In this paper the revised Kajantie-Byckling approach and improved phase space sampling techniques for the massive multi-particle final states are presented. The application of the developed ...procedures to the processes representative for LHC physics indicates the possibility of a substantial simplification of multi-particle phase space sampling while retaining a respectable weight variance reduction and unweighing efficiencies in the event generation process.
The
AcerMC Monte Carlo Event Generator is dedicated for the generation of Standard Model background processes at
pp LHC collisions. The program itself provides a library of the massive matrix ...elements and phase space modules for generation of a set of selected processes:
gg,q
q
̄
→t
t
̄
b
b
̄
,
q
q
̄
W(→ℓν)b
b
̄
,
q
q
̄
W(→ℓν)t
t
̄
,
gg,q
q
̄
→Z/γ
∗(→ℓℓ)b
b
̄
,
gg,q
q
̄
→Z/γ
∗(→ℓℓ,νν,b
b
̄
)t
t
̄
and complete electroweak
gg→(Z/W/γ
∗→)b
b
̄
t
t
̄
process. The hard process event, generated with one of these modules, can be completed by the initial and final state radiation, hadronization and decays, simulated with either
PYTHIA or
HERWIG Monte Carlo event generator. Interfaces to both of these generators are provided in the distribution version. The matrix element codes have been derived with the help of the
MADGRAPH package. The phase-space generation is based on the multi-channel self-optimizing approach as proposed in
NEXTCALIBUR event generator. Eventually, additional smoothing of the phase space was obtained by using a modified
ac-VEGAS routine in order to improve the generation efficiency.
Lifetime and oscillations of B-s(0) mesons have been studied in events with a large transverse momentum lepton and a D-s of opposite electric charge in the same hemisphere, selected from about 3.6 ...million hadronic Z(0) decays accumulated by DELPHI between
Neutral Higgs bosons of the Standard Model (SM) and the Minimal Supersymmetric Standard Model (MSSM) were searched for in the data collected in 1999 by the DELPHI experiment at centre-of-mass ...energies between 191.6 and 201.7 GeV with a total integrated luminosity of 228 pb(-1). These analyses, in combination with our results at lower energies, set 95% confidence level lower mass bounds on the Standard Model Higgs boson (107.3 GeV/c(2)) and on the lightest neutral scalar (85.9 GeV/c(2)) and neutral pseudoscalar (86.5 GeV/c(2)) Higgs bosons in representative scans of the MSSM parameter space. An extended scan of the MSSM parameter space was also performed to test the robustness of these limits.
A measurement of the FV mass and width has been performed by the DELPHI Collaboration using the data collected during 1998. The data sample has an integrated luminosity of 155 pb(-1) and an average ...centre-of-mass energy of 188.6 GeV. Results are obtained
A search for pair-produced charged Higgs bosons was performed in the high energy data collected by the DELPHI detector at LEP II at centre-of-mass energies from 189 GeV to 202 GeV. The three ...different final states, taunutaunu, c (s) over bar(c) over bars and c (s) over bar taunu were considered. New methods were applied to reject wrong hadronic jet pairings and for the tau identification, where a discriminator based on tau polarisation and polar angles was used. No excess of data compared to the expected Standard Model processes was observed and the existence of a charged Higgs boson with mass lower than 71.5 GeV/c(2) is excluded at the 95% confidence level. (C) 2002 Published by Elsevier Science B.V.
Searches for neutral Higgs bosons in the Standard Model and the MSSM have been performed using data collected by the DELPHI experiment at a centre-of-mass energy of 188.7 GeV, corresponding to an ...integrated luminosity of 158 pb(-1). These analyses are use
Observation is made of rapidity-alignment of K+K- and (p) over barp pairs which results from their asymmetric orientation in rapidity, with respect to the direction from primary quark to antiquark. ...The K+K- and (p) over barp data are consistent with predictions from the fragmentation string model. However, the (p) over barp data strongly disagree with the conventional implementation of the cluster model. The non-perturbative process of 'gluon splitting to diquarks' has to be incorporated into the cluster model for it to agree with the data. Local conservation of PT between particles nearby in rapidity (i.e., p(T) compensation) is analysed with respect to the thrust direction for pi(+)pi(-), K+K-, and (p) over barp pairs. In this case, the string model provides fair agreement with the data. The cluster model is incompatible with the data for all three particle pairs. The model with its central premiss of isotropically-decaying clusters predicts a p(T) correlation not seen in the data. (C) 2002 Elsevier Science B.V. All rights reserved.
A search for pair-production of neutralinos at a LEP centre-of-mass energy of 189 GeV gave no evidence for a signal. This limits the neutralino production cross-section and excludes regions in the ...parameter space of the Minimal Supersymmetric Standard Mod
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