563 research outputs found
On the Top Mass Reconstruction Using Leptons
I discuss the feasibility of measuring the top quark mass by the using of
final states with leptons and J/\psi at hadron colliders. I also investigate
the impact of matrix-element corrections to the HERWIG simulation of top
decays.Comment: 4 pages, 3 figures. Talk given at the UK Phenomenology Workshop on
Collider Physics, Durham, U. K., 19-24 September 1999. Revised version with
updated result
Bottom Quark Mass Determination from low-n Sum Rules
We study the uncertainties in the MSbar bottom quark mass determination using
relativistic sum rules to O(alpha_S^2). We include charm mass effects and
secondary b bbar production and treat the experimental continuum region more
conservatively than previous analyses. The PDG treatment of the region between
the resonances Upsilon (4S) and Upsilon (5S) is reconsidered. Our final result
reads: m_b(m_b)=(4.20 \pm 0.09) GeV.Comment: 4 pages, Talk given at QCD 03, Montpellier, France, 2-9 July 200
Bottom-quark fragmentation: comparing results from tuned event generators and resummed calculations
We study bottom-quark fragmentation in e+e- annihilation, top and Higgs decay
H -> b bbar, using Monte Carlo event generators, as well as calculations, based
on the formalism of perturbative fragmentation functions, which resum soft- and
collinear-radiation effects in the next-to-leading logarithmic approximation.
We consider the PYTHIA and HERWIG generators, and implement matrix-element
corrections to the parton shower simulation of the H -> b bbar process in
HERWIG. We tune the Kartvelishvili, string and cluster models to B-hadron data
from LEP and SLD, and present results in both x_B and moment spaces. The
B-hadron spectra yielded by HERWIG, PYTHIA and resummed calculations show small
discrepancies, which are due to the different approaches and models employed
and to the quality of the fits to the e+e- data.Comment: 22 pages, 11 colour figures. Minor changes in the text, published
versio
A Comparison of two different jet algorithms for the top mass reconstruction at the LHC
We compare the abilities of the cluster-type jet algorithm, KtJet, and a
mid-point iterating cone algorithm to reconstruct the top mass at the LHC. We
discuss the information contained in the merging scales of cluster-type
algorithms, and how this can be used in experimental analyses, as well as the
different sources of systematic errors for the two algorithms. We find that the
sources of systematic error are different for the two algorithms, which may
help to better constrain the systematic error on the top mass at the LHC.Comment: 21 pages, 16 figures, accepted by JHE
On azimuthal spin correlations in Higgs plus jet events at LHC
We consider the recent proposal that the distribution of the difference
between azimuthal angles of the two accompanying jets in gluon-fusion induced
Higgs-plus-two-jet events at LHC reflects the CP of the Higgs boson produced.
We point out that the hierarchy between the Higgs boson mass and the jet
transverse energy makes this observable vulnerable to logarithmically enhanced
higher-order perturbative corrections. We present an evolution equation that
describes the scale variation of the azimuthal angular correlation for the two
jets. The emission of extra partons leads to a significant suppression of the
correlation. Using the HERWIG Monte Carlo event generator, we carry out a
parton-shower analysis to confirm the findings.Comment: Published version. 11 pages, 4 figures, uses JHEP3.cl
Measurement of charged jet cross sections and jet shapes in proton-proton collisions at sqrt(s) = 2.76 TeV with the ALICE detector at LHC
We present measurements of charged jet cross sections and jet shape
observables in leading jet in proton-proton (pp) collisions at sqrt(s) = 2.76
TeV with the ALICE detector at LHC. Jets are reconstructed at the midrapidity
from charged particle using sequential recombination anti-kT jet finding
algorithm for various R values. The results are compared to measurements from
HERWIG, PHOJET and different tunes of PYTHIA6 and earlier measurements at 7
TeV.Comment: Proceedings of XXII DAE-BRNS High Energy Physics Symposium 2016
conference, 12-16 December, 201
Angular ordering and parton showers for non-global QCD observables
We study the mismatch between a full calculation of non-global
single-logarithms in the large-N_c limit and an approximation based on free
azimuthal averaging, and the consequent angular-ordered pattern of soft gluon
radiation in QCD. We compare the results obtained in either case to those
obtained from the parton showers in the Monte Carlo event generators HERWIG and
PYTHIA, with the aim of assessing the accuracy of the parton showers with
regard to such observables where angular ordering is merely an approximation
even at leading-logarithmic accuracy and which are commonly employed for the
tuning of event generators to data.Comment: 20 pages, 8 figure
Resummation
We review the work discussed and developed under the topic ``Resummation'' at
Working Group 2 ``Multijet final states and energy flow'', of the HERA-LHC
Workshop. We emphasise the role played by HERA observables in the development
of resummation tools via, for instance, the discovery and resummation of
non-global logarithms. We describe the event-shapes subsequently developed for
hadron colliders and present resummed predictions for the same using the
automated resummation program CAESAR. We also point to ongoing studies at HERA
which can be of benefit for future measurements at hadron colliders such as the
LHC, specifically dijet and angular spectra and the transverse momentum
of the Breit current hemisphere.Comment: 15 pages, 6 figures. Submitted to the HERA-LHC workshop proceeding
Commissioning ATLAS and CMS with top quarks
The large ttbar production cross-section at the LHC suggests the use of top
quark decays to calibrate several critical parts of the detectors, such as the
trigger system, the jet energy scale and b-tagging.Comment: 6 pages, 5 figures. Talk given at `V Workshop Italiano sulla Fisica
pp a LHC', Perugia, Italy, 30 January - 2 February 200
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