5,634 research outputs found
Measurements of Diffractive Processes at CDF
We review the results of measurements on hard diffractive processes performed
by the CDF Collaboration and report preliminary CDF results on two soft
diffractive processes with a leading antiproton and a rapidity gap in addition
to that associated with the antiproton. All results have been obtained from
data collected in Run I of the Fermilab Tevatron collider.Comment: 7 pages, Presented at 14 Topical Conference on Hadron Collider
Physics, HCP-2002, Karlsruhe, Germany, 29 Sep - 4 Oct 200
Energy Level Diagrams for Black Hole Orbits
A spinning black hole with a much smaller black hole companion forms a
fundamental gravitational system, like a colossal classical analog to an atom.
In an appealing if imperfect analogy to atomic physics, this gravitational atom
can be understood through a discrete spectrum of periodic orbits. Exploiting a
correspondence between the set of periodic orbits and the set of rational
numbers, we are able to construct periodic tables of orbits and energy level
diagrams of the accessible states around black holes. We also present a closed
form expression for the rational q, thereby quantifying zoom-whirl behavior in
terms of spin, energy, and angular momentum. The black hole atom is not just a
theoretical construct, but corresponds to extant astrophysical systems
detectable by future gravitational wave observatories.Comment: 8 page
Diffraction in hadron-hadron interactions
Results on soft and hard diffraction in and collisions are
reviewed with emphasis on factorization and scaling properties of differential
cross sections. While conventional factorization breaks down at high energies,
a scaling behavior emerges, which leads to a universal description of
diffractive processes in terms of a (re)normalized rapidity gap probability
distribution.Comment: 12 pages, Late
The Ratio of W + N jets To Z/gamma + N jets As a Precision Test of the Standard Model
We suggest replacing measurements of the individual cross-sections for the
production of W + N jets and Z/gamma + N jets in searches for new high-energy
phenomena at hadron colliders by the precision measurement of the ratios (W+0
jet)/(Z+0 jet), (W+1 jet)/(Z+1 jet), (W+2 jets)/(Z+2 jets),... (W+N jets)/(Z+N
jets), with N as large as 6 (the number of jets in ttbarH). These ratios can
also be formed for the case where one or more of the jets is tagged as a b or c
quark. Existing measurements of the individual cross sections for Wenu + N jets
at the Tevatron have systematic uncertainties that grow rapidly with N, being
dominated by uncertainties in the identification of jets and the jet energy
scale. These systematics, and also those associated with the luminosity, parton
distribution functions (PDF's), detector acceptance and efficiencies, and
systematics of jet finding and b-tagging, are expected to substantially cancel
in calculating the ratio of W to Z production in each N-jet channel, allowing a
greater sensitivity to new contributions in these channels in Run II at the
Tevatron and at the LHC.Comment: 10 pages, 8 figures, added reference
QCD at high energy (experiments)
Recent measurements of QCD interactions involving large momentum transfers
are reviewed. The status of measurements of the strong coupling constant is
summarised. Recent developments in the measurement and interpretation of deep
inelastic scattering, proton-anti-proton collisions and two-photon processes
are discussed. While QCD at next-to-leading order gives a qualitative
description of many processes, next-to-NLO calculations are now required to
allow quantitative information to be extracted from hadron-initiated multijet
data. This is illustrated by a discussion of recent data on the photoproduction
of dijet events at HERA.Comment: Talk presented at the International Conference on High
Energy Physics, Amsterdam, 24-31 July 2002. 18 pages, 30 figure
Squark Mixing in Electron-Positron Reactions
Squark mixing plays a large role in the phenomenology of the minimal
supersymmetric standard model, determining the mass of the lightest Higgs boson
and the electroweak interactions of the squarks themselves. We examine how
mixing may be investigated in high energy reactions, both at LEP-II
and the proposed linear collider. In particular, off-diagonal production of one
lighter and one heavier squark allows one to measure the squark mixing angle,
and would allow one to test the mass relations for the light Higgs boson. In
some cases off-diagonal production may provide the best prospects to discover
supersymmetry. In the context of the light bottom squark scenario, we show that
existing data from LEP-II should show definitive evidence for the heavier
bottom squark provided that its mass GeV.Comment: 22 pages, latex, 6 figure
On recent puzzles in the production of heavy quarkonia
Recently, several surprising experimental observations in the production of
heavy quarkonium have been reported. In annihilation at
GeV, Belle Collaboration finds that mesons are
predominantly produced in association with an extra pair, with
, and the BaBar collaboration reports that the
produced 's have mostly longitudinal polarization. In
collisions at the Tevatron, the CDF Collaboration reported an excess of
and mesons at high over the perturbative
QCD predictions; non--perturbative approach of NRQCD can accomodate the
magnitude of the production cross section but not the observed experimentally
polarization of quarkonia. In this note we propose possible solutions to these
puzzles, and devise further experimental tests.Comment: 3 pages, 2 figure
Polarization of Upsilon(nS) at the Tevatron
The polarization of inclusive Upsilon(nS) at the Fermilab Tevatron is
calculated within the nonrelativistic QCD factorization framework. We use a
recent determination of the NRQCD matrix elements from fitting the CDF data on
bottomonium production from Run IB of the Tevatron. The result for the
polarization of Upsilon(1S) integrated over the transverse momentum bin 8 < p_T
< 20 GeV is consistent with a recent measurement by the CDF Collaboration. The
transverse polarization of Upsilon(1S) is predicted to increase steadily for
p_T greater than about 10 GeV. The Upsilon(2S) and Upsilon(3S) are predicted to
have significantly larger transverse polarizations than Upsilon(1S).Comment: 15 pages, 3 figure
Systematic event generator tuning for the LHC
In this article we describe Professor, a new program for tuning model
parameters of Monte Carlo event generators to experimental data by
parameterising the per-bin generator response to parameter variations and
numerically optimising the parameterised behaviour. Simulated experimental
analysis data is obtained using the Rivet analysis toolkit. This paper presents
the Professor procedure and implementation, illustrated with the application of
the method to tunes of the Pythia 6 event generator to data from the LEP/SLD
and Tevatron experiments. These tunes are substantial improvements on existing
standard choices, and are recommended as base tunes for LHC experiments, to be
themselves systematically improved upon when early LHC data is available.Comment: 28 pages. Submitted to European Physical Journal C. Program sources
and extra information are available from
http://projects.hepforge.org/professor
Resonant and Non-Resonant Effects in Photon-Technipion Production at Lepton Colliders
Lepton collider experiments can search for light technipions in final states
made striking by the presence of an energetic photon: e+e- \to
\photon\technipion. To date, searches have focused on either production
through anomalous coupling of the technipions to electroweak gauge bosons or on
production through a technivector meson (\technirho, \techniomega) resonance.
This paper creates a combined framework in which both contributions are
included. This will allow stronger and more accurate limits on technipion
production to be set using existing data from LEP or future data from a
higher-energy linear collider. We provide explicit formulas and sample
calculations (analytic and Pythia) in the framework of the Technicolor Straw
Man Model, a model that includes light technihadrons.Comment: 11 pages, including title page, 3 figures; version 2: references
adde
- …