3,251 research outputs found
TORCH: A Cherenkov Based Time-of-Flight Detector
TORCH is a novel high-precision time-of-flight detector suitable for large area applications and
covering the momentum range up to 10 GeV/c. The concept uses Cherenkov photons produced
in a fused silica radiator which are propagated to focussing optics coupled to fast photodetectors.
For this purpose, custom MCP-PMTs are being produced in collaboration with industrial partners.
The development is divided into three phases. Phase 1 addresses the lifetime requirements for
TORCH, Phase 2 will customize the MCP-PMT granularity and Phase 3 will deliver prototypes
that meet the TORCH requirements. Phase 1 devices have been successfully delivered and initial
tests show stable gain performance for integrated anode current >5 C/cm2
and a single photon
time resolution of †30 ps. Initial simulations indicate the single photon timing resolution of the
TORCH detector will be âŒ70 ps
Analysis and correction of the magnetic field effects in the Hybrid Photo-Detectors of the RICH2 Ring Imaging Cherenkov detector of LHCb
The Ring Imaging Cherenkov detectors of the LHCb experiment at the Large
Hadron Collider at CERN are equipped with Hybrid Photo-Detectors. These vacuum
photo-detectors are affected by the stray magnetic field of the LHCb magnet,
which degrades their imaging properties. This effect increases the error on the
Cherenkov angle measurement and would reduce the particle identification
capabilities of LHCb. A system has been developed for the RICH2 Ring Imaging
Cherenkov detector to perform a detailed characterisation of the magnetic
distortion effects. It is described, along with the methods implemented to
correct for these effects, restoring the optimal resolution.Comment: 16 pages, 11 figure
TORCH: A Cherenkov Based Time-of-Flight Detector
TORCH is a novel high-precision time-of-flight detector suitable for large area applications and
covering the momentum range up to 10 GeV/c. The concept uses Cherenkov photons produced
in a fused silica radiator which are propagated to focussing optics coupled to fast photodetectors.
For this purpose, custom MCP-PMTs are being produced in collaboration with industrial partners.
The development is divided into three phases. Phase 1 addresses the lifetime requirements for
TORCH, Phase 2 will customize the MCP-PMT granularity and Phase 3 will deliver prototypes
that meet the TORCH requirements. Phase 1 devices have been successfully delivered and initial
tests show stable gain performance for integrated anode current >5 C/cm2
and a single photon
time resolution of †30 ps. Initial simulations indicate the single photon timing resolution of the
TORCH detector will be âŒ70 ps
Heavy Quark Spectroscopy and Matrix Elements: A Lattice Study using the Static Approximation
We present results of a lattice analysis of the parameter, , the
decay constant , and several mass splittings using the static
approximation. Results were obtained for 60 quenched gauge configurations
computed at on a lattice size of . Light quark
propagators were calculated using the -improved Sheikholeslami-Wohlert
action. We find \Bbstat(m_b) = 0.69\er{3}{4} {\rm(stat)}\er{2}{1}
{\rm(syst)}, corresponding to \Bbstat = 1.02\er{5}{6}\er{3}{2}, and \fbstat
= 266\err{18}{20}\err{28}{27} \mev, f_{B_s}^2 B_{B_s}/f_B^2 B_B =
1.34\er{9}{8}\er{5}{3}, where a variational fitting technique was used to
extract \fbstat. For the mass splittings we obtain M_{B_s}-M_{B_d} =
87\err{15}{12}\err{6}{12} \mev, M_{\Lambda_b}-M_{B_d} =
420\errr{100}{90}\err{30}{30} \mev and M_{B^*}^2-M_B^2 =
0.281\err{15}{16}\err{40}{37} \gev^2. We compare different smearing techniques
intended to improve the signal/noise ratio. From a detailed assessment of
systematic effects we conclude that the main systematic uncertainties are
associated with the renormalisation constants relating a lattice matrix element
to its continuum counterpart. The dependence of our findings on lattice
artefacts is to be investigated in the future.Comment: 40 pages, uuencoded compressed tar file, containing one LaTeX file
and 14 postscript files (to be included with epsf). Minor change in the value
of the B parameter. Contains corrected value for the B*-B mass splitting.
Version accepted for publication in Phys. Rev.
