118735700
PQCD Analysis of Inclusive Heavy Hadrons Decays
We develop the perturbative QCD formalism for inclusive heavy hadron decays. Transverse degrees of freedom of partons are introduced to facilitate the factorization of the heavy hadron decays.
120093276
CONSISTENT FACTORIZATION AND TWIST-3 CONTRIBUTIONS TO THE POLARIZED NUCLEON STRUCTURE FUNCTION g2(x,Q2)
Quark mass effects are clarified in the parton model approach to the transversely polarized nucleon structure function. The special propagator technique is employed to obtain manifestly gauge invariant results and extract the buried short-distance contributions inside the soft part after momentum factorization in the collinear expansion approach. A generalized massive special propagator for a massive quark is constructed. We identify the corresponding matrix elements of the transversely polarized structure function in deep inelastic scattering by the massive special propagator technique.
10063732
Effective Lagrangian approach to weak radiative decays of heavy hadrons.
Motivated by the observation of the decay B\ifmmode\bar\else\textasciimacron\fi{}\ensuremath{\rightarrow}K${\mathrm{\ifmmode\bar\else\textasciimacron\fi{}}}^{\mathrm{*}}$\ensuremath{\gamma} by the CLEO Collaboration, we have systematically analyzed the two-body weak radiative decays of bottom and charmed hadrons. There exist two types of weak radiative decays: One proceeds through the short-distance b\ensuremath{\rightarrow}s\ensuremath{\gamma} transition and the other occurs through W exchange accompanied by a photon emission. Effective Lagrangians are derived for the W-exchange bremsstrahlung processes at the quark level and then applied to various weak electromagnetic decays of heavy hadrons. Predictions for the branching ratios of B${\mathrm{\ifmmode\bar\else\textasciimacron\fi{}}}^{0}$\ensuremath{\rightarrow}${\mathit{D}}^{\mathrm{*}0}$\ensuremath{\gamma}, ${\mathrm{\ensuremath{\Lambda}}}_{\mathit{b}}^{0}$\ensuremath{\rightarrow}${\mathrm{\ensuremath{\Sigma}}}_{\mathit{c}}^{0}$\ensuremath{\gamma}, ${\mathrm{\ensuremath{\Xi}}}_{\mathit{b}}^{0}$\ensuremath{\rightarrow}${\mathrm{\ensuremath{\Xi}}}_{\mathit{c}}^{0}$\ensuremath{\gamma}, and ${\mathrm{\ensuremath{\Xi}}}_{\mathit{b}}^{0}$\ensuremath{\rightarrow}\ensuremath{\Xi}${\mathcal{'}}_{\mathit{b}}^{0}$\ensuremath{\gamma} are given. In particular, we find scrB(B${\mathrm{\ifmmode\bar\else\textasciimacron\fi{}}}^{0}$\ensuremath{\rightarrow}${\mathit{D}}^{\mathrm{*}0}$\ensuremath{\gamma})\ensuremath{\approxeq}0.9\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}6}$. Order of magnitude estimates for the weak radiative decays of charmed hadrons, ${\mathit{D}}^{0}$\ensuremath{\rightarrow}K${\mathrm{\ifmmode\bar\else\textasciimacron\fi{}}}^{\mathrm{*}0}$\ensuremath{\gamma}, ${\mathrm{\ensuremath{\Lambda}}}_{\mathit{c}}^{+}$\ensuremath{\rightarrow}${\mathrm{\ensuremath{\Sigma}}}^{+}$\ensuremath{\gamma}, and ${\mathrm{\ensuremath{\Xi}}}_{\mathit{c}}^{0}$\ensuremath{\rightarrow}${\mathrm{\ensuremath{\Xi}}}^{0}$\ensuremath{\gamma}, are also presented. Within this approach, the decay asymmetry for antitriplet to antitriplet heavy baryon weak radiative transitions is uniquely predicted by heavy quark symmetry. The electromagnetic penguin contribution to ${\mathrm{\ensuremath{\Lambda}}}_{\mathit{b}}^{0}$\ensuremath{\rightarrow}\ensuremath{\Lambda}\ensuremath{\gamma} is estimated by two different methods and its branching ratio is found to be of the order of 1\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}5}$. We conclude that weak radiative decays of bottom hadrons are dominated by the short-distance b\ensuremath{\rightarrow}s\ensuremath{\gamma} mechanism.
36067168
Dimensional regularization and perturbative solution of the chiral Schwinger model.
The anomalous chiral Schwinger model is regulated by the method of dimensional regularization and is solved by diagrammatic perturbative expansion. It is shown that there is a regulation ambiguity in the solution. The result disagrees with Das's assertion and agrees with that of Jackiw, Rajaraman, and others.
34810684
Restudy of the open-superstring tree amplitudes by looking at their field-theoretical limits.
We carry out complete computations of some open- and closed-superstring tree amplitudes by using the bosonized covariant vertices. Some open-superstring amplitudes so obtained are shown to be different from those obtained in the light-cone gauge approach by some numerical factors. The low-energy limits of our five open-superstring amplitudes are then shown to match the five super Yang-Mills field amplitudes while the five light-cone gauge open-superstring amplitudes fail to do so.
