1,792 research outputs found
W and Z Cross Sections at the Tevatron
The CDF and D0 experiments at the Tevatron have used p-pbar collisions at
sqrt(s)=1.96 TeV to measure the cross section of W and Z boson production using
several leptonic final states. An indirect measurement of the total W width has
been extracted, and the lepton charge asymmetry in Drell-Yan production has
been studied up to invariant masses of 600 GeV/c^2.Comment: 4 pages, 6 figures, proceedings of Moriond QCD 2003, Les Arcs 22-29
march 2003, to be published by World Scientific (ed. T.T.Vanh
Recent CMS Results
The CMS experiment obtained a large number of groundbreaking results from the
analysis of 7- and 8-TeV proton-proton collisions produced so far by the Large
Hadron Collider at CERN. In this brief summary only a sample of those results
will be discussed. A new particle with mass m(H) = 125.3 +- 0.4(stat.) +-
0.5(syst.) GeV and characteristics compatible with those expected for a
standard model Higgs boson has been observed in its decays to photon pairs, WW
pairs, and ZZ pairs. Searches for the rare decays B_d -> mu mu and B_s -> mu mu
have allowed to set limits on the branching fractions which are close to
standard model predictions, strongly constraining new physics models. The top
quark has been studied with great detail, obtaining among other results the
world's best measurement of its mass as m(top) = 173.49 +- 0.43(stat. + JES) +-
0.98(syst.) GeV. New physics models have been strongly constrained with the
available data.Comment: 13 pages. Proceedings of the 1st International Conference on Frontier
Physics, Kolymbari, Crete (GR) June 201
Higgs Pair Production: Choosing Benchmarks With Cluster Analysis
New physics theories often depend on a large number of free parameters. The
precise values of those parameters in some cases drastically affect the
resulting phenomenology of fundamental physics processes, while in others
finite variations can leave it basically invariant at the level of detail
experimentally accessible. When designing a strategy for the analysis of
experimental data in the search for a signal predicted by a new physics model,
it appears advantageous to categorize the parameter space describing the model
according to the corresponding kinematical features of the final state. A
multi-dimensional test statistic can be used to gauge the degree of similarity
in the kinematics of different models; a clustering algorithm using that metric
may then allow the division of the space into homogeneous regions, each of
which can be successfully represented by a benchmark point. Searches targeting
those benchmark points are then guaranteed to be sensitive to a large area of
the parameter space. In this document we show a practical implementation of the
above strategy for the study of non-resonant production of Higgs boson pairs in
the context of extensions of the standard model with anomalous couplings of the
Higgs bosons. A non-standard value of those couplings may significantly enhance
the Higgs pair production cross section, such that the process could be
detectable with the data that the Large Hadron Collider will collect in Run 2.Comment: Editorial changes, improvements in figures and changes in the
appendi
Energy Calibration of b-Quark Jets with Z->b-bbar Decays at the Tevatron Collider
The energy measurement of jets produced by b-quarks at hadron colliders
suffers from biases due to the peculiarities of the hadronization and decay of
the originating B hadron. The impact of these effects can be estimated by
reconstructing the mass of Z boson decays into pairs of b-quark jets. From a
sample of 584 pb-1 of data collected by the CDF experiment in 1.96 TeV
proton-antiproton collisions at the Tevatron collider, we show how the Z signal
can be identified and measured. Using the reconstructed mass of Z candidates we
determine a jet energy scale factor for b-quark jets with a precision better
than 2%. This measurement allows a reduction of one of the dominant source of
uncertainty in analyses based on high transverse momentum b-quark jets. We also
determine, as a cross-check of our analysis, the Z boson cross section in
hadronic collisions using the b-bbar final state as sigma x B(Z->b-bbar) = 1578
+636 -410 pb.Comment: 35 pages, 9 figures, submitted to Nuclear Instruments and Methods in
Physics Research Section
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