191 research outputs found

    New Approach for Measuring Vub|V_{ub}| at Future BB-Factories

    Full text link
    It is suggested that the measurements of hadronic invariant mass (mXm_X) distributons in the inclusive BXc(u)lνB \rightarrow X_{c(u)} l \nu decays can be useful in extracting the CKM matrix element Vub|V_{ub}|. We investigated hadronic invariant mass distributions within the various theoretical models of HQET, FAC and chiral lagrangian as well as ACCMM model. It is also emphasized that the mXm_X distribution even at the region mX>mDm_{X} > m_{D} in the inclusive bub\rightarrow u are effetive in selecting the events, experimentally viable at the future asymmetric BB factories, with better theoretical understandings.Comment: 11 pages not including 1 figur

    Decay Constants and Semileptonic Decays of Heavy Mesons in Relativistic Quark Model

    Get PDF
    We investigate the BB and DD mesons in the relativistic quark model by applying the variational method with the Gaussian wave function. We calculate the Fermi momentum parameter pFp_{_F}, and obtain pF=0.500.54p_{_F} = 0.50 \sim 0.54 GeV, which is almost independent of the input parameters, αs\alpha_s, mbm_b, mcm_c and mspm_{sp}. We then calculate the ratio fBf_B/fDf_D, and obtain the result which is larger, by the factor of about 1.3, than MD/MB\sqrt{M_D / M_B} given by the naive nonrelativistic analogy. This result is in a good agreement with the recent Lattice calculations. We also calculate the ratio (MBMB)(M_{B^*}-M_{B})/(MDMD)(M_{D^*}-M_{D}). In these calculations the wave function at origin ψ(0)\psi (0) is essential. We also determine pFp_{_F} by comparing the theoretical prediction of the ACCMM model with the lepton energy spectrum of BeνXB \rightarrow e \nu X from the recent ARGUS analysis, and find that pF=0.27 ± 0.270.22p_{_F}=0.27~\pm~^{0.22}_{0.27} GeV, when we use mc=1.5m_c=1.5 GeV. However, this experimentally determined value of pFp_{_F} is strongly dependent on the value of input parameter mcm_c.Comment: 15 pages (Latex) (uses epsfig.sty, 1 figure appended as a uuencoded compressed ps-file

    Dependence of Variational Perturbation Expansions on Strong-Coupling Behavior. Inapplicability of delta-Expansion to Field Theory

    Get PDF
    We show that in applications of variational theory to quantum field theory it is essential to account for the correct Wegner exponent omega governing the approach to the strong-coupling, or scaling limit. Otherwise the procedure either does not converge at all or to the wrong limit. This invalidates all papers applying the so-called delta-expansion to quantum field theory.Comment: Author Information under http://www.physik.fu-berlin.de/~kleinert/institution.html . Latest update of paper (including all PS fonts) at http://www.physik.fu-berlin.de/~kleinert/34

    Dependence of Vub/Vcb|V_{ub}/V_{cb}| on Fermi momentum pFp_{_F} in ACCMM model

    Full text link
    The Gaussian width of Fermi momentum, pFp_{_F}, is the most important parameter of the ACCMM model, and its value is essential in the determination of Vub/Vcb|V_{ub}/V_{cb}| because the experimental analysis is allowed only at the end-point region of inclusive semileptonic BB-decay spectrum. We extract the value of Vub/Vcb|V_{ub}/V_{cb}| as a function of pFp_{_F}. We also calculate the parameter pFp_{_F} in the relativistic quark model using the variational method, and obtain pF=0.54p_{_F} = 0.54 GeV which is much larger than the commonly used value, 0.3\sim 0.3 GeV, in experimental analyses. When we use pF=0.5p_{_F} = 0.5 GeV instead of 0.3 GeV, the value of Vub/Vcb|V_{ub}/V_{cb}| from ACCMM model is increased by a factor 1.81, and can give a good agreement with Isgur {\it et al.} model.Comment: 1. Section 2 has been revised by considering the fact that in the real experimental situation the only measured quantity is the number of events in the high ElE_l region compared to the total semi- leptonic event number. 2. The article by C. Greub and D. Wyler (Phys. Lett. B295 (1992) 293) has been included in references, which reports a similar conclusion for the value of pFp_{_F} (pFp_{_F}=566 MeV), even though they used the different approach. 3. This article will be published in Z. Phys. C (1995

    High frequencies of elevated alkaline phosphatase activity and rickets exist in extremely low birth weight infants despite current nutritional support

