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W and Z physics at CDF

Description: The authors present recent measurements of W and Z-boson physics using data collected by CDF experiment at run II of the Fermilab Tevatron collider.
Date: December 1, 2004
Creator: Martin, Victoria & U., /Northwestern
Partner: UNT Libraries Government Documents Department

Searches for New Physics Using High Mass Dimuons at the CDF II Experiment

Description: This work describes the measurement of inclusive jets cross section in the D0 experiment. This cross section is computed as a function of jet transverse momentum, in several rapidity intervals. This quantity is sensitive to the proton structure and is crucial for the determination of parton distribution functions (PDF), essentially for the gluon at high proton momentum fraction. The measurement presented here gives the first values obtained for Tevatron Run II for the cross section in several rapidity intervals, for an integrated luminosity of 143 pb{sup -1}. The results are in agreement, within the uncertainties, with theoretical Standard Model predictions, showing no evidence for new physics. This work points out the aspects of the detector which need better understanding to reach Run I precision and to constrain the PDFs.
Date: December 1, 2004
Creator: Karagoz Unel, Muge & U., /Northwestern
Partner: UNT Libraries Government Documents Department

Wire bond vibration of forward pixel tracking detector of CMS

Description: Wire bonds of the Forward Pixel (FPix) tracking detectors are oriented in the direction that maximizes Lorentz Forces relative to the 4 Tesla field of the Compact Muon Solenoid (CMS) Detector's magnet. The CMS Experiment is under construction at the Large Hadron Collider at CERN, Geneva, Switzerland. We were concerned about Lorentz Force oscillating the wires at their fundamental frequencies and possibly fracturing or breaking them at their heels, as happened with the CDF wire bonds. This paper reports a study to understand what conditions break such bonds.
Date: October 1, 2006
Creator: Atac, M.; /Fermilab; Gobbi, B.; U., /Northwestern; Kwan, S.; Pischalnikov, Y. et al.
Partner: UNT Libraries Government Documents Department

Proposal to study the k+- charge exchange reactions at high energies

Description: An experiment is proposed for measurement of the K{sup {+-}} {yields} K-Long charge-exchange reactions using unseparated beams; useful rates are obtained for p{sub inc}{le}100 GeV/c and -t {le} 1 (GeV/c){sup 2}. A V-spectrometer with resolution {+-}1% is used downstream of the target for detection of the decays K-long {yields} {pi}{sup +}{pi}{sup -}. Using hydrogen and deuterium targets, the detection system is designed to measure: (1) d{sigma}/dt for K{sup -}p {yields} {bar K}{sup 0}n. The reaction will be distinguished from background processes involving N* and K* production by kinematics and supplementary detectors surrounding the target. (2) d{sup 2}{sigma}/dpdt for K{sup -}d {yields} {bar K}{sup 0}nn. This final state will be distinguished from those involving production of {pi}{sup 0}'s or charged particles primarily by the supplementary target veto array. Use of a deuterium target will provide partial clarification of the problems to be encountered in achieving part 3. In principle, some information on the relative sizes of the spin-flip and non-spin-flip amplitudes will be obtained. (3) d{sup 2}{sigma}/dpdt for K{sup +}d {yields} K{sup 0}pp. Since charged particles are produced at the interaction vortex, this final state can be reliably extracted only with the insight gained in parts (1) and (2) and a detailed study of the distributions in the target veto counter array.
Date: February 1, 1971
Creator: Meyer, Stuart L.; Miller, Donald H.; Hicks, George & U., /Northwestern
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

Precision measurement of a particle mass at the linear collider

Description: Precision measurement of the stop mass at the ILC is done in a method based on cross-sections measurements at two different center-of-mass energies. This allows to minimize both the statistical and systematic errors. In the framework of the MSSM, a light stop, compatible with electro-weak baryogenesis, is studied in its decay into a charm jet and neutralino, the Lightest Supersymmetric Particle (LSP), as a candidate of dark matter. This takes place for a small stop-neutralino mass difference.
Date: June 1, 2007
Creator: Milstene, C.; /Fermilab; Freitas, A.; U., /Zurich; Schmitt, M.; U., /Northwestern et al.
Partner: UNT Libraries Government Documents Department