The TORCH time-of-flight detector
AbstractThe TORCH time-of-flight detector is being developed to provide particle identification between 2 and 10GeV/c momentum over a flight distance of 10m. TORCH is designed for large-area coverage, up to 30m2, and has a DIRC-like construction. The goal is to achieve a 15ps time-of-flight resolution per incident particle by combining arrival times from multiple Cherenkov photons produced within quartz radiator plates of 10mm thickness. A four-year R&D programme is underway with an industrial partner (Photek, UK) to produce 53Ă53mm2 Micro-Channel Plate (MCP) detectors for the TORCH application. The MCP-PMT will provide a timing accuracy of 40ps per photon and it will have a lifetime of up to at least 5Ccmâ2 of integrated anode charge by utilizing an Atomic Layer Deposition (ALD) coating. The MCP will be read out using charge division with customised electronics incorporating the NINO chipset. Laboratory results on prototype MCPs are presented. The construction of a prototype TORCH module and its simulated performance are also described
La fuerza de los grupos guerrilleros
Publicat a Diario 16
Test-beam and laboratory characterisation of the TORCH prototype detector
The TORCH time-of-flight (TOF) detector is being developed to provide particle identification up to a momentum of 10 GeV/c over a flight distance of 10 m. It has a DIRC-like construction with View the MathML source10mm thick synthetic amorphous fused-silica plates as a Cherenkov radiator. Photons propagate by total internal reflection to the plate periphery where they are focused onto an array of customised position-sensitive micro-channel plate (MCP) detectors. The goal is to achieve a 15 ps time-of-flight resolution per incident particle by combining arrival times from multiple photons. The MCPs have pixels of effective size 0.4 mmĂ6.6 mm2 in the vertical and horizontal directions, respectively, by incorporating a novel charge-sharing technique to improve the spatial resolution to better than the pitch of the readout anodes. Prototype photon detectors and readout electronics have been tested and calibrated in the laboratory. Preliminary results from testbeam measurements of a prototype TORCH detector are also presented
Measurement of the CKM angle Îł from a combination of B±âDh± analyses
A combination of three LHCb measurements of the CKM angle Îł is presented. The decays B±âD K± and
B±âDϱ are used, where D denotes an admixture of D0 and D0 mesons, decaying into K+Kâ, Ï+Ïâ, K±Ïâ, K±ÏâϱÏâ, K0SÏ+Ïâ, or K0S K+Kâ ïŹnal states. All measurements use a dataset corresponding to 1.0 fbâ1 of integrated luminosity. Combining results from B±âD K± decays alone a best-ïŹt value of
Îł =72.0⊠is found, and conïŹdence intervals are set
Îł â [56.4,86.7]⊠at 68% CL,
Îł â [42.6,99.6]⊠at 95% CL.
The best-ïŹt value of Îł found from a combination of results from B±âDϱ decays alone, is Îł =18.9âŠ,
and the conïŹdence intervals
Îł â [7.4,99.2]⊠âȘ [167.9,176.4]⊠at 68% CL
are set, without constraint at 95% CL. The combination of results from B± â D K± and B± â Dϱ
decays gives a best-ïŹt value of Îł =72.6⊠and the conïŹdence intervals
Îł â [55.4,82.3]⊠at 68% CL,
Îł â [40.2,92.7]⊠at 95% CL
are set. All values are expressed modulo 180âŠ, and are obtained taking into account the effect of D0âD0
mixing
Measurement of the ratio of branching fractions BR(B0 -> K*0 gamma)/BR(Bs0 -> phi gamma)
The ratio of branching fractions of the radiative B decays B0 -> K*0 gamma
and Bs0 -> phi gamma has been measured using 0.37 fb-1 of pp collisions at a
centre of mass energy of sqrt(s) = 7 TeV, collected by the LHCb experiment. The
value obtained is BR(B0 -> K*0 gamma)/BR(Bs0 -> phi gamma) = 1.12 +/- 0.08
^{+0.06}_{-0.04} ^{+0.09}_{-0.08}, where the first uncertainty is statistical,
the second systematic and the third is associated to the ratio of fragmentation
fractions fs/fd. Using the world average for BR(B0 -> K*0 gamma) = (4.33 +/-
0.15) x 10^{-5}, the branching fraction BR(Bs0 -> phi gamma) is measured to be
(3.9 +/- 0.5) x 10^{-5}, which is the most precise measurement to date.Comment: 15 pages, 1 figure, 2 table
- âŠ