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On constraints for heavy-meson form factors

Description: We examine the recent work of de Rafael and Taron where model-independent bounds on the Isgur-Wise function are presented. We first argue that the bounds cannot hold in as much generality as implied. We show that the effects of resonances omitted in their discussion (such as heavy-heavy ``onium`` states below threshold) modify the bound. The resulting bound is much weaker but may be useful where the size of the additional contribution may be computed or estimated.
Date: November 1, 1992
Creator: Grinstein, B. & Mende, P.F.
Partner: UNT Libraries Government Documents Department

Prospects for the Precision Measurement of {alpha}{sub s}

Description: The prospects for the measurement of the strong coupling constant {alpha}{sub MS}(M{sub Z}) to a relative uncertainty of 1 % are discussed. Particular emphasis is placed on the implications relating to future High Energy Physics facilities.
Date: December 1996
Creator: Burrows, P. N.; Dixon, L. & El-Khadra, A. X.
Partner: UNT Libraries Government Documents Department

Light Threshold Effects in Supersymmetric Grand Unified Theories

Description: Supersymmetric Grand Unified Theories have a rich spectrum of particles barely heavier than the intermediate vector bosons. As their non-supersymmetric counterparts, they lead to many relations among low energy observables. But the precise form of the predictions is modified by the extended spectrum. If the masses of these new particles are comparable to M{sub Z}, the standard computation of their effect becomes inaccurate. The authors, present a detailed discussion of the correct procedure, and carry out the relevant computations to one loop order. Attention is paid to the special treatment that the top and Higgs particles must receive. The size of the effect is explored for a range of parameters in the minimal supersymmetric SU(5) grand-unified theory with radiative breaking. It is found that the naive (leading-log) computation can be fairly inaccurate.
Date: August 1, 1993
Creator: Faraggi, A. E. & Grinstein, B.
Partner: UNT Libraries Government Documents Department

Axionic hot dark matter in the hadronic axion window

Description: Mixed dark matter scenario can reconcile the COBE data and the observed large scale structure. So far the massive neutrino with a mass of a few eV has been the only discussed candidate for the hot dark matter component. We point out that the hadronic axion in the so-called hadronic axion window, f{sub a} {approx} 10{sup 6} GeV, is a perfect candidate as hot dark matter within the mixed dark matter scenario. The current limits on the hadronic axion are summarized. The most promising methods to verify the hadronic axion in this window are the resonant absorption of almost-monochromatic solar axions from M1 transition of the thermally excited {sup 57}Fe in the Sun, and the observation of the ''axion burst'' in water Cerenkov detectors from another supernova.
Date: May 23, 1998
Creator: Moroi, Takeo & Murayama, Hitoshi
Partner: UNT Libraries Government Documents Department

The role of supersymmetry phenomenology in particle physics

Description: Supersymmetry phenomenology is an important component of particle physics today. I provide a definition of supersymmetry phenomenology, outline the scope of its activity, and argue its legitimacy. This essay derives from a presentation given at the 2000 SLAC Summer Institute.
Date: December 14, 2000
Creator: Wells, James D.
Partner: UNT Libraries Government Documents Department

Tau appearance in atmospheric neutrino interactions

Description: If the correct interpretation of the Super-Kamiokande atmospheric neutrino data is {nu}{sub {mu}} {yields} {nu}{sub {tau}} oscillation, the contained data sample should already have more than 10 {tau} appearance events. We study the challenging task of detecting the {tau}, focusing on the decay chain {tau}{sup {+-}} {yields} {rho}{sup {+-}} {yields} {pi}{sup {+-}}{pi}{sup 0} in events with quasi-elastic {tau} production. The background level, which is currently quite uncertain because of a lack of relevant neutral current data, can be measured by the near detector in the K2K experiment. Our estimates of the background suggest that it may be possible to detect {tau} appearance in Super-Kamiokande with 5-10 years of running.
Date: October 24, 1998
Creator: Hall, Lawrence J. & Murayama, Hitoshi
Partner: UNT Libraries Government Documents Department

