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Measurement of the Top Quark Mass at CDF II

Description: The authors describe a measurement of the top quark mass using events with two charged leptons collected by the CDF II Detector from p{bar p} collisions with {radical}s = 1.96 TeV at the Fermilab Tevatron. The posterior probability distribution of the top quark pole mass is calculated using the differential cross-section for the t{bar t} production and decay expressed with respect to observed leptons and jets momenta. The presence of background events in the collected sample is modeled using calculations of the differential cross-sections for major background processes. This measurement represents the first application of this method to events with two charged leptons. In a data sample with integrated luminosity of 340 pb{sup -1}, they observe 33 candidate events and measure M{sub top} = 165.2 {+-} 61.{sub stat} {+-} 3.4{sub syst} GeV/c{sup 2}.
Date: November 1, 2003
Creator: Kovalev, Andrew N. & U., /Pennsylvania
Partner: UNT Libraries Government Documents Department

Measurements of top quark properties at CDF

Description: The top quark with its mass of about 172 GeV/c{sup 2} is the most massive fundamental particle observed by experiment. In this talk they highlight the most recent measurements of several top quark properties performed with the CDF detector based on data samples corresponding to integrated luminosities up to 1 fb{sup -1}. These results include a search for top quark pair production via new massive resonances, measurements of the helicity of the W boson from top-quark decay, and a direct limit on the lifetime of the top quark.
Date: November 1, 2006
Creator: Kraan, Aafke C. & U., /Pennsylvania
Partner: UNT Libraries Government Documents Department

CDF b-tagging: Measuring efficiency and false positive rate

Description: The CDF experiment has developed several high p{sub T} b-jet identification tools for the Run II physics program at the Tevatron. Herein we describe in detail one such b-tagging tool that exploits the long- lifetime of the b quark by identifying decay vertices significantly displaced from the primary interaction point. The b-tag efficiency is extracted from a b enriched data sample; the method is described, including a discussion of the important systematic effects. The data-driven measurement of the false positive tag rate is also described, as well as an explanation of how the per-jet false positive rate is used to predict the background contribution to the selected sample. Finally we conclude with a discussion of issues that have proven critical for b-tagging at CDF and should be given attention as we prepare b-tagging tools for LHC experiments.
Date: June 1, 2006
Creator: Neu, Christopher & U., /Pennsylvania
Partner: UNT Libraries Government Documents Department

Study of Rare Radiative B Decay to K*(1430) Meson Using the BABAR Detector

Description: Radiative B Meson decay through the b {yields} s{gamma} process has been one of the most sensitive probe of new physics beyond the Standard Model, because of its importance in understanding the phenomenon of CP violation, which is believed to be necessary to explain the excess of matter over anti-matter in our universe. The inclusive picture of the b {yields} s{gamma} process is well established; however, our knowledge of the exclusive final states in radiative B meson decays is rather limited. We have investigated one of them, the exclusive, radiative B decay to the charmless K*{sub 2}(1430) meson, in a sample of 88.5 x 10{sup 6} B{bar B} events with the BABAR detector at the PEP-II storage ring. We present a measurement of the branching fractions {Beta}(B{sup 0} {yields} K*{sub 2}(1430){sup 0}{gamma}) = (1.22 {+-} 0.25 {+-} 0.10) x 10{sup -5} and {Beta}(B{sup +} {yields} K*{sub 2}(1430){sup +}){gamma} = (1.45 {+-} 0.40 {+-} 0.15) x 10{sup -5}, where the first error is statistical and the second systematic. In addition, we have performed the first search for direct CP violation in this decay with the measured asymmetry in B{sup 0} {yields} K*{sub 2}(1430){sup 0}{gamma} of {Alpha}{sub CP} = -0.08 {+-} 0.15 {+-} 0.01.
Date: September 14, 2005
Creator: Guo, Qinghua & U., /Pennsylvania
Partner: UNT Libraries Government Documents Department

Tevatron results on the discovery of sigma^(*)_b, b_s oscillations and the measurement of delta m_s, the lifetime difference delta gamma_s and the cp-violating phase phi

Description: The author discusses results from the Tevatron experiments on mixing and CP-violation in B{sub s} mesons, including the observation of B{sub s} oscillations and the first precision measurement of the mixing frequency, as well as a measurement of the lifetime difference {Delta}{Lambda}{sub s} and the first measurement of the CP-violating phase {delta}{sub s}. The author also briefly reports on the observation of four new bottom baryons at CDF.
Date: October 1, 2007
Creator: Heijboer, Aart & U., /Pennsylvania
Partner: UNT Libraries Government Documents Department

