| 1. |
- Akhmedov, Evgeny, et al.
(författare)
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T violation in neutrino oscillations in matter
- 2001
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Ingår i: Nuclear Physics B. - : Elsevier Science B.V.. - 0550-3213 .- 1873-1562. ; 608:02-jan, s. 394-422
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Tidskriftsartikel (refereegranskat)abstract
- We consider the interplay of fundamental and matter-induced T violation effects in neutrino oscillations in matter. After discussing the general features of these effects we derive a simple approximate analytic expression for the T-violating probability asymmetry DeltaP(ab)(T) for three-flavour neutrino oscillations in a matter with an arbitrary density profile in terms of the two-flavour neutrino amplitudes. Explicit examples are given for the cases of a two-layer medium and for the adiabatic Emit in the general case. We then discuss implications of the obtained results for long baseline experiments. We show, in particular, that asymmetric matter effects cannot hinder the determination of the fundamental CP- and T-violating phase delta (CP) in the long baseline experiments as far as the error in this determination is larger than 1% at 99% CL. Since there are no T-violating effects in the two-flavour case, and in the limits of vanishing theta (13) or Deltam(21)(2) the three-flavour neutrino oscillations effectively reduce to the two-flavour ones, studying the T-violating asymmetries ApT ab can in principle provide us with a complementary means of measuring theta (13) and Deltam(21)(2).
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| 2. |
- Ambjørn, J., et al.
(författare)
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Stochastic confinement and dimensional reduction. (I). Four-dimensional SU(2) lattice gauge theory
- 1984
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Ingår i: Nuclear Physics, Section B. - : Elsevier BV. - 0550-3213. ; 240:2, s. 189-212
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Tidskriftsartikel (refereegranskat)abstract
- By Monte Carlo calculations on a 124 lattice we investigate four-dimensional SU(2) lattice gauge theory with respect to the conjecture that at large distances this theory reduces approximately to two-dimensional SU(2) lattice gauge theory. We find good numerical evidence for this conjecture. As a by-product we also measure the SU(2) string tension and find reasonable agreement with scaling. The "adjoint string tension" is also found to have a reasonable scaling behaviour.
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| 3. |
- Ambjørn, J., et al.
(författare)
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Stochastic confinement and dimensional reduction (II). Three-dimensional SU(2) lattice gauge theory
- 1984
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Ingår i: Nuclear Physics, Section B. - : Elsevier BV. - 0550-3213. ; 240:4, s. 533-542
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Tidskriftsartikel (refereegranskat)abstract
- We study 3-dimensional SU(2) lattice gauge theory with respect to dimensional reduction. By Monte Carlo calculations we find that this reduction is valid to a good approximation (within ≈10%). The adjoint string tension is found to scale approximately. We also compare the adjoint string tension with a string theory.
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| 4. |
- Ambjørn, J., et al.
(författare)
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The complex langevin equation and Monte Carlo simulations of actions with static charges
- 1986
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Ingår i: Nuclear Physics, Section B. - 0550-3213. ; 275:3, s. 375-397
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Tidskriftsartikel (refereegranskat)abstract
- We explore the possibilities of using the complex Langevin equation to Monte Carlo generate configurations of gauge theories with static charges present in the action. Successful results are obtained for systems that possess nontrivial saddle-point (classical) solutions. For that reason the algorithm works impressively for two-dimensional U(1) in the entire β-range whereas for three- and four-dimensional U(1) the applicability is limited to the weak coupling regime (large β). The method fails completely for SU(2) and SU(3).
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| 5. |
- Ambjørn, J., et al.
(författare)
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Three-dimensional lattice gauge theory and strings
- 1984
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Ingår i: Nuclear Physics, Section B. - : Elsevier BV. - 0550-3213. ; 244:1, s. 262-276
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Tidskriftsartikel (refereegranskat)abstract
- We consider SU(2) lattice gauge theory in three dimensions. The Wilson loops are found to be well described by a simple string model in the approximate scaling region.
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| 6. |
- Amoros, G., et al.
(författare)
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QCD isospin breaking in meson masses, decay constants and quark mass ratios
- 2001
-
Ingår i: Nuclear Physics B. - 0550-3213. ; 602:1-2, s. 87-108
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Tidskriftsartikel (refereegranskat)abstract
- The procedure to calculate masses and matrix-elements in the presence of mixing of the basis states is explained in detail. We then apply this procedure to the two-loop calculation in Chiral Perturbation Theory of pseudoscalar masses and decay constants including quark mass isospin breaking. These results are used to update our analysis of Kℓ4 done previously and obtain a value of mu/md in addition to values for the low-energy-constants Li r.
