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## Differential cross section measurements for the production of a W boson in association with jets in proton–proton collisions at √s=7 eV

Fonte: Universidade Rice
Publicador: Universidade Rice

Tipo: Artigo de Revista Científica

Português

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Measurements are reported of differential cross sections for the production of a W boson, which decays into a muon and a neutrino, in association with jets, as a function of several variables, including the transverse momenta (pT) and pseudorapidities of the four leading jets, the scalar sum of jet transverse momenta (HT), and the difference in azimuthal angle between the directions of each jet and the muon. The data sample of pp collisions at a centre-of-mass energy of 7 TeV was collected with the CMS detector at the LHC and corresponds to an integrated luminosity of 5.0 fb−1. The measured cross sections are compared to predictions from Monte Carlo generators, MADGRAPH + PYTHIA and SHERPA, and to next-to-leading-order calculations from BLACKHAT + SHERPA. The differential cross sections are found to be in agreement with the predictions, apart from the pT distributions of the leading jets at high pT values, the distributions of the HT at high-HT and low jet multiplicity, and the distribution of the difference in azimuthal angle between the leading jet and the muon at low values.

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## Study of jets produced in association with a W boson in pp collisions at √s=7TeV with the ATLAS detector

Fonte: Universidade Autônoma de Madrid
Publicador: Universidade Autônoma de Madrid

Tipo: Artigo de Revista Científica

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Artículo escrito por muchos autores, sólo se referencian el primero, los autores que firman como Universidad Autónoma de Madrid y el grupo de colaboración en el caso de que aparezca en el artículo; We report a study of final states containing a W boson and hadronic jets, produced in proton-proton collisions at a center-of-mass energy of 7 TeV. The data were collected with the ATLAS detector at the CERN LHC and comprise the full 2010 data sample of 36 pb-1. Cross sections are determined using both the electron and muon decay modes of the W boson and are presented as a function of inclusive jet multiplicity, Njet, for up to five jets. At each multiplicity, cross sections are presented as a function of jet transverse momentum, the scalar sum of the transverse momenta of the charged lepton, missing transverse momentum, and all jets, the invariant mass spectra of jets, and the rapidity distributions of various combinations of leptons and final-state jets. The results, corrected for all detector effects and for all backgrounds such as diboson and top quark pair production, are compared with particle-level predictions from perturbative QCD. Leading-order multiparton event generators, normalized to the next-to-next-to-leading-order total cross section for inclusive W-boson production...

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## Differential cross section measurements for the production of a W boson in association with jets in proton-proton collisions at √s=7 TeV

Fonte: Elsevier B.V.
Publicador: Elsevier B.V.

Tipo: Artigo de Revista Científica
Formato: 12-37

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Measurements are reported of differential cross sections for the production of a W boson, which decays into a muon and a neutrino, in association with jets, as a function of several variables, including the transverse momenta (p(T)) and pseudorapidities of the four leading jets, the scalar sum of jet transverse momenta (H-T), and the difference in azimuthal angle between the directions of each jet and the muon. The data sample of pp collisions at a centre-of-mass energy of 7 TeV was collected with the CMS detector at the LHC and corresponds to an integrated luminosity of 5.0 fb (1). The measured cross sections are compared to predictions from Monte Carlo generators, MADGRAPH + PYTHIA and SHERPA, and to next-to-leading-order calculations from BLACKHAT + SHERPA. The differential cross sections are found to be in agreement with the predictions, apart from the p(T) distributions of the leading jets at high p(T) values, the distributions of the H-T at high-H-T and low jet multiplicity, and the distribution of the difference in azimuthal angle between the leading jet and the muon at low values. (C) 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/3.0/).

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## Chris Eagle: Attacking Obfuscated Code with IDA Pro-(Partial Japanese)

Fonte: Escola de Pós-Graduação Naval
Publicador: Escola de Pós-Graduação Naval

Tipo: Áudio

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#Black Hat#BlackHat#Blackhat#BriefingsBlackhat#Briefings and Training#Blackhat Japan#2004#Chris Eagle#Computers#Hacking#Computers

Virtually every virus and worm that circulates the Internet today is ""protected"" by some form of obfuscation that hides the code's true intent. In the Window's world where worms prevail, the use of tools such as UPX, ASPack, and teLock has become standard. Protection of malicious code is not the only goal of binary obfuscators however which can be used to protect intellectual property. In the Linux world, tools such as Burneye and Shiva exist which can be used in ways similar to any Window's obfuscation tool. To fight such methods, analysts have created specific tools or techniques for unraveling these code obfuscators in order to reveal the software within. To date, in the fight against malware, anti-virus vendors have had the luxury of focusing on signature development since obfuscation of malware has presented little challenge. To combat this, malware authors are rapidly morphing their code in order to evade quickly developed and deployed signature-matching routines. What will happen when malware authors begin to morph their obfuscation techniques as rapidly as they morph their worms? While not designed specifically as a malware protection tool, one program, Shiva, aims to do exactly that. Shiva forces analysis of malicious code to be delayed while analysts fight through each novel mutation of Shiva's obfuscation mechanism. This...

