| 51. |
- BRYNGEMARK, LENE, et al.
(författare)
-
A search for an excited muon decaying to a muon and two jets in pp collisions at √ s = 8 TeV with the ATLAS detector
- 2016
-
Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 18:7
-
Tidskriftsartikel (refereegranskat)abstract
- Anew search signature for excited leptons is explored. Excited muons are sought in the channel pp → μμ∗→ μμ jet jet, assuming both the production and decay occur via a contact interaction. The analysis is based on 20.3 fb-1 of pp collision data at a centre-of-mass energy of s = 8 TeV taken with the ATLAS detector at the large hadron collider. No evidence of excited muons is found, and limits are set at the 95% confidence level on the cross section times branching ratio as a function of the excited-muonmass μμ∗. For μμ∗between 1.3 and 3.0 TeV, the upper limit on φB (μ∗→ μqq) is between 0.6 and 1 fb. Limits on sB are converted to lower bounds on the compositeness scale. In the limiting case L = μμ∗, excitedmuonswith amass below2.8 TeVare excluded.With the samemodel assumptions, these limits at larger μ∗masses improve upon previous limits fromtraditional searches based on the gauge-mediated decay μ∗→ μγ. © 2016 CERN for the benefit of the ATLAS Collaboration.
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| 52. |
- Milstead, David A., et al.
(författare)
-
Search for scalar leptoquarks in pp collisions at √S = 13TeV with the ATLAS experiment
- 2016
-
Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 18:9, s. 1-25
-
Tidskriftsartikel (refereegranskat)abstract
- An inclusive search for a new-physics signature of lepton-jet resonances has been performed by the ATLAS experiment. Scalar leptoquarks, pair-produced in pp collisions at s √S13 TeV at the large hadron collider, have been considered. An integrated luminosity of 3.2 fb−1, corresponding to the full 2015 dataset was used. First (second) generation leptoquarks were sought in events with two electrons (muons) and two or more jets. The observed event yield in each channel is consistent with Standard Model background expectations. The observed (expected) lower limits on the leptoquark mass at 95% confidence level are 1100 and 1050 GeV (1160 and 1040 GeV) for first and second generation leptoquarks, respectively, assuming a branching ratio into a charged lepton and a quark of 100%. Upper limits on the aforementioned branching ratio are also given as a function of leptoquark mass. Compared with the results of earlier ATLAS searches, the sensitivity is increased for leptoquark masses above 860 GeV, and the observed exclusion limits confirm and extend the published results. © 2016 CERN for the benefit of the ATLAS Collaboration.
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| 53. |
- Ahlberg, Sebastian, et al.
(författare)
-
Many-body effects on tracer particle diffusion with applications for single-protein dynamics on DNA
- 2015
-
Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 17
-
Tidskriftsartikel (refereegranskat)abstract
- 30% of the DNA in E. coli bacteria is covered by proteins. Such a high degree of crowding affects the dynamics of generic biological processes (e.g. gene regulation, DNA repair, protein diffusion etc) in ways that are not yet fully understood. In this paper, we theoretically address the diffusion constant of a tracer particle in a one-dimensional system surrounded by impenetrable crowder particles. While the tracer particle always stays on the lattice, crowder particles may unbind to a surrounding bulk and rebind at another, or the same, location. In this scenario we determine how the long time diffusion constant D (after many unbinding events) depends on (i) the unbinding rate of crowder particles k(off), and (ii) crowder particle line density rho, from simulations (using the Gillespie algorithm) and analytical calculations. For small k(off), we find D similar to k(off)/rho(2) when crowder particles do not diffuse on the line, and D similar to root Dk(off)/rho when they are diffusing; D is the free particle diffusion constant. For large k(off), we find agreement with mean-field results which do not depend on k(off). From literature values of k(off) and D, we show that the small k(off) -limit is relevant for in vivo protein diffusion on crowded DNA. Our results apply to single-molecule tracking experiments.
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| 54. |
- Amann, M. C., et al.
(författare)
-
Focus on advanced semiconductor heterostructures for optoelectronics
- 2009
-
Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 11, s. 125012 artno-
-
Tidskriftsartikel (refereegranskat)abstract
- Semiconductor heterostructures are the basic materials underlying optoelectronic devices, particularly lasers and light-emitting diodes (LEDs). Made from various III-V-, II-VI-, SiGe- and other compound semiconductors, modern semiconductor devices are available for the generation, detection and modulation of light covering the entire ultra-violet to far-infrared spectral region. Recent approaches that introduced multilayer heterostructures tailored on the lower nanometre scale made possible artificial semiconductors with new properties, such as extended wavelength coverage, that enabled new applications. Together with ongoing progress on wide-gap semiconductors, the optical wavelengths accessible by semiconductor devices are steadily expanding towards the short-wavelength ultra-violet regime, as well as further into the far-infrared and terahertz spectral regions. It is the aim of this focus issue to present cutting-edge research topics on the most recent optoelectronic material and device developments in this field using advanced semiconductor heterostructures.
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| 55. |
- Andreev, N. E., et al.
