| 1. |
- Abulaiti, Yiming, et al.
(författare)
-
Search for an invisibly decaying Higgs boson or dark matter candidates produced in association with a Z boson in pp collisions at root s=13 TeV with the ATLAS detector
- 2018
-
Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445 .- 0009-2614 .- 1873-4448. ; 776, s. 318-337
-
Tidskriftsartikel (refereegranskat)abstract
- A search for an invisibly decaying Higgs boson or dark matter candidates produced in association with a leptonically decaying Z boson in proton-proton collisions at root s = 13 TeV is presented. This search uses 36.1 fb(-1) of data collected by the ATLAS experiment at the Large Hadron Collider. No significant deviation from the expectation of the Standard Model backgrounds is observed. Assuming the Standard Model ZH production cross-section, an observed (expected) upper limit of 67% (39%) at the 95% confidence level is set on the branching ratio of invisible decays of the Higgs boson with mass m(H) = 125 GeV. The corresponding limits on the production cross-section of the ZH process with the invisible Higgs boson decays are also presented. Furthermore, exclusion limits on the dark matter candidate and mediator masses are reported in the framework of simplified dark matter models.
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| 2. |
- Milstead, David A., et al.
(författare)
-
Measurement of differential cross sections of isolated-photon plus heavy-flavour jet production in pp collisions at s=8 TeV using the ATLAS detector
- 2018
-
Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693 .- 0009-2614 .- 1873-4448 .- 1873-2445. ; 776, s. 295-317
-
Tidskriftsartikel (refereegranskat)abstract
- This Letter presents the measurement of differential cross sections of isolated prompt photons produced in association with a b-jet or a c-jet. These final states provide sensitivity to the heavy-flavour content of the proton and aspects related to the modelling of heavy-flavour quarks in perturbative QCD. The measurement uses proton–proton collision data at a centre-of-mass energy of 8 TeV recorded by the ATLAS detector at the LHC in 2012 corresponding to an integrated luminosity of up to 20.2 fb−1. The differential cross sections are measured for each jet flavour with respect to the transverse energy of the leading photon in two photon pseudorapidity regions: |ηγ|<1.37 and 1.56<|ηγ|<2.37. The measurement covers photon transverse energies 25
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| 3. |
- Ohlsson, Tommy, 1973-, et al.
(författare)
-
Neutrino oscillations with three flavors in matter : Applications to neutrinos traversing the earth
- 2000
-
Ingår i: Physics Letters B. - : Elsevier Science B.V.. - 0370-2693 .- 1873-2445. ; 474:1-2, s. 153-162
-
Tidskriftsartikel (refereegranskat)abstract
- Analytic formulas are presented for three flavor neutrino oscillations in matter in the plane wave approximation. We calculate in particular the time evolution operator in both mass and flavor bases. We also find the transition probabilities expressed as functions of the vacuum mass squared differences, the vacuum mixing angles, and the matter density parameter. The application of this to neutrino oscillations for both atmospheric and long baseline neutrinos in a mantle-core-mantle step function model of the Earth's matter density profile is discussed.
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| 4. |
- 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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| 5. |
- Jacobsson, Björn, et al.
(författare)
-
Effects of random matter density fluctuations on the neutrino oscillation transition probabilities in the Earth
- 2002
-
Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 532:04-mar, s. 259-266
-
Tidskriftsartikel (refereegranskat)abstract
- In this Letter, we investigate the effects of random fluctuations of the Earth matter density for long baselines on the neutrino oscillation transition probabilities. We especially identify relevant parameters characterizing the matter density noise and calculate their effects by averaging over statistical ensembles of a large number of matter density profiles. For energies and baselines appropriate to neutrino factories, absolute errors on the relevant appearance probabilities are at the level of \DeltaP(alphabeta)\ similar to 10(-4) (with perhaps \P-mue similar to 1% for neutrinos), whereby a modest improvement in understanding of the geophysical data should render such effects unimportant.
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| 6. |
- Ohlsson, Tommy, 1973-, et al.
