Search

The $n=2$ and $n=3$ levels for muonic Helium are calculated using a potential that includes all one-loop and recoil effects. Electronic vacuum polarization corrections are calculated using an extension of Kinoshita and Nio method. For $n=2$, the results are $2p_{1/2}-2s_{1/2}=1375.05\pm 1.4$ meV and $2p_{3/2}-2s_{1/2}=1521.65\pm 1.4$ meV, essentially in agreement with the latest summary of the current calculations. The $n=3$ results are summarized in tabular form and give $3p_{1/2}-3s_{1/2}=394.76\pm 0.43$ meV and $3d_{3/2}-3p_{3/2}=111.40$ meV.

To gain some sense about the likelihood of measuring the Higgs boson quartic coupling, we calculate the contribution to the triple Higgs production cross section from the subprocesses $q\bar{q}\to ZHHH$ and $q\bar{q}'\to WHHH$. Our results illustrate that determining this coupling, or even providing experimental evidence that it exists, will be very difficult.

We show that the dominant channel proposed for the determination of the Higgs boson trilinear coupling, $pp\to HH+X$ via gluon fusion, exhibits an interference structure that is independent of the collider energy for collider energies in the range $8\,{\rm TeV}\leq \sqrt{s}\leq 100\,{\rm TeV}$ and is almost maximally destructive. This insensitivity to the collider energy remains approximately true for a variety of other two Higgs production mechanisms although the magnitude of the interference varies widely., Comment: 8 pages, 4 figures, additional references,publication version

The Dalitz decay $H\ensuremath{\rightarrow}f\overline{f}\ensuremath{\gamma}$ is calculated for very small $f\overline{f}$ invariant masses where the $f\overline{f}$ pair could be mistaken for a photon in the analysis of $H\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma}$ decays. Using the ATLAS cuts and the full Dalitz decay amplitude, we estimate this fraction to be 7.06%.

A precise comparison is made between the Dalitz decay $H\to\ell\bar{\ell}\gamma$ and the two body decay $H\to\gamma Z,Z\to\ell\bar{\ell}$ for electrons and for muons including experimental cuts appropriate for the ATLAS detector. The widths for these two processes differ by 8% for electrons and 3% for muons. Given that there remain QCD radiative corrections of this order that are not included, this suggests that the isolation of the Dalitz decay will be challenging.

We study the production of neutral scalar (CP even) Higgs bosons in the process $e\gamma\to e h$ by including supersymmetric corrections to the dominant $t$-channel photon exchange amplitude. In addition to the standard model $W^{\pm}$ and fermion loops, there are substantial contributions from chargino loops. For some cases, these contributions can exceed those of the $W$'s and ordinary fermions. The cross sections in this channel are generally one or two orders of magnitude larger than those in the related channel $e\bar{e}\to\gamma h$.

We use the behavior of the photon-photon scattering for photon energies $\omega$ less than the electron mass, $m_e$, to examine the implications of treating the Euler-Heisenberg Lagrangian as an effective field theory. Specifically, we determine the $\omega^2/m_e^2$ behavior of the scattering amplitude predicted by including one-loop corrections to the Euler-Heisenberg effective Lagrangian together with the counterterms required by renomalizability. This behavior is compared with the energy dependence obtained by expanding the exact QED photon-photon scattering amplitude. If the introduction of counterterms in the effective field theory is restricted to those determined by renormalizability, the $\omega^2/m_e^2$ dependences of the two expansions differ., Comment: 10 pages, ReVTeX, 2 postscript figures included

We present cross sections for the reaction {mu}{bar {mu}}{r_arrow}H{gamma} over a range of {mu}{bar {mu}} collider energies. The amplitudes for this process receive tree level contributions and one-loop contributions, which are of comparable magnitude. The tree level amplitudes are dominated by helicity non-flip terms and the one-loop amplitudes are dominated by helicity flip terms. As a consequence, the interference terms between the tree level and one-loop contributions are negligible. For a 500 GeV {mu}{bar {mu}} collider, the cross section for H{gamma} associated production approaches 0.1 fb. {copyright} {ital 1997} {ital The American Physical Society}

