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Tai Tsun Wu

Publications and source records attributed to Tai Tsun Wu.

At least 19 recordsLinked to original sources
arXiv2018

Gauge invariance for a class of tree diagrams in the standard model

For gauge theory, the matrix element for any physical process is independent of the gauge used. Since this is a formal statement and examples are known where gauge invariance is violated, for any specific process this gauge invariance needs to be checked by explicit calculation. In this paper, gauge invariance is found to hold for a large non-trivial class of processes described by tree diagrams in the standard model -- tree diagrams with two external $W$ bosons and any number of external Higgs bosons. This verification of gauge invariance is quite complicated, and is based on a direct study of the difference between different gauges through induction on the number of external Higgs bosons.

hep-ph↗
arXiv2018

Fermion-boson symmetry and quantum field theory

The application of fermion-boson symmetry to the standard model leads to the following: first, there are three generations of scalar quarks and scalar leptons in addition to the known quarks and leptons, and, secondly, the divergences in the perturbation series for the standard model are reduced. In the light of experimental data from LEP, Tevatron Collider, and LHC, some consequences of these two statements taken together are discussed. A series of experiments are proposed to search for the scalar quarks and scalar leptons at the Large Hadron Collider. The first step in this search is to look for new fermions by analyzing events with a pair of oppositely changed leptons both with large transverse momenta. The scalar quarks and the scalar leptons are then searched for through their decays into these new fermions plus a known quark or lepton.

physics.gen-ph↗
arXiv2014

Impact picture for near-forward elastic scattering up to LHC energies

We will recall the main feaatures of an accurate phenomenological model to describe successfully near-forward elastic scattering in a wide energy range, including ISR, SPS and Tevatron colliders. A large step in energy domain is accomplished with the LHC collider, presently running, giving the opportunity to confront the new data with the predictions of our theoretical approach.

hep-ph↗
arXiv2014

Do we understand near-forward elastic scattering up to TeV energies?

In 1970, on purely theoretical grounds, all total hadronic total cross sections were predicted to increase without limit for higher and higher energies. This was contrary to the conventional belief at that time. In 1978, an accurate phenomenological model was formulated for the case of proton-proton and antiproton-proton interactions. The parameters for this model were slightly improved in 1984 using the additional available experimental data. Since then, for thirty years these parameters have not changed. This development, including especially the difficult task of formulating this phenomenological model and the comparison of the predictions of this model with later experimental results, is summarized.

hep-ph↗
arXiv2013

Scalar Quarks at the Large Hadron Collider

The properties of scalar quarks are studied, especially the formation of fermionic mesons with an anti-quark. On the basis of this theoretical investigation together with the experimental data, both from last year and from this year, of the ATLAS Collaboration and the CMS Collaboration at the Large Hadron Collider, it is proposed that the standard model of Glashow, Weinberg, and Salam should be augmented by scalar quarks, scalar leptons, and additional fermions. If these scalar quarks and scalar leptons are in one-to-one correspondence with the ordinary quarks and ordinary leptons, either in number or in the degrees of freedom, then there may be a fermion-boson symmetry. The fermion-boson symmetry obtained this way is of a different nature from that of supersymmetry.

hep-ph↗
arXiv2012

High-energy asymptotic behavior of the Bourrely-Soffer-Wu model for elastic scattering

Some time ago, an accurate phenomenological approach, the BSW model, was developed for proton-proton and antiproton-proton elastic scattering cross sections at center-of-mass energies above 10 GeV. This model has been used to give successful theoretical predictions for these processes, at successive collider energies. The BSW model involves a combination of integrals that, while computable numerically at fairly high energies, require some mathematical analysis to reveal the high-energy asymptotic behavior. In this paper we present a high-energy asymptotic representation of the scattering amplitude at moderate momentum transfer, for the leading order in an expansion parameter closely related to the logarithm of the center-of-mass energy. The fact that the expansion parameter goes as the logarithm of the energy means that the asymptotic behavior is accurate only for energies greatly beyond any foreseeable experiment. However, we compare the asymptotic representation against the numerically calculated model for energies in a less extreme region of energy. The asymptotic representation is given by a simple formula which, in particular, exhibits the oscillations of the differential cross section with momentum transfer. We also compare the BSW asymptotic behavior with the Singh-Roy unitarity upper bound for the diffraction peak.

hep-ph↗
arXiv2011

Higgs Decay into Two Photons, Revisited

The one-loop calculation of the amplitude for the Higgs decay H-->γγ due to virtual W's in the unitary gauge is presented. As the Higgs does not directly couple to the massless photons, the one-loop amplitude is finite. The calculation is performed in a straightforward way, without encountering divergences. In particular, artifacts like dimensional regularization are avoided. This is achieved by judiciously routing the external momenta through the loop and by combining the integrands of the amplitudes before carrying out the integration over the loop momentum. The present result satisfies the decoupling theorem for infinite Higgs mass, and is thus different from the earlier results obtained in the ξ=1 gauge using dimensional regularization. The difference between the results is traced to the use of dimensional regularization.

hep-ph↗
arXiv2011

Higgs Decay H -->γγ through a W Loop: Difficulty with Dimensional Regularization

Since the photon has no mass, it does not couple directly to the Higgs particle. This implies that the one-loop correction to the decay H --> γγ is necessarily finite. Therefore, this correction should be calculable without introducing either regularization or ghosts. Such a calculation is carried out in this paper for the case of one W loop. The result obtained this way turns out not to agree with the previous, well-known one, and it is argued that the present result is to be preferred because it satisfies the decoupling theorem. The discrepancy can be traced to the use of dimensional regularization in the previous result.

