| 1. |
- Niemi, MEK, et al.
(author)
-
- 2021
-
swepub:Mat__t
|
|
| 2. |
- Kanai, M, et al.
(author)
-
- 2023
-
swepub:Mat__t
|
|
| 3. |
- Aad, G, et al.
(author)
-
- 2015
-
swepub:Mat__t
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
|
|
| 8. |
- Schael, S, et al.
(author)
-
Precision electroweak measurements on the Z resonance
- 2006
-
In: Physics Reports. - : Elsevier BV. - 0370-1573 .- 1873-6270. ; 427:5-6, s. 257-454
-
Research review (peer-reviewed)abstract
- We report on the final electroweak measurements performed with data taken at the Z resonance by the experiments operating at the electron-positron colliders SLC and LEP. The data consist of 17 million Z decays accumulated by the ALEPH, DELPHI, L3 and OPAL experiments at LEP, and 600 thousand Z decays by the SLID experiment using a polarised beam at SLC. The measurements include cross-sections, forward-backward asymmetries and polarised asymmetries. The mass and width of the Z boson, m(Z) and Gamma(Z), and its couplings to fermions, for example the p parameter and the effective electroweak mixing angle for leptons, are precisely measured: m(Z) = 91.1875 +/- 0.0021 GeV, Gamma(Z) = 2.4952 +/- 0.0023 GeV, rho(l) = 1.0050 +/- 0.0010, sin(2)theta(eff)(lept) = 0.23153 +/- 0.00016. The number of light neutrino species is determined to be 2.9840 +/- 0.0082, in agreement with the three observed generations of fundamental fermions. The results are compared to the predictions of the Standard Model (SM). At the Z-pole, electroweak radiative corrections beyond the running of the QED and QCD coupling constants are observed with a significance of five standard deviations, and in agreement with the Standard Model. Of the many Z-pole measurements, the forward-backward asymmetry in b-quark production shows the largest difference with respect to its SM expectation, at the level of 2.8 standard deviations. Through radiative corrections evaluated in the framework of the Standard Model, the Z-pole data are also used to predict the mass of the top quark, m(t) = 173(+10)(+13) GeV, and the mass of the W boson, m(W) = 80.363 +/- 0.032 GeV. These indirect constraints are compared to the direct measurements, providing a stringent test of the SM. Using in addition the direct measurements of m(t) and m(W), the mass of the as yet unobserved SM Higgs boson is predicted with a relative uncertainty of about 50% and found to be less than 285 GeV at 95% confidence level. (c) 2006 Elsevier B.V. All rights reserved.
|
|
| 9. |
- Schael, S., et al.
(author)
-
Electroweak measurements in electron positron collisions at W-boson-pair energies at LEP
- 2013
-
In: Physics Reports. - : Elsevier BV. - 0370-1573 .- 1873-6270. ; 532:4, s. 119-244
-
Research review (peer-reviewed)abstract
- Electroweak measurements performed with data taken at the electron positron collider LEP at CERN from 1995 to 2000 are reported. The combined data set considered in this report corresponds to a total luminosity of about 3 fb(-1) collected by the four LEP experiments ALEPH, DELPHI, 13 and OPAL, at centre-of-mass energies ranging from 130 GeV to 209 GeV. Combining the published results of the four LEP experiments, the measurements include total and differential cross-sections in photon-pair, fermion-pair and four-fermion production, the latter resulting from both double-resonant WW and ZZ production as well as singly resonant production. Total and differential cross-sections are measured precisely, providing a stringent test of the Standard Model at centre-of-mass energies never explored before in electron positron collisions. Final-state interaction effects in four-fermion production, such as those arising from colour reconnection and Bose Einstein correlations between the two W decay systems arising in WW production, are searched for and upper limits on the strength of possible effects are obtained. The data are used to determine fundamental properties of the W boson and the electroweak theory. Among others, the mass and width of the W boson, m(w) and Gamma(w), the branching fraction of W decays to hadrons, B(W -> had), and the trilinear gauge-boson self-couplings g(1)(Z), K-gamma and lambda(gamma), are determined to be: m(w) = 80.376 +/- 0.033 GeV Gamma(w) = 2.195 +/- 0.083 GeV B(W -> had) = 67.41 +/- 0.27% g(1)(Z) = 0.984(-0.020)(+0.018) K-gamma - 0.982 +/- 0.042 lambda(gamma) = 0.022 +/- 0.019. (C) 2013 Elsevier B.V. All rights reserved.
|
|
| 10. |
|
|
| 11. |
-
- 2017
-
In: Physical Review D. - 2470-0010 .- 2470-0029. ; 96:2
-
Journal article (peer-reviewed)
|
|
| 12. |
- Mishra, A, et al.
