arXiv subjects

K. Mawatari

Publications and source records attributed to K. Mawatari.

28 records · Page 2Linked to original sources

arXiv2011

An H-alpha search for over-dense regions at z=2.23

We present the results of a narrow-band (H2S1, 2.121/0.021um) imaging search with WFCAM/UKIRT for H-alpha emitters around several potential signposts of rare (10^-7-10^-8 Mpc^-3) over-dense regions at z=2.23: an over-density of QSOs (2QZ cluster), a powerful, high-redshift radio galaxy (HzRG), and a concentration of submillimetre galaxies (SMGs) and optically faint radio galaxies (OFRGs). In total, we detect 137 narrow-band emitter candidates down to emission-line fluxes of 0.5-1 x 10^-16 erg s^-1 cm^-2, across a total area of 0.56 sq. degrees (2.1 x 10^5 comoving Mpc at z=2.23) in these fields. The BzK colours of the emitters suggest that at least 80% of our sample are likely to be H-alpha emitters (HAEs) at z=2.23. This is one of the largest HAE samples known at z>2. We find modest (~3-sigma) local over-densities of emitters associated with all the three targets. In the 2QZ cluster field, the emitters show a striking filamentary structure connecting four of the z=2.23 QSOs extending over 30Mpc (comoving). In the HzRG and SMG/OFRG fields, the structures appear to be smaller and seen only in the vicinities of the targets. The K-band magnitudes and the H-alpha equivalent widths of the emitters are weakly correlated with the over-density of the emitters: emitters in over-dense region are more evolved systems compared to those in under-dense regions at z=2.23. We find several examples of extended HAEs in our target fields, including a striking example with a spatial extent of 7.5 arcsec (60 kpc at z=2.23) in the 2QZ field, suggesting that these are relatively common in high-density regions. We conclude that narrow-band H-alpha surveys are efficient routes to map over-dense regions at high-z and thus to understand the relation between the growth of galaxies and their surrounding large-scale structures.

astro-ph.CO↗

arXiv2011

HELAS and MadGraph with spin-3/2 particles

Fortran subroutines to calculate helicity amplitudes with massive spin-3/2 particles, such as massive gravitinos, which couple to the standard model and supersymmetric particles via the supercurrent, are added to the HELAS (HELicity Amplitude Subroutines) library. They are coded in such a way that arbitrary amplitudes with external gravitinos can be generated automatically by MadGraph, after slight modifications. All the codes have been tested carefully by making use of the gauge invariance of the helicity amplitudes.

hep-ph↗

arXiv2006

Spin Analysis of Supersymmetric Particles

The spin of supersymmetric particles can be determined at $e^+e^-$ colliders unambiguously. This is demonstrated for a characteristic set of non-colored supersymmetric particles -- smuons, selectrons, and charginos/neutralinos. The analysis is based on the threshold behavior of the excitation curves for pair production in $e^+e^-$ collisions, the angular distribution in the production process and decay angular distributions. In the first step we present the observables in the helicity formalism for the supersymmetric particles. Subsequently we confront the results with corresponding analyses of Kaluza-Klein particles in theories of universal extra space dimensions which behave distinctly different from supersymmetric theories. It is shown in the third step that a set of observables can be designed which signal the spin of supersymmetric particles unambiguously without any model assumptions. Finally in the fourth step it is demonstrated that the determination of the spin of supersymmetric particles can be performed experimentally in practice at an $e^+e^-$ collider.

hep-ph↗

arXiv2006

$τ$ Polarization in SUSY Cascade Decays

$τ$ leptons emitted in cascade decays of supersymmetric particles are polarized. The polarization may be exploited to determine spin and mixing properties of the neutralinos and stau particles involved.

hep-ph↗

arXiv2006

Correlated decays of pair-produced scalar taus

We study the quantum mechanical correlation between two identical neutralinos in the decays of minimal supersymmetric standard model (MSSM) scalar tau (stau) pair produced in e+e- annihilation. Generally, the decay products of scalar (spinless) particles are not correlated. We show that a correlation between two neutralinos appears near pair production threshold, due to a finite stau width and mixing of the staus and/or neutralinos, and because the neutralinos are Majorana. Because the correlation is significant only in a specific kinematical configuration, it can be observed only in supersymmetric models where the neutralino momenta can be kinematically reconstructed, such as in models with R-parity violation.

hep-ph↗

arXiv2004

0^+ and 1^+ States of B and B_s Mesons

Predicted masses of J^P=0^+ and 1^+ states of D_{sJ} and D by a potential model proposed some time ago by two of us (T.M. and T.M.), in which the Hamiltonian and wave functions are expanded in 1/m_Q with m_Q heavy quark mass respecting heavy quark symmetry, have recently been confirmed by BaBar and Belle experiments within one percent accuracy. In this Letter, decay modes of 0^+ and 1^+ states of B and B_s mesons are discussed using the predicted masses of this model.

hep-ph↗

arXiv2004

Polarization effects in tau production by neutrino

We studied polarization effects in tau production by neutrino-nucleon scattering. Quasi-elastic scattering, $Delta$ resonance production and deep inelastic scattering processes are taken into account for the CERN-to-Gran Sasso projects. We show that the tau produced by neutrino has high degree of polarization, and its spin direction depends non-trivially on the energy and the scattering angle of tau in the laboratory frame.

hep-ph↗

arXiv2004

Spinor Operator Giving Both Angular Momentum and Parity

In heavy quark effective theory, heavy mesons which contain a heavy quark (or antiquark) are classified by $s_l^{pi_l}$, i.e., the total angular momentum $s_l$ and the parity $pi_l$ of the light quark degrees of freedom around a static heavy quark. In this case, however, one needs to separately estimate the parity other than the angular momentum of a light quark to describe heavy mesons. A new operator $K$ was proposed some time ago by two of us (T.M. and T.M.). In this Letter, we show that the quantum number $k$ of this operator is enough to describe both the total angular momentum of the light quark degrees of freedom and the parity of a heavy meson, and derive a simple relation between $k$ and $s_l^{pi_l}$.

hep-ph↗

arXiv2004

Pseudoscalar Form Factors in Tau-Neutrino Nucleon Scattering

We investigate the pseudoscalar transition form factors of nucleon for quasi-elastic scattering and Δresonance production in tau-neutrino nucleon scattering via the charged current interactions. Although the pseudoscalar form factors play an important role for the τproduction in neutrino-nucleon scattering, these are not known well. In this article, we examine their effects in quasi-elastic scattering and Δresonance production and find that the cross section, Q^{2} distribution, and spin polarization of the produced τ^{\pm} leptons are quite sensitive to the pseudoscalar form factors.

hep-ph↗

arXiv2004

Tau Polarization in Tau-Neutrino Nucleon Scattering

We investigate the spin polarization of τ^{\pm} leptons produced in ν_τ and \barν_τ nucleon scattering via charged currents. Quasi-elastic scattering, Δresonance production and deep inelastic scattering processes are studied. The polarization information is essential for measuring the τ^{\pm} appearance rate in long baseline neutrino oscillation experiments, because the decay particle distributions depend crucially on the τ^{\pm} spin. In this article, we calculate the spin density matrix of each process and estimate the spin polarization vector in medium and high neutrino energy interactions. We find that the produced τ^{\pm}'s have high degree of polarization, and their spin direction depends non-trivially on the energy and the scattering angle of τ^{\pm} in the laboratory frame.

hep-ph↗