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Kingman Cheung

Publications and source records attributed to Kingman Cheung.

At least 253 records · Page 14Linked to original sources
arXiv1995

Recent Progress on Perturbative QCD Fragmentation Functions

The recent development of perturbative QCD (PQCD) fragmentation functions has strong impact on quarkonium production. I shall summarize $B_c$ meson production based on these PQCD fragmentation functions, as well as, the highlights of some recent activities on applying these PQCD fragmentation functions to explain anomalous $J/ψ$ and $ψ'$ production at the Tevatron. Finally, I discuss a fragmentation model based on the PQCD fragmentation functions for heavy quarks fragmenting into heavy-light mesons.

hep-ph↗
arXiv1995

An Update on Strong $W_L W_L$ Scattering at the LHC

I summarize an update on our previous study (J. Bagger et al. Phys. Rev. D49, 1246) for a strongly interacting electroweak symmetry breaking sector via longitudinal vector boson scattering at the 14 TeV Large Hadron Collider. In the update, the decay mode $ZZ\to \ell^+\ell^- ν\bar ν$ and a new vector-resonance signal via $q\bar q' \to V \to W^+W^-/ W^\pm Z$ are also included.

hep-ph↗
arXiv1995

Probing Strongly-interacting Electroweak Dynamics through $W^+W^-/ZZ$ Ratios at Future $e^+e^-$ Colliders

We point out that the ratio of $W^+ W^- \to W^+ W^-$ and $W^+W^- \to ZZ$ cross sections is a sensitive probe of the dynamics of electroweak symmetry breaking, in the CM energy region $\sqrt {s_{\rm ww}^{}} \agt 1$~TeV where vector boson scattering may well become strong. We suggest ways in which this ratio can be extracted at a 1.5 TeV $e^+e^-$ linear collider, using $W^\pm,Z \to jj$ hadronic decays and relying on dijet mass resolution to provide statistical discrimination between $W^\pm$ and $Z$. $WW$ fusion processes studied here are unique for exploring scalar resonances of mass about 1 TeV and are complementary to studies via the direct channel $e^+ e^- \rightarrow W^+W^-$ for the vector and non-resonant cases. With an integrated luminosity of 200 fb$^{-1}$, the signals obtained are statistically significant. Comparison with a study of $e^-e^- \rightarrow ννW^-W^-$ process is made. Enhancements of the signal rate from using a polarized electron beam, or at a 2 TeV $e^+e^-$ linear collider and possible higher energy $μ^+μ^-$ colliders, are also presented.

hep-ph↗
arXiv1994

Signatures of Higgs-Triplet Representations at Tev--e+e- Colliders

We investigate the potential of future TeV linear e^+e^- colliders to observe singly-charged Higgs bosons ($H^\pm$) via the coupling $H^\pm W^\mp Z$, which would signal the existence of exotic Higgs representations. In the context of a Higgs-triplet model compatible with the electroweak oblique parameters, we estimate the cross section for pro- ducing charged Higgs-triplet bosons that couple predominantly to $W$ and $Z$ bosons in 0.5--2 TeV-$e^+e^-$ colliders. The principal backgrounds are evaluated and the viability of the signal is discussed and illustrated.

hep-ph↗
arXiv1994

Detecting the Intermediate-Mass Neutral Higgs Boson at the LHC Through $pp \to W H$

We examine the exclusive signature $pp \to WH \to \ell ν\;b \bar b$ at the LHC. Although the backgrounds, principally arising from top production and $Wjj$, are quite severe, it is shown that judicious application of phase-space cuts and the use of $b$-tagging can in fact greatly enhance the detectability of this channel. (Presented at the Eighth Meeting of the Division of Particles and Fields Albuquerque, New Mexico, August 2-6, 1994.)

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arXiv1994

Signature of the Intermediate Mass Higgs Boson at the LHC With Flavor Tagging

We revisit the exclusive signature $e^\pm (μ^\pm) + b\bar b$ in the associated production of the intermediate mass Higgs boson with a $W$ boson. We show that it is feasible to use this signature to identify the Higgs boson in the lower intermediate mass region ($90$ to $130$ GeV) at the LHC with reasonable acceptance cuts by assuming effective bottom-jet identification. We further demonstrate that the background can be reduced with judicious cuts down to the level of the signal.

hep-ph↗
arXiv1994

Studies of Strong Electroweak Symmetry Breaking at Photon Colliders

It has recently been shown that the studies of strongly-interacting electroweak symmetry breaking (EWSB) at photon colliders, via photon splitting into $W$ pair followed by longitudinal $W$-boson scattering, could be possible. Here we present a signal-background analysis for the scattering channels $W^+_L W^-_L \to Z_L Z_L$ and $W^+_L W^-_L \to W^+_L W^-_L$ with background coming from the standard model (SM) production of $γγ\to WW ZZ$ and $WWWW$, respectively. We illustrate the analysis using the SM with a heavy Higgs boson $(m_H\approx 1$ TeV) to represent a typical strongly-interacting EWSB model and the SM with a light Higgs boson ($m_H\approx 0.1$ TeV) to represent the background. We come up with a set of kinematic acceptance to enhance the signal-to-background ratio. Extension of the kinematic acceptance to other strongly-interacting EWSB models is then trivial, and the signal cross sections for various EWSB models are calculated. We found that it is very feasible to probe the EWSB sector at a photon collider of center-of-mass energy of 2 TeV with a luminosity of just 10~fb$^{-1}$.

hep-ph↗
arXiv1994

Beauty Quark Fragmentation Into Strange B Mesons

Using the recent measurement of the total production rate for $B_s$ and $B_s^*$ mesons in electron-positron annihilation to determine the strange quark mass parameter in the $\bar b\to B_s,\, B_s^*$ fragmentation functions we calculate the momentum distributions of the $B_s$ and $B_s^*$ mesons.

