Top Quark Physics at the Tevatron
We discuss physics of the top quark at the Fermilab Tevatron. By the year 2000, many properties of the top quark can be measured at the Tevatron.
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arXiv subjects
C. -P. Yuan
Publications and source records attributed to C. -P. Yuan.
Equivalence Theorem as a Criterion for Probing the Electroweak Symmetry Breaking Mechanism
Based upon our recent study on the Lorentz non-invariance ambiguity in the longitudinal weak-boson scatterings and the precise conditions for the validity of the Equivalence Theorem (ET), we further examine the intrinsic connection between the longitudinal weak-boson scatterings and probing the electroweak symmetry breaking (EWSB) mechanism. We reveal the profound physical content of the ET as being able to discriminate processes which are insensitive to probing the EWSB sector. With this physical content as a criterion, we analyze the sensitivities to various effective operators for probing the mechanism of the EWSB.
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Sensitivity of the LHC to Electroweak Symmetry Breaking: Equivalence Theorem as a Criterion
Based upon our recent study on the intrinsic connection between the longitudinal weak-boson scatterings and probing the electroweak symmetry breaking (EWSB) mechanism, we reveal the profound physical content of the Equivalence Theorem (ET) as being able to discriminate physical processes which are sensitive/insensitive to probing the EWSB sector. With this physical content of the ET as a criterion, we analyze the complete set of the bosonic operators in the electroweak chiral Lagrangian and systematically classify the sensitivities to probing all these operators at the CERN LHC via the weak-boson fusion in $W^\pm W^\pm$ channel. This is achieved by developing a precise power counting rule (a generalization from Weinberg's counting method) to {\it separately} count the power dependences on the energy $E$ and all relevant mass scales.
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Longitudinal/Goldstone boson equivalence and phenomenology of probing the electroweak symmetry breaking
We formulate the equivalence between the longitudinal weak-boson and the Goldstone boson as a criterion for sensitively probing the electroweak symmetry breaking mechanism and develop a precise power counting rule for chiral Lagrangian formulated electroweak theories. With these we semi-quatitatively analyze the sensitivities to various effective operators related to electrowaeak symmetry breaking via weak-boson scatterings at the CERN Large Hadron Collider (LHC).
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High-p_T Higgs Boson Production at Hadron Colliders to Order(alpha_s G_Fermi^3)
We study high--$p_T$ Higgs boson production at hadron colliders to order($α_s$ $G_F^3$) in hadron collisions. In particular, we investigate the process $g+q/\bar{q}\ra q/\bar{q}+H$, where $q=u,d,c,s,$ or $b$, for the LHC (a $\sqrt{s}=$14~TeV, proton--proton collider). Our results are compared to the order($α_s^3$ $G_F$) calculation. The associated production of a high--$p_T$ Higgs boson with a $b$--quark or anti--quark is comparable to the order($α_s^3$ $G_F$) calculation because of the large top quark mass and the additional contribution of electroweak gauge and Goldstone bosons. The associated production of light quarks, however, is not significant. We also comment on new physics effects in the framework of the electroweak chiral Lagrangian.
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Top Quark Physics
In these three lectures, I review the physics of top quark. Each of the lectures is self-contained.
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Equivalence Theorem and Probing the Electroweak Symmetry Breaking Sector
We examine the Lorentz non-invariance ambiguity in longitudinal weak-boson scatterings and the precise conditions for the validity of the Equivalence Theorem (ET). {\it Safe} Lorentz frames for applying the ET are defined, and the intrinsic connection between the longitudinal weak-boson scatterings and probing the symmetry breaking sector is analyzed. A universal precise formulation of the ET is presented for both the Standard Model and the Chiral Lagrangian formulated Electro-Weak Theories. It is shown that in electroweak theories with strongly interacting symmetry breaking sector, the longitudinal weak-boson scattering amplitude {\it under proper conditions} can be replaced by the corresponding Goldstone-boson scattering amplitude in which all the internal weak-boson lines and fermion loops are ignored.
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Strategies for Probing CP Properties in the Top Quark System at $e^-e^+$ and Hadron Colliders
I discuss strategies for probing CP properties in the top quark system at $e^-e^+$ and hadron Colliders. The magnitudes of CP violation effects predicted by various models are reviewed. I also discuss the potential of various current and future colliders in measuring the CP asymmetry associated with the productions and/or decays of the top quarks.
