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Träfflista för sökning "L773:0370 2693 OR L773:1873 2445 srt2:(1990-1999)"

Sökning: L773:0370 2693 OR L773:1873 2445 > (1990-1999)

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1.
  • Fjelstad, Jens, 1971-, et al. (författare)
  • Equivalence of Chern-Simons gauge theory and WZNW model using a BRST symmetry
  • 1999
  • Ingår i: Physics Letters B. - : Elsevier. - 0370-2693 .- 1873-2445. ; 466:2-4, s. 227-233
  • Tidskriftsartikel (refereegranskat)abstract
    • The equivalence between the Chern-Simons gauge theory on a three-dimensional manifold with boundary and the WZNW model on the boundary is established in a simple and general way using the BRST symmetry. Our approach is based on restoring gauge invariance of the Chern-Simons theory in the presence of a boundary. This gives a correspondence to the WZNW model that does not require solving any constraints, fixing the gauge or specifying boundary conditions.
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2.
  • Allasia, D, et al. (författare)
  • Inelastic J ψ production in deep inelastic scattering from hydrogen and deuterium and the gluon distribution of free nucleons
  • 1991
  • Ingår i: Physics Letters B. - : Elsevier. - 0370-2693 .- 1873-2445. ; 258:3-4, s. 493-498
  • Tidskriftsartikel (refereegranskat)abstract
    • We present results on inelastic J/PSI-production from muon interactions with hydrogen and deuterium at an incident muon energy of 280 GeV. The measured cross section ratio per nucleon for muon-induced J/PSI-production in deuterium and hydrogen was found to be R(D2/H2) = 1.01 +/- 0.15. The colour singlet model is shown to provide a good description of the observed differential cross section apart from a normalisation factor. The comparison between the observed cross section and the colour singlet model prediction allows the extraction of the gluon structure function G(chi) of the nucleon. The momentum fraction-chi of the nucleon carried by the gluon is measured in the range of chi = [0.02, 0.30]. The normalised gluon distribution of free nucleons thus found can be parametrised as chi-G(chi) = 1/2 (eta + 1)(1 - chi)eta, with eta = 5.1 +/- 0.9 (stat).
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3.
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4.
  • Amaudruz, P, et al. (författare)
  • Measurements of Rd-Rp and RCa-Rc in deep inelastic muon scattering
  • 1992
  • Ingår i: Physics Letters B. - : Elsevier. - 0370-2693 .- 1873-2445. ; 294:1, s. 120-126
  • Tidskriftsartikel (refereegranskat)abstract
    • Results are presented on the difference in R, the ratio of longitudinally to transversely polarised virtual photon absorption cross sections, for the deuteron and the proton. They are obtained by comparing the ratio of cross sections for the deep inelastic scattering of muons from deuterium and hydrogen targets at 90 and 280 GeV incident energy. The results cover the range x = 0.01 -0.30, at an average Q2 of 9 GeV2. The measured difference R(d)-R(p) shows no significant x dependence and is compatible with zero, as well as with expectations from perturbative QCD. We use the same method to obtain the difference R(Ca)-R(C) from cross section ratios measured on carbon and calcium targets at 90 and 200 GeV incident energy.
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5.
  • Amaudruz, P, et al. (författare)
  • Proton and deuteron F2 structure functions in deep inelastic muon scattering
  • 1992
  • Ingår i: Physics Letters B. - : Elsevier. - 0370-2693 .- 1873-2445. ; 295:1-2, s. 159-168
  • Tidskriftsartikel (refereegranskat)abstract
    • The structure functions F2p and F2d measured by deep inelastic muon scattering at incident energies of 90 and 280 GeV are presented. These measurements cover a large kinematic range, 0.006 less-than-or-equal-to x less-than-or-equal-to 0.6 and 0.5 less-than-or-equal-to Q2 less-than-or-equal-to 55 GeV2, and include the first precise data at small x, where large scaling violations are observed. The data agree with earlier results from SLAC and BCDMS but exhibit differences with respect to those of EMC-NA2. Extrapolations to small x of recent phenomenological parton distributions are shown to disagree with the present results.