Higgs boson radiative decays of the form H{r_arrow}f{bar f}{gamma} are calculated in the standard model using the complete one-loop expressions for the decay amplitudes. Contributions to the radiative width from leptons and light quarks are given. We also present e{bar e}-invariant mass distributions for H{r_arrow}e{bar e}{gamma}, which illustrate the importance of the photon pole contribution and the effects of the box diagrams. {copyright} {ital 1997} {ital The American Physical Society}

We revisit an earlier calculation of the decay $H\ensuremath{\rightarrow}e\overline{e}\ensuremath{\gamma}$ using the recently reported mass value of the Higgs boson candidate observed in the ATLAS and CMS experiments together with cuts that are appropriate for experimental analyses.

We have extended our earlier treatment of the gauge-boson scattering with radiative corrections in the standard model at supercollider energies, and computed the rates for gauge-boson scattering modes in {ital pp} collisions leading to the final states {ital W}{sup +}{ital W}{sup {minus}}, {ital ZZ}(4{ital l}), {ital ZZ}(2{ital l}2{nu}), {ital W}{sup {plus_minus}}{ital Z}, and {ital W}{sup {plus_minus}}{ital W}{sup {plus_minus}}. Our results at the CERN LHC energy of {radical}{ital s}=14 TeV for {ital m}{sub {ital H}}=1000 GeV are compared with those recently obtained by Bagger {ital et} {ital al}. These results will be useful in the search for the Higgs bosons at supercollider energies as well as for experimentally distinguishing the standard model from nonminimal Higgs models. {copyright} {ital 1996 The American Physical Society.}

The effective interaction for two neutrino-two photon coupling is used to find an approximate width for the decay of the $Z$ boson into the $\ensuremath{\nu}\overline{\ensuremath{\nu}}\ensuremath{\gamma}\ensuremath{\gamma}$ final state.

We present complete analytical expressions for the amplitudes of the process e\ifmmode \bar{e}\else \={e}\fi{}\ensuremath{\rightarrow}H\ensuremath{\gamma}. The calculation is performed using nonlinear gauges, which significantly simplifies both the actual analytical calculation and the check of its gauge invariance. After comparing our results with a previous numerical calculation, we extend the range of Higgs boson masses and center of mass energies to those appropriate to CERN LEP 200 and a future linear collider.

The invariant-mass distributions for the production of [ital W][sup [minus]][ital Z][sup 0] ([ital W][sup +][ital Z][sup 0]) via gauge-boson fusion at [ital pp] colliders of energies 16 and 40 TeV are calculated using the effective-[ital W] approximation supplemented by [ital K]-matrix unitarization. Included in the unitarization is the effect of transverse degrees of freedom on the production of [ital W][sub [ital L]][sup [minus]][ital Z][sub [ital L]][sup 0] ([ital W][sub [ital L]][sup +][ital Z][sub [ital L]][sup 0]) gauge bosons. These results are compared with the corresponding results for [ital W][sup [minus]][ital Z][sup 0] ([ital W][sup +][ital Z][sup 0]) production via [ital q[bar q]] annihilation.

A theoretical explanation of the observed splittings among the $P$ states of charmonium is given with the use of a nonsingular potential model for heavy quarkonia. We also show that the recently observed mass difference between the center of gravity of the $^{3}P_{J}$ states and the $^{1}P_{1}$ state of $c\overline{c}$ does not provide a direct test of the color hyperfine interaction in heavy quarkonia. Our theoretical value for the mass of the $^{1}P_{1}$ state is in agreement with the experimental result, and its $E1$ transition width is 341.8 keV. The mass of the ${\ensuremath{\eta}}_{c}^{\ensuremath{'}}$ state is predicted to be 3622.3 MeV.

