303 research outputs found
The clustering of ultra-high energy cosmic rays and their sources
The sky distribution of cosmic rays with energies above the 'GZK cutoff'
holds important clues to their origin. The AGASA data, although consistent with
isotropy, shows evidence for small-angle clustering, and it has been argued
that such clusters are aligned with BL Lacertae objects, implicating these as
sources. It has also been suggested that clusters can arise if the cosmic rays
come from the decays of very massive relic particles in the Galactic halo, due
to the expected clumping of cold dark matter. We examine these claims and show
that both are in fact not justified.Comment: 13 pages, 8 figures, version in press at Phys. Rev.
Search for TeV Scale Physics in Heavy Flavour Decays
The subject of heavy flavour decays as probes for physics beyond the TeV
scale is covered from the experimental perspective. Emphasis is placed on the
more traditional Beyond the Standard Model topics that have potential for
impact in the short term, with the physics explained. We do unabashedly promote
our own phemonenology work.Comment: 10 pages, 9 figures (now fixed); Submitted for the SUSY07 proceeding
flavour tagging using charm decays at the LHCb experiment
An algorithm is described for tagging the flavour content at production of
neutral mesons in the LHCb experiment. The algorithm exploits the
correlation of the flavour of a meson with the charge of a reconstructed
secondary charm hadron from the decay of the other hadron produced in the
proton-proton collision. Charm hadron candidates are identified in a number of
fully or partially reconstructed Cabibbo-favoured decay modes. The algorithm is
calibrated on the self-tagged decay modes and using of data collected by the LHCb
experiment at centre-of-mass energies of and
. Its tagging power on these samples of
decays is .Comment: All figures and tables, along with any supplementary material and
additional information, are available at
http://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2015-027.htm
Comprehensive analysis of epigenetic clocks reveals associations between disproportionate biological ageing and hippocampal volume
The concept of age acceleration, the difference between biological age and chronological age, is of growing interest, particularly with respect to age-related disorders, such as Alzheimerâs Disease (AD). Whilst studies have reported associations with AD risk and related phenotypes, there remains a lack of consensus on these associations. Here we aimed to comprehensively investigate the relationship between five recognised measures of age acceleration, based on DNA methylation patterns (DNAm age), and cross-sectional and longitudinal cognition and AD-related neuroimaging phenotypes (volumetric MRI and Amyloid-ÎČ PET) in the Australian Imaging, Biomarkers and Lifestyle (AIBL) and the Alzheimerâs Disease Neuroimaging Initiative (ADNI). Significant associations were observed between age acceleration using the Hannum epigenetic clock and cross-sectional hippocampal volume in AIBL and replicated in ADNI. In AIBL, several other findings were observed cross-sectionally, including a significant association between hippocampal volume and the Hannum and Phenoage epigenetic clocks. Further, significant associations were also observed between hippocampal volume and the Zhang and Phenoage epigenetic clocks within Amyloid-ÎČ positive individuals. However, these were not validated within the ADNI cohort. No associations between age acceleration and other Alzheimerâs disease-related phenotypes, including measures of cognition or brain Amyloid-ÎČ burden, were observed, and there was no association with longitudinal change in any phenotype. This study presents a link between age acceleration, as determined using DNA methylation, and hippocampal volume that was statistically significant across two highly characterised cohorts. The results presented in this study contribute to a growing literature that supports the role of epigenetic modifications in ageing and AD-related phenotypes
Observation of the B0 â Ï0Ï0 decay from an amplitude analysis of B0 â (Ï+Ïâ)(Ï+Ïâ) decays
Protonâproton collision data recorded in 2011 and 2012 by the LHCb experiment, corresponding to
an integrated luminosity of 3.0 fbâ1, are analysed to search for the charmless B0 â Ï0Ï0 decay.
More than 600 B0 â (Ï+Ïâ)(Ï+Ïâ) signal decays are selected and used to perform an amplitude
analysis, under the assumption of no CP violation in the decay, from which the B0 â Ï0Ï0 decay is
observed for the first time with 7.1 standard deviations significance. The fraction of B0 â Ï0Ï0 decays
yielding a longitudinally polarised final state is measured to be fL = 0.745+0.048
â0.058(stat) ± 0.034(syst).
