179 research outputs found
Determination of the angle from nonleptonic decays
We note that the two body nonleptonic pure tree decays and the corresponding vector-vector modes are well suited to extract the weak phase
of the unitarity triangle. The CP violating phase can be determined
cleanly as these decay modes are free from the penguin pollutions.Comment: 12 pages, LaTeX, 2 references added, Minor changes in the text, to
appear in Phys. Rev.
Final-State Phases in Doubly-Cabibbo-Suppressed Charmed Meson Nonleptonic Decays
Cabibbo-favored nonleptonic charmed particle decays exhibit large final-state
phase differences in and but not
channels. It is of interest to know the corresponding pattern of final-state
phases in doubly-Cabibbo-suppressed decays, governed by the
subprocess. An experimental program is outlined for determining such phases via
measurements of rates for and channels,
and determination of interference between bands in Dalitz plots. Such a program
is feasible at planned high-intensity sources of charmed particles.Comment: 12 pages, LaTeX, 2 figures, to be submitted to Phys. Rev. D. Revised
versio
Neonatal Pain-Related Stress and NFKBIA Genotype Are Associated with Altered Cortisol Levels in Preterm Boys at School Age
Neonatal pain-related stress is associated with elevated salivary cortisol levels to age 18 months in children born very preterm, compared to full-term, suggesting early programming effects. Importantly, interactions between immune/inflammatory and neuroendocrine systems may underlie programming effects. We examined whether cortisol changes persist to school age, and if common genetic variants in the promoter region of the NFKBIA gene involved in regulation of immune and inflammatory responses, modify the association between early experience and later life stress as indexed by hair cortisol levels, which provide an integrated index of endogenous HPA axis activity. Cortisol was assayed in hair samples from 128 children (83 born preterm ≤ 32 weeks gestation and 45 born full-term) without major sensory, motor or cognitive impairments at age 7 years. We found that hair cortisol levels were lower in preterm compared to term-born children. Downregulation of the HPA axis in preterm children without major impairment, seen years after neonatal stress terminated, suggests persistent alteration of stress system programming. Importantly, the etiology was gender-specific such that in preterm boys but not girls, specifically those with the minor allele for NFKBIA rs2233409, lower hair cortisol was associated with greater neonatal pain (number of skin-breaking procedures from birth to term), independent of medical confounders. Moreover, the minor allele (CT or TT) of NFKBIA rs2233409 was associated with higher secretion of inflammatory cytokines, supporting the hypothesis that neonatal pain-related stress may act as a proinflammatory stimulus that induces long-term immune cell activation. These findings are the first evidence that a long-term association between early pain-related stress and cortisol may be mediated by a genetic variants that regulate the activity of NF-κB, suggesting possible involvement of stress/inflammatory mechanisms in HPA programming in boys born very preterm
Leptonic and Semileptonic Decays of Charm and Bottom Hadrons
We review the experimental measurements and theoretical descriptions of
leptonic and semileptonic decays of particles containing a single heavy quark,
either charm or bottom. Measurements of bottom semileptonic decays are used to
determine the magnitudes of two fundamental parameters of the standard model,
the Cabibbo-Kobayashi-Maskawa matrix elements and . These
parameters are connected with the physics of quark flavor and mass, and they
have important implications for the breakdown of CP symmetry. To extract
precise values of and from measurements, however,
requires a good understanding of the decay dynamics. Measurements of both charm
and bottom decay distributions provide information on the interactions
governing these processes. The underlying weak transition in each case is
relatively simple, but the strong interactions that bind the quarks into
hadrons introduce complications. We also discuss new theoretical approaches,
especially heavy-quark effective theory and lattice QCD, which are providing
insights and predictions now being tested by experiment. An international
effort at many laboratories will rapidly advance knowledge of this physics
during the next decade.Comment: This review article will be published in Reviews of Modern Physics in
the fall, 1995. This file contains only the abstract and the table of
contents. The full 168-page document including 47 figures is available at
http://charm.physics.ucsb.edu/papers/slrevtex.p
Experimental Tests of Factorization in Charmless Non-Leptonic Two-Body B Decays
Using a theoretical framework based on the next-to-leading order QCD-improved
effective Hamiltonian and a factorization Ansatz for the hadronic matrix
elements of the four-quark operators, we reassess branching fractions in
two-body non-leptonic decays , involving the lowest lying
light pseudoscalar and vector mesons in the standard model. Using
the sensitivity of the decay rates on the effective number of colors, , as
a criterion of theoretical predictivity, we classify all the current-current
(tree) and penguin transitions in five different classes. The recently measured
charmless two-body decays and charge conjugates) are
dominated by the -stable QCD penguins (class-IV transitions) and their
estimates are consistent with data. The measured charmless and transition ,
on the other hand, belong to the penguin (class-V) and tree (class-III)
transitions. The class-V penguin transitions are in general more difficult to
predict. We propose a number of tests of the factorization framework in terms
of the ratios of branching ratios for some selected decays
involving light hadrons and , which depend only moderately on the
form factors. We also propose a set of measurements to determine the effective
coefficients of the current-current and QCD penguin operators. The potential
impact of decays on the CKM phenomenology is emphasized by
analyzing a number of decay rates in the factorization framework.Comment: 64 pages (LaTex) including 13 figures, requires epsfig.sty; submitted
to Phys. Rev.