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| 7. |
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| 8. |
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| 9. |
- Andersson, B., et al.
(författare)
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A statistical model for quark fragmentation into mesons with emphasis on vector meson contributions
- 1978
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Ingår i: Nuclear Physics, Section B. - : Elsevier BV. - 0550-3213. ; 135:2, s. 273-284
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Tidskriftsartikel (refereegranskat)abstract
- This paper is the first part of a program to deal with the relative importance of the different effects in a colour dipole field when the field energy is transformed into hadrons according to a statistical scheme with the sole constraints coming from energy and momentum conservation and the requirements of scaling. In this paper we treat the meson distributions from quark fragmentation with particular emphasis on the importance of a vector meson production of the size observed at present. We neglect diquark formation and the baryon distributions as a first approximation. The simplicity of the approach will make it possible to easily understand the size and the shape of the different contributions.
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| 10. |
- Andersson, Bo, et al.
(författare)
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Bose-Einstein correlations in the Lund model
- 1998
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Ingår i: Nuclear Physics B. - 0550-3213. ; 513:3, s. 627-644
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Tidskriftsartikel (refereegranskat)abstract
- By providing the Lund Model fragmentation process with a quantum-mechanical framework we extend the results of previous work to situations where there are very many identical bosons. We investigate the features of the weight distributions in some detail and in particular exhibit three-particle BE-correlations, the influence on the rho-spectrum and the difference between charged and neutral pion correlations.
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| 11. |
- Andersson, Bo, et al.
(författare)
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Gluon Splitting in the Color Dipole Cascades
- 1990
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Ingår i: Nuclear Physics B. - 0550-3213. ; 339:2, s. 393-405
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Tidskriftsartikel (refereegranskat)abstract
- We present a method to implement the gluon splitting process, g → QQ, into the dipole approximation to QCD cascades. It is known that due to the uncertainties in the interpolation between the pole regions, there are large uncertainties in the results. We show that there are further uncertainties due to the ordering in phase space of the gluon emission and gluon splitting processes. We present two options called the IO scheme (for independent dipoles) and another, the DO scheme (corresponding to an ordering in transverse momentum of the emissions) both of which lead to enhanced (hard) QQ-pair production, as compared to conventional cascades. We compare to present experimental data and give predictions for LEP energies.
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| 12. |
- Andersson, Bo, et al.
(författare)
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The lambda-measure and the generalised dipoles in the Lund model
- 2002
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Ingår i: Nuclear Physics, Section B. - 0550-3213. ; 646:1-2, s. 102-126
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate that the multiple gluon emission phase space in the dipole cascade model has a strong linear correlation with the number of gluons emitted. The number of gluons per unit available phase space at a certain resolution scale is found to be remarkably independent of the cms energy and global event properties like thrust, and even changes in the ordering variable or resolution scale. We show that the distribution of sizes of gluon-gluon dipoles in a parton cascade has stability properties which are sufficient to account for those of the phase space variable. We observe that certain more abstract entities, defined in the context of hadronisation and related to the gluon emission phase space, share those properties of colour dipoles and name them generalised dipoles. We also present an analytical model to qualitatively describe our findings. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 13. |
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| 14. |
- Bengtsson, Mats, et al.
(författare)
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QCD effects on the event structure in leptoproduction
- 1988
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Ingår i: Nuclear Physics, Section B. - : Elsevier BV. - 0550-3213. ; 301:4, s. 554-582
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Tidskriftsartikel (refereegranskat)abstract
- Perturbative QCD corrections to leptoproduction events can be introduced either in the form of matrix elements or of parton showers. Each of these approaches has its advantages and disadvantages, making a comparison of the two interesting. At present energies, both methods can be made to agree reasonably well with data, whereas differences appear at higher energies. The influence of these QCD effects on the expected event structure at ep colliders, HERA in particular, is investigated in detail. This includes multiplicity and momentum distributions, transverse momentum flow and correlations, as well as jet properties.
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| 15. |
- Bijnens, Johan, et al.
