Monte Carlo study of gg->H+jets contribution to Vector Boson Fusion Higgs production at the LHC

The contribution of gg->H+jets production process to the vector boson fusion production of the Higgs boson, VV->H, at LHC was evaluated with the ALPGEN generator and the PYTHIA shower Monte Carlo including a jet-parton matching procedure. After the experimental like event selections applied at PYTHIA particle level, the contribution was found to be 4-5 % for a Higgs boson mass of 120 GeV

Bosonic and fermionic Weinberg-Joos (j,0)+ (0,j) states of arbitrary spins as Lorentz-tensors or tensor-spinors and second order theory

We propose a general method for the description of arbitrary single spin-j states transforming according to (j,0)+(0,j) carrier spaces of the Lorentz algebra in terms of Lorentz-tensors for bosons, and tensor-spinors for fermions, and by means of second order Lagrangians. The method allows to avoid the cumbersome matrix calculus and higher \partial^{2j} order wave equations inherent to the Weinberg-Joos approach. We start with reducible Lorentz-tensor (tensor-spinor) representation spaces hosting one sole (j,0)+(0,j) irreducible sector and design there a representation reduction algorithm based on one of the Casimir invariants of the Lorentz algebra. This algorithm allows us to separate neatly the pure spin-j sector of interest from the rest, while preserving the separate Lorentz- and Dirac indexes. However, the Lorentz invariants are momentum independent and do not provide wave equations. Genuine wave equations are obtained by conditioning the Lorentz-tensors under consideration to satisfy the Klein-Gordon equation. In so doing, one always ends up with wave equations and associated Lagrangians that are second order in the momenta. Specifically, a spin-3/2 particle transforming as (3/2,0)+ (0,3/2) is comfortably described by a second order Lagrangian in the basis of the totally antisymmetric Lorentz tensor-spinor of second rank, \Psi_[ \mu\nu]. Moreover, the particle is shown to propagate causally within an electromagnetic background. In our study of (3/2,0)+(0,3/2) as part of \Psi_[\mu\nu] we reproduce the electromagnetic multipole moments known from the Weinberg-Joos theory. We also find a Compton differential cross section that satisfies unitarity in forward direction. The suggested tensor calculus presents itself very computer friendly with respect to the symbolic software FeynCalc.Comment: LaTex 34 pages, 1 table, 8 figures. arXiv admin note: text overlap with arXiv:1312.581

Spin-exchange relaxation free magnetometry with Cs vapor

We describe a Cs atomic magnetometer operating in the spin-exchange relaxation-free (SERF) regime. With a vapor cell temperature of $103^\circ\rm{C}$ we achieve intrinsic magnetic resonance widths $\Delta B=17 {\rm \mu G}$ corresponding to an electron spin-relaxation rate of $300 {\rm s^{-1}}$ when the spin-exchange rate is $\Gamma_{SE}=14000 {\rm s^{-1}}$. We also observe an interesting narrowing effect due to diffusion. Signal-to-noise measurements yield a sensitivity of about $400\thinspace{\rm pG/\sqrt{Hz}}$. Based on photon shot noise, we project a sensitivity of $40 {\rm pG/\sqrt{Hz}}$. A theoretical optimization of the magnetometer indicates sensitivities on the order of $2 {\rm pG/\sqrt{Hz}}$ should be achievable in a $1 {\rm cm^3}$ volume. Because Cs has a higher saturated vapor pressure than other alkali metals, SERF magnetometers using Cs atoms are particularly attractive in applications requiring lower temperatures.Comment: 8 pages, 6 figures. submitted to PR

Top quark physics in hadron collisions

The top quark is the heaviest elementary particle observed to date. Its large mass makes the top quark an ideal laboratory to test predictions of perturbation theory concerning heavy quark production at hadron colliders. The top quark is also a powerful probe for new phenomena beyond the Standard Model of particle physics. In addition, the top quark mass is a crucial parameter for scrutinizing the Standard Model in electroweak precision tests and for predicting the mass of the yet unobserved Higgs boson. Ten years after the discovery of the top quark at the Fermilab Tevatron top quark physics has entered an era where detailed measurements of top quark properties are undertaken. In this review article an introduction to the phenomenology of top quark production in hadron collisions is given, the lessons learned in Tevatron Run I are summarized, and first Run II results are discussed. A brief outlook to the possibilities of top quark research a the Large Hadron Collider, currently under construction at CERN, is included.Comment: 84 pages, 32 figures, accepted for publication by Reports on Progress in Physic

Cancellation of nonlinear Zeeman shifts with light shifts

Nonlinear Zeeman (NLZ) shifts arising from magnetic-field mixing of the two hyperfine ground-states in alkali atoms lead to splitting of magnetic-resonance lines. This is a major source of sensitivity degradation and the so-called "heading errors" of alkali-vapor atomic magnetometers operating in the geophysical field range (B approx. 0.2-0.7 G). Here, it is shown theoretically and experimentally that NLZ shifts can be effectively canceled by light shifts caused by a laser field of appropriate intensity, polarization and frequency, a technique that can be readily applied in practical situations.Comment: 5 pages, 5 figures, to be published in PR