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Full-Text Articles in Physical Sciences and Mathematics

The Window Distribution Of Multiple Tcps With Random Loss Queues, Archan Misra, Teunis Ott, John Baras Dec 1999

The Window Distribution Of Multiple Tcps With Random Loss Queues, Archan Misra, Teunis Ott, John Baras

Research Collection School Of Computing and Information Systems

Two approximate techniques for analyzing the window size distribution of TCP flows sharing a RED-like bottleneck queue are presented. Both methods presented first use a fixed point algorithm to obtain the mean window sizes of the flows, and the mean queue length in the bottleneck buffer. The simpler of the two methods then uses the ‘square root formula’ for TCP; the other method is more complicated. More often than not, the simpler method is slightly more accurate; this is probably due to the fact that window sizes of the different flows are negatively correlated.


Mpeg-4 Systems And Applications, Hari Kalva, Lai-Tee Cheok, Alexandros Eleftheriadis Nov 1999

Mpeg-4 Systems And Applications, Hari Kalva, Lai-Tee Cheok, Alexandros Eleftheriadis

Research Collection School Of Computing and Information Systems

MPEG-4, under the auspices of the ISO, is specifying tools to enable object-based audio-visual presentations [3]. These include tools to encode individual objects, compose presentations with objects, store these object-based presentations and access these presentations in a distributed manner over networks. The main distinguishing feature of object-based audio-visual presentations is the scene composition at the user terminal. The objects that are part of a scene are composed and displayed at the user end as opposed to encoding the composed scenes as is done in the case of MPEG-2. Such object-based representation and presentation has several benefits including compression efficiency and …


Zbroker: A Query Routing Broker For Z39.50 Databases, Yong Lin, Jian Xu, Ee Peng Lim, Wee-Keong Ng Nov 1999

Zbroker: A Query Routing Broker For Z39.50 Databases, Yong Lin, Jian Xu, Ee Peng Lim, Wee-Keong Ng

Research Collection School Of Computing and Information Systems

A query routing broker is a software agent that determines from a large set of accessing information sources the ones most relevant to a user's information need. As the number of information sources on the Internet increases dramatically, future users will have to rely on query routing brokers to decide a small number of information sources to query without incurring too much query processing overheads. In this paper, we describe a query routing broker known as ZBroker developed for bibliographic database servers that support the Z39.50 protocol. ZBroker samples the content of each bibliographic database by using training queries and …


Wedagen: A Synthetic Web Database Generator, Pallavi Priyardarshini, Fengqiong Qin, Ee Peng Lim, Wee-Keong Ng Sep 1999

Wedagen: A Synthetic Web Database Generator, Pallavi Priyardarshini, Fengqiong Qin, Ee Peng Lim, Wee-Keong Ng

Research Collection School Of Computing and Information Systems

At the Centre for Advanced Information Systems (CAIS), a Web warehousing system is being developed to store and manipulate Web information. The system named WHOWEDA (WareHouse Of WEb DAta) stores extracted Web information as Web tables and provides several Web operators, eg. Web join, Web select, global coupling, etc., to manipulate Web tables. During the implementation of WHOWEDA, it is necessary to perform systematic testing on the system and to evaluate its system performance. While it is possible for WHOWEDA to be tested or evaluated using actual Web pages downloaded from WWW, the amount of time required for such testing …


Motion Tracking Of Human Mouth By Generalized Deformable Models, Syin Chan, Chong-Wah Ngo, Kok F. Lai Sep 1999

Motion Tracking Of Human Mouth By Generalized Deformable Models, Syin Chan, Chong-Wah Ngo, Kok F. Lai

Research Collection School Of Computing and Information Systems

We propose and evaluate four trackers for tracking the shape, motion and deformation of a human mouth in video sequences. The trackers are suitable for use in very low bitrate video coding systems. (C) 1999 Elsevier Science B.V. All rights reserved.