(författare)
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Comment on the pion pole part of the light-by-light contribution to the muon g-2
- 2002
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Ingår i: Nuclear Physics, Section B. - 0550-3213. ; 626:1-2, s. 410-411
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Tidskriftsartikel (refereegranskat)abstract
- We comment on the recent calculations of the pion pole part of the light-by-light contribution to the muon anomalous magnetic moment and we point out where the analysis in our previous work was mistaken.
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| 16. |
- Bijnens, Johan, et al.
(författare)
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K -> 3 pi decays in chiral perturbation theory
- 2003
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Ingår i: Nuclear Physics, Section B. - 0550-3213. ; 648:1-2, s. 317-344
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Tidskriftsartikel (refereegranskat)abstract
- The CP conserving amplitudes for the decays K --> 3pi are calculated in chiral perturbation theory at the next-to-leading order. We present the expressions in a compact form with single parameter functions only. These expressions are then fitted to all available K --> 2pi and K --> 3pi data to obtain a fit of the parameters that occur. We compare with the work of Kambor, Missimer and Wyler. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 17. |
- Bijnens, Johan, et al.
(författare)
-
K-l3 decays in chiral perturbation theory
- 2003
-
Ingår i: Nuclear Physics, Section B. - 0550-3213. ; 669:1-2, s. 341-362
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Tidskriftsartikel (refereegranskat)abstract
- The process K-l3 is calculated to two-loop order (p(6)) in chiral perturbation theory (ChPT) in the isospin conserved case. We present expressions suitable for use with previous work in two-loop ChPT where the order p(4) parameters (L-i(r)) were determined from experiment. We point out that all the order p(6) parameters (C-i(r)) that appear in the value of f(+)(0) relevant for the determination of V-us can be determined from K-l3 measurements via the slope and the curvature of the scalar form-factor. As by product we update the value of the CKM matrix element V-us. (C) 2003 Elsevier B.V. All rights reserved.
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| 18. |
- Bijnens, Johan, et al.
(författare)
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Obtaining K → ππ from off-shell K → π amplitudes
- 1998
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Ingår i: Nuclear Physics B. - 0550-3213. ; 521:1-2, s. 305-333
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Tidskriftsartikel (refereegranskat)abstract
- We properly define off-shell K → π transition amplitudes and use them to extract information for on-shell K → ππ amplitudes within Chiral Perturbation Theory. At order p2 in the chiral expansion all three parameters of weak interaction can be determined. At order p4 we are able to fix eleven additional constants out of thirteen contributing to off-shell K → π transitions, which leaves four undetermined constants in the on-shell K → ππ amplitudes. All script O sign(p4) contributions have been exactly derived with m2 π ≠ 0. We finally discuss the weak mass term issue and find contributions to on-shell ΔS = ±1 kaon decays, in particular to transitions like KL → γγ, KL → μ+μ- and KS → π0γγ at the lowest non-zero order.
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| 19. |
- Bijnens, J., et al.
(författare)
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Pion-pion scattering at low energy
- 1997
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Ingår i: Nuclear Physics B. - 0550-3213. ; 508:1-2, s. 263-310
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Tidskriftsartikel (refereegranskat)abstract
- We present technical details of the evaluation of the elastic ππ scattering amplitude to two loops in chiral perturbation theory. In particular, we elaborate on the renormalization procedure at the two-loop order and on the evaluation of the relevant Feynman diagrams that can all be expressed in terms of elementary functions. For the sake of clarity, we discuss these matters both in the N-component φ4 theory (in its symmetric phase) and in chiral perturbation theory. Estimates for the relevant low-energy constants of O(p6) are presented. Threshold parameters and phase shifts are then calculated for two sets of O(p4) coupling constants and compared with experiment. We comment on the extraction of threshold parameters from phase shift data.
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| 20. |
- Bijnens, J., et al.
(författare)
-
Vector meson masses in chiral perturbation theory
- 1997
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Ingår i: Nuclear Physics B. - 0550-3213. ; 501:2, s. 495-517
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Tidskriftsartikel (refereegranskat)abstract
- We discuss the vector meson masses within the context of chiral perturbation theory performing an expansion in terms of the momenta, quark masses and 1/Nc. We extend the previous analysis to include isospin breaking effects and also include up to order p4. We discuss vector meson chiral perturbation theory in some detail and present a derivation from a relativistic Lagrangian. The unknown coefficients are estimated in various ways. We also discuss the relevance of electromagnetic corrections and the implications of the present calculation for the determination of quark masses.
