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Search for Supersymmetry with Gauge-Mediated Breaking in Diphoton Events with Missing Transverse Energy at CDF II

Description: The authors present the results of a search for supersymmetry with gauge-mediated breaking and {tilde {chi}}{sub 1}{sup 0} {yields} {gamma}{tilde G} in the {gamma}{gamma} + missing transverse energy final state. In 2.6 {+-} 0.2 fb{sup -1} of p{bar p} collisions at {radical}s = 1.96 TeV recorded by the CDF II detector they observe no candidate events, consistent with a standard model background expectation of 1.4 {+-} 0.4 events. They set limits on the cross section at the 95% C.L. and place the world's best limit of 149 GeV/c{sup 2} on the {tilde {chi}}{sub 1}{sup 0} mass at {tau}{sub {tilde {chi}}{sub 1}{sup 0}} << 1 ns. They also exclude regions in the {tilde {chi}}{sub 1}{sup 0} mass-lifetime plane of {tau}{sub {tilde {chi}}{sub 1}{sup 0}} {approx}< 2 ns.
Date: October 1, 2009
Creator: Aaltonen, T.; Phys., /Helsinki Inst. of; Adelman, J.; /Chicago U., EFI; Alvarez Gonzalez, B.; Phys., /Cantabria Inst. of et al.
Partner: UNT Libraries Government Documents Department

Search for heavy, long-lived particles that decay to photons at CDF II

Description: The authors present the first search for heavy, long-lived particles that decay to photons at a hadron collider. They use a sample of {gamma} + jet + missing transverse energy events in p{bar p} collisions at {radical}s = 1.96 TeV taken with the CDF II detector. Candidate events are selected based on the arrival time of the photon at the detector. Using an integrated luminosity of 570 pb{sup -1} of collision data, they observe 2 events, consistent with the background estimate of 1.3 {+-} 0.7 events. While the search strategy does not rely on model-specific dynamics, they set cross section limits in a supersymmetric model with {tilde {chi}}{sub 1}{sup 0} {yields} {gamma}{tilde G} and place the world-best 95% C.L. lower limit on the {tilde {chi}}{sub 1}{sup 0} mass of 101 GeV/c{sup 2} at {tau}{sub {tilde {chi}}{sub 1}{sup 0}} = 5 ns.
Date: April 1, 2007
Creator: Abulencia, A.; /Illinois U., Urbana; Adelman, J.; U., /Chicago; Affolder, T.; /UC, Santa Barbara et al.
Partner: UNT Libraries Government Documents Department

Search for Fermion-Pair Decays $Q\Qbar \to (\t\Wmp)(\tbar\Wpm)$ in Same-Charge Dilepton Events

Description: We report the most restrictive direct limits on masses of fourth-generation down-type quarks b{prime}, and quark-like composite fermions (B or T{sub 5/3}), decaying promptly to tW{sup {-+}}. We search for a significant excess of events with two same-charge leptons (e, {mu}), several hadronic jets, and missing transverse energy. An analysis of data from p{bar p} collisions with an integrated luminosity of 2.7 fb{sup -1} collected with the CDF II detector at Fermilab yields no evidence for such a signal, setting mass limits m{sub b{prime}}, m{sub B} > 338 GeV/c{sup 2} and m{sub T{sub 5/3}} > 365 GeV/c{sup 2} at 95% confidence level.
Date: December 1, 2009
Creator: Aaltonen, T.; Phys., /Helsinki Inst. of; Adelman, J.; /Chicago U., EFI; Alvarez Gonzalez, B.; Phys., /Cantabria Inst. of et al.
Partner: UNT Libraries Government Documents Department

Search for gluino and squark production in multi-jets plus missing transverse energy final states at the Tevatron using the CDF detector