We study the effects of a strongly interacting Higgs sector on the amplitudes for $\ensuremath{\gamma}\ensuremath{\gamma}\ensuremath{\rightarrow}{W}_{L}^{+}{W}_{L}^{\ensuremath{-}}$, ${Z}_{L}^{0}{Z}_{L}^{0}$ by unitarizing the ${W}_{L}^{+}{W}_{L}^{\ensuremath{-}}$, ${Z}_{L}^{0}{Z}_{L}^{0}$, $\ensuremath{\gamma}\ensuremath{\gamma}$ system using the $K$-matrix technique. Unitarization produces substantial corrections to the cross sections for gauge boson pair production by photon fusion when ${m}_{H}\ensuremath{\gtrsim}5\ensuremath{-}10$ TeV. We also investigate the extent to which including transverse $W$'s modifies the unitarized $\ensuremath{\gamma}\ensuremath{\gamma}\ensuremath{\rightarrow}{W}_{L}^{+}{W}_{L}^{\ensuremath{-}}$ amplitude.

We explore the consequences of the neutrino mass matrix having a hidden Z{sub 2} symmetry and one zero eigenvalue. When implemented, these two conditions give relations among the mixing angles. In addition, fitting these relations to the existing oscillation data allows limits to be placed on the parameter of the symmetry.

We show that the Pade unitarized [ital I]=1, [ital J]=1 partial wave amplitude for [ital W][sub [ital L]][sup +][ital W][sub [ital L]][sup [minus]] elastic scattering exhibits resonant behavior for relatively low values of the Higgs-boson mass parameter [ital m][sub [ital H]]. The [ital p]-wave resonance can occur when [radical][ital s] [approx gt][ital m][sub [ital H]]. This is in contrast with the [ital I]=0, [ital J]=0 resonance which occurs in the [ital W][sub [ital L]][sup +][ital W][sub [ital L]][sup [minus]-][ital Z][sub [ital L]][sup 0][ital Z][sub [ital L]][sup 0] system for [radical][ital s] [much lt][ital m][sub [ital H]]. The observability of the [ital I]=1 resonance in high-energy [ital pp] collisions is examined.

Using the effective-[ital W] approximation, we calculate the invariant-mass distribution for the production of [ital W][sup +][ital W+] ([ital W][sup [minus]][ital W[minus]]) via [ital W][sup +][ital W+] ([ital W][sup [minus]][ital W[minus]]) fusion at a [ital pp] collider with an energy of 40 TeV. These results are compared with the corresponding results for the production of [ital W][sup +][ital W[minus]] via [ital W][sup +][ital W[minus]] fusion. All [ital W] polarizations are taken into account. We also study the effects of the unitarity in the [ital W][sup +][ital W+] ([ital W][sup [minus]][ital W[minus]]) scattering, with particular attention to the possibility that the signal for longitudinally polarized [ital W]'s will be enhanced when the Higgs sector is strongly interacting.

We investigate the spectroscopy and decays of the charm-strange quarkonium system in a potential model consisting of a relativistic kinetic energy term, a linear confining term including its scalar and vector relativistic corrections, and the complete perturbative one-loop quantum chromodynamic short distance potential. The unperturbed wave functions of the various states are obtained using a variational technique. These are then used in a perturbative treatment of the potential to fit the mass spectrum of the $c\overline{s}$ system and calculate the radiative decay widths. Our results compare well with the available data for the spectrum of ${D}_{s}$ states. We include a discussion of the effect of mixing and investigation of the Lorentz nature of the confining potential.

We investigate the behavior of the critical charge for spontaneous pair production, $Z_C$, defined as the charge at which the total energy of a $K$-shell electron is $E=-m_e$, as a function of the radius $R$ of the charge distribution. Our approach is to solve the Dirac equation for a potential $V(r)$ consisting of a spherically symmetrical charge distribution of radius $R$ and a Coulomb tail. For a spherical shell distribution of the type usually associated with color-flavor locked strange quark nuggets, we confirm the relation $Z_C=0.71 R({\rm fm})$ for sufficiently large $R$ obtained by Madsen, who used an approach based on the Thomas-Fermi model. We also present results for a uniformly charged sphere and again find that $Z_C\sim R$ for large enough $R$. Also discussed is the behavior of $Z_C$ when simple {\it ad hoc} modifications are made to the potential for $0\leq r < R$., 7 pages, 6 figures