(författare)
-
Bilarge leptonic mixing from Abelian horizontal symmetries
- 2002
-
Ingår i: Physics Letters B. - : Elsevier Science B.V.. - 0370-2693 .- 1873-2445. ; 537:02-jan, s. 95-102
-
Tidskriftsartikel (refereegranskat)abstract
- We construct and present a model for leptonic mixing based on higher-dimensional operators, using the Froggatt-Nielsen mechanism. and Abelian horizontal symmetries (flavor symmetries) of continuous and discrete type. Our model naturally yields bilarge leptonic mixing. coming from both the charged leptons and the neutrinos, and an inverted neutrino mass hierarchy spectrum. The obtained values of the parameters, i.e.. the leptonic mixing parameters and the neutrino mass squared differences, are all consistent with the atmospheric neutrino data and the Mikheyev-Smirnov-Wolfenstein large mixing angle solution for the solar neutrino problem.
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| 7. |
- Ohlsson, Tommy, 1973-
(författare)
-
Effects and influences on neutrino oscillations due to a thin density layer perturbation added to a matter density profile
- 2001
-
Ingår i: Physics Letters B. - : Elsevier Science B.V.. - 0370-2693 .- 1873-2445. ; 522:04-mar, s. 280-286
-
Tidskriftsartikel (refereegranskat)abstract
- In this Letter, we show the effects on the transition probabilities for neutrino oscillations due to a thin constant density layer perturbation added to an arbitrary matter density profile, In the case of two neutrino flavors, we calculate the effects both analytically and numerically, whereas in the case of three neutrino flavors, we perform the studies purely numerically. As an realistic example we consider the effects of the Earth's atmosphere when added to the Earth's matter density profile on the neutrino oscillation transition probabilities for atmospheric neutrinos.
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| 8. |
- Ohlsson, Tommy, 1973-
(författare)
-
Equivalence between Gaussian averaged neutrino oscillations and neutrino decoherence
- 2001
-
Ingår i: Physics Letters B. - : Elsevier B.V.. - 0370-2693 .- 1873-2445. ; 502:04-jan, s. 159-166
-
Tidskriftsartikel (refereegranskat)abstract
- In this Letter, we show that a Gaussian averaged neutrino oscillation model is equivalent to a neutrino decoherence model. Without loss of generality, the analysis is performed with two neutrino flavors. We also estimate the damping (or decoherence) parameter for atmospheric neutrinos and compare it to earlier obtained results.
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| 9. |
- Ohlsson, Tommy, 1973-, et al.
(författare)
-
Reconstruction of the Earth's matter density profile using a single neutrino baseline
- 2001
-
Ingår i: Physics Letters B. - : Elsevier Science B.V.. - 0370-2693 .- 1873-2445. ; 512:04-mar, s. 357-364
-
Tidskriftsartikel (refereegranskat)abstract
- In this Letter, we show numerically that a symmetric Earth matter density profile can, in principle, be reconstructed from a single baseline energy spectrum up to a certain precision. For the numerical evaluations in the high-dimensional parameter space we use a genetic algorithm.
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| 10. |
- Adiels, L., et al.
(författare)
-
Search for narrow exotic states in annihilations on 4He
- 1984
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 138:1-3, s. 235-240
-
Tidskriftsartikel (refereegranskat)abstract
- After having found evidence for narrow exotic states in p annihilation, the production of such states on a nuclear target was studied with similar techniques. The γ spectrum associated with annihilation on 4He at rest was measured. The spectrum shows two peaks, at energies of 161.9 and 203.0 MeV, corresponding to intermediate narrow states of masses which seem to be related to states found in p annihilations. The confidence is better than 4 σ.
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| 11. |
- Adiels, L., et al.
