During 2014 the PVLAS experiment has started data taking with a new apparatus
installed at the INFN Section of Ferrara, Italy. The main target of the
experiment is the observation of magnetic ...birefringence of vacuum. According to
QED, the ellipticity generated by the magnetic birefringence of vacuum in the
experimental apparatus is expected to be $\psi^{\rm(QED)} \approx
5\times10^{-11}$. No ellipticity signal is present so far with a noise floor
$\psi^{\rm(noise)} \approx 2.5\times10^{-9}$ after 210 hours of data taking.
The resulting ellipticity limit provides the best model independent upper limit
on the coupling of axions to $\gamma\gamma$ for axion masses above $10^{-3}$eV.
The design and construction of the BaBar silicon vertex tracker Bozzi, C.; Carassiti, V.; Ramusino, A.Cotta ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
06/2000, Letnik:
447, Številka:
1
Journal Article
Recenzirano
The Silicon Vertex Tracker (SVT) of the BaBar experiment at the PEP-II asymmetric B factory consists of five layers of double-sided, AC-coupled silicon strip detectors. The detectors are readout with ...a custom IC, capable of simultaneous acquisition, digitization and transmission of data. The SVT geometry is shown and the construction phases of its modules are described in detail, with emphasis on the bending procedures needed for the arch-modules of the outer layers.
The BaBar silicon vertex tracker, performance and running experience Re, V.; Borean, C.; Bozzi, C. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
06/2002, Letnik:
485, Številka:
1
Journal Article
Recenzirano
The Silicon Vertex Tracker (SVT) of the BaBar experiment at the PEP-II asymmetric B factory is a five-layer double-sided, AC-coupled silicon microstrip detector. It represents the crucial element to ...precisely measure the decay position of B mesons and extract time-dependent CP asymmetries. The SVT architecture is shown and its performance is described, with emphasis on hit resolutions and efficiencies.
A prototype hadron calorimeter, of similar design to the Warm Iron Calorimeter (WIC) planned for the SLD experiment, has been built and its performance has been studied in a test beam. The WIC is an ...iron sampling calorimeter whose active elements are plastic streamer tubes similar to those used for the Mont-Blanc proton decay experiment. The construction and operation of the tubes will be briefly described together with their use in an iron calorimeter - muon tracker. Efficiency, resolution and linearity have been measured in a hadron/muon beam up to 11 GeV. The measured values correspond to the SLD design goals.
Several groups are carrying out experiments to observe and measure vacuum magnetic birefringence, predicted by Quantum Electrodynamics (QED). We have started running the new PVLAS apparatus installed ...in Ferrara, Italy, and have measured a noise floor value for the unitary field magnetic birefringence of vacuum \(\Delta n_u^{\rm (vac)}= (4\pm 20) \times 10^{-23}\) T\(^{-2}\) (the error represents a 1\(\sigma\) deviation). This measurement is compatible with zero and hence represents a new limit on vacuum magnetic birefringence deriving from non linear electrodynamics. This result reduces to a factor 50 the gap to be overcome to measure for the first time the value of \(\Delta n_u^{\rm (vac,QED)}\) predicted by QED: \(\Delta n_u^{\rm (vac,QED)}= 4\times 10^{-24}\) ~T\(^{-2}\). These birefringence measurements also yield improved model-independent bounds on the coupling constant of axion-like particles to two photons, for masses greater than 1 meV, along with a factor two improvement of the fractional charge limit on millicharged particles (fermions and scalars), including neutrinos.
The BaBar silicon vertex tracker Bozzi, C; Carassiti, V; Ramusino, A.Cotta ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2000, Letnik:
453, Številka:
1
Journal Article
Recenzirano
The BaBar Silicon Vertex Tracker (SVT) is designed to provide the high-precision vertexing necessary for making measurements of CP violation at the SLAC B-Factory PEP-II. The instrument consists of ...five layers of double-sided silicon strip detectors and has been installed in the BaBar experiment and taking colliding beam data since May 1999. An overview of the design as well as performance and experience from the initial running will be presented.
First-year experience with the BaBar silicon vertex tracker Bozzi, C; Carassiti, V; Cotta Ramusino, A ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2001, Letnik:
473, Številka:
1
Journal Article
Recenzirano
Within its first year of operation, the BaBar Silicon Vertex Tracker (SVT) has accomplished its primary design goal, measuring the
z vertex coordinate with sufficient accuracy as to allow the ...measurement of the time-dependent CP asymmetry in the neutral B-meson system. The SVT consists of five layers of double-sided, AC-coupled silicon-strip detectors of
300
μm
thickness with a readout strip pitch of
50–210
μm
and a stereo angle of 90° between the strips on the two sides. Detector alignment and performance with respect to spatial resolution and efficiency in the reconstruction of single hits are discussed. In the day-to-day operation of the SVT, radiation damage and protection issues were of primary concern. The SVT is equipped with a dedicated system (SVTRAD) for radiation monitoring and protection, using reverse-biased photodiodes. The evolution of the SVTRAD thresholds on the tolerated radiation level is described. Results on the first-year radiation exposure as measured with the SVTRAD system and on the so far accumulated damage are presented. The implications of test-irradiation results and possible future PEP-II luminosity upgrades on the radiation limited lifetime of the SVT are discussed.
The PVLAS collaboration is presently assembling a new apparatus (at the INFN section of Ferrara, Italy) to detect vacuum magnetic birefringence (VMB). VMB is related to the structure of the QED ...vacuum and is predicted by the Euler-Heisenberg-Weisskopf effective Lagrangian. It can be detected by measuring the ellipticity acquired by a linearly polarised light beam propagating through a strong magnetic field. Using the very same optical technique it is also possible to search for hypothetical low-mass particles interacting with two photons, such as axion-like (ALP) or millicharged particles (MCP). Here we report results of a scaled-down test setup and describe the new PVLAS apparatus. This latter one is in construction and is based on a high-sensitivity ellipsometer with a high-finesse Fabry-Perot cavity (\(>4\times 10^5\)) and two 0.8 m long 2.5 T rotating permanent dipole magnets. Measurements with the test setup have improved by a factor 2 the previous upper bound on the parameter \(A_e\), which determines the strength of the nonlinear terms in the QED Lagrangian: \(A_e^{\rm (PVLAS)} < 3.3 \times 10^{-21}\) T\(^{-2}\) 95% c.l. Furthermore, new laboratory limits have been put on the inverse coupling constant of ALPs to two photons and confirmation of previous limits on the fractional charge of millicharged particles is given.
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