The decay Bs->J/\psi\pi+\pi- can be exploited to study CP violation. A detailed understanding of its structure is imperative in order to optimize its usefulness. An analysis of this three-body final ...state is performed using a 1.0/fb sample of data produced in 7 TeV pp collisions at the LHC and collected by the LHCb experiment. A modified Dalitz plot analysis of the final state is performed using both the invariant mass spectra and the decay angular distributions. The \pi+\pi- system is shown to be dominantly in an S-wave state, and the CP-odd fraction in this Bs decay is shown to be greater than 0.977 at 95% confidence level. In addition, we report the first measurement of the J/\psi\pi+\pi- branching fraction relative to J/\psi\phi\ of (21.28 +/- 0.51 +/- 0.56)%.
The DEPFET collaboration develops highly granular, ultra-transparent active pixel detectors for high-performance vertex reconstruction at future collider experiments. The characterization of detector ...prototypes has proven that the key principle, the integration of a first amplification stage in a detector-grade sensor material, can provide a comfortable signal to noise ratio of over 40 for a sensor thickness of 50-75 \(\mathrm{\mathbf{\mu m}}\). ASICs have been designed and produced to operate a DEPFET pixel detector with the required read-out speed. A complete detector concept is being developed, including solutions for mechanical support, cooling and services. In this paper the status of DEPFET R & D project is reviewed in the light of the requirements of the vertex detector at a future linear \(\mathbf{e^+ e^-}\) collider.
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.
We report on an improved measurement of the Cabibbo-Kobayashi-Maskawa {\it CP}-violating phase $\gamma$ through a Dalitz plot analysis of neutral $D$ meson decays to $K_S^0 \pi^+ \pi^-$ and $K_S^0 ...K^+ K^-$ in the processes $B^\mp \to D K^\mp$, $B^\mp \to D^* K^\mp$ with $D^* \to D\pi^0,D\gamma$, and $B^\mp \to D K^{*\mp}$ with $K^{*\mp} \to K_S^0 \pi^\mp$. Using a sample of 383 million $B\bar{B}$ pairs collected by the BABAR detector, we measure $\gamma=(76 \pm 22 \pm 5 \pm 5)^\circ$ (mod $180^\circ$), where the first error is statistical, the second is the experimental systematic uncertainty and the third reflects the uncertainty on the description of the Dalitz plot distributions. The corresponding two standard deviation region is $29^\circ < \gamma < 122^\circ$. This result has a significance of direct {\it CP} violation ($\gamma \ne 0$) of 3.0 standard deviations.
A brand new Mass Storage System solution called “Grid-Enabled Mass Storage System” (GEMSS) -based on the Storage Resource Manager (StoRM) developed by INFN, on the General Parallel File System by IBM ...and on the Tivoli Storage Manager by IBM -has been tested and deployed at the INFNCNAF Tier-1 Computing Centre in Italy. After a successful stress test phase, the solution is now being used in production for the data custodiality of the CMS experiment at CNAF. All data previously recorded on the CASTOR system have been transferred to GEMSS. As final validation of the GEMSS system, some of the computing tests done in the context of the WLCG “Scale Test for the Experiment Program” (STEP’09) challenge were repeated in September-October 2009 and compared with the results previously obtained with CASTOR in June 2009. In this paper, the GEMSS system basics, the stress test activity and the deployment phase -as well as the reliability and performance of the system -are overviewed. The experiences in the use of GEMSS at CNAF in preparing for the first months of data taking of the CMS experiment at the Large Hadron Collider are also presented.
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