Description: In this thesis, the results of the search for squarks and gluinos in multiple jets plus missing transverse energy final states have been presented. No evidence of these new particles have been found in 371 pb{sup -1} of CDF Run II data. New limits have been set which exclude gluino masses below 220 GeV and, in the region where M{sub {tilde g}} {approx} M{sub {tilde q}}, masses below 380 GeV/c{sup 2} are excluded. These limits are valid in a mSUGRA scenario with tan {beta} = 5, A = 0 and {mu} < 0 assuming the lightest four squark flavours degenerate in mass. To obtain these results a careful study of the beam conditions and their contribution to events with E{sub T} final states has been performed. Special attention has been taken in studying the different SM backgrounds and their normalizations at NLO. Dedicated cuts have been introduced to remove the background processes and main discriminating variables have been optimized for different signal regions. The different systematic uncertainties have also been considered. This is the first time that this search is performed at CDF Run II and the results presented here show significant improvements with respect to the constraints from previous experiments. Thus, this analysis has established the procedure to continue searching for squarks and gluinos with the new data samples that CDF is collecting from Tevatron. Some improvements may also be implemented by considering other hadron final states with different jet multiplicities. This could help extending the sensitivity of the analysis to regions where gluino and squark masses are not similar. At the forthcoming LHC, the search for squarks and gluinos in this inclusive channel constitutes one of the first analyses to be performed. The E{sub T} and multiple jets final states are present in multiple decay modes of many ...
Date: January 1, 2007
Creator: Portell i Bueso, Xavier & /Barcelona, IFAE
Partner: UNT Libraries Government Documents Department

Search for large extra dimensions in final states containing one photon or jet and large missing transverse energy produced in p anti-p collisions at s**(1/2) = 1.96-TeV

Description: The authors present the results of searches for large extra dimensions in samples of events with large missing transverse energy E{sub T} and either a photon or a jet produced in p{bar p} collisions at {radical}s = 1.96 TeV collected with the CDF II detector. For {gamma} + E{sub T} and jet + E{sub T} candidate samples corresponding to 2.0 fb{sup -1} and 1.1 fb{sup -1} of integrated luminosity respectively, they observe good agreement with standard model expectations and obtain a combined lower limit on the fundamental parameter of the large extra dimensions model, M{sub D}, as a function of the number of extra dimensions in the model.
Date: July 1, 2008
Creator: Aaltonen, T.; Phys., /Helsinki Inst. of; Adelman, J.; /Chicago U., EFI; Akimoto, T.; U., /Tsukuba et al.
Partner: UNT Libraries Government Documents Department

Recent QCD results from CDF

Description: CDF has recently concluded a very successful 1992--93 data run in which an integrated luminosity of 21.3 pb {sup {minus}1} was written to tape. The large data sample allows for a greater discovery potential for new phenomena and for better statistical and systematic precision in analysis of conventional physics. This paper summarizes some of the new results from QCD analyses for this run.
Date: January 1, 1994
Creator: Huston, J. & Collaboration, CDF
Partner: UNT Libraries Government Documents Department

Combination of CDF and D0 limits on a gauge mediated SUSY model using diphoton and missing transverse energy channel

Description: We combine the results of the CDF and D0 searches for chargino and neutralino production in Gauge-Mediated SUSY using the two-photon and missing E{sub T} channel. The data are p{bar p} collisions produced at the Tevatron with {radical}s = 1.96 TeV, with 202 pb{sup -1} collected at CDF and 263 pb{sup -1} collected at D0. The combined limit excludes a chargino mass less than 209 GeV/c{sup 2}. This result significantly extends the individual experimental limits.
Date: April 1, 2005
Creator: Buescher, V.; Culbertson, R.; Conway, J.; Gershtein, Y.; Grivaz, J-F.; Heinemann, B. et al.
Partner: UNT Libraries Government Documents Department

Negative transverse impedance

Description: Recently, measurements in the SPS show that the coherent tune shift in the horizontal direction has positive values whereas that in the vertical direction has negative ones. Thus the existence of negative transverse impedance gets confirmed in a real machine. This stimulates us to start a new round of systematic studies on this interesting phenomenon. The results obtained from our computer simulations are presented in this note. Our simulations demonstrate that the negative transverse impedance may appear when the rotational symmetry embedded in a discontinuity is broken, and that the geometries that we have studies may be the source of the positive horizontal tune shift measured in the SPS.
Date: June 12, 1989
Creator: Chou, W.
Partner: UNT Libraries Government Documents Department

