arXiv subjects

T. Przedzinski

Publications and source records attributed to T. Przedzinski.

At least 19 recordsLinked to original sources

arXiv2022

Methodology for development of scientific software and test frameworks in function of precision of the expected results

This dissertation focuses on the development process of scientific software. It presents a methodology that has emerged over time during development of Monte Carlo tools for high energy physics experiments. A short description of the physics background needed to understand the subjects presented in this dissertation is included and the different types of software created for the physics experiments are outlined. Challenges related to the scientific software development are presented. The development process of several projects is described. The development of subsequent milestones of these projects follow the cycle of improving the physics model, describing the model using mathematical formalism, implementing the model with numerical approximations, creating the software framework, documenting and validating results. The relation between increased precision of the results and increased complexity of tests and test frameworks is also demonstrated based on these projects. The subject of scientific software testing is addressed and the taxonomy of the scientific software tests is presented including testing techniques used in the development of this software. Author of this dissertation co-authored tools presented in it. Some of these tools have been introduced into the HEP community. Some gained large user base and are in active use by the community. Some of them are part of analyses performed by experiments around Large Hadron Collider. The analysis of the development process of these tools can help estimate the effort needed to improve the design and precision of complex algorithms.

cs.SE↗

arXiv2022

Mini-Proceedings of the STRONG2020 Virtual Workshop on "Space-like and Time-like determination of the Hadronic Leading Order contribution to the Muon $g-2$"

The mini-proceedings of the STRONG2020 Virtual Workshop "Space-like and Time-like determination of the Hadronic Leading Order contribution to the Muon $g-2$", November 24--26 2021, are presented. This is the first workshop of the STRONG2020 WP21: JRA3-PrecisionSM: Precision Tests of the Standard Model (http://www.strong-2020.eu/joint-research-activity/jra3-precisionsm.html). The workshop was devoted to review of the working group activitity on: $(\it i)$ Radiative Corrections and Monte Carlo tools for low-energy hadronic cross sections in $e^+ e^-$ collisions; $(\it ii)$ Annotated database for $e^+e^-$ into hadrons processes at low energy; $(\it iii)$ Radiative Corrections and Monte Carlo tools for $\mu$-$e$ elastic scattering.

hep-ph↗

arXiv2021

The tau lepton Monte Carlo Event Generation -- imprinting New Physics models with exotic scalar or vector states into simulation samples

hep-ph↗

arXiv2021

Monte Carlo Event Generator updates, for tau pair events at Belle II energies

The Monte Carlo for lepton pair production and tau decays consist of KKMC for lepton pair production, tauola for tau lepton decays and photos for radiative corrections in decays. An effort for adaptation of the system for precision data to be collected at Belle II experiment lead to extension of phase space generation modules both in photos and tauola to enable decays and/or radiative corrections of additional light lepton pairs. The phase-space and matrix element parts of the programs are separated, that is why extension to processes where lepton pair is produced through narrow resonances, like dark photon, was straight forward. In the present version of tauola, list of tau decay channels is enriched with multitude of exotic ones, useful for searches of new physics. The hadronic currents parametrizations of main decay channels is prepared for basic simulation in the experiment. The basis for future work on precise fits of hadronic currents including Machine Learning is retained, but development of necessary software solutions is left for the forthcoming years. Presented programs versions are available in stand-alone format from gitlab or through the basf2 system of Belle II software. Official distribution web pages, documenting programs tests, are retained but not necessarily up to the date.

hep-ph↗

arXiv2018

Documentation of TauSpinner algorithms -- program for simulating spin effects in tau-lepton production at LHC

