Because of their narrow width,
τ 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
τ decays. Effects of spin, including transverse degrees of freedom, genuine weak corrections or of new physics may be taken into account at the time when a
τ decay is generated and written into an event record. The physics content of the C++ interface is already now richer than its FORTRAN predecessor.
Program title: TAUOLA++, versions 1.0.2, 1.0.3, 1.0.4, 1.0.5, 1.0.6
Catalogue identifier: AELH_v1_0
Program summary URL:
http://cpc.cs.qub.ac.uk/summaries/AELH_v1_0.html
Program obtainable from: CPC Program Library, Queenʼs University, Belfast, N. Ireland
Licensing provisions: Standard CPC licence,
http://cpc.cs.qub.ac.uk/licence/licence.html
No. of lines in distributed program, including test data, etc.: 649 068
No. of bytes in distributed program, including test data, etc.: 6 544 479
Distribution format: tar.gz
Programming language: C++, FORTRAN77
Computer: PCs, workstations
Operating system: Linux, MacOS
RAM:
<
10
MB
Classification: 11.2
External routines: HepMC (
http://lcgapp.cern.ch/project/simu/HepMC/), optional; PYTHIA8 (
http://home.thep.lu.se/~torbjorn/Pythia.html)
Subprograms used:
Cat Id
Title
Reference
ADSM_v2_0
MC-TESTER
Comput. Phys. Commun. 182 (2011) 779
Nature of problem: The code of Monte Carlo generators often has to be tuned to the needs of large HEP Collaborations and experiments. In particular
τ lepton decays need to be added (or modified) to the previously generated (or measured) events encapsulated in an event record.
Solution method: The new algorithm, the universal interface of TAUOLA which works with the HepMC event record of C++ applications is documented. It uses the
τ decay generator as described in 2 with the updates explained in 1. For the new interface spin treatment was improved. For example it features complete spin effects in processes mediated by
Z
/
γ
⁎
interactions. The effects of electroweak corrections can be taken into account in this case as well. In general, the program superseeds its FORTRAN predecessor 1. The event record analysis as well as initialization is also modernized.
Restrictions: The input event record must meet the requirements described in Section 2.3.1 of the documentation.
Unusual features: Two sets of installation scripts; an additional tool for calculating tables for electroweak corrections.
Running time: Depends on the size and complexity of the events. Small events (<50 particles), require 1 to 7 minutes for processing 1 M events on PC/Linux with a 2.4 GHz processor.
References:
1
P. Golonka, B. Kersevan, T. Pierzchala, E. Richter-Was, Z. Was, M. Worek, Comput. Phys. Commun. 174 (2006) 818.
2
S. Jadach, Z. Was, R. Decker, J.H. Kühn, Comput. Phys. Commun. 76 (1993) 361.
Radiative corrections to the neutral current Drell–Yan-like processes are considered. Complete one-loop electroweak corrections are calculated within the SANC system. Theoretical uncertainties are ...discussed. Numerical results are presented for typical conditions of LHC experiments.
Scalar QED, NLO and PHOTOS Monte Carlo Nanava, G.; Wa̧s, Z.
The European physical journal. C, Particles and fields,
08/2007, Letnik:
51, Številka:
3
Journal Article
Recenzirano
Odprti dostop
Recently, QED bremsstrahlung in B meson decays into pair of scalars (πs and/or Ks) has become of interest. If experimental acceptance must be taken into account, the PHOTOS Monte Carlo technique is ...often used in experimental simulations. We will use scalar QED to benchmark PHOTOS, even though this theory is of limited use for complex objects. We present the analytical form of the kernel used in the older versions of PHOTOS, and the new, exact (scalar QED) one. Matrix element and phase-space Jacobians are separated in the final weight, and future extensions based on measurable electromagnetic form-factors are thus possible. The massive phase-space is controlled in the program with no approximations. Thanks to the iterative solution, all leading and next to leading logarithmic terms are properly reproduced by the Monte Carlo simulation. Simultaneously, full differential distributions over the complete multiple-body phase-space are provided. An agreement of better than 0.01% with independent calculations of scalar QED is demonstrated.