Scattering in a magnetic field

Description: The fixed target program at Fermilab has come to an end. New projects are in the planning stage. Among them is a muon storage ring. Up to the present, all storage rings in high-energy physics have carried stable particles, namely the electron and proton and their antiparticles. The muon is unstable and decays with a mean lifetime of 2.0 x 10{sup -6} sec. Two types of cooling have been used in the past. One is stochastic cooling where an electrode is used to detect the positions of the particles and send a signal to another position across the ring. Through successive applications of this technique, the phase space is ultimately greatly reduced and beams can be made to collide with a useful event rate. The second type of cooling is electron cooling. Here protons and electrons are made to travel together for a short distance. Equipartition causes transfer of transverse energy of the protons to that of the electrons. Neither of these methods is fast enough to allow acceleration of a sufficient number of muons up to maximum energy before they decay. A new method known as ionization cooling has been proposed.[1] The muons are cooled by passing them through a container of liquid hydrogen. The energy loss reduces both transverse and longitudinal momentum. The longitudinal momentum is restored with RF cavities. The net result is to maintain the longitudinal momentum while cooling the transverse momentum. To minimize the total travel distance of the muons the liquid hydrogen is placed inside the focusing solenoids. The question arises as to whether the presence of the solenoids influences the phase space occupied by the muons. After the muon scatters it has transverse momentum. In a constant longitudinal magnetic field the trajectory wraps around the field lines and coincides in momentum and position ...
Date: August 19, 2002
Creator: Carey, David C.
Partner: UNT Libraries Government Documents Department

Emittance measurements for the Illinois/CEBAF polarized electron source

Description: The transverse thermal properties of the electrons photoemitted from GaAs determine the intrinsic beam emittance, an important quantity in applications such as polarized electron sources and high-brightness sources. In this paper, emittance measurements using the Illinois/CEBAF polarized electron source are described. The emittance was measured as a function of both the laser beam spot size and laser wavelength at low currents. The data was used to infer the transverse thermal energy of the electrons photoemitted from GaAs for wavelengths between 514 and 840 nm. Near the bandgap the transverse energy is {approximately}34 meV, a factor of 3 lower than that of the beam from a typical thermionic electron gun. 8 refs., 2 figs.
Date: January 1, 1995
Creator: Dunham, B.M.; Cardman, L.S. & Sinclair, C.K.
Partner: UNT Libraries Government Documents Department

Energy flow and particle spectra with respect to the reaction plane for Au+Au collisions at AGS energies

Description: Transverse energy flow is studied by exploiting the near 4{pi} calorimetric coverage of experiment E877. A Fourier decomposition of the azimuthal transverse energy distributions in different regions of pseudorapidity is performed as a function of the centrality in order to describe the event shape. The extracted coefficients are compared to model predictions. Using the E877 forward spectrometer, triple differential cross section for protons and {pi}{sup +} are measured with respect to the reaction plane determined by calorimeters. The variation of slope parameters at different orientations to the reaction plane is obtained by fitting to thermal Boltzmann distributions.
Date: December 31, 1995
Creator: Zhang, Yingchao; Wessels, J.P. & Collaboration, The E877
Partner: UNT Libraries Government Documents Department

Prospects for observing Higgs in ZH (r-arrow) (nu nubar, l(superscript +)l(superscript -)) b bbar channel at TeV33

Description: We report the feasibility study of observing associated production of Higgs and {ital Z{sup 0}} bosons with {ital H} {r_arrow} {ital b{anti b}} and {ital Z{sup 0}} {r_arrow} {ital {nu}{anti {nu}}, l{sup +}l{sup -}} at {radical}{ital s} = 2 TeV high luminosity Tevatron (TeV33). The signature of such decay is a resonance of two {ital b} tagged jets, plus wither large missing {ital E{sub T}} (E{sub T} > 35 GeV) or dilepton pair mass near the {ital Z{sup 0}} mass. The signal and backgrounds are estimated using the CDF II detector configuration and the numbers are cross checked against the existing CDF Run I E{sub T} data. It may be possible to detect a Standard Model Higgs boson mass up to 120 GeV with 30 {ital fb{sup -1}} of integrated luminosity by combining a result with {ital W{sup {+-}}H} {r_arrow} {ital l{sup {+-}} {nu}b{anti b}} channel.
Date: October 1, 1996
Creator: Yao, W.-M.
Partner: UNT Libraries Government Documents Department

