6,372 research outputs found
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
Present Limits on the Precision of SM Predictions for Jet Energies
We investigate the impact of theoretical uncertainties on the accuracy of
measurements involving hadronic jets. The analysis is performed using events
with a Z boson and a single jet observed in collisions at
= 1.96 TeV in 4.6 of data from the Collider Detector at
Fermilab (CDF). The transverse momenta (\pt) of the jet and the boson should
balance each other due to momentum conservation in the plane transverse to the
direction of the and beams. We evaluate the dependence of the
measured \pt-balance on theoretical uncertainties associated with initial and
final state radiation, choice of renormalization and factorization scales,
parton distribution functions, jet-parton matching, calculations of matrix
elements, and parton showering. We find that the uncertainty caused by parton
showering at large angles is the largest amongst the listed uncertainties. The
proposed method can be re-applied at the LHC experiments to investigate and
evaluate the uncertainties on the predicted jet energies. The distributions
produced at the CDF environment are intended for comparison to those from
modern event generators and new tunes of parton showering.Comment: Submitted to Nucl. Instr. and Meth.
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
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
Heavy Flavours in Collider Experiments
Current issues in the studies of Heavy Flavours in colliders are described
with particular emphasis on experiments in which the UK is involved. Results on
charm production at HERA are examined and compared to those at the Tevatron. B
production rates at the Tevatron as well as the status of B lifetimes and
mixing in the LEP collaborations and at the Tevatron are highlighted. The
measurement of sin2beta from CDF is described as well as the most recent
results on top physics at the Tevatron
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
Electrical Properties of Carbon Fiber Support Systems
Carbon fiber support structures have become common elements of detector
designs for high energy physics experiments. Carbon fiber has many mechanical
advantages but it is also characterized by high conductivity, particularly at
high frequency, with associated design issues. This paper discusses the
elements required for sound electrical performance of silicon detectors
employing carbon fiber support elements. Tests on carbon fiber structures are
presented indicating that carbon fiber must be regarded as a conductor for the
frequency region of 10 to 100 MHz. The general principles of grounding
configurations involving carbon fiber structures will be discussed. To
illustrate the design requirements, measurements performed with a silicon
detector on a carbon fiber support structure at small radius are presented. A
grounding scheme employing copper-kapton mesh circuits is described and shown
to provide adequate and robust detector performance.Comment: 20 pages, 11 figures, submitted to NI
Determination of the Jet Energy Scale at the Collider Detector at Fermilab
A precise determination of the energy scale of jets at the Collider Detector
at Fermilab at the Tevatron collider is described. Jets are used in
many analyses to estimate the energies of partons resulting from the underlying
physics process. Several correction factors are developed to estimate the
original parton energy from the observed jet energy in the calorimeter. The jet
energy response is compared between data and Monte Carlo simulation for various
physics processes, and systematic uncertainties on the jet energy scale are
determined. For jets with transverse momenta above 50 GeV the jet energy scale
is determined with a 3% systematic uncertainty
Popping out the Higgs boson off vacuum at Tevatron and LHC
In the prospect of diffractive Higgs production at the LHC collider, we give
an extensive study of Higgs boson, dijet, diphoton and dilepton production at
hadronic colliders via diffraction at both hadron vertices. Our model, based on
non factorizable Pomeron exchange, describes well the observed dijet rate
observed at Tevatron Run I. Taking the absolute normalization from data, our
predictions are given for diffractive processes at Tevatron and LHC. Stringent
tests of our model and of its parameters using data being taken now at Tevatron
Run II are suggested. These measurements will also allow to discriminate
between various models and finally to give precise predictions on diffractive
Higgs boson production cross-section at the LHC.Comment: 27 pages, 16 figures. Published version, incorporating corrections
listed in the Erratum to appea
Helicity conservation in inclusive nonleptonic decay B to VX: Test of long-distance final state interaction
The polarization measurement in the inclusive B decay provides us with a
simple test of how much the long-distance final-state interaction takes place
as the energy of the observed meson varies in the final state. We give the
expectation of the perturbative QCD for the energy dependence of the helicity
fractions in a semiquantitative form. Experiment will tell us for which decay
processes the perturbative calculation should be applicable.Comment: 15 pages in Revtex with 3 figures embedde
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