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6.
  • Angelopoulos, A., et al. (författare)
  • K 0–KÌ„0 mass and decay-width differences : CPLEAR evaluation
  • 1999
  • Ingår i: Physics Letters B. - : Elsevier. - 0370-2693 .- 1873-2445. ; 471:2, s. 332-338
  • Tidskriftsartikel (refereegranskat)abstract
    • The CPT-violation parameters Re(δ) and Im(δ) determined recently by CPLEAR are used to evaluate the K0– mass and decay-width differences, as given by the difference between the diagonal elements of the neutral-kaon mixing matrix (M−iΓ/2). The results – GeV and GeV – are consistent with CPT invariance. The CPT invariance is also shown to hold within a few times 10−3–10−4 for many of the amplitudes describing neutral-kaon decays to different final states.
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7.
  • Apostolakis, A, et al. (författare)
  • A determination of the CP violation parameter η+- from the decay of strangeness-tagged neutral kaons
  • 1999
  • Ingår i: Physics Letters B. - : Elsevier. - 0370-2693 .- 1873-2445. ; 458:4, s. 545-552
  • Tidskriftsartikel (refereegranskat)abstract
    • LEAR offered unique opportunities to study the symmetries which exist between matter and antimatter. At variance with other approaches at this facility, CPLEAR was an experiment devoted to the study of CP, T and CPT symmetries in the neutral-kaon system. A variety of measurements allowed us to determine with high precision the parameters which describe the time evolution of the neutral kaons and their antiparticles, including decay amplitudes, and the related symmetry properties. Limits concerning quantum-mechanical predictions (EPR, coherence of the wave function) or the equivalence principle of general relativity have been obtained. An account of the main features of the experiment and its performances is given here, together with the results achieved.
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8.
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9.
  • Beausang, C W, et al. (författare)
  • Lifetimes of yrast and excited superdeformed states in Gd-150 : effect of particle-hole excitations on the deformation
  • 1998
  • Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 417:1-2, s. 13-19
  • Tidskriftsartikel (refereegranskat)abstract
    • The quadrupole moments and deformations have been measured for six superdeformed bands in Gd-150. The results indicate evidence for deformation driving properties of both the high-hi intruder and also low-N natural parity states at the superdeformed Fermi surface. Several new transitions have been identified and placed in the low spin non-yrast portion of one of the SD bands.
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10.
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11.
  • Bondar, A., et al. (författare)
  • The pp → ppπ0 reaction near the kinematical threshold
  • 1995
  • Ingår i: Physics Letters B. - : Elsevier. - 0370-2693 .- 1873-2445. ; 356:1, s. 8-12
  • Tidskriftsartikel (refereegranskat)abstract
    • The reaction pp → ppπ0 has been measured using electron-cooled protons incident on an internal gas-jet target at seven different incident beam energies, from 280.7 MeV (1 MeV above the reaction threshold) up to 310.2 MeV. The pions were measured by their decay photons. In the overlapping energy region, the measured total cross sections agree with those measured in a recent Indiana experiment. The angular distributions are consistent with a 3P0 → 1S0S0 transition in the full energy range studied. The kinematical distributions are well described when taking into account the final state and the Coulomb interactions.
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12.
  • Calén, H., et al. (författare)
  • Deuteron breakup by 1.15 GeV protons and excitation of the Δ isobar
  • 1993
  • Ingår i: Physics Letters B. - : Elsevier. - 0370-2693 .- 1873-2445. ; 303:1-2, s. 10-15
  • Tidskriftsartikel (refereegranskat)abstract
    • The pd→npp reaction has been measured using circulating 1.15 GeV protons, a gas jet target and scintillation detectors selecting scattered protons with energy above 30 MeV. The distribution of the two-proton invariant mass has a maximum at 2.13 ± 0.01 GeV/c2 and a width of 130 ± 10 MeV/c2 (FWHM). We see no evidence of narrow (Γ < 30 MeV/c2) peaks in the phase-space region selected. The mass of X, excited in the pN→nX elementary process, is 40 MeV/c2 smaller than the mass of a real Δ isobar.
