Hadron collider limits on anomalous WWγWW\gamma couplings

A next-to-leading log calculation of the reactions $pp$ and $p\overline{p}\rightarrow W^\pm\gamma X$ is presented including a tri-boson gauge coupling from non-Standard Model contributions. Two approaches are made for comparison. The first approach considers the tri-boson $WW\gamma$ coupling as being uniquely fixed by tree level unitarity at high energies to its Standard Model form and, consequently, suppresses the non-Standard Model contributions with form factors. The second approach is to ignore such considerations and calculate the contributions to non-Standard Model tri-boson gauge couplings without such suppressions. It is found that at Tevatron energies, the two approaches do not differ much in quantitative results, while at Large Hadron Collider (LHC) energies the two approaches give significantly different predictions for production rates. At the Tevatron and LHC, however, the sensitivity limits on the anomalous coupling of $WW\gamma$ are too weak to usefully constrain parameters in effective Lagrangian models.Comment: Revtex 23 pages + 8 figures, UIOWA-94-1

Vector Boson Pair Production in Hadronic Collisions at Order αs\alpha_s: Lepton Correlations and Anomalous Couplings

We present cross sections for production of electroweak vector boson pairs, $WW$, $WZ$ and $ZZ$, in $p\bar{p}$ and $pp$ collisions, at next-to-leading order in $\alpha_s$. We treat the leptonic decays of the bosons in the narrow-width approximation, but retain all spin information via decay angle correlations. We also include the effects of $WWZ$ and $WW\gamma$ anomalous couplings.Comment: 23 pages, 8 figures, 3 table

Heavy ion beam lifetimes at relativistic and ultrarelativistic colliders

The effects of higher order corrections in ultra-relativistic nuclear collisions are considered. It is found that higher order contributions are small at low energy, large at intermediate energy and small again at very high energy. An explanation for this effect is given. This means that the Weizsacker-Williams formula is a good approximation to use in calculating cross sections and beam lifetimes at energies relevant to RHIC and LHC.Comment: 10 pages, 2 tables, 4 figure

Amplitude Zeros in W±ZW^\pm Z Production

We demonstrate that the Standard Model amplitude for $f_1 \bar f_2 \rightarrow W^\pm Z$ at the Born-level exhibits an approximate zero located at $\cos\theta = (g^{f_1}_{-} + g^{f_2}_{-}) / (g^{f_1}_{-} - g^{f_2}_{-})$ at high energies, where the $g^{f_i}_{-}$ ($i=1,2$) are the left-handed couplings of the $Z$-boson to fermions and $\theta$ is the center of mass scattering angle of the $W$-boson. The approximate zero is the combined result of an exact zero in the dominant helicity amplitudes ${\cal M}(\pm,\mp)$ and strong gauge cancelations in the remaining amplitudes. For non-standard $WWZ$ couplings these cancelations no longer occur and the approximate amplitude zero is eliminated.Comment: 11 pages, 4 figures submitted separately as uuencoded tar-ed postscript files, FSU-HEP-940307, UCD-94-

Exclusive W + photon production in proton-antiproton collisions I: general formalism

We present a detailed computation of the fully exclusive cross section of p + antip --> W + photon + X with X = 0 and 1 jet in the framework of the factorization theorem and dimensional regularization. Order alpha-strong and photon bremsstrahlung contributions are discussed in the MS-bar mass factorization scheme. The resulting expressions are ready to be implemented numerically using Monte Carlo techniques to compute single and double differential cross sections and correlations between outgoing pairs of particles.Comment: ITP-SB-93-72, 40 pages, LateX. 3*4 figures in separate file. ([email protected]) ([email protected]

Probing Electroweak Top Quark Couplings at Hadron Colliders

We consider QCD t\bar{t}\gamma and t\bar{t}Z production at hadron colliders as a tool to measure the tt\gamma and ttZ couplings. At the Tevatron it may be possible to perform a first, albeit not very precise, test of the tt\gamma vector and axial vector couplings in t\bar{t}\gamma production, provided that more than 5 fb^{-1} of integrated luminosity are accumulated. The t\bar{t}Z cross section at the Tevatron is too small to be observable. At the CERN Large Hadron Collider (LHC) it will be possible to probe the tt\gamma couplings at the few percent level, which approaches the precision which one hopes to achieve with a next-generation e^+e^- linear collider. The LHC's capability of associated QCD t\bar{t}V (V=\gamma, Z) production has the added advantage that the tt\gamma and ttZ couplings are not entangled. For an integrated luminosity of 300 fb^{-1}, the ttZ vector (axial vector) coupling can be determined with an uncertainty of 45-85% (15-20%), whereas the dimension-five dipole form factors can be measured with a precision of 50-55%. The achievable limits improve typically by a factor of 2-3 for the luminosity-upgraded (3 ab^{-1}) LHC.Comment: Revtex3, 30 pages, 9 Figures, 6 Table

Electron-lattice coupling and the broken symmetries of the molecular salt (TMTTF)2_2SbF6_6

(TMTTF)$_2$SbF$_6$ is known to undergo a charge ordering (CO) phase transition at $T_{CO}\approx156K$ and another transition to an antiferromagnetic (AF) state at $T_N\approx 8K$. Applied pressure $P$ causes a decrease in both $T_{CO}$ and $T_N$. When $P>0.5 GPa$, the CO is largely supressed, and there is no remaining signature of AF order. Instead, the ground state is a singlet. In addition to establishing an expanded, general phase diagram for the physics of TMTTF salts, we establish the role of electron-lattice coupling in determining how the system evolves with pressure.Comment: 4 pages, 5 figure

Torsion pairs and rigid objects in tubes

We classify the torsion pairs in a tube category and show that they are in bijection with maximal rigid objects in the extension of the tube category containing the Pruefer and adic modules. We show that the annulus geometric model for the tube category can be extended to the larger category and interpret torsion pairs, maximal rigid objects and the bijection between them geometrically. We also give a similar geometric description in the case of the linear orientation of a Dynkin quiver of type A.Comment: 25 pages, 13 figures. Paper shortened. Minor errors correcte

Higher Order Processes in Electromagnetic Production of Electron Positron Pairs in Relativistic Heavy Ion Collisions

We study higher-order effects in the electromagnetic production of electron-positron pairs in relativistic heavy ion collisions. Treating the field of the heavy ions as an external field and neglecting the interaction among electrons and positrons, we show that the $N$-pair creation amplitude is the antisymmetrised product of $N$ one-pair creation amplitudes and the vacuum amplitude. Neglecting contributions coming from exchange terms, we show that the total probability for $N$ pairs is approximately a Poisson distribution. We investigate further the structure of the reduced one-pair amplitude, concentrating especially on multiple-particle corrections. We calculate the first of these corrections in second order Magnus theory based on our previous result in second-order Born approximation for impact parameter $b$ zero. Explicit calculations show that the total probability is increased up to 10 \% by this correction for realistic collider parameters. The calculations can also be used to confirm the use of the Poisson distribution for the total probability.Comment: 29 pages RevTeX and 12 uuencoded figures (compressed postscript