A SEARCH FOR B+ ---> K+ NU ANTI-NU

Abstract

A search for the rare, flavour-changing neutral current decay B + → K + νν is presented using 81.9 fb −1 of data collected at the Υ (4S) resonance by the BABAR experiment. Signal candidate events are selected through the identification of a high momentum charged kaon and significant missing energy, where the companion B − in the event has decayed semileptonically via B − → D 0 − ν X and X is kinematically constrained to be either nothing or a low momentum transition photon or π 0. The analysis was performed blind and 6 candidates were selected with a background expectation of 3.4±1.2. This leads to a limit on the branching fraction of B (B + → K + νν) < 7.2 × 10 −5 at 90% confidence level. We also search for the reaction B + → π + νν and extract a limit on the branching fraction of B (B + → π + νν) < 2.5 × 10 −4 at 90% confidence level.

Structures, magnetic properties, and electronic counting rule of metals‐encapsulated cage‐like M2 Si18 (M = Ti‐Zn) clusters

“…In recent years, the way of locating a guest atom into the cage was used to obtain a stable silicon cage. [4][5][6][7][8][9][10] The atom used to stabilized cage could be nonmetal atom, [11][12][13][14] reactive metal, [15,16] rare earth metal, [17] noble metal [18] and transition metal (TM). Most of the researches focused on the structures, magnetic properties, and stability of the TM-encapsulated silicon cage clusters TMSi n , due to its specific electronic and magnetic properties.…”

Photoelectron spectroscopy of chromium-doped silicon cluster anions

“…The earliest experimental study of metal-doped silicon clusters was conducted by Beck. 13,14 He reported a mass spectrometric study of MSi n + cluster cations ͑M = Cr, Mo, W, and Cu͒, finding MSi 15 + and MSi 16 + to be the most intense species when M = Cr, Mo, or W. The earliest reported theoretical calculations on such cluster systems were performed by Jackson et al 15 who found Zr@Si 20 to be a very stable cluster. Subsequent theoretical calculations by Han and Shi 16 on MSi 15 ͑M = Cr, Mo, and W͒ and by Kumar and Kawazoe 17 on MSi 16 ͑M = Hf, Zr, and Ti͒ were carried out to study their stability and electronic structure.…”