2,739 research outputs found
Neutrino Mixing and Neutrino Telescopes
Measuring flux ratios of ultra-high energy neutrinos is an alternative method
to determine the neutrino mixing angles and the CP phase delta. We conduct a
systematic analysis of the neutrino mixing probabilities and of various flux
ratios measurable at neutrino telescopes. The considered cases are neutrinos
from pion, neutron and muon-damped sources. Explicit formulae in case of mu-tau
symmetry and its special case tri-bimaximal mixing are obtained, and the
leading corrections due to non-zero theta_{13} and non-maximal theta_{23} are
given. The first order correction is universal as it appears in basically all
ratios. We study in detail its dependence on theta_{13}, theta_{23} and the CP
phase, finding that the dependence on theta_{23} is strongest. The flavor
compositions for the considered neutrino sources are evaluated in terms of this
correction. A measurement of a flux ratio is a clean measurement of the
universal correction (and therefore of theta_{13}, theta_{23} and delta) if the
zeroth order ratio does not depend on theta_{12}. This favors pion sources over
the other cases, which in turn are good candidates to probe theta_{12}. The
only situations in which the universal correction does not appear are certain
ratios in case of a neutron and muon-damped source, which depend mainly on
theta_{12} and receive only quadratic corrections from the other parameters. We
further show that there are only two independent neutrino oscillation
probabilities, give the allowed ranges of the considered flux ratios and of all
probabilities, and show that none of the latter can be zero or one.Comment: 29 pages, 8 figures. Minor changes, to appear in JCA
Test of CPT Symmetry and Quantum Mechanics with Experimental data from CPLEAR
We use fits to recent published CPLEAR data on neutral kaon decays to
and to constrain the CPT--violation parameters
appearing in a formulation of the neutral kaon system as an open
quantum-mechanical system. The obtained upper limits of the CPT--violation
parameters are approaching the range suggested by certain ideas concerning
quantum gravity.Comment: 9 pages of uuencoded postscript (includes 3 figures
Opposite-side flavour tagging of B mesons at the LHCb experiment
The calibration and performance of the oppositeside
flavour tagging algorithms used for the measurements
of time-dependent asymmetries at the LHCb experiment
are described. The algorithms have been developed using
simulated events and optimized and calibrated with
B
+ âJ/ÏK
+, B0 âJ/ÏK
â0 and B0 âD
ââ
Ό
+
ΜΌ decay
modes with 0.37 fbâ1 of data collected in pp collisions
at
â
s = 7 TeV during the 2011 physics run. The oppositeside
tagging power is determined in the B
+ â J/ÏK
+
channel to be (2.10 ± 0.08 ± 0.24) %, where the first uncertainty
is statistical and the second is systematic
Measurement of the lifetime
Using a data set corresponding to an integrated luminosity of ,
collected by the LHCb experiment in collisions at centre-of-mass energies
of 7 and 8 TeV, the effective lifetime in the
decay mode, , is measured to be ps. Assuming
conservation, corresponds to the lifetime of the light
mass eigenstate. This is the first measurement of the effective
lifetime in this decay mode.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2016-017.htm
Search for CP violation in decays
A model-independent search for direct CP violation in the Cabibbo suppressed
decay in a sample of approximately 370,000 decays is
carried out. The data were collected by the LHCb experiment in 2010 and
correspond to an integrated luminosity of 35 pb. The normalized Dalitz
plot distributions for and are compared using four different
binning schemes that are sensitive to different manifestations of CP violation.
No evidence for CP asymmetry is found.Comment: 13 pages, 8 figures, submitted to Phys. Rev.
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
Model-independent evidence for contributions to decays
The data sample of decays acquired with the
LHCb detector from 7 and 8~TeV collisions, corresponding to an integrated
luminosity of 3 fb, is inspected for the presence of or
contributions with minimal assumptions about
contributions. It is demonstrated at more than 9 standard deviations that
decays cannot be described with
contributions alone, and that contributions play a dominant role in
this incompatibility. These model-independent results support the previously
obtained model-dependent evidence for charmonium-pentaquark
states in the same data sample.Comment: 21 pages, 12 figures (including the supplemental section added at the
end
Measurements of the branching fractions of the decays B°s â Dâs K± and B°s â DÂŻsÏ+
The decay mode B°s â Dâs K± allows for one of the theoretically cleanest measurements of the CKM angle Îł through the study of time-dependent CP violation. This paper reports a measurement of its branching fraction relative to the Cabibbo-favoured mode B°s â DÂŻsÏ+ based on a data sample corresponding to 0.37 fbÂŻÂč of proton-proton collisions at âs = 7TeV collected in 2011 with the LHCb detector. In addition, the ratio of B meson production fractions fs/fd, determined from semileptonic decays, together with the known branching fraction of the control channel B°s â DÂŻsÏ+ is used to perform an absolute measurement of the branching fractions: B(B°s â DÂŻsÏ+) = (2.95 ± 0.05 ± 0.17 -0.22 +0.18) Ă 10ÂŻÂł ; B(B°s â Dâs K±) = (1.90 ± 0.12 ± 0.13 -0.14 +0.12) Ă 10ÂŻ4 ; where the first uncertainty is statistical, the second the experimental systematic uncertainty, and the third the uncertainty due to f s/f
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