(författare)
-
Analysis of laser wakefield dynamics in capillary tubes
- 2010
-
Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 12
-
Tidskriftsartikel (refereegranskat)abstract
- A general approach to the modifications of the spectrum of a laser pulse interacting with matter is elaborated and used for spectral diagnostics of laser wakefield generation in guiding structures. Analytical predictions of the laser frequency red shift due to the wakefield excited in a capillary waveguide are confirmed by self-consistent modeling results. The role of ionization blue shift, and nonlinear laser pulse and wakefield dynamics on the spectrum modification, is analyzed for recent experiments on plasma wave excitation by an intense laser pulse guided in hydrogen-filled glass capillary tubes up to 8 cm long. The dependence of the spectral frequency shift, measured as a function of filling pressure, capillary tube length and incident laser energy, is in excellent agreement with the simulation results, and the associated longitudinal accelerating field is in the range 1-10 GV m(-1).
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| 56. |
- Axelsson, S., et al.
(författare)
-
Theoretical and experimental investigations of three-terminal carbon nanotube nanorelays
- 2005
-
Ingår i: New J. Phys. - : IOP Publishing. - 1367-2630. ; 7
-
Tidskriftsartikel (refereegranskat)abstract
- We present theoretical and experimental investigations of three-terminal nanoelectromechanical relays based on suspended carbon nanotubes. A charge is induced in the nanotube by applying a voltage to an underlying gate electrode thus inducing the nanotube to bend and make contact with a drain electrode. Such devices have potential applications as fast switches, logic devices, memory elements and pulse generators. We describe two modes of operation: a contact mode where the nanotube makes physical contact with the drain electrode and a non-contact mode where electrical contact between the nanotube and the drain electrode is made via a field emission current.
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| 57. |
- Batani, D., et al.
(författare)
-
Effects of laser prepulses on laser-induced proton generation
- 2010
-
Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 12
-
Tidskriftsartikel (refereegranskat)abstract
- Low-intensity laser prepulses (<10(13) W cm(-2), nanosecond duration) are a major issue in experiments on laser-induced generation of protons, often limiting the performances of proton sources produced by high-intensity lasers (approximate to 10(19) W cm(-2), picosecond or femtosecond duration). Depending on the intensity regime, several effects may be associated with the prepulse, some of which are discussed in this paper: (i) destruction of thin foil targets by the shock generated by the laser prepulse; (ii) creation of preplasma on the target front side affecting laser absorption; (iii) deformation of the target rear side; and (iv) whole displacement of thin foil targets affecting the focusing condition. In particular, we show that under oblique high-intensity irradiation and for low prepulse intensities, the proton beam is directed away from the target normal. Deviation is towards the laser forward direction, with an angle that increases with the level and duration of the ASE pedestal. Also, for a given laser pulse, the beam deviation increases with proton energy. The observations are discussed in terms of target normal sheath acceleration, in combination with a laser-controllable shock wave locally deforming the target surface.
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| 58. |
- Bishop, Lev S., et al.
(författare)
-
Proposal for generating and detecting multi-qubit GHZ states in circuit QED
- 2009
-
Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 11, s. 073040-
-
Tidskriftsartikel (refereegranskat)abstract
- We propose methods for the preparation and entanglement detectionof multi-qubit Greenberger–Horne–Zeilinger (GHZ) states in circuit quantumelectrodynamics. Using quantum trajectory simulations appropriate for thesituation of a weak continuous measurement, we show that the joint dispersivereadout of several qubits can be utilized for the probabilistic production ofhigh-fidelity GHZ states. When employing a nonlinear filter on the recordedhomodyne signal, the selected states are found to exhibit values of theBell–Mermin operator exceeding 2 under realistic conditions. We discuss thepotential of the dispersive readout to demonstrate a violation of the Merminbound, and present a measurement scheme avoiding the necessity for fulldetector tomography.
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| 59. |
- Brueggemann, Ben, et al.
(författare)
-
Nonperturbative modeling of fifth-order coherent multidimensional spectroscopy in light harvesting antennas
- 2011
-
Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 13:2
-
Tidskriftsartikel (refereegranskat)abstract
- Recent advances in coherent multidimensional spectroscopy have boosted interest in exciton coherences in light harvesting complexes. We present nonperturbative calculations of two-dimensional (2D) electronic spectroscopy from a fifth-order phase-matching direction. The calculations show clear patterns that correspond to the electronic structure of one- and two-exciton manifolds of a Fenna-Matthews-Olsson light harvesting complex. Such signals can provide new information about the coherent properties of antenna pigment protein complexes.
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| 60. |
- Burza, Matthias, et al.
(författare)
-
Hollow microspheres as targets for staged laser-driven proton acceleration
- 2011
-
Ingår i: New Journal of Physics. - : Institute of Physics Publishing (IOPP). - 1367-2630. ; 13, s. 013030-
-
Tidskriftsartikel (refereegranskat)abstract
- A coated hollow core microsphere is introduced as a novel targetin ultra-intense laser–matter interaction experiments. In particular, it facilitates staged laser-driven proton acceleration by combining conventional target normal sheath acceleration (TNSA), power recycling of hot laterally spreading electrons and staging in a very simple and cheap target geometry. During TNSA of protons from one area of the sphere surface, laterally spreading hot electrons form a charge wave. Due to the spherical geometry, this wave refocuses on the opposite side of the sphere, where an opening has been laser micromachined.This leads to a strong transient charge separation field being set up there, which can post-accelerate those TNSA protons passing through the hole at the right time. Experimentally, the feasibility of using such targets is demonstrated. A redistribution is encountered in the experimental proton energy spectra, as predicted by particle-in-cell simulations and attributed to transient fields set up by oscillating currents on the sphere surface.
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