Design Approaches To Model-Based Simulation In Intelligent Computer Assisted Instruction, Bjoern Helfesrieder, Venky Shankararaman Sep 1999

Design Approaches To Model-Based Simulation In Intelligent Computer Assisted Instruction, Bjoern Helfesrieder, Venky Shankararaman

Research Collection School Of Computing and Information Systems

Model-based simulation systems have been created in various fields of engineering to train personnel or students in operation, maintenance and troubleshooting of complex devices and systems. A review of literature indicates a lack of good overviews of the approaches to system design of model-based training simulations in Intelligent Computer Assisted Instruction (ICAI). Though single systems have to some extent been evaluated with regard to their performance, an organised evaluation, especially a comparative evaluation of the systems that have been created within the field is lacking. To be able to successfully conduct an in-depth review under these conditions, we concentrate and …


Research Issues In Web Data Mining, Sanjay Kumar Madria, Sourav S. Bhowmick, Wee-Keong Ng, Ee Peng Lim Sep 1999

Research Issues In Web Data Mining, Sanjay Kumar Madria, Sourav S. Bhowmick, Wee-Keong Ng, Ee Peng Lim

Research Collection School Of Computing and Information Systems

In this paper, we discuss mining with respect to web data referred here as web data mining. In particular, our focus is on web data mining research in context of our web warehousing project called WHOWEDA (Warehouse of Web Data). We have categorized web data mining into threes areas; web content mining, web structure mining and web usage mining. We have highlighted and discussed various research issues involved in each of these web data mining category. We believe that web data mining will be the topic of exploratory research in near future.


Locating Web Information Using Web Checkpoints, Aik Kee Luah, Wee-Keong Ng, Ee Peng Lim, Wee Peng Lee, Yinyan Cao Sep 1999

Locating Web Information Using Web Checkpoints, Aik Kee Luah, Wee-Keong Ng, Ee Peng Lim, Wee Peng Lee, Yinyan Cao

Research Collection School Of Computing and Information Systems

Conventional search engines locate information by letting users establish a single web checkpoint1. By specifying one or more keywords, users direct search engines to return a set of documents that contain those keywords. From the documents (links) returned by search engines, user proceed to further probe the WWW from there. Hence, these initial set of documents (contingent upon the occurrence of keyword(s)) serve as a web checkpoint. Generally, these links are numerous and may not result in much fruitful searches. By establishing multiple web checkpoints, a richer and controllable search procedure can be constructed to obtain more relevant Web information. …


Non-Repudiation In An Agent-Based E-Commerce System, Chin Chuan Liew, Wee-Keong Ng, Ee Peng Lim, Beng Suang Tan, Kok-Leong Ong Sep 1999

Non-Repudiation In An Agent-Based E-Commerce System, Chin Chuan Liew, Wee-Keong Ng, Ee Peng Lim, Beng Suang Tan, Kok-Leong Ong

Research Collection School Of Computing and Information Systems

Abecos is an agent-based e-commerce system under development at the Nanyang Technological University. A key factor in making this system usable in practice is strict security controls. One aspect of security is the provision of non-repudiation services. As protocols for non-repudiation have focused on -message non-repudiation, its adaptation to afford non-repudiation in a communication session for two agents in Abecos is inefficient. In this work, we investigate and propose a protocol for enforcing non-repudiation in a session. The protocol is believed to be applicable in any e-commerce system; agent- or not agent-based.


Cluster-Based Database Selection Techniques For Routing Bibliographic Queries, Jian Xu, Ee Peng Lim, Wee-Keong Ng Aug 1999

Cluster-Based Database Selection Techniques For Routing Bibliographic Queries, Jian Xu, Ee Peng Lim, Wee-Keong Ng

Research Collection School Of Computing and Information Systems

In this paper, we focus on the database selection problem in the context of a global digital library consisting of a large number of online bibliographic servers. Each server hosts a bibliographic database that contains bibliographic records each of which consists of text values for a number of pre-defined bibliographic attributes such as title, author, call number, subject, etc.. Each bibliographic database supports user queries on the bibliographic attributes. Since bibliographic records are relatively small in size, we only consider bibliographic databases that support boolean queries on the bibliographic attributes, and the query results are not ranked. While focusing on …


Detection Of Gradual Transitions Through Temporal Slice Analysis, Chong-Wah Ngo, T. C. Pong, R. T. Chin Jun 1999

Detection Of Gradual Transitions Through Temporal Slice Analysis, Chong-Wah Ngo, T. C. Pong, R. T. Chin

Research Collection School Of Computing and Information Systems

In this paper, we present approaches for detecting camera cuts, wipes and dissolves based on the analysis of spatio-temporal slices obtained from videos. These slices are composed of spatial ly and temporal ly coherent regions which can be perceived as shots. In the proposed methods, camera breaks are located by performing color-texture segmentation and statistical analysis on these video slices. In addition to detecting camera breaks, our methods can classify the detected breaks as camera cuts, wipes and dissolves in an efficient manner


Camera Break Detection By Partitioning Of 2d Spatio-Temporal Images In Mpeg Domain, Chong-Wah Ngo Jun 1999

Camera Break Detection By Partitioning Of 2d Spatio-Temporal Images In Mpeg Domain, Chong-Wah Ngo

Research Collection School Of Computing and Information Systems

In this paper, we propose a new approach to detect camera cuts and wipes. The approach projects a video into two images representing the spatio-temporal continuity of a video life. Visually, these images are composed by regions of different patterns, each region represents the temporal location of a shot. The shape of a region boundary inherently classifies cut and wipe, and most importantly, marks the start and end of a wipe sequence. We hence formulate algorithms to locate the color and texture discontinuities occurring at the boundaries of image regions.


