209420918
Muon reconstruction and identification with the Run II D0 detector
We present an overview of the muon reconstruction and identification methods employed by the DO collaboration to analyze the Run II (2001-2011) p (p) over bar data of the Fermilab Tevatron collider at root s = 1.96 TeV. We discuss the performance of these methods, how it is measured using DO data, and how it is properly modeled by the DO simulation program. In its pseudorapidity acceptance, vertical bar eta vertical bar < 2, the muon system identifies high-p(T) muons (p(T) greater than or similar to 10 GeV) with efficiencies ranging from 72% to 89%. Muons tracks are reconstructed in the DO central tracking system with efficiencies ranging from 85% to 92% and with a typical relative momentum resolution of 10% for p(T) = 40 GeV. Isolation criteria reject multijet background with efficiencies of 87-99%.
12420090
Observation and properties of the orbitally excited B_(s2)(*) meson.
We report the direct observation of the excited L=1 state B_(s2)(*) in fully reconstructed decays to B+K-. The mass of the B_(s2)(*) meson is measured to be 5839.6+/-1.1(stat)+/-0.7(syst) MeV/c(2), and its production rate relative to the B+ meson is measured to be [1.15+/-0.23(stat)+/-0.13(syst)]%.
208869198
Measurement of angular correlations of jets at s=1.96 TeV and determination of the strong coupling at high momentum transfers
We present a measurement of the average value of a new observable at hadron colliders that is sensitive to QCD dynamics and to the strong coupling constant, while being only weakly sensitive to parton distribution functions. The observable measures the angular correlations of jets and is defined as the number of neighboring jets above a given transverse momentum threshold which accompany a given jet within a given distance Delta-R in the plane of rapidity and azimuthal angle. The ensemble average over all jets in an inclusive jet sample is measured and the results are presented as a function of transverse momentum of the inclusive jets, in different regions of Delta-R and for different transverse momentum requirements for the neighboring jets. The measurement is based on a data set corresponding to an integrated luminosity of 0.7 fb-1 collected with the D0 detector at the Fermilab Tevatron Collider in pp-bar collisions at sqrt(s)=1.96 The results are well described by a perturbative QCD calculation in next-to-leading order in the strong coupling constant, corrected for non-perturbative effects. From these results, we extract the strong coupling and test the QCD predictions for its running over a range of momentum transfers of 50-400 GeV.
12834301
Jet energy scale determination in the D0 experiment
The calibration of jet energy measured in the DO detector is presented, based on p (p) over bar collisions at a center-of-mass energy of 1.96 TeV at the Fermilab Tevatron collider, jet energies are measured using a sampling calorimeter composed of uranium and liquid argon as the passive and active media, respectively. This paper describes the energy calibration of jets performed with gamma+jet, Z+jet and dilet events, with jet transverse momentum p(T) > 6 GeV and pseudorapidity range vertical bar eta vertical bar < 3.6, The corrections are measured separately for data and simulation, achieving a precision of 1.4-1.8% for jets in the central part of the calorimeter ancl up to 3.5% for the jets with pseudorapidity vertical bar eta vertical bar = 3.0. Specific corrections are extracted to enhance the description of jet energy in simulation and in particular of the effects due to the flavor of the parton originating the jet, correcting biases up to 3-4% in jets with low PT originating from gluons and up to 6-8% in jets from b quarks. Published by Elsevier B.V.
15350493
Search for long-lived particles decaying into electron or photon pairs with the D0 detector.
In this Letter we report on a search for long-lived particles that decay into final states with two electrons or photons. Such long-lived particles arise in a variety of theoretical models, such as hidden valleys and supersymmetry with gauge-mediated breaking. By precisely reconstructing the direction of the electromagnetic shower we are able to probe much longer lifetimes than previously explored. We see no evidence of the existence of such long-lived particles and interpret this search as a quasi model-independent limit on their production cross section, as well as a limit on a long-lived fourth generation quark.
195944
Precision measurement of the top quark mass in lepton + jets final States.
We measure the mass of the top quark in lepton+jets final states using the full sample of pp collision data collected by the D0 experiment in Run II of the Fermilab Tevatron Collider at sqrt[s] = 1.96 TeV, corresponding to 9.7 fb(-1) of integrated luminosity. We use a matrix element technique that calculates the probabilities for each event to result from tt production or background. The overall jet energy scale is constrained in situ by the mass of the W boson. We measure m(t) = 174.98 ± 0.76 GeV. This constitutes the most precise single measurement of the top-quark mass.
15694618
Open N=2 strings in a B-field background and noncommutative self-dual Yang–Mills
Abstract In the presence of D-branes, fermionic N =2 strings in 2+2 dimensions can be coupled to a Kahler NS–NS two-form B . We present the corresponding action which produces N =2 supersymmetric boundary conditions and discuss the Seiberg–Witten zero-slope limit. After recalling the constraints on the Chan–Paton gauge group, we demonstrate for U ( n ) groups that the open N =2 string with a nonzero B -field coincides on tree level with noncommutative self-dual Yang–Mills. Several misconceptions of hep-th/0011206 are corrected.
18716315
On the integrability of covariant field theory for open N=2 strings
Abstract We discuss the integrability of the Berkovits–Siegel open string field equations and derive an infinite set of their non-local (solution-generating) symmetries. The string field equations are embedded in an infinite system of overdetermined equations (BS hierarchy) associated with hidden string symmetries. The latter enforce the vanishing of most scattering amplitudes for the open N =2 string.
16752674
Non-Abelian Vortices, Super Yang–Mills Theory and Spin(7)-Instantons
We consider a complex vector bundle $${\mathcal{E}}$$ endowed with a connection $${\mathcal{A}}$$ over the eight-dimensional manifold $${\mathbb{R}^2\times G/H}$$, where G/H = SU(3)/U(1) × U(1) is a homogeneous space provided with a never-integrable almost-complex structure and a family of SU(3)-structures. We establish an equivalence between G-invariant solutions $${\mathcal{A}}$$ of the Spin(7)-instanton equations on $${\mathbb{R}^2\times G/H}$$ and general solutions of non-Abelian coupled vortex equations on $${\mathbb{R}^2}$$. These vortices are BPS solitons in a d = 4 gauge theory obtained from $${\mathcal{N} =1}$$ supersymmetric Yang–Mills theory in ten dimensions compactified on the coset space G/H with an SU(3)-structure. The novelty of the obtained vortex equations lies in the fact that Higgs fields, defining morphisms of vector bundles over $${\mathbb{R}^2}$$, are not holomorphic in the generic case. Finally, we introduce BPS vortex equations in $${\mathcal{N} =4}$$ super Yang–Mills theory and show that they have the same feature.
15062455
Supertwistors and cubic string field theory for open N=2 strings
Abstract The known Lorentz invariant string field theory for open N = 2 strings is combined with a generalization of the twistor description of anti-self-dual (super-)Yang–Mills theories. We introduce a Chern–Simons-type Lagrangian containing twistor variables and derive the Berkovits–Siegel covariant string field equations of motion via the twistor correspondence. Both the purely bosonic and the maximally space–time supersymmetric cases are considered.
117994569
Hyperbolic strings, bosonized ghosts, and fermions