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13.
  • Calén, H., et al. (författare)
  • The pp → ppη reaction near the kinematical threshold
  • 1996
  • Ingår i: Physics Letters B. - : Elsevier. - 0370-2693 .- 1873-2445. ; 366:1-4, s. 39-43
  • Tidskriftsartikel (refereegranskat)abstract
    • The pp → ppη reaction has been measured at six energies close to threshold, from 1258 MeV to 1352 MeV, using an internal cluster gas jet target in the CELSIUS storage ring. The η is detected through its decay photons, in an array of CsI detectors, and the forward-going protons are detected in a plastic scintillator spectrometer. A complete event reconstruction is obtained at the higher energies in the measured interval. The new data, together with earlier data, give an accurate determination of the energy dependence close to threshold. The influence of the η-proton FSI is seen in the total cross section data as well as in a Dalitz plot of the η-p invariant mass distributions.
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14.
  • Carius, Staffan, et al. (författare)
  • The log-normal distribution for cascade multiplicities in hadron collisions
  • 1990
  • Ingår i: Physics Letters B. - : Elsevier. - 0370-2693 .- 1873-2445. ; 252:4, s. 647-652
  • Tidskriftsartikel (refereegranskat)abstract
    • We introduce the log-normal distribution as a simple parametrization of multiplicities in hadron-hadron minimum-bias scattering and show that it fits data at all available energies, including the highest energy (pp̄ at √s=900 GeV) were the negative binomial distribution cannot describe the data well. The log-normal distribution is a two-parameter statistical probability function that has a simple and appealing physical interpretation. In statistics theory it arises in the case of multi-step cascade processes where each step multiplies the previous outcome. This gives a natural connection to state-of-the-art models for multiparticle production involving QCD parton cascades and hadronization.
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15.
  • Cederwall, Bo, et al. (författare)
  • Collective rotational-vibrational transition in the very neutron-deficient nuclei (171,172)-Pt
  • 1998
  • Ingår i: Physics Letters B. - AMSTERDAM, NETHERLANDS : ELSEVIER SCIENCE. - 0370-2693 .- 1873-2445. ; 443:1-4, s. 69-76
  • Tidskriftsartikel (refereegranskat)abstract
    • Excited states have been identified for the first time in very neutron deficient Pt-171.172 nuclei using the recoil-or-decay tagging technique. The ground-state band in Pt-172 has been established up to I-pi = 8+. A similar level sequence, presumably built on the I-pi = 13/2(+) state, is observed for Pt-171. The data are compared with theoretical calculations based on the mean field approach and the random phase approximation and are put into the context of the systematics of platinum isotopes. (C) 1998 Elsevier Science B.V. All rights reserved.
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16.
  • Cederwall, Bo, et al. (författare)
  • PROPERTIES OF SUPERDEFORMED BANDS IN DY-153
  • 1995
  • Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 346:3-4, s. 244-250
  • Tidskriftsartikel (refereegranskat)abstract
    • Two new superdeformed (SD) bands in Dy-153, in addition to the three previously observed, have been studied with the GAMMASPHERE detector array. Assignments to single-neutron orbits in the SD potential are made based on the band properties. Evidence for a band interaction at very high spins, possibly involving the first N = 7 proton intruder orbital, is observed in the strongest populated SD band. Furthermore, evidence far a Delta I = 2 staggering is also found in this SD band.
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17.
  • CLARK, RM, et al. (författare)
  • A PAIR OF IDENTICAL SUPERDEFORMED BANDS IN ND-136
  • 1995
  • Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 343:1-4, s. 59-63
  • Tidskriftsartikel (refereegranskat)abstract
    • High-spin states in Nd-136 were populated via the Mo-100(Ar-40, 4n) reaction at beam energies of 176 and 182 MeV, and resulting gamma-rays were detected using the GAMMASPHERE spectrometer. Analysis of the data has revealed the existence of an excited superdeformed (SD) band in Nd-136. Th, yrast SD band in Nd-136 has been extended by the addition of four (possibly five) transitions at high frequency. The new band displays the remarkable property of having transition energies identical (to within +/- 1 keV) to those of the half-points of the yrast SD band of Nd-136. Possible explanations in terms of cranked Woods-Saxon single-particle calculations are discussed.
