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Development of a Non-Magnetic Inertial Sensor for Vibration Stabilization in a Linear Collider

Description: One of the options for controlling vibration of the final focus magnets in a linear collider is to use active feedback based on accelerometers. While commercial geophysics sensors have noise performance that substantially exceeds the requirements for a linear collider, they are physically large, and cannot operate in the strong magnetic field of the detector. Conventional nonmagnetic sensors have excessive noise for this application. We report on the development of a non-magnetic inertial sensor, and on a novel commercial sensor both of which have demonstrated the required noise levels for this application.
Date: September 1, 2006
Creator: Frisch, Josef; Decker, Valentin; Doyle, Eric; Hendrickson, Linda; Himel, Thomas; Markiewicz, Thomas et al.
Partner: UNT Libraries Government Documents Department

Ultrafast Time-Resolved Electron Diffraction with Megavolt Electron Beams

Description: An rf photocathode electron gun is used as an electron source for ultrafast time-resolved pump-probe electron diffraction. We observed single-shot diffraction patterns from a 160 nm Al foil using the 5.4 MeV electron beam from the Gun Test Facility at the Stanford Linear Accelerator. Excellent agreement with simulations suggests that single-shot diffraction experiments with a time resolution approaching 100 fs are possible.
Date: October 24, 2006
Creator: Hastings, J.B.; /SLAC; Rudakov, F.M.; U., /Brown; Dowell, D.H.; Schmerge, J.F. et al.
Partner: UNT Libraries Government Documents Department

Radiation damage to scintillator in the D0 luminosity monitor

Description: We report the result of evaluating radiation damage to Bicron BC408 plastic scintillator used in the D0 Luminosity Monitor during Run IIa. The Luminosity Monitor provides pseudo-rapidity coverage over the range 2.7 < |{eta}| < 4.4, with the radiation dose in Run IIa estimated to be 0.5 MRad for the region closest to the beams. We find the light yield is degraded by 10-15% due to radiation damage by comparing new and old scintillator in four observables: (1) visual inspection, (2) optical transmittance, (3) response to the radioactive source of {sup 90}Sr and (4) light yield for cosmic rays.
Date: December 1, 2006
Creator: Casey, Brendan; DeVaughan, Kayle; U., /Brown U. /Nebraska; Enari, Yuji; Partridge, Richard; U., /Brown et al.
Partner: UNT Libraries Government Documents Department

Searches for non-standard-model Higgs bosons at the Tevatron

Description: Search for non-Standard-Model Higgs bosons is one of the major goals of the ongoing Fermilab Tevatron run. Large data sets accumulated by the CDF and D{O} experiments break new grounds in sensitivity. We review recent Tevatron results on searches for Higgs bosons in Minimal Supersymmetric Model in the multi b-jet and {tau}{tau} final states, as well as a search for fermiophobic Higgs in the multiphoton final state.
Date: May 1, 2007
Creator: Landsberg, Greg L. & U., /Brown
Partner: UNT Libraries Government Documents Department

The D0 experiment's integrated luminosity for Tevatron Run IIa

Description: An essential ingredient in all cross section measurements is the luminosity used to normalize the data sample. In this note, we present the final assessment of the integrated luminosity recorded by the D0 experiment during Tevatron Run IIa. The luminosity measurement is derived from hit rates from the products of inelastic proton-antiproton collisions registered in two arrays of scintillation counters called the luminosity monitor (LM) detectors. Measured LM rates are converted to absolute luminosity using a normalization procedure that is based on previously measured inelastic cross sections and the geometric acceptance and efficiency of the LM detectors for registering inelastic events. During Run IIa, the LM detector performance was improved by a sequence of upgrades to the electronic readout system and other factors summarized in this note. The effects of these changes on the reported luminosity were tracked carefully during the run. Due to the changes, we partition the run into periods for which different conversions from measured LM rates to absolute luminosity apply. The primary upgrade to the readout system late in Run IIa facilitated a reevaluation of the overall normalization of the luminosity measurement for the full data sample. In this note, we first review the luminosity measurement technique employed by D0. We then summarize the changes to the LM system during Run IIa and the corresponding normalization adjustments. The effect of the adjustments is to increase D0's assessment of its recorded integrated luminosity compared to what was initially reported during Run IIa. The overall increase is 13.4% for data collected between April 20, 2002 (the beginning of Run IIa data used for physics analysis) and February 22, 2006 (the end of Run IIa).
Date: April 1, 2007
Creator: Andeen, T.; Casey, B.C.K.; DeVaughan, K.; Enari, Y.; Gallas, E.; Krop, D. et al.
Partner: UNT Libraries Government Documents Department

