arXiv subjects

Kentarou Mawatari

Publications and source records attributed to Kentarou Mawatari.

62 records · Page 4Linked to original sources

arXiv2009

Jet angular correlation in vector-boson fusion processes at hadron colliders

Higgs boson and massive-graviton productions in association with two jets via vector-boson fusion (VBF) processes and their decays into a vector-boson pair at hadron colliders are studied. They include scalar and tensor boson production processes via weak-boson fusion in quark-quark collisions, gluon fusion in quark-quark, quark-gluon and gluon-gluon collisions, as well as their decays into a pair of weak bosons or virtual gluons which subsequently decay into $\ell\bar\ell$, $q\bar q$ or $gg$. We give the helicity amplitudes explicitly for all the VBF subprocesses, and show that the VBF amplitudes dominate the exact matrix elements not only for the weak-boson fusion processes but also for all the gluon fusion processes when appropriate selection cuts are applied, such as a large rapidity separation between two jets and a slicing cut for the transverse momenta of the jets. We also show that our off-shell vector-boson current amplitudes reduce to the standard quark and gluon splitting amplitudes with appropriate gluon-polarization phases in the collinear limit. Nontrivial azimuthal angle correlations of the jets in the production and in the decay of massive spin-0 and -2 bosons are manifestly expressed as the quantum interference among different helicity states of the intermediate vector-bosons. Those correlations reflect the spin and the CP nature of the Higgs bosons and the massive gravitons.

hep-ph↗

arXiv2008

Determining Spin through Quantum Azimuthal-Angle Correlations

Determining the spin of new particles is critical in identifying the true theory among various extensions of the Standard Model at the next generation of colliders. Quantum interference between different helicity amplitudes was shown to be effective when the final state is fully reconstructible. However, many interesting new physics processes allow only for partial reconstruction. In this paper, we show how the interference effect can be unambiguously extracted even in processes that have two-fold ambiguity, by considering the correlation between two decay planes in e+ e- collisions.

hep-ph↗

arXiv2008

HELAS and MadGraph/MadEvent with spin-2 particles

Fortran subroutines to calculate helicity amplitudes with massive spin-2 particles (massive gravitons), which couple to the standard model particles via the energy momentum tensor, are added to the {\tt HELAS} ({\tt HEL}icity {\tt A}mplitude {\tt S}ubroutines) library. They are coded in such a way that arbitrary scattering amplitudes with one graviton production and its decays can be generated automatically by {\tt MadGraph} and {\tt MadEvent}, after slight modifications. All the codes have been tested carefully by making use of the invariance of the helicity amplitudes under the gauge and general coordinate transformations.

hep-ph↗

arXiv2008

Graviton production with 2 jets at the LHC in large extra dimensions

We study Kaluza-Klein (KK) graviton production in the large extra dimensions model via 2 jets plus missing transverse momentum signatures at the LHC. We make predictions for both the signal and the dominant Zjj and Wjj backgrounds, where we introduce missing P_T-dependent jet selection cuts that ensure the smallness of the 2-jet rate over the 1-jet rate. With the same jet selection cuts, the distributions of the two jets and their correlation with the missing transverse momentum provide additional evidence for the production of an invisible massive object.

hep-ph↗

arXiv2007

T-odd asymmetries in radiative top-quark decays

We study the angular distribution of the charged lepton in the top-quark decay into a bottom quark and a W boson which subsequently decays into \ellν_{\ell}, when a hard gluon is radiated off. The absorptive part of the t \to bWg decay amplitudes, which gives rise to T-odd asymmetries in the distribution, is calculated at the one-loop level in perturbative QCD. The asymmetries at a few percent level are predicted, which may be observable at future colliders.

hep-ph↗

arXiv2007

Tau polarization in SUSY cascade decays at LHC

We explore how the polarization of the tau leptons in the cascade decay $\tilde{q}\to q\tildeχ^0_2\to qτ\tildeτ\to qττ\tildeχ^0_1$ can be exploited to study mixing properties of neutralinos and staus. We present details of the analysis including experimental effects such as transverse momentum cuts for the $τ\toπν$ decay mode, and show that the di-pion invariant mass distribution provides valuable information on their properties.

hep-ph↗

arXiv2006

Tau polarization effects in the CNGS tau-neutrino appearance experiments

We studied tau polarization effects on the decay distributions of tau produced in the CNGS tau-neutrino appearance experiments. We show that energy and angular distributions for the decay products in the laboratory frame are significantly affected by the tau polarization. Rather strong azimuthal asymmetry about the tau momentum axis is predicted, which may have observable consequences in experiments even with small statistics.

hep-ph↗

arXiv2005

The Decay of Tau Leptons Produced in Neutrino-Nucleon Scatterings

Energy and angular distributions of the tau decay products in the CERN-to-Gran Sasso $ν_τ$ appearance experiments are studied for the decay modes $τ\toπν$ and $τ\to l\barνν$ (l=e or mu). We find that the decay particle distributions in the laboratory frame are significantly affected by the tau polarization. Rather strong azimuthal asymmetry of $pi^-$ and $l^-$ about the tau momentum axis is predicted, which may have observable consequences even at small statistics experiments.

hep-ph↗