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1.
The scalar mesons in the 1 GeV region constitute the Higgs sector of the strong interactions. They are responsible for the
masses of all light flavour hadrons. However, the composition of these scalar states is far from clear, despite decades of
experimental effort. The two photon couplings of the 's are a guide to their structure. Two photon results from Mark II, Crystal Ball and CELLO prompt a new Amplitude Analysis
of , cross-sections. Despite their currently limited angular coverage and lack of polarized photons, we use a methodology that
provides the nearest one can presently achieve to a model-independent partial wave separation. We find two distinct classes
of solutions. Both have very similar two photon couplings for the and . Hopefully these definitive results will be a spur to dynamical calculations that will bring us a better understanding of
these important states.
Received: 10 Decmeber 1998 / Published online: 27 April 1999 相似文献
2.
Nils A. Törnqvist 《Foundations of Physics》1981,11(1-2):171-177
Since weakly decaying particles are their own polarimeters, reactions like \(\eta _c \to \Lambda \bar \Lambda , \psi \to \Lambda \bar \Lambda ,e^ + e^ - \to \mu ^ + \mu ^ -\) , etc. are interesting for testing the non-locality of quantum mechanical predictions. Although such reactions, in principle, do not exclude all classes of hidden variable theories, they can be used to complement current experiments with external polarimeters. The reaction \(\eta _c \to \Lambda \bar \Lambda \to \pi ^ - p\pi ^{ + - } \bar p\) is conceptually the simplest and most useful as agedanken experiment, although it has not yet been seen experimentally. The reaction \(e^ + e^ - \to \Lambda \bar \Lambda \to \pi ^ - p\pi ^ + \bar p\) near threshold or at the φ resonance can be used for essentially the same test. This is feasible with presently available data and would be the first EPR experiment involving weak interactions. 相似文献
3.
S. Abdel-Samad J. Bojowald A. Budzanowski A. Chatterjee J. Ernst D. Frekers P. Hawranek J. Ilieva L. Jarczyk K. Kilian S. Kliczewski W. Klimala D. Kolev M. Kravcíková T. Kutsarova J. Lieb H. Machner A. Magiera G. Martinská H. Nann L. Pentchev D. Protic P. von Rossen B. J. Roy R. Siudak A. Strzalkowski R. Tsenov M. Ulicný J. Urbán K. Zwoll 《The European Physical Journal A - Hadrons and Nuclei》2003,18(2-3):367-370
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We present a general parametrization of , and , decays, taking into account both electroweak penguin and rescattering effects. This formalism allows – among other things
– a generalized implementation of the strategies that were recently proposed by Neubert and Rosner to probe the CKM angle
with the help of , decays. In particular, it allows us to investigate the sensitivity of the extracted value of to the basic assumptions of their approach. We find that certain rescattering processes may have an important impact and
emphasize that additional hadronic uncertainties may be due to non-factorizable SU(3)-breaking effects. The former can be controlled by using SU(3) flavour symmetry arguments and additional experimental information provided by modes. We propose a new strategy to probe the angle with the help of the neutral decays , , which is theoretically cleaner than the , approach. Here rescattering processes can be taken into account by just measuring the CP-violating observables of the decay
. Finally, we point out that an experimental analysis of modes would also be very useful to probe the CKM angle , as well as electroweak penguins, and we critically compare the virtues and weaknesses of the various approaches discussed
in this paper. As a by-product, we point out a strategy to include the electroweak penguins in the determination of the CKM
angle from decays.
Received: 14 June 1999 / Published online: 28 September 1999 相似文献
6.
The reaction $e^ + e^ - \to \gamma \pi ^0 \to \gamma v\overline v $ is considered. It is shown that this reaction possesses a clear signature, producing in the resonance region practically monochromatic photons, which can easily be distinguished from background bremsstrahlung photons. Since the cross section of the reaction is proportional to the square of the neutrino mass, such a reaction can be used as a probe for neutrino mass. 相似文献
7.
The process \(\pi ^0 \to \lambda _\gamma \bar \lambda _\gamma \) is investigated as an alternative to \(\pi ^0 \to v\bar v\) . It is shown that the experimental bound on the branching fraction for missing energy (in the form of \(\lambda _\gamma \bar \lambda _\gamma \) and/or \(v\bar v\) ) may be understood in terms of \(\pi ^0 \to \lambda _\gamma \bar \lambda _\gamma \) for the kinematically allowed photino mass, if the squark mass is >8 GeV. 相似文献
8.
We applied QCD light-cone sum rules to estimate power corrections to the helicity-conserving amplitude in the process . We found that above GeV power corrections are numerically small and the twist-2 part dominates.The amplitude can be reliably calculated in this region
using models of distribution amplitudes as input. We found that the magnitude of the NLO corrections depends rather strongly on the normalization
of the gluonic distribution amplitude. 相似文献
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M.N. Achasov A.V. Berdyugin A.V. Bozhenok D.A. Bukin S.V. Burdin T.V. Dimova V.P. Druzhinin M.S. Dubrovin I.A. Gaponenko V.B. Golubev V.N. Ivanchenko A.A. Korol S.V. Koshuba E.V. Pakhtusova A.A. Salnikov S.I. Serednyakov V.V. Shary Yu.M. Shatunov V.A. Sidorov Z.K. Silagadze 《The European Physical Journal C - Particles and Fields》2000,12(1):25-33
11.
