Long-distant contribution and χc1\chi_{c1} radiative decays to light vector meson

The discrepancy between the PQCD calculation and the CLEO data for $\chi_{c1}\to \gamma V$ ($V=\rho^0,\,\omega,\,\phi$) stimulates our interest in exploring extra mechanism of $\chi_{c1}$ decay. In this work, we apply an important non-perturbative QCD effect, i.e., hadronic loop mechanism, to study $\chi_{c1}\to \gamma V$ radiative decay. Our numerical result shows that the theoretical results including the hadronic loop contribution and the PQCD calculation of $\chi_{c1}\to \gamma V$ are consistent with the corresponding CLEO data of $\chi_{c1}\to \gamma V$. We expect further experimental measurement of $\chi_{c1}\to \gamma V$ at BES-III, which will be helpful to test the hadronic loop effect on $\chi_{c1}$ decay.Comment: 7 pages, 2 figures. Accepted for publication in Eur. Phys. J.

Applicability of perturbative QCD to Λb→Λc\Lambda_b \to \Lambda_c decays

We develop perturbative QCD factorization theorem for the semileptonic heavy baryon decay $\Lambda_b \to \Lambda_c l\bar{\nu}$, whose form factors are expressed as the convolutions of hard $b$ quark decay amplitudes with universal $\Lambda_b$ and $\Lambda_c$ baryon wave functions. Large logarithmic corrections are organized to all orders by the Sudakov resummation, which renders perturbative expansions more reliable. It is observed that perturbative QCD is applicable to $\Lambda_b \to \Lambda_c$ decays for velocity transfer greater than 1.2. Under requirement of heavy quark symmetry, we predict the branching ratio $B(\Lambda_b \to \Lambda_c l{\bar\nu})\sim 2$, and determine the $\Lambda_b$ and $\Lambda_c$ baryon wave functions.Comment: 12 pages in Latex file, 3 figures in postscript files, some results are changed, but the conclusion is the sam

Exclusive semileptonic B_s decays to excited D_s mesons: Search of D_{sJ}(2317) and D_{sJ}(2460)

We study the exclusive semileptonic decays B_s->D_{s0}^*\ell\bar\nu and B_s->D_{s1}^*\ell\bar\nu, where p-wave excited D_{s0}^* and D_{s1}^* states are identified with the newly observed D_{sJ}(2317) and D_{sJ}(2460) states. Within the framework of HQET the Isgur-Wise functions up to the subleading order of the heavy quark expansion are calculated by QCD sum rules. The decay rates and branching ratios are computed with the inclusion of the order of 1/m_Q corrections. We point out that the investigation of the B_s semileptonic decays to excited D_s mesons may provide some information about the nature of the new D_{sJ}^* mesons.Comment: 15 pages, 6 eps figures, RevTeX 4, accepted for publication in Phys. Rev.

Semileptonic B decays into even parity charmed mesons

By using a constituent quark model we compute the form factors relevant to semileptonic transitions of B mesons into low-lying p-wave charmed mesons. We evaluate the q^2 dependence of these form factors and compare them with other model calculations. The Isgur-Wise functions tau(1/2) and tau(3/2) are also obtained in the heavy quark limit of our results.Comment: 11 pages, 2 figure

Charmless Exclusive Baryonic B Decays

We present a systematical study of two-body and three-body charmless baryonic B decays. Branching ratios for two-body modes are in general very small, typically less than $10^{-6}$, except that \B(B^-\to p \bar\Delta^{--})\sim 1\times 10^{-6}. In general, $\bar B\to N\bar\Delta>\bar B\to N\bar N$ due to the large coupling constant for $\Sigma_b\to B\Delta$. For three-body modes we focus on octet baryon final states. The leading three-dominated modes are $\bar B^0\to p\bar n\pi^-(\rho^-), n\bar p\pi^+(\rho^+)$ with a branching ratio of order $3\times 10^{-6}$ for $\bar B^0\to p\bar n\pi^-$ and $8\times 10^{-6}$ for $\bar B^0\to p\bar n\rho^-$. The penguin-dominated decays with strangeness in the meson, e.g., $B^-\to p\bar p K^{-(*)}$ and $\bar B^0\to p\bar n K^{-(*)}, n\bar n \bar K^{0(*)}$, have appreciable rates and the $N\bar N$ mass spectrum peaks at low mass. The penguin-dominated modes containing a strange baryon, e.g., $\bar B^0\to \Sigma^0\bar p\pi^+, \Sigma^-\bar n\pi^+$, have branching ratios of order $(1\sim 4)\times 10^{-6}$. In contrast, the decay rate of $\bar B^0\to\Lambda\bar p\pi^+$ is smaller. We explain why some of charmless three-body final states in which baryon-antibaryon pair production is accompanied by a meson have a larger rate than their two-body counterparts: either the pole diagrams for the former have an anti-triplet bottom baryon intermediate state, which has a large coupling to the $B$ meson and the nucleon, or they are dominated by the factorizable external $W$-emission process.Comment: 46 pages and 3 figures, to appear in Phys. Rev. D. Major changes are: (i) Calculations of two-body baryonic B decays involving a Delta resonance are modified, and (ii) Penguin-dominated modes B-> Sigma+N(bar)+p are discusse

