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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2011). Study of Y(3S, 2S) -> eta Y(1S) and Y(3S, 2S) -> pi(+) pi(-) Y(1S) hadronic transitions. Phys. Rev. D, 84(9), 092003–8pp.
Abstract: We study the Y(3S, 2S) -> eta Y(1S) and Y (3S,2S) -> pi(+)pi(-) transitions with 122 x 10(6) x Y(3S) and 100 x 10(6) Y (2S) mesons collected by the BABAR detector at the PEP-II asymmetric-energy e(+)e(-) collider. We measure B[Y(2S) -> eta Y(1S)] = (2.39 +/- 0.31 (stat) +/- 0.14(syst)) x 10(-4) and Gamma[Y(2S) -> eta Y(1S)]/Gamma[Y(2S) ->pi(+)pi(-)(1S)] – (2.39 +/- 0.31(stat) +/- 0.14(syst)) x 10(-3). We find no evidence for Y(3S) -> eta Y (1S) and obtain B[Y(3S) -> eta Y(1S)] < 1.0 x 10(-4) and Gamma[Y (3S) -> eta Y(1S)/Gamma[Y(3S) -> pi(+)pi(-) Y(1S)] < 2.3 x 10(-3) as upper limits at the 90% confidence level. We also provide improved measurements of the Y(S) – Y(1S) and Y(3S) – Y (1S) mass differences, 562.170 +/- 0.007(stat) +/- 0.088(syst). MeV/c(2) and 893.813 +/- 0: 015(stat) +/- 0.107(syst.) MeV/c(2), respectively.
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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). Search for a Standard Model Higgs Boson in the H -> ZZ -> l(+)l(-)v(v)over-bar Decay Channel with the ATLAS Detector. Phys. Rev. Lett., 107(22), 221802–18pp.
Abstract: A search for a heavy standard model Higgs boson decaying via H -> ZZ -> l(+)l(-)v (v) over bar, where l = e, mu, is presented. It is based on proton-proton collision data at root s = 7 TeV, collected by the ATLAS experiment at the LHC in the first half of 2011 and corresponding to an integrated luminosity of 1.04 fb(-1). The data are compared to the expected standard model backgrounds. The data and the background expectations are found to be in agreement and upper limits are placed on the Higgs boson production cross section over the entire mass window considered; in particular, the production of a standard model Higgs boson is excluded in the region 340 < m(H) < 450 GeV at the 95% confidence level.
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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). Search for neutral MSSM Higgs bosons decaying to tau(+)tau(-) pairs in proton-proton collisions sqrt(s)=7 TeV with the ATLAS detector. Phys. Lett. B, 705(3), 174–192.
Abstract: A search for neutral Higgs bosons decaying to pairs of tau leptons with the ATLAS detector at the LHC is presented. The analysis is based on proton-proton collisions at a center-of-mass energy of 7 TeV, recorded in 2010 and corresponding to an integrated luminosity of 36 pb(-1). After signal selection, 276 events are observed in this data sample. The observed number of events is consistent with the total expected background of 269 +/- 36 events. Exclusion limits at the 95% confidence level are derived for the production cross section of a generic Higgs boson phi as a function of the Higgs boson mass and for A/H/h production in the Minimal Supersymmetric Standard Model (MSSM) as a function of the parameters m(A) and tan beta.
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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). Search for diphoton events with large missing transverse energy with 36 pb(-1) of 7 TeV proton-proton collision data with the ATLAS detector. Eur. Phys. J. C, 71(10), 1744–21pp.
Abstract: Making use of 36 pb(-1) of proton-proton collision data at root s = 7 TeV, the ATLAS Collaboration has performed a search for diphoton events with large missing transverse energy. Observing no excess of events above the Standard Model prediction, a 95% Confidence Level ( CL) upper limit is set on the cross section for new physics of sigma < 0.38-0.65 pb in the context of a generalised model of gauge-mediated supersymmetry breaking (GGM) with a bino-like lightest neutralino, and of sigma < 0.18-0.23 pb in the context of a specific model with one universal extra dimension (UED). A 95% CL lower limit of 560 GeV, for bino masses above 50 GeV, is set on the GGM gluino mass, while a lower limit of 1/R > 961 GeV is set on the UED compactification radius R. These limits provide the most stringent tests of these models to date.
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BABAR Collaboration(Lees, J. P. et al), Lopez-March, N., Martinez-Vidal, F., & Oyanguren, A. (2011). Evidence for the h(b)(1P) meson in the decay Y(3S) -> pi(0)h(b)(1P). Phys. Rev. D, 84(9), 091101–8pp.