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## Vector Boson + Jets with BlackHat and Sherpa

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 20/05/2010
Português

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We review recent NLO QCD results for W,Z + 3-jet production at hadron
colliders, computed using BlackHat and SHERPA. We also include some new results
for Z + 3-jet production at the LHC at 7 TeV. We report new progress towards
the NLO cross section for W + 4-jet production. In particular, we show that the
virtual matrix elements produced by BlackHat are numerically stable. We also
show that with an improved integrator and tree-level matrix elements from
BlackHat, SHERPA produces well-behaved real-emission contributions. As an
illustration, we present the real-emission contributions -- including
dipole-subtraction terms -- to the p_T distribution of the fourth jet, for a
single subprocess with the maximum number of gluons.; Comment: 6 pages, 4 figures, presented at Loops and Legs 2010

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## Differential cross section measurements for the production of a W boson in association with jets in proton-proton collisions at sqrt(s) = 7 TeV

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Português

Relevância na Pesquisa

16.777803%

Measurements are reported of differential cross sections for the production
of a W boson, which decays into a muon and a neutrino, in association with
jets, as a function of several variables, including the transverse momenta (pt)
and pseudorapidities of the four leading jets, the scalar sum of jet transverse
momenta (HT), and the difference in azimuthal angle between the directions of
each jet and the muon. The data sample of pp collisions at a centre-of-mass
energy of 7 TeV was collected with the CMS detector at the LHC and corresponds
to an integrated luminosity of 5.0 inverse femtobarns. The measured cross
sections are compared to predictions from Monte Carlo generators, MADGRAPH +
PYTHIA and SHERPA, and to next-to-leading-order calculations from BLACKHAT +
SHERPA. The differential cross sections are found to be in agreement with the
predictions, apart from the pt distributions of the leading jets at high pt
values, the distributions of the HT at high-HT and low jet multiplicity, and
the distribution of the difference in azimuthal angle between the leading jet
and the muon at low values.; Comment: Replaced with published version. Added journal reference and DOI

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## Next-to-Leading Order Jet Physics with BlackHat

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Português

Relevância na Pesquisa

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We present several results obtained using the BlackHat next-to-leading order
QCD program library, in conjunction with SHERPA. In particular, we present
distributions for vector boson plus 1,2,3-jet production at the Tevatron and at
the asymptotic running energy of the Large Hadron Collider, including new
Z+3-jet distributions. The Z+2-jet predictions for the second-jet P_T
distribution are compared to CDF data. We present the jet-emission probability
at NLO in W+2-jet events at the LHC, where the tagging jets are taken to be the
ones furthest apart in pseudorapidity. We analyze further the large left-handed
W polarization, identified in our previous study, for W bosons produced at high
P_T at the LHC.; Comment: Presented at RADCOR 2009 - 9th International Symposium on Radiative
Corrections (Applications of Quantum Field Theory to Phenomenology), October
25 - 30 2009, Ascona, Switzerland}, 12 pages, 9 figures, LaTeX, v2 updated
small correction to polarization effect plot

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## Next-to-Leading Order Gamma Gamma + 2-Jet Production at the LHC

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 17/02/2014
Português

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We present next-to-leading order QCD predictions for cross sections and for a
comprehensive set of distributions in diphoton + 2-jet production at the Large
Hadron Collider. We consider the contributions from loop amplitudes for two
photons and four gluons, but we neglect top quarks. We use BlackHat together
with SHERPA to carry out the computation. We use a Frixione cone isolation for
the photons. We study standard sets of cuts on the jets and the photons, and
also sets of cuts appropriate for studying backgrounds to Higgs-boson
production via vector-boson fusion.; Comment: RevTex, 20 figures, 16 tables

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## Next-to-Leading Order QCD Predictions for W+3-Jet Distributions at Hadron Colliders

