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Top Jets at the LHC

Description: We investigatethe reconstruction of high pT hadronically-decaying top quarksat the Large Hadron Collider. One of the main challenges in identifying energetictop quarks is that the decay products become increasingly collimated. This reducesthe efficacy of conventional reconstruction methods that exploit the topology of thetop quark decay chain. We focus on the cases where the decay products of the topquark are reconstructed as a single jet, a"top-jet." The most basic"top-tag"… more
Date: October 6, 2008
Creator: Almeida, L.G.; Lee, S.J.; Perez, G.; Sung, I. & Virzi, J.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Resonance--Continuum Interference in Light Higgs Boson Production at a Photon Collider

Description: We study the effect of interference between the Standard Model Higgs boson resonance and the continuum background in the process {gamma}{gamma} {yields} H {yields} b{bar b} at a photon collider. Taking into account virtual gluon exchange between the final-state quarks, we calculate the leading corrections to the height of the resonance for the case of a light (m{sub H} < 160 GeV) Higgs boson. We find that the interference is destructive and around 0.1-0.2% of the peak height, depending on th… more
Date: January 6, 2009
Creator: Dixon, Lance J.; Sofianatos, Yorgos & /SLAC /Stanford U., Phys. Dept.
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Partner: UNT Libraries Government Documents Department
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Task J: Outstanding Junior Investigator (OJI). Technical progress report, [November 1, 1993--October 31, 1993]

Description: We report on an existing program of research on the production and decay of particles containing the charm and beauty quarks. Charm is studied in Fermilab fixed target experiments E769 and E691. Design and development for a hadron collider beauty experiment is studied in CERN test experiment P238 and in simulation studies for the SSC.
Date: July 6, 1993
Creator: Karchin, P. E.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Anti-B-B Mixing Constrains Topcolor-Assisted Technicolor

Description: We argue that extended technicolor augmented with topcolor requires that all mixing between the third and the first two quark generations resides in the mixing matrix of left-handed down quarks. Then, the anti-B_d--B_d mixing that occurs in topcolor models constrains the coloron and Z' boson masses to be greater than about 5 TeV. This implies fine tuning of the topcolor couplings to better than 1percent.
Date: December 6, 2000
Creator: Burdman, Gustavo; Lane, Kenneth & Rador, Tonguc
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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A Little Solution to the Little Hierarchy Problem: A Vector-like Generation

Description: We present a simple solution to the little hierarchy problem in the minimal supersymmetric standard model: a vectorlike fourth generation. With O(1) Yukawa couplings for the new quarks, the Higgs mass can naturally be above 114 GeV. Unlike a chiral fourth generation, a vectorlike generation can solve the little hierarchy problem while remaining consistent with precision electroweak and direct production constraints, and maintaining the success of the grand unified framework. The new quarks are … more
Date: April 6, 2012
Creator: Graham, Peter W.; Ismail, Ahmed; /Stanford U., Phys. Dept.; Rajendran, Surjeet; /MIT, LNS /SLAC /Stanford U., Phys. Dept.; Saraswat, Prashant et al.
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Partner: UNT Libraries Government Documents Department
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The Conformal Template and New Perspectives for Quantum Chromodynamics

Description: Conformal symmetry provides a systematic approximation to QCD in both its perturbative and nonperturbative domains. One can use the AdS/CFT correspondence between Anti-de Sitter space and conformal gauge theories to obtain an analytically tractable approximation to QCD in the regime where the QCD coupling is large and constant. For example, there is an exact correspondence between the fifth-dimensional coordinate of AdS space and a specific impact variable which measures the separation of the q… more
Date: March 6, 2007
Creator: Brodsky, Stanley J.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Novel QCD Phenomena

Description: I discuss a number of novel topics in QCD, including the use of the AdS/CFT correspondence between Anti-de Sitter space and conformal gauge theories to obtain an analytically tractable approximation to QCD in the regime where the QCD coupling is large and constant. In particular, there is an exact correspondence between the fifth-dimension coordinate z of AdS space and a specific impact variable {zeta} which measures the separation of the quark constituents within the hadron in ordinary space-t… more
Date: July 6, 2007
Creator: Brodsky, Stanley J.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Determination of the CKM Element V(Ub)

