86 research outputs found
The renormalized B-meson light-cone distribution amplitude
I discuss the renormalization-group equation governing the leading order
light-cone distribution amplitude of the B-meson phi^B_+(omega,mu) and its
exact analytic solution. The solution displays two features concerning the
asymptotic behaviour of phi^B_+(omega,mu) for small and large values of omega.
I comment on further applications and argue that the loss of normalizability is
not a problem in practice.Comment: 3 pages, 3 figures, invited talk at the international conference EPS
'03, Aachen, German
Theory of Charmless Inclusive B Decays and the Extraction of V_{ub}
We present ``state-of-the-art'' theoretical expressions for the triple
differential B->X_u l^- nu decay rate and for the B->X_s gamma photon spectrum,
which incorporate all known contributions and smoothly interpolate between the
``shape-function region'' of large hadronic energy and small invariant mass,
and the ``OPE region'' in which all hadronic kinematical variables scale with
M_B. The differential rates are given in a form which has no explicit reference
to the mass of the b quark, avoiding the associated uncertainties. Dependence
on m_b enters indirectly through the properties of the leading shape function,
which can be determined by fitting the B->X_s gamma photon spectrum. This
eliminates the dominant theoretical uncertainties from predictions for B->X_u
l^- nu decay distributions, allowing for a precise determination of |V_{ub}|.
In the shape-function region, short-distance and long-distance contributions
are factorized at next-to-leading order in renormalization-group improved
perturbation theory. Higher-order power corrections include effects from
subleading shape functions where they are known. When integrated over
sufficiently large portions in phase space, our results reduce to standard OPE
expressions up to yet unknown O(alpha_s^2) terms. Predictions are presented for
partial B->X_u l^- nu decay rates with various experimental cuts. An elaborate
error analysis is performed that contains all significant theoretical
uncertainties, including weak annihilation effects. We suggest that the latter
can be eliminated by imposing a cut on high lepton invariant mass.Comment: 45 pages, 4 figures; several minor revisions, more systematic
treatment of subleading shape-function effects, numerical results and tables
updated; version to appear in Physical Review
B-Meson Light-Cone Distribution Amplitude: Perturbative Constraints and Asymptotic Behaviour in Dual Space
Based on the dual representation in terms of the recently established
eigenfunctions of the evolution kernel in heavy-quark effective theory, we
investigate the description of the B-meson light-cone distribution amplitude
(LCDA) beyond tree-level. In particular, in dual space, small and large momenta
do not mix under renormalization, and therefore perturbative constraints from a
short-distance expansion in the parton picture can be implemented independently
from non-perturbative modelling of long-distance effects. It also allows to
(locally) resum perturbative logarithms from large dual momenta at fixed values
of the renormalization scale. We construct a generic procedure to combine
perturbative and non-perturbative information on the B-meson LCDA and compare
different model functions and the resulting logarithmic moments which are the
relevant hadronic parameters in QCD factorization theorems for exclusive
B-meson decays.Comment: 13 pages, 5 figures, minor layout issues resolve
On Glauber modes in Soft-Collinear Effective Theory
Gluon interactions involving spectator partons in collisions at hadronic
machines are investigated. We find a class of examples in which a mode, called
Glauber gluons, must be introduced to the effective theory for consistency.Comment: 19 pages, three figures. Uses JHEP3.cl
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Research and Design of a Routing Protocol in Large-Scale Wireless Sensor Networks
无线传感器网络,作为全球未来十大技术之一,集成了传感器技术、嵌入式计算技术、分布式信息处理和自组织网技术,可实时感知、采集、处理、传输网络分布区域内的各种信息数据,在军事国防、生物医疗、环境监测、抢险救灾、防恐反恐、危险区域远程控制等领域具有十分广阔的应用前景。 本文研究分析了无线传感器网络的已有路由协议,并针对大规模的无线传感器网络设计了一种树状路由协议,它根据节点地址信息来形成路由,从而简化了复杂繁冗的路由表查找和维护,节省了不必要的开销,提高了路由效率,实现了快速有效的数据传输。 为支持此路由协议本文提出了一种自适应动态地址分配算——ADAR(AdaptiveDynamicAddre...As one of the ten high technologies in the future, wireless sensor network, which is the integration of micro-sensors, embedded computing, modern network and Ad Hoc technologies, can apperceive, collect, process and transmit various information data within the region. It can be used in military defense, biomedical, environmental monitoring, disaster relief, counter-terrorism, remote control of haz...学位:工学硕士院系专业:信息科学与技术学院通信工程系_通信与信息系统学号:2332007115216
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