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A Probe of New Physics in Top Quark Pair Production at $e^-e^+$ Colliders
We describe how to probe new physics through examination of the form factors describing the Ztt couplings via the scattering process e^-e^+->t+tbar. We focus on experimental methods on how the top quark momentum can be determined and show how this can be applied to select polarized samples of $t\bar{t}$ pairs through the angular correlations in the final state leptons. We also study the dependence on the energy and luminosity of an \ee\ collider to probe a CP violating asymmetry at the $10^{-2}$ level.}
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Report of the Subgroup on the Top Quark
The top group studied discovery issues as well as measurements to be made at the Tevatron, the LHC and the SSC.
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Top Quark Physics at Hadron Colliders
I briefly report on what we can learn about the top quark at hadron colliders.
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Leading Electroweak Corrections to the Production of Heavy Top Quarks at Hadron Colliders
We calculate the electroweak corrections of the order $O({m_t^2\over v^2})$ to the QCD production of $t\bar{t}$ pairs via $q+qbar->t+tbar$ at hadron colliders and show that these corrections to the total production rate are small. This correction can be characterized as increasing the cross section most near the threshold region, where top quark signals are important, while the corrections become negative at higher $t\bar{t}$ energies where the top quark is a background for heavy Higgs boson searches or investigations involving the strongly interacting longitudinal $W$ system. The polarization of the $t\bar t$ pair is also discussed, including the effect that this has on proposed techniques for measuring the the top quark mass.
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Studying the Top Quark via the W-Gluon Fusion Process
We show that studying the single top quark production via the $W$--gluon fusion process can provide unique information on: (i) the measurement of the decay width $\width$; (ii) probing the symmetry breaking mechanism by measuring the form factor of~\tbW; (iii) testing the Effective--$W$ Approximation prior to supercolliders; (iv) testing CP violation by observing different production rates of $\bar p p \ra t X $ and $\bar p p \ra \bar t X$; (v) testing CP violation from the almost hundred percent longitudinally polarized top quark decay; in addition to the measurement of the top quark mass. In contrast to the recent claim by R. K. Ellis and S. Parke, we show that this process is extremely useful at the Tevatron.
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Inelastic Channels in WW Scattering
If the electroweak symmetry-breaking sector becomes strongly interacting at high energies, it can be probed through longitudinal $W$ scattering. We present a model with many inelastic channels in the $W_L W_L$ scattering process, corresponding to the production of heavy fermion pairs. These heavy fermions affect the elastic scattering of $W_L$'s by propagating in loops, greatly reducing the amplitudes in some charge channels. We conclude that the symmetry-breaking sector cannot be fully explored by using, for example, the $W_L^\pm W_L^\pm$ mode alone, even when no resonance is present; all $W_L W_L \to W_L W_L$ scattering modes must be measured.
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Proposals for Studying TeV $W_L W_L \rightarrow W_L W_L$ Interactions Experimentally
We discuss how to experimentally study the symmetry breaking sector by observing $W_L W_L \rightarrow W_L W_L$ interactions in the TeV region. We discuss some general features of the event structure in the signal and background events. Various tricks to enhance the signal--to--background ratio are also presented. We show how to detect longitudinal $W$--bosons either in the central rapidity region of the detector or in the beam pipe direction.
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Can the Electroweak Symmetry-breaking Sector Be Hidden?
In a recent paper, Chivukula and Golden claimed that the electroweak symmetry--breaking sector could be hidden if there were many inelastic channels in the longitudinal $WW$ scattering process. They presented a model in which the $W$'s couple to pseudo--Goldstone bosons, which may be difficult to detect experimentally. Because of these inelastic channels, the $WW$ interactions do not become strong in the TeV region. We demonstrate that, despite the reduced $WW$ elastic amplitudes in this model, the total event rate ($\sim 5000$ extra longitudinal $W^+W^-$ pairs produced in one standard SSC year) does not decrease with an increasing number of inelastic channels, and is roughly the same as in a model with a broad high--energy resonance and no inelastic channels.
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Inelastic Channels in the Electroweak Symmetry-Breaking Sector
It has been argued that if light Higgs bosons do not exist then the self--interactions of $W$'s become strong in the TeV region and can be observed in longitudinal $WW$ scattering. We present a model with many inelastic channels in the $WW$ scattering process, corresponding to the creation of heavy fermion pairs. The presence of these heavy fermions affects the elastic scattering of $W$'s by propagating in loops, greatly reducing the amplitudes in some charge channels. Consequently, the symmetry--breaking sector cannot be fully explored by using, for example, the $W^+W^+$ mode alone; all $WW \rightarrow WW$ scattering modes must be measured.}
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