233 research outputs found
Boosted Higgs in vector-boson associated production at 14 TeV
The production of the Standard Model Higgs boson in association with a vector
boson, followed by the dominant decay to , is a strong
prospect for confirming and measuring the coupling to -quarks in
collisions at TeV. We present an updated study of the prospects
for this analysis, focussing on the most sensitive highly Lorentz-boosted
region. The evolution of the efficiency and composition of the signal and main
background processes as a function of the transverse momentum of the vector
boson are studied covering the region GeV, comparing both a
conventional dijet and jet substructure selection. The lower transverse
momentum region ( GeV) is identified as the most sensitive region for
the Standard Model search, with higher transverse momentum regions not
improving the statistical sensitivity. For much of the studied region
( GeV), a conventional dijet selection performs as well as the
substructure approach, while for the highest transverse momentum regions ( GeV), which are particularly interesting for Beyond the Standard Model and
high luminosity measurements, the jet substructure techniques are essential.Comment: 13 pages.(Fixed figure layout error
Soft interactions in Herwig++
We describe the recent developments to extend the multi-parton interaction
model of underlying events in Herwig++ into the soft, non-perturbative, regime.
This allows the program to describe also minimum bias collisions in which there
is no hard interaction, for the first time. It is publicly available from
versions 2.3 onwards and describes the Tevatron underlying event and minimum
bias data. The extrapolations to the LHC nevertheless suffer considerable
ambiguity, as we discuss.Comment: 10 pages, talk given by Manuel Bahr at First International Workshop
on Multiple Partonic Interactions at the LHC, "MPI@LHC'08", Perugia, Italy,
October 27-31 200
Discovering baryon-number violating neutralino decays at the LHC.
Recently there has been much interest in the use of single-jet mass and jet substructure to identify boosted particles decaying hadronically at the LHC. We develop these ideas to address the challenging case of a neutralino decaying to three quarks in models with baryonic violation of R parity. These decays have previously been found to be swamped by QCD backgrounds. We demonstrate for the first time that such a decay might be observed directly at the LHC with high significance, by exploiting characteristics of the scales at which its composite jet breaks up into subjets
Jet substructure as a new Higgs search channel at the LHC
It is widely considered that, for Higgs boson searches at the Large Hadron
Collider, WH and ZH production where the Higgs boson decays to b anti-b are
poor search channels due to large backgrounds. We show that at high transverse
momenta, employing state-of-the-art jet reconstruction and decomposition
techniques, these processes can be recovered as promising search channels for
the standard model Higgs boson around 120 GeV in mass.Comment: 4 pages, 3 figure
Jet substructure as a new Higgs search channel at the Large Hadron Collider
We show that W H and Z H production where the Higgs boson decays to bbbar can
be recovered as good search channels for the Standard Model Higgs at the Large
Hadron Collider. This is done by requiring the Higgs to have high transverse
momentum, and employing state-of-the-art jet reconstruction and decomposition
techniques.Comment: Talk presented by J.M.Butterworth at 34th International Conference on
High Energy Physics, ICHEP08, Philadelphia, July 200
The Underlying Event and the Total Cross Section from Tevatron to the LHC
Multiple partonic interactions are widely used to simulate the hadronic final
state in high energy hadronic collisions, and successfully describe many
features of the data. It is important to make maximum use of the available
physical constraints on such models, particularly given the large extrapolation
from current high energy data to LHC energies. In eikonal models, the rate of
multiparton interactions is coupled to the energy dependence of the total cross
section. Using a Monte Carlo implementation of such a model, we study the
connection between the total cross section, the jet cross section, and the
underlying event. By imposing internal consistency on the model, we derive
constraints on its parameters at the LHC. By imposing internal consistency on
the model and comparing to current data we constrain the allowed range of its
parameters. We show that measurements of the total proton-proton cross-section
at the LHC are likely to break this internal consistency, and thus to require
an extension of the model. Likely such extensions are that hard scatters probe
a denser matter distribution inside the proton in impact parameter space than
soft scatters, a conclusion also supported by Tevatron data on double-parton
scattering, and/or that the basic parameters of the model are energy dependent.Comment: 17 pages, 6 figures, version accepted by JHE
Reconstructing Sparticle Mass Spectra using Hadronic Decays
Most sparticle decay cascades envisaged at the Large Hadron Collider (LHC)
involve hadronic decays of intermediate particles. We use state-of-the art
techniques based on the \kt jet algorithm to reconstruct the resulting hadronic
final states for simulated LHC events in a number of benchmark supersymmetric
scenarios. In particular, we show that a general method of selecting
preferentially boosted massive particles such as W, Z or Higgs bosons decaying
to jets, using sub-jets found by the \kt algorithm, suppresses QCD backgrounds
and thereby enhances the observability of signals that would otherwise be
indistinct. Consequently, measurements of the supersymmetric mass spectrum at
the per-cent level can be obtained from cascades including the hadronic decays
of such massive intermediate bosons.Comment: 1+29 pages, 12 figure
Jet Shapes and Jet Algorithms in SCET
Jet shapes are weighted sums over the four-momenta of the constituents of a
jet and reveal details of its internal structure, potentially allowing
discrimination of its partonic origin. In this work we make predictions for
quark and gluon jet shape distributions in N-jet final states in e+e-
collisions, defined with a cone or recombination algorithm, where we measure
some jet shape observable on a subset of these jets. Using the framework of
Soft-Collinear Effective Theory, we prove a factorization theorem for jet shape
distributions and demonstrate the consistent renormalization-group running of
the functions in the factorization theorem for any number of measured and
unmeasured jets, any number of quark and gluon jets, and any angular size R of
the jets, as long as R is much smaller than the angular separation between
jets. We calculate the jet and soft functions for angularity jet shapes \tau_a
to one-loop order (O(alpha_s)) and resum a subset of the large logarithms of
\tau_a needed for next-to-leading logarithmic (NLL) accuracy for both cone and
kT-type jets. We compare our predictions for the resummed \tau_a distribution
of a quark or a gluon jet produced in a 3-jet final state in e+e- annihilation
to the output of a Monte Carlo event generator and find that the dependence on
a and R is very similar.Comment: 62 pages plus 21 pages of Appendices, 13 figures, uses JHEP3.cls. v2:
corrections to finite parts of NLO jet functions, minor changes to plots,
clarified discussion of power corrections. v3: Journal version. Introductory
sections significantly reorganized for clarity, classification of logarithmic
accuracy clarified, results for non-Mercedes-Benz configurations adde
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