Femtosecond Time-Resolved Reflectivity of Ge

Description: We have measured the transient reflectivity changes of bulk Ge after excitation with 140 fs laser pulses at 1.5 eV. The electron and hole carrier dynamics arc calculated using an ensemble Monte Carlo method. The observed reflectivity changes are due to three mechanisms: Diffusion, band gap renormalization, and carrier dynamics, particularly scattering of light holes to the heavy hole band via optical phonons.
Date: October 1, 1996
Creator: Myers, K. D.; Zollner, S.; Lange, R.; Jensen, K. G. & Dolan, J. M.
Partner: UNT Libraries Government Documents Department

Unitarity-based techniques for one-loop calculations in QCD

Description: Perturbative QCD, and jet physics in particular, have matured sufficiently that rather than being merely subjects of experimental studies, they are now tools in the search for new physics. This role can be seen in the search for the top quark, as well as in recent speculations about the implications of supposed high-E{sub T} deviations of the inclusive-jet differential cross section at the Tevatron. One of the important challenges to both theorists and experimenters in coming years will be to hone jet physics as a tool in the quest for physics underlying the standard model. As such, it will be important to measurements of parameters of the theory or of non-perturbative quantities such as the parton distribution functions, as well as to searches for new physics at the LHC. Jet production, or jet production in association with identified photons or electroweak vector bosons, appears likely to provide the best information on the gluon distribution in the proton, and may also provide useful information on the strong coupling {alpha}{sub s}. In order to make use of these final states, the authors need a wider variety of higher-order calculations of matrix elements. Indeed, as the authors shall review, next-to-leading order calculations are in a certain sense the minimal useful ones. On the other hand, these calculations are quite difficult with conventional Feynman rules. In the following sections, the authors will discuss some of the techniques developed in recent years to simplify such calculations.
Date: June 1, 1996
Creator: Bern, Z.; Dixon, L. & Kosower, D.A.
Partner: UNT Libraries Government Documents Department

Cosmology of one extra dimension with localized gravity

Description: The authors examine the cosmology of the two recently proposed scenarios for a five dimensional universe with localized gravity. They find that the scenario with a non-compact fifth dimension is potentially viable, while the scenario which might solve the hierarchy problem predicts a contracting universe, leading to a variety of cosmological problems.
Date: June 1999
Creator: Csaki, Csaba; Graesser, Michael; Kolda, Christopher & Terning, John
Partner: UNT Libraries Government Documents Department

Software engineering methods and standards used int he sloan digital sky survey

Description: We present an integrated science software development environment, code maintenance and support system for the Sloan Digital Sky Survey (SDSS) now being actively used throughout the collaboration. The SDSS is a collaboration between the Fermi National Accelerator Laboratory, the Institute for Advanced Study, The Japan Promotion Group, Johns Hopkins University, Princeton University, The United States Naval Observatory, the University of Chicago, and the University of Washington. The SDSS will produce a five-color imaging survey of 1/4 of the sky about the north galactic cap and image 10{sup 8} Stars, 10{sup 8} galaxies, and 10{sup 5} Quasars. Spectra will be obtained for 10{sup 6} galaxies and 10{sup 5} Quasars as well. The survey will utilize a dedicated 2.5 meter telescope at the Apache Point Observatory in New Mexico. Its imaging camera will hold 54 Charge-Coupled Devices (CADS). The SDSS will take five years to complete, acquiring well over 12 TB of data.
Date: April 1, 1995
Creator: Petravick, D.; Berman, E.; Gurbani, V.; Nicinski, T.; Pordes, R.; Rechenmacher, R. et al.
Partner: UNT Libraries Government Documents Department