(författare)
-
Search for narrow signals in the [gamma]-spectrum from [Proton-antiproton] annihilation at rest
- 1986
-
Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 182:3-4, s. 405-408
-
Tidskriftsartikel (refereegranskat)abstract
- The [gamma]-spectrum originating from pp[combining macron] annihilations at rest in liquid hydrogen was measured with two BGO spectrometers. A total of 24 ï¿œ 106[gamma]’s were accumulated. No narrow peaks indicating exotic states such as baryonium were observed. The upper limit for the branching ratio with 1040 [less-than-or-equals, slant] mx [less-than-or-equals, slant] 1770 MeV/c2 and with [lambda]x [less-than-or-equals, slant] 25 MeV/c2 is less than 10-3 with more than 99.96% confidence.
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| 12. |
- Adiels, L., et al.
(författare)
-
Search for narrow signals in the γ-spectrum from pp̄ annihilation at rest
- 1986
-
Ingår i: Physics Letters B. - : Elsevier. - 0370-2693 .- 1873-2445. ; 182:3-4, s. 405-408
-
Tidskriftsartikel (refereegranskat)abstract
- The γ-spectrum originating from pp̄ annihilations at rest in liquid hydrogen was measured with two BGO spectrometers. A total of 24 × 10 6 γ's were accumulated. No narrow peaks indicating exotic states such as baryonium were observed. The upper limit for the branching ratio p p ̄ → γ + X with 1040 ≤ m x ≤ 1770 MeV/c 2 and with λ x ≤ 25 MeV/c 2 is less than 10 -3 with more than 99.96% confidence. © 1986.
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| 13. |
- Allasia, D, et al.
(författare)
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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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| 14. |
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| 15. |
- 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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| 16. |
- 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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| 17. |
- Ambrosio, M, et al.
(författare)
-
Atmospheric neutrino oscillations from upward throughgoing muon multiple scattering in MACRO
- 2003
-
Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 566:1-2, s. 35-44
-
Tidskriftsartikel (refereegranskat)abstract
- The energy of atmospheric neutrinos detected by MACRO was estimated using multiple Coulomb scattering of upward throughgoing muons. This analysis allows a test of atmospheric neutrino oscillations, relying on the distortion of the muon energy distribution. These results have been combined with those coming from the upward throughgoing muon angular distribution only. Both analyses are independent of the neutrino flux normalization and provide strong evidence, above the for level, in favour of neutrino oscillations. (C) 2003 Published by Elsevier B.V.
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| 18. |
- Ambrosio, M, et al.
(författare)
-
Matter effects in upward-going muons and sterile neutrino oscillations
- 2001
-
Ingår i: Physics Letters B. - : Elsevier. - 0370-2693 .- 1873-2445. ; 517:1-2, s. 59-66
-
Tidskriftsartikel (refereegranskat)abstract
- The angular distribution of upward-going muons produced by atmospheric neutrinos in the rock below the MACRO detector shows anomalies in good agreement with two flavor nu (mu) --> nu (tau) oscillations with maximum mixing and Deltam(2) around 0.0024 eV(2). Exploiting the dependence of magnitude of the matter effect on oscillation channel, and using a set of 809 upward-going muons observed in MACRO, we show that the two flavor nu (mu) --> nu (s) oscillation is disfavored with 99% C.L. with respect to nu (mu) --> nu (tau). (C) 2001 Elsevier Science B.V. All rights reserved.
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| 19. |
- 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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| 20. |
- 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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| 21. |
- Apostolakis, A., et al.
(författare)
-
Measurement of the energy dependence of the form factor f+ in K 0 e3 decay
- 2000
-
Ingår i: Physics Letters B. - : Elsevier. - 0370-2693 .- 1873-2445. ; 473:1, s. 186-192
-
Tidskriftsartikel (refereegranskat)abstract
- Neutral-kaon decays to πeν were analysed to determine the q2 dependence of the K0e3 electroweak form factor f+. Based on 365612 events, this form factor was found to have a linear dependence on q2 with a slope λ+=0.0245±0.0012stat±0.0022syst.
