496 research outputs found
A simple merging algorithm for jet angular correlation studies
A tree level merging algorithm which guarantees the leading order (LO)
accuracy of angular correlations between jets is proposed and studied. The
algorithm is designed so that n-jet events are generated exclusively according
to the LO n-parton production cross section and each of the n-jet is close to
each of the n-parton in terms of the jet measure. As a result, the LO accuracy
of angular correlations between the n-jet is robust. Furthermore, as long as
the n-jet events are exclusively subjects to a study, only the LO n-parton
production cross section is needed and hence event generation is efficient.
Correlations in the azimuthal angle difference between the two highest
transverse momentum jets with large rapidity separations in the top quark pair
production are evaluated as examples. The algorithm is validated by discussing
numerical differences between its predictions and the predictions of a
well-established merging algorithm.Comment: 15 pages, 2 figure
A set of new observables in the process
Consequences of non-standard Higgs couplings in the final-state distributions
of the process are studied. We derive an analytic
expression for the differential cross section, which has in the most general
case 9 non-zero functions. These functions are the coefficients of 9 angular
terms, depend on the Higgs couplings, and can be experimentally measured as
observables. Symmetry properties of these 9 functions are carefully discussed,
and they are divided into 4 categories under CP and . The
relations between our observables and the observables which exist in the
literature are also clarified. We numerically study the dependence of our
observables on the parameters in an effective Lagrangian for the Higgs
couplings. It is shown that these new observables depend on most of the
effective Lagrangian parameters in different ways from the total cross section.
A benefit from longitudinally polarized beams is also discussed.Comment: 11 pages, v2: the explanation of Section 4 is improve
Jet azimuthal angle correlations in the production of a Higgs boson pair plus two jets at hadron colliders
Azimuthal angle correlations of two jets in the process are
studied. The loop induced gluon fusion
(GF) sub-process and the weak boson fusion (WBF)
sub-process are considered. The GF sub-process exhibits strong correlations in
the azimuthal angles of the two jets measured from the
production plane of the Higgs boson pair and the difference between these two
angles , and a very small correlation in the sum of them
. The impact of using a finite top mass value on
the correlations is found crucial. The transverse momentum of the Higgs boson
can be used to enhance or suppress the correlations. The impact of a
non-standard value for the triple Higgs self-coupling on the correlations is
found much smaller than that on other observables, such as the invariant mass
of the two Higgs bosons. The peak shifts of the azimuthal angle distributions
reflect the magnitude of parity violation in the amplitude and the
dependence of the distributions on parity violating phases is analytically
clarified. The WBF sub-process also produces correlated distributions and it is
found that they are not induced by the quantum effect of the intermediate weak
bosons but mainly by a kinematic effect. This kinematic effect is a
characteristic feature of the WBF sub-process and is not observed in the GF
sub-process. It is found that the correlations are different in the GF and in
the WBF sub-processes. As part of the process dependent information, they will
be helpful in the analyses of both the GF sub-process and the WBF sub-process
at the LHC.Comment: 35 pages, 12 figures, 3 table
TauDecay: a library to simulate polarized tau decays via FeynRules and MadGraph5
TauDecay is a library of helicity amplitudes to simulate polarized tau
decays, constructed in the FeynRules and MadGraph5 framework. Together with the
leptonic mode, the decay library includes the main hadronic modes, \tau \to
\nu_{\tau}+\pi, 2\pi, and 3\pi, which are introduced as effective vertices by
using FeynRules. The model file allows us to simulate tau decays when the
on-shell tau production is kinematically forbidden. We also demonstrate that
all possible correlations among the decay products of pair-produced taus
through a Z boson and a scalar/pseudoscalar Higgs boson are produced
automatically. The program has been tested carefully by making use of the
standard tau decay library Tauola.Comment: 10 pages, 12 figures, 3 tables; v2: typo in Eq.(20b) corrected,
references added, version accepted by EPJC. 'Note added' also included for
the brief TauDecay instruction in MadGraph5_aMC@NL
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