    Get PDF
    <p>Abstract</p> <p>Background</p> <p>Osteopenia and rickets are common among extremely low birth weight infants (ELBW, <1000 g birth weight) despite current practices of vitamin and mineral supplementation. Few data are available evaluating the usual course of markers of mineral status in this population. Our objectives in this study were to determine the relationship between birth weight (BW) and peak serum alkaline phosphatase activity (P-APA) in ELBW infants and evaluate our experience with the diagnosis of rickets in these infants.</p> <p>Methods</p> <p>We evaluated all ELBW infants admitted to Texas Children's Hospital NICU in 2006 and 2007. Of 211 admissions, we excluded 98 patients who were admitted at >30 days of age or did not survive/stay for >6 weeks. Bone radiographs obtained in 32 infants were reviewed by a radiologist masked to laboratory values.</p> <p>Results</p> <p>In this cohort of 113 infants, P-APA was found to have a significant inverse relationship with BW, gestational age and serum phosphorus. In paired comparisons, P-APA of infants <600 g (957 ± 346 IU/L, n = 20) and infants 600–800 g (808 ± 323 IU/L, n = 43) were both significantly higher than P-APA of infants 800–1000 g (615 ± 252 IU/L, n = 50), p < 0.01. Thirty-two patients had radiographic evaluation for evidence of rickets, based on P-APA greater than 800 IU/L, parenteral nutrition greater than 3 to 4 weeks, or clinical suspicion. Of these, 18 showed radiologic rickets and 14 showed osteopenia without rickets. Infants with BW <600 g were more likely to have radiologic rickets (10/20 infants) compared to those with BW 600–800 g (6/43 infants) and BW 800–1000 g (2/50 infants), p < 0.01 for each. P-APA was not significantly higher in infants with radiologic rickets (1078 ± 356 IU/L) compared to those without radiologic evidence of rickets (943 ± 346, p = 0.18).</p> <p>Conclusion</p> <p>Elevation of P-APA >600 IU/L was very common in ELBW infants. BW was significantly inversely related to both P-APA and radiologic rickets. No single value of P-APA was related to radiological findings of rickets. Given the very high risk of osteopenia and rickets among ELBW infants, we recommend consideration of early screening and early mineral supplementation, especially among infants <600 g BW.</p

    Severe vitamin D deficiency in 6 Canadian First Nation formula-fed infants

    Get PDF
    Background. Rickets was first described in the 17th century and vitamin D deficiency was recognized as the underlying cause in the early 1900s. Despite this long history, vitamin D deficiency remains a significant health concern. Currently, vitamin D supplementation is recommended in Canada for breast fed infants. There are no recommendations for supplementation in formula-fed infants. Objective. The objective of this report is to bring attention to the risk of severe vitamin D deficiency in high risk, formula fed infants. Design. A retrospective chart review was used to create this clinical case series. Results. Severe vitamin D deficiency was diagnosed in six formula-fed infants over a two-and-a-half year period. All six infants presented with seizures and they resided in First Nation communities located at latitude 54 in the province of Manitoba. While these infants had several risk factors for vitamin D deficiency, they were all receiving cow&#x0027;s milk based formula supplemented with 400 IU/L of vitamin D. Conclusion. This report suggests that current practice with regards to vitamin D supplementation may be inadequate, especially for high-risk infants. Health care professionals providing service to infants in a similar situation should be aware of this preventable condition. Hopefully this would contribute to its prevention, diagnosis and management

    Wide Contact Structures for Low-Noise Nanochannel Devices Based on a Carbon Nanotube Network

    Get PDF
    We have developed a wide contact structure for low-noise nanochannel devices based on a carbon nanotube (CNT) network. This low-noise CNT network-based device has a dumbbell-shaped channel, which has wide CNT/electrode contact regions and, in effect, reduces the contact noise. We also performed a systematic analysis of structured CNT networks and established an empirical formula that can explain the noise behavior of arbitrary-shaped CNT network-based devices including the effect of contact regions and CNT alignment. Interestingly, our analysis revealed that the noise amplitude of aligned CNT networks behaves quite differently compared with that of randomly oriented CNT networks. Our results should be an important guideline in designing low-noise nanoscale devices based on a CNT network for various applications such as a highly sensitive low-noise sensor

    CP Violation in the Semileptonic Bl4B_{l4} (B->D \pi l \nu) Decays: A Model Independent Analysis

    Full text link
    CP violation from physics beyond the Standard Model is investigated in Bl4B_{l4} decays: BDπlνˉlB\to D\pi l\bar{\nu}_l. The semileptonic BB-meson decay to a DD-meson with an emission of single pion is analyzed with heavy quark effective theory and chiral perturbation theory. In the decay process, we include various excited states as intermediate states decaying to the final hadrons, D+πD+\pi. The CP violation is implemented in a model independent way, in which we extend leptonic current by including complex couplings of the scalar sector and those of the vector sector in extensions of the Standard Model. With these complex couplings, we calculate the CP-odd rate asymmetry and the optimal asymmetry. We find that the optimal asymmetry is sizable and can be detected at 1σ1\sigma level with about 10610^6-10710^7 BB-meson pairs, for some reference values of new physics effects.Comment: 25 pages, Latex, 4 figures include
    corecore