(author)
-
Diminishing benefits of urban living for children and adolescents' growth and development
- 2023
-
In: Nature. - : Springer Science and Business Media LLC. - 1476-4687 .- 0028-0836. ; 615:7954, s. 874-883
-
Journal article (peer-reviewed)abstract
- Optimal growth and development in childhood and adolescence is crucial for lifelong health and well-being1–6. Here we used data from 2,325 population-based studies, with measurements of height and weight from 71 million participants, to report the height and body-mass index (BMI) of children and adolescents aged 5–19 years on the basis of rural and urban place of residence in 200 countries and territories from 1990 to 2020. In 1990, children and adolescents residing in cities were taller than their rural counterparts in all but a few high-income countries. By 2020, the urban height advantage became smaller in most countries, and in many high-income western countries it reversed into a small urban-based disadvantage. The exception was for boys in most countries in sub-Saharan Africa and in some countries in Oceania, south Asia and the region of central Asia, Middle East and north Africa. In these countries, successive cohorts of boys from rural places either did not gain height or possibly became shorter, and hence fell further behind their urban peers. The difference between the age-standardized mean BMI of children in urban and rural areas was <1.1 kg m–2 in the vast majority of countries. Within this small range, BMI increased slightly more in cities than in rural areas, except in south Asia, sub-Saharan Africa and some countries in central and eastern Europe. Our results show that in much of the world, the growth and developmental advantages of living in cities have diminished in the twenty-first century, whereas in much of sub-Saharan Africa they have amplified.
|
|
| 13. |
- Abadie, J., et al.
(author)
-
Implementation and testing of the first prompt search for gravitational wave transients with electromagnetic counterparts
- 2012
-
In: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 539
-
Journal article (peer-reviewed)abstract
- Aims. A transient astrophysical event observed in both gravitational wave (GW) and electromagnetic (EM) channels would yield rich scientific rewards. A first program initiating EM follow-ups to possible transient GW events has been developed and exercised by the LIGO and Virgo community in association with several partners. In this paper, we describe and evaluate the methods used to promptly identify and localize GW event candidates and to request images of targeted sky locations. Methods. During two observing periods (Dec. 17, 2009 to Jan. 8, 2010 and Sep. 2 to Oct. 20, 2010), a low-latency analysis pipeline was used to identify GW event candidates and to reconstruct maps of possible sky locations. A catalog of nearby galaxies and Milky Way globular clusters was used to select the most promising sky positions to be imaged, and this directional information was delivered to EM observatories with time lags of about thirty minutes. A Monte Carlo simulation has been used to evaluate the low-latency GW pipeline's ability to reconstruct source positions correctly. Results. For signals near the detection threshold, our low-latency algorithms often localized simulated GW burst signals to tens of square degrees, while neutron star/neutron star inspirals and neutron star/black hole inspirals were localized to a few hundred square degrees. Localization precision improves for moderately stronger signals. The correct sky location of signals well above threshold and originating from nearby galaxies may be observed with similar to 50% or better probability with a few pointings of wide-field telescopes.
|
|
| 14. |
- Clementini, G., et al.
(author)
-
Testing parallaxes with local Cepheids and RR Lyrae stars
- 2017
-
In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 605
-
Journal article (peer-reviewed)abstract
- Context. Parallaxes for 331 classical Cepheids, 31 Type II Cepheids, and 364 RR Lyrae stars in common between Gaia and the HIPPARCOS and Tycho-2 catalogues are published in Gaia Data Release 1 (DR1) as part of the Tycho-Gaia Astrometric Solution (TGAS). Aims. In order to test these first parallax measurements of the primary standard candles of the cosmological distance ladder, which involve astrometry collected by Gaia during the initial 14 months of science operation, we compared them with literature estimates and derived new period-luminosity (PL), period-Wesenheit (PW) relations for classical and Type II Cepheids and infrared PL, PL-metallicity (PLZ), and optical luminosity-metallicity (MV-[Fe/H]) relations for the RR Lyrae stars, with zero points based on TGAS.Methods. Classical Cepheids were carefully selected in order to discard known or suspected binary systems. The final sample comprises 102 fundamental mode pulsators with periods ranging from 1.68 to 51.66 days (of which 33 with sigma(omega)/omega < 0 : 5). The Type II Cepheids include a total of 26 W Virginis and BL Herculis stars spanning the period range from 1.16 to 30.00 days (of which only 7 with sigma(omega)/omega 0 : 5). The RR Lyrae stars include 200 sources with pulsation period ranging from 0.27 to 0.80 days (of which 112 with sigma(omega)/omega < 0 : 5). The new relations were computed using multi- band (V; I; J; K-s) photometry and spectroscopic metal abundances available in the literature, and by applying three alternative approaches: (i) linear least-squares fitting of the absolute magnitudes inferred from direct transformation of the TGAS parallaxes; (ii) adopting astrometry-based luminosities; and (iii) using a Bayesian fitting approach. The last two methods work in parallax space where parallaxes are used directly, thus maintaining symmetrical errors and allowing negative parallaxes to be used. The TGAS-based PL; PW; PLZ, and MV [Fe/H] relations are discussed by comparing the distance to the Large Magellanic Cloud provided by different types of pulsating stars and alternative fitting methods.Results. Good agreement is found from direct comparison of the parallaxes of RR Lyrae stars for which both TGAS and HST measurements are available. Similarly, very good agreement is found between the TGAS values and the parallaxes inferred from the absolute magnitudes of Cepheids and RR Lyrae stars analysed with the Baade-Wesselink method. TGAS values also compare favourably with the parallaxes inferred by theoretical model fitting of the multi-band light curves for two of the three classical Cepheids and one RR Lyrae star, which were analysed with this technique in our samples. The K-band PL relations show the significant improvement of the TGAS parallaxes for Cepheids and RR Lyrae stars with respect to the HIPPARCOS measurements. This is particularly true for the RR Lyrae stars for which improvement in quality and statistics is impressive.Conclusions. TGAS parallaxes bring a significant added value to the previous HIPPARCOS estimates. The relations presented in this paper represent the first Gaia-calibrated relations and form a work-in-progress milestone report in the wait for Gaia-only parallaxes of which a first solution will become available with Gaia Data Release 2 (DR2) in 2018.