Precision measurements of the top quark mass at the Tevatron

Description: We report precision measurements of the top quark mass using events collected by the D0 and CDF II detectors from p{bar p} collisions at {radical}s = 1.96 TeV at the Fermilab Tevatron. Measurements are presented in multiple decay channels. In addition, we present a combination of the most precise measurements in each channel to date: M{sub top} = 172.5 {+-} 1.3{sub stat} {+-} 1.9{sub syst} GeV/c{sup 2}.
Date: May 1, 2006
Creator: Whiteson, Daniel & U., /Pennsylvania
Partner: UNT Libraries Government Documents Department

Study of Charged Particle Species Produced in Association with B0, B-, and Bs Mesons in proton - anti-proton collisions at s**(1/2) = 1.96-TeV

Description: The authors study the yields of charged kaons, charged pions, and protons produced in association with B mesons produced in proton-antiproton collisions at center of mass energy 1960 GeV using 355 pb{sup -1} of data collected with the CDF detector at the Fermilab Tevatron. This is the first reported measurements of these yields at a hadron collider. The B mesons are reconstructed using their semileptonic decays: B{sup 0} {yields} {ell}{sup +}D{sup -}X, D{sup -} {yields} K{sup +}{pi}{sup -}{pi}{sup -}; B{sup 0} {yields} {ell}{sup +}D*{sup -}X, D*{sup -} {yields} {pi}{sup -}{bar D}{sup 0},{bar D}{sup 0} {yields} K{sup +}{pi}{sup -}; B{sup +} {yields} {ell}{sup +}{bar D}{sup 0}X, {bar D}{sup 0} {yields} K{sup +}{pi}{sup -}; B{sub s}{yields}{ell}{sup +}D{sub s}{sup -}X, D{sub s}{sup -} {yields} {pi}{sup -}{phi},{phi} {yields} K{sup +}K{sup -}. The K, {pi}, and p are identified using the Time of Flight detector (TOF), the CDF spectrometer, and the specific ionization (dE/dx) measured in the central drift chamber (COT). The fraction of charged kaons produced in association with {bar B}{sub s}{sup 0} mesons is found to be larger than the fraction produced in association with the {bar B}{sup 0} and B{sup -} mesons, as expected from naive models of heavy quark hadronization to mesons. The particle species yields are found to be in qualitative agreement with simulation of B meson production in hadron collisions from the PYTHIA Monte Carlo, although the yield of kaons around {bar B}{sub s}{sup 0} mesons is found to be larger in the simulation when compared to the data. These studies are important for understanding methods of identifying the flavor of {bar B}{sub s}{sup 0} mesons in measurement of {bar B}{sub s}{sup 0} flavor oscillations and charge conjugation-parity (CP) violation in {bar B}{sub s}{sup 0} meson decays.
Date: December 1, 2005
Creator: Usynin, Denys & U., /Pennsylvania
Partner: UNT Libraries Government Documents Department

Progress in top quark physics

Description: Experimental measurements of the properties of the top quark have improved and will continue to improve significantly, with the excellent operation of the CDF and D0 experiments and the Tevatron p{bar p} collider at the Fermi National Accelerator Laboratory. All of the final state experimental signatures from top quark production and decay are being analyzed to test if this most massive quark is sensitive to new physics beyond the standard model. So far, observations are consistent with the standard model. New techniques have dramatically improved the precision of the top quark mass measurement to 1.7% and set the stage for a sub-1% measurement by 2008. This improved knowledge of the top quark mass sharpens the standard model prediction for the mass of the undiscovered Higgs boson, with implications for Higgs studies at the future LHC and ILC.
Date: February 1, 2006
Creator: Thomson, Evelyn J. & U., /Pennsylvania
Partner: UNT Libraries Government Documents Department

Search for High-Mass Resonances Decaying into Leptons of Different Flavor (e mu, e tau, mu tau) in p anti-p Collisions at sqrt(s) = 1.96 TeV

