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Recent results from the search for new phenomena at D0

Description: We present results from several new searches for physics beyond the Standard Model. We describe a search based on the scalar sum of the transverse energy of the event, a global quantity nearly independent of the event topology. We summarize our searches for first generation leptoquarks into all three decay channels, eq{ovr eq}, eq{ovr {nu}q}, and {nu}q{ovr {nu}q} and note that this is the first time that the triumvirate of decay channels has been searched. We do not find any evidence for production of first generation leptoquarks and set a lower limit on the mass of the leptoquark of 175 GeV/c{sup 2} , assuming the decay is exclusively into eq{ovr eq}. We also present results from the first search for a third generation leptoquark with charge {+-}1/3. Again, we find no evidence for its existence for a mass less than 80 GeV/c{sup 2} Finally, we discuss one of our searches for supersymmetry, specifically the pair-production of {tilde e}, {tilde {nu}}, and {tilde {chi}}{sup 0}{sub 2} where the decay yields final states with two photons plus missing transverse energy (E{sub T}). We set limits on the production cross section ranging from 1 pb to 400 fb, depending on the mass. This analysis also sets a model-independent limit of {sigma} {center_dot} B(pp - {gamma}{gamma} {vert_bar} E{sub T} {vert_bar} X) < 185 fb at the 95% CL for E{sub T}{sup ({gamma})} > 12 GeV and {vert_bar}{eta}{vert_bar} < 1.1 T and E{sub T}> 25 GeV.
Date: June 1, 1997
Creator: Wightman, J.A.
Partner: UNT Libraries Government Documents Department

Multijet production and double parton scattering at Tevatron

Description: We report the differential cross-section for events with large total transverse energies, based on 112 pb{sup -1} p{anti p} collisions at {radical}s = 1.8 TeV. The ratio of number of 3-jet to 2-jet events as a function of total transverse energy is also presented. Obtained results are compared with the QCD expectations. The properties of high mass six-jet events have been studied. Observed distributions are compared with the predictions of HER- WIG parton shower QCD, NJETS matrix element QCD, and a phase-space model in which events are uniformly distributed in the kinematic allowed region of phase space. A strong signal for Double Parton Scattering (DP) is observed in the process {anti p}p {yields} {gamma} + 3 jets + X, using data from the CDF experiment. The fundamental DP parameter {sigma}{sub eff} obtained, {sigma}{sub eff} = 14.5 + 1.7{sup 1.7}{sub -2.3} mb, represents a significant improvement over previous measurements.
Date: June 1, 1997
Creator: Chang, P. & Collaborations, CDF and DO
Partner: UNT Libraries Government Documents Department

A Study of the Effects of Betatron Coupling the Accumulator Using a Tracking Program

Description: This report will summarize some tracking simulations I performed to demonstrate that in a strongly coupled machine all or most of the transverse energy associated with betatron motion can at times reside in a single dimension. In this case the maximum excursion from the closed orbit is larger than what is expected from the known emittances, and can cause beam loss when it otherwise is not expected.
Date: February 7, 1992
Creator: Halling, Mike
Partner: UNT Libraries Government Documents Department

High {Sigma}E{sub {Tau}} multijets at CDF

Description: The CDF collaboration has studied properties of 3-, 4- and 5-jet events with very high total transverse energy. An appropriate set of kinematic variables is described and two calculations based on QCD and with a phase space model. The QCD calculations are in reasonably good agreement with the data.
Date: October 1, 1996
Creator: Devlin, T.
Partner: UNT Libraries Government Documents Department

Color coherence in p{bar p} collisions at {radical}s = 1.8 TeV

Description: We report on two preliminary studies of color coherence effects in pp collisions based on data collected by the D{O} detector during the 1992-1993 and 1994-1995 runs of the Fermilab Tevatron collider at a center of mass energy {radical}s = 1.8 TeV. Demonstration of initial-to-final state color interference effects is done in a higher energy region by measuring spatial correlations between the softer third jet and the second leading-ET jet in multi-jet events and in a lower energy regime by examining particle distribution patterns in W+Jet events. The data are compared to Monte Carlo simulations with different color coherence implementations and to the predictions of a NLO parton-level calculation.
Date: September 1, 1996
Creator: Cullen-Vidal, D.E.
Partner: UNT Libraries Government Documents Department

