6,782 research outputs found
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 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
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
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
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
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
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
Machine learning classification: case of Higgs boson CP state in H to tau tau decay at LHC
Machine Learning (ML) techniques are rapidly finding a place among the
methods of High Energy Physics data analysis. Different approaches are explored
concerning how much effort should be put into building high-level variables
based on physics insight into the problem, and when it is enough to rely on
low-level ones, allowing ML methods to find patterns without explicit physics
model.
In this paper we continue the discussion of previous publications on the CP
state of the Higgs boson measurement of the H to tau tau decay channel with the
consecutive tau^pm to rho^pm nu; rho^pm to pi^pm pi^0 and tau^pm to a_1^pm nu;
a_1^pm to rho^0 pi^pm to 3 pi^pm cascade decays. The discrimination of the
Higgs boson CP state is studied as a binary classification problem between
CP-even (scalar) and CP-odd (pseudoscalar), using Deep Neural Network (DNN).
Improvements on the classification from the constraints on directly
non-measurable outgoing neutrinos are discussed. We find, that once added, they
enhance the sensitivity sizably, even if only imperfect information is
provided. In addition to DNN we also evaluate and compare other ML methods:
Boosted Trees (BT), Random Forest (RF) and Support Vector Machine (SVN).Comment: 1+20 pages, 9 figures, 6 tables, extended content and improved
readabilit
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