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| 22. |
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| 23. |
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| 24. |
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| 25. |
- Babaev, Egor
(författare)
-
Mass generation without symmetry breakdown in the chiral Gross-Neveu model at finite temperature and finite N in 2+1 dimensions
- 2001
-
Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 497:04-mar, s. 323-327
-
Tidskriftsartikel (refereegranskat)abstract
- The chiral Gross-Neveu model is one of the most popular toy models for QCD being a generic testing field for many ideas in particle physics. It has been studied in the past in detail in the limit of infinite number of flavors of fermions. Quite astonishingly, the study of this model was not carried through in all its facets. The most important omission is the study of the onset of quasi-long-range order in the decoupled massless phase field. The present work eliminates this deficiency. In this paper we derive behavior of the Kosterlitz-Thouless transition in this model at finite temperature in 2 + 1 dimensions in the regime when the number N of field components is large but finite. We also prove the anticipated before key feature of the model, namely, that in the regime of infinite N the temperature of the Kosterlitz-Thouless transition merges with the critical temperature T*, given by a mean-field equation for the gap modulus, thus recovering the BCS-like scenario [(T* - T-KT)/T* --> 0] of the phase transition at N --> infinity.
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| 26. |
- 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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| 27. |
- Bergström, Lars, et al.
(författare)
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Estimates of recoil nucleon spectra in high-energy hadron-nucleus collisions
- 1977
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 68:2, s. 177-179
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Tidskriftsartikel (refereegranskat)abstract
- It is shown that recent data on the recoil nucleon spectrum in 10.5 GeV/c pion-neon collisions are in excellent agreement with a parameter free estimate from the so called tube model for high-energy hadron-nucleus collisions. A simple independent collision model is also treated.
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| 28. |
- Bergström, Lars, et al.
(författare)
-
Is the recently published counterproof of the tube model credible?
- 1978
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 78:2-3, s. 337-341
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Tidskriftsartikel (refereegranskat)abstract
- It is shown that recent data from pion and proton collision with emulsion nuclei at 200 GeV/c are in perfect agreement with expectations from the collective tube model. The opposite conclusion in publications by Azimov et al. came about because the authors ignored the important effects of target fragmentation.
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| 29. |
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| 30. |
- Bondar, A., et al.
(författare)
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The pp → ppπ0 reaction near the kinematical threshold
- 1995
-
Ingår i: Physics Letters B. - : Elsevier. - 0370-2693 .- 1873-2445. ; 356:1, s. 8-12
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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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| 31. |
- Calén, H., et al.
(författare)
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Deuteron breakup by 1.15 GeV protons and excitation of the Δ isobar
- 1993
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Ingår i: Physics Letters B. - : Elsevier. - 0370-2693 .- 1873-2445. ; 303:1-2, s. 10-15
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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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| 32. |
- Calén, H., et al.
(författare)
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The pp → ppη reaction near the kinematical threshold
- 1996
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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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| 33. |
- Carius, Staffan, et al.
(författare)
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The log-normal distribution for cascade multiplicities in hadron collisions
- 1990
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Ingår i: Physics Letters B. - : Elsevier. - 0370-2693 .- 1873-2445. ; 252:4, s. 647-652
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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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| 34. |
- Cederwall, Bo, et al.
(författare)
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Collective rotational-vibrational transition in the very neutron-deficient nuclei (171,172)-Pt
- 1998
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Ingår i: Physics Letters B. - AMSTERDAM, NETHERLANDS : ELSEVIER SCIENCE. - 0370-2693 .- 1873-2445. ; 443:1-4, s. 69-76
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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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| 35. |
- Cederwall, Bo, et al.
(författare)
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PROPERTIES OF SUPERDEFORMED BANDS IN DY-153
- 1995
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 346:3-4, s. 244-250
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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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| 36. |
- CLARK, RM, et al.
(författare)
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A PAIR OF IDENTICAL SUPERDEFORMED BANDS IN ND-136
- 1995
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Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 343:1-4, s. 59-63
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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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| 37. |
- CRISTANCHO, F, et al.