Measurement of W + 1 jet/W + 0 jets cross sections

Description: A preliminary measurement of the ratio W + 1 Jet/W + 0 Jets in {ital p}{ital {anti p}} collisions at {radical}s = 1800 GeV is presented. A comparison to next-to-leading order QCD finds the theory to be well below the experimental ratio even after accounting for the systematic uncertainties of the measurement. In addition, a study of both the measured and theoretical ratios as a function of minimum jet transverse energy (E{sub T}) shows that the theoretical predictions are systematically lower than the data.
Date: August 1996
Creator: Guglielmo, G.
Partner: UNT Libraries Government Documents Department

Study of transverse loss factor for the tapered sections in the APS storage ring

Description: In the 7-GeV Advanced Photon Source (APS) storage ring, the tapered sections are considered to be the main contributor to the transverse impedance. The large tube represents the beam chamber, and the small one the insertion device section. Both are connected by a tapered transition with angle {theta}. This note presents a power law dependence of the transverse loss factor on the taper angle for this structure.
Date: June 6, 1990
Partner: UNT Libraries Government Documents Department

Search for ZX {yields} {nu}{anti {nu}} b {anti b} Events in the D-Zero Detector

Description: We report on a search for a new particle, X, decaying via X {yields} b{anti b}, made through associated production with a Z boson. We use data collected with the D0 detector operating at the Fermilab Tevatron p{anti p} collider with {radical}s = 1.8 TeV. We utilize muon-tagged jets to identify b-quarks and the {nu}{anti {nu}} channel to detect Z bosons. Preliminary results on cross section limits for X masses between 90 GeV/c{sup 2} and 180 GeV/c{sup 2} are presented.
Date: October 1, 1997
Creator: Abbott, B.
Partner: UNT Libraries Government Documents Department

Diffractive dijet production in CDF

Description: We have studied events with a high-x{sub F} antiproton and two central jets in CDF, with p{anti p} collisions at {radical}s = 630 and 1800 GeV. These events are expected to be dominated by diffraction (pomeron exchange). The jet E{sub T} spectra are very similar to those of non-diffractively produced jets but slightly steeper; their azimuthal difference {Delta}{phi} is more peaked at 180{degree}.
Date: April 17, 1998
Creator: Albrow, M.G.
Partner: UNT Libraries Government Documents Department

Extracting {ital alpha}{sub s}from Tevatron data

Description: In this contribution we explore one of the many possibilities of determining the strong coupling constant {alpha}{sub s} at hadron colliders. The method considered is quite unique compared to other methods in that the value of {alpha}{sub s} is determined by the ``evolution rate`` of the parton density functions rather than by the ``event rate``.
Date: July 1, 1997
Creator: Giele, W.T.
Partner: UNT Libraries Government Documents Department

Jet physics at CDF

Description: We present high E{sub T} jet measurements from CDF at the Fermilab Tevatron Collider. The incfilusive jet cross section at {radical}s = 1800 GeV with {approximately} 5 times more data is compared to the published CDF results, preliminary D0 results, and next-to-leading order QCD predictions. The {summation}E{sub T} cross section is also compared to QCD predictions and the dijet angular distribution is used to place a limit on quark compositeness. The inclusive jet cross section at {radical}s = 630 GeV is compared with that at 1800 GeV to test the QCD predictions for the scaling of jet cross sections with {radical}s. Finally, we present momentum distributions of charged particles in jets and compare them to Modified Leading Log Approximation predictions.
Date: May 1, 1997
Creator: Melese, P.
Partner: UNT Libraries Government Documents Department

MSSM and Higgs Searches at the Tevatron

Description: In this paper a summary of present CDF and D0/ results on supersymmetry and Higgs searches at Tevatron is presented. Analysis include results from a variety of signatures: missing E{sub T} and jets (or leptons and jets) for squark/gluino searches, trileptons and missing E{sub T} for gaugino searches and, for the first time, charmed-tagged jets and missing E{sub T} as a new signature for stop quark pair production. We show also results for various searches of standard and non-standard model Higgs bosons in hadron collisions. The seeked signature is Higgs associated production with a vector boson. Different channels involve jets and leptons from vector boson decays and b-tagged jets or photons from Higgs decays.
Date: September 1, 1998
Creator: Valls, J.A.
Partner: UNT Libraries Government Documents Department

Search for SUSY with missing E{sub T} and jets at CDF

Description: Events with signatures involving large missing transverse energy (E{sub T}) are among the quintessential search modes for R-parity conserving supersymmetry. CDF has conducted two recent analyses for supersymmetry which use E{sub T} and jets. The E{sub T} and monojet signature is employed to determine process independent limits for the production of new physics beyond the Standard Model and then applied to models of spontaneous breaking of supersymmetry to determine limits on the supersymmetry breaking parameter and the gravitino mass. Direct searches for scalar top and scalar bottom quarks within the framework of supersymmetric models are performed using a signature of E{sub T} and two heavy flavor jets. Since the data is found to be consistent with Standard Model expectations, limits are determined in the mass planes m({tilde {chi}}{sub 1}{sup 0})-m({tilde t}{sub 1}) and m({tilde {chi}}{sub 1}){sup 0}-m({tilde b}{sub 1}).
Date: December 21, 2000
Creator: CDF, Search for SUSY with Missing ET and Jets at
Partner: UNT Libraries Government Documents Department

