22,827 research outputs found
Longest Common Extensions in Sublinear Space
The longest common extension problem (LCE problem) is to construct a data
structure for an input string of length that supports LCE
queries. Such a query returns the length of the longest common prefix of the
suffixes starting at positions and in . This classic problem has a
well-known solution that uses space and query time. In this paper
we show that for any trade-off parameter , the problem can
be solved in space and query time. This
significantly improves the previously best known time-space trade-offs, and
almost matches the best known time-space product lower bound.Comment: An extended abstract of this paper has been accepted to CPM 201
MadGraph/MadEvent v4: The New Web Generation
We present the latest developments of the MadGraph/MadEvent Monte Carlo event
generator and several applications to hadron collider physics. In the current
version events at the parton, hadron and detector level can be generated
directly from a web interface, for arbitrary processes in the Standard Model
and in several physics scenarios beyond it (HEFT, MSSM, 2HDM). The most
important additions are: a new framework for implementing user-defined new
physics models; a standalone running mode for creating and testing matrix
elements; generation of events corresponding to different processes, such as
signal(s) and backgrounds, in the same run; two platforms for data analysis,
where events are accessible at the parton, hadron and detector level; and the
generation of inclusive multi-jet samples by combining parton-level events with
parton showers. To illustrate the new capabilities of the package some
applications to hadron collider physics are presented:
1) Higgs search in pp \to H \to W^+W^-: signal and backgrounds.
2) Higgs CP properties: pp \to H jj$in the HEFT.
3) Spin of a new resonance from lepton angular distributions.
4) Single-top and Higgs associated production in a generic 2HDM.
5) Comparison of strong SUSY pair production at the SPS points.
6) Inclusive W+jets matched samples: comparison with the Tevatron data.Comment: 38 pages, 15 figure
PHOTOS Monte Carlo for precision simulation of QED in decays - History and properties of the project
Because of properties of QED, the bremsstrahlung corrections to decays of
particles or resonances can be calculated, with a good precision, separately
from other effects. Thanks to the widespread use of event records such
calculations can be embodied into a separate module of Monte Carlo simulation
chains, as used in High Energy Experiments of today. The PHOTOS Monte Carlo
program is used for this purpose since nearly 20 years now. In the following
talk let us review the main ideas and constraints which shaped the program
version of today and enabled it widespread use. We will concentrate specially
on conflicting requirements originating from the properties of QED matrix
elements on one side and degrading (evolving) with time standards of event
record(s). These issues, quite common in other modular software applications,
become more and more difficult to handle as precision requirements become
higher.Comment: Prepared for XI International Workshop on Advanced Computing and
Analysis Techniques in Physics Research, Amsterdam, the Netherlands, April 23
200
Learning How to Count: A High Multiplicity Search for the LHC
We introduce a search technique that is sensitive to a broad class of signals
with large final state multiplicities. Events are clustered into large radius
jets and jet substructure techniques are used to count the number of subjets
within each jet. The search consists of a cut on the total number of subjets in
the event as well as the summed jet mass and missing energy. Two different
techniques for counting subjets are described and expected sensitivities are
presented for eight benchmark signals. These signals exhibit diverse
phenomenology, including 2-step cascade decays, direct three body decays, and
multi-top final states. We find improved sensitivity to these signals as
compared to previous high multiplicity searches as well as a reduced reliance
on missing energy requirements. One benefit of this approach is that it allows
for natural data driven estimates of the QCD background.Comment: 36 pages, 12 Figures, 5 Tables; journal versio
Quark-gluon discrimination in the search for gluino pair production at the LHC
We study the impact of including quark- and gluon-initiated jet
discrimination in the search for strongly interacting supersymmetric particles
at the LHC. Taking the example of gluino pair production, considerable
improvement is observed in the LHC search reach on including the jet
substructure observables to the standard kinematic variables within a
multivariate analysis. In particular, quark and gluon jet separation has higher
impact in the region of intermediate mass-gap between the gluino and the
lightest neutralino, as the difference between the signal and the standard
model background kinematic distributions is reduced in this region. We also
compare the predictions from different Monte Carlo event generators to estimate
the uncertainty originating from the modelling of the parton shower and
hadronization processes.Comment: 22 pages, 8 figures, 1 table; v2: statistical treatment improved and
figures update
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