1,722,734 research outputs found
Observation of and atoms
No full textThe observation of hydrogen-like atoms, consisting of or mesons, is presented. The atoms have been produced by 24 GeV/ protons from the CERN PS accelerator, interacting with platinum or nickel foil targets. The breakup (ionisation) of atoms in the same targets yields characteristic pairs, called ``atomic pairs'', with small relative momenta in the pair centre-of-mass system. The upgraded DIRAC experiment has observed such atomic pairs, corresponding to a signal of 5.6 standard deviations.The observation of hydrogenlike πK atoms, consisting of π-K+ or π+K- mesons, is presented. The atoms are produced by 24 GeV/c protons from the CERN PS accelerator, interacting with platinum or nickel foil targets. The breakup (ionization) of πK atoms in the same targets yields characteristic πK pairs, called “atomic pairs,” with small relative momenta Q in the pair center-of-mass system. The upgraded DIRAC experiment observed 349±62 such atomic πK pairs, corresponding to a signal of 5.6 standard deviations. This is the first statistically significant observation of the strange dimesonic πK atom.The observation of hydrogen-like atoms, consisting of or mesons, is presented. The atoms have been produced by 24 GeV/ protons from the CERN PS accelerator, interacting with platinum or nickel foil targets. The breakup (ionisation) of atoms in the same targets yields characteristic pairs, called "atomic pairs", with small relative momenta in the pair centre-of-mass system. The upgraded DIRAC experiment has observed such atomic pairs, corresponding to a signal of 5.6 standard deviations
First atom lifetime and scattering length measurements
No full textThe results of a search for hydrogen-like atoms consisting of mesons are presented. Evidence for atom production by 24 GeV/c protons from CERN PS interacting with a nickel target has been seen in terms of characteristic pairs from their breakup in the same target () and from Coulomb final state interaction (). Using these results the analysis yields a first value for the atom lifetime of fs and a first model-independent measurement of the S-wave isospin-odd scattering length ( for isospin ).The results of a search for hydrogen-like atoms consisting of mesons are presented. Evidence for atom production by 24 GeV/c protons from CERN PS interacting with a nickel target has been seen in terms of characteristic pairs from their breakup in the same target (178±49) as well as in terms of produced πK atoms ( 653±42 ). Using these results, the analysis yields a first value for the πK atom lifetime of fs and a first measurement of the S-wave isospin-odd scattering length ( for isospin ).The results of a search for hydrogen-like atoms consisting of mesons are presented. Evidence for atom production by 24 GeV/c protons from CERN PS interacting with a nickel target has been seen in terms of characteristic pairs from their breakup in the same target () and from Coulomb final state interaction (). Using these results the analysis yields a first value for the atom lifetime of fs and a first model-independent measurement of the S-wave isospin-odd scattering length ( for isospin )
Measurement of the atom lifetime and the scattering length
No full textAfter having announced the statistically significant observation (5.6~) of the new exotic atom, the DIRAC experiment at the CERN proton synchrotron presents the measurement of the corresponding atom lifetime, based on the full data sample: . By means of a precise relation () between atom lifetime and scattering length, the following value for the S-wave isospin-odd scattering length has been derived: .After having announced the statistically significant observation (5.6~) of the new exotic atom, the DIRAC experiment at the CERN proton synchrotron presents the measurement of the corresponding atom lifetime, based on the full data sample: . By means of a precise relation () between atom lifetime and scattering length, the following value for the S-wave isospin-odd scattering length has been derived:
The Puzzle: A Status Report
No full textWe discuss the theoretical interpretation of the system in the light of new data. Using the branching ratio and direct CP asymmetry of , the picture of the direct CP violation in could be clarified: we predict , which favours the BaBar measurement, and extract , in agreement with the Standard-Model fits of the unitarity triangle. All modes with colour-suppressed electroweak penguin contributions are found in excellent agreement with the Standard Model. The data for the ratios of the charged and neutral branching ratios, which are sizeably affected by electroweak penguin contributions, have moved quite a bit towards the Standard-Model predictions, which are almost unchanged, thereby reducing the " puzzle". On the other hand, the mixing-induced CP violation of still looks puzzling and could be accommodated through a modified electroweak penguin sector with a large CP-violating new-physics phase, while the observed non-vanishing difference between the direct CP asymmetries of and seems to be caused by hadronic and not by new physics.We discuss the theoretical interpretation of the system in the light of new data. Using the branching ratio and direct CP asymmetry of , the picture of the direct CP violation in could be clarified: we predict , which favours the BaBar measurement, and extract , in agreement with the Standard-Model fits of the unitarity triangle. All modes with colour-suppressed electroweak penguin contributions are found in excellent agreement with the Standard Model. The data for the ratios of the charged and neutral branching ratios, which are sizeably affected by electroweak penguin contributions, have moved quite a bit towards the Standard-Model predictions, which are almost unchanged, thereby reducing the puzzle. On the other hand, the mixing-induced CP violation of still looks puzzling and could be accommodated through a modified electroweak penguin sector with a large CP-violating new-physics phase, while the observed non-vanishing difference between the direct CP asymmetries of and seems to be caused by hadronic and not by new physics
Energy and decay width of the pi-K atom
No full text37 pages, 5 figures, uses Axodraw - PTHThe energy and decay width of the pi-K atom are evaluated in the framework of the quasipotential-constraint theory approach. The main electromagnetic and isospin symmetry breaking corrections to the lowest-order formulas for the energy shift from the Coulomb binding energy and for the decay width are calculated. They are estimated to be of the order of a few per cent. We display formulas to extract the strong interaction S-wave pi-K scattering lengths from future experimental data concerning the pi-K atom
Investigation of and atoms for pion-pion and pion-kaon scattering length measurements
No full textTheory, using Low Energy QCD, calculated with high precision the and scattering length. Lifetime of atoms are related with a difference of pion-pion s-wave scattering lengths with isospin 0 and 2: . Energy splitting between p-states (long-lived atoms) and s-states of atoms allows to investigate another combination: . Lifetime of atoms gives information about difference of pion-kaon s-wave scattering lengths with isospin 1/2 and 3/2: . Experimental measurements of pion-kaon lifetimes and observation of long-lived atoms at experiment DIRAC are presente
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Axion-like particles resolve the and g-2 anomalies
Get PDFWe offer a new solution to an old puzzle in the penguin-dominated
decays. The puzzle is the inconsistency among the measurements of the branching
ratios and CP asymmetries of the four decays: ,
, , . We solve the
puzzle by considering the effect of an axion-like particle (ALP)
that mixes with the and has mass close to the mass. We show
that the ALP can also explain the anomalies in the electron and muon anomalous
magnetic moments.Comment: 6 pages, 3 tables. Version to appear as a Letter in PR
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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