@article{CernaVelazcoFaberJonesPerezetal.2017, author = {Cerna-Velazco, Nhell and Faber, Thomas and Jones-P{\´e}rez, Joel and Porod, Werner}, title = {Constraining sleptons at the LHC in a supersymmetric low-scale seesaw scenario}, series = {European Physical Journal C}, volume = {77}, journal = {European Physical Journal C}, doi = {10.1140/epjc/s10052-017-5231-9}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-173809}, year = {2017}, abstract = {We consider a scenario inspired by natural supersymmetry, where neutrino data is explained within a low-scale seesaw scenario. We extend the Minimal Supersymmetric Standard Model by adding light right-handed neutrinos and their superpartners, the R-sneutrinos, and consider the lightest neutralinos to be higgsino-like. We consider the possibilities of having either an R-sneutrino or a higgsino as lightest supersymmetric particle. Assuming that squarks and gauginos are heavy, we systematically evaluate the bounds on slepton masses due to existing LHC data.}, language = {en} } @article{ChiesaGreinerSchoenherretal.2017, author = {Chiesa, Mauro and Greiner, Nicolas and Sch{\"o}nherr, Marek and Tramontano, Francesco}, title = {Electroweak corrections to diphoton plus jets}, series = {Journal of High Energy Physics}, journal = {Journal of High Energy Physics}, number = {10}, doi = {10.1007/JHEP10(2017)181}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-173512}, year = {2017}, abstract = {We calculate the next-to-leading order electroweak corrections to the production of a photon pair in association with zero, one and two jets at the LHC. We use GoSam and Sherpa to obtain the results in a fully automated way. For a typical set of fiducial cuts the electroweak corrections lead to a modification of the total cross section of up to 3\%, depending on the jet multiplicity. We find substantial contributions in differential distributions, leading to tens of per cent corrections for phase space regions within the reach of the LHC. Furthermore we investigate the importance of photon induced processes as well as subleading contributions. Photon induced processes are found to be negligible, subleading contributions can have a sizeable impact however they can be removed by appropriate phase space cuts.}, language = {en} } @article{BistiRogalevKarolaketal.2017, author = {Bisti, F. and Rogalev, V. A. and Karolak, M. and Paul, S. and Gupta, A. and Schmitt, T. and G{\"u}ntherodt, G. and Eyert, V. and Sangiovanni, G. and Profeta, G. and Strocov, V. N.}, title = {Weakly-correlated nature of ferromagnetism in nonsymmorphic CrO\(_2\) revealed by bulk-sensitive soft-X-ray ARPES}, series = {Physical Review X}, volume = {7}, journal = {Physical Review X}, number = {4}, doi = {10.1103/PhysRevX.7.041067}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-172251}, year = {2017}, abstract = {Chromium dioxide CrO\(_2\) belongs to a class of materials called ferromagnetic half-metals, whose peculiar aspect is that they act as a metal in one spin orientation and as a semiconductor or insulator in the opposite one. Despite numerous experimental and theoretical studies motivated by technologically important applications of this material in spintronics, its fundamental properties such as momentumresolved electron dispersions and the Fermi surface have so far remained experimentally inaccessible because of metastability of its surface, which instantly reduces to amorphous Cr\(_2\)O\(_3\). In this work, we demonstrate that direct access to the native electronic structure of CrO\(_2\) can be achieved with soft-x-ray angle-resolved photoemission spectroscopy whose large probing depth penetrates through the Cr\(_2\)O\(_3\) layer. For the first time, the electronic dispersions and Fermi surface of CrO\(_2\) are measured, which are fundamental prerequisites to solve the long debate on the nature of electronic correlations in this material. Since density functional theory augmented by a relatively weak local Coulomb repulsion gives an exhaustive description of our spectroscopic data, we rule out strong-coupling theories of CrO\(_2\). Crucial for the correct interpretation of our experimental data in terms of the valence-band dispersions is the understanding of a nontrivial spectral response of CrO\(_2\) caused by interference effects in the photoemission process originating from the nonsymmorphic space group of the rutile crystal structure of CrO\(_2\).