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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

CMS Collaboration; Adair, A.; Akgun, B.; Ecklund, K.M.; Geurts, F.J.M.; Li, W.; Michlin, B.; Padley, B.P.; Redjimi, R.; Roberts, J.; Zabel, J.
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.

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

Aad, G.; Barreiro, F.; Cantero, J.; De la Torre, H.; Del Peso, J.; Glasman, C.; Labarga, L.; Llorente Merino, J.; March, L.; Nebot, E.; Terrón, J.; ATLAS Collaboration
Tipo: Artigo de Revista Científica
Português
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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...

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

Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A. .; Adam, W.; Bergauer, T.; Dragicevic, M.; Eroe, J.; Fabjan, C.; Friedl, M.; Fruehwirth, R.; Ghete, V. M.; Hartl, C.; Hoermann, N.; Hrubec, J.; Jeitler, M.; Kiesenhofer, W.; Knuenz, V.; Krammer, M.; Kraetschm
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/).

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

Eagle, Chris
Tipo: Áudio
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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...

## Vector Boson + Jets with BlackHat and Sherpa

Berger, C. F.; Bern, Z.; Dixon, L. J.; Cordero, F. Febres; Forde, D.; Gleisberg, T.; Ita, H.; Kosower, D. A.; Maitre, D.
Tipo: Artigo de Revista Científica
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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

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

CMS Collaboration
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

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

Berger, C. F.; Bern, Z.; Dixon, L. J.; Cordero, F. Febres; Forde, D.; Gleisberg, T.; Ita, H.; Kosower, D. A.; Maitre, D.
Tipo: Artigo de Revista Científica
Português
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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

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

Bern, Z.; Dixon, L. J.; Cordero, F. Febres; Hoeche, S.; Ita, H.; Kosower, D. A.; Presti, N. A. Lo; Maitre, D.
Tipo: Artigo de Revista Científica
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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

Berger, C. F.; Bern, Z.; Dixon, L. J.; Cordero, F. Febres; Forde, D.; Gleisberg, T.; Ita, H.; Kosower, D. A.; Maitre, D.
Tipo: Artigo de Revista Científica
Português
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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...

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

Bern, Z.; Diana, G.; Dixon, L. J.; Cordero, F. Febres; Hoeche, S.; Kosower, D. A.; Ita, H.; Maitre, D.; Ozeren, K.
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

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

Bern, Z.; Dixon, L. J.; Cordero, F. Febres; Hoeche, S.; Ita, H.; Kosower, D. A.; Maitre, D.; Ozeren, K. J.
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

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

Berger, C. F.; Bern, Z.; Dixon, L. J.; Cordero, F. Febres; Forde, D.; Ita, H.; Kosower, D. A.; Maitre, D.
Tipo: Artigo de Revista Científica
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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

## NLO vector boson production with light jets

Bern, Z.; Diana, G.; Dixon, L. J.; Cordero, F. Febres; Forde, D.; Gleisberg, T.; Hoeche, S.; Ita, H.; Kosower, D. A.; Maitre, D.; Ozeren, K.
Tipo: Artigo de Revista Científica
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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

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

Berger, C. F.; Bern, Z.; Dixon, L. J.; Cordero, F. Febres; Forde, D.; Gleisberg, T.; Ita, H.; Kosower, D. A.; Maitre, D.
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

## One-Loop Calculations with BlackHat

Berger, C. F.; Bern, Z.; Dixon, L. J.; Cordero, F. Febres; Forde, D.; Ita, H.; Kosower, D. A.; Maitre, D.
Tipo: Artigo de Revista Científica
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

## High multiplicity processes at NLO with BlackHat and Sherpa

Bern, Zvi; Ozeren, Kemal; Dixon, Lance J.; Hoeche, Stefan; Cordero, Fernando Febres; Ita, Harald; Kosower, David; Maître, Daniel
Tipo: Artigo de Revista Científica
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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

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

Berger, C. F.; Bern, Z.; Dixon, L. J.; Cordero, F. Febres; Forde, D.; Gleisberg, T.; Ita, H.; Kosower, D. A.; Maitre, D.
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

## The BlackHat Library for One-Loop Amplitudes

Bern, Z.; Dixon, L. J.; Cordero, F. Febres; Hoeche, S.; Ita, H.; Kosower, D. A.; Maitre, D.; Ozeren, K. J.
Tipo: Artigo de Revista Científica
Português
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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

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

Berger, C. F.; Bern, Z.; Dixon, L. J.; Cordero, F. Febres; Forde, D.; Ita, H.; Kosower, D. A.; Maitre, D.
Tipo: Artigo de Revista Científica