683 research outputs found
Heavy-to-light B meson form factors at large recoil energy -- spectator-scattering corrections
We complete the investigation of loop corrections to hard
spectator-scattering in exclusive B meson to light meson transitions by
computing the short-distance coefficient (jet-function) from the hard-collinear
scale. Adding together the two coefficients from matching QCD to SCET_I to
SCET_II, we investigate the size of loop effects on the ratios of
heavy-to-light meson form factors at large recoil. We find the corrections from
the hard and hard-collinear scales to be of approximately the same size, and
significant, but the perturbative expansions appear to be well-behaved. Our
calculation provides a non-trivial verification of the factorization arguments.
We observe considerable differences between the predictions based on
factorization in the heavy-quark limit and current QCD sum rule calculations of
the form factors. We also include the hard-collinear correction in the B -> pi
pi tree amplitudes, and find an enhancement of the colour-suppressed amplitude
relative to the colour-allowed amplitude.Comment: 55 pages, LaTeX, uses axodraw.st
Photon Distribution Amplitudes in QCD
We develop a consistent technique for the calculation of real photon emission
in hard exclusive processes, which is based on the background field formalism
and allows a convenient separation of hard electromagnetic and soft hadronic
components of the photon. The latter ones are related to matrix-elements of
light-cone operators in the electromagnetic background field and can be
parametrized in terms of photon distribution amplitudes. We construct a
complete set of photon distribution amplitudes up to and including twist-4, for
both chirality-conserving and chirality-violating operators. The distribution
amplitudes involve several nonperturbative parameters and, most importantly,
the magnetic susceptibility of the quark condensate. We review and update
previous estimates of the susceptibility and also give new estimates of
parameters describing higher-twist amplitudes from QCD sum rules.Comment: 33 pages Late
Subaru high-z exploration of low-luminosity quasars (SHELLQs). I. Discovery of 15 quasars and bright galaxies at 5.7 < z < 6.9
We report the discovery of 15 quasars and bright galaxies at 5.7 < z < 6.9.
This is the initial result from the Subaru High-z Exploration of Low-Luminosity
Quasars (SHELLQs) project, which exploits the exquisite multiband imaging data
produced by the Subaru Hyper Suprime-Cam (HSC) Strategic Program survey. The
candidate selection is performed by combining several photometric approaches
including a Bayesian probabilistic algorithm to reject stars and dwarfs. The
spectroscopic identification was carried out with the Gran Telescopio Canarias
and the Subaru Telescope for the first 80 deg2 of the survey footprint. The
success rate of our photometric selection is quite high, approaching 100 % at
the brighter magnitudes (zAB < 23.5 mag). Our selection also recovered all the
known high-z quasars on the HSC images. Among the 15 discovered objects, six
are likely quasars, while the other six with interstellar absorption lines and
in some cases narrow emission lines are likely bright Lyman-break galaxies. The
remaining three objects have weak continua and very strong and narrow Ly alpha
lines, which may be excited by ultraviolet light from both young stars and
quasars. These results indicate that we are starting to see the steep rise of
the luminosity function of z > 6 galaxies, compared with that of quasars, at
magnitudes fainter than M1450 ~ -22 mag or zAB ~24 mag. Follow-up studies of
the discovered objects as well as further survey observations are ongoing.Comment: Published in ApJ (828:26, 2016
General CP Violation in Minimal Left-Right Symmetric Model and Constraints on the Right-Handed Scale
In minimal left-right symmetric theories, the requirement of parity
invariance allows only one complex phase in the Higgs potential and one in the
Yukawa couplings, leading to a two-phase theory with both spontaneous and
explicit CP violations. We present a systematic way to solve the right-handed
quark mixing matrix analytically in this model and find that the leading order
solution has the same hierarchical structure as the left-handed CKM matrix with
one more CP-violating phase coming from the complex Higgs vev. Armed with this
explicit right-handed mixing matrix, we explore its implications for flavor
changing and conserving processes in detail, low-energy CP-violating
observables in particular. We report an improved lower bound on the mass
of 2.5 TeV from and , and a somewhat higher bound (4
TeV) from kaon decay parameters , , and neutron electric
dipole moment. The new bound on the flavor-changing neutral Higgs mass is 25
TeV.Comment: 35 pages, 14 figure
Direct CP Violation in K-decay and Minimal Left-Right Symmetry Scale
We calculate the new contribution to the direct CP-violation parameter
in decay in the minimal left-right symmetric model
with the recently-obtained right-handed quark Cabibbo-Kobayashi-Maskawa mixing.