Notepals: Lightweight Note Sharing By The Group, For The Group, Richard C. Davis, James A. Landay, Victor Chen, Jonathan Huang, Rebecca B. Lee, Francis Li, James Lin, Charles B. Morrey, Morgan N. Price, Bill N. Schilit May 1999

Notepals: Lightweight Note Sharing By The Group, For The Group, Richard C. Davis, James A. Landay, Victor Chen, Jonathan Huang, Rebecca B. Lee, Francis Li, James Lin, Charles B. Morrey, Morgan N. Price, Bill N. Schilit

Research Collection School Of Computing and Information Systems

NotePals is a lightweight note sharing system that gives group members easy access to each others experiences through their personal notes. The system allows notes taken by group members in any context to be uploaded to a shared repository. Group members view these notes with browsers that allow them to retrieve all notes taken in a given context or to access notes from other related notes or documents. This is possible because NotePals records the context in which each note is created (e.g., its author, subject, and creation time). The system is lightweight because it fits easily into group members …


Pi-Web Join In A Web Warehouse, Sourav S. Bhowmick, Sanjay Kumar Madria, Wee-Keong Ng, Ee Peng Lim Apr 1999

Pi-Web Join In A Web Warehouse, Sourav S. Bhowmick, Sanjay Kumar Madria, Wee-Keong Ng, Ee Peng Lim

Research Collection School Of Computing and Information Systems

With the enormous amount of data stored in the World Wide Web, it is increasingly important to design and develop powerful web warehousing tools. The key objective of our web warehousing project, called WHOWEDA (Warehouse of Web Data), is to design and implement a web warehouse that materializes and manages useful information from the Web. In this paper, we introduce the concept of Pi-web join in the context of WHOWEDA. Pi-web join operator is a web information manipulation operator to combine relevant web information residing in two web tables. Informally, it is the combination of web join and web project …


The Window Distribution Of Idealized Tcp Congestion Avoidance With Variable Packet Loss, Archan Misra, Teunis J. Ott Mar 1999

The Window Distribution Of Idealized Tcp Congestion Avoidance With Variable Packet Loss, Archan Misra, Teunis J. Ott

Research Collection School Of Computing and Information Systems

This paper analyzes the stationary behavior of the TCP congestion window performing ideal congestion avoidance when the packet loss probability is not constant, but varies as a function of the window size. By neglecting the detailed window behavior during fast recovery, we are able to derive a Markov process that is then approximated by a continuous-time, continuous state space process. The stationary distribution of this process is analyzed and derived numerically and then extrapolated to obtain the stationary distribution of the TCP window. This numerical analysis enables us to predict the behavior of the TCP congestion window when interacting with …


Resource Scheduling In A High-Performance Multimedia Server, Hwee Hwa Pang, Bobby Jose, M. S. Krishnan Mar 1999

Resource Scheduling In A High-Performance Multimedia Server, Hwee Hwa Pang, Bobby Jose, M. S. Krishnan

Research Collection School Of Computing and Information Systems

Supporting continuous media data-such as video and audio-imposes stringent demands on the retrieval performance of a multimedia server. In this paper, we propose and evaluate a set of data placement and retrieval algorithms to exploit the full capacity of the disks in a multimedia server. The data placement algorithm declusters every object over all of the disks in the server-using a time-based declustering unit-with the aim of balancing the disk load. As for runtime retrieval, the quintessence of the algorithm is to give each disk advance notification of the blocks that have to be fetched in the impending time periods, …


Making Sharing Pervasive: Ubiquitous Computing For Shared Note Taking, James A. Landay, Richard C. Davis Jan 1999

Making Sharing Pervasive: Ubiquitous Computing For Shared Note Taking, James A. Landay, Richard C. Davis