Description: The precise determination of the CKM matrix element |V{sub ub}| is crucial in testing the Standard Model mechanism for CP violation. From a sample of 88 million B{bar B} pairs collected with the BABAR detector, charmless semileptonic B decays are selected using simultaneous requirements on the electron energy, E{sub e}, and the invariant mass squared of the electron-neutrino pair, q{sup 2}. The partial branching fraction, unfolded for detector effects, is determined in a region of the q{sup 2}-… more
Date: April 6, 2007
Creator: Fortin, Dominique
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Charmless B Decays

Description: Rare charmless hadronic B decays are a good testing ground for the standard model. The dominant amplitudes contributing to this class of B decays are CKM suppressed tree diagrams and b {yields} s or b {yields} d loop diagrams (''penguins''). These decays can be used to study interfering standard model (SM) amplitudes and CP violation. They are sensitive to the presence of new particles in the loops, and they provide valuable information to constrain theoretical models of B decays. The B factori… more
Date: March 6, 2007
Creator: Gradl, Wolfgang & U., /Edinburgh
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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LHC Signals from Warped Extra Dimensions

Description: We study production of Kaluza-Klein gluons (KKG) at the Large Hadron Collider (LHC) in the framework of a warped extra dimension with the Standard Model (SM) fields propagating in the bulk. We show that the detection of KK gluon is challenging since its production is suppressed by small couplings to the proton's constituents. Moreover, the KK gluon decaysmostly to top pairs due to an enhanced coupling and hence is broad. Nevertheless, we demonstrate that for MKKG<~;; 4 TeV, 100 fb-1 of data … more
Date: December 6, 2006
Creator: Agashe, K.; Belyaev, A.; Krupovnickas, T.; Perez, G. & Virzi, J.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Electroproduction of Photons and of Pawns on the Proton in Quadrimoment of Transfer Q2=1.0GeV2. Measure Cross Sections and Extraction of Polarizabilities Generalities; Electroproduction de Photons et de Pions sur le Proton au Quadrimoment de Transfert Q2=1.0GeV2. Mesure des Sections Efficaces et Extraction des Polarisabilites Generalisees

Description: In hadronic physics, the nucleon structure and the quarks confinement are still topical issues. The neutral pion electroproduction and virtual Compton scattering (VCS) reactions allow us to access new observables that describe this structure. This work is focused on the VCS experiment performed at Jefferson Lab in 1998.
Date: November 6, 2001
Creator: Laveissiere, Geraud
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries Government Documents Department
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Static hybrid quarkonium potential with improved staggered quarks

Description: The authors are studying the effects of light dynamical quarks on the excitation energies of a flux tube between a static quark and antiquark. They report preliminary results of an analysis of the ground state potential and the {Sigma}{prime}{sub g}{sup +} and II{sub u} potentials. They have measured these potentials on closely matched ensembles of gauge configurations, generated in the quenched approximation and with 2+1 flavors of Asqtad improved staggered quarks.
Date: January 6, 2004
Creator: Bernard, C.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Recent results using all point quark propagators

Description: Pseudofermion methods for extracting all-point quark propagators are reviewed, with special emphasis on techniques for reducing or eliminating autocorrelations induced by low eigenmodes of the quark Dirac operator. Recent applications, including high statistics evaluations of hadronic current correlators and the pion form factor, are also described.
Date: January 6, 2004
Creator: Duncan, A. & Yoo, E. Eichten and J.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Polarized parton distributions and the polarized gluon asymmetry.

