arXiv · 0707.1007
This short review reports on recent results from CDF and D0 experiments at the Tevatron collider on Bs mixing and the lifetimes of Bs and Lambdab.
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Mossadek Talby. 2007-07-11. Bs Mixing and decays at the Tevatron. https://arxiv.org/abs/0707.1007
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Germanium charge-coupled devices (Ge-CCDs) extend CCD imaging beyond the silicon cutoff and are candidate detectors for the near-infrared channel of future astronomical instruments, in particular the spectrographs of next-generation wide-field surveys. We report the laboratory characterization at Brookhaven National Laboratory (BNL) of a prototype fabricated at MIT Lincoln Laboratory. We describe the cryogenic test system and readout, and present measurements of the output waveform, dark current, readout noise, and X-ray response. The dark current at 94.69 K is $26.12 \pm 0.08$ e$^-$ pixel$^{-1}$ s$^{-1}$. Under $^{55}$Fe irradiation without on-chip binning, the charge generated by an X-ray is confined within $2\times2$ pixels, and the Mn K$α$ line has a full width at half maximum (FWHM) of $8.5 \pm 0.1$% for single-pixel events. Since the charge generated by X-rays above about 30 keV spreads over $3\times3$ or more pixels, the CCD was operated with $2\times2$ on-chip binning at higher energies. This yielded FWHMs of $8.4\pm0.4$% at 30.9 keV ($^{133}$Ba, ASCA grades 0, 2, 3, 4, and 6) and $7.45\pm0.04$% at 59.5 keV ($^{241}$Am, all grades). These results establish a baseline for the device and for the BNL test system. Measurements of the temperature dependence, optical response, and charge-transfer performance will connect this baseline to the requirements of near-infrared astronomical instruments.
The N$ν$DEx experiment is designed to search for neutrinoless double-beta decay ($0νββ$) of $\mathrm{^{82}Se}$ and is planned to be deployed at the China Jinping Underground Laboratory (CJPL). It employs a high-pressure time projection chamber (TPC) filled with $\mathrm{^{82}SeF_6}$ gas and a Topmetal pixelated charge readout system. The high $Q_{ββ}$ value of $\mathrm{^{82}Se}$, together with the track reconstruction capability of a gaseous TPC, provides strong potential for background suppression. In this work, we develop a full simulation and reconstruction framework for the N$ν$DEx experiment based on the REST (Rare Event Searches Toolkit) software framework. To meet the detector-specific requirements of N$ν$DEx, customized simulation processes are implemented to describe the detector geometry, electron drift and diffusion, the Topmetal readout plane, signal formation, and electronics response. These developments enable a complete software description of the detector response from energy deposition to digitized waveforms. A waveform-fitting-based reconstruction method is further applied to the simulated signals to extract the deposited charge and reconstruct the event energy. For simulated signal events, the reconstructed energy resolution reaches a full width at half maximum (FWHM) of less than 1\%, satisfying the design requirement of the experiment. The resulting simulation and reconstruction chain provides a basis for future studies of detector response, background rejection, event classification, and optimization of the N$ν$DEx detector design.
The PandaX-4T liquid xenon detector uses Hamamatsu 3-inch R11410-23 photomultiplier tubes (PMTs) as the light sensors for ultra-low radioactivity, high quantum efficiency, and long-term stability of all PMTs at cryogenic temperature. Each PMT was thoroughly tested in a dedicated chamber before being installed in the detector to ensure compliance with experimental requirements. Main PMT characteristics, including gain, dark count rate, and after-pulse probability, were measured and the distributions of these parameters were presented. Additionally, all PMTs were tested in a cryogenic environment to simulate their operating conditions in an actual detector environment. Finally, we report the long-term performance of all PMTs during the commissioning run of the PandaX-4T experiment, and most of the PMTs worked well.