32 research outputs found
A time resolved study of injection backgrounds during the first commissioning phase of SuperKEKB
We report on measurements of beam backgrounds during the first commissioning
phase of the SuperKEKB collider in 2016, performed with the plastic
scintillator and silicon photomultiplier-based CLAWS detector system. The
sub-nanosecond time resolution and single particle detection capability of the
sensors allow bunch-by-bunch measurements, enable CLAWS to perform a novel time
resolved analysis of beam backgrounds, and make the system uniquely suited for
the study of injection backgrounds. We present measurements of various aspects
of regular beam background and injection backgrounds which include time
structure and decay behavior of injection backgrounds, hit-energy spectra and
overall background rates. These measurements show that the elevated background
rates following an injection generally last for several milliseconds, with the
majority of the background particles typically observed within the first 500
us. The injection backgrounds exhibit pronounced patterns in time, connected to
betatron and synchrotron oscillations in the accelerator rings. The frequencies
of these patterns are determined from detector data.Comment: 19 pages, 12 figures, published in EPJ
Measurement of ISR-FSR interference in the processes e+ e- --> mu+ mu- gamma and e+ e- --> pi+ pi- gamma
Charge asymmetry in processes e+ e- --> mu+ mu- gamma and e+ e- --> pi+ pi-
gamma is measured using 232 fb-1 of data collected with the BABAR detector at
center-of-mass energies near 10.58 GeV. An observable is introduced and shown
to be very robust against detector asymmetries while keeping a large
sensitivity to the physical charge asymmetry that results from the interference
between initial and final state radiation. The asymmetry is determined as
afunction of the invariant mass of the final-state tracks from production
threshold to a few GeV/c2. It is compared to the expectation from QED for e+ e-
--> mu+ mu- gamma and from theoretical models for e+ e- --> pi+ pi- gamma. A
clear interference pattern is observed in e+ e- --> pi+ pi- gamma, particularly
in the vicinity of the f_2(1270) resonance. The inferred rate of lowest order
FSR production is consistent with the QED expectation for e+ e- --> mu+ mu-
gamma, and is negligibly small for e+ e- --> pi+ pi- gamma.Comment: 32 pages,29 figures, to be submitted to Phys. Rev.
Study of the e(+)e(-) -> K+K- reaction in the energy range from 2.6 to 8.0 GeV
The cross section and charged-kaon electromagnetic form
factor are measured in the center-of-mass energy range () from 2.6
to 8.0 GeV using the initial-state radiation technique with an undetected
photon. The study is performed using 469 fb of data collected with the
BABAR detector at the PEP-II collider at center-of-mass energies near
10.6 GeV. The form factor is found to decrease with energy faster than ,
and approaches the asymptotic QCD prediction. Production of the final
state through the and intermediate states is observed. The
results for the kaon form factor are used together with data from other
experiments to perform a model-independent determination of the relative phases
between single-photon and strong amplitudes in and decays. The values of the branching fractions measured in the reaction
are shifted relative to their true values due to
interference between resonant and nonresonant amplitudes. The values of these
shifts are determined to be about for the meson and
for the meson.Comment: 18 pages, 19 postscript figure
BaBar Forward Endcap upgrade
The muon and neutral hadron detector (instrumented flux return or IFR) in the forward endcap of the BaBar detector at SLAC was upgraded by the installation of a new generation of resistive plate chambers (RPCs) and by increasing the absorber. The chamber replacement was made necessary by the rapid aging and efficiency loss of the original BaBar RPCs. Based on our experience with those original RPCs and 24 RPCs with thinner linseed oil treatments, improvements in the design, construction, and testing of the new generation RPCs were implemented and are described in detail. (C) 2004 Elsevier B.V. All rights reserved
Performance and aging studies of BaBar resistive plate chambers
The BaBar detector is currently operating nearly 200 Resistive Plate Chambers (RPCs), constructed as part of an upgrade of the forward endcap, muon detector in 2002. Although the average RPC efficiency remains high, numerous changes in the RPC performance (increased currents and rates) have been observed. A few of the highest rate RPCs have suffered efficiency losses of more than 15%. Several types of efficiency loss have been observed. Tests with humidified gas have shown that some of the lost efficiency is recoverable. However, efficiency losses in the highest rate regions have not yet improved with humid gases