1,399 research outputs found
Penguin-induced Radiative Baryonic B Decays Revisited
Weak radiative baryonic B decays mediated by
the electromagnetic penguin process are re-examined within the
framework of the pole model. The meson pole contribution that has been
neglected before is taken into account in this work. It is found that the
intermediate contribution dominates in the mode and
is comparable to the baryon pole effect in and
modes. The branching ratios for and are of order
and , respectively. The threshold enhancement effect in the
dibaryon mass spectrum is responsible by the meson pole diagram. We also study
the angular distribution of the baryon in the dibaryon rest frame. The baryon
pole diagrams imply that the antibaryon tends to emerge in the direction of the
photon in the baryon-pair rest frame. The predicted angular asymmetry agrees
with experiment for . Measurements of the
correlation of the photon with the baryon allow us to discriminate between
different models for describing the radiative baryonic B decays. For decays
, a large correlation of the photon to the
and a broad bump in the dibaryon mass spectrum are predicted.Comment: 10 pages, 4 figure
Final-State Phases in Baryon-Antibaryon Decays
The recent observation of the decay \ob \to \Lambda_c^+ \bar p suggests
that related decays may soon be visible at colliders. It is shown how
these decays can shed light on strong final-state phases and amplitudes
involving the spectator quark, both of which are normally expected to be small
in B decays.Comment: 14 pages, LaTeX, 2 figures, submitted to Phys. Rev. D, references and
discussion of helicity amplitudes adde
An emic science of climate. Reindeer Evenki environmental knowledge and the notion of an “extreme process”
Human-environment relationships in Siberia and Northeast China.
Knowledge, rituals, mobility and politics among the Tungus peoples,followed by Vari
Colour Connection and Diquark Fragmentation in e^+e^- \to c \bar c q \bar q \to h's Process
The hadronization effects induced by different colour connections of
system in annihilation are investigated by a toy
model where diquark fragmentation is employed based on Pythia. It is found that
the correlations between the charm baryons and charm antibaryons produced via
diquark pair fragmentation are much stronger, and their momentum spectra are
harder than those from the standard colour connection in Pythia.Comment: 10 pages, 7 figures and 1 table in latex with axodraw.sty, version to
appear in PL
A Detailed Monte-Carlo Simulation for the Belle TOF System
We have developed a detailed Monte Carlo simulation program for the Belle TOF
system. Based on GEANT simulation, it takes account of all physics processes in
the TOF scintillation counters and readout electronics. The simulation
reproduces very well the performance of the Belle TOF system, including the
dE/dx response, the time walk effect, the time resolution, and the hit
efficiency due to beam background. In this report, we will describe the Belle
TOF simulation program in detail.Comment: To be submitted to NI
EFFECTIVE CONTRACT FOR HIGHER SCHOOL LECTURER STAFF
В работе обсуждаются проблемы и вопросы эффективного контракта для преподавателей вузов: что это такое, на какой срок заключается такой контракт, надо ли «переводить» на часы ненормированную часть работы преподавателя, каково соотношение составляющий частей деятельности преподавателя, каковы показатели и критерии стимулирующих выплат.This paper discusses the problems and questions of an effective contract for university professors, lecturers and their assistant staff: its sense, contract period, bonus payments criteria, main indicators
Partial waves of baryon-antibaryon in three-body B meson decay
The conspicuous threshold enhancement has been observed in the
baryon-antibaryon subchannels of many three-body B decay modes. By examining
the partial waves of baryon-antibaryon, we first show for B- -->pp-bar K- that
the pK- angular correlation rules out dominance of a single pp-bar partial wave
for the enhancement, for instance, the resonance hypothesis or the strong
final-state interaction in a single channel. The measured pK- angular
correlation turns out to be opposite to the naive expectation of the
short-distance picture. We study the origin of this reversed angular
correlation in the context of the pp-bar partial waves and argue that NN-bar
bound states may be the cause of this sign reversal. Dependence of the angular
correlation on the pp-bar invariant mass is very important to probe the
underlying problem from the experimental side.Comment: 16 pages, 9 figures, the version for journal publicatio
Light-Front Approach for Heavy Pentaquark Transitions
Assuming the two diquark structure for the pentaquark state as advocated in
the Jaffe-Wilczek model, there exist exotic parity-even anti-sextet and
parity-odd triplet heavy pentaquark baryons. The theoretical estimate of
charmed and bottom pentaquark masses is quite controversial and it is not clear
whether the ground-state heavy pentaquark lies above or below the strong-decay
threshold. We study the weak transitions of heavy pentaquark states using the
light-front quark model. In the heavy quark limit, heavy-to-heavy pentaquark
transition form factors can be expressed in terms of three Isgur-Wise
functions: two of them are found to be normalized to unity at zero recoil,
while the third one is equal to 1/2 at the maximum momentum transfer, in
accordance with the prediction of the large-Nc approach or the quark model.
Therefore, the light-front model calculations are consistent with the
requirement of heavy quark symmetry. Numerical results for form factors and
Isgur-Wise functions are presented. Decay rates of the weak decays Theta_b+ to
Theta_c0 pi+ (rho+), Theta_c0 to Theta+ pi- (rho-), Sigma'_{5b}+ to
Sigma'_{5c}0 pi+ (rho+) and Sigma'_{5c}0 to N_8+ pi- (rho-) with Theta_Q,
Sigma'_{5Q} and N_8 being the heavy anti-sextet, heavy triplet and light
octet pentaquarks, respectively, are obtained. For weakly decaying Theta_b+ and
Theta_c0, the branching ratios of Theta_b+ to Theta_c0 pi+, Theta_c0 to Theta+
pi- are estimated to be at the level of 10^{-3} and a few percents,
respectively.Comment: 33 pages, 3 figures, version to be published in Phys. Rev.
Hadronic B Decays to Charmed Baryons
We study exclusive B decays to final states containing a charmed baryon
within the pole model framework. Since the strong coupling for is larger than that for , the two-body charmful decay
has a rate larger than
as the former proceeds via the pole while the latter via the
pole. By the same token, the three-body decay receives less baryon-pole contribution than
. However, because the important charmed-meson
pole diagrams contribute constructively to the former and destructively to the
latter, has a rate slightly larger than
. It is found that one quarter of the rate comes from the resonant contributions. We discuss
the decays and
and stress that they are not color suppressed even though they can only proceed
via an internal W emission.Comment: 25 pages, 6 figure
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