(författare)
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MULTIPLE SUPERDEFORMED BANDS IN SR-81
- 1995
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Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 357:3, s. 281-286
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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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| 38. |
- de, Angelis G, et al.
(författare)
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Rotation induced octupole correlations in the neutron-deficient Te-109 nucleus
- 1998
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Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 437:3-4, s. 236-242
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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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| 39. |
- de Angelis, G., et al.
(författare)
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Coherent proton-neutron contribution to octupole correlations in the neutron-deficient Xe-114 nucleus
- 2002
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Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 535:04-jan, s. 93-102
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Tidskriftsartikel (refereegranskat)abstract
- Gamma ray linear polarization and picosecond lifetimes have been measured for levels in the neutron deficient nucleus Xe-114 using the EUROBALL IV spectrometer and the Cologne plunger device. The EUCLIDES Si-ball was used to improve the reaction channel selectivity. The linear polarization results have, for the first time, unambiguously determined the electromagnetic character of the dipole transitions de-exciting the negative parity level sequence, providing clear evidence for enhanced octupole collectivity. The discovery of two E3 transitions and the measurement of the lifetimes of the states depopulated by these transitions have allowed a quantitative determination of the octupole collectivity in the A approximate to 112 mass region. The large measured B(E3) values, close to approximate to 70 W.u., are among the strongest observed hitherto and indicate a coherent proton-neutron contribution to the octupole moment.
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| 40. |
- Ekelin, Svante, et al.
(författare)
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Large-pT protons from constituent diquark scattering
- 1984
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 149:6, s. 509-513
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Tidskriftsartikel (refereegranskat)abstract
- Recent data from the CERN ISR on the fractional proton yield in pp collisions are explained within the Stockholm diquark model. Describing the proton as a u(ud)0 system, the observed high magnitude and fall-off pT, θ and √s of the proton yield are natural consequences of constituent diquark elastic scattering. The pT and θ dependence favour a value of around 10 GeV2/c2 for the size parameter in the diquark form factor, corresponding to a diquark rms radius of around 0.2 fm. This is consistent with earlier results of the model applied to deep inelastic lepton-nucleon scattering and e+e- annihilation
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| 41. |
- Enberg, Rikard, et al.
(författare)
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Hard colour singlet exchange and gaps between jets at the Tevatron
- 2002
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Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 524:3-4, s. 273-282
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Tidskriftsartikel (refereegranskat)abstract
- The new kind of events with a rapidity gap between two high-ET jets, observed in high energy collisions at the Tevatron, is found to be well described by the exchange of a colour singlet gluon system in the BFKL framework. This requires going beyond the conventional asymptotic Mueller–Tang approximation, which results in qualitatively different features of the basic parton–parton scattering amplitude. Non-leading corrections to the BFKL equation are included by incorporation of the consistency constraint and the running QCD coupling. Hadronisation and other non-perturbative QCD effects are treated through a complete Monte Carlo simulation, providing a gap survival probability that varies event-by-event, facilitating comparison with experimental results.
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| 42. |
- Fredriksson, Sverker
(författare)
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A phenomenological two-component picture of large transverse momentum production
- 1976
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 63:3, s. 321-323
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Tidskriftsartikel (refereegranskat)abstract
- It is suggested that large-pT hadrons can be classified into two categories with completely different properties according to whether they contain a leading quark or just sea quarks from the initial projectile-target system. From simple quark counting we get relations between hadron ratios at large pT, which are consistent with data.
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| 43. |
- Fredriksson, Sverker, et al.
(författare)
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New ideas on the proton-neutron differences in deep inelastic structure functions
- 1985
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 162:4-6, s. 373-378
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Tidskriftsartikel (refereegranskat)abstract
- It is shown how future data from deep inelastic scattering of charged leptons on protons and neutrons can be used to discriminate between the two main possible scale-breaking QCD effects - perturbative gluon processes and non-perturbative diquark formation. Current data from the Stanford Linear Accelerator Center and from CERN on the structure function combinations Fp2-Fn2, Fn2/Fp2 and σL/σT are in line with both the Stockholm diquark model and perturbative QCD, considering the low statistics as well as the possibility of a substantial normalisation error between the two data sets. This calls for a new high-statistics experiment on a deuterium target before any definite conclusions can be made.