Deuterons and flow: At intermediate AGS energies

Description: A quantitative model, based on hadronic physics and Monte Carlo cascading is applied to heavy ion collisions at BNL-AGS and BEVALAC energies. The model was found to be in excellent agreement with particle spectra where data previously existed, for Si beams, and was able to successfully predict the spectra where data was initially absent, for Au beams. For Si + Au collisions baryon densities of three or four times the normal nuclear matter density ({rho}{sub 0}) are seen in the theory, while for Au + Au collisions, matter at densities up to 10 {rho}{sub 0} is anticipated. The possibility that unusual states of matter may be created in the Au beams and potential signatures for its observation, in particular deuterons and collective flow, are considered.
Date: June 1996
Creator: Kahana, D. E.; Pang, Y. & Kahana, S. H.
Partner: UNT Libraries Government Documents Department

Seiberg duality and e+e- experiments

Description: Seiberg duality in supersymmetric gauge theories is the claim that two different theories describe the same physics in the infrared limit. However, one cannot easily work out physical quantities in strongly coupled theories and hence it has been difficult to compare the physics of the electric and magnetic theories. In order to gain more insight into the equivalence of two theories, we study the ''e{sup +}e{sup -}'' cross sections into ''hadrons'' for both theories in the superconformal window. We describe a technique which allows us to compute the cross sections exactly in the infrared limit. They are indeed equal in the low-energy limit and the equality is guaranteed because of the anomaly matching condition. The ultraviolet behavior of the total ''e{sup +}e{sup -}'' cross section is different for the two theories. We comment on proposed nonsupersymmetric dualities. We also analyze the agreement of the ''{gamma}{gamma}'' and ''WW'' scattering amplitudes in both theories, and in particular try to understand if their equivalence can be explained by the anomaly matching condition.
Date: October 2, 1998
Creator: De Gouvea, Andre; Friedland, Alexander & Murayama, Hitoshi
Partner: UNT Libraries Government Documents Department

Gaugino mass without singlets

Description: In models with dynamical supersymmetry breaking in the hidden sector, the gaugino masses in the observable sector have been believed to be extremely suppressed (below 1 keV), unless there is a gauge singlet in the hidden sector with specific couplings to the observable sector gauge multiplets. We point out that there is a pure supergravity contribution to gaugino masses at the quantum level arising from the superconformal anomaly. Our results are valid to all orders in perturbation theory and are related to the ''exact'' beta functions for soft terms. There is also an anomaly contribution to the A terms proportional to the beta function of the corresponding Yukawa coupling. The gaugino masses are proportional to the corresponding gauge beta functions, and so do not satisfy the usual GUT relations.
Date: December 21, 1998
Creator: Giudice, Gian F.; Luty, Markus A.; Murayama, Hitoshi & Rattazzi, Riccardo
Partner: UNT Libraries Government Documents Department

Magnetization reversal of uncompensated Fe moments in exchangebiased Ni/FeF2 bilayers

Description: The magnetization reversal of uncompensated Fe moments in exchange biased Ni/FeF{sub 2} bilayers was determined using soft x-ray magnetic circular and linear dichroism. The hysteresis loops resulting from the Fe moments are almost identical to those of the ferromagnetic Ni layer. However, a vertical loop shift indicates that some Fe moments are pinned in the antiferromagnetically ordered FeF{sub 2}. The pinned moments are oriented antiparallel to small cooling fields leading to negative exchange bias, but parallel to large cooling fields resulting in positive exchange bias. No indication for the formation of a parallel antiferromagnetic domain wall in the FeF{sub 2} layer upon magnetization reversal in the Ni layer was found.
Date: January 1, 2006
Creator: Arenholz, Elke; Liu, Kai; Li, Zhipan & Schuller, Ivan K.
Partner: UNT Libraries Government Documents Department

J/{psi} and {psi}{prime} production at CDF

Description: This paper presents measurements of the J/{psi} and {psi}{prime} production cross sections in p{ovr p} collisions at {radical}s = 1.8 TeV. The cross sections are measured in the kinematic region P{sub T} {gt} 5 GeV/c, {vert_bar}{eta}{vert_bar} {lt} 0.6 using the dimuon decay channel. The fraction of events from B decays is measured and used to calculate the J/{psi} and {psi}{prime} cross sections from B decay. The fraction of J/{psi} events from {chi}{sub c} decays is also measured and used to calculate the J/{psi} cross section from direct production. 11 refs., 5 figs., 1 tab.
Date: July 1, 1996
Creator: Abe, F.
Partner: UNT Libraries Government Documents Department

