67 research outputs found
Operation and Performance of the ATLAS Silicon Micro-strip Tracker
No full textThe SemiConductor Tracker (SCT) is the key precision tracking device in ATLAS, made from silicon micro-strip detectors processed in the planar p-in-n technology. The completed SCT has been installed inside the ATLAS experimental hall since 2007 and has been operational since then. In this paper the current status of the SemiConductor Tracker is reviewed, including results from the latest data-taking periods in 2009 and 2010, and from the detector alignment. The main emphasis is given to the performance of the SemiConductor Tracker with the LHC in collision mode and to the performance of individual electronic components
Search for associated Higgs boson production with a W or Z boson and decaying to a bbar pair with the ATLAS detector
No full textA summary of the ATLAS search for Higgs boson decaying into a pair of b-quarks and produced in association with W or Z boson is presented. No evidence of signal is observed in sqrt(s)=7 TeV proton-proton collision data collected by the ATLAS detector in 2011, corresponding to 4.7 fb-1 of integrated luminosity. The upper limits on Higgs boson production cross-section are reported for the mass range between 110 and 130 GeV
Measurement of the Upsilon production cross section in 920 GeV fixed-target proton-nucleus collisions
No full textThe cross section ratio RJ/ψ=Br(Υ→l+l−)dσ(Υ)/dy|y=0/σ(J/ψ) has been measured with the HERA-B spectrometer in fixed-target proton–nucleus collisions at 920 GeV proton beam energy corresponding to a proton–nucleon c.m.s. energy of √s=41.6 GeV. The combined results for the decay channels Υ→e+e− and Υ→μ+μ− yield a ratio RJ/ψ=(9.0±2.1)×10−6. The corresponding Υ production cross section per nucleon at mid-rapidity (y=0) has been determined to be Br(Υ→l+l−)dσ(Υ)/dy|y=0=4.5±1.1 pb/nucleon
Limits for the central production of Θ+ and Ξ-- pentaquarks in 920-GeV pA collisions
No full textWe have searched for Θ+(1540) and Ξ--(1862) pentaquark candidates in proton-inducedreactions on C, Ti, and W targets at midrapidity and s√=41.6 GeV. In 2×108 inelastic eventswe find no evidence for narrow (σ≈5 MeV) signals in the Θ+→pK0S and Ξ--→Ξ-π- channels; our 95% C.L. upper limits (UL) forthe inclusive production cross section times branching fraction B dσ/dy $y ≈0 are (4-16) μb/N for a Θ+ mass between 1521 and 1555 MeV,and 2.5μb/N for the Ξ--. The UL of the yield ratio of Θ+/Λ(1520)<(3-12)% is significantly lower than model predictions.Our UL of B Ξ--/Ξ(1530)0<4% is at variance with the results that have provided the first evidencefor the Ξ--
Dynamics of isolated-photon plus jet production in pp collisions at √s=7 TeV with the ATLAS detector
No full textThe dynamics of isolated-photon plus jet production in pp collisions at a centre-of-mass energy of 7 TeV has been studied with the ATLAS detector at the LHC using an integrated luminosity of 37 pb−1. Measurements of isolated-photon plus jet bin-averaged cross sections are presented as functions of photon transverse energy, jet transverse momentum and jet rapidity. In addition, the bin-averaged cross sections as functions of the difference between the azimuthal angles of the photon and the jet, the photon–jet invariant mass and the scattering angle in the photon–jet centre-of-mass frame have been measured. Next-to-leading-order QCD calculations are compared to the measurements and provide a good description of the data, except for the case of the azimuthal opening angle
Dynamics of isolated-photon plus jet production in pp collisions at (√s)=7 TeV with the ATLAS detector
No full textThe dynamics of isolated-photon plus jet production in pp collisions at a centre-of-mass energy of 7 TeV has been studied with the ATLAS detector at the LHC using an integrated luminosity of 37 pb−1. Measurements of isolated-photon plus jet bin-averaged cross sections are presented as functions of photon transverse energy, jet transverse momentum and jet rapidity. In addition, the bin-averaged cross sections as functions of the difference between the azimuthal angles of the photon and the jet, the photon--jet invariant mass and the scattering angle in the photon--jet centre-of-mass frame have been measured. Next-to-leading-order QCD calculations are compared to the measurements and provide a good description of the data, except for the case of the azimuthal opening angle. The dynamics of isolated-photon plus jet production in pp collisions at a centre-of-mass energy of 7 TeV has been studied with the ATLAS detector at the LHC using an integrated luminosity of 37 pb^-^1. Measurements of isolated-photon plus jet bin-averaged cross sections are presented as functions of photon transverse energy, jet transverse momentum and jet rapidity. In addition, the bin-averaged cross sections as functions of the difference between the azimuthal angles of the photon and the jet, the photon-jet invariant mass and the scattering angle in the photon-jet centre-of-mass frame have been measured. Next-to-leading-order QCD calculations are compared to the measurements and provide a good description of the data, except for the case of the azimuthal opening angle
Measurement of the production cross section in 920-GeV/c fixed-target proton-nucleus interactions
No full textThe mid-rapidity ( dσpN/dy at y=0 ) and total ( σpN ) production cross sections of Jψ mesons are measured in proton–nucleus interactions. Data collected by the HERA-B experiment in interactions of 920 GeV/c protons with carbon, titanium and tungsten targets are used for this analysis. The Jψ mesons are reconstructed by their decay into lepton pairs. The total production cross section obtained is σpNJ/ψ=663±74±46 nb/nucleon . In addition, our result is compared with previous measurements
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