Expulsion of Magnetic Flux Lines from the Growing Superconducting Core of a Magnetized Quark Star
The expulsion of magnetic flux lines from a growing superconducting core of a
quark star has been investigated. The idea of impurity diffusion in molten
alloys and an identical mechanism of baryon number transport from hot
quark-gluon-plasma phase to hadronic phase during quark-hadron phase transition
in the early universe, micro-second after big bang has been used. The
possibility of Mullins-Sekerka normal-superconducting interface instability has
also been studied.Comment: Thoroughly revised version. Accepted for Astrophysics & Space Scienc
Exploring CP violation with decays
We note that it is possible to determine the weak phase \gamma from the time
dependent measurements of the decays B_s^0(t) (\bar B_s^0 (t)) \to \bar D^{* 0} \phi {\cal O} (10^{-5}-10^{-6})$, the
strategies presented here appear to be particularly interesting for the "second
generation" experiments at hadronic B factories.Comment: 13 pages, LaTeX, 2 references added, Minor changes in the text, to
appear in Phys. Rev.
Bs-Bs.bar Mixing, CP Violation and Extraction of CKM Phases from Untagged Bs Data Samples
A width difference of the order of 20\% has previously been predicted for the
two mass eigenstates of the meson. The dominant contributor to the width
difference is the transition, with final states common
to both and . All current experimental analyses fit the
time-dependences of flavor-specific -modes to a single exponential, which
essentially determines the average lifetime. We stress that the same data
sample allows even the measurement of the width difference. To see that, this
note reviews the time-dependent formulae for tagged decays, which involve
rapid oscillatory terms depending on . In untagged data samples the
rapid oscillatory terms cancel. Their time-evolutions depend only on the much
more slowly varying exponential falloffs. We discuss in detail the extraction
of the two widths, and identify the large (small) CP-even (-odd) rate with that
of the light (heavy) mass eigenstate. It is demonstrated that decay
length distributions of some \underline{untagged} modes, such as , can be used to extract the notoriously
difficult CKM unitarity triangle angle . Sizable CP violating effects
may be seen with such untagged data samples. Listing as an
observable allows for additional important standard model constraints. Within
the CKM model, the ratio involves no CKM parameters,
only a QCD uncertainty. Thus a measurement of would
predict , up to the QCD uncertainty. A large width
difference would automatically solve the puzzle of the number of charmed
hadrons per decay in favor of theory. We also derive an upper limit of . Further, we must abandon the notion of
branching fractions of , and instead consider , in analogy to the neutral kaons.Comment: 46 pages, revte
On the Low Surface Magnetic Field Structure of Quark Stars
Following some of the recent articles on hole super-conductivity and related
phenomena by Hirsch \cite{H1,H2,H3}, a simple model is proposed to explain the
observed low surface magnetic field of the expected quark stars. It is argued
that the diamagnetic moments of the electrons circulating in the electro-sphere
induce a magnetic field, which forces the existing quark star magnetic flux
density to become dilute. We have also analysed the instability of
normal-superconducting interface due to excess accumulation of magnetic flux
lines, assuming an extremely slow growth of superconducting phase through a
first order bubble nucleation type transition.Comment: 24 pages REVTEX, one .eps figure, psfig.sty is include
Cabibbo-Suppressed Decays of D^+ \to \pi^+\pi^0, K^+\bar{K}^0, K^+\pi^0
Using a 13.7 fb-1 data sample collected with the CLEO II and II.V detectors,
we report new branching fraction measurements for two Cabibbo-suppressed decay
modes of the D+ meson: BR(D+ -> pi+ pi0) = (1.31 +/- 0.17 +/- 0.09 +/- 0.09) x
10^(-3)and BR(D+ -> K+ K0bar) = (5.24 +/- 0.43 +/- 0.20 +/- 0.34) x 10^(-3)
which are significant improvements over past measurements. The errors reflect
statistical and systematical uncertainties as well as the uncertainty in the
absolute D+ branching fraction scale. We also set the first 90% confidence
level upper limit on the branching fraction of the doubly Cabibbo-suppressed
decay mode BR(D+ -> K+ pi0) < 4.2 x 10^(-4).Comment: 8 pages postscript, also available through
http://w4.lns.cornell.edu/public/CLNS, submitted to PR
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