Electroweak and QCD Results from DO

We present some of the results in the areas of QCD and Electroweak physics for Run II of the DO experiment at the Fermilab Tevatron. QCD results include dijet angular decorrelations and inclusive jet and dijet cross sections. Electroweak results include the decay of Z bosons to tau pairs and several results on gauge boson pairs. No deviations from the Standard Model have been observed.Comment: 5 pages, 7 figures, to appear in the Proceedings of the 2005 Lake Louise Winter Institut

EtherAnnotate: a transparent malware analysis tool for integrating dynamic and static examination

Software security researchers commonly reverse engineer and analyze current malicious software (malware) to determine what the latest techniques malicious attackers are utilizing and how to protect computer systems from attack. The most common analysis methods involve examining how the program behaves during execution and interpreting its machine-level instructions. However, modern malicious applications use advanced anti-debugger, anti-virtualization, and code packing techniques to obfuscate the malware\u27s true activities and divert security analysts. Malware analysts currently do not have a simple method for tracing malicious code activity at the instruction-level in a highly undetectable environment. There also lacks a simple method for combining actual run-time register and memory values with statically disassembled code. Combining statically disassembled code with the run-time values found in the memory and registers being accessed would create a new level of analysis possible by combining key aspects of static analysis with dynamic analysis. This thesis presents EtherAnnotate, a new extension to the Xen Ether virtualization framework and the IDA Pro disassembler to aid in the task of malicious software analysis. This new extension consists of two separate components - an enhanced instruction tracer and a graphical annotation and visualization plug-in for IDA Pro. The specialized instruction tracer places a malware binary into a virtualized environment and records the contents of all processor general register values that occur during its execution. The annotation plug-in for IDA Pro interprets the output of the instruction tracer and adds line comments of the register values in addition to visualizing code coverage of all disassembled instructions that were executed during the malware\u27s execution. These two tools can be combined to provide a new level of introspection for advanced malware that was not available with the previous state-of-the-art analysis tools --Abstract, page iii

Wy Production and Limits on Anomalous WWy Couplings in pp̅ Collisions √s = 1.96 TeV

We measure the cross section and the difference in rapidities between photons and charged leptons for inclusive W(→ lv) + y production in ey and µy final states. Using data corresponding to an integrated luminosity of 4.2 fb-1 collected with the D0 detector at the Fermilab Tevatron Collider, the measured cross section times branching fraction for the process pp̅ → Wy + X → lvy + X and the distribution of the charge-signed photon-lepton rapidity difference are found to be in agreement with the standard model. These results provide the most stringent limits on anomalous WW[1] couplings for data from hadron colliders: -0.4 \u3c ∆ky \u3c 0.4 and -0.08 \u3c λy \u3c 0.07 at the 95% C.L

Wy Production and Limits on Anomalous WWy Couplings in pp̅ Collisions √s = 1.96 TeV

We measure the cross section and the difference in rapidities between photons and charged leptons for inclusive W(→ lv) + y production in ey and µy final states. Using data corresponding to an integrated luminosity of 4.2 fb-1 collected with the D0 detector at the Fermilab Tevatron Collider, the measured cross section times branching fraction for the process pp̅ → Wy + X → lvy + X and the distribution of the charge-signed photon-lepton rapidity difference are found to be in agreement with the standard model. These results provide the most stringent limits on anomalous WW[1] couplings for data from hadron colliders: -0.4 \u3c ∆ky \u3c 0.4 and -0.08 \u3c λy \u3c 0.07 at the 95% C.L

Search for a Fermiophobic and Standard Model Higgs Boson in Diphoton Final States

We present a search for the standard model Higgs boson and a fermiophobic Higgs boson in the diphoton final states based on 8.2 fb-1 of pp̅ collisions at √s= 1.96 TeV collected with the D0 detector at the Fermilab Tevatron Collider. No excess of data above background predictions is observed and upper limits at the 95% C.L. on the cross section multiplied by the branching fraction are set which are the most restrictive to date. A fermiophobic Higgs boson with a mass below 112.9 GeV is excluded at the 95% C.L

Search for a Fourth Generation tl Quark in pp̅ Collisions at √s= 1.96 TeV

We present a search for pair production of a fourth generation tl quark and its antiparticle, followed by their decays to a W boson and a jet, based on an integrated luminosity of 5.3 fb-1 of proton-antiproton collisions at √s= 1.96 TeV collected by the D0 Collaboration at the Fermilab Tevatron Collider. We set upper limits on the tlt-l production cross section that exclude at the 95% C.L. a tl quark that decays exclusively to W + jet with a mass below 285 GeV. We observe a small excess in the µ + jets channel which reduces the mass range excluded compared to the expected limit of 320 GeV in the absence of a signal

Direct measurement of the mass difference between top and antitop quarks

We present a direct measurement of the mass difference between top and antitop quarks (∆m) in lepton + jets tt final states using the ‘‘matrix element’’ method. The purity of the lepton + jets sample is enhanced for tt events by identifying at least one of the jets as originating from a b quark. The analyzed data correspond to 3.6 fb-1 of pp collisions at √s = 1.96 TeV acquired by D0 in Run II of the Fermilab Tevatron Collider. The combination of the e + jets and µ + jets channels yields ∆m =0.8 ± 1,8 stat ± 0.5(syst) GeV, which is in agreement with the standard model expectation of no mass difference

Search for associated Higgs boson production using like charge dilepton events in pp̅ collisions at √s= 1.96 TeV

We present a search for associated Higgs boson production in the process pp̅ → W / ZH → l±l± + X in ee, eµ, and µµ final states. The search is based on data collected by the D0 experiment at the Fermilab Tevatron Collider at √s = 1.96 TeV corresponding to 5.3 fb-1 of integrated luminosity. We require two isolated leptons (electrons or muons) with the same electric charge and additional kinematic requirements. No significant excess above background is observed, and we set 95% C.L. observed (expected) upper limits on ratio of the production cross section to the standard model prediction of 6.4 (7.3) for a Higgs boson mass of 165 GeV and 13.5 (19.8) for a mass of 115 GeV

Measurement of the inclusive jet cross section in pp̅ collisions at √s= 1.96 TeV

We present a measurement of the inclusive jet cross section using the Run II cone algorithm and data collected by the D0 experiment in pp̅ collisions at a center-of-mass energy √s= 1.96 TeV, corresponding to an integrated luminosity of 0.70 fb-1. The jet energy calibration and the method used to extract the inclusive jet cross section are described.We discuss the main uncertainties, which are dominated by the jet energy scale uncertainty. The results cover jet transverse momenta from 50 GeV to 600 GeV with jet rapidities in the range -2.4 to 2.4 and are compared to predictions using recent proton parton distribution functions. Studies of correlations between systematic uncertainties in transverse momentum and rapidity are presented

Search for New Physics with a Monojet and Missing Transverse Energy in pp Collisions at √s= 7 TeV

A study of events with missing transverse energy and an energetic jet is performed using pp collision data at a center-of-mass energy of 7 TeV. The data were collected by the CMS detector at the LHC, and correspond to an integrated luminosity of 36 pb-1. An excess of these events over standard model contributions is a signature of new physics such as large extra dimensions and unparticles. The number of observed events is in good agreement with the prediction of the standard model, and significant extension of the current limits on parameters of new physics benchmark models is achieved