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18.
  • CRISTANCHO, F, et al. (författare)
  • MULTIPLE SUPERDEFORMED BANDS IN SR-81
  • 1995
  • Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 357:3, s. 281-286
  • Tidskriftsartikel (refereegranskat)abstract
    • Four superdeformed bands extending over five to twelve transitions have been identified in Sr-81 from a study With the Gammasphere array and the Microball charged-particle array, One of the bands shows an upbend in the dynamic moment of inertia at a rotational frequency of 1.2 MeV and all bands exhibit a nearly constant moment of inertia below that frequency.
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19.
  • de, Angelis G, et al. (författare)
  • Rotation induced octupole correlations in the neutron-deficient Te-109 nucleus
  • 1998
  • Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 437:3-4, s. 236-242
  • Tidskriftsartikel (refereegranskat)abstract
    • High spin states in the neutron deficient nucleus 109Te have been populated with the 58Ni+54Fe reaction at 220 MeV and investigated through γ-spectroscopy methods at the GASP spectrometer making use of reaction channel selection with the ISIS Si-ball. The level scheme has been extended up to an excitation energy of ≈12.1 MeV. The spins and parities of the observed levels are assigned tentatively supporting the identification of two bands of opposite parity connected by strong dipole transitions inferred to be of E1 character. Octupole correlations in 109Te induced by rotation are suggested as the cause of this effect.
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20.
  • King, S L, et al. (författare)
  • First observation of excited states in the neutron deficient nuclei (PT)-P-168 and Pt-170
  • 1998
  • Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 443:1-4, s. 82-88
  • Tidskriftsartikel (refereegranskat)abstract
    • Excited states have been observed for the first time in (XPt)-X-168 and Pt-170 using the alpha-decay recoil-tagging technique. The trend of decreasing deformation moving away from the N = 104 mid-shell continues far Pt-170 but the structure of Pt-168 is significantly different. The low spin level energy systematics in Pt168-184 are presented and discussed within the framework of the interacting boson model. (C) 1998 Elsevier Science B.V. All rights reserved.
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21.
  • LAFOSSE, DR, et al. (författare)
  • CHARACTERIZATION OF THE FIRST SUPERDEFORMED BAND IN THE A-APPROXIMATE-TO-80 REGION
  • 1995
  • Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 354:1-2, s. 34-40
  • Tidskriftsartikel (refereegranskat)abstract
    • The recently discovered superdeformed band in one of the strontium isotopes has been identified as belonging to Sr-83 from a study with the Gammasphere array and the Microball charged-particle detector system. From its decay pattern, a spin of (81 +/- 2)/2 ($) over bar h is deduced for the highest level of this band. Evidence for very fast transition rates and agreement of the characteristics of this band with the theoretical predictions establish the yrast superdeformed nature of this band in Sr-83.
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22.
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23.
  • Langmann, Edwin, et al. (författare)
  • Gauge Theories on a Cylinder
  • 1992
  • Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 296, s. 117-120
  • Tidskriftsartikel (refereegranskat)
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24.
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25.
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26.
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27.
  • NISIUS, D, et al. (författare)
  • IDENTICAL SUPERDEFORMED BAND IN DY-151 - FURTHER EVIDENCE FOR THE PSEUDOSPIN COUPLING SCHEME
  • 1995
  • Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 346:1-2, s. 15-20
  • Tidskriftsartikel (refereegranskat)abstract
    • One of the four new excited superdeformed bands found in Dy-151 is characterized by transition energies that lie midway between the gamma-ray energies of the yrast superdeformed band in Dy-152. This result adds significant new information on the issue of ''identical'' bands, as it confirms predictions based on the strong coupling model and the pseudospin coupling scheme.
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28.