Description: We present a search for high-mass resonances decaying into two leptons of different flavor: e{mu}, e{tau}, and {mu}{tau}. These resonances are predicted by several models beyond the standard model, such as the R-parity-violating MSSM. The search is based on 1 fb{sup -1} of data collected at the Collider Detector at Fermilab (CDF II) in proton anti-proton collisions. Our observations are consistent with the standard model expectations. The results are interpreted to set 95% C.L. upper limits on {sigma} x BR of {tilde {nu}}{sub {tau}} {yields} e{mu}, e{tau}, {mu}{tau}.
Date: October 1, 2008
Creator: Tu, Yanjun & U., /Pennsylvania
Partner: UNT Libraries Government Documents Department


Description: We describe a general search for resonances decaying to a neutral e{mu} final state in p{bar p} collisions at a center-of-mass energy of 1.96 TeV. Using a data sample representing 344 pb{sup -1} of integrated luminosity recorded by the CDF II experiment, we compare Standard Model predictions with the number of observed events for invariant masses between 50 and 800 GeV/c{sup 2}. Finding no significant excess (5 events observed vs. 7.7 {+-} 0.8 expected for M{sub e{mu}} > 100 GeV/c{sup 2}), we set limits on sneutrino and Z' masses as functions of lepton family number violating couplings.
Date: August 1, 2006
Creator: Hahn, Kristian Allan & U., /Pennsylvania
Partner: UNT Libraries Government Documents Department

A proposal to study particle production spectra and multiplicities in high energy hadron-hadron collisions, and for a beam survey and quark search

Description: We propose an experimental study at the new 500 GeV accelerator of the differential cross-section for particle production in hadron-hadron collisions. The projectile, and the observed single particle, will range over all combinations of positive and negative {pi}, K and p, with momenta extending up to the highest available. Enough of the secondary particle momentum range will be covered to permit us to determine by integration the multiplicity of the produced particle. Single particles will be detected in a simple spectrometer consisting of wire chambers and a small bending magnet. The configuration of the spectrometer components will be variable so that the overall spectrometer length can be kept proportional to the secondary momentum. The momentum resolution {male}P/P = {+-}0.8% and the invariant phase space acceptance P{sup 2}d{Omega}dP/E = 1.3x10{sup -3} (GeV/c){sup 2} will then be the same at all momenta. Particle identification will be by means of threshold Cherenkov counters, with 10{sup 4}: 1 rejection up to at least 250 GeV/c. Our experimental arrangement is thought to be simple and yet powerful, and we propose its use initially with incident protons and a nuclear target for a beam survey and quark search. Subsequent measurements will be carried out with a hydrogen target in a high intensity secondary beam.
Date: June 15, 1970
Creator: Beier, E.W.; Kreinick, D.L.; Weisberg, H. & U., /Pennsylvania
Partner: UNT Libraries Government Documents Department

SPi User Manual V0.1

Description: This document describes the Serial Powering Interface (SPi) ASIC. SPi is a general purpose ASIC prototype designed for use in serial powering of silicon detector instrumentation. This description is written as a user manual to aid application, not as a design description. SPi is a generic custom ASIC, manufactured in 0.25 {mu}m CMOS by TSMC, to interface between a constant current source and silicon detector read-out chips. There is no SEU (single event upset) protection, but most (not all) components are radiation tolerant design. An operating voltage of 1.2 to 2.5 volts and other design features make the IC suitable for a variety of serial powering architectures and ROICs. It should be noted that the device is likely to be a prototype for demonstration rather than a product for inclusion in a detector. The next design(s), SPin, are likely to be designed for a specific application (eg SLHC). The component includes: (1) Seven bi-directional LVDS-like buffers for high data rate links to/from the read-out chips. These are AC coupled (series capacitor) off-chip for DC level conversion; (2) A programmable internal programmable shunt regulator to provide a defined voltage to readout chips when linked in a serial powering chain; (3) A programmable internal shunt regulator control circuit for external transistor control; (4) Shunt current measurement (for internal shunt regulator); (5) A programmable internal shunt regulator current alarm; and (6) Two programmable linear regulators.
Date: May 1, 2011
Creator: Trimpl, M.; Yarema, R.; /Fermilab; Newcomer, M.; Dressnandt, N.; U., /Pennsylvania et al.
Partner: UNT Libraries Government Documents Department

An Excursion Set Model of the Cosmic Web: the Abundance of Sheets, Filaments And Halos

