1,188 research outputs found
Addendum: New approach to the resummation of logarithms in Higgs-boson decays to a vector quarkonium plus a photon [Phys. Rev. D 95, 054018 (2017)]
In this addendum to Phys.\ Rev.\ D {\bf 95}, 054018 (2017) we recompute the
rates for the decays of the Higgs boson to a vector quarkonium plus a photon,
where the vector quarkonium is , , , or
. We correct an error in the Abel-Pad\'e summation formula that
was used to carry out the evolution of the quarkonium light-cone distribution
amplitude in Phys.\ Rev.\ D {\bf 95}, 054018 (2017). We also correct an error
in the scale of quarkonium wave function at the origin in Phys.\ Rev.\ D {\bf
95}, 054018 (2017) and introduce several additional refinements in the
calculation.Comment: 7 pages, [v2] Abel-Pade summation formula corrected, [v3] PRD versio
New approach to the resummation of logarithms in Higgs-boson decays to a vector quarkonium plus a photon
We present a calculation of the rates for Higgs-boson decays to a vector
heavy-quarkonium state plus a photon, where the heavy quarkonium states are the
J/psi and the Upsilon(nS) states, with n=1, 2, or 3. The calculation is carried
out in the light-cone formalism, combined with nonrelativistic QCD
factorization, and is accurate at leading order in m_Q^2/m_H^2, where m_Q is
the heavy-quark mass and m_H is the Higgs-boson mass. The calculation contains
corrections through next-to-leading order in the strong-coupling constant
alpha_s and the square of the heavy-quark velocity v, and includes a
resummation of logarithms of m_H^2/m_Q^2 at next-to-leading logarithmic
accuracy. We have developed a new method, which makes use of Abel summation,
accelerated through the use of Pade approximants, to deal with divergences in
the resummed expressions for the quarkonium light-cone distribution amplitudes.
This approach allows us to make definitive calculations of the resummation
effects. Contributions from the order-alpha_s and order-v^2 corrections to the
light-cone distribution amplitudes that we obtain with this new method differ
substantially from the corresponding contributions that one obtains from a
model light-cone distribution amplitude [M. Koenig and M. Neubert, J. High
Energy Phys. 08 (2015) 012]. Our results for the real parts of the
direct-process amplitudes are considerably smaller than those from one earlier
calculation [G. T. Bodwin, H. S. Chung, J.-H. Ee, J. Lee, and F. Petriello,
Phys. Rev. D 90, 113010 (2014)], reducing the sensitivity to the
Higgs-boson--heavy-quark couplings, and are somewhat smaller than those from
another earlier calculation [M. Koenig and M. Neubert, J. High Energy Phys. 08
(2015) 012]. However, our results for the standard-model Higgs-boson branching
fractions are in good agreement with those in M. Koenig and M. Neubert, J. High
Energy Phys. 08 (2015) 012.Comment: 40 pages, improved discussion of the convergence of the
nonrelativistic expansion, minor corrections and changes in nomenclature,
version published in Phys. Rev.
-boson decays to a vector quarkonium plus a photon
We compute the decay rates for the processes , where is
the boson, is the photon, and is one of the vector quarkonia
or , with , , or . Our computations include
corrections through relative orders and and resummations of
logarithms of , to all orders in , at NLL accuracy. (
is the velocity of the heavy quark or the heavy antiquark in the
quarkonium rest frame, and and are the masses of and ,
respectively.) Our calculations are the first to include both the
order- correction to the light-cone distributions amplitude and the
resummation of logarithms of and are the first calculations for
the and final states. The resummations of
logarithms of that are associated with the order- and
order- corrections are carried out by making use of the Abel-Pad\'e
method. We confirm the analytic result for the order- correction that was
presented in a previous publication, and we correct the relative sign of the
direct and indirect amplitudes and some choices of scales in that publication.