hep-ph↗
arXiv1994

Spin Alignment in the Production of Vector Mesons with Charm and/or Beauty via Heavy Quark Fragmentation

We calculate the process-independent fragmentation functions for a $\bar b$ antiquark to fragment into longitudinally and transversely polarized $B_c^*$ ($^3S_1$) mesons to leading order in the QCD strong coupling constant. In the special case of equal quark mass we recover previous results for the fragmentation of $c\to ψ$ and $b\toΥ$. Various spin asymmetry parameters are defined as measures of the relative population of the longitudinally and transversely polarized vector meson states. In the heavy quark mass limit $m_b \to \infty$ our polarized fragmentation functions obey heavy quark spin symmetry, we therefore apply them as a model to describe the fragmentation of charm and bottom into heavy-light mesons like $D^*$ and $B^*$. The spin asymmetry parameter, $α(z)$, is consistent with the existing CLEO data for $D^*$. The scaling behavior of $\langle z \rangle$ is studied in detail. We find excellent agreement between the predictions of $\langle z \rangle$ from our fragmentation functions and the experimental data for $D^*$ and $B^*$ from the LEP, CLEO, and ARGUS detectors. Finally, we also point out that the spin asymmetry depends significantly on the transverse momentum $p_\perp$ of the vector mesons relative to the fragmentation axis.

hep-ph↗
arXiv1994

Production of Weak Bosons and Higgs Bosons at e-e- Colliders

We present calculations of cross sections for single $W^-$ and $Z$ production and $W^-W^-, W^-Z, W^-γ, ZZ$, and $W^+W^-$ pair production within the Standard Model at $e^-e^-$ linear colliders. We evaluate Standard-Model Higgs boson production in the channels $e^-e^- \to e^-e^- H$, $e^-νW^- H$, and $e^-e^- ZH$. We also illustrate the enhancements in the $W^-W^-$ cross section that would result from a strongly-interacting Higgs sector or from a $H^{--}$ resonance in a Higgs doublet + triplet model.

hep-ph↗
arXiv1994

Photoproduction of $WH$ signal at electron-proton Colliders

We present the photoproduction of an intermediate mass Higgs (IMH) boson associated with a $W$ boson at the future electron-proton colliders using bremsstrahlung photon beam or laser backscattered photon beam. With bremsstrahlung photon beam the search for the IMH boson is unfavorable because of the small signal rate. But with laser photon beam the search is viable due to a much larger rate, and provided that the $B$-identification is efficient and $m(b\bar b)$ measurement has a good resolution.

hep-ph↗
arXiv1993

$B_c$ Meson Productions Via Induced Gluon Fragmentation

Gluons cannot directly fragment into $B_c$ mesons until at order $α_s^3$. However, the Altarelli-Parisi evolution of the $\bar b$-quark fragmentation functions $D_{\bar b \to B_c}(z)$ and $D_{\bar b \to B_c^*}(z)$ from the heavy quark mass scales up to the collider energy scale $Q$ can induce the gluon fragmentation functions $D_{g \to B_c}(z)$ and $D_{g \to B_c^*}(z)$, respectively, through the gluon splitting $g\to \bar b$ at the order $α_s^3 \, {\rm log} (Q/m_{b,c})$. We will determine these induced gluon fragmentation functions. The $B_c$ meson productions due to the induced gluon fragmentation will be evaluated and compared to the productions by the direct $\bar b$-quark fragmentation. The contribution from the induced gluon fragmentation is found to be a significant portion of the total $B_c$ and $B_c^*$ meson productions, and therefore cannot be ignored.

hep-ph↗
arXiv1993

Possibility of Studying Electroweak Symmetry Breaking at γγColliders

The studies of the electroweak symmetry breaking sector (EWSBS) at $γγ$ colliders were considered previously in the loop processes of $γγ\to w_Lw_L,\,z_Lz_L$, but they are suffered from the huge $W_T W_T$ and $Z_TZ_T$ backgrounds. Here we present another possible process that involves spectator $W$'s and $W_L$'s, the latter of which are scattered strongly by the interactions of the EWSBS. We also show that this process should be safe from the transverse backgrounds and it can probe the structure of the EWSBS.

hep-ph↗
arXiv1993

$B_c$ Mesons Production at Hadron Colliders by Heavy Quark Fragmentation

We present a reliable estimate on the production rate of $B_c$ mesons in $1S$ and $2S$ states in the large transverse momentum region at hadronic colliders using heavy quark fragmentation functions derived within the framework of perturbative QCD. We also present the transverse momentum distribution for the $B_c$ mesons. The production rate is large enough for the $B_c$ mesons to be identified at the Tevatron. At the SSC/LHC the rate is so large that their properties can be studied in details.

hep-ph↗
arXiv1993

Strong $W_L W_L$ Scattering at Hadronic Supercolliders

We will summarize some aspects of the scenario of a strongly interacting symmetry breaking sector via which the longitudinal vector boson scattering becomes strong. We will examine the feasibility of observing such strong $W_L W_L$ signal at the future hadronic supercolliders.

hep-ph↗
arXiv1993

Finding the Leptonic $WW$ Decay Mode of a Heavy Higgs Boson

We reanalyze the extraction of the heavy Higgs boson signal $H\rightarrow W^+W^-\rightarrow \bar\ellν,\ell\barν$ $(\ell=e\hbox{ or }μ)$ from the Standard Model background at hadron supercolliders, taking into account revised estimates of the top quark background. With new acceptance criteria the detection of the signal remains viable. Requiring a forward jet-tag, a central jet-veto, and a large relative transverse momentum of the two charged leptons yields $S/\sqrt B>6$ for one year of running at the SSC or LHC.

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