Recently published measurements of the branching ratios B({psi}(1S){yields}{gamma}{eta}{sub C}(1S)) and B({psi}(2S){yields}{gamma}{eta}{sub C}(1S)) by the CLEO Collaboration are examined in the context of a potential model that includes both relativistic and one-loop QCD corrections to the quark-antiquark interaction. The prediction for the width {gamma}({psi}(1S){yields}{gamma}{eta}{sub C}(1S)) is in excellent agreement with the new data, but the prediction for {gamma}({psi}(2S){yields}{gamma}{eta}{sub C}(1S)) is too small. In an effort to understand this discrepancy, we derive an upper bound on {gamma}({psi}(2S){yields}{gamma}{eta}{sub C}(1S)) and point out its experimental value saturates this bound.

The effect of unitarization on the {ital s}-wave amplitudes for the coupled {ital W}{sub {ital L}}{sup +}{ital W}{sub {ital L}}{sup {minus}}{endash}{ital Z}{sub {ital L}}{sup 0}{ital Z}{sub {ital L}}{sup 0} system is studied using the Pade-approximant method and the complete one-loop expressions for the perturbative amplitudes. For values of the Higgs-boson-mass parameter {ital m}{sub {ital H}} less than 1.0 TeV, the Pade amplitudes and those unitarized using the one-loop {ital K}-matrix method are essentially identical. When {ital m}{sub {ital H}}, which also determines the strength of the Higgs-boson self-coupling in the standard model, exceeds 2.6 TeV, the Pade amplitudes begin to develop a resonant feature {ital below} the value of {ital m}{sub {ital H}}. The {ital K}-matrix amplitudes {ital do} {ital not} develop a low-mass resonance. At {ital m}{sub {ital H}}=10 TeV, this peak occurs at about 1.4 TeV, while at {ital m}{sub {ital H}}=50 TeV, it occurs at 950 GeV with a width of about 325 GeV. The Argand diagrams exhibit resonant behavior at these energies. By examining the Argand diagrams for a large range of values of {ital m}{sub {ital H}}, it appears that this Higgs-boson-like resonance has a mass that does not exceed 2.6 TeV. It is alsomore » evident that both the mass and width of the resonance decrease as {ital m}{sub {ital H}} increases beyond 10 TeV. The couplings of the resonance to {ital W}{sub {ital L}}{sup +}{ital W}{sub {ital L}}{sup {minus}} and {ital Z}{sub {ital L}}{sup 0}{ital Z}{sub {ital L}}{sup 0} are similar to the standard-model couplings of a low-mass elementary Higgs boson. We compare our conclusions with those reached by Dobado, Herrero, and Truong for {ital W}{sub {ital L}}{sup +}{ital W}{sub {ital L}}{sup {minus}} scattering.« less

We provide an analytic solution to the short wave length limit of the integro-differential equation describing the damping of the tensor modes of gravitational waves., Minor changes to abstract and references

We compute the total cross section as well as angular and energy distributions for process ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma}\ensuremath{\gamma}$ with both unpolarized and polarized beams in the framework of noncommutative quantum electrodynamics (NCQED). The calculation is performed in the center of mass of colliding electron and positron and is evaluated for energies and integrated luminosities appropriate to future linear colliders. We find that by using unpolarized beams it is possible to probe the Lorentz symmetry violating azimuthal dependence of the cross section. Furthermore, with polarized beams the left-right asymmetry of the $CP$ violating NCQED amplitudes can be used to obtain bounds on the noncommutative scale ${\ensuremath{\Lambda}}_{\mathrm{NC}}$ which exceed 1.0 TeV.