Deep Underground Science and Engineering Lab: S1 Dark Matter Working Group

Description: In this report we have described the broad and compelling range of astrophysical and cosmological evidence that defines the dark matter problem, and the WIMP hypothesis, which offers a solution rooted in applying fundamental physics to the dynamics of the early universe. The WIMP hypothesis is being vigorously pursued, with a steady march of sensitivity improvements coming both from astrophysical searches and laboratory efforts. The connections between these approaches are profound and will reveal new information from physics at the smallest scales to the origin and workings of the entire universe. Direct searches for WIMP dark matter require sensitive detectors that have immunity to electromagnetic backgrounds, and are located in deep underground laboratories to reduce the flux from fast cosmic-ray-muon-induced neutrons which is a common background to all detection methods. With US leadership in dark matter searches and detector R&D, a new national laboratory will lay the foundation of technical support and facilities for the next generation of scientists and experiments in this field, and act as magnet for international cooperation and continued US leadership. The requirements of depth, space and technical support for the laboratory are fairly generic, regardless of the approach. Current experiments and upgraded versions that run within the next few years will probe cross sections on the 10{sup -45}-10{sup -44} cm{sup 2} scale, where depths of 3000-4000 m.w.e. are sufficient to suppress the neutron background. On the longer term, greater depths on the 5000-6000 level are desirable as cross sections down to 10{sup -46} cm{sup 2} are probed, and of course, if WIMPs are discovered then building up a statistical sample free of neutron backgrounds will be essential to extracting model parameters and providing a robust solution to the dark matter problem. While most of the detector technologies are of comparable physical scale, i.e., the various ...
Date: June 9, 2006
Creator: Akerib, Daniel S.; Aprile, E.; U., /Case Western Reserve U. /Columbia; Baltz, E.A.; /KIPAC, Menlo Park; Dragowsky, M.R. et al.
Partner: UNT Libraries Government Documents Department

Top quark pair production cross section in the lepton+jets channel using b-tagging at D0

Description: The top quark pair production cross section measurement in the lepton+jets channel with b-tagging algorithm is described. About 900 pb{sup -1} data collected by the D0 detector at the Fermilab Tevatron are used for this analysis. In this thesis, event selection, background estimation, and cross section calculation are discussed in detail. In addition, calibration of the Luminosity Monitor readout electronics and a new b-tagging algorithm, the SLTNN tagger, are also discussed in this thesis.
Date: May 1, 2008
Creator: Yoo, H.D. & U., /Brown
Partner: UNT Libraries Government Documents Department

Search for Charged Massive Long-Lived Particles Using the D0 Detector

Description: A search for charged massive stable particles has been performed with the D0 detector using 1.1 fb{sup -1} of data. The speed of the particle has been calculated based on the time-of-flight and position information in the muon system. The present research is limited to direct pair-production of the charged massive long-lived particles. We do not consider CMSPs that result from the cascade decays of heavier particles. In this analysis, the exact values of the model parameters of the entire supersymmetric particle mass spectrum, relevant for cascade decays, are not important. We found no evidence of the signal. 95% CL cross-section upper limits have been set on the pair-productions of the stable scaler tau lepton, the gaugino-like charginos, and the higgsino-like charginos. The upper cross section limits vary from 0.31 pb to 0.04 pb, for stau masses in the range between 60 GeV and 300 GeV. We use the nominal value of the theoretical cross section to set limits on the mass of the pair produced charginos. We exclude the pair-produced stable gaugino-like charginos with mass below 206 GeV, and higgsino-like charginos below 171 GeV, respectively. Although the present sensitivity is insufficient to test the model of the pair produced stable staus, we do set cross section limits which can be applied to the pair production of any charged massive stable particle candidates with similar kinematics. These are the most restrictive limits to the present on the cross sections for CMSPs and the first published from the Tevatron Collider Run II. The manuscript has been published by Physical Review Letters in April 2009 and is available at arXiv as.
Date: May 1, 2009
Creator: Xie, Yunhe & U., /Brown
Partner: UNT Libraries Government Documents Department