  • SEWERYNIAK, D, et al. (författare)
  • IN-BEAM SPECTROSCOPY AT THE PROTON-DRIP LINE - FIRST OBSERVATION OF EXCITED-STATES IN SB-106 AND SB-107
  • 1994
  • Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 321:4, s. 323-328
  • Tidskriftsartikel (refereegranskat)abstract
    • Neutron deficient nuclei close to Sn-100 have been investigated in-beam using the NORDBALL detector array. A target of Fe-54 was bombarded with a beam of Ni-58 at 270 MeV. Evaporation residues were identified by detecting protons and alpha particles in a 4 pi charged particle multi-detector set-up and neutrons in a 1 pi neutron detector wall in coincidence with gamma rays. Excited states of the proton drip line nucleus Sb-106 and of Sb-107 were identified for the first time. The yrast level schemes constructed from gamma-gamma-particle coincidence and gamma-gamma angular correlation analysis are presented and discussed within the framework of the nuclear shell model.
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29.
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30.
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31.
  • Adamovich, M.I., et al. (författare)
  • Rescattering probed by the emission of slow target associated particles in high-energy heavy-ion interactions
  • 1995
  • Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 363:4, s. 230-236
  • Tidskriftsartikel (refereegranskat)abstract
    • In this letter the distribution of slow target associated particles emitted in Au + Emulsion interactions at 11.6 A GeV/c is studied, The three models RQMD, FRITIOF and VENUS are used for comparisons and especially their treatment of rescattering is investigated.
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32.
  • Andersson, Bo, et al. (författare)
  • A String dynamical description of gluon and ocean quark structure functions
  • 1992
  • Ingår i: Physics Letters B. - 0370-2693. ; 277:3, s. 359-365
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a model based upon string dynamics for the small x and large k⊥ parts of the structure functions of a hadron. These ocean partons are taken as those available in the virtual string states, which are resolved by the field pulse q, in case the process is considered as a measuring process. The resulting distributions will for sufficiently small x (x⩽O(Q−4)) behave as 1/x in case we use the prescriptions of the Lund dipole model ([1,2]) and the soft radiation model ([3]).
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33.
  • Andersson, Bo, et al. (författare)
  • The flavouring of a gluon jet
  • 1990
  • Ingår i: Physics Letters B. - 0370-2693. ; 236:4, s. 461-465
  • Tidskriftsartikel (refereegranskat)abstract
    • We show that the hard qq̄ production is very sensitive to the details of the parton shower and that our treatment based on the dipole approximation gives significantly larger production than “conventional” parton showers. For our model we find qualitative agreement with experimental data for the Kπ ratio and D-meson production in high-pT jets.
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34.
  • Andersson, Bo, et al. (författare)
  • Transverse and longitudinal Bose-Einstein correlations
  • 1998
  • Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 421:1-4, s. 283-288
  • Tidskriftsartikel (refereegranskat)abstract
    • We show how a difference in the correlation length longitudinally and transversely, with respect to the jet axis in e+e− annihilation, arises naturally in a model for Bose-Einstein correlations based on the Lund string model. In genuine three-particle correlations the difference is even more apparent and they provide therefore a good probe for the longitudinal stretching of the string field. The correlation length between pion pairs is found to be rather independent of the pion multiplicity and the kaon content of the final state.
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35.
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36.
  • Baillie, C. F., et al. (författare)
  • Scaling in Steiner random surfaces
  • 1994
  • Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 325:1-2, s. 45-50
  • Tidskriftsartikel (refereegranskat)abstract
    • It has been suggested that the modified Steiner action functional has desirble properties for a random surface action. In this paper we investigate the scaling of the string tension and massgap in a variant of this action on dynamically triangulated random surfaces and compare the results with the gaussian plus extrinsic curvature actions that have been used previously.
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37.
  • Bijnens, J., et al. (författare)
  • Chiral corrections to vector meson decay constants
  • 1998
  • Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 429:1-2, s. 111-120
  • Tidskriftsartikel (refereegranskat)abstract
    • We calculate the leading quark mass corrections of order mqlog(mq), mq and m3/2 q to the vector meson decay constants within heavy vector meson chiral perturbation theory. We discuss the issue of electromagnetic gauge invariance and the heavy mass expansion. Reasonably good fits to the observed decay constants are obtained.