Research Collection School Of Computing and Information Systems

As a variety of low-cost note-taking devices becomes pervasive, shared notes can help work groups better communicate ideas and information. To explore this idea further, we carried out three related case studies of how members of a large research group shared meeting notes. The group found value in combining personal notes and presentation slides with a single, unifying document, such as regular meeting minutes. The minutes provided structure when there were too many sources of notes. We used this insight in our design of NotePals, a note-sharing system with a lightweight process, an interface, and hardware that distinguish it from …


Study Of T Decays Involving Kaons, Spectral Functions And Determination Of The Strange Quark Mass, R. Barate, M. Thulasidas Jan 1999

Study Of T Decays Involving Kaons, Spectral Functions And Determination Of The Strange Quark Mass, R. Barate, M. Thulasidas

Research Collection School Of Computing and Information Systems

All ALEPH measurements of branching ratios of ττ decays involving kaons are summarized including a combination of results obtained with K0SKS0 and K0LKL0 detection. The decay dynamics are studied, leading to the determination of contributions from vector K∗(892)K∗(892) and K∗(1410)K∗(1410), and axial-vector K1(1270)K1(1270) and K1(1400)K1(1400) resonances. Agreement with isospin symmetry is observed among the different final states. Under the hypothesis of the conserved vector current, the spectral function for the KK¯¯¯¯¯πKK¯π mode is compared with the corresponding cross section for low energy e+e−e+e− annihilation, yielding an axial-vector fraction of (94+6−8)%(94−8+6)% for this mode. The branching ratio for ττ decay into …


One-Prong Τ Decays With Kaons, R. Barate, M. Thulasidas Jan 1999

One-Prong Τ Decays With Kaons, R. Barate, M. Thulasidas

Research Collection School Of Computing and Information Systems

One-prong ττ decays into final states involving kaons are studied with about 161 000 τ+τ−τ+τ− events collected by the ALEPH detector from 1991 to 1995. Charged kaons are identified by dE/dx measurement, while K0LKL0's are detected through their interaction in calorimeters. Branching ratios are measured for the inclusive mode, B(τ−→K−Xντ)=(1.52±0.04±0.04)%B(τ−→K−Xντ)=(1.52±0.04±0.04)%, where X can be any system of neutral particles, and for the exclusive modesB(τ−→K−ντ)=(6.96±0.25±0.14)×10−3,B(τ−→K−π0ντ)=(4.44±0.26±0.24)×10−3,B(τ−→K−π0π0ντ)=(0.56±0.20±0.15)×10−3,B(τ−→K−π0π0π0ντ)=(0.37±0.21±0.11)×10−3,B(τ−→K−K0ντ)=(1.62±0.21±0.11)×10−3,B(τ−→K−K0π0ντ)=(1.43±0.25±0.15)×10−3,B(τ−→K0¯¯¯¯¯¯¯π−ντ)=(9.28±0.45±0.34)×10−3,B(τ−→K0¯¯¯¯¯¯¯π−π0ντ)=(3.47±0.53±0.37)×10−3,B(τ−→K−ντ)=(6.96±0.25±0.14)×10−3,B(τ−→K−π0ντ)=(4.44±0.26±0.24)×10−3,B(τ−→K−π0π0ντ)=(0.56±0.20±0.15)×10−3,B(τ−→K−π0π0π0ντ)=(0.37±0.21±0.11)×10−3,B(τ−→K−K0ντ)=(1.62±0.21±0.11)×10−3,B(τ−→K−K0π0ντ)=(1.43±0.25±0.15)×10−3,B(τ−→K0¯π−ντ)=(9.28±0.45±0.34)×10−3,B(τ−→K0¯π−π0ντ)=(3.47±0.53±0.37)×10−3,where the first error is statistical and the second is systematical. Upper limits for B(τ−→K0¯¯¯¯¯¯¯π−π0π0ντ)B(τ−→K0¯π−π0π0ντ) and B(τ−→K−K0π0π0ντ)B(τ−→K−K0π0π0ντ) are also obtained. Mass spectra in the final states are investigated in order to study the relevant dynamics.


Monitoring The Stability Of The Aleph Vertex Detector, G. Sguazzoni, Manoj Thulasidas Jan 1999

Monitoring The Stability Of The Aleph Vertex Detector, G. Sguazzoni, Manoj Thulasidas

Research Collection School Of Computing and Information Systems

The ALEPH Silicon Vertex Detector features an optical fibre laser system to monitor its mechanical stability. The operating principle and the general performance of the laser system are described. The experience obtained during 1997 and 1998 operations confirms the important role that such a system can have with respect to the detector alignment requirements. In particular, the laser system has been used to monitor short-term temperature-related effects and long-term movements. These results and a description of the laser-based alignment correction applied to the 1998 data are presented.