Searches for long lived particles at the Tevatron

Description: Several searches have been performed for long lived particles using data collected by the CDF and D0 detectors at the Fermilab Tevatron collider. These include searches for charged massive stable particles, stopped gluinos, neutral long-lived particles decaying to muons, and magnetic monopoles. These proceedings [1] review recent experimental results from Run II analyses.
Date: April 1, 2008
Creator: Bose, Tulika & U., /Brown
Partner: UNT Libraries Government Documents Department

Collider searches for extra dimensions

Description: Searches for extra spatial dimensions remain among the most popular new directions in our quest for physics beyond the Standard Model. High-energy collider experiments of the current decade should be able to find an ultimate answer to the question of their existence in a variety of models. Until the start of the LHC in a few years, the Tevatron will remain the key player in this quest. In this paper, we review the most recent results from the Tevatron on searches for large, TeV{sup -1}-size, and Randall-Sundrum extra spatial dimensions, which have reached a new level of sensitivity and currently probe the parameter space beyond the existing constraints. While no evidence for the existence of extra dimensions has been found so far, an exciting discovery might be just steps away.
Date: December 1, 2004
Creator: Landsberg, Greg & U., /Brown
Partner: UNT Libraries Government Documents Department

Determination of the effective inelastic p anti-p cross-section for the D0 Run II luminosity measurement

Description: The authors determine the effective inelastic p{bar p} cross-section into the D0 Luminosity Monitor for all run periods prior to September 2004. This number is used to relate the measured inelastic collision rate to the delivered luminosity. The key ingredients are the inelastic p{bar p} cross-section, the Luminosity Monitor efficiency, and the modeling of kinematic distributions for various inelastic processes used to determine the detector acceptance. The resulting value is {sigma}{sub p{bar p},eff} = 46 {+-} 3 mb.
Date: November 1, 2004
Creator: Edwards, T.; U., /Manchester; Yacoob, S.; Andeen, T.; U., /Northwestern; Begel, M. et al.
Partner: UNT Libraries Government Documents Department

Search for Gauge Mediated Supersymmetry in the gamma gamma missing ET Channel

Description: We present results on a search for Gauge Mediated Supersymmetry in the di-photon final state using Run II data collected by the D0 Experiment at the Fermilab Tevatron Collider. We discuss event selection, Standard Model backgrounds, and the lower limits on the lightest neutralino and chargino masses resulted from this analysis.
Date: December 1, 2004
Creator: Kesisoglou, Stilianos Isaak & U., /Brown
Partner: UNT Libraries Government Documents Department

The SuperCDMS Experiment

Description: Modest improvements in the level and/or discrimination of backgrounds are needed to keep backgrounds negligible during the three phases of SuperCDMS. By developing production designs that require only modest testing, detector production rates may be improved sufficiently to allow an exposure of 500 ton d within a reasonable time and budget. Overall, the improvement estimates described above are conservative. Previous development efforts have shown that some areas prove easier and provide larger factors while others prove more difficult. The conservative estimates together with the broad approach reduce the risk and give us confidence that we will succeed, providing the surest way to probe to WIMP-nucleon cross sections of 10{sup -46} cm{sup 2}.
Date: February 1, 2005
Creator: Schnee, Richard W.; Akerib, D. S.; Attisha, M. J.; Bailey, C. N.; Baudis, L.; Bauer, Daniel A. et al.
Partner: UNT Libraries Government Documents Department