55671747
Improved determination of the sample composition of dimuon events produced in $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV
We use a new method to estimate with 5% accuracy the contribution of pion and kaon in-flight-decays to the dimuon data set acquired with the CDF detector. Based on this improved estimate, we show that the total number and the properties of the collected dimuon events are not yet accounted for by ordinary sources of dimuons which also include the contributions, as measured in the data, of heavy flavor, ϒ, and Drell–Yan production in addition to muons mimicked by hadronic punchthrough. The number of unaccounted events corresponds to (12.8±3.2)% of the $b\bar{b}$ production. We find that (23±6)% of the unaccounted events contain additional muon candidates. For comparison, this fraction is (6.9±0.4)% for events due to $b\bar{b}$ production.
8753620
Search for the standard model Higgs boson decaying to a bb pair in events with one charged lepton and large missing transverse energy using the full CDF data set.
We present a search for the standard model Higgs boson produced in association with a W boson in sqrt[s]=1.96  TeV pp collision data collected with the CDF II detector at the Tevatron corresponding to an integrated luminosity of 9.45  fb(-1). In events consistent with the decay of the Higgs boson to a bottom-quark pair and the W boson to an electron or muon and a neutrino, we set 95% credibility level upper limits on the WH production cross section times the H→bb branching ratio as a function of Higgs boson mass. At a Higgs boson mass of 125  GeV/c(2), we observe (expect) a limit of 4.9 (2.8) times the standard model value.
56395246
Operational Experience with the CDF Run II Silicon Detector
Abstract The CDF Run II Silicon Detector is the largest operating silicon detector in High Energy Physics. Its 722,000 channels spread over 7 m 2 of silicon micro-strip sensors allow precision tracking and vertexing. The CDF silicon detector played a critical role in the discovery of B s mixing and is used extensively for the current Higgs Boson searches. Over the last 7 years, the detector efficiency has remained stable at 95% after the Run II commissioning period. The infrastructure (cooling, power supplies) problems dealt with are discussed.
1075188
Studying the Underlying Event in Drell-Yan and High Transverse Momentum Jet Production at the Tevatron
21 paginas, 15 figuras, 3 tablas.-- PACS numbers: 13.87.Ce, 14.60.Cd, 14.60.-- CDF Collaboration: et al.
12577786
Measurement of the WW + WZ production cross section using the lepton + jets final state at CDF II.
We report two complementary measurements of the WW + WZ cross section in the final state consisting of an electron or muon, missing transverse energy, and jets, performed using pp collision data at square root of s = 1.96 TeV collected by the CDF II detector. The first method uses the dijet invariant mass distribution while the second more sensitive method uses matrix-element calculations. The result from the second method has a signal significance of 5.4sigma and is the first observation of WW + WZ production using this signature. Combining the results gives sigma(WW + WZ) = 16.0 +/- 3.3 pb, in agreement with the standard model prediction.
3580212
Search for anomalous production of multiple leptons in association with $W$ and $Z$ bosons at CDF
This paper presents a search for anomalous production of multiple low-energy leptons in association with a W or Z boson using events collected at the CDF experiment corresponding to 5.1 fb{sup -1} of integrated luminosity. This search is sensitive to a wide range of topologies with low-momentum leptons, including those with the leptons near one another. The observed rates of production of additional electrons and muons are compared with the standard model predictions. No indications of phenomena beyond the standard model are found. A 95% confidence level limit is presented on the production cross section for a benchmark model of supersymmetric hidden-valley Higgs production. Particle identification efficiencies are also provided to enable the calculation of limits on additional models.
15676784
Entropy considerations in constraining the mSUGRA parameter space
We explore the use of two criteria to constraint the allowed parameter space in mSUGRA models. Both criteria are based in the calculation of the present density of neutralinos as dark matter in the Universe. The first one is the usual ''abundance'' criterion which is used to calculate the relic density after the ''freeze-out'' era. To compute the relic density we used the numerical public code micrOMEGAs. The second criterion applies the microcanonical definition of entropy to a weakly interacting and self-gravitating gas evaluating then the change in the entropy per particle of this gas between the ''freeze-out'' era and present day virialized structures (i.e systems in virial equilibrium). An ''entropy-consistency'' criterion emerges by comparing theoretical and empirical estimates of this entropy. The main objective of our work is to determine for which regions of the parameter space in the mSUGRA model are both criteria consistent with the 2{sigma} bounds according to WMAP for the relic density: 0.0945 < {omega}CDMh2 < 0.1287. As a first result, we found that for A0 = 0, sgn{mu} +, small values of tan{beta} are not favored; only for tan{beta} {approx_equal} 50 are both criteria significantly consistent.
119194568
Quark sector of S3 models: classification and comparison with experimental data
S3 models offer a low energy approach to describe the observed pattern of masses and mixing, of both quarks and leptons. In this work, we first revisit an S3 model with only one Higgs electroweak doublet, where the flavour symmetry must be broken in order to produce an acceptable pattern of masses and mixing for fermions. Then, we analyse different S3 models, where the flavour symmetry is preserved as an exact, but hidden symmetry of the low energy spectra, after the electroweak symmetry breaking. The latter models require the addition of two more Higgs electroweak doublets which are accommodated in an S3 doublet. We also explore the consequences of adding a fourth Higgs electroweak doublet, thus occupying all three irreducible representations of S3. We show how the various S3-invariant mass matrices of the different models can reproduce the two texture zeroes and Nearest Neighbour Interaction matrix forms, which have been found to provide a viable and universal treatment of mixing for both quarks and leptons. We also find analytical and exact expressions for the CKM matrix of the models in terms of quark mass ratios. Finally, we compare the expressions of the CKM matrix of the different S3 models with the most up to date values of masses and mixing in the quark sector, via a chi^2 analysis. We find that the analytical expressions we derived reproduce remarkably well the most recent experimental data of the CKM matrix, suggesting that S3 is a symmetry of the quark sector.
115528129
SU(5) finite unified theories and the mass of the top quark