|
|
| 15. |
- Prusti, T., et al.
(author)
-
The Gaia mission
- 2016
-
In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 595
-
Journal article (peer-reviewed)abstract
- Gaia is a cornerstone mission in the science programme of the European Space Agency (ESA). The spacecraft construction was approved in 2006, following a study in which the original interferometric concept was changed to a direct-imaging approach. Both the spacecraft and the payload were built by European industry. The involvement of the scientific community focusses on data processing for which the international Gaia Data Processing and Analysis Consortium (DPAC) was selected in 2007. Gaia was launched on 19 December 2013 and arrived at its operating point, the second Lagrange point of the Sun-Earth-Moon system, a few weeks later. The commissioning of the spacecraft and payload was completed on 19 July 2014. The nominal five-year mission started with four weeks of special, ecliptic-pole scanning and subsequently transferred into full-sky scanning mode. We recall the scientific goals of Gaia and give a description of the as-built spacecraft that is currently (mid-2016) being operated to achieve these goals. We pay special attention to the payload module, the performance of which is closely related to the scientific performance of the mission. We provide a summary of the commissioning activities and findings, followed by a description of the routine operational mode. We summarise scientific performance estimates on the basis of in-orbit operations. Several intermediate Gaia data releases are planned and the data can be retrieved from the Gaia Archive, which is available through the Gaia home page.
|
|
| 16. |
- van Leeuwen, F., et al.
(author)
-
Gaia Data Release 1 : Open cluster astrometry: Performance, limitations, and future prospects
- 2017
-
In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 601
-
Journal article (peer-reviewed)abstract
- Context. The first Gaia Data Release contains the Tycho-Gaia Astrometric Solution (TGAS). This is a subset of about 2 million stars for which, besides the position and photometry, the proper motion and parallax are calculated using Hipparcos and Tycho-2 positions in 1991.25 as prior information. Aims. We investigate the scientific potential and limitations of the TGAS component by means of the astrometric data for open clusters. Methods. Mean cluster parallax and proper motion values are derived taking into account the error correlations within the astrometric solutions for individual stars, an estimate of the internal velocity dispersion in the cluster, and, where relevant, the effects of the depth of the cluster along the line of sight. Internal consistency of the TGAS data is assessed. Results. Values given for standard uncertainties are still inaccurate and may lead to unrealistic unit-weight standard deviations of least squares solutions for cluster parameters. Reconstructed mean cluster parallax and proper motion values are generally in very good agreement with earlier Hipparcos-based determination, although the Gaia mean parallax for the Pleiades is a significant exception. We have no current explanation for that discrepancy. Most clusters are observed to extend to nearly 15 pc from the cluster centre, and it will be up to future Gaia releases to establish whether those potential cluster-member stars are still dynamically bound to the clusters. Conclusions. The Gaia DR1 provides the means to examine open clusters far beyond their more easily visible cores, and can provide membership assessments based on proper motions and parallaxes. A combined HR diagram shows the same features as observed before using the Hipparcos data, with clearly increased luminosities for older A and F dwarfs.
|
|
| 17. |
- Brown, A. G. A., et al.
(author)
-
Gaia Data Release 1 Summary of the astrometric, photometric, and survey properties
- 2016
-
In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 595
-
Journal article (peer-reviewed)abstract
- Context. At about 1000 days after the launch of Gaia we present the first Gaia data release, Gaia DR1, consisting of astrometry and photometry for over 1 billion sources brighter than magnitude 20.7. Aims. A summary of Gaia DR1 is presented along with illustrations of the scientific quality of the data, followed by a discussion of the limitations due to the preliminary nature of this release. Methods. The raw data collected by Gaia during the first 14 months of the mission have been processed by the Gaia Data Processing and Analysis Consortium (DPAC) and turned into an astrometric and photometric catalogue. Results. Gaia DR1 consists of three components: a primary astrometric data set which contains the positions, parallaxes, and mean proper motions for about 2 million of the brightest stars in common with the HIPPARCOS and Tycho-2 catalogues - a realisation of the Tycho-Gaia Astrometric Solution (TGAS) - and a secondary astrometric data set containing the positions for an additional 1.1 billion sources. The second component is the photometric data set, consisting of mean G-band magnitudes for all sources. The G-band light curves and the characteristics of similar to 3000 Cepheid and RR Lyrae stars, observed at high cadence around the south ecliptic pole, form the third component. For the primary astrometric data set the typical uncertainty is about 0.3 mas for the positions and parallaxes, and about 1 mas yr(-1) for the proper motions. A systematic component of similar to 0.3 mas should be added to the parallax uncertainties. For the subset of similar to 94 000 HIPPARCOS stars in the primary data set, the proper motions are much more precise at about 0.06 mas yr(-1). For the secondary astrometric data set, the typical uncertainty of the positions is similar to 10 mas. The median uncertainties on the mean G-band magnitudes range from the mmag level to similar to 0.03 mag over the magnitude range 5 to 20.7. Conclusions. Gaia DR1 is an important milestone ahead of the next Gaia data release, which will feature five-parameter astrometry for all sources. Extensive validation shows that Gaia DR1 represents a major advance in the mapping of the heavens and the availability of basic stellar data that underpin observational astrophysics. Nevertheless, the very preliminary nature of this first Gaia data release does lead to a number of important limitations to the data quality which should be carefully considered before drawing conclusions from the data.