Charmonium suppression in nuclear collisions

Description: Measurements of {psi} and {psi}{prime} production from experiment NA50 at the CERN SPS are compared to calculations based on a hadronic model of charmonium suppression developed previously. Data on centrality dependence and total cross sections are in good accord with these predictions. Uncertainties in theoretical quantities such as NA50`s L parameter are discussed.
Date: November 1996
Creator: Gavin, S.
Partner: UNT Libraries Government Documents Department

High E{sub {Tau}} jets at CDF

Description: Results of QCD tests using hadronic jets from hard parton-parton collisions at the Fermilab Tevatron are presented. CDF has measured the inclusive jet cross-section as a function of jet transverse energy and collision center of mass energy. The angular distribution of dijet production has also been measured.
Date: October 1, 1996
Creator: Plunkett, R.
Partner: UNT Libraries Government Documents Department

Overview of kinematic variables in top production

Description: A selection of simple kinematic variables chosen to be sensitive to different aspects of {ital t{anti t}} production in W + {>=} 3 jets events are studied. Monte Carlo comparisons are made between different top generators (Herwig, Pythia, and Isajet) and a QCD background generator (VECBOS). Finally, Monte Carlo predictions with the {ital t{anti t}} fraction constrained by the SVX {ital b}-tagging rate and measured top mass are compared with 110 pb{sup -1} of CDF data. We conclude that the CDF data is consistent with standard predictions using the studied generators.
Date: September 1, 1996
Creator: Binkley, M. & Beretvas, A.
Partner: UNT Libraries Government Documents Department

QCD physics at CDF

Description: The CDF collaboration is engaged in a broad program of QCD measurements at the Fermilab Tevatron Collider. I will discuss inclusive jet production at center-of-mass energies of 1800 GeV and 630 GeV, properties of events with very high total transverse energy and dijet angular distributions.
Date: October 1, 1996
Creator: Devlin, T.
Partner: UNT Libraries Government Documents Department

Search for squarks and gluinos in p{bar p} collisions at the D0 detector with the jets and missing energy signature

Description: A search for squarks and gluinos has been performed using the D{null} detector at {radical}s = 1.8 TeV Tevatron {ital p{anti p}} collider. Data from the 1992-1993 collider run corresponding to an integrated luminosity of 13.5 pb{sup -1} were examined via the missing {ital E{sub T}} plus jets signature with two separate analyses. No events above the Standard Model backgrounds were observed.
Date: September 1, 1996
Creator: The DO Collaboration
Partner: UNT Libraries Government Documents Department

`Pipetron` beam dynamics with noise

Description: Extra-large hadron collider, ``Pipetron``, at 100 TeV energy is currently under consideration. In this article we study the Pipetron transverse and longitudinal beam dynamics under influence of external noises. The major effects are growths of transverse and longitudinal emittances of the beam caused by noisy forces which vary over the revolution period or synchrotron oscillation period, respectively; and closed orbit distortions induced by slow drift of magnet positions. Based on analytical consideration of these phenomena, we estimate tolerable levels of these noises and compare them with available experimental data. Although it is concluded that transverse and, probably, longitudinal feedback systems are necessary for the emittance`s preservation, and sophisticated beam-based orbit correction methods should be used at the Pipetron, we observe no unreasonable requirements which present and impenetrable barrier to the project.
Date: October 1, 1996
Creator: Shiltsev, V.D.
Partner: UNT Libraries Government Documents Department

CDF searches for new phenomena

Description: We present results of recent searches for new physics using the CDF detector at the Fermilab Tevatron. Presented are searches for Higgs {yields} {gamma}{gamma}, as well as more general searches in {gamma}{gamma} + X where X is /E{sub T}, jets, charged leptons, b-quarks or extra photons. The CDF ee{gamma}{gamma}/E{sub T} candidate event is discussed along with estimates of the expected rates in the Standard Model. Other searches for SUSY, Higgs and Technicolor look for particles which decay to vector bosons and b-quarks.
Date: June 1, 1998
Creator: Toback, D.
Partner: UNT Libraries Government Documents Department

Calculation of Fragmentation Functions in Two-Hadron Semi-Inclusive Processes.

