E. Arik

Measurement of the cross section for the production of a W boson in association with b-jets in pp collisions at root s=7 TeV with the ATLAS detector

A measurement is presented of the cross section for the produ cti n of aW boson with one or two jets, of which at least one must be a b-jet, in pp collisions at √ s = 7 TeV. Production via top decay is not included in the signal definition. The measurement is based on 35 pb −1of data collected with the ATLAS detector at the LHC. The W+b-jet cross section is defined for jets reconstructed with the anti -kt clustering algorithm with transverse momentum above 25 GeV and rapidity within±2.1. Theb-jets are identified by reconstructing secondary vertices. The fiducial cross section is measured both for the electron and muon decay chan nel of theW boson and is found to be 10.2 ± 1.9 (stat) ± 2.6 (syst) pb for one lepton flavour. The results are compared with next-to-leading order QCD calculations, which predict a cross section smaller than, though consistent wit h, the measured value.

Particle identification using the time-over-threshold method in the ATLAS Transition Radiation Tracker

Abstract Test-beam studies of the ATLAS Transition Radiation Tracker (TRT) straw tube performance in terms of electron–pion separation using a time-over-threshold method are described. The test-beam data are compared with Monte Carlo simulations of charged particles passing through the straw tubes of the TRT. For energies below 10 GeV , the time-over-threshold method combined with the standard transition-radiation cluster-counting technique significantly improves the electron–pion separation in the TRT. The use of the time-over-threshold information also provides some kaon–pion separation, thereby significantly enhancing the B-physics capabilities of the ATLAS detector.

Coherent single charged pion production by neutrinos

Abstract We report on a measurement of coherent single charged pion production in neutrino-nucleus scattering. The analysis is based on data taken with the CHARM II detector in beams of muon-neutrinos and -antineutrinos. The event numbers amount to N ( μ − π ) = 748 and N ( μ + π ) = 631. Cross sections and their dependence on the neutrino energy are determined. The results are in agreement with the predictions of models based on the PCAC hypothesis.

Experimental study of electromagnetic properties of the muon-neutrino in neutrino - electron scattering

Abstract We report new bounds on electromagnetic properties of the muon neutrino obtained from a study of neutrino-electron scattering. The results are based on the analysis of differential cross section data collected with the CHARM II detector. The 90% C.L. limit on the magnetic moment of the muon-neutrino μ ν μ −9 μ B confirms limits obtained at much lower energies. The limit on the anomalous charge radius of the muon neutrino |〈 r 2 〉 anom | −33 cm 2 im earlier results by nearly a factor three.

With four standard model families, the LHC could discover the Higgs boson with a few fb-1

The existence of a 4th SM family would produce a large enhancement of the gluon fusion channel of Higgs boson production at hadron colliders. In this case, the SM Higgs boson could be seen at the CERN Large Hadron Collider (LHC) via the golden mode (H->4l) with an integral luminosity of only a few fb^-1.

A Precise measurement of the cross-section of the inverse muon decay muon-neutrino + e- --> mu- + electron-neutrino

We report our final results from the analysis of the full high statistics sample of events of the reaction up + e- --+ /*- + v, collected with the CHARM II detector in the CERN wide-band neutrino beam during the years 1988 to 1991. From a signal of 15 758 f 324 inverse muon decay events we derived, in the Born approximation, a value of ( 16.51 f 0.93) x lO-42 cm*GeV-’ for the asymptotic cross section slope a/E,, in good agreement with the Standard Model prediction of 17.23 x IO-” cm* GeV- ‘. The result constrains the scalar coupling of the electron and the muon to [&l’ < 0.475 at 90% CL.

Recent aging studies for the ATLAS transition radiation tracker

The transition radiation tracker (TRT) is one of the three subsystems of the inner detector of the ATLAS experiment. It is designed to operate for 10 yr at the LHC, with integrated charges of /spl sim/10 C/cm of wire and radiation doses of about 10 Mrad and 2/spl times/10/sup 14/ neutrons/cm/sup 2/. These doses translate into unprecedented ionization currents and integrated charges for a large-scale gaseous detector. This paper describes studies leading to the adoption of a new ionization gas regime for the ATLAS TRT. In this new regime, the primary gas mixture is 70%Xe-27%CO/sub 2/-3%O/sub 2/. It is planned to occasionally flush and operate the TRT detector with an Ar-based ternary mixture, containing a small percentage of CF/sub 4/, to remove, if needed, silicon pollution from the anode wires. This procedure has been validated in realistic conditions and would require a few days of dedicated operation. This paper covers both performance and aging studies with the new TRT gas mixture.

Fourth generation pseudoscalar quarkonium production and observability at hadron colliders

The pseudoscalar quarkonium state, eta_4 1^S_0, formed by the Standard Model (SM) fourth generation quarks, is the best candidate among the fourth generation quarkonia to be produced at the LHC and VLHC. The production of this J^{PC} = 0^{-+} resonance is discussed and the background processes are studied to obtain the integrated luminosity limits for the discovery, depending on its mass.

A Search for Vector Diquarks at the CERN LHC

Resonant production of the flrst generation vector diquarks at the CERN Large Hadron Collider (LHC) is investigated. It is shown that the LHC will be able to discover vector diquarks with masses up to 9TeV for quark-diquark-quark coupling fiD = 0:1 and 4TeV for fiD = 5£ 10 i4 .

Flavour universality of neutrino couplings with the Z

Abstract We are reporting the first experimental result of the coupling of the muon neutrino with the Z. This result is in good agreement with the average value of the coupling of the three neutrino families as derived from the invisible decay width of the Z. We also determined g ν τ assuming N ν =3.