| 1. |
- Aaron, F. D., et al.
(author)
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Events with an isolated lepton and missing transverse momentum and measurement of W production at HERA
- 2010
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In: Journal of High Energy Physics. - 1029-8479. ; 2010:3, s. 1-19
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Journal article (peer-reviewed)abstract
- A search for events containing an isolated electron or muon and missing trans verse momentum produced in e(+/-)p collisions is performed with the H1 and ZEUS detectors at HERA. The data were taken in the period 1994-2007 and correspond to an integrated luminosity of 0.98 fb(-1). The observed event yields are in good overall agreement with the Standard Model prediction, which is dominated by single W production. In the e(+)p data, at large hadronic transverse momentum P-T(X) > 25GeV, a total of 23 events are observed compared to a prediction of 14.0 +/- 1.9. The total single W boson production cross section is measured as 1.06 +/- 0.16 (stat.) +/- 0.07 (sys.) pb, in agreement with an Standard Model (SM) expectation of 1.26 +/- 0.19 pb.
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| 2. |
- Aaron, F. D., et al.
(author)
-
Multi-leptons with high transverse momentum at HERA
- 2009
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In: Journal of High Energy Physics. - : Springer Science and Business Media LLC. - 1029-8479. ; :10
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Journal article (peer-reviewed)abstract
- Events with at least two high transverse momentum leptons (electrons or muons) are studied using the H1 and ZEUS detectors at HERA with an integrated luminosity of 0.94 fb(-1). The observed numbers of events are in general agreement with the Standard Model predictions. Seven di- and tri-lepton events are observed in e(+)p collision data with a scalar sum of the lepton transverse momenta above 100 GeV while 1.94 +/- 0.17 events are expected. Such events are not observed in e(-)p collisions for which 1.19 +/- 0.12 are predicted. Total visible and differential di-electron and di-muon photoproduction cross sections are extracted in a restricted phase space dominated by photon-photon collisions.
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| 3. |
- Aaron, F. D., et al.
(author)
-
Combined measurement and QCD analysis of the inclusive e(+/-)p scattering cross sections at HERA
- 2010
-
In: Journal of High Energy Physics. - 1029-8479. ; :1
-
Journal article (peer-reviewed)abstract
- A combination is presented of the inclusive deep inelastic cross sections measured by the H1 and ZEUS Collaborations in neutral and charged current unpolarised e(+/-)p scattering at HERA during the period 1994-2000. The data span six orders of magnitude in negative four-momentum-transfer squared, Q(2), and in Bjorken x. The combination method used takes the correlations of systematic uncertainties into account, resulting in an improved accuracy. The combined data are the sole input in a NLO QCD analysis which determines a new set of parton distributions, HERAPDF1.0, with small experimental uncertainties. This set includes an estimate of the model and parametrisation uncertainties of the fit result.
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| 4. |
- Aberg, Jan, et al.
(author)
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Multialphabet coding with separate alphabet description
- 1997
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In: Proceedings. Compression and Complexity of SEQUENCES 1997. - 0818681322 ; , s. 56-65
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Conference paper (peer-reviewed)abstract
- For lossless universal source coding of memoryless sequences with an a priori unknown alphabet size (multialphabet coding), the alphabet of the sequence must be described as well as the sequence itself. Usually an efficient description of the alphabet can be made only by taking into account some additional information. We show that these descriptions can be separated in such a way that the encoding of the actual sequence can be performed independently of the alphabet description, and present sequential coding methods for such sequences. Such methods have applications in coding methods where the alphabet description is made available sequentially, such as PPM.
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| 5. |
- Aberg, J., et al.
(author)
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Non-uniform PPM and context tree models
- 1998
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In: Proceedings DCC '98 Data Compression Conference. - 0818684062 ; , s. 279-288
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Conference paper (peer-reviewed)abstract
- The problem of optimizing PPM with the help of different choices of estimators and their parameters for different subsets of nodes in the context tree is considered. Methods of such optimization for Markov chain and context tree models for individual files and over given sets of files are presented, and it is demonstrated that the extension from Markov chain models to context tree models is necessary to receive significant improvements of the compression ratio.
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| 6. |
- Aberg, J., et al.
(author)
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Towards understanding and improving escape probabilities in PPM
- 1997
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In: Proceedings DCC '97. Data Compression Conference. - 0818677619 ; , s. 22-31
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Conference paper (peer-reviewed)abstract
- The choice of expressions for the coding probabilities in general, and the escape probability in particular, is of great importance in the family of PPM algorithms. We present a parameterized version of the escape probability estimator which, together with a 'compactness' criterion, provides guidelines for the estimator design given a 'representative' set of files. This parameterization also makes it possible to adapt the expression of the escape probability during one-pass coding. Finally, we present results for one such compression scheme that illustrates the usefulness of our approach.
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| 7. |
- Åberg, Jan, et al.
(author)
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Estimation of escape probabilities for PPM based on universal source coding theory
- 1997
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In: Proceedings 1997 IEEE International Symposium on Information Theory. - 2157-8095. - 0780339568 - 9780780339569 ; , s. 65-65
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Conference paper (peer-reviewed)abstract
- Some of the best compression ratios for text compression are provided by the PPM (prediction by partial matching) class of algorithms. These algorithms are based on arithmetic coding using a fixed-depth Markov chain model of the source, i.e., the subsequence of symbols generated in any state s of the source is assumed to be the output of a memoryless subsource w=w(s). One of the most crucial steps in any PPM algorithm is the choice of the escape probability, i.e., the probability of a previously unseen symbol appearing in a given state. Let A={1,...,M} be the source alphabet, x/sup k/=x/ix/ i...x/sub k//spl isin/A/sup k/ be a sequence of symbols generated by a subsource w with unknown parameters, and m=m(x/sup k/) be the number of different symbols in x/sup k/. In most incarnations of PPM, the expression for the escape probability used for coding is of the form /spl thetav/(E|x/sup k/)=k(k,m)/k+m/spl alpha/+k(k,m), where /spl alpha/ is a parameter. The encoding of the "escape symbol" E is followed by a description of the new symbol, which is independent of the choice of escape probability and is not discussed. In almost all PPM schemes, the expression for the escape probability has been chosen heuristically. Following the method of Shtarkov et al. (see Probl. of Information Transmission, vol.31, no.2, p.20-35, 1995) we use a universal coding approach.
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