Radiative corrections to the charged current Drell–Yan processes are revisited. Complete one-loop electroweak corrections are calculated within the automatic SANC system. Electroweak scheme ...dependence and the choice of the factorization scale are discussed. Comparisons with earlier calculations are presented.
Monte Carlo is often used for simulation of QED effects in decay of intermediate particles and resonances. Momenta are generated in such a way that samples of events cover the whole bremsstrahlung ...phase space. With the help of selection cuts, experimental acceptance can then be taken into account.
The program is based on an exact multi-photon phase space. A crude matrix element is obtained by iteration of a universal multidimensional kernel. It ensures exact distribution in the soft photon region. The algorithm is compatible with exclusive exponentiation. To evaluate the program’s precision, it is necessary to control the kernel with the help of perturbative results. If available, the kernel is constructed from the exact first order matrix element. This ensures that all terms necessary for non-leading logarithms are taken into account. In the present paper we will focus on the
W
→
l
ν and
γ
∗
→
π
+
π
−
decays. The Born level cross sections for both processes approach zero in some points of the phase space.
A process dependent compensating weight is constructed to incorporate the exact matrix element, but is recommended for use in tests only. In the hard photon region, where scalar QED is not expected to be reliable, the compensating weight for
γ
∗
decay can be large. With respect to the total rate, the effect remains at the permille level. It is nonetheless of interest. The terms leading to the effect are analogous to some terms appearing in QCD.
The present paper can be understood either as a contribution to discussion on how to match two collinear emission chains resulting from charged sources in a way compatible with the exact and complete phase space, exclusive exponentiation and the first order matrix element of QED (scalar QED), or as the practical study of predictions for accelerator experiments.
In this article we have summarized the status of the system
SANC version
1.00. We have implemented theoretical predictions for many high energy interactions of fundamental particles at the one-loop ...precision level for up to 4-particle processes. In the present part of our
SANC description we place emphasis on an extensive discussion of an important first step of calculations of the one-loop amplitudes of 3- and 4-particle processes in QED, QCD and EW theories.
Title of program:
SANC
Catalogue identifier: ADXK_v1_0
Program summary URL:
http://cpc.cs.qub.ac.uk/summaries/ADXK_v1_0
Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland
Designed for: platforms on which Java and FORM3 are available
Tested on: Intel-based PC's
Operating systems: Linux, Windows
Programming languages used: Java, FORM3, PERL, FORTRAN
Memory required to execute with typical data: 10 Mb
No. of bytes in distributed program, including test data, etc.: 3 658 844
No. of bits in a word: 32
No. of processors used: 1 on
SANC server, 1 on
SANC client
Distribution format: tar.gz
Nature of physical problem: Automatic calculation of pseudo- and realistic observables for various processes and decays in the Standard Model of Electroweak interactions, QCD and QED at one-loop precision level. Form factors and helicity amplitudes free of UV divergences are produced. For exclusion of IR singularities the soft photon emission is included.
Method of solution: Numerical computation of analytical formulae of form factors and helicity amplitudes. For simulation of two fermion radiative decays of Standard Model bosons
(
W
±
,
Z
)
and the Higgs boson a Monte Carlo technique is used.
Restrictions on the complexity: In the current version of
SANC there are 3 and 4 particle processes and decays available at one-loop precision level.
Typical running time: The running time depends on the selected process. For instance, the symbolic calculation of form factors (with precomputed building blocks) of Bhabha scattering in the Standard Model takes about 15 s, helicity amplitudes—about 30 s, and bremsstrahlung—10 s. The numerical computation of cross-section for this process takes about 5 s (CPU 3 GHz IP4, RAM 512 Mb, L2 1024 KB).
A Monte Carlo simulation of decays under the SANC project Nanava, G.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2003, Letnik:
502, Številka:
2
Journal Article
Recenzirano
The library of Monte Carlo programs for simulation of two particle leptonic and quark decays of the W, Z and H (Higgs) bosons with single bremsstrahlung photon emission as a part of the SANC system ...is described. The QED and EW
O(
α) radiative corrections are implemented. The decay amplitudes are numerically evaluated using the Kleiss–Stirling spinor method. Comparisons with KORALZ and PHOTOS are also presented (Comput. Phys. Commun. 66 (1991) 113; Comput. Phys. Commun. 79 (1994) 503).
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