The tau-lepton plays an important role in the physics program at the Large Hadron Collider (LHC). It offers a probe in searches for New Physics and to measure parameters of the Standard Model. Spin of tau lepton is an interesting phenomenological quantity for separation of signal from background or in measuring properties of particles. A proper treatment of tau spin effects in the Monte Carlo simulations is important for understanding the detector acceptance as well as for the measurements/use of tau polarization and tau spin correlations. The TauSpinner is a tool to modify tau$spin effects in any sample. Also production matrix elements can be modified with its help. The general principle of TauSpinner algorithm rely on the kinematic of outgoing particles (or jets) only, and to average over all possible initial states accordingly to assumed parton distributions and cross-sections. Incoming on mass-shell parton four-momenta are reconstructed in approximation, but energy-momentum conservation is obeyed. Samples of events featuring tau leptons with their decay products, can be used as an input. The information on the polarization and spin correlations, and production/decay matrix elements is reconstructed from the kinematics of the tau lepton(s) (also nu_tau in case of W-mediated processes) and tau decay products (also jets). No other information is required. By calculating spin (or production/decay matrix element) weights, attributed to each event, it enables evaluation of modifications without regenerating events. Elements of program functionalities together with explanation of the use are given in Appendices. Present publication collect program documentation, previously scattered over several publiications.

hep-ph↗

arXiv2016

Study of the lowest tensor and scalar resonances in the $\tau \to \pi\pi\pi \nu_\tau$ decay

In this note we present a new parametrization of the hadronic current for the decay $\tau \to \pi\pi\pi \nu_\tau$ derived from the chiral lagrangian with explicit inclusion of resonances. We have included both scalar, vector and axial-vector resonances. For the first time, the lowest tensor resonance ($f_2(1270)$) is included as well. Both single and double-resonance contributions to the hadronic form factors are taken into account. To satisfy the correct high energy behaviour of the hadronic form factors, constraints on numerical values of the vertex constants are obtained.

hep-ph↗

arXiv2016

TAUOLA of tau lepton decays-- framework for hadronic currens, matrix elements and anomalous decays

We present an update of the Monte Carlo event generator TAUOLA for tau lepton decays, with substantially increased list of decay channels and new initialization options. The core of the program remains written in FORTRAN but necessary arrangements have been made to allow handling of the user-provided hadronic currents and matrix elements at the execution time. Such solution may simplify preparation of new hadronic currents and may be useful for fitting to the experimental data as well. We have implemented as default for TAUOLA a set of hadronic currents, which is compatible with the default initialization used by BaBar collaboration. Options for currents available in previous releases are still stored in the code, sometimes left defunct or activated by internal flags only. The new version of the program, includes also implementation of Lepton Flavour Violating tau decays. Finally, we present, as an example, a set of C++ methods for handling user-provided currents, matrix elements or complete new decay channels initialization which can be performed at the program execution time.

hep-ph↗

arXiv2015

PHOTOS Interface in C++; Technical and Physics Documentation

For five years now, PHOTOS Monte Carlo for bremsstrahlung in the decay of particles and resonances has been available with an interface to the C++ HepMC event record. The main purpose of the present paper is to document the technical aspects of the PHOTOS Monte Carlo installation and present version use. A multitude of test results and examples are distributed together with the program code. The PHOTOS C++ physics precision is better than its FORTRAN predecessor and more convenient steering options are also available. An algorithm for the event record interface necessary for process dependent photon emission kernel is implemented. It is used in Z and W decays for kernels of complete first order matrix elements of the decays. Additional emission of final state lepton pairs is also available. Physics assumptions used in the program and properties of the solution are reviewed. In particular, it is explained how the second order matrix elements were used in design and validation of the program iteration procedure. Also, it is explained that the phase space parametrization used in the program is exact.

hep-ph↗

arXiv2015

RChL currents in Tauola: implementation and fit parameters

We present the results of a partial upgrade to the Monte Carlo event generator TAUOLA using Resonance Chiral Theory for the two and three meson final states. These modes account for 88% of total hadronic width of the tau meson. The first results of the model parameters have been obtained using Preliminary BaBar data for the three pion mode.

