Successive Combination Jet Algorithm For Hadron Collisions

Jet finding algorithms, as they are used in $e^+ e^-$ and hadron collisions, are reviewed and compared. It is suggested that a successive combination style algorithm, similar to that used in $e^+ e^-$ physics, might be useful also in hadron collisions, where cone style algorithms have been used previously.Comment: 18 pages plus four uuencoded postscript figures, REVTEX 3.0, CERN-TH.6860/9

QCD Corrections to Production of Higgs Pseudoscalars

Models of electroweak symmetry breaking with more than a single doublet of Higgs scalars contain a neutral pseudoscalar boson. The production of such a pseudoscalar in hadron collisions proceeds primarily via gluon fusion through a top-quark loop (except for those models in which the pseudoscalar coupling to bottom quarks is strongly enhanced). We compute the QCD corrections to this process in the heavy-quark limit, using an effective Lagrangian derived from the axial anomaly.Comment: 9 pages, (BNL number added, 1 typo corrected, PHYZZX format, 4 figures not included, available on request), BNL-4906

Symmetric Informationally Complete Measurements of Arbitrary Rank

There has been much interest in so-called SIC-POVMs: rank 1 symmetric informationally complete positive operator valued measures. In this paper we discuss the larger class of POVMs which are symmetric and informationally complete but not necessarily rank 1. This class of POVMs is of some independent interest. In particular it includes a POVM which is closely related to the discrete Wigner function. However, it is interesting mainly because of the light it casts on the problem of constructing rank 1 symmetric informationally complete POVMs. In this connection we derive an extremal condition alternative to the one derived by Renes et al.Comment: Contribution to proceedings of International Conference on Quantum Optics, Minsk, 200

The Production of Z′Z' Associated With Photons or Jets as a Probe of New Gauge Boson Couplings

We examine the production of a new $Z'$ gauge boson in association with photons or jets at future hadron supercolliders as a probe of its couplings to fermions. Associated jet production is found to be rather insensitive to these couplings and suffers from large uncertainties as well as substantial backgrounds. On the other hand, the ratio of rates for associated photon $Z'$ production to that of conventional $Z'$ production has a rather clean signature (once appropriate cuts are made), and is found to be quite sensitive to the choice of extended electroweak model, while being simultaneously insensitive to structure function uncertainties and QCD corrections. Rates at both the SSC and LHC are significant for $Z'$ masses in the 1 TeV range.Comment: 14pp, 6 figs(not included), LaTex, ANL-HEP-PR-92-5

Transverse Momentum Distributions for Heavy Quark Pairs

We study the transverse momentum distribution for a $pair$ of heavy quarks produced in hadron-hadron interactions. Predictions for the large transverse momentum region are based on exact order $\alpha_s^3$ QCD perturbation theory. For the small transverse momentum region, we use techniques for all orders resummation of leading logarithmic contributions associated with initial state soft gluon radiation. The combination provides the transverse momentum distribution of heavy quark pairs for all transverse momenta. Explicit results are presented for $b\bar b$ pair production at the Fermilab Tevatron collider and for $c\bar c$ pair production at fixed target energies.Comment: LaTeX (27 pages text, 8 figures not included, but available on request

Multiparton interactions and production of minijets in high energy hadronic collisions

We discuss the inclusive cross section to produce two minijets with a large separation in rapidity in high energy hadronic collisions. The contribution to the inclusive cross section from the exchange of a BFKL Pomeron is compared with the contribution from the exchange of two BFKL Pomerons, which is induced by the unitarization of the semi-hard interaction. The effect of the multiple exchange is studied both as a function of the azimuthal correlation and as a function of the transverse momentum of the observed minijets.Comment: TeX file, 20 pages, 4 figures available on reques

Enhancing the top signal at Tevatron using Neural Nets

We show that Neural Nets can be useful for top analysis at Tevatron. The main features of $t\bar t$ and background events on a mixed sample are projected in a single output, which controls the efficiency and purity of the $t\bar t$ signal.Comment: 11 pages, 6 figures (not included and available from the authors), Latex, UB-ECM-PF 94/1

Testing the Equivalence Principle by Lamb shift Energies

The Einstein Equivalence Principle has as one of its implications that the non-gravitational laws of physics are those of special relativity in any local freely-falling frame. We consider possible tests of this hypothesis for systems whose energies are due to radiative corrections, i.e. which arise purely as a consequence of quantum field theoretic loop effects. Specifically, we evaluate the Lamb shift transition (as given by the energy splitting between the $2S_{1/2}$ and $2P_{1/2}$ atomic states) within the context of violations of local position invariance and local Lorentz invariance, as described by the $T H \epsilon\mu$ formalism. We compute the associated red shift and time dilation parameters, and discuss how (high-precision) measurements of these quantities could provide new information on the validity of the equivalence principle.Comment: 40 pages, latex, epsf, 1 figure, final version which appears in Physical Review

Hilbert--Schmidt volume of the set of mixed quantum states

We compute the volume of the convex N^2-1 dimensional set M_N of density matrices of size N with respect to the Hilbert-Schmidt measure. The hyper--area of the boundary of this set is also found and its ratio to the volume provides an information about the complex structure of M_N. Similar investigations are also performed for the smaller set of all real density matrices. As an intermediate step we analyze volumes of the unitary and orthogonal groups and of the flag manifolds.Comment: 13 revtex pages, ver 3: minor improvement

Searching for G3G^3 in t \tbar Production

The triple gluon field strength operator $G^3$ represents the only genuinely gluonic CP conserving term which can appear at dimension-6 within an effective strong interaction Lagrangian. Previous studies of this operator have revealed that its effect on gluon scattering is surprisingly difficult to detect. In this article, we analyze the impact of $G^3$ upon top quark pair production. We find that it will generate observable cross section deviations from QCD at the LHC for even relatively small values of its coefficient. Furthermore, $G^3$ affects the transverse momentum distribution of the produced top quarks more strongly at high energies than dimension-6 four-quark and chromomagnetic moment terms in the effective Lagrangian. Top-antitop production at the LHC will therefore provide a sensitive and clean probe for the elusive triple gluon field strength operator.Comment: 20 pages, 8 figures (3 updated figures not included but available upon request), CALT-68-1941, BUHEP-94-18. (Some previously overlooked graphs are now included. Our conclusions remain unchanged.