Recent results in p{anti p} collisions at {radical}s = 1.8 TeV from the CDF Collaboration at the Fermilab Tevatron collider

Description: During the 1992--95 Tevatron collider Run 1, the Collider Detector at Fermilab (CDF) collected a data sample of {anti p}p collisions at a center of mass energy of 1.8 TeV with an integrated luminosity of > 100 pb{sup {minus}1}. This was split into two separate data-taking runs: Run 1A ({approximately} 20 pb{sup {minus}1}) and the present Run 1B (> 80 pb{sup {minus}1}). Data-taking is planned to continue into 1996 and a total sample of about 120 pb{sup {minus}1} is expected. This data sample, in combination with improvements to the data acquisition system, the muon coverage, and the installation of the CDF SVX silicon vertex detector, has allowed many new effects to be studied. This paper reports results on heavy quark (charm, bottom and top) physics, electroweak phenomena, quantum chromodynamics, and searches for new particles beyond the Standard Model.
Date: February 1, 1996
Creator: Barnett, B. A.
Partner: UNT Libraries Government Documents Department

Efficient analytic computation of higher-order QCD amplitudes

Description: The authors review techniques simplifying the analytic calculation of one-loop QCD amplitudes with many external legs, for use in next-to-leading-order corrections to multi-jet processes. Particularly useful are the constraints imposed by perturbative unitarity, collinear singularities and a supersymmetry-inspired organization of helicity amplitudes. Certain sequences of one-loop helicity amplitudes with an arbitrary number of external gluons have been obtained using these constraints.
Date: March 1, 1995
Creator: Bern, Z.; Chalmers, G.; Dixon, L.; Dunbar, D.C. & Kosower, D.A.
Partner: UNT Libraries Government Documents Department

Logarithmic unification from symmetries enhanced in the sub-millimeter infrared

Description: In theories with TeV string scale and sub-millimeter extra dimensions the attractive picture of logarithmic gauge coupling unification at 10{sup 16} GeV is seemingly destroyed. In this paper we argue to the contrary that logarithmic unification can occur in such theories. The rationale for unification is no longer that a gauge symmetry is restored at short distances, but rather that a geometric symmetry is restored at large distances in the bulk away from our 3-brane. The apparent ''running'' of the gauge couplings to energies far above the string scale actually arises from the logarithmic variation of classical fields in (sets of) two large transverse dimensions. We present a number of N = 2 and N = 1 supersymmetric D-brane constructions illustrating this picture for unification.
Date: August 21, 1999
Creator: Arkani-Hamed, Nima; Dimopoulos, Savas & March-Russell, John
Partner: UNT Libraries Government Documents Department

Less minimal supersymmetric standard model

Description: Most of the phenomenological studies of supersymmetry have been carried out using the so-called minimal supergravity scenario, where one assumes a universal scalar mass, gaugino mass, and trilinear coupling at M{sub GUT}. Even though this is a useful simplifying assumption for phenomenological analyses, it is rather too restrictive to accommodate a large variety of phenomenological possibilities. It predicts, among other things, that the lightest supersymmetric particle (LSP) is an almost pure B-ino, and that the {mu}-parameter is larger than the masses of the SU(2){sub L} and U(1){sub Y} gauginos. We extend the minimal supergravity framework by introducing one extra parameter: the Fayet'Iliopoulos D-term for the hypercharge U(1), D{sub Y}. Allowing for this extra parameter, we find a much more diverse phenomenology, where the LSP is {tilde {nu}}{sub {tau}}, {tilde {tau}} or a neutralino with a large higgsino content. We discuss the relevance of the different possibilities to collider signatures. The same type of extension can be done to models with the gauge mediation of supersymmetry breaking. We argue that it is not wise to impose cosmological constraints on the parameter space.
Date: March 28, 1998
Creator: de Gouvea, Andre; Friedland, Alexander & Murayama, Hitoshi
Partner: UNT Libraries Government Documents Department

