Vortices, strings, and pseudoinstantons

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: Solutions of Yang-Mills and Yang-Mills-Higgs equations

title: Integrable noncommutative sine-Gordon model
abstract: Requiring an infinite number of conserved local charges or the existence of an underlying linear system does not uniquely determine the Moyal deformation of ( 1 + 1 ) -dimensional integrable field theories. As an example, the sine-Gordon model may be obtained by dimensional and algebraic reduction from ( 2 + 2 ) -dimensional self-dual U(2) Yang–Mills through a ( 2 + 1 ) -dimensional integrable U(2) sigma model, with some freedom in the noncommutative extension of this algebraic reduction. Relaxing the latter from U ( 2 ) → U ( 1 ) to U ( 2 ) → U ( 1 ) × U ( 1 ) , we arrive at novel noncommutative sine-Gordon equations for a pair of scalar fields. The dressing method is employed to construct its multi-soliton solutions. Finally, we evaluate various tree-level amplitudes to demonstrate that our model possesses a factorizable and causal S-matrix in spite of its time–space noncommutativity.

title: On nonperturbative solutions of superstring field theory
abstract: Nonperturbative solutions to the nonlinear field equations in the NS sector of cubic as well as nonpolynomial superstring field theory can be obtained from a linear equation which includes a “spectral” parameter λ and a coboundary operator Q ( λ ). We borrow a simple ansatz from the dressing method (for generating solitons in integrable field theories) and show that classical superstring fields can be constructed from any string field  T subject merely to Q ( λ ) T =0. Following the decay of the non-BPS D9 brane in IIA theory and shifting the background to the tachyon vacuum, we repeat the arguments in vacuum superstring field theory and outline how to compute classical solutions explicitly.

title: Solving string field equations: new uses for old tools
abstract: It is argued that the (NS-sector) superstring field equations are integrable, i.e. their solutions are obtainable from linear equations. We adapt the 25-year-old solution-generating “dressing” method and reduce the construction of nonperturbative superstring configurations to a specific cohomology problem. The application to vacuum superstring field theory is outlined.

title: Forward-backward asymmetry in top quark-antiquark production
abstract: We present a measurement of forward-backward asymmetry in top quark-antiquark production in proton-antiproton collisions in the final state containing a lepton and at least four jets. Using a data set corresponding to an integrated luminosity of 5.4 fb(-1), collected by the D0 experiment at the Fermilab Tevatron Collider, we measure the t (t) over bar forward-backward asymmetry to be (9.2 +/- 3.7)% at the reconstruction level. When corrected for detector acceptance and resolution, the asymmetry is found to be (19.6 +/- 6.5)%. We also measure a corrected asymmetry based on the lepton from a top quark decay, found to be (15.2 +/- 4.0)%. The results are compared to predictions based on the next-to-leading-order QCD generator MC@NLO. The sensitivity of the measured and predicted asymmetries to the modeling of gluon radiation is discussed.

title: Combination of the top-quark mass measurements from the Tevatron collider
abstract: We thank the Fermilab staff and technical staffs of the 
participating institutions for their vital contributions and 
acknowledge support from the DOE and NSF (USA), ARC 
(Australia), CNPq, FAPERJ, FAPESP, and FUNDUNESP 
(Brazil), NSERC (Canada), NSC, CAS, and CNSF 
(China), Colciencias (Colombia), MSMT and GACR 
(Czech Republic), the Academy of Finland, CEA, and 
CNRS/IN2P3 (France), BMBF and DFG (Germany), 
DAE and DST (India), SFI (Ireland), INFN (Italy), 
MEXT (Japan), the Korean World Class University 
Program and NRF (Korea), CONACyT (Mexico), FOM 
(Netherlands), MON, NRC KI, and RFBR (Russia), the 
Slovak R&D Agency, the Ministerio de Ciencia e 
Innovacio´n, and Programa Consolider-Ingenio 2010 
(Spain), The Swedish Research Council (Sweden), SNSF 
(Switzerland), STFC and the Royal Society (United 
Kingdom), and the A. P. Sloan Foundation (USA).

title: $W\gamma$ production and limits on anomalous $WW\gamma$ couplings in $p\bar{p}$ collisions
abstract: We measure the cross section and the difference in rapidities between photons and charged leptons for inclusive W({yields} l{nu})+{gamma} production in e{gamma} and {mu}{gamma} final states. Using data corresponding to an integrated luminosity of 4.2 fb{sup -1} collected with the D0 detector at the Fermilab Tevatron Collider, the measured cross section times branching fraction for the process p{bar p} {yields} W{gamma} + X {yields} l{nu}{gamma} + 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{gamma} couplings for data from hadron colliders: -0.4 < {Delta}{Kappa}{sub {gamma}} < 0.4 and -0.08 < {lambda}{sub {gamma}} < 0.07 at the 95% C.L.

title: Search for production of single top quarks via tcg and tug flavor-changing-neutral-current couplings.
abstract: We search for the production of single top quarks via flavor-changing-neutral-current couplings of a gluon to the top quark and a charm (c) or up (u) quark. We analyze 230 pb{-1} of lepton+jets data from pp[over] collisions at a center of mass energy of 1.96 TeV collected by the D0 detector at the Fermilab Tevatron Collider. We observe no significant deviation from standard model predictions, and hence set upper limits on the anomalous coupling parameters kappa{g}{c}/Lambda and kappa{g}{u}/Lambda, where kappa{g} define the strength of tcg and tug couplings, and Lambda defines the scale of new physics. The limits at 95% C.L. are kappa{g}{c}/Lambda<0.15 TeV-1 and kappa{g}{u}/Lambda<0.037 TeV-1.

title: Direct measurement of the mass difference between top and antitop quarks.
abstract: 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.