We have calculated the width of the rare decay $H\to\gamma\gamma Z$ at one-loop level in the standard model for Higgs boson masses in the range $115 {\rm GeV} \leq m_H \leq 160 {\rm GeV}$ . For this range of Higgs boson masses we find that $Z$ boson is predominantly longitudinally polarized, and the photons have the same helicity. A comparison of the decay width $\Gamma(H\to \gamma\gamma Z)$ to those of $H\to\gamma\gamma$ and $H\to\gamma Z$ shows that, for the Higgs boson mass of $m_H \sim 135 \rm{GeV}$, the ratios of the decay widths are $\Gamma(H\to\gamma\gamma Z) / \Gamma(H\to\gamma\gamma) \sim \Gamma(H\to\gamma\gamma Z) / \Gamma(H\to\gamma Z) \sim 10^{-5}-10^{-6}$., Comment: 4 pages, 5 figures, RevTeX

Using the one-loop helicity amplitudes for low-energy $\nu\gamma\to\nu\gamma$ and $\bar\nu\gamma\to\bar\nu\gamma$ scattering in the standard model with massless neutrinos, we study the optical activity of a sea of neutrinos and antineutrinos. In particular, we estimate the values of the index of refraction and rotary power of this medium in the absence of dispersion., Comment: Additional references

The cross section for photon neutrino scattering is calculated in the standard model assuming that the neutrino is massless and that the center of mass energy is small compared to any charged lepton mass. Although the scattered photons can acquire a (parity violating) circular polarization of order unity, the cross section in this limit is highly suppressed., 8 pages including figures; DOE-40200-014,CPP-14,MSUHEP 93/08. Figures, one style file, and latex file available by anonymous ftp to utaphy.ph.utexas.edu, in directory [anonymous.cpp-preprints.ggtonunu]

We compute the cross section for neutrino-photon scattering taking into account a neutrino mass. We explore the possibility of using intense neutrino beams, such as those available at proposed muon colliders, together with high powered lasers to probe the neutrino mass in photon-neutrino collisions., 10 pages, 5 postscript figures included, ReVTeX4

The Higgs boson decay, H -> mu mubar gamma, is studied in the Standard Model at the tree and one-loop levels. It is shown that for Higgs boson masses above 110 GeV, the contribution to the radiative width from the one-loop level exceeds the contribution from the tree level, and for Higgs boson masses above 140 GeV, it even exceeds the contribution from the tree level decay H -> mu mubar. We also show that the contributions to the radiative decay width from the interference terms between the tree and one-loop diagrams are negligible.

We calculate the rates and lepton ({ital l}) invariant mass distributions for decays of the form 0{sup {minus}+}{r_arrow}l{sup +}l{sup {minus}}{gamma}, which are important radiative corrections to the purely leptonic decays 0{sup {minus}+}{r_arrow}l{sup +}l{sup {minus}}. Our approach uses the loop diagrams which arise by including the two photon intermediate state and we retain the imaginary parts of the loops{emdash}a radiative extension of the {open_quotes}unitarity bound{close_quotes} for the process. These results are compared with those obtained using a model in which the meson couples directly to the leptons. {copyright} {ital 1999} {ital The American Physical Society}

A general decomposition of the amplitudes for the $2\to 2$ processes $\gamma\nu\to\gamma\nu$ and $\gamma\gamma\to\nu\bar{\nu}$ is obtained using gauge invariance and Bose symmetry. The restrictions implied by this decomposition are investigated for the reaction $\gamma\gamma\to\nu\bar{\nu}$ by computing the one-loop helicity amplitudes in the standard model. In the center of mass, where $\sqrt{s} = 2\omega$, the cross section grows roughly as $\omega^6$ up to the threshold for $W$-boson production, $\sqrt{s} = 2m_W$. Astrophysical implications of very high energy photon-neutrino interactions are discussed., Comment: 11 pages LaTeX, 4 postscript figures included

The cross sections for the processes {gamma}{nu}{r_arrow}{gamma}{gamma}{nu}, {gamma}{gamma}{r_arrow}{gamma}{nu}{bar {nu}} and {nu}{bar {nu}}{r_arrow}{gamma}{gamma}{gamma} are calculated for a range of center of mass energies from below m{sub e} to considerably above m{sub e}, but much less than m{sub W}. This enables us to treat the neutrino-electron coupling as a four-Fermi interaction and results in amplitudes which are electron box diagrams with three real photons and one virtual photon at their vertices. These calculations extend our previous low-energy effective interaction results to higher energies and enable us to determine where the effective theory is reliable. {copyright} {ital 1998} {ital The American Physical Society}