Direct measurement of the mass difference between top and antitop quarks.
We present a measurement of the mass difference between t and t[over] quarks in lepton + jets final states of tt[over] events in 1 fb;{-1} of data collected with the D0 detector from Fermilab Tevatron Collider pp[over] collisions at sqrt[s] = 1.96 TeV. The measured mass difference of 3.8 +/- 3.7 GeV is consistent with the equality of t and t[over ] masses. This is the first direct measurement of a mass difference between a quark and its antiquark partner.

title: Measurement of angular correlations of jets at s=1.96 TeV and determination of the strong coupling at high momentum transfers
abstract: 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.

title: Jet energy scale determination in the D0 experiment
abstract: 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.

title: Precision measurement of the top quark mass in lepton + jets final States.
abstract: 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.

title: Search for long-lived particles decaying into electron or photon pairs with the D0 detector.
abstract: 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.

title: Observation and properties of the orbitally excited B_(s2)(*) meson.
abstract: 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)]%.

title: Constraints, complex structures and quantization

title: Heterotic string plus five-brane systems with asymptotic $\mathrm{AdS}_3$
abstract: We present NS1+NS5-brane solutions of heterotic supergravity on curved geometries. They interpolate between a near horizon AdS3 × X k × T 7−k region and R 1,1 × c(X k ) × T 7−k , where X k (with k = 3,5,6,7) is a k-dimensional geometric Killing spinor manifold, c(X k ) its Ricciflat cone and T 7−k a (7 k)-torus. The solutions require first order � ′ -corrections to the field equations, and special point-like instantons play an important role, whose singular support is a calibrated submanifold wrapped by the NS5-brane. It is also possible to add a gauge anti-5brane. We determine the super isometries of the near horizon geometry which are supposed to appear as symmetries of the holographically dual two-dimensional conformal field theory.

title: Explicit non-Abelian monopoles and instantons in SU ( N ) pure Yang-Mills theory
abstract: It is well known that there are no static non-Abelian monopole solutions in pure Yang-Mills theory on Minkowski space ${\mathbb{R}}^{3,1}$. I show that such solutions exist in $\mathrm{SU}(N)$ gauge theory on the spaces ${\mathbb{R}}^{2}\ifmmode\times\else\texttimes\fi{}{S}^{2}$ and $\mathbb{R}\ifmmode\times\else\texttimes\fi{}{S}^{1}\ifmmode\times\else\texttimes\fi{}{S}^{2}$ with Minkowski signature $(\ensuremath{-}+++)$. In the temporal gauge they are solutions of pure Yang-Mills theory on $\mathbb{T}\ifmmode\times\else\texttimes\fi{}{S}^{2}$, where $\mathbb{T}$ is $\mathbb{R}$ or ${S}^{1}$. Namely, imposing SO(3) invariance and some reality conditions, I consistently reduce the Yang-Mills model on the above spaces to a non-Abelian analog of the ${\ensuremath{\phi}}^{4}$ kink model whose static solutions give $\mathrm{SU}(N)$ monopole (-antimonopole) configurations on the space ${\mathbb{R}}^{1,1}\ifmmode\times\else\texttimes\fi{}{S}^{2}$ via the above-mentioned correspondence. These solutions can also be considered as instanton configurations of Yang-Mills theory in $2+1$ dimensions. The kink model on $\mathbb{R}\ifmmode\times\else\texttimes\fi{}{S}^{1}$ admits also periodic sphaleron-type solutions describing chains of $n$ kink-antikink pairs spaced around the circle ${S}^{1}$ with arbitrary $ng0$. They correspond to chains of $n$ static monopole-antimonopole pairs on the space $\mathbb{R}\ifmmode\times\else\texttimes\fi{}{S}^{1}\ifmmode\times\else\texttimes\fi{}{S}^{2}$ which can also be interpreted as instanton configurations in $2+1$ dimensional pure Yang-Mills theory at finite temperature (thermal time circle). I also describe similar solutions in Euclidean $\mathrm{SU}(N)$ gauge theory on ${S}^{1}\ifmmode\times\else\texttimes\fi{}{S}^{3}$ interpreted as chains of $n$ instanton\char21{}anti-instanton pairs.

title: Dimensional reduction method and meson mass spectrum in unified multidimensional field theory
abstract: A new method is suggested for dimensional reduction of a langrangian defined in a 4+N-dimensional spacetime fiber bundle into a four-dimensional “effective” langrangian. The method is considered for the particular case of N=4. Mass formulas are obtained for mesons with charge, isospin etc., mass splitting of meson multiplets neglected. Taking the mass of the pion as an input, other mesons' masses are computed. The masses predicted are in good agreement with the experiment (Δm/m<0.04).

title: HOLOMORPHIC CHERN-SIMONS-WITTEN THEORY : FROM 2D TO 4D CONFORMAL FIELD THEORIES
abstract: It is well known that rational 2D conformal field theories are connected with Chern-Simons theories defined on 3D real manifolds. We consider holomorphic analogues of Chern-Simons theories defined on 3D complex manifolds (six real dimensions) and describe 4D conformal field theories connected with them. All these models are integrable. We describe analogues of the Virasoro and affine Lie algebras, the local action of which on fields of holomorphic analogues of Chern-Simons theories becomes non-local after pushing down to the action on fields of integrable 4D conformal field theories. Quantization of integrable 4D conformal field theories and relations to string theories are briefly discussed.