hep-ph↗

arXiv2014

TauSpinner: a tool for simulating CP effects in H to tau tau decays at LHC

In this paper, we discuss application of the TauSpinner package as a simulation tool for measuring the CP state of the newly discovered Higgs boson using the transverse spin correlations in the H to tau tau decay channel. We discuss application for its main background Z/gamma* to tau tau as well. The TauSpinner package allows one to add, with the help of weights, transverse spin correlations corresponding to any mixture of scalar/pseudoscalar state, on already existing events using information from the kinematics of outgoing tau leptons and their decay products only. This procedure can be used when polarimetric vectors of the taus decays and density matrix for tau-pair production are not stored with the event sample. We concentrate on the well-defined effects for the Higgs (or Higgs-like scalar) decays, which are physically separated from the production processes. TauSpinner also allows to reintroduce (or remove) spin correlations to events from Drell-Yan Z/gamma* to tau tau process, the main background for the Higgs parity observables, again with the help of weights only. From the literature, we recall well-established observables, developed for measuring the CP of the Higgs, and use them as benchmarks for illustrating applications of the TauSpinner package. We also include a description of the code and prepared testing examples.

hep-ph↗

arXiv2014

Application of TauSpinner for studies on tau-lepton polarization and spin correlations in Z, W and H decays at LHC

The tau-lepton plays an important role in the physics program at LHC. Its spin can be used for separation of signal from background or in measuring properties of New Particles decaying to tau leptons. The TauSpinner package represents a tool to modify tau spin effects in any sample containing tau leptons. Generated events, featuring taus produced from intermediate state W, Z, H bosons can be used as an input. The information on the polarization and spin correlations is reconstructed from the kinematics of the tau lepton(s) (nutau in case of W-mediated processes) and tau decay products. By weights, attributed on the event-by-event basis, it enables numerical evaluation and/or modification of the spin effects. We review distributions to monitor spin effects in leptonic and hadronic tau decays with up to three pions, to provide benchmarks for validation of spin content of the event sample and to visualize the tau lepton spin polarization and correlation effects. The demonstration examples for use of TauSpinner libraries, are documented. New validation methods of such an approach are provided. Other topics, like TauSpinner systematic errors or sensitivity of experimental distributions to spin, are addressed in part only. This approach is of interest for implementation of spin effects in embedded tau lepton samples, where Z to mu mu events from data of muons are replaced by simulated tau leptons. Embedding is used at LHC for estimating Z to tau tau background to H to tau tau signatures.

hep-ph↗

arXiv2013

Resonance Chiral Lagrangian Currents and Experimental Data for $τ^-\toπ^{-}π^{-}π^{+}ν_τ$

In this paper we document the modifications introduced to the previous version of the Resonance Chiral Lagrangian current ({\it Phys.Rev.} {\bf D86} (2012) 113008) of the $τ^\pm \to π^\pm π^\pm π^\mp ν_τ$ decay which enable the one dimensional distributions measured by the BaBar collaboration to be well modeled. The main change required to model the data is the addition of the $σ$ resonance. Systematic errors, theoretical and experimental ones, limitations due to fits of one dimensional distributions only, and resulting difficulties and statistical/systematic errors for fitted parameters are addressed. The current and fitting environment is ready for comparisons with the fully exclusive experimental data. The present result for $τ^\pm \to π^\pm π^\pm π^\mp ν_τ$ is encouraging for work on other $τ$ decay modes and Resonance Chiral Lagrangian based currents.

hep-ph↗

arXiv2013

Resonance chiral Lagrangian currents and tau decay Monte Carlo

Measurements of tau lepton, because of its long lifetime, large mass and parity sensitive couplings lead to broad physics interest. From the perspective of high-energy experiments such as at LHC, knowledge of tau lepton properties offers an important ingredient of new physics signatures. From the perspective of lower energies, tau lepton decays constitute an excellent laboratory for hadronic interactions. At present,hundreds of millions of tau decays have been amassed by both Belle and BaBar experiments. It is of utmost importance to represent such data in a form as useful for general applications as possible. In the present paper we describe the set of form factors for hadronic tau decays based on Resonance Chiral Theory. The technical implementation of the form factors in FORTRAN code is also explained. It is shown how it can be installed into TAUOLA Monte Carlo program. Then it is rather easy to implement into software environments of not only Belle and BaBar collaborations but also for FORTRAN and C++ applications of LHC. Description of the current for each tau decay mode is complemented with technical numerical tests. The set is ready for fits, parameters to be used in fits are explained. Arrangements to work with the experimental data not requiring unfolding are prepared. Hadronic currents, ready for confrontation with the tau decay data, but not yet ready for the general use, cover more than 88% of hadronic tau decay width.

