This report describes the present status of the detector design for SuperB. It is one of four separate progress reports that, taken collectively, describe progress made on the SuperB Project since ...the publication of the SuperB Conceptual Design Report in 2007 and the Proceedings of SuperB Workshop VI in Valencia in 2008. The other three reports relate to Physics, Accelerator and Computing.
The BaBar instrumented flux return performance: lessons learned Anulli, F; Bagnasco, S; Baldini, R ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2002, Letnik:
494, Številka:
1
Journal Article
Recenzirano
The BaBar Collaboration has operated an instrumented flux return (IFR) system covering over
2000
m
2
with resistive plate chambers (RPCs) for nearly 3 years. The chambers are constructed of bakelite ...sheets separated by
2
mm
. The inner surfaces are coated with linseed oil. This system provides muon and neutral hadron detection for BaBar. Installation and commissioning were completed in 1998, and operation began mid-year 1999. While initial performance of the system reached design, over time, a significant fraction of the RPCs demonstrated significant degradation, marked by increased currents and reduced efficiency. A coordinated effort of investigations have identified many of the elements responsible for the degradation. This article presents our current understanding of the aging process of the BaBar RPCs along with the action plan to combat performance degradation of the IFR system.
Using the entire BaBar \(\Upsilon(4S)\) data set, the first two-dimensional unbinned angular analysis of the semileptonic decay \(\overline{B} \rightarrow D \ell^- \overline{\nu}_\ell\) is performed, ...employing hadronic reconstruction of the tag-side \(B\) meson from \(\Upsilon(4S)\to B\overline{B}\). Here, \(\ell\) denotes the light charged leptons \(e\) and \(\mu\). A novel data-driven signal-background separation procedure with minimal dependence on simulation is developed. This procedure preserves all multi-dimensional correlations present in the data. The expected \(\sin^2\theta_\ell\) dependence of the differential decay rate in the Standard Model is demonstrated, where \(\theta_\ell\) is the lepton helicity angle. Including input from the latest lattice QCD calculations and previously available experimental data, the underlying form factors are extracted using both model-independent (BGL) and dependent (CLN) methods. Comparisons with lattice calculations show flavor SU(3) symmetry to be a good approximation in the \(B_{(s)}\to D_{(s)}\) sector. Using the BGL results, the CKM matrix element \(|V_{cb}|=(41.09\pm 1.16)\times 10^{-3}\) and the Standard Model prediction of the lepton-flavor universality violation variable \(\mathcal{R}(D)=0.300\pm 0.004\), are extracted. The value of \(|V_{cb}|\) from \(\overline{B} \rightarrow D \ell^- \overline{\nu}_\ell\) tends to be higher than that extracted using \(\overline{B} \rightarrow D \ell^- \overline{\nu}_\ell\). The Standard Model \(\mathcal{R}(D)\) calculation is at a \(1.97\sigma\) tension with the latest HFLAV experimental average.
The BaBar Collaboration has operated a system covering over 2000 m/sup 2/ with resistive plate chambers for nearly three years. The chambers are constructed of bakelite sheets separated by 2 mm. The ...inner surfaces are coated with linseed oil. This system provides muon and neutral hadron detection for BaBar. Installation and commissioning were completed in 1998, and operation began mid-1999. While initial performance of the system reached design, over time, a significant fraction of the resistive plate chambers demonstrated significant degradation, marked by increased currents and reduced efficiency. A coordinated investigative effort has identified many of the elements responsible for the degradation.
Events containing only energetic photons are analysed in a sample of 628 pb -1 of data recorded from e+e- collisions at centre-of-mass energies between 189 and 209 GeV by the ALEPH detector at LEP. ...The $\reenunug$ and $\reeggg$ cross sections are measured and found to be in agreement with the Standard Model predictions. The number of light neutrino generations is determined to be N_\nu = 2.86 \pm 0.09. Upper limits are derived on the cross sections for photon production in the context of several supersymmetric models. Limits are also set on the parameters of models with extra spatial dimensions with contact interactions and with excited electrons.
An improved search for Bs oscillations is performed in the ALEPH data sample collected during the first phase of LEP, and reprocessed in 1998. Three analyses based on complementary event selections ...are presented. First, decays of Bs mesons into hadronic flavour eigenstates are fully reconstructed. This selection yields a small sample of candidates with excellent decay length and momentum resolution and high average Bs purity. Semileptonic decays with a reconstructed Ds- meson provide a second sample with larger statistics, high average Bs purity, but a poorer momentum and decay length resolution due to the partial decay reconstruction. Finally, semileptonic b-hadron decays are inclusively selected and yield the data sample with the highest sensitivity to Bs oscillations, as the much higher statistics compensate for the low average Bs purity and poorer time resolution. A lower limit is set at 10.9 ps-1 at 95% CL, significantly lower than the expected limit of 15.7 ps-1.
The production rates of the orbitally excited Ds** mesons, Ds1 and Ds2*, are measured with the 4.1 million hadronic Z decays recorded by the ALEPH detector during 1991--1995. The Ds** mesons are ...reconstructed in the decay modes Ds1+ -> D*+ K0, Ds1+ -> D*0 K+ and Ds2*+ -> D0 K+. The production rate of the Ds1 is measured to be n(Z->Ds1+-)=(0.52+-0.09+-0.06)%, under the assumption that the two considered decay modes of the Ds1 saturate the branching ratio. The production rate of the Ds2* is determined to be n(Z->Ds2*+-)=(0.83+-0.29+0.07-0.13)%, assuming that the branching fraction of the decay Ds2*+ -> D0 K+ is 45%. The production rates in Z->cc and Z->bbar decays are measured separately.
A search for events with a photon pair arising from the decay of a Higgs boson produced in association with a fermion pair, is performed in 893pb^-1 of data recorded by the ALEPH detector at LEP at ...centre-of-mass energies up to 209GeV. No excess of such events is found over the expected background. An upper limit is derived on the product of the e^+e^- -> HZ cross section and the H -> gamma gamma branching fraction as a function of the Higgs boson mass. A fermiophobic Higgs boson produced with the Standard Model cross section is excluded at 95\% confidence level for all masses below 105.4GeV/c2
A search for the pseudoscalar meson eta_b is performed in two-photon interactions at LEP~2 with an integrated luminosity of 699 pb^-1 collected at e+e- centre-of-mass energies from 181 GeV to 209 ...GeV. One candidate event is found in the six-charged-particle final state and none in the four-charged-particle final state, in agreement with the total expected background of about one event. Upper limits of Gamma_gammagamma(eta_b) * BR(eta_b -> 4 charged particles) 48 eV Gamma_gammagamma(eta_b) * BR(eta_b -> 6 charged particles) 132 eV are obtained at 95\% confidence level, which correspond to 95\% confidence level upper limits of $9.0\%$ and $25\%$ on these branching ratios.