Abstract: Using a sample of 122 x 10(6) Y(3S) events recorded with the BABAR detector at the PEP-II asymmetric-energy e(+)e(-) collider at SLAC, we search for the h(b)(1P) spin-singlet partner of the P-wave X(bJ)(1P) states in the sequential decay Y(3S) -> pi(0)h(b) (1P), hb(1P) -> gamma eta(b)(1S). We observe an excess of events above background in the distribution of the recoil mass against the pi(0) at mass 9902 +/- 4(stat) +/- 2(syst) MeV/c(2). The width of the observed signal is consistent with experimental resolution, and its significance is 3.1 sigma, including systematic uncertainties. We obtain the value (4.3 +/- 1.1(stat) +/- 0.9(syst) x 10(-4) for the product branching fraction B(Y(3S) -> pi(0)h(b)) XB (h(b) -> gamma eta(b))
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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 W gamma and Z gamma production in proton-proton collisions at sqrt(s)=7 TeV with the ATLAS detector. J. High Energy Phys., 09(9), 072–42pp.
Abstract: We present studies of W and Z bosons with associated high energy photons produced in pp collisions at sqrt(s) = 7 TeV. The analysis uses 35 pb(-1) of data collected by the ATLAS experiment in 2010. The event selection requires W and Z bosons decaying into high pT leptons (electrons or muons) and a photon with E(T) > 15 GeV separated from the lepton(s) by a distance Delta R(l, gamma) > 0.7 in eta-phi space. A total of 95 (97) pp -> e(+/-)nu gamma + X (pp -> mu(+/-)nu gamma + X) and 25 (23) pp -> e(+)e(-)gamma + X (pp -> mu(+)mu(-)gamma + X) event candidates are selected. The kinematic distributions of the leptons and photons and the production cross sections are measured. The data are found to agree with Standard Model predictions that include next-to-leading-order O(alpha alpha(s)) contributions.
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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 dijet production with a veto on additional central jet activity in pp collisions at sqrt(s)=7 TeV using the ATLAS detector. J. High Energy Phys., 09(9), 053–36pp.
Abstract: A measurement of jet activity in the rapidity interval bounded by a dijet system is presented. Events are vetoed if a jet with transverse momentum greater than 20 GeV is found between the two boundary jets. The fraction of dijet events that survive the jet veto is presented for boundary jets that are separated by up to six units of rapidity and with mean transverse momentum 50 < <(p)over bar>T < 500 GeV. The mean multiplicity of jets above the veto scale in the rapidity interval bounded by the dijet system is also presented as an alternative method for quantifying perturbative QCD emission. The data are compared to a next-to-leading order plus parton shower prediction from the POWHEG-BOX, an all-order resummation using the HEJ calculation and the PYTHIA, HERWIG++ and ALPGEN event generators. The measurement was performed using pp collisions at sqrt(s) = 7 TeV using data recorded by the ATLAS detector in 2010.
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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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ANTARES Collaboration(Adrian-Martinez, S. et al), Aguilar, J. A., Bigongiari, C., Dornic, D., Emanuele, U., Gomez-Gonzalez, J. P., et al. (2011). First Search For Point Sources Of High-Energy Cosmic Neutrinos With The Antares Neutrino Telescope. Astrophys. J. Lett., 743(1), L14–6pp.
Abstract: Results are presented of a search for cosmic sources of high-energy neutrinos with the ANTARES neutrino telescope. The data were collected during 2007 and 2008 using detector configurations containing between 5 and 12 detection lines. The integrated live time of the analyzed data is 304 days. Muon tracks are reconstructed using a likelihood-based algorithm. Studies of the detector timing indicate a median angular resolution of 0.5 +/- 0.1 deg. The neutrino flux sensitivity is 7.5 x 10(-8)(E(v)/GeV)(-2) GeV(-1) s(-1) cm(-2) for the part of the sky that is always visible (delta < -48 deg), which is better than limits obtained by previous experiments. No cosmic neutrino sources have been observed.
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Langer, C., Algora, A., Couture, A., Csatlos, M., Gulyas, J., Heil, M., et al. (2011). Simulations and developments of the Low Energy Neutron detector Array LENA. Nucl. Instrum. Methods Phys. Res. A, 659(1), 411–418.
Abstract: Prototypes of the Low Energy Neutron detector Array (LENA) have been tested and compared with detailed GEANT simulations. LENA will consist of plastic scintillation bars with the dimensions 1000 x 45 x 10 mm(3). The tests have been performed with gamma-ray sources and neutrons originating from the neutron-induced fission of (235)U. The simulations agreed very well with the measured response and were therefore used to simulate the response to mono-energetic neutrons with different detection thresholds. LENA will be used to detect low-energy neutrons from (p,n)-type reactions with low momentum transfer foreseen at the R(3)B and EXL setups at FAIR, Darmstadt.
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