1,433 research outputs found
The Monte Carlo Event Generator YFSWW3 version 1.16 for W-Pair Production and Decay at LEP2/LC Energies
We present the Monte Carlo event generator YFSWW3 version 1.16 for theprocess
of W-pair production and decay in electron-positron collisions. It includes
electroweak radiative corrections in the WW production stage
together with the initial-state-radiation (ISR)
corrections in the leading-logarithmic (LL) approximation, implemented within
the Yennie-Frautschi-Suura (YFS) exclusive exponentiation framework. The photon
radiation in the W decays is generated by the dedicated program PHOTOS up to
LL, normalised to the W branching ratios. The program is
interfaced with the decay library TAUOLA and the quark
fragmentation/hadronization package JETSET. The semi-analytical code KORWAN for
the calculations of the differential and total cross-sections at the Born level
and in the ISR approximation is included.Comment: submitted to Comput. Physics Commu
The Monte Carlo Program KoralW version 1.51 and The Concurrent Monte Carlo KoralW&YFSWW3 with All Background Graphs and First Order Corrections to W-Pair Production
The version 1.51 of the Monte Carlo (MC) program KoralW for all processes is presented. The most important change
since the previous version 1.42 is the facility for writing MC events on the
mass storage device and re-processing them later on. In the re-processing one
may modify parameters of the Standard Model in order to fit them to
experimental data. Another important new feature is a possibility of including
complete corrections to double-resonant W-pair
component-processes in addition to all background (non-WW) graphs. The
inclusion is done with the help of the YFSWW3 MC event generator for fully
exclusive differential distributions (event-per-event). Technically, it is done
in such a way that YFSWW3 runs concurrently with KoralW as a separate slave
process, reading momenta of the MC event generated by KoralW and returning the
correction weight to KoralW. KoralW introduces the
correction using this weight, and finishes processing the event (rejection due
to total MC weight, hadronization, etc.). The communication between KoralW and
YFSWW3 is done with the help of the FIFO facility of the UNIX/Linux operating
system. This does not require any modifications of the FORTRAN source codes.
The resulting Concurrent MC event generator KoralW&YFSWW3 looks from the user's
point of view as a regular single MC event generator with all the standard
features.Comment: 8 figures, 5 tables, submitted to Comput. Phys. Commu
Linear Programming in the Semi-streaming Model with Application to the Maximum Matching Problem
In this paper, we study linear programming based approaches to the maximum
matching problem in the semi-streaming model. The semi-streaming model has
gained attention as a model for processing massive graphs as the importance of
such graphs has increased. This is a model where edges are streamed-in in an
adversarial order and we are allowed a space proportional to the number of
vertices in a graph.
In recent years, there has been several new results in this semi-streaming
model. However broad techniques such as linear programming have not been
adapted to this model. We present several techniques to adapt and optimize
linear programming based approaches in the semi-streaming model with an
application to the maximum matching problem. As a consequence, we improve
(almost) all previous results on this problem, and also prove new results on
interesting variants
Penguin Effects in and
Controlling the contributions from doubly Cabibbo-suppressed penguin topologies in the decays and is mandatory to reach the highest possible precision in the measurement of the -- () mixing phases and . The penguin contributions can be determined using a strategy based on the flavour symmetry of QCD. Using the latest experimental data, we update our combined analysis of the decays , and their control channels , and . This allows us to simultaneously determine the penguin parameters and both mixing phases. We discuss how the branching fractions of these decays can be used to probe the size of non-factorisable -breaking effects, which form the main theoretical uncertainty associated with our -based strategy, and provide new insights into the factorisation approach
Strong and Weak Phases from Time-Dependent Measurements of
Time-dependence in and \ob(t) \to \pi^+ \pi^- is
utilized to obtain a maximal set of information on strong and weak phases. One
can thereby check theoretical predictions of a small strong phase
between penguin and tree amplitudes. A discrete ambiguity between and may be resolved by comparing the observed
charge-averaged branching ratio predicted for the tree amplitude alone, using
measurements of and factorization, or by direct comparison of
parameters of the Cabibbo-Kobayashi-Maskawa (CKM) matrix with those determined
by other means. It is found that with 150 fb from BaBar and Belle, this
ambiguity will be resolvable if no direct CP violation is found. In the
presence of direct CP violation, the discrete ambiguity between and
becomes less important, vanishing altogether as . The role of measurements involving the lifetime difference between
neutral eigenstates is mentioned briefly.Comment: 14 pages, LaTeX, 5 figures, to be published in Phys. Rev. D. Updated
version with one reference change
Combining CP Asymmetries in Decays
We prove an approximate relation, to leading order in dominant terms, between
CP-violating rate differences in and
. We show how data from these two processes may be
combined in order to enhance the significance of a nonzero result.Comment: 9 pages, latex, no figures, submitted to Phys. Rev. Letters, revise
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