Tomohiko Tanabe

Physics Case for the International Linear Collider

We summarize the physics case for the International Linear Collider (ILC). We review the key motivations for the ILC presented in the literature, updating the projected measurement uncertainties for the ILC experiments in accord with the expected schedule of operation of the accelerator and the results of the most recent simulation studies.

The 2+2 and 4+1 states of the even isotopes 78–86Kr excited in the inelastic scattering of 51.9 MeV protons

Abstract The 2 + 2 and 4 + 1 states of the even isotopes 78–86 Kr have been studied by the inelastic scattering of protons. The B (E2;0 + g → 2 + 2 ) values of these isotopes are roughly equal, where as the B (E4; + g → 4 + 1 ) values decrease to a minimum at 82 Kr and then increase with neutron number. Comparison of the experimental results with current theoretical models implies an abrupt change of structure between 78–82 Kr and 84–86 Kr.

Systematics of low-lying octupole states in the doubly-even nuclei from Ge to Sr

Abstract Low-lying octupole states of doubly-even 78–86Kr isotopes have been studied with inelastic scattering of 51.9 MeV protons. It is shown that in the doubly-even nuclei from Ge to Sr with N = 42–50, the lowest octupole vibrational energies of nuclei with equal neutron excess are almost the same. The transition strengths of these states increase with Z.

Splitting of low-lying octupole vibrational strength in 76,78,80,82Kr

Abstract Two low-lying octupole states of 78,80,82Kr, which were previously observed in inelastic proton scattering to share the low-lying octupole vibrational strength, were found to be strongly excited in the (p,t) reaction. Characteristics of these states and a comparison with the IBM model strongly suggest that the splittings in the lighter isotopes 76,78,80,82Kr are due to a coupling of the octupole vibration to the quadrupole degree of freedom.

Measuring the top Yukawa coupling at the ILC at

We report on the feasibility of the direct measurement of the top Yukawa coupling g_t at the International Linear Collider (ILC) during its first phase of operation with a center-of-mass energy of 500 GeV. The signal and background models incorporate the non-relativistic QCD corrections which enhance the production cross section near the t-tbar threshold. The e+e- -> t tbar H signal is reconstructed in the 6-jet + lepton and the 8-jet modes. The results from the two channels are combined. The background processes considered are e+e- -> t bbar W- / tbar b W+ (which includes e+e- -> t tbar), e+e- -> t tbar Z, and e+e- -> t tbar g* -> t tbar b bar. We use a realistic fast Monte-Carlo detector simulation. Signal events are selected using event shape variables, through jet clustering, and by identifying heavy flavor jets. Assuming a Higgs mass of 120 GeV, polarized electron and positron beams with (Pe-,Pe+) = (-0.8,+0.3), and an integrated luminosity of 1 ab-1, we estimate that the e+e- -> t tbar H events can be seen with a statistical significance of 5.2 sigma, corresponding to the relative top Yukawa coupling measurement accuracy of |Delta g_t / g_t| = 10%.

\sqrt{s}=500

Abstract High spin states in the 2s-1d shell nuclei of 18F, 20F, 22Na, 24Na, 26Al, and 30P have been investigated by (α, d) reactions at incident energies of 64.3–65.3 MeV. The ( f 7 2 ) 2 7 + states in 20F, 22Na and 24Na, and the ( f 7 2 d 5 2 )6 − states in 20F and 24Na are proposed. The systematic dependenc of the Q-value and intensity on the mass number for the (α, d) reaction leading to the 5+, 6−, and 7+ states is obtained. For the 7+ states, the dependence of the Q-values on the mass number in the mass region below 26 deviates from the line expected from the results of heavier 2s-1d shell nuclei. The excitation energies of the ( f 7 2 ) 2 7 + states expected from a crude shell-model calculation are in good agreement with the experimental data. Using the Q-values for the 7+ states and empirical binding energies for the single-particle f 7 2 shell orbit, a mass dependency of the p-n interaction energies for the ( f 7 2 ) 2 7 + configuration has been found to be E[( f 7 2 ) 2 7 + ] = − 100 A of these 2s-1d shell nuclei.

GeV

Abstract We report on the progress in flavor identification tools developed for a future e + e − linear collider such as the International Linear Collider (ILC) and Compact Linear Collider (CLIC). Building on the work carried out by the LCFIVertex collaboration, we employ new strategies in vertex finding and jet finding, and introduce new discriminating variables for jet flavor identification. We present the performance of the new algorithms in the conditions simulated using a detector concept designed for the ILC. The algorithms have been successfully used in ILC physics simulation studies, such as those presented in the ILC Technical Design Report.

High spin states of 2s-1d shell nuclei excited by (α, d) reactions

Abstract The reactions ( 3 He, t), ( 3 He, 3 He), ( 3 He, α) and ( 3 He, d) on 48 Ca have been studied at an incident energy of 82 MeV. The obtained angular distributions for the ( 3 He, t) reaction have been analyzed in terms of second-order DWBA theory, using a zero-range approximation. The relative ratio of the cross sections for the excitation of the f in 7 2 f 7 2 −1 multiplets of 48 Sc could not be explained consistently by the one-step charge-exchange process only. However, the ratio was reproduced in order of magnitude by second-order DWBA calculations including the effect of two-step processes, such as ( 3 He-α-t) and ( 3 He-d-t) channels. The effects of the d- and α-channels on the elastic scattering of 3 He from 48 Ca were also examined in the framework of second-order full finite-range DWBA.

LCFIPlus: A Framework for Jet Analysis in Linear Collider Studies

Abstract The 27 Al(α, t) and (α, 3 He) reactions have been measured at E α = 64.5 MeV. The experimental angular distributions were analyzed by the exact finite-range DWBA calculations assuming a nucleon stripping mechanism. The distributions of spectroscopic strengths for the single-particle transitions with transferred angular momenta l = 0, 1, 2, 3 and 4 have been obtained. The strengths for the transitions to the stretched 6 − states in 28 Si and 28 Al are compared to those obtained from inelastic scattering on 28 Si. The present results show no distinctive differences in the structures for 6 − T = 0 and 1 states in 28 Si such as are observed in proton and pion inelastic scattering on 28 Si.

Study of the (3He, t) reaction on 48Ca at 82 MeV

A core prediction of natural Supersymmetry is the existence of four light higgsinos not too far above the mass of the