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Concept

Tau

Summary

Tau 'tɔː,_'taʊ (uppercase Τ, lowercase τ, or \boldsymbol\tau; ταυ taf) is the nineteenth letter of the Greek alphabet, representing the voiceless dental or alveolar plosive t. In the system of Greek numerals, it has a value of 300. The name in English is pronounced taʊ or tɔː, but in Greek it is taf. This is because the pronunciation of the combination of Greek letters αυ can have the pronunciation of either [ai], [av] or [af], depending on what follows and if a diaeresis is present on the second vowel (see Greek orthography). Tau was derived from the Phoenician letter taw (𐤕). Letters that arose from tau include Roman T and Cyrillic Te (Т, т). The letter occupies the Unicode slots U+03C4 (lowercase) and U+03A4 (uppercase). In HTML, they can be produced with named entities (τ and Τ), decimal references (τ and Τ), or hexadecimal references (τ and Τ). Modern usage Greek letters used in mathematics, science

Official source

https://en.wikipedia.org/wiki/Tau

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Measurement of lifetimes for heavy flavour mesons using semileptonic B decays at LHCb

Brice Emile Maurin

This thesis work presents lifetime measurements of heavy-flavour mesons made with semileptonic

B^0

and

B^0_s

decays based on

3~{\rm fb}^{-1}

of data collected with the LHCb detector in proton-proton collisions at centre-of-mass energies of 7 and 8 TeV. The study of meson lifetimes is important to constrain phenomenological models for hadronic interactions based on the Standard Model of particle physics. Better understanding of hadronic interactions is essential for making precise predictions, which can then be confronted to experimental data in order to look for signs of physics beyond the Standard Model. We measure the differences between the decay widths of the

B^0_s

and

B^0

mesons,

\Delta(B)

, and between that of the

D_s^-

and

D^-

mesons,

\Delta(D)

, by analysing approximately 410000

B^0_s \to D_{s}^{(*)-}\mu^{+}\nu_{\mu}

and 110000

B^0 \to D^{(*)-}\mu^{+}\nu_{\mu}

decays, which are partially reconstructed in the same

K^+K^-\pi^-\mu^+

final state. We measure

\Delta(B) = -0.0115 \pm 0.0053~{\rm(stat)} \pm 0.0041~{\rm(syst)}~{\rm ps}^{-1}

and

\Delta(D) = 1.0131 \pm 0.0117~{\rm(stat)} \pm 0.0065~{\rm(syst)}~{\rm ps}^{-1}.

Using the obtained values of

\Delta(D)

and

\Delta(B)

and the

B^0

and

D^-

lifetimes as external inputs, we obtain a measurement of the flavour-specific

B^0_s

lifetime,

\tau_s^{\rm fs} = 1.547 \pm 0.013~{\rm(stat)} \pm 0.010~{\rm (syst)} \pm 0.004~{\rm(\tau_{B^0})}~{\rm ps},

and of the

D_s^-

lifetime,

\tau_{D_s^-} = 0.5064 \pm 0.0030~{\rm(stat)} \pm 0.0017~{\rm (syst)} \pm 0.0017~{\rm(\tau_{D^-})}~{\rm ps},

where the last uncertainties originate from the limited knowledge of the

B^0

and

D^-

lifetimes, respectively. Both results are compatible with, and improve upon, previous determinations. A feasibility study of a

D^0

lifetime measurement is performed, by measuring the difference between the decay widths of the

D^0

and

D^-

mesons,

\Delta(D)'

. We reconstruct approximately

2.2\times 10^6

B^0\to D^{*-}(\to \bar{D}^0 (\to K^+\pi^-)\pi^-)\mu^+\nu_{\mu}

and

1.6\times 10^6

B^0\to D^{(*)-}(\to K^+\pi^-\pi^- (X))\mu^+\nu_{\mu}

decays. We measure

\Delta(D)' = 1.4644 \pm 0.0043~{\rm(stat)} \pm 0.0132~{\rm(syst)}~{\rm ps}^{-1}

and with the

D^-

lifetime as external input, we get an estimate of the

D^0

lifetime,

\tau_{D^0} = 0.4122 \pm 0.0007~{\rm(stat)} \pm 0.0022~{\rm (syst)} \pm 0.0011~{\rm(\tau_{D^-})}~{\rm ps}.

This result is compatible with, but less precise than, current precision and thus validates the method. We discuss possible improvements with larger simulation samples and data sets.

EPFL2018

Non-invasive diagnostic biomarkers for estimating the onset time of permanent cerebral ischemia

Corinne Benakis, Lara Buscemi Estefanell, Rolf Gruetter, Hongxia Lei, Lijing Xin

The treatments for ischemic stroke can only be administered in a narrow time-window. However, the ischemia onset time is unknown in ~30% of stroke patients (wake-up strokes). The objective of this study was to determine whether MR spectra of ischemic brains might allow the precise estimation of cerebral ischemia onset time. We modeled ischemic stroke in male ICR-CD1 mice using a permanent middle cerebral artery filament occlusion model with laser Doppler control of the regional cerebral blood flow. Mice were then subjected to repeated MRS measurements of ipsilateral striatum at 14.1[thinsp]T. A striking initial increase in [gamma]-aminobutyric acid (GABA) and no increase in glutamine were observed. A steady decline was observed for taurine (Tau), N-acetyl-aspartate (NAA) and similarly for the sum of NAA+Tau+glutamate that mimicked an exponential function. The estimation of the time of onset of permanent ischemia within 6[thinsp]hours in a blinded experiment with mice showed an accuracy of 33[plusmn]10[thinsp]minutes. A plot of GABA, Tau, and neuronal marker concentrations against the ratio of acetate/NAA allowed precise separation of mice whose ischemia onset lay within arbitrarily chosen time-windows. We conclude that 1H-MRS has the potential to detect the clinically relevant time of onset of ischemic stroke.

