arXiv subjects

H. Yamamoto

Publications and source records attributed to H. Yamamoto.

96 records · Page 6Linked to original sources

arXiv1999

Analyses of Long Lived Slepton NLSP in GMSB Model at Linear Collider

We performed an analysis on the detection of a long lived stau at a linear collider with $\sqrt{s}=500$ GeV. In GMSB models a long lived NLSP is predicted for large value of the supersymmetry breaking scale F. Furthermore in a large portion of the parameter space this particle is a stau. Such heavy charged particles will leave a track in the tracking volume and hit the muon detector. In order to disentangle this signal from the muon background we explore kinematics and particle identification tools: time of flight device, dE/dX and Cerenkov devices.

hep-ph↗

arXiv1998

Optical vernier technique for in-situ measurement of the length of long Fabry-Perot cavities

We propose a method for in-situ measurement of the length of kilometer size Fabry-Perot cavities in laser gravitational wave detectors. The method is based on the vernier, which occurs naturally when the laser incident on the cavity has a sideband. By changing the length of the cavity over several wavelengths we obtain a set of carrier resonances alternating with sideband resonances. From the measurement of the separation between the carrier and a sideband resonance we determine the length of the cavity. We apply the technique to the measurement of the length of a Fabry-Perot cavity in the Caltech 40m Interferometer and discuss the accuracy of the technique.

physics.ins-det↗

arXiv1997

Gluonic Hadrons and Charmless B Decays

Hybrid charmonium with mass ~4 GeV could be produced via a c c.bar color-octet component in b->c c.bar s. These states could be narrow and could have a significant branching ratio to light hadrons, perhaps enhanced by glueballs. Decays to gluonic hadrons could make a sizable contribution to B->no charm decays. Experimental signatures and search strategies are discussed.

hep-ph↗

arXiv1996

Tests of a High Resolution Time of Flight System Based on Long and Narrow Scintillator

We have tested a prototype time-of-flight system based on bulk scintillator block of dimensions $2.5 \times 2.5 \times 200$ cm. Using a calibration scheme similar to the one used in actual collider experiments, we have achieved a resolution of 71 ps using Amperex XP2020/UR photomultipliers and 81 ps using proximity-focusing fine-mesh photomultipliers (Hamamatsu R2021). Results are also obtained for scintillating fiber blocks of the same dimensions. Good internal reflectivity of the bulk scintillator block resulted in resolutions superior to the fibre blocks. A single-photon pulsed laser system was used to study photomultipliers and the results were used in a Monte Carlo simulation of the system to study the critical elements that determine the resolution.

hep-ex↗

arXiv1996

A lattice fermion without doubling

A free fermion without doubler is formulated on 1+D dimensional discrete Minkowski space-time. The action is not hermitian but causes no harm. In 1+3 dimensional massless case the equation describes a single species of Dirac particle in the continuous space-time limit. In 1+1 dimensional massless case the equation is the same as the automaton equation by 't Hooft and describes a chiral fermion. The time evolution operator is unitary and the norm is conserved. For interacting fermions with gauge fields the evolution operator is not unitary. If it is considered as an approximation for the theory on continuous space-time, the path integral formalism can be applied, where the fermion without doubling is used. Consequences of loosening the unitarity condition on the time evolution operator is discussed.

hep-lat↗

arXiv1995

Interference Between Cabibbo Allowed and Doubly Forbidden Transitions in $D\ra K_{S,L} + π'$s Decays

Both Cabibbo allowed and doubly forbidden transitions contribute coherently to $D\rightarrow K_{S,L}+π's$ decays. This leads to several intriguing and even quantitatively significant consequences, among them: (i) A difference between $Γ(D^+\rightarrow K_S π^+)$ and $Γ(D^+\rightarrow K_L π^+)$ and between $Γ(D^0\rightarrow K_S π^0)$ and $Γ(D^0\rightarrow K_L π^0)$ of roughly 10\% ; similarly $Γ(D^+\rightarrow [K_Sπ^0]_{K^*} π^+) \neq \frac{1}{4}Γ(D^+\rightarrow [K^-π^+]_{K^*} π^+)$, and more generally $Γ(D\rightarrow \bar K^0+π's) \neq 2Γ(D\rightarrow K_S+π's)$. (ii) A change in the relative phase between the isospin 3/2 and 1/2 amplitudes as extracted from the observed branching ratios for $D^+\rightarrow K_Sπ^+$, $D^0\rightarrow K_Sπ^0 ,\, K^-π^+$. (iii) If New Physics intervenes to provide the required {\em weak} phase, then CP asymmetries of up to a few per cent can arise in $D^+\rightarrow K_Sπ^+$ vs. $D^-\rightarrow K_Sπ^-$, $D^0\rightarrow K_Sπ^0$ vs. $\bar D^0\rightarrow K_Sπ^0$, $D^+\rightarrow [K_Sπ^0]_{K^*}π^+$ vs. $D^-\rightarrow [K_Sπ^0]_{K^*}π^-$, etc.; an asymmetry of the same size, but opposite in sign occurs when the $K_S$ is replaced by a $K_L$ in the final state.

hep-ph↗