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38.
  • Bijnens, J., et al. (författare)
  • Double chiral logs
  • 1998
  • Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 441:1-4, s. 437-446
  • Tidskriftsartikel (refereegranskat)abstract
    • We determine the full structure of the leading (double-pole) divergences of O(p6) in the meson sector of chiral perturbation theory. The field theoretic basis for this calculation is described. We then use an extension of this result to determine the p6 contributions containing double chiral logarithms (L2), single logarithms times p4 constants (L × Lr i) and products of two p4 constants (Lr i × Lr j) for Fπ, FK/Fπ, Kl3 and Ke4 form factors. Numerical results are presented for these quantities.
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39.
  • Borge, M. J. G., et al. (författare)
  • Beta-Decay to the Proton Halo State in F-17
  • 1993
  • Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 317:1-2, s. 25-30
  • Tidskriftsartikel (refereegranskat)abstract
    • In the first experiment at the newly constructed ISOLDE Facility the first-forbidden beta-decay of Ne-17 into the first excited state of F-17 has been measured. It is a factor two faster than the corresponding mirror decay and thus gives one of the largest recorded asymmetries for beta decays feeding bound final states. Shell-model calculations can only reproduce the asymmetry if the halo structure of the F-17 state is taken into account.
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40.
  • Friberg, C., et al. (författare)
  • QCD aspects of leptoquark production at HERA
  • 1997
  • Ingår i: Physics Letters B. - 0370-2693. ; 403:3-4, s. 329-334
  • Tidskriftsartikel (refereegranskat)abstract
    • If a leptoquark is produced at HERA as a narrow resonance, various effects tend to broaden the measurable mass distribution considerably. These effects are discussed here, with special emphasis on initial- and final-state QCD radiation. A proper understanding is important to assess the significance of data and to devise strategies for better mass reconstruction.
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41.
  • Garpman, S., et al. (författare)
  • Rapidity density distributions and their fluctuations in violent Au-induced nuclear interactions at 11.6 A GeV/c
  • 1994
  • Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 433:1-2, s. 166-170
  • Tidskriftsartikel (refereegranskat)abstract
    • The first rapidity density distributions from relativistic collisions between truly heavy nuclei are presented. The distributions are compared with expectations from a linear extrapolation of results obtained from collisions with lighter nuclei. Fluctuations are essentially described by a simple scenario with stochastic emission.
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42.
  • Gustafson, Gösta, et al. (författare)
  • Lambda-polarization in e+e--annihilation at the Z0-pole
  • 1993
  • Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 303:3-4, s. 350-354
  • Tidskriftsartikel (refereegranskat)abstract
    • Strange quarks produced in e+e--annihilation at the Z0-pole are very strongly polarized. To study to which extent this polarization is transferred to the observable hadrons would give interesting information on the hadronization mechanism. Γ-particles produced with relatively large x-values are expected to frequently contain an originally produced s-quark. We estimate that Γ-particles with x>0.3 should have a longitudinal polarization of about 30%.
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43.
  • Hamamoto, Ikuko, et al. (författare)
  • Deformation dependence of magnetic dipole strength below 4 MeV in doubly even rare earth nuclei
  • 1991
  • Ingår i: Physics Letters B. - 0370-2693. ; 260:1-2, s. 6-10
  • Tidskriftsartikel (refereegranskat)abstract
    • We show: (1) In the presence of the pair correlation the M1 transition strength calculated in the deformed oscillator model has a dependence on the quadrupole deformation parameter δ which is considerably stronger than linear and, in fact, it varies quadratically with δ in the limit of small deformation; (2) The deformation dependence in samarium isotopes calculated using the quasiparticle random phase approximation (QRPA) reproduces the qualitative behaviour of the recent experimental data of Ziegler, Rangacharyulu, Richter and Spieler.
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44.