Neutrino mass hierarchy, vacuum oscillations, and vanishing |U(e3)|

Description: Is the relatively isolated member of the neutrino mass spectrum heavier or lighter than the two closely-spaced members? This question--the character of the neutrino mass hierarchy--is of great theoretical interest. All previously identified experiments for addressing it via neutrino oscillations require that the currently unknown size of the U{sub e3} element of the leptonic mixing matrix (parameterized by the unknown {theta}{sub 13} mixing angle) be sufficiently large, and will utterly fail in the limit {theta}{sub 13} {yields} 0. For this reason, we explore alternative oscillation approaches that would still succeed even if {theta}{sub 13} vanishes. We identify several alternatives that require neither a nonzero |U{sub e3}| nor the presence of significant matter effects. All include multiple percent-level neutrino oscillation measurements, usually involving muon-neutrino (or antineutrino) disappearance and very long baselines. We comment on the degree of promise that these alternative approaches show.
Date: March 1, 2005
Creator: de Gouvea, Andre; /Fermilab, /Northwestern U.; Jenkins, James; U., /Northwestern; Kayser, Boris & /Fermilab
Partner: UNT Libraries Government Documents Department

A Method for the Precision Mass Measurement of the Stop Quark at the International Linear Collider

Description: Many supersymmetric models predict new particles within the reach of the next generation of colliders. For an understanding of the model structure and the mechanism(s) of symmetry breaking, it is important to know the masses of the new particles precisely. In this article the measurement of the mass of the scalar partner of the top quark (stop) at an e+e- collider is studied. A relatively light stop is motivated by attempts to explain electroweak baryogenesis and can play an important role in dark matter relic density. A method is presented which makes use of cross-section measurements near the pair-production threshold as well as at higher center-of-mass energies. It is shown that this method not only increases the statistical precision, but also greatly reduces the systematic uncertainties, which can be important. Numerical results are presented, based on a realistic event simulation, for two signal selection strategies: using conventional selection cuts, and using an Iterative Discriminant Analysis (IDA). Our studies indicate that a precision of {Delta}m{tilde t}{sub 1} = 0.42 GeV can be achieved, representing a major improvement over previous studies. While the analysis of stops is particularly challenging due to the possibility of stop hadronization, the general procedure could be applied to the mass measurement of other particles as well. We also comment on the potential of the IDA to discover a stop quark in this scenario, and we revisit the accuracy of the theoretical predictions for the neutralino relic density
Date: June 1, 2008
Creator: Freitas, Ayres; U., /Chicago U. /Argonne /Zurich; Milstene, Caroline; U., /Fermilab /Wayne State; Schmitt, Michael; U., /Northwestern et al.
Partner: UNT Libraries Government Documents Department

A 3-D model of superfluid helium suitable for numerical analysis

Description: The two-fluid description is a very successful phenomenological representation of the properties of Helium II. A 3-D model suitable for numerical analysis based on the Landau-Khalatnikov description of Helium II is proposed. In this paper we introduce a system of partial differential equations that is both complete and consistent as well as practical, to be used for a 3-D solution of the flow of Helium II. The development of a 3-D numerical model for Helium II is motivated by the need to validate experimental results obtained by observing the normal component velocity distribution in a Helium II thermal counter-flow using the Particle Image Velocimetry (PIV) technique.
Date: January 1, 2008
Creator: Darve, C.; U., /Fermilab /Northwestern; Patankar, N.A.; U., /Northwestern; Van Sciver, S.W. & Lab., /Natl. High Mag. Field
Partner: UNT Libraries Government Documents Department