|
|
| 18. |
|
|
| 19. |
|
|
| 20. |
|
|
| 21. |
- Abreu, P., et al.
(author)
-
Search for sleptons in e+e- collisions at √s = 183 to 189 GeV
- 2001
-
In: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 19:1, s. 29-42
-
Journal article (peer-reviewed)abstract
- Data taken by the DELPHI experiment at centre-of-mass energies of 183 GeV and 189 GeV with a total integrated luminosity of 212 pb-1 have been used to search for the supersymmetric partners of the electrons, muons, and taus in the context of the Minimal Supersymmetric Standard Model (MSSM). The decay topologies searched for were the direct decay (ℓ̃ → ℓx̃), producing acoplanar lepton pairs plus missing energy, and the cascade decay (ℓ → ℓx̃0 2 → ℓγx̃0 1), producing acoplanar lepton and photon pairs plus missing energy. The observed number of events is in agreement with Standard Model predictions. The 95% CL excluded mass limits for selectrons, smuons and staus are mẽ ≤ 87 GeV/c2, mμ̃ ≤ 80 GeV/c2 and mτ̃ 75 GeV/c2, respectively, for values of μ=-200 GeV/c2 and tanβ=1.5.
|
|
| 22. |
|
|
| 23. |
- Abreu, P., et al.
(author)
-
Measurement of the gluon fragmentation function and a comparison of the scaling violation in gluon and quark jets
- 2000
-
In: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 13:4, s. 573-589
-
Journal article (peer-reviewed)abstract
- The fragmentation functions of quarks and gluons are measured in various three-jet topologies in Z decays from the full data set collected with the DELPHI detector at the Z resonance between 1992 and 995. The results at different values of transverse momentum-like scales are compared. A parameterization of the quark and gluon fragmentation functions at a fixed reference scale is given. The quark and gluon fragmentation functions show the predicted pattern of scaling violations. The scaling violation for quark jets as a function of a transverse momentum-like scale is in a good agreement with that observed in lower energy e+e- annihilation experiments. For gluon jets it appears to be significantly stronger. The scale dependences of the gluon and quark fragmentation functions agree with the prediction of the DGLAP evolution equations from which the colour factor ratio CA/CF is measured to be: CA/CF = 2.26 ± 0.09stat. ± 0.06sys. ± 0.12clus.,scale..
|
|
| 24. |
- Abreu, P., et al.
(author)
-
Study of dimuon production in photon-photon collisions and measurement of QED photon structure functions at LEP
- 2001
-
In: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 19:1, s. 15-28
-
Journal article (peer-reviewed)abstract
- Muon pair production in the process e+e- → e+e- μ+μ- is studied using the data taken at LEP1 (√s ≃ mz) with the DELPHI detector during the years 1992-1995. The corresponding integrated luminosity is 138.5 pb-1. The QED predictions have been tested over the whole Q2 range accessible at LEP1 (from several GeV2/c4 to several hundred GeV2/c4) by comparing experimental distributions with distributions resulting from Monte Carlo simulations using various generators. Selected events are used to extract the leptonic photon structure function Fγ 2. Azimuthal correlations are used to obtain information on additional structure functions, Fγ A and Fγ B, which originate from interference terms of the scattering amplitudes. The measured ratios Fγ A/Fγ 2 and FγB/Fγ 2 are significantly different from zero and consistent with QED predictions.
|
|
| 25. |
|
|
| 26. |
|
|
| 27. |
- Abdallah, J., et al.
(author)
-
Study of double-tagged gamma gamma events at LEPII
- 2006
-
In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 46:3, s. 559-568
-
Journal article (peer-reviewed)abstract
- Double-tagged interactions of photons with virtualities Q(2) between 10 GeV2 and 200 GeV2 are studied with the data collected by DELPHI at LEPII from 1998 to 2000, corresponding to an integrated luminosity of 550 pb(-1). The gamma*gamma* -> mu(+)mu(-) data agree with QED predictions. The cross-section of the reaction gamma*gamma* -> hadrons is measured and compared to the LO and NLO BFKL calculations.
|
|
| 28. |
|
|
| 29. |
|
|
| 30. |
|
|
| 31. |
- Abdallah, J., et al.