}, language = {en} } @article{ErdmengerFernandezFloryetal.2017, author = {Erdmenger, Johanna and Fern{\´a}ndez, Daniel and Flory, Mario and Meg{\´i}as, Eugenio and Straub, Ann-Kathrin and Witkowski, Piotr}, title = {Time evolution of entanglement for holographic steady state formation}, series = {Journal of High Energy Physics}, volume = {2017}, journal = {Journal of High Energy Physics}, number = {10}, doi = {10.1007/JHEP10(2017)034}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-173798}, year = {2017}, abstract = {Within gauge/gravity duality, we consider the local quench-like time evolution obtained by joining two 1+1-dimensional heat baths at different temperatures at time \(t\) = 0. A steady state forms and expands in space. For the 2+1-dimensional gravity dual, we find that the "shockwaves" expanding the steady-state region are of spacelike nature in the bulk despite being null at the boundary. However, they do not transport information. Moreover, by adapting the time-dependent Hubeny-Rangamani-Takayanagi prescription, we holographically calculate the entanglement entropy and also the mutual information for different entangling regions. For general temperatures, we find that the entanglement entropy increase rate satisfies the same bound as in the 'entanglement tsunami' setups. For small temperatures of the two baths, we derive an analytical formula for the time dependence of the entanglement entropy. This replaces the entanglement tsunami-like behaviour seen for high temperatures. Finally, we check that strong subadditivity holds in this time-dependent system, as well as further more general entanglement inequalities for five or more regions recently derived for the static case.}, language = {en} } @article{TuanScharfŽutičetal.2017, author = {Tuan, Dinh Van and Scharf, Benedikt and Žutič, Igor and Dery, Hanan}, title = {Marrying excitons and plasmons in monolayer transition-metal dichalcogenides}, series = {Physical Review X}, volume = {7}, journal = {Physical Review X}, number = {4}, doi = {10.1103/PhysRevX.7.041040}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-173030}, year = {2017}, abstract = {Just as photons are the quanta of light, plasmons are the quanta of orchestrated charge-density oscillations in conducting media. Plasmon phenomena in normal metals, superconductors, and doped semiconductors are often driven by long-wavelength Coulomb interactions. However, in crystals whose Fermi surface is comprised of disconnected pockets in the Brillouin zone, collective electron excitations can also attain a shortwave component when electrons transition between these pockets. In this work, we show that the band structure of monolayer transition-metal dichalcogenides gives rise to an intriguing mechanism through which shortwave plasmons are paired up with excitons. The coupling elucidates the origin for the optical sideband that is observed repeatedly in monolayers of WSe\(_2\) and WS\(_2\) but not understood. The theory makes it clear why exciton-plasmon coupling has the right conditions to manifest itself distinctly only in the optical spectra of electron-doped tungsten-based monolayers.}, language = {en} } @article{TymoshenkoOnykiienkoMuelleretal.2017, author = {Tymoshenko, Y. V. and Onykiienko, Y. A. and M{\"u}ller, T. and Thomale, R. and Rachel, S. and Cameron, A. S. and Portnichenko, P. Y. and Efremov, D. V. and Tsurkan, V. and Abernathy, D. L. and Ollivier, J. and Schneidewind, A. and Piovano, A. and Felea, V. and Loidl, A. and Inosov, D. S.}, title = {Pseudo-Goldstone magnons in the frustrated \(S=3/2\) Heisenberg helimagnet \(ZnCr_2Se_4\) with a pyrochlore magnetic sublattice}, series = {Physical Review X}, volume = {7}, journal = {Physical Review X}, number = {4}, doi = {10.1103/PhysRevX.7.041049}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-172770}, year = {2017}, abstract = {Low-energy spin excitations in any long-range ordered magnetic system in the absence of magnetocrystalline anisotropy are gapless Goldstone modes emanating from the ordering wave vectors. In helimagnets, these modes hybridize into the so-called helimagnon excitations. Here we employ neutron spectroscopy supported by theoretical