Our branching fractions for and
differ by and , respectively, from the branching
fractions that are given in the most recent publication on this topic (in units
of the uncertainties that are given in that publication). However, we argue
that the uncertainties in the rates are underestimated in that publication.Comment: 26 pages, [v2] references added / [v3] Equation (27) modified, 3
sentences added after Eq. (27), Reference [17] added / [v4] PRD versio
Operation of a Stark decelerator with optimum acceptance
With a Stark decelerator, beams of neutral polar molecules can be
accelerated, guided at a constant velocity, or decelerated. The effectiveness
of this process is determined by the 6D volume in phase space from which
molecules are accepted by the Stark decelerator. Couplings between the
longitudinal and transverse motion of the molecules in the decelerator can
reduce this acceptance. These couplings are nearly absent when the decelerator
operates such that only every third electric field stage is used for
deceleration, while extra transverse focusing is provided by the intermediate
stages. For many applications, the acceptance of a Stark decelerator in this
so-called mode significantly exceeds that of a decelerator in the
conventionally used () mode. This has been experimentally verified by
passing a beam of OH radicals through a 2.6 meter long Stark decelerator. The
experiments are in quantitative agreement with the results of trajectory
calculations, and can qualitatively be explained with a simple model for the 6D
acceptance. These results imply that the 6D acceptance of a Stark decelerator
in the mode of operation approaches the optimum value, i.e. the value
that is obtained when any couplings are neglected.Comment: 13 pages, 11 figure
Hormonal modifications in patients admitted to an internal intensive care unit for acute hypoxaemic respiratory failure
AbstractTo clarify which endocrine modifications can be observed in acute hypoxaemic respiratory failure, 15 severely ill male patients [PAT; median age: 61 (range: 48 years); median height: 173 (range: 12) cm; median mass: 73 (range 31) kg] were investigated immediately upon admission to an intensive care unit (ICU) for this clinical disorder. Before starting treatment, the blood gases were measured and a number of selected hormones with special relevance for an ICU setting were determined. These are known to be modified by acute hypoxaemia in healthy subjects and to possess glucoregulatory properties, or an influence upon cardiocirculation or the vascular volume regulation: insulin, cortisol, adrenaline, noradrenaline, atrial natriuretic peptide, renin, aldosterone, angiotensin converting enzyme, and endothelin-I (ET). To elucidate whether potential endocrine changes resulted from acute hypoxaemia alone, the underlying disease, or unspecific influences connected with the ICU setting, all measurements were compared to those of a completely healthy reference group (REF) with comparable acute experimental hypoxaemia. The latter state was achieved by having the REF breathe a gas mixture with the oxygen content reduced to 14% (H).In the REF, neither the medians nor the distribution of endocrinologic measurements were modified significantly by acute hypoxaemia. In the PAT, the medians were increased considerably, yet with a slight diminution of ET. The distribution of individual values was considerably broader than in the REF with H.In conclusion, considerable increases in the means of the above hormones, with the exception of ET, can be registered in severely ill patients admitted to ICUs with acute hypoxaemic failure. However, such modifications cannot be considered attributable exclusively to acute arterial hypoxaemia. The underlying clinical disorders, such as septicaemia or an unspecific endocrine epiphenomenon, including severe and not only hypoxaemic stress, seem to be predominant
Types of problems elicited by verbal protocols for blind and sighted participants
Verbal protocols are often used in user-based studies of interactive technologies. This study investigated whether different types of problems are revealed by concurrent and retrospective verbal protocols (CVP and RVP) for blind and sighted participants. Eight blind and eight sighted participants undertook both CVP and RVP on four websites. Overall, interactivity problems were significantly more frequent in comparison to content or information architecture problems. In addition, RVP revealed significantly more interactivity problems than CVP for both user groups. Finally, blind participants encountered significantly more interactivity problems than sighted participants. The findings have implications for which protocol is appropriate, depending on the purpose of a particular study and the user groups involved
Selectivity and Sustainability of Electroenzymatic Process for Glucose Conversion to Gluconic Acid
Electroenzymatic processes are interesting solutions for the development of new processes based on renewable feedstocks, renewable energies, and green catalysts. High-selectivity and sustainability of these processes are usually assumed. In this contribution, these two aspects were studied in more detail. In a membrane-less electroenzymatic reactor, 97% product selectivity at 80% glucose conversion to gluconic acid was determined. With the help of nuclear magnetic resonance spectroscopy, two main side products were identified. The yields of D-arabinose and formic acid can be controlled by the flow rate and the electroenzymatic reactor mode of operation (fuel cell or ion-pumping). The possible pathways for the side product formation have been discussed. The electroenzymatic cathode was found to be responsible for a decrease in selectivity. The choice of the enzymatic catalyst on the cathode side led to 100% selectivity of gluconic acid at somewhat reduced conversion. Furthermore, sustainability of the electroenzymatic process is estimated based on several sustainability indicators. Although some indicators (like Space Time Yield) are favorable for electroenzymatic process, the E-factor of electroenzymatic process has to improve significantly in order to compete with the fermentation process. This can be achieved by an increase of a cycle time and/or enzyme utilization which is currently low
Are Race, Ethnicity, and Medical School Affiliation Associated with NIH R01 Type Award Probability for Physician Investigators?
This is a non-final version of an article published in final form in Acad Med. 2012 November ; 87(11): 1516–1524. doi:10.1097/ACM.0b013e31826d726b.PURPOSE: To analyze the relationship among NIH R01 Type 1 applicant degree, institution type, and race/ethnicity, and application award probability. METHOD: The authors used 2000–2006 data from the NIH IMPAC II grants database and other sources to determine which individual and institutional characteristics of applicants may affect the probability of applications being awarded funding. They used descriptive statistics and probit models to estimate correlations between race/ethnicity, degree (MD or PhD), and institution type (medical school or other institution), and application award probability, controlling for a large set of observable characteristics. RESULTS: Applications from medical schools were significantly more likely than those from other institutions to receive funding, as were applications from MDs versus PhDs. Overall, applications from blacks and Asians were less likely than those from whites to be awarded funding; however, among applications from MDs at medical schools, there was no difference in funding probability between whites and Asians and the difference between blacks and whites decreased to 7.8 percentage points. The inclusion of human subjects significantly decreased the likelihood of receiving funding. CONCLUSIONS: Compared with applications from whites, applications from blacks have a lower probability of being awarded R01 Type 1 funding, regardless of the investigator’s degree. However, funding probability is increased for applications with MD investigators and for those from medical schools. To some degree, these advantages combine so that applications from black MDs at medical schools have the smallest difference in funding probability compared with those from whites
- …