hep-ph↗

arXiv2012

MC generator TAUOLA: implementation of Resonance Chiral Theory for two and three meson modes. Comparison with experiment

We present a partial upgrade of the Monte Carlo event generator TAUOLA with the two and three hadron decay modes using the theoretical models based on Resonance Chiral Theory. These modes account for 88% of total hadronic width of the tau meson. First results of the model parameters have been obtained using BaBar data for three pion mode.

hep-ph↗

arXiv2012

Theoretical inputs and errors in the new hadronic currents in TAUOLA

The new hadronic currents implemented in the TAUOLA library are obtained in the unified and consistent framework of Resonance Chiral Theory: a Lagrangian approach in which the resonances exchanged in the hadronic tau decays are active degrees of freedom included in a way that reproduces the low-energy results of Chiral Perturbation Theory. The short-distance QCD constraints on the imaginary part of the spin-one correlators yield relations among the couplings that render the theory predictive. In this communication, the obtaining of the two- and three-meson form factors is sketched. One of the criticisms to our framework is that the error may be as large as 1/3, since it is a realization of the large-N_C limit of QCD in a meson theory. A number of arguments are given which disfavor that claim pointing to smaller errors, which would explain the phenomenological success of our description in these decays. Finally, other minor sources of error and current improvements of the code are discussed.

hep-ph↗

arXiv2012

TauSpinner program for studies on spin effect in tau production at the LHC

Final states involving tau leptons are important components of searches for new particles at the Large Hadron Collider (LHC). A proper treatment of tau spin effects in the Monte Carlo (MC) simulations is important for understanding the detector acceptance as well as for the measurements of tau polarization and tau spin correlations. In this note we present a TauSpinner package designed to simulate the spin effects. It relies on the availability of the four-momenta of the taus and their decay products in the analyzed data. The flavor and the four-momentum of the boson decaying to the tau-tau+ or tau+- nu pair need to be known. In the Z/gamma* case the initial state quark configuration is attributed from the intermediate boson kinematics, and the parton distribution functions (PDF's). TauSpinner is the first algorithm suitable for emulation of tau spin effects in tau-embedded samples. It is also the first tool that offers the user the flexibility to simulate a desired spin effect at the analysis level. An algorithm to attribute tau helicity states to a previously generated sample is also provided.

hep-ph↗

arXiv2010

MC-TESTER v. 1.23: a universal tool for comparisons of Monte Carlo predictions for particle decays in high energy physics

Theoretical predictions in high energy physics are routinely provided in the form of Monte Carlo generators. Comparisons of predictions from different programs and/or different initialization set-ups are often necessary. MC-TESTER can be used for such tests of decays of intermediate states (particles or resonances) in a semi-automated way. Since 2002 new functionalities were introduced into the package. In particular, it now works with the HepMC event record, the standard for C++ programs. The complete set-up for benchmarking the interfaces, such as interface between tau-lepton production and decay, including QED bremsstrahlung effects is shown. The example is chosen to illustrate the new options introduced into the program. From the technical perspective, our paper documents software updates and supplements previous documentation. As in the past, our test consists of two steps. Distinct Monte Carlo programs are run separately; events with decays of a chosen particle are searched, and information is stored by MC-TESTER. Then, at the analysis step, information from a pair of runs may be compared and represented in the form of tables and plots. Updates introduced in the progam up to version 1.24.3 are also documented. In particular, new configuration scripts or script to combine results from multitude of runs into single information file to be used in analysis step are explained.

hep-ph↗

arXiv2010

Universal Interface of TAUOLA Technical and Physics Documentation

Because of their narrow width, tau decays can be well separated from their production process. Only spin degrees of freedom connect these two parts of the physics process of interest for high energy collision experiments. In the following, we present a Monte Carlo algorithm which is based on that property. The interface supplements events generated by other programs, with tau decays. Effects of spin, genuine weak corrections or of new physics may be taken into account at the time when a tau decay is generated and written into an event record.

hep-ph↗