122917668
Dimensional reduction method and meson mass spectrum in unified multidimensional field theory
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).
15238001
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.
119274504
Instantons on the six-sphere and twistors
We consider the six-sphere S6 = G2/SU(3) and its twistor space Z=G2/U(2) associated with the SU(3)-structure on S6. It is shown that a Hermitian Yang-Mills connection (instanton) on a smooth vector bundle over S6 is equivalent to a flat partial connection on a vector bundle over the twistor space Z. The relation with Tian's tangent instantons on R7 and their twistor description are briefly discussed.
121271402
Meron-type solutions of the Yang-Mills equations in 4n dimensions
The Yang-Mills theory in d = 4n with an arbitrary gauge group G is considered. Using the generalization of the Corrigan-Fairlie-'t Hooft-Wilczek ansatz, we reduce the Yang-Mills equation in 4n dimensions to simpler equations. As an example, for G = SU(2) we write out the explicit form of some solutions that are 4n-dimensional analogues of the d = 4 meron solutions.
14915418
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.
26487031
Yang-Mills instantons on cones and sine-cones over nearly Kähler manifolds
We present a unified eight-dimensional approach to instanton equations on several seven-dimensional manifolds associated to a six-dimensional homogeneous nearly Kähler manifold. The cone over the sine-cone on a nearly Kähler manifold has holonomy group Spin(7) and can befoliated by submanifolds with either holonomy group G2, a nearly parallel G2-structure or a cocalibrated G2-structure. We show that there is a G2-instanton on each of these seven-dimensional manifolds which gives rise to a Spin(7)-instanton in eight dimensions. The well-known octonionic instantons on $ {\mathbb{R}^7} $ and $ {\mathbb{R}^8} $ are contained in our construction as the special cases of an instanton on the cone and on the cone over the sine-cone, both over the six-sphere, respectively.
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.
118241188
Search for Neutral Higgs Bosons in Events with Multiple Bottom Quarks at the Tevatron
The combination of searches performed by the CDF and D0 collaborations at the Fermilab Tevatron Collider for neutral Higgs bosons produced in association with b quarks is reported. The data, corresponding to 2.6 fb-1 of integrated luminosity at CDF and 5.2 fb-1 at D0, have been collected in final states containing three or more b jets. Upper limits are set on the cross section multiplied by the branching ratio varying between 44 pb and 0.7 pb in the Higgs boson mass range 90 to 300 GeV, assuming production of a narrow scalar boson. Significant enhancements to the production of Higgs bosons can be found in theories beyond the standard model, for example in supersymmetry. The results are interpreted as upper limits in the parameter space of the minimal supersymmetric standard model in a benchmark scenario favoring this decay mode.
118463247
Search for pair production of the scalar top quark in muon+tau final states
We present a search for the pair production of scalar top quarks ($\tilde{t}_{1}$), the lightest supersymmetric partners of the top quarks, in $p\bar{p}$ collisions at a center-of-mass energy of 1.96 TeV, using data corresponding to an integrated luminosity of {7.3 $fb^{-1}$} collected with the \dzero experiment at the Fermilab Tevatron Collider. Each scalar top quark is assumed to decay into a $b$ quark, a charged lepton, and a scalar neutrino ($\tilde{\nu}$). We investigate final states arising from $\tilde{t}_{1} \bar{\tilde{t}_{1}} \rightarrow b\bar{b}\mu\tau \tilde{\nu} \tilde{\nu}$ and $\tilde{t}_{1} \bar{\tilde{t}_{1}} \rightarrow b\bar{b}\tau\tau \tilde{\nu} \tilde{\nu}$. With no significant excess of events observed above the background expected from the standard model, we set exclusion limits on this production process in the ($m_{\tilde{t}_{1}}$,$m_{\tilde{\nu}}$) plane.
122059751
Experimental evidence for hadroproduction of exotic mesons
New measurements of peripheral meson production are presented. The data confirm the existence of exotic mesons at 1.4 and 1.6 GeV/c2. The latter state dominates the eta'pi- decay spectrum. The data on eta pi+pi-pi- decay show large strength in several exotic (Jpc = 1- +) waves as well.
18518405
Search for anomalous top-quark couplings with the D0 detector.
Anomalous Wtb couplings modify the angular correlations of the top-quark decay products and change the single top-quark production cross section. We present limits on anomalous top-quark couplings by combining information from W boson helicity measurements in top-quark decays and anomalous coupling searches in the single top-quark final state. We set limits on right-handed vector couplings as well as left-handed and right-handed tensor couplings based on about 1 fb(-1) of data collected by the D0 experiment.