Description: The flavor-dependent valence, sea quark and antiquark spin distributions can be determined separately from theoretical assumptions and experimental data. The authors have determined the valence distributions using the Bjorken sum rule and have extracted polarized sea distributions, assuming that the quarks and anti-quarks for each flavor are symmetric. Other experiments have been proposed which will allow them to completely break the SU(3) symmetry of the sea flavors. To create a physical model… more
Date: February 6, 2002
Creator: Ramsey, G. P.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Topological susceptibility with the improved Asqtad action

Description: As a test of the chiral properties of the improved Asqtad (staggered fermion) action, we have been measuring the topological susceptibility as a function of quark masses for 2 + 1 dynamical flavors. We report preliminary results, which show reasonable agreement with leading order chiral perturbation theory for lattice spacing less than 0.1 fm. The total topological charge, however, shows strong persistence over Monte Carlo time.
Date: January 6, 2004
Creator: Bernard, C.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Exploring heavy-quark energy loss via b-tagging in heavy ion collisions at the LHC

Description: A strategy to study flavor-dependent parton energy loss by tagging heavy quark jets in p+p, p+Pb and Pb+Pb collisions at the LHC is discussed. Estimates for production cross-sections and experimental techniques employed at collider detectors to search for Q{bar Q} jets are presented and a brief evaluation of the capabilities of CMS, ALICE and ATLAS detectors are given.
Date: January 6, 2005
Creator: Klay, J L
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Search for B- -> Ds+(*)- Phi

Description: We report on searches for B{sup -} {yields} D{sub S}{sup -}{phi} and B{sup -} {yields} D*{sub S}{sup -}{phi}. In the context of the Standard Model the branching fractions for these decays are expected to be highly suppressed, since they proceed through annihilation of the b and {bar u} quarks in the B{sup -} meson. Our results are based on 234 million {Upsilon}(42) {yields} B{bar B} decays collected with the BABAR detector at SLAC. We find no evidence for these decays, and we set 90% confidence… more
Date: July 6, 2005
Creator: Aubert, B.; Barate, R.; Boutigny, D.; Couderc, F.; Karyotakis, Y.; Lees, J. P. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Measurement of Inclusive Radiative B -Meson Decay B -> X_s gamma

Description: Radiative decays of the B meson, B {yields} X{sub s}{gamma}, proceed via virtual flavor changing neutral current processes that are sensitive to contributions from high mass scales, either within the Standard Model of electroweak interactions or beyond. In the Standard Model, these transitions are sensitive to the weak interactions of the top quark, and relatively robust predictions of the inclusive decay rate exist. Significant deviation from these predictions could be interpreted as indicatio… more
Date: January 6, 2006
Creator: Ozcan, V.E. & /SLAC /Stanford U., Appl. Phys. Dept.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Anti-Lambda Polarization in High Energy pp Collisions withPolarized Beams

Description: We study the polarization of the anti-Lambda particle in polarized high energy pp collisions at large transverse momenta. The anti-Lambda polarization is found to be sensitive to the polarization of the anti-strange sea of the nucleon. We make predictions using different parameterizations of the polarized quark distribution functions. The results show that the measurement of longitudinal anti-Lambda polarization can distinguish different parameterizations, and that similar measurements in the t… more
Date: November 6, 2005
Creator: Xu, Qing-hua; Liang, Zuo-tang & Sichtermann, Ernst
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Direct CP Violation in Charmless Hadronic B-Meson Decays at the PEP-II Asymmetric B-Meson Factory

Description: The study of the quark transition b {yields} s{bar s}s, which is a pure loop-level (''penguin'') process leading to several B-meson-decay final states, most notably {phi}K, is arguably the hottest topic in B-meson physics today. The reason is the sensitivity of the amplitudes and the CP-violating asymmetries in such processes to physics beyond the Standard Model. By performing these measurements, we improve our understanding of the phenomenon of combined-parity (CP) violation, which is believed… more
Date: May 6, 2005
Creator: Telnov, Alexandre Valerievich
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Probing the strange nature of the nucleon with phi photoproduction

Description: The presence inside the nucleon of a significant component of strange-antistrange quark pairs has been invoked to explain a number of current puzzles in the low energy realm of QCD. The {sigma} term in {pi}N scattering is a venerable conundrum which can be explained with a 10%--20% admixture. The spin crisis brought on by the EMC result and follow on experiments was first interpreted as requiring a large strange content of s quarks whose spin helped cancel the contribution of the u and d quarks… more
Date: March 6, 1997
Creator: Lowry, M.M.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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