(author)
-
A measurement of the tau hadronic branching ratios
- 2006
-
In: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 46:1, s. 1-26
-
Journal article (peer-reviewed)abstract
- The exclusive and semi-exclusive branching ratios of the tau lepton hadronic decay modes (h(-)upsilon(tau), h(-)pi(0)upsilon(tau), h(-)pi(0)pi(0)upsilon(tau), h(-) >= 2 pi(0)nu(tau), 2h(-)h(+)upsilon(tau), 2h(-)h(+)>= 2 pi(0)upsilon(tau), 3h(-)2h(+)upsilon(tau) and 3h(-)2h(+) >= 1 pi(0)upsilon(tau)) were measured with data from the DELPHI detector at LEP.
|
|
| 32. |
- Abdallah, J, et al.
(author)
-
A precise measurement of the B+, B-0 and mean b-hadron lifetime with the DELPHI detector at LEP I
- 2004
-
In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 33:3, s. 307-324
-
Journal article (peer-reviewed)abstract
- Final results from the DELPHI Collaboration on the lifetime of B+ and B-0 mesons and the mean b-hadron lifetime, are presented using the data collected at the Z(0) peak in 1994 and 1995. Elaborate, inclusive, secondary vertexing methods have been employed to ensure a b-hadron reconstruction with good efficiency. To separate samples of B+ and B-0 mesons, high performance neural network techniques are used that achieve very high purity signals. The results obtained are: tau(B+) = 1.624+/-0.014 (stat)+/-0.018 (syst) ps tau(B)0 = 1.531+/-0.021 (stat)+/-0.031 (syst) ps tau(B+)/tau(B)0 = 1.060+/-0.021 (stat)+/-0.024 (syst) and for the average b-hadron lifetime: taub/tau(B)0 = 1.570+/-0.005 (stat)+/-0.008 (syst) ps.
|
|
| 33. |
- Abdallah, J, et al.
(author)
-
Bose-Einstein correlations in W+W- events at LEP2
- 2005
-
In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 44:2, s. 161-174
-
Journal article (peer-reviewed)abstract
- Bose-Einstein correlations (BEC) between final state particles in the reaction e(+)e(-) -> W+ W- -> q(1)(q(2)) over barq(3)(q(4)over bar>) over bar) have been studied. Data corresponding to a total integrated luminosity of 550 pb(-1), recorded by the DELPHI detector at centre-of-mass energies ranging from 189 to 209 GeV, were analysed. An indication for inter-W BEC between like-sign particles has been found at the level of 2.4 standard deviations of the combined statistical and systematic uncertainties.
|
|
| 34. |
- Abdallah, J, et al.
(author)
-
Determination of the e(+)e(-)->gamma gamma(gamma) cross-section at LEP 2
- 2004
-
In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 37:4, s. 405-419
-
Journal article (peer-reviewed)abstract
- A test of the benchmark QED process e(+) e(-) -->gammagamma(gamma) is reported, using the data collected with the DELPHI detector at LEP 2. The data analysed were recorded at centre-of-mass energies ranging from 161 GeV to 208 GeV and correspond to a total integrated luminosity of 656.4 pb(-1). The Born cross-section for the process e(+) e(-)-->gammagamma(gamma) was determined, confirming the validity of QED at the highest energies ever attained in electron-positron collisions. Lower limits on the parameters of a number of possible deviations from QED, predicted within theoretical frameworks expressing physics beyond the Standard Model, were derived.
|
|
| 35. |
- Abdallah, J, et al.
(author)
-
Measurement of the energy dependence of hadronic jet rates and the strong coupling alpha(s) from the four-jet rate with the DELPHI detector at LEP
- 2005
-
In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 38:4, s. 413-426
-
Journal article (peer-reviewed)abstract
- Hadronic events from the data collected with the DELPHI detector at LEP within the energy range from 89 GeV to 209 GeV are selected, their jet rates are determined and compared to predictions of four different event generators. One of them is the recently developed APACIC++ generator which performs a massive matrix element calculation matched to a parton shower followed by string fragmentation. The four-jet rate is used to measure alpha(s) in the next-to-leading-order approximation yielding alpha(s)(M-Z(2)) = 0.1175 +/- 0.0030. The running of alpha(s) determined by using four-jet events has been tested. The logarithmic energy slope is measured to be dalpha(s)(-1)/d log E-cm = 1.14 +/- 0.36. Since the analysis is based on four-jet final states it represents an alternative approach to previous DELPHI alpha(s) measurements using event shape distributions.
|
|
| 36. |
- Abdallah, J, et al.