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Português

Relevância na Pesquisa

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We present next-to-leading order QCD predictions for a variety of
distributions in W+3-jet production at both the Tevatron and the Large Hadron
Collider. We include all subprocesses and incorporate the decay of the W boson
into leptons. Our results are in excellent agreement with existing Tevatron
data and provide the first quantitatively precise next-to-leading order
predictions for the LHC. We include all terms in an expansion in the number of
colors, confirming that the specific leading-color approximation used in our
previous study is accurate to within three percent. The dependence of the cross
section on renormalization and factorization scales is reduced significantly
with respect to a leading-order calculation. We study different dynamical scale
choices, and find that the total transverse energy is significantly better than
choices used in previous phenomenological studies. We compute the one-loop
matrix elements using on-shell methods, as numerically implemented in the
BlackHat code. The remaining parts of the calculation, including generation of
the real-emission contributions and integration over phase space, are handled
by the SHERPA package.; Comment: 64 pages, 37 figures, v2 minor changes in table X, cross sections and
distributions unaffected; other minor corrections to text...

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## Four-Jet Production at the Large Hadron Collider at Next-to-Leading Order in QCD

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Português

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We present the cross sections for production of up to four jets at the Large
Hadron Collider, at next-to-leading order in the QCD coupling. We use the
BlackHat library in conjunction with SHERPA and a recently developed algorithm
for assembling primitive amplitudes into color-dressed amplitudes. We adopt the
cuts used by ATLAS in their study of multi-jet events in pp collisions at
\sqrt{s} = 7 TeV. We include estimates of nonperturbative corrections and
compare to ATLAS data. We store intermediate results in a framework that allows
the inexpensive computation of additional results for different choices of
scale or parton distributions.; Comment: 5 pages, 2 figures, 2 tables. v2: references added, additional
discussion of scale and PDF uncertainties, other minor clarifications

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## Next-to-Leading Order W + 5-Jet Production at the LHC

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Português

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We present next-to-leading order QCD predictions for the total cross section
and for a comprehensive set of transverse-momentum distributions in W + 5-jet
production at the Large Hadron Collider. We neglect the small contributions
from subleading-color virtual terms, top quarks and some terms containing four
quark pairs. We also present ratios of total cross sections, and use them to
obtain an extrapolation formula to an even larger number of jets. We include
the decay of the $W$ boson into leptons. This is the first such computation
with six final-state vector bosons or jets. We use BlackHat together with
SHERPA to carry out the computation.; Comment: RevTex, 27 pages, 7 figures, v2 minor corrections and corrected
references

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## One-Loop Multi-Parton Amplitudes with a Vector Boson for the LHC

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 07/08/2008
Português

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In this talk, we present the first, numerically stable, results for the
one-loop amplitudes needed for computing W,Z + 3 jet cross sections at the LHC
to next-to-leading order in the QCD coupling. We implemented these processes in
BlackHat, an automated program based on on-shell methods. These methods scale
very well with increasing numbers of external partons, and are applicable to a
wide variety of problems of phenomenological interest at the LHC.; Comment: Parallel talk in QCD session of the 34th International Conference on
High Energy Physics, Philadelphia, USA, July 2008. 4 pages, LaTeX, 3 eps
figures

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## NLO vector boson production with light jets

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 25/01/2012
Português

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In this contribution we present recent progress in the computation of
next-to-leading order (NLO) QCD corrections for the production of an
electroweak vector boson in association with jets at hadron colliders. We focus
on results obtained using the virtual matrix element library BLACKHAT in
conjunction with SHERPA, focusing on results relevant to understanding the
background to top production.; Comment: 4+2 epsilon pages, Submitted for the proceedings of TOP2011 - 4th
International Workshop on Top Quark Physics, 25-30th September 2011, Sant
Feliu de Guixols, Spain

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## Precise Predictions for W + 4 Jet Production at the Large Hadron Collider

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Português

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We present the first next-to-leading order QCD results for W + 4-jet
production at hadron colliders. Total cross sections, as well as distributions
in the jet transverse momenta and in the total transverse energy H_T are
provided for the initial LHC energy of \sqrt{s} = 7 TeV. We use a leading-color
approximation, known to be accurate to 3% for W production with fewer jets. The
virtual matrix elements and the most complicated real-emission matrix elements
are handled by the BlackHat library, based on on-shell methods. The remaining
parts of the calculation, including the integration over phase space, are
performed by the SHERPA package.; Comment: 5 pages, 3 figures, 2 tables. v2: W^+ + 4 jets NLO results added,
plus minor typo corrections

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## One-Loop Calculations with BlackHat