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| 21. |
- Coste, Antoine, et al.
(författare)
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Finite Size Effects and Twisted Boundary Conditions
- 1987
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Ingår i: Nuclear Physics B. - : Elsevier BV. - 0550-3213. ; 287, s. 569-588
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Tidskriftsartikel (refereegranskat)abstract
- We explore the possibility of reducing finite size effects in the weak coupling region of glueball correlations and Wilson loops. Our analysis indicates that twisted boundary conditions do diminish finite size effects and numerical evidence for this is given for the glueball correlation.
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| 22. |
- Fjelstad, Jens, 1971-, et al.
(författare)
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CFT description of three-dimensional Kerr-de Sitter space-time
- 2002
-
Ingår i: Nuclear Physics B. - : Elsevier. - 0550-3213 .- 1873-1562. ; 641:1-2, s. 376-392
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Tidskriftsartikel (refereegranskat)abstract
- We describe three-dimensional Kerr-de Sitter space using similar methods as recently applied to the BTZ black hole. A rigorous form of the classical connection between gravity in three dimensions and two-dimensional conformal field theory is employed, where the fundamental degrees of freedom are described in terms of two dependent SL(2,C) currents. In contrast to the BTZ case, however, quantization does not give the Bekenstein-Hawking entropy connected to the cosmological horizon of Kerr-de Sitter space.
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| 23. |
- Fjelstad, Jens, 1971-, et al.
(författare)
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Sectors of solutions in three-dimensional gravity and black holes
- 2002
-
Ingår i: Nuclear Physics B. - : Elsevier. - 0550-3213 .- 1873-1562. ; 628:1-2, s. 331-360
-
Tidskriftsartikel (refereegranskat)abstract
- We examine the connection between three dimensional gravity with negative cosmological constant and two-dimensional CFT via the Chern-Simons formulation. A set of generalized spectral flow transformations are shown to yield new sectors of solutions. One implication is that the microscopic calculation of the entropy of the Banados-Teitelboim-Zanelli (BTZ) black hole is corrected by a multiplicative factor with the result that it saturates the Bekenstein-Hawking expression.
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| 24. |
- Flensburg, M., et al.
(författare)
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String model potentials and lattice gauge theories
- 1987
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Ingår i: Nuclear Physics, Section B. - : Elsevier BV. - 0550-3213. ; 283, s. 141-164
-
Tidskriftsartikel (refereegranskat)abstract
- The static potentials from bosonic string models are examined to the two-loop level. Available MC data for 4-dimensional SU(3) are in approximate agreement with the universal leading order predictions but fail to reproduce the Nambu string when the two-loop terms are included in the analysis. We also confront Nambu string model predictions for Tc σ with SU(2), SU(3) and SU(N → ∞) MC data. In the SU(2) case, impressive agreement is found both in 3 and 4 dimensions. In contrast, the data for SU(3) and SU(N → ∞) differ from the string model prediction. These theories have identical values for Tc σ, indicating that N → ∞ is a good approximation to N = 3.
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| 25. |
- Friberg, Christer, et al.
(författare)
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Colour Connections in e+e- annihilation
- 1997
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Ingår i: Nuclear Physics, Section B. - 0550-3213. ; B490, s. 289-305
-
Tidskriftsartikel (refereegranskat)abstract
- We have a very limited knowledge about how the confinement mechanism works in processes like $\epea\epe\ra\epq\epqa\ggn\ldots\ggn$, when there are identical colour charges. In this case the partons can be colour connected by a string or a cluster chain in several different ways. We do not know if in such a situation Nature chooses a particular configuration at random, or if some configuration is dynamically favoured. Also in the perturbative parton cascade we have no well founded recipe for describing the interference effects, which correspond to non planar diagrams and are caused by identical colour charges. We have studied two different models, and are in particular interested in the possibility that a colour singlet gluon system hadronizes isolated from the remainder of the state. Using double tagged events with heavy $\epc\epca$ or $\epb\epba$ quarks, it appears to be possible to find a significant signal, if such events appear in Nature. If this type of (re)connected states appear in Z decays it may also be an indication that reconnection might appear between the decay products of two W's in the reaction $\epea\epe\ra\gwp\gwm\ra\epq_1\epqa_2\epQ_1\epQa_2$ at LEP2. This would be important e.g. for a precision measurement of the W mass.