(author)
-
Measurement of the forward-backward asymmetries of e(+)e(-)-> Z -> b(b)over-bar and e(+)e(-)-> Z -> c(c)over-bar using prompt leptons
- 2004
-
In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 34:2, s. 109-125
-
Journal article (peer-reviewed)abstract
- The forward-backward asymmetries of the processes e(+) e(-) --> Z --> b (b) over bar and e(+)e(-) --> Z --> c (c) over bar were measured from a sample of hadronic Z decays collected by the DELPHI experiment between 1993 and 1995. Enriched samples of b (b) over bar and c (c) over bar events were obtained using lifetime information. The tagging of b and c quarks in these samples was based on the semileptonic decay channels b/c --> X + mu and b/c --> X + e combined with charge flow information from the hemisphere opposite to the lepton. Combining the A(FB)(b (b) over bar) and A(FB)(c (c) over bar) measurements presented in this paper with published results based on 1991 and 1992 DELPHI data samples, the following pole asymmetries were obtained: A(FB)(0,b) = 0.1021 +/- 0.0052 (stat) +/- 0.0024 (syst) A(FB)(0,c) = 0.0728 +/- 0.0086 (stat) +/- 0.0063 (syst) The effective value of the weak mixing angle derived from these measurements is sin(2) theta(W,eff)(lept) = 0.23170 +/- 0.00097.
|
|
| 37. |
- Abdallah, J, et al.
(author)
-
Measurement of the W-pair production cross-section and W branching ratios in e(+)e(-) collisions at root s=161-209 GeV
- 2004
-
In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 34:2, s. 127-144
-
Journal article (peer-reviewed)abstract
- These final results on e(+) e(-) W+ W- production cross-section measurements at LEP2 use data collected by the DELPHI detector at centre-of-mass energies up to 209 GeV. Measurements of total cross-sections, W angular differential distributions and decay branching fractions, and the value of the CKM element |V-cs| are compared to the expectations of the Standard Model. These results supersede all values previously published by DELPHI.
|
|
| 38. |
- Abdallah, J, et al.
(author)
-
Measurement of vertical bar Vcb vertical bar using the semileptonic decay (B)d(0))over-bar -> D*+l(-)(nu)over-barl
- 2004
-
In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 33:2, s. 213-232
-
Journal article (peer-reviewed)abstract
- Data from Z decays in DELPHI have been searched for <(B-d(o))over bar> --> D*+ l(-) (ν) over bar (l) with the D*+ decaying to D(0)pi(+) and D-0 --> K(-)pi(+), K(-)pi(+)pi(+)pi(-) or K- pi(+)(pi(0)). These events are used to measure the CKM matrix element V-cb and the form factor slope, rho(A1)(2): F-D*(1) V-cb = 0.0392 +/- 0.0018 +/- 0.0023; rho(A1)(2) = 1.32 +/- 0.15 +/- 0.33 corresponding to a branching fraction: BR(<(B-d(0))over bar> --> D(*+)l(-)(ν) over bar (l)) = (5.90 +/- 0.22 +/- 0.50)%. Combining these and previous DELPHI measurements gives: FD*(1)V-cb = 0.0377 +/- 0.0011 +/- 0.0019, rho(A1)(2) = 1.39 +/- 0.10 +/- 0.33 and BR(<(B-d(0))over bar> --> D(*+)l(-)(ν) over bar (l)) = (5.39 +/- 0.11 +/- 0.34)% Using F-D*(1) = 0.91 +/- 0.04, yields: V-cb = 0.0414 +/- 0.0012(stat.) +/- 0.0021(syst.) +/- 0.0018 (theory). The b-quark semileptonic branching fraction into a D*+ emitted from higher mass charmed excited states has also been measured to be: BR(b --> D*+ Xl(-)(ν) over bar (l)) = (0.67 +/- 0.08 +/- 0.10)%.
|
|
| 39. |
- Abdallah, J, et al.
(author)
-
Search for B-s(0)-(B-s(0))over-bar oscillations in DELPHI using high-p(t) leptons
- 2004
-
In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 35:1, s. 35-52
-
Journal article (peer-reviewed)abstract
- Oscillations in the B-s(0)- <(B-s(0))over bar> system were studied in events selected from about 4.3 million hadronic Z(0) decays registered by DELPHI between 1992 and 2000. This paper presents updates of two published analyses ([11, 12]). The first analysis, which utilizes leptons emitted with large momentum transverse to a jet, was improved by means of a better algorithm for the vertex reconstuction and a new algorithm for flavour-tagging at production time. The second analysis, which utilizes D-s-lepton events, was improved by optimizing the treatment of proper time resolution. No signal of B-s(0) oscillations was observed and limits on the mass difference between the physical B-s(0) states were obtained to be: Deltam(s)>8.0 ps-1 at the 95% C.L. with a sensitivity of Deltam(s)= 9.1 ps(-1) in the high p(t) lepton analysis and Deltam(s)>4.9 ps(-1) at the 95% C.L. with a sensitivity of Deltam(s)=8.6 ps(-1) in the D-s-lepton analysis. Previously published results on these analyses are superseded. The combination of these results with those obtained in other independent analyses previously performed in DELPHI (D-s-hadron, exclusive B-s(0), inclusive vertex) gives: Deltam(s)>8.5 ps(-1) at the 95% C.L. with a sensitivity of Deltam(s)=12.0 ps(-1).
|
|
| 40. |
- Abdallah, J., et al.