13594754
Heavy-flavor-conserving nonleptonic weak decays of heavy baryons.
The heavy-flavor-conserving nonleptonic weak decays of heavy baryons are studied in a formalism that incorporates both heavy-quark symmetry and chiral symmetry. The phenomenological {Delta}{ital S}=1 nonleptonic weak chiral Lagrangian for these transitions contains two independent coupling constants that describe the transitions between two flavor-SU(3) antitriplet heavy baryons, and the transitions between two flavor-SU(3) sextet heavy baryons. In the MIT bag model and the diquark model, only transitions between antitriplets are allowed. The coupling constants for these transitions are calculated in both models. The result is applied to specific nonleptonic decays such as {Xi}{sub {ital c}}{r arrow}{Lambda}{sub {ital c}}{pi}, and the branching ratios are found to be of the order of 10{sup {minus}4}. An example of a nonleptonic decay due to symmetry breaking is provided by {Omega}{sub {ital c}}{r arrow}{Xi}{sub {ital c}}{sup {prime}}{pi}, which is estimated to have a smaller branching ratio, of the order of 10{sup {minus}5}.
125027666
Restudies of Searching for 1~(-+) Exotic State
In order to convenience for the data analysis of BES some new relations which can be used to search for the 1~(-+) exotic state in J/φ→ωX, X→KKπ have been obtained. How to search for the 1~(-+) exotic state in the three--step two--body hadronic decay process J/φ→ωX, X→KK~*, K~*→Kπ is also discussed.
29651175
Spontaneous excitation of an accelerated multilevel atom in dipole coupling to the derivative of a scalar field
We study the spontaneous excitation of an accelerated multilevel atom in dipole coupling to the derivative of a massless quantum scalar field and separately calculate the contributions of the vacuum fluctuation and radiation reaction to the rate of change of the mean atomic energy of the atom. It is found that, in contrast to the case where a monopole-like interaction between the atom and the field is assumed, there appear extra corrections proportional to the acceleration squared, in addition to corrections which can be viewed as a result of an ambient thermal bath at the Unruh temperature, as compared with the inertial case, and the acceleration induced correction terms show anisotropy with the contribution from longitudinal polarization being four times that from the transverse polarization for isotropically polarized accelerated atoms. Our results suggest that the effect of acceleration on the rate of change of the mean atomic energy is dependent not only on the quantum field to which the atom is coupled, but also on the type of the interaction even if the same scalar quantum field is considered.
118937109
Entanglement generation in atoms immersed in a thermal bath of external quantum scalar fields with a boundary
We examine the entanglement creation between two mutually independent two-level atoms immersed in a thermal bath of quantum scalar fields in the presence of a perfectly reflecting plane boundary. With the help of the master equation that describes the evolution in time of the atom subsystem obtained, in the weak-coupling limit, by tracing over environment (scalar fields) degrees of freedom, we find that the presence of the boundary may play a significant role in the entanglement creation in some circumstances and the new parameter, the distance of the atoms from the boundary, besides the bath temperature and the separation between the atoms, gives us more freedom in manipulating entanglement generation. Remarkably, the final remaining entanglement in the equilibrium state is independent of the presence of the boundary.
118458603
Thermal relics in hidden sectors
Dark matter may be hidden, with no standard model gauge interactions. At the same time, in WIMPless models (WIMP: weakly interacting massive particles) with hidden matter masses proportional to hidden gauge couplings squared, the hidden dark matter's thermal relic density may naturally be in the right range, preserving the key quantitative virtue of WIMPs. We consider this possibility in detail. We first determine model-independent constraints on hidden sectors from big bang nucleosynthesis and the cosmic microwave background. Contrary to conventional wisdom, large hidden sectors are easily accommodated. A flavour-free version of the standard model is allowed if the hidden sector is just 30% colder than the observable sector after reheating. Alternatively, if the hidden sector contains a one-generation version of the standard model with characteristic mass scale below 1 MeV, even identical reheating temperatures are allowed. We then analyse hidden sector freeze-out in detail for a concrete model, solving the Boltzmann equation numerically and explaining the results from both observable and hidden sector points of view. We find that WIMPless dark matter does indeed obtain the correct relic density for masses in the range . The upper bound results from the requirement of perturbativity, and the lower bound assumes that the observable and hidden sectors reheat to the same temperature, and is raised to the MeV scale if the hidden sector is ten times colder. WIMPless dark matter therefore generalizes the WIMP paradigm to the largest mass range possible for viable thermal relics and provides a unified framework for exploring dark matter signals across nine orders of magnitude in dark matter mass.
16163396
Lightcone fluctuations in quantum gravity and extra dimensions
Abstract We discuss how compactified extra dimensions may have potentially observable effects which grow as the compactification scale decreases. This arises because of lightcone fluctuations in the uncompactified dimensions which can result in the broadening of the spectral lines from distant sources. We analyze this effect in a five dimensional model, and argue that data from gamma ray burst sources require the compactification length to be greater than about 105 cm in this model.