114794158
KOTO detector status
The KOTO experiment at the J-PARC laboratory seeks to achieve the first observation of the KL→ π0νν decay, as a direct measurement of the CP-violating parameter in the Standard Model. Many improvements are being made over the previous KEK E391a experiment. Almost all the detector subsystems have been fabricated and installed by December 2012. This paper describes the detector performance and calibration methods based on the experience of the engineering run in January 2013.
16792463
CsI Calorimeter and low power PMT base for KOTO experiment
KOTO is the first experiment in the world specialized in observing the decay KL → π0νν . The decay is sensitive to new physics scenarios beyond the Standard Model. The most important detector of KOTO is the CsI calorimeter, which measures positions and energies of gammas from KL, in order to reconstruct the vertexes of them. There are mainly three requirements for the calorimeter. First, dynamic range for each channel of CsI is more than 3 order of magnitude. Second, single counting rate is about 120 kHz comes from beam intensity. And linearity is required less than ±5% in order to discriminate the signals and backgrounds. Finally, to suppress the backgrounds, we will put the calorimeter at the vacuum level of 0.1Pa. So we must reduce its power consumption. That is why we plan to use the Cockcroft-Walton circuit as a high voltage supply for PMTs. It can reduce power down to about 150mW.
119113969
Constraints on a class of classical solutions in open string field theory
A bstractWe calculate boundary states for general string fields in the KBc subalgebra under some regularity conditions based on the construction by Kiermaier, Okawa, and Zwiebach. The resulting boundary states are always proportional to that for the perturbative vacuum |B〉. In this framework, the equation of motion implies that boundary states are independent of the auxiliary parameter s associated with the length of the boundary. By requiring the s-independence, we show that the boundary states for classical solutions in our class are restricted to ±|B〉 and 0. In particular, there exist no string fields which reproduce boundary states for multiple D-brane backgrounds. While we know that the boundary states |B〉 and 0 are reproduced by solutions for the perturbative vacuum and the tachyon vacuum, respectively, no solutions reproducing −|B〉 have been constructed. In this paper we also propose a candidate for such a solution, which may describe the ghost D-brane.
119231802
Gauge-invariant observables and marginal deformations in open string field theory
A bstractThe level-truncation analysis of open string field theory for a class of periodic marginal deformations indicates that a branch of solutions in Siegel gauge exists only for a finite range of values of the marginal field. The periodicity in the deformation parameter is thus obscure. We use the relation between gauge-invariant observables and the closed string tadpole on a disk conjectured by Ellwood to construct a map between the deformation parameter of the boundary conformal field theory and the parameter labeling classical solutions of open string field theory. We evaluate the gauge-invariant observables for the numerical solutions in Siegel gauge up to level 12 and find that our results qualitatively agree with the analysis by Sen using the energy-momentum tensor and are consistent with the picture that the finite range of the branch covers one fundamental domain of the periodic moduli space.