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| 44. |
- Freyhult, Lisa, et al.
(författare)
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Chirality and fermion number in a knotted soliton background
- 2003
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Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 557:1-2, s. 121-124
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Tidskriftsartikel (refereegranskat)abstract
- We consider the coupling of a single Dirac fermion to the three component unit vector field which appears as an order parameter in the Faddeev model. Classically, the coupling is determined by requiring that it preserves a certain local frame independence. But quantum mechanically the separate left- and right-chiral fermion number currents suffer from a frame anomaly. We employ this anomaly to compute the fermion number of a knotted soliton. The result coincides with the self-linking number of the soliton. In particular, the anomaly structure of the fermions relates directly to the inherent chiral properties of the soliton. Our result suggests that interactions between fermions and knotted solitons can lead to phenomena akin the Callan–Rubakov effect.
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| 45. |
- Guigas, R., et al.
(författare)
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Strong interaction effects in antiprotonic 6Li/7Li atoms
- 1984
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 137:56, s. 323-328
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Tidskriftsartikel (refereegranskat)abstract
- The effects of strong interaction on the 3 –> 2 X-ray transition in antiprotonic 6Li/7Li atoms have been measured at the low energy -beam at CERN. For the shifts and widths of the levels the values [epsilon]2p = (-230 ï¿œ 72) eV, [Gamma]2p = (443 ï¿œ 210) eV, and [Gamma]3d = (0.130 ï¿œ 0.045) eV for 6Li, and [epsilon]2p = (-336 ï¿œ 60) eV, [Gamma]2p = (456 ï¿œ 190) eV, and [Gamma]3d = (0.210 ï¿œ 0.062) eV for 7Li were found. The data are compared with optical model predictions.
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| 46. |
- Ideguchi, Eiji, et al.
(författare)
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Superdeformation in 91Tc
- 2000
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Ingår i: Physics Letters B. - : Elsevier. - 0370-2693 .- 1873-2445. ; 492:3-4, s. 245-253
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Tidskriftsartikel (refereegranskat)abstract
- A high-spin rotational band with 11 gamma -ray transitions has barn observed in Tc-91. The dynamical moment of inertia as well as the transition quadrupole moment of 8.1(-1.4)(+1.9) eb measured for this band show the characteristics of a superdeformed band. However, the shape is more elongated than in the neighbouring A = 80-90 superdeformed nuclei. Theoretical interpretations of the band within the cranked Strutinsky approach based on two different Woods-Saxon potential parameterisations are presented. Even though an unambiguous configuration assignment proved difficult, both calculations indicate a larger deformation and at least three additional high-N intruder orbitals occupied compared to the lighter SD nuclei. (C) 2000 Elsevier Science B.V. All rights reserved.
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| 47. |
- King, S L, et al.
(författare)
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First observation of excited states in the neutron deficient nuclei (PT)-P-168 and Pt-170
- 1998
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Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 443:1-4, s. 82-88
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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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| 48. |
- Köhler, Th., et al.
(författare)
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Precision measurement of strong interaction isotope effects in antiprotonic 16O, 17O, and 18O atoms
- 1986
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 176:3-4, s. 327-333
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Tidskriftsartikel (refereegranskat)abstract
- The strong-interaction effects in antiprotonic 16O, 17O, and 18O atoms were measured at the CERN antiproton facility, LEAR. The shifts ε{lunate} and the widths Γ of the 3d level were determined to be -112±20 eV (16O), -140±46 eV (17O), -195±20 eV (18O), and 495±45 eV (16O), 540±150 (17O), 640±40 eV (18O), respectively. © 1986.
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| 49. |
- LAFOSSE, DR, et al.
(författare)
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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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| 50. |
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