162 research outputs found
Weak Coupling Phase from Decays of Charged B Mesons to and
The theory of violation based on phases in weak couplings in the
Cabibbo-Kobayashi-Maskawa (CKM) matrix requires the phase (in a standard convention) to be nonzero. A measurement of
is proposed based on charged meson decay rates to ,
, , and the charge-conjugate states. The corresponding
branching ratios are expected to be of the order of . (submitted to
Physical Review Letters)Comment: LaTeX, 8 pages, 2 figures (not included, available upon request),
TECHNION-PH-94-7, EFI-94-14, UdeM-LPN-TH-94-19
Recommended from our members
Transcriptionally active HERV-H retrotransposons demarcate topologically associating domains in human pluripotent stem cells.
Chromatin architecture has been implicated in cell type-specific gene regulatory programs, yet how chromatin remodels during development remains to be fully elucidated. Here, by interrogating chromatin reorganization during human pluripotent stem cell (hPSC) differentiation, we discover a role for the primate-specific endogenous retrotransposon human endogenous retrovirus subfamily H (HERV-H) in creating topologically associating domains (TADs) in hPSCs. Deleting these HERV-H elements eliminates their corresponding TAD boundaries and reduces the transcription of upstream genes, while de novo insertion of HERV-H elements can introduce new TAD boundaries. The ability of HERV-H to create TAD boundaries depends on high transcription, as transcriptional repression of HERV-H elements prevents the formation of boundaries. This ability is not limited to hPSCs, as these actively transcribed HERV-H elements and their corresponding TAD boundaries also appear in pluripotent stem cells from other hominids but not in more distantly related species lacking HERV-H elements. Overall, our results provide direct evidence for retrotransposons in actively shaping cell type- and species-specific chromatin architecture
Oblique Corrections To The W Width
The lowest-order expression for the partial width to , has no oblique radiative
corrections from new physics if the measured mass is used. Here GeV/ is the muon decay constant. For
the present value of GeV/, and with
GeV, one expects MeV. The total
width is also expected to lack oblique corrections from
new physics, so that . Present data are consistent with this prediction.Comment: 15 pages (LaTeX), one PostScript figure not included (available upon
request
Annihilation, Rescattering, and CP Asymmetries in B Meson Decays
A number of meson decays may proceed only through participation of the
spectator quark, whether through amplitudes proportional to or via
rescattering from other less-suppressed amplitudes. An expected hierarchy of
amplitudes in the absence of rescattering will be violated by rescattering
corrections. Such violations could point the way toward channels in which
final-state interactions could be important. Cases in which final state phases
can lead to large CP asymmetries are pointed out.Comment: 9 page
iPSCORE: A Resource of 222 iPSC Lines Enabling Functional Characterization of Genetic Variation across a Variety of Cell Types.
Large-scale collections of induced pluripotent stem cells (iPSCs) could serve as powerful model systems for examining how genetic variation affects biology and disease. Here we describe the iPSCORE resource: a collection of systematically derived and characterized iPSC lines from 222 ethnically diverse individuals that allows for both familial and association-based genetic studies. iPSCORE lines are pluripotent with high genomic integrity (no or low numbers of somatic copy-number variants) as determined using high-throughput RNA-sequencing and genotyping arrays, respectively. Using iPSCs from a family of individuals, we show that iPSC-derived cardiomyocytes demonstrate gene expression patterns that cluster by genetic background, and can be used to examine variants associated with physiological and disease phenotypes. The iPSCORE collection contains representative individuals for risk and non-risk alleles for 95% of SNPs associated with human phenotypes through genome-wide association studies. Our study demonstrates the utility of iPSCORE for examining how genetic variants influence molecular and physiological traits in iPSCs and derived cell lines
The Higgs as a Probe of Supersymmetric Extra Sectors
We present a general method for calculating the leading contributions to h ->
gg and h -> gamma gamma in models where the Higgs weakly mixes with a nearly
supersymmetric extra sector. Such mixing terms can play an important role in
raising the Higgs mass relative to the value expected in the MSSM. Our method
applies even when the extra sector is strongly coupled, and moreover does not
require a microscopic Lagrangian description. Using constraints from holomorphy
we fix the leading parametric form of the contributions to these Higgs
processes, including the Higgs mixing angle dependence, up to an overall
coefficient. Moreover, when the Higgs is the sole source of mass for a
superconformal sector, we show that even this coefficient is often calculable.
For appropriate mixing angles, the contribution of the extra states to h -> gg
and h -> gamma gamma can vanish. We also discuss how current experimental
limits already lead to non-trivial constraints on such models. Finally, we
provide examples of extra sectors which satisfy the requirements necessary to
use the holomorphic approximation.Comment: v4: 34 pages, 2 figures, typo corrected and clarification adde
Charmless decays using flavor SU(3) symmetry
The decays of mesons to a pair of charmless pseudoscalar () mesons are
analyzed within a framework of flavor SU(3). Symmetry breaking is taken into
account in tree () amplitudes through ratios of decay constants; exact SU(3)
is assumed elsewhere. Acceptable fits to and
branching ratios and CP asymmetries are obtained with tree, color-suppressed
(), penguin (), and electroweak penguin () amplitudes. Crucial
additional terms for describing processes involving and include
a large flavor-singlet penguin amplitude () as proposed earlier and a
penguin amplitude associated with intermediate and quarks. For
the mode a term associated with intermediate
and quarks also may be needed. Values of the weak phase are
obtained consistent with an earlier analysis of decays, where
denotes a vector meson, and with other analyses of CKM parameters.Comment: 26 pages, 1 figure. To be submitted to Phys. Rev. D. Reference
update
ELECTROWEAK PENGUINS AND TWO-BODY B DECAYS
We discuss the role of electroweak penguins in decays to two light
pseudoscalar mesons. We confirm that the extraction of the weak phase
through the isospin analysis involving decays is largely
unaffected by such operators. However, the methods proposed to obtain weak and
strong phases by relating , and decays
through flavor SU(3) will be invalidated if electroweak penguins are large. We
show that, although the introduction of electroweak penguin contributions
introduces no new amplitudes of flavor SU(3), there are a number of ways to
experimentally measure the size of such effects. Finally, using SU(3) amplitude
relations we present a new way of measuring the weak angle which holds
even in the presence of electroweak penguins.Comment: 18 pages, 3 figures, LaTeX file. The full postscript manuscript is
available by anonymous ftp at
ftp://lpsvsh.lps.umontreal.ca/theorie/hep-ph/EWpenguins.ps (a VAX so use the
format theorie.hep-ph if you change by more than one directory at a time
Information on Provided by the Semileptonic Process
Analysis of the present data on the semileptonic process
indicates that they have not yet reached the precision to provide adequate
information on the form factor , which for is known to be related to the factorized color-favored (``'', or
``tree'') contribution to . It is shown here that with
around 500 events in which rate and spectrum are measured
one can improve the accuracy of by a significant amount. A recent CLEO
determination of the coupling constant is compared with an earlier
prediction, and its role in the description of the form factors is
noted. When combined with an estimate of the penguin amplitude (``'')
obtained using flavor SU(3) symmetry from decays, information on
allows one to gauge the effects of the penguin amplitude on extraction of
the weak phase from the time-dependent CP-violating rate
asymmetry in . The constraint on implied by a
recent experimental result on this asymmetry is described.Comment: 17 pages, LaTeX, 7 figures, revised version resubm. to Phys. Rev. D.
Further modifications in abstract, text, and reference
- …