Description: We discuss an analytic approach for modeling structure formation in sheets, filaments and knots. This is accomplished by combining models of triaxial collapse with the excursion set approach: sheets are defined as objects which have collapsed along only one axis, filaments have collapsed along two axes, and halos are objects in which triaxial collapse is complete. In the simplest version of this approach, which we develop here, large scale structure shows a clear hierarchy of morphologies: the mass in large-scale sheets is partitioned up among lower mass filaments, which themselves are made-up of still lower mass halos. Our approach provides analytic estimates of the mass fraction in sheets, filaments and halos, and its evolution, for any background cosmological model and any initial fluctuation spectrum. In the currently popular {Lambda}CDM model, our analysis suggests that more than 99% of the mass in sheets, and 72% of the mass in filaments, is stored in objects more massive than 10{sup 10}M{sub {circle_dot}} at the present time. For halos, this number is only 46%. Our approach also provides analytic estimates of how halo abundances at any given time correlate with the morphology of the surrounding large-scale structure, and how halo evolution correlates with the morphology of large scale structure.
Date: January 11, 2006
Creator: Shen, Jiajian; /Penn State U., Astron. Astrophys.; Abel, Tom; /KIPAC, Menlo Park; Mo, Houjun; /Massachusetts U., Amherst et al.
Partner: UNT Libraries Government Documents Department

The Approach to Scaling in Single Particle Inclusive Hadron Scattering from 4-GeV/c to 250 GeV/c

Description: Measurements of the dependence on s = (p{sub a} + p{sub b}){sup 2} of the cross section for single charged hadron production in the reactions a + b {yields} c + anything are presented. Particle c is detected in a fixed interval of laboratory momentum and angle in the fragmentation region of the target proton. For the energy range studied there are significant departures from A + Bs{sup -1/2} energy dependence. When these departures are taken into account, asymptotic predictions such as Pomeron factorization can be tested.
Date: July 1, 1976
Creator: Beier, E.W.; Brody, H.; Patton, R.; Raychaudhuri, K.; Takeda, H.; Thern, R. et al.
Partner: UNT Libraries Government Documents Department

D-brane Instantons in Type II String Theory

Description: We review recent progress in determining the effects of D-brane instantons in N=1 supersymmetric compactifications of Type II string theory to four dimensions. We describe the abstract D-brane instanton calculus for holomorphic couplings such as the superpotential, the gauge kinetic function and higher fermionic F-terms. This includes a discussion of multi-instanton effects and the implications of background fluxes for the instanton sector. Our presentation also highlights, but is not restricted to the computation of D-brane instanton effects in quiver gauge theories on D-branes at singularities. We then summarize the concrete consequences of stringy D-brane instantons for the construction of semi-realistic models of particle physics or SUSY-breaking in compact and non-compact geometries.
Date: June 19, 2009
Creator: Blumenhagen, Ralph; /Munich, Max Planck Inst.; Cvetic, Mirjam; U., /Pennsylvania; Kachru, Shamit; /Stanford U., Phys. Dept. /SLAC et al.
Partner: UNT Libraries Government Documents Department

Stable massive particles at colliders

Description: We review the theoretical motivations and experimental status of searches for stable massive particles (SMPs) which could be sufficiently long-lived as to be directly detected at collider experiments. The discovery of such particles would address a number of important questions in modern physics including the origin and composition of dark matter in the universe and the unification of the fundamental forces. This review describes the techniques used in SMP-searches at collider experiments and the limits so far obtained on the production of SMPs which possess various colour, electric and magnetic charge quantum numbers. We also describe theoretical scenarios which predict SMPs, the phenomenology needed to model their production at colliders and interactions with matter. In addition, the interplay between collider searches and open questions in cosmology such as dark matter composition are addressed.
Date: November 1, 2006
Creator: Fairbairn, M.; U., /Stockholm; Kraan, A.C.; U., /Pennsylvania; Milstead, D.A.; U., /Stockholm et al.
Partner: UNT Libraries Government Documents Department

CDF level 2 trigger upgrade

Description: We describe the new CDF Level 2 Trigger, which was commissioned during Spring 2005. The upgrade was necessitated by several factors that included increased bandwidth requirements, in view of the growing instantaneous luminosity of the Tevatron, and the need for a more robust system, since the older system was reaching the limits of maintainability. The challenges in designing the new system were interfacing with many different upstream detector subsystems, processing larger volumes of data at higher speed, and minimizing the impact on running the CDF experiment during the system commissioning phase. To meet these challenges, the new system was designed around a general purpose motherboard, the PULSAR, which is instrumented with powerful FPGAs and modern SRAMs, and which uses mezzanine cards to interface with upstream detector components and an industry standard data link (S-LINK) within the system.
Date: January 1, 2006
Creator: Anikeev, K.; Bogdan, M.; DeMaat, R.; Fedorko, W.; Frisch, H.; Hahn, K. et al.
Partner: UNT Libraries Government Documents Department

A search for the most massive galaxies: double trouble?

