Measurement of charged-particle multiplicities in gluon and quark jets in pp collisions at square root of s = 1.8 TeV.
Phys Rev Lett 94:17 (2005) 171802
Abstract:
We report the first largely model independent measurement of charged particle multiplicities in quark and gluon jets, Nq and Ng, produced at the Fermilab Tevatron in pp collisions with a center-of-mass energy of 1.8 TeV and recorded by the Collider Detector at Fermilab. The measurements are made for jets with average energies of 41 and 53 GeV by counting charged particle tracks in cones with opening angles of theta(c) = 0.28, 0.36, and 0.47 rad around the jet axis. The corresponding jet hardness Q = Ejet theta c varies in the range from 12 to 25 GeV. At Q = 19.2 GeV, the ratio of multiplicities r = Ng/Nq is found to be 1.64+/-0.17, where statistical and systematic uncertainties are added in quadrature. The results are in agreement with resummed perturbative QCD calculations.Search for ZZ and ZW production in pp̄ collisions at s=1.96TeV
Physical Review D - Particles, Fields, Gravitation and Cosmology 71:9 (2005) 1-7
Abstract:
We present a search for ZZ and ZW vector boson pair production in pp̄ collisions at s=1.96TeV using the leptonic decay channels ZZ→llνν, ZZ→lll′l′, and ZW→lll′ν. In a data sample corresponding to an integrated luminosity of 194pb-1 collected with the Collider Detector at Fermilab, 3 candidate events are found with an expected background of 1.0±0.2 events. We set a 95% confidence level upper limit of 15.2pb on the cross section for ZZ plus ZW production, compared to the standard model prediction of 5.0±0.4pb. © 2005 The American Physical Society.High precision survey and alignment of large linear accelerators
XXII International Linear Accelerator Conference (LINAC 2004) Joint Accelerator Conferences Website (JACoW) (2005) 690-692
Abstract:
Future linear accelerators require new survey techniques to achieve the necessary alignment precision. For TESLA, the demanded accuracy for the alignment of the components is 0.5mm horizontal and 0.2mm vertical, both on each 600m section. Other proposed linear colliders require similar accuracies. These demands can not be fulfilled with common, open-air geodetic methods, mainly because of refraction in the tunnel. Therefore the RTRS (Rapid Tunnel Reference Surveyor), a 25m long measurement train performing overlapping multipoint alignment on a regular tunnel reference network is being developed. Two refraction-free realizations of this concept are being developed at the moment: GeLiS measures the horizontal co-ordinates using multipoint alignment with stretched wires as strightness reference. In areas of the tunnel where the accelerator is following the earth curvature GeLiS measures the vertical co-ordinate using a new hydrostatic levelling system (HLS). LiCAS is based on laser straightness monitors (LSM) combined with frequency scanning interferometry (FSI) in an evacuated system. LiCAS measures both coordinates with respect to its LSM-beam and thus is suitable for geometrically straight tunnel sections. Both measurement systems will be placed on a train, which could do the reference survey autonomous or semiautonomous.Measurement of partial widths and search for direct CP violation in D0 meson decays to K-K+ and pi-pi+.
Phys Rev Lett 94:12 (2005) 122001
Abstract:
We present a measurement of relative partial widths and decay rate CP asymmetries in K-K+ and pi(-)pi(+) decays of D0 mesons produced in pp collisions at sqrt[s]=1.96 TeV. We use a sample of 2x10(5) D(*+)-->D0pi(+) (and charge conjugate) decays with the D0 decaying to K-pi(+), K-K+, and pi(-)pi(+), corresponding to 123 pb(-1) of data collected by the Collider Detector at Fermilab II experiment at the Fermilab Tevatron collider. No significant direct CP violation is observed. We measure Gamma(D0-->K-K+)/Gamma(D0-->K-pi(+))=0.0992+/-0.0011+/-0.0012, Gamma(D0-->pi(-)pi(+))/Gamma(D0-->K-pi(+))=0.035 94+/-0.000 54+/-0.000 40, A(CP)(K-K+)=(2.0+/-1.2+/-0.6)%, and A(CP)(pi(-)pi(+))=(1.0+/-1.3+/-0.6)%, where, in all cases, the first uncertainty is statistical and the second is systematic.Measurement of the tt̄ production cross section in pp̄ collisions at √s=1:96 TeV using kinematic fitting of b-tagged lepton+jet events
Physical Review D - Particles, Fields, Gravitation and Cosmology 71:7 (2005) 1-11