119221579
Observation of Single Top Quark Production at D0
This paper presents the observation of the electroweak production of single top quarks in the D0 detector at the Fermilab Tevatron pp Collider at a center‐of‐mass energy of 1.96 TeV. Events containing an isolated electron or muon and missing transverse energy, together with jets originating from the fragmentation of b quarks are used to measure a cross section for single top‐quark production of σ(pp→tb+X,tqb+X) = 3.94±0.88 pb. The probability to measure a cross section at this value or higher in the absence of signal is 2.5×10−7, corresponding to a 5.0 standard deviation significance.
16864354
Evidence for single top quark production at D0
We present evidence for the production of single top quarks at the Fermilab Tevatron p collider. Using a 0.9 fb-1 dataset collected with D0 detector, the analysis is performed in the electron+jets and muon+jets decay modes, taking special care in modeling the large backgrounds, applying a new powerful b-quark tagging algorithm and using three multivariate techniques to extract the small signal. The combined measured production cross section is σ(p tb + X, tqb + X) = 4.7 ± 1.3 pb. The probability to measure a cross section at this value or higher in the absence of signal is 0.014%, corresponding to a 3.6 standard deviation significance. We use the cross section measurement to directly determine the CKM matrix element that describes the Wtb coupling and find 0.68 < |Vtb|≤ 1 at 95% C.L. within the standard model.
117840720
Top Quark Production at the Tevatron Collider
Top quark physics has been a rich testing ground for the standard model since the top quark discovery in 1995. The large mass of top quark suggests that it could play a special role in searches for new phenomena. In this paper I provide an overview of recent top quark production cross section measurements from both CDF and D0 collaborations and also some new physics searches done in the top quark sector.
125836359
Test of QCD using multijets in neutral current DIS at HERA
122970197
Multijet production in neutral current deep inelastic scattering at HERA and determination of alpha(s)
Multijet production rates in neutral current deep inelastic scattering (DIS) have been measured in the range of exchanged boson virtualities 10<Q2<5000 GeV2. The data were taken at the ep collider HERA with centre-of-mass energy using the ZEUS detector and correspond to an integrated luminosity of 82.2 pb-1. Jets were identified in the Breit frame using the kT cluster algorithm in the longitudinally invariant inclusive mode. Measurements of differential multijet cross sections are presented as functions of jet transverse energy , pseudorapidity and Q2 with and . Next-to-leading-order QCD calculations describe the data well. The value of the strong coupling constant αs(MZ), determined from the ratio of the trijet to dijet cross sections, is .
10496964
Asymptotically universal crossover in perturbation theory with a field cutoff
We discuss the crossover between the small and large field cutoff (denoted as x max ) limits of the perturbative coefficients for a simple integral and anharmonic oscillators. We show that in the limit where the order k of the perturbative coefficient a k (x max ) becomes large and for x max in the crossover region, a k (x max ) ∝ ∫ xmax -∞ e -A(x-x 0 (k))2 dx. The order-independent constant A and the function x 0 (k) are determined empirically and compared with exact (for the integral) and approximate (for the anharmonic oscillator) calculations. Numerically, our best estimates are A ≃ 1.5, 1.3 and 1.2 for a λx 4 , λx 6 and λx 8 perturbation respectively.
18809945
Quark mass and phase transition for strange matter
We have derived the popularly used mass parametrization formula for light quarks and modified the corresponding formula for strange quarks with the mass-densitydependent model. A simple expression for the critical density of phase transition of strange quark matter at zero temperature is thus found and its value is estimated to be over 6 times the normal nuclear density.
5616752
A flux tube solar dynamo model based on the competing role of buoyancy and downflows
A magnetic flux tube can be considered both as a separate body and as a confined field. As a field, it is affected by both differential rotation (Ω-effect) and cyclonic convection (α-effect). As a body, the tube experiences not only a buoyant force, but also a dynamic pressure due to downflows above the tube. These two competing dynamic effects are incorporated into the α-Ω dynamo equations through the total magnetic turbulent diffusivity, leading to a flux tube dynamo operating in the convection zone. We analyze and solve the extended dynamo equations in the linear approximation by adopting the observed solar internal rotation and assuming a downflow effect derived from numerical simulations of a solar convection zone. The model reproduces the 22 yr cycle period; the extended butterfly diagram with the confinement of strong activity to low heliographic latitudes |Φ| ≤ 35°; the evidence that at low latitudes the radial field is in an approximately π phase lag compared to the toroidal field at the same latitude; the evidence that the poleward branch is in a π/2 phase lag with respect to the equatorward branch; and the evidence that most of the magnetic flux is present in an intermittent form, concentrated into strong flux tubes.
119183267
Entanglement entropy in holographic p-wave superconductor/insulator model
A bstractWe continue our study of entanglement entropy in the holographic superconducting phase transitions. In this paper we consider the holographic p-wave superconductor/insulator model, where as the back reaction increases, the transition is changed from second order to first order. We find that unlike the s-wave case, there is no additional first order transition in the superconducting phase. We calculate the entanglement entropy for two strip geometries. One is parallel to the super current, and the other is orthogonal to the super current. In both cases, we find that the entanglement entropy monotonically increases with respect to the chemical potential.