We pay particular attention to the uncertainty in the hadronic matrix element
of a leading four-quark operator . We find that it can be related to
the standard model electromagnetic penguin operator through chiral symmetry. Using the lattice and large
calculations, we obtain a robust constraint on the minimal left-right symmetric
scale TeV from the experimental data on .Comment: 2 figure
Discovery of the First Low-Luminosity Quasar at z > 7
We report the discovery of a quasar at z = 7.07, which was selected from the
deep multi-band imaging data collected by the Hyper Suprime-Cam (HSC) Subaru
Strategic Program survey. This quasar, HSC J124353.93+010038.5, has an order of
magnitude lower luminosity than do the other known quasars at z > 7. The
rest-frame ultraviolet absolute magnitude is M1450 = -24.13 +/- 0.08 mag and
the bolometric luminosity is Lbol = (1.4 +/- 0.1) x 10^{46} erg/s. Its spectrum
in the optical to near-infrared shows strong emission lines, and shows evidence
for a fast gas outflow, as the C IV line is blueshifted and there is indication
of broad absorption lines. The Mg II-based black hole mass is Mbh = (3.3 +/-
2.0) x 10^8 Msun, thus indicating a moderate mass accretion rate with an
Eddington ratio 0.34 +/- 0.20. It is the first z > 7 quasar with sub-Eddington
accretion, besides being the third most distant quasar, known to date. The
luminosity and black hole mass are comparable to, or even lower than, those
measured for the majority of low-z quasars discovered by the Sloan Digital Sky
Survey, and thus this quasar likely represents a z > 7 counterpart to quasars
commonly observed in the low-z universe.Comment: Accepted for publication in ApJ Letter
Speech and language therapy for aphasia following stroke
Background Aphasia is an acquired language impairment following brain damage that affects some or all language modalities: expression and understanding of speech, reading, and writing. Approximately one third of people who have a stroke experience aphasia. Objectives To assess the effects of speech and language therapy (SLT) for aphasia following stroke. Search methods We searched the Cochrane Stroke Group Trials Register (last searched 9 September 2015), CENTRAL (2015, Issue 5) and other Cochrane Library Databases (CDSR, DARE, HTA, to 22 September 2015), MEDLINE (1946 to September 2015), EMBASE (1980 to September 2015), CINAHL (1982 to September 2015), AMED (1985 to September 2015), LLBA (1973 to September 2015), and SpeechBITE (2008 to September 2015). We also searched major trials registers for ongoing trials including ClinicalTrials.gov (to 21 September 2015), the Stroke Trials Registry (to 21 September 2015), Current Controlled Trials (to 22 September 2015), and WHO ICTRP (to 22 September 2015). In an effort to identify further published, unpublished, and ongoing trials we also handsearched theInternational Journal of Language and Communication Disorders(1969 to 2005) and reference lists of relevant articles, and we contacted academic institutions and other researchers. There were no language restrictions. Selection criteria Randomised controlled trials (RCTs) comparing SLT (a formal intervention that aims to improve language and communication abilities, activity and participation) versus no SLT; social support or stimulation (an intervention that provides social support and communication stimulation but does not include targeted therapeutic interventions); or another SLT intervention (differing in duration, intensity, frequency, intervention methodology or theoretical approach). Data collection and analysis We independently extracted the data and assessed the quality of included trials. We sought missing data from investigators. Main results We included 57 RCTs (74 randomised comparisons) involving 3002 participants in this review (some appearing in more than one comparison). Twenty-seven randomised comparisons (1620 participants) assessed SLT versus no SLT; SLT resulted in clinically and statistically significant benefits to patients' functional communication (standardised mean difference (SMD) 0.28, 95% confidence interval (CI) 0.06 to 0.49, P = 0.01), reading, writing, and expressive language, but (based on smaller numbers) benefits were not evident at follow-up. Nine randomised comparisons (447 participants) assessed SLT with social support and stimulation; meta-analyses found no evidence of a difference in functional communication, but more participants withdrew from social support interventions than SLT. Thirty-eight randomised comparisons (1242 participants) assessed two approaches to SLT. Functional communication was significantly better in people with aphasia that received therapy at a high intensity, high dose, or over a long duration compared to those that received therapy at a lower intensity, lower dose, or over a shorter period of time. The benefits of a high intensity or a high dose of SLT were confounded by a significantly higher dropout rate in these intervention groups. Generally, trials randomised small numbers of participants across a range of characteristics (age, time since stroke, and severity profiles), interventions, and outcomes. Authors' conclusions Our review provides evidence of the effectiveness of SLT for people with aphasia following stroke in terms of improved functional communication, reading, writing, and expressive language compared with no therapy. There is some indication that therapy at high intensity, high dose or over a longer period may be beneficial. HIgh-intensity and high dose interventions may not be acceptable to all
The preventative effect of ramosetron on postoperative nausea and vomiting after total thyroidectomy
Rare Decays of \Lambda_b->\Lambda + \gamma and \Lambda_b ->\Lambda + l^{+} l^{-} in the Light-cone Sum Rules
Within the Standard Model, we investigate the weak decays of and with the light-cone
sum rules approach. The higher twist distribution amplitudes of
baryon to the leading conformal spin are included in the sum rules for
transition form factors. Our results indicate that the higher twist
distribution amplitudes almost have no influences on the transition form
factors retaining the heavy quark spin symmetry, while such corrections can
result in significant impacts on the form factors breaking the heavy quark spin
symmetry. Two phenomenological models (COZ and FZOZ) for the wave function of
baryon are also employed in the sum rules for a comparison, which can
give rise to the form factors approximately 5 times larger than that in terms
of conformal expansion. Utilizing the form factors calculated in LCSR, we then
perform a careful study on the decay rate, polarization asymmetry and
forward-backward asymmetry, with respect to the decays of , .Comment: 38 pages, 15 figures, some typos are corrected and more references
are adde
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