17120432
Measurement of the Top Quark Mass using Quantities with Minimal Dependence on the Jet Energy Scale
We present three measurements of the top quark mass in the lepton plus jets channel with 1.9fb 1 of data using quantities with minimal dependence on the jet energy scale in the lepton plus jets channel at CDF. One measurement uses the mean transverse decay length of b-tagged jets (L2d) to determine the top mass, another uses the transverse momentum of the lepton (LepPt) to determine the top mass, and a third measurement uses both variables simultaneously. Using the L2d variable we measure a top mass of (176.7 +10.0 8.9 (stat)± 3.4(syst)) GeV/c 2 , using the LepPt variable we measure a top mass of (173.5 +8.9 9.1 (stat)± 4.2(syst)) GeV/c 2 , and doing the combined measurement using both variables we arrive at a top mass result of (175.3 ± 6.2(stat) ± 3.0(syst)) GeV/c2. Since some of the systematic uncertainties are statistically limited, these results are expected to improve significantly if more data is added at the Tevatron in the future, or if the measurement is done at the LHC.
119530771
Acceleration in the linear non-scaling fixed-field alternating-gradient accelerator EMMA
In a fixed-field alternating-gradient (FFAG) accelerator, eliminating pulsed magnet operation permits rapid acceleration to synchrotron energies, but with a much higher beam-pulse repetition rate. Conceived in the 1950s, FFAGs are enjoying renewed interest, fuelled by the need to rapidly accelerate unstable muons for future high-energy physics colliders. Until now a ‘scaling’ principle has been applied to avoid beam blow-up and loss. Removing this restriction produces a new breed of FFAG, a non-scaling variant, allowing powerful advances in machine characteristics. We report on the first non-scaling FFAG, in which orbits are compacted to within 10 mm in radius over an electron momentum range of 12–18 MeV/c. In this strictly linear-gradient FFAG, unstable beam regions are crossed, but acceleration via a novel serpentine channel is so rapid that no significant beam disruption is observed. This result has significant implications for future particle accelerators, particularly muon and high-intensity proton accelerators.
125438498
Top quark mass measurements
The top quark, with its extraordinarily large mass (nearly that of a gold atom), plays a significant role in the phenomenology of EWSB in the Standard Model. In particular, the top quark mass when combined with the W mass constrains the mass of the as yet unobserved Higgs boson. Thus, a precise determination of the mass of the top quark is a principal goal of the CDF and D0 experiments. With the data collected thus far in Runs 1 and 2 of the Tevatron, CDF and D0 have measured the top quark mass in both the lepton+jets and dilepton decay channels using a variety of complementary experimental techniques. The author presents an overview of the most recent of the measurements.
111000899
Operational experience and performance of the CDFII silicon detector
The CDFII silicon detector consists of 8 layers of double-sided silicon micro-strip sensors totaling 722,432 readout channels, making it one of the largest silicon detectors in present use by an HEP experiment. After nearly 2 years of data taking, we report on our experience operating the complex device. The performance of the CDFII silicon detector is presented and its effect on physics analyses is discussed. The CDFII silicon detector has begun to show measurable effects of radiation damage. These results and their impact on the expected lifetime of the detector are briefly reviewed.
53579013
Observability of Higgs produced with top quarks and decaying to bottom quarks
The decay, H → bb, is dominant for a Standard Model Higgs boson in the mass range just above the exclusion limit of 114.4 GeV/c 2 reported by the LEP experiments. Unfortunately, an overwhelming abundance of b¯ b events arising from more mundane sources, together with the lack of precision inherent in the reconstruction of the Higgs mass, renders this decay modeaprioriundetectable in the case of direct Higgs production at the LHC. It is therefore of no small interest to investigate whether H → bb can be observed in those cases where the Higgs is produced in association with other massive particles. In this note, the results of a study of Higgs bosons produced in association with top quarks and decaying via H → bb are presented. The study was performed as realistically as possible by employing a full and detailed Monte Carlo simulation of the CMS detector followed by the application of trigger and reconstruction algorithms that were developed for use with real data. Important systematic effects resulting from such sources as the uncertainties in the jet energy scale and the estimated rates for correctly tagging b jets or mistagging non-b jets have been taken into account. The impact of large theoretical uncertainties in the cross sections for t tp lusN jets processes due to an absence of next-to-leading order calculations is also considered.