(author)
-
Search for excited leptons in e(+)e(-) collisions at root s=189-209 GeV
- 2006
-
In: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 46:2, s. 277-293
-
Journal article (peer-reviewed)abstract
- A search for excited lepton production in e(+)e(-) collisions was performed using the data collected by the DELPHI detector at LEP at centre-of-mass energies ranging from 189 GeV to 209 GeV, corresponding to an integrated luminosity of approximately 600 pb(-1). No evidence for excited lepton production was found. In searches for pair-produced excited leptons, lower mass limits were established in the range 94-103 GeV/c(2), depending on the channel and model assumptions. In searches for singly-produced excited leptons, upper limits on the parameter f/Lambda were established as a function of the mass.
|
|
| 41. |
- Abdallah, J, et al.
(author)
-
Search for SUSY in the AMSB scenario with the DELPHI detector
- 2004
-
In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 34:2, s. 145-156
-
Journal article (peer-reviewed)abstract
- The DELPHI experiment at the LEP e (+) e(-) collider collected almost 700 pb(-1) at centre-of-mass energies above the Z(0) mass pole and up to 208 GeV. Those data were used to search for SUSY in the Anomaly Mediated SUSY Breaking (AMSB) scenario with a flavour independent common sfermion mass parameter. The searches covered several possible signatures experimentally accessible at LEP, with either the neutralino, the sneutrino or the stau being the Lightest Supersymmetric Particle (LSP). They included: the search for nearly mass-degenerate chargino and neutralino, which is a typical feature of AMSB; the search for Standard-Model-like or invisibly decaying Higgs boson; the search for stable staus; the search for cascade decays of SUSY particles resulting in the LSP and a low multiplicity final state containing neutrinos. No evidence of a signal was found, and thus constraints were set in the space of the parameters of the model.
|
|
| 42. |
- Abdallah, J., et al.
(author)
-
A determination of the centre-of-mass energy at LEP2 using radiative two-fermion events
- 2006
-
In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 46:2, s. 295-305
-
Journal article (peer-reviewed)abstract
- Using e(+)e(-) -> mu(+)mu(-)(gamma) and e(+)e(-) -> q (q) over bar(gamma) events radiative to the Z pole, DELPHI has determined the centre-of-mass energy, root s, using energy and momentum constraint methods. The results are expressed as deviations from the nominal LEP centre-of-mass energy, measured using other techniques. The results are found to be compatible with the LEP Energy Working Group estimates for a combination of the 1997 to 2000 data sets.
|
|
| 43. |
- Abdallah, J, et al.
(author)
-
A precise measurement of the tau lifetime
- 2004
-
In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 36:3, s. 283-296
-
Journal article (peer-reviewed)abstract
- The tau lepton lifetime has been measured with the e(+) e(-) --> tau(+) tau(-) events collected by the DELPHI detector at LEP in the years 1991 - 1995. Three different methods have been exploited, using both one-prong and three-prong tau decay channels. Two measurements have been made using events in which both taus decay to a single charged particle. Combining these measurements gave tau(tau) ( 1 prong) = 291.8 +/- 2.3(stat) +/- 1.5(sys) fs. A third measurement using taus which decayed to three charged particles yielded tau(tau) (3 prong) = 288.6 +/- 2.4(stat) +/- 1.3(sys) fs. These were combined with previous DELPHI results to measure the tau lifetime, using the full LEP1 data sample, to be tau(tau) = 290.9 +/- 1.4(stat) +/- 1.0(sys) fs.
|
|
| 44. |
- Abdallah, J, et al.
(author)
-
A study of the energy evolution of event shape distributions and their means with the DELPHI detector at LEP
- 2003
-
In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 29:3, s. 285-312
-
Journal article (peer-reviewed)abstract
- Infrared and collinear safe event shape distributions and their mean values are determined in e(+)e(-) collisions at centre-of-mass energies between 45 and 202GeV. A phenomenological analysis based on power correction models including hadron mass effects for both differential distributions and mean values is presented. Using power corrections, alpha(s) is extracted from the mean values and shapes. In an alternative approach, renormalisation group invariance (RGI) is used as an explicit constraint, leading to a consistent description of mean values without the need for sizeable power corrections. The QCD beta-function is precisely measured using this approach. From the DELPHI data on Thrust, including data from low energy experiments, one finds beta(0) = 7.86 +/- 0.32 for the one loop coefficient of the beta-function or, assuming QCD, n(f) = 4.75 +/- 0.44 for the number of active flavours. These values agree well with the QCD expectation of beta(0) = 7.67 and n(f) 5. A direct measurement of the full logarithmic energy slope excludes light gluinos with a mass below 5GeV.
|
|
| 45. |
- Abdallah, J, et al.
(author)
-
Coherent soft particle production in Z decays into three jets
- 2005
-
In: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 605:1-2, s. 37-48
-
Journal article (peer-reviewed)abstract
- Low-energy particle production perpendicular to the event plane in three-jet events produced in Z decays in e(+)e(-) annihilation is measured and compared to that perpendicular to the event axis in two-jet events. The topology dependence of the hadron production ratio is found to agree with a leading-order QCD prediction. This agreement and especially the need for the presence of a destructive interference term gives evidence for the coherent nature of gluon radiation. Hadron production in three-jet events is found to be directly proportional to a single topological scale function of the inter-jet angles. The slope of the dependence of the multiplicity with respect to the topological scale was measured to be 2.211 +/- 0.014(stat.) +/- 0.053(syst.) in good agreement with the expectation given by the colour-factor ratio C-A/C-F = 9/4. This result strongly supports the assumption of local parton-hadron duality, LPHD, at low hadron momentum.
|
|
| 46. |
- Abdallah, J., et al.