calculations to investigate the magnetic excitation spectrum of the isotropic Heisenberg helimagnet \({ZnCr_2Se_4}\) with a cubic spinel structure, in which spin\(-3/2\) magnetic \({Cr^{3+}}\) ions are arranged in a geometrically frustrated pyrochlore sublattice. Apart from the conventional Goldstone mode emanating from the \((0~ 0~ {q_h})\) ordering vector, low-energy magnetic excitations in the single-domain proper-screw spiral phase show soft helimagnon modes with a small energy gap of \({∼0.17~ meV}\), emerging from two orthogonal wave vectors \(({q_h}~ 0~ 0)\) and \({(0~ {q_h}~ 0)}\) where no magnetic Bragg peaks are present. We term them pseudo-Goldstone magnons, as they appear gapless within linear spinwave theory and only acquire a finite gap due to higher-order quantum-fluctuation corrections. Our results are likely universal for a broad class of symmetric helimagnets, opening up a new way of studying weak magnon-magnon interactions with accessible spectroscopic methods.}, language = {en} } @article{AdrianMartinezAlbertAndreetal.2017, author = {Adri{\´a}n-Mart{\´i}nez, S. and Albert, A. and Andr{\´e}, M. and Anghinolfi, M. and Anton, G. and Ardid, M. and Aubert, J.-J. and Baret, B. and Barrios-Marti, J. and Basa, S. and Bertin, V. and Biagi, S. and Bormuth, R. and Bouwhuis, M.C. and Bruijn, R. and Brunner, J. and Buto, J. and Capone, A. and Caramete, L. and Carr, J. and Chiarusi, T. and Circella, M. and Coniglione, R. and Costantini, H. and Coyle, P. and Creusot, A. and Dekeyser, I. and Deschamps, A. and De Bonis, G. and Distefano, C.}, title = {Stacked search for time shifted high energy neutrinos from gamma ray bursts with the ANTARES neutrino telescope}, series = {European Physical Journal C}, volume = {77}, journal = {European Physical Journal C}, number = {1}, doi = {10.1140/epjc/s10052-016-4496-8}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-181251}, pages = {10}, year = {2017}, abstract = {A search for high-energy neutrino emission correlated with gamma-ray bursts outside the electromagnetic prompt-emission time window is presented. Using a stacking approach of the time delays between reported gamma-ray burst alerts and spatially coincident muon-neutrino signatures, data from the Antares neutrino telescope recorded between 2007 and 2012 are analysed. One year of public data from the IceCube detector between 2008 and 2009 have been also investigated. The respective timing profiles are scanned for statistically significant accumulations within 40 days of the Gamma Ray Burst, as expected from Lorentz Invariance Violation effects and some astrophysical models. No significant excess over the expected accidental coincidence rate could be found in either of the two data sets. The average strength of the neutrino signal is found to be fainter than one detectable neutrino signal per hundred gamma-ray bursts in the Antares data at 90\% confidence level.}, language = {en} } @article{LindertPozzoriniBoughezaletal.2017, author = {Lindert, J. M. and Pozzorini, S. and Boughezal, R. and Campbell, J. M. and Denner, A. and Dittmaier, S. and Gehrmann-De Ridder, A. and Gehrmann, T. and Glover, N. and Huss, A. and Kallweit, S. and Maierh{\"o}fer, P. and Mangano, M. L. and Morgan, T. A. and M{\"u}ck, A. and Petriello, F. and Salam, G. P. and Sch{\"o}nherr, M. and Williams, C.}, title = {Precise predictions for \(V+\)jets dark matter backgrounds}, series = {European Physical Journal C}, volume = {77}, journal = {European Physical Journal C}, doi = {10.1140/epjc/s10052-017-5389-1}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-172555}, year = {2017}, abstract = {High-energy jets recoiling against missing transverse energy (MET) are powerful probes of dark matter at the LHC. Searches based on large MET signatures require a precise control of the \({Z(ν\overline{ν})}+\) jet background in the signal region. This can be achieved by taking accurate data in control regions dominated by \(Z(ℓ^+ℓ^-)+\) jet, \(W(ℓν)+\) jet and \(γ+\) jet production, and extrapolating to the \({Z(ν\overline{ν})}+\) jet background by means of precise theoretical predictions. In this context, recent advances in perturbative calculations open the door to significant sensitivity improvements in dark matter searches. In this spirit, we present a combination of state-of-the-art