| 1. |
- Abulaiti, Yiming, et al.
(författare)
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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
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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)
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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
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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
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Ingår i: Physics Letters B. - : Elsevier Science B.V.. - 0370-2693 .- 1873-2445. ; 474:1-2, s. 153-162
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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)
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Equivalence of Chern-Simons gauge theory and WZNW model using a BRST symmetry
- 1999
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Ingår i: Physics Letters B. - : Elsevier. - 0370-2693 .- 1873-2445. ; 466:2-4, s. 227-233
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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
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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
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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)
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Effects and influences on neutrino oscillations due to a thin density layer perturbation added to a matter density profile
- 2001
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Ingår i: Physics Letters B. - : Elsevier Science B.V.. - 0370-2693 .- 1873-2445. ; 522:04-mar, s. 280-286
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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)
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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
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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)
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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
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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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