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

Trefoil knot and ad-hoc classification of elementary fields in the Standard Model

We present an arbitrary model based on the trefoil knot to construct objects of the same spectrum as that of elementary particles. It includes `waves' and three identical sets of sources. Due to Lorentz invariance, `waves' group into 3 types of 1, 3 and 8 objects and `sources' consists of 3 identical sets of 30+2 elements, which separate into: 1 * 1 * 2 + 1 * 2 * 2 + 3 * 2 * 2 + 3 * 1 * 2 + 3 * 1 * 2 and another 1 * 1 * 2 group (which does not match classification of the Standard Model fields). On the other hand, there is no room in this construction for objects directly corresponding to Higgs-like degrees of freedom.Comment: uuencoded and gtar: was.tex was1.eps was2.eps. Use latex; in total 8 pages including front and 2 figure page

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

Spin polarization and the Einstein--Podolsky--Rosen paradox in the Monte Carlo event records

In the future high energy physics experiments, the question of properly matching the phenomenological programs that describe different parts of the physics processes (such as hard scattering, hadronization, decay of resonances, detector response, etc.) is very important. In the past, FORTAN common blocks filled with lists of objects (particles, strings, clusters, etc.) of defined properties, origins and descendants were in use. Similar structures are now envisaged, for future programs, to be written in languages such as C++ or Java. From the physics point of view such an approach is not correct, since this kind of data structures impose certain approximations on the physics content. In the present paper, we will explore their limits, using examples from the physics of W's, tau's and the Higgs boson, still to be discovered.Comment: latex 10 pages, including 10 attachments in postscript forma

The tauola-photos_F environment for versioning the TAUOLA and PHOTOS packages

We present the system for versioning two packages: the TAUOLA of tau lepton decay and PHOTOS for radiative corrections in decays. The following features can be chosen in automatic or semi-automatic way: (1) format of the common block HEPEVT; (2) version of the physics input (for TAUOLA): as published, as initialized by CLEO collaboration, as initialized by ALEPH collaboration (it is suggested to use this version only with the help of the collaboration advice); (3) type of application: stand-alone, universal interface through HEPEVT, interface for KKMC Monte Carlo; (4) random number generators; (5) compiler options.Comment: nine pages, late

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

Next to Leading Logarithms and the PHOTOS Monte Carlo

With the approaching start-up of the experiments at LHC, the urgency to quantify systematic uncertainties of the generators, used in the interpretation of the data, is becoming pressing. The PHOTOS Monte Carlo program is often used for the simulationof experimental, selection-sensitive, QED radiative corrections in decays of Z bosons and other heavy resonances and particles. Thanks to its complete phase-space coverage it is possible, with no approximations for any decay channel, to implement the matrix-element. The present paper will be devoted to those parts of the next-to-leading order corrections for Z decays which are normally missing in PHOTOS. The analytical form of the exact and truncated (standard) kernel used in PHOTOS will be explicitly given. The correction, being the ratio of the exact to the approximate kernel, can be activated as an optional contribution to the internal weight of PHOTOS. To calculate the weight, the information on the effective Born-level Z/gamma* couplings and even directions of the incoming beams, is needed. A universal implementation would have made the PHOTOS solution less modular and less convenient for the users. That is why, for the time being, we will keep the correcting weight as an extra option, available for special tests only. We will quantify the numerical effect of the approximation with the help of a multitude of distributions. The numerical size of the effect is in general below 0.1%; however, in some corners of the phase-space (well defined and contributing less than 0.5% to the total rate), it may reach up to about 20% of their relative size.Comment: 23+1 pages 6 groups of figure

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

How to use SANC to improve the PHOTOS Monte Carlo simulation of bremsstrahlung in leptonic W-Boson decays

Using the SANC system we study the one-loop electroweak standard model predictions, including virtual and real photon emission, for the decays of the on-shell vector boson, W --> L ANTI-NU (GAMMA). The complete one-loop corrections and exact photon emission matrix element are taken into account. For the phase-space integration, the Monte Carlo technique is used. This provides a useful element, first for the evaluation of the theoretical uncertainty of PHOTOS. Later we analyse the source of the differences between SANC and PHOTOS and we calculate the additional weight, which once installed, improves predictions of PHOTOS simulations. We can conclude that, after the correction of the weight is implemented, the theoretical uncertainty of PHOTOS simulations due to an incomplete first-order matrix element is reduced to below alpha/pi, for observables not tagging the photon in a direct way, and to 10% otherwise. This is interesting for applications in the phenomenology of the ongoing LEP2 and future LC and LHC experimental studies.Comment: Submitted to Acta Physica Polonica. 8 pages, 5 figure