Nature Publishing Group2014

, , , , ,

Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene cause late-onset, autosomal dominant Parkinson's disease (PD). The clinical and neurochemical features of LRRK2-linked PD are similar to idiopathic disease although neuropathology is somewhat heterogeneous. Dominant mutations in LRRK2 precipitate neurodegeneration through a toxic gain-of-function mechanism which can be modeled in transgenic mice overexpressing human LRRK2 variants. A number of LRRK2 transgenic mouse models have been developed that display abnormalities in dopaminergic neurotransmission and alterations in tau metabolism yet without consistently inducing dopaminergic neurodegeneration. To directly explore the impact of mutant LRRK2 on the nigrostriatal dopaminergic pathway, we developed conditional transgenic mice that selectively express human R1441C LRRK2 in dopaminergic neurons from the endogenous murine ROSA26 promoter. The expression of R1441C LRRK2 does not induce the degeneration of substantia nigra dopaminergic neurons or striatal dopamine deficits in mice up to 2 years of age, and fails to precipitate abnormal protein inclusions containing alpha-synuclein, tau, ubiquitin or autophagy markers (LC3 and p62). Furthermore, mice expressing R1441C LRRK2 exhibit normal motor activity and olfactory function with increasing age. Intriguingly, the expression of R1441C LRRK2 induces age-dependent abnormalities of the nuclear envelope in nigral dopaminergic neurons including reduced nuclear circularity and increased invaginations of the nuclear envelope. In addition, R1441C LRRK2 mice display increased neurite complexity of cultured midbrain dopaminergic neurons. Collectively, these novel R1441C LRRK2 conditional transgenic mice reveal altered dopaminergic neuronal morphology with advancing age, and provide a useful tool for exploring the pathogenic mechanisms underlying the R1441C LRRK2 mutation in PD. (C) 2014 Elsevier Inc All rights reserved.

Elsevier2014

Measurement of lifetimes for heavy flavour mesons using semileptonic B decays at LHCb

Brice Emile Maurin

This thesis work presents lifetime measurements of heavy-flavour mesons made with semileptonic

B^0

and

B^0_s

decays based on

3~{\rm fb}^{-1}

B^0_s

and

B^0

mesons,

\Delta(B)

, and between that of the

D_s^-

and

D^-

mesons,

\Delta(D)

, by analysing approximately 410000

B^0_s \to D_{s}^{(*)-}\mu^{+}\nu_{\mu}

and 110000

B^0 \to D^{(*)-}\mu^{+}\nu_{\mu}

decays, which are partially reconstructed in the same

K^+K^-\pi^-\mu^+

final state. We measure

\Delta(B) = -0.0115 \pm 0.0053~{\rm(stat)} \pm 0.0041~{\rm(syst)}~{\rm ps}^{-1}

and

\Delta(D) = 1.0131 \pm 0.0117~{\rm(stat)} \pm 0.0065~{\rm(syst)}~{\rm ps}^{-1}.

Using the obtained values of

\Delta(D)

and

\Delta(B)

and the

B^0

and

D^-

lifetimes as external inputs, we obtain a measurement of the flavour-specific

B^0_s

lifetime,

\tau_s^{\rm fs} = 1.547 \pm 0.013~{\rm(stat)} \pm 0.010~{\rm (syst)} \pm 0.004~{\rm(\tau_{B^0})}~{\rm ps},

and of the

D_s^-

lifetime,

\tau_{D_s^-} = 0.5064 \pm 0.0030~{\rm(stat)} \pm 0.0017~{\rm (syst)} \pm 0.0017~{\rm(\tau_{D^-})}~{\rm ps},

where the last uncertainties originate from the limited knowledge of the

B^0

and

D^-

lifetimes, respectively. Both results are compatible with, and improve upon, previous determinations. A feasibility study of a

D^0

lifetime measurement is performed, by measuring the difference between the decay widths of the

D^0

and

D^-

mesons,

\Delta(D)'

. We reconstruct approximately

2.2\times 10^6

B^0\to D^{*-}(\to \bar{D}^0 (\to K^+\pi^-)\pi^-)\mu^+\nu_{\mu}

and

1.6\times 10^6

B^0\to D^{(*)-}(\to K^+\pi^-\pi^- (X))\mu^+\nu_{\mu}

decays. We measure

\Delta(D)' = 1.4644 \pm 0.0043~{\rm(stat)} \pm 0.0132~{\rm(syst)}~{\rm ps}^{-1}

and with the

D^-

lifetime as external input, we get an estimate of the

D^0

lifetime,

\tau_{D^0} = 0.4122 \pm 0.0007~{\rm(stat)} \pm 0.0022~{\rm (syst)} \pm 0.0011~{\rm(\tau_{D^-})}~{\rm ps}.

This result is compatible with, but less precise than, current precision and thus validates the method. We discuss possible improvements with larger simulation samples and data sets.

EPFL2018