Description: We investigate the properties of interference fragmentation functions arising from the emission of two leading hadrons inside the same jet for inclusive lepton-nucleon deep inelastic scattering. Using an extended spectator model for the mechanism of the hadronization, we give a complete calculation and numerical estimates for the examples of a proton-pion pair produced with invariant mass on the Roper resonance, and of two pions produced with invariant mass close to the {rho} mass. We discuss azimuthal angular dependence of the leading order cross section to point up favourable conditions for extracting transversity from experimental data.
Date: April 24, 2001
Creator: Bianconi, A.; Boffi, S.; Boer, D.; Jakob, R. & Radici, M.
Partner: UNT Libraries Government Documents Department

Is there elliptic flow without transverse flow?

Description: Azimuthal anisotropy of final particle distributions was originally introduced as a signature of transverse collective flow. We show that finite anisotropy in momentum space can result solely from the shape of the particle emitting source. However, by comparing the differential anisotropy to recent data from STAR collaboration we can exclude such a scenario, but instead show that the data favour strong flow as resulting from a hydrodynamical evolution.
Date: April 3, 2001
Creator: Huovinen, Pasi; Kolb, Peter F. & Heinz, Ulrich
Partner: UNT Libraries Government Documents Department

A Search for new physics in photon-lepton events in proton-antiproton collisions at {radical} s = 1.8 TeV

Description: We present the results of a search in p{bar p} collisions at {radical}s = 1.8 TeV for anomalous production of events containing a photon with large transverse energy and a lepton (e or {mu}) with large transverse energy, using 86 pb{sup -1} of data collected at the Collider Detector at Fermilab during the 1994-95 collider run at the Fermilab Tevatron. The presence of large missing transverse energy (E{sub T}), additional photons, or additional leptons in these events is also analyzed. The results are consistent with standard model expectations, with the possible exception of photon-lepton events with large E{sub T}, for which the probability of a statistical fluctuation of the standard model expectation up to and above the observed level is 0.7%.
Date: April 30, 2001
Creator: Berryhill, J. W.
Partner: UNT Libraries Government Documents Department

Implications of the Tevatron jet results on PDF

Description: We report a new measurement of the pseudorapidity ({eta}) and transverse-energy (E{sub T}) dependence of the inclusive jet production cross section in p{bar p} collisions at {radical}s = 1:8 TeV using 95 pb{sup {minus}1} of data collected with the D0 detector at the Fermilab Tevatron. The differential cross section d{sup 2}{sigma}/(dE{sub T}d{eta}) is presented up to {vert_bar}{eta}{vert_bar} = 3, significantly extending previous measurements. The results are in good overall agreement with next-to-leading order predictions from QCD, indicate a preference for certain parton distribution functions, and provide the world's best constraint on the gluon distribution at high parton momentum fraction x.
Date: July 3, 2001
Creator: Babukhadia, Levan
Partner: UNT Libraries Government Documents Department

Jet Production at D-Zero

Description: The authors report on a new measurement of the rapidity dependence of the inclusive jet production cross section in p{bar p} collisions at {radical}s = 1:8 TeV using 92 pb{sup {minus}1} of data collected by the DO detector at the Tevatron collider. The differential cross sections, <d{sup 2}{sigma}/dE{sub T}d{eta}>, are presented as a function of jet transverse energy (E{sub T}) in five pseudorapidity ({eta}) intervals, up to {vert_bar}{eta}{vert_bar} = 3, significantly extending previous measurements beyond {vert_bar}{eta}{vert_bar} = 0.7. They also present recent results on the ratio of central ({vert_bar}{eta}{vert_bar} < 0.5) inclusive cross sections from two center-of-mass energies, 0.63 TeV and 1.8 TeV, as a function of jet x{sub T}. Experimental results are compared to next-to-leading order QCD predictions.
Date: October 17, 2000
Creator: Varelas, Nikos
Partner: UNT Libraries Government Documents Department