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| 26. |
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| 27. |
- Gupta, Sourendu, et al.
(författare)
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Finite-size scaling at phase coexistence
- 1993
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Ingår i: Nuclear Physics, Section B. - 0550-3213. ; 409:3, s. 663-683
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Tidskriftsartikel (refereegranskat)abstract
- From a finite-size scaling (FSS) theory of cumulants of the order parameter at phase-coexistence points, we reconstruct the scaling of the moments. Assuming that the cumulants allow a reconstruction of the free energy density no better than as an asymptotic expansion, we find that FSS for moments of low order is still complete. We suggest ways of using this theory for the analysis of numerical simulations. We test these methods numerically through the scaling of cumulants and moments of the magnetisation in the low-temperature phase of the two-dimensional Ising model.
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| 28. |
- Gustafson, Gösta, et al.
(författare)
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Rescattering effects in the decay of the A1
- 1976
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Ingår i: Nuclear Physics, Section B. - : Elsevier BV. - 0550-3213. ; 116:2, s. 301-316
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Tidskriftsartikel (refereegranskat)abstract
- Rescattering effects in the 3π system in the A1 region are studied with a method, which fulfils unitarity and has the proper analytic structure. Fairly small effects are obtained which confirm the result found in amplitude analyses, neglecting rescattering corrections, that the phases of the JP = 1+ amplitudes vary only very little over the A1 region. Similar results hold for the Q enhancement.
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| 29. |
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| 30. |
- Lindner, Manfred, et al.
(författare)
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A combined treatment of neutrino decay and neutrino oscillations
- 2001
-
Ingår i: Nuclear Physics B. - : Elsevier Science B.V.. - 0550-3213 .- 1873-1562. ; 607:02-jan, s. 326-354
-
Tidskriftsartikel (refereegranskat)abstract
- Neutrino decay in vacuum has often been considered as an alternative to neutrino oscillations. Because nonzero neutrino masses imply the possibility of both neutrino decay and neutrino oscillations, we present a model-independent formal treatment of these combined scenarios. For that, we show for the example of Majoron decay that in many cases decay products are observable and may even oscillate. Furthermore, we construct a minimal scenario in which we study the physical implications of neutrino oscillations with intermediate decays.
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| 31. |
- Lindner, Manfred, et al.
(författare)
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Decays of supernova neutrinos
- 2002
-
Ingår i: Nuclear Physics B. - : Elsevier Science B.V.. - 0550-3213 .- 1873-1562. ; 622:02-jan, s. 429-456
-
Tidskriftsartikel (refereegranskat)abstract
- Supernova neutrinos could be well-suited for probing neutrino decay, since decay may be observed even for very small decay rates or coupling constants. We will introduce an effective operator framework for the combined description of neutrino decay and neutrino oscillations for supernova neutrinos, which can especially take into account two properties: one is the radially symmetric neutrino flux, allowing a decay product to be re-directed towards the observer even if the parent neutrino had a different original direction of propagation. The other is decoherence because of the long baselines for coherently produced neutrinos. We will demonstrate how to use this effective theory to calculate the time-dependent fluxes at the detector. In addition, we will show the implications of a Majoron-like decay model. As a result, we will demonstrate that for certain parameter values one may observe some effects which could also mimic signals similar to the ones expected from supernova models, making it in general harder to separate neutrino and supernova properties.
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| 32. |
- Lönnblad, Leif, et al.
(författare)
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Using neural networks to identify jets
- 1991
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Ingår i: Nuclear Physics, Section B. - 0550-3213. ; 349:3, s. 675-702
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Tidskriftsartikel (refereegranskat)abstract
- A neural network method for identifying the ancestor of a hadron jet is presented. The idea is to find an efficient mapping between certain observed hadronic kinematical variables and the quark-gluon identity. This is done with a neuronic expansion in terms of a network of sigmoidal functions using a gradient descent procedure, where the errors are back-propagated through the network. With this method we are able to separate gluon from quark jets originating from Monte Carlo generated e+e- events with ≈85% approach. The result is independent of the MC model used. This approach for isolating the gluon jet is then used to study the so-called string effect. In addition, heavy quarks (b and c) in e+e- reactions can be identified on the 50% level by just observing the hadrons. In particular we are able to separate b-quarks with an efficiency and purity, which is comparable with what is expected from vertex detectors. We also speculate on how the neutral network method can be used to disentangle different hadronization schemes by compressing the dimensionality of the state space of hadrons.
