Separating Electroweak and Strong interactions in Drell-Yan processes at LHC: leptons angular distributions and reference frames

Among the physics goals of LHC experiments, precision tests of the Standard Model in the Strong and Electroweak sectors play an important role. Because of nature of the proton-proton processes, observables based on the measurement of the direction and energy of leptons provide the most precise signatures. In the present paper, we concentrate on the angular distribution of Drell-Yan process leptons, in the lepton-pair rest-frame. The vector nature of the intermediate state imposes that distributions are to a good precision described by spherical polynomials of at most second order. We show that with the proper choice of the coordinate frames, only one coefficient in this polynomial decomposition remains sizable, even in the presence of one or two high $p_T$ jets. The necessary stochastic choice of the frames relies on probabilities independent from any coupling constants. This remains true when one or two partons accompany the lepton pairs. In this way electroweak effects can be better separated from strong interaction ones for the benefit of the interpretation of the measurements. Our study exploits properties of single gluon emission matrix elements which are clearly visible if a conveniently chosen form of their representation is used. We rely also on distributions obtained from matrix element based Monte Carlo generated samples of events with two leptons and up to two additional partons in test samples. Incoming colliding protons' partons are distributed accordingly to PDFs and are strictly collinear to the corresponding beams.Comment: 22 pages 9 figure

Status of TAUOLA and related projects

Status of new hadronic currents for tau lepton decay Monte Carlo generator TAUOLA was revieved in other talks of the conference. Efforts on comparison with BaBar and Belle collaboration data were carefully discussed. Also use of the program in phenomenology of W decays measured by ATLAS collaboration was presented in these talks as well. That is why, in my talk, I will concentrate on other aspects of our work necessary for development of tau lepton Monte Carlo programs and their phenomenological use. Presented results illustrate the status of the projects performed in collaboration with Swagato Banerjee, Zofia Czyczula, Nadia Davidson, Jan Kalinowski, Wojciech Kotlarski Tomasz Przedzinski, Olga Shekhovtsova, Elzbieta Richter-Was, Pablo Roig, Jakub Zaremba, Qingjun Xu and others.Comment: 4 pages, Presented at International workshop on Tau Lepton Physics, TAU12 Nagoya, Japan, September, 201

Prospect for the Higgs searches with the ATLAS detector

The investigation of the electroweak symmetry breaking is one of the primary tasks of the experiments at the CERN Large Hadron Collider (LHC). The potential of the ATLAS experiment for the discovery of the Higgs boson(s) in Standard Model and Minimal Supersymmetric Standard Model is presented, with emphasis on studies which have been completed recently.Comment: Presented at Cracow Epiphany Conference on Hadron Interactions at the Dawn of the LHC, dedicated to memory of J. Kwiecinski, Krakow, Poland, 5-7 January 2009, 22page

How to Generate Four-Fermion Phase Space

We present a scheme for integrating the matrix element of an arbitrary e^+e^-\to f_1f_2\bar f_3\bar f_4 process over the complete four-fermion phase space, or its any part, by means of the Monte Carlo technique. The presented algorithm has been successfully implemented in the KORALW Monte Carlo code.Comment: 16 page

Inclusion of tau anomalous magnetic and electric dipole moments in the KORALZ Monte Carlo

We describe modifications made to KORALZ version 4.03 in order to allow for anomalous magnetic and electric dipole moments of the tau. We discuss the verification of the method at LEP 1 energies.Comment: 14 pages, 9 figure

PHOTOS as a pocket parton shower: flexibility tests for the algorithm

In this note we will recall the main tests that document robustness and flexibility of the PHOTOS design. This aspect may be of broader use and may find extensions in future applications, also outside the simple case of purely QED bremsstrahlung in decays. The components of the PHOTOS algorithm will be presented using operator language. The results of some flexibility tests, not documented before, will also be presented

Production of tau tau jj final states at the LHC and the TauSpinner algorithm: the spin-2 case

The TauSpinner algorithm is a tool that allows to modify the physics model of the Monte Carlo generated samples due to the changed assumptions of event production dynamics, but without the need of re-generating events. With the help of weights $\tau$-lepton production or decay processes can be modified accordingly to a new physics model. In a recent paper a new version TauSpinner ver.2.0.0 has been presented which includes a provision for introducing non-standard states and couplings and study their effects in the vector-boson-fusion processes by exploiting the spin correlations of $\tau$-lepton pair decay products in processes where final states include also two hard jets. In the present paper we document how this can be achieved taking as an example the non-standard spin-2 state that couples to Standard Model particles and tree-level matrix elements with complete helicity information included for the parton-parton scattering amplitudes into a $\tau$-lepton pair and two outgoing partons. This implementation is prepared as the external (user provided) routine for the TauSpinner algorithm. It exploits amplitudes generated by MadGraph5 and adopted to the TauSpinner algorithm format. Consistency tests of the implemented matrix elements, reweighting algorithm and numerical results for observables sensitive to $\tau$ polarization are presented.Comment: 17 pages, 6 figures; version published in EPJ