calculations for all relevant \(V+\) jets processes, including throughout NNLO QCD corrections and NLO electroweak corrections supplemented by Sudakov logarithms at two loops. Predictions at parton level are provided together with detailed recommendations for their usage in experimental analyses based on the reweighting of Monte Carlo samples. Particular attention is devoted to the estimate of theoretical uncertainties in the framework of dark matter searches, where subtle aspects such as correlations across different \(V+\) jet processes play a key role. The anticipated theoretical uncertainty in the \({Z(ν\overline{ν})}+\) jet background is at the few percent level up to the TeV range.}, language = {en} } @article{OPUS4-17217, title = {All-sky search for high-energy neutrinos from gravitational wave event GW170104 with the ANTARES neutrino telescope}, series = {European Physical Journal C}, volume = {77}, journal = {European Physical Journal C}, organization = {The ANTARES Collaboration}, doi = {10.1140/epjc/s10052-017-5451-z}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-172174}, year = {2017}, abstract = {Advanced LIGO detected a significant gravitational wave signal (GW170104) originating from the coalescence of two black holes during the second observation run on January 4th, 2017. An all-sky high-energy neutrino follow-up search has been made using data from the Antares neutrino telescope, including both upgoing and downgoing events in two separate analyses. No neutrino candidates were found within ±500 s around the GW event time nor any time clustering of events over an extended time window of ±3 months. The non-detection is used to constrain isotropic-equivalent high-energy neutrino emission from GW170104 to less than ∼ 1.2 × \(10^{55}\) erg for a \(E^{-2}\) spectrum. This constraint is valid in the energy range corresponding to the 5-95\% quantiles of the neutrino flux [3.2 TeV; 3.6 PeV], if the GW emitter was below the Antares horizon at the alert time.}, language = {en} } @article{BiedermannDennerDittmaieretal.2017, author = {Biedermann, Benedikt and Denner, Ansgar and Dittmaier, Stefan and Hofer, Lars and J{\"a}ger, Barbara}, title = {Next-to-leading-order electroweak corrections to the production of four charged leptons at the LHC}, series = {Journal of High Energy Physics}, journal = {Journal of High Energy Physics}, number = {1}, doi = {10.1007/JHEP01(2017)033}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-171966}, year = {2017}, abstract = {We present a state-of-the-art calculation of the next-to leading-order electroweak corrections to ZZ production, including the leptonic decays of the Z bosons into μ\(^+\)μ\(^ -\)e\(^+\)e\(^-\) or μ\(^+\)μ\(^-\)μ\(^+\)μ\(^-\) final states. We use complete leading-order and next-to-leading-order matrix elements for four-lepton production, including contributions of virtual photons and all off-shell effects of Z bosons, where the finite Z-boson width is taken into account using the complex-mass scheme. The matrix elements are implemented into Monte Carlo programs allowing for the evaluation of arbitrary differential distributions. We present integrated and differential cross sections for the LHC at 13 TeV both for an inclusive setup where only lepton identification cuts are applied, and for a setup motivated by Higgs-boson analyses in the four-lepton decay channel. The electroweak corrections are divided into photonic and purely weak contributions. The former show the well-known pronounced tails near kinematical thresholds and resonances; the latter are generically at the level of ∼ -5\% and reach several -10\% in the high-energy tails of distributions. Comparing the results for μ\(^+\)μ\(^-\)e\(^+\)e\(^-\) and μ\(^+\)μ\(^-\)μ\(^+\)μ\(^-\) final states, we find significant differences mainly in distributions that are sensitive to the μ\(^+\)μ\(^-\) pairing in the μ\(^+\)μ\(^-\)μ\(^+\)μ\(^-\) final state. Differences between μ\(^+\)μ\(^-\)e\(^+\)e\(^-\) and μ\(^+\)μ\(^-\)μ\(^+\)μ\(^-\) channels due to interferences of equal-flavour leptons in the final state can reach up to 10\% in off-shell-sensitive regions. Contributions induced by incoming photons, i.e. photon-photon and quark-photon channels, are included, but turn out to be phenomenologically unimportant.}, language = {en} }