Web-Based Interlibrary Loan System, Ee Peng Lim, Schubert Foo, Cheng Hai Tan, Kwang-Yong Tan Jan 1999

Web-Based Interlibrary Loan System, Ee Peng Lim, Schubert Foo, Cheng Hai Tan, Kwang-Yong Tan

Research Collection School Of Computing and Information Systems

Interlibrary loan (ILL) system is one of the important library services provided by most public libraries. Through ILL, public libraries share their collections of reading material and library users are able to access library resources beyond their affiliated libraries. However, the present manual ILL process is inconvenient, inefficient and error-prone. In this project, we developed a system that automated many tedious procedures in the existing ILL system. The new ILL system is realized by a number of Java applets customized for librarians and library users. The new ILL system allows library users to submit ILL requests at any time using …


Search For Charginos And Neutralinos In E+E- Collisions At Centre-Of-Mass Energies Near 183 Gev And Constraints On The Mssm Parameter Space, R. Barate, M. Thulasidas Jan 1999

Search For Charginos And Neutralinos In E+E- Collisions At Centre-Of-Mass Energies Near 183 Gev And Constraints On The Mssm Parameter Space, R. Barate, M. Thulasidas

Research Collection School Of Computing and Information Systems

Searches for charginos and neutralinos are performed with the data collected by the ALEPH detector at LEP at centre-of-mass energies near 183 GeV. In these searches, it is assumed that R-parity is conserved and that the lightest neutralino is the LSP. No evidence of a signal is observed in the 57 pb−1−1 accumulated, which excludes chargino and associated neutralino production up to the kinematic limit over large regions of the MSSM parameter space. Under the assumptions of common gaugino and common sfermion masses at the unification scale, the interplay between the chargino, neutralino and slepton exclusion limits allows a lower …


Decision Analytic Approach To Severe Head Injury Management., Harmanec D., Tze-Yun Leong, Sundaresh S., Poh K., Yeo T., Ng I., Lew T. Jan 1999

Decision Analytic Approach To Severe Head Injury Management., Harmanec D., Tze-Yun Leong, Sundaresh S., Poh K., Yeo T., Ng I., Lew T.

Research Collection School Of Computing and Information Systems

Severe head injury management in the intensive care unit is extremely challenging due to the complex domain, the uncertain intervention efficacies, and the time-critical setting. We adopt a decision analytic approach to automate the management process. We document our experience in building a simplified influence diagram that involves about 3000 numerical parameters. We identify the inherent problems in structuring a model with unclear domain relationships, numerous interacting variables, and real-time multiple inputs. We analyze the effectiveness and limitations of the decision analytic approach and present a set of desiderata for effective knowledge acquisition in this setting. We also propose a …


Determination Of The Lep Centre-Of-Mass Energy From Zγ Events, R. Barate, Manoj Thulasidas Jan 1999

Determination Of The Lep Centre-Of-Mass Energy From Zγ Events, R. Barate, Manoj Thulasidas

Research Collection School Of Computing and Information Systems

A study of events with photons and missing energy has been performed with the data sample obtained with the ALEPH detector at centre-of-mass energies from 161 to 184 GeV, corresponding to a total integrated luminosity of about 80 pb−1. The measured distributions are in agreement with Standard Model predictions, leading to constraints on WWγ gauge coupling parameters ∆κγ and λγ. The results from the fit to the cross sections and to the energy and angular distributions of the photons are: ∆κγ = 0.05+1.15 −1.10(stat)±0.25(syst) λγ = −0.05+1.55 −1.45(stat)±0.30(syst).


Search For Invisible Higgs Boson Decays In E+E- Collisions At Centre-Of-Mass Energies Up To 184 Gev, R. Barate, Manoj Thulasidas Jan 1999

Search For Invisible Higgs Boson Decays In E+E- Collisions At Centre-Of-Mass Energies Up To 184 Gev, R. Barate, Manoj Thulasidas

Research Collection School Of Computing and Information Systems

In a data sample of 78.3 pb−1 collected in 1996 and 1997 by the ALEPH detector at centre-of-mass energies from 161 to 184 GeV, invisible decays of a Higgs boson have been searched for in the reaction e+e− → hZ, where the Z can decay into e+e−, µ+µ− or q¯q. No evidence for a signal is found and limits on the production cross section are derived as a function of the Higgs boson mass. These results are combined with those obtained in an update of the analyses of the ALEPH data taken at LEP 1. For a production cross section …