Properties of events with a rapidity gap between jets in CDF

Description: We present the {eta} and E{sub T} dependence of dijet events produced by color-singlet exchange in {anti p}p collisions at {radical}s = 1.8 TeV using data collected by the CDF collaboration at the Fermilab Tevatron. In a sample of events with two forward jets, where the jets are on opposite sides in rapidity with {vert_bar}{eta}{vert_bar} > 1. 8 and E{sub T} > 20 GeV, we find 1.13 {+-} 0.12(stat) {+-} 0. 11(syst)% have a rapidity gap between the jets consistent with color- singlet exchange. This signal has no significant dependence on the jet E{sub T} or the rapidity interval between the jets.
Date: June 1, 1997
Creator: Melese, P.
Partner: UNT Libraries Government Documents Department

Reduction of the calorimeter data with {sup 208}Pb projectiles at 158 GeV/Nucleon in the CERN experiment NA49

Description: The first heavy ion run involving a {sup 208}Pb beam at E{sub LAB} = 158 GeV/Nucleon was performed at the CERN Super Proton Synchrotron (SPS) in November-December 1994. The calibration procedures and the analysis of the calorimeter data are present.
Date: December 1, 1995
Creator: Huang, I.; Margetis, S.; Seyboth, P. & Vranic, D.
Partner: UNT Libraries Government Documents Department

A first look at Pb on Pb collisions at 160 GeV/c at CERN SPS

Description: Last year marked a major milestone in the field of relativistic nuclear collisions. Lead beams were successfully accelerated at CERN SPS to an energy of about 160 GeV per nucleon in the projectile (i.e. to about 32 TeV total energy) and the first preliminary results of the analysis of Pb on Pb interactions are already available and discussed. Before going on to the discussion of these results, it would be helpful to stand back for a moment and try to recapitulate what we have learned from light {open_quotes}heavy{close_quotes} ion experiments at CERN SPS with oxygen and sulphur beams. In the first part of this overview we shall shortly summarize the results of the experimental program with {sup 16}O and {sup 32}S beams at CERN SPS. Next, we shall describe the concept of an event-by-event (e-b-e) analysis proposed for study of individual Pb+Pb collisions with several thousand identified hadrons in the final state. The main section of this paper will be focused on the results (very preliminary) of the analysis of the first run with the lead projectiles. To conclude, we will present plans for the future (as we understand them now).
Date: February 1, 1996
Creator: Odyniec, G.J.
Partner: UNT Libraries Government Documents Department

Probing hard color singlet exchange at D Zero

Description: We present latest preliminary results on hard color-singlet exchange in proton-antiproton collisions. The fraction of dijet events produced via color-singlet exchange is measured as a function of jet transverse energy, dijet pseudorapidity separation, and proton-antiproton center-of-mass energy. The results favour a color-singlet fraction that increases with increasing quark-initiated processes.
Date: June 1, 1998
Creator: Goussiou, A.
Partner: UNT Libraries Government Documents Department

Top physics: measurement of the tt-bar production cross section in pp-bar collisions at s**(1/2) = 1.96 tev using dilepton event

Description: We report a measurement of the t{bar t} production cross section using dilepton events with jets and missing transverse energy in p{bar p} collisions at a center-of-mass energy of 1.96 TeV. Using a 197 {+-} 12 pb{sup -1} data sample recorded by the upgraded Collider Detector at Fermilab, we use two complementary techniques to select candidate events. We compare the number of observed events and selected kinematical distributions with the predictions of the standard model and find good agreement. The combined result of the two techniques yields a t{bar t} production cross section of 7.0{sub -2.1}{sup +2.4}(stat){sub -1.1}{sup _1.6}(syst) {+-} 0.4(lum) pb.
Date: October 14, 2004
Creator: Acosta, D.
Partner: UNT Libraries Government Documents Department

Transverse Mode Structure and Pattern Formation in Oxide Confined Vertical Cavity Semiconductor Lasers