11057739
Initial experience with the CDF layer 00 silicon detector
We report on initial experience with the CDF Layer 00 Detector. Layer 00 is an innovative, low-mass, silicon detector installed in CDF during the upgrade for Run 2A of the Tevatron. Noise pickup present during operation at CDF is discussed. An event-by-event pedestal correction implemented by CDF is presented. This off-line solution prevents L00 from being used in the current incarnation of the on-line displaced track trigger. Preliminary performance of Layer 00 is described.
121635635
Topcolor: top quark condensation in a gauge extension of the standard model
Abstract We describe a color embedding, SU(3) c →SU(3) 1 ×SU(3) 2 , that is designed to break electroweak symmetries through top quark condensation. The minimal scheme of Bardeen, Hill and Lindner can be recovered by taking the scale of embedding large and fine-tunning the ratio of coupling constants. Models of this kind allow computation of the strength of higher dimension operators which are found to be small. Perhaps fine-tunning can ultimately be avoided in this scheme.
122396660
Theoretical Expectations for Mass Scales of the Fourth Generation and Higgs Bosons
We discuss two classes of theories that have something to say about fourth generation quark and lepton masses (as well as Higgs). One is based upon universality of low energy parameters as determined by the renormalization group: infra-red fixed points. The other is a toy model of geometric heirarchy which may arise in a novel scheme of dimensional reduction without compactification.
122660180
Dynamical Symmetry Breaking of the Electroweak Interactions and the Renormalization Group
We discuss dynamical symmetry breaking with an emphasis on the renormalization group as the key tool to obtaining reliable predictions. In particular we discuss the mechanism for breaking the electroweak interactions which relies upon the formation of condensates involving the conventional quarks and leptons. Such a scheme indicates that the top quark is heavy, greater than or of order 200 GeV, and gives further predictions for the Higgs boson mass. We also briefly describe recent attempts to incorporate a 4th generation in a more natural scheme. 13 refs., 3 figs., 1 tab.
123523434
Effect of a biased probe on the afterglow operation of an ECR4 ion source
Various experiments have been performed on a 14.5 GHz ECR4 in order to improve the ion yield. The source runs in pulsed afterglow mode, and provides currents ∼120 eμA of Pb27+ to the CERN Heavy Ion Facility on an operational basis. In the search for higher beam intensities, the effects of a pulsed biased disk on axis at the injection side were investigated with different pulse timing and voltage settings. No proof for absolute higher intensities was seen for any of these modifications. However, the yield from a poorly tuned/low-performing source could be improved and the extracted pulse was less noisy with bias voltage applied. The fast response on the bias implies that increases/decreases are not due to ionization processes. A good tune for high yield of high charge states during the afterglow coincides with a high plasma potential.
7781549
Top quark seesaw model, vacuum structure, and electroweak precision constraints
We present a complete study of the vacuum structure of top quark seesaw models of the electroweak symmetry breaking, including bottom quark mass generation. Such models emerge naturally from bosonic extra dimensions. We perform a systematic gap equation analysis and develop an improved broken phase formulation for including exact seesaw mixings. The composite Higgs boson spectrum is studied in the large-${N}_{c}$ fermion-bubble approximation and an improved renormalization group approach. The theoretically allowed parameter space is restrictive, leading to well-defined predictions. We further analyze the electroweak precision constraints. Generically, a heavy composite Higgs boson with a mass of $\ensuremath{\sim}1 \mathrm{TeV}$ is predicted, yet fully compatible with the precision data.