  • Karlsson, Lennart B., et al. (författare)
  • Identical bands in superdeformed nuclei
  • 1998
  • Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 416:1-2, s. 16-22
  • Tidskriftsartikel (refereegranskat)abstract
    • Using the configuration constrained, cranked Nilsson-Strutinsky model, we point to a mechanism that could explain why identical bands are much more likely to occur in superdeformed than in normal-deformed nuclei. The role of the high-N orbitals in the superdeformed configuration is stressed, and correlated with the observed peaks in the fractional change distribution of the script J sign(2) moment of inertia. Also (fractional) changes of the electric quadrupole moment due to changes of the high-N content are discussed.
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45.
  • Khoze, Valery A., et al. (författare)
  • A Phenomenological Investigation of the String Effect
  • 1990
  • Ingår i: Physics Letters B. - 0370-2693. ; 241:1, s. 123-126
  • Tidskriftsartikel (refereegranskat)abstract
    • We present results from Monte Carlo calculations of the string effect and the double inclusive correlation of particle flows for three-fold symmetric three-jet events in e+e− annihilation reactions at different energies. We find that the perturbative phase of the jet evolution quickly becomes dominant as energy increases.
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46.
  • Lönnblad, L., et al. (författare)
  • Mass reconstruction with a neural network
  • 1992
  • Ingår i: Physics Letters B. - 0370-2693. ; 278:1-2, s. 181-186
  • Tidskriftsartikel (refereegranskat)abstract
    • A feed-forward neural network method is developed for reconstructing the invariant mass of hadronic jets appearing in a calorimeter. The approach is illustrated in W→qq, where W-bosons are produced in pp reactions at SPS collider energies. The neural network method yields results that are superior to conventional methods. This neural network application differs from the classification ones in the sense that an analog number (the mass) is computed by the network, rather than a binary decision being made. As a by-product our application clearly demonstrates the need for using "intelligent" variables in instances when the amount of training instances is limited.
  •  
47.
  • Miu, Gabriela, et al. (författare)
  • W production in an improved parton-shower approach
  • 1999
  • Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 449:3-4, s. 313-320
  • Tidskriftsartikel (refereegranskat)abstract
    • In the description of the production properties of gauge bosons (W±, Z0, γ*) at colliders, the lowest-order graph normally is not sufficient. The contributions of higher orders can be introduced either by an explicit order-by-order matrix-element calculation, by a resummation procedure or by a parton-shower algorithm. Each approach has its advantages and disadvantages. We here introduce a method that allows the parton-shower algorithm to be augmented by higher-order information, thereby offering an economical route to a description of all event properties. It is tested by comparing with the P⊥ spectrum of W bosons at the Tevatron.
  •  
48.
  • Mukha, I., et al. (författare)
  • Observation of the Li-11(beta d) decay
  • 1996
  • Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 367:1-4, s. 65-69
  • Tidskriftsartikel (refereegranskat)abstract
    • Experimental data from the decay of Li-11 show for the first time the presence of beta-delayed deuterons with a branching ratio larger than 10(-4). To distinguish between beta d and beta t events the decays of the daughter nuclei Li-9 and Li-8 were identified in the energy and decay time spectra. Furthermore, a time correlation analysis between the beta d events and the subsequent daughter decays was performed.
  •  
49.
  • Norrbin, E., et al. (författare)
  • Production mechanisms of charm hadrons in the string model
  • 1998
  • Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 442:1-4, s. 407-416
  • Tidskriftsartikel (refereegranskat)abstract
    • In the hadroproduction of charm in the context of string fragmentation, the pull of a beam remnant at the other end of a string may give a charm hadron more energy than the perturbatively produced charm quark. The collapse of a low-mass string to a single hadron is the extreme case in this direction, and gives rise to asymmetries between charm and anticharm hadron spectra. We study these phenomena, and develop models that describe the characteristics not only of the charm hadrons but also of the associated event.
  •  
50.
  • Pérez, M. García, et al. (författare)
  • Minimum action solutions for SU(2) gauge theory on the torus with non-orthogonal twist
  • 1990
  • Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 235:1-2, s. 117-123
  • Tidskriftsartikel (refereegranskat)abstract
    • We use the cooling method and the lattice approximation to study the form and properties of the minimum action configurations for the SU(2) Yang-Mills theory on a space-time torous with twist k=m=(1, 1, 1).
  •  
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