A method for the three-dimensional simulation of superfluid helium

Description: Transport phenomena in superfluid helium can be described using the two-fluid Landau-Khalatnikov model and the Gorter-Mellink mutual friction. Here we discuss a mathematical formulation of the two-fluid model that uses macroscopic conservation balances of mass, momentum and energy of each species, and assumes local thermodynamic equilibrium. A particularity of this model is that it describes the state of He II as well as that of each of the two-fluid components in terms of pressure p and temperature T, which is convenient for stable numerical solution. The equations of the model form a system of partial differential equations (PDE) that can be written in matrix form for convenience. On this base, a three-dimensional numerical model using a complete and consistent, while still practical, system of PDEs was developed. In the form described, the PDE can be solved using three-dimensional Lagrangian finite element in space supplemented by a Beam-Warming time-2marching algorithm. Once validated, this solver will allow to simulate He II thermal counterflow applied to arbitrary geometry.
Date: January 1, 2008
Creator: Bottura, L.; /CERN; Darve, C.; U., /Fermilab /Northwestern; Patankar, N.A.; U., /Northwestern 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

A Method for the Precision Mass Measurement of the Stop Quark at the International Linear Collider

Description: Many supersymmetric models predict new particles within the reach of the next generation of colliders. For an understanding of the model structure and the mechanism(s) of symmetry breaking, it is important to know the masses of the new particles precisely. In this article the measurement of the mass of the scalar partner of the top quark (stop) at an e{sup +}e{sup -} collider is studied. A relatively light stop is motivated by attempts to explain electroweak baryogenesis and can play an important role in dark matter relic density. A method is presented which makes use of cross-section measurements near the pair-production threshold as well as at higher center-of-mass energies. It is shown that this method not only increases the statistical precision, but also greatly reduces the systematic uncertainties, which can be important. numerical results are presented, based on a realistic event simulation, for two signal selection strategies: using conventional selection cuts, and using an Iterative Discriminant Analysis (IDA). The studies indicate that a precision of {Delta}m{sub {bar t}{sub 1}} = 0.42 GeV can be achieved, representing a major improvement over previous studies. While the analysis of stops is particularly challenging due to the possibility of stop hadronization, the general procedure could be applied to the mass measurement of other particles as well. They also comment on the potential of the IDA to discover a stop quark in this scenario, and they revisit the accuracy of the theoretical predictions for the neutralino relic density.
Date: December 1, 2007
Creator: Freitas, Ayres; U., /Chicago U. /Argonne /Zurich; Milstene, Caroline; /Fermilab; Schmitt, Michael; U., /Northwestern et al.
Partner: UNT Libraries Government Documents Department

QCD Precision Measurements and Structure Function Extraction at a High Statistics, High Energy Neutrino Scattering Experiment: NuSOnG

Description: We extend the physics case for a new high-energy, ultra-high statistics neutrino scattering experiment, NuSOnG (Neutrino Scattering On Glass) to address a variety of issues including precision QCD measurements, extraction of structure functions, and the derived Parton Distribution Functions (PDFs). This experiment uses a Tevatron-based neutrino beam to obtain a sample of Deep Inelastic Scattering (DIS) events which is over two orders of magnitude larger than past samples. We outline an innovative method for fitting the structure functions using a parameterized energy shift which yields reduced systematic uncertainties. High statistics measurements, in combination with improved systematics, will enable NuSOnG to perform discerning tests of fundamental Standard Model parameters as we search for deviations which may hint of 'Beyond the Standard Model' physics.
Date: June 1, 2009
Creator: Adams, T.; U., /Florida State; Batra, P.; U., /Columbia; Bugel, Leonard G.; U., /Columbia et al.
Partner: UNT Libraries Government Documents Department

A Proposal to Continue Measurements of Direct Muon Production in the Forward Direction

