557 research outputs found
Relative distributions of W's and Z's at low transverse momenta
Despite large uncertainties in the and transverse momentum
() distributions for q_T\lsim 10 GeV, the ratio of the distributions
varys little. The uncertainty in the ratio of to distributions is
on the order of a few percent, independent of the details of the
nonperturbative parameterization.Comment: 13 pages in revtex, 5 postscript figures available upon request,
UIOWA-94-0
Towards a Precise Parton Luminosity Determination at the CERN LHC
A new approach to determine the LHC luminosity is investigated. Instead of
employing the proton-proton luminosity measurement, we suggest to measure
directly the parton-parton luminosity. It is shown that the electron and muon
pseudorapidity distributions, originating from the decay of W+, W- and Z0
bosons produced at 14 TeV pp collisions (LHC), constrain the x distributions of
sea and valence quarks and antiquarks in the range from about 3 x 10**-4 to
about 10**-1 at a Q**2 of about 10**4 GeV**2. Furthermore, it is demonstrated
that, once the quark and antiquark structure functions are constrained from the
W+,W- and Z0 production dynamics, other quark-antiquark related scattering
processes at the LHC like q-qbar --> W+W- can be predicted accurately. Thus,
the lepton pseudorapidity distributions provide the key to a precise parton
luminosity monitor at the LHC, with accuracies of about +-1% compared to the so
far considered goal of +-5%.Comment: plain tex, 14 pages, 5 figure
N-representability and stationarity in time-dependent density functional theory
To construct an N-representable time-dependent density-functional theory, a
generalization to the time domain of the Levy-Lieb (LL) constrained search
algorithm is required. That the action is only stationary in the Dirac-Frenkel
variational principle eliminates the possibility of basing the search on the
action itself. Instead, we use the norm of the partial functional derivative of
the action in the Hilbert space of the wave functions in place of the energy of
the LL search. The electron densities entering the formalism are
-representable, and the resulting universal action functional has a unique
stationary point in the density at that corresponding to the solution of the
Schr\"{o}dinger equation. The original Runge-Gross (RG) formulation is subsumed
within the new formalism. Concerns in the literature about the meaning of the
functional derivatives and the internal consistency of the RG formulation are
allayed by clarifying the nature of the functional derivatives entering the
formalism.Comment: 9 pages, 0 figures, Phys. Rev. A accepted. Introduction was expanded,
subsections reorganized, appendix and new references adde
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 and background events on a mixed sample are projected in
a single output, which controls the efficiency and purity of the
signal.Comment: 11 pages, 6 figures (not included and available from the authors),
Latex, UB-ECM-PF 94/1
Hadronic production and the Gottfried Sum Rule
The difference in production rate between and at hadron colliders
is very sensitive to the the difference between up- and down-quark
distributions in the proton. This sensitivity allows for a variety of useful
measurements. We consider the difference in the sea
distributions and the difference in the
polarized parton distribution functions. In both cases we construct an
asymmetry to reduce systematic uncertainties. Although we discuss measurements
at the Tevatron and future hadron colliders, we find that the Brookhaven
Relativistic Heavy Ion Collider (RHIC) is the most appropriate hadron collider
for these measurements.Comment: 19 pages (20 figures available from the authors), MAD/PH/74
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
Searching for in t \tbar Production
The triple gluon field strength operator 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 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,
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.
An update on vector boson pair production at hadron colliders
We present numerical results (including full one-loop QCD corrections) for
the processes p p-bar and pp -> W+ W-, W+/- Z/gamma* and Z/gamma* Z/gamma*
followed by the decay of the massive vector bosons into leptons. In addition to
their intrinsic importance as tests of the standard model, these processes are
also backgrounds to conjectured non-standard model processes. Because of the
small cross sections at the Tevatron, full experimental control of these
backgrounds will be hard to achieve. This accentuates the need for up-to-date
theoretical information. A comparison is made with earlier work and cross
section results are presented for p p-bar collisions at sqrt{s}=2 TeV and pp
collisions at sqrt{s}=14 TeV. Practical examples of the use of our calculations
are presented.Comment: 18 pages, 5 embedded figures, included extra reference [7
Large Jets at Hadron Colliders at Order : A Look Inside
Results from the study of hadronic jets in hadron-hadron collisions at order
in perturbation theory are presented. The focus is on various
features of the internal structure of jets. The numerical results of the
calculation are compared with data where possible and exhibit reasonable
agreement.Comment: 7 pages, 1 table and 2 figures (appended as postscript files), Late
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