199 research outputs found
Time evolution of ground motion-dependent depolarisation at linear colliders
Future linear colliders plan to collide polarised beams and the planned
physics reach requires knowledge of the state of polarisation as precisely as
possible. The polarised beams can undergo depolarisation due to various
mechanisms. In order to quantify the uncertainty due to depolarisation, spin
tracking simulations in the International Linear Collider (ILC) Beam Delivery
System (BDS) and at the Interaction Point (IP) have been performed. Spin
tracking in the BDS was achieved using the BMAD subroutine library, and the
CAIN program was used to do spin tracking through the beam-beam collision.
Assuming initially aligned beamline elements in the BDS, a ground motion model
was applied to obtain realistic random misalignments over various time scales.
Depolarisation at the level of 0.1% occurs within a day of ground motion at a
noisy site. Depolarisation at the IP also exceeds 0.1% for the nominal
parameter sets for both the ILC and for the Compact Linear Collider (CLIC).
Theoretical work is underway to include radiative corrections in the
depolarisation processes and simulation of the depolarisation through the
entire collider is envisaged.Comment: 8 pages, 4 figures, PST09 proceedings; Proceedings of the 13th
International Workshop on Polarised Sources, Targets and Polarimetry 2009,
World Scientific 201
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Executive Summary of the Workshop on Polarization and Beam Energy Measurements at the ILC
This note summarizes the results of the 'Workshop on Polarization and Beam Energy Measurements at the ILC', held at DESY (Zeuthen) April 9-11 2008. The topics for the workshop included (1) physics requirements, (2) polarized sources and low energy polarimetry, (3) BDS polarimeters, (4) BDS energy spectrometers, and (5) physics-based measurements of beam polarization and beam energy from collider data. Discussions focused on the current ILC baseline program as described in the Reference Design Report (RDR), which includes physics runs at beam energies between 100 and 250 GeV, as well as calibration runs on the Z-pole. Electron polarization of P{sub e{sup -}} {approx}> 80% and positron polarization of P{sub e{sup +}} {approx}> 30% are part of the baseline configuration of the machine. Energy and polarization measurements for ILC options beyond the baseline, including Z-pole running and the 1 TeV energy upgrade, were also discussed
Measurement of the charm and beauty structure functions using the H1 vertex detector at HERA
Inclusive charm and beauty cross sections are measured in e − p and e + p neutral current collisions at HERA in the kinematic region of photon virtuality 5≤Q 2≤2000 GeV2 and Bjorken scaling variable 0.0002≤x≤0.05. The data were collected with the H1 detector in the years 2006 and 2007 corresponding to an integrated luminosity of 189 pb−1. The numbers of charm and beauty events are determined using variables reconstructed by the H1 vertex detector including the impact parameter of tracks to the primary vertex and the position of the secondary vertex. The measurements are combined with previous data and compared to QCD predictions
Study of Charm Fragmentation into D^{*\pm} Mesons in Deep-Inelastic Scattering at HERA
The process of charm quark fragmentation is studied using meson
production in deep-inelastic scattering as measured by the H1 detector at HERA.
Two different regions of phase space are investigated defined by the presence
or absence of a jet containing the meson in the event. The
parameters of fragmentation functions are extracted for QCD models based on
leading order matrix elements and DGLAP or CCFM evolution of partons together
with string fragmentation and particle decays. Additionally, they are
determined for a next-to-leading order QCD calculation in the fixed flavour
number scheme using the independent fragmentation of charm quarks to
mesons.Comment: 33 pages, submitted to EPJ
Jet production in ep collisions at high Q(2) and determination of alpha(s)
The production of jets is studied in deep-inelastic e(+/-) p scattering at large negative four momentum transfer squared 150 LT Q(2) LT 15000 GeV2 using HERA data taken in 1999-2007, corresponding to an integrated luminosity of 395 pb(-1). Inclusive jet, 2-jet and 3-jet cross sections, normalised to the neutral current deep-inelastic scattering cross sections, are measured as functions of Q(2), jet transverse momentum and proton momentum fraction. The measurements are well described by perturbative QCD calculations at next-to-leading order corrected for hadronisation effects. The strong coupling as determined from these measurement
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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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