Description: The authors recently have measured the direct muon production in the forward direction at small p{perpendicular} and find a large direct muon to pion ratio. At x = 0.3 the ratio is {mu}{sup -}/{pi}{sup -} = 1.83 {+-} 0.43 x 10{sup -4} for negatives and {mu}{sup +}/{pi}{sup +} = 6.4 {+-} 1.3 x 10{sup -5} for positives. The direct production of {mu}{sup +} and {mu}{sup -} are equal although the {pi}{sup +}/{pi}{sup -} ratios is large. They propose to continue these measurements and extend them to higher x. These new measurements would also include the A dependence of the {mu}/{pi} ratio. Based on their experience with this apparatus, they believe it is possible to extend these measurements of single lepton production to production by incident pions and kaons.
Date: October 20, 1975
Creator: Buchholz, D.; U., /Northwestern; Frisch, H.J.; Shochet, M.J.; /Chicago U., EFI; Johnson, Rolland P. et al.
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

Decay Properties of p pi- Systems Produced in Neutron Dissociation at Fermilab Energies

Description: The authors have examined the decay distributions of (p{pi}{sup -}) systems produced in the reaction n + p {yields} (p{pi}{sup -}) + p for neutron momenta between 120 GeV/c and 300 GeV/c. Preliminary analysis of decay moments indicates the presence of large helicity-flip amplitudes even for small (p{pi}{sup -}) mass values, and does not support the hypothesis that the helicity non-flip (p{pi}{sup -}) states are produced peripherally in impact parameter. These results are in approximate agreement with predictions of the Deck mechanism. The experiment was performed at the M-3 neutral beam of Fermilab.
Date: June 1, 1975
Creator: Biel, J.; U., /Rochester; Bleser, E.J.; /Fermilab; Duke, D.; Ferbel, T. et al.
Partner: UNT Libraries Government Documents Department

Updated Search for the Flavor-Changing Neutral-Current Decay $D^0 \to \mu^+ \mu^-$

Description: We report on a search for the flavor-changing neutral-current decay D{sup 0} {yields} {mu}{sup +}{mu}{sup -} in p{bar p} collisions at {radical}s = 1.96TeV using 360 pb{sup -1} of integrated luminosity collected by the CDF II detector at the Fermilab Tevatron collider. A displaced vertex trigger selects long-lived D{sup 0} candidates in the {mu}{sup +}{mu}{sup -}, {pi}{sup +}{pi}{sup -}, and K{sup -}{pi}{sup +} decay modes. We use the Cabibbo-favored D{sup 0} {yields} K{sup -}{pi}{sup +} channel to optimize the selection criteria in an unbiased manner, and the kinematically similar D{sup 0} {yields} {pi}{sup +}{pi}{sup -} channel for normalization. We set an upper limit on the branching fraction {Beta}(D{sup 0} {yields} {mu}{sup +}{mu}{sup -}) < 2.1 x 10{sup -7} (3.0 x 10{sup -7}) at the 90% (95%) confidence level.
Date: August 1, 2010
Creator: Aaltonen, T.; Phys., /Helsinki Inst. of; Alvarez Gonzalez, B.; Phys., /Oviedo U. /Cantabria Inst. of; Amerio, S.; /INFN, Padua et al.
Partner: UNT Libraries Government Documents Department

Diffractive W and Z Production at the Fermilab Tevatron

Description: We report on a measurement of the fraction of events with a W or Z boson produced diffractively in {bar p}p collisions at {radical}s = 1.96 TeV, using data from 0.6 fb{sup -1} of integrated luminosity collected with the CDF II detector equipped with a Roman-pot spectrometer that detects the {bar p} from {bar p} + p {yields} {bar p}+[X+W/Z]. We find that (0.97 {+-} 0.11)% of Ws and (0.85 {+-} 0.22)% of Zs are produced diffractively in a region of (anti)proton fractional momentum loss {zeta} of 0.03 < {zeta} < 0.10 and 4-momentum transferred squared t of -1 < t < 0 (GeV/c){sup 2}. We also report on searches for W and Z production in double Pomeron exchange, p+{bar p} {yields} p+[X+W/z]+{bar p}, and on exclusive Z production, {bar p}p {yields} {bar p}+Z+p. No signal is seen above background for these processes, and comparisons are made with expectations.
Date: July 1, 2010
Creator: Aaltonen, T.; Phys., /Helsinki Inst. of; Alvarez Gonzalez, B.; Phys., /Cantabria Inst. of; Amerio, S.; /INFN, Padua et al.
Partner: UNT Libraries Government Documents Department

