53462197
Searches for new physics at Tevatron: Most recent results
The most recent results obtained from searches of particles and phenomena beyond the Standard Model (new physics) in the D0 and CDF experiments at the Tevatron accelerator (FNAL, USA) on the basis of statistics corresponding to the integrated luminosity of up to 4 fb−1 in 2009 are considered. Particular attention is given to the most recent results on searches for a supersymmetric Higgs boson.
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.
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.
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)]%.
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.
18484217
Noncommutative solitons in a supersymmetric chiral model in 2+1 dimensions
We consider a supersymmetric Bogomolny-type model in 2+1 dimensions originating from twistor string theory. By a gauge fixing this model is reduced to a modified U(n) chiral model with 2N ≤8 supersymmetries in 2+1 dimensions. After a Moyal-type deformation of the model, we employ the dressing method to explicitly construct multi-soliton configurations on noncommutative R 2,1 and analyze some of their properties.
12712451
Non-Abelian Vortices on Riemann Surfaces: an Integrable Case
We consider U(n + 1) Yang–Mills instantons on the space Σ × S2, where Σ is a compact Riemann surface of genus g. Using an SU(2)-equivariant dimensional reduction, we show that the U(n + 1) instanton equations on Σ × S2 are equivalent to non-Abelian vortex equations on Σ. Solutions to these equations are given by pairs (A,ϕ), where A is a gauge potential of the group U(n) and ϕ is a Higgs field in the fundamental representation of the group U(n). We briefly compare this model with other non-Abelian Higgs models considered recently. Afterwards we show that for g > 1, when Σ × S2 becomes a gravitational instanton, the non-Abelian vortex equations are the compatibility conditions of two linear equations (Lax pair) and therefore the standard methods of integrable systems can be applied for constructing their solutions.
16586702
HOLOMORPHIC CHERN-SIMONS-WITTEN THEORY : FROM 2D TO 4D CONFORMAL FIELD THEORIES
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.
16831652
Instantons and Yang–Mills Flows on Coset Spaces
We consider the Yang–Mills flow equations on a reductive coset space G/H and the Yang–Mills equations on the manifold $${\mathbb{R}\times G/H}$$. On non-symmetric coset spaces G/H one can introduce geometric fluxes identified with the torsion of the spin connection. The condition of G-equivariance imposed on the gauge fields reduces the Yang–Mills equations to $${\phi^4}$$-kink equations on $${\mathbb{R}}$$. Depending on the boundary conditions and torsion, we obtain solutions to the Yang–Mills equations describing instantons, chains of instanton–anti-instanton pairs or modifications of gauge bundles. For Lorentzian signature on $${\mathbb{R}\times G/H}$$, dyon-type configurations are constructed as well. We also present explicit solutions to the Yang–Mills flow equations and compare them with the Yang–Mills solutions on $${\mathbb{R}\times G/H}$$.
119253503
Integrable vortex-type equations on the two-sphere
We consider the Yang-Mills instanton equations on the four-dimensional manifold ${S}^{2}\ifmmode\times\else\texttimes\fi{}\ensuremath{\Sigma}$, where $\ensuremath{\Sigma}$ is a compact Riemann surface of genus $gg1$ or its covering space ${H}^{2}=\mathrm{SU}(1,1)/\mathrm{U}(1)$. Introducing a natural ansatz for the gauge potential, we reduce the instanton equations on ${S}^{2}\ifmmode\times\else\texttimes\fi{}\ensuremath{\Sigma}$ to vortex-type equations on the sphere ${S}^{2}$. It is shown that when the scalar curvature of the manifold ${S}^{2}\ifmmode\times\else\texttimes\fi{}\ensuremath{\Sigma}$ vanishes, the vortex-type equations are integrable, i.e., can be obtained as compatibility conditions of two linear equations (Lax pair), which are written down explicitly. Thus, the standard methods of integrable systems can be applied for constructing their solutions. However, even if the scalar curvature of ${S}^{2}\ifmmode\times\else\texttimes\fi{}\ensuremath{\Sigma}$ does not vanish, the vortex equations are well defined and have solutions for any values of the topological charge $N$. We show that any solution to the vortex equations on ${S}^{2}$ with a fixed topological charge $N$ corresponds to a Yang-Mills instanton on ${S}^{2}\ifmmode\times\else\texttimes\fi{}\ensuremath{\Sigma}$ of charge $(g\ensuremath{-}1)N$.