The BaBar Muon System Upgrade

Abstract

Resistive Plate Chambers (RPCs) were used for the instrumentation of the iron flux return of the BABARdetector as a muon system. Unfortunately the efficiency of the original RPCs degraded rapidly with time. Limited Streamer Tubes (LSTs) were chosen for an upgrade of the barrel portion of the detector.The phased installation started in summer 2004 with replacing two sextants of the BABARbarrel muon system with LSTs. The modules for the remaining four sextants are under long-term test at SLAC and ready for installation, expected in 2006. The modules become inaccessible once installed in BABAR, so it is critical to select only perfectly working tubes. To accomplish this a strong QC system was established during the prototype phase, and fully implemented throughout pre-production and construction. To spot any damage during transport, the final modules are subjected to comprehensive tests at SLAC immediately after arrival and kept under long-term test till installation into BABAR. Details of these tests and results from long-term testing will be discussed. Since spring 2005 the PEP-II accelerator is running and BABARis collecting data. First experience from data taking with the LSTs will be presented and the performance of the detector discussed.

Limited Streamer Tube System for Detecting Contamination in the Gas Used in the BaBar Instrumented Flux Return

“…For this test, we varied the voltage from 4800 V to 5500 V and recorded the number of detections in 10 seconds. Functional LSTs usually show an edge on this curve at 5300 V and a plateau around 5500 V [5]. We found that our LSTs meet these expectations (see Figure 7).…”

“…As attempts made to repair them were unsuccessful, two of the six RPC The LSTs contain long cells filled with a gas composed of 3% argon, 8% isobutane, and 89% carbon dioxide by volume [5]. When charged particles enter the LSTs, they ionize the gas, causing a small number of free electrons to be produced.…”

Exclusive measurements ofb→sγtransition rate and photon energy spectrum

“…The SVT, DCH, DIRC, and EMC operate inside of a 1.5 T magnet. Charged π/µ separation is done using the instrumented flux return of the magnetic field, originally instrumented with resistive plate chambers [16] and later with limited streamer tubes [17].…”

Study of B-Meson Decays to Final States with a Single Charm Baryon

“…Limited streamer tubes (LSTs) were chosen to replace 6 the RPCs, and the upgrade proceeded in stages during 2002 − 2006 [38][39][40].…”