Improved Search for a Higgs Boson Produced in Association with Z->l+l- in proton antiproton Collisions at sqrt(s) = 1.96 TeV

Description: We present a search for the standard model Higgs boson produced with a Z boson in 4.1 fb{sup -1} of data collected with the CDF II detector at the Tevatron. In events consistent with the decay of the Higgs boson to a bottom-quark pair and the Z boson to electrons or muons, we set 95% credibility level upper limits on the ZH production cross section times the H {yields} b{bar b} branching ratio. Improved analysis methods enhance signal sensitivity by 20% relative to previous searches beyond the gain due to the larger data sample. At a Higgs boson mass of 115 GeV/c{sup 2} we set a limit of 5.9 times the standard model value.
Date: September 1, 2010
Creator: Aaltonen, T.; Phys., /Helsinki Inst. of; Alvarez Gonzalez, B.; Phys., /Oviedo U. /Cantabria Inst. of; Amerio, S.; /INFN, Padua et al.
Partner: UNT Libraries Government Documents Department

A Direct Top-Quark Width Measurement from Lepton + Jets Events at CDF II

Description: We present a measurement of the top-quark width using t{bar t} events produced in p{bar p} collisions at Fermilab's Tevatron collider and collected by the CDF II detector. In the mode where the top quark decays to a W boson and a bottom quark, we select events in which one W decays leptonically and the other hadronically (lepton + jets channel) . From a data sample corresponding to 4.3 fb{sup -1} of integrated luminosity, we identify 756 candidate events. The top-quark mass and the mass of W boson that decays hadronically are reconstructed for each event and compared with templates of different top-quark widths ({Lambda}{sub t}) and deviations from nominal jet energy scale ({Delta}{sub JES}) to perform a simultaneous fit for both parameters, where {Delta}{sub JES} is used for the in situ calibration of the jet energy scale. By applying a Feldman-Cousins approach, we establish an upper limit at 95% confidence level (CL) of {Lambda}{sub t} < 7.6 GeV and a two-sided 68% CL interval of 0.3 GeV < {Lambda}{sub t} < 4.4 GeV for a top-quark mass of 172.5 GeV/c{sup 2}, which are consistant with the standard model prediction. This is the first direct measurement of {Lambda}{sub t} to set a lower limit with 68% CL.
Date: August 1, 2010
Creator: Aaltonen, T.; Phys., /Helsinki Inst. of; Alvarez Gonzalez, B.; Phys., /Oviedo U. /Cantabria Inst. of; Amerio, S.; /INFN, Padua et al.
Partner: UNT Libraries Government Documents Department

Exclusion of an Exotic Top Quark with -4/3 Electric Charge Using Soft Lepton Tagging

Description: We present a measurement of the electric charge of the top quark using p{bar p} collisions corresponding to an integrated luminosity of 2.7 fb{sup -1} at the CDF II detector. We reconstruct t{bar t} events in the lepton+jets final state and use kinematic information to determine which b-jet is associated with the leptonically- or hadronically-decaying t-quark. Soft lepton taggers are used to determine the b-jet flavor. Along with the charge of the W boson decay lepton, this information permits the reconstruction of the top quark's electric charge. Out of 45 reconstructed events with 2.4 {+-} 0.8 expected background events, 29 are reconstructed as tt with the standard model +2/3 charge, whereas 16 are reconstructed as t{bar t} with an exotic -4/3 charge. This is consistent with the standard model and excludes the exotic scenario at 95% confidence level. This is the strongest exclusion of the exotic charge scenario and the first to use soft leptons for this purpose.
Date: June 1, 2010
Creator: Aaltonen, T.; Phys., /Helsinki Inst. of; Adelman, J.; /Chicago U., EFI; Alvarez Gonzalez, B.; Phys., /Oviedo U. /Cantabria Inst. of et al.
Partner: UNT Libraries Government Documents Department