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| 33. |
- Norrbin, E., et al.
(författare)
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QCD radiation off heavy particles
- 2001
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Ingår i: Nuclear Physics B. - 0550-3213. ; 603:1-2, s. 297-342
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Tidskriftsartikel (refereegranskat)abstract
- We study QCD radiation in decay processes involving heavy particles. As input, the first-order gluon emission rate is calculated in a number of reactions, and comparisons of the energy flow patterns show a non-negligible process dependence. To proceed further, the QCD parton shower language offers a convenient approach to include multi-gluon emission effects, and to describe exclusive event properties. An existing shower algorithm is extended to take into account the process-dependent mass, spin and parity effects, as given by the matrix element calculations. This allows an improved description of multiple gluon emission effects off b and t quarks, and also off nonstandard particles like squarks and gluinos. Phenomenological applications are presented for bottom production at LEP, Higgs particle decay to heavy flavours, top production and decay at linear colliders, and some simple supersymmetric processes.
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| 34. |
- Ohlsson, Tommy, 1973-, et al.
(författare)
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A flavor symmetry model for bilarge leptonic mixing and the lepton masses
- 2002
-
Ingår i: Nuclear Physics B. - : Elsevier Science B.V.. - 0550-3213 .- 1873-1562. ; 643:03-jan, s. 247-279
-
Tidskriftsartikel (refereegranskat)abstract
- We present a model for leptonic mixing and the lepton masses based on flavor symmetries and higher-dimensional mass operators. The model predicts bilarge leptonic mixing (i.e., the mixing angles theta(12) and theta(23) are large and the mixing angle theta(13) is small) and an inverted hierarchical neutrino mass spectrum. Furthermore, it approximately yields the experimental hierarchical mass spectrum of the charged leptons. The obtained values for the leptonic mixing parameters and the neutrino mass squared differences are all in agreement with atmospheric neutrino data, the Mikheyev-Smirnov-Wolfenstein large mixing angle solution of the solar neutrino problem, and consistent with the upper bound on the reactor mixing angle. Thus, we have a large, but not close to maximal, solar mixing angle theta(12), a nearly maximal atmospheric mixing angle theta(23), and a small reactor mixing angle theta(13). In addition, the model predicts theta(12) similar or equal to pi/4 - theta(13).
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| 35. |
- Peterson, C., et al.
(författare)
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Direct observation of string vibrations in three-dimensional compact QED
- 1985
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Ingår i: Nuclear Physics, Section B. - : Elsevier BV. - 0550-3213. ; 255:C, s. 365-382
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Tidskriftsartikel (refereegranskat)abstract
- Three-dimensional compact U(1) is studied on a 16×32×16 lattice with emphasis on roughening around the crossover region. Configurations including two static charges are generated using the dual formulation of the theory. In this way the flux patterns between the charges are mapped out. Very convincing evidence for roughening is found. In particular we show that the average transverse spread of the flux tube follows a simple string model prediction as a function of charge separation. We also establish a nonvanishing string tension unambiguously. Its value turns out to be a factor two larger than what has been found in the more conventional Wilson loop approach.
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| 36. |
- Sjöstrand, Torbjörn, et al.
(författare)
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Baryon number violation and string topologies
- 2003
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Ingår i: Nuclear Physics, Section B. - 0550-3213. ; 659:1-2, s. 243-298
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Tidskriftsartikel (refereegranskat)abstract
- In supersymmetric scenarios with broken R-parity, baryon number violating sparticle decays become possible. In order to search for such decays, a good understanding of expected event properties is essential. We here develop a complete framework that allows detailed studies. Special attention is given to the hadronization phase, wherein the baryon number violating vertex is associated with the appearance of a junction in the colour confinement field. This allows us to tell where to look for the extra (anti)baryon directly associated with the baryon number violating decay. (C) 2003 Elsevier Science B.V. All rights reserved.