Search For The Standard Model Higgs Boson At The Lep2 Collider Near √S = 183 Gev, R. Barate, M. Thulasidas Jan 1999

Search For The Standard Model Higgs Boson At The Lep2 Collider Near √S = 183 Gev, R. Barate, M. Thulasidas

Research Collection School Of Computing and Information Systems

During 1997 the ALEPH experiment at LEP gathered 57pb−1 of data at centre-of-mass energies near 183 GeV. These data are used to look for possible signals from the production of the Standard Model Higgs boson in the reaction e+e−→HZ. No evidence of a signal is found in the data; seven events are selected, in agreement with the expectation of 7.2 events from background processes. This observation results in an improved lower limit on the mass of the Higgs boson: mH>87.9GeV/c2 at 95% confidence level.


Search For Bs0 Oscillations Using Inclusive Lepton Events, R. Barate, M. Thulasidas Jan 1999

Search For Bs0 Oscillations Using Inclusive Lepton Events, R. Barate, M. Thulasidas

Research Collection School Of Computing and Information Systems

A search for B0sBs0 oscillations is performed using a sample of semileptonic b-hadron decays collected by the ALEPH experiment during 1991–95. Compared to previous inclusive lepton analyses, the proper time resolution and b-flavour mistag rate are significantly improved. Additional sensitivity to B0sBs0 mixing is obtained by identifying subsamples of events having a B0sBs0 purity which is higher than the average for the whole data sample. Unbinned maximum likelihood amplitude fits are performed to derive a lower limit of Δms>9.5ps−1Δms>9.5ps−1 at the 95% confidence limit (95% CL). Combining with the ALEPH D−sDs−-based analyses yields Δms>9.6ps−1Δms>9.6ps−1 at 95% …


Harp: A Distributed Query System For Legacy Public Libraries And Structured Databases, Ee Peng Lim, Ying Lu Jan 1999

Harp: A Distributed Query System For Legacy Public Libraries And Structured Databases, Ee Peng Lim, Ying Lu

Research Collection School Of Computing and Information Systems

The main purpose of a digital library is to facilitate users easy access to enormous amount of globally networked information. Typically, this information includes preexisting public library catalog data, digitized document collections, and other databases. In this article, we describe the distributed query system of a digital library prototype system known as HARP. In the HARP project, we have designed and implemented a distributed query processor and its query front-end to support integrated queries to preexisting public library catalogs and structured databases. This article describes our experiences in the design of an extended Sequel (SQL) query language known as HarpSQL. …


A Study Of Single W Production In E+E- Collisions At √S = 161-183 Gev, R. Barate, Manoj Thulasidas Jan 1999

A Study Of Single W Production In E+E- Collisions At √S = 161-183 Gev, R. Barate, Manoj Thulasidas

Research Collection School Of Computing and Information Systems

Single W production is studied in the data recorded with the ALEPH detector at LEP at centre-of-mass energies between 161 and 183 GeV. The cross section is measured to be σw = 0.41 ± 0.17(stat.) ± 0.04(syst.) pb at 183 GeV, consistent with the Standard Model expectation. Limits on non-standard WWγ couplings are deduced as -1.6 γ γ = 0) and -1.6 γ γ = 1) at 95% C.L. A search for effectively invisible decays of the W boson in W pair production is performed, leading to an upper limit on the branching ratio of 1.3% (Γinv = 27 MeV) …


Measurement Of W-Pair Production In E+E- Collisions At 183 Gev, R. Barate, Manoj Thulasidas Jan 1999

Measurement Of W-Pair Production In E+E- Collisions At 183 Gev, R. Barate, Manoj Thulasidas

Research Collection School Of Computing and Information Systems

The production of W+W− pairs is analysed in a data sample collected by ALEPH at a mean centre-of-mass energy of 182.7 GeV, corresponding to an integrated luminosity of 57 pb−1 . Cross sections are given for different topologies of W decays into leptons or hadrons. Under Standard Model assumptions for the W-pair production and decay, the W-pair cross section is measured to be 15.57 ± 0.62(stat.) ± 0.29(syst.) pb. Using also the W-pair data samples collected by ALEPH at lower centre-of-mass energies, the decay branching ratio of the W boson into hadrons is measured to be B(W → hadrons) = …