Description: We analyze the transverse profiles of oxide-confined vertical cavity laser diodes as a function of aperture size. For small apertures we demonstrate that thermal lensing can be the dominant effect in determining the transverse resonator properties. We also analyze pattern formation in lasers with large apertures where we observe the appearance of tilted waves.
Date: July 6, 1999
Creator: Choquette, K.D.; Geib, K.M.; Hegarty, S.P.; Hou, H.Q.; Huyet, G.; McInerney, J.G. et al.
Partner: UNT Libraries Government Documents Department

Search for light top squarks with the D{O} detector

Description: We present preliminary results of a search for pair produced top squarks, the supersymmetric partners to the top quark, under the assumption that the two-body decay {bar t}{sub 1} {yields} b{bar W}{sub 1} and three-body decay {bar t}{sub 1} {yields} bW{bar Z}{sub 1} are kinematically forbidden. This scenario is realized if {bar t}{sub 1} is considerably lighter than all other squarks as well as {bar W}{sub 1}, all {bar v}s, and the top quark. Such light top squarks will dominantly decay via {bar t}{sub 1} {yields} c{bar Z}{sub 1} yielding a signal of two acollinear jets with (E){sub T}. The data reported here were taken during the 1992-1993 run of the D0 detector at the Fermilab Tevatron p{bar p} collider operating at {radical}s = 1.8 TeV.
Date: July 1, 1995
Creator: Abachi, S.
Partner: UNT Libraries Government Documents Department

Search for quirks at the Fermilab Tevatron Collider

Description: We report results of a search for particles with anomalously high ionization in events with a high transverse energy jet and large missing transverse energy in 2.4 fb{sup -1} of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron p{bar p} collider. Production of such particles (quirks) is expected in scenarios with extra QCD-like SU(N) sectors, and this study is the first dedicated search for such signatures. We find no evidence of a signal and set a lower mass limit of 107 GeV for the mass of a charged quirk with strong dynamics scale {Lambda} in the range from 10 keV to 1 MeV.
Date: August 1, 2010
Creator: Abazov, V.M.; /Dubna, JINR; Abbott, B.; U., /Oklahoma; Abolins, M.; U., /Michigan State et al.
Partner: UNT Libraries Government Documents Department

Measurement of trilinear gauge boson couplings from at {\boldmath$\sqrt{s}=1.96$} TeV

Description: We present a direct measurement of trilinear gauge boson couplings at gammaWW and ZWW vertices in WW and WZ events produced in p{bar p} collisions at {radical}s = 1.96 TeV. We consider events with one electron or muon, missing transverse energy, and at least two jets. The data were collected using the D0 detector and correspond to 1.1 fb{sup -1} of integrated luminosity. Considering two different relations between the couplings at the gammaWW and ZWW vertices, we measure these couplings at 68% C.L. to be kappa{sub gamma} = 1.07{sub -0.29}{sup +0.26}, lambda = 0.00{sub -0.06}{sup +0.06}, and g{sub 1}{sup Z} = 1.04{sup -0.09}{sup +0.09} in a scenario respecting SU(2){sub L}[direct-product]U(1){sub Y} gauge symmetry and kappa = 1.04{sub -0.11}{sup +0.11} and lambda=0.00{sub -0.06}{sup +0.06} in an 'equal couplings' scenario.
Date: July 1, 2009
Creator: Abazov, Victor Mukhamedovich; Abbott, Braden Keim; Abolins, Maris A.; Acharya, Bannanje Sripath; Adams, Mark Raymond; Adams, Todd et al.
Partner: UNT Libraries Government Documents Department

A Cone Jet-Finding Algorithm for Heavy-Ion Collisions at LHCEnergies

Description: Standard jet finding techniques used in elementary particle collisions have not been successful in the high track density of heavy-ion collisions. This paper describes a modified cone-type jet finding algorithm developed for the complex environment of heavy-ion collisions. The primary modification to the algorithm is the evaluation and subtraction of the large background energy, arising from uncorrelated soft hadrons, in each collision. A detailed analysis of the background energy and its event-by-event fluctuations has been performed on simulated data, and a method developed to estimate the background energy inside the jet cone from the measured energy outside the cone on an event-by-event basis. The algorithm has been tested using Monte-Carlo simulations of Pb+Pb collisions at {radical}s = 5.5 TeV for the ALICE detector at the LHC. The algorithm can reconstruct jets with a transverse energy of 50 GeV and above with an energy resolution of {approx} 30%.
Date: July 27, 2006
Creator: Blyth, S.-L.; Horner, M.J.; Awes, T.C.; Cormier, T.; Gray, H.M.; Klay, J.L. et al.
Partner: UNT Libraries Government Documents Department