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 23/07/2008
Português

Relevância na Pesquisa

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We describe BlackHat, an automated C++ program for calculating one-loop
amplitudes, and the techniques used in its construction. These include the
unitarity method and on-shell recursion. The other ingredients are compact
analytic formulae for tree amplitudes for four-dimensional helicity states. The
program computes amplitudes numerically, using analytic formulae only for the
tree amplitudes, the starting point for the recursion, and the loop integrals.
We make use of recently developed on-shell methods for evaluating coefficients
of loop integrals, in particular a discrete Fourier projection as a means of
improving numerical stability. We illustrate the good numerical stability of
this approach by computing six-, seven- and eight-gluon amplitudes in QCD and
comparing against known analytic results.; Comment: To appear in the proceedings of 9th Workshop on Elementary Particle
Theory: Loops and Legs in Quantum Field Theory, Sondershausen, Germany, 20-25
Apr 2008

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## High multiplicity processes at NLO with BlackHat and Sherpa

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 24/10/2012
Português

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In this contribution we review recent progress with fixed-order QCD
predictions for the production of a vector boson in association with jets at
hadron colliders, using the programs BlackHat and SHERPA. We review general
features of next-to-leading-order (NLO) predictions for the production of a
massive vector boson in association with four jets. We also discuss how precise
descriptions of vector-boson production can be applied to the determination of
backgrounds to new physics signals. Here we focus on data-driven backgrounds to
a missing-energy-plus-jets search performed by CMS. Finally, we review recent
progress in developing theoretical tools for high-multiplicity loop-computation
within the BlackHat-library. In particular, we discuss methods for handling the
color degrees of freedom in multi-jet predictions at NLO.; Comment: 12 pages, contribution to the proceedings of Loops and Legs 2012

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## Precise Predictions for W + 3 Jet Production at Hadron Colliders

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Português

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We report on the first next-to-leading order QCD computation of W + 3-jet
production in hadronic collisions including all partonic subprocesses. We
compare the results with CDF data from the Tevatron, and find excellent
agreement. The renormalization and factorization scale dependence is reduced
substantially compared to leading-order calculations. The required one-loop
matrix elements are computed using on-shell methods, implemented in a numerical
program, BlackHat. We use the SHERPA package to generate the real-emission
contributions and to integrate the various contributions over phase space. We
use a leading-color (large-N_c) approximation for the virtual part, which we
confirm in W + 1,2-jet production to be valid to within three percent. The
present calculation demonstrates the utility of on-shell methods for computing
next-to-leading-order corrections to processes important to physics analyses at
the Large Hadron Collider.; Comment: 5 pages, 3 figures, RevTex, v3 small change in values, no changes in
conclusions

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## The BlackHat Library for One-Loop Amplitudes

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Português

Relevância na Pesquisa

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We present recent next-to-leading order (NLO) results in perturbative QCD
obtained using the BlackHat software library. We discuss the use of n-tuples to
separate the lengthy matrix-element computations from the analysis process. The
use of n-tuples allows many analyses to be carried out on the same phase-space
samples, and also allows experimenters to conduct their own analyses using the
original NLO computation.; Comment: Talk given at ACAT 2013, Beijing, China, May 16--21, 2013; 6 pages, 2
figures; added references

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## An Automated Implementation of On-Shell Methods for One-Loop Amplitudes

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 28/03/2008
Português

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We present the first results from BlackHat, an automated C++ program for
calculating one-loop amplitudes. The program implements the unitarity method
and on-shell recursion to construct amplitudes. As input to the calculation, it
uses compact analytic formulae for tree amplitudes for four-dimensional
helicity states. The program performs all related computations numerically. We
make use of recently developed on-shell methods for evaluating coefficients of
loop integrals, introducing a discrete Fourier projection as a means of
improving efficiency and numerical stability. We illustrate the numerical
stability of our approach by computing and analyzing six-, seven- and
eight-gluon amplitudes in QCD and comparing against previously-obtained
analytic results.; Comment: 38 pages, 10 figures, RevTex

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## Multi-jet cross sections at NLO with BlackHat and Sherpa

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 17/05/2009
Português

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In this talk, we report on a recent next-to-leading order QCD calculation of
the production of a W boson in association with three jets at hadron colliders.
The computation is performed by combining two programs, BlackHat for the
computation of the virtual one-loop matrix elements and Sherpa for the real
emission part.; Comment: 4 pages, contribution to the proceedings of the XLIIIth Rencontres de
Moriond (QCD)

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