hep-ph↗
arXiv2011

An upper bound on the total inelastic cross-section as a function of the total cross-section

Recently André Martin has proved a rigorous upper bound on the inelastic cross-section $σ_{inel}$ at high energy which is one-fourth of the known Froissart-Martin-Lukaszuk upper bound on $σ_{tot}$. Here we obtain an upper bound on $σ_{inel}$ in terms of $σ_{tot}$ and show that the Martin bound on $σ_{inel}$ is improved significantly with this added information.

hep-ph↗
arXiv2009

Low-energy potential scattering in two and three dimensions

Conditions are established for the existence of a scattering length and an effective range in the low-energy expansion of the S-wave phase-shift of a central potential in two and three dimensions. The behavior of the phase-shift as a function of the momentum is also derived for longer-range power-law potentials which do not fulfill these conditions.

math-ph↗
arXiv2007

Impact picture for the analyzing power $A_N$ in very forward $pp$ elastic scattering

In the framework of the impact picture we compute the analyzing power $A_N$ for $pp$ elastic scattering at high energy and in the very forward direction. We consider the full set of Coulomb amplitudes and show that the interference between the hadronic non-flip amplitude and the single-flip Coulomb amplitude is sufficient to obtain a good agreement with the present experimental data. This leads us to conclude that the single-flip hadronic amplitude is small in this low momentum transfer region and it strongly suggests that this process can be used as an absolute polarimeter at the BNL-RHIC $pp$ collider.

hep-ph↗
arXiv2004

Universality of Low-Energy Scattering in 2+1 Dimensions: The Non Symmetric Case

For a very large class of potentials, $V(\vec{x})$, $\vec{x}\in R^2$, we prove the universality of the low energy scattering amplitude, $f(\vec{k}', \vec{k})$. The result is $f=\sqrt{\fracπ{2}}\{1/log k)+O(1/(log k)^2)$. The only exceptions occur if $V$ happens to have a zero energy bound state. Our new result includes as a special subclass the case of rotationally symmetric potentials, $V(|\vec{x}|)$.

hep-th↗
arXiv2003

Bound states in two spatial dimensions in the non-central case

We derive a bound on the total number of negative energy bound states in a potential in two spatial dimensions by using an adaptation of the Schwinger method to derive the Birman-Schwinger bound in three dimensions. Specifically, counting the number of bound states in a potential gV for g=1 is replaced by counting the number of g_i's for which zero energy bound states exist, and then the kernel of the integral equation for the zero-energy wave functon is symmetrized. One of the keys of the solution is the replacement of an inhomogeneous integral equation by a homogeneous integral equation.

math-ph↗
arXiv2002

Yang-Mills theory for non-semisimple groups

For semisimple groups, possibly multiplied by U(1)'s, the number of Yang-Mills gauge fields is equal to the number of generators of the group. In this paper, it is shown that, for non-semisimple groups, the number of Yang-Mills fields can be larger. These additional Yang-Mills fields are not irrelevant because they appear in the gauge transformations of the original Yang-Mills fields. Such non-semisimple Yang-Mills theories may lead to physical consequences worth studying. The non-semisimple group with only two generators that do not commute is studied in detail.

hep-th↗
arXiv2002

Neutrino masses from universal Fermion mixing

If three right-handed neutrinos are added to the Standard Model, then, for the three known generations, there are six quarks and six leptons. It is then natural to assume that the symmetry considerations that have been applied to the quark matrices are also valid for the lepton mass matrices. Under this assumption, the solar and atmospheric neutrino data can be used to determine the individual neutrino masses. Using the χ^2 fit, it is found that the mass of the lightest neutrino is (2-5)\times10^{-3} eV, that of the next heavier neutrino is (10-13)\times10^{-3} eV, while the mass of the heaviest neutrino is (52-54)\times10^{-3} eV.

hep-ph↗
arXiv2002

Impact-Picture Phenomenology for $π^{\pm}p, K^{\pm}p$ and $pp, \bar p p$

We present an extension to $π^{\pm} p$ and $K^{\pm} p$ elastic scattering at high energies of the impact-picture phenomenology we first proposed more than twenty years ago, for $p p$ and $\bar p p$ elastic scattering. We show, in particular, that the analytic form of the opacity function for the proton obtained previously is compatible with the experimental results on $πp$ and $K p$ elastic scattering at high energies. It is proposed that $π^{\pm}$ and $K^{\pm}$ external beams be provided from CERN-LHC, so that their elastic scattering from protons can be studied at higher energies. Our phenomenology for $p p$ and $\bar p p$ elastic scattering is updated by including new data and we give predictions for future experiments at BNL-RHIC and CERN-LHC.

hep-ph↗
arXiv2002

Quantum memory: Write, read and reset

A model is presented for the quantum memory, the content of which is a pure quantum state. In this model, the fundamental operations of writing on, reading, and resetting the memory are performed through scattering from the memory. The requirement that the quantum memory must remain in a pure state after scattering implies that the scattering is of a special type, and only certain incident waves are admissible. An example, based on the Fermi pseudo-potential in one dimension, is used to demonstrate that the requirements on the scattering process are consistent and can be satisfied. This model is compared with the commonly used model for the quantum memory; the most important difference is that the spatial dimensions and interference play a central role in the present model.

quant-ph↗