The LHCb RICH silica aerogel performance with LHC data Perego, D.L.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2011, Letnik:
639, Številka:
1
Journal Article
Recenzirano
Odprti dostop
In the LHCb experiment at the Large Hadron Collider, powerful charged particle identification is performed by Ring Imaging CHerenkov (RICH) technology. In order to cover the full geometric acceptance ...and the wide momentum range (1–100
GeV/
c), two detectors with three Cherenkov radiators have been designed and installed. In the medium (10–40
GeV/
c) and high (30–100
GeV/
c) momentum ranges, gas radiators are used (C
4F
10 and CF
4, respectively). In the low momentum range (1–10
GeV/
c), pion, kaon and proton separation is performed with solid silica aerogel radiator. A set of 16 tiles, with large transverse dimensions of up to
200
×
200
mm
2
and nominal refractive index 1.03 have been produced and integrated in the detector. These tiles have excellent optical properties and homogeneity of the refractive index at the percent level within the tile. The first data collected at the LHC are used to investigate the behaviour of the RICH; preliminary results of the performance of silica aerogel are presented and discussed.
Refractive index of silica aerogel: Uniformity and dispersion law Bellunato, T.; Calvi, M.; Matteuzzi, C. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2008, Letnik:
595, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Two methods for the measurement of the uniformity of the refractive index
n
within a single block of silica aerogel are described. One is based on the deflection of a laser beam induced by transverse ...index gradients. The second exploits the Cherenkov effect, measuring the emission angle of photons radiated by 500
MeV electrons traversing the aerogel. The beam can scan the full aerogel surface providing information on point to point variations of
n
.
The measurement of the dispersion law
n
(
λ
)
is also reported. An Xe lamp coupled to a diffraction grating provides the monochromatic source. The index for each
λ
is measured by the prism method at a corner of an aerogel sample. A Sellmeier functional form for
n
(
λ
)
is assumed, and the parameters best fitting the experimental data are given.
Refractive index dispersion law of silica aerogel Bellunato, T.; Calvi, M.; Matteuzzi, C. ...
The European physical journal. C, Particles and fields,
11/2007, Letnik:
52, Številka:
3
Journal Article
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Odprti dostop
This paper presents measurements of the refractive index of a hygroscopic silica aerogel block at several wavelengths. The measurements, performed with a monochromator, have been compared with ...different parameterisations for n(λ), in order to determine the best chromaticity law for the aerogel. This is an important input for design and operation of RICH detectors with silica aerogel radiator.
Background
Lanadelumab demonstrated efficacy in preventing hereditary angioedema (HAE) attacks in the phase 3 HELP Study.
Objective
To assess time to onset of effect and long‐term efficacy of ...lanadelumab, based on exploratory findings from the HELP Study.
Methods
Eligible patients with HAE type I/II received lanadelumab 150 mg every 4 weeks (q4wks), 300 mg q4wks, 300 mg q2wks, or placebo. Ad hoc analyses evaluated day 0‐69 findings using a Poisson regression model accounting for overdispersion. Least‐squares mean monthly HAE attack rate for lanadelumab was compared with placebo. Intrapatient comparisons for days 0‐69 versus steady state (days 70‐182) used a paired t test for continuous endpoints or Kappa statistics for categorical endpoints.
Results
One hundred twenty‐five patients were randomized and treated. During days 0‐69, mean monthly attack rate was significantly lower with lanadelumab (0.41‐0.76) vs placebo (2.04), including attacks requiring acute treatment (0.33‐0.61 vs 1.66) and moderate/severe attacks (0.31‐0.48 vs 1.33, all P ≤ .001). More patients receiving lanadelumab vs placebo were attack free (37.9%‐48.1% vs 7.3%) and responders (85.7%‐100% vs 26.8%). During steady state, the efficacy of lanadelumab vs placebo was similar or improved vs days 0‐69. Intrapatient differences were significant with lanadelumab 300 mg q4wks for select outcomes. Lanadelumab efficacy was durable—HAE attack rate was consistently lower vs placebo, from the first 2 weeks of treatment through study end. Treatment emergent adverse events were comparable during days 0‐69 and 70‐182.
Conclusion
Protection with lanadelumab started from the first dose and continued throughout the entire study period.
During days 0‐69, lanadelumab‐treated patients had a significantly lower mean monthly hereditary angioedema (HAE) attack rate vs placebo and were more likely to be responders and attack free. Protection starts early and is sustained; during steady state, lanadelumab efficacy was similar or improved vs days 0‐69. Prophylactic agents with rapid onset, sustained effect, and convenient dosing frequency can improve HAE management plans. Abbreviations: HAE, hereditary angioedema; q2wks, every 2 weeks.