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| 37. |
- Skadhauge, Solveig
(författare)
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Probing CPT violation with atmospheric neutrinos
- 2002
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Ingår i: Nuclear Physics, Section B. - 0550-3213. ; 639:1-2, s. 281-289
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the recently suggested scheme of independent mass matrices for neutrinos and antineutrinos. Such a CPT violating scheme is able to account for all neutrino data with the three known flavors. For atmospheric neutrinos this means that it is possible to have different mass squared differences driving the oscillation for neutrinos and antineutrinos. We analyze the atmospheric and K2K data within the simplest scheme of two neutrino oscillation, neglecting electron neutrino oscillation. We find that the preferred region is close to the CPT conserving mass spectra. However the spectra with the antineutrino mass squared difference about or larger than 0.1 eV(2) and the neutrino mass squared difference about 2 x 10(-3) eV(2) is not significantly disfavored. In this parameter region the atmospheric data are independent of the antineutrino mass squared difference. Therefore only rather weak bounds can be put on CPT violation effects contributing to different masses for the neutrinos and antineutrinos. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 38. |
- Söderberg, B.
(författare)
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On the complex Langevin equation
- 1988
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Ingår i: Nuclear Physics, Section B. - : Elsevier BV. - 0550-3213. ; 295:3, s. 396-408
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Tidskriftsartikel (refereegranskat)abstract
- We discuss the Langevin equation for a complex Boltzmann distribution, allowing for modifications of the process. The relation between the two different time development operators involved is analyzed, with emphasis on their spectra.
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| 39. |
- Amaudruz, P, et al.
(författare)
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A re-evaluation of the nuclear structure function ratios for D, He, 6Li, C and Ca
- 1995
-
Ingår i: Nuclear Physics B. - : Elsevier. - 0550-3213 .- 1873-1562. ; 441:1-2, s. 3-11
-
Tidskriftsartikel (refereegranskat)abstract
- We present a re-evaluation of the structure function ratios F-2(He)/F-2(D), F-2(C)/F-2(D) and F-2(Ca)/F-2(D) measured in deep inelastic muon-nucleus scattering at an incident muon momentum of 200 GeV. We also present the ratios F-2(C)/F-2(Li), F-2(Ca)/F-2(Li) and F-2(Ca)/F-2(C) measured at 90 GeV. The results are based on data already published by NMC; the main difference in the analysis is a correction for the masses of the deuterium targets and an improvement in the radiative corrections. The kinematic range covered is 0.0035 < x < 0.65, 0.5 < Q(2) < 90 GeV2 for the He/D, C/D and Ca/D data and 0.0085 < x < 0.6, 0.84 < Q(2) < 17 GeV2 for the Li/C/Ca ones.
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| 40. |
- Amaudruz, P, et al.
(författare)
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The ratio F2 n/F2 p in deep inelastic muon scattering
- 1992
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Ingår i: Nuclear Physics B. - : Elsevier. - 0550-3213 .- 1873-1562. ; 371:1-2, s. 3-31
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Tidskriftsartikel (refereegranskat)abstract
- Results are presented on the ratio of neutron and proton structure functions, F2n/F2p, deduced from deep inelastic scattering of muons from hydrogen and deuterium. The data, which were obtained at the CERN muon beam at 90 and 280 GeV incident energy, cover the kinematic range x = 0.002-0.80 and Q2 = 0.1-190 GeV2. The measured structure function ratios have small statistical and systematic errors, particularly at small and intermediate x. The observed Q2 dependence in the range x = 0.1-0.4 is stronger than predicted by perturbative QCD. From the present data together with results from other experiments it is suggested that the twist-four coefficient for the proton is smaller than that for the neutron for x larger than 0.2.
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| 41. |
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| 42. |
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| 43. |
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| 44. |
- Fjelstad, Jens, 1971-, et al.
(författare)
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Logarithmic conformal field theories via logarithmic deformations
- 2002
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Ingår i: Nuclear Physics B. - : Elsevier. - 0550-3213 .- 1873-1562. ; 633:3, s. 379-413
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Tidskriftsartikel (refereegranskat)abstract
- We construct logarithmic conformal field theories starting from an ordinary conformal field theory -- with a chiral algebra C and the corresponding space of states V -- via a two-step construction: i) deforming the chiral algebra representation on V\tensor End K[[z,1/z]], where K is an auxiliary finite-dimensional vector space, and ii) extending C by operators corresponding to the endomorphisms End K. For K=C^2, with End K being the two-dimensional Clifford algebra, our construction results in extending C by an operator that can be thought of as \partial^{-1}E, where \oint E is a fermionic screening. This covers the (2,p) Virasoro minimal models as well as the sl(2) WZW theory.