H. Pichl 《The European Physical Journal C - Particles and Fields》2001,20(2):371-388
The branching ratios of the measured decay and of the still unmeasured decay are calculated to next-to-leading order in chiral perturbation theory (CHPT). Recent experimental results are used to determine
two possible values of the combination of weak low-energy couplings (LECs) from the chiral Lagrangian. The values obtained are compared to the predictions of theoretical approaches to weak counterterm couplings
to distinguish between the two values. Using the favoured value of the combination and taking into account additional assumptions suggested by the considered models, one obtains the branching ratio of the
second decay as a function of the unknown combination of weak low-energy couplings. Finally, using values of the individual LECs derived from a particular model, one predicts
the branching ratio of the decay.
Received: 27 February 2001 / Published online: 11 May 2001 相似文献
12.
A. E. Kudryavtsev V. E. Tarasov J. Haidenbauer C. Hanhart J. Speth 《Physics of Atomic Nuclei》2003,66(10):1946-1952
The reactions pp → dπ + η and pn → dπ 0 η are of special interest for investigating the a 0(980) (J P=0+) resonance in the process NN → da 0 → dπη. We study some aspects of those reactions within a general formalism and also in a concrete phenomenological model. In particular, it is shown that the presence of nonresonant (i.e., without excitation of the a 0 resonance) contributions to these reactions yields nonvanishing values for specific polarization observables, i.e., to effects like those generated by a 0 0 -f 0 mixing. An experimental determination of these observables for the reaction $\vec pp \to d\pi ^ + \eta $ would provide concrete information on the magnitude of those nonresonant contributions to πη production. We also discuss the possibility of extracting information about a 0 0 -f 0 mixing from the reaction $\vec pn \to d\pi ^0 \eta $ with a polarized proton beam. 相似文献
13.
S. A. Akimenko V. N. Bolotov G. I. Britvich K. V. Datsko V. A. Duk A. P. Filin E. N. Gushchin A. V. Inyakin V. A. Khmelnikov A. S. Konstantinov V. F. Konstantinov I. Yu. Korolkov S. V. Laptev V. A. Lebedev V. M. Leontiev A. E. Mazurov V. P. Novikov V. F. Obraztsov V. A. Polyakov A. Yu. Polyarush V. E. Postoev V. I. Romanovsky V. I. Shelikhov O. G. Tchikilev V. A. Uvarov O. P. Yushchenko 《Physics of Atomic Nuclei》2007,70(4):702-708
Results of study of the $K^ - \to \pi ^0 e^ - \overline \nu \gamma $ decay at the ISTRA+ setup are presented. We observed 4476 events of this decay. The branching ratio is found to be $R = \frac{{Br(K^ - \to \pi ^0 e^ - \overline \nu _e \gamma )}}{{Br(K^ - \to \pi ^0 e^ - \overline \nu _e )}}$ = (1.81±0.03(stat.)±0.07(syst.)) × 10?2 for E*γ > 10 MeV and θ*eγ > 10°. For comparison with the previous experiment the branching ratio with cuts E*γ > 10 MeV, 0.6 < cos θ*eγ < 0.9 is calculated: R = $\frac{{Br(K^ - \to \pi ^0 e^ - \overline \nu _e \gamma )}}{{Br(K^ - \to \pi ^0 e^ - \overline \nu _e )}}$ = (0.47±0.02(stat.) ± 0.03(syst.)) × 10?2. For the cuts E*γ > 30 MeV and θ*eγ > 20°, used in most theoretical papers, Br = (3.06 ± 0.09(stat.) ± 0.14(syst.)) × 10?4. For the asymmetry we get A ξ = ?0.015 ± 0.021. At present it is the best estimate of this asymmetry. 相似文献
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Partial wave analysis of the reactions $p\bar p \to \pi \pi ,\eta \eta ,\eta \eta '$ in the region of invariant masses 1900–2400 MeV indicates the existence of four relatively narrow tensor-isoscalar resonances ? 2(1920), ? 2(2020), ? 2(2240), ? 2(2300), as well as the broad state ? 2(2000). The determined decay couplings of the broad resonance ? 2(2000) → π0π0, ηη, ηη′ satisfy the relations appropriate to those of a tensor glueball, while the couplings of other tensor states do not, thus verifying the glueball nature of ? 2(2000). 相似文献
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We study ¯pp annihilation at rest intoπφ andγφ. Rescattering by ¯K*K+K*¯K and ρ+ρ? for ¯pp→πφ states is sizable, of order (0.90 to 2.6) × 10?4 in the branching ratio, but smaller than experiment. For ¯pp→γφ the rescattering contributions are negligible, but theγφ channel is well explained by aρφ intermediate state combined with vector meson dominance. 相似文献
20.
Bauer DA Belcinski R Berg RC Bingham HH Buchanan CD Caldwell DO Chun SB Clark AR Dahl OI Daoudi M Eastman JJ Eisner AM Fairfield KH Godfrey G Greenbaum GS Hauptman JM Hofmann W Holtzapple RL Khacheryan S Knöpfle KT Kofler RR Lambert DJ Layter JG Lin WT Loken SC Lu A Lynch GR Lys JE Madaras RJ Masek GE Miller ES Nicol NA Nygren DR Oyang JY Paar HP Palounek AP Pellett DE Ronan MT Ross RR Shapiro G Shen BC Stephens RW Stevenson ML Strauss MG Sullivan MK Vernon W Wang EM Wang YX Wenzel WA 《Physical review D: Particles and fields》1993,48(9):3976-3986