Description: We describe the results of a search for galaxies with large ({approx}> 350 kms{sup -1}) velocity dispersions. The largest systems we have found appear to be the extremes of the early-type galaxy population: compared to other galaxies with similar luminosities, they have the largest velocity dispersions and the smallest sizes. However, they are not distant outliers from the Fundamental Plane and mass-to-light scaling relations defined by the bulk of the early-type galaxy population. They may host the most massive black holes in the Universe, and their abundance and properties can be used to constrain galaxy formation models. Clear outliers from the scaling relations tend to be objects in superposition (angular separations smaller than 1 arcsec), evidence for which comes sometimes from the spectra, sometimes from the images, and sometimes from both. The statistical properties of the superposed pairs, e.g., the distribution of pair separations and velocity dispersions, can be used to provide useful information about the expected distribution of image multiplicities, separations and flux ratios due to gravitational lensing by multiple lenses, and may also constrain models of their interaction rates.
Date: October 1, 2005
Creator: Bernardi, Mariangela; Sheth, R.K.; U., /Pennsylvania; Nichol, R.C.; /Portsmouth U., ICG; Miller, C.J. et al.
Partner: UNT Libraries Government Documents Department

Report of the Dark Energy Task Force

Description: Dark energy appears to be the dominant component of the physical Universe, yet there is no persuasive theoretical explanation for its existence or magnitude. The acceleration of the Universe is, along with dark matter, the observed phenomenon that most directly demonstrates that our theories of fundamental particles and gravity are either incorrect or incomplete. Most experts believe that nothing short of a revolution in our understanding of fundamental physics will be required to achieve a full understanding of the cosmic acceleration. For these reasons, the nature of dark energy ranks among the very most compelling of all outstanding problems in physical science. These circumstances demand an ambitious observational program to determine the dark energy properties as well as possible.
Date: September 1, 2006
Creator: Albrecht, Andreas; /UC, Davis; Bernstein, Gary; U., /Pennsylvania; Cahn, Robert; /LBL, Berkeley et al.
Partner: UNT Libraries Government Documents Department

Fermilab Steering Group Report

Description: The Fermilab Steering Group has developed a plan to keep U.S. accelerator-based particle physics on the pathway to discovery, both at the Terascale with the LHC and the ILC and in the domain of neutrinos and precision physics with a high-intensity accelerator. The plan puts discovering Terascale physics with the LHC and the ILC as Fermilab's highest priority. While supporting ILC development, the plan creates opportunities for exciting science at the intensity frontier. If the ILC remains near the Global Design Effort's technically driven timeline, Fermilab would continue neutrino science with the NOVA experiment, using the NuMI (Neutrinos at the Main Injector) proton plan, scheduled to begin operating in 2011. If ILC construction must wait somewhat longer, Fermilab's plan proposes SNuMI, an upgrade of NuMI to create a more powerful neutrino beam. If the ILC start is postponed significantly, a central feature of the proposed Fermilab plan calls for building an intense proton facility, Project X, consisting of a linear accelerator with the currently planned characteristics of the ILC combined with Fermilab's existing Recycler Ring and the Main Injector accelerator. The major component of Project X is the linac. Cryomodules, radio-frequency distribution, cryogenics and instrumentation for the linac are the same as or similar to those used in the ILC at a scale of about one percent of a full ILC linac. Project X's intense proton beams would open a path to discovery in neutrino science and in precision physics with charged leptons and quarks. World-leading experiments would allow physicists to address key questions of the Quantum Universe: How did the universe come to be? Are there undiscovered principles of nature: new symmetries, new physical laws? Do all the particles and forces become one? What happened to the antimatter? Building Project X's ILC-like linac would offer substantial support for ILC ...
Date: January 1, 2007
Creator: Beier, Eugene; U., /Pennsylvania; Butler, Joel; /Fermilab; Dawson, Sally; /Brookhaven et al.
Partner: UNT Libraries Government Documents Department