We report an observation of the decay B{sup 0}{yields}D*{sup -}{tau}{sup +}{nu}{sub {tau}} in a data sample containing 535x10{sup 6} BB pairs collected with the Belle detector at the KEKB ...asymmetric-energy e{sup +}e{sup -} collider. We find a signal with a significance of 5.2{sigma} and measure the branching fraction B(B{sup 0}{yields}D*{sup -}{tau}{sup +}{nu}{sub {tau}})=(2.02{sub -0.37}{sup +0.40}(stat){+-}0.37(syst)) = %. This is the first observation of an exclusive B decay with a b{yields}c{tau}{nu}{sub {tau}} transition.
Future vertex detection at an upgraded KEK-B Factory, currently the highest luminosity collider in the world, will require a detector technology capable of withstanding the increased track density ...and the larger radiation exposure. Near the beam pipe the current silicon strip detectors have projected occupancies in excess of 100%. Advances in monolithic active pixel sensors (MAPS) look very promising to address this problem. These devices are also quite attractive due to the possibility of making them very thin - essential for improved tracking and vertexing in the low momenta environment of a B-factory. In the context of the Belle vertex detector upgrade, the major obstacles to realizing such a device have been concerns about radiation hardness and readout speed. Two prototypes implemented in the TSMC 0.35 /spl mu/m process have been developed to address these issues. Denoted the continuous acquisition pixel, or CAP, the two variants of this architecture are distinguished in that CAP2 includes an 8-deep sampling pipeline within each 22.5 /spl mu/m/sup 2/ pixel. Experience with this deep sub-micron process indicates tolerable threshold voltage shifts for ionizing radiation in excess of 20 Mrad. In order to maintain low occupancy and insensitivity to radiation-induced increased leakage current, correlated double sampling with a 10 /spl mu/s frame period is needed. Device description, hit resolution and irradiation results are presented.
We report the first observation of the doubly Cabibbo-suppressed decay D_{s};{+}-->K;{+}K;{+}pi;{-} using 605 fb;{-1} of data collected with the Belle detector at the KEKB asymmetric-energy ...e;{+}e;{-} collider. The branching ratio with respect to its Cabibbo-favored counterpart B(D_{s};{+}-->K;{+}K;{+}pi;{-})/B(D_{s};{+}-->K;{+}K;{-}pi;{+}) is (0.229+/-0.028+/-0.012)%, where the first uncertainty is statistical and the second is systematic. We also report a significantly improved measurement of the doubly Cabibbo-suppressed decay D;{+}-->K;{+}pi;{+}pi;{-}, with a branching ratio B(D;{+}-->K;{+}pi;{+}pi;{-})/B(D;{+}-->K;{-}pi;{+}pi;{+})=(0.569+/-0.018+/-0.014)%.
The load capacitance of the single-sided silicon microstrip detector with double-metal layers was studied. In order to understand the capacitance due to the double-metal structure, we have fabricated ...single-sided microstrip detectors with different double-metal structure on the junction (p) side or the ohmic (n) side. The measured capacitance was compared with the prediction of LEPSI-CRN model.
K + K- production in two-photon collisions has been studied using a large data sample of 67 fb-1 accumulated with the Belle detector at the KEKB asymmetric e + e- collider. We have measured the cross ...section for the process \(\gamma\gamma\to K^ + K^-\) for center-of-mass energies between 1.4 and 2.4 GeV, and found three new resonant structures in the energy region between 1.6 and 2.4 GeV. The angular differential cross sections have also been measured.
We propose a new splittable pseudorandom number generator (PRNG) based on a cryptographic hash function. Splittable PRNGs, in contrast to linear PRNGs, allow the creation of two (seemingly) ...independent generators from a given random number generator. Splittable PRNGs are very useful for structuring purely functional programs, as they avoid the need for threading around state. We show that the currently known and used splittable PRNGs are either not efficient enough, have inherent flaws, or lack formal arguments about their randomness. In contrast, our proposed generator can be implemented efficiently, and comes with a formal statements and proofs that quantify how 'random' the results are that are generated. The provided proofs give strong randomness guarantees under assumptions commonly made in cryptography.
We present the results of a study of the charmless vector-vector decay B0-->omegaK*0 with 657 x 10(6) BB pairs collected with the Belle detector at the KEKB e+e- collider. We measure the branching ...fraction to be B(B0-->omegaK*0) = 1.8+/-0.7(stat)+/-0.3(syst)x 10(-6) with 3.0sigma significance. We also perform a helicity analysis of the omega and K*0 vector mesons, and obtain the longitudinal polarization fraction fL(B0-->omegaK*0) = 0.56+/-0.29(stat) -0.08(+0.18)(syst). Finally, we measure a large nonresonant branching fraction BB0-->omegaK+pi(-);M Kpi in(0.755,1.250) GeV/c2 = 5.1+/-0.7(stat)+/-0.7(syst)x 10(-6) with a significance of 9.5sigma.
PDF
