5,178 research outputs found
The CKM angle γ/φ3 - B-factories results review
International audienceγ /φ3 is the less precisely known of the Unitarity Triangle angles. The general problematics of measurements of this parameter are discussed and recent experimental results from Babar and Belle are presented
New technique to measure the cavity defects of Fabry-Perot interferometers
(Abridged):
We define and test a new technique to accurately measure the cavity defects
of air-spaced FPIs, including distortions due to the spectral tuning process
typical of astronomical observations. We further develop a correction technique
to maintain the shape of the cavity as constant as possible during the spectral
scan. These are necessary steps to optimize the spectral transmission profile
of a two-dimensional spectrograph using one or more FPIs.
We devise a generalization of the techniques developed for the so-called
phase-shifting interferometry to the case of FPIs. The technique is applicable
to any FPI that can be tuned via changing the cavity spacing (-axis), and
can be used for any etalon regardless of the coating' reflectivity. The major
strength of our method is the ability to fully characterize the cavity during a
spectral scan, allowing for the determination of scan-dependent modifications
of the plates. As a test, we have applied this technique to three 50 mm
diameter interferometers, with cavity gaps ranging between 600 micron and 3 mm,
coated for use in the visible range.
We obtain accurate and reliable measures of the cavity defects of air-spaced
FPIs, and of their evolution during the entire spectral scan. Our main, and
unexpected, result is that the relative tilt between the two FPI plates varies
significantly during the spectral scan, and can dominate the cavity defects; in
particular, we observe that the tilt component at the extremes of the scan is
sensibly larger than at the center of the scan. Exploiting the capability of
the electronic controllers to set the reference plane at any given spectral
step, we develop a correction technique that allows the minimization of the
tilt during a complete spectral scan. The correction remains highly stable over
long periods, well beyond the typical duration of astronomical observations.Comment: 15 pages, 20+ figures, accepted for publication in A&A. Two
additional movies are available in the online version of the pape
Update of the Unitarity Triangle Analysis
We present the status of the Unitarity Triangle Analysis (UTA), within the
Standard Model (SM) and beyond, with experimental and theoretical inputs
updated for the ICHEP 2010 conference. Within the SM, we find that the general
consistency among all the constraints leaves space only to some tension
(between the UTA prediction and the experimental measurement) in BR(B -> tau
nu), sin(2 beta) and epsilon_K. In the UTA beyond the SM, we allow for New
Physics (NP) effects in (Delta F)=2 processes. The hint of NP at the 2.9 sigma
level in the B_s-\bar B_s mixing turns out to be confirmed by the present
update, which includes the new D0 result on the dimuon charge asymmetry but not
the new CDF measurement of phi_s, being the likelihood not yet released.Comment: 4 pages, 2 figures, Proceedings of the 35th International Conference
of High Energy Physics - ICHEP2010 (July 22-28, 2010, Paris
Improved Determination of the CKM Angle alpha from B to pi pi decays
Motivated by a recent paper that compares the results of the analysis of the
CKM angle alpha in the frequentist and in the Bayesian approaches, we have
reconsidered the information on the hadronic amplitudes, which helps
constraining the value of alpha in the Standard Model. We find that the
Bayesian method gives consistent results irrespective of the parametrisation of
the hadronic amplitudes and that the results of the frequentist and Bayesian
approaches are equivalent when comparing meaningful probability ranges or
confidence levels. We also find that from B to pi pi decays alone the 95%
probability region for alpha is the interval [80^o,170^o], well consistent with
recent analyses of the unitarity triangle where, by using all the available
experimental and theoretical information, one gets alpha = (93 +- 4)^o. Last
but not least, by using simple arguments on the hadronic matrix elements, we
show that the unphysical region alpha ~ 0, present in several experimental
analyses, can be eliminated.Comment: 16 pages, 7 figure
Exploring the parameter space of texture 4 zero quark mass matrices
We have attempted to extend the parameter space of the elements of the
texture 4 zero Hermitian quark mass matrices, to include the case of `weak
hierarchy' amongst them along with the usually considered `strong hierarchy'
case. This has been carried out by giving wide variation to the hierarchy
defining parameters D_U and D_D, having implications for the structural
features of the mass matrices. We find that not only the weakly hierarchical
mass matrices are able to reproduce the strongly hierarchical mixing angles but
also both the phases having their origin in the mass matrices have to be non
zero to achieve compatibility of these matrices with recent quark mixing data.
Further noting the difference between the exclusive and inclusive values of
V_ub, we have carried out separate analyses corresponding to these.Comment: 13 pages, 4 figures, version accepted for publication in Journal Of
Physics
GIADA performance during Rosetta mission scientific operations at comet 67P
The Grain Impact Analyser and Dust Accumulator (GIADA) instrument onboard Rosetta studied the dust environment of comet 67P/Churyumov–Gerasimenko from 3.7 au inbound, through perihelion, to 3.8 au outbound, measuring the dust flow and the dynamic properties of individual particles. GIADA is composed of three subsystems: 1) Grain Detection System (GDS); 2) Impact Sensor (IS); and 3) Micro-Balances System (MBS). Monitoring the subsystems’ performance during operations is an important element for the correct calibration of scientific measurements. In this paper, we analyse the GIADA inflight calibration data obtained by internal calibration devices for the three subsystems during the period from 1 August 2014 to 31 October 2015. The calibration data testify a nominal behaviour of the instrument during these fifteen months of mission; the only exception is a minor loss of sensitivity for one of the two GDS receivers, attributed to dust contamination
The dust-to-ices ratio in comets and Kuiper belt objects
Comet 67P/Churyumov-Gerasimenko (67P hereinafter) is characterized by a dust transfer from the southern hemi-nucleus to the night-side northern dust deposits, which constrains the dust-to-ices mass ratio inside the nucleus to values a factor of 2 larger than that provided by the lost mass of gas and non-volatiles. This applies to all comets because the gas density in all night comae cannot prevent the dust fallback. Taking into account Grain Impact Analyser and Dust Accumulator (GIADA) data collected during the entire Rosetta mission, we update the average dust bulk density to ρD=785 +520/−115 kg m that, coupled to the 67P nucleus bulk density, confirms an average dust-to-ices mass ratio δ = 7.5 inside 67P. The improved dust densities are consistent with a mixture of (20 ± 8) per cent of ices, (4 ± 1) per cent of Fe sulphides, (22 ± 2) per cent of silicates and (54 ± 5) per cent of hydrocarbons, on average volume abundances. These values correspond to solar chemical abundances, as suggested by the elemental C/Fe ratio observed in 67P. The ice content in 67P matches that inferred in Kuiper belt objects, (20 ± 12) per cent on average volume abundance and suggests a water content in all trans-Neptunian objects lower than in CI chondrites. The 67P icy pebbles and the dust collected by GIADA have a microporosity of (49 ± 5) and (59 ± 8) per cent, respectively
First evidence of new physics in b ↔ s transitions
We combine all the available experimental information on Bs mixing, including the very
recent tagged analyses of Bs → J/Ψϕ by the CDF and DØ collaborations. We find that the
phase of the Bs mixing amplitude deviates more than 3σ from the Standard Model
prediction. While no single measurement has a 3σ significance yet, all the constraints show
a remarkable agreement with the combined result. This is a first evidence of physics
beyond the Standard Model. This result disfavours New Physics models with Minimal
Flavour Violation with the same significance
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