ATLAS Collaboration(Aad, G. et al), Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Ferrer, A., Fiorini, L., et al. (2012). Search for Magnetic Monopoles in root s=7 TeV pp Collisions with the ATLAS Detector. Phys. Rev. Lett., 109(26), 261803–18pp.
Abstract: This Letter presents a search for magnetic monopoles with the ATLAS detector at the CERN Large Hadron Collider using an integrated luminosity of 2.0 fb(-1) of pp collisions recorded at a center-of-mass energy root s = 7 TeV. No event is found in the signal region, leading to an upper limit on the production cross section at 95% confidence level of 1.6/epsilon fb for Dirac magnetic monopoles with the minimum unit magnetic charge and with mass between 200 GeV and 1500 GeV, where epsilon is the monopole reconstruction efficiency. The efficiency epsilon is high and uniform in the fiducial region given by pseudorapidity vertical bar eta vertical bar < 1: 37 and transverse kinetic energy 600-700<E-kin sin theta< 1400 GeV. The minimum value of 700 GeV is for monopoles of mass 200 GeV, whereas the minimum value of 600 GeV is applicable for higher mass monopoles. Therefore, the upper limit on the production cross section at 95% confidence level is 2 fb in this fiducial region. Assuming the kinematic distributions from Drell-Yan pair production of spin-1= 2 Dirac magnetic monopoles, the efficiency is in the range 1%-10%, leading to an upper limit on the cross section at 95% confidence level that varies from 145 fb to 16 fb for monopoles with mass between 200 GeV and 1200 GeV. This limit is weaker than the fiducial limit because most of these monopoles lie outside the fiducial region.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2012). Search for Low-Mass Dark-Sector Higgs Bosons. Phys. Rev. Lett., 108(21), 211801–7pp.
Abstract: Recent astrophysical and terrestrial experiments have motivated the proposal of a dark sector with GeV-scale gauge boson force carriers and new Higgs bosons. We present a search for a dark Higgs boson using 516 fb(-1) of data collected with the BABAR detector. We do not observe a significant signal and we set 90% confidence level upper limits on the product of the standard model-dark-sector mixing angle and the dark-sector coupling constant.
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ATLAS Collaboration(Aad, G. et al), Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Ferrer, A., Fiorini, L., et al. (2012). Search for light scalar top-quark pair production in final states with two leptons with the ATLAS detector in root s=7 TeV proton-proton collisions. Eur. Phys. J. C, 72(11), 2237–20pp.
Abstract: A search is presented for the pair production of light scalar top quarks in root s = 7 TeV proton-proton collisions recorded with the ATLAS detector at the Large Hadron Collider. This analysis uses the full data sample collected during 2011 running that corresponds to a total integrated luminosity of 4.7 fb(-1). Light scalar top quarks are searched for in events with two opposite-sign leptons (e, mu), large missing transverse momentum and at least one jet in the final state. No excess over Standard Model expectations is found, and the results are interpreted under the assumption that the light scalar top decays to a b-quark in addition to an on-shell chargino whose decay occurs through a virtual W boson. If the chargino mass is 106 GeV, light scalar top-quark masses up to 130 GeV are excluded for neutralino masses below 70 GeV.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2012). Search for lepton-number violating processes in B+ -> h(-)l(+)l(+) decays. Phys. Rev. D, 85(7), 071103–8pp.
Abstract: We have searched for the lepton-number violating processes B+ -> h(-)l(+)l(+) with h(-) = K-/pi(-) and l(+) = e(+)/mu(+), using a sample of 471 +/- 3 million B (B) over bar events collected with the BABAR detector at the PEP-II e(+)e(-) collider at the SLAC National Accelerator Laboratory. We find no evidence for these decays and place 90%-confidence-level upper limits on their branching fractions B(B+ -> pi(-)e(+)e(+)) < 2.3 x 10(-8), B(B+ -> K(-)e(+)e(+)) < 3.0 x 10(-8), B(B+ -> pi(-)mu(+)mu(+)) < 10.7 x 10(-8), and B(B+ -> K-mu(+)mu(+)) < 6.7 x 10(-8).
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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. (2012). Search for lepton flavour violation in the e-mu continuum with the ATLAS detector in root s=7 TeV pp collisions at the LHC. Eur. Phys. J. C, 72(6), 2040–19pp.
Abstract: This paper presents a search for the t-channel exchange of an R-parity violating scalar top quark ((t) over tilde) in the e(+/-)mu(-/+) continuum using 2.1 fb(-1) of data collected by the ATLAS detector in root s = 7 TeV pp collisions at the Large Hadron Collider. Data are found to be consistent with the expectation from the Standard Model backgrounds. Limits on R-parity-violating couplings at 95 % C.L. are calculated as a function of the scalar top mass (m((t) over tilde)). The upper limits on the production cross section for pp -> e μX, through the t-channel exchange of a scalar top quark, ranges from 170 fb for m((t) over tilde) = 95 GeV to 30 fb for m((t) over tilde) = 1000 GeV.
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