The B0 â Ï0Ï0 branching fraction, using the B0 â ÏKâ(892)0 decay as reference, is also reported as
B(B0 â Ï0Ï0) = (0.94 ± 0.17(stat) ± 0.09(syst) ± 0.06(BF)) Ă 10â6
Observation of the decay B0s â Ï(2S)K +Ïâ
The decay B0
s â Ï(2S)K +Ïâ is observed using a data set corresponding to an integrated luminosity of
3.0 fbâ1 collected by the LHCb experiment in pp collisions at centre-of-mass energies of 7 and 8 TeV.
The branching fraction relative to the B0 â Ï(2S)K +Ïâ decay mode is measured to be
B(B0
s â Ï(2S)K +Ïâ)
B(B0 â Ï(2S)K +Ïâ) = 5.38 ± 0.36 (stat) ± 0.22 (syst) ± 0.31 (f s/ fd)%,
where f s/ fd indicates the uncertainty due to the ratio of probabilities for a b quark to hadronise into
a B0
s or B0 meson. Using an amplitude analysis, the fraction of decays proceeding via an intermediate
Kâ(892)0 meson is measured to be 0.645 ± 0.049 (stat) ± 0.049 (syst) and its longitudinal polarisation
fraction is 0.524 ± 0.056 (stat) ± 0.029 (syst). The relative branching fraction for this component is
determined to be
B(B0
s â Ï(2S)Kâ(892)0)
B(B0 â Ï(2S)Kâ(892)0) = 5.58 ± 0.57 (stat) ± 0.40 (syst) ± 0.32 (f s/ fd)%.
In addition, the mass splitting between the B0
s and B0 mesons is measured as
M(B0
s ) â M(B0) = 87.45 ± 0.44 (stat) ± 0.09 (syst) MeV/c2
Measurement of the CP-violating phase ÎČ in B0 â J/ÏÏ+Ïâ decays and limits on penguin effects
Time-dependent CP violation is measured in the (â)
B 0 â J/ÏÏ+Ïâ channel for each Ï+Ïâ resonant
final state using data collected with an integrated luminosity of 3.0 fbâ1 in pp collisions using the LHCb
detector. The final state with the largest rate, J/ÏÏ0(770), is used to measure the CP-violating angle
2ÎČeff to be (41.7 ± 9.6+2.8
â6.3)âŠ. This result can be used to limit the size of penguin amplitude contributions
to CP violation measurements in, for example, (â)
B 0
s â J/ÏÏ decays. Assuming approximate SU(3) flavour
symmetry and neglecting higher order diagrams, the shift in the CP-violating phase Ïs is limited to be
within the interval [â1.05âŠ,+1.18âŠ] at 95% confidence level. Changes to the limit due to SU(3) symmetry
breaking effects are also discussed
Erratum: first observation of the rare BĂŸ â DĂŸKĂŸÏâ decay [Phys. Rev. D 93, 051101(R) (2016)]
No abstract available
Expanding the clinical phenotype of individuals with a 3-bp in-frame deletion of the NF1 gene (c.2970_2972del): an update of genotypeâphenotype correlation
Purpose: Neurofibromatosis type 1 (NF1) is characterized by a highly variable clinical presentation, but almost all NF1-affected adults present with cutaneous and/or subcutaneous neurofibromas. Exceptions are individuals heterozygous for the NF1 in-frame deletion, c.2970_2972del (p.Met992del), associated with a mild phenotype without any externally visible tumors. Methods: A total of 135 individuals from 103 unrelated families, all carrying the constitutional NF1 p.Met992del pathogenic variant and clinically assessed using the same standardized phenotypic checklist form, were included in this study. Results: None of the individuals had externally visible plexiform or histopathologically confirmed cutaneous or subcutaneous neurofibromas. We did not identify any complications, such as symptomatic optic pathway gliomas (OPGs) or symptomatic spinal neurofibromas; however, 4.8% of individuals had nonoptic brain tumors, mostly low-grade and asymptomatic, and 38.8% had cognitive impairment/learning disabilities. In an individual with the NF1 constitutional c.2970_2972del and three astrocytomas, we provided proof that all were NF1-associated tumors given loss of heterozygosity at three intragenic NF1 microsatellite markers and c.2970_297
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