7,875 research outputs found
Separation of \gamma/\pi^0 showers at high energies
We have designed and carried out simulation studies of a two layer Shower
Maximum Detector diagonally off-set (SMD-dos) optimized for the separation of
\pi^0 showers from \gamma showers in the 30 to 150 GeV energy range. For 90%
\gamma acceptance the SMD-dos yields \pi^0 rejection efficiency of 92+-4%,
87+-4% and 32+-2%, respectively, for 30, 50 and 150 GeV incident energies. We
find that the SMD-dos is superior to a conventional geometry single-layer or
mutiple-layer shower maximum detector (SMD), of equal granularity, by an
average factor of ~1.5 over the 50 to 150 GeV energy range. We also find that
the SMD-dos gives better \pi^0 rejection, for the same number of channels, than
a SMD. At hadron - hadron colliders the signature of choice for the detection
of the Higgs particle, in the mass range of 120 to 160 GeV, is via the decay
H-->\gamma\gamma. The addition of a SMD-dos to the planned detectors at the LHC
would significantly reduce the background to the \gamma-signal coming from
prolific \pi^0 production.Comment: 16 pages, 6 figures, LaTeX. Submitted to Nuclear Instruments and
Method
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
Quench Performance of the First Pre-series AUP Cryo-assembly
The High Luminosity upgrade of the Large Hadron Collider (HL-LHC) at CERN
will include eight cryo-assemblies that are expected to be fabricated and
delivered to CERN by the US HL-LHC Accelerator Upgrade Project (AUP) as part of
the U.S. contributions to the HL-LHC. These cryostat assemblies are the
quadrupole magnetic components of the HL-LHC Q1 and Q3 inner triplet optical
elements in front of the two interaction points. Each cryo-assembly consists of
two 4.2 m long Nb3Sn quadrupole magnets with aperture 150 mm and operating
gradient 132.6 T/m. The first pre-series cryo-assembly has been fabricated and
successfully tested at the horizontal test facility at Fermi National
Accelerator Laboratory. In this manuscript we report the quench test results of
the LQXFA/B-01 cryo-assembly. The primary objective of the horizontal test is
full cryo-assembly qualification and validation of the performance
requirements.Comment: MT28 International Conference on Magnet Technology, Accepted Versio
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
Search for charged Higgs decays of the top quark using hadronic tau decays
We present the result of a search for charged Higgs decays of the top quark,
produced in collisions at 1.8 TeV. When the charged
Higgs is heavy and decays to a tau lepton, which subsequently decays
hadronically, the resulting events have a unique signature: large missing
transverse energy and the low-charged-multiplicity tau. Data collected in the
period 1992-1993 at the Collider Detector at Fermilab, corresponding to
18.70.7~pb, exclude new regions of combined top quark and charged
Higgs mass, in extensions to the standard model with two Higgs doublets.Comment: uuencoded, gzipped tar file of LaTeX and 6 Postscript figures; 11 pp;
submitted to Phys. Rev.
Inclusive jet cross section in collisions at TeV
The inclusive jet differential cross section has been measured for jet
transverse energies, , from 15 to 440 GeV, in the pseudorapidity region
0.10.7. The results are based on 19.5 pb of data
collected by the CDF collaboration at the Fermilab Tevatron collider. The data
are compared with QCD predictions for various sets of parton distribution
functions. The cross section for jets with GeV is significantly
higher than current predictions based on O() perturbative QCD
calculations. Various possible explanations for the high- excess are
discussed.Comment: 8 pages with 2 eps uu-encoded figures Submitted to Physical Review
Letter
Measurement of Dijet Angular Distributions at CDF
We have used 106 pb^-1 of data collected in proton-antiproton collisions at
sqrt(s)=1.8 TeV by the Collider Detector at Fermilab to measure jet angular
distributions in events with two jets in the final state. The angular
distributions agree with next to leading order (NLO) predictions of Quantum
Chromodynamics (QCD) in all dijet invariant mass regions. The data exclude at
95% confidence level (CL) a model of quark substructure in which only up and
down quarks are composite and the contact interaction scale is Lambda_ud(+) <
1.6 TeV or Lambda_ud(-) < 1.4 TeV. For a model in which all quarks are
composite the excluded regions are Lambda(+) < 1.8 TeV and Lambda(-) < 1. 6
TeV.Comment: 16 pages, 2 figures, 2 tables, LaTex, using epsf.sty. Submitted to
Physical Review Letters on September 17, 1996. Postscript file of full paper
available at http://www-cdf.fnal.gov/physics/pub96/cdf3773_dijet_angle_prl.p
Search for the Supersymmetric Partner of the Top-Quark in Collisions at
We report on a search for the supersymmetric partner of the top quark (stop)
produced in events using of
collisions at recorded with the Collider Detector at
Fermilab. In the case of a light stop squark, the decay of the top quark into
stop plus the lightest supersymmetric particle (LSP) could have a significant
branching ratio. The observed events are consistent with Standard Model production and decay. Hence, we set limits on the branching ratio of
the top quark decaying into stop plus LSP, excluding branching ratios above 45%
for a LSP mass up to 40 {\rm GeV/c}.Comment: 11 pages, 4 figure
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