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| 45. |
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| 46. |
- Fredriksson, Sverker
(författare)
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On large transverse momentum production in high-energy proton-nucleus collisions
- 1976
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Ingår i: Nuclear Physics B. - : Elsevier BV. - 0550-3213 .- 1873-1562. ; 111:1, s. 167-177
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Tidskriftsartikel (refereegranskat)abstract
- Experimental data from inclusive production of large pT hadronsin high-energy proton-nucleus collisions are analysed with emphasis on the influence of the size of the target nucleus. It is found that data at pT≤3 GeV/c are consistent with the hypothesis that the incoming proton collides "simultaneously" with all the nucleons in its way, resulting in an effective collision energy larger than the one expected in a single proton-nucleon hit. At pT > 3 GeV/c, data are in conflict with such a simple model, a result we think is a consequence of the dominance of hard parton collisions at very large pT.
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| 47. |
- Fredriksson, Sverker
(författare)
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Particle ratios in the central region of high-energy proton-proton collisions
- 1975
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Ingår i: Nuclear Physics B. - : Elsevier BV. - 0550-3213 .- 1873-1562. ; 84:1, s. 234-252
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Tidskriftsartikel (refereegranskat)abstract
- Recent data from NAL on particle ratios ... large transverse momentum are analysed with emphasis on the surprising discovery that pions increase their dominance over heavier hadrons at increasing transverse momentum. It is argued that this is not a phase space or threshold effect but a dynamical feature that can be used to test theoretical models of multiparticle production. Most models of interest, such as for instance the parton, the hydrodynamical and the two-component model, may however be extended, in a simple-minded way, to kaon and antiproton production as to predict ratios of heavier to lighter hadrons to fall with increasing large transverse momentum.
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| 48. |
- Frohlich J,, et al.
(författare)
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Asymptotic form of zero energy wave functions in supersymmetric matrix models
- 2000
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Ingår i: Nuclear Physics B. - 0550-3213 .- 1873-1562. ; 567:1-2, s. 231-248
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Tidskriftsartikel (refereegranskat)abstract
- We derive the power law decay, and asymptotic form, of SU(2) X Spin(d) invariant wavefunctions satisfying Q(beta)psi=0 for all s(d) = 2(d - 1) supercharges of reduced (d + 1)-dimensional supersymmetric SU(2) Yang-Mills theory, of, respectively, the SU(2) matrix model related to supermembranes in d + 2 dimensions.
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| 49. |
- Grosse, H., et al.
(författare)
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Chiral Schwinger models without gauge anomalies
- 2000
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Ingår i: Nuclear Physics B. - 0550-3213 .- 1873-1562. ; 587:03-jan, s. 568-584
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Tidskriftsartikel (refereegranskat)abstract
- We find a large class of quantum gauge models with massless fermions where the coupling to the gauge fields is not chirally symmetric and which nevertheless do not suffer from gauge anomalies. To be specific we study two dimensional Abelian models in the Hamiltonian framework which can be constructed and solved by standard techniques. The general model describes Np photon fields and NF flavors of Dirac fermions with 2N(F)N(P) different coupling constants, i.e., the chiral component of each fermion can he coupled to the gauge fields differently We construct these models and find conditions so that no gauge anomaly appears. If these conditions hold it is possible to construct and solve the model explicitly, so that gauge- and Lorentz invariance are manifest.
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| 50. |
- Hoppe, Jens, et al.
(författare)
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Dimensionally reduced SYM4 as solvable matrix quantum mechanics
- 2000
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Ingår i: Nuclear Physics B. - 0550-3213 .- 1873-1562. ; 571:1-2, s. 479-509
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Tidskriftsartikel (refereegranskat)abstract
- We study the quantum mechanical model obtained as a dimensional reduction of N = 1 super Yang-Mills theory to a periodic light cone "time''. After mapping the theory to a cohomological field theory, the partition function (with periodic boundary conditions) regularized by a massive term appears to be equal to the partition function of the twisted matrix oscillator. We show that this partition function perturbed by the operator of the holonomy around the time circle is a tau function of Toda hierarchy. We solve the model in the large N limit and study the universal properties of the solution in the scaling limit of vanishing perturbation. We find in this limit a phase transition of Gross-Witten type.
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