First experience and results with the LHCb Silicon Tracker Fave, V.; Bay, A.; Blanc, F. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2010, Letnik:
617, Številka:
1
Journal Article
Recenzirano
The LHCb experiment is designed to perform high-precision measurements of CP violation and rare decays of b hadrons. The construction and installation of the Silicon Tracker (ST) was completed by the ...summer of 2008. Here, we report on first results obtained using the data taken during injection tests (‘TED’ run) in August and September 2008.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted) A search for the B super(0)arrowrightK +K- decay is performed using pp-collision data collected by LHCb. The data set corresponds to ...integrated luminosities of 1.0 and 2.0 fb super(-1) at center-of-mass energies of 7 and 8 TeV, respectively. This decay is observed for the first time, with a significance of more than 5 standard deviations. The analysis also results in an improved measurement of the branching fraction for the ... decay. The measured branching fractions are scriptB(B super(0)arrowrightK+K-)=(7.80+ or -1.27+ or -0.81+ or -0.21) x 10 super(-8) and ... = (6.91+ or -0.54+ or -0.63+ or -0.19+ or -0.40) x 10 super(-7). The first uncertainty is statistical, the second is systematic, the third is due to the uncertainty on the B super(0)arrowrightK +pi super(-) branching fraction used as a normalization. For the ... mode, the fourth accounts for the uncertainty on the ratio of the probabilities for b quarks to hadronize into ... and B super(0) mesons.
Decays of the Xi sub()band Omega sub()bbaryons to the charmless final states ph super(-)h' super(-), where h(') denotes a kaon or pion, are searched for with the LHCb detector. The analysis is based ...on a sample of proton-proton collision data collected at center-of-mass energies radicals= 7 and 8 TeV, corresponding to an integrated luminosity of 3fb super(-1). The decay Xi sub()barrowrightpK super(-)K super(-) is observed with a significance of 8.7 standard deviations, and evidence at the level of 3.4 standard deviations is found for the XI sub()barrowrightpK super(-)pi super(-) decay. Results are reported, relative to the B super(-)arrowrightK+K-K- normalization channel, for the products of branching fractions and b-hadron production fractions. The branching fractions of Xi sub()barrowrightpK super(-)pi super(-) and Xi sub()barrowrightppi super(-)pi super(-) relative to Xi sub()barrowrightpK super(-)K super(-) decays are also measured.
LHCb Silicon Tracker DAQ and ECS Online Systems Esperante, Daniel; Rodriguez, P; Buchler, A ...
IEEE transactions on nuclear science,
2010-April, 2010-04-00, 20100401, Letnik:
57, Številka:
2
Journal Article
Recenzirano
The LHCb experiment at CERN is designed to perform precision measurements of b quark decays. The Silicon Tracker plays a crucial role in reconstructing particle trajectories and consists of two ...silicon micro-strip detectors, the Tracker Turicensis and the Inner Tracker. The radiation environment and the magnetic field represent new challenges for the implementation of the Experiment Control System (ECS) and the data acquisition (DAQ). The DAQ has to deal with ~272 000 analog read-out channels and real-time DAQ at a rate of ~ 1.1 MHz with data processing at the Trigger Electronics and L1 (TELL1) board level. The TELL1 real-time algorithms for clustering thresholds and other computations run on dedicated FPGAs. After data processing the total throughput amounts to about 6.4 GB from an input data rate of ~ 337 GB per second. The ECS is based on the hierarchical finite state machine paradigm and allows distributed control access and multi-platform use. The ECS is able to control and monitor the detector hardware infrastructure (power supplies, DAQ electronics ...) as well as monitor the environmental parameters. It can also take automated actions on warnings or alarms. Finally a completely independent, hardware based safety system ensures the detector safe operation.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted) The polarization of photons produced in radiative ... decays is studied for the first time. The data are recorded by the LHCb ...experiment in pp collisions corresponding to an integrated luminosity of 3fb super(-1) at center-of-mass energies of 7 and 8 TeV. A time-dependent analysis of the ... decay rate is conducted to determine the parameter scriptA super(white triangle up), which is related to the ratio of right- over left-handed photon polarization amplitudes in barrowrightsgamma transitions. A value of ... is measured. This result is consistent with the standard model prediction within 2 standard deviations.
The first full amplitude analysis of super(B) super(+)arrowrightJ/psivarphiK super(+) with J/psiarrowrightmu super(+)mu super(?), varphiarrowrightK super(+)K super(?) decays is performed with a data ...sample of 3fb super(?1) of pp collision data collected at radicals=7 and 8 TeV with the LHCb detector. The data cannot be described by a model that contains only excited kaon states decaying into varphiK super(+), and four J/psivarphi structures are observed, each with significance over 5 standard deviations. The quantum numbers of these structures are determined with significance of at least 4 standard deviations. The lightest has mass consistent with, but width much larger than, previous measurements of the claimed X(4140) state.
The CP violation observables S and C in the decay channel B super(0)arrowrightD super(+)D super( -) are determined from a sample of proton-proton collisions at center-of-mass energies of 7 and 8 TeV, ...collected by the LHCb experiment and corresponding to an integrated luminosity of 3fb super(-1). The observable S describes CP violation in the interference between mixing and the decay amplitude, and C parametrizes direct CP violation in the decay. The following values are obtained from a flavor-tagged, decay-time-dependent analysis: (ProQuest: Formulae and/or non-USASCII text omitted). These values provide evidence for CP violation at a significance level of 4.0 standard deviations. The phase shift due to higher-order standard model corrections is constrained to a small value of (ProQuest: Formulae and/or non-USASCII text omitted) rad.
DIRAC: A high resolution spectrometer for pionium detection Adeva, B.; Afanasyev, L.; Benayoun, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2003, Letnik:
515, Številka:
3
Journal Article
Recenzirano
Odprti dostop
The DIRAC spectrometer has been commissioned at CERN with the aim of detecting π+π− atoms produced by a 24GeV/c high intensity proton beam in thin foil targets. A challenging apparatus is required to ...cope with the high interaction rates involved, the triggering of pion pairs with very low relative momentum and the measurement of the latter with resolution around 0.6MeV/c. The general characteristics of the apparatus are explained and each part is described in some detail. The main features of the trigger system, data-acquisition, monitoring and set-up performances are also given.
PDF