Octet magnetic moments and the Coleman-Glashow sum rule violation in the chiral quark model

Baryon octet magnetic moments when calculated within the chiral quark model, incorporating the orbital angular momentum as well as the quark sea contribution through the Cheng-Li mechanism, not only show improvement over the non relativistic quark model results but also gives a non zero value for the right hand side of Coleman-Glashow sum rule. When effects due to spin-spin forces between constituent quarks as well as `mass adjustments' due to confinement are added, it leads to an excellent fit for the case of p, \Sigma^+, \Xi^o and violation of Coleman-Glashow sum rule, whereas in almost all the other cases the results are within 5% of the data.Comment: 5 RevTeX pages, accepted for publication in PRD(Rapid Communication

Semileptonic decays of Bs1B_{s1}, Bs2∗B_{s2}^*, Bs0B_{s0} and Bs1′B_{s1}'

Stimulated by recent observations of the excited bottom-strange mesons $B_{s1}$ and $B_{s2}^*$, we calculate the semileptonic decays $B_{s0}, B_{s1}^{\prime}, B_{s1}, B_{s2}^*\to [D_s(1968), D_{s}^*(2112), D_{sJ}(2317), D_{sJ}(2460)]\ell\bar{\nu}$, which is relevant for the exploration of the potential of searching these semileptonic decays in experiment.Comment: 11 pages, 3 figures, 9 tables. More discussion added, some descriptions changed. The version to appear in EPJ

Baryon number violation, baryogenesis and defects with extra dimensions

In generic models for grand unified theories(GUT), various types of baryon number violating processes are expected when quarks and leptons propagate in the background of GUT strings. On the other hand, in models with large extra dimensions, the baryon number violation in the background of a string is not trivial because it must depend on the mechanism of the proton stabilization. In this paper we argue that cosmic strings in models with extra dimensions can enhance the baryon number violation to a phenomenologically interesting level, if the proton decay is suppressed by the mechanism of localized wavefunctions. We also make some comments on baryogenesis mediated by cosmological defects. We show at least two scenarios will be successful in this direction. One is the scenario of leptogenesis where the required lepton number conversion is mediated by cosmic strings, and the other is the baryogenesis from the decaying cosmological domain wall. Both scenarios are new and have not been discussed in the past.Comment: 20pages, latex2e, comments and references added, to appear in PR

Ammonia combustion in furnaces: A review

Ammonia is a formidable chemical that has been investigated over 150 years for its use in the chemical processing field. The potential of the molecule to be used in farming applications has enabled a demographic explosion whilst its implementation in refrigeration technologies ensure continuous operation of cooling systems at high efficiencies. Other areas have also benefited from ammonia, whilst the use of the molecule in fuelling applications was scarce until the 2010s. A combination of factors that include climate change and energy dependency have reignited the interest of using ammonia as an energy vector that can potentially support applications that range from small devices to large power applications, thus supporting the transition to a net zero economy. Therefore, ammonia appears as a tangible option towards the reduction of emissions that can support a truly carbon-free energy transition in the coming years. As the recognition of the molecule increases, research areas based on combustion processes have also expanded towards the utilization of ammonia. The research around the topic has considerably augmented not only in the academic community, but also across governmental institutions and industrial consortia willing to demonstrate the potential of such a chemical. Therefore, this review approaches the latest findings and state-of-the-art research on the use of ammonia as a combustion fuel for furnaces. Different to other reviews, the present work attempts to gather the latest fundamental research, the most critical technologies evaluating ammonia for system operation, and novel approaches that suggest various breakthrough concepts that will ensure the reliable, cleaner consumption of the molecule as furnace fuel. Further, the present manuscript includes the latest research from all corners of the world, in an attempt to summarise the extensive work that dozens of groups are currently conducting. Finally, future trends and requirements are also addressed, providing guidance to those interested in doing research and development in ammonia-fuelling systems

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 $\Lambda_b \to \Lambda + \gamma$ and $\Lambda_b \to \Lambda + l^{+} l^{-}$ with the light-cone sum rules approach. The higher twist distribution amplitudes of $\Lambda$ 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 $\Lambda$ 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 $\Lambda_b \to \Lambda \gamma$, $\Lambda l^{+}l^{-}$.Comment: 38 pages, 15 figures, some typos are corrected and more references are adde