolated prompt photons in pp collisions at a center-of-mass energy sqrt(s) = 7 TeV is presented. The measurement covers the pseudorapidity ranges vertical bar eta vertical bar < 1.37 and 1.52 <= vertical bar eta vertical bar < 2.37 in the transverse energy range 45 <= E(T) < 400 GeV. The results are based on an integrated luminosity of 35 pb(-1), collected with the ATLAS detector at the LHC. The yields of the signal photons are measured using a data-driven technique, based on the observed distribution of the hadronic energy in a narrow cone around the photon candidate and the photon selection criteria. The results are compared with next-to-leading order perturbative QCD calculations and found to be in good agreement over four orders of magnitude in cross-section.
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Forero, D. V., Morisi, S., Tortola, M., & Valle, J. W. F. (2011). Lepton flavor violation and non-unitary lepton mixing in low-scale type-I seesaw. J. High Energy Phys., 09(9), 142–18pp.
Abstract: Within low-scale seesaw mechanisms, such as the inverse and linear seesaw, one expects (i) potentially large lepton flavor violation (LFV) and (ii) sizeable non-standard neutrino interactions (NSI). We consider the interplay between the magnitude of non-unitarity effects in the lepton mixing matrix, and the constraints that follow from LFV searches in the laboratory. We find that NSI parameters can be sizeable, up to percent level in some cases, while LFV rates, such as that for μ-> e gamma, lie within current limits, including the recent one set by the MEG collaboration. As a result the upcoming long baseline neutrino experiments offer a window of opportunity for complementary LFV and weak universality tests.
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