(author)
-
Determination of the b quark mass at the M-Z scale with the DELPHI detector at LEP
- 2006
-
In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 46:3, s. 569-583
-
Journal article (peer-reviewed)abstract
- An experimental study of the normalized three-jet rate of b quark events with respect to light quarks events (light = l equivalent to u, d, s) has been performed using the CAMBRIDGE and DURHAM jet algorithms. The data used were collected by the DELPHI experiment at LEP on the Z peak from 1994 to 2000. The results are found to agree with theoretical predictions treating mass corrections at next-to-leading order. Measurements of the b quark mass have also been performed for both the b pole mass: M-b and the b running mass: m(b)(M-Z). Data are found to be better described when using the running mass. The measurement yields: m(b)(M-Z) = 2.85 +/- 0.18(stat) +/- 0.13(exp) +/- 0.19(had) +/- 0.12(theo) GeV/c(2). for the CAMBRIDGE algorithm. This result is the most precise measurement of the b mass derived from a high energy process. When compared to other b mass determinations by experiments at lower energy scales, this value agrees with the prediction of quantum chromodynamics for the energy evolution of the running mass. The mass measurement is equivalent to a test of the flavour independence of the strong coupling constant with an accuracy of 7 parts per thousand.
|
|
| 47. |
- Abdallah, J., et al.
(author)
-
Di-jet production in gamma gamma collisions at LEP2
- 2008
-
In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; C:58, s. 531-541
-
Journal article (peer-reviewed)
|
|
| 48. |
- Abdallah, J., et al.
(author)
-
Evidence for an excess of soft photons in hadronic decays of Z(0)
- 2006
-
In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 47:2, s. 273-294
-
Journal article (peer-reviewed)abstract
- Soft photons inside hadronic jets converted in front of the DELPHI main tracker (TPC) in events of qq disintegrations of the Z(0) were studied in the kinematic range 0.2 < E-y < I GeV and transverse momentum with respect to the closest jet direction P-T < 80 MeV/c. A clear excess of photons in the experimental data as compared to the Monte Carlo predictions is observed. This excess (uncorrected for the photon detection efficiency) is (1.17 +/- 0.06 +/- 0.27) x 10(-3) gamma/jet in the specified kinematic region, while the expected level of the inner hadronic bremsstrahlung (which is not included in the Monte Carlo) is (0.340 +/- 0.001 +/- 0.038) X 10(-3) gamma/jet. The ratio of the excess to the predicted bremsstrahlung rate is then (3.4 +/- 0.2 +/- 0.8), which is similar in strength to the anomalous soft photon signal observed in fixed target experiments with hadronic beams.
|
|
| 49. |
- Abdallah, J, et al.
(author)
-
Final results from DELPHI on the searches for SM and MSSM neutral Higgs bosons
- 2004
-
In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 32:2, s. 145-183
-
Journal article (peer-reviewed)abstract
- These final results from DELPHI searches for the Standard Model (SM) Higgs boson, together with benchmark scans of the Minimal Supersymmetric Standard Model (MSSM) neutral Higgs bosons, used data taken at centre-of-mass energies between 200 and 209 GeV with a total integrated luminosity of 224 pb(-1). The data from 192 to 202 GeV are reanalysed with improved b-tagging for MSSM final states decaying to four b-quarks. The 95% confidence level lower mass bound on the Standard Model Higgs boson is 114.1 GeV/c(2). Limits are also given on the lightest scalar and pseudo-scalar Higgs bosons of the MSSM.
|
|
| 50. |
- Abdallah, J., et al.
(author)
-
Higgs boson searches in CP-conserving and CP-violating MSSM scenarios with the DELPHI detector
- 2008
-
In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; C:54, s. 1-35
-
Journal article (peer-reviewed)abstract
- This paper presents the final interpretation of the results from DELPHI on the searches for Higgs bosons in the minimal supersymmetric extension of the Standard Model (MSSM). A few representative scenarios are considered, that include CP conservation and explicit CP violation in the Higgs sector. The experimental results encompass the searches for neutral Higgs bosons at LEP1 and LEP2 in final states as expected in the MSSM, as well as LEP2 searches for charged Higgs bosons and for neutral Higgs bosons decaying into hadrons independent of the quark flavour. The data reveal no significant excess with respect to background expectations. The results are translated into excluded regions of the parameter space in the various scenarios. In the CP-conserving case, these lead to limits on the masses of the lightest scalar and pseudoscalar Higgs bosons, h and A, and on tan beta. The dependence of these limits on the top quark mass is discussed. Allowing for CP violation reduces the experimental sensitivity to Higgs bosons. It is shown that this effect depends strongly on the values of the parameters responsible for CP violation in the Higgs sector.
|
|