On certificates and lookahead in dynamic graph problems

Description: Recent work in dynamic graph algorithms has led to efficient algorithms for dynamic undirected graph problems such as connectivity. However, no efficient algorithms are known for the dynamic versions of fundamental directed graph problems like strong connectivity and transitive closure, as well as some undirected graph problems such as maximum matchings and cuts. We provide some explanation for this lack of success by presenting quadratic lower bounds on the certificate complexity of the seemingly difficult problems, in contrast to the known linear certificate complexity for the problems which have efficient dynamic algorithms. A direct outcome of our lower bounds is the demonstration that a generic technique for designing efficient dynamic graph algorithms, viz., sparsification, will not apply to the difficult problems. More generally, it is our belief that the boundary between tractable and intractable dynamic graph problems can be demarcated in terms of certificate complexity. In many applications of dynamic (di)graph problems, a certain form of lookahead is available. Specifically, we consider the problems of assembly planning in robotics and the maintenance of relations in databases. These give rise to dynamic strong connectivity and dynamic transitive closure problems, respectively. We explain why it is reasonable, and indeed natural and desirable, to assume that lookahead is available in these two applications. Exploiting lookahead to circumvent their inherent complexity, we obtain efficient fully-dynamic algorithms for strong connectivity and transitive closure.
Date: May 5, 1995
Creator: Khanna, S.; Motwani, R. & Wilson, R.H.
Partner: UNT Libraries Government Documents Department

Highlights of B physics at CDF

Description: The CDF experiment at the Fermilab Tevatron collider has produced many B physics results. Recent measurements on B meson masses, B lifetimes, B branching ratios, limits on rare B decays, and B flavour tagging studies are reviewed.
Date: August 1, 1995
Creator: Paulini, M.
Partner: UNT Libraries Government Documents Department

Observation of {pi} - B meson charge-flavor correlations and measurement of time dependent B{sup 0} Bbar{sup 0} mixing in p{bar p} collisions

Description: We present evidence for charge correlations of {ital B} mesons with charged particles produced in {ital p{anti p}} Collisions at 1.8 TeV. Such correlations are expected to arise from pious produced in the fragmentation chain and from {ital B}{sup **} decays. We measure the efficiency and purity of this flavor tagging method for both charged and neutral {ital B} mesons. We apply these correlations to {ital B} mesons reconstructed in 110 pb{sup -1} of data collected with the CDF detector at the Fermilab Tevatron Collider. {ital B} mesons are either partially reconstructed, using the semileptonic decays {ital B}{sup 0} {yields} {ital l}{sup +}{ital D}{sup (*)-}{ital X} and {ital B}{sup +} {yields} {ital l}{sup +}{ital {anti D}X}, or fully reconstructed, using the decay modes {ital B}{sup 0} {yields} {ital J/{Psi}K{sup *0}} and {ital B}{sup +} {yields} {ital J/{Psi}K{sup +}}. Application of this new flavor tagging method to neutral {ital B} mesons yields a measurement of the frequency of the oscillation {ital B}{sup 0} {yields} {ital {anti B}}{sup 0}. We obtain {Delta}{ital m{sub d}} = 0.446 {+-} 0.057{sup +0.034}{sub -0.031}.
Date: September 1, 1996
Creator: CDF Collaboration
Partner: UNT Libraries Government Documents Department

Search for new exotic particles at CDF

Description: We present recent results of searches for new particles beyond the Standard Model at the Collider Detector at Fermilab (CDF). These include searches for heavy gauge bosons (Z{prime}, W{prime}), leptoquarks and stable massive charged particles. For most of these particles we set the currently most stringent limits. 15 refs., 7 figs.
Date: July 1, 1996
Creator: Wensel, H.
Partner: UNT Libraries Government Documents Department