Ageing tests and recovery procedures of silica aerogel Perego, D.L.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2008, Letnik:
595, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Silica aerogel has been extensively used in RICH detectors for the identification of charged particles over the momentum range between 1 and
10
GeV
/
c
. Tiles of hygroscopic aerogel with large ...transverse dimensions
(
20
×
20
cm
2
)
and refractive index
n
=
1.03
have recently been produced for use in the LHCb experiment, allowing pion–kaon identification up to
10
GeV
/
c
. The tiles have excellent optical properties (clarity factor better than
0.006
μ
m
4
/
cm
and homogeneity
σ
(
n
-
1
)
/
(
n
-
1
)
∼
1
%
within the tile). Extensive R&D tests on aerogel samples have been performed. Samples have been exposed to intense irradiation (proton, neutron and gamma), to humid air, to standard black varnish (used to paint the inner surface of RICH detectors), and to C
4F
10
and CO
2
gases. The optical properties of the aerogel have been monitored during these tests and, when required, recovery procedures have been investigated and applied. In particular, regeneration of the tiles has been realized through exposure to dry atmosphere (gaseous N
2) or through baking for several hours at
500
∘
C
. The measurements demonstrate that the optical properties have been successfully restored to their values at the production stage, and in no case permanent degradation has been observed.
ABSTRACT
Multimessenger astronomy received a great boost following the discovery of kilonova (KN) AT2017gfo, the optical counterpart of the gravitational wave source GW170817 associated with the ...short gamma-ray burst GRB 170817A. AT2017gfo was the first KN that could be extensively monitored in time using both photometry and spectroscopy. Previously, only few candidates have been observed against the glare of short GRB afterglows. In this work, we aim to search the fingerprints of AT2017gfo-like KN emissions in the optical/NIR light curves of 39 short GRBs with known redshift. For the first time, our results allow us to study separately the range of luminosity of the blue and red components of AT2017gfo-like kilonovae in short GRBs. In particular, the red component is similar in luminosity to AT2017gfo, while the blue KN can be more than 10 times brighter. Finally, we exclude a KN as luminous as AT2017gfo in GRBs 050509B and 061201.
ABSTRACT
Neutron star mergers eject neutron-rich matter in which heavy elements are synthesized. The decay of these freshly synthesized elements powers electromagnetic transients (‘macronovae’ or ...‘kilonovae’) whose luminosity and colour strongly depend on their nuclear composition. If the ejecta are very neutron-rich (electron fraction Ye < 0.25), they contain fair amounts of lanthanides and actinides that have large opacities and therefore efficiently trap the radiation inside the ejecta so that the emission peaks in the red part of the spectrum. Even small amounts of this high-opacity material can obscure emission from lower lying material and therefore act as a ‘lanthanide curtain’. Here, we investigate how a relativistic jet that punches through the ejecta can potentially push away a significant fraction of the high opacity material before the macronova begins to shine. We use the results of detailed neutrino-driven wind studies as initial conditions and explore with 3D special relativistic hydrodynamic simulations how jets are propagating through these winds. Subsequently, we perform Monte Carlo radiative transfer calculations to explore the resulting macronova emission. We find that the hole punched by the jet makes the macronova brighter and bluer for on-axis observers during the first few days of emission, and that more powerful jets have larger impacts on the macronova.
The performance of a proximity focusing Ring Imaging Cherenkov detector equipped with a radiator of silica aerogel is presented. The aerogel tile used is a monolith with variable index of refraction. ...Cherenkov photons are detected with high granularity by eight Hamamatsu H9500 flat panel multi anode phototubes.
Quenching the scintillation in CF4 Cherenkov gas radiator Blake, T.; D׳Ambrosio, C.; Easo, S. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2015, Letnik:
791
Journal Article
Recenzirano
Odprti dostop
CF4 is used as a Cherenkov gas radiator in one of the Ring Imaging Cherenkov detectors at the LHCb experiment at the CERN Large Hadron Collider. CF4 is well known to have a high scintillation photon ...yield in the near and far VUV, UV and in the visible wavelength range. A large flux of scintillation photons in our photon detection acceptance between 200 and 800nm could compromise the particle identification efficiency. We will show that this scintillation photon emission system can